Ultrashort megaelectronvolt positron beam generation based on laser-accelerated electrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Tongjun; Shen, Baifei, E-mail: bfshen@mail.shcnc.ac.cn; Xu, Jiancai, E-mail: jcxu@siom.ac.cn

Experimental generation of ultrashort MeV positron beams with high intensity and high density using a compact laser-driven setup is reported. A high-density gas jet is employed experimentally to generate MeV electrons with high charge; thus, a charge-neutralized MeV positron beam with high density is obtained during laser-accelerated electrons irradiating high-Z solid targets. It is a novel electron–positron source for the study of laboratory astrophysics. Meanwhile, the MeV positron beam is pulsed with an ultrashort duration of tens of femtoseconds and has a high peak intensity of 7.8 × 10{sup 21} s{sup −1}, thus allows specific studies of fast kinetics in millimeter-thick materials withmore » a high time resolution and exhibits potential for applications in positron annihilation spectroscopy.« less

A novel source of MeV positron bunches driven by energetic protons for PAS application

NASA Astrophysics Data System (ADS)

Tan, Zongquan; Xu, Wenzhen; Liu, Yanfen; Xiao, Ran; Kong, Wei; Ye, Bangjiao

2014-11-01

This paper proposes a novel methodology of MeV positrons generation for PAS application. Feasibility of this proposal analyzed by G4Beamline and Transport have shown reasonable success. Using 2 Hz, 1.6 GeV, 100 ns and 1.5 μC/bunch proton bunches for bombarding a graphite target, about 100 ns e+ bunches are generated. Quasi-monochromatic positrons in the range of 1-10 MeV included in these bunches have a flux of >107/s, peak brightness of 1014/s. A magnetic-confinement beamline is utilized to transport the positrons and a "Fast Beam Chopper" is unprecedentedly extended to chop those relativistic bunches. The positron beam can be finally characterized by the energy range of 1-10 MeV and bunch width from one hundred ps up to 1 ns. Such ultrashort bunches can be useful in tomography-type positron annihilation spectroscopy (PAS) as well as other applications.

Efficient injection of an intense positron beam into a dipole magnetic field

NASA Astrophysics Data System (ADS)

Saitoh, H.; Stanja, J.; Stenson, E. V.; Hergenhahn, U.; Niemann, H.; Pedersen, T. Sunn; Stoneking, M. R.; Piochacz, C.; Hugenschmidt, C.

2015-10-01

We have demonstrated efficient injection and trapping of a cold positron beam in a dipole magnetic field configuration. The intense 5 eV positron beam was provided by the NEutron induced POsitron source MUniCh facility at the Heinz Maier-Leibnitz Zentrum, and transported into the confinement region of the dipole field trap generated by a supported, permanent magnet with 0.6 T strength at the pole faces. We achieved transport into the region of field lines that do not intersect the outer wall using the {E}× {B} drift of the positron beam between a pair of tailored plates that created the electric field. We present evidence that up to 38% of the beam particles are able to reach the intended confinement region and make at least a 180° rotation around the magnet where they annihilate on an insertable target. When the target is removed and the {E}× {B} plate voltages are switched off, confinement of a small population persists for on the order of 1 ms. These results lend optimism to our larger aims to apply a magnetic dipole field configuration for trapping of both positrons and electrons in order to test predictions of the unique properties of a pair plasma.

Accelerator based epithermal neutron source

NASA Astrophysics Data System (ADS)

Taskaev, S. Yu.

2015-11-01

We review the current status of the development of accelerator sources of epithermal neutrons for boron neutron capture therapy (BNCT), a promising method of malignant tumor treatment. Particular attention is given to the source of epithermal neutrons on the basis of a new type of charged particle accelerator: tandem accelerator with vacuum insulation and lithium neutron-producing target. It is also shown that the accelerator with specialized targets makes it possible to generate fast and monoenergetic neutrons, resonance and monoenergetic gamma-rays, alpha-particles, and positrons.

Monte Carlo simulation study of positron generation in ultra-intense laser-solid interactions

NASA Astrophysics Data System (ADS)

Yan, Yonghong; Wu, Yuchi; Zhao, Zongqing; Teng, Jian; Yu, Jinqing; Liu, Dongxiao; Dong, Kegong; Wei, Lai; Fan, Wei; Cao, Leifeng; Yao, Zeen; Gu, Yuqiu

2012-02-01

The Monte Carlo transport code Geant4 has been used to study positron production in the transport of laser-produced hot electrons in solid targets. The dependence of the positron yield on target parameters and the hot-electron temperature has been investigated in thick targets (mm-scale), where only the Bethe-Heitler process is considered. The results show that Au is the best target material, and an optimal target thickness exists for generating abundant positrons at a given hot-electron temperature. The positron angular distributions and energy spectra for different hot electron temperatures were studied without considering the sheath field on the back of the target. The effect of the target rear sheath field for positron acceleration was studied by numerical simulation while including an electrostatic field in the Monte Carlo model. It shows that the positron energy can be enhanced and quasi-monoenergetic positrons are observed owing to the effect of the sheath field.

Methods and apparatus for producing and storing positrons and protons

DOEpatents

Akers, Douglas W [Idaho Falls, ID

2010-07-06

Apparatus for producing and storing positrons may include a trap that defines an interior chamber therein and that contains an electric field and a magnetic field. The trap may further include a source material that includes atoms that, when activated by photon bombardment, become positron emitters to produce positrons. The trap may also include a moderator positioned adjacent the source material. A photon source is positioned adjacent the trap so that photons produced by the photon source bombard the source material to produce the positron emitters. Positrons from the positron emitters and moderated positrons from the moderator are confined within the interior chamber of the trap by the electric and magnetic fields. Apparatus for producing and storing protons are also disclosed.

Polarization observables using positron beams

NASA Astrophysics Data System (ADS)

Schmidt, Axel

2018-05-01

The discrepancy between polarized and unpolarized measurements of the proton's electromagnetic form factors is striking, and suggests that two-photon exchange (TPE) may be playing a larger role in elastic electron-proton scattering than is estimated in standard radiative corrections formulae. While TPE is difficult to calculate in a model-independent way, it can be determined experimentally from asymmetries between electron-proton and positron-proton scattering. The possibility of a polarized positron beam at Jefferson Lab would open the door to measurements of TPE using polarization observables. In these proceedings, I examine the feasibility of measuring three such observables with positron scattering. Polarization-transfer, specifically the ɛ-dependence for fixed Q2, is an excellent test of TPE, and the ability to compare electrons and positrons would lead to a drastic reduction of systematics. However, such a measurement would be severely statistically limited. Normal single-spin asymmetries (SSAs) probe the imaginary part of the TPE amplitude and can be improved by simultaneous measurements with electron and positron beams. Beam-normal SSAs are too small to be measured with the proposed polarized positron beam, but target-normal SSAs could be feasibly measured with unpolarized positrons in the spectrometer halls. This technique should be included in the physics case for developing a positron source for Jefferson Lab.

Conceptual design of an intense positron source based on an LIA

NASA Astrophysics Data System (ADS)

Long, Ji-Dong; Yang, Zhen; Dong, Pan; Shi, Jin-Shui

2012-04-01

Accelerator based positron sources are widely used due to their high intensity. Most of these accelerators are RF accelerators. An LIA (linear induction accelerator) is a kind of high current pulsed accelerator used for radiography. A conceptual design of an intense pulsed positron source based on an LIA is presented in the paper. One advantage of an LIA is its pulsed power being higher than conventional accelerators, which means a higher amount of primary electrons for positron generations per pulse. Another advantage of an LIA is that it is very suitable to decelerate the positron bunch generated by bremsstrahlung pair process due to its ability to adjustably shape the voltage pulse. By implementing LIA cavities to decelerate the positron bunch before it is moderated, the positron yield could be greatly increased. These features may make the LIA based positron source become a high intensity pulsed positron source.

Development of an Electron-Positron Source for Positron Annihilation Lifetime Spectroscopy

DTIC Science & Technology

2007-01-01

positron source for positron annihilation lifetime spectroscopy Final Report Report Title...Development of an Electron- Positron Source for Position Annihilation Lifetime Spectroscopy DAAD19-03-1-0287 Final Report 2/17/2007... annihilation lifetime spectroscopy REPORT DOCUMENTATION PAGE 18. SECURITY CLASSIFICATION ON THIS PAGE UNCLASSIFIED 2. REPORT DATE: 12b. DISTRIBUTION

Slow positron beam generator for lifetime studies

NASA Technical Reports Server (NTRS)

Singh, Jag J. (Inventor); Eftekhari, Abe (Inventor); St.clair, Terry L. (Inventor)

1991-01-01

A slow positron beam generator uses a conductive source residing between two test films. Moderator pieces are placed next to the test film on the opposite side of the conductive source. A voltage potential is applied between the moderator pieces and the conductive source. Incident energetic positrons: (1) are emitted from the conductive source; (2) are passed through test film; and (3) isotropically strike moderator pieces before diffusing out of the moderator pieces as slow positrons, respectively. The slow positrons diffusing out of moderator pieces are attracted to the conductive source which is held at an appropriate potential below the moderator pieces. The slow positrons have to pass through the test films before reaching the conductive source. A voltage is adjusted so that the potential difference between the moderator pieces and the conductive source forces the positrons to stop in the test films. Measurable annihilation radiation is emitted from the test film when positrons annihilate (combine) with electrons in the test film.

High intensity positron source at HFR: Basic concept, scoring and design optimisation

NASA Astrophysics Data System (ADS)

Zeman, A.; Tuček, K.; Debarberis, L.; Hogenbirk, A.

2012-01-01

Recent applications of positron beam techniques in various fields of research have led to an increasing demand for high intensity positron sources required for advanced applications, particularly in materials science. Considerable efforts are being made worldwide to design and set-up high intensity positron sources and beam systems that are based on several principles. Such positron sources could be used in fundamental and applied research experiments, as well as in industrial applications, especially in the field of condensed matter characterisation at the nanometre scale. Phenomena involving positrons are also important in other applied science fields such as medicine, biology, physics, energy, etc. However, such studies are often limited due to the relative lack of suitable positron sources. Results from the recently completed Exploratory Research Project called "HIPOS" are discussed in this paper, which describes the principles behind such a powerful very high intensity positron beam experimental facility that is based on a reactor source. Details of a proposed concept that uses nuclear reactions [(n, γ) and (γ, pair)] within a designed positron generator at the High Flux Reactor (HFR) in Petten are also discussed. The HIPOS source has been designed to produce slow positrons with intensity of the order of 10 10 e +/s.

Slow positron beam production by a 14 MeV C.W. electron accelerator

NASA Astrophysics Data System (ADS)

Begemann, M.; Gräff, G.; Herminghaus, H.; Kalinowsky, H.; Ley, R.

1982-10-01

A 14 MeV c.w. electron accelerator is used for pair production in a tungsten target of 0.7 radiation lengths thickness. A small fraction of the positrons is thermalized and diffuses out of the surface ofsurface of a well annealed tungsten foil coated with MgO which is positioned immediately behind the target. The slow positrons are extracted from the target region and magnetically guided over a distance of 10 m onto a channelplate multiplier at the end of an S-shaped solenoid. The positrons are identified by their annihilation radiation using two NaI-detectors. The intensity of the slow positrons is proportional to the accelerator electron beam current. The maximum intensity of 2.2 × 10 5 slow positrons per second reaching thedetector at an accelerator current of 15 μA was limited by the power deposited in the uncooled target. The energy of the positrons is concentrated in a small region at about 1 eV and clearly demonstrates the emission of thermal positrons.

Status and Perspectives for a Slow Positron Beam Facility at the HH—NIPNE Bucharest

NASA Astrophysics Data System (ADS)

Constantin, Florin; Craciun, Liviu Stefan; Constantinescu, Olimpiu; Ghita, Ionica Alina; Ionescu, Cristina; Racolta, Petru Mihai; Straticiuc, Mihai; Vasilescu, Angela; Braic, Viorel; Zoita, Catalin; Kiss, Adrian; Bojin, Dionezie

2009-03-01

The development of a positron annihilation spectroscopy laboratory at the HH-NIPNE Bucharest-to be used for material studies and applications was started in the last 10 years. In the framework of a national research project extended over the last 3 years, was designed a low energy positron accelerator, as a high-vacuum dedicated beam line with two options: a 25 mCi 22NaCl source and in line with the NIPNE-cyclotron or a new intense compact cyclotron. The construction of the beam line was planned as a sequence of modules: source- moderator system; magnetical filter for fast positrons in order to select the positrons energies in the range 0.8-1 keV; a modular system for focusing, transport and acceleration of monoenergetic positrons in the energy range 0.8-50 keV and a CDBS analysis chamber. The moderator proposed—is tungsten as a foil of about 3 μm prepared at the Optoelectronics Institute were put into a thermal treatment vacuum chamber and bombarded with electrons from a 100 W electron gun After the treatment, they were tested for changes of elemental composition of the surface and structure at the Polytechnic University. The structure tests were performed on a DRON 3 M diffractometer, with a Co tube (λKα = 1.7903 A)—the angular regions studied were around 34° (1 0 0) and 69° (2 0 0). In the present time, the trajectories of the positron are going to be simulated with dedicated software (an ion and electron optics simulator). For the coincidence measurements (CDBS) set-up we used a home-made 22NaCl source, by separation without carrier from a metallic Mg target irradiated with 12 MeV protons and separated by columnar cation exchange. A home- made biparametric system for CDBS measurements will be reported, also.

Status and Perspectives for a Slow Positron Beam Facility at the HH-NIPNE Bucharest

NASA Astrophysics Data System (ADS)

Straticiuc, Mihai; Craciun, Liviu Stefan; Constantinescu, Olimpiu; Ghita, Ionica Alina; Ionescu, Cristina; Racolta, Petru Mihai; Vasilescu, Angela; Braic, Viorel; Zoita, Catalin; Kiss, Adrian; Bojin, Dionezie

2009-03-01

The development of a positron annihilation spectroscopy laboratory at the HH-NIPNE Bucharest-to be used for material studies and applications was started in the last 10 years. In the framework of a national research project extended over the last 3 years, was designed a low energy positron accelerator, as a high-vacuum dedicated beam line with two options: a 25 mCi 22NaCl source and in line with the NIPNE-cyclotron or a new intense compact cyclotron. The construction of the beam line was planned as a sequence of modules: source- moderator system; magnetical filter for fast positrons in order to select the positrons energies in the range 0.8-1 keV; a modular system for focusing, transport and acceleration of monoenergetic positrons in the energy range 0.8-50 keV and a CDBS analysis chamber. The moderator proposed-is tungsten as a foil of about 3 μm prepared at the Optoelectronics Institute were put into a thermal treatment vacuum chamber and bombarded with electrons from a 100 W electron gun After the treatment, they were tested for changes of elemental composition of the surface and structure at the Polytechnic University. The structure tests were performed on a DRON 3 M diffractometer, with a Co tube (λKα = 1.7903 A)-the angular regions studied were around 34° (1 0 0) and 69° (2 0 0). In the present time, the trajectories of the positron are going to be simulated with dedicated software (an ion and electron optics simulator). For the coincidence measurements (CDBS) set-up we used a home-made 22NaCl source, by separation without carrier from a metallic Mg target irradiated with 12 MeV protons and separated by columnar cation exchange. A home- made biparametric system for CDBS measurements will be reported, also.

Development of an Electron-Positron Source for Positron Annihilation Lifetime Spectroscopy

DTIC Science & Technology

2009-12-19

REPORT Development of an electron- positron source for positron annihilation lifetime spectroscopy : FINAL REPORT 14. ABSTRACT 16. SECURITY...to generate radiation, to accelerate particles, and to produce electrons and positrons from vacuum. From applications using existing high-repetition...theoretical directions. This report reviews work directed toward the application of positron generation from laser interaction with matter 1. REPORT DATE

Emittance of positron beams produced in intense laser plasma interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen Hui; Hazi, A.; Link, A.

2013-01-15

The first measurement of the emittance of intense laser-produced positron beams has been made. The emittance values were derived through measurements of positron beam divergence and source size for different peak positron energies under various laser conditions. For one of these laser conditions, we used a one dimensional pepper-pot technique to refine the emittance value. The laser-produced positrons have a geometric emittance between 100 and 500 mm{center_dot}mrad, comparable to the positron sources used at existing accelerators. With 10{sup 10}-10{sup 12} positrons per bunch, this low emittance beam, which is quasi-monoenergetic in the energy range of 5-20 MeV, may be usefulmore » as an alternative positron source for future accelerators.« less

Positron Beam Characteristics at NEPOMUC Upgrade

NASA Astrophysics Data System (ADS)

Hugenschmidt, C.; Ceeh, H.; Gigl, T.; Lippert, F.; Piochacz, C.; Reiner, M.; Schreckenbach, K.; Vohburger, S.; Weber, J.; Zimnik, S.

2014-04-01

In 2012, the new neutron induced positron source NEPOMUC upgrade was put into operation at FRMII. Major changes have been made to the source which consists of a neutron-γ-converter out of Cd and a Pt foil structure for electron positron pair production and positron moderation. The new design leads to an improvement of both intensity and brightness of the mono-energetic positron beam. In addition, the application of highly enriched 113Cd as neutron-γ-converter extends the lifetime of the positron source to 25 years. A new switching and remoderation device has been installed in order to allow toggling from the high-intensity primary beam to a brightness enhanced remoderated positron beam. At present, an intensity of more than 109 moderated positrons per second is achieved at NEPOMUC upgrade. The main characteristics are presented which comprise positron yield and beam profile of both the primary and the remoderated positron beam.

A slow positron beam generator for lifetime studies

NASA Technical Reports Server (NTRS)

Singh, Jag J.; Eftekhari, Abe; St.clair, Terry L.

1989-01-01

A slow positron beam generator using well-annealed polycrystalline tungsten moderators and a Na-22 positron source was developed. A 250 micro c source, deposited on a 2.54 micron thick aluminized mylar, is sandwiched between two (2.54 cm x 2.54 cm x 0.0127 cm) tungsten pieces. Two (2.54 cm x 2.54 cm x t cm) test polymer films insulate the two tungsten moderator pieces from the aluminized mylar source holder (t=0.00127 to 0.0127). A potential difference of 10 to 100 volts--depending on the test polymer film thickness (t)--is applied between the tungsten pieces and the source foil. Thermalized positrons diffusing out of the moderator pieces are attracted to the source foil held at an appropriate potential below the moderator pieces. These positrons have to pass through the test polymer films before they can reach the source foil. The potential difference between the moderator pieces and the aluminized mylar is so adjusted as to force the positrons to stop in the test polymer films. Thus the new generator becomes an effective source of positrons for assaying thin polymer films for their molecular morphology.

Positron annihilation lifetime and Doppler broadening spectroscopy at the ELBE facility

NASA Astrophysics Data System (ADS)

Wagner, Andreas; Butterling, Maik; Liedke, Maciej O.; Potzger, Kay; Krause-Rehberg, Reinhard

2018-05-01

The Helmholtz-Zentrum Dresden-Rossendorf operates a superconducting linear accelerator for electrons with energies up to 35 MeV and average beam currents up to 1.6 mA with bunch charges up to 120 pC. The electron beam is employed to produce several secondary beams including X-rays from bremsstrahlung production, coherent IR light in a Free Electron Laser, superradiant THz radiation, neutrons, and positrons. The secondary positron beam after moderation feeds the Monoenergetic Positron Source (MePS) where positron annihilation lifetime (PALS) and positron annihilation Doppler-broadening experiments in materials science are performed. The adjustable repetition rate of the continuous-wave electron beams allows matching of the pulse separation to the positron lifetime in the sample under study. The energy of the positron beam can be set between 0.5 keV and 20 keV to perform depth resolved defect spectroscopy and porosity studies especially for thin films. Bulk materials, fluids, gases, and even radioactive samples can be studied at the unique Gamma-induced Positron Source (GiPS) where an intense bremsstrahlung source generates positrons directly inside the material under study. A 22Na-based monoenergetic positron beam serves for offline experiments and additional depth-resolved Doppler-broadening studies complementing both accelerator-based sources.

Studies of discrete symmetries in a purely leptonic system using the Jagiellonian Positron Emission Tomograph

NASA Astrophysics Data System (ADS)

Moskal, P.; Alfs, D.; Bednarski, T.; Białas, P.; Curceanu, C.; Czerwiński, E.; Dulski, K.; Gajos, A.; Głowacz, B.; Gupta-Sharma, N.; Gorgol, M.; Hiesmayr, B. C.; Jasińska, B.; Kamińska, D.; Khreptak, O.; Korcyl, G.; Kowalski, P.; Krzemień, W.; Krawczyk, N.; Kubicz, E.; Mohammed, M.; Niedźwiecki, Sz.; Pawlik-Niedńwiecka, M.; Raczyński, L.; Rudy, Z.; Silarski, M.; Smyrski, J.; Wieczorek, A.; Wiślicki, W.; Zgardzińska, B.; Zieliński, M.

2016-11-01

Discrete symmetries such as parity (P), charge-conjugation (C) and time reversal (T) are of fundamental importance in physics and cosmology. Breaking of charge conjugation symmetry (C) and its combination with parity (CP) constitute necessary conditions for the existence of the asymmetry between matter and antimatter in the observed Universe. The presently known sources of discrete symmetries violations can account for only a tiny fraction of the excess of matter over antimatter. So far CP and T symmetries violations were observed only for systems involving quarks and they were never reported for the purely leptonic objects. In this article we describe briefly an experimental proposal for the test of discrete symmetries in the decays of positronium atom which is made exclusively of leptons. The experiments are conducted by means of the Jagiellonian Positron Emission Tomograph (J-PET) which is constructed from strips of plastic scintillators enabling registration of photons from the positronium annihilation. J-PET tomograph together with the positronium target system enable to measure expectation values for the discrete symmetries odd operators constructed from (i) spin vector of the ortho-positronium atom, (ii) momentum vectors of photons originating from the decay of positronium, and (iii) linear polarization direction of annihilation photons. Linearly polarized positronium will be produced in the highly porous aerogel or polymer targets, exploiting longitudinally polarized positrons emitted by the sodium 22Na isotope. Information about the polarization vector of orthopositronium will be available on the event by event basis and will be reconstructed from the known position of the positron source and the reconstructed position of the orthopositronium annihilation. In 2016 the first tests and calibration runs are planned, and the data collection with high statistics will commence in the year 2017.

Target material dependence of positron generation from high intensity laser-matter interactions

DOE PAGES

Williams, G. J.; Barnak, D.; Fiksel, G.; ...

2016-12-06

Here, the effective scaling of positron-electron pair production by direct, ultraintense laser-matter interaction is investigated for a range of target materials and thicknesses. An axial magnetic field, acting as a focusing lens, was employed to measure positron signals for targets with atomic numbers as low as copper (Z – 29). The pair production yield was found to be consistent with the Bethe-Heitler mechanism, where the number of positrons emitted into a 1 steradian cone angle from the target rear was found to be proportional to Z 2. The unexpectedly low scaling results from Coulomb collisions that act to stop ormore » scatter positrons into high angles. Monte Carlo simulations support the experimental results, providing a comprehensive power-law scaling relationship for all elemental materials and densities.« less

Ultra-Intense Short-Pulse Pair Creation Using the Texas Petawatt Laser

NASA Astrophysics Data System (ADS)

Liang, Edison; Henderson, Alexander; Clarke, Taylor; Taylor, Devin; Chaguine, Petr; Serratto, Kristina; Riley, Nathan; Dyer, Gilliss; Donovan, Michael; Ditmire, Todd

2013-10-01

We report results from the 2012 pair creation experiment using the Texas Petawatt Laser. Up to 1011 positrons per steradian were detected using 100 Joule pulses from the Texas Petawatt Laser to irradiate gold targets, with peak laser intensities up to 1.9 × 1021W/cm2 and pulse durations as short as 130 fs. Positron-to-electron ratios exceeding 20% were measured on some shots. The positron energy, positron yield per unit laser energy, and inferred positron density are significantly higher than those reported in previous experiments. This confirms that, for a given laser energy, higher intensity and shorter pulses irradiating thicker targets are more favorable for pair creation. Narrow-band high-energy positrons up to 23 MeV were observed from thin targets. Supported by DOE Grant DE-SC-0001481 and Rice FIF.

Progress towards an intense beam of positrons created by a Van de Graaff accelerator

NASA Astrophysics Data System (ADS)

Lund, K. R.; Weber, M. H.; Lynn, K. G.; Jennings, J.; Minnal, C.; Narimannezhad, A.; Rao, R.; Monster, K. A. W.

2017-12-01

A 4MV Van de Graaff accelerator was used to induce the nuclear reaction 12C(d,n)13N in order to produce an intense beam of positrons. The graphite target was heated so the radioactive 13N would desorb from the bulk into the vacuum. This radioactive gas is frozen onto a cryogenic freezer where it decays to produce an antiparticle beam of positrons. This high current beam is then guided into a superconducting magnet with field strength up to 7 Tesla where the positrons will be stored in a newly designed Micro-Penning-Malmberg trap. Several source geometries have been experimented on and found a maximum antimatter beam with a positron flux of greater than 0.55 ± 0.03 × 106 e+s-1 was achieved. This beam was produced using a solid rare gas moderator composed of krypton (Kr) at a temperature of 25 ± 5 K. Due to geometric restrictions on this set up and other loss mechanisms, 107-108 e+s-1 of the total number of positrons are lost. Simulations and preliminary experiments suggest a new geometry, currently under testing, will produce a beam of 107 e+s-1 or more. The setup and preliminary results for the new geometry will be discussed as well.

Determination of radionuclides and radiochemical impurities produced by in-house cyclotron irradiation and subsequent radiosynthesis of PET tracers.

PubMed

Ishiwata, Kiichi; Hayashi, Kunpei; Sakai, Masanari; Kawauchi, Sugio; Hasegawa, Hideaki; Toyohara, Jun

2017-01-01

To elucidate the radionuclides and radiochemical impurities included in radiosynthesis processes of positron emission tomography (PET) tracers. Target materials and PET tracers were produced using a cyclotron/synthesis system from Sumitomo Heavy Industry. Positron and γ-ray emitting radionuclides were quantified by measuring radioactivity decay and using the high-purity Ge detector, respectively. Radiochemical species in gaseous and aqueous target materials were analyzed by gas and ion chromatography, respectively. Target materials had considerable levels of several positron emitters in addition to the positron of interest, and in the case of aqueous target materials extremely low levels of many γ-emitters. Five 11 C-, 15 O-, or 18 F-labeled tracers produced from gaseous materials via chemical reactions had no radionuclidic impurities, whereas 18 F-FDG, 18 F-NaF, and 13 N-NH 3 produced from aqueous materials had several γ-emitters as well as impure positron emitters. 15 O-Labeled CO 2 , O 2 , and CO had a radionuclidic impurity 13 N-N 2 (0.5-0.7 %). Target materials had several positron emitters other than the positron of interest, and extremely low level γ-emitters in the case of aqueous materials. PET tracers produced from gaseous materials except for 15 O-labeled gases had no impure radionuclides, whereas those derived from aqueous materials contained acceptable levels of impure positron emitters and extremely low levels of several γ-emitters.

Beam position monitoring system at CESR

NASA Astrophysics Data System (ADS)

Billing, M. G.; Bergan, W. F.; Forster, M. J.; Meller, R. E.; Rendina, M. C.; Rider, N. T.; Sagan, D. C.; Shanks, J.; Sikora, J. P.; Stedinger, M. G.; Strohman, C. R.; Palmer, M. A.; Holtzapple, R. L.

2017-09-01

The Cornell Electron-positron Storage Ring (CESR) has been converted from a High Energy Physics electron-positron collider to operate as a dedicated synchrotron light source for the Cornell High Energy Synchrotron Source (CHESS) and to conduct accelerator physics research as a test accelerator, capable of studying topics relevant to future damping rings, colliders and light sources. Some of the specific topics that were targeted for the initial phase of operation of the storage ring in this mode, labeled CESRTA (CESR as a Test Accelerator), included 1) tuning techniques to produce low emittance beams, 2) the study of electron cloud development in a storage ring and 3) intra-beam scattering effects. The complete conversion of CESR to CESRTA occurred over a several year period and is described elsewhere. As a part of this conversion the CESR beam position monitoring (CBPM) system was completely upgraded to provide the needed instrumental capabilities for these studies. This paper describes the new CBPM system hardware, its function and representative measurements performed by the upgraded system.

Searching for dark photon with positrons at Jefferson lab

NASA Astrophysics Data System (ADS)

Marsicano, Luca

2018-05-01

The interest in the Dark Photon (A' or U) has recently grown, since it could act as a light mediator to a new sector of Dark Matter particles. In this paradigm, the electron-positron annihilation can rarely produce a γA' pair. Various experiments (e.g. PADME@LNF [1], VEPP-3 [2]) have been proposed to detect this process using positron beams impinging on fixed targets. In such experiments, the energy of the photon from the e+e-→ γA' process is measured with an electromagnetic calorimeter and the missing mass is computed (the A' interacts weakly with Standard Model matter so it can't be detected). However, the A' mass range that can be explored with this technique is limited by the accessible energy in the center of mass frame, which goes as the square root of the beam energy. The realization of a 11 GeV positron beam at Jefferson Lab would allow to search for A' masses up to ˜ 100 MeV, reaching unexplored regions of the A' parameter space. A preliminary study on the feasibility of a PADME-like experiment at Jefferson Lab has been carried out, assuming a 11 GeV positron beam with a ˜ 100 nA current. The achievable sensitivity was estimated, studying the main sources of background (positron bremsstrahlung, annihilation into 2 gammas) using CALCHEP [3] and GEANT4 [4] simulations.

Pediatric radiation dosimetry for positron-emitting radionuclides using anthropomorphic phantoms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Tianwu; Bolch, Wesley E.; Lee, Choonsik

2013-10-15

Purpose: Positron emission tomography (PET) plays an important role in the diagnosis, staging, treatment, and surveillance of clinically localized diseases. Combined PET/CT imaging exhibits significantly higher sensitivity, specificity, and accuracy than conventional imaging when it comes to detecting malignant tumors in children. However, the radiation dose from positron-emitting radionuclide to the pediatric population is a matter of concern since children are at a particularly high risk when exposed to ionizing radiation.Methods: The authors evaluate the absorbed fractions and specific absorbed fractions (SAFs) of monoenergy photons/electrons as well as S-values of 9 positron-emitting radionuclides (C-11, N-13, O-15, F-18, Cu-64, Ga-68, Rb-82,more » Y-86, and I-124) in 48 source regions for 10 anthropomorphic pediatric hybrid models, including the reference newborn, 1-, 5-, 10-, and 15-yr-old male and female models, using the Monte Carlo N-Particle eXtended general purpose Monte Carlo transport code.Results: The self-absorbed SAFs and S-values for most organs were inversely related to the age and body weight, whereas the cross-dose terms presented less correlation with body weight. For most source/target organ pairs, Rb-82 and Y-86 produce the highest self-absorbed and cross-absorbed S-values, respectively, while Cu-64 produces the lowest S-values because of the low-energy and high-frequency of electron emissions. Most of the total self-absorbed S-values are contributed from nonpenetrating particles (electrons and positrons), which have a linear relationship with body weight. The dependence of self-absorbed S-values of the two annihilation photons varies to the reciprocal of 0.76 power of the mass, whereas the self-absorbed S-values of positrons vary according to the reciprocal mass.Conclusions: The produced S-values for common positron-emitting radionuclides can be exploited for the assessment of radiation dose delivered to the pediatric population from various PET radiotracers used in clinical and research settings. The mass scaling method for positron-emitters can be used to derive patient-specific S-values from data of reference phantoms.« less

Theoretical survey on positronium formation and ionisation in positron atom scattering

NASA Technical Reports Server (NTRS)

Basu, Madhumita; Ghosh, A. S.

1990-01-01

The recent theoretical studies are surveyed and reported on the formation of exotic atoms in positron-hydrogen, positron-helium and positron-lithium scattering specially at intermediate energy region. The ionizations of these targets by positron impact was also considered. Theoretical predictions for both the processes are compared with existing measured values.

Measurement of positron annihilation lifetimes for positron burst by multi-detector array

NASA Astrophysics Data System (ADS)

Wang, B. Y.; Kuang, P.; Liu, F. Y.; Han, Z. J.; Cao, X. Z.; Zhang, P.

2018-03-01

It is currently impossible to exploit the timing information in a gamma-ray pulse generated within nanoseconds when a high-intensity positron burst annihilation event occurs in a target using conventional single-detector methods. A state-of-the-art solution to the problem is proposed in this paper. In this approach, a multi-detector array composed of many independent detection cells mounted spherically around the target is designed to detect the time distribution of the annihilated gamma rays generated following, in particular, a positron burst emitting huge amounts of positrons in a short pulse duration, even less than a few nano- or picoseconds.

The Upgrade of the Neutron Induced Positron Source NEPOMUC

NASA Astrophysics Data System (ADS)

Hugenschmidt, C.; Ceeh, H.; Gigl, T.; Lippert, F.; Piochacz, C.; Pikart, P.; Reiner, M.; Weber, J.; Zimnik, S.

2013-06-01

In summer 2012, the new NEutron induced POsitron Source MUniCh (NEPOMUC) was installed and put into operation at the research reactor FRM II. At NEPOMUC upgrade 80% 113Cd enriched Cd is used as neutron-gamma converter in order to ensure an operation time of 25 years. A structure of Pt foils inside the beam tube generates positrons by pair production. Moderated positrons leaving the Pt front foil are electrically extracted and magnetically guided to the outside of the reactor pool. The whole design, including Pt-foils, the electric lenses and the magnetic fields, has been improved in order to enhance both the intensity and the brightness of the positron beam. After adjusting the potentials and the magnetic guide and compensation fields an intensity of about 3·109 moderated positrons per second is expected. During the first start-up, the measured temperatures of about 90°C ensure a reliable operation of the positron source. Within this contribution the features and the status of NEPOMUC upgrade are elucidated. In addition, an overview of recent positron beam experiments and current developments at the spectrometers is given.

Chaos of energetic positron orbits in a dipole magnetic field and its potential application to a new injection scheme

NASA Astrophysics Data System (ADS)

Saitoh, H.; Yoshida, Z.; Yano, Y.; Nishiura, M.; Kawazura, Y.; Horn-Stanja, J.; Pedersen, T. Sunn

2016-10-01

We study the behavior of high-energy positrons emitted from a radioactive source in a magnetospheric dipole field configuration. Because the conservation of the first and second adiabatic invariants is easily destroyed in a strongly inhomogeneous dipole field for high-energy charged particles, the positron orbits are nonintegrable, resulting in chaotic motions. In the geometry of a typical magnetospheric levitated dipole experiment, it is shown that a considerable ratio of positrons from a 22Na source, located at the edge of the confinement region, has chaotic long orbit lengths before annihilation. These particles make multiple toroidal circulations and form a hollow toroidal positron cloud. Experiments with a small 22Na source in the Ring Trap 1 (RT-1) device demonstrated the existence of such long-lived positrons in a dipole field. Such a chaotic behavior of high-energy particles is potentially applicable to the formation of a dense toroidal positron cloud in the strong-field region of the dipole field in future studies.

Development of a Slow Positron Facility at Hebrew University of Jerusalem

NASA Astrophysics Data System (ADS)

Kelleher, Aidan

2013-03-01

Positron annihilation spectroscopy provides both depth of penetration to study bulk defects in materials as well as nano-scale resolution. This measurement range is achieved by slowing positrons from a radioactive source, typically 22Na, by sending them through a moderator, typically W or solid Ne. The nearly thermal positrons are then accelerated to the desired energy by means of an electrostatic potential. The SPOT project at The Hebrew University of Jerusalem proposes to increase the luminosity of the beam by applying the best practices currently in us, as well as using a short-lived source of positrons, 18F. Simulations based on our current designs indicate this project will be able to deliver positrons in the energy range of 50-50000eV with an energy resolution of 1eV is possible. We will present the unique technical challenges of using this source of positrons, how we plan to overcome them, the results of simulations, and facility construction progress.

Tertiary particle physics with ELI: from challenge to chance (Conference Presentation)

NASA Astrophysics Data System (ADS)

Drska, Ladislav

2017-05-01

nteraction of high-intensity laser pulses with solid state targets results in generation of intense pulses of secondary particles via electromagnetic interaction : electrons, ions, hard x-rays. The beams of these particles can be used to produce various types of third-generation particles, beyond electromagnetic also other types of fundamental interactions can be involved in this process [1]. As the most interesting tertiary particles could be mentioned positrons, neutron, muons. This paper shall extend our previous analysis of this topic [2]: it discusses selected technical problems of design and realization of applicable sources of these particles and presents some more elaborated proposals for potential meaningful / hopefuly realistic exploitations of this technology. (1)Tertiary Sources (TS) : First Development Steps. This part of the presentation includes the topics as follows: (11) Pulsed positron sources: Verified solutions of laser-driven positron sources [3] [4] [5], development towards applicable facilities. Some unconventional concepts of application of lasers for positron production [6]. Techniques for realization of low/very-low energy positrons. (12) Taylored neutron sources [7]: Neutron sources with demanded space distribution, strongly beamed and isotropic solutions [8] [9]. Neutron generation with taylored energy distribution. Problem of the direct production of neutrons with very low energy [10] [11]. (13) Potential muon sources: Proof-of-principle laser experiment on electron / photon driven muon production [12] [13]. Study of the possibility of effective generation of surface muons. Problems of the production of muons with very low energy. (2) Fundamental & Applied Physics with TS: This part of the talk presents the themes: (21) Diagnostic potential of TS: Lepton emission as a signature of processes in extreme systems. Passive and active diagnostics using positrons, problems of detection and evaluation. Potential diagnostic applications of muons. Concrete application study: muon tomography. (22) Antilepton gravity studies [14]: Possibility of antimattter gravity research using positronium and muonium [15] [16]. Lepton / antilepton gravity studiesactive with relativistic particle beams [17]. First-phase practical application : positron production for filling (commertial) particle traps, development base for multiple microtrap systems. (23) Hidden world searching [18] : Potential laser-based production / detection of selected dark mattter particles - axions, hidden photons [19] [20]. Search for hidden particles in nuclear decay processes [21]. Potential application output: intense positronium source. Conclusion: The extensive feasibility study confirms the potential of ELI to contribute to the solution of Grand Challenge Problems of physics. Laser-produced tertiary particles will play important role in this effort. : References [1] L.Drska et al.: Physics of Extreme Systems. Course ATHENS CTU18, Prague 12 - 19 Nov., 2016. http://vega.fjfi.cvut.cz/docs/athens2016/ [2] L.Drska : Lepton Diagnostics and Antimatter Physics. In: SPIE Optics+Optoelectronics, Prague, April 13 - 16, 2015 . [3] H. Chen et al.: Scaling the Yield of Laser-Driven Electron-Positron Jets to Laboratory Astrophysics Applications. Rep. LLNL-JRNL-665381, Dec. 11, 2014. [4] E Liang et al.: High e+ / e- Ratio Dense Pair Creation with 1022 W.cm-2 Laser Irradiating Solid Targets. Scientific Reports, Sept. 14, 2015. www.nature.com/scientificreports [5] G. Sarri et al.: Spectral and Spatial Characterization of Laser-driven Positron Beams. Plasma Phys. Control. Fusion 59 (2017) 014015. [6] B. Schoch: A Method to Produce Intense Positron Beams via Electro Pair Production on Electrons. arXiv:1607.03847v1 [physics.acc-ph] [7] I. Pomerantz: Laser Generation of Neutrons: Science and Applications. In: ELI-NP Summer School, Magurele, Sept. 21 - 25, 2015. http://www.eli-np.ro/2015-summer-school/presentations/23.09/Pomerantz_Eli-NP-Summer-school-2015.pdf [8] V.P. Kovalev: Secondary Radiation of Electron Accelerators (in Russian). Atomizdat 1969. [9] M. Lebois et al.: Development of a Kinematically Focused Neutron Source with p(Li7,n)Be7 Inverse Reaction. Nucl. Instr. Meth. Phys. Res. A 735 (2014), 145. [10] D. Habs et al.: Neutron Halo Isomers in Stable Nuclei and their Possible Application for the Production of Low Energy, Pulsed, Polarized Neutron Beams of High Intensity and High Brilliance. Appl. Phys B103 (2011),485. [11] T. Masuda et al.: A New Method of Creating High/Intensity Neutron Source. arXiv:1604.02818v1[nucl-ex] [12] A.I. Titov et al.: Dimuon Production by Laser-wakefield Accelerated Electrons. Phys. Rev. ST Accel. Beams 12 (2009) 111301. [13] W. Dreesen et al.: Detection of Petawatt Laser-Induced Muon Source for Rapid High-Gamma Material Detection. DOE/NV/25946-2262. [14] F. Castelli: Positronium and Fundamental Physics: What Next ? In: What Next, Florence 2015. [15] G. Dufour et al. : Prospects for Studies of the Free Fall and Gravitation Quantum States of Antimatter. Advances in High Energy Physics 2015 (2015) 379642. [16] D.M. Kaplan et al.. Antimatter Gravity with Muonium. IIT-CAPP-16-1. arXiv:1601.07222v2 [physics.ins-det] [17] T. Kalaydzhyan: Gravitational Mass of Positron from LEP Synchrotron Losses. arXiv:1508.04377v3 [hep-ph] [18] J. Alexander et al.: Dark Sector 2016 Workshop: Community Report. arXiv:1608.08632[hep-ph] [19] M.A. Wahud et al.: Axion-like Particle Production in a Laser-Induced Dynamical Spacertime. arXiv:1612.07743v1 [hep-ph] [20] V. Kozhuharov et al: New Projects on Dark Photon Search. arXiv:1610.04389v1 [hep-ex] [21] A.J. Krasznahorkay et al.: Observation of Anomalous Internal Pair Creation in Be8: A Possible Signature of a Light, Neutral Boson. arXiv:1504.01527v1 [nucl-ex

Non-destructive testing method and apparatus

DOEpatents

Akers, Douglas W [Idaho Falls, ID

2011-10-04

Non-destructive testing apparatus may comprise a photon source and a source material that emits positrons in response to bombardment of the source material with photons. The source material is positionable adjacent the photon source and a specimen so that when the source material is positioned adjacent the photon source it is exposed to photons produced thereby. When the source material is positioned adjacent the specimen, the specimen is exposed to at least some of the positrons emitted by the source material. A detector system positioned adjacent the specimen detects annihilation gamma rays emitted by the specimen. Another embodiment comprises a neutron source and a source material that emits positrons in response to neutron bombardment.

Probing the positron moderation process using high-intensity, highly polarized slow-positron beams

NASA Technical Reports Server (NTRS)

Van House, J.; Zitzewitz, P. W.

1984-01-01

A highly polarized (P = 0.48 + or - 0.02) intense (500,000/sec) beam of 'slow' (Delta E = about 2 eV) positrons (e+) is generated, and it is shown that it is possible to achieve polarization as high as P = 0.69 + or - 0.04 with reduced intensity. The measured polarization of the slow e+ emitted by five different positron moderators showed no dependence on the moderator atomic number (Z). It is concluded that only source positrons with final kinetic energy below 17 keV contribute to the slow-e+ beam, in disagreement with recent yield functions derived from low-energy measurements. Measurements of polarization and yield with absorbers of different Z between the source and moderator show the effects of the energy and angular distributions of the source positrons on P. The depolarization of fast e+ transmitted through high-Z absorbers has been measured. Applications of polarized slow-e+ beams are discussed.

Diffuse Galactic antimatter from faint thermonuclear supernovae in old stellar populations

NASA Astrophysics Data System (ADS)

Crocker, Roland M.; Ruiter, Ashley J.; Seitenzahl, Ivo R.; Panther, Fiona H.; Sim, Stuart; Baumgardt, Holger; Möller, Anais; Nataf, David M.; Ferrario, Lilia; Eldridge, J. J.; White, Martin; Tucker, Brad E.; Aharonian, Felix

2017-06-01

Our Galaxy hosts the annihilation of a few 1043 low-energy positrons every second. Radioactive isotopes capable of supplying such positrons are synthesized in stars, stellar remnants and supernovae. For decades, however, there has been no positive identification of a main stellar positron source, leading to suggestions that many positrons originate from exotic sources like the Galaxy's central supermassive black hole or dark matter annihilation. Here we show that a single type of transient source, deriving from stellar populations of age 3-6 Gyr and yielding ∼0.03 M ⊙ of the positron emitter 44Ti, can simultaneously explain the strength and morphology of the Galactic positron annihilation signal and the Solar System abundance of the 44Ti decay product 44Ca. This transient is likely the merger of two low-mass white dwarfs, observed in external galaxies as the sub-luminous, thermonuclear supernova known as SN 1991bg-like.

Effect of the diffusion parameters on the observed γ-ray spectrum of sources and their contribution to the local all-electron spectrum: The EDGE code

NASA Astrophysics Data System (ADS)

López-Coto, R.; Hahn, J.; BenZvi, S.; Dingus, B.; Hinton, J.; Nisa, M. U.; Parsons, R. D.; Greus, F. Salesa; Zhang, H.; Zhou, H.

2018-11-01

The positron excess measured by PAMELA and AMS can only be explained if there is one or several sources injecting them. Moreover, at the highest energies, it requires the presence of nearby ( ∼ hundreds of parsecs) and middle age (maximum of ∼ hundreds of kyr) sources. Pulsars, as factories of electrons and positrons, are one of the proposed candidates to explain the origin of this excess. To calculate the contribution of these sources to the electron and positron flux at the Earth, we developed EDGE (Electron Diffusion and Gamma rays to the Earth), a code to treat the propagation of electrons and compute their diffusion from a central source with a flexible injection spectrum. Using this code, we can derive the source's gamma-ray spectrum, spatial extension, the all-electron density in space, the electron and positron flux reaching the Earth and the positron fraction measured at the Earth. We present in this paper the foundations of the code and study how different parameters affect the gamma-ray spectrum of a source and the electron flux measured at the Earth. We also studied the effect of several approximations usually performed in these studies. This code has been used to derive the results of the positron flux measured at the Earth in [1].

A positron remoderator for the high intensity positron source NEPOMUC

NASA Astrophysics Data System (ADS)

Piochacz, Christian; Kögel, Gottfried; Egger, Werner; Hugenschmidt, Christoph; Mayer, Jakob; Schreckenbach, Klaus; Sperr, Peter; Stadlbauer, Martin; Dollinger, Günther

2008-10-01

A remoderator for the high intensity positron source NEPOMUC was developed and installed at the beam facility. A beam of remoderated positrons could be produced with different energies and a diameter of less than 2 mm was obtained. The efficiency of the remoderation setup was determined to be 5%. Due to the brilliance of the remoderated beam, the measurements at the coincidence Doppler broadening spectrometer (CDBS) and at the positron annihilation induced Auger electron spectrometer (PAES) could be improved. The setup and functionality of the remoderation device is presented as well as the first measurements at the remoderator, CDBS and PAES.

Formation of a high intensity low energy positron string

NASA Astrophysics Data System (ADS)

Donets, E. D.; Donets, E. E.; Syresin, E. M.; Itahashi, T.; Dubinov, A. E.

2004-05-01

The possibility of a high intensity low energy positron beam production is discussed. The proposed Positron String Trap (PST) is based on the principles and technology of the Electron String Ion Source (ESIS) developed in JINR during the last decade. A linear version of ESIS has been used successfully for the production of intense highly charged ion beams of various elements. Now the Tubular Electron String Ion Source (TESIS) concept is under study and this opens really new promising possibilities in physics and technology. In this report, we discuss the application of the tubular-type trap for the storage of positrons cooled to the cryogenic temperatures of 0.05 meV. It is intended that the positron flux at the energy of 1-5 eV, produced by the external source, is injected into the Tubular Positron Trap which has a similar construction as the TESIS. Then the low energy positrons are captured in the PST Penning trap and are cooled down because of their synchrotron radiation in the strong (5-10 T) applied magnetic field. It is expected that the proposed PST should permit storing and cooling to cryogenic temperature of up to 5×109 positrons. The accumulated cooled positrons can be used further for various physics applications, for example, antihydrogen production.

A Central Positron Source to Perform the Timing Alignment of Detectors in a PET Scanner

NASA Astrophysics Data System (ADS)

Thompson, C. J.; Camborde, M.-L.; Casey, M. E.

2005-10-01

Accurate timing alignment and stability are important to maximize the true counts and minimize the random counts in positron emission tomography. Its importance increases in time-of-flight (TOF) scanners. We propose using a central positron emitting source enclosed in a detector which detects the excess energy of the positron before it annihilates as a timing reference. All crystals can be time-aligned with respect to this central source. We evaluated 10 /spl mu/Ci /sup 22/Na and /sup 68/Ge sources embedded in cylinders of plastic scintillator coupled to a fast PMT. Light flashes produced after the parent isotope emits positrons are detected, and the anode signals from the PMT are the reference time for each positron decay. The time delay before the gamma ray is detected by the scanner's conventional gamma ray detectors is the time offset to be applied to that crystal. Since all detectors are almost the same distance from the central source, TOF errors are minimized. Preliminary results show a mean signal amplitude of >0.5 V from /sup 22/Na at 1000-V PMT bias, a timing FWHM of 850 ps with respect to a small LSO crystal. This suggests it could be useful to align both conventional and TOF PET scanners.

ILC TARGET WHEEL RIM FRAGMENT/GUARD PLATE IMPACT ANALYSIS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hagler, L

2008-07-17

A positron source component is needed for the International Linear Collider Project. The leading design concept for this source is a rotating titanium alloy wheel whose spokes rotate through an intense localized magnetic field. The system is composed of an electric motor, flexible motor/drive-shaft coupling, stainless steel drive-shaft, two Plumber's Block tapered roller bearings, a titanium alloy target wheel, and electromagnet. Surrounding the target wheel and magnet is a steel frame with steel guarding plates intended to contain shrapnel in case of catastrophic wheel failure. Figure 1 is a layout of this system (guard plates not shown for clarity). Thismore » report documents the FEA analyses that were performed at LLNL to help determine, on a preliminary basis, the required guard plate thickness for three potential plate steels.« less

High-flux low-divergence positron beam generation from ultra-intense laser irradiated a tapered hollow target

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Jian-Xun; College of Electronic Engineering, Wuhan 430019; Ma, Yan-Yun, E-mail: yanyunma@126.com

By using two-dimensional particle-in-cell simulations, we demonstrate high-flux dense positrons generation by irradiating an ultra-intense laser pulse onto a tapered hollow target. By using a laser with an intensity of 4 × 10{sup 23 }W/cm{sup 2}, it is shown that the Breit-Wheeler process dominates the positron production during the laser-target interaction and a positron beam with a total number >10{sup 15} is obtained, which is increased by five orders of magnitude than in the previous work at the same laser intensity. Due to the focusing effect of the transverse electric fields formed in the hollow cone wall, the divergence angle of the positronmore » beam effectively decreases to ∼15° with an effective temperature of ∼674 MeV. When the laser intensity is doubled, both the positron flux (>10{sup 16}) and temperature (963 MeV) increase, while the divergence angle gets smaller (∼13°). The obtained high-flux low-divergence positron beam may have diverse applications in science, medicine, and engineering.« less

On the empirical determination of positron trapping coefficient at nano-scale helium bubbles in steels irradiated in spallation target

NASA Astrophysics Data System (ADS)

Krsjak, Vladimir; Kuriplach, Jan; Vieh, Christiane; Peng, Lei; Dai, Yong

2018-06-01

In the present work, the specific positron trapping rate of small helium bubbles was empirically derived from positron annihilation lifetime spectroscopy (PALS) and transmission electron microscopy (TEM) studies of Fe9Cr martensitic steels. Both techniques are well known to be sensitive to nanometer-sized helium-filled cavities induced during irradiation in a mixed proton-neutron spectrum of spallation target. Complementary TEM and PALS studies show that positrons are being trapped to these defects at a rate of 1.2 ± 0.8 × 10-14 m3s-1. This suggests that helium bubbles in ferritic/martensitic steels are attractive traps for positrons comparable to mono-vacancies and quantitative analysis of the bubbles by PALS technique is plausible.

A self-consistent model of cosmic-ray fluxes and positron excess: roles of nearby pulsars and a sub-dominant source population

NASA Astrophysics Data System (ADS)

Joshi, Jagdish C.; Razzaque, Soebur

2017-09-01

The cosmic-ray positron flux calculated using the cosmic-ray nuclei interactions in our Galaxy cannot explain observed data above 10 GeV. An excess in the measured positron flux is therefore open to interpretation. Nearby pulsars, located within sub-kiloparsec range of the Solar system, are often invoked as plausible sources contributing to the excess. We show that an additional, sub-dominant population of sources together with the contributions from a few nearby pulsars can explain the latest positron excess data from the Alpha Magnetic Spectrometer (AMS). We simultaneously model, using the DRAGON code, propagation of cosmic-ray proton, Helium, electron and positron and fit their respective flux data. Our fit to the Boron to Carbon ratio data gives a diffusion spectral index of 0.45, which is close to the Kraichnan turbulent spectrum.

A self-consistent model of cosmic-ray fluxes and positron excess: roles of nearby pulsars and a sub-dominant source population

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joshi, Jagdish C.; Razzaque, Soebur, E-mail: jjagdish@uj.ac.za, E-mail: srazzaque@uj.ac.za

The cosmic-ray positron flux calculated using the cosmic-ray nuclei interactions in our Galaxy cannot explain observed data above 10 GeV. An excess in the measured positron flux is therefore open to interpretation. Nearby pulsars, located within sub-kiloparsec range of the Solar system, are often invoked as plausible sources contributing to the excess. We show that an additional, sub-dominant population of sources together with the contributions from a few nearby pulsars can explain the latest positron excess data from the Alpha Magnetic Spectrometer (AMS). We simultaneously model, using the DRAGON code, propagation of cosmic-ray proton, Helium, electron and positron and fitmore » their respective flux data. Our fit to the Boron to Carbon ratio data gives a diffusion spectral index of 0.45, which is close to the Kraichnan turbulent spectrum.« less

Texas Intense Positron Source (TIPS)

NASA Astrophysics Data System (ADS)

O'Kelly, D.

2003-03-01

The Texas Intense Positron Source (TIPS) is a state of the art variable energy positron beam under construction at the Nuclear Engineering Teaching Laboratory (NETL). Projected intensities on the order of the order of 10^7 e+/second using ^64Cu as the positron source are expected. Owing to is short half-life (t1/2 12.8 hrs), plans are to produce the ^64Cu isotope on-site using beam port 1 of NETL TRIGA Mark II reactor. Following tungsten moderation, the positrons will be electrostatically focused and accelerated from few 10's of eV up to 30 keV. This intensity and energy range should allow routine performance of several analytical techniques of interest to surface scientists (PALS, PADB and perhaps PAES and LEPD.) The TIPS project is being developed in parallel phases. Phase I of the project entails construction of the vacuum system, source chamber, main beam line, electrostatic/magnetic focusing and transport system as well as moderator design. Initial construction, testing and characterization of moderator and beam transport elements are underway and will use a commercially available 10 mCi ^22Na radioisotope as a source of positrons. Phase II of the project is concerned primarily with the Cu source geometry and thermal properties as well as production and physical handling of the radioisotope. Additional instrument optimizing based upon experience gained during Phase I will be incorporated in the final design. Current progress of both phases will be presented along with motivations and future directions.

Method for non-destructive testing

DOEpatents

Akers, Douglas W [Idaho Falls, ID

2011-08-30

Non-destructive testing method may include providing a source material that emits positrons in response to bombardment of the source material with photons. The source material is exposed to photons. The source material is positioned adjacent the specimen, the specimen being exposed to at least some of the positrons emitted by the source material. Annihilation gamma rays emitted by the specimen are detected.

New parameter-free polarization potentials in low-energy positron collisions

NASA Technical Reports Server (NTRS)

Jain, Ashok

1990-01-01

The polarization potential plays a decisive role in shaping up the cross sections in low energy positron collisions with atoms and molecules. However, its inclusion without involving any adjustable parameter, is still a challenge. Various other techniques employed so far for positron collisions are summarized, and a new, nonadjustable and very simple form of the polarization potential for positron-atom (molecule) collisions below the threshold of positronium formation is discussed. This new recently proposed potential is based on the correlation energy of a single positron in a homogeneous electron gas. The correlation energy was calculated by solving the Schrodinger equation of the positron-electron system and fitted to an analytical form in various ranges of the density parameter. In the outside region, the correlation energy is joined smoothly with the correct asymptotic form. This new positron correlation polarization (PCOP) potential was tested on several atomic and molecular targets such as the Ar, CO, and CH4. The results on the total and differential cross sections on these targets are shown along with the experimental data where available.

The scaling of electron and positron generation in intense laser-solid interactions

DOE PAGES

Chen, Hui; Link, A.; Sentoku, Y.; ...

2015-05-27

This study presents experimental scalings of the electrons and positrons produced by intense laser-target interactions at relativistic laser intensities (10 18–10 20 W cm -2). The data were acquired from three short-pulse laser facilities with laser energies ranging from 80 to 1500 J. We found a non-linear (≈E L 2) scaling of positron yield [Chen et al., Phys. Rev. Lett. 114, 215001 (2015)] and a linear scaling of electron yield with the laser energy. These scalings are explained by theoretical and numerical analyses. Positron acceleration by the target sheath field is confirmed by the positron energy spectrum, which has amore » pronounced peak at energies near the sheath potential, as determined by the observed maximum energies of accelerated protons. The parameters of laser-produced electron-positron jets are summarized together with the theoretical energy scaling. Finally, the measured energy-squared scaling of relativistic electron-positron jets indicates the possibility to create an astrophysically relevant experimental platform with such jets using multi-kilojoule high intensity lasers currently under construction.« less

The scaling of electron and positron generation in intense laser-solid interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Hui; Link, A.; Fiuza, F.

2015-05-15

This paper presents experimental scalings of the electrons and positrons produced by intense laser-target interactions at relativistic laser intensities (10{sup 18}–10{sup 20} W cm{sup −2}). The data were acquired from three short-pulse laser facilities with laser energies ranging from 80 to 1500 J. We found a non-linear (≈E{sub L}{sup 2}) scaling of positron yield [Chen et al., Phys. Rev. Lett. 114, 215001 (2015)] and a linear scaling of electron yield with the laser energy. These scalings are explained by theoretical and numerical analyses. Positron acceleration by the target sheath field is confirmed by the positron energy spectrum, which has a pronouncedmore » peak at energies near the sheath potential, as determined by the observed maximum energies of accelerated protons. The parameters of laser-produced electron-positron jets are summarized together with the theoretical energy scaling. The measured energy-squared scaling of relativistic electron-positron jets indicates the possibility to create an astrophysically relevant experimental platform with such jets using multi-kilojoule high intensity lasers currently under construction.« less

Calculation of radiation therapy dose using all particle Monte Carlo transport

DOEpatents

Chandler, William P.; Hartmann-Siantar, Christine L.; Rathkopf, James A.

1999-01-01

The actual radiation dose absorbed in the body is calculated using three-dimensional Monte Carlo transport. Neutrons, protons, deuterons, tritons, helium-3, alpha particles, photons, electrons, and positrons are transported in a completely coupled manner, using this Monte Carlo All-Particle Method (MCAPM). The major elements of the invention include: computer hardware, user description of the patient, description of the radiation source, physical databases, Monte Carlo transport, and output of dose distributions. This facilitated the estimation of dose distributions on a Cartesian grid for neutrons, photons, electrons, positrons, and heavy charged-particles incident on any biological target, with resolutions ranging from microns to centimeters. Calculations can be extended to estimate dose distributions on general-geometry (non-Cartesian) grids for biological and/or non-biological media.

Calculation of radiation therapy dose using all particle Monte Carlo transport

DOEpatents

Chandler, W.P.; Hartmann-Siantar, C.L.; Rathkopf, J.A.

1999-02-09

The actual radiation dose absorbed in the body is calculated using three-dimensional Monte Carlo transport. Neutrons, protons, deuterons, tritons, helium-3, alpha particles, photons, electrons, and positrons are transported in a completely coupled manner, using this Monte Carlo All-Particle Method (MCAPM). The major elements of the invention include: computer hardware, user description of the patient, description of the radiation source, physical databases, Monte Carlo transport, and output of dose distributions. This facilitated the estimation of dose distributions on a Cartesian grid for neutrons, photons, electrons, positrons, and heavy charged-particles incident on any biological target, with resolutions ranging from microns to centimeters. Calculations can be extended to estimate dose distributions on general-geometry (non-Cartesian) grids for biological and/or non-biological media. 57 figs.

Method for on-line evaluation of materials using prompt gamma ray analysis

DOEpatents

Akers, Douglas W [Idaho Falls, ID

2009-12-08

A method for evaluating a material specimen comprises: Mounting a neutron source and a detector adjacent the material specimen; bombarding the material specimen with neutrons from the neutron source to create prompt gamma rays within the material specimen, some of the prompt gamma rays being emitted from the material specimen, some of the prompt gamma rays resulting in the formation of positrons within the material specimen by pair production; collecting positron annihilation data by detecting with the detector at least one emitted annihilation gamma ray resulting from the annihilation of a positron; storing the positron annihilation data on a data storage system for later retrieval and processing; and continuing to collect and store positron annihilation data, the continued collected and stored positron annihilation data being indicative of an accumulation of lattice damage over time.

Apparatus for photon activation positron annihilation analysis

DOEpatents

Akers, Douglas W [Idaho Falls, ID

2007-06-12

Non-destructive testing apparatus according to one embodiment of the invention comprises a photon source. The photon source produces photons having predetermined energies and directs the photons toward a specimen being tested. The photons from the photon source result in the creation of positrons within the specimen being tested. A detector positioned adjacent the specimen being tested detects gamma rays produced by annihilation of positrons with electrons. A data processing system operatively associated with the detector produces output data indicative of a lattice characteristic of the specimen being tested.

Is There a Dark Matter Signal in the Galactic Positron Annihilation Radiation?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lingenfelter, R. E.; Rothschild, R. E.; Higdon, J. C.

2009-07-17

Assuming Galactic positrons do not go far before annihilating, a difference between the observed 511 keV annihilation flux distribution and that of positron production, expected from beta{sup +} decay in Galactic iron nucleosynthesis, was evoked as evidence of a new source and signal of dark matter. We show, however, that the dark matter sources cannot account for the observed positronium fraction without extensive propagation. Yet with such propagation, standard nucleosynthetic sources can fully account for the spatial differences and positronium fraction, leaving no new signal for dark matter to explain.

Positron source position sensing detector and electronics

DOEpatents

Burnham, Charles A.; Bradshaw, Jr., John F.; Kaufman, David E.; Chesler, David A.; Brownell, Gordon L.

1985-01-01

A positron source, position sensing device, particularly with medical applications, in which positron induced gamma radiation is detected using a ring of stacked, individual scintillation crystals, a plurality of photodetectors, separated from the scintillation crystals by a light guide, and high resolution position interpolation electronics. Preferably the scintillation crystals are several times more numerous than the photodetectors with each crystal being responsible for a single scintillation event from a received gamma ray. The light guide will disperse the light emitted from gamma ray absorption over several photodetectors. Processing electronics for the output of the photodetectors resolves the location of the scintillation event to a fraction of the dimension of each photodetector. Because each positron absorption results in two 180.degree. oppositely traveling gamma rays, the detection of scintillation in pairs permits location of the positron source in a manner useful for diagnostic purposes. The processing electronics simultaneously responds to the outputs of the photodetectors to locate the scintillations to the source crystal. While it is preferable that the scintillation crystal include a plurality of stacked crystal elements, the resolving power of the processing electronics is also applicable to continuous crystal scintillators.

Positron annihilation lifetime spectroscopy study of Kapton thin foils

NASA Astrophysics Data System (ADS)

Kanda, G. S.; Ravelli, L.; Löwe, B.; Egger, W.; Keeble, D. J.

2016-01-01

Variable energy positron annihilation lifetime spectroscopy (VE-PALS) experiments on polyimide material Kapton are reported. Thin Kapton foils are widely used in a variety of mechanical, electronic applications. PALS provides a sensitive probe of vacancy-related defects in a wide range of materials, including open volume in polymers. Varying the positron implantation energy enables direct measurement of thin foils. Thin Kapton foils are also commonly used to enclose the positron source material in conventional PALS measurements performed with unmoderated radionuclide sources. The results of depth-profiled positron lifetime measurements on 7.6 μm and 25 μm Kapton foils are reported and determine a dominant 385(1) ps lifetime component. The absence of significant nanosecond lifetime component due to positronium formation is confirmed.

Positron radiography of ignition-relevant ICF capsules

NASA Astrophysics Data System (ADS)

Williams, G. J.; Chen, Hui; Field, J. E.; Landen, O. L.; Strozzi, D. J.

2017-12-01

Laser-generated positrons are evaluated as a probe source to radiograph in-flight ignition-relevant inertial confinement fusion capsules. Current ultraintense laser facilities are capable of producing 2 × 1012 relativistic positrons in a narrow energy bandwidth and short time duration. Monte Carlo simulations suggest that the unique characteristics of such positrons allow for the reconstruction of both capsule shell radius and areal density between 0.002 and 2 g/cm2. The energy-downshifted positron spectrum and angular scattering of the source particles are sufficient to constrain the conditions of the capsule between preshot and stagnation. We evaluate the effects of magnetic fields near the capsule surface using analytic estimates where it is shown that this diagnostic can tolerate line integrated field strengths of 100 T mm.

Stable confinement of electron plasma and initial results on positron injection in RT-1

NASA Astrophysics Data System (ADS)

Saitoh, H.; Yoshida, Z.; Morikawa, J.; Yano, Y.; Kasaoka, N.; Sakamoto, W.; Nogami, T.

2013-03-01

The Ring Trap 1 (RT-1) device is a dipole field configuration generated by a levitated superconducting magnet. It offers very interesting opportunities for research on the fundamental properties on non-neutral plasmas, such as self-organization of charged particles in the strongly positive and negative charged particles on magnetic surfaces. When strong positron sources will be available in the future, the dipole field configuration will be potentially applicable to the formation of an electron-positron plasma. We have realized stable, long trap of toroidal pure electron plasma in RT-1; Magnetic levitation of the superconducting magnet resulted in more than 300s of confinement for electron plasma of ˜ 1011 m-3. Aiming for the confinement of positrons as a next step, we started a positron injection experiment. For the formation of positron plasma in the closed magnetic surfaces, one of the key issues to be solved is the efficient injection method of positron across closed magnetic surfaces. In contrast to linear configurations, toroidal configurations have the advantage that they are capable of trapping high energy positrons in the dipole field configuration and consider the possibility of direct trapping of positrons emitted from a 22Na source.

Cyclotrons and positron emitting radiopharmaceuticals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolf, A.P.; Fowler, J.S.

1984-01-01

The state of the art of Positron Emission Tomography (PET) technology as related to cyclotron use and radiopharmaceutical production is reviewed. The paper discusses available small cyclotrons, the positron emitters which can be produced and the yields possible, target design, and radiopharmaceutical development and application. 97 refs., 12 tabs. (ACR)

Monte Carlo investigation of positron annihilation in medical positron emission tomography

NASA Astrophysics Data System (ADS)

Chin, P. W.; Spyrou, N. M.

2007-09-01

A number of Monte Carlo codes are available for simulating positron emission tomography (PET), however, physics approximations differ. A number of radiation processes are deemed negligible, some without rigorous investigation. Some PET literature quantify approximations to be valid, without citing the data source. The radiation source is the first step in Monte Carlo simulations, for some codes this is 511 keV photons 180° apart, not polyenergetic positrons with radiation histories of their own. Without prior assumptions, we investigated electron-positron annihilation under clinical PET conditions. Just before annihilation, we tallied the positron energy and position. Right after annihilation, we tallied the energy and separation angle of photon pairs. When comparing PET textbooks with theory, PENELOPE and EGSnrc, only the latter three agreed. From 10 6 radiation histories, a positron source of 15O in a chest phantom annihilated at as high as 1.58 MeV, producing photons with energies 0.30-2.20 MeV, 79-180° apart. From 10 6 radiation histories, an 18F positron source in a head phantom annihilated at energies as high as 0.56 MeV, producing 0.33-1.18 MeV photons 109-180° apart. 2.5% and 0.8% annihilation events occurred inflight in the chest and the head phantoms, respectively. PET textbooks typically either do not mention any deviation from 180°, or state a deviation of 0.25° or 0.5°. Our findings are founded on the well-established Heitler cross-sections and relativistic kinematics, both adopted unanimously by PENELOPE, EGSnrc and GEANT4. Our results highlight the effects of annihilation in-flight, a process sometimes forgotten within the PET community.

Pair production by high intensity picosecond laser interacting with thick solid target at XingGuangIII

NASA Astrophysics Data System (ADS)

Wu, Yuchi; Dong, Kegong; Yan, Yonghong; Zhu, Bin; Zhang, Tiankui; Chen, Jia; Yu, Minghai; Tan, Fang; Wang, Shaoyi; Han, Dan; Lu, Feng; Gu, Yuqiu

2017-06-01

An experiment for pair production by high intensity laser irradiating thick solid targets is present. The experiment used picosecond beam of the XingGuangIII laser facility, with intensities up to several 1019 W/cm2, pulse durations about 0.8 ps and laser energies around 120 J. Pairs were generated from 1 mm-thick tantalum disk targets with different diameters from 1 mm to 10 mm. Energy spectra of hot electron from targetrear surface represent a Maxwellian distribution and obey a scaling of ∼(Iλ2)0.5. Large quantity of positrons were observed at the target rear normal direction with a yield up to 2.8 × 109 e+/sr. Owing to the target rear surface sheath field, the positrons behave as a quasi-monoenergetic beam with peak energy of several MeV. Our experiment shows that the peak energy of positron beam is inversely proportional to the target diameter.

Thick-target-method study of Mα β x-ray production cross sections of Pb and Bi impacted by positrons up to 9 keV

NASA Astrophysics Data System (ADS)

Wu, Y.; Liang, Y.; Xu, M. X.; Yuan, Y.; Chang, C. H.; Qian, Z. C.; Wang, B. Y.; Kuang, P.; Zhang, P.

2018-03-01

Atomic M -shell x-ray production cross sections induced by positrons near the threshold energy have been presented in this paper. In the experiment, online monitoring technology, which utilizes a high-purity germanium detector to record the annihilation photons emitted from the pure thick target impacted by positrons, was developed to obtain the accurate number of the incident positrons. The effects of the multiple scattering of incident positrons, from the bremsstrahlung and annihilation photons and other secondary particles on the experimental characteristic x-ray yield, were eliminated by Monte Carlo simulation in combination with theoretical integral calculation. The Tikhonov regularization method was adopted to handle the ill-posed inverse problem involved in the thick-target method, i.e., x-ray production cross sections by the corrected characteristic x-ray yield. Experimental results of Mα β x-ray production cross sections for Pb and Bi impacted by 6-9-keV positrons were compared with the corresponding values predicted by the distorted-wave Born approximation (DWBA). Good agreement was found between the two. Moreover, we have presented the experimental results on the ratios of the Mα β x-ray production cross sections by electron impact in the literature to that by 6-9-keV positron impact in this work. They were also in accordance with the theoretical ratios calculated by the predictions of DWBA theory.

Positron radiography of ignition-relevant ICF capsules

DOE PAGES

Williams, G. J.; Chen, Hui; Field, J. E.; ...

2017-12-11

Laser-generated positrons are evaluated as a probe source to radiograph in-flight ignition-relevant inertial confinement fusion capsules. Current ultraintense laser facilities are capable of producing 2 ×10 12 relativistic positrons in a narrow energy bandwidth and short time duration. Monte Carlo simulations suggest that the unique characteristics of such positrons allow for the reconstruction of both capsule shell radius and areal density between 0.002 and 2g/cm 2. The energy-downshifted positron spectrum and angular scattering of the source particles are sufficient to constrain the conditions of the capsule between preshot and stagnation. Here, we evaluate the effects of magnetic fields near themore » capsule surface using analytic estimates where it is shown that this diagnostic can tolerate line integrated field strengths of 100 T mm.« less

Positron radiography of ignition-relevant ICF capsules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williams, G. J.; Chen, Hui; Field, J. E.

Laser-generated positrons are evaluated as a probe source to radiograph in-flight ignition-relevant inertial confinement fusion capsules. Current ultraintense laser facilities are capable of producing 2 ×10 12 relativistic positrons in a narrow energy bandwidth and short time duration. Monte Carlo simulations suggest that the unique characteristics of such positrons allow for the reconstruction of both capsule shell radius and areal density between 0.002 and 2g/cm 2. The energy-downshifted positron spectrum and angular scattering of the source particles are sufficient to constrain the conditions of the capsule between preshot and stagnation. Here, we evaluate the effects of magnetic fields near themore » capsule surface using analytic estimates where it is shown that this diagnostic can tolerate line integrated field strengths of 100 T mm.« less

Production of Highly Polarized Positrons Using Polarized Electrons at MeV Energies

NASA Astrophysics Data System (ADS)

Abbott, D.; Adderley, P.; Adeyemi, A.; Aguilera, P.; Ali, M.; Areti, H.; Baylac, M.; Benesch, J.; Bosson, G.; Cade, B.; Camsonne, A.; Cardman, L. S.; Clark, J.; Cole, P.; Covert, S.; Cuevas, C.; Dadoun, O.; Dale, D.; Dong, H.; Dumas, J.; Fanchini, E.; Forest, T.; Forman, E.; Freyberger, A.; Froidefond, E.; Golge, S.; Grames, J.; Guèye, P.; Hansknecht, J.; Harrell, P.; Hoskins, J.; Hyde, C.; Josey, B.; Kazimi, R.; Kim, Y.; Machie, D.; Mahoney, K.; Mammei, R.; Marton, M.; McCarter, J.; McCaughan, M.; McHugh, M.; McNulty, D.; Mesick, K. E.; Michaelides, T.; Michaels, R.; Moffit, B.; Moser, D.; Muñoz Camacho, C.; Muraz, J.-F.; Opper, A.; Poelker, M.; Réal, J.-S.; Richardson, L.; Setiniyaz, S.; Stutzman, M.; Suleiman, R.; Tennant, C.; Tsai, C.; Turner, D.; Ungaro, M.; Variola, A.; Voutier, E.; Wang, Y.; Zhang, Y.; PEPPo Collaboration

2016-05-01

The Polarized Electrons for Polarized Positrons experiment at the injector of the Continuous Electron Beam Accelerator Facility has demonstrated for the first time the efficient transfer of polarization from electrons to positrons produced by the polarized bremsstrahlung radiation induced by a polarized electron beam in a high-Z target. Positron polarization up to 82% have been measured for an initial electron beam momentum of 8.19 MeV /c , limited only by the electron beam polarization. This technique extends polarized positron capabilities from GeV to MeV electron beams, and opens access to polarized positron beam physics to a wide community.

Production of Highly Polarized Positrons Using Polarized Electrons at MeV Energies

DOE PAGES

Abbott, D.; Adderley, P.; Adeyemi, A.; ...

2016-05-27

The Polarized Electrons for Polarized Positrons experiment at the injector of the Continuous Electron Beam Accelerator Facility has demonstrated for the first time the efficient transfer of polarization from electrons to positrons produced by the polarized bremsstrahlung radiation induced by a polarized electron beam in a high-Z target. Positron polarization up to 82% have been measured for an initial electron beam momentum of 8.19~MeV/c, limited only by the electron beam polarization. We report that this technique extends polarized positron capabilities from GeV to MeV electron beams, and opens access to polarized positron beam physics to a wide community.

Positron elastic scattering from alkaline earth targets

NASA Astrophysics Data System (ADS)

Poveda, Luis A.; Assafrão, Denise; Mohallem, José R.

2016-07-01

A previously reported model potential approach [Poveda et al., Phys. Rev. A 87, 052702 (2013)] was extended to study low energy positron elastic scattering from beryllium and magnesium. The cross sections were computed for energies ranging from 10-5 eV up to well above the positronium formation threshold. The present results are in good agreement with previous reports, including the prediction of a p-wave resonance in the cross section for magnesium. The emergence of this shape resonance is connected to a trend observed in the evolution of the partial wave cross section in going from Be to Mg target. This trend lead us to speculate that a sharp d-wave resonance should be observed in positron elastic scattering from calcium. The positron-target binding energies are investigated in detail, both using the scattering information and by direct computation of the bound state energies using the model potentials. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.Supplementary material in the form of one pdf file available from the Journal web page at http://dx.doi.org/10.1140/epjd/e2016-70120-y

Triply differential measurements of single ionization of argon by 1-keV positron and electron impact

NASA Astrophysics Data System (ADS)

Gavin, J.; de Lucio, O. G.; DuBois, R. D.

2017-06-01

By establishing coincidences between target ions and scattered projectiles, and coincidences between target ions, scattered projectiles, and ejected electrons, triply differential cross-section (TDCS) information was generated in terms of projectile energy loss and scattering angles for interactions between 1-keV positrons and electrons and Ar atoms. The conversion of the raw experimental information to the TDCS is discussed. The single-ionization TDCS exhibits two distinguishable regions (lobes) where binary and recoil interactions can be described by two peaks. A comparison of the positron and electron impact data shows that the relative intensity of both binary and recoil interactions decreases exponentially as a function of the momentum transfer and is larger when ionization is induced by positron impact, when compared with electron impact.

Radio frequency elevator for a pulsed positron beam

NASA Astrophysics Data System (ADS)

Dickmann, Marcel; Mitteneder, Johannes; Kögel, Gottfried; Egger, Werner; Sperr, Peter; Ackermann, Ulrich; Piochacz, Christian; Dollinger, Günther

2016-06-01

An elevator increases the potential energy of a particle beam with respect to ground potential without any alteration of kinetic energy and other beam parameters. This elevator is necessary for the implementation of the Munich Scanning Positron Microscope (SPM) at the intense positron source NEPOMUC at the research reactor FRM II in Munich. The principles of the rf elevator for pure electrostatically guided positrons are described. Measurements of beam quality behind the elevator are reported, which confirm that after the implementation of elevator and SPM at NEPOMUC the SPM can be operated at a considerably improved resolution (~ 0.3 μm) and event rate (~3.7 kHz) compared to the laboratory based β+-source.

Electron and Positron Stopping Powers of Materials

National Institute of Standards and Technology Data Gateway

SRD 7 NIST Electron and Positron Stopping Powers of Materials (PC database for purchase)   The EPSTAR database provides rapid calculations of stopping powers (collisional, radiative, and total), CSDA ranges, radiation yields and density effect corrections for incident electrons or positrons with kinetic energies from 1 keV to 10 GeV, and for any chemically defined target material.

The status of the positron beam facility at NEPOMUC

NASA Astrophysics Data System (ADS)

Hugenschmidt, C.

2011-01-01

The NEutron induced POsitron source MUniCh NEPOMUC provides a high intensity positron beam with 9·108 moderated positrons per second with a primary beam energy of 1keV. After remoderation, the positron beam is magnetically guided to five experimental setups: a coincident Doppler-broadening spectrometer (CDBS), a positron annihilation induced Auger-electron spectrometer (PAES), a pulsed low-energy positron system (PLEPS) as well as an interface for providing a pulsed beam with further improved brightness. An apparatus for the production of the negatively charged positronium ion Ps- is currently in operation at the open multi-purpose beam port, where additional experiments can be realized. Within this contribution, an overview of the positron beam facility NEPOMUC with its instrumentation at the research reactor FRMII is given.

Extended gamma-ray sources around pulsars constrain the origin of the positron flux at Earth

NASA Astrophysics Data System (ADS)

Abeysekara, A. U.; Albert, A.; Alfaro, R.; Alvarez, C.; Álvarez, J. D.; Arceo, R.; Arteaga-Velázquez, J. C.; Avila Rojas, D.; Ayala Solares, H. A.; Barber, A. S.; Bautista-Elivar, N.; Becerril, A.; Belmont-Moreno, E.; BenZvi, S. Y.; Berley, D.; Bernal, A.; Braun, J.; Brisbois, C.; Caballero-Mora, K. S.; Capistrán, T.; Carramiñana, A.; Casanova, S.; Castillo, M.; Cotti, U.; Cotzomi, J.; Coutiño de León, S.; De León, C.; De la Fuente, E.; Dingus, B. L.; DuVernois, M. A.; Díaz-Vélez, J. C.; Ellsworth, R. W.; Engel, K.; Enríquez-Rivera, O.; Fiorino, D. W.; Fraija, N.; García-González, J. A.; Garfias, F.; Gerhardt, M.; González Muñoz, A.; González, M. M.; Goodman, J. A.; Hampel-Arias, Z.; Harding, J. P.; Hernández, S.; Hernández-Almada, A.; Hinton, J.; Hona, B.; Hui, C. M.; Hüntemeyer, P.; Iriarte, A.; Jardin-Blicq, A.; Joshi, V.; Kaufmann, S.; Kieda, D.; Lara, A.; Lauer, R. J.; Lee, W. H.; Lennarz, D.; Vargas, H. León; Linnemann, J. T.; Longinotti, A. L.; Luis Raya, G.; Luna-García, R.; López-Coto, R.; Malone, K.; Marinelli, S. S.; Martinez, O.; Martinez-Castellanos, I.; Martínez-Castro, J.; Martínez-Huerta, H.; Matthews, J. A.; Miranda-Romagnoli, P.; Moreno, E.; Mostafá, M.; Nellen, L.; Newbold, M.; Nisa, M. U.; Noriega-Papaqui, R.; Pelayo, R.; Pretz, J.; Pérez-Pérez, E. G.; Ren, Z.; Rho, C. D.; Rivière, C.; Rosa-González, D.; Rosenberg, M.; Ruiz-Velasco, E.; Salazar, H.; Salesa Greus, F.; Sandoval, A.; Schneider, M.; Schoorlemmer, H.; Sinnis, G.; Smith, A. J.; Springer, R. W.; Surajbali, P.; Taboada, I.; Tibolla, O.; Tollefson, K.; Torres, I.; Ukwatta, T. N.; Vianello, G.; Weisgarber, T.; Westerhoff, S.; Wisher, I. G.; Wood, J.; Yapici, T.; Yodh, G.; Younk, P. W.; Zepeda, A.; Zhou, H.; Guo, F.; Hahn, J.; Li, H.; Zhang, H.

2017-11-01

The unexpectedly high flux of cosmic-ray positrons detected at Earth may originate from nearby astrophysical sources, dark matter, or unknown processes of cosmic-ray secondary production. We report the detection, using the High-Altitude Water Cherenkov Observatory (HAWC), of extended tera–electron volt gamma-ray emission coincident with the locations of two nearby middle-aged pulsars (Geminga and PSR B0656+14). The HAWC observations demonstrate that these pulsars are indeed local sources of accelerated leptons, but the measured tera–electron volt emission profile constrains the diffusion of particles away from these sources to be much slower than previously assumed. We demonstrate that the leptons emitted by these objects are therefore unlikely to be the origin of the excess positrons, which may have a more exotic origin.

A next generation positron microscope and a survey of candidate samples for future positron studies

NASA Astrophysics Data System (ADS)

Dull, Terry Lou

A positron microscope has been constructed and is nearing the conclusion of its assembly and testing. The instrument is designed to perform positron and electron microscopy in both scanning and magnifying modes. In scanning mode, a small beam of particles is rastered across the target and the amplitude of a positron or electron related signal is recorded as a function of position. For positrons this signal may come from Doppler Broadening Spectroscopy, Reemitted Positron Spectroscopy or Positron Annihilation Lifetime Spectroscopy. For electrons this signal may come from the number of secondary electrons or Auger Electron Spectroscopy. In magnifying mode an incident beam of particles is directed onto the target and emitted particles, either secondary electrons or reemitted positrons, are magnified to form an image. As a positron microscope the instrument will primarily operate in magnifying mode, as a positron reemission microscope. As an electron microscope the instrument will be able to operate in both magnifying and scanning modes. Depth-profiled Doppler Broadening Spectroscopy studies using a non-microscopic low-energy positron beam have also been performed on a series of samples to ascertain the applicability of positron spectroscopies and/or microscopy to their study. All samples have sub-micron film and/or feature size and thus are only susceptible to positron study with low-energy beams. Several stoichiometries and crystallinities of chalcogenide thin films (which can be optically reversibly switched between crystalline states) were studied and a correlation was found to exist between the amorphous/FCC S-parameter difference and the amorphous/FCC switching time. Amorphous silicon films were studied in an attempt to observe the well-established Staebler-Wronski effect as well as the more controversial photodilatation effect. However, DBS was not able to detect either effect. The passive oxide films on titanium and aluminum were studied in an attempt to verify the Point Defect Model, a detailed, but as yet microscopically unconfirmed, theory of the corrosive breakdown of passive films. DBS results supportive of the PDM were observed. Graphitic carbon fibers were also studied and DBS indicated the presence of a 200 nm thick outer fiber skin possibly characterized by a high degree of graphitic crystallite alignment.

Measurement techniques for low emittance tuning and beam dynamics at CESR

NASA Astrophysics Data System (ADS)

Billing, M. G.; Dobbins, J. A.; Forster, M. J.; Kreinick, D. L.; Meller, R. E.; Peterson, D. P.; Ramirez, G. A.; Rendina, M. C.; Rider, N. T.; Sagan, D. C.; Shanks, J.; Sikora, J. P.; Stedinger, M. G.; Strohman, C. R.; Williams, H. A.; Palmer, M. A.; Holtzapple, R. L.; Flanagan, J.

2018-03-01

After operating as a High Energy Physics electron-positron collider, the Cornell Electron-positron Storage Ring (CESR) has been converted to become a dedicated synchrotron light source for the Cornell High Energy Synchrotron Source (CHESS). Over the course of several years CESR was adapted for accelerator physics research as a test accelerator, capable of studying topics relevant to future damping rings, colliders and light sources. Initially some specific topics were targeted for accelerator physic research with the storage ring in this mode, labeled CesrTA. These topics included 1) tuning techniques to produce low emittance beams, 2) the study of electron cloud (EC) development in a storage ring and 3) intra-beam scattering effects. The complete conversion of CESR to CesrTA occurred over a several year period, described elsewhere [1–3]. A number of specific instruments were developed for CesrTA. Much of the pre-existing instrumentation was modified to accommodate the scope of these studies and these are described in a companion paper [4]. To complete this research, a number of procedures were developed or modified, often requiring coordinated measurements among different instruments [5]. This paper provides an overview of types of measurements employed for the study of beam dynamics during the operation of CesrTA.

Development of slow positron beam lines and applications

NASA Astrophysics Data System (ADS)

Mondal, Nagendra Nath

2018-05-01

A positron is an antiparticle of an electron that can be formed in diverse methods: natural or artificial β-decay process, fission and fusion reactions, and a pair production of electron-positron occurred in the reactor and the high energy accelerator centers. Usually a long-lifetime radio isotope is customized for the construction of a slow positron beam lines in many laboratories. The typical intensity of this beam depends upon the strength of the positron source, moderator efficiency, and guiding, pulsing, focusing and detecting systems. This article will review a few positron beam lines and their potential applications in research, especially in the Positronium Bose-Einstein Condensation.

Estimate of S-values for children due to six positron emitting radionuclides used in PET examinations

NASA Astrophysics Data System (ADS)

Belinato, Walmir; Santos, William S.; Perini, Ana P.; Neves, Lucio P.; Caldas, Linda V. E.; Souza, Divanizia N.

2017-11-01

Positron emission tomography (PET) has revolutionized the diagnosis of cancer since its conception. When combined with computed tomography (CT), PET/CT performed in children produces highly accurate diagnoses from images of regions affected by malignant tumors. Considering the high risk to children when exposed to ionizing radiation, a dosimetric study for PET/CT procedures is necessary. Specific absorbed fractions (SAF) were determined for monoenergetic photons and positrons, as well as the S-values for six positron emitting radionuclides (11C, 13N, 18F, 68Ga, 82Rb, 15O), and 22 source organs. The study was performed for six pediatric anthropomorphic hybrid models, including the newborn and 1 year hermaphrodite, 5 and 10-year-old male and female, using the Monte Carlo N-Particle eXtended code (MCNPX, version 2.7.0). The results of the SAF in source organs and S-values for all organs showed to be inversely related to the age of the phantoms, which includes the variation of body weight. The results also showed that radionuclides with higher energy peak emission produces larger auto absorbed S-values due to local dose deposition by positron decay. The S-values for the source organs are considerably larger due to the interaction of tissue with non-penetrating particles (electrons and positrons) and present a linear relationship with the phantom body masses. The results of the S-values determined for positron-emitting radionuclides can be used to assess the radiation dose delivered to pediatric patients subjected to PET examination in clinical settings. The novelty of this work is associated with the determination of auto absorbed S-values, in six new pediatric virtual anthropomorphic phantoms, for six emitting positrons, commonly employed in PET exams.

Nondestructive examination using neutron activated positron annihilation

DOEpatents

Akers, Douglas W.; Denison, Arthur B.

2001-01-01

A method is provided for performing nondestructive examination of a metal specimen using neutron activated positron annihilation wherein the positron emitter source is formed within the metal specimen. The method permits in situ nondestructive examination and has the advantage of being capable of performing bulk analysis to determine embrittlement, fatigue and dislocation within a metal specimen.

Electron- and positron-molecule scattering: development of the molecular convergent close-coupling method

NASA Astrophysics Data System (ADS)

Zammit, Mark C.; Fursa, Dmitry V.; Savage, Jeremy S.; Bray, Igor

2017-06-01

Starting from first principles, this tutorial describes the development of the adiabatic-nuclei convergent close-coupling (CCC) method and its application to electron and (single-centre) positron scattering from diatomic molecules. We give full details of the single-centre expansion CCC method, namely the formulation of the molecular target structure; solving the momentum-space coupled-channel Lippmann-Schwinger equation; deriving adiabatic-nuclei cross sections and calculating V-matrix elements. Selected results are presented for electron and positron scattering from molecular hydrogen H2 and electron scattering from the vibrationally excited molecular hydrogen ion {{{H}}}2+ and its isotopologues (D2 +, {{{T}}}2+, HD+, HT+ and TD+). Convergence in both the close-coupling (target state) and projectile partial-wave expansions of fixed-nuclei electron- and positron-molecule scattering calculations is demonstrated over a broad energy-range and discussed in detail. In general, the CCC results are in good agreement with experiments.

Intense positron beam as a source for production of electron-positron plasma

NASA Astrophysics Data System (ADS)

Stoneking, M. R.; Horn-Stanja, J.; Stenson, E. V.; Pedersen, T. Sunn; Saitoh, H.; Hergenhahn, U.; Niemann, H.; Paschkowski, N.; Hugenschmidt, C.; Piochacz, C.

2016-10-01

We aim to produce magnetically confined, short Debye length electron-positron plasma and test predicted properties for such systems. A first challenge is obtaining large numbers of positrons; a table-top experiment (system size 5 cm) with a temperature less than 5 eV requires about 1010 positrons to have more than 10 Debye lengths in the system. The NEPOMUC facility at the FRM II research reactor in Germany is one of the world's most intense positron sources. We report on characterization (using a retarding field energy analyzer with magnetic field gradient) of the NEPOMUC beam as delivered to the open beam port at various beam energies and in both the re-moderated and primary beam configurations in order to design optimal trapping (and accumulation) schemes for production of electron-positron plasma. The intensity of the re-moderated (primary) beam is in the range 2 -3 x 107 /s (1 - 5 x 108 /s). The re-moderated beam is currently the most promising for direct injection and confinement experiments; it has a parallel energy spread of 15 - 35% and the transverse energy spread is 6 - 15% of the parallel energy. We report on the implications for injection and trapping in a dipole magnetic field as well as plans for beam development, in situ re-moderation, and accumulation. We also report results demonstrating a difference in phosphor luminescent response to low energy positrons versus electrons.

Positron Lifetime Modulation by Electric Field Induced Positronium Formation on a Gold Surface

DTIC Science & Technology

2012-03-22

Angular Momentum (3) ......................................................................... 11 Stopping Power (4...isotope from which it was born, diffused into the material before annihilation occurred. 6 The radioisotope used in this experiment is Na-22 which...that positrons may be useful in studying the internal structure of a wide variety of materials. The radioisotope positron source used in this

A proposed intense slow positron source based on 58Co

NASA Astrophysics Data System (ADS)

Brown, Benjamin L.; Denison, Art; Makowitz, Henry; Gidley, Dave; Frieze, Bill; Griffin, Henry; Encarnación, Pedro

1994-06-01

Positron beams have proven very useful for condensed matter and surface research. The highest intensity of the current operating positron beams is ˜109 slow e+/second. The goal of our proposal is to build an Intense Slow Positron Source (ISPS) demonstration beam (Phase I) of unprecedented brightness at the Idaho National Engineering Laboratory, INEL (up to 1010 slow e+/s at 5 keV over a <0.03 cm. diameter). This Phase I beam will prove the principles necessary to build a larger facility scale ISPS Phase II beam which will have a potential of 1013 e+/s, or ≳1012 e+/s over 0.03 cm. The INEL is an ideal location for the ISPS because of the fast breeder reactor EBR-II, which is perfectly suited to creating the positron emitting isotope 58Co, and the excellent radioactive materials handling capability and expertise. Sufficient expertise is available at INEL for the construction and operation of a user facility (Phase II).

Resonances in low-energy positron-alkali scattering

NASA Technical Reports Server (NTRS)

Horbatsch, M.; Ward, S. J.; Mceachran, R. P.; Stauffer, A. D.

1990-01-01

Close-coupling calculations were performed with up to five target states at energies in the excitation threshold region for positron scattering from Li, Na and K. Resonances were discovered in the L = 0, 1 and 2 channels in the vicinity of the atomic excitation thresholds. The widths of these resonances vary between 0.2 and 130 MeV. Evidence was found for the existence of positron-alkali bound states in all cases.

Answer to Question {number_sign}30 [{open_quote}{open_quote}How are positrons moderated?,{close_quote}{close_quote} Thomas D. Rossing, Am. J. Phys. {bold 63}(12), 1065 (1995)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weber, M.; Lynn, K.G.

1996-07-01

The positrons from {beta}{sup +} decaying sources loss energyat a much faster rate than they annihilate. As the energy of the positrons drops, core excitations, plasmon excitation, electron/hole pair creation, and phonon scattering are the dominant processes of further energy loss.

Extended gamma-ray sources around pulsars constrain the origin of the positron flux at Earth.

PubMed

Abeysekara, A U; Albert, A; Alfaro, R; Alvarez, C; Álvarez, J D; Arceo, R; Arteaga-Velázquez, J C; Avila Rojas, D; Ayala Solares, H A; Barber, A S; Bautista-Elivar, N; Becerril, A; Belmont-Moreno, E; BenZvi, S Y; Berley, D; Bernal, A; Braun, J; Brisbois, C; Caballero-Mora, K S; Capistrán, T; Carramiñana, A; Casanova, S; Castillo, M; Cotti, U; Cotzomi, J; Coutiño de León, S; De León, C; De la Fuente, E; Dingus, B L; DuVernois, M A; Díaz-Vélez, J C; Ellsworth, R W; Engel, K; Enríquez-Rivera, O; Fiorino, D W; Fraija, N; García-González, J A; Garfias, F; Gerhardt, M; González Muñoz, A; González, M M; Goodman, J A; Hampel-Arias, Z; Harding, J P; Hernández, S; Hernández-Almada, A; Hinton, J; Hona, B; Hui, C M; Hüntemeyer, P; Iriarte, A; Jardin-Blicq, A; Joshi, V; Kaufmann, S; Kieda, D; Lara, A; Lauer, R J; Lee, W H; Lennarz, D; Vargas, H León; Linnemann, J T; Longinotti, A L; Luis Raya, G; Luna-García, R; López-Coto, R; Malone, K; Marinelli, S S; Martinez, O; Martinez-Castellanos, I; Martínez-Castro, J; Martínez-Huerta, H; Matthews, J A; Miranda-Romagnoli, P; Moreno, E; Mostafá, M; Nellen, L; Newbold, M; Nisa, M U; Noriega-Papaqui, R; Pelayo, R; Pretz, J; Pérez-Pérez, E G; Ren, Z; Rho, C D; Rivière, C; Rosa-González, D; Rosenberg, M; Ruiz-Velasco, E; Salazar, H; Salesa Greus, F; Sandoval, A; Schneider, M; Schoorlemmer, H; Sinnis, G; Smith, A J; Springer, R W; Surajbali, P; Taboada, I; Tibolla, O; Tollefson, K; Torres, I; Ukwatta, T N; Vianello, G; Weisgarber, T; Westerhoff, S; Wisher, I G; Wood, J; Yapici, T; Yodh, G; Younk, P W; Zepeda, A; Zhou, H; Guo, F; Hahn, J; Li, H; Zhang, H

2017-11-17

The unexpectedly high flux of cosmic-ray positrons detected at Earth may originate from nearby astrophysical sources, dark matter, or unknown processes of cosmic-ray secondary production. We report the detection, using the High-Altitude Water Cherenkov Observatory (HAWC), of extended tera-electron volt gamma-ray emission coincident with the locations of two nearby middle-aged pulsars (Geminga and PSR B0656+14). The HAWC observations demonstrate that these pulsars are indeed local sources of accelerated leptons, but the measured tera-electron volt emission profile constrains the diffusion of particles away from these sources to be much slower than previously assumed. We demonstrate that the leptons emitted by these objects are therefore unlikely to be the origin of the excess positrons, which may have a more exotic origin. Copyright © 2017, American Association for the Advancement of Science.

Practical experience and challenges in the operation of medical cyclotron.

PubMed

Kumar, Rajeev; Sonkawade, Rajendra G; Pandey, Anil K; Tripathi, Madhavi; Damle, Nishikant A; Kumar, Praveen; Bal, Chandra S

2017-01-01

The aim of this article was to share 10 years of operational experience of medical cyclotron and to provide working knowledge on the same. This experience has helped us gain working knowledge on cyclotron operation with practical points, which may help in improving F yield, minimizing the breakdown time, and help in the prevention of the occurrence of unusual events. Our facility has a self-shielded radioisotope delivery system eclipse 111 medical cyclotron with an 11 MeV proton beam in use for the past 10 years to produce positron emitters - namely, F, N, and F-2 gas - for PET imaging. During F production, we have followed a set protocol comprising the following: monitoring target pressure, rinsing the target with O water just immediately after bombardment, ion source feedback, radiofrequency (RF) feedback, and recording any unusual events that occurred during the operation. Besides this, enrichment of O water, target volume, target current, energy of the beam, variation in argon pressure on the target, bombardment duration, target status (new or old target or total number of previous bombardments on the same target), status of the delivery lines from target to the radiochemistry module (old or new) were also recorded. Rinsing with O water immediately after bombardment increases the life of the target and delivery line. The frequent problems encountered were with the ion source, RF, and target foil rupture. These problems were solved by rebuilding the ion source, changing the fuse of RF, and rebuilding the target. F yield can be increased by rinsing with O water immediately after bombardment. The effect of target leak - that is, rupture of vacuum window - can be avoided by immediate stoppage of bombardment.

Decaying fermionic dark matter search with CALET

NASA Astrophysics Data System (ADS)

Bhattacharyya, S.; Motz, H.; Torii, S.; Asaoka, Y.

2017-08-01

The ISS-based CALET (CALorimetric Electron Telescope) detector can play an important role in indirect search for Dark Matter (DM), measuring the electron+positron flux in the TeV region for the first time directly. With its fine energy resolution of approximately 2% and good proton rejection ratio (1:105) it has the potential to search for fine structures in the Cosmic Ray (CR) electron spectrum. In this context we discuss the ability of CALET to discern between signals originating from astrophysical sources and DM decay. We fit a parametrization of the local interstellar electron and positron spectra to current measurements, with either a pulsar or 3-body decay of fermionic DM as the extra source causing the positron excess. The expected CALET data for scenarios in which DM decay explains the excess are calculated and analyzed. The signal from this particular 3-body DM decay which can explain the recent measurements from the AMS-02 experiment is shown to be distinguishable from a single pulsar source causing the positron excess by 5 years of observation with CALET, based on the shape of the spectrum. We also study the constraints from diffuse γ-ray data on this DM-only explanation of the positron excess and show that especially for the possibly remaining parameter space a clearly identifiable signature in the CR electron spectrum exists.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhattacharyya, S.; Torii, S.; Motz, H.

The ISS-based CALET (CALorimetric Electron Telescope) detector can play an important role in indirect search for Dark Matter (DM), measuring the electron+positron flux in the TeV region for the first time directly. With its fine energy resolution of approximately 2% and good proton rejection ratio (1:10{sup 5}) it has the potential to search for fine structures in the Cosmic Ray (CR) electron spectrum. In this context we discuss the ability of CALET to discern between signals originating from astrophysical sources and DM decay. We fit a parametrization of the local interstellar electron and positron spectra to current measurements, with eithermore » a pulsar or 3-body decay of fermionic DM as the extra source causing the positron excess. The expected CALET data for scenarios in which DM decay explains the excess are calculated and analyzed. The signal from this particular 3-body DM decay which can explain the recent measurements from the AMS−02 experiment is shown to be distinguishable from a single pulsar source causing the positron excess by 5 years of observation with CALET, based on the shape of the spectrum. We also study the constraints from diffuse γ-ray data on this DM-only explanation of the positron excess and show that especially for the possibly remaining parameter space a clearly identifiable signature in the CR electron spectrum exists.« less

Physical models and primary design of reactor based slow positron source at CMRR

NASA Astrophysics Data System (ADS)

Wang, Guanbo; Li, Rundong; Qian, Dazhi; Yang, Xin

2018-07-01

Slow positron facilities are widely used in material science. A high intensity slow positron source is now at the design stage based on the China Mianyang Research Reactor (CMRR). This paper describes the physical models and our primary design. We use different computer programs or mathematical formula to simulate different physical process, and validate them by proper experiments. Considering the feasibility, we propose a primary design, containing a cadmium shield, a honeycomb arranged W tubes assembly, electrical lenses, and a solenoid. It is planned to be vertically inserted in the Si-doping channel. And the beam intensity is expected to be 5 ×109

Positron total scattering cross-sections for alkali atoms

NASA Astrophysics Data System (ADS)

Sinha, Nidhi; Singh, Suvam; Antony, Bobby

2018-01-01

Positron-impact total scattering cross-sections for Li, Na, K, Rb, Cs and Fr atoms are calculated in the energy range from 5-5000 eV employing modified spherical complex optical potential formalism. The main aim of this work is to apply this formalism to the less studied positron-target collision systems. The results are compared with previous theoretical and experimental data, wherever available. In general, the present data show overall agreement and consistency with other results. Furthermore, we have done a comparative study of the results to investigate the effect of atomic size on the cross-sections as we descend through the group in the periodic table. We have also plotted a correlation graph of the present total cross-sections with polarizability and number of target electrons. The two correlation plots confirm the credibility and consistency of the present results. Besides, this is the first theoretical attempt to report positron-impact total cross-sections of alkali atoms over such a wide energy range.

Sgr A* as Source of the Positrons Observed in the Galactic Center Region

NASA Astrophysics Data System (ADS)

Jean, Pierre; Guessoum, Nidhal; Ferrière, Katia

2017-01-01

We explore the possibility that a substantial fraction of the positrons observed to annihilate in the central region of our Galaxy come from the supermassive black hole Sgr A* that lies at the center. This idea was proposed by several authors, but the propagation of the emitted positrons into the bulge and beyond remained a serious problem for models of the origin of GC positrons. We assume models of positron production with different energies. The propagation of positrons from their production site is followed in detail with Monte-Carlo simulations, taking into account the physical conditions of the propagation regions as well as various physical interactions. Using the known physics of positron annihilation in astrophysical environments, we calculate the properties of the annihilation emission (time evolution and spatial distribution) for the different models under consideration. We present the results of these simulations and the conclusions/constraints that can be inferred from them.

An overview of Laser-Produced Relativistic Positrons in the Laboratory

NASA Astrophysics Data System (ADS)

Edghill, Brandon; Williams, Gerald; Chen, Hui; Beg, Farhat

2017-10-01

The production of relativistic positrons using ultraintense lasers can facilitate studies of fundamental pair plasma science in the relativistic regime and laboratory studies of scaled energetic astrophysical mechanisms such as gamma ray bursts. The positron densities and spatial scales required for these applications, however, are larger than current capabilities. Here, we present an overview of the experimental laser-produced positron results and their respective modeling for both the direct laser-irradiated process and the indirect process (laser wakefield accelerated electrons irradiating a high-Z converter). Conversion efficiency into positrons and positron beam characteristics are compared, including total pair yield, mean energy, angular divergence, and inferred pair density for various laser and target conditions. Prospects towards increasing positron densities and beam repetition rates will also be discussed. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, and funded by LDRD (#17-ERD-010).

Astrophysical signatures of leptonium

NASA Astrophysics Data System (ADS)

Ellis, Simon C.; Bland-Hawthorn, Joss

2018-01-01

More than 1043 positrons annihilate every second in the centre of our Galaxy yet, despite four decades of observations, their origin is still unknown. Many candidates have been proposed, such as supernovae and low mass X-ray binaries. However, these models are difficult to reconcile with the distribution of positrons, which are highly concentrated in the Galactic bulge, and therefore require specific propagation of the positrons through the interstellar medium. Alternative sources include dark matter decay, or the supermassive black hole, both of which would have a naturally high bulge-to-disc ratio. The chief difficulty in reconciling models with the observations is the intrinsically poor angular resolution of gamma-ray observations, which cannot resolve point sources. Essentially all of the positrons annihilate via the formation of positronium. This gives rise to the possibility of observing recombination lines of positronium emitted before the atom annihilates. These emission lines would be in the UV and the NIR, giving an increase in angular resolution of a factor of 104 compared to gamma ray observations, and allowing the discrimination between point sources and truly diffuse emission. Analogously to the formation of positronium, it is possible to form atoms of true muonium and true tauonium. Since muons and tauons are intrinsically unstable, the formation of such leptonium atoms will be localised to their places of origin. Thus observations of true muonium or true tauonium can provide another way to distinguish between truly diffuse sources such as dark matter decay, and an unresolved distribution of point sources. Contribution to the Topical Issue "Low Energy Positron and Electron Interactions", edited by James Sullivan, Ron White, Michael Bromley, Ilya Fabrikant and David Cassidy.

Scattering of positrons and electrons by alkali atoms

NASA Technical Reports Server (NTRS)

Stein, T. S.; Kauppila, W. E.; Kwan, C. K.; Lukaszew, R. A.; Parikh, S. P.; Wan, Y. J.; Zhou, S.; Dababneh, M. S.

1990-01-01

Absolute total scattering cross sections (Q sub T's) were measured for positrons and electrons colliding with sodium, potassium, and rubidium in the 1 to 102 eV range, using the same apparatus and experimental approach (a beam transmission technique) for both projectiles. The present results for positron-sodium and -rubidium collisions represent the first Q sub T measurements reported for these collision systems. Features which distinguish the present comparisons between positron- and electron-alkali atom Q sub T's from those for other atoms and molecules (room-temperature gases) which have been used as targets for positrons and electrons are the proximity of the corresponding positron- and electron-alkali atom Q sub T's over the entire energy range of overlap, with an indication of a merging or near-merging of the corresponding positron and electron Q sub T's near (and above) the relatively low energy of about 40 eV, and a general tendency for the positron-alkali atom Q sub T's to be higher than the corresponding electron values as the projectile energy is decreased below about 40 eV.

Probing vacancy-type free-volume defects in Li2B4O7 single crystal by positron annihilation lifetime spectroscopy

NASA Astrophysics Data System (ADS)

Shpotyuk, O.; Adamiv, V.; Teslyuk, I.; Ingram, A.; Demchenko, P.

2018-01-01

Vacancy-type free-volume defects in lithium tetraborate Li2B4O7 single crystal, grown by the Czochralski technique, are probed with positron annihilation spectroscopy in the lifetime measuring mode. The experimental positron lifetime spectrum is reconstructed within the three-component fitting, involving channels of positron and positronium Ps trapping, as well as within the two-component fitting with a positronium-compensating source input. Structural configurations of the most efficient positron traps are considered using the crystallographic specificity of lithium tetraborate with the main accent on cation-type vacancies. Possible channels of positron trapping are visualized using the electronic structure calculations with density functional theory at the basis of structural parameters proper to Li2B4O7. Spatially-extended positron-trapping complexes involving singly-ionized lithium vacancies, with character lifetime close to 0.32 ns, are responsible for positron trapping in the nominally undoped lithium tetraborate Li2B4O7 crystal.

Surface and bulk investigations at the high intensity positron beam facility NEPOMUC

NASA Astrophysics Data System (ADS)

Hugenschmidt, C.; Dollinger, G.; Egger, W.; Kögel, G.; Löwe, B.; Mayer, J.; Pikart, P.; Piochacz, C.; Repper, R.; Schreckenbach, K.; Sperr, P.; Stadlbauer, M.

2008-10-01

The NEutron-induced POsitron source MUniCh (NEPOMUC) at the research reactor FRM II delivers a low-energy positron beam ( E = 15-1000 eV) of high intensity in the range between 4 × 10 7 and 5 × 10 8 moderated positrons per second. At present four experimental facilities are in operation at NEPOMUC: a coincident Doppler-broadening spectrometer (CDBS) for defect spectroscopy and investigations of the chemical vicinity of defects, a positron annihilation-induced Auger-electron spectrometer (PAES) for surface studies and an apparatus for the production of the negatively charged positronium ion Ps -. Recently, the pulsed low-energy positron system (PLEPS) has been connected to the NEPOMUC beam line, and first positron lifetime spectra were recorded within short measurement times. A positron remoderation unit which is operated with a tungsten single crystal in back reflection geometry has been implemented in order to improve the beam brilliance. An overview of NEPOMUC's status, experimental results and recent developments at the running spectrometers are presented.

Electron and positron interaction with pyrimidine: A theoretical investigation

NASA Astrophysics Data System (ADS)

Sinha, Nidhi; Antony, Bobby

2018-03-01

Pyrimidine (C4H4N2) is considered as the building block of nucleobases, viz., cytosine, thymine and uracil. They provide a blueprint for probing the scattering of radiation by DNA and RNA bases. In this article, we report the elastic and total scattering cross-sections for electron and positron scattering from the pyrimidine molecule, employing a spherical complex optical potential (SCOP) formalism for an extensive energy range of 10 eV to 5 keV. In the case of positron scattering, the original SCOP formalism is modified to adequately solve the positron-target dynamics. Moreover, a reasonable agreement is observed between the present results and other available datasets, for both electron and positron scattering. The cross-sections for electron and positron impact scattering by pyrimidine are necessary input data for codes that seek to simulate radiation damage, and hence are useful to model biomolecular systems.

THE GALACTIC POSITRON ANNIHILATION RADIATION AND THE PROPAGATION OF POSITRONS IN THE INTERSTELLAR MEDIUM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Higdon, J. C.; Lingenfelter, R. E.; Rothschild, R. E.

2009-06-10

The ratio of the luminosity of diffuse 511 keV positron annihilation radiation, measured by INTEGRAL in its four years, from a Galactic 'positron bulge' (<1.5 kpc) compared to that of the disk is {approx}1.4. This ratio is roughly 4 times larger than that expected simply from the stellar bulge-to-disk ratio of {approx}0.33 of the Galactic supernovae (SNe), which are thought to be the principal source of the annihilating positrons through the decay of radionuclei made by explosive nucleosynthesis in the SNe. This large discrepancy has prompted a search for new sources. Here, however, we show that the measured 511 keVmore » luminosity ratio can be fully understood in the context of a Galactic SN origin when the differential propagation of these {approx} MeV positrons in the various phases of the interstellar medium is taken into consideration, since these relativistic positrons must first slow down to energies {<=}10 eV before they can annihilate. Moreover, without propagation, none of the proposed positron sources, new or old, can explain the two basic properties on the Galactic annihilation radiation: the fraction of the annihilation that occurs through positronium formation and the ratio of the broad/narrow components of the 511 keV line. In particular, we show that in the neutral phases of the interstellar medium, which fill most of the disk (>3.5 kpc), the cascade of the magnetic turbulence, which scatters the positrons, is damped by ion-neutral friction, allowing positrons to stream along magnetic flux tubes. We find that nearly 1/2 of the positrons produced in the disk escape from it into the halo. On the other hand, we show that within the extended, or interstellar, bulge (<3.5 kpc), essentially all of the positrons are born in the hot plasmas which fill that volume. We find that the diffusion mean free path is long enough that only a negligible fraction annihilate there and {approx}80% of them escape down into the H II and H I envelopes of molecular clouds that lie within 1.5 kpc before they slow down and annihilate, while the remaining {approx}20% escape out into the halo and the disk beyond. This propagation accounts for the low observed annihilation radiation luminosity of the disk compared to the bulge. In addition, we show that the primary annihilation sites of the propagating positrons in both the bulge and the disk are in the warm ionized phases of the interstellar medium. Such annihilation can also account for those two basic properties of the emission, the fraction ({approx}93% {+-} 7%) of annihilation via positronium and the ratio ({approx}0.5) of broad ({approx}5.4 keV) to narrow ({approx}1.3 keV) components of the bulge 511 keV line emission. Moreover, we expect that the bulk of this broad line emission comes from the tilted disk region (0.5 < R < 1.5 kpc) with a very large broad/narrow flux ratio of {approx}6, while much of the narrow line emission comes from the inner bulge (R < 0.5 kpc) with a negligible broad/narrow flux ratio. Separate spectral analyses of the 511 keV line emission from these two regions should be able to test this prediction, and further probe the structure of the interstellar medium. Lastly, we show that the asymmetry in the inner disk annihilation line flux, which has been suggested as added evidence for new sources, can also be fully understood from positron propagation and the asymmetry in the inner spiral arms as viewed from our solar perspective without any additional sources.« less

Account of the intratrack radiolytic processes for interpretation of the AMOC spectrum of liquid water

NASA Astrophysics Data System (ADS)

Zvezhinskiy, D. S.; Butterling, M.; Wagner, A.; Krause-Rehberg, R.; Stepanov, S. V.

2013-06-01

Recent development of the Gamma-induced Positron Spectroscopy (GiPS) setup significantly extends applicability of the Age-Momentum Correlation technique (AMOC) for studies of the bulk samples. It also provides many advantages comparing with conventional positron annihilation experiments in liquids, such as extremely low annihilation fraction in vessel walls, absence of a positron source and positron annihilations in it. We have developed a new approach for processing and interpretation of the AMOC-GiPS data based on the diffusion recombination model of the intratrack radiolytic processes. This approach is verified in case of liquid water, which is considered as a reference medium in the positron and positronium chemistry.

Duoplasmatron source modifications for 3He+ operation

NASA Astrophysics Data System (ADS)

Schmidt, C. W.; Popovic, M.

1998-02-01

A duoplasmatron ion source is used to produce 25 mA of 3He+ with a pulse width of ˜80 ms at 360 Hz for acceleration to 10.5 MeV. At this energy, 3He striking water or carbon targets can produce short lived isotopes of 11C, 13N, 15O, and 18F for medical positron emission tomography (PET). A duoplasmatron ion source was chosen originally since it is capable of a sufficient singly charged helium beam with an acceptable gas consumption. Stable long-term operation of the source required a change in the filament material to molybdenum, and a careful understanding of the oxide filament conditioning, operation and geometry. Other improvements, particularly in the electronics, were helpful to increasing the reliability. The source has operated for many months at ˜2.5% duty factor without significant problems and with good stability. We report here the effort that was done to make this source understandable and reliable.

Gamma rays from pulsar wind shock acceleration

NASA Technical Reports Server (NTRS)

Harding, Alice K.

1990-01-01

A shock forming in the wind of relativistic electron-positron pairs from a pulsar, as a result of confinement by surrounding material, could convert part of the pulsar spin-down luminosity to high energy particles through first order Fermi acceleration. High energy protons could be produced by this mechanism both in supernova remnants and in binary systems containing pulsars. The pion-decay gamma-rays resulting from interaction of accelerated protons with surrounding target material in such sources might be observable above 70 MeV with EGRET (Energetic Gamma-Ray Experimental Telescope) and above 100 GeV with ground-based detectors. Acceleration of protons and expected gamma-ray fluxes from SN1987A, Cyg X-3 type sources and binary pulsars are discussed.

Cosmic Ray Positrons from Pulsars

NASA Technical Reports Server (NTRS)

Harding, Alice K.

2010-01-01

Pulsars are potential Galactic sources of positrons through pair cascades in their magnetospheres. There are, however, many uncertainties in establishing their contribution to the local primary positron flux. Among these are the local density of pulsars, the cascade pair multiplicities that determine the injection rate of positrons from the pulsar, the acceleration of the injected particles by the pulsar wind termination shock, their rate of escape from the pulsar wind nebula, and their propagation through the interstellar medium. I will discuss these issues in the context of what we are learning from the new Fermi pulsar detections and discoveries.

Characterization of a transmission positron/positronium converter for antihydrogen production

NASA Astrophysics Data System (ADS)

Aghion, S.; Amsler, C.; Ariga, T.; Bonomi, G.; Brusa, R. S.; Caccia, M.; Caravita, R.; Castelli, F.; Cerchiari, G.; Comparat, D.; Consolati, G.; Demetrio, A.; Di Noto, L.; Doser, M.; Ereditato, A.; Evans, C.; Ferragut, R.; Fesel, J.; Fontana, A.; Gerber, S.; Giammarchi, M.; Gligorova, A.; Guatieri, F.; Haider, S.; Hinterberger, A.; Holmestad, H.; Kellerbauer, A.; Krasnický, D.; Lagomarsino, V.; Lansonneur, P.; Lebrun, P.; Malbrunot, C.; Mariazzi, S.; Matveev, V.; Mazzotta, Z.; Müller, S. R.; Nebbia, G.; Nedelec, P.; Oberthaler, M.; Pacifico, N.; Pagano, D.; Penasa, L.; Petracek, V.; Povolo, L.; Prelz, F.; Prevedelli, M.; Ravelli, L.; Resch, L.; Rienäcker, B.; Robert, J.; Røhne, O. M.; Rotondi, A.; Sacerdoti, M.; Sandaker, H.; Santoro, R.; Scampoli, P.; Simon, M.; Smestad, L.; Sorrentino, F.; Testera, G.; Tietje, I. C.; Widmann, E.; Yzombard, P.; Zimmer, C.; Zmeskal, J.; Zurlo, N.; Andersen, S. L.; Chevallier, J.; Uggerhøj, U. I.; Lyckegaard, F.

2017-09-01

In this work a characterization study of forward emission from a thin, meso-structured silica positron/positronium (Ps) converter following implantation of positrons in light of possible antihydrogen production is presented. The target consisted of a ∼1 μm thick ultraporous silica film e-gun evaporated onto a 20 nm carbon foil. The Ps formation and emission was studied via Single Shot Positron Annihilation Lifetime Spectroscopy measurements after implantation of pulses with 3 - 4 ·107 positrons and 10 ns temporal width. The forward emission of implanted positrons and secondary electrons was investigated with a micro-channel plate - phosphor screen assembly, connected either to a CCD camera for imaging of the impinging particles, or to a fast photomultiplier tube to extract information about their time of flight. The maximum Ps formation fraction was estimated to be ∼10%. At least 10% of the positrons implanted with an energy of 3.3 keV are forward-emitted with a scattering angle smaller than 50° and maximum kinetic energy of 1.2 keV. At least 0.1-0.2 secondary electrons per implanted positron were also found to be forward-emitted with a kinetic energy of a few eV. The possible application of this kind of positron/positronium converter for antihydrogen production is discussed.

Positron annihilation lifetime measurements of austenitic stainless and ferritic/martensitic steels irradiated in the SINQ target irradiation program

NASA Astrophysics Data System (ADS)

Sato, K.; Xu, Q.; Yoshiie, T.; Dai, Y.; Kikuchi, K.

2012-12-01

Titanium-doped austenitic stainless steel (JPCA) and reduced activated ferritic/martensitic steel (F82H) irradiated with high-energy protons and spallation neutrons were investigated by positron annihilation lifetime measurements. Subnanometer-sized (<˜0.8 nm) helium bubbles, which cannot be observed by transmission electron microscopy, were detected by positron annihilation lifetime measurements for the first time. For the F82H steel, the positron annihilation lifetime of the bubbles decreased with increasing irradiation dose and annealing temperature because the bubbles absorb additional He atoms. In the case of JPCA steel, the positron annihilation lifetime increased with increasing annealing temperature above 773 K, in which case the dissociation of complexes of vacancy clusters with He atoms and the growth of He bubbles was detected. He bubble size and density were also discussed.

Development of a Simple Positron Age-Momentum Setup

NASA Astrophysics Data System (ADS)

Sheffield, Thomas; Quarles, C. A.

2009-04-01

A positron age-momentum setup that uses NIM Bin electronic modules and a conventional multichannel analyzer (MCA) is described. The essential idea is to accumulate a Doppler broadened spectrum (sensitive to the annihilation electron momentum) using a high purity Germanium detector in coincidence with a BaF2 scintillation counter, which also serves as the stop signal in a conventional positron lifetime setup. The MCA that collects the Doppler spectrum is gated by a selected region of the lifetime spectrum. Thus we can obtain Doppler broadening spectra as a function of positron lifetime: an age-momentum spectrum. The apparatus has been used so far to investigate a ZnO sample where the size of different vacancy trapping sites may affect the positron lifetime and the Doppler broadening spectrum. We are also looking at polymer and rubber carbon-black composite samples where differences in the Doppler spectrum may arise from positron trapping or positronium formation in the samples. Correction for background and contribution from the positron source itself to the Doppler spectrum will be discussed.

CIRCULAR POLARIZATION OF PULSAR WIND NEBULAE AND THE COSMIC-RAY POSITRON EXCESS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Linden, Tim, E-mail: trlinden@uchicago.edu

2015-02-01

Recent observations by the PAMELA and AMS-02 telescopes have uncovered an anomalous rise in the positron fraction at energies above 10 GeV. One possible explanation for this excess is the production of primary electron/positron pairs through electromagnetic cascades in pulsar magnetospheres. This process results in a high multiplicity of electron/positron pairs within the wind-termination shock of pulsar wind nebulae (PWNe). A consequence of this scenario is that no circular polarization should be observed within PWNe, since the contributions from electrons and positrons exactly cancel. Here we note that current radio instruments are capable of setting meaningful limits on the circular polarizationmore » of synchrotron radiation in PWNe, which observationally test the model for pulsar production of the local positron excess. The observation of a PWN with detectable circular polarization would cast strong doubt on pulsar interpretations of the positron excess, while observations setting strong limits on the circular polarization of PWNe would lend credence to these models. Finally, we indicate which PWNe are likely to provide the best targets for observational tests of the AMS-02 excess.« less

Apparatus for the analysis of surfaces in gas environments using Positron Spectroscopy

NASA Astrophysics Data System (ADS)

Satyal, Suman; Lim, Lawrence; Joglekar, Vibek; Kalaskar, Sushant; Shastry, Karthik; Weiss, Alex

2010-10-01

Positron spectroscopy performed with low energy beams can provide highly surface specific information due to the trapping of positrons in an image potential surface state at the time of annihilation. Here we describe a spectrometer that will employ differential pumping to enable us to transport the positrons most of the way from the source to the sample under high vacuum and then to traverse a thin gas layer surrounding the sample. The positrons will be implanted into the sample at energies less than ˜10 keV ensuring that a large fraction will diffuse back to the surface before annihilation. The Elemental content of the surface interacting with the gas environment will then be determined from the Doppler broadened gamma spectra. This system will include a time of flight positron annihilation induced Auger spectrometer (TOF-PAES) which correlates with the Doppler measurements at lower pressures.

Origin of the positron excess in cosmic rays.

PubMed

Blasi, Pasquale

2009-07-31

We show that the positron excess measured by the PAMELA experiment in the region between 10 and 100 GeV may well be a natural consequence of the standard scenario for the origin of Galactic cosmic rays. The "excess" arises because of positrons created as secondary products of hadronic interactions inside the sources, but the crucial physical ingredient which leads to a natural explanation of the positron flux is the fact that the secondary production takes place in the same region where cosmic rays are being accelerated. Therefore secondary positrons (and electrons) participate in the acceleration process and turn out to have a very flat spectrum, which is responsible, after propagation in the Galaxy, for the observed positron excess. This effect cannot be avoided though its strength depends on the values of the environmental parameters during the late stages of evolution of supernova remnants.

Radiolabelling and positron emission tomography of PT70, a time-dependent inhibitor of InhA, the Mycobacterium tuberculosis enoyl-ACP reductase

DOE PAGES

Wang, Hui; Liu, Li; Lu, Yang; ...

2015-07-14

PT70 is a diaryl ether inhibitor of InhA, the enoyl-ACP reductase in the Mycobacterium tuberculosis fatty acid biosynthesis pathway. It has a residence time of 24 min on the target, and also shows antibacterial activity in a mouse model of tuberculosis infection. Due to the interest in studying target tissue pharmacokinetics of PT70, we developed a method to radiolabel PT70 with carbon-11 and have studied its pharmacokinetics in mice and baboons using positron emission tomography.

Radiolabelling and positron emission tomography of PT70, a time-dependent inhibitor of InhA, the Mycobacterium tuberculosis enoyl-ACP reductase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hui; Liu, Li; Lu, Yang

PT70 is a diaryl ether inhibitor of InhA, the enoyl-ACP reductase in the Mycobacterium tuberculosis fatty acid biosynthesis pathway. It has a residence time of 24 min on the target, and also shows antibacterial activity in a mouse model of tuberculosis infection. Due to the interest in studying target tissue pharmacokinetics of PT70, we developed a method to radiolabel PT70 with carbon-11 and have studied its pharmacokinetics in mice and baboons using positron emission tomography.

Search for Cosmic-Ray Electron and Positron Anisotropies with Seven Years of Fermi Large Area Telescope Data.

PubMed

Abdollahi, S; Ackermann, M; Ajello, M; Albert, A; Atwood, W B; Baldini, L; Barbiellini, G; Bellazzini, R; Bissaldi, E; Bloom, E D; Bonino, R; Bottacini, E; Brandt, T J; Bruel, P; Buson, S; Caragiulo, M; Cavazzuti, E; Chekhtman, A; Ciprini, S; Costanza, F; Cuoco, A; Cutini, S; D'Ammando, F; de Palma, F; Desiante, R; Digel, S W; Di Lalla, N; Di Mauro, M; Di Venere, L; Donaggio, B; Drell, P S; Favuzzi, C; Focke, W B; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Giglietto, N; Giordano, F; Giroletti, M; Green, D; Guiriec, S; Harding, A K; Jogler, T; Jóhannesson, G; Kamae, T; Kuss, M; Larsson, S; Latronico, L; Li, J; Longo, F; Loparco, F; Lubrano, P; Magill, J D; Malyshev, D; Manfreda, A; Mazziotta, M N; Meehan, M; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monzani, M E; Morselli, A; Negro, M; Nuss, E; Ohsugi, T; Omodei, N; Paneque, D; Perkins, J S; Pesce-Rollins, M; Piron, F; Pivato, G; Principe, G; Rainò, S; Rando, R; Razzano, M; Reimer, A; Reimer, O; Sgrò, C; Simone, D; Siskind, E J; Spada, F; Spandre, G; Spinelli, P; Strong, A W; Tajima, H; Thayer, J B; Torres, D F; Troja, E; Vandenbroucke, J; Zaharijas, G; Zimmer, S

2017-03-03

The Large Area Telescope on board the Fermi Gamma-ray Space Telescope has collected the largest ever sample of high-energy cosmic-ray electron and positron events since the beginning of its operation. Potential anisotropies in the arrival directions of cosmic-ray electrons or positrons could be a signature of the presence of nearby sources. We use almost seven years of data with energies above 42 GeV processed with the Pass 8 reconstruction. The present data sample can probe dipole anisotropies down to a level of 10^{-3}. We take into account systematic effects that could mimic true anisotropies at this level. We present a detailed study of the event selection optimization of the cosmic-ray electrons and positrons to be used for anisotropy searches. Since no significant anisotropies have been detected on any angular scale, we present upper limits on the dipole anisotropy. The present constraints are among the strongest to date probing the presence of nearby young and middle-aged sources.

Positron production by x rays emitted by betatron motion in a plasma wiggler.

PubMed

Johnson, D K; Auerbach, D; Blumenfeld, I; Barnes, C D; Clayton, C E; Decker, F J; Deng, S; Emma, P; Hogan, M J; Huang, C; Ischebeck, R; Iverson, R; Joshi, C; Katsouleas, T C; Kirby, N; Krejcik, P; Lu, W; Marsh, K A; Mori, W B; Muggli, P; O'Connell, C L; Oz, E; Siemann, R H; Walz, D; Zhou, M

2006-10-27

Positrons in the energy range of 3-30 MeV, produced by x rays emitted by betatron motion in a plasma wiggler of 28.5 GeV electrons from the SLAC accelerator, have been measured. The extremely high-strength plasma wiggler is an ion column induced by the electron beam as it propagates through and ionizes dense lithium vapor. X rays in the range of 1-50 MeV in a forward cone angle of 0.1 mrad collide with a 1.7 mm thick tungsten target to produce electron-positron pairs. The positron spectra are found to be strongly influenced by the plasma density and length as well as the electron bunch length. By characterizing the beam propagation in the ion column these influences are quantified and result in excellent agreement between the measured and calculated positron spectra.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zammit, Mark C.; Fursa, Dmitry V.; Savage, Jeremy S.

Starting from first principles, this tutorial describes the development of the adiabatic-nuclei convergent close-coupling (CCC) method and its application to electron and (single-centre) positron scattering from diatomic molecules. In this paper, we give full details of the single-centre expansion CCC method, namely the formulation of the molecular target structure; solving the momentum-space coupled-channel Lippmann-Schwinger equation; deriving adiabatic-nuclei cross sections and calculatingmore » $V$-matrix elements. Selected results are presented for electron and positron scattering from molecular hydrogen H$$_2$$ and electron scattering from the vibrationally excited molecular hydrogen ion H$$_2^+$$ and its isotopologues (D$$_2^+$$, T$$_2^+$$, HD$^+$, HT$^+$ and TD$^+$). Finally, convergence in both the close-coupling (target state) and projectile partial-wave expansions of fixed-nuclei electron- and positron-molecule scattering calculations is demonstrated over a broad energy-range and discussed in detail. In general the CCC results are in good agreement with experiments.« less

High-temperature studies of grain boundaries in ultrafine grained alloys by means of positron lifetime

NASA Astrophysics Data System (ADS)

Würschum, R.; Shapiro, E.; Dittmar, R.; Schaefer, H.-E.

2000-11-01

Atomic free volumes and vacancies in the ultrafine grained alloys Pd84Zr16, Cu 0.1 wt % ZrO2, and Fe91Zr9 were studied by means of positron lifetime. The thermally stable microstructures serve as a novel type of model system for studying positron trapping and annihilation as well as the thermal behavior of vacancy-sized free volumes over a wide temperature range up to ca. 1200 K by making use of a metallic 58Co positron source. In ultrafine grained Cu the thermal formation of lattice vacancies could be observed. In Pd84Zr16 an increase of the specific positron trapping rate of nanovoids and, in addition, detrapping of positrons from free volumes with a mean size slightly smaller than one missing atom in the grain boundaries contributes to a reversible increase of the positron lifetime of more than 60 ps with measuring temperature. In Fe91Zr9 similar linear high-temperature increases of the positron lifetime are observed in the nanocrystalline and the amorphous state. The question of thermal vacancy formation in grain boundaries is addressed taking into account the different types of interface structures of the present alloys.

The multi-scattering model for calculations of positron spatial distribution in the multilayer stacks, useful for conventional positron measurements

NASA Astrophysics Data System (ADS)

Dryzek, Jerzy; Siemek, Krzysztof

2013-08-01

The spatial distribution of positrons emitted from radioactive isotopes into stacks or layered samples is a subject of the presented report. It was found that Monte Carlo (MC) simulations using GEANT4 code are not able to describe correctly the experimental data of the positron fractions in stacks. The mathematical model was proposed for calculations of the implantation profile or positron fractions in separated layers or foils being components of a stack. The model takes into account only two processes, i.e., the positron absorption and backscattering at interfaces. The mathematical formulas were applied in the computer program called LYS-1 (layers profile analysis). The theoretical predictions of the model were in the good agreement with the results of the MC simulations for the semi infinite sample. The experimental verifications of the model were performed on the symmetrical and non-symmetrical stacks of different foils. The good agreement between the experimental and calculated fractions of positrons in components of a stack was achieved. Also the experimental implantation profile obtained using the depth scanning of positron implantation technique is very well described by the theoretical profile obtained within the proposed model. The LYS-1 program allows us also to calculate the fraction of positrons which annihilate in the source, which can be useful in the positron spectroscopy.

PET/CT alignment calibration with a non-radioactive phantom and the intrinsic 176Lu radiation of PET detector

NASA Astrophysics Data System (ADS)

Wei, Qingyang; Ma, Tianyu; Wang, Shi; Liu, Yaqiang; Gu, Yu; Dai, Tiantian

2016-11-01

Positron emission tomography/computed tomography (PET/CT) is an important tool for clinical studies and pre-clinical researches which provides both functional and anatomical images. To achieve high quality co-registered PET/CT images, alignment calibration of PET and CT scanner is a critical procedure. The existing methods reported use positron source phantoms imaged both by PET and CT scanner and then derive the transformation matrix from the reconstructed images of the two modalities. In this paper, a novel PET/CT alignment calibration method with a non-radioactive phantom and the intrinsic 176Lu radiation of the PET detector was developed. Firstly, a multi-tungsten-alloy-sphere phantom without positron source was designed and imaged by CT and the PET scanner using intrinsic 176Lu radiation included in LYSO. Secondly, the centroids of the spheres were derived and matched by an automatic program. Lastly, the rotation matrix and the translation vector were calculated by least-square fitting of the centroid data. The proposed method was employed in an animal PET/CT system (InliView-3000) developed in our lab. Experimental results showed that the proposed method achieves high accuracy and is feasible to replace the conventional positron source based methods.

Positron annihilation spectroscopy techniques applied to the study of an HPGe detector

NASA Astrophysics Data System (ADS)

Nascimento, E. do; Vanin, V. R.; Maidana, N. L.; Silva, T. F.; Rizzutto, M. A.; Fernández-Varea, J. M.

2013-05-01

Doppler Broadening Spectroscopy of the large Ge crystal of an HPGe detector was performed using positrons from pair production of 6.13 MeV γ-rays from the 19F(p,αγ)16O reaction. Two HPGe detectors facing opposite sides of the Ge crystal acting as target provided both coincidence and singles spectra. Changes in the shape of the annihilation peak were observed when the high voltage applied to the target detector was switched on or off, amounting to somewhat less than 20% when the areas of equivalent energy intervals in the corresponding normalized spectra are compared.

Experimental Verification of Predicted Oscillations near a Spin Resonance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kolanoski, Hermann; /Humboldt U., Berlin

2011-12-05

The E166 experiment at the Stanford Linear Accelerator Center (SLAC) has demonstrated a scheme for the production of polarized positrons which is suitable for implementation in a future Linear Collider. A multi-GeV electron beam passed through a helical undulator to generate multi-MeV, circularly polarized photons which were then converted in a thin target to produce positrons (and electrons) with longitudinal polarization above 80% at 6 MeV. The results are in agreement with GEANT4 simulations that include the dominant polarization-dependent interactions of electrons, positrons and photons in matter.

PET imaging for receptor occupancy: meditations on calculation and simplification.

PubMed

Zhang, Yumin; Fox, Gerard B

2012-03-01

This invited mini-review briefly summarizes procedures and challenges of measuring receptor occupancy with positron emission tomography. Instead of describing the detailed analytic procedures of in vivo ligand-receptor imaging, the authors provide a pragmatic approach, along with personal perspectives, for conducting positron emission tomography imaging for receptor occupancy, and systematically elucidate the mathematics of receptor occupancy calculations in practical ways that can be understood with elementary algebra. The authors also share insights regarding positron emission tomography imaging for receptor occupancy to facilitate applications for the development of drugs targeting receptors in the central nervous system.

PET imaging for receptor occupancy: meditations on calculation and simplification

PubMed Central

Zhang, Yumin; Fox, Gerard B.

2012-01-01

This invited mini-review briefly summarizes procedures and challenges of measuring receptor occupancy with positron emission tomography. Instead of describing the detailed analytic procedures of in vivo ligand-receptor imaging, the authors provide a pragmatic approach, along with personal perspectives, for conducting positron emission tomography imaging for receptor occupancy, and systematically elucidate the mathematics of receptor occupancy calculations in practical ways that can be understood with elementary algebra. The authors also share insights regarding positron emission tomography imaging for receptor occupancy to facilitate applications for the development of drugs targeting receptors in the central nervous system. PMID:23554733

Rapid production of positron emitting labeled compounds for use in cardiology PET studies

NASA Astrophysics Data System (ADS)

Bolomey, Leonard

1985-05-01

Large scale clinical application of positron emission tomography requires a variety of short-lived positron emitting radionuclides to be produced in Curie quantities up to 20 times per day. Rapid routine production of these radiopharmaceuticals requires the collaboration of engineers and chemists to achieve production targetry compatible with high beam current (up to 100 μA) and radionuclide production in a chemical form compatible with the rapid radiochemical synthesis. Chemical processing is further complicated by the need to repeat the procedures several times per day and maintain sterility within the shielded area. At our cyclotron facility primary production targets for 11C, 13N, 15O, and 18F (half lives from 2 min to 2 h) are mounted on a vertical gantr that indexes to position the required target on the beam line. Target changes are handled under microprocessor control remotely from the control room such that all valves, cooling, evacuation of target manifold, and testing of interlocks are handled automatically. This system enables us to change targets, energy and particles in less than five minutes. Since the installation of the cyclotron up to fifteen batches of routine radiopharmaceuticals have been produced per day with very low radiation doses to all personnel involved. These radiopharmaceuticals will be used to measure perfusion, metabolism and other biochemical functions in man non invasively with PET.

The Effect of Magnetic Field on Positron Range and Spatial Resolution in an Integrated Whole-Body Time-Of-Flight PET/MRI System.

PubMed

Huang, Shih-Ying; Savic, Dragana; Yang, Jaewon; Shrestha, Uttam; Seo, Youngho

2014-11-01

Simultaneous imaging systems combining positron emission tomography (PET) and magnetic resonance imaging (MRI) have been actively investigated. A PET/MR imaging system (GE Healthcare) comprised of a time-of-flight (TOF) PET system utilizing silicon photomultipliers (SiPMs) and 3-tesla (3T) MRI was recently installed at our institution. The small-ring (60 cm diameter) TOF PET subsystem of this PET/MRI system can generate images with higher spatial resolution compared with conventional PET systems. We have examined theoretically and experimentally the effect of uniform magnetic fields on the spatial resolution for high-energy positron emitters. Positron emitters including 18 F, 124 I, and 68 Ga were simulated in water using the Geant4 Monte Carlo toolkit in the presence of a uniform magnetic field (0, 3, and 7 Tesla). The positron annihilation position was tracked to determine the 3D spatial distribution of the 511-keV gammy ray emission. The full-width at tenth maximum (FWTM) of the positron point spread function (PSF) was determined. Experimentally, 18 F and 68 Ga line source phantoms in air and water were imaged with an investigational PET/MRI system and a PET/CT system to investigate the effect of magnetic field on the spatial resolution of PET. The full-width half maximum (FWHM) of the line spread function (LSF) from the line source was determined as the system spatial resolution. Simulations and experimental results show that the in-plane spatial resolution was slightly improved at field strength as low as 3 Tesla, especially when resolving signal from high-energy positron emitters in the air-tissue boundary.

The magnetic toroidal sector: a broad-band electron-positron pair spectrometer

NASA Astrophysics Data System (ADS)

Hagmann, Siegbert; Hillenbrand, Pierre-Michel; Litvinov, Yuri; Spillmann, Uwe

2016-05-01

At the future relativistic storage-ring HESR at FAIR the study of electron-positron pairs from non-nuclear, atomic processes will be one of the goals of the experimental program with kinematically complete experiments focusing on momentum spectroscopy of coincident emission of electrons and positrons from free-free pairs and corresponding recoil ions. The underlying production mechanisms belong to central topics of QED in strong fields. We present first results on the electron-optical properties of a magnetic toroidal sector configuration enabling coincident detection of free-free electron-positron pairs; this spectrometer is suitable for implementation into a storage ring with a supersonic jet target and covering a wide range of lepton emission into the forward hemisphere. The simulation calculations are performed using the OPERA code.

Search for Cosmic-Ray Electron and Positron Anisotropies with Seven Years of Fermi Large Area Telescope Data

DOE PAGES

Abdollahi, S.; Ackermann, M.; Ajello, M.; ...

2017-03-01

We present the Large Area Telescope on board the Fermi Gamma-ray Space Telescope that has collected the largest ever sample of high-energy cosmic-ray electron and positron events since the beginning of its operation. Potential anisotropies in the arrival directions of cosmic-ray electrons or positrons could be a signature of the presence of nearby sources. We use almost seven years of data with energies above 42 GeV processed with the Pass 8 reconstruction. The present data sample can probe dipole anisotropies down to a level of 10 -3. We take into account systematic effects that could mimic true anisotropies at thismore » level. We present a detailed study of the event selection optimization of the cosmic-ray electrons and positrons to be used for anisotropy searches. Since no significant anisotropies have been detected on any angular scale, we present upper limits on the dipole anisotropy. Lastly, the present constraints are among the strongest to date probing the presence of nearby young and middle-aged sources.« less

Electrons in a closed galaxy model of cosmic rays

NASA Technical Reports Server (NTRS)

Ramaty, R.; Westergaard, N. J.

1976-01-01

The consistency of positrons and electrons was studied using a propagation model in which the cosmic rays are stopped by nuclear collisions or energy losses before they can escape from the galaxy (the closed-galaxy model). The fact that no inconsistency was found between the predictions and the data implies that the protons which produce the positrons by nuclear reactions could have their origin in a large number of distant sources, as opposed to the heavier nuclei which in this model come from a more limited set of sources. The closed-galaxy model predicts steep electron and positron spectra at high energies. None of these are inconsistent with present measurements; but future measurements of the spectrum of high-energy positrons could provide a definite test for the model. The closed-galaxy model also predicts that the interstellar electron intensity below a few GeV is larger than that implied by other models. The consequence of this result is that electron bremsstrahlung is responsible for about 50% of the galactic gamma-ray emission at photon energies greater than 100 MeV.

NLC Injector Systems

Science.gov Websites

text only NLC Home Page NLC Technical SLAC Sources Damping Rings S & L Band Linacs Engineering ; Presentations Injector System Documentation Talks and Presentations The NLC ZDR ISG Reports Sources Lasers Photocathodes Electron Source Laser Maintenance Facility Positron Source Sources Technical Notes Sources Meeting

Positron kinetics in an idealized PET environment

PubMed Central

Robson, R. E.; Brunger, M. J.; Buckman, S. J.; Garcia, G.; Petrović, Z. Lj.; White, R. D.

2015-01-01

The kinetic theory of non-relativistic positrons in an idealized positron emission tomography PET environment is developed by solving the Boltzmann equation, allowing for coherent and incoherent elastic, inelastic, ionizing and annihilating collisions through positronium formation. An analytic expression is obtained for the positronium formation rate, as a function of distance from a spherical source, in terms of the solutions of the general kinetic eigenvalue problem. Numerical estimates of the positron range - a fundamental limitation on the accuracy of PET, are given for positrons in a model of liquid water, a surrogate for human tissue. Comparisons are made with the ‘gas-phase’ assumption used in current models in which coherent scattering is suppressed. Our results show that this assumption leads to an error of the order of a factor of approximately 2, emphasizing the need to accurately account for the structure of the medium in PET simulations. PMID:26246002

High-resolution Auger-electron spectroscopy induced by positron annihilation on Fe, Ni, Cu, Zn, Pd, and Au

NASA Astrophysics Data System (ADS)

Hugenschmidt, C.; Mayer, J.; Schreckenbach, K.

2010-04-01

Positron annihilation induced Auger electron spectroscopy (PAES) enables almost background free, non-destructive surface analysis with high surface selectivity. The Auger-spectrometer at the high intense positron source NEPOMUC now allows to record positron annihilation induced Auger spectra within a short data acquisition time of 10-80 minutes. With a new hemispherical electron energy analyzer and due to the exceptional peak to noise ratio, we succeeded to measure Auger-transitions such as the M2,3V V double peak of nickel with high energy resolution. The relative Auger-electron intensities are obtained by the analysis of the recorded positron annihilation induced Auger spectra for the surfaces of Fe, Ni, Cu, Pd and Au. It is demonstrated, that high-resolution PAES allows to determine experimentally the relative surface core annihilation probability of various atomic levels.

High-field penning-malmberg trap: confinement properties and use in positron accumulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hartley, J.H.

1997-09-01

This dissertation reports on the development of the 60 kG cryogenic positron trap at Lawrence Livermore National Laboratory, and compares the trap`s confinement properties with other nonneutral plasma devices. The device is designed for the accumulation of up to 2{times}10{sup 9} positrons from a linear-accelerator source. This positron plasma could then be used in Bhabha scattering experiments. Initial efforts at time-of-flight accumulation of positrons from the accelerator show rapid ({approximately}100 ms) deconfinement, inconsistent with the long electron lifetimes. Several possible deconfinement mechanisms have been explored, including annihilation on residual gas, injection heating, rf noise from the accelerator, magnet field curvature,more » and stray fields. Detailed studies of electron confinement demonstrate that the empirical scaling law used to design the trap cannot be extrapolated into the parameter regime of this device. Several possible methods for overcoming these limitations are presented.« less

Nonlinear excitations for the positron acoustic shock waves in dissipative nonextensive electron-positron-ion plasmas

NASA Astrophysics Data System (ADS)

Saha, Asit

2017-03-01

Positron acoustic shock waves (PASHWs) in unmagnetized electron-positron-ion (e-p-i) plasmas consisting of mobile cold positrons, immobile positive ions, q-nonextensive distributed electrons, and hot positrons are studied. The cold positron kinematic viscosity is considered and the reductive perturbation technique is used to derive the Burgers equation. Applying traveling wave transformation, the Burgers equation is transformed to a one dimensional dynamical system. All possible vector fields corresponding to the dynamical system are presented. We have analyzed the dynamical system with the help of potential energy, which helps to identify the stability and instability of the equilibrium points. It is found that the viscous force acting on cold mobile positron fluid is a source of dissipation and is responsible for the formation of the PASHWs. Furthermore, fully nonlinear arbitrary amplitude positron acoustic waves are also studied applying the theory of planar dynamical systems. It is also observed that the fundamental features of the small amplitude and arbitrary amplitude PASHWs are significantly affected by the effect of the physical parameters q e , q h , μ e , μ h , σ , η , and U. This work can be useful to understand the qualitative changes in the dynamics of nonlinear small amplitude and fully nonlinear arbitrary amplitude PASHWs in solar wind, ionosphere, lower part of magnetosphere, and auroral acceleration regions.

X-ray flares from runaway pair production in active galactic nuclei

NASA Technical Reports Server (NTRS)

Kirk, J. G.; Mastichiadis, A.

1992-01-01

The hard X-ray spectrum of AGNs is nonthermal, probably arising from an electron-positron pair cascade, with some emission reflected off relatively cold matter. There has been interest in models on which protons are accelerated and create relativistic electrons on interaction with a local radiation field. It is shown here that a sufficient column density of protons can lead to runaway pair production: photons generated by the relativistic pairs are the targets for the protons to produce more pairs. This can produce X-ray fluxes with the characteristics observed in AGN. The model predicts the maximum ratio of luminosity to source size as well as their spectrum in the early phases. The same mechanism may also be able to create the knots of synchrotron-radiating pair plasma seen in sources such as 3C273.

A Brief Review of Caprylidene (Axona) and Coconut Oil as Alternative Fuels in the Fight Against Alzheimer's Disease.

PubMed

Chintapenta, Monica; Spence, Justin; Kwon, Hyanggi Irene; Blaszczyk, Amie Taggart

2017-12-01

Type 3 diabetes mellitus has been coined to describe an alternative pathologic pathway of Alzheimer's disease (AD). The insulin resistance and impaired insulin signaling seen on positron-emission tomography scans in the brain of those affected by AD support this disease hypothesis. Two products-the medical food caprylidene (Axona) and coconut oil-seek to target the underlying pathology of type 3 diabetes mellitus by providing an alternative fuel source in the brain. Rather than improving glucose utilization, these two products seek to supply ketone bodies in sufficient quantities to pass through the blood-brain barrier and provide an alternative energy source to glucose. This review will provide an overview of the research behind these two modalities, as well as information necessary to ensure the safe use of these supplements.

Instrumentation for the study of low emittance tuning and beam dynamics at CESR

NASA Astrophysics Data System (ADS)

Billing, M. G.; Dobbins, J. A.; Forster, M. J.; Kreinick, D. L.; Meller, R. E.; Peterson, D. P.; Ramirez, G. A.; Rendina, M. C.; Rider, N. T.; Sagan, D. C.; Shanks, J.; Sikora, J. P.; Stedinger, M. G.; Strohman, C. R.; Williams, H. A.; Palmer, M. A.; Holtzapple, R. L.; Flanagan, J.

2017-11-01

The Cornell Electron-positron Storage Ring (CESR) has been converted from a High Energy Physics electron-positron collider to operate as a dedicated synchrotron light source for the Cornell High Energy Synchrotron Source (CHESS) and to conduct accelerator physics research as a test accelerator, capable of studying topics relevant to future damping rings, colliders and light sources. Some of the specific topics that were targeted for the initial phase of operation of the storage ring in this mode for CESR as a Test Accelerator (CesrTA) included 1) tuning techniques to produce low emittance beams, 2) the study of electron cloud development in a storage ring and 3) intra-beam scattering effects. The complete conversion of CESR to CesrTA occurred over a several year period, described elsewhere [1-3]. In addition to instrumentation for the storage ring, which was created for CesrTA, existing instrumentation was modified to facilitate the entire range of investigations to support these studies. Procedures were developed, often requiring coordinated measurements among different instruments [4]. This paper describes the instruments utilized for the study of beam dynamics during the operation of CesrTA. The treatment of these instruments will remain fairly general in this paper as it focusses on an overview of the instruments themselves. Their interaction and inter-relationships during sequences of observations is found in a companion paper describing the associated measurement techniques. More detailed descriptions and detailed operational performance for some of the instrumentation may be found elsewhere and these will be referenced in the related sections of this paper.

Ghost beams and the energy spectra of anomalous positrons

NASA Astrophysics Data System (ADS)

Fox, J. D.; Kemper, K. W.; Cottle, P. D.

1995-05-01

It is suggested that nuclear reactions induced by medium mass projectiles, with {A}/{q} close to that of the primary beam, could explain the anomalous positron-electron peaks observed in sub-barrier collisions of very heavy nuclei. The reactions result in prominent γ-rays which convert to e +e - pairs in material near the target. Possible experiments to examine this hypothesis are suggested.

Differential Cross Sections for Ionization of Argon by 1 keV Positron and Electron Impact

NASA Astrophysics Data System (ADS)

Gavin, J.; DuBois, R. D.; de Lucio, O. G.

2014-04-01

Differential information was generated by establishing coincidences and imposing conditions on data recorded for target ions, scattered projectiles, and ejected electrons, as a function of projectile energy loss and scattering angles; in order to describe the interaction between a positron (electron) 1 keV beam and a simple Ar jet. Single ionization triply differential cross section (TDCS) results exhibit two distinct regions (lobes) for which binary (events arising from 2-body interaction) and recoil (events which can only be produced by many-body interactions) interactions are associated. Results indicate that binary events are significantly larger for positron impact, in accordance with theoretical predictions. A similar feature is found for different energy losses and scattering angles. Intensity of the recoil lobe for both projectiles, positron and electron, is observed to depend on the energy loss and scattering angle. Also, it can be noticed that for positron impact the recoil interactions intensity is larger than that observed for electron impact.

About cosmic gamma ray lines

NASA Astrophysics Data System (ADS)

Diehl, Roland

2017-06-01

Gamma ray lines from cosmic sources convey the action of nuclear reactions in cosmic sites and their impacts on astrophysical objects. Gamma rays at characteristic energies result from nuclear transitions following radioactive decays or high-energy collisions with excitation of nuclei. The gamma-ray line from the annihilation of positrons at 511 keV falls into the same energy window, although of different origin. We present here the concepts of cosmic gamma ray spectrometry and the corresponding instruments and missions, followed by a discussion of recent results and the challenges and open issues for the future. Among the lessons learned are the diffuse radioactive afterglow of massive-star nucleosynthesis in 26Al and 60Fe gamma rays, which is now being exploited towards the cycle of matter driven by massive stars and their supernovae; large interstellar cavities and superbubbles have been recognised to be of key importance here. Also, constraints on the complex processes making stars explode as either thermonuclear or core-collapse supernovae are being illuminated by gamma-ray lines, in this case from shortlived radioactivities from 56Ni and 44Ti decays. In particular, the three-dimensionality and asphericities that have recently been recognised as important are enlightened in different ways through such gamma-ray line spectroscopy. Finally, the distribution of positron annihilation gamma ray emission with its puzzling bulge-dominated intensity disctribution is measured through spatially-resolved spectra, which indicate that annihilation conditions may differ in different parts of our Galaxy. But it is now understood that a variety of sources may feed positrons into the interstellar medium, and their characteristics largely get lost during slowing down and propagation of positrons before annihilation; a recent microquasar flare was caught as an opportunity to see positrons annihilate at a source.

Positron emission tomography with [ 18F]-FDG in oncology

NASA Astrophysics Data System (ADS)

Talbot, J. N.; Petegnief, Y.; Kerrou, K.; Montravers, F.; Grahek, D.; Younsi, N.

2003-05-01

Positron Emission Tomography (PET) is a several decade old imaging technique that has more recently demonstrated its utility in clinical applications. The imaging agents used for PET contain a positron emmiter coupled to a molecule that drives the radionuclide to target organs or to tissues performing the targetted biological function. PET is then part of functional imaging. As compared to conventional scintigraphy that uses gamma photons, the coincidence emission of two 511 keV annihilation photons in opposite direction that finally results from by beta plus decay makes it possible for PET to get rid of the collimators that greatly contribute to the poor resolution of scintigraphy. In this article, the authors describe the basics of physics for PET imaging and report on the clinical performances of the most commonly used PET tracer: [ 18F]-fluorodeoxyglucose (FDG). A recent and promising development in this field is fusion of images coming from different imaging modalities. New PET machines now include a CT and this fusion is therefore much easier.

Electron– and positron–molecule scattering: development of the molecular convergent close-coupling method

DOE PAGES

Zammit, Mark C.; Fursa, Dmitry V.; Savage, Jeremy S.; ...

2017-05-22

Starting from first principles, this tutorial describes the development of the adiabatic-nuclei convergent close-coupling (CCC) method and its application to electron and (single-centre) positron scattering from diatomic molecules. In this paper, we give full details of the single-centre expansion CCC method, namely the formulation of the molecular target structure; solving the momentum-space coupled-channel Lippmann-Schwinger equation; deriving adiabatic-nuclei cross sections and calculatingmore » $V$-matrix elements. Selected results are presented for electron and positron scattering from molecular hydrogen H$$_2$$ and electron scattering from the vibrationally excited molecular hydrogen ion H$$_2^+$$ and its isotopologues (D$$_2^+$$, T$$_2^+$$, HD$^+$, HT$^+$ and TD$^+$). Finally, convergence in both the close-coupling (target state) and projectile partial-wave expansions of fixed-nuclei electron- and positron-molecule scattering calculations is demonstrated over a broad energy-range and discussed in detail. In general the CCC results are in good agreement with experiments.« less

New Baseline Design of the ILC RTML System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seletskiy, S.; Kapin, V. V.; Solyak, N.

2012-05-01

The new ILC baseline was proposed in 2009 (Strawman baseline - SB2009) to minimize cost of the machine and accommodate many changes made in the design of the accelerator systems. The biggest changes are made in the central area, where BDS, RTM L, DR, electron and positron sources are sharing the tunnels. A new layout of the compact DR and re-location of the electron and positron sources to the main tunnel requires a new lattice design for all beamlines in this area. The lattice design was coord inated between accelerator systems and Convention Facility and Siting (CFS) group to eliminatemore » conflicts between beamlines and satisfy construction requirements. In this paper we present a new design of the RTML electron and positron lattices in the centr al area and other modifications made in the RTML line to accommodate changes to the beamline layouts.« less

Ultra-bright γ-ray flashes and dense attosecond positron bunches from two counter-propagating laser pulses irradiating a micro-wire target.

PubMed

Li, Han-Zhen; Yu, Tong-Pu; Hu, Li-Xiang; Yin, Yan; Zou, De-Bin; Liu, Jian-Xun; Wang, Wei-Quan; Hu, Shun; Shao, Fu-Qiu

2017-09-04

We propose a novel scheme to generate ultra-bright ultra-short γ-ray flashes and high-energy-density attosecond positron bunches by using multi-dimensional particle-in-cell simulations with quantum electrodynamics effects incorporated. By irradiating a 10 PW laser pulse with an intensity of 10 23 W/cm 2 onto a micro-wire target, surface electrons are dragged-out of the micro-wire and are effectively accelerated to several GeV energies by the laser ponderomotive force, forming relativistic attosecond electron bunches. When these electrons interact with the probe pulse from the other side, ultra-short γ-ray flashes are emitted with an ultra-high peak brightness of 1.8 × 10 24 photons s -1 mm -2 mrad -2 per 0.1%BW at 24 MeV. These photons propagate with a low divergence and collide with the probe pulse, triggering the Breit-Wheeler process. Dense attosecond e - e + pair bunches are produced with the positron energy density as high as 10 17 J/m 3 and number of 10 9 . Such ultra-bright ultra-short γ-ray flashes and secondary positron beams may have potential applications in fundamental physics, high-energy-density physics, applied science and laboratory astrophysics.

Asymmetric 511 keV Positron Annihilation Line Emission from the Inner Galactic Disk

NASA Technical Reports Server (NTRS)

Skinner, Gerry; Weidenspointner, Georg; Jean, Pierre; Knodlseder, Jurgen; Ballmoos, Perer von; Bignami, Giovanni; Diehl, Roland; Strong, Andrew; Cordier, Bertrand; Schanne, Stephane;

Satellite Observations of Annihilation of Positrons Produced at the Sun, the Earth, and Center of our Galaxy

NASA Astrophysics Data System (ADS)

Share, G. H.; Murphy, R. J.; Lin, R. P.

2007-05-01

Positrons are created in nuclear interactions that produce β +-unstable nuclei and pi+ mesons. Satellites remotely observe positron production when they annihilate with electrons yielding the characteristic line at 511 keV. Radiation detectors such as the germanium diodes on the Ramaty High-Energy Solar Spectrocopic Imager (RHESSI) observe this line from positrons by nuclei activated in the spacecraft by proton interactions during transit through the Earth's radiation belts and from cosmic radiation. This forms an intense background for solar and astrophysical observations. RHESSI and other satellites have observed positron annihilation in over 50 solar flares. These measurements provide information on the temperature, density, and ionization state of solar atmosphere where the positrons annihilate. The measurements suggest that up to a few kg of positrons are produced in these flares. Detectable annihilation-line radiation is also emitted from the Earth's atmosphere in interactions of cosmic rays and solar energetic particles. An extended annihilation-line source has also been detected within about 10 degrees of the center of the Milky Way that is attributed to positrons released in radioactive decays of nuclei with long half-lives produced in supernovae, novae, and other stellar explosions. From 1980 to 1988 NASA's Solar Maximum Mission satellite also detected belts of positrons emitted by nuclear reactors onboard KOSMOS satellites and trapped temporarily in the Earth's magnetic field. This work was supported by NASA Supporting Research & Technology grants.

Evaluating the purity of a {sup 57}Co flood source by PET

DOE Office of Scientific and Technical Information (OSTI.GOV)

DiFilippo, Frank P., E-mail: difilif@ccf.org

2014-11-01

Purpose: Flood sources of {sup 57}Co are commonly used for quality control of gamma cameras. Flood uniformity may be affected by the contaminants {sup 56}Co and {sup 58}Co, which emit higher energy photons. Although vendors specify a maximum combined {sup 56}Co and {sup 58}Co activity, a convenient test for flood source purity that is feasible in a clinical environment would be desirable. Methods: Both {sup 56}Co and {sup 58}Co emit positrons with branching 19.6% and 14.9%, respectively. As is known from {sup 90}Y imaging, a positron emission tomography (PET) scanner is capable of quantitatively imaging very weak positron emission inmore » a high single-photon background. To evaluate this approach, two {sup 57}Co flood sources were scanned with a clinical PET/CT multiple times over a period of months. The {sup 56}Co and {sup 58}Co activity was clearly visible in the reconstructed PET images. Total impurity activity was quantified from the PET images after background subtraction of prompt gamma coincidences. Results: Time-of-flight PET reconstruction was highly beneficial for accurate image quantification. Repeated measurements of the positron-emitting impurities showed excellent agreement with an exponential decay model. For both flood sources studied, the fit parameters indicated a zero intercept and a decay half-life consistent with a mixture of {sup 56}Co and {sup 58}Co. The total impurity activity at the reference date was estimated to be 0.06% and 0.07% for the two sources, which was consistent with the vendor’s specification of <0.12%. Conclusions: The robustness of the repeated measurements and a thorough analysis of the detector corrections and physics suggest that the accuracy is acceptable and that the technique is feasible. Further work is needed to validate the accuracy of this technique with a calibrated high resolution gamma spectrometer as a gold standard, which was not available for this study, and for other PET detector models.« less

GigaGauss solenoidal magnetic field inside bubbles excited in under-dense plasma

PubMed Central

Lécz, Zs.; Konoplev, I. V.; Seryi, A.; Andreev, A.

2016-01-01

This paper proposes a novel and effective method for generating GigaGauss level, solenoidal quasi-static magnetic fields in under-dense plasma using screw-shaped high intensity laser pulses. This method produces large solenoidal fields that move with the driving laser pulse and are collinear with the accelerated electrons. This is in contrast with already known techniques which rely on interactions with over-dense or solid targets and generates radial or toroidal magnetic field localized at the stationary target. The solenoidal field is quasi-stationary in the reference frame of the laser pulse and can be used for guiding electron beams. It can also provide synchrotron radiation beam emittance cooling for laser-plasma accelerated electron and positron beams, opening up novel opportunities for designs of the light sources, free electron lasers, and high energy colliders based on laser plasma acceleration. PMID:27796327

GigaGauss solenoidal magnetic field inside bubbles excited in under-dense plasma

NASA Astrophysics Data System (ADS)

Lécz, Zs.; Konoplev, I. V.; Seryi, A.; Andreev, A.

2016-10-01

This paper proposes a novel and effective method for generating GigaGauss level, solenoidal quasi-static magnetic fields in under-dense plasma using screw-shaped high intensity laser pulses. This method produces large solenoidal fields that move with the driving laser pulse and are collinear with the accelerated electrons. This is in contrast with already known techniques which rely on interactions with over-dense or solid targets and generates radial or toroidal magnetic field localized at the stationary target. The solenoidal field is quasi-stationary in the reference frame of the laser pulse and can be used for guiding electron beams. It can also provide synchrotron radiation beam emittance cooling for laser-plasma accelerated electron and positron beams, opening up novel opportunities for designs of the light sources, free electron lasers, and high energy colliders based on laser plasma acceleration.

Measurement of cosmic ray positron and negatron spectra between 50 and 800 MeV. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Daugherty, J. K.

1974-01-01

A balloon-borne magnetic spectrometer was used to measure the spectra of cosmic ray positrons and negatrons at energies between 50 and 800 MeV. Comparisons of the separate positron and negatron spectra observed near the earth with their expected intensities in interstellar space can be used to investigate the complex (and variable) interaction of galactic cosmic rays with the expanding solar wind. The present measurements, which have established finite values or upper limits for the positron and negatron spectral between 50 and 800 MeV, have confirmed earlier evidence for the existence of a dominant component of negatrons from primary sources in the galaxy. The present results are shown to be consistent with the hypothesis that the positron component is in fact mainly attributable to collisions between cosmic ray nuclei and the interstellar gas. The estimate of the absolute intensities confirm the indications from neutron monitors that in 1972 the interplanetary cosmic ray intensities were already recovering toward their high levels observed in 1965.

Nonlinear Breit–Wheeler pair creation with bremsstrahlung γ rays

NASA Astrophysics Data System (ADS)

Blackburn, T. G.; Marklund, M.

2018-05-01

Electron–positron pairs are produced through the Breit–Wheeler process when energetic photons traverse electromagnetic fields of sufficient strength. Here we consider a possible experimental geometry for observation of pair creation in the highly nonlinear regime, in which bremsstrahlung of an ultrarelativistic electron beam in a high-Z target is used to produce γ rays that collide with a counter-propagating laser pulse. We show how the target thickness may be chosen to optimize the yield of Breit–Wheeler positrons, and verify our analytical predictions with simulations of the cascade in the material and in the laser pulse. The electron beam energy and laser intensity required are well within the capability of today’s high-intensity laser facilities.

Clinical and Radiographic Response of Extramedullary Leukemia in Patients Treated With Gemtuzumab Ozogamicin.

PubMed

McNeil, Michael J; Parisi, Marguerite T; Hijiya, Nobuko; Meshinchi, Soheil; Cooper, Todd; Tarlock, Katherine

2018-05-04

Extramedullary leukemia (EML) is common in pediatric acute leukemia and can present at diagnosis or relapse. CD33 is detected on the surface of myeloid blasts in many patients with acute myelogenous leukemia and is the target of the antibody drug conjugate gemtuzumab ozogamicin (GO). Here we present 2 patients with CD33 EML treated with GO. They achieved significant response, with reduction of EML on both clinical and radiographic exams, specifically fluorine fluorodeoxyglucose positron emission tomography/computed tomography, demonstrating potential for targeted therapy with GO as a means of treating EML in patients with CD33 leukemia and the utility of fluorine fluorodeoxyglucose positron emission tomography/computed tomography monitoring in EML.

Inelastic collisions of positrons with one-valence-electron targets

NASA Technical Reports Server (NTRS)

Abdel-Raouf, Mohamed Assad

1990-01-01

The total elastic and positronium formation cross sections of the inelastic collisions between positrons and various one-valence-electron atoms, (namely hydrogen, lithium, sodium, potassium and rubidium), and one-valence-electron ions, (namely hydrogen-like, lithium-like and alkaline-earth positive ions) are determined using an elaborate modified coupled-static approximation. Special attention is devoted to the behavior of the Ps cross sections at the energy regions lying above the Ps formation thresholds.

Dipole anisotropy in cosmic electrons and positrons: inspection on local sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manconi, S.; Donato, F.; Mauro, M. Di, E-mail: manconi@to.infn.it, E-mail: mdimauro@slac.stanford.edu, E-mail: donato@to.infn.it

The cosmic electrons and positrons have been measured with unprecedented statistics up to several hundreds GeV, thus permitting to explore the role that close single sources can have in shaping the flux at different energies. In the present analysis, we consider electrons and positrons in cosmic rays to be produced by spallations of hadron fluxes with the interstellar medium, by a smooth Supernova Remnant (SNR) population, by all the ATNF catalog pulsars, and by few discrete, local SNRs. We test several source models on the e {sup ++} e {sup −} and e {sup +} AMS-02 flux data. For themore » configurations compatible with the data, we compute the dipole anisotropy in e {sup ++} e {sup −}, e {sup +}, e {sup +}/ e {sup −} from single sources. Our study includes a dedicated analysis to the Vela SNR. We show that Fermi -LAT present data on dipole anisotropy of e {sup ++} e {sup −} start to explore some of the models for the Vela SNR selected by AMS-02 flux data. We also investigate how the observed anisotropy could result from a combination of local sources. Our analysis shows that the search of anisotropy in the lepton fluxes up to TeV energies can be an interesting tool for the inspection of properties of close SNRs, complementary to the high precision flux data.« less

Recent Progress on Laser Produced Positron Research At LLN

NASA Astrophysics Data System (ADS)

Chen, Hui; Hermann, M.; Kalantar, D.; Kemp, A.; Link, A.; Jiang, S.; Martinez, D.; Park, J.; Remington, B.; Sherlock, M.; Williams, Gj; Beg, F.; Edghill, B.; Fedosejevs, R.; Kerr, S.; D'Humieres, E.; Fiuza, F.; Willingale, L.; Fiksel, G.; Nakai, N.; Arikawa, Y.; Morace, A.; Sentoku, Y.

2017-10-01

We report the recent results on laser-produced relativistic electron-positron plasma jets. This includes: the prepulse and material dependence of pair generation; time dependent positron acceleration and maximum achieved pair density. We will highlight the results from recent experiments on the Omega EP laser testing nanostructured target to increase pair yield. We will also report on a newly commissioned platform using the NIF ARC lasers which was developed for efficient pair creation using 10 ps laser duration at near relativistic laser intensity. This work was performed under the auspices of the U.S. DOE by LLNL under Contract DE-AC52-07NA27344, and funded by LDRD (#17-ERD-010).

Neurobiology of Chronic Stress-Related Psychiatric Disorders: Evidence from Molecular Imaging Studies

PubMed Central

Davis, Margaret T.; Holmes, Sophie E.; Pietrzak, Robert H.; Esterlis, Irina

2018-01-01

Chronic stress accounts for billions of dollars of economic loss annually in the United States alone, and is recognized as a major source of disability and mortality worldwide. Robust evidence suggests that chronic stress plays a significant role in the onset of severe and impairing psychiatric conditions, including major depressive disorder, bipolar disorder, and posttraumatic stress disorder. Application of molecular imaging techniques such as positron emission tomography and single photon emission computed tomography in recent years has begun to provide insight into the molecular mechanisms by which chronic stress confers risk for these disorders. The present paper provides a comprehensive review and synthesis of all positron emission tomography and single photon emission computed tomography imaging publications focused on the examination of molecular targets in individuals with major depressive disorder, posttraumatic stress disorder, or bipolar disorder to date. Critical discussion of discrepant findings and broad strengths and weaknesses of the current body of literature is provided. Recommended future directions for the field of molecular imaging to further elucidate the neurobiological substrates of chronic stress-related disorders are also discussed. This article is part of the inaugural issue for the journal focused on various aspects of chronic stress. PMID:29862379

Low-energy positron scattering upon endohedrals

NASA Astrophysics Data System (ADS)

Amusia, M. Ya.; Chernysheva, L. V.

2017-07-01

We investigate positron scattering upon endohedrals and compare it with electron-endohedral scattering. We show that the polarization of the fullerene shell considerably alters the polarization potential of an atom, stuffed inside a fullerene. This essentially affects both the positron and electron elastic scattering phases as well as corresponding cross sections. Of great importance is also the interaction between the incoming positron and the target electrons that leads to formation of the virtual positronium P˜s. We illustrate the general trend by concrete examples of positron and electron scattering upon endohedrals He@C60 and Ar@C60, and compare it to scattering upon fullerene C60. To obtain the presented results, we have employed new simplified approaches that permit to incorporate the effect of fullerenes polarizability into the He@C60 and Ar@C60 polarization potential and to take into account the virtual positronium formation. Using these approaches, we obtained numeric results that show strong variations in shape and magnitudes of scattering phases and cross sections due to effect of endohedral polarization and P˜s formation.

Progress toward magnetic confinement of a positron-electron plasma: nearly 100% positron injection efficiency into a dipole trap

NASA Astrophysics Data System (ADS)

Stoneking, Matthew

2017-10-01

The hydrogen atom provides the simplest system and in some cases the most precise one for comparing theory and experiment in atomics physics. The field of plasma physics lacks an experimental counterpart, but there are efforts underway to produce a magnetically confined positron-electron plasma that promises to represent the simplest plasma system. The mass symmetry of positron-electron plasma makes it particularly tractable from a theoretical standpoint and many theory papers have been published predicting modified wave and stability properties in these systems. Our approach is to utilize techniques from the non-neutral plasma community to trap and accumulate electrons and positrons prior to mixing in a magnetic trap with good confinement properties. Ultimately we aim to use a levitated superconducting dipole configuration fueled by positrons from a reactor-based positron source and buffer-gas trap. To date we have conducted experiments to characterize and optimize the positron beam and test strategies for injecting positrons into the field of a supported permanent magnet by use of ExB drifts and tailored static and dynamic potentials applied to boundary electrodes and to the magnet itself. Nearly 100% injection efficiency has been achieved under certain conditions and some fraction of the injected positrons are confined for as long as 400 ms. These results are promising for the next step in the project which is to use an inductively energized high Tc superconducting coil to produce the dipole field, initially in a supported configuration, but ultimately levitated using feedback stabilization. Work performed with the support of the German Research Foundation (DFG), JSPS KAKENHI, NIFS Collaboration Research Program, and the UCSD Foundation.

Defect studies of nanocrystalline zirconia powders and sintered ceramics

NASA Astrophysics Data System (ADS)

Čížek, Jakub; Melikhova, Oksana; Procházka, Ivan; Kuriplach, Jan; Kužel, Radomír; Brauer, Gerhard; Anwand, Wolfgang; Konstantinova, Tatyana E.; Danilenko, Igor A.

2010-01-01

The main objective of the present paper is to communicate a study of defects behavior in zirconia-based nanomaterials—pressure-compacted yttria-stabilized zirconia (YSZ) nanopowders with different contents of Y2O3 and ceramics obtained by sintering the YZS nanopowders. In addition, YZS single crystals were also investigated. Positron annihilation techniques including positron lifetime and coincidence Doppler broadening with a conventional positron source and Doppler broadening experiments on a monoenergetic positron beam were involved in this study as the principal tools. These techniques were supplemented with transmission electron microscopy and x-ray diffraction observations. In order to get better support of the experimental data interpretation, the state-of-art theoretical calculations of positron parameters were performed for the perfect ZrO2 lattice and selected defect configurations in the YSZ. Theoretical calculations have indicated that neither the oxygen vacancies nor their neutral complexes with substitutional yttrium atoms are capable of positron trapping. On the other hand, the zirconium vacancies are deep positron traps and obviously are responsible for the saturated positron trapping observed in the YSZ single crystals. In the compacted YSZ nanopowders, a majority of positrons is trapped either in the vacancylike defects situated in the negative space-charge layers along grain boundaries (τ1≈185ps) or in vacancy clusters at intersections of grain boundaries (τ2≈370ps) . The intensity ratio I2/I1 was found to be correlated with the mean grain size d as I2/I1˜d-2 . A small fraction of positrons (≈10%) form positronium in large pores (τ3≈2ns,τ4≈30ns) . A significant grain growth during sintering of the YSZ nanopowders above 1000°C was observed.

Study of defects in an electroresistive Au/La2/3Sr1/3MnO3/SrTiO3(001) heterostructure by positron annihilation

NASA Astrophysics Data System (ADS)

Ferragut, R.; Dupaquier, A.; Brivio, S.; Bertacco, R.; Egger, W.

2011-09-01

Defects in an ultrathin Au/La2/3Sr1/3MnO3/SrTiO3 (Au/LSMO/STO) heterostructure displaying electroresistive behavior were studied using variable energy positron annihilation spectroscopy. Vacancy-like defects were found to be the dominant positron traps in the LSMO and STO thin perovskite oxides with a number density >1017 cm-3 and 2 × 1017 cm-3 in the STO substrate. High defect density was revealed by strong positron trapping at the Au/LSMO interface. Oxygen deficiency in LSMO would be the main source of these traps. Besides, a low density of sub-nano voids of ˜6 Å was found in the substrate and in the thin LSMO/STO films.

18F-Labeling of Sensitive Biomolecules for Positron Emission Tomography

PubMed Central

Krishnan, Hema S.; Ma, Longle; Vasdev, Neil; Liang, Steven H.

2017-01-01

Positron emission tomography (PET) imaging study of fluorine-18 labeled biomolecules is an emerging and rapidly growing area for preclinical and clinical research. The present review focuses on recent advances in radiochemical methods for incorporating fluorine-18 into biomolecules via ‘direct’ or ‘indirect’ bioconjugation. Recently developed prosthetic groups and pre-targeting strategies, as well as representative examples in 18F-labeling of biomolecules in PET imaging research studies are highlighted. PMID:28704575

Directional Antineutrino Detection

NASA Astrophysics Data System (ADS)

Safdi, B. R.; Suerfu, J.

2014-12-01

We propose the first truly directional antineutrino detector for antineutrinos near the threshold for the inverse beta decay (IBD) of hydrogen, with potential applications including the spatial mapping of geo-neutrinos, searches for stellar antineutrinos, and the monitoring of nuclear reactors. The detector consists of adjacent and separated target and neutron-capture layers. The IBD events, which result in a neutron and a positron, take place in the target layers. These layers are thin enough so that the neutrons escape without scattering elastically. The neutrons are detected in the thicker neutron-capture layers. The location of the IBD event is determined from the energy deposited by the positron as it slows in the medium and from the two gamma rays that come from the positron annihilation. Since the neutron recoils in the direction of the antineutrino's motion, a line may then be drawn between the IBD event location and the neutron-capture location to approximate the antineutrino's velocity. In some events, we may even measure the positron's velocity, which further increases our ability to reconstruct the antineutrino's direction of motion. Our method significantly improves upon previous methods by allowing the neutron to freely travel a long distance before diffusing and being captured. Moreover, our design is a straightforward modification of existing antineutrino detectors; a prototype could easily be built with existing technology. We verify our design through Monte Carlo simulations in Geant4, using commercially-available boron-loaded plastic scintillators for the target and neutron-capture layer materials. We are able to discriminate from background using multiple coincidence signatures within a short, ~microsecond time interval. We conclude that the detector could likely operate above ground with minimal shielding.

Routine Production of 89Zr Using an Automated Module

DOE PAGES

Wooten, A.; Madrid, Evelyn; Schweitzer, Gordon; ...

2013-07-12

89Zr has emerged as a useful radioisotope for targeted molecular imaging via positron emission tomography (PET) in both animal models and humans. This isotope is particularly attractive for cancer research because its half-life (t 1/2 = 3.27 days) is well-suited for in vivo targeting of macromolecules and nanoparticles to cell surface antigens expressed by cancer cells. Furthermore, 89Zr emits a low-energy positron (E β+,mean = 0.40 MeV), which is favorable for high spatial resolution in PET, with an adequate branching ratio for positron emission (BR = 23%). The demand for 89Zr for research purposes is increasing; however, 89Zr also emitsmore » significant gamma radiation (Γ 15 keV = 6.6 R∙cm 2/mCi∙h), which makes producing large amounts of this isotope by hand unrealistic from a radiation safety standpoint. Fortunately, a straightforward method exists for production of 89Zr by bombarding a natural Y target in a biomedical cyclotron and then separation of 89Zr from the target material by column chromatography. The chemical separation in this method lends itself to remote processing using an automated module placed inside a hot cell. In this work, we have designed, built and commissioned a module that has performed the chemical separation of 89Zr safely and routinely, at activities in excess of 50 mCi, with radionuclidic purity > 99.9% and satisfactory effective specific activity (ESA).« less

Development of activity pencil beam algorithm using measured distribution data of positron emitter nuclei generated by proton irradiation of targets containing (12)C, (16)O, and (40)Ca nuclei in preparation of clinical application.

PubMed

Miyatake, Aya; Nishio, Teiji; Ogino, Takashi

2011-10-01

The purpose of this study is to develop a new calculation algorithm that is satisfactory in terms of the requirements for both accuracy and calculation time for a simulation of imaging of the proton-irradiated volume in a patient body in clinical proton therapy. The activity pencil beam algorithm (APB algorithm), which is a new technique to apply the pencil beam algorithm generally used for proton dose calculations in proton therapy to the calculation of activity distributions, was developed as a calculation algorithm of the activity distributions formed by positron emitter nuclei generated from target nuclear fragment reactions. In the APB algorithm, activity distributions are calculated using an activity pencil beam kernel. In addition, the activity pencil beam kernel is constructed using measured activity distributions in the depth direction and calculations in the lateral direction. (12)C, (16)O, and (40)Ca nuclei were determined as the major target nuclei that constitute a human body that are of relevance for calculation of activity distributions. In this study, "virtual positron emitter nuclei" was defined as the integral yield of various positron emitter nuclei generated from each target nucleus by target nuclear fragment reactions with irradiated proton beam. Compounds, namely, polyethylene, water (including some gelatin) and calcium oxide, which contain plenty of the target nuclei, were irradiated using a proton beam. In addition, depth activity distributions of virtual positron emitter nuclei generated in each compound from target nuclear fragment reactions were measured using a beam ON-LINE PET system mounted a rotating gantry port (BOLPs-RGp). The measured activity distributions depend on depth or, in other words, energy. The irradiated proton beam energies were 138, 179, and 223 MeV, and measurement time was about 5 h until the measured activity reached the background level. Furthermore, the activity pencil beam data were made using the activity pencil beam kernel, which was composed of the measured depth data and the lateral data including multiple Coulomb scattering approximated by the Gaussian function, and were used for calculating activity distributions. The data of measured depth activity distributions for every target nucleus by proton beam energy were obtained using BOLPs-RGp. The form of the depth activity distribution was verified, and the data were made in consideration of the time-dependent change of the form. Time dependence of an activity distribution form could be represented by two half-lives. Gaussian form of the lateral distribution of the activity pencil beam kernel was decided by the effect of multiple Coulomb scattering. Thus, the data of activity pencil beam involving time dependence could be obtained in this study. The simulation of imaging of the proton-irradiated volume in a patient body using target nuclear fragment reactions was feasible with the developed APB algorithm taking time dependence into account. With the use of the APB algorithm, it was suggested that a system of simulation of activity distributions that has levels of both accuracy and calculation time appropriate for clinical use can be constructed.

Cosmic ray electrons, positrons and the synchrotron emission of the Galaxy: consistent analysis and implications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bernardo, Giuseppe Di; Evoli, Carmelo; Gaggero, Daniele

2013-03-01

A multichannel analysis of cosmic ray electron and positron spectra and of the diffuse synchrotron emission of the Galaxy is performed by using the DRAGON code. This study is aimed at probing the interstellar electron source spectrum down to E ∼< 1GeV and at constraining several propagation parameters. We find that above 4GeV the e{sup −} source spectrum is compatible with a power-law of index ∼ 2.5. Below 4GeV instead it must be significantly suppressed and the total lepton spectrum is dominated by secondary particles. The positron spectrum and fraction measured below a few GeV are consistently reproduced only withinmore » low reacceleration models. We also constrain the scale-height z{sub t} of the cosmic-ray distribution using three independent (and, in two cases, original) arguments, showing that values of z{sub t} ∼< 2kpc are excluded. This result may have strong implications for particle dark matter searches.« less

Positron Radiography of Ignition-Relevant ICF Capsules

NASA Astrophysics Data System (ADS)

Williams, Jackson; Chen, Hui; Field, John; Landen, Nino; Strozzi, David

2017-10-01

X-ray and neutron radiography are currently used to infer residual ICF shell and fuel asymmetries and areal density non-uniformities near and at peak compression that can impede ignition. Charged particles offer an alternative probe source that, in principle, are capable of radiographing the shell shape and areal density at arbitrary times, even in the presence of large x-ray self-emission. Laser-generated positrons are evaluated as a source to radiograph ICF capsules where current ultraintense laser facilities are capable of producing 2 ×1012 relativistic positrons in a narrow energy bandwidth and short duration. Monte Carlo simulations suggest that both the areal density and shell radius can be reconstructed for ignition-relevant capsules conditions between 0.002-2 g/cm2, and that this technique might be better suited to direct-drive. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and funded by the LDRD Program under project tracking code 17-ERD-010.

High average power, diode pumped petawatt laser systems: a new generation of lasers enabling precision science and commercial applications

NASA Astrophysics Data System (ADS)

Haefner, C. L.; Bayramian, A.; Betts, S.; Bopp, R.; Buck, S.; Cupal, J.; Drouin, M.; Erlandson, A.; Horáček, J.; Horner, J.; Jarboe, J.; Kasl, K.; Kim, D.; Koh, E.; Koubíková, L.; Maranville, W.; Marshall, C.; Mason, D.; Menapace, J.; Miller, P.; Mazurek, P.; Naylon, A.; Novák, J.; Peceli, D.; Rosso, P.; Schaffers, K.; Sistrunk, E.; Smith, D.; Spinka, T.; Stanley, J.; Steele, R.; Stolz, C.; Suratwala, T.; Telford, S.; Thoma, J.; VanBlarcom, D.; Weiss, J.; Wegner, P.

2017-05-01

Large laser systems that deliver optical pulses with peak powers exceeding one Petawatt (PW) have been constructed at dozens of research facilities worldwide and have fostered research in High-Energy-Density (HED) Science, High-Field and nonlinear physics [1]. Furthermore, the high intensities exceeding 1018W/cm2 allow for efficiently driving secondary sources that inherit some of the properties of the laser pulse, e.g. pulse duration, spatial and/or divergence characteristics. In the intervening decades since that first PW laser, single-shot proof-of-principle experiments have been successful in demonstrating new high-intensity laser-matter interactions and subsequent secondary particle and photon sources. These secondary sources include generation and acceleration of charged-particle (electron, proton, ion) and neutron beams, and x-ray and gamma-ray sources, generation of radioisotopes for positron emission tomography (PET), targeted cancer therapy, medical imaging, and the transmutation of radioactive waste [2, 3]. Each of these promising applications requires lasers with peak power of hundreds of terawatt (TW) to petawatt (PW) and with average power of tens to hundreds of kW to achieve the required secondary source flux.

Contribution from individual nearby sources to the spectrum of high-energy cosmic-ray electrons

NASA Astrophysics Data System (ADS)

Sedrati, R.; Attallah, R.

2014-04-01

In the last few years, very important data on high-energy cosmic-ray electrons and positrons from high-precision space-born and ground-based experiments have attracted a great deal of interest. These particles represent a unique probe for studying local comic-ray accelerators because they lose energy very rapidly. These energy losses reduce the lifetime so drastically that high-energy cosmic-ray electrons can attain the Earth only from rather local astrophysical sources. This work aims at calculating, by means of Monte Carlo simulation, the contribution from some known nearby astrophysical sources to the cosmic-ray electron/positron spectra at high energy (≥ 10 GeV). The background to the electron energy spectrum from distant sources is determined with the help of the GALPROP code. The obtained numerical results are compared with a set of experimental data.

Using polarized positrons to probe physics beyond the standard model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Furletova, Yulia; Mantry, Sonny

A high intensity polarized positron beam, as part of the JLAB 12 GeV program and the proposed electron-ion collider (EIC), can provide a unique opportunity for testing the Standard Model (SM) and probing for new physics. The combination of high luminosity with polarized electrons and positrons incident on protons and deuterons can isolate important effects and distinguish between possible new physics scenarios in a manner that will complement current experimental efforts. Here, a comparison of cross sections between polarized electron and positron beams will allow for an extraction of the poorly known weak neutral current coupling combination 2C 3u -more » C 3d and would complement the proposed plan for a precision extraction of the combination 2C 2u - C d at the EIC. Precision measurements of these neutral weak couplings would constrain new physics scenarios including Leptoquarks, R-parity violating supersymmetry, and electron and quark compositeness. The dependence of the charged current cross section on the longitudinal polarization of the positron beam will provide an independent probe to test the chiral structure of the electroweak interactions. A polarized positron can probe charged lepton flavor violation (CLFV) through a search for e + → τ + transitions in a manner that is independent and complementary to the proposed e - → τ - search at the EIC. A positron beam incident on an electron in a stationary nuclear target will also allow for a dark-photon (A') search via the annihilation process e + + e - → A' + γ.« less

Using polarized positrons to probe physics beyond the standard model

DOE PAGES

Furletova, Yulia; Mantry, Sonny

2018-05-25

A high intensity polarized positron beam, as part of the JLAB 12 GeV program and the proposed electron-ion collider (EIC), can provide a unique opportunity for testing the Standard Model (SM) and probing for new physics. The combination of high luminosity with polarized electrons and positrons incident on protons and deuterons can isolate important effects and distinguish between possible new physics scenarios in a manner that will complement current experimental efforts. Here, a comparison of cross sections between polarized electron and positron beams will allow for an extraction of the poorly known weak neutral current coupling combination 2C 3u -more » C 3d and would complement the proposed plan for a precision extraction of the combination 2C 2u - C d at the EIC. Precision measurements of these neutral weak couplings would constrain new physics scenarios including Leptoquarks, R-parity violating supersymmetry, and electron and quark compositeness. The dependence of the charged current cross section on the longitudinal polarization of the positron beam will provide an independent probe to test the chiral structure of the electroweak interactions. A polarized positron can probe charged lepton flavor violation (CLFV) through a search for e + → τ + transitions in a manner that is independent and complementary to the proposed e - → τ - search at the EIC. A positron beam incident on an electron in a stationary nuclear target will also allow for a dark-photon (A') search via the annihilation process e + + e - → A' + γ.« less

Using polarized positrons to probe physics beyond the standard model

NASA Astrophysics Data System (ADS)

Furletova, Yulia; Mantry, Sonny

2018-05-01

A high intensity polarized positron beam, as part of the JLAB 12 GeV program and the proposed electron-ion collider (EIC), can provide a unique opportunity for testing the Standard Model (SM) and probing for new physics. The combination of high luminosity with polarized electrons and positrons incident on protons and deuterons can isolate important effects and distinguish between possible new physics scenarios in a manner that will complement current experimental efforts. A comparison of cross sections between polarized electron and positron beams will allow for an extraction of the poorly known weak neutral current coupling combination 2C3u - C3d and would complement the proposed plan for a precision extraction of the combination 2C2u - Cd at the EIC. Precision measurements of these neutral weak couplings would constrain new physics scenarios including Leptoquarks, R-parity violating supersymmetry, and electron and quark compositeness. The dependence of the charged current cross section on the longitudinal polarization of the positron beam will provide an independent probe to test the chiral structure of the electroweak interactions. A polarized positron can probe charged lepton flavor violation (CLFV) through a search for e+ → τ+ transitions in a manner that is independent and complementary to the proposed e- → τ- search at the EIC. A positron beam incident on an electron in a stationary nuclear target will also allow for a dark-photon (A') search via the annihilation process e+ + e- → A' + γ.

Directional Antineutrino Detection

NASA Astrophysics Data System (ADS)

Safdi, Benjamin R.; Suerfu, Burkhant

2015-02-01

We propose the first event-by-event directional antineutrino detector using inverse beta decay (IBD) interactions on hydrogen, with potential applications including monitoring for nuclear nonproliferation, spatially mapping geoneutrinos, characterizing the diffuse supernova neutrino background and searching for new physics in the neutrino sector. The detector consists of adjacent and separated target and capture scintillator planes. IBD events take place in the target layers, which are thin enough to allow the neutrons to escape without scattering elastically. The neutrons are detected in the thicker boron-loaded capture layers. The location of the IBD event and the momentum of the positron are determined by tracking the positron's trajectory through the detector. Our design is a straightforward modification of existing antineutrino detectors; a prototype could be built with existing technology.

High resolution positron annihilation induced Auger electron spectroscopy of the CuM 2,3VV-transition and of Cu sub-monolayers on Pd and Fe

NASA Astrophysics Data System (ADS)

Mayer, J.; Hugenschmidt, C.; Schreckenbach, K.

2010-09-01

We present a high resolution positron annihilation induced Auger Electron Spectroscopy (PAES) of the CuM 2,3VV-transition with the unprecedented energy resolution of Δ/EE <1%. This energy resolution and the highly intense positron source NEPOMUC enabled us to resolve the double peak structure with PAES for the first time within a measurement time of only 5.5 h. In addition, sub-monolayers of Cu were deposited on Fe- and Pd-samples in order to investigate the surface selectivity of PAES in comparison with EAES. The extremely high surface selectivity of PAES due to the different positron affinity of Cu and Fe lead to the result that with only 0.96 monolayer of Cu on Fe more than 55% of the emitted Auger electrons stem from Cu, whereas with EAES the Cu Auger fraction amounted to less than 6%.

Positron annihilation lifetime spectroscopy (PALS) study of the as prepared and calcined MFI zeolites

NASA Astrophysics Data System (ADS)

Bosnar, Sanja; Vrankić, Martina; Bosnar, Damir; Ren, Nan; Šarić, Ankica

2017-11-01

The synthesis of high silica zeolites in many cases implies the usage of organic structural direction agents (SDA). However, to manifest their functionalities, the SDA occluded inside the channels of the as-synthesized structure should be removed, usually by a high temperature treatment (calcination). In this paper, the positron annihilation lifetime spectroscopy (PALS) was used to monitor the development of accessible spaces, their sizes and distributions in MFI zeolites, ZSM-5 and silicalite-1 in order to give an additional insight in the process of the SDA removal. For that purpose, a conventional PALS setup with 22Na positron source was applied. It was established that there is a pronounced difference between positron annihilation data for these two zeolites of the same structural type. The samples were additionally analysed by X-ray powder diffraction at room temperature with a crystal structure refinement and thermogravimetry.

Development and Testing of the Positron Identification By Coincident Annihilation Photons (PICAP) System

NASA Astrophysics Data System (ADS)

Tran, D.; Connell, J. J.; Lopate, C.; Bickford, B.

2014-12-01

Moderate energy positrons (~few to 10 MeV) have seldom been observed in the Heliosphere, due primarily to there not having been dedicated instruments for such measurements. Their detection would have implications in the study of Solar energetic particle events and the transport and modulation of the Solar wind and Galactic cosmic rays. The Positron Identification by Coincident Annihilation Photons (PICAP) system is designed specifically to measure these moderate energy positrons by simultaneously detecting the two 511-keV γ-ray photons that result from a positron stopping in the instrument and the subsequent electron-positron annihilation. This method is also expected to effectively discriminate positrons from protons by measuring the amount of energy deposited in the detectors (dE/dx versus residual energy). PICAP offers a low-mass, low-power option for measuring positrons, electrons, and ions in space. Following Monte Carlo modeling, a PICAP laboratory prototype, adaptable to a space-flight design, was designed, built, and tested. This instrument is comprised of (Si) solid-state detectors, plastic scintillation detectors, and high-Z BGO crystal scintillator suitable for detecting the 511-keV γ rays. The prototype underwent preliminary laboratory testing and calibration using radioactive sources for the purpose of establishing functionality. It has since been exposed to beams of energetic protons (up to ~200 MeV) at Massachusetts General Hospital's Francis H. Burr Proton Beam Therapy Center and positrons and electrons (up to ~10 MeV) at Idaho State University's Idaho Accelerator Center. The goal is to validate modeling and determine the performance of the instrument concept. We will present a summary of modeling calculations and analysis of data taken at the accelerator tests. This work is 95% supported by NASA Grant NNX10AC10G.

18 F-Labeling of Sensitive Biomolecules for Positron Emission Tomography.

PubMed

Krishnan, Hema S; Ma, Longle; Vasdev, Neil; Liang, Steven H

2017-11-07

Positron emission tomography (PET) imaging study of fluorine-18 labeled biomolecules is an emerging and rapidly growing area for preclinical and clinical research. The present review focuses on recent advances in radiochemical methods for incorporating fluorine-18 into biomolecules via "direct" or "indirect" bioconjugation. Recently developed prosthetic groups and pre-targeting strategies, as well as representative examples in 18 F-labeling of biomolecules in PET imaging research studies are highlighted. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Semiempirical potentials for positron scattering by atoms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Assafrao, Denise; Walters, H. R. J.; Arretche, Felipe

2011-08-15

We report calculations of differential and integral cross sections for positron scattering by noble gas and alkaline-earth atoms within the same methodology. The scattering potentials are constructed by scaling adiabatic potentials so that their minima coincide with the covalent radii of the target atoms. Elastic differential and integral cross sections are calculated for Ne, Ar, Be, and Mg, and the results are very close to experimental and best theoretical data. Particularly, elastic differential cross sections for Be and Mg at low energies are reported.

NLC Special Projects

Science.gov Websites

Measurement (with NLC RF group) LCLS and related technologies (LCLS work related to NLC work) Collimation Systems (with Beam Delivery group) Combined Laser System (with NLC sources group) Polarized Positron Sources (with NLC sources group) Crab Cavity Phase Control System Timing and RF distribution System (with

A device to measure the effects of strong magnetic fields on the image resolution of PET scanners

NASA Astrophysics Data System (ADS)

Burdette, D.; Albani, D.; Chesi, E.; Clinthorne, N. H.; Cochran, E.; Honscheid, K.; Huh, S. S.; Kagan, H.; Knopp, M.; Lacasta, C.; Mikuz, M.; Schmalbrock, P.; Studen, A.; Weilhammer, P.

2009-10-01

Very high resolution images can be achieved in small animal PET systems utilizing solid state silicon pad detectors. As these systems approach sub-millimeter resolutions, the range of the positron is becoming the dominant contribution to image blur. The size of the positron range effect depends on the initial positron energy and hence the radioactive tracer used. For higher energy positron emitters, such as Ga68 and Tc94m, which are gaining importance in small animal studies, the width of the annihilation point distribution dominates the spatial resolution. This positron range effect can be reduced by embedding the field of view of the PET scanner in a strong magnetic field. In order to confirm this effect experimentally, we developed a high resolution PET instrument based on silicon pad detectors that can operate in a 7 T magnetic field. In this paper, we describe the instrument and present initial results of a study of the effects of magnetic fields up to 7 T on PET image resolution for Na22 and Ga68 point sources.

Study of PRIMAVERA steel samples by a positron annihilation spectroscopy technique

NASA Astrophysics Data System (ADS)

Grafutin, V.; Ilyukhina, O.; Krsjak, V.; Burcl, R.; Hähner, P.; Erak, D.; Zeman, A.

2010-11-01

In the present article, a positron annihilation spectroscopy investigation of VVER-440/230 weld materials is discussed. Important characteristics of metals such as Fermi energy, concentration of electrons in the conduction band, size and concentration of defects were experimentally determined for three model materials with higher level of copper (0.16 wt.%) and phosphorus (0.027-0.038 wt.%). The impact of neutron irradiation and subsequent annealing on crystal lattice parameters was investigated. The experiments with the angular correlation of positron annihilation radiation (ACAR) complement the published positron annihilation spectroscopy (PAS) studies of the radiation treated VVER materials as well as previous experiments on PRIMAVERA materials. The availability of the experimental reactor to prepare strong 64Cu positron sources provided for unique experimental conditions, such as good resolution of spectra (0.4 mrad) and reasonable short time of measurement (36 h). The present paper aims to contribute to further understanding of RPV (reactor pressure vessel) steels behaviour under irradiation conditions as well as annealing recovery procedures, which have already been applied at several VVER NPP units in Europe.

Controlled Synthesis and Understanding of Growth Mechanism – Parameters for Atmospheric Pressure Hydrothermal Synthesis of Ultrathin Secondary ZnO Nanowires

DOE PAGES

Jiao, Mingzhi; Nguyen, Duc; Nguyen, Van; ...

2015-11-10

We measured luminescence and scintillation in ZnO single crystals by photoluminescence and X-ray-induced luminescence (XRIL). XRIL allowed a direct comparison to be made between the near-band emission (NBE) and trap emissions providing insight into the carrier recombination efficiency in the ZnO crystals. In the origin of green emission, the dominant trap emission in ZnO, was investigated by gamma-induced positron spectroscopy (GIPS) - a unique defect spectroscopy method that enables positron lifetime measurements to be made for a sample without contributions from positron annihilation in the source materials or the surroundings. Moreover, the measurements showed the absence of positron traps inmore » the crystals and yielded a bulk positron lifetime value that is in complete agreement with the predicted theoretical value = thereby confirming the advantage of the GIPS method. By combining scintillation measurements with XRIL, the fast scintillation in ZnO crystals was found to be strongly correlated with the ratio between the defect luminescence and NBE.« less

Positron cooling of antiprotons: precursor of recombination

NASA Astrophysics Data System (ADS)

Tan, J. N.; Estrada, J.; Yesley, P.; Bowden, N.; Oxley, P.; Storry, C.; Wessels, M.; Tan, J.; Gabrielse, G.; Oelert, W.; Scheppers, G.; Gronzonka, D.; Sefsick, T.; Fermann, H.; Zmeskal, H.; Breunlich, W.; Kalinowsky, H.; Wesdorp, C.

2001-05-01

The quest for cold antihydrogen, interrupted with the shut-down of LEAR, resumed with the operation of the newest antiproton decelerator (AD) at CERN.[See G.Gabrielse,Adv. in AMO Physics,vol.45,pp.1-38(2001).] Antiprotons injected into the AD with 2.75 GeV of kinetic energy slow to 5.31 MeV before extraction into the ATRAP apparatus, built for antihydrogen recombination experiments. Antiprotons extracted from the AD and positrons emitted from a 112 mCi ^22Na source are simultaneously accumulated in the ultra-high vacuum and 6 T field of a prototype Penning trap incorporating a miniature rotatable electrode. Preloaded electrons are used to thermalize ~ 10^5 antiprotons with the LHe-cooled trap (4.2K). Over 10^6 positrons/hr can be loaded with a new mechanism involving Rydberg positronium. After accumulation, the positrons are moved through the rotatable electrode into close proximity with the antiprotons to study their interactions. We report the first observation of positron cooling of antiprotons in a nested trap configuration suited for three-body recombination and other mechanisms.

Theoretical Interpretation of Pass 8 Fermi -LAT e + + e - Data

DOE PAGES

Di Mauro, M.; Manconi, S.; Vittino, A.; ...

2017-08-17

The flux of positrons and electrons (e + + e -) has been measured by the Fermi Large Area Telescope (LAT) in the energy range between 7 GeV and 2 TeV. Here, we discuss a number of interpretations of Pass 8 Fermi-LAT e + + e - spectrum, combining electron and positron emission from supernova remnants (SNRs) and pulsar wind nebulae (PWNe), or produced by the collision of cosmic rays (CRs) with the interstellar medium. We also found that the Fermi-LAT spectrum is compatible with the sum of electrons from a smooth SNR population, positrons from cataloged PWNe, and amore » secondary component. If we include in our analysis constraints from the AMS-02 positron spectrum, we obtain a slightly worse fit to the e + + e - Fermi-LAT spectrum, depending on the propagation model. As an additional scenario, we replace the smooth SNR component within 0.7 kpc with the individual sources found in Green's catalog of Galactic SNRs. We find that separate consideration of far and near sources helps to reproduce the e + + e - Fermi-LAT spectrum. However, we show that the fit degrades when the radio constraints on the positron emission from Vela SNR (which is the main contributor at high energies) are taken into account. We find that a break in the power-law injection spectrum at about 100 GeV can also reproduce the measured e + + e -spectrum and, among the CR propagation models that we consider, no reasonable break of the power-law dependence of the diffusion coefficient can modify the electron flux enough to reproduce the observed shape.« less

COSMIC-RAY POSITRONS FROM MILLISECOND PULSARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Venter, C.; Kopp, A.; Büsching, I.

2015-07-10

Observations by the Fermi Large Area Telescope of γ-ray millisecond pulsar (MSP) light curves imply copious pair production in their magnetospheres, and not exclusively in those of younger pulsars. Such pair cascades may be a primary source of Galactic electrons and positrons, contributing to the observed enhancement in positron flux above ∼10 GeV. Fermi has also uncovered many new MSPs, impacting Galactic stellar population models. We investigate the contribution of Galactic MSPs to the flux of terrestrial cosmic-ray electrons and positrons. Our population synthesis code predicts the source properties of present-day MSPs. We simulate their pair spectra invoking an offset-dipolemore » magnetic field. We also consider positrons and electrons that have been further accelerated to energies of several TeV by strong intrabinary shocks in black widow (BW) and redback (RB) systems. Since MSPs are not surrounded by pulsar wind nebulae or supernova shells, we assume that the pairs freely escape and undergo losses only in the intergalactic medium. We compute the transported pair spectra at Earth, following their diffusion and energy loss through the Galaxy. The predicted particle flux increases for non-zero offsets of the magnetic polar caps. Pair cascades from the magnetospheres of MSPs are only modest contributors around a few tens of GeV to the lepton fluxes measured by the Alpha Magnetic Spectrometer, PAMELA, and Fermi, after which this component cuts off. The contribution by BWs and RBs may, however, reach levels of a few tens of percent at tens of TeV, depending on model parameters.« less

Theoretical Interpretation of Pass 8 Fermi -LAT e + + e - Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Di Mauro, M.; Manconi, S.; Vittino, A.

The flux of positrons and electrons (e + + e -) has been measured by the Fermi Large Area Telescope (LAT) in the energy range between 7 GeV and 2 TeV. Here, we discuss a number of interpretations of Pass 8 Fermi-LAT e + + e - spectrum, combining electron and positron emission from supernova remnants (SNRs) and pulsar wind nebulae (PWNe), or produced by the collision of cosmic rays (CRs) with the interstellar medium. We also found that the Fermi-LAT spectrum is compatible with the sum of electrons from a smooth SNR population, positrons from cataloged PWNe, and amore » secondary component. If we include in our analysis constraints from the AMS-02 positron spectrum, we obtain a slightly worse fit to the e + + e - Fermi-LAT spectrum, depending on the propagation model. As an additional scenario, we replace the smooth SNR component within 0.7 kpc with the individual sources found in Green's catalog of Galactic SNRs. We find that separate consideration of far and near sources helps to reproduce the e + + e - Fermi-LAT spectrum. However, we show that the fit degrades when the radio constraints on the positron emission from Vela SNR (which is the main contributor at high energies) are taken into account. We find that a break in the power-law injection spectrum at about 100 GeV can also reproduce the measured e + + e -spectrum and, among the CR propagation models that we consider, no reasonable break of the power-law dependence of the diffusion coefficient can modify the electron flux enough to reproduce the observed shape.« less

Light yield and energy resolution studies for SoLid phase 1

NASA Astrophysics Data System (ADS)

Boursette, Delphine; SoLid Collaboration

2017-09-01

The SoLid experiment is searching for sterile neutrinos at a nuclear research reactor. It looks for inverse beta decays (producing a positron and a neutron in delayed coincidence) with a very segmented detector made of thousands of scintillating cubes. SoLid has a very innovative hybrid technology with two different scintillators which have different light emissions: polyvynil-toluene cubes (PVT) to detect the positrons and 6LiF:ZnS sheets on two faces of each PVT cube to detect the neutrons. It allows us to do an efficient pulse shape analysis to identify the signals from neutrons and positrons. The 288 kg detector prototype (SM1) took data in 2015. It demonstrated the detection principle and background rejection efficiency. The construction of SoLid phase I (˜ 1.5 t) has now started. To improve the energy resolution of SoLid phase I, we have tried to increase the light yield studying separately the two scintillators: PVT and ZnS. A test bench has been built to fully characterize and improve the neutron detection with the ZnS using an AmBe source. To study the positron light yield on the PVT, we have built another test bench with a 207Bi source. We have improved the design of the cubes, their wrapping or the type and the configuration of the fibers. We managed to increase the PVT light yield by about 66 % and improve the resolution of the positron energy on the test bench from 21 % to 16 % at 1 MeV.

Impenetrable barriers for positrons in neighbourhood of superheavy nuclei with Z>118

NASA Astrophysics Data System (ADS)

Neznamov, V. P.

2017-12-01

Analysis of quantum mechanical motion of charged half-spin particles in the repulsive Coulomb field results in that an impenetrable potential barrier not explored earlier was found. For a particle at rest with a reduced mass m, the barrier radius is equal to half classical radius: the barrier radius decreases with increase in the particle energy. For the stable and quasi-stable nuclei with Z > 118, presence of an impenetrable barrier as β +-decay leads to the existence of “traps” for positrons in the neighbourhood of nuclei and as Zcr ≃ 170 (with emission of electron-positron pairs by vacuum) leads to the existence of a quasi-constant source of annihilation quanta.

Dense electron-positron plasmas and ultraintense γ rays from laser-irradiated solids.

PubMed

Ridgers, C P; Brady, C S; Duclous, R; Kirk, J G; Bennett, K; Arber, T D; Robinson, A P L; Bell, A R

2012-04-20

In simulations of a 10 PW laser striking a solid, we demonstrate the possibility of producing a pure electron-positron plasma by the same processes as those thought to operate in high-energy astrophysical environments. A maximum positron density of 10(26) m(-3) can be achieved, 7 orders of magnitude greater than achieved in previous experiments. Additionally, 35% of the laser energy is converted to a burst of γ rays of intensity 10(22) W cm(-2), potentially the most intense γ-ray source available in the laboratory. This absorption results in a strong feedback between both pair and γ-ray production and classical plasma physics in the new "QED-plasma" regime.

BEST medical radioisotope production cyclotrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sabaiduc, Vasile; Milton, Bruce; Suthanthiran, Krishnan

2013-04-19

Best Cyclotron Systems Inc (BCSI) is currently developing 14 MeV, 25 MeV, 35MeV and 70MeV cyclotrons for radioisotope production and research applications as well as the entire spectrum of targets and nuclear synthesis modules for the production of Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT) and radiation therapy isotopes. The company is a subsidiary of Best Medical International, renowned in the field of medical instrumentation and radiation therapy. All cyclotrons have external negative hydrogen ion sources, four radial sectors with two dees in opposite valleys, cryogenic vacuum system and simultaneous beam extraction on opposite lines. The beammore » intensity ranges from 400 {mu}A to 1000 {mu}A, depending on the cyclotron energy and application.« less

BEST medical radioisotope production cyclotrons

NASA Astrophysics Data System (ADS)

Sabaiduc, Vasile; Milton, Bruce; Suthanthiran, Krishnan; Gelbart, W. Z.; Johnson, Richard R.

2013-04-01

Best Cyclotron Systems Inc (BCSI) is currently developing 14 MeV, 25 MeV, 35MeV and 70MeV cyclotrons for radioisotope production and research applications as well as the entire spectrum of targets and nuclear synthesis modules for the production of Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT) and radiation therapy isotopes. The company is a subsidiary of Best Medical International, renowned in the field of medical instrumentation and radiation therapy. All cyclotrons have external negative hydrogen ion sources, four radial sectors with two dees in opposite valleys, cryogenic vacuum system and simultaneous beam extraction on opposite lines. The beam intensity ranges from 400 μA to 1000 μA, depending on the cyclotron energy and application [1].

Electron- and positron-impact ionization of inert gases

NASA Astrophysics Data System (ADS)

Campeanu, R. I.; Walters, H. R. J.; Whelan, Colm T.

2018-06-01

Triple-differential cross sections (TDCS) are presented for the electron and positron impact ionization of inert gas atoms in a range of geometries where a number of significant few body effects compete to define the shape of the TDCS. Using both positrons and electrons as projectiles has opened up the possibility of performing complementary studies which could effectively isolate competing interactions which cannot be separately detected in an experiment with a single projectile. A comparison is presented between theory and the recent experiments of [Gavin, deLucio, and DuBois, Phys. Rev. A 95, 062703 (2017), 10.1103/PhysRevA.95.062703] for e± and contrasted with the results from earlier electron experiments. For the special case of xenon(5 p ), cross sections are presented for both electron- and positron-impact ionization in kinematics where the electron case appears well understood. The kinematics are then varied in order to focus on the possible role of distortion, exchange, and target wave-function effects.

FAST TRACK COMMUNICATION: Stable propagation of a modulated positron beam in a bent crystal channel

NASA Astrophysics Data System (ADS)

Kostyuk, A.; Korol, A. V.; Solov'yov, A. V.; Greiner, W.

2010-08-01

The propagation of a modulated positron beam in a planar crystal channel is investigated. It is demonstrated that the beam preserves its modulation at sufficiently large penetration depths, which opens the prospect of using a crystalline undulator as a coherent source of hard x-rays. This finding is a crucial milestone in developing a new type of laser radiating in the hard x-ray and gamma-ray range.

Could a plasma in quasi-thermal equilibrium be associated to the "orphan" TeV flares?

NASA Astrophysics Data System (ADS)

Fraija, N.

2015-12-01

TeV γ-ray detections in flaring states without activity in X-rays from blazars have attracted much attention due to the irregularity of these "orphan" flares. Although the synchrotron self-Compton model has been very successful in explaining the spectral energy distribution and spectral variability of these sources, it has not been able to describe these atypical flaring events. On the other hand, an electron-positron pair plasma at the base of the AGN jet was proposed as the mechanism of bulk acceleration of relativistic outflows. This plasma in quasi-thermal equilibrium called Wein fireball emits radiation at MeV-peak energies serving as target of accelerated protons. In this work we describe the "orphan" TeV flares presented in blazars 1ES 1959+650 and Mrk 421 assuming geometrical considerations in the jet and evoking the interactions of Fermi-accelerated protons and MeV-peak target photons coming from the Wein fireball. After describing successfully these "orphan" TeV flares, we correlate the TeV γ-ray, neutrino and UHECR fluxes through pγ interactions and calculate the number of high-energy neutrinos and UHECRs expected in IceCube/AMANDA and TA experiment, respectively. In addition, thermal MeV neutrinos produced mainly through electron-positron annihilation at the Wein fireball will be able to propagate through it. By considering two- (solar, atmospheric and accelerator parameters) and three-neutrino mixing, we study the resonant oscillations and estimate the neutrino flavor ratios as well as the number of thermal neutrinos expected on Earth.

Positron annihilation signatures associated with the outburst of the microquasar V404 Cygni.

PubMed

Siegert, Thomas; Diehl, Roland; Greiner, Jochen; Krause, Martin G H; Beloborodov, Andrei M; Bel, Marion Cadolle; Guglielmetti, Fabrizia; Rodriguez, Jerome; Strong, Andrew W; Zhang, Xiaoling

2016-03-17

Microquasars are stellar-mass black holes accreting matter from a companion star and ejecting plasma jets at almost the speed of light. They are analogues of quasars that contain supermassive black holes of 10(6) to 10(10) solar masses. Accretion in microquasars varies on much shorter timescales than in quasars and occasionally produces exceptionally bright X-ray flares. How the flares are produced is unclear, as is the mechanism for launching the relativistic jets and their composition. An emission line near 511 kiloelectronvolts has long been sought in the emission spectrum of microquasars as evidence for the expected electron-positron plasma. Transient high-energy spectral features have been reported in two objects, but their positron interpretation remains contentious. Here we report observations of γ-ray emission from the microquasar V404 Cygni during a recent period of strong flaring activity. The emission spectrum around 511 kiloelectronvolts shows clear signatures of variable positron annihilation, which implies a high rate of positron production. This supports the earlier conjecture that microquasars may be the main sources of the electron-positron plasma responsible for the bright diffuse emission of annihilation γ-rays in the bulge region of our Galaxy. Additionally, microquasars could be the origin of the observed megaelectronvolt continuum excess in the inner Galaxy.

Physical and engineering aspect of carbon beam therapy

NASA Astrophysics Data System (ADS)

Kanai, Tatsuaki; Kanematsu, Nobuyuki; Minohara, Shinichi; Yusa, Ken; Urakabe, Eriko; Mizuno, Hideyuki; Iseki, Yasushi; Kanazawa, Mitsutaka; Kitagawa, Atsushi; Tomitani, Takehiro

2003-08-01

Conformal irradiation system of HIMAC has been up-graded for a clinical trial using a technique of a layer-stacking method. The system has been developed for localizing irradiation dose to target volume more effectively than the present irradiation dose. With dynamic control of the beam modifying devices, a pair of wobbler magnets, and multileaf collimator and range shifter, during the irradiation, more conformal radiotherapy can be achieved. The system, which has to be adequately safe for patient irradiations, was constructed and tested from a viewpoint of safety and the quality of the dose localization realized. A secondary beam line has been constructed for use of radioactive beam in heavy-ion radiotherapy. Spot scanning method has been adapted for the beam delivery system of the radioactive beam. Dose distributions of the spot beam were measured and analyzed taking into account of aberration of the beam optics. Distributions of the stopped positron-emitter beam can be observed by PET. Pencil beam of the positron-emitter, about 1 mm size, can also be used for measurements ranges of the test beam in patients using positron camera. The positron camera, consisting of a pair of Anger-type scintillation detectors, has been developed for this verification before treatment. Wash-out effect of the positron-emitter was examined using the positron camera installed. In this report, present status of the HIMAC irradiation system is described in detail.

High resolution Cerenkov light imaging of induced positron distribution in proton therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamamoto, Seiichi, E-mail: s-yama@met.nagoya-u.ac.jp; Fujii, Kento; Morishita, Yuki

2014-11-01

Purpose: In proton therapy, imaging of the positron distribution produced by fragmentation during or soon after proton irradiation is a useful method to monitor the proton range. Although positron emission tomography (PET) is typically used for this imaging, its spatial resolution is limited. Cerenkov light imaging is a new molecular imaging technology that detects the visible photons that are produced from high-speed electrons using a high sensitivity optical camera. Because its inherent spatial resolution is much higher than PET, the authors can measure more precise information of the proton-induced positron distribution with Cerenkov light imaging technology. For this purpose, theymore » conducted Cerenkov light imaging of induced positron distribution in proton therapy. Methods: First, the authors evaluated the spatial resolution of our Cerenkov light imaging system with a {sup 22}Na point source for the actual imaging setup. Then the transparent acrylic phantoms (100 × 100 × 100 mm{sup 3}) were irradiated with two different proton energies using a spot scanning proton therapy system. Cerenkov light imaging of each phantom was conducted using a high sensitivity electron multiplied charge coupled device (EM-CCD) camera. Results: The Cerenkov light’s spatial resolution for the setup was 0.76 ± 0.6 mm FWHM. They obtained high resolution Cerenkov light images of the positron distributions in the phantoms for two different proton energies and made fused images of the reference images and the Cerenkov light images. The depths of the positron distribution in the phantoms from the Cerenkov light images were almost identical to the simulation results. The decay curves derived from the region-of-interests (ROIs) set on the Cerenkov light images revealed that Cerenkov light images can be used for estimating the half-life of the radionuclide components of positrons. Conclusions: High resolution Cerenkov light imaging of proton-induced positron distribution was possible. The authors conclude that Cerenkov light imaging of proton-induced positron is promising for proton therapy.« less

The great galactic centre mystery

NASA Technical Reports Server (NTRS)

Riegler, G. R.

1982-01-01

Gamma-ray observations of the center of the Galaxy show a varying positron-electron annihilation radiation emission, while at radio wavelengths a non-thermal compact source surrounded by ionized gas moving at high velocities can be seen. Line emission maps for atomic and ionized hydrogen and molecular gas suggest gas expulsion and a massive collapsed object. IR observations show that ionized gas in the central few parsecs of the Galactic center is concentrated in at least 14 small clouds. Charge-coupled device images show a pair of faint, very red sources within a few arc seconds of IRS 16 and the compact non-thermal radio source. The positron-electron annihilation line emission implies an annihilation rate of 10 to the 43rd per sec, compared with an observed luminosity at IR wavelengths of 10 to the 40 erg per sec. Some models are briefly discussed.

The accelerator neutron source for boron neutron capture therapy

NASA Astrophysics Data System (ADS)

Kasatov, D.; Koshkarev, A.; Kuznetsov, A.; Makarov, A.; Ostreinov, Yu; Shchudlo, I.; Sorokin, I.; Sycheva, T.; Taskaev, S.; Zaidi, L.

2016-11-01

The accelerator based epithermal neutron source for Boron Neutron Capture Therapy (BNCT) is proposed, created and used in the Budker Institute of Nuclear Physics. In 2014, with the support of the Russian Science Foundation created the BNCT laboratory for the purpose to the end of 2016 get the neutron flux, suitable for BNCT. For getting 3 mA 2.3 MeV proton beam, was created a new type accelerator - tandem accelerator with vacuum isolation. On this moment, we have a stationary proton beam with 2.3 MeV and current 1.75 mA. Generation of neutrons is carried out by dropping proton beam on to lithium target as a result of threshold reaction 7Li(p,n)7Be. Established facility is a unique scientific installation. It provides a generating of neutron flux, including a monochromatic energy neutrons, gamma radiation, alpha-particles and positrons, and may be used by other research groups for carrying out scientific researches. The article describes an accelerator neutron source, presents and discusses the result of experiments and declares future plans.

Beta decay and the origins of biological chirality - Experimental results

NASA Technical Reports Server (NTRS)

Gidley, D. W.; Rich, A.; Van House, J.; Zitzewitz, P. W.

1982-01-01

Preliminary experimental results are presented of an investigation of the possible role of preferential radiolysis by electrons emitted in the beta decay of radionuclides, a parity-nonconserving process, in the universal causation of the optical activity of biological compounds. Experiments were designed to measure the asymmetry in the production of triplet positronium upon the bombardment of an amino acid powder target by a collimated beam of positrons as positron helicity or target chirality is reversed. No asymmetry down to a level of 0.0007 is found in experiments on the D and L forms of cystine and tryptophan, indicating an asymmetry in positronium formation cross section of less than 0.01, while an asymmetry of 0.0031 is found for leucine, corresponding to a formation cross section asymmetry of about 0.04

Insights into neutrino decoupling gleaned from considerations of the role of electron mass

NASA Astrophysics Data System (ADS)

Grohs, E.; Fuller, George M.

2017-10-01

We present calculations showing how electron rest mass influences entropy flow, neutrino decoupling, and Big Bang Nucleosynthesis (BBN) in the early universe. To elucidate this physics and especially the sensitivity of BBN and related epochs to electron mass, we consider a parameter space of rest mass values larger and smaller than the accepted vacuum value. Electromagnetic equilibrium, coupled with the high entropy of the early universe, guarantees that significant numbers of electron-positron pairs are present, and dominate over the number of ionization electrons to temperatures much lower than the vacuum electron rest mass. Scattering between the electrons-positrons and the neutrinos largely controls the flow of entropy from the plasma into the neutrino seas. Moreover, the number density of electron-positron-pair targets can be exponentially sensitive to the effective in-medium electron mass. This entropy flow influences the phasing of scale factor and temperature, the charged current weak-interaction-determined neutron-to-proton ratio, and the spectral distortions in the relic neutrino energy spectra. Our calculations show the sensitivity of the physics of this epoch to three separate effects: finite electron mass, finite-temperature quantum electrodynamic (QED) effects on the plasma equation of state, and Boltzmann neutrino energy transport. The ratio of neutrino to plasma-component energy scales manifests in Cosmic Microwave Background (CMB) observables, namely the baryon density and the radiation energy density, along with the primordial helium and deuterium abundances. Our results demonstrate how the treatment of in-medium electron mass (i.e., QED effects) could translate into an important source of uncertainty in extracting neutrino and beyond-standard-model physics limits from future high-precision CMB data.

Cross section measurements for production of positron emitters for PET imaging in carbon therapy

NASA Astrophysics Data System (ADS)

Salvador, S.; Colin, J.; Cussol, D.; Divay, C.; Fontbonne, J.-M.; Labalme, M.

2017-04-01

In light ion beam therapy, positron (β+) emitters are produced by the tissue nuclei through nuclear interactions with the beam ions. They can be used for the verification of the delivered dose using positron emission tomography by comparing the spatial distribution of the β+ emitters activity to a computer simulation taking into account the patient morphology and the treatment plan. However, the accuracy of the simulation greatly depends on the method used to generate the nuclear interactions producing these emitters. In the case of Monte Carlo (MC) simulations, the nuclear interaction models still lack the required accuracy due to insufficient experimental cross section data. This is particularly true for carbon therapy where literature data on fragmentation cross sections of a carbon beam with targets of medical interest are very scarce. Therefore, we performed at GANIL in July 2016 measurements on β+ emitter production cross sections with a carbon beam at 25, 50, and 95 MeV/nucleon on thin targets (C, N, O, and PMMA). We extracted the production cross section of C,1110, 13N, and O,1514 that are essential to constrain or develop MC nuclear fragmentation models.

Study of the surface contamination of copper with the improved positron annihilation-induced Auger electron spectrometer at NEPOMUC

NASA Astrophysics Data System (ADS)

Mayer, J.; Hugenschmidt, C.; Schreckenbach, K.

2008-10-01

The high intensity positron source NEPOMUC at the FRM-II in Munich enables measurement times for positron annihilation-induced Auger electron spectroscopy (PAES) of only 2.4 h/spectrum, in contrast to usual lab beams with measurement times up to several days. The high electron background due to surrounding experiments in the experimental hall of the FRM-II has been eliminated and hence background free experiments have become possible. Due to this, the signal to noise ratio has been enhanced to 4.5:1, compared to 1:3 with EAES. In addition, a long-term measurement has been performed in order to observe the contamination of a polycrystalline copper foil at 150 °C.

Synchrotron VUV-UV and positron lifetime spectroscopy study of vacancy-type defects in reactor neutron-irradiated MgO.nAl2O3 (n = 2)

NASA Astrophysics Data System (ADS)

Rahman, Abu Zayed Mohammad Saliqur; Cao, Xingzhong; Wang, Baoyi; Evslin, Jarah; Xu, Qiu; Atobe, Kozo

2016-12-01

We investigated neutron-irradiation-induced point defects in spinel single crystals using a synchrotron VUV-UV source and positron lifetime spectroscopy. Photoexcitation (PE) spectra near 230 nm and their corresponding photoluminescence (PL) spectra at 475 nm were attributed to F-centers. With increasing irradiation temperature and fluence, PE efficiency and PL intensity decreased dramatically. Positron lifetimes (PLT) of neutron-irradiated and non-irradiated samples were measured to identify the cation vacancies. A PLT measurement of 250 ps was obtained in a neutron-irradiated (20 K) sample which is tentatively attributed to an aluminum monovacancy. Decreasing PLT with higher irradiation indicates the formation of oxygen-vacancy complex centers.

Investigation of soft component in cosmic ray detection

NASA Astrophysics Data System (ADS)

Oláh, László; Varga, Dezső

2017-07-01

Cosmic ray detection is a research area which finds various applications in tomographic imaging of large size objects. In such applications, the background sources which contaminate cosmic muon signal require a good understanding of the creation processes, as well as reliable simulation frameworks with high predictive power are needed. One of the main background source is the ;soft component;, that is electrons and positrons. In this paper a simulation framework based on GEANT4 has been established to pin down the key features of the soft component. We have found that the electron and positron flux shows a remarkable invariance against various model parameters including the muon emission altitude or primary particle energy distribution. The correlation between simultaneously arriving particles have been quantitatively investigated, demonstrating that electrons and positrons tend to arrive within a close distance and with low relative angle. This feature, which is highly relevant for counting detectors, has been experimentally verified under open sky and at shallow depth underground. The simulation results have been compared to existing other measurements as well as other simulation programs.

Evaluation of ion-implanted-silicon detectors for use in intraoperative positron-sensitive probes.

PubMed

Raylman, R R; Wahl, R L

1996-11-01

The continuing development of probes for use with beta (positron and electron) emitting radionuclides may result in more complete excision of tracer-avid tumors. Perhaps one of the most promising radiopharmaceuticals for this task is 18F-labeled-Fluoro-2-Deoxy-D-Glucose (FDG). This positron-emitting agent has been demonstrated to be avidly and rapidly absorbed by many human cancers. We have investigated the use of ion-implanted-silicon detectors in intraoperative positron-sensitive surgical probes for use with FDG. These detectors possess very high positron detection efficiency, while the efficiency for 511 keV photon detection is low. The spatial resolution, as well as positron and annihilation photon detection sensitivity, of an ion-implanted-silicon detector used with 18F was measured at several energy thresholds. In addition, the ability of the device to detect the presence of relatively small amounts of FDG during surgery was evaluated by simulating a surgical field in which some tumor was left intact following lesion excision. The performance of the ion-implanted-silicon detector was compared to the operating characteristics of a positron-sensitive surgical probe which utilizes plastic scintillator. In all areas of performance the ion-implanted-silicon detector proved superior to the plastic scintillator-based probe. At an energy threshold of 14 keV positron sensitivity measured for the ion-implanted-silicon detector was 101.3 cps/kBq, photon sensitivity was 7.4 cps/kBq. In addition, spatial resolution was found to be relatively unaffected by the presence of distant sources of annihilation photon flux. Finally, the detector was demonstrated to be able to localize small amounts of FDG in a simulated tumor bed; indicating that this device has promise as a probe to aid in FDG-guided surgery.

Cross-sections for (p,x) reactions on natural chromium for the production of 52,52m,54Mn radioisotopes

DOE PAGES

Wooten, A. Lake; Lewis, Benjamin C.; Lapi, Suzanne E.

2014-12-11

The production of positron-emitting isotopes of manganese is potentially important for developing contrast agents for dual-modality positron emission tomography and magnetic resonance (PET/MR) imaging, as well as for in vivo imaging of the biodistribution and toxicity of manganese. Furthermore, the decay properties of 52Mn make it an excellent candidate for these applications, and it can easily be produced by bombardment of a chromium target with protons or deuterons from a low-energy biomedical cyclotron. There are several parameters essential to this mode of production—target thickness, beam energy, beam current, and bombardment time—depend heavily on the availability of reliable, reproducible cross-section data.more » Our paper contributes to the routine production of 52gMn for biomedical research by contributing experimental cross-sections for natural chromium ( natCr) targets for the natCr(p,x) 52gMn reaction, as well as for the production of the radiocontaminants 52m, 54Mn.« less

Electric-field distribution in Au-semi-insulating GaAs contact investigated by positron-lifetime technique

NASA Astrophysics Data System (ADS)

Ling, C. C.; Shek, Y. F.; Huang, A. P.; Fung, S.; Beling, C. D.

1999-02-01

Positron-lifetime spectroscopy has been used to investigate the electric-field distribution occurring at the Au-semi-insulating GaAs interface. Positrons implanted from a 22Na source and drifted back to the interface are detected through their characteristic lifetime at interface traps. The relative intensity of this fraction of interface-trapped positrons reveals that the field strength in the depletion region saturates at applied biases above 50 V, an observation that cannot be reconciled with a simple depletion approximation model. The data, are, however, shown to be fully consistent with recent direct electric-field measurements and the theoretical model proposed by McGregor et al. [J. Appl. Phys. 75, 7910 (1994)] of an enhanced EL2+ electron-capture cross section above a critical electric field that causes a dramatic reduction of the depletion region's net charge density. Two theoretically derived electric field profiles, together with an experimentally based profile, are used to estimate a positron mobility of ~95+/-35 cm2 V-1 s-1 under the saturation field. This value is higher than previous experiments would suggest, and reasons for this effect are discussed.

Target and orbit feedback simulations of a muSR beam line at BNL

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacKay, W.; Blaskiewicz, M.; Fischer, W.

Well-polarized positive surface muons are a tool to measure the magnetic properties of materials since the precession rate of the spin can be determined from the observation of the positron directions when the muons decay. For a dc beam an ideal µSR flux for surface µ + should be about 40 kHz/mm 2. In this report we show how this flux could be achieved in a beam line using the AGS complex at BNL for a source of protons. We also determined that an orbit feedback system with a pair of thin silicon position monitors and kickers would miss themore » desired flux by at least an order of magnitude, even with perfect time resolution and no multiple scattering.« less

Tomographic Positron Annihilation Lifetime Spectroscopy

NASA Astrophysics Data System (ADS)

Wagner, A.; Anwand, W.; Butterling, M.; Fiedler, F.; Fritz, F.; Kempe, M.; Cowan, T. E.

2014-04-01

Positron annihilation lifetime spectroscopy serves as a perfect tool for studies of open-volume defects in solid materials such as vacancies, vacancy agglomerates, and dislocations. Moreover, structures in porous media can be investigated ranging from 0.3 nm to 30 nm employing the variation of the Positronium lifetime with the pore size. While lifetime measurements close to the material's surface can be performed at positron-beam installations bulk materials, fluids, bio-materials or composite structures cannot or only destructively accessed by positron beams. Targeting those problems, a new method of non-destructive positron annihilation lifetime spectroscopy has been developed which features even a 3-dimensional tomographic reconstruction of the spatial lifetime distribution. A beam of intense bremsstrahlung is provided by the superconducting electron linear accelerator ELBE (Electron Linear Accelerator with high Brilliance and low Emittance) at Helmholtz-Zentrum Dresden-Rossendorf. Since the generation of bremsstrahlung and the transport to the sample preserves the sharp timing of the electron beam, positrons generated inside the entire sample volume by pair production feature a sharp start time stamp for lifetime studies. In addition to the existing technique of in-situ production of positrons inside large (cm3) bulk samples using high-energy photons up to 16 MeV from bremsstrahlung production, granular position-sensitive photon detectors have been employed. The detector system will be described and results for experiments using samples with increasing complexity will be presented. The Lu2SiO5:Ce scintillation crystals allow resolving the total energy to 5.1 % (root-mean-square, RMS) and the annihilation lifetime to 225 ps (RMS). 3-dimensional annihilation lifetime maps have been created in an offline-analysis employing well-known techniques from PET.

Are We Ready for Positron Emission Tomography/Computed Tomography-based Target Volume Definition in Lymphoma Radiation Therapy?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yeoh, Kheng-Wei; Mikhaeel, N. George, E-mail: George.Mikhaeel@gstt.nhs.uk

2013-01-01

Fluorine-18 fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) has become indispensable for the clinical management of lymphomas. With consistent evidence that it is more accurate than anatomic imaging in the staging and response assessment of many lymphoma subtypes, its utility continues to increase. There have therefore been efforts to incorporate PET/CT data into radiation therapy decision making and in the planning process. Further, there have also been studies investigating target volume definition for radiation therapy using PET/CT data. This article will critically review the literature and ongoing studies on the above topics, examining the value and methods of adding PET/CTmore » data to the radiation therapy treatment algorithm. We will also discuss the various challenges and the areas where more evidence is required.« less

GEANT4-based full simulation of the PADME experiment at the DAΦNE BTF

NASA Astrophysics Data System (ADS)

Leonardi, E.; Kozhuharov, V.; Raggi, M.; Valente, P.

2017-10-01

A possible solution to the dark matter problem postulates that dark particles can interact with Standard Model particles only through a new force mediated by a “portal”. If the new force has a U(1) gauge structure, the “portal” is a massive photon-like vector particle, called dark photon or A‧. The PADME experiment at the DAΦNE Beam-Test Facility (BTF) in Frascati is designed to detect dark photons produced in positron on fixed target annihilations decaying to dark matter (e+e-→γA‧) by measuring the final state missing mass. The experiment will be composed of a thin active diamond target where a 550 MeV positron beam will impinge to produce e+e- annihilation events. The surviving beam will be deflected with a magnet while the photons produced in the annihilation will be measured by a calorimeter composed of BGO crystals. To reject the background from Bremsstrahlung gamma production, a set of segmented plastic scintillator vetoes will be used to detect positrons exiting the target with an energy lower than that of the beam, while a fast small angle calorimeter will be used to reject the e+e-→γγ(γ) background. To optimize the experimental layout in terms of signal acceptance and background rejection, the full layout of the experiment was modelled with the GEANT4 simulation package. In this paper we will describe the details of the simulation and report on the results obtained with the software.

Evaluating the Efficacy of ERG-Targeted Therapy in Vivo for Prostate Tumors

DTIC Science & Technology

2015-04-01

DeWeese (PI) 5/15/2015-3/31/2017 NIH/NCI “ PSMA -Directed PET/MR Imaging and Image-Guided Therapy of Prostate Cancer” The overall goal is to validate a...positron-emitting, PSMA -targeted imaging agent clinically so it may be used to full advantage in supporting existing and emerging therapies for a

Dynamical orientation effects in atomic ionization by impact of protons and positrons

NASA Astrophysics Data System (ADS)

Fregenal, Daniel; Barrachina, Raúl; Bernardi, Guillermo; Suárez, Sergio; Fiol, Juan

2011-10-01

Recent results in ionization collisions with positrons and protons showed that just above the two-body threshold, for electron velocities close to the final projectile's velocity, the electron-projectile continuum dipole is narrowly oriented along the direction of motion of its centre-of-mass, with the negative charge pointing towards the residual target. Although a forward-backward asymmetry in the vicinity of the two-body threshold has been studied many year ago in ion impact ionization collisions, that was by far a much milder effect that left no fingerprint on the cusp position. Our results show that the phenomena is present for ionization by impact of both protons and positrons. In this communication, through measurements on H+ + He and calculations we analyze in detail this effect that can be linked to a dynamical alignment of the two-body subsystem in the continuum. Recent results in ionization collisions with positrons and protons showed that just above the two-body threshold, for electron velocities close to the final projectile's velocity, the electron-projectile continuum dipole is narrowly oriented along the direction of motion of its centre-of-mass, with the negative charge pointing towards the residual target. Although a forward-backward asymmetry in the vicinity of the two-body threshold has been studied many year ago in ion impact ionization collisions, that was by far a much milder effect that left no fingerprint on the cusp position. Our results show that the phenomena is present for ionization by impact of both protons and positrons. In this communication, through measurements on H+ + He and calculations we analyze in detail this effect that can be linked to a dynamical alignment of the two-body subsystem in the continuum. This work was partially supported by the Consejo Nacional de Investigaciones Cientificas y Tecnicas, Universidad Nacional de Cuyo and Fundacion Balseiro.

Diagnosis of abnormal biliary copper excretion by positron emission tomography with targeting of 64Copper-asialofetuin complex in LEC rat model of Wilson’s disease

PubMed Central

Bahde, Ralf; Kapoor, Sorabh; Bhargava, Kuldeep K; Palestro, Christopher J; Gupta, Sanjeev

2014-01-01

Identification by molecular imaging of key processes in handling of transition state metals, such as copper (Cu), will be of considerable clinical value. For instance, the ability to diagnose Wilson’s disease with molecular imaging by identifying copper excretion in an ATP7B-dependent manner will be very significant. To develop highly effective diagnostic approaches, we hypothesized that targeting of radiocopper via the asialoglycoprotein receptor will be appropriate for positron emission tomography, and examined this approach in a rat model of Wilson’s disease. After complexing 64Cu to asialofetuin we studied handling of this complex compared with 64Cu in healthy LEA rats and diseased homozygous LEC rats lacking ATP7B and exhibiting hepatic copper toxicosis. We analyzed radiotracer clearance from blood, organ uptake, and biliary excretion, including sixty minute dynamic positron emission tomography recordings. In LEA rats, 64Cu-asialofetuin was better cleared from blood followed by liver uptake and greater biliary excretion than 64Cu. In LEC rats, 64Cu-asialofetuin activity cleared even more rapidly from blood followed by greater uptake in liver, but neither 64Cu-asialofetuin nor 64Cu appeared in bile. Image analysis demonstrated rapid visualization of liver after 64Cu-asialofetuin administration followed by decreased liver activity in LEA rats while liver activity progressively increased in LEC rats. Image analysis resolved this difference in hepatic activity within one hour. We concluded that 64Cu-asialofetuin complex was successfully targeted to the liver and radiocopper was then excreted into bile in an ATP7B-dependent manner. Therefore, hepatic targeting of radiocopper will be appropriate for improving molecular diagnosis and for developing drug/cell/gene therapies in Wilson’s disease. PMID:25250203

Monte Carlo dose calculations in homogeneous media and at interfaces: a comparison between GEPTS, EGSnrc, MCNP, and measurements.

PubMed

Chibani, Omar; Li, X Allen

2002-05-01

Three Monte Carlo photon/electron transport codes (GEPTS, EGSnrc, and MCNP) are bench-marked against dose measurements in homogeneous (both low- and high-Z) media as well as at interfaces. A brief overview on physical models used by each code for photon and electron (positron) transport is given. Absolute calorimetric dose measurements for 0.5 and 1 MeV electron beams incident on homogeneous and multilayer media are compared with the predictions of the three codes. Comparison with dose measurements in two-layer media exposed to a 60Co gamma source is also performed. In addition, comparisons between the codes (including the EGS4 code) are done for (a) 0.05 to 10 MeV electron beams and positron point sources in lead, (b) high-energy photons (10 and 20 MeV) irradiating a multilayer phantom (water/steel/air), and (c) simulation of a 90Sr/90Y brachytherapy source. A good agreement is observed between the calorimetric electron dose measurements and predictions of GEPTS and EGSnrc in both homogeneous and multilayer media. MCNP outputs are found to be dependent on the energy-indexing method (Default/ITS style). This dependence is significant in homogeneous media as well as at interfaces. MCNP(ITS) fits more closely the experimental data than MCNP(DEF), except for the case of Be. At low energy (0.05 and 0.1 MeV), MCNP(ITS) dose distributions in lead show higher maximums in comparison with GEPTS and EGSnrc. EGS4 produces too penetrating electron-dose distributions in high-Z media, especially at low energy (<0.1 MeV). For positrons, differences between GEPTS and EGSnrc are observed in lead because GEPTS distinguishes positrons from electrons for both elastic multiple scattering and bremsstrahlung emission models. For the 60Co source, a quite good agreement between calculations and measurements is observed with regards to the experimental uncertainty. For the other cases (10 and 20 MeV photon sources and the 90Sr/90Y beta source), a good agreement is found between the three codes. In conclusion, differences between GEPTS and EGSnrc results are found to be very small for almost all media and energies studied. MCNP results depend significantly on the electron energy-indexing method.

Prostate Specific Membrane Antigen Positron Emission Tomography May Improve the Diagnostic Accuracy of Multiparametric Magnetic Resonance Imaging in Localized Prostate Cancer.

PubMed

Rhee, H; Thomas, P; Shepherd, B; Gustafson, S; Vela, I; Russell, P J; Nelson, C; Chung, E; Wood, G; Malone, G; Wood, S; Heathcote, P

2016-10-01

Positron emission tomography using ligands targeting prostate specific membrane antigen has recently been introduced. Positron emission tomography imaging with (68)Ga-PSMA-HBED-CC has been shown to detect metastatic prostate cancer lesions at a high rate. In this study we compare multiparametric magnetic resonance imaging and prostate specific membrane antigen positron emission tomography of the prostate with whole mount ex vivo prostate histopathology to determine the true sensitivity and specificity of these imaging modalities for detecting and locating tumor foci within the prostate. In a prospective clinical trial setting 20 patients with localized prostate cancer and a planned radical prostatectomy were recruited. All patients underwent multiparametric magnetic resonance imaging and positron emission tomography before surgery, and whole mount histopathology slides were directly compared to the images. European Society of Urogenital Radiology guidelines for reporting magnetic resonance imaging were used as a template for regional units of analysis. The uropathologist and radiologists were blinded to individual components of the study, and the final correlation was performed by visual and deformable registration analysis. A total of 50 clinically significant lesions were identified from the whole mount histopathological analysis. Based on regional analysis the sensitivity, specificity, positive predictive value and negative predictive value for multiparametric magnetic resonance imaging were 44%, 94%, 81% and 76%, respectively. With prostate specific membrane antigen positron emission tomography the sensitivity, specificity, positive predictive value and negative predictive value were 49%, 95%, 85% and 88%, respectively. Prostate specific membrane antigen positron emission tomography yielded a higher specificity and positive predictive value. A significant proportion of cancers are potentially missed and underestimated by both imaging modalities. Prostate specific membrane antigen positron emission tomography may be used in addition to multiparametric magnetic resonance imaging to help improve local staging in those patients undergoing retropubic radical prostatectomy. Copyright © 2016 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Carbon-11 and Fluorine-18 Labeled Amino Acid Tracers for Positron Emission Tomography Imaging of Tumors

NASA Astrophysics Data System (ADS)

Sun, Aixia; Liu, Xiang; Tang, Ganghua

2017-12-01

Tumor cells have an increased nutritional demand for amino acids(AAs) to satisfy their rapid proliferation. Positron-emitting nuclide labeled AAs are interesting probes and are of great importance for imaging tumors using positron emission tomography (PET). Carbon-11 and fluorine-18 labeled AAs include the [1-11C] amino acids, labeling alpha-C- amino acids, the branched-chain of amino acids and N-substituted carbon-11 labeled amino acids. These tracers target protein synthesis or amino acid(AA) transport, and their uptake mechanism mainly involves AA transport. AA PET tracers have been widely used in clinical settings to image brain tumors, neuroendocrine tumors, prostate cancer, breast cancer, non–small cell lung cancer (NSCLC) and hepatocellular carcinoma. This review focuses on the fundamental concepts and the uptake mechanism of AAs, AA PET tracers and their clinical applications.

DAΦNE operation with electron-cloud-clearing electrodes.

PubMed

Alesini, D; Drago, A; Gallo, A; Guiducci, S; Milardi, C; Stella, A; Zobov, M; De Santis, S; Demma, T; Raimondi, P

2013-03-22

The effects of an electron cloud (e-cloud) on beam dynamics are one of the major factors limiting performances of high intensity positron, proton, and ion storage rings. In the electron-positron collider DAΦNE, namely, a horizontal beam instability due to the electron-cloud effect has been identified as one of the main limitations on the maximum stored positron beam current and as a source of beam quality deterioration. During the last machine shutdown in order to mitigate such instability, special electrodes have been inserted in all dipole and wiggler magnets of the positron ring. It has been the first installation all over the world of this type since long metallic electrodes have been installed in all arcs of the collider positron ring and are currently used during the machine operation in collision. This has allowed a number of unprecedented measurements (e-cloud instabilities growth rate, transverse beam size variation, tune shifts along the bunch train) where the e-cloud contribution is clearly evidenced by turning the electrodes on and off. In this Letter we briefly describe a novel design of the electrodes, while the main focus is on experimental measurements. Here we report all results that clearly indicate the effectiveness of the electrodes for e-cloud suppression.

ZnO Luminescence and scintillation studied via photoexcitation, X-ray excitation, and gamma-induced positron spectroscopy.

PubMed

Ji, J; Colosimo, A M; Anwand, W; Boatner, L A; Wagner, A; Stepanov, P S; Trinh, T T; Liedke, M O; Krause-Rehberg, R; Cowan, T E; Selim, F A

2016-08-23

The luminescence and scintillation properties of ZnO single crystals were studied by photoluminescence and X-ray-induced luminescence (XRIL) techniques. XRIL allowed a direct comparison to be made between the near-band emission (NBE) and trap emissions providing insight into the carrier recombination efficiency in the ZnO crystals. It also provided bulk luminescence measurements that were not affected by surface states. The origin of a green emission, the dominant trap emission in ZnO, was then investigated by gamma-induced positron spectroscopy (GIPS) - a unique defect spectroscopy method that enables positron lifetime measurements to be made for a sample without contributions from positron annihilation in the source materials. The measurements showed a single positron decay curve with a 175 ps lifetime component that was attributed to Zn vacancies passivated by hydrogen. Both oxygen vacancies and hydrogen-decorated Zn vacancies were suggested to contribute to the green emission. By combining scintillation measurements with XRIL, the fast scintillation in ZnO crystals was found to be strongly correlated with the ratio between the defect luminescence and NBE. This study reports the first application of GIPS to semiconductors, and it reveals the great benefits of the XRIL technique for the study of emission and scintillation properties of materials.

ZnO Luminescence and scintillation studied via photoexcitation, X-ray excitation, and gamma-induced positron spectroscopy

NASA Astrophysics Data System (ADS)

Ji, J.; Colosimo, A. M.; Anwand, W.; Boatner, L. A.; Wagner, A.; Stepanov, P. S.; Trinh, T. T.; Liedke, M. O.; Krause-Rehberg, R.; Cowan, T. E.; Selim, F. A.

2016-08-01

The luminescence and scintillation properties of ZnO single crystals were studied by photoluminescence and X-ray-induced luminescence (XRIL) techniques. XRIL allowed a direct comparison to be made between the near-band emission (NBE) and trap emissions providing insight into the carrier recombination efficiency in the ZnO crystals. It also provided bulk luminescence measurements that were not affected by surface states. The origin of a green emission, the dominant trap emission in ZnO, was then investigated by gamma-induced positron spectroscopy (GIPS) - a unique defect spectroscopy method that enables positron lifetime measurements to be made for a sample without contributions from positron annihilation in the source materials. The measurements showed a single positron decay curve with a 175 ps lifetime component that was attributed to Zn vacancies passivated by hydrogen. Both oxygen vacancies and hydrogen-decorated Zn vacancies were suggested to contribute to the green emission. By combining scintillation measurements with XRIL, the fast scintillation in ZnO crystals was found to be strongly correlated with the ratio between the defect luminescence and NBE. This study reports the first application of GIPS to semiconductors, and it reveals the great benefits of the XRIL technique for the study of emission and scintillation properties of materials.

ZnO Luminescence and scintillation studied via photoexcitation, X-ray excitation, and gamma-induced positron spectroscopy

PubMed Central

Ji, J.; Colosimo, A. M.; Anwand, W.; Boatner, L. A.; Wagner, A.; Stepanov, P. S.; Trinh, T. T.; Liedke, M. O.; Krause-Rehberg, R.; Cowan, T. E.; Selim, F. A.

2016-01-01

The luminescence and scintillation properties of ZnO single crystals were studied by photoluminescence and X-ray-induced luminescence (XRIL) techniques. XRIL allowed a direct comparison to be made between the near-band emission (NBE) and trap emissions providing insight into the carrier recombination efficiency in the ZnO crystals. It also provided bulk luminescence measurements that were not affected by surface states. The origin of a green emission, the dominant trap emission in ZnO, was then investigated by gamma-induced positron spectroscopy (GIPS) - a unique defect spectroscopy method that enables positron lifetime measurements to be made for a sample without contributions from positron annihilation in the source materials. The measurements showed a single positron decay curve with a 175 ps lifetime component that was attributed to Zn vacancies passivated by hydrogen. Both oxygen vacancies and hydrogen-decorated Zn vacancies were suggested to contribute to the green emission. By combining scintillation measurements with XRIL, the fast scintillation in ZnO crystals was found to be strongly correlated with the ratio between the defect luminescence and NBE. This study reports the first application of GIPS to semiconductors, and it reveals the great benefits of the XRIL technique for the study of emission and scintillation properties of materials. PMID:27550235

On the use of positron counting for radio-Assay in nuclear pharmaceutical production.

PubMed

Maneuski, D; Giacomelli, F; Lemaire, C; Pimlott, S; Plenevaux, A; Owens, J; O'Shea, V; Luxen, A

2017-07-01

Current techniques for the measurement of radioactivity at various points during PET radiopharmaceutical production and R&D are based on the detection of the annihilation gamma rays from the radionuclide in the labelled compound. The detection systems to measure these gamma rays are usually variations of NaI or CsF scintillation based systems requiring costly and heavy lead shielding to reduce background noise. These detectors inherently suffer from low detection efficiency, high background noise and very poor linearity. They are also unable to provide any reasonably useful position information. A novel positron counting technique is proposed for the radioactivity assay during radiopharmaceutical manufacturing that overcomes these limitations. Detection of positrons instead of gammas offers an unprecedented level of position resolution of the radiation source (down to sub-mm) thanks to the nature of the positron interaction with matter. Counting capability instead of charge integration in the detector brings the sensitivity down to the statistical limits at the same time as offering very high dynamic range and linearity from zero to any arbitrarily high activity. This paper reports on a quantitative comparison between conventional detector systems and the proposed positron counting detector. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Magnetic measurements of the 10 T superconducting wiggler for the SPring-8 storage ring

NASA Astrophysics Data System (ADS)

Batrakov, A.; Borovikov, V.; Bekhtenev, E.; Fedurin, M.; Hara, M.; Karpov, G.; Kuzin, M.; Mezentsev, N.; Miahara, Y.; Shimada, T.; Shkaruba, V.; Soutome, K.; Tzumaki, K.

2001-07-01

In 1999, in the frame of the project ISTC #767 "Budker INP/RIKEN Slow Positron Source", the Budker Institute of Nuclear Physics had made a 10 T Three-pole Superconducting Wiggler. The wiggler will be the keystone of this project by its installation on the SPring-8 storage ring for powerful gamma ray generation ( λ c=450 keV ), that will be used for slow positron production ( Nγ( ɛ>1 MeV)˜10 15, γ/s I e=0.1 A ). A. Ando et al., Proposal of the high magnetic field super conducting WLS for slow positron source at SPring-8, presented at SR1 '97 Conference. In January, 2000, the wiggler was transported to SPring-8, where the last test and measurements were carried out in collaboration with Japan. In this article, the results of measurements of the magnetic field, finding the magnetic field amplitude by an NMR probe, the definition of feed current relations by stretch current wire method, the calibration of a Hall probe in the high magnetic field, and the measurement of the magnetic field profile by a Hall probe are presented.

Novel time-of-flight spectrometer for the analysis of positron annihilation induced Auger electrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hugenschmidt, Christoph; Legl, Stefan; Physik-Department E21, Technische Universitaet Muenchen, James-Franck-Strasse, 85748 Garching

2006-10-15

Positron annihilation induced Auger-electron spectroscopy (PAES) has several advantages over conventional Auger-electron spectroscopy such as extremely high surface sensitivity and outstanding signal-to-noise ratio at the Auger-transition energy. In order to benefit from these prominent features a low-energy positron beam of high intensity is required for surface sensitive PAES studies. In addition, an electron energy analyzer is required, which efficiently detects the Auger electrons with acceptable energy resolution. For this reason a novel time-of-flight (TOF) spectrometer has been developed at the intense positron source NEPOMUC that allows PAES studies within short measurement time. This TOF-PAES setup combines a trochoidal filter andmore » a flight tube in a Faraday cage in order to achieve an improved energy resolution of about 1 eV at high electron energies up to E{approx_equal}1000 eV. The electron flight time is the time between the annihilation radiation at the sample and when the electron hits a microchannel plate detector at the end of the flight tube.« less

Novel time-of-flight spectrometer for the analysis of positron annihilation induced Auger electrons

NASA Astrophysics Data System (ADS)

Hugenschmidt, Christoph; Legl, Stefan

2006-10-01

Positron annihilation induced Auger-electron spectroscopy (PAES) has several advantages over conventional Auger-electron spectroscopy such as extremely high surface sensitivity and outstanding signal-to-noise ratio at the Auger-transition energy. In order to benefit from these prominent features a low-energy positron beam of high intensity is required for surface sensitive PAES studies. In addition, an electron energy analyzer is required, which efficiently detects the Auger electrons with acceptable energy resolution. For this reason a novel time-of-flight (TOF) spectrometer has been developed at the intense positron source NEPOMUC that allows PAES studies within short measurement time. This TOF-PAES setup combines a trochoidal filter and a flight tube in a Faraday cage in order to achieve an improved energy resolution of about 1eV at high electron energies up to E ≈1000eV. The electron flight time is the time between the annihilation radiation at the sample and when the electron hits a microchannel plate detector at the end of the flight tube.

Dark matter "transporting" mechanism explaining positron excesses

NASA Astrophysics Data System (ADS)

Kim, Doojin; Park, Jong-Chul; Shin, Seodong

2018-04-01

We propose a novel mechanism to explain the positron excesses, which are observed by satellite-based telescopes including PAMELA and AMS-02, in dark matter (DM) scenarios. The novelty behind the proposal is that it makes direct use of DM around the Galactic Center where DM populates most densely, allowing us to avoid tensions from cosmological and astrophysical measurements. The key ingredients of this mechanism include DM annihilation into unstable states with a very long laboratory-frame life time and their "retarded" decay near the Earth to electron-positron pair(s) possibly with other (in)visible particles. We argue that this sort of explanation is not in conflict with relevant constraints from big bang nucleosynthesis and cosmic microwave background. Regarding the resultant positron spectrum, we provide a generalized source term in the associated diffusion equation, which can be readily applicable to any type of two-"stage" DM scenarios wherein production of Standard Model particles occurs at completely different places from those of DM annihilation. We then conduct a data analysis with the recent AMS-02 data to validate our proposal.

Optical and positron annihilation spectroscopic studies on PMMA polymer doped by rhodamine B/chloranilic acid charge transfer complex: Special relevance to the effect of γ-ray irradiation

NASA Astrophysics Data System (ADS)

Hassan, H. E.; Refat, Moamen S.; Sharshar, T.

2016-04-01

Polymeric sheets of poly (methylmethaclyerate) (PMMA) containing charge transfer (CT) complex of rhodamine B/chloranilic acid (Rho B/CHA) were synthesized in methanol solvent at room temperature. The systematic analysis done on the Rho B and its CT complex in the form of powder or polymeric sheets confirmed their structure and thermal stability. The IR spectra interpreted the charge transfer mode of interaction between the CHA central positions and the terminal carboxylic group. The polymer sheets were irradiated with 70 kGy of γ radiation using 60Co source to study the enhanced changes in the structure and optical parameters. The microstructure changes of the PMMA sheets caused by γ-ray irradiation were analyzed using positron annihilation lifetime (PAL) and positron annihilation Doppler broadening (PADB) techniques. The positron life time components (τi) and their corresponding intensities (Ii) as well as PADB line-shape parameters (S and W) were found to be highly sensitive to the enhanced disorder occurred in the organic chains of the polymeric sheets due to γ-irradiation.

Positron induced scattering cross sections for hydrocarbons relevant to plasma

NASA Astrophysics Data System (ADS)

Singh, Suvam; Antony, Bobby

2018-05-01

This article explores positron scattering cross sections by simple hydrocarbons such as ethane, ethene, ethyne, propane, and propyne. Chemical erosion processes occurring on the surface due to plasma-wall interactions are an abundant source of hydrocarbon molecules which contaminate the hydrogenic plasma. These hydrocarbons play an important role in the edge plasma region of Tokamak and ITER. In addition to this, they are also one of the major components in the planetary atmospheres and astrophysical mediums. The present work focuses on calculation of different positron impact interactions with simple hydrocarbons in terms of the total cross section (Qtot), elastic cross section (Qel), direct ionization cross section (Qion), positronium formation cross section (Qps), and total ionization cross section (Qtion). Knowing that the positron-plasma study is one of the trending fields, the calculated data have diverse plasma and astrophysical modeling applications. A comprehensive study of Qtot has been provided where the inelastic cross sections have been reported for the first time. Comparisons are made with those available from the literature, and a good agreement is obtained with the measurements.

Cosmic ray electrons and positrons from supernova explosions of massive stars.

PubMed

Biermann, P L; Becker, J K; Meli, A; Rhode, W; Seo, E S; Stanev, T

2009-08-07

We attribute the recently discovered cosmic ray electron and cosmic ray positron excess components and their cutoffs to the acceleration in the supernova shock in the polar cap of exploding Wolf-Rayet and red supergiant stars. Considering a spherical surface at some radius around such a star, the magnetic field is radial in the polar cap as opposed to most of 4pi (the full solid angle), where the magnetic field is nearly tangential. This difference yields a flatter spectrum, and also an enhanced positron injection for the cosmic rays accelerated in the polar cap. This reasoning naturally explains the observations. Precise spectral measurements will be the test, as this predicts a simple E;{-2} spectrum for the new components in the source, steepened to E;{-3} in observations with an E;{-4} cutoff.

An experimental approach to improve the Monte Carlo modelling of offline PET/CT-imaging of positron emitters induced by scanned proton beams

NASA Astrophysics Data System (ADS)

Bauer, J.; Unholtz, D.; Kurz, C.; Parodi, K.

2013-08-01

We report on the experimental campaign carried out at the Heidelberg Ion-Beam Therapy Center (HIT) to optimize the Monte Carlo (MC) modelling of proton-induced positron-emitter production. The presented experimental strategy constitutes a pragmatic inverse approach to overcome the known uncertainties in the modelling of positron-emitter production due to the lack of reliable cross-section data for the relevant therapeutic energy range. This work is motivated by the clinical implementation of offline PET/CT-based treatment verification at our facility. Here, the irradiation induced tissue activation in the patient is monitored shortly after the treatment delivery by means of a commercial PET/CT scanner and compared to a MC simulated activity expectation, derived under the assumption of a correct treatment delivery. At HIT, the MC particle transport and interaction code FLUKA is used for the simulation of the expected positron-emitter yield. For this particular application, the code is coupled to externally provided cross-section data of several proton-induced reactions. Studying experimentally the positron-emitting radionuclide yield in homogeneous phantoms provides access to the fundamental production channels. Therefore, five different materials have been irradiated by monoenergetic proton pencil beams at various energies and the induced β+ activity subsequently acquired with a commercial full-ring PET/CT scanner. With the analysis of dynamically reconstructed PET images, we are able to determine separately the spatial distribution of different radionuclide concentrations at the starting time of the PET scan. The laterally integrated radionuclide yields in depth are used to tune the input cross-section data such that the impact of both the physical production and the imaging process on the various positron-emitter yields is reproduced. The resulting cross-section data sets allow to model the absolute level of measured β+ activity induced in the investigated targets within a few per cent. Moreover, the simulated distal activity fall-off positions, representing the central quantity for treatment monitoring in terms of beam range verification, are found to agree within 0.6 mm with the measurements at different initial beam energies in both homogeneous and heterogeneous targets. Based on work presented at the Third European Workshop on Monte Carlo Treatment Planning (Seville, 15-18 May 2012).

Synthesis and characterization of theranostic poly(HPMA)-c(RGDyK)-DOTA-64Cu copolymer targeting tumor angiogenesis: tumor localization visualized by positron emission tomography.

PubMed

Yuan, Jianchao; Zhang, Haiyuan; Kaur, Harpreet; Oupicky, David; Peng, Fangyu

2013-05-01

Poly(HPMA)-c(RGDyK)-DOTA-64Cu copolymers were synthesized and characterized for tumor localization in vivo as a theranostic scaffold for cancer imaging and anticancer drug delivery targeting tumor angiogenesis. Tumor localization of the poly(HPMA)-c(RGDyK)-DOTA-64Cu copolymers was visualized in mice bearing human prostate cancer xenografts by positron emission tomography (PET) using a microPET scanner. PET quantitative analysis demonstrated that tumor 64Cu radioactivity (2.75 ± 0.34 %ID/g) in tumor-bearing mice 3 hours following intravenous injection of the poly(HPMA)-c(RGDyK)-DOTA-64Cu copolymers was significantly higher than the tumor 64Cu radioactivity (1.29 ± 0.26 %ID/g) in tumor-bearing mice injected with the nontargeted poly(HPMA)-DOTA-64Cu copolymers (p = .004). The poly(HPMA)-c(RGDyK)-DOTA-64Cu copolymers hold potential as a theranostic scaffold for cancer imaging and radiochemotherapy of prostate cancer targeting tumor angiogenesis by noninvasive tracking with PET.

Particle Acceleration and Magnetic Field Generation in Electron-Positron Relativistic Shocks

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Hardee, P.; Richardson, G.; Preece, R.; Sol, H.; Fishman, G. J.

2004-01-01

Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., Buneman, Weibel and other two-stream instabilities) created in collisionless shocks are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic electron-positron jet front propagating into an ambient electron-positron plasma with and without initial magnetic fields. We find small differences in the results for no ambient and modest ambient magnetic fields. Simulations show that the Weibel instability created in the collisionless shock front accelerates jet and ambient particles both perpendicular and parallel to the jet propagation direction. The non-linear fluctuation amplitudes of densities, currents, electric, and magnetic fields in the electron-positron shock are larger than those found in the electron-ion shock studied in a previous paper. This comes from the fact that both electrons and positrons contribute to generation of the Weibel instability. Additionally, we have performed simulations with different electron skin depths. We find that growth times scale inversely with the plasma frequency, and the sizes of structures created by the Weibel instability scale proportional to the electron skin depth. This is the expected result and indicates that the simulations have sufficient grid resolution. While some Fermi acceleration may occur at the jet front, the majority of electron and positron acceleration takes place behind the jet front and cannot be characterized as Fermi acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying nonuniform, small-scale magnetic fields which contribute to the electron's (positron's) transverse deflection behind the jet head. This small scale magnetic field structure is appropriate to the generation of "jitter" radiation from deflected electrons (positrons) as opposed to synchrotron radiation. The jitter radiation has different properties than synchrotron radiation calculated assuming a a uniform magnetic field. The jitter radiation resulting from small scale magnetic field structures may be important for understanding the complex time structure and spectral evolution observed in gamma-ray bursts or other astrophysical sources containing relativistic jets and relativistic collisionless shocks.

Particle Acceleration and Magnetic Field Generation in Electron-Positron Relativistic Shocks

NASA Technical Reports Server (NTRS)

Nishikawa, K.-L.; Hardee, P.; Richardson, G.; Preece, R.; Sol, H.; Fishman, G. J.

2004-01-01

Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., Buneman, Weibel and other two-stream instabilities) created in collisionless shocks are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic electron-positron jet front propagating into an ambient electron-positron plasma with and without initial magnetic fields. We find small differences in the results for no ambient and modest ambient magnetic fields. Simulations show that the Weibel instability created in the collisionless shock front accelerates jet and ambient particles both perpendicular and parallel to the jet propagation direction. The non-linear fluctuation amplitudes of densities, currents, electric, and magnetic fields in the electron-positron shock are larger than those found in the electron-ion shock studied in a previous paper at the comparable simulation time. This comes from the fact that both electrons and positrons contribute to generation of the Weibel instability. Additionally, we have performed simulations with different electron skin depths. We find that growth times scale inversely with the plasma frequency, and the sizes of structures created by the Weibel instability scale proportional to the electron skin depth. This is the expected result and indicates that the simulations have sufficient grid resolution. While some Fermi acceleration may occur at the jet front, the majority of electron and positron acceleration takes place behind the jet front and cannot be characterized as Fermi acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying nonuniform: small-scale magnetic fields which contribute to the electron's (positron's) transverse deflection behind the jet head. This small scale magnetic field structure is appropriate to the generation of jitter radiation from deflected electrons (positrons) as opposed to synchrotron radiation. The jitter radiation has different properties than synchrotron radiation calculated assuming a a uniform magnetic field. The jitter radiation resulting from small scale magnetic field structures may be important for understanding the complex time structure and spectral evolution observed in gamma-ray bursts or other astrophysical sources containing relativistic jets and relativistic collisionless shocks.

Particle Acceleration and Magnetic Field Generation in Electron-Positron Relativistic Shocks

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Hardee, P.; Richardson, G.; Preece, R.; Sol, H.; Fishman, G. J.

2005-01-01

Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., Buneman, Weibel, and other two-stream instabilities) created in collisionless shocks are responsible for particle (electron, positron, and ion) acceleration. Using a three-dimensional relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic electron-positron jet front propagating into an ambient electron-positron plasma with and without initial magnetic fields. We find small differences in the results for no ambient and modest ambient magnetic fields. New simulations show that the Weibel instability created in the collisionless shock front accelerates jet and ambient particles both perpendicular and parallel to the jet propagation direction. Furthermore, the nonlinear fluctuation amplitudes of densities, currents, and electric and magnetic fields in the electron-positron shock are larger than those found in the electron-ion shock studied in a previous paper at a comparable simulation time. This comes from the fact that both electrons and positrons contribute to generation of the Weibel instability. In addition, we have performed simulations with different electron skin depths. We find that growth times scale inversely with the plasma frequency, and the sizes of structures created by tine Weibel instability scale proportionally to the electron skin depth. This is the expected result and indicates that the simulations have sufficient grid resolution. While some Fermi acceleration may occur at the jet front, the majority of electron and positron acceleration takes place behind the jet front and cannot be characterized as Fermi acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying nonuniform, small-scale magnetic fields, which contribute to the electron s (positron s) transverse deflection behind the jet head. This small- scale magnetic field structure is appropriate to the generation of "jitter" radiation from deflected electrons (positrons) as opposed to synchrotron radiation. The jitter radiation has different properties than synchrotron radiation calculated assuming a uniform magnetic field. The jitter radiation resulting from small-scale magnetic field structures may be important for understanding the complex time structure and spectral evolution observed in gamma-ray bursts or other astrophysical sources containing relativistic jets and relativistic collisionless shocks.

Earth, air, fire and water: A targetry quartet

NASA Astrophysics Data System (ADS)

Valdovinos, Hector F.; Graves, Stephen; Ellison, Paul; Barnhart, Todd; Nickles, Robert J.

2017-05-01

Cyclotron targets have made steady progress in terms of current capabilities, automated handling and application to isotopically-enriched material. These advances have followed a distinct trajectory at the University of Wisconsin, with the emphasis on maximizing the yield of the desired radionuclide within the strict constraints of heat transfer of beam power and the ultimate recycling of precious target stock. This approach leads to four target families, each employed in the production of the positron-emitting transition metals of the 3d- and 4d-subshells, with importance now arising as targeted molecular imaging agents.

Detection efficiency calculation for photons, electrons and positrons in a well detector. Part I: Analytical model

NASA Astrophysics Data System (ADS)

Pommé, S.

2009-06-01

An analytical model is presented to calculate the total detection efficiency of a well-type radiation detector for photons, electrons and positrons emitted from a radioactive source at an arbitrary position inside the well. The model is well suited to treat a typical set-up with a point source or cylindrical source and vial inside a NaI well detector, with or without lead shield surrounding it. It allows for fast absolute or relative total efficiency calibrations for a wide variety of geometrical configurations and also provides accurate input for the calculation of coincidence summing effects. Depending on its accuracy, it may even be applied in 4π-γ counting, a primary standardisation method for activity. Besides an accurate account of photon interactions, precautions are taken to simulate the special case of 511 keV annihilation quanta and to include realistic approximations for the range of (conversion) electrons and β -- and β +-particles.

Design and Modular Construction of A Polymeric Nanoparticle for Targeted Atherosclerosis Positron Emission Tomography Imaging: A Story of 25% 64Cu-CANF-Comb

PubMed Central

Woodard, Pamela K.; Liu, Yongjian; Pressly, Eric D.; Luehmann, Hannah P.; Detering, Lisa; Sultan, Deborah; Laforest, Richard; McGrath, Alaina J.; Gropler, Robert J.; Hawker, Craig J.

2016-01-01

Purpose To assess the physicochemical properties, pharmacokinetic profiles, and in vivo positron emission tomography (PET) imaging of natriuretic peptide clearance receptors (NPRC) expressed on atherosclerotic plaque of a series of targeted, polymeric nanoparticles. Methods To control their structure, non-targeted and targeted polymeric (comb) nanoparticles, conjugated with various amounts of c-atrial natriuretic peptide (CANF, 0, 5, 10 and 25%), were synthesized by controlled and modular chemistry. In vivo pharmacokinetic evaluation of these nanoparticles was performed in wildtype (WT) C57BL/6 mice after 64Cu radiolabeling. PET imaging was performed on an apolipoprotein E–deficient (ApoE−/−) mouse atherosclerosis model to assess the NPRC targeting efficiency. For comparison, an in vivo blood metabolism study was carried out in WT mice. Results All three 64Cu-CANF-comb nanoparticles showed improved biodistribution profiles, including significantly reduced accumulation in both liver and spleen, compared to the non-targeted 64Cu-comb. Of the three nanoparticles, the 25% 64Cu-CANF-comb demonstrated the best NPRC targeting specificity and sensitivity in ApoE−/− mice. Metabolism studies showed that the radiolabeled CANF-comb was stable in blood up to 9 days. Histopathological analyses confirmed the up-regulation of NPRC along the progression of atherosclerosis. Conclusion The 25% 64Cu-CANF-comb demonstrated its potential as a PET imaging agent to detect atherosclerosis progression and status. PMID:27286872

Harvesting the decay energy of 26Al to drive lightning discharge in protoplanetary discs

NASA Astrophysics Data System (ADS)

Johansen, Anders; Okuzumi, Satoshi

2018-01-01

Chondrules in primitive meteorites likely formed by recrystallisation of dust aggregates that were flash-heated to nearly complete melting. Chondrules may represent the building blocks of rocky planetesimals and protoplanets in the inner regions of protoplanetary discs, but the source of ubiquitous thermal processing of their dust aggregate precursors remains elusive. Here we demonstrate that escape of positrons released in the decay of the short-lived radionuclide 26Al leads to a large-scale charging of dense pebble structures, resulting in neutralisation by lightning discharge and flash-heating of dust and pebbles. This charging mechanism is similar to a nuclear battery where a radioactive source charges a capacitor. We show that the nuclear battery effect operates in circumplanetesimal pebble discs. The extremely high pebble densities in such discs are consistent with conditions during chondrule heating inferred from the high abundance of sodium within chondrules. The sedimented mid-plane layer of the protoplanetary disc may also be prone to charging by the emission of positrons, if the mass density of small dust there is at least an order of magnitude above the gas density. Our results imply that the decay energy of 26Al can be harvested to drive intense lightning activity in protoplanetary discs. The total energy stored in positron emission is comparable to the energy needed to melt all solids in the protoplanetary disc. The efficiency of transferring the positron energy to the electric field nevertheless depends on the relatively unknown distribution and scale-dependence of pebble density gradients in circumplanetesimal pebble discs and in the protoplanetary disc mid-plane layer.

Radiation absorbed dose to bladder walls from positron emitters in the bladder content.

PubMed

Powell, G F; Chen, C T

1987-01-01

A method to calculate absorbed doses at depths in the walls of a static spherical bladder from a positron emitter in the bladder content has been developed. The beta ray dose component is calculated for a spherical model by employing the solutions to the integration of Loevinger and Bochkarev point source functions over line segments and a line segment source array technique. The gamma ray dose is determined using the specific gamma ray constant. As an example, absorbed radiation doses to the bladder walls from F-18 in the bladder content are presented for static spherical bladder models having radii of 2.0 and 3.5 cm, respectively. Experiments with ultra-thin thermoluminescent dosimeters (TLD's) were performed to verify the results of the calculations. Good agreement between TLD measurements and calculations was obtained.

Upgrade of the Surface Spectrometer at NEPOMUC for PAES, XPS and STM Investigations

NASA Astrophysics Data System (ADS)

Zimnik, S.; Lippert, F.; Hugenschmidt, C.

2014-04-01

The characterization of the elemental composition of surfaces is of great importance for the understanding of many surface processes, such as surface segregation or oxidation. Positron-annihilation-induced Auger Electron Spectroscopy (PAES) is a powerful technique for gathering information about the elemental composition of only the topmost atomic layer of a sample. The upgraded surface spectrometer at NEPOMUC (NEtron induced POsitron source MUniCh) enables a comprehensive surface analysis with the complementary techniques STM, XPS and PAES. A new X-ray source for X-ray induced photoelectron spectroscopy (XPS) was installed to gather additional information on oxidation states. A new scanning tunneling microscope (STM) is used as a complementary method to investigate with atomic resolution the surface electron density. The combination of PAES, XPS and STM allows the characterization of both the elemental composition, and the surface topology.

Dust Ion-Acoustic Shock Waves in a Multicomponent Magnetorotating Plasma

NASA Astrophysics Data System (ADS)

Kaur, Barjinder; Saini, N. S.

2018-02-01

The nonlinear properties of dust ion-acoustic (DIA) shock waves in a magnetorotating plasma consisting of inertial ions, nonextensive electrons and positrons, and immobile negatively charged dust are examined. The effects of dust charge fluctuations are not included in the present investigation, but the ion kinematic viscosity (collisions) is a source of dissipation, leading to the formation of stable shock structures. The Zakharov-Kuznetsov-Burgers (ZKB) equation is derived using the reductive perturbation technique, and from its solution the effects of different physical parameters, i.e. nonextensivity of electrons and positrons, kinematic viscosity, rotational frequency, and positron and dust concentrations, on the characteristics of shock waves are examined. It is observed that physical parameters play a very crucial role in the formation of DIA shocks. This study could be useful in understanding the electrostatic excitations in dusty plasmas in space (e.g. interstellar medium).

The Positronium Radiative Combination Spectrum: Calculation in the Limit of Thermal Positrons and Low Densities

NASA Technical Reports Server (NTRS)

Wallyn, P.; Mahoney, W. A.; Durouchoux, Ph.; Chapuis, C.

1996-01-01

We calculate the intensities of the positronium de-excitation lines for two processes: (1) the radiative combination of free thermal electrons and positrons for transitions with principal quantum number n less than 20, and (2) charge exchange between free positrons and hydrogen and helium atoms, restricting our evaluation to the Lyman-alpha line. We consider a low-density medium modeled by the case A assumption of Baker & Menzel and use the "nL method" of Pengelly to calculate the absolute intensities. We also evaluate the positronium fine and hyperfine intensities and show that these transitions are in all cases much weaker than positronium de-excitation lines in the same wavelength range. We also extrapolate our positronium de-excitation intensities to the submillimeter, millimeter, and centimeter wavelengths. Our results favor the search of infrared transitions of positronium lines for point sources when the visual extinction A, is greater than approx. 5.

Bruno Touschek: From Betatrons to Electron-Positron Colliders

NASA Astrophysics Data System (ADS)

Bernardini, Carlo; Pancheri, Giulia; Pellegrini, Claudio

Bruno Touschek's life as a physicist spanned the period from World War II to the 1970s. He was a key figure in the developments of electron-positron colliders and storage rings, and made important contributions to theoretical high energy physics. Storage rings, initially developed for high energy physics, are being widely used in many countries as synchrotron radiation sources and are a tool for research in physics, chemistry, biology, environmental sciences and cultural heritage studies. We describe Touschek's life in Austria, where he was born, in Germany, where he participated in the construction of a betatron during WWII, and in Italy, where he proposed and led to completion the first electron-positron storage ring in 1960, in Frascati. We highlight how his central European culture influenced his lifestyle and work, and his main contributions to physics, such as the discovery of the Touschek effect and beam instabilities in the larger storage ring ADONE.

Bruno Touschek: From Betatrons to Electron-Positron Colliders

NASA Astrophysics Data System (ADS)

Bernardini, Carlo; Pancheri, Giulia; Pellegrini, Claudio

Bruno Touschek’s life as a physicist spanned the period from World War II to the 1970s. He was a key figure in the developments of electron-positron colliders and storage rings, and made important contributions to theoretical high energy physics. Storage rings, initially developed for high energy physics, are being widely used in many countries as synchrotron radiation sources and are a tool for research in physics, chemistry, biology, environmental sciences and cultural heritage studies. We describe Touschek’s life in Austria, where he was born, in Germany, where he participated in the construction of a betatron during WWII, and in Italy, where he proposed and led to completion the first electron-positron storage ring in 1960, in Frascati. We highlight how his central European culture influenced his lifestyle and work, and his main contributions to physics, such as the discovery of the Touschek effect and beam instabilities in the larger storage ring ADONE.

Four-Dimensional Positron Emission Tomography: Implications for Dose Painting of High-Uptake Regions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aristophanous, Michalis, E-mail: maristophanous@lroc.harvard.edu; Yap, Jeffrey T.; Killoran, Joseph H.

Purpose: To investigate the behavior of tumor subvolumes of high [18F]-fluorodeoxyglucose (FDG) uptake as seen on clinical four-dimensional (4D) FDG-positron emission tomography (PET) scans. Methods and Materials: Four-dimensional FDG-PET/computed tomography scans from 13 patients taken before radiotherapy were available. The analysis was focused on regions of high uptake that are potential dose-painting targets. A total of 17 lesions (primary tumors and lymph nodes) were analyzed. On each one of the five phases of the 4D scan a classification algorithm was applied to obtain the region of highest uptake and segment the tumor volume. We looked at the behavior of bothmore » the high-uptake subvolume, called 'Boost,' and the segmented tumor volume, called 'Target.' We measured several quantities that characterize the Target and Boost volumes and quantified correlations between them. Results: The behavior of the Target could not always predict the behavior of the Boost. The shape deformation of the Boost regions was on average 133% higher than that of the Target. The gross to internal target volume expansion was on average 27.4% for the Target and 64% for the Boost, a statistically significant difference (p < 0.05). Finally, the inhale-to-exhale phase (20%) had the highest shape deformation for the Boost regions. Conclusions: A complex relationship between the measured quantities for the Boost and Target volumes is revealed. The results suggest that in cases in which advanced therapy techniques such as dose painting are being used, a close examination of the 4D PET scan should be performed.« less

Cerenkov radiation allows in vivo optical imaging of positron emitting radiotracers

NASA Astrophysics Data System (ADS)

Spinelli, Antonello E.; D'Ambrosio, Daniela; Calderan, Laura; Marengo, Mario; Sbarbati, Andrea; Boschi, Federico

2010-01-01

In this paper, we showed that Cerenkov radiation (CR) escaping from the surface of small living animals injected with 18F-FDG can be detected with optical imaging techniques. 18F decays by emitting positrons with a maximum energy of 0.635 MeV; such positrons, when travelling into tissues faster than the speed of light in the same medium, are responsible of CR emission. A detailed model of the CR spectrum considering the positron energy spectrum was developed in order to quantify the amount of light emission. The results presented in this work were obtained using a commercial optical imager equipped with charged coupled detectors (CCD). Our data open the door to optical imaging (OI) in vivo of the glucose metabolism, at least in pre-clinical research. We found that the heart and bladder can be clearly identified in the animal body reflecting the accumulation of the 18F-FDG. Moreover, we describe two different methods based on the spectral analysis of the CR that can be used to estimate the depth of the source inside the animal. We conclude that 18F-FDG can be employed as it is as a bimodal tracer for positron emission tomography (PET) and OI techniques. Our results are encouraging, suggesting that it could be possible to apply the proposed approach not only to β+ but also to pure β- emitters.

Cerenkov radiation allows in vivo optical imaging of positron emitting radiotracers.

PubMed

Spinelli, Antonello E; D'Ambrosio, Daniela; Calderan, Laura; Marengo, Mario; Sbarbati, Andrea; Boschi, Federico

2010-01-21

In this paper, we showed that Cerenkov radiation (CR) escaping from the surface of small living animals injected with (18)F-FDG can be detected with optical imaging techniques. (18)F decays by emitting positrons with a maximum energy of 0.635 MeV; such positrons, when travelling into tissues faster than the speed of light in the same medium, are responsible of CR emission. A detailed model of the CR spectrum considering the positron energy spectrum was developed in order to quantify the amount of light emission. The results presented in this work were obtained using a commercial optical imager equipped with charged coupled detectors (CCD). Our data open the door to optical imaging (OI) in vivo of the glucose metabolism, at least in pre-clinical research. We found that the heart and bladder can be clearly identified in the animal body reflecting the accumulation of the (18)F-FDG. Moreover, we describe two different methods based on the spectral analysis of the CR that can be used to estimate the depth of the source inside the animal. We conclude that (18)F-FDG can be employed as it is as a bimodal tracer for positron emission tomography (PET) and OI techniques. Our results are encouraging, suggesting that it could be possible to apply the proposed approach not only to beta(+) but also to pure beta(-) emitters.

Positron-induced Auger-electron study of the Ge(100) surface: Positron thermal desorption and surface condition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soininen, E.; Schwab, A.; Lynn, K.G.

1991-05-01

Positron-annihilation-induced Auger-electron spectroscopy (PAES) was used to study the effects of oxygen, residual gases, and temperature on a Ge(100) surface. Three low-energy Auger peaks were detected at 50, 90, and 100--150 eV, attributed to {ital M}{sub 2,3}{ital M4}{ital M4}, {ital M}{sub 2,3}{ital M4}{ital V}, and {ital M}{sub 1}{ital M4}{ital M4} Auger transitions, respectively. An estimated (4{plus minus}1)% of the surface-trapped positrons annihilate with Ge 3{ital p}--level electrons. The sensitivity of PAES to the surface condition is demonstrated. The PAES yield from a Ge(100) surface is reduced at elevated temperatures, in accord with an activation process earlier found in several positroniummore » (Ps) -fraction experiments. A desorption model adopted from these studies does not describe accurately the PAES results at higher temperatures ({gt}500 {degree}C), where the PAES intensity levels off to 5% of the room-temperature value. Possible sources for the discrepancy are discussed and models for positron trapping to deep surface traps are introduced. On the Ge(100) surface, an upper limit for Ps emission near the melting point is 97%. The error in calibration parameters due to the earlier assumption of 100% Ps emission seems to introduce only small errors into the Ps-fraction measurements.« less

A diamond active target for the PADME experiment

NASA Astrophysics Data System (ADS)

Chiodini, G.

2017-02-01

The PADME (Positron Annihilation into Dark Mediator Experiment) collaboration searches for dark photons produced in the annihilation e++e-→γ+A' of accelerated positrons with atomic electrons of a fixed target at the Beam Test Facility of Laboratori Nazionali di Frascati. The apparatus can detect dark photons decaying into visible A'→e+e- and invisible A'→χχ channels, where χ's are particles of a secluded sector weakly interacting and therefore undetected. In order to improve the missing mass resolution and to measure the beam flux, PADME has an active target able to reconstruct the beam spot position and the bunch multiplicity. In this work the active target is described, which is made of a detector grade polycrystalline synthetic diamond with strip electrodes on both surfaces. The electrodes segmentation allows to measure the beam profile along X and Y and evaluate the average beam position bunch per bunch. The results of beam tests for the first two diamond detector prototypes are shown. One of them holds innovative graphitic electrodes built with a custom process developed in the laboratory, and the other one with commercially available traditional Cr-Au electrodes. The front-end electronics used in the test beam is discussed and the performance observed is presented. Finally, the final design of the target to be realized at the beginning of 2017 to be ready for data taking in 2018 is illustrated.

Targeted Lymphoma Cell Death by Novel Signal Transduction Modifications

DTIC Science & Technology

2010-07-14

CD22 -binding peptides that initiate signal transduction and apoptosis in non-Hodgkin’s lymphoma (NHL), 2) optimize CD22 -mediated signal transduction...and lymphomacidal properties of ligand blocking anti- CD22 monoclonal antibodies (mAbs) and peptides with CD22 -specific phosphatase inhibition and 3...correlate mAb-mediated and anti- CD22 peptide-mediated in vivo physiologic changes, efficacy, and tumor targeting using advanced immuno-positron

Syntheses of precursors and reference compounds of the melanin-concentrating hormone receptor 1 (MCHR1) tracers [¹¹C]SNAP-7941 and [¹⁸F]FE@SNAP for positron emission tomography.

PubMed

Schirmer, Eva; Shanab, Karem; Datterl, Barbara; Neudorfer, Catharina; Mitterhauser, Markus; Wadsak, Wolfgang; Philippe, Cécile; Spreitzer, Helmut

2013-09-30

The MCH receptor has been revealed as a target of great interest in positron emission tomography imaging. The receptor's eponymous substrate melanin-concentrating hormone (MCH) is a cyclic peptide hormone, which is located predominantly in the hypothalamus with a major influence on energy and weight regulation as well as water balance and memory. Therefore, it is thought to play an important role in the pathophysiology of adiposity, which is nowadays a big issue worldwide. Based on the selective and high-affinity MCH receptor 1 antagonist SNAP-7941, a series of novel SNAP derivatives has been developed to provide different precursors and reference compounds for the radiosyntheses of the novel PET radiotracers [(11)C]SNAP-7941 and [(18)F]FE@SNAP. Positron emission tomography promotes a better understanding of physiologic parameters on a molecular level, thus giving a deeper insight into MCHR1 related processes as adiposity.

Optical and positron annihilation spectroscopic studies on PMMA polymer doped by rhodamine B/chloranilic acid charge transfer complex: Special relevance to the effect of γ-ray irradiation.

PubMed

Hassan, H E; Refat, Moamen S; Sharshar, T

2016-04-15

Polymeric sheets of poly (methylmethaclyerate) (PMMA) containing charge transfer (CT) complex of rhodamine B/chloranilic acid (Rho B/CHA) were synthesized in methanol solvent at room temperature. The systematic analysis done on the Rho B and its CT complex in the form of powder or polymeric sheets confirmed their structure and thermal stability. The IR spectra interpreted the charge transfer mode of interaction between the CHA central positions and the terminal carboxylic group. The polymer sheets were irradiated with 70 kGy of γ radiation using (60)Co source to study the enhanced changes in the structure and optical parameters. The microstructure changes of the PMMA sheets caused by γ-ray irradiation were analyzed using positron annihilation lifetime (PAL) and positron annihilation Doppler broadening (PADB) techniques. The positron life time components (τ(i)) and their corresponding intensities (I(i)) as well as PADB line-shape parameters (S and W) were found to be highly sensitive to the enhanced disorder occurred in the organic chains of the polymeric sheets due to γ-irradiation. Copyright © 2016 Elsevier B.V. All rights reserved.

On possible interpretations of the high energy electron–positron spectrum measured by the Fermi Large Area Telescope

DOE PAGES

Grasso, D.; Profumo, S.; Strong, A. W.; ...

2009-07-11

The Fermi-LAT experiment recently reported high precision measurements of the spectrum of cosmic-ray electrons-plus-positrons (CRE) between 20 GeV and 1 TeV. The spectrum shows no prominent spectral features, and is significantly harder than that inferred from several previous experiments. In this paper, we discuss several interpretations of the Fermi results based either on a single large scale Galactic CRE component or by invoking additional electron–positron primary sources, e.g. nearby pulsars or particle dark matter annihilation. We show that while the reported Fermi-LAT data alone can be interpreted in terms of a single component scenario, when combined with other complementary experimentalmore » results, specifically the CRE spectrum measured by H.E.S.S. and especially the positron fraction reported by PAMELA between 1 and 100 GeV, that class of models fails to provide a consistent interpretation. Rather, we find that several combinations of parameters, involving both the pulsar and dark matter scenarios, allow a consistent description of those results. Finally, we also briefly discuss the possibility of discriminating between the pulsar and dark matter interpretations by looking for a possible anisotropy in the CRE flux.« less

Target depth dependence of damage rate in metals by 150 MeV proton irradiation

NASA Astrophysics Data System (ADS)

Yoshiie, T.; Ishi, Y.; Kuriyama, Y.; Mori, Y.; Sato, K.; Uesugi, T.; Xu, Q.

2015-01-01

A series of irradiation experiments with 150 MeV protons was performed. The relationship between target depth (or shield thickness) and displacement damage during proton irradiation was obtained by in situ electrical resistance measurements at 20 K. Positron annihilation lifetime measurements were also performed at room temperature after irradiation, as a function of the target thickness. The displacement damage was found to be high close to the beam incident surface area, and decreased with increasing target depth. The experimental results were compared with damage production calculated with an advanced Monte Carlo particle transport code system (PHITS).

Theoretical Interpretation of Pass 8 Fermi -LAT e {sup +} + e {sup −} Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Di Mauro, M.; Manconi, S.; Donato, F.

The flux of positrons and electrons ( e {sup +} + e {sup −}) has been measured by the Fermi Large Area Telescope (LAT) in the energy range between 7 GeV and 2 TeV. We discuss a number of interpretations of Pass 8 Fermi -LAT e {sup +} + e {sup −} spectrum, combining electron and positron emission from supernova remnants (SNRs) and pulsar wind nebulae (PWNe), or produced by the collision of cosmic rays (CRs) with the interstellar medium. We find that the Fermi -LAT spectrum is compatible with the sum of electrons from a smooth SNR population, positronsmore » from cataloged PWNe, and a secondary component. If we include in our analysis constraints from the AMS-02 positron spectrum, we obtain a slightly worse fit to the e {sup +} + e {sup −} Fermi -LAT spectrum, depending on the propagation model. As an additional scenario, we replace the smooth SNR component within 0.7 kpc with the individual sources found in Green’s catalog of Galactic SNRs. We find that separate consideration of far and near sources helps to reproduce the e {sup +} + e {sup −} Fermi -LAT spectrum. However, we show that the fit degrades when the radio constraints on the positron emission from Vela SNR (which is the main contributor at high energies) are taken into account. We find that a break in the power-law injection spectrum at about 100 GeV can also reproduce the measured e {sup +} + e {sup −} spectrum and, among the CR propagation models that we consider, no reasonable break of the power-law dependence of the diffusion coefficient can modify the electron flux enough to reproduce the observed shape.« less

Minimum length Pb/SCIN detector for efficient cosmic ray identification

NASA Technical Reports Server (NTRS)

Snyder, H. David

1989-01-01

A study was made of the performance of a minimal length cosmic ray shower detector that would be light enough for space flight and would provide efficient identification of positions and protons. Cosmic ray positions are mainly produced in the decay chain of: Pion yields Muon yields Positron and they provide a measure of the matter density traversed by primary protons. Present positron flux measurements are consistent with the Leaky Box and Halo models for sources of cosmic rays. Abundant protons in the space environment are a significant source of background that would wash out the positron signal. Protons and positrons produced very distictive showers of particles when they enter matter; many studies have been published on their behavior on large calorimeter detectors. The challenge is to determine the minimal material necessary (minimal calorimeter depth) for positive particles identification. The primary instrument for the investigation is the Monte Carlo code GEANT, a library of programs from CERN that can be used to model experimental geometry, detector responses and particle interaction processes. The use of the Monte Carlo approach is crucial since statistical fluctuations in shower shape are significant. Studies conducted during the 1988 summer program showed that straightforward approaches to the problem achieved 85 to 90 percent correct identification, but left a residue of 10 to 15 percent misidentified particles. This percentage improved to a few percent when multiple shower-cut criteria were applied to the data. This summer, the same study was extended to employ several physical and statistical methods of identifying response of the calorimeter and the efficiency of the optimal shower cuts to off-normal incidence particle was determined.

a Positron 2D-ACAR Study of the Silicon-Dioxide Interface and the Point Defects in the Semi-Insulating Gallium Arsenide

NASA Astrophysics Data System (ADS)

Peng, Jianping

The SiO_2-Si system has been the subject of extensive study for several decades. Particular interest has been paid to the interface between Si single crystal and the amorphous SiO_2 which determines the properties and performances of devices. This is significant because of the importance of Si technology in the semiconductor industry. The development of the high-intensity slow positron beam at Brookhaven National Laboratory make it possible to study this system for the first time using the positron two-dimensional angular correlation of annihilation radiation (2D-ACAR) technique. 2D-ACAR is a well established and is a non-destructive microscopic probe for studying the electronic structure of materials, and for doing the depth-resolved measurements. Some unique information was obtained from the measurements performed on the SiO_2-Si system: Positronium (Ps) atoms formation and trapping in microvoids in both oxide and interface regions; and positron annihilation at vacancy-like defects in the interface region which can be attributed to the famous Pb centers. The discovery of the microvoids in the interface region may have some impact on the fabrication of the next generation electronic devices. Using the conventional 2D-ACAR setup with a ^{22}Na as positron source, we also studied the native arsenic (As) vacancy in the semi -insulating gallium-arsenide (SI-GaAs), coupled with in situ infrared light illumination. The defect spectrum was obtained by comparing the spectrum taken without photo -illumination to the spectrum taken with photo-illumination. The photo-illumination excited electrons from valence band to the defect level so that positrons can become localized in the defects. The two experiments may represent a new direction of the application of positron 2D-ACAR technique on the solid state physics and materials sciences.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Radchenko, Valery; Meyer, Catherine Anne Louise; Engle, Jonathan Ward

Scandium-44 g (half-life 3.97 h) shows promise for positron emission tomography (PET) imaging of longer biological processes than that of the current gold standard, 18F, due to its favorable decay parameters. One source of 44gSc is the long-lived parent nuclide 44Ti (half-life 60.0 a). A 44Ti/ 44gSc generator would have the ability to provide radionuclidically pure 44gSc on a daily basis. The production of 44Ti via the 45Sc(p,2n) reaction requires high proton beam currents and long irradiation times. Recovery and purification of no-carrier added (nca) 44Ti from scandium metal targets involves complex separation chemistry. In this study, separation systems basedmore » on solid phase extraction chromatography were investigated, including branched diglycolamide (BDGA) resin and hydroxamate based ZR resin. Lastly, results indicate that ZR resin in HCl media represents an effective 44Ti/ 44gSc separation system.« less

THERANOSTICS: From Molecular Imaging Using Ga-68 Labeled Tracers and PET/CT to Personalized Radionuclide Therapy - The Bad Berka Experience

PubMed Central

Baum, Richard P.; Kulkarni, Harshad R.

2012-01-01

The acronym THERANOSTICS epitomizes the inseparability of diagnosis and therapy, the pillars of medicine and takes into account personalized management of disease for a specific patient. Molecular phenotypes of neoplasms can be determined by molecular imaging with specific probes using positron emission tomography (PET), single photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), or optical methods, so that the treatment is specifically targeted against the tumor and its environment. To meet these demands, we need to define the targets, ligands, coupling and labeling chemistry, the most appropriate radionuclides, biodistribution modifiers, and finally select the right patients for the personalized treatment. THERANOSTICS of neuroendocrine tumors (NETs) using Ga-68 labeled tracers for diagnostics with positron emission tomography/ computed tomography (PET/CT), and using Lu-177 or other metallic radionuclides for radionuclide therapy by applying the same peptide proves that personalized radionuclide therapy today is already a fact and not a fiction. PMID:22768024

THERANOSTICS: From Molecular Imaging Using Ga-68 Labeled Tracers and PET/CT to Personalized Radionuclide Therapy - The Bad Berka Experience.

PubMed

Baum, Richard P; Kulkarni, Harshad R

2012-01-01

The acronym THERANOSTICS epitomizes the inseparability of diagnosis and therapy, the pillars of medicine and takes into account personalized management of disease for a specific patient. Molecular phenotypes of neoplasms can be determined by molecular imaging with specific probes using positron emission tomography (PET), single photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), or optical methods, so that the treatment is specifically targeted against the tumor and its environment. To meet these demands, we need to define the targets, ligands, coupling and labeling chemistry, the most appropriate radionuclides, biodistribution modifiers, and finally select the right patients for the personalized treatment. THERANOSTICS of neuroendocrine tumors (NETs) using Ga-68 labeled tracers for diagnostics with positron emission tomography/ computed tomography (PET/CT), and using Lu-177 or other metallic radionuclides for radionuclide therapy by applying the same peptide proves that personalized radionuclide therapy today is already a fact and not a fiction.

PREFACE: 13th International Workshop on Slow Positron Beam Techniques and Applications (SLOPOS13)

NASA Astrophysics Data System (ADS)

2014-04-01

These proceedings originate from the 13th International Workshop on Slow Positron Beam Techniques and Applications SLOPOS13 which was held at the campus of the Technische Universität München in Garching between 15th-20th September, 2013. This event is part of a series of triennial SLOPOS conferences. In total 123 delegates from 21 countries participated in the SLOPOS13. The excellent scientific program comprised 50 talks and 58 posters presented during two poster sessions. It was very impressive to learn about novel technical developments on positron beam facilities and the wide range of their applications all over the world. The workshop reflected the large variety of positron beam experiments covering fundamental studies, e.g., for efficient production of anti-hydrogen as well as applied research on defects in bulk materials, thin films, surfaces, and interfaces. The topics comprised: . Positron transport and beam technology . Pulsed beams and positron traps . Defect profiling in bulk and layered structures . Nanostructures, porous materials, thin films . Surfaces and interfaces . Positronium formation and emission . Positron interactions with atoms and molecules . Many positrons and anti-hydrogen . Novel experimental techniques The international advisory committee of SLOPOS awarded student prizes for the best presented scientific contributions to a team of students from Finland, France, and the NEPOMUC team at TUM. The conference was overshadowed by the sudden death of Professor Klaus Schreckenbach immediately before the workshop. In commemoration of him as a spiritus rectus of the neutron induced positron source a minutes' silence was hold. We are most grateful for the hard work of the Local Organising Committee, the help of the International Advisory Committee, and all the students for their friendly and efficient support during the meeting. The workshop could not have occurred without the generous support of the Heinz Maier-Leibnitz Zentrum (MLZ), Deutsche Forschungsgemeinschaft (DFG), and IOP publishing. Finally we would like to thank all attendees for their outstanding scientific contributions to SLOPOS13, and for the fruitful scientific discussions also in informal atmosphere during the social events. We are looking forward to SLOPOS14 in Japan in 2016! Christoph Hugenschmidt and Christian Piochacz (Guest Editors) Garching, March 2014 Further conference and committee information, as well as the conference picture, can be viewed in the pdf.

A novel fluorine-18 β-fluoroethoxy organophosphate positron emission tomography imaging tracer targeted to central nervous system acetylcholinesterase.

PubMed

James, Shelly L; Ahmed, S Kaleem; Murphy, Stephanie; Braden, Michael R; Belabassi, Yamina; VanBrocklin, Henry F; Thompson, Charles M; Gerdes, John M

2014-07-16

Radiosynthesis of a fluorine-18 labeled organophosphate (OP) inhibitor of acetylcholinesterase (AChE) and subsequent positron emission tomography (PET) imaging using the tracer in the rat central nervous system are reported. The tracer structure, which contains a novel β-fluoroethoxy phosphoester moiety, was designed as an insecticide-chemical nerve agent hybrid to optimize handling and the desired target reactivity. Radiosynthesis of the β-fluoroethoxy tracer is described that utilizes a [(18)F]prosthetic group coupling approach. The imaging utility of the [(18)F]tracer is demonstrated in vivo within rats by the evaluation of its brain penetration and cerebral distribution qualities in the absence and presence of a challenge agent. The tracer effectively penetrates brain and localizes to cerebral regions known to correlate with the expression of the AChE target. Brain pharmacokinetic properties of the tracer are consistent with the formation of an OP-adducted acetylcholinesterase containing the fluoroethoxy tracer group. Based on the initial favorable in vivo qualities found in rat, additional [(18)F]tracer studies are ongoing to exploit the technology to dynamically probe organophosphate mechanisms of action in mammalian live tissues.

Review of Gallium-68 PSMA PET/CT Imaging in the Management of Prostate Cancer

PubMed Central

Lenzo, Nat P.; Meyrick, Danielle; Turner, J. Harvey

2018-01-01

Over 90% of prostate cancers over-express prostate specific membrane antigen (PSMA) and these tumor cells may be accurately targeted for diagnosis by 68Ga-PSMA-positron emission tomography/computed tomography (68Ga-PSMA-PET/CT) imaging. This novel molecular imaging modality appears clinically to have superseded CT, and appears superior to MR imaging, for the detection of metastatic disease. 68Ga-PSMA PET/CT has the ability to reliably stage prostate cancer at presentation and can help inform an optimal treatment approach. Novel diagnostic applications of 68Ga-PSMA PET/CT include guiding biopsy to improve sampling accuracy, and guiding surgery and radiotherapy. In addition to facilitating the management of metastatic castrate resistant prostate cancer (mCRPC), 68Ga-PSMA can select patients who may benefit from targeted systemic radionuclide therapy. 68Ga-PSMA is the diagnostic positron-emitting theranostic pair with the beta emitter Lutetium-177 PSMA (177Lu-PSMA) and alpha-emitter Actinium-225 PSMA (225Ac-PSMA) which can both be used to treat PSMA-avid metastases of prostate cancer in the molecular tumor-targeted approach of theranostic nuclear oncology. PMID:29439481

Conceptual achievement of 1GBq activity in a Plasma Focus driven system.

PubMed

Tabbakh, Farshid; Sadat Kiai, Seyed Mahmood; Pashaei, Mohammad

2017-11-01

This is an approach to evaluate the radioisotope production by means of typical dense plasma focus devices. The production rate of the appropriate positron emitters, F-18, N-13 and O-15 has been studied. The beam-target mechanism was simulated by GEANT4 Monte Carlo tool using QGSP_BIC and QGSP_INCLXX physic models as comparison. The results for positron emitters have been evaluated by reported experimental data and found conformity between simulations and experimental reports that leads to using this code as a reliable tool in optimizing the DPF driven systems for achieving to 1GBq activity of produced radioisotope. Copyright © 2017 Elsevier Ltd. All rights reserved.

Nonmetastatic Castration-resistant Prostate Cancer: A Modern Perspective.

PubMed

Cancian, Madeline; Renzulli, Joseph F

2018-06-01

Nonmetastatic castration-resistant prostate cancer (nmCRPC) presents a challenge to urologists as currently there are no Food and Drug Administration-approved therapies. However, there are new imaging modalities, including fluciclovine positron emission tomography-computed tomography and Ga-PSMA (prostate specific membrane antigent) positron emission tomography-computed tomography, which are improving accuracy of diagnosis. With improved imaging, we are better able to target therapy. Today there are 3 ongoing clinical trials studying second-generation antiandrogens in nmCRPC, which hold the promise of a new treatment paradigm. In this article, we will review the new imaging techniques and the rationale behind novel treatment modalities in nmCRPC. Copyright © 2018 Elsevier Inc. All rights reserved.

A promising new mechanism of ionizing radiation detection for positron emission tomography: Modulation of optical properties

PubMed Central

Tao, Li; Daghighian, Henry M.; Levin, Craig S.

2016-01-01

Using conventional scintillation detection, the fundamental limit in positron emission tomography (PET) time resolution is strongly dependent on the inherent temporal variances generated during the scintillation process, yielding an intrinsic physical limit for the coincidence time resolution of around 100 ps. On the other hand, modulation mechanisms of the optical properties of a material exploited in the optical telecommunications industry can be orders of magnitude faster. In this paper we borrow from the concept of optics pump-probe measurement to for the first time study whether ionizing radiation can produce modulations of optical properties, which can be utilized as a novel method for radiation detection. We show that a refractive index modulation of approximately 5 × 10−6 is induced by interactions in a cadmium telluride (CdTe) crystal from a 511 keV photon source. Furthermore, using additional radionuclide sources, we show that the amplitude of the optical modulation signal varies linearly with both the detected event rate and average photon energy of the radiation source. PMID:27716640

DOE Office of Scientific and Technical Information (OSTI.GOV)

Motz, H.; Asaoka, Y.; Torii, S.

CALET (Calorimetric Electron Telescope), installed on the ISS in August 2015, directly measures the electron+positron cosmic rays flux up to 20 TeV. With its proton rejection capability of 1 : 10{sup 5} and an aperture of 1200 cm{sup 2·} sr, it will provide good statistics even well above one TeV, while also featuring an energy resolution of 2%, which allows it to detect fine structures in the spectrum. Such structures may originate from Dark Matter annihilation or decay, making indirect Dark Matter search one of CALET's main science objectives among others such as identification of signatures from nearby supernova remnants, study ofmore » the heavy nuclei spectra and gamma astronomy. The latest results from AMS-02 on positron fraction and total electron+positron flux can be fitted with a parametrization including a single pulsar as an extra power law source with exponential cut-off, which emits an equal amount of electrons and positrons. This single pulsar scenario for the positron excess is extrapolated into the TeV region and the expected CALET data for this case are simulated. Based on this prediction for CALET data, the sensitivity of CALET to Dark Matter annihilation in the galactic halo has been calculated. It is shown that CALET could significantly improve the limits compared to current data, especially for those Dark Matter candidates that feature a large fraction of annihilation directly into e{sup +} + e{sup −}, such as the LKP (Lightest Kaluza-Klein particle)« less

Theranostics Targeting Metastatic Breast Cancer

DTIC Science & Technology

The emphasis of this first year of the award, as planned, has been on synthetic chemistry to obtain materials to test in histology, PET (positron...the previous, highly cytotoxic, compound maytensin A. We have also prepared an agent intended solely for PET , i.e. compound 4; this takes advantage of

Occupancy of Norepinephrine Transporter by Duloxetine in Human Brains Measured by Positron Emission Tomography with (S,S)-[18F]FMeNER-D2.

PubMed

Moriguchi, Sho; Takano, Harumasa; Kimura, Yasuyuki; Nagashima, Tomohisa; Takahata, Keisuke; Kubota, Manabu; Kitamura, Soichiro; Ishii, Tatsuya; Ichise, Masanori; Zhang, Ming-Rong; Shimada, Hitoshi; Mimura, Masaru; Meyer, Jeffrey H; Higuchi, Makoto; Suhara, Tetsuya

2017-12-01

The norepinephrine transporter in the brain has been targeted in the treatment of psychiatric disorders. Duloxetine is a serotonin and norepinephrine reuptake inhibitor that has been widely used for the treatment of depression. However, the relationship between dose and plasma concentration of duloxetine and norepinephrine transporter occupancy in the human brain has not been determined. In this study, we examined norepinephrine transporter occupancy by different doses of duloxetine. We calculated norepinephrine transporter occupancies from 2 positron emission tomography scans using (S,S)-[18F]FMeNER-D2 before and after a single oral dose of duloxetine (20 mg, n = 3; 40 mg, n = 3; 60 mg, n =2). Positron emission tomography scans were performed from 120 to 180 minutes after an i.v. bolus injection of (S,S)-[18F]FMeNER-D2. Venous blood samples were taken to measure the plasma concentration of duloxetine just before and after the second positron emission tomography scan. Norepinephrine transporter occupancy by duloxetine was 29.7% at 20 mg, 30.5% at 40 mg, and 40.0% at 60 mg. The estimated dose of duloxetine inducing 50% norepinephrine transporter occupancy was 76.8 mg, and the estimated plasma drug concentration inducing 50% norepinephrine transporter occupancy was 58.0 ng/mL. Norepinephrine transporter occupancy by clinical doses of duloxetine was approximately 30% to 40% in human brain as estimated using positron emission tomography with (S,S)-[18F]FMeNER-D2. © The Author 2017. Published by Oxford University Press on behalf of CINP.

Positron Scanner for Locating Brain Tumors

DOE R&D Accomplishments Database

Rankowitz, S.; Robertson, J. S.; Higinbotham, W. A.; Rosenblum, M. J.

1962-03-01

A system is described that makes use of positron emitting isotopes for locating brain tumors. This system inherently provides more information about the distribution of radioactivity in the head in less time than existing scanners which use one or two detectors. A stationary circular array of 32 scintillation detectors scans a horizontal layer of the head from many directions simultaneously. The data, consisting of the number of counts in all possible coincidence pairs, are coded and stored in the memory of a Two-Dimensional Pulse-Height Analyzer. A unique method of displaying and interpreting the data is described that enables rapid approximate analysis of complex source distribution patterns. (auth)

Short-pulse, high-energy radiation generation from laser-wakefield accelerated electron beams

NASA Astrophysics Data System (ADS)

Schumaker, Will

2013-10-01

Recent experimental results of laser wakefield acceleration (LWFA) of ~GeV electrons driven by the 200TW HERCULES and the 400TW ASTRA-GEMINI laser systems and their subsequent generation of photons, positrons, and neutrons are presented. In LWFA, high-intensity (I >1019 W /cm2), ultra-short (τL < 1 / (2 πωpe)) laser pulses drive highly nonlinear plasma waves which can trap ~ nC of electrons and accelerate them to ~GeV energies over ~cm lengths. These electron beams can then be converted by a high-Z target via bremsstrahlung into low-divergence (< 20 mrad) beams of high-energy (<600 MeV) photons and subsequently into positrons via the Bethe-Heitler process. By increasing the material thickness and Z, the resulting Ne+ /Ne- ratio can approach unity, resulting in a near neutral density plasma jet. These quasi-neutral beams are presumed to retain the short-pulse (τL < 40 fs) characteristic of the electron beam, resulting in a high peak density of ne- /e+ ~ 1016 cm-3 , making the source an excellent candidate for laboratory study of astrophysical leptonic jets. Alternatively, the electron beam can be interacted with a counter-propagating, ultra-high intensity (I >1021 W /cm2) laser pulse to undergo inverse Compton scattering and emit a high-peak brightness beam of high-energy photons. Preliminary results and experimental sensitivities of the electron-laser beam overlap are presented. The high-energy photon beams can be spectrally resolved using a forward Compton scattering spectrometer. Moreover, the photon flux can be characterized by a pixelated scintillator array and by nuclear activation and (γ,n) neutron measurements from the photons interacting with a secondary solid target. Monte-Carlo simulations were performed using FLUKA to support the yield estimates. This research was supported by DOE/NSF-PHY 0810979, NSF CAREER 1054164, DARPA AXiS N66001-11-1-4208, SF/DNDO F021166, and the Leverhulme Trust ECF-2011-383.

High Purity Pion Beam at TRIUMF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kettell, S.; Kettell, S.; Aguilar-Arevalo, A.

An extension of the TRIUMF M13 low-energy pion channel designed to suppress positrons based on an energy-loss technique is described. A source of beam channel momentum calibration from the decay {pi}{sup +} {yields} e{sup +}{nu} is also described.

Functional anatomy of nonvisual feedback loops during reaching: a positron emission tomography study.

PubMed

Desmurget, M; Gréa, H; Grethe, J S; Prablanc, C; Alexander, G E; Grafton, S T

2001-04-15

Reaching movements performed without vision of the moving limb are continuously monitored, during their execution, by feedback loops (designated nonvisual). In this study, we investigated the functional anatomy of these nonvisual loops using positron emission tomography (PET). Seven subjects had to "look at" (eye) or "look and point to" (eye-arm) visual targets whose location either remained stationary or changed undetectably during the ocular saccade (when vision is suppressed). Slightly changing the target location during gaze shift causes an increase in the amount of correction to be generated. Functional anatomy of nonvisual feedback loops was identified by comparing the reaching condition involving large corrections (jump) with the reaching condition involving small corrections (stationary), after subtracting the activations associated with saccadic movements and hand movement planning [(eye-arm-jumping minus eye-jumping) minus (eye-arm-stationary minus eye-stationary)]. Behavioral data confirmed that the subjects were both accurate at reaching to the stationary targets and able to update their movement smoothly and early in response to the target jump. PET difference images showed that these corrections were mediated by a restricted network involving the left posterior parietal cortex, the right anterior intermediate cerebellum, and the left primary motor cortex. These results are consistent with our knowledge of the functional properties of these areas and more generally with models emphasizing parietal-cerebellar circuits for processing a dynamic motor error signal.

Possibility of testing the light dark matter hypothesis with the alpha magnetic spectrometer.

PubMed

Hooper, Dan; Xue, Wei

2013-01-25

The spectrum and morphology of gamma rays from the Galactic center and the spectrum of synchrotron emission observed from the Milky Way's radio filaments have each been interpreted as possible signals of ∼ 7-10 GeV dark matter particles annihilating in the inner Galaxy. In dark matter models capable of producing these signals, the annihilations should also generate significant fluxes of ∼ 7-10 GeV positrons which can lead to a distinctive bumplike feature in a local cosmic ray positron spectrum. In this Letter, we show that while such a feature would be difficult to detect with PAMELA, it would likely be identifiable by the currently operating Alpha Magnetic Spectrometer experiment. As no known astrophysical (i.e., nondark matter) sources or mechanisms are likely to produce such a sharp feature, the observation of a positron bump at around 7-10 GeV would significantly strengthen the case for a dark matter interpretation of the reported gamma-ray and radio anomalies.

SU-C-204-01: A Fast Analytical Approach for Prompt Gamma and PET Predictions in a TPS for Proton Range Verification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kroniger, K; Herzog, M; Landry, G

2015-06-15

Purpose: We describe and demonstrate a fast analytical tool for prompt-gamma emission prediction based on filter functions applied on the depth dose profile. We present the implementation in a treatment planning system (TPS) of the same algorithm for positron emitter distributions. Methods: The prediction of the desired observable is based on the convolution of filter functions with the depth dose profile. For both prompt-gammas and positron emitters, the results of Monte Carlo simulations (MC) are compared with those of the analytical tool. For prompt-gamma emission from inelastic proton-induced reactions, homogeneous and inhomogeneous phantoms alongside with patient data are used asmore » irradiation targets of mono-energetic proton pencil beams. The accuracy of the tool is assessed in terms of the shape of the analytically calculated depth profiles and their absolute yields, compared to MC. For the positron emitters, the method is implemented in a research RayStation TPS and compared to MC predictions. Digital phantoms and patient data are used and positron emitter spatial density distributions are analyzed. Results: Calculated prompt-gamma profiles agree with MC within 3 % in terms of absolute yield and reproduce the correct shape. Based on an arbitrary reference material and by means of 6 filter functions (one per chemical element), profiles in any other material composed of those elements can be predicted. The TPS implemented algorithm is accurate enough to enable, via the analytically calculated positron emitters profiles, detection of range differences between the TPS and MC with errors of the order of 1–2 mm. Conclusion: The proposed analytical method predicts prompt-gamma and positron emitter profiles which generally agree with the distributions obtained by a full MC. The implementation of the tool in a TPS shows that reliable profiles can be obtained directly from the dose calculated by the TPS, without the need of full MC simulation.« less

Study of transport of laser-driven relativistic electrons in solid materials

NASA Astrophysics Data System (ADS)

Leblanc, Philippe

With the ultra intense lasers available today, it is possible to generate very hot electron beams in solid density materials. These intense laser-matter interactions result in many applications which include the generation of ultrashort secondary sources of particles and radiation such as ions, neutrons, positrons, x-rays, or even laser-driven hadron therapy. For these applications to become reality, a comprehensive understanding of laser-driven energy transport including hot electron generation through the various mechanisms of ionization, and their subsequent transport in solid density media is required. This study will focus on the characterization of electron transport effects in solid density targets using the state-of- the-art particle-in-cell code PICLS. A number of simulation results will be presented on the topics of ionization propagation in insulator glass targets, non-equilibrium ionization modeling featuring electron impact ionization, and electron beam guiding by the self-generated resistive magnetic field. An empirically derived scaling relation for the resistive magnetic in terms of the laser parameters and material properties is presented and used to derive a guiding condition. This condition may prove useful for the design of future laser-matter interaction experiments.

On the feasibility to perform integral transmission experiments in the GELINA target hall at IRMM

NASA Astrophysics Data System (ADS)

Leconte, Pierre; Jean, Cyrille De Saint; Geslot, Benoit; Plompen, Arjan; Belloni, Francesca; Nyman, Markus

2017-09-01

Shielding experiments are relevant to validate elastic and inelastic scattering cross sections in the fast energy range. In this paper, we are focusing on the possibility to use the pulsed white neutron time-of-flight facility GELINA to perform this kind of measurement. Several issues need to be addressed: neutron source intensity, room return effect, distance of the materials to be irradiated from the source, and the sensitivity of various reaction rate distributions through the material to different input cross sections. MCNP6 and TRIPOLI4 calculations of the outgoing neutron spectrum are compared, based on electron/positron/gamma/neutron simulations. A first guess of an integral transmission experiment through a 238U slab is considered. It shows that a 10 cm thickness of uranium is sufficient to reach a high sensitivity to the 238U inelastic scattering cross section in the [2-5 MeV] energy range, with small contributions from elastic and fission cross sections. This experiment would contribute to reduce the uncertainty on this nuclear data, which has a significant impact on the power distribution in large commercial reactors. Other materials that would be relevant for the ASTRID 4th generation prototype reactor are also tested, showing that a sufficient sensitivity to nuclear data would be obtained by using a 50 to 100cm thick slab of side 60x60cm. This study concludes on the feasibility and interest of such experiments in the target hall of the GELINA facility.

Resonant production of dark photons in positron beam dump experiments

NASA Astrophysics Data System (ADS)

Nardi, Enrico; Carvajal, Cristian D. R.; Ghoshal, Anish; Meloni, Davide; Raggi, Mauro

2018-05-01

Positrons beam dump experiments have unique features to search for very narrow resonances coupled superweakly to e+e- pairs. Due to the continued loss of energy from soft photon bremsstrahlung, in the first few radiation lengths of the dump a positron beam can continuously scan for resonant production of new resonances via e+ annihilation off an atomic e- in the target. In the case of a dark photon A' kinetically mixed with the photon, this production mode is of first order in the electromagnetic coupling α , and thus parametrically enhanced with respect to the O (α2)e+e-→γ A' production mode and to the O (α3)A' bremsstrahlung in e- -nucleon scattering so far considered. If the lifetime is sufficiently long to allow the A' to exit the dump, A'→e+e- decays could be easily detected and distinguished from backgrounds. We explore the foreseeable sensitivity of the Frascati PADME experiment in searching with this technique for the 17 MeV dark photon invoked to explain the Be 8 anomaly in nuclear transitions.

Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data

NASA Astrophysics Data System (ADS)

Adikaram, D.; Rimal, D.; Weinstein, L. B.; Raue, B.; Khetarpal, P.; Bennett, R. P.; Arrington, J.; Brooks, W. K.; Adhikari, K. P.; Afanasev, A. V.; Amaryan, M. J.; Anderson, M. D.; Anefalos Pereira, S.; Avakian, H.; Ball, J.; Battaglieri, M.; Bedlinskiy, I.; Biselli, A. S.; Bono, J.; Boiarinov, S.; Briscoe, W. J.; Burkert, V. D.; Carman, D. S.; Careccia, S.; Celentano, A.; Chandavar, S.; Charles, G.; Colaneri, L.; Cole, P. L.; Contalbrigo, M.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Dodge, G. E.; Dupre, R.; Egiyan, H.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Eugenio, P.; Fedotov, G.; Fegan, S.; Filippi, A.; Fleming, J. A.; Fradi, A.; Garillon, B.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Goetz, J. T.; Gohn, W.; Golovatch, E.; Gothe, R. W.; Griffioen, K. A.; Guegan, B.; Guidal, M.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hanretty, C.; Harrison, N.; Hattawy, M.; Hicks, K.; Holtrop, M.; Hughes, S. M.; Hyde, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Jenkins, D.; Jiang, H.; Jo, H. S.; Joo, K.; Joosten, S.; Kalantarians, N.; Keller, D.; Khandaker, M.; Kim, A.; Kim, W.; Klein, A.; Klein, F. J.; Koirala, S.; Kubarovsky, V.; Kuhn, S. E.; Livingston, K.; Lu, H. Y.; MacGregor, I. J. D.; Markov, N.; Mattione, P.; Mayer, M.; McKinnon, B.; Mestayer, M. D.; Meyer, C. A.; Mirazita, M.; Mokeev, V.; Montgomery, R. A.; Moody, C. I.; Moutarde, H.; Movsisyan, A.; Camacho, C. Munoz; Nadel-Turonski, P.; Niccolai, S.; Niculescu, G.; Osipenko, M.; Ostrovidov, A. I.; Park, K.; Pasyuk, E.; Peña, C.; Pisano, S.; Pogorelko, O.; Price, J. W.; Procureur, S.; Prok, Y.; Protopopescu, D.; Puckett, A. J. R.; Ripani, M.; Rizzo, A.; Rosner, G.; Rossi, P.; Roy, P.; Sabatié, F.; Salgado, C.; Schott, D.; Schumacher, R. A.; Seder, E.; Sharabian, Y. G.; Simonyan, A.; Skorodumina, I.; Smith, E. S.; Smith, G. D.; Sober, D. I.; Sokhan, D.; Sparveris, N.; Stepanyan, S.; Stoler, P.; Strauch, S.; Sytnik, V.; Taiuti, M.; Tian, Ye; Trivedi, A.; Ungaro, M.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Watts, D. P.; Wei, X.; Wood, M. H.; Zachariou, N.; Zana, L.; Zhang, J.; Zhao, Z. W.; Zonta, I.; CLAS Collaboration

2015-02-01

There is a significant discrepancy between the values of the proton electric form factor, GEp, extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of GEp from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (ɛ ) and momentum transfer (Q2) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ɛ at Q2=1.45 GeV2 . This measurement is consistent with the size of the form factor discrepancy at Q2≈1.75 GeV2 and with hadronic calculations including nucleon and Δ intermediate states, which have been shown to resolve the discrepancy up to 2 - 3 GeV2 .

Time-frequency analysis of backscattered signals from diffuse radar targets

NASA Astrophysics Data System (ADS)

Kenny, O. P.; Boashash, B.

1993-06-01

The need for analysis of time-varying signals has led to the formulation of a class of joint time-frequency distributions (TFDs). One of these TFDs, the Wigner-Ville distribution (WVD), has useful properties which can be applied to radar imaging. The authors discuss time-frequency representation of the backscattered signal from a diffuse radar target. It is then shown that for point scatterers which are statistically dependent or for which the reflectivity coefficient has a nonzero mean value, reconstruction using time of flight positron emission tomography on time-frequency images is effective for estimating the scattering function of the target.

The macrophage marker translocator protein (TSPO) is down-regulated on pro-inflammatory 'M1' human macrophages.

PubMed

Narayan, Nehal; Mandhair, Harpreet; Smyth, Erica; Dakin, Stephanie Georgina; Kiriakidis, Serafim; Wells, Lisa; Owen, David; Sabokbar, Afsie; Taylor, Peter

2017-01-01

The translocator protein (TSPO) is a mitochondrial membrane protein, of as yet uncertain function. Its purported high expression on activated macrophages, has lent utility to TSPO targeted molecular imaging in the form of positron emission tomography (PET), as a means to detect and quantify inflammation in vivo. However, existing literature regarding TSPO expression on human activated macrophages is lacking, mostly deriving from brain tissue studies, including studies of brain malignancy, and inflammatory diseases such as multiple sclerosis. Here, we utilized three human sources of monocyte derived macrophages (MDM), from THP-1 monocytes, healthy peripheral blood monocytes and synovial fluid monocytes from patients with rheumatoid arthritis, to undertake a detailed investigation of TSPO expression in activated macrophages. In this work, we demonstrate a consistent down-regulation of TSPO mRNA and protein in macrophages activated to a pro-inflammatory, or 'M1' phenotype. Conversely, stimulation of macrophages to an M2 phenotype with IL-4, dexamethasone or TGF-β1 did not alter TSPO expression, regardless of MDM source. The reasons for this are uncertain, but our study findings add some supporting evidence for recent investigations concluding that TSPO may be involved in negative regulation of inflammatory responses in macrophages.

Consequences of electroplated targets on radiopharmaceutical preparations

NASA Astrophysics Data System (ADS)

Finn, R. D.; Tirelli, S.; Sheh, Y.; Knott, A.; Gelbard, A. S.; Larson, S. M.; Dahl, J. R.

1991-05-01

The staff of the cyclotron facility at Memorial Sloan-Kettering Cancer Center is involved in a comprehensive radionuclide preparation program which culminates with the formulation of numerous requested short-lived, positron-emitting radiopharmaceutical agents for clinical investigation. Both the produced radionuclide as well as the final radiolabeled compound are subjected to stringent quality control standards including assays for radiochemical and chemical purity. The subtle chemical consequences resulting from the irradiation of a nickel-plated target for 13N production serve to emphasize some of these potential technical difficulties.

Calibration and operational data for a compact photodiode detector useful for monitoring the location of moving sources of positron emitting radioisotopes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marsland, M. G.; Dehnel, M. P.; Theroux, J.

2013-04-19

D-Pace has developed a compact cost-effective gamma detector system based on technology licensed from TRIUMF. These photodiode detectors are convenient for detecting the presence of positron emitting radioisotopes, particularly for the case of transport of radioisotopes from a PET cyclotron to hotlab, or from one location to another in an automated radiochemistry processing unit. This paper describes recent calibration experiments undertaken at the Turku PET Centre for stationary and moving sources of F18 and C11 in standard setups. The practical diagnostic utility of using several of these devices to track the transport of radioisotopes from the cyclotron to hotlab ismore » illustrated. For example, such a detector system provides: a semi-quantitative indication of total activity, speed of transport, location of any activity lost en route and effectiveness of follow-up system flushes, a means of identifying bolus break-up, feedback useful for deciding when to change out tubing.« less

High Peak Power Test and Evaluation of S-band Waveguide Switches

NASA Astrophysics Data System (ADS)

Nassiri, A.; Grelick, A.; Kustom, R. L.; White, M.

1997-05-01

The injector and source of particles for the Advanced Photon Source is a 2856-MHz S-band electron-positron linear accelerator (linac) which produces electrons with energies up to 650 MeV or positrons with energies up to 450 MeV. To improve the linac rf system availability, an additional modulator-klystron subsystem is being constructed to provide a switchable hot spare unit for each of the five exsisting S-band transmitters. The switching of the transmitters will require the use of SF6-pressurized S-band waveguide switches at a peak operating power of 35 MW. Such rf switches have been successfully operated at other accelerator facilities but at lower peak powers. A test stand has been set up at the Stanford Linear Accelerator Center (SLAC) Klystron Factory to conduct tests comparing the power handling characteristics of two WR-284 and one WR-340 switches. Test results are presented and their implications for the design of the switching system are discussed.

64Cu, a powerful positron emitter for immunoimaging and theranostic: Production via natZnO and natZnO-NPs.

PubMed

Karimi, Zahra; Sadeghi, Mahdi; Mataji-Kojouri, Naimeddin

2018-07-01

64 Cu is one of the most beneficial radionuclide that can be used as a theranostic agent in Positron Emission Tomography (PET) imaging. In this current work, 64 Cu was produced with zinc oxide nanoparticles ( nat ZnONPs) and zinc oxide powder ( nat ZnO) via the 64 Zn(n,p) 64 Cu reaction in Tehran Research Reactor (TRR) and the activity values were compared with each other. The theoretical activity of 64 Cu also was calculated with MCNPX-2.6 and the cross sections of this reaction were calculated by using TALYS-1.8, EMPIRE-3.2.2 and ALICE/ASH nuclear codes and were compared with experimental values. Transmission Electronic Microscopy (TEM), Scanning Electronic Microscopy (SEM) and X-Ray Diffraction (XRD) analysis were used for samples characterizations. From these results, it's concluded that 64 Cu activity value with nanoscale target was achieved more than the bulk state target and had a good adaptation with the MCNPX result. Copyright © 2018 Elsevier Ltd. All rights reserved.

SU-F-T-368: Improved HPGe Detector Precise Efficiency Calibration with Monte Carlo Simulations and Radioactive Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhai, Y. John

2016-06-15

Purpose: To obtain an improved precise gamma efficiency calibration curve of HPGe (High Purity Germanium) detector with a new comprehensive approach. Methods: Both of radioactive sources and Monte Carlo simulation (CYLTRAN) are used to determine HPGe gamma efficiency for energy range of 0–8 MeV. The HPGe is a GMX coaxial 280 cm{sup 3} N-type 70% gamma detector. Using Momentum Achromat Recoil Spectrometer (MARS) at the K500 superconducting cyclotron of Texas A&M University, the radioactive nucleus {sup 24} Al was produced and separated. This nucleus has positron decays followed by gamma transitions up to 8 MeV from {sup 24} Mg excitedmore » states which is used to do HPGe efficiency calibration. Results: With {sup 24} Al gamma energy spectrum up to 8MeV, the efficiency for γ ray 7.07 MeV at 4.9 cm distance away from the radioactive source {sup 24} Al was obtained at a value of 0.194(4)%, by carefully considering various factors such as positron annihilation, peak summing effect, beta detector efficiency and internal conversion effect. The Monte Carlo simulation (CYLTRAN) gave a value of 0.189%, which was in agreement with the experimental measurements. Applying to different energy points, then a precise efficiency calibration curve of HPGe detector up to 7.07 MeV at 4.9 cm distance away from the source {sup 24} Al was obtained. Using the same data analysis procedure, the efficiency for the 7.07 MeV gamma ray at 15.1 cm from the source {sup 24} Al was obtained at a value of 0.0387(6)%. MC simulation got a similar value of 0.0395%. This discrepancy led us to assign an uncertainty of 3% to the efficiency at 15.1 cm up to 7.07 MeV. The MC calculations also reproduced the intensity of observed single-and double-escape peaks, providing that the effects of positron annihilation-in-flight were incorporated. Conclusion: The precision improved gamma efficiency calibration curve provides more accurate radiation detection and dose calculation for cancer radiotherapy treatment.« less

Monte Carlo modeling and optimization of buffer gas positron traps

NASA Astrophysics Data System (ADS)

Marjanović, Srđan; Petrović, Zoran Lj

2017-02-01

Buffer gas positron traps have been used for over two decades as the prime source of slow positrons enabling a wide range of experiments. While their performance has been well understood through empirical studies, no theoretical attempt has been made to quantitatively describe their operation. In this paper we apply standard models as developed for physics of low temperature collision dominated plasmas, or physics of swarms to model basic performance and principles of operation of gas filled positron traps. The Monte Carlo model is equipped with the best available set of cross sections that were mostly derived experimentally by using the same type of traps that are being studied. Our model represents in realistic geometry and fields the development of the positron ensemble from the initial beam provided by the solid neon moderator through voltage drops between the stages of the trap and through different pressures of the buffer gas. The first two stages employ excitation of N2 with acceleration of the order of 10 eV so that the trap operates under conditions when excitation of the nitrogen reduces the energy of the initial beam to trap the positrons without giving them a chance to become annihilated following positronium formation. The energy distribution function develops from the assumed distribution leaving the moderator, it is accelerated by the voltage drops and forms beams at several distinct energies. In final stages the low energy loss collisions (vibrational excitation of CF4 and rotational excitation of N2) control the approach of the distribution function to a Maxwellian at room temperature but multiple non-Maxwellian groups persist throughout most of the thermalization. Optimization of the efficiency of the trap may be achieved by changing the pressure and voltage drops and also by selecting to operate in a two stage mode. The model allows quantitative comparisons and test of optimization as well as development of other properties.

Charged and Neutral Particles Channeling Phenomena Channeling 2008

NASA Astrophysics Data System (ADS)

Dabagov, Sultan B.; Palumbo, Luigi

2010-04-01

On the discovery of coherent Bremsstrahlung in a single crystal at the Frascati National Laboratories / C. Barbiellini, G. P. Murtas and S. B. Dabagov -- Advances in coherent Bremsstrahlung and LPM-effect studies (to the lOOth anniversary from the birth of L. D. Landau) / N. F. Shul'ga -- Spectra of radiation and created particles at intermediate energy in oriented crystal taking into account energy loss / V. N. Baier and V. M. Katkov -- The coherent Bremsstrahlung beam at MAX-lab facility / K. Fissum ... [et al.] -- Radiation from thin, structured targets (CERN NA63) / A. Dizdar -- Hard incoherent radiation in thick crystals / N. F. Shul'ga, V. V. Syshchenko and A. I. Tarnovsky -- Coherent Bremsstrahlung in periodically deformed crystals with a complex base / A. R. Mkrtchyan, A. A. Saharian and V. V. Parazian -- Induction of coherent x-ray Bremsstrahlung in crystals under the influence of acoustic waves / A. R. Mkrtchyan and V. V. Parazian -- Coherent processes in bent single crystals / V. A. Maisheev -- Experimental and theoretical investigation of complete transfer phenomenon for media with various heat exchange coefficients / A. R. Mkrtchyan, A. E. Movsisyan and V. R. Kocharyan -- Coherent pair production in crystals / A. R. Mkrtchyan, A. A. Saharian and V. V. Parazian -- Negative particle planar and axial channeling and channeling collimation / R. A. Carrigan, Jr. -- CERN crystal-based collimation in modern hadron colliders / W. Scandale -- Studies and application of bent crystals for beam steering at 70 GeV IHEP accelerator / A. G. Afonin ... [et al.] -- Crystal collimation studies at the Tevatron (T-980) / N. V. Mokhov ... [et al.] -- Fabrication of crystals for channeling of particles in accellerators / A. Mazzolari ... [et al.] -- New possibilities to facilitate collimation of both positively and negatively charged particle beams by crystals / V. Guidi, A. Mazzolari and V. V. Tikhomirov -- Increase of probability of particle capture into the channeling regime by a buried oxide layer / V. Guidi, A. Mazzolari and V. V. Tikhomirov -- A positron source using channeling in crystals for linear colliders / X. Artru ... [et al.] -- Parametric channeling and collapse of charged particles beams in crystals / M. Vysotskyy and V. Vysotskii.The formation and usage of coherent correlated charged particles states in the physics of channeling in crystals / S. V. Adamenko, V. I. Vysotskii and M. V. Vysotskyy -- Surface channeling of magnetic-charged particles on multilayer surface / S. V. Adamenko and V. I. Vysotskii -- Coherent creation of anti-hydrogen atoms in a crystal by relativistic antiproton / Yu. P. Kunashenko -- Thermal equilibrium of light ions in heavy crystals / E. Tsyganov -- Photon emission of electrons in a crystalline undulator / H. Backe ... [et al.] -- Channeling radiation from relativistic electrons in a crystal target as complementary x-ray and gamma ray source at synchrotron light facilities / K. B. Korotchenko, Yu. L. Pivovarov and T. A. Tukhfatullin -- Diffracted channeling radiation and other compound radiation processes / H. Nitta -- Collective scattering on the atom planes under the condition of full transition / A. R. Mkrtchyan ... [et al.] -- The proposal of the experiment on the research of the diffracted channeling radiation / D. A. Baklanov ... [et al.] -- Positron channeling at the DaOne BTF Facility: the cup experiment / L. Quintieri ... [et al.] -- Radiation spectra of 200 MeV electrons in diamond and silicon crystals at axial and planar orientations / K. Fissum ... [et al.] -- Channeling experiments with electrons at the Mainz Microtron Mami / W. Lauth ... [et al.] -- Dechanneling of positrons by dislocations: effects of anharmonic interactions / J. George and A. P. Pathak -- Diffracted channeling radiation from axially channeled relativistic electrons / K. B. Korotchenko ... [et al.] -- Intensive quasi-monochromatic, directed x-ray radiation of planar channeled positron bunch / L. Gevorgian -- Probing channeling radiation influenced by ultrasound / W. Wagner ... [et al.] -- Radiation characteristics under electrons planar channeling and quasichanneling in complex crystals / L. Gevorgian -- Formation of relativistic positron atoms by axially channeled positrons and their decay on [symbol]-rays / A. Gevorkyan, A. R. Mkrtchyan and K. Oganesyan -- New features of diffracted channeling radiation from electrons in Si and LiF Crystals / K. B. Korotchenko, Yu. L. Pivovarov and T. A. Tukhfatullin -- Modulated particle beam in a crystal channel / A. Kostyuk ... [et al.] -- Computer simulations of resonant coherent excitation of heavy hydrogenlike ions under planar channeling / A. A. Babaev and Yu. L. Pivovarov -- Parametric x-ray and diffracted transition radiation of 4.5 GeV electrons in diamond / R. O. Avakian ... [et al.] -- Possible use of small accelerators in student laboratory for engineering education / I. Endo, M. Tanaka and T. Yoshimura.The Status of the SPARC Project / A. Cianchi -- Laser-plasma acceleration: first experimental results from the Plasmon-X Project / L. A. Gizzi ... [et al.] -- The powerful nanosecond duration electron beam effect on the crystalline tungsten target / Y. N. Adischev ... [et al.] -- "Shadowing" of the electromagnetic field of a relativistic electron / G. Naumenko ... [et al.] -- The acceleration of the charged particles in a low temperature acoustoplasma / A. S. Abrahamyan, A. R. Mkrtchyan and R. B. Kostanyan -- The experimental study of the surface current excitation by a relativistic electron electromagnetic field / G. A. Naumenko ... [et al.] -- Synchrotron radiation from a charge moving along helical orbit around a dielectric cylinder / A. A. Saharian and A. S. Kotanjyan -- Particle acceleration in a helical wave guide / X. Artru and C. Ray -- Effect of heavy ion charge fluctuations on Cherenkov radiation / V. S. Malyshevsky -- Hard photons powerful radiation of electron bunch interacting with plasma beat waves / A. Shamamian and L. Gevorgian -- Diffraction radiation as a diagnostics tool at flash / M. Castellano, E. Chiadroni and A. Cianchi -- Methods of charged particle beam cooling / E. G. Bessonov -- Ray tracing calculation of PXR produced in curved and flat crystals by electron beams with large emittance / K. A. Ispirian ... [et al.] -- On dynamic effects in coherent x-radiation of relativistic electron in Bragg scattering geometry / S. V. Blazhevich and A. V. Noskov -- Optimization of relativistic electron diffracted transition radiation yield / S. V. Blazhevich and A. V. Noskov -- Geometrical effect of target crystal on PXR generation as a coherent x-ray source / Y. Hayakawa ... [et al.] -- Observation of dynamical maxima of parametric x-ray radiation for 20 Me V electron energy beam / A. R. Mkrtchyan ... [et al.] -- The comparison of monochromatic x-ray sources based on compact electron accelerators and x-ray tube / Yu. N. Adischev ... [et al.] -- Labsync: a project to develop a European facility based on a table-top synchrotron light source / G. Di Domenico ... [et al.] -- New experimental results with optical diffraction radiation diagnostics / E. Chiadroni ... [et al.] -- The radiation yield in different spectral ranges from low density structured laser plasma with different high Z-admixture / V. Rozanov and G. Vergunova -- Time and angular distributions of ions transmitted through insulating capillaries / F. F. Komarov and A. S. Kamyshan -- X-ray propagation in multiwall carbon nanotubes / P. A. Childs ... [et al.] -- Tunable x-ray source based on mosaic crystals using for medicine applications / D. A. Baklanov ... [et al.] -- Capillary optics based x-ray micro-imaging elemental analysis / D. Hampai ... [et al.] -- Neutron number enhancement in uranium thin film waveguides / S. P. Pogossian -- Schwinger scattering of fast neutrons in aligned crystal / Yu. P. Kunashenko and Yu. L. Pivovarov -- Experimental investigation of Smith-Purcell radiation focusing by using the parabolic gratings / G. A. Naumenko ... [et al.] -- Plasma channels in air produced by UV laser beam: mechanisms of photoionization and possible applications/ V. D. Zvorykin ... [et al.].

Optical spectroscopy of atomic and molecular positronium

NASA Astrophysics Data System (ADS)

Mills, A. P., Jr.

2014-04-01

Positronium (Ps) is a purely leptonic hydrogen-like atom formed from an electron and a positron. Since the interactions of electrons and positrons are thought to be almost entirely electromagnetic, precision measurements of the Ps energy levels should constitute a good test of QED theory. The ultimate precision is limited by the rapid annihilation of the various Ps states and the number of Ps atoms available. Much progress in making better Ps sources has been made since the 1950's when Ps was discovered and its principle characteristics measured in by the pioneering experiments of Martin Deutsch. The most notable milestones were the first reproducible schemes for making slow positrons and Ps in vacuum by Canter and his co-workers in the 1970's and the discovery of the enabling technology for accumulating slow positrons by Surko and co-workers in 1989. These techniques have made it possible to generate high density bursts of slow Ps atoms that has led to the production of di-positronium molecules, Ps2, and the observation of the Lyman-alpha-like transition in Ps2 at a wavelength of 251 nm predicted by Varga and co-workers. The possibilities for 1S-2S spectroscopy of triplet and singlet Ps with precisions relevant to the proton charge radius problem and efficient production of slow Rydberg Ps atoms useful for measuring Ps free fall are discussed.

The production of molecular positronium

NASA Astrophysics Data System (ADS)

Cassidy, D. B.; Mills, A. P.

2007-09-01

It has been known for many years that an electron and its antiparticle, the positron, may together form a metastable hydrogen-like atom, known as positronium or Ps (ref. 1). In 1946, Wheeler speculated that two Ps atoms may combine to form the di-positronium molecule (Ps2), with a binding energy of 0.4eV. More recently, this molecule has been studied theoretically; however, because Ps has a short lifetime and it is difficult to obtain low-energy positrons in large numbers, Ps2 has not previously been observed unambiguously. Here we show that when intense positron bursts are implanted into a thin film of porous silica, Ps2 is created on the internal pore surfaces. We found that molecule formation occurs much more efficiently than the competing process of spin exchange quenching, which appears to be suppressed in the confined pore geometry. This result experimentally confirms the existence of the Ps2 molecule and paves the way for further multi-positronium work. Using similar techniques, but with a more intense positron source, we expect to increase the Ps density to the point where many thousands of atoms interact and can undergo a phase transition to form a Bose-Einstein condensate. As a purely leptonic, macroscopic quantum matter-antimatter system this would be of interest in its own right, but it would also represent a milestone on the path to produce an annihilation gamma-ray laser.

The production of molecular positronium.

PubMed

Cassidy, D B; Mills, A P

2007-09-13

It has been known for many years that an electron and its antiparticle, the positron, may together form a metastable hydrogen-like atom, known as positronium or Ps (ref. 1). In 1946, Wheeler speculated that two Ps atoms may combine to form the di-positronium molecule (Ps2), with a binding energy of 0.4 eV. More recently, this molecule has been studied theoretically; however, because Ps has a short lifetime and it is difficult to obtain low-energy positrons in large numbers, Ps2 has not previously been observed unambiguously. Here we show that when intense positron bursts are implanted into a thin film of porous silica, Ps2 is created on the internal pore surfaces. We found that molecule formation occurs much more efficiently than the competing process of spin exchange quenching, which appears to be suppressed in the confined pore geometry. This result experimentally confirms the existence of the Ps2 molecule and paves the way for further multi-positronium work. Using similar techniques, but with a more intense positron source, we expect to increase the Ps density to the point where many thousands of atoms interact and can undergo a phase transition to form a Bose-Einstein condensate. As a purely leptonic, macroscopic quantum matter-antimatter system this would be of interest in its own right, but it would also represent a milestone on the path to produce an annihilation gamma-ray laser.

Time Dependence of the Electron and Positron Components of the Cosmic Radiation Measured by the PAMELA Experiment between July 2006 and December 2015.

PubMed

Adriani, O; Barbarino, G C; Bazilevskaya, G A; Bellotti, R; Boezio, M; Bogomolov, E A; Bongi, M; Bonvicini, V; Bottai, S; Bruno, A; Cafagna, F; Campana, D; Carlson, P; Casolino, M; Castellini, G; De Santis, C; Di Felice, V; Galper, A M; Karelin, A V; Koldashov, S V; Koldobskiy, S A; Krutkov, S Y; Kvashnin, A N; Leonov, A; Malakhov, V; Marcelli, L; Martucci, M; Mayorov, A G; Menn, W; Mergé, M; Mikhailov, V V; Mocchiutti, E; Monaco, A; Mori, N; Munini, R; Osteria, G; Panico, B; Papini, P; Pearce, M; Picozza, P; Ricci, M; Ricciarini, S B; Simon, M; Sparvoli, R; Spillantini, P; Stozhkov, Y I; Vacchi, A; Vannuccini, E; Vasilyev, G I; Voronov, S A; Yurkin, Y T; Zampa, G; Zampa, N; Potgieter, M S; Vos, E E

2016-06-17

Cosmic-ray electrons and positrons are a unique probe of the propagation of cosmic rays as well as of the nature and distribution of particle sources in our Galaxy. Recent measurements of these particles are challenging our basic understanding of the mechanisms of production, acceleration, and propagation of cosmic rays. Particularly striking are the differences between the low energy results collected by the space-borne PAMELA and AMS-02 experiments and older measurements pointing to sign-charge dependence of the solar modulation of cosmic-ray spectra. The PAMELA experiment has been measuring the time variation of the positron and electron intensity at Earth from July 2006 to December 2015 covering the period for the minimum of solar cycle 23 (2006-2009) until the middle of the maximum of solar cycle 24, through the polarity reversal of the heliospheric magnetic field which took place between 2013 and 2014. The positron to electron ratio measured in this time period clearly shows a sign-charge dependence of the solar modulation introduced by particle drifts. These results provide the first clear and continuous observation of how drift effects on solar modulation have unfolded with time from solar minimum to solar maximum and their dependence on the particle rigidity and the cyclic polarity of the solar magnetic field.

Dense GeV electron–positron pairs generated by lasers in near-critical-density plasmas

PubMed Central

Zhu, Xing-Long; Yu, Tong-Pu; Sheng, Zheng-Ming; Yin, Yan; Turcu, Ion Cristian Edmond; Pukhov, Alexander

2016-01-01

Pair production can be triggered by high-intensity lasers via the Breit–Wheeler process. However, the straightforward laser–laser colliding for copious numbers of pair creation requires light intensities several orders of magnitude higher than possible with the ongoing laser facilities. Despite the numerous proposed approaches, creating high-energy-density pair plasmas in laboratories is still challenging. Here we present an all-optical scheme for overdense pair production by two counter-propagating lasers irradiating near-critical-density plasmas at only ∼1022 W cm−2. In this scheme, bright γ-rays are generated by radiation-trapped electrons oscillating in the laser fields. The dense γ-photons then collide with the focused counter-propagating lasers to initiate the multi-photon Breit–Wheeler process. Particle-in-cell simulations indicate that one may generate a high-yield (1.05 × 1011) overdense (4 × 1022 cm−3) GeV positron beam using 10 PW scale lasers. Such a bright pair source has many practical applications and could be basis for future compact high-luminosity electron–positron colliders. PMID:27966530

Gravitational mass of positron from LEP synchrotron losses.

PubMed

Kalaydzhyan, Tigran

2016-07-27

General relativity(GR) is the current description of gravity in modern physics. One of the cornerstones of GR, as well as Newton's theory of gravity, is the weak equivalence principle (WEP), stating that the trajectory of a freely falling test body is independent of its internal structure and composition. WEP is known to be valid for the normal matter with a high precision. However, due to the rarity of antimatter and weakness of the gravitational forces, the WEP has never been confirmed for antimatter. The current direct bounds on the ratio between the gravitational and inertial masses of the antihydrogen do not rule out a repulsive nature for the antimatter gravity. Here we establish an indirect bound of 0.13% on the difference between the gravitational and inertial masses of the positron (antielectron) from the analysis of synchrotron losses at the Large Electron-Positron collider (LEP). This serves as a confirmation of the conventional gravitational properties of antimatter without common assumptions such as, e.g., coupling of gravity to virtual particles, dynamics of distant astrophysical sources and the nature of absolute gravitational potentials.

Gravitational mass of positron from LEP synchrotron losses

PubMed Central

Kalaydzhyan, Tigran

2016-01-01

General relativity(GR) is the current description of gravity in modern physics. One of the cornerstones of GR, as well as Newton’s theory of gravity, is the weak equivalence principle (WEP), stating that the trajectory of a freely falling test body is independent of its internal structure and composition. WEP is known to be valid for the normal matter with a high precision. However, due to the rarity of antimatter and weakness of the gravitational forces, the WEP has never been confirmed for antimatter. The current direct bounds on the ratio between the gravitational and inertial masses of the antihydrogen do not rule out a repulsive nature for the antimatter gravity. Here we establish an indirect bound of 0.13% on the difference between the gravitational and inertial masses of the positron (antielectron) from the analysis of synchrotron losses at the Large Electron-Positron collider (LEP). This serves as a confirmation of the conventional gravitational properties of antimatter without common assumptions such as, e.g., coupling of gravity to virtual particles, dynamics of distant astrophysical sources and the nature of absolute gravitational potentials. PMID:27461548

Effects of displacement damage and helium production rates on the nucleation and growth of helium bubbles - Positron annihilation spectroscopy aspects

NASA Astrophysics Data System (ADS)

Krsjak, Vladimir; Degmova, Jarmila; Sojak, Stanislav; Slugen, Vladimir

2018-02-01

Fe-12 wt% Cr model alloy samples were implanted by 250 keV He2+ ions to three different fluencies (3 × 1017, 9 × 1017 and 1.5 × 1018 cm-2) at T < 100 °C. In a depth profile manner, the implantation impact according to defined peak profile was investigated using variable energy slow positrons, with the primary focus on the 2-13 dpa region. The obtained data were compared to published data on Optifer IX steel samples [1] irradiated in the frame of a two-years irradiation program of the Swiss Spallation Neutron Source. Bi-modal defect distribution represented by two defect components in positron lifetime spectrum reveals two distinct helium bubbles growth mechanisms. While at the lower helium production rate of the spallation environment, the bubbles grow primarily by migration and coalescence, at the high production rates of helium in the implanted samples, the results indicate this growth is driven by Ostwald ripening mechanism. A competitive growth process via emission of interstitial atoms (clusters) is discussed in terms of low-temperature He implantations.

Application of Positron Doppler Broadening Spectroscopy to the Measurement of the Uniformity of Composite Materials

NASA Astrophysics Data System (ADS)

Quarles, C. A.; Sheffield, Thomas; Stacy, Scott; Yang, Chun

2009-03-01

The uniformity of rubber-carbon black composite materials has been investigated with positron Doppler Broadening Spectroscopy (DBS). The number of grams of carbon black (CB) mixed into one hundred grams of rubber, phr, is used to characterize a sample. A typical concentration for rubber in tires is 50 phr. The S parameter measured by DBS has been found to depend on the phr of the sample as well as the type of rubber and carbon black. The variation in carbon black concentration within a surface area of about 5 mm diameter can be measured by moving a standard Na-22 or Ge-68 positron source over an extended sample. The precision of the concentration measurement depends on the dwell time at a point on the sample. The time required to determine uniformity over an extended sample can be reduced by running with much higher counting rate than is typical in DBS and correcting for the systematic variation of S parameter with counting rate. Variation in CB concentration with mixing time at the level of about 0.5% has been observed.

Positronium formation at surfaces and studies towards the production of low energy antihydrogen

NASA Astrophysics Data System (ADS)

Cassidy, David Barry

A magnetically guided slow positron beam has been used to measure positronium formation fractions via spectroscopy of annihilation radiation. Positrons with energies in the range 0-3 keV were implanted into tungsten, copper, magnesium oxide powder and silica aerogel targets at room temperature and at cryogenic temperatures ( 30 K). This was done with and without nitrogen gas condensed on the surface of these materials. The resulting gamma rays were detected by a CsI detector and an associated PC-based spectroscopy system. In most cases studied the measured energy dependence of the positronium fractions was consistent with previous similar work, however, anomalous behaviour was found in some of the data when gas was condensed on metal surfaces. Using the same positron beam initial measurements of positronium energy distributions have been made. This was accomplished using a HPGe detector to measure the Doppler shift of the energy' of the positronium annihilation radiation. This novel technique has not yet been refined and estimates of its potential are reported. A Monte Carlo simulation of the reaction to form antihydrogen by positronium impact upon antiprotons has been undertaken. Total and differential cross sections have been utilised as input to the simulation which models the conditions foreseen in planned antihydrogen formation experiments using antiprotons and positrons held in Penning traps. Thus, predictions of antihydrogen production rates, angular distributions and the variation of the mean antihydrogen temperature as a function of the incident positronium energy have been made.

Anti-leucine rich glioma inactivated 1 protein and anti-N-methyl-D-aspartate receptor encephalitis show distinct patterns of brain glucose metabolism in 18F-fluoro-2-deoxy-d-glucose positron emission tomography

PubMed Central

2014-01-01

Background Pathogenic autoantibodies targeting the recently identified leucine rich glioma inactivated 1 protein and the subunit 1 of the N-methyl-D-aspartate receptor induce autoimmune encephalitis. A comparison of brain metabolic patterns in 18F-fluoro-2-deoxy-d-glucose positron emission tomography of anti-leucine rich glioma inactivated 1 protein and anti-N-methyl-D-aspartate receptor encephalitis patients has not been performed yet and shall be helpful in differentiating these two most common forms of autoimmune encephalitis. Methods The brain 18F-fluoro-2-deoxy-d-glucose uptake from whole-body positron emission tomography of six anti-N-methyl-D-aspartate receptor encephalitis patients and four patients with anti-leucine rich glioma inactivated 1 protein encephalitis admitted to Hannover Medical School between 2008 and 2012 was retrospectively analyzed and compared to matched controls. Results Group analysis of anti-N-methyl-D-aspartate encephalitis patients demonstrated regionally limited hypermetabolism in frontotemporal areas contrasting an extensive hypometabolism in parietal lobes, whereas the anti-leucine rich glioma inactivated 1 protein syndrome was characterized by hypermetabolism in cerebellar, basal ganglia, occipital and precentral areas and minor frontomesial hypometabolism. Conclusions This retrospective 18F-fluoro-2-deoxy-d-glucose positron emission tomography study provides novel evidence for distinct brain metabolic patterns in patients with anti-leucine rich glioma inactivated 1 protein and anti-N-methyl-D-aspartate receptor encephalitis. PMID:24950993

Measurement of two-photon exchange effect by comparing elastic e ± p cross sections

DOE PAGES

Rimal, D.; Adikaram, D.; Raue, B. A.; ...

2017-06-01

Here, the electromagnetic form factors of the proton measured by unpolarized and polarized electron scattering experiments show a significant disagreement that grows with the squared four momentum transfer (more » $$Q^{2}$$). Calculations have shown that the two measurements can be largely reconciled by accounting for the contributions of two-photon exchange (TPE). TPE effects are not typically included in the standard set of radiative corrections since theoretical calculations of the TPE effects are highly model dependent, and, until recently, no direct evidence of significant TPE effects has been observed. We measured the ratio of positron-proton to electron-proton elastic-scattering cross sections in order to determine the TPE contribution to elastic electron-proton scattering and thereby resolve the proton electric form factor discrepancy. We produced a mixed simultaneous electron-positron beam in Jefferson Lab's Hall B by passing the 5.6 GeV primary electron beam through a radiator to produce a bremsstrahlung photon beam and then passing the photon beam through a convertor to produce electron/positron pairs. The mixed electron-positron (lepton) beam with useful energies from approximately 0.85 to 3.5 GeV then struck a 30-cm long liquid hydrogen (LH$$_2$$) target located within the CEBAF Large Acceptance Spectrometer (CLAS). By detecting both the scattered leptons and the recoiling protons we identified and reconstructed elastic scattering events and determined the incident lepton energy. A detailed description of the experiment is presented.« less

10 CFR 30.32 - Application for specific licenses.

Code of Federal Regulations, 2013 CFR

2013-01-01

... of the source or device are adequate to protect health and minimize danger to life and property. Such... lower than the release fraction shown § 30.72 due to the chemical or physical form of the material; (iv..., educational institution, or Federal facility to produce Positron Emission Tomography (PET) radioactive drugs...

10 CFR 30.32 - Application for specific licenses.

Code of Federal Regulations, 2014 CFR

2014-01-01

... of the source or device are adequate to protect health and minimize danger to life and property. Such... lower than the release fraction shown § 30.72 due to the chemical or physical form of the material; (iv..., educational institution, or Federal facility to produce Positron Emission Tomography (PET) radioactive drugs...

10 CFR 30.32 - Application for specific licenses.

Code of Federal Regulations, 2012 CFR

2012-01-01

... of the source or device are adequate to protect health and minimize danger to life and property. Such... the release fraction shown § 30.72 due to the chemical or physical form of the material; (iv) The..., educational institution, or Federal facility to produce Positron Emission Tomography (PET) radioactive drugs...

Elemental composition, isotopes, electrons and positrons in cosmic rays

NASA Technical Reports Server (NTRS)

Balasubrahmanyan, V. K.

1979-01-01

Papers presented at the 16th International Cosmic Ray Conference, Kyoto, Japan, dealing with the composition of cosmic rays are reviewed. Particular interest is given to data having bearing on nucleosynthesis sites, supernovae, gamma-process, comparison with solar system composition, multiplicity of sources, and the energy dependence of composition.

Method of using 5,10,15,20-tetrakis(carboxyphenyl)porphine for detecting cancers of the lung

DOEpatents

Cole, Dean A.; Moody, III, David C.; Ellinwood, L. Edward; Klein, M. Gerard

1992-01-01

Method using tetra-aryl porphyrins for and, in particular, 5,10,15,20-tetrakis(4-carboxyphenyl)porphine as a fluorescent tracer for cancers of the lung, and as a radiotracer therefor as a complex with .sup.67 Cu. The latter complex also provides a source of beta radiation for selective destruction of lung malignancies as well as gamma radiation useful for image analysis of the situs thereof by single photon emission computed tomography, as an example, both in vivo. Copper-64 may be substituted for the .sup.67 Cu if only radiotracer characteristics are of interest. This lighter isotope of copper is a positron emitter, and positron emission tomography techniques cna be used to locate the malignant tissue mass.

Method using 5,10,15,20-tetrakis(4-carboxyphenyl)porphine for treating cancers of the lung

DOEpatents

Cole, Dean A.; Moody, III, David C.; Ellinwood, L. Edward; Klein, M. Gerard

1995-01-01

Method using tetra-aryl porphyrins for and, in particular, 5,10,15,20-tetrakis(4-carboxyphenyl)porphine as a fluorescent tracer for cancers of the lung, and as a radiotracer therefor as a complex with .sup.67 Cu. The latter complex also provides a source of beta radiation for selective destruction of lung malignancies as well as gamma radiation useful for image analysis of the situs thereof by single photon emission computed tomography, as an example, both in vivo. Copper-64 may be substituted for the .sup.67 Cu if only radiotracer characteristics are of interest. This lighter isotope of copper is a positron emitter, and positron emission tomography techniques can be used to locate the malignant tissue mass.

A singly charged ion source for radioactive {sup 11}C ion acceleration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katagiri, K.; Noda, A.; Nagatsu, K.

2016-02-15

A new singly charged ion source using electron impact ionization has been developed to realize an isotope separation on-line system for simultaneous positron emission tomography imaging and heavy-ion cancer therapy using radioactive {sup 11}C ion beams. Low-energy electron beams are used in the electron impact ion source to produce singly charged ions. Ionization efficiency was calculated in order to decide the geometric parameters of the ion source and to determine the required electron emission current for obtaining high ionization efficiency. Based on these considerations, the singly charged ion source was designed and fabricated. In testing, the fabricated ion source wasmore » found to have favorable performance as a singly charged ion source.« less

Compact D-D/D-T neutron generators and their applications

NASA Astrophysics Data System (ADS)

Lou, Tak Pui

2003-10-01

Neutron generators based on the 2H(d,n)3He and 3H(d,n)4He fusion reactions are the most commonly available neutron sources. The applications of current commercial neutron generators are often limited by their low neutron yield and their short operational lifetime. A new generation of D-D/D-T fusion-based neutron generators has been designed at Lawrence Berkeley National Laboratory (LBNL) by using high current ion beams hitting on a self-loading target that has a large surface area to dissipate the heat load. This thesis describes the rationale behind the new designs and their potential applications. A survey of other neutron sources is presented to show their advantages and disadvantages compared to the fusion-based neutron generator. A prototype neutron facility was built at LBNL to test these neutron generators. High current ion beams were extracted from an RF-driven ion source to produce neutrons. With an average deuteron beam current of 24 mA and an energy of 100 keV, a neutron yield of >109 n/s has been obtained with a D-D coaxial neutron source. Several potential applications were investigated by using computer simulations. The computer code used for simulations and the variance reduction techniques employed were discussed. A study was carried out to determine the neutron flux and resolution of a D-T neutron source in thermal neutron scattering applications for condensed matter experiments. An error analysis was performed to validate the scheme used to predict the resolution. With a D-T neutron yield of 1014 n/s, the thermal neutron flux at the sample was predicted to be 7.3 x 105 n/cm2s. It was found that the resolution of cold neutrons was better than that of thermal neutrons when the duty factor is high. This neutron generator could be efficiently used for research and educational purposes at universities. Additional applications studied were positron production and Boron Neutron Capture Therapy (BNCT). The neutron flux required for positron production could not be provided with a single D-T neutron generator. Therefore, a subcritical fission multiplier was designed to increase the neutron yield. The neutron flux was increased by a factor of 25. A D-D driven fission multiplier was also studied for BNCT and a gain of 17 was obtained. The fission multiplier system gain was shown to be limited by the neutron absorption in the fuel and the reduction of source brightness. A brief discussion was also given regarding the neutron generator applications for fast neutron brachytherapy and neutron interrogation systems. It was concluded that new designs of compact D-D/D-T neutron generators are feasible and that superior quality neutron beams could be produced and used for various applications.

Background sources at PEP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lynch, H.; Schwitters, R.F.; Toner, W.T.

Important sources of background for PEP experiments are studied. Background particles originate from high-energy electrons and positrons which have been lost from stable orbits, ..gamma..-rays emitted by the primary beams through bremsstrahlung in the residual gas, and synchrotron radiation x-rays. The effect of these processes on the beam lifetime are calculated and estimates of background rates at the interaction region are given. Recommendations for the PEP design, aimed at minimizing background are presented. 7 figs., 4 tabs.

Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adikaram, D.; Rimal, D.; Weinstein, L. B.

There is a significant discrepancy between the values of the proton electric form factor, GpE, extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of GpE from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (epsilon) and momentummore » transfer (Q2) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ε at Q2=1.45 GeV2. This measurement is consistent with the size of the form factor discrepancy at Q2≈1.75 GeV2 and with hadronic calculations including nucleon and Delta intermediate states, which have been shown to resolve the discrepancy up to 2-3 GeV2.« less

Intrinsic radiolabeling of Titanium-45 using mesoporous silica nanoparticles.

PubMed

Chen, Feng; Valdovinos, Hector F; Hernandez, Reinier; Goel, Shreya; Barnhart, Todd E; Cai, Weibo

2017-06-01

Titanium-45 ( 45 Ti) with a three-hour half-life (t 1/2 =3.08 h), low maximum positron energy and high positron emission branching ratio, is a suitable positron emission tomography (PET) isotope whose potential has not yet been fully explored. Complicated radiochemistry and rapid hydrolysis continue to be major challenges to the development of 45 Ti compounds based on a traditional chelator-based radiolabeling strategy. In this study we introduced an intrinsic (or chelator-free) radiolabeling technique for the successful labeling of 45 Ti using mesoporous silica nanoparticle (MSN). We synthesized uniform MSN with an average particle size of ∼150 nm in diameter. The intrinsic 45 Ti-labeling was accomplished through strong interactions between 45 Ti (hard Lewis acid) and hard oxygen donors (hard Lewis bases), the deprotonated silanol groups (-Si-O-) from the outer surface and inner meso-channels of MSN. In vivo tumor-targeted PET imaging of as-developed PEGylated [ 45 Ti]MSN was further demonstrated in the 4T1 murine breast tumor-bearing mice. This MSN-based intrinsic radiolabeling strategy could open up new possibilities and speed up the biomedical applications of 45 Ti in the future.

Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data

DOE PAGES

Adikaram, D.; Rimal, D.; Weinstein, L. B.; ...

2015-02-10

There is a significant discrepancy between the values of the proton electric form factor, GpE, extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of GpE from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (epsilon) and momentummore » transfer (Q2) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ε at Q2=1.45 GeV2. This measurement is consistent with the size of the form factor discrepancy at Q2≈1.75 GeV2 and with hadronic calculations including nucleon and Delta intermediate states, which have been shown to resolve the discrepancy up to 2-3 GeV2.« less

Towards a resolution of the proton form factor problem: new electron and positron scattering data.

PubMed

Adikaram, D; Rimal, D; Weinstein, L B; Raue, B; Khetarpal, P; Bennett, R P; Arrington, J; Brooks, W K; Adhikari, K P; Afanasev, A V; Amaryan, M J; Anderson, M D; Anefalos Pereira, S; Avakian, H; Ball, J; Battaglieri, M; Bedlinskiy, I; Biselli, A S; Bono, J; Boiarinov, S; Briscoe, W J; Burkert, V D; Carman, D S; Careccia, S; Celentano, A; Chandavar, S; Charles, G; Colaneri, L; Cole, P L; Contalbrigo, M; Crede, V; D'Angelo, A; Dashyan, N; De Vita, R; De Sanctis, E; Deur, A; Djalali, C; Dodge, G E; Dupre, R; Egiyan, H; El Alaoui, A; El Fassi, L; Elouadrhiri, L; Eugenio, P; Fedotov, G; Fegan, S; Filippi, A; Fleming, J A; Fradi, A; Garillon, B; Gilfoyle, G P; Giovanetti, K L; Girod, F X; Goetz, J T; Gohn, W; Golovatch, E; Gothe, R W; Griffioen, K A; Guegan, B; Guidal, M; Guo, L; Hafidi, K; Hakobyan, H; Hanretty, C; Harrison, N; Hattawy, M; Hicks, K; Holtrop, M; Hughes, S M; Hyde, C E; Ilieva, Y; Ireland, D G; Ishkhanov, B S; Jenkins, D; Jiang, H; Jo, H S; Joo, K; Joosten, S; Kalantarians, N; Keller, D; Khandaker, M; Kim, A; Kim, W; Klein, A; Klein, F J; Koirala, S; Kubarovsky, V; Kuhn, S E; Livingston, K; Lu, H Y; MacGregor, I J D; Markov, N; Mattione, P; Mayer, M; McKinnon, B; Mestayer, M D; Meyer, C A; Mirazita, M; Mokeev, V; Montgomery, R A; Moody, C I; Moutarde, H; Movsisyan, A; Camacho, C Munoz; Nadel-Turonski, P; Niccolai, S; Niculescu, G; Osipenko, M; Ostrovidov, A I; Park, K; Pasyuk, E; Peña, C; Pisano, S; Pogorelko, O; Price, J W; Procureur, S; Prok, Y; Protopopescu, D; Puckett, A J R; Ripani, M; Rizzo, A; Rosner, G; Rossi, P; Roy, P; Sabatié, F; Salgado, C; Schott, D; Schumacher, R A; Seder, E; Sharabian, Y G; Simonyan, A; Skorodumina, I; Smith, E S; Smith, G D; Sober, D I; Sokhan, D; Sparveris, N; Stepanyan, S; Stoler, P; Strauch, S; Sytnik, V; Taiuti, M; Tian, Ye; Trivedi, A; Ungaro, M; Voskanyan, H; Voutier, E; Walford, N K; Watts, D P; Wei, X; Wood, M H; Zachariou, N; Zana, L; Zhang, J; Zhao, Z W; Zonta, I

2015-02-13

There is a significant discrepancy between the values of the proton electric form factor, G(E)(p), extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of G(E)(p) from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (ϵ) and momentum transfer (Q(2)) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ϵ at Q(2)=1.45  GeV(2). This measurement is consistent with the size of the form factor discrepancy at Q(2)≈1.75  GeV(2) and with hadronic calculations including nucleon and Δ intermediate states, which have been shown to resolve the discrepancy up to 2-3  GeV(2).

Spot-welding solid targets for high current cyclotron irradiation

PubMed Central

Ellison, Paul A.; Valdovinos, Hector F.; Graves, Stephen A.; Barnhart, Todd E.; Nickles, Robert J.

2016-01-01

Zirconium-89 finds broad application for use in positron emission tomography. Its cyclotron production has been limited by the heat transfer from yttrium targets at high beam currents. A spot welding technique allows a three-fold increase in beam current, without affecting 89Zr quality. An yttrium foil, welded to a jet-cooled tantalum support base accommodates a 50 μA proton beam degraded to 14 MeV. The resulting activity yield of 48 ± 4 MBq/(μA·hr) now extends the outreach of 89Zr for a broader distribution. PMID:27771445

Target and orbit feedback simulations of a muSR beamline at BNL

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacKay, W. W.; Fischer, W.; Blaskiewicz, M.

Well-polarized positive surface muons are a tool to measure the magnetic properties of materials since the precession rate of the spin can be determined from the observation of the positron directions when the muons decay. The use of the AGS complex at BNL has been explored for a muSR facility previously. Here we report simulations of a beamline with a target inside a solenoidal field, and of an orbit feed-back system with single muon beam positioning monitors based on technology available today

A General Quantum Mechanical Method to Predict Positron Spectroscopy

DTIC Science & Technology

2007-06-01

7 2.1 Positron Annihilation Spectroscopy . . . . . . . . . . . . . 7 2.1.1 Positron Transport and Annihilation in Condensed Matter...8 2.1.2 Traditional Positron Annihilation Spectroscopy . . 10 2.1.3 Vibrational Feshbach Resonances of Positrons with... positron annihilation lifetime spectroscopy system . . . 63 11. Tungsten positron lifetime spectrum . . . . . . . . . . . . . . . . . . 66 12. K2B12H12

Theranostic Unimolecular Micelles Based on Brush-Shaped Amphiphilic Block Copolymers for Tumor-Targeted Drug Delivery and Positron Emission Tomography Imaging

PubMed Central

2015-01-01

Brush-shaped amphiphilic block copolymers were conjugated with a monoclonal antibody against CD105 (i.e., TRC105) and a macrocyclic chelator for 64Cu-labeling to generate multifunctional theranostic unimolecular micelles. The backbone of the brush-shaped amphiphilic block copolymer was poly(2-hydroxyethyl methacrylate) (PHEMA) and the side chains were poly(l-lactide)-poly(ethylene glycol) (PLLA-PEG). The doxorubicin (DOX)-loaded unimolecular micelles showed a pH-dependent drug release profile and a uniform size distribution. A significantly higher cellular uptake of TRC105-conjugated micelles was observed in CD105-positive human umbilical vein endothelial cells (HUVEC) than nontargeted micelles due to CD105-mediated endocytosis. In contrast, similar and extremely low cellular uptake of both targeted and nontargeted micelles was observed in MCF-7 human breast cancer cells (CD105-negative). The difference between the in vivo tumor accumulation of 64Cu-labeled TRC105-conjugated micelles and that of nontargeted micelles was studied in 4T1 murine breast tumor-bearing mice, by serial positron emission tomography (PET) imaging and validated by biodistribution studies. These multifunctional unimolecular micelles offer pH-responsive drug release, noninvasive PET imaging capability, together with both passive and active tumor-targeting abilities, thus making them a desirable nanoplatform for cancer theranostics. PMID:24628452

Radiolabeled, Antibody-Conjugated Manganese Oxide Nanoparticles for Tumor Vasculature Targeted Positron Emission Tomography and Magnetic Resonance Imaging.

PubMed

Zhan, Yonghua; Shi, Sixiang; Ehlerding, Emily B; Graves, Stephen A; Goel, Shreya; Engle, Jonathan W; Liang, Jimin; Tian, Jie; Cai, Weibo

2017-11-08

Manganese oxide nanoparticles (Mn 3 O 4 NPs) have attracted a great deal of attention in the field of biomedical imaging because of their ability to create an enhanced imaging signal in MRI as novel potent T 1 contrast agents. In this study, we present tumor vasculature-targeted imaging in mice using Mn 3 O 4 NPs through conjugation to the anti-CD105 antibody TRC105 and radionuclide copper-64 ( 64 Cu, t 1/2 : 12.7 h). The Mn 3 O 4 conjugated NPs, 64 Cu-NOTA-Mn 3 O 4 @PEG-TRC105, exhibited sufficient stability in vitro and in vivo. Serial positron emission tomography (PET) and magnetic resonance imaging (MRI) studies evaluated the pharmacokinetics and demonstrated targeting of 64 Cu-NOTA-Mn 3 O 4 @PEG-TRC105 to 4T1 murine breast tumors in vivo, compared to 64 Cu-NOTA-Mn 3 O 4 @PEG. The specificity of 64 Cu-NOTA-Mn 3 O 4 @PEG-TRC105 for the vascular marker CD105 was confirmed through in vivo, in vitro, and ex vivo experiments. Since Mn 3 O 4 conjugated NPs exhibited desirable properties for T 1 enhanced imaging and low toxicity, the tumor-specific Mn 3 O 4 conjugated NPs reported in this study may serve as promising multifunctional nanoplatforms for precise cancer imaging and diagnosis.

Spin structure in high energy processes: Proceedings

DOE Office of Scientific and Technical Information (OSTI.GOV)

DePorcel, L.; Dunwoodie, C.

1994-12-01

This report contains papers as the following topics: Spin, Mass, and Symmetry; physics with polarized Z{sup 0}s; spin and precision electroweak physics; polarized electron sources; polarization phenomena in quantum chromodynamics; polarized lepton-nucleon scattering; polarized targets in high energy physics; spin dynamics in storage rings and linear accelerators; spin formalism and applications to new physics searches; precision electroweak physics at LEP; recent results on heavy flavor physics from LEP experiments using 1990--1992 data; precise measurement of the left-right cross section asymmetry in Z boson production by electron-positron collisions; preliminary results on heavy flavor physics at SLD; QCD tests with SLD andmore » polarized beams; recent results from TRISTAN at KEK; recent B physics results from CLEO; searching for the H dibaryon at Brookhaven; recent results from the compton observatory; the spin structure of the deuteron; spin structure of the neutron ({sup 3}HE) and the Bjoerken sum rule; a consumer`s guide to lattice QCD results; top ten models constrained by b {yields} sy; a review of the Fermilab fixed target program; results from the D0 experiment; results from CDF at FNAL; quantum-mechanical suppression of bremsstrahlung; report from the ZEUS collaboration at HERA; physics from the first year of H1 at HERA, and hard diffraction. These papers have been cataloged separately elsewhere.« less

Rationale and design of dal-PLAQUE: A study assessing efficacy and safety of dalcetrapib on progression or regression of atherosclerosis using magnetic resonance imaging and 18F-fluorodeoxyglucose positron emission tomography/computed tomography

PubMed Central

Fayad, Zahi A.; Mani, Venkatesh; Woodward, Mark; Kallend, David; Bansilal, Sameer; Pozza, Joseph; Burgess, Tracy; Fuster, Valentin; Rudd, James H. F.; Tawakol, Ahmed; Farkouh, Michael E.

2014-01-01

dal-PLAQUE is a placebo-controlled multicenter study designed to assess the effect of dalcetrapib on imaging measures of plaque inflammation and plaque burden. dal-PLAQUE is a multimodality imaging study in the context of the large dal-HEART Program. Decreased high-density lipoprotein cholesterol is linked to increased risk of coronary heart disease (CHD). Dalcetrapib, a compound that increases high-density lipoprotein cholesterol by modulating cholesteryl ester transfer protein, is being studied to assess if it can reduce the progression of atherosclerotic disease and thereby decrease cardiovascular morbidity and mortality. Patients with CHD or CHD-risk equivalents were randomized to receive 600 mg dalcetrapib or placebo daily for 24 months, in addition to conventional lipid-lowering medication and other medications for cardiovascular risk factors. The primary outcomes are the effect of dalcetrapib on 18F-fluorodeoxyglucose positron emission tomography target-to-background ratio after 6 months and magnetic resonance imaging (MRI) plaque burden (wall area, wall thickness, total vessel area, and wall area/total vessel area ratio) after 12 months. Secondary objectives include positron emission tomography target-to-background ratio at 3 months and MRI plaque burden at 6 and 24 months; plaque composition at 6, 12, and 24 months; and aortic compliance at 6 months. A tertiary objective is to examine the dynamic contrast-enhanced MRI parameters of plaque neovascularization. In total, 189 subjects entered screening, and 130 were randomized. dal-PLAQUE will provide important information on the effects of dalcetrapib on markers of inflammation and atherosclerotic plaque burden and, thereby, on the safety of cholesteryl ester transfer protein modulation with dalcetrapib. Results are expected in 2011. PMID:21835280

Production of no-carrier-added 64Cu from zinc metal irradiated under boron shielding.

PubMed

Zinn, K R; Chaudhuri, T R; Cheng, T P; Morris, J S; Meyer, W A

1994-02-01

Positron emission tomography offers advantages for radioimmunodiagnosis of cancer but requires radionuclides of appropriate half-life that have high specific activity and high radio-purity. This work was designed to develop a viable method to produce and purify 64Cu, which has high specific activity, for positron emission tomography. 64Cu was produced at the University of Missouri Research Reactor by the nuclear reaction, 64Zn(n,p)64Cu. Highly pure zinc metal (99.9999%) was irradiated in a specially designed boron nitrite lined container, which minimized thermal neutron reactions during irradiation. A new two-step procedure was developed to chemically separate the no-carrier-added 64Cu from the zinc metal target. 64Cu recovery for 24 runs averaged 0.393 (+/- 0.007) mCi per milligram of zinc irradiated. The boron-lined irradiation container reduced unwanted zinc radionuclides 14.3-fold. Zinc radionuclides and non-radioactive zinc were separated successfully from the 64Cu. The new separation technique was fast (2 hours total time) and highly efficient for removing the zinc. The zinc separation factor for this technique averaged 8.5 x 10(-8), indicating less than 0.0000085% of the zinc remained after separation. Thus far, the highest 64Cu specific activity at end of irradiation was 683 Ci/mg Cu, with an average of 512 Ci/mg Cu for the last six analyzed runs. The boron-lined irradiation container has sufficient capacity for 75-fold larger-sized zinc targets (up to 45 g). The new separation technique was excellent for separating 64Cu, which appears to be a radionuclide with great potential for positron emission tomography.

Searching for New Physics at SuperB - The Super Flavor Factory

ScienceCinema

Hiltin, David

2018-01-05

SuperB – a Super Flavor Factory, an electron-positron collider with a luminosity of 1036 cm-2 s-1, can conduct conduct unique sensitive searches for New Physics effects such as lepton flavor violation and new sources of CP violation in the quark and lepton sectors.

Dark matter vs. astrophysics in the interpretation of AMS-02 electron and positron data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mauro, Mattia Di; Donato, Fiorenza; Fornengo, Nicolao

We perform a detailed quantitative analysis of the recent AMS-02 electron and positron data. We investigate the interplay between the emission from primary astrophysical sources, namely Supernova Remnants and Pulsar Wind Nebulae, and the contribution from a dark matter annihilation or decay signal. Our aim is to assess the information that can be derived on dark matter properties when both dark matter and primary astrophysical sources are assumed to jointly contribute to the leptonic observables measured by the AMS-02 experiment. We investigate both the possibility to set robust constraints on the dark matter annihilation/decay rate and the possibility to lookmore » for dark matter signals within realistic models that take into account the full complexity of the astrophysical background. Our results show that AMS-02 data enable to probe efficiently vast regions of the dark matter parameter space and, in some cases, to set constraints on the dark matter annihilation/decay rate that are comparable or even stronger than the ones derived from other indirect detection channels.« less

Optimization of a Scintillator for the Measurement of Positrons from Trapped, Polarized 37K

NASA Astrophysics Data System (ADS)

France, Erin; Melconian, Dan

2011-10-01

Precision beta decay experiments can be used to test the Standard Model via their value of correlation parameters. The TRINAT Collaboration is performing such an experiment using a source of polarized 37K from a magneto optical trap. The momentum of an emitted positron will be detected using a Silicon strip detector backed by a plastic scintillator. The goal of my research was to optimize the readout of the scintillator by testing different experimental setups. The front face and sides of the scintillator and light guide were wrapped with various reflective materials to find which maximized the light output. We found that one layer of Teflon tape on the front face with a loose wrapping of 3M-ESR (Enhanced Spectral Reflector) on the sides was optimal. We then tested the position dependence of this detector by moving a collimated source of betas across the front face, showing only a (5.9 +/- 0.5)% reduction in light collection at the edge compared to the center. The product of this work will be used in the upcoming TRINAT experiment measuring the beta asymmetry of 37K.

Experimental Evaluation of Depth-of-Interaction Correction in a Small-Animal Positron Emission Tomography Scanner

PubMed Central

Green, Michael V.; Ostrow, Harold G.; Seidel, Jurgen; Pomper, Martin G.

2013-01-01

Human and small-animal positron emission tomography (PET) scanners with cylindrical geometry and conventional detectors exhibit a progressive reduction in radial spatial resolution with increasing radial distance from the geometric axis of the scanner. This “depth-of-interaction” (DOI) effect is sufficiently deleterious that many laboratories have devised novel schemes to reduce the magnitude of this effect and thereby yield PET images of greater quantitative accuracy. Here we examine experimentally the effects of a particular DOI correction method (dual-scintillator phoswich detectors with pulse shape discrimination) implemented in a small-animal PET scanner by comparing the same phantom and same mouse images with and without DOI correction. The results suggest that even this relatively coarse, two-level estimate of radial gamma ray interaction position significantly reduces the DOI parallax error. This study also confirms two less appreciated advantages of DOI correction: a reduction in radial distortion and radial source displacement as a source is moved toward the edge of the field of view and a resolution improvement detectable in the central field of view likely owing to improved spatial sampling. PMID:21084028

Experimental evaluation of depth-of-interaction correction in a small-animal positron emission tomography scanner.

PubMed

Green, Michael V; Ostrow, Harold G; Seidel, Jurgen; Pomper, Martin G

2010-12-01

Human and small-animal positron emission tomography (PET) scanners with cylindrical geometry and conventional detectors exhibit a progressive reduction in radial spatial resolution with increasing radial distance from the geometric axis of the scanner. This "depth-of-interaction" (DOI) effect is sufficiently deleterious that many laboratories have devised novel schemes to reduce the magnitude of this effect and thereby yield PET images of greater quantitative accuracy. Here we examine experimentally the effects of a particular DOI correction method (dual-scintillator phoswich detectors with pulse shape discrimination) implemented in a small-animal PET scanner by comparing the same phantom and same mouse images with and without DOI correction. The results suggest that even this relatively coarse, two-level estimate of radial gamma ray interaction position significantly reduces the DOI parallax error. This study also confirms two less appreciated advantages of DOI correction: a reduction in radial distortion and radial source displacement as a source is moved toward the edge of the field of view and a resolution improvement detectable in the central field of view likely owing to improved spatial sampling.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawanaka, Norita; Ioka, Kunihito; Nojiri, Mihoko M., E-mail: norita.kawanaka@kek.j

We investigate the observed spectrum of cosmic ray electrons and positrons from astrophysical sources, especially pulsars, and the physical processes for making the spectrum spiky or smooth via continuous and multiple electron/positron injections. We find that (1) the average electron spectrum predicted from nearby pulsars is consistent with PAMELA, Fermi, and H.E.S.S. data. However, the ATIC/PPB-BETS peak around 500 GeV is hard to produce by the sum of multiple pulsar contributions and requires a single (or a few) energetic pulsar(s). (2) A continuous injection produces a broad peak and a high-energy tail above the peak, which can constrain the sourcemore » duration ({approx}<10{sup 5} years with the current data). (3) The H.E.S.S. data in the TeV range suggest that young sources with age less than {approx}6 x 10{sup 4} years are less energetic than {approx}10{sup 48} erg. (4) We also expect a large dispersion in the TeV spectrum due to the small number of sources that may cause the high-energy cutoff inferred by H.E.S.S. and potentially provide a smoking gun for the astrophysical origin. These spectral diagnostics can be refined in the near future by the CALET experiments to discriminate different astrophysical and dark matter origins.« less

A constraint on antigravity of antimatter from precision spectroscopy of simple atoms

NASA Astrophysics Data System (ADS)

Karshenboim, S. G.

2009-10-01

Consideration of antigravity for antiparticles is an attractive target for various experimental projects. There are a number of theoretical arguments against it but it is not quite clear what kind of experimental data and theoretical suggestions are involved. In this paper we present straightforward arguments against a possibility of antigravity based on a few simple theoretical suggestions and some experimental data. The data are: astrophysical data on rotation of the Solar System in respect to the center of our galaxy and precision spectroscopy data on hydrogen and positronium. The theoretical suggestions for the case of absence of the gravitational field are: equality of electron and positron mass and equality of proton and positron charge. We also assume that QED is correct at the level of accuracy where it is clearly confirmed experimentally.

Positron emission tomography imaging as a key enabling technology in drug development.

PubMed

McCarthy, T J

2007-01-01

The use of positron emission tomography (PET) in drug development has become more common in the pharmaceutical industry in recent years. One of the biggest challenges to gaining acceptance of this technology is for project teams to understand when to use PET. This chapter reviews the usage of PET in drug development in the context of target, mechanism and efficacy biomarkers. Examples are drawn from a number of therapeutic areas, but we also show that the relative penetration of this technology beyond CNS and oncology applications has been relatively small. However, with the increasing availability of PET and development of novel radiotracers it is expected that the utilization will be much broader in future years, with the additional expectation that the use of PET as an efficacy biomarker will also become more evident.

Positron transport in solids and the interaction of positrons with surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kong, Yuan.

1991-01-01

In studying positron transport in solids, a two-stream model is proposed to account for the epithermal positrons. Thus positron implantation, thermalization, and diffusion processes are completely modeled. Experimentally, positron mobility in thermally grown SiO[sub 2] is measured in a sandwiched structure by using the Doppler broadening technique. Positron drift motion and the electric field configuration in a Si surface buried under overlayers are measured with the positron annihilation [gamma]-ray centroid shift technique. These studies are not only important in measuring positron transport and other properties in complicated systems, they are also of practical significance for material characterizations. In studying positronmore » interactions with surfaces, a multiple-encounter picture is proposed of thermal positrons participating in the surface escape processes. Positron trapping into the surface image potential is also studied, considering the long-range nature of the image potential. Experimentally, the positron annihilation induced Auger electron spectroscopy (PAES) is used to study an ionic insulator surface KCl(100).« less

Mechanism and non-mechanism based imaging biomarkers for assessing biological response to treatment in non-small cell lung cancer.

PubMed

Weller, A; O'Brien, M E R; Ahmed, M; Popat, S; Bhosle, J; McDonald, F; Yap, T A; Du, Y; Vlahos, I; deSouza, N M

2016-05-01

Therapeutic options in locally advanced non-small cell lung cancer (NSCLC) have expanded in the past decade to include a palate of targeted interventions such as high dose targeted thermal ablations, radiotherapy and growing platform of antibody and small molecule therapies and immunotherapies. Although these therapies have varied mechanisms of action, they often induce changes in tumour architecture and microenvironment such that response is not always accompanied by early reduction in tumour mass, and evaluation by criteria other than size is needed to report more effectively on response. Functional imaging techniques, which probe the tumour and its microenvironment through novel positron emission tomography and magnetic resonance imaging techniques, offer more detailed insights into and quantitation of tumour response than is available on anatomical imaging alone. Use of these biomarkers, or other rational combinations as readouts of pathological response in NSCLC have potential to provide more accurate predictors of treatment outcomes. In this article, the robustness of the more commonly available positron emission tomography and magnetic resonance imaging biomarker indices is examined and the evidence for their application in NSCLC is reviewed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Method for photon activation positron annihilation analysis

DOEpatents

Akers, Douglas W.

2006-06-06

A non-destructive testing method comprises providing a specimen having at least one positron emitter therein; determining a threshold energy for activating the positron emitter; and determining whether a half-life of the positron emitter is less than a selected half-life. If the half-life of the positron emitter is greater than or equal to the selected half-life, then activating the positron emitter by bombarding the specimen with photons having energies greater than the threshold energy and detecting gamma rays produced by annihilation of positrons in the specimen. If the half-life of the positron emitter is less then the selected half-life, then alternately activating the positron emitter by bombarding the specimen with photons having energies greater then the threshold energy and detecting gamma rays produced by positron annihilation within the specimen.

The macrophage marker translocator protein (TSPO) is down-regulated on pro-inflammatory ‘M1’ human macrophages

PubMed Central

Mandhair, Harpreet; Smyth, Erica; Dakin, Stephanie Georgina; Kiriakidis, Serafim; Wells, Lisa; Owen, David; Sabokbar, Afsie; Taylor, Peter

2017-01-01

The translocator protein (TSPO) is a mitochondrial membrane protein, of as yet uncertain function. Its purported high expression on activated macrophages, has lent utility to TSPO targeted molecular imaging in the form of positron emission tomography (PET), as a means to detect and quantify inflammation in vivo. However, existing literature regarding TSPO expression on human activated macrophages is lacking, mostly deriving from brain tissue studies, including studies of brain malignancy, and inflammatory diseases such as multiple sclerosis. Here, we utilized three human sources of monocyte derived macrophages (MDM), from THP-1 monocytes, healthy peripheral blood monocytes and synovial fluid monocytes from patients with rheumatoid arthritis, to undertake a detailed investigation of TSPO expression in activated macrophages. In this work, we demonstrate a consistent down-regulation of TSPO mRNA and protein in macrophages activated to a pro-inflammatory, or ‘M1’ phenotype. Conversely, stimulation of macrophages to an M2 phenotype with IL-4, dexamethasone or TGF-β1 did not alter TSPO expression, regardless of MDM source. The reasons for this are uncertain, but our study findings add some supporting evidence for recent investigations concluding that TSPO may be involved in negative regulation of inflammatory responses in macrophages. PMID:28968465

Method of using 5,10,15,20-tetrakis(carboxyphenyl)porphine for detecting cancers of the lung

DOEpatents

Cole, D.A.; Moody, D.C. III; Ellinwood, L.E.; Klein, M.G.

1992-11-10

A method is described for using tetra-aryl porphyrins for and, in particular, 5,10,15,20-tetrakis(4-carboxyphenyl)porphine as a fluorescent tracer for cancers of the lung, and as a radiotracer therefor as a complex with [sup 67]Cu. The latter complex also provides a source of beta radiation for selective destruction of lung malignancies as well as gamma radiation useful for image analysis of the lungs by single photon emission computed tomography, as an example, both in vivo. Copper-64 may be substituted for the [sup 67]Cu if only radiotracer characteristics are of interest. This lighter isotope of copper is a positron emitter, and positron emission tomography techniques can be used to locate the malignant tissue mass. 1 figure.

Vacancy-induced ferromagnetism in ZnO probed by spin-polarized positron annihilation spectroscopy

NASA Astrophysics Data System (ADS)

Maekawa, Masaki; Abe, Hiroshi; Miyashita, Atsumi; Sakai, Seiji; Yamamoto, Shunya; Kawasuso, Atsuo

2017-04-01

We investigated the ferromagnetism of ZnO induced by oxygen implantation by using spin-polarized positron annihilation spectroscopy together with magnetization measurements. The magnetization measurements showed the appearance of ferromagnetism after oxygen implantation and its disappearance during post-implantation annealing at temperatures above 573 K. The Doppler broadening of annihilation radiation (DBAR) spectrum showed asymmetry upon field reversal after oxygen implantation. The obtained differential DBAR spectrum between positive and negative magnetic fields was well-explained with a theoretical calculation considering zinc vacancies. The disappearance of the field-reversal asymmetry of the DBAR spectrum as a result of annealing agreed with the observations of ferromagnetism by magnetization measurements. These results suggest the radiation-induced zinc vacancies to be the source of the observed ferromagnetism of ZnO.

Design and Construction of a Positron Emission Tomography (PET) Unit and Medical Applications with GEANT Detector Simulation Package

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karagoz, Muge

1998-01-01

In order to investigate the possibility of the construction of a sample PET coincidence unit in our HEP laboratory, a setup with two face to face PMTs and two 2x8 Csi(Tl) scintillator matrices has been constructed. In this setup, 1-D projections of a pointlike 22 Na positron source at different angles have been measured. Using these projections a 2-D image has been formed. Monte Carlo studies of this setup have been implemented using the detector simulation tool in CERN program library, GEANT. Again with GEANT a sample human body is created to study the effects of proton therapy. Utilization ofmore » the simulation as a pretherapy tool is also investigated.« less

Effect of respiratory motion on internal radiation dosimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Tianwu; Zaidi, Habib, E-mail: habib.zaidi@hcuge.ch; Geneva Neuroscience Center, Geneva University, Geneva CH-1205

Purpose: Estimation of the radiation dose to internal organs is essential for the assessment of radiation risks and benefits to patients undergoing diagnostic and therapeutic nuclear medicine procedures including PET. Respiratory motion induces notable internal organ displacement, which influences the absorbed dose for external exposure to radiation. However, to their knowledge, the effect of respiratory motion on internal radiation dosimetry has never been reported before. Methods: Thirteen computational models representing the adult male at different respiratory phases corresponding to the normal respiratory cycle were generated from the 4D dynamic XCAT phantom. Monte Carlo calculations were performed using the MCNP transportmore » code to estimate the specific absorbed fractions (SAFs) of monoenergetic photons/electrons, the S-values of common positron-emitting radionuclides (C-11, N-13, O-15, F-18, Cu-64, Ga-68, Rb-82, Y-86, and I-124), and the absorbed dose of {sup 18}F-fluorodeoxyglucose ({sup 18}F-FDG) in 28 target regions for both the static (average of dynamic frames) and dynamic phantoms. Results: The self-absorbed dose for most organs/tissues is only slightly influenced by respiratory motion. However, for the lung, the self-absorbed SAF is about 11.5% higher at the peak exhale phase than the peak inhale phase for photon energies above 50 keV. The cross-absorbed dose is obviously affected by respiratory motion for many combinations of source-target pairs. The cross-absorbed S-values for the heart contents irradiating the lung are about 7.5% higher in the peak exhale phase than the peak inhale phase for different positron-emitting radionuclides. For {sup 18}F-FDG, organ absorbed doses are less influenced by respiratory motion. Conclusions: Respiration-induced volume variations of the lungs and the repositioning of internal organs affect the self-absorbed dose of the lungs and cross-absorbed dose between organs in internal radiation dosimetry. The dynamic anatomical model provides more accurate internal radiation dosimetry estimates for the lungs and abdominal organs based on realistic modeling of respiratory motion. This work also contributes to a better understanding of model-induced uncertainties in internal radiation dosimetry.« less

Absolute cross-section measurements of inner-shell ionization

NASA Astrophysics Data System (ADS)

Schneider, Hans; Tobehn, Ingo; Ebel, Frank; Hippler, Rainer

1994-12-01

Cross section ratios for K- and L-shell ionization of thin silver and gold targets by positron and electron impact have been determined at projectile energies of 30 70 keV. The experimental results are confirmed by calculations in plane wave Born approximation (PWBA) which include an electron exchange term and account for the deceleration or acceleration of the incident projectile in the nuclear field of the target atom. We report first absolute cross sections for K- and L-shell ionization of silver and gold targets by lepton impact in the threshold region. We have measured the corresponding cross sections for electron (e-) impact with an electron gun and the same experimental set-up.

Particle dynamics and pair production in tightly focused standing wave

NASA Astrophysics Data System (ADS)

Jirka, M.; Klimo, O.; Vranić, M.; Weber, S.; Korn, G.

2017-05-01

With the advent of 10 PW laser facilities, new regimes of laser-matter interaction are opening since effects of quantum electrodynamics, such as electron-positron pair production and cascade development, start to be important. The dynamics of light charged particles, such as electrons and positrons, is affected by the radiation reaction force. This effect can strongly influence the interaction of intense laser pulses with matter since it lowers the energy of emitting particles and transforms their energy to the gamma radiation. Consequently, electron-positron pairs can be generated via Breit-Wheeler process. To study this new regime of interaction, numerical simulations are required. With their help it is possible to predict and study quantum effects which may occur in future experiments at modern laser facilities. In this work we present results of electron interaction with an intense standing wave formed by two colliding laser pulses. Due to the necessity to achieve ultra intense laser field, the laser beam has to be focused to a μm-diameter spot. Since the paraxial approximation is not valid for tight focusing, the appropriate model describing the tightly focused laser beam has to be employed. In tightly focused laser beam the longitudinal component of the electromagnetic field becomes significant and together with the ponderomotive force they affect the dynamics of interacting electrons and also newly generated Breit-Wheeler electron-positron pairs. Using the Particle-In-Cell code we study electron dynamics, gamma radiation and pair production in such a configuration for linear polarization and different types of targets.

Monte-Carlo Simulation and Measurements of Electrons, Positrons, And Gamma-Rays Generated by Laser-Solid Interactions

NASA Astrophysics Data System (ADS)

Henderson, Alexander Hastings

Lasers have grown more powerful in recent years, opening up new frontiers in physics. From early intensities of less than 1010 W/cm 2, lasers can now achieve intensities over 1021 W/cm 2. Ultraintense laser can become powerful new tools to produce relativistic electrons, positron-electron pairs, and gamma-rays. The pair production efficiency is equal to or greater than that of linear accelerators, the most common method of antimatter generation in the past. The gamma-rays and electrons produced can be highly collimated, making these interactions of interest for beam generation. Monte-Carlo particle transport simulation has long been used in physics for simulating various particle and radiation processes, and is well-suited to simulating both electromagnetic cascades resulting from laser-solid interactions and the response of electron/positron spectrometers and gamma-ray detectors. We have used GEANT4 Monte-Carlo particle transport simulation to design and calibrate charged-particle spectrometers using permanent magnets as well as a Forward Compton Electron Spectrometer to measure gamma-rays of higher energies than have previously been achieved. We have had some success simulating and measuring high positron and gamma-rays yields from laser-solid interactions using gold target at the Texas Petawatt Laser (TPW). While similar spectrometers have been developed in the past, we are to our knowledge the first to successfully use permanent magnet spectrometers to detect positrons originating from laser-solid interactions in this energy range. We believe we are also the first to successfully detect multi-MeV gamma rays using a permanent magnet Forward Compton Electron Spectrometer. Monte-Carlo particle transport simulation has been used by other groups to model positron production from laser-solid ineraction, but at the time that we began we were, as far as we know, the first to have a significant amount of empirical data to work with. We were thus at liberty to estimate the initial conditions, compare simulation results to data, and adjust as needed to obtain a better estimate of the actual initial conditions. We have also developed a new method for measuring the yield and angular distribution of gamma-rays using a two-dimensional dosimeter array. In this work, we examine the experimental and simulation results as well as the physical processes behind them. In addition, the gamma-rays produced by our experiments could be useful for photo-nuclear reactors and homeland security purposes. In our experiments, we measured narrow energy-band positrons and electrons which have potential medical uses.

Two-component density functional theory calculations of positron lifetimes for small vacancy clusters in silicon

NASA Astrophysics Data System (ADS)

Makhov, D. V.; Lewis, Laurent J.

2005-05-01

The positron lifetimes for various vacancy clusters in silicon are calculated within the framework of the two-component electron-positron density functional theory. The effect of the trapped positron on the electron density and on the relaxation of the structure is investigated. Our calculations show that, contrary to the usual assumption, the positron-induced forces do not compensate in general for electronic inward forces. Thus, geometry optimization is required in order to determine positron lifetime accurately. For the monovacancy and the divacancy, the results of our calculations are in good agreement with the experimental positron lifetimes, suggesting that this approach gives good estimates of positron lifetimes for larger vacancy clusters, required for their correct identification with positron annihilation spectroscopy. As an application, our calculations show that fourfold trivacancies and symmetric fourfold tetravacancies have positron lifetimes similar to monovacancies and divacancies, respectively, and can thus be confused in the interpretation of positron annihilation experiments.

Positron Emission Tomography - Computed Tomography (PET/CT)

MedlinePlus

... A-Z Positron Emission Tomography - Computed Tomography (PET/CT) Positron emission tomography (PET) uses small amounts of ... What is Positron Emission Tomography – Computed Tomography (PET/CT) Scanning? Positron emission tomography, also called PET imaging ...

Gravitational mass of positron from LEP synchrotron losses

DOE PAGES

Kalaydzhyan, Tigran

2016-07-27

General relativity(GR) is the current description of gravity in modern physics. One of the cornerstones of GR, as well as Newton’s theory of gravity, is the weak equivalence principle (WEP), stating that the trajectory of a freely falling test body is independent of its internal structure and composition. WEP is known to be valid for the normal matter with a high precision. However, due to the rarity of antimatter and weakness of the gravitational forces, the WEP has never been confirmed for antimatter. The current direct bounds on the ratio between the gravitational and inertial masses of the antihydrogen domore » not rule out a repulsive nature for the antimatter gravity. Here we establish an indirect bound of 0.13% on the difference between the gravitational and inertial masses of the positron (antielectron) from the analysis of synchrotron losses at the Large Electron-Positron collider (LEP). As a result, this serves as a confirmation of the conventional gravitational properties of antimatter without common assumptions such as, e.g., coupling of gravity to virtual particles, dynamics of distant astrophysical sources and the nature of absolute gravitational potentials.« less

Properties of the electron cloud in a high-energy positron and electron storage ring

DOE PAGES

Harkay, K. C.; Rosenberg, R. A.

2003-03-20

Low-energy, background electrons are ubiquitous in high-energy particle accelerators. Under certain conditions, interactions between this electron cloud and the high-energy beam can give rise to numerous effects that can seriously degrade the accelerator performance. These effects range from vacuum degradation to collective beam instabilities and emittance blowup. Although electron-cloud effects were first observed two decades ago in a few proton storage rings, they have in recent years been widely observed and intensely studied in positron and proton rings. Electron-cloud diagnostics developed at the Advanced Photon Source enabled for the first time detailed, direct characterization of the electron-cloud properties in amore » positron and electron storage ring. From in situ measurements of the electron flux and energy distribution at the vacuum chamber wall, electron-cloud production mechanisms and details of the beam-cloud interaction can be inferred. A significant longitudinal variation of the electron cloud is also observed, due primarily to geometrical details of the vacuum chamber. Furthermore, such experimental data can be used to provide realistic limits on key input parameters in modeling efforts, leading ultimately to greater confidence in predicting electron-cloud effects in future accelerators.« less

Spatiotemporal distributions of pair production and cascade in solid targets irradiated by ultra-relativistic lasers with different polarizations

NASA Astrophysics Data System (ADS)

Yuan, T.; Yu, J. Y.; Liu, W. Y.; Weng, S. M.; Yuan, X. H.; Luo, W.; Chen, M.; Sheng, Z. M.; Zhang, J.

2018-06-01

Two-dimensional particle-in-cell simulations have been performed to study electron-positron pair production and cascade development in single ultra-relativistic laser interaction with solid targets. The spatiotemporal distributions of particles produced via QED processes are illustrated and their dependence on laser polarizations is investigated. The evolution of particle generation displays clear QED cascade characters. Studies show that although a circularly polarized laser delays the QED process due to the effective ion acceleration, it can reduce the target heating and confine high-energy charged particles, which leads to deeper QED cascade order and denser pair plasma production than linearly polarized lasers. These findings may benefit the understanding of the coming experimental studies of ultra-relativistic laser target interaction in the QED dominated regime.

Spot-welding solid targets for high current cyclotron irradiation.

PubMed

Ellison, Paul A; Valdovinos, Hector F; Graves, Stephen A; Barnhart, Todd E; Nickles, Robert J

2016-12-01

Zirconium-89 finds broad application for use in positron emission tomography. Its cyclotron production has been limited by the heat transfer from yttrium targets at high beam currents. A spot welding technique allows a three-fold increase in beam current, without affecting 89 Zr quality. An yttrium foil, welded to a jet-cooled tantalum support base accommodates a 50µA proton beam degraded to 14MeV. The resulting activity yield of 48±4 MBq/(μA∙hr) now extends the outreach of 89 Zr for a broader distribution. Copyright © 2016 Elsevier Ltd. All rights reserved.

Diffracted diffraction radiation and its application to beam diagnostics

NASA Astrophysics Data System (ADS)

Goponov, Yu. A.; Shatokhin, R. A.; Sumitani, K.; Syshchenko, V. V.; Takabayashi, Y.; Vnukov, I. E.

2018-03-01

We present theoretical considerations for diffracted diffraction radiation and also propose an application of this process to diagnosing ultra-relativistic electron (positron) beams for the first time. Diffraction radiation is produced when relativistic particles move near a target. If the target is a crystal or X-ray mirror, diffraction radiation in the X-ray region is expected to be diffracted at the Bragg angle and therefore be detectable. We present a scheme for applying this process to measurements of the beam angular spread, and consider how to conduct a proof-of-principle experiment for the proposed method.

Assessment of a Three-Dimensional Line-of-Response Probability Density Function System Matrix for PET

PubMed Central

Yao, Rutao; Ramachandra, Ranjith M.; Mahajan, Neeraj; Rathod, Vinay; Gunasekar, Noel; Panse, Ashish; Ma, Tianyu; Jian, Yiqiang; Yan, Jianhua; Carson, Richard E.

2012-01-01

To achieve optimal PET image reconstruction through better system modeling, we developed a system matrix that is based on the probability density function for each line of response (LOR-PDF). The LOR-PDFs are grouped by LOR-to-detector incident angles to form a highly compact system matrix. The system matrix was implemented in the MOLAR list mode reconstruction algorithm for a small animal PET scanner. The impact of LOR-PDF on reconstructed image quality was assessed qualitatively as well as quantitatively in terms of contrast recovery coefficient (CRC) and coefficient of variance (COV), and its performance was compared with a fixed Gaussian (iso-Gaussian) line spread function. The LOR-PDFs of 3 coincidence signal emitting sources, 1) ideal positron emitter that emits perfect back-to-back γ rays (γγ) in air; 2) fluorine-18 (18F) nuclide in water; and 3) oxygen-15 (15O) nuclide in water, were derived, and assessed with simulated and experimental phantom data. The derived LOR-PDFs showed anisotropic and asymmetric characteristics dependent on LOR-detector angle, coincidence emitting source, and the medium, consistent with common PET physical principles. The comparison of the iso-Gaussian function and LOR-PDF showed that: 1) without positron range and acolinearity effects, the LOR-PDF achieved better or similar trade-offs of contrast recovery and noise for objects of 4-mm radius or larger, and this advantage extended to smaller objects (e.g. 2-mm radius sphere, 0.6-mm radius hot-rods) at higher iteration numbers; and 2) with positron range and acolinearity effects, the iso-Gaussian achieved similar or better resolution recovery depending on the significance of positron range effect. We conclude that the 3-D LOR-PDF approach is an effective method to generate an accurate and compact system matrix. However, when used directly in expectation-maximization based list-mode iterative reconstruction algorithms such as MOLAR, its superiority is not clear. For this application, using an iso-Gaussian function in MOLAR is a simple but effective technique for PET reconstruction. PMID:23032702

F-18-FDG-PET Confined Radiotherapy of Locally Advanced NSCLC With Concomitant Chemotherapy: Results of the PET-PLAN Pilot Trial

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fleckenstein, Jochen; Hellwig, Dirk; Kremp, Stephanie

2011-11-15

Purpose: The integration of fluoro-deoxy-D-glucose positron emission tomography (FDG-PET) in the process of radiotherapy (RT) planning of locally advanced non-small-cell lung cancer (NSCLC) may improve diagnostic accuracy and minimize interobserver variability compared with target volume definition solely based on computed tomography. Furthermore, irradiating only FDG-PET-positive findings and omitting elective nodal regions may allow dose escalation by treating smaller volumes. The aim of this prospective pilot trial was to evaluate the therapeutic safety of FDG-PET-based RT treatment planning with an autocontour-derived delineation of the primary tumor. Methods and Materials: Eligible patients had Stages II-III inoperable NSCLC, and simultaneous, platinum-based radiochemotherapy wasmore » indicated. FDG-PET and computed tomography acquisitions in RT treatment planning position were coregistered. The clinical target volume (CTV) included the FDG-PET-defined primary tumor, which was autodelineated with a source-to-background algorithm, plus FDG-PET-positive lymph node stations. Limited by dose restrictions for normal tissues, prescribed total doses were in the range of 66.6 to 73.8 Gy. The primary endpoint was the rate of out-of-field isolated nodal recurrences (INR). Results: As per intent to treat, 32 patients received radiochemotherapy. In 15 of these patients, dose escalation above 66.6 Gy was achieved. No Grade 4 toxicities occurred. After a median follow-up time of 27.2 months, the estimated median survival time was 19.3 months. During the observation period, one INR was observed in 23 evaluable patients. Conclusions: FDG-PET-confined target volume definition in radiochemotherapy of NSCLC, based on a contrast-oriented source-to-background algorithm, was associated with a low risk of INR. It might provide improved tumor control because of dose escalation.« less

In vivo targeting and imaging of tumor vasculature with radiolabeled, antibody-conjugated nanographene.

PubMed

Hong, Hao; Yang, Kai; Zhang, Yin; Engle, Jonathan W; Feng, Liangzhu; Yang, Yunan; Nayak, Tapas R; Goel, Shreya; Bean, Jero; Theuer, Charles P; Barnhart, Todd E; Liu, Zhuang; Cai, Weibo

2012-03-27

Herein we demonstrate that nanographene can be specifically directed to the tumor neovasculature in vivo through targeting of CD105 (i.e., endoglin), a vascular marker for tumor angiogenesis. The covalently functionalized nanographene oxide (GO) exhibited excellent stability and target specificity. Pharmacokinetics and tumor targeting efficacy of the GO conjugates were investigated with serial noninvasive positron emission tomography imaging and biodistribution studies, which were validated by in vitro, in vivo, and ex vivo experiments. The incorporation of an active targeting ligand (TRC105, a monoclonal antibody that binds to CD105) led to significantly improved tumor uptake of functionalized GO, which was specific for the neovasculature with little extravasation, warranting future investigation of these GO conjugates for cancer-targeted drug delivery and/or photothermal therapy to enhance therapeutic efficacy. Since poor extravasation is a major hurdle for nanomaterial-based tumor targeting in vivo, this study also establishes CD105 as a promising vascular target for future cancer nanomedicine. © 2012 American Chemical Society

Apparatus and method for preparing oxygen-15 labeled water H.sub.2 [.sup.15 O] in an injectable form for use in positron emission tomography

DOEpatents

Ferrieri, Richard A.; Schlyer, David J.; Alexoff, David

1996-01-09

A handling and processing apparatus for preparing Oxygen-15 labeled water (H.sub.2 [.sup.15 O]) in injectable form for use in Positron Emission Tomography from preferably H.sub.2 [.sup.15 O] produced by irradiating a flowing gas target of nitrogen and hydrogen. The apparatus includes a collector for receiving and directing a gas containing H.sub.2 [.sup.15 O] gas and impurities, mainly ammonia (NH.sub.3) gas into sterile water to trap the H.sub.2 [.sup.15 O] and form ammonium (NH.sub.4.sup.+) in the sterile water. A device for displacing the sterile water containing H.sub.2 [.sup.15 O] and NH.sub.4.sup.+ through a cation resin removes NH.sub.4.sup.+ from the sterile water. A device for combining the sterile water containing H.sub.2 [.sup.15 O] with a saline solution produces an injectable solution. Preferably, the apparatus includes a device for delivering the solution to a syringe for injection into a patient. Also, disclosed is a method for preparing H.sub.2 [.sup.15 O] in injectable form for use in Positron Emission Tomography in which the method neither requires isotopic exchange reaction nor application of high temperature.

Hydroxypyridinone Chelators: From Iron Scavenging to Radiopharmaceuticals for PET Imaging with Gallium-68

PubMed Central

Cusnir, Ruslan; Imberti, Cinzia; Hider, Robert C.; Blower, Philip J.; Ma, Michelle T.

2017-01-01

Derivatives of 3,4-hydroxypyridinones have been extensively studied for in vivo Fe3+ sequestration. Deferiprone, a 1,2-dimethyl-3,4-hydroxypyridinone, is now routinely used for clinical treatment of iron overload disease. Hexadentate tris(3,4-hydroxypyridinone) ligands (THP) complex Fe3+ at very low iron concentrations, and their high affinities for oxophilic trivalent metal ions have led to their development for new applications as bifunctional chelators for the positron emitting radiometal, 68Ga3+, which is clinically used for molecular imaging in positron emission tomography (PET). THP-peptide bioconjugates rapidly and quantitatively complex 68Ga3+ at ambient temperature, neutral pH and micromolar concentrations of ligand, making them amenable to kit-based radiosynthesis of 68Ga PET radiopharmaceuticals. 68Ga-labelled THP-peptides accumulate at target tissue in vivo, and are excreted largely via a renal pathway, providing high quality PET images. PMID:28075350

A Review on Segmentation of Positron Emission Tomography Images

PubMed Central

Foster, Brent; Bagci, Ulas; Mansoor, Awais; Xu, Ziyue; Mollura, Daniel J.

2014-01-01

Positron Emission Tomography (PET), a non-invasive functional imaging method at the molecular level, images the distribution of biologically targeted radiotracers with high sensitivity. PET imaging provides detailed quantitative information about many diseases and is often used to evaluate inflammation, infection, and cancer by detecting emitted photons from a radiotracer localized to abnormal cells. In order to differentiate abnormal tissue from surrounding areas in PET images, image segmentation methods play a vital role; therefore, accurate image segmentation is often necessary for proper disease detection, diagnosis, treatment planning, and follow-ups. In this review paper, we present state-of-the-art PET image segmentation methods, as well as the recent advances in image segmentation techniques. In order to make this manuscript self-contained, we also briefly explain the fundamentals of PET imaging, the challenges of diagnostic PET image analysis, and the effects of these challenges on the segmentation results. PMID:24845019

Hydroxypyridinone Chelators: From Iron Scavenging to Radiopharmaceuticals for PET Imaging with Gallium-68.

PubMed

Cusnir, Ruslan; Imberti, Cinzia; Hider, Robert C; Blower, Philip J; Ma, Michelle T

2017-01-08

Derivatives of 3,4-hydroxypyridinones have been extensively studied for in vivo Fe 3+ sequestration. Deferiprone, a 1,2-dimethyl-3,4-hydroxypyridinone, is now routinely used for clinical treatment of iron overload disease. Hexadentate tris(3,4-hydroxypyridinone) ligands (THP) complex Fe 3+ at very low iron concentrations, and their high affinities for oxophilic trivalent metal ions have led to their development for new applications as bifunctional chelators for the positron emitting radiometal, 68 Ga 3+ , which is clinically used for molecular imaging in positron emission tomography (PET). THP-peptide bioconjugates rapidly and quantitatively complex 68 Ga 3+ at ambient temperature, neutral pH and micromolar concentrations of ligand, making them amenable to kit-based radiosynthesis of 68 Ga PET radiopharmaceuticals. 68 Ga-labelled THP-peptides accumulate at target tissue in vivo, and are excreted largely via a renal pathway, providing high quality PET images.

Prospective of 68Ga-Radiopharmaceutical Development

PubMed Central

Velikyan, Irina

2014-01-01

Positron Emission Tomography (PET) experienced accelerated development and has become an established method for medical research and clinical routine diagnostics on patient individualized basis. Development and availability of new radiopharmaceuticals specific for particular diseases is one of the driving forces of the expansion of clinical PET. The future development of the 68Ga-radiopharmaceuticals must be put in the context of several aspects such as role of PET in nuclear medicine, unmet medical needs, identification of new biomarkers, targets and corresponding ligands, production and availability of 68Ga, automation of the radiopharmaceutical production, progress of positron emission tomography technologies and image analysis methodologies for improved quantitation accuracy, PET radiopharmaceutical regulations as well as advances in radiopharmaceutical chemistry. The review presents the prospects of the 68Ga-based radiopharmaceutical development on the basis of the current status of these aspects as well as wide range and variety of imaging agents. PMID:24396515

Neutron dosimetry at a high-energy electron-positron collider

NASA Astrophysics Data System (ADS)

Bedogni, Roberto

Electron-positron colliders with energy of hundreds of MeV per beam have been employed for studies in the domain of nuclear and sub-nuclear physics. The typical structure of such a collider includes an LINAC, able to produce both types of particles, an accumulator ring and a main ring, whose diameter ranges from several tens to hundred meters and allows circulating particle currents of several amperes per beam. As a consequence of the interaction of the primary particles with targets, shutters, structures and barriers, a complex radiation environment is produced. This paper addresses the neutron dosimetry issues associated with the operation of such accelerators, referring in particular to the DAΦ NE complex, operative since 1997 at INFN-Frascati National Laboratory (Italy). Special attention is given to the active and passive techniques used for the spectrometric and dosimetric characterization of the workplace neutron fields, for radiation protection dosimetry purposes.

Detector for measuring the π + → e +v branching fraction

DOE PAGES

Aguilar-Arevalo, A. A.; Aoki, M.; Blecher, M.; ...

2015-04-13

The PIENU experiment at TRIUMF is aimed at a measurement of the branching ratio R e/u = Γ((π + → e +v e) + (π + → e +v eγ))/Γ((π + → μ +v μ) + (π + → μ +v μγ)) with precision < 0.1%. Incident pions, delivered at the rate of 60 kHz with momentum 75 MeV/c, were degraded and stopped in a plastic scintillator target. Pions and their decay product positrons were detected with plastic scintillators and tracked with multiwire proportional chambers and silicon strip detectors. The energies of the positrons were measured in a spectrometer consistingmore » of a large NaI(Tℓ) crystal surrounded by an array of pure CsI crystals. This paper provides a description of the PIENU experimental apparatus and its performance in pursuit of R e/u« less

The pinching method for Galactic cosmic ray positrons: Implications in the light of precision measurements

NASA Astrophysics Data System (ADS)

Boudaud, M.; Bueno, E. F.; Caroff, S.; Genolini, Y.; Poulin, V.; Poireau, V.; Putze, A.; Rosier, S.; Salati, P.; Vecchi, M.

2017-09-01

Context. Two years ago, the Ams-02 collaboration released the most precise measurement of the cosmic ray positron flux. In the conventional approach, in which positrons are considered as purely secondary particles, the theoretical predictions fall way below the data above 10 GeV. One suggested explanation for this anomaly is the annihilation of dark matter particles, the so-called weakly interactive massive particles (WIMPs), into standard model particles. Most analyses have focused on the high-energy part of the positron spectrum, where the anomaly lies, disregarding the complicated GeV low-energy region where Galactic cosmic ray transport is more difficult to model and solar modulation comes into play. Aims: Given the high quality of the latest measurements by Ams-02, it is now possible to systematically re-examine the positron anomaly over the entire energy range, this time taking into account transport processes so far neglected, such as Galactic convection or diffusive re-acceleration. These might impact somewhat on the high-energy positron flux so that a complete and systematic estimate of the secondary component must be performed and compared to the Ams-02 measurements. The flux yielded by WIMPs also needs to be re-calculated more accurately to explore how dark matter might source the positron excess. Methods: We devise a new semi-analytical method to take into account transport processes thus far neglected, but important below a few GeV. It is essentially based on the pinching of inverse Compton and synchrotron energy losses from the magnetic halo, where they take place, inside the Galactic disc. The corresponding energy loss rate is artificially enhanced by the so-called pinching factor, which needs to be calculated at each energy. We have checked that this approach reproduces the results of the Green function method at the per mille level. This new tool is fast and allows one to carry out extensive scans over the cosmic ray propagation parameters. Results: We derive the positron flux from sub-GeV to TeV energies for both gas spallation and dark matter annihilation. We carry out a scan over the cosmic ray propagation parameters, which we strongly constrain by requiring that the secondary component does not overshoot the Ams-02 measurements. We find that only models with large diffusion coefficients are selected by this test. We then add to the secondary component the positron flux yielded by dark matter annihilation. We carry out a scan over WIMP mass to fit the annihilation cross-section and branching ratios, successively exploring the cases of a typical beyond-the-standard-model WIMP and an annihilation through light mediators. In the former case, the best fit yields a p-value of 0.4% for a WIMP mass of 264 GeV, a value that does not allow to reproduce the highest energy data points. If we require the mass to be larger than 500 GeV, the best-fit χ2 per degree of freedom always exceeds a value of 3. The case of light mediators is even worse, with a best-fit χ2 per degree of freedom always larger than 15. Conclusions: We explicitly show that the cosmic ray positron flux is a powerful and independent probe of Galactic cosmic ray propagation. It should be used as a complementary observable to other tracers such as the boron-to-carbon ratio. This analysis shows also that the pure dark matter interpretation of the positron excess is strongly disfavoured. This conclusion is based solely on the positron data, and no other observation, such as the antiproton flux or the CMB anisotropies, needs to be invoked.

Nuclear model calculation and targetry recipe for production of 110mIn.

PubMed

Kakavand, T; Mirzaii, M; Eslami, M; Karimi, A

2015-10-01

(110m)In is potentially an important positron emitting that can be used in positron emission tomography. In this work, the excitation functions and production yields of (110)Cd(d, 2n), (111)Cd(d, 3n), (nat)Cd(d, xn), (110)Cd(p, n), (111)Cd(p, 2n), (112)Cd(p, 3n) and (nat)Cd(p, xn) reactions to produce the (110m)In were calculated using nuclear model code TALYS and compared with the experimental data. The yield of isomeric state production of (110)In was also compared with ground state production ones to reach the optimal energy range of projectile for the high yield production of metastable state. The results indicate that the (110)Cd(p, n)(110m)In is a high yield reaction with an isomeric ratio (σ(m)/σ(g)) of about 35 within the optimal incident energy range of 15-5 MeV. To make the target, cadmium was electroplated on a copper substrate in varying electroplating conditions such as PH, DC current density, temperature and time. A set of cold tests were also performed on the final sample under several thermal shocks to verify target resistance. The best electroplated cadmium target was irradiated with 15 MeV protons at current of 100 µA for one hour and the production yield of (110m)In and other byproducts were measured. Copyright © 2015 Elsevier Ltd. All rights reserved.

Interrogating Tumor Metabolism and Tumor Microenvironments Using Molecular Positron Emission Tomography Imaging. Theranostic Approaches to Improve Therapeutics

PubMed Central

Jacobson, Orit

2013-01-01

Positron emission tomography (PET) is a noninvasive molecular imaging technology that is becoming increasingly important for the measurement of physiologic, biochemical, and pharmacological functions at cellular and molecular levels in patients with cancer. Formation, development, and aggressiveness of tumor involve a number of molecular pathways, including intrinsic tumor cell mutations and extrinsic interaction between tumor cells and the microenvironment. Currently, evaluation of these processes is mainly through biopsy, which is invasive and limited to the site of biopsy. Ongoing research on specific target molecules of the tumor and its microenvironment for PET imaging is showing great potential. To date, the use of PET for diagnosing local recurrence and metastatic sites of various cancers and evaluation of treatment response is mainly based on [18F]fluorodeoxyglucose ([18F]FDG), which measures glucose metabolism. However, [18F]FDG is not a target-specific PET tracer and does not give enough insight into tumor biology and/or its vulnerability to potential treatments. Hence, there is an increasing need for the development of selective biologic radiotracers that will yield specific biochemical information and allow for noninvasive molecular imaging. The possibility of cancer-associated targets for imaging will provide the opportunity to use PET for diagnosis and therapy response monitoring (theranostics) and thus personalized medicine. This article will focus on the review of non-[18F]FDG PET tracers for specific tumor biology processes and their preclinical and clinical applications. PMID:24064460

The role of FDG-PET in detecting rejection after liver transplantation.

PubMed

Watson, Ashley M; Bhutiani, Neal; Philips, Prejesh; Davis, Eric G; Eng, Mary; Cannon, Robert M; Jones, Christopher M

2018-05-15

The activation and increased metabolic activity of T cells in acute cellular rejection could allow fluoro-2-deoxyglucose positron emission tomography to be utilized for detection of acute cellular rejection. The objective of this study was to evaluate the effectiveness of fluoro-2-deoxyglucose positron emission tomography in detecting acute cellular rejection in the clinical setting. Fluoro-2-deoxyglucose positron emission tomography studies were performed on 88 orthotopic liver transplant patients at 7 and 17 days postoperatively (first positron emission tomography and second positron emission tomography, respectively). Additional studies were performed if patients had suspicion of rejection and at resolution of rejection (third positron emission tomography and fourth positron emission tomography, respectively). A circular region of interest was placed over the liver for semiquantitative evaluation of fluoro-2-deoxyglucose positron emission tomography images by means of standard uptake values. Eighteen of 88 patients in our study (20.5%) had histologically proven acute cellular rejection during a 16 ± 11 day follow-up. There was no significant difference between the standard uptake values of first positron emission tomography among non-rejecters versus rejecters (2.05 ±0.46 non-rejecters versus 1.82 ± 0.40 rejecters, P = .127). Within the rejection cohort, the standard uptake values from the third positron emission tomography (rejection) were higher compared to the first positron emission tomography (baseline) (2.41 ± 0.48 third positron emission tomography versus 1.82 ± 0.41 first positron emission tomography, P < .001). Increased signal on fluoro-2-deoxyglucose positron emission tomography over baseline is associated with acute cellular rejection in liver transplant recipients. Additional prospective validation studies are essential to define the role of fluoro-2-deoxyglucose positron emission tomography scan as an early marker for acute cellular rejection. Copyright © 2018 Elsevier Inc. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hogan, Mark

Plasma wakefield acceleration has the potential to dramatically shrink the size and cost of particle accelerators. Research at the SLAC National Accelerator Laboratory has demonstrated that plasmas can provide 1,000 times the acceleration in a given distance compared with current technologies. Developing revolutionary and more efficient acceleration techniques that allow for an affordable high-energy collider is the focus of FACET, a National User Facility at SLAC. The existing FACET National User Facility uses part of SLAC’s two-mile-long linear accelerator to generate high-density beams of electrons and positrons. FACET-II is a new test facility to develop advanced acceleration and coherent radiationmore » techniques with high-energy electron and positron beams. It is the only facility in the world with high energy positron beams. FACET-II provides a major upgrade over current FACET capabilities and the breadth of the potential research program makes it truly unique. It will synergistically pursue accelerator science that is vital to the future of both advanced acceleration techniques for High Energy Physics, ultra-high brightness beams for Basic Energy Science, and novel radiation sources for a wide variety of applications. The design parameters for FACET-II are set by the requirements of the plasma wakefield experimental program. To drive the plasma wakefield requires a high peak current, in excess of 10kA. To reach this peak current, the electron and positron design bunch size is 10μ by 10μ transversely with a bunch length of 10μ. This is more than 200 times better than what has been achieved at the existing FACET. The beam energy is 10 GeV, set by the Linac length available and the repetition rate is up to 30 Hz. The FACET-II project is scheduled to be constructed in three major stages. Components of the project discussed in detail include the following: electron injector, bunch compressors and linac, the positron system, the Sector 20 sailboat and W chicanes, and experimental area and infrastructure.« less

Applications of slow positrons to cancer research: Search for selectivity of positron annihilation to skin cancer

NASA Astrophysics Data System (ADS)

Jean, Y. C.; Li, Ying; Liu, Gaung; Chen, Hongmin; Zhang, Junjie; Gadzia, Joseph E.

2006-02-01

Slow positrons and positron annihilation spectroscopy (PAS) have been applied to medical research in searching for positron annihilation selectivity to cancer cells. We report the results of positron lifetime and Doppler broadening energy spectroscopies in human skin samples with and without cancer as a function of positron incident energy (up to 8 μm depth) and found that the positronium annihilates at a significantly lower rate and forms at a lower probability in the samples having either basal cell carcinoma (BCC) or squamous cell carcinoma (SCC) than in the normal skin. The significant selectivity of positron annihilation to skin cancer may open a new research area of developing positron annihilation spectroscopy as a novel medical tool to detect cancer formation externally and non-invasively at the early stages.

Manipulation of positron orbits in a dipole magnetic field with fluctuating electric fields

NASA Astrophysics Data System (ADS)

Saitoh, H.; Horn-Stanja, J.; Nißl, S.; Stenson, E. V.; Hergenhahn, U.; Pedersen, T. Sunn; Singer, M.; Dickmann, M.; Hugenschmidt, C.; Stoneking, M. R.; Danielson, J. R.; Surko, C. M.

2018-01-01

We report the manipulation of positron orbits in a toroidal dipole magnetic field configuration realized with electric fields generated by segmented electrodes. When the toroidal circulation motion of positrons in the dipole field is coupled with time-varying electric fields generated by azimuthally segmented outer electrodes, positrons undergo oscillations of their radial positions. This enables quick manipulation of the spatial profiles of positrons in a dipole field trap by choosing appropriate frequency, amplitude, phase, and gating time of the electric fields. According to numerical orbit analysis, we applied these electric fields to positrons injected from the NEPOMUC slow positron facility into a prototype dipole field trap experiment with a permanent magnet. Measurements with annihilation γ-rays clearly demonstrated the efficient compression effects of positrons into the strong magnetic field region of the dipole field configuration. This positron manipulation technique can be used as one of essential tools for future experiments on the formation of electron-positron plasmas.

Radiolabeled Cyclic RGD Peptides as Radiotracers for Imaging Tumors and Thrombosis by SPECT

PubMed Central

Zhou, Yang; Chakraborty, Sudipta; Liu, Shuang

2011-01-01

The integrin family is a group of transmembrane glycoprotein comprised of 19 α- and 8 β-subunits that are expressed in 25 different α/β heterodimeric combinations on the cell surface. Integrins play critical roles in many physiological processes, including cell attachment, proliferation, bone remodeling, and wound healing. Integrins also contribute to pathological events such as thrombosis, atherosclerosis, tumor invasion, angiogenesis and metastasis, infection by pathogenic microorganisms, and immune dysfunction. Among 25 members of the integrin family, the αvβ3 is studied most extensively for its role of tumor growth, progression and angiogenesis. In contrast, the αIIbβ3 is expressed exclusively on platelets, facilitates the intercellular bidirectional signaling (“inside-out” and “outside-in”) and allows the aggregation of platelets during vascular injury. The αIIbβ3 plays an important role in thrombosis by its activation and binding to fibrinogen especially in arterial thrombosis due to the high blood flow rate. In the resting state, the αIIbβ3 on platelets does not bind to fibrinogen; on activation, the conformation of platelet is altered and the binding sites of αIIbβ3 are exposed for fibrinogen to crosslink platelets. Over the last two decades, integrins have been proposed as the molecular targets for diagnosis and therapy of cancer, thrombosis and other diseases. Several excellent review articles have appeared recently to cover a broad range of topics related to the integrin-targeted radiotracers and their nuclear medicine applications in tumor imaging by single photon emission computed tomography (SPECT) or a positron-emitting radionuclide for positron emission tomography (PET). This review will focus on recent developments of αvβ3-targeted radiotracers for imaging tumors and the use of αIIbβ3-targeted radiotracers for thrombosis imaging, and discuss different approaches to maximize the targeting capability of cyclic RGD peptides and improve the radiotracer excretion kinetics from non-cancerous organs. Improvement of target uptake and target-to-background ratios is critically important for target-specific radiotracers. PMID:21547153

Matrix Isolation Spectroscopy Applied to Positron Moderatioin in Cryogenic Solids

DTIC Science & Technology

2011-07-01

Current Positron Applications • 2-γ decay exploited in Positron Emission Tomography (PET) scanners. • Positrons localize & annihilate preferentially at...Air Force  Eglin Air Force Base AFRL-RW-EG-TP-2011-024 Matrix Isolation Spectroscopy Applied to Positron Moderation in Cryogenic Solids Distribution... Spectroscopy Applied to Positron Moderation in Cryogenic Solids 5a. CONTRACT NUMBER 5b. GRANT NUMBER 62602F 5c. PROGRAM ELEMENT NUMBER 6

Reflection of Low Energy Positrons from the Surface of Highly Oriented Pyrolytic Graphite and Single Layer Graphene.

NASA Astrophysics Data System (ADS)

Imam, S. K.; Chirayath, V. A.; Chrysler, M. D.; Fairchild, A. J.; Gladen, R. W.; Koymen, A. R.; Weiss, A. H.; UT Arlington Positron Surface Laboratory Team

A time of flight positron annihilation induced Auger electron spectrometer (TOF-PAES) was utilized to measure the reflection of positrons as a function of incident positron energy (0 to 10 eV) from the surface of highly oriented pyrolytic graphite (HOPG) and from a single layer graphene (SLG) on a Cu foil. A NaI scintillation detector was used to measure the annihilation gamma from the reflected positrons as a function of incident positron kinetic energy. The annihilation of the positrons on HOPG and SLG were simultaneously measured using another NaI detector near the sample. The Auger electrons emitted as a result of the annihilation of positrons from the surface of the sample were also measured concurrently. As the positron kinetic energy was increased, the number of reflected positrons calculated from the intensity under the annihilation gamma peak showed a steady decrease. The positronium formation measured at the sample using the gamma spectrum showed a peak at 6 eV. The intensity of the carbon KVV Auger peak showed a dip at the same energy. The correlation of the three signals, intensity of reflected positrons, positrons annihilating at the sample and the Auger intensity are discussed for both samples. This work was supported by NSF Grant No. DMR 1508719 and DMR 1338130.

Variable soft X-ray excesses in active galactic nuclei from nonthermal electron-positron pair cascades

NASA Technical Reports Server (NTRS)

Zdziarski, Andrzej A.; Coppi, Paolo S.

1991-01-01

In the present study of the formation of steep soft X-ray excesses that are superposed on flatter, hard X-ray power-law spectra in nonthermal electron-positron pair cascade sources, the soft excess in pair-cascade AGN models appears as a steep power law superposed on the tail of the UV bump and the flat nonthermal (hard X-ray) power law. The model-parameter space in which an excess in soft X-rays is visible is ascertained, and the time-variability of soft excesses in pair cascade models is examined. It is established that the parameter space in which soft excesses appear encompasses the range of preferred input parameters for a recently development Compton reflection model of UV and X-ray emission from the central engine of an AGN.

Magnetic resonance imaging-guided attenuation correction of positron emission tomography data in PET/MRI

PubMed Central

Izquierdo-Garcia, David; Catana, Ciprian

2018-01-01

Synopsis Attenuation correction (AC) is one of the most important challenges in the recently introduced combined positron emission tomography/magnetic resonance imaging (PET/MR) scanners. PET/MR AC (MR-AC) approaches aim to develop methods that allow accurate estimation of the linear attenuation coefficients (LACs) of the tissues and other components located in the PET field of view (FoV). MR-AC methods can be divided into three main categories: segmentation-, atlas- and PET-based. This review aims to provide a comprehensive list of the state of the art MR-AC approaches as well as their pros and cons. The main sources of artifacts such as body-truncation, metallic implants and hardware correction will be presented. Finally, this review will discuss the current status of MR-AC approaches for clinical applications. PMID:26952727

18F-AV-1451 positron emission tomography in Alzheimer's disease and progressive supranuclear palsy.

PubMed

Passamonti, Luca; Vázquez Rodríguez, Patricia; Hong, Young T; Allinson, Kieren S J; Williamson, David; Borchert, Robin J; Sami, Saber; Cope, Thomas E; Bevan-Jones, W Richard; Jones, P Simon; Arnold, Robert; Surendranathan, Ajenthan; Mak, Elijah; Su, Li; Fryer, Tim D; Aigbirhio, Franklin I; O'Brien, John T; Rowe, James B

2017-03-01

The ability to assess the distribution and extent of tau pathology in Alzheimer's disease and progressive supranuclear palsy in vivo would help to develop biomarkers for these tauopathies and clinical trials of disease-modifying therapies. New radioligands for positron emission tomography have generated considerable interest, and controversy, in their potential as tau biomarkers. We assessed the radiotracer 18F-AV-1451 with positron emission tomography imaging to compare the distribution and intensity of tau pathology in 15 patients with Alzheimer's pathology (including amyloid-positive mild cognitive impairment), 19 patients with progressive supranuclear palsy, and 13 age- and sex-matched controls. Regional analysis of variance and a support vector machine were used to compare and discriminate the clinical groups, respectively. We also examined the 18F-AV-1451 autoradiographic binding in post-mortem tissue from patients with Alzheimer's disease, progressive supranuclear palsy, and a control case to assess the 18F-AV-1451 binding specificity to Alzheimer's and non-Alzheimer's tau pathology. There was increased 18F-AV-1451 binding in multiple regions in living patients with Alzheimer's disease and progressive supranuclear palsy relative to controls [main effect of group, F(2,41) = 17.5, P < 0.0001; region of interest × group interaction, F(2,68) = 7.5, P < 0.00001]. More specifically, 18F-AV-1451 binding was significantly increased in patients with Alzheimer's disease, relative to patients with progressive supranuclear palsy and with control subjects, in the hippocampus and in occipital, parietal, temporal, and frontal cortices (t's > 2.2, P's < 0.04). Conversely, in patients with progressive supranuclear palsy, relative to patients with Alzheimer's disease, 18F-AV-1451 binding was elevated in the midbrain (t = 2.1, P < 0.04); while patients with progressive supranuclear palsy showed, relative to controls, increased 18F-AV-1451 uptake in the putamen, pallidum, thalamus, midbrain, and in the dentate nucleus of the cerebellum (t's > 2.7, P's < 0.02). The support vector machine assigned patients' diagnoses with 94% accuracy. The post-mortem autoradiographic data showed that 18F-AV-1451 strongly bound to Alzheimer-related tau pathology, but less specifically in progressive supranuclear palsy. 18F-AV-1451 binding to the basal ganglia was strong in all groups in vivo. Postmortem histochemical staining showed absence of neuromelanin-containing cells in the basal ganglia, indicating that off-target binding to neuromelanin is an insufficient explanation of 18F-AV-1451 positron emission tomography data in vivo, at least in the basal ganglia. Overall, we confirm the potential of 18F-AV-1451 as a heuristic biomarker, but caution is indicated in the neuropathological interpretation of its binding. Off-target binding may contribute to disease profiles of 18F-AV-1451 positron emission tomography, especially in primary tauopathies such as progressive supranuclear palsy. We suggest that 18F-AV-1451 positron emission tomography is a useful biomarker to assess tau pathology in Alzheimer's disease and to distinguish it from other tauopathies with distinct clinical and pathological characteristics such as progressive supranuclear palsy. © The Author (2017). Published by Oxford University Press on behalf of the Guarantors of Brain.

Defect imaging and detection of precipitates using a new scanning positron microbeam

NASA Astrophysics Data System (ADS)

Gigl, T.; Beddrich, L.; Dickmann, M.; Rienäcker, B.; Thalmayr, M.; Vohburger, S.; Hugenschmidt, C.

2017-12-01

We report on a newly developed scanning positron microbeam based on threefold moderation of positrons provided by the high intensity positron source NEPOMUC. For brightness enhancement a remoderation unit with a 100 nm thin Ni(100) foil and 9.6% efficiency is applied to reduce the area of the beam spot by a factor of 60. In this way, defect spectroscopy is enabled with a lateral resolution of 33 μm over a large scanning range of 19 × 19 mm2. Moreover, 2D defect imaging using Doppler broadening spectroscopy (DBS) is demonstrated to be performed within exceptional short measurement times of less than two minutes for an area of 1 × 1 mm2 (100 × 100 μm2) with a resolution of 250 μm (50 μm). We studied the defect structure in laser beam welds of the high-strength age-hardened Al alloy (AlCu6Mn, EN AW-2219 T87) by applying (coincident) DBS with unprecedented spatial resolution. The visualization of the defect distribution revealed a sharp transition between the raw material and the welded zone as well as a very small heat affected zone. Vacancy-like defects and Cu rich precipitates are detected in the as-received material and, to a lesser extent, in the transition zone of the weld. Most notably, in the center of the weld vacancies without forming Cu-vacancy complexes, and the dissolution of the Cu atoms in the crystal lattice, i.e. formation of a supersaturated solution, could be clearly identified.

Positron annihilation in a metal-oxide semiconductor studied by using a pulsed monoenergetic positron beam

NASA Astrophysics Data System (ADS)

Uedono, A.; Wei, L.; Tanigawa, S.; Suzuki, R.; Ohgaki, H.; Mikado, T.; Ohji, Y.

1993-12-01

The positron annihilation in a metal-oxide semiconductor was studied by using a pulsed monoenergetic positron beam. Lifetime spectra of positrons were measured as a function of incident positron energy for a polycrystalline Si(100 nm)/SiO2(400 nm)/Si specimen. Applying a gate voltage between the polycrystalline Si film and the Si substrate, positrons implanted into the specimen were accumulated at the SiO2/Si interface. From the measurements, it was found that the annihilation probability of ortho-positronium (ortho-Ps) drastically decreased at the SiO2/Si interface. The observed inhibition of the Ps formation was attributed to an interaction between positrons and defects at the SiO2/Si interface.

Positron confinement in embedded lithium nanoclusters

NASA Astrophysics Data System (ADS)

van Huis, M. A.; van Veen, A.; Schut, H.; Falub, C. V.; Eijt, S. W.; Mijnarends, P. E.; Kuriplach, J.

2002-02-01

Quantum confinement of positrons in nanoclusters offers the opportunity to obtain detailed information on the electronic structure of nanoclusters by application of positron annihilation spectroscopy techniques. In this work, positron confinement is investigated in lithium nanoclusters embedded in monocrystalline MgO. These nanoclusters were created by means of ion implantation and subsequent annealing. It was found from the results of Doppler broadening positron beam analysis that approximately 92% of the implanted positrons annihilate in lithium nanoclusters rather than in the embedding MgO, while the local fraction of lithium at the implantation depth is only 1.3 at. %. The results of two-dimensional angular correlation of annihilation radiation confirm the presence of crystalline bulk lithium. The confinement of positrons is ascribed to the difference in positron affinity between lithium and MgO. The nanocluster acts as a potential well for positrons, where the depth of the potential well is equal to the difference in the positron affinities of lithium and MgO. These affinities were calculated using the linear muffin-tin orbital atomic sphere approximation method. This yields a positronic potential step at the MgO||Li interface of 1.8 eV using the generalized gradient approximation and 2.8 eV using the insulator model.

Production and Extraction of [10C]-CO2 From Proton Bombardment of Molten 10B2O3

NASA Astrophysics Data System (ADS)

Schueller, M. J.; Nickles, R. J.; Roberts, A. D.; Jensen, M.

2003-08-01

This work describes the production of 10C (t1/2 = 19 s) from an enriched 10B2O3 target using a CTI RDS-112 11 MeV proton cyclotron. Proton beam heating is used to raise the target to a molten state (˜ 1300 °C), enabling the activity to diffuse to the surface of the melt. An infrared thermocouple monitors the melt temperature. Helium sweep gas then transports the activity to flow-through chemistry processing for human inhalation of 10CO2 for blood flow imaging with Positron Emission Tomography. The temperature-related diffusion of activity out of the white-hot molten glass target is discussed.

Electroplating targets for production of unique PET radionuclides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bui, V.; Sheh, Y.; Finn, R.

1994-12-31

The past decade has witnessed the applications of Positron Emission Tomography (PET) evolving from a purely research endeavour to a procedure which has specific clinical applications in the areas of cardiology, neurology and oncology. The growth of PET has been facilitated by developments in medical instrumentation and radiopharmaceutical chemistry efforts. Included in this latter effort has been the low energy accelerator production and processing of unique PET radionuclides appropriate for the radiolabeling of biomolecules i.e. monoclonal antibodies and pepetides. The development and application of electroplated targets of antimony and copper for the production of iodine-124 and gallium-66 respectively, utilizing themore » Memorial Sloan-Kettering Cancer Center cyclotron are examples of target design and development applicable to many medical accelerators.« less

Electroplated targets for production of unique PET radionuclides

NASA Astrophysics Data System (ADS)

Bui, V.; Sheh, Y.; Finn, R.; Francesconi, L.; Cai, S.; Schlyer, D.; Wieland, B.

1995-12-01

The past decade has witnessed the applications of positron emission tomography (PET) evolving from a purely research endeavor to a procedure which has specific clinical applications in the areas of cardiology, neurology and oncology. The growth of PET has been facilitated by developments in both medical instrumentation and radiopharmaceutical chemistry efforts. Included in this latter effort has been the low energy accelerator production and processing of unique PET radionuclides appropriate for the radiolabeling of biomolecules, i.e. monoclonal antibodies and peptides. The development and application of electroplated targets of antimony and copper for the production of iodine-124 and gallium-66 respectively, utilizing the Memorial Sloan-Kettering Cancer Center (MSKCC) cyclotron are examples of target design and development applicable to many medical accelerators.

Theranostics of prostate cancer: from molecular imaging to precision molecular radiotherapy targeting the prostate specific membrane antigen.

PubMed

Kulkarni, Harshad R; Singh, Aviral; Langbein, Thomas; Schuchardt, Christiane; Mueller, Dirk; Zhang, Jingjing; Lehmann, Coline; Baum, Richard P

2018-06-01

Alterations at the molecular level are a hallmark of cancer. Prostate cancer is associated with the overexpression of prostate-specific membrane antigen (PSMA) in a majority of cases, predominantly in advanced tumors, increasing with the grade or Gleason's score. PSMA can be selectively targeted using radiolabeled PSMA ligands. These small molecules binding the PSMA can be radiolabeled with γ-emitters like 99m Tc and 111 In or positron emitters like 68 Ga and 18 F for diagnosis as well as with their theranostic pairs such as 177 Lu (β-emitter) or 225 Ac (α-emitter) for therapy. This review summarizes the theranostic role of PSMA ligands for molecular imaging and targeted molecular radiotherapy, moving towards precision oncology.

Prostate-Specific Membrane Antigen Is a Potential Antiangiogenic Target in Adrenocortical Carcinoma.

PubMed

Crowley, Michael J P; Scognamiglio, Theresa; Liu, Yi-Fang; Kleiman, David A; Beninato, Toni; Aronova, Anna; Liu, He; Jhanwar, Yuliya S; Molina, Ana; Tagawa, Scott T; Bander, Neil H; Zarnegar, Rasa; Elemento, Olivier; Fahey, Thomas J

2016-03-01

Adrenocortical carcinoma (ACC) is a rare tumor type with a poor prognosis and few therapeutic options. Assess prostate-specific membrane antigen (PSMA) expression as a potential novel therapeutic target for ACC. Expression of PSMA was evaluated in benign and malignant adrenal tumors and 1 patient with metastatic ACC. This study took place at a tertiary referral center. Fifty adrenal samples were evaluated, including 16 normal adrenal glands, 16 adrenocortical adenomas, 15 primary ACC, and 3 ACC metastases. Demographics, PSMA expression levels via real-time quantitative polymerase chain reaction and immunohistochemistry and whole-body positron emission tomography-computed tomography standardized uptake values for 1 patient. qPCR demonstrated an elevated level of PSMA in ACC relative to all benign tissues (P < .05). Immunohistochemistry localized PSMA expression to the neovasculature of ACC and confirmed overexpression of PSMA in ACC relative to benign tissues both in intensity and percentage of vessels stained (78% of ACC, 0% of normal adrenal, and 3.27% of adenoma-associated neovasculature; P < .001). Those with more than 25% PSMA-positive vessels were 33 times more likely to be malignant than benign (odds ratio, P < .001). Whole-body positron emission tomography-computed tomography imaging showed targeting of anti-PSMA Zr89-J591 to 5/5 of the patient's multiple lung masses with an average measurement of 3.49 ± 1.86 cm and a standardized uptake value of 1.4 ± 0.65 relative to blood pool at 0.8 standardized uptake value. PSMA is significantly overexpressed in ACC neovasculature when compared with normal and benign adrenal tumors. PSMA expression can be used to image ACC metastases in vivo and may be considered as a potential diagnostic and therapeutic target in ACC.

Breast imaging technology: Recent advances in imaging endogenous or transferred gene expression utilizing radionuclide technologies in living subjects - applications to breast cancer

PubMed Central

Berger, Frank; Sam Gambhir, Sanjiv

2001-01-01

A variety of imaging technologies is being investigated as tools for studying gene expression in living subjects. Two technologies that use radiolabeled isotopes are single photon emission computed tomography (SPECT) and positron emission tomography (PET). A relatively high sensitivity, a full quantitative tomographic capability, and the ability to extend small animal imaging assays directly into human applications characterize radionuclide approaches. Various radiolabeled probes (tracers) can be synthesized to target specific molecules present in breast cancer cells. These include antibodies or ligands to target cell surface receptors, substrates for intracellular enzymes, antisense oligodeoxynucleotide probes for targeting mRNA, probes for targeting intracellular receptors, and probes for genes transferred into the cell. We briefly discuss each of these imaging approaches and focus in detail on imaging reporter genes. In a PET reporter gene system for in vivo reporter gene imaging, the protein products of the reporter genes sequester positron emitting reporter probes. PET subsequently measures the PET reporter gene dependent sequestration of the PET reporter probe in living animals. We describe and review reporter gene approaches using the herpes simplex type 1 virus thymidine kinase and the dopamine type 2 receptor genes. Application of the reporter gene approach to animal models for breast cancer is discussed. Prospects for future applications of the transgene imaging technology in human gene therapy are also discussed. Both SPECT and PET provide unique opportunities to study animal models of breast cancer with direct application to human imaging. Continued development of new technology, probes and assays should help in the better understanding of basic breast cancer biology and in the improved management of breast cancer patients. PMID:11250742

The application of positron emission tomography/computed tomography in radiation treatment planning: effect on gross target volume definition and treatment management.

PubMed

Iğdem, S; Alço, G; Ercan, T; Unalan, B; Kara, B; Geceer, G; Akman, C; Zengin, F O; Atilla, S; Okkan, S

2010-04-01

To analyse the effect of the use of molecular imaging on gross target volume (GTV) definition and treatment management. Fifty patients with various solid tumours who underwent positron emission tomography (PET)/computed tomography (CT) simulation for radiotherapy planning from 2006 to 2008 were enrolled in this study. First, F-18 fluorodeoxyglucose (FDG)-PET and CT scans of the treatment site in the treatment position and then a whole body scan were carried out with a dedicated PET/CT scanner and fused thereafter. FDG-avid primary tumour and lymph nodes were included into the GTV. A multidisciplinary team defined the target volume, and contouring was carried out by a radiation oncologist using visual methods. To compare the PET/CT-based volumes with CT-based volumes, contours were drawn on CT-only data with the help of site-specific radiologists who were blind to the PET/CT results after a median time of 7 months. In general, our PET/CT volumes were larger than our CT-based volumes. This difference was significant in patients with head and neck cancers. Major changes (> or =25%) in GTV delineation were observed in 44% of patients. In 16% of cases, PET/CT detected incidental second primaries and metastatic disease, changing the treatment strategy from curative to palliative. Integrating functional imaging with FDG-PET/CT into the radiotherapy planning process resulted in major changes in a significant proportion of our patients. An interdisciplinary approach between imaging and radiation oncology departments is essential in defining the target volumes. Copyright 2010 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

Search for Magnetically Broadened Cascade Emission from Blazars with VERITAS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Archambault, S.; Griffin, S.; Archer, A.

2017-02-01

We present a search for magnetically broadened gamma-ray emission around active galactic nuclei (AGNs), using VERITAS observations of seven hard-spectrum blazars. A cascade process occurs when multi-TeV gamma-rays from an AGN interact with extragalactic background light (EBL) photons to produce electron–positron pairs, which then interact with cosmic microwave background photons via inverse-Compton scattering to produce gamma-rays. Due to the deflection of the electron–positron pairs, a non-zero intergalactic magnetic field (IGMF) would potentially produce detectable effects on the angular distribution of the cascade emission. In particular, an angular broadening compared to the unscattered emission could occur. Through non-detection of angularly broadenedmore » emission from 1ES 1218+304, the source with the largest predicted cascade fraction, we exclude a range of IGMF strengths around 10{sup −14} G at the 95% confidence level. The extent of the exclusion range varies with the assumptions made about the intrinsic spectrum of 1ES 1218+304 and the EBL model used in the simulation of the cascade process. All of the sources are used to set limits on the flux due to extended emission.« less

Fluorine-18-FDG PET/CT in a patient with angiomyolipoma: Response to mammalian target of rapamycin inhibitor therapy.

PubMed

Anwar, Hoda; Sachpekidis, Christos; Schwarzbach, Matthias; Dimitrakopoulou-Strauss, Antonia

2017-01-01

We report on a 27 years old female patient who was referred to our department for whole-body as well as dynamic positron emission tomography/computed tomography (dPET/CT) scan of the upper and middle abdomen with fluorine-18-fluorodeoxy glucose ( 18 F-FDG), for further evaluation of a mass in the left adrenal gland region. Positron emission tomography showed a suspicious, enlarged, hypermetabolic mass with an average standardized uptake value (SUV) of 4.5 and a maximum SUV of 5.9. The patient was referred for biopsy, which revealed an angiomyolipoma, a perivascular epithelioid cell tumor (PEComa) of the adrenal gland. Perivascular epithelioid cell tumors are mesenchymal tumors consisting of blood vessels, smooth muscles and fat cells. The patient received anti-proliferative treatment with Afinitor, a mammalian target of rapamycin (mTOR) inhibitor, and was referred again one month after onset of therapy for early response assessment. The follow-up 18 F-FDG PET/CT scan showed a nearly complete resolution of the previously detected adrenal mass, with very low tracer uptake and a decrease in its functional volume. Fluorine- 18-FDG PET/CT can be used for treatment response evaluation of angiomyolipoma treated with mTOR-inhibitors.

Preparation of clinical-grade 89Zr-panitumumab as a positron emission tomography biomarker for evaluating epidermal growth factor receptor-targeted therapy

PubMed Central

Wei, Ling; Shi, Jianfeng; Afari, George; Bhattacharyya, Sibaprasad

2014-01-01

Panitumumab is a fully human monoclonal antibody approved for the treatment of epidermal growth factor receptor (EGFR) positive colorectal cancer. Recently, panitumumab has been radiolabeled with 89Zr and evaluated for its potential to be used as immuno-positron emission tomography (PET) probe for EGFR positive cancers. Interesting preclinical results published by several groups of researchers have prompted us to develop a robust procedure for producing clinical-grade 89Zr-panitumumab as an immuno-PET probe to evaluate EGFR-targeted therapy. In this process, clinical-grade panitumumab is bio-conjugated with desferrioxamine chelate and subsequently radiolabeled with 89Zr resulting in high radiochemical yield (>70%, n=3) and purity (>98%, n=3). All quality control (QC) tests were performed according to United States Pharmacopeia specifications. QC tests showed that 89Zr-panitumumab met all specifications for human injection. Herein, we describe a step-by-step method for the facile synthesis and QC tests of 89Zr-panitumumab for medical use. The entire process of bioconjugation, radiolabeling, and all QC tests will take about 5h. Because the synthesis is fully manual, two rapid, in-process QC tests have been introduced to make the procedure robust and error free. PMID:24448743

Technical aspects of positron emission tomography/computed tomography in radiotherapy treatment planning.

PubMed

Scripes, Paola G; Yaparpalvi, Ravindra

2012-09-01

The usage of functional data in radiation therapy (RT) treatment planning (RTP) process is currently the focus of significant technical, scientific, and clinical development. Positron emission tomography (PET) using ((18)F) fluorodeoxyglucose is being increasingly used in RT planning in recent years. Fluorodeoxyglucose is the most commonly used radiotracer for diagnosis, staging, recurrent disease detection, and monitoring of tumor response to therapy (Lung Cancer 2012;76:344-349; Lung Cancer 2009;64:301-307; J Nucl Med 2008;49:532-540; J Nucl Med 2007;48:58S-67S). All the efforts to improve both PET and computed tomography (CT) image quality and, consequently, lesion detectability have a common objective to increase the accuracy in functional imaging and thus of coregistration into RT planning systems. In radiotherapy, improvement in target localization permits reduction of tumor margins, consequently reducing volume of normal tissue irradiated. Furthermore, smaller treated target volumes create the possibility of dose escalation, leading to increased chances of tumor cure and control. This article focuses on the technical aspects of PET/CT image acquisition, fusion, usage, and impact on the physics of RTP. The authors review the basic elements of RTP, modern radiation delivery, and the technical parameters of coregistration of PET/CT into RT computerized planning systems. Copyright © 2012 Elsevier Inc. All rights reserved.

Radiolabeled inorganic nanoparticles for positron emission tomography imaging of cancer: an overview

PubMed Central

CHAKRAVARTY, Rubel; GOEL, Shreya; DASH, Ashutosh; CAI, Weibo

2017-01-01

Over the last few years, a plethora of radiolabeled inorganic nanoparticles have been developed and evaluated for their potential use as probes in positron emission tomography (PET) imaging of a wide variety of cancers. Inorganic nanoparticles represent an emerging paradigm in molecular imaging probe design, allowing the incorporation of various imaging modalities, targeting ligands, and therapeutic payloads into a single vector. A major challenge in this endeavor is to develop disease-specific nanoparticles with facile and robust radiolabeling strategies. Also, the radiolabeled nanoparticles should demonstrate adequate in vitro and in vivo stability, enhanced sensitivity for detection of disease at an early stage, optimized in vivo pharmacokinetics for reduced non-specific organ uptake, and improved targeting for achieving high efficacy. Owing to these challenges and other technological and regulatory issues, only a single radiolabeled nanoparticle formulation, namely “C-dots” (Cornell dots), has found its way into clinical trials thus far. This review describes the available options for radiolabeling of nanoparticles and summarizes the recent developments in PET imaging of cancer in preclinical and clinical settings using radiolabeled nanoparticles as probes. The key considerations toward clinical translation of these novel PET imaging probes are discussed, which will be beneficial for advancement of the field. PMID:28124549

Present and future experiments using bright low-energy positron beams

NASA Astrophysics Data System (ADS)

Hugenschmidt, Christoph

2017-01-01

Bright slow positron beams enable not only experiments with drastically reduced measurement time and improved signal-to-noise ratio but also the realization of novel experimental techniques. In solid state physics and materials science positron beams are usually applied for the depth dependent analysis of vacancy-like defects and their chemical surrounding using positron lifetime and (coincident) Doppler broadening spectroscopy. For surface studies, annihilation induced Auger-electron spectroscopy allows the analysis of the elemental composition in the topmost atomic layer, and the atomic positions at the surface can be determined by positron diffraction with outstanding accuracy. In fundamental research low-energy positron beams are used for the production of e.g. cold positronium or positronium negative ions. All the aforementioned experiments benefit from the high intensity of present positron beam facilities. In this paper, we scrutinize the technical constraints limiting the achievable positron intensity and the available kinetic energy at the sample position. Current efforts and future developments towards the generation of high intensity spin-polarized slow positron beams paving the way for new positron experiments are discussed.

PREFACE: The International Workshop on Positron Studies of Defects 2014

NASA Astrophysics Data System (ADS)

Sugita, Kazuki; Shirai, Yasuharu

2016-01-01

The International Workshop on Positron Studies of Defects 2014 (PSD-14) was held in Kyoto, Japan from 14-19 September, 2014. The PSD Workshop brought together positron scientists interested in studying defects to an international platform for presenting and discussing recent results and achievements, including new experimental and theoretical methods in the field. The workshop topics can be characterized as follows: • Positron studies of defects in semiconductors and oxides • Positron studies of defects in metals • New experimental methods and equipment • Theoretical calculations and simulations of momentum distributions, positron lifetimes and other characteristics for defects • Positron studies of defects in combination with complementary methods • Positron beam studies of defects at surfaces, interfaces, in sub-surface regions and thin films • Nanostructures and amorphous materials

Separation of 44Ti from proton irradiated scandium by using solid-phase extraction chromatography and design of 44Ti/44Sc generator system.

PubMed

Radchenko, V; Meyer, C A L; Engle, J W; Naranjo, C M; Unc, G A; Mastren, T; Brugh, M; Birnbaum, E R; John, K D; Nortier, F M; Fassbender, M E

2016-12-16

Scandium-44g (half-life 3.97h [1]) shows promise for positron emission tomography (PET) imaging of longer biological processes than that of the current gold standard, 18 F, due to its favorable decay parameters. One source of 44g Sc is the long-lived parent nuclide 44 Ti (half-life 60.0 a). A 44 Ti/ 44g Sc generator would have the ability to provide radionuclidically pure 44g Sc on a daily basis. The production of 44 Ti via the 45 Sc(p,2n) reaction requires high proton beam currents and long irradiation times. Recovery and purification of no-carrier added (nca) 44 Ti from scandium metal targets involves complex separation chemistry. In this study, separation systems based on solid phase extraction chromatography were investigated, including branched diglycolamide (BDGA) resin and hydroxamate based ZR resin. Results indicate that ZR resin in HCl media represents an effective 44 Ti/ 44g Sc separation system. Copyright © 2016 Elsevier B.V. All rights reserved.

Boron Neutron Capture Therapy for Malignant Brain Tumors

PubMed Central

MIYATAKE, Shin-Ichi; KAWABATA, Shinji; HIRAMATSU, Ryo; KUROIWA, Toshihiko; SUZUKI, Minoru; KONDO, Natsuko; ONO, Koji

2016-01-01

Boron neutron capture therapy (BNCT) is a biochemically targeted radiotherapy based on the nuclear capture and fission reactions that occur when non-radioactive boron-10, which is a constituent of natural elemental boron, is irradiated with low energy thermal neutrons to yield high linear energy transfer alpha particles and recoiling lithium-7 nuclei. Therefore, BNCT enables the application of a high dose of particle radiation selectively to tumor cells in which boron-10 compound has been accumulated. We applied BNCT using nuclear reactors for 167 cases of malignant brain tumors, including recurrent malignant gliomas, newly diagnosed malignant gliomas, and recurrent high-grade meningiomas from January 2002 to May 2014. Here, we review the principle and history of BNCT. In addition, we introduce fluoride-18-labeled boronophenylalanine positron emission tomography and the clinical results of BNCT for the above-mentioned malignant brain tumors. Finally, we discuss the recent development of accelerators producing epithermal neutron beams. This development could provide an alternative to the current use of specially modified nuclear reactors as a neutron source, and could allow BNCT to be performed in a hospital setting. PMID:27250576

Boron Neutron Capture Therapy for Malignant Brain Tumors.

PubMed

Miyatake, Shin-Ichi; Kawabata, Shinji; Hiramatsu, Ryo; Kuroiwa, Toshihiko; Suzuki, Minoru; Kondo, Natsuko; Ono, Koji

2016-07-15

Boron neutron capture therapy (BNCT) is a biochemically targeted radiotherapy based on the nuclear capture and fission reactions that occur when non-radioactive boron-10, which is a constituent of natural elemental boron, is irradiated with low energy thermal neutrons to yield high linear energy transfer alpha particles and recoiling lithium-7 nuclei. Therefore, BNCT enables the application of a high dose of particle radiation selectively to tumor cells in which boron-10 compound has been accumulated. We applied BNCT using nuclear reactors for 167 cases of malignant brain tumors, including recurrent malignant gliomas, newly diagnosed malignant gliomas, and recurrent high-grade meningiomas from January 2002 to May 2014. Here, we review the principle and history of BNCT. In addition, we introduce fluoride-18-labeled boronophenylalanine positron emission tomography and the clinical results of BNCT for the above-mentioned malignant brain tumors. Finally, we discuss the recent development of accelerators producing epithermal neutron beams. This development could provide an alternative to the current use of specially modified nuclear reactors as a neutron source, and could allow BNCT to be performed in a hospital setting.

Cardiac Sarcoidosis: Clinical Manifestations, Imaging Characteristics, and Therapeutic Approach

PubMed Central

Houston, Brian A; Mukherjee, Monica

2014-01-01

Sarcoidosis is a multi-system disease pathologically characterized by the accumulation of T-lymphocytes and mononuclear phagocytes into the sine qua non pathologic structure of the noncaseating granuloma. Cardiac involvement remains a key source of morbidity and mortality in sarcoidosis. Definitive diagnosis of cardiac sarcoidosis, particularly early enough in the disease course to provide maximal therapeutic impact, has proven a particularly difficult challenge. However, major advancements in imaging techniques have been made in the last decade. Advancements in imaging modalities including echocardiography, nuclear spectroscopy, positron emission tomography, and magnetic resonance imaging all have improved our ability to diagnose cardiac sarcoidosis, and in many cases to provide a more accurate prognosis and thus targeted therapy. Likewise, therapy for cardiac sarcoidosis is beginning to advance past a “steroids-only” approach, as novel immunosuppressant agents provide effective steroid-sparing options. The following focused review will provide a brief discussion of the epidemiology and clinical presentation of cardiac sarcoidosis followed by a discussion of up-to-date imaging modalities employed in its assessment and therapeutic approaches. PMID:25452702

Separation of 44Ti from proton irradiated scandium by using solid-phase extraction chromatography and design of 44Ti/ 44Sc generator system

DOE PAGES

Radchenko, Valery; Meyer, Catherine Anne Louise; Engle, Jonathan Ward; ...

2016-11-24

Scandium-44 g (half-life 3.97 h) shows promise for positron emission tomography (PET) imaging of longer biological processes than that of the current gold standard, 18F, due to its favorable decay parameters. One source of 44gSc is the long-lived parent nuclide 44Ti (half-life 60.0 a). A 44Ti/ 44gSc generator would have the ability to provide radionuclidically pure 44gSc on a daily basis. The production of 44Ti via the 45Sc(p,2n) reaction requires high proton beam currents and long irradiation times. Recovery and purification of no-carrier added (nca) 44Ti from scandium metal targets involves complex separation chemistry. In this study, separation systems basedmore » on solid phase extraction chromatography were investigated, including branched diglycolamide (BDGA) resin and hydroxamate based ZR resin. Lastly, results indicate that ZR resin in HCl media represents an effective 44Ti/ 44gSc separation system.« less

Depth-dependent positron annihilation in different polymers

NASA Astrophysics Data System (ADS)

Yang, J.; Zhang, P.; Cheng, G. D.; Li, D. X.; Wu, H. B.; Li, Z. X.; Cao, X. Z.; Jia, Q. J.; Yu, R. S.; Wang, B. Y.

2013-09-01

Depth-dependent positron annihilation Doppler broadening measurements were conducted for polymers with different chemical compositions. Variations of the S parameter with respect to incident positron energy were observed. For pure hydrocarbons PP, HDPE and oxygen-containing polymer PC, S parameter rises with increasing positron implantation depth. While for PI and fluoropolymers like PTFE, ETFE and PVF, S parameter decreases with higher positron energy. For chlorine-containing polymer PVDC, S parameter remains nearly constant at all incident positron energies. It is suggested that these three variation trends are resulted from a competitive effect between the depth-dependent positronium formation and the influence of highly electronegative atoms on positron annihilation characteristics.

Elastic and inelastic scattering of positrons in gases and solids

NASA Technical Reports Server (NTRS)

Mcgowan, J. W.

1972-01-01

Three apparatuses were designed and built: The first, which is now operative, was designed to study the details of positron thermalization in solids and the subsequent emission of the low energy positrons from moderating foils; The second apparatus now under test is a positron bottle similar in design to an electron trap. It was built to store positrons at a fixed energy and to look at the number of stored positrons (storage time) as a function of a scattering gas in the vacuum chamber. The third apparatus is a crossed beam apparatus where positron-, alkali scattering will be studied. Much of the apparatus is now under test with electrons.

Positron studies in catalysis research

NASA Astrophysics Data System (ADS)

During the past eight months, the authors have made progress in several areas relevant to the eventual use of positron techniques in catalysis research. They have come closer to the completion of their positron microscope, and at the same time have performed several studies in their non-microscopic positron spectrometer which should ultimately be applicable to catalysis. The current status of the efforts in each of these areas is summarized in the following sections: Construction of the positron microscope (optical element construction, data collection software, and electronic sub-assemblies); Doppler broadening spectroscopy of metal silicide; Positron lifetime spectroscopy of glassy polymers; and Positron lifetime measurements of pore-sizes in zeolites.

Organ and effective dose rate coefficients for submersion exposure in occupational settings

DOE PAGES

Veinot, K. G.; Y-12 National Security Complex, Oak Ridge, TN; Dewji, S. A.; ...

2017-08-24

External dose coefficients for environmental exposure scenarios are often computed using assumption on infinite or semi-infinite radiation sources. For example, in the case of a person standing on contaminated ground, the source is assumed to be distributed at a given depth (or between various depths) and extending outwards to an essentially infinite distance. In the case of exposure to contaminated air, the person is modeled as standing within a cloud of infinite, or semi-infinite, source distribution. However, these scenarios do not mimic common workplace environments where scatter off walls and ceilings may significantly alter the energy spectrum and dose coefficients.more » In this study, dose rate coefficients were calculated using the International Commission on Radiological Protection (ICRP) reference voxel phantoms positioned in rooms of three sizes representing an office, laboratory, and warehouse. For each room size calculations using the reference phantoms were performed for photons, electrons, and positrons as the source particles to derive mono-energetic dose rate coefficients. Since the voxel phantoms lack the resolution to perform dose calculations at the sensitive depth for the skin, a mathematical phantom was developed and calculations were performed in each room size with the three source particle types. Coefficients for the noble gas radionuclides of ICRP Publication 107 (e.g., Ne, Ar, Kr, Xe, and Rn) were generated by folding the corresponding photon, electron, and positron emissions over the mono-energetic dose rate coefficients. Finally, results indicate that the smaller room sizes have a significant impact on the dose rate per unit air concentration compared to the semi-infinite cloud case. For example, for Kr-85 the warehouse dose rate coefficient is 7% higher than the office dose rate coefficient while it is 71% higher for Xe-133.« less

Organ and effective dose rate coefficients for submersion exposure in occupational settings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Veinot, K. G.; Y-12 National Security Complex, Oak Ridge, TN; Dewji, S. A.

External dose coefficients for environmental exposure scenarios are often computed using assumption on infinite or semi-infinite radiation sources. For example, in the case of a person standing on contaminated ground, the source is assumed to be distributed at a given depth (or between various depths) and extending outwards to an essentially infinite distance. In the case of exposure to contaminated air, the person is modeled as standing within a cloud of infinite, or semi-infinite, source distribution. However, these scenarios do not mimic common workplace environments where scatter off walls and ceilings may significantly alter the energy spectrum and dose coefficients.more » In this study, dose rate coefficients were calculated using the International Commission on Radiological Protection (ICRP) reference voxel phantoms positioned in rooms of three sizes representing an office, laboratory, and warehouse. For each room size calculations using the reference phantoms were performed for photons, electrons, and positrons as the source particles to derive mono-energetic dose rate coefficients. Since the voxel phantoms lack the resolution to perform dose calculations at the sensitive depth for the skin, a mathematical phantom was developed and calculations were performed in each room size with the three source particle types. Coefficients for the noble gas radionuclides of ICRP Publication 107 (e.g., Ne, Ar, Kr, Xe, and Rn) were generated by folding the corresponding photon, electron, and positron emissions over the mono-energetic dose rate coefficients. Finally, results indicate that the smaller room sizes have a significant impact on the dose rate per unit air concentration compared to the semi-infinite cloud case. For example, for Kr-85 the warehouse dose rate coefficient is 7% higher than the office dose rate coefficient while it is 71% higher for Xe-133.« less

Application Of Positron Beams For The Characterization Of Nano-scale Pores In Thin Films

NASA Astrophysics Data System (ADS)

Hirata, K.; Ito, K.; Kobayashi, Y.; Suzuki, R.; Ohdaira, T.; Eijt, S. W. H.; Schut, H.; van Veen, A.

2003-08-01

We applied three positron annihilation techniques, positron 3γ-annihilation spectroscopy, positron annihilation lifetime spectroscopy, and angular correlation of annihilation radiation, to the characterization of nano-scale pores in thin films by combining them with variable-energy positron beams. Characterization of pores in thin films is an important part of the research on various thin films of industrial importance. The results of our recent studies on pore characterization of thin films by positron beams will be reported here.

Experimental verification of a 4D MLEM reconstruction algorithm used for in-beam PET measurements in particle therapy

NASA Astrophysics Data System (ADS)

Stützer, K.; Bert, C.; Enghardt, W.; Helmbrecht, S.; Parodi, K.; Priegnitz, M.; Saito, N.; Fiedler, F.

2013-08-01

In-beam positron emission tomography (PET) has been proven to be a reliable technique in ion beam radiotherapy for the in situ and non-invasive evaluation of the correct dose deposition in static tumour entities. In the presence of intra-fractional target motion an appropriate time-resolved (four-dimensional, 4D) reconstruction algorithm has to be used to avoid reconstructed activity distributions suffering from motion-related blurring artefacts and to allow for a dedicated dose monitoring. Four-dimensional reconstruction algorithms from diagnostic PET imaging that can properly handle the typically low counting statistics of in-beam PET data have been adapted and optimized for the characteristics of the double-head PET scanner BASTEI installed at GSI Helmholtzzentrum Darmstadt, Germany (GSI). Systematic investigations with moving radioactive sources demonstrate the more effective reduction of motion artefacts by applying a 4D maximum likelihood expectation maximization (MLEM) algorithm instead of the retrospective co-registration of phasewise reconstructed quasi-static activity distributions. Further 4D MLEM results are presented from in-beam PET measurements of irradiated moving phantoms which verify the accessibility of relevant parameters for the dose monitoring of intra-fractionally moving targets. From in-beam PET listmode data sets acquired together with a motion surrogate signal, valuable images can be generated by the 4D MLEM reconstruction for different motion patterns and motion-compensated beam delivery techniques.

Proton-induced production and radiochemical isolation of 44Ti from scandium metal targets for 44Ti/44Sc generator development.

PubMed

Radchenko, Valery; Engle, Jonathan W; Medvedev, Dmitri G; Maassen, Joel M; Naranjo, Cleo M; Unc, George A; Meyer, Catherine A L; Mastren, Tara; Brugh, Mark; Mausner, Leonard; Cutler, Cathy S; Birnbaum, Eva R; John, Kevin D; Nortier, F Meiring; Fassbender, Michael E

2017-07-01

Scandium-44g (half-life 3.97h) shows promise for application in positron emission tomography (PET), due to favorable decay parameters. One of the sources of 44g Sc is the 44 Ti/ 44g Sc generator, which can conveniently provide this radioisotope on a daily basis at a diagnostic facility. Titanium-44 (half-life 60.0 a), in turn, can be obtained via proton irradiation of scandium metal targets. A substantial 44 Ti product batch, however, requires high beam currents, long irradiation times and an elaborate chemical procedure for 44 Ti isolation and purification. This study describes the production of a combined 175MBq (4.7mCi) batch yield of 44 Ti in week long proton irradiations at the Los Alamos Isotope Production Facility (LANL-IPF) and the Brookhaven Linac Isotope Producer (BNL-BLIP). A two-step ion exchange chromatography based chemical separation method is introduced: first, a coarse separation of 44 Ti via anion exchange sorption in concentrated HCl results in a 44 Tc/Sc separation factor of 10 2 -10 3 . A second, cation exchange based step in HCl media is then applied for 44 Ti fine purification from residual Sc mass. In summary, this method yields a 90-97% 44 Ti recovery with an overall Ti/Sc separation factor of ≥10 6 . Copyright © 2017 Elsevier Inc. All rights reserved.

Proton induced production and radiochemical isolation of 44Ti from scandium metal targets for 44Ti/ 44Sc generator development

DOE PAGES

Radchenko, Valery; Engle, Jonathan Ward; Medvedev, Dmitri G.; ...

2017-04-07

Scandium-44 g (half-life 3.97 h) shows promise for application in positron emission tomography (PET), due to favorable decay parameters. One of the sources of 44gSc is the 44Ti/ 44gSc generator, which can conveniently provide this radioisotope on a daily basis at a diagnostic facility. Titanium-44 (half-life 60.0 a), in turn, can be obtained via proton irradiation of scandium metal targets. A substantial 44Ti product batch, however, requires high beam currents, long irradiation times and an elaborate chemical procedure for 44Ti isolation and purification. This study describes the production of a combined 175 MBq (4.7 mCi) batch yield of 44Ti inmore » week long proton irradiations at the Los Alamos Isotope Production Facility (LANL-IPF) and the Brookhaven Linac Isotope Producer (BNL-BLIP). A two-step ion exchange chromatography based chemical separation method is introduced: first, a coarse separation of 44Ti via anion exchange sorption in concentrated HCl results in a 44Tc/Sc separation factor of 10 2–10 3. A second, cation exchange based step in HCl media is then applied for 44Ti fine purification from residual Sc mass. In conclusion, this method yields a 90–97% 44Ti recovery with an overall Ti/Sc separation factor of ≥10 6.« less

Positron accumulation effect in particles embedded in a low-density matrix

NASA Astrophysics Data System (ADS)

Dryzek, Jerzy; Siemek, Krzysztof

2015-02-01

Systematic studies of the so-called positron accumulation effect for samples with particles embedded in a matrix are reported. This effect is related to energetic positrons which penetrate inhomogeneous medium. Due to differences in the linear absorption coefficient, different amounts of positrons are accumulated and annihilate in the identical volume of both materials. Positron lifetime spectroscopy and Doppler broadening of the annihilation line using Na-22 positrons were applied to the studies of the epoxy resin samples with embedded micro-sized particles of transition metals, i.e., Ni, Sn, Mo, W, and nonmetal particles, i.e., Si and NaF. The significant difference between the determined fraction of positrons annihilating in the particles and the particle volume fraction indicates the positron accumulation effect. The simple phenomenological model and Monte Carlo simulations are able to describe the main features of the obtained dependencies. The aluminum alloy with embedded Sn nanoparticles is also considered for demonstration differences between the accumulation and another related effect, i.e., the positron affinity.

Demonstration of a novel technique to measure two-photon exchange effects in elastic e±p scattering

DOE PAGES

Moteabbed, Maryam; Niroula, Megh; Raue, Brian A.; ...

2013-08-30

The discrepancy between proton electromagnetic form factors extracted using unpolarized and polarized scattering data is believed to be a consequence of two-photon exchange (TPE) effects. However, the calculations of TPE corrections have significant model dependence, and there is limited direct experimental evidence for such corrections. The TPE contributions depend on the sign of the lepton charge in e±p scattering, but the luminosities of secondary positron beams limited past measurement at large scattering angles, where the TPE effects are believe to be most significant. We present the results of a new experimental technique for making direct e±p comparisons, which has themore » potential to make precise measurements over a broad range in Q 2 and scattering angles. We use the Jefferson Laboratory electron beam and the Hall B photon tagger to generate a clean but untagged photon beam. The photon beam impinges on a converter foil to generate a mixed beam of electrons, positrons, and photons. A chicane is used to separate and recombine the electron and positron beams while the photon beam is stopped by a photon blocker. This provides a combined electron and positron beam, with energies from 0.5 to 3.2 GeV, which impinges on a liquid hydrogen target. The large acceptance CLAS detector is used to identify and reconstruct elastic scattering events, determining both the initial lepton energy and the sign of the scattered lepton. The data were collected in two days with a primary electron beam energy of only 3.3 GeV, limiting the data from this run to smaller values of Q 2 and scattering angle. Nonetheless, this measurement yields a data sample for e±p with statistics comparable to those of the best previous measurements. We have shown that we can cleanly identify elastic scattering events and correct for the difference in acceptance for electron and positron scattering. Because we ran with only one polarity for the chicane, we are unable to study the difference between the incoming electron and positron beams. This systematic effect leads to the largest uncertainty in the final ratio of positron to electron scattering: R=1.027±0.005±0.05 for < Q 2 >=0.206 GeV 2 and 0.830 ≤ ε ≤ 0.943. We have demonstrated that the tertiary e ± beam generated using this technique provides the opportunity for dramatically improved comparisons of e±p scattering, covering a significant range in both Q 2 and scattering angle. Combining data with different chicane polarities will allow for detailed studies of the difference between the incoming e + and e - beams.« less

Demonstration of a novel technique to measure two-photon exchange effects in elastic e±p scattering

NASA Astrophysics Data System (ADS)

Moteabbed, M.; Niroula, M.; Raue, B. A.; Weinstein, L. B.; Adikaram, D.; Arrington, J.; Brooks, W. K.; Lachniet, J.; Rimal, Dipak; Ungaro, M.; Afanasev, A.; Adhikari, K. P.; Aghasyan, M.; Amaryan, M. J.; Anefalos Pereira, S.; Avakian, H.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Batourine, V.; Bedlinskiy, I.; Bennett, R. P.; Biselli, A. S.; Bono, J.; Boiarinov, S.; Briscoe, W. J.; Burkert, V. D.; Carman, D. S.; Celentano, A.; Chandavar, S.; Cole, P. L.; Collins, P.; Contalbrigo, M.; Cortes, O.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Doughty, D.; Dupre, R.; Egiyan, H.; Fassi, L. El; Eugenio, P.; Fedotov, G.; Fegan, S.; Fersch, R.; Fleming, J. A.; Gevorgyan, N.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Goetz, J. T.; Gohn, W.; Golovatch, E.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Guler, N.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hanretty, C.; Harrison, N.; Heddle, D.; Hicks, K.; Ho, D.; Holtrop, M.; Hyde, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Jo, H. S.; Joo, K.; Keller, D.; Khandaker, M.; Kim, A.; Klein, F. J.; Koirala, S.; Kubarovsky, A.; Kubarovsky, V.; Kuhn, S. E.; Kuleshov, S. V.; Lewis, S.; Lu, H. Y.; MacCormick, M.; MacGregor, I. J. D.; Martinez, D.; Mayer, M.; McKinnon, B.; Mineeva, T.; Mirazita, M.; Mokeev, V.; Montgomery, R. A.; Moriya, K.; Moutarde, H.; Munevar, E.; Munoz Camacho, C.; Nadel-Turonski, P.; Nasseripour, R.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Osipenko, M.; Ostrovidov, A. I.; Pappalardo, L. L.; Paremuzyan, R.; Park, K.; Park, S.; Phelps, E.; Phillips, J. J.; Pisano, S.; Pogorelko, O.; Pozdniakov, S.; Price, J. W.; Procureur, S.; Protopopescu, D.; Puckett, A. J. R.; Ripani, M.; Rosner, G.; Rossi, P.; Sabatié, F.; Saini, M. S.; Salgado, C.; Schott, D.; Schumacher, R. A.; Seder, E.; Seraydaryan, H.; Sharabian, Y. G.; Smith, E. S.; Smith, G. D.; Sober, D. I.; Sokhan, D.; Stepanyan, S.; Strauch, S.; Tang, W.; Taylor, C. E.; Tian, Ye; Tkachenko, S.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Wood, M. H.; Zachariou, N.; Zana, L.; Zhang, J.; Zhao, Z. W.; Zonta, I.

2013-08-01

Background: The discrepancy between proton electromagnetic form factors extracted using unpolarized and polarized scattering data is believed to be a consequence of two-photon exchange (TPE) effects. However, the calculations of TPE corrections have significant model dependence, and there is limited direct experimental evidence for such corrections.Purpose: The TPE contributions depend on the sign of the lepton charge in e±p scattering, but the luminosities of secondary positron beams limited past measurement at large scattering angles, where the TPE effects are believe to be most significant. We present the results of a new experimental technique for making direct e±p comparisons, which has the potential to make precise measurements over a broad range in Q2 and scattering angles.Methods: We use the Jefferson Laboratory electron beam and the Hall B photon tagger to generate a clean but untagged photon beam. The photon beam impinges on a converter foil to generate a mixed beam of electrons, positrons, and photons. A chicane is used to separate and recombine the electron and positron beams while the photon beam is stopped by a photon blocker. This provides a combined electron and positron beam, with energies from 0.5 to 3.2 GeV, which impinges on a liquid hydrogen target. The large acceptance CLAS detector is used to identify and reconstruct elastic scattering events, determining both the initial lepton energy and the sign of the scattered lepton.Results: The data were collected in two days with a primary electron beam energy of only 3.3 GeV, limiting the data from this run to smaller values of Q2 and scattering angle. Nonetheless, this measurement yields a data sample for e±p with statistics comparable to those of the best previous measurements. We have shown that we can cleanly identify elastic scattering events and correct for the difference in acceptance for electron and positron scattering. Because we ran with only one polarity for the chicane, we are unable to study the difference between the incoming electron and positron beams. This systematic effect leads to the largest uncertainty in the final ratio of positron to electron scattering: R=1.027±0.005±0.05 for =0.206 GeV2 and 0.830⩽ɛ⩽0.943.Conclusions: We have demonstrated that the tertiary e± beam generated using this technique provides the opportunity for dramatically improved comparisons of e±p scattering, covering a significant range in both Q2 and scattering angle. Combining data with different chicane polarities will allow for detailed studies of the difference between the incoming e+ and e- beams.

Measuring temporal stability of positron emission tomography standardized uptake value bias using long-lived sources in a multicenter network.

PubMed

Byrd, Darrin; Christopfel, Rebecca; Arabasz, Grae; Catana, Ciprian; Karp, Joel; Lodge, Martin A; Laymon, Charles; Moros, Eduardo G; Budzevich, Mikalai; Nehmeh, Sadek; Scheuermann, Joshua; Sunderland, John; Zhang, Jun; Kinahan, Paul

2018-01-01

Positron emission tomography (PET) is a quantitative imaging modality, but the computation of standardized uptake values (SUVs) requires several instruments to be correctly calibrated. Variability in the calibration process may lead to unreliable quantitation. Sealed source kits containing traceable amounts of [Formula: see text] were used to measure signal stability for 19 PET scanners at nine hospitals in the National Cancer Institute's Quantitative Imaging Network. Repeated measurements of the sources were performed on PET scanners and in dose calibrators. The measured scanner and dose calibrator signal biases were used to compute the bias in SUVs at multiple time points for each site over a 14-month period. Estimation of absolute SUV accuracy was confounded by bias from the solid phantoms' physical properties. On average, the intrascanner coefficient of variation for SUV measurements was 3.5%. Over the entire length of the study, single-scanner SUV values varied over a range of 11%. Dose calibrator bias was not correlated with scanner bias. Calibration factors from the image metadata were nearly as variable as scanner signal, and were correlated with signal for many scanners. SUVs often showed low intrascanner variability between successive measurements but were also prone to shifts in apparent bias, possibly in part due to scanner recalibrations that are part of regular scanner quality control. Biases of key factors in the computation of SUVs were not correlated and their temporal variations did not cancel out of the computation. Long-lived sources and image metadata may provide a check on the recalibration process.

Automated production of 124I and 64Cu using IBA Terimo and Pinctada metal electroplating and processing modules

NASA Astrophysics Data System (ADS)

Poniger, S. S.; Tochon-Danguy, H. J.; Panopoulos, H. P.; O'Keefe, G. J.; Peake, D.; Rasool, R.; Scott, A. M.

2012-12-01

There is worldwide growing interest for the production of long-lived positron emitters for molecular imaging and the development of novel immuno-PET techniques for drugs discovery. The desire to produce solid target isotopes in Australia has significantly increased over the years and several research projects for labelling of peptides, proteins and biomolecules, including labelling of recombinant antibodies has been limited due to the availability of suitable isotopes. This has led to the recent installation and commissioning of a new lab dedicated to fully automated solid target isotope production, including 124I, 64Cu, 89Zr and 86Y.

Radiobromine production, isolation and radiosynthesis for the development of a novel prostate cancer radiotherapeutic agent

NASA Astrophysics Data System (ADS)

Ellison, Paul A.; Graves, Stephen A.; Murali, Dhanabalan; De Jesus, Onofre T.; Barnhart, Todd E.; Thomadsen, Bruce R.; Speer, Tod; Nickles, Robert J.

2017-05-01

The radioactive isotopes of bromine accessible with low energy medical cyclotrons have unique potential for diagnostic and radiotherapeutic nuclear medicine applications. These include bromine-76 (t1/2 = 16 h) for positron emission tomography and bromine-77 (t1/2 = 57 h) for Auger radionuclide therapy. Methods are presented to synthesize NiSe discs from elemental starting materials for proton irradiation in a 4π water cooling target configuration. Radiobromide was isolated from the irradiated NiSe material by dry distillation and used to radiolabel 7α-BrDHT for investigation as an Androgen-receptor-targeted theranostic radiopharmaceutical.

Enhanced Compton Backscattering in a Periodic Mirror System for Polarized Positron Beam Generation

NASA Astrophysics Data System (ADS)

Miyahara, Yoshikazu

2002-05-01

By colliding a circularly polarized high power laser beam with a high-energy electron beam, intense circularly polarized γ-rays can be generated, which in turn can be used to produce a longitudinally polarized positron beam for a linear collider. In the present paper, an optical mirror system with periodic focal points is considered to generate intense polarized γ-rays. A CO2 laser beam propagates back and forth in a series of holed mirrors in a straight line. The diffraction loss through the holes is negligibly small, so that the laser beam can be used repeatedly for the collision. The beam size is reduced to 22 μm at a minimum and kept the same in 20 unit cells, ten of which are combined in series. A 5.8 GeV electron beam is focused to 30 μm at a minimum in a series of triplets of permanent quadrupole magnets to generate γ-rays of 60 MeV at a maximum. A γ-ray yield required for a positron beam in a linear collider can be obtained by 10 laser sources with a power of 3.1 kW each, which is considerably lower than the total power assumed in a previous proposal.

The role of positron emission tomography and positron emission tomography/computed tomography in thyroid tumours: an overview.

PubMed

Treglia, Giorgio; Muoio, Barbara; Giovanella, Luca; Salvatori, Massimo

2013-05-01

Positron emission tomography (PET) and PET/computed tomography (PET/CT) with different tracers have been increasingly used in patients with thyroid tumours. The aim of this article is to perform an overview based on literature data about the usefulness of PET imaging in this setting. The role of Fluorine-18-Fluorodeoxyglucose (FDG) PET and PET/CT in differentiated thyroid carcinoma (DTC) is well established, particularly in patients presenting with elevated serum thyroglobulin levels and negative radioiodine whole-body scan. Iodine-124 PET and PET/CT may serve a role in staging DTC and obtaining lesional dosimetry for a better and more rationale planning of treatment with Iodine-131. FDG-PET and PET/CT are useful in the post-thyroidectomy staging of high-risk patients with less differentiated histological subtypes. PET and PET/CT with different tracers seem to be useful methods in localizing the source of elevated calcitonin levels in patients with recurrent medullary thyroid carcinoma. Incorporation of FDG-PET or PET/CT into the initial workup of patients with indeterminate thyroid nodules at fine needle aspiration biopsy deserves further investigation. FDG-PET report should suggest further evaluation when focal thyroid incidentalomas are described because these findings are associated with a significant risk of cancer.

PAES study of the positron thermal desorption from a Ge(100) surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soininen, E.; Schwab, A.; Lynn, K.G.

1991-02-01

Positron induced Auger electron spectroscopy (PAES) from a clean Ge(100) surface was studied as a function of temperature. Three low-energy Auger peaks were detected at 50 eV, 90 eV and 100--150 eV, attributed to M{sub 2,3}M{sub 4}M{sub 4}, M{sub 2,3}M{sub 4}V and M{sub 1}M{sub 4}M{sub 4} Auger transitions, respectively. An estimated 4({plus minus}1)% of the surface trapped positrons annihilate with Ge 3p level electrons. The PAES yield from a Ge(100) surface is reduced at elevated temperatures, in accordance with an activation process found earlier in several Ps fraction experiments. A desorption model adopted from these studies does not accurately describemore » the PAES intensity at higher temperatures ({gt}500 {degree}C), which levels off at 5% of the room temperature value. Possible sources for the discrepancy are discussed. On a Ge(100) surface, an upper limit for the Ps emission near the melting point is 97%. The error in calibration parameters due to the earlier assumption of 100% Ps emission from Ge surfaces seems to induce only small errors to the Ps fraction measurements.« less

Properties of an ideal PET perfusion tracer: new PET tracer cases and data.

PubMed

Maddahi, Jamshid

2012-02-01

An ideal positron emission tomography (PET) tracer should be highly extractable by the myocardium and able to provide high-resolution images, should enable quantification of absolute myocardial blood flow (MBF), should be compatible with both pharmacologically induced and exercise-induced stress imaging, and should not require an on-site cyclotron. The PET radionuclides nitrogen-13 ammonia and oxygen-15 water require an on-site cyclotron. Rubidium-82 may be available locally due to the generator source, but greater utilization is limited because of its relatively low myocardial extraction fraction, long positron range, and generator cost. Flurpiridaz F 18, a novel PET tracer in development, has a high-extraction fraction, short positron range, and relatively long half-life (as compared to currently available tracers), and may be produced at regional cyclotrons. Results of early clinical trials suggest that both pharmacologically and exercise-induced stress PET imaging protocols can be completed more rapidly and with lower patient radiation exposure than with single-photon emission computerized tomography (SPECT) tracers. As compared to SPECT images in the same patients, flurpiridaz F 18 PET images showed better defect contrast. Flurpiridaz F 18 is a potentially promising tracer for assessment of myocardial perfusion, measurement of absolute MBF, calculation of coronary flow reserves, and assessment of cardiac function at the peak of the stress response.

Slow positron applications at slow positron facility of institute of materials structure science, KEK

NASA Astrophysics Data System (ADS)

Hyodo, Toshio; Mochizuki, Izumi; Wada, Ken; Toge, Nobukazu; Shidara, Tetsuo

2018-05-01

Slow Positron Facility at High Energy Accelerator Research Organization (KEK) is a user dedicated facility with an energy-tunable (0.1 - 35 keV) slow positron beam created by a dedicated ˜ 50 MeV linac. It operates in a short pulse (width 1-12 ns, variable, 5×106 e+/s) and a long pulse (width 1.2 µs, 5×107 e+/s) modes of 50 Hz. High energy positrons from pair creation are moderated by reemission after thermalization in W foils. The reemitted positrons are then electrostatically accelerated to a desired energy up to 35 keV and magnetically transported. A pulse-stretching section (pulse stretcher) is installed in the middle of the beamline. It stretches the slow positron pulse for the experiments where too many positrons annihilating in the sample at the same time has to be avoided. Four experiment stations for TRHEPD (total-reflection high-energy positron diffraction), LEPD (low-energy positron diffraction), Ps- (positronium negative ion), and Ps-TOF (positronium time-of-flight) experiments are connected to the beamline branches, SPF-A3, SPF-A4, SPF-B1 and SPF-B2, respectively. Recent results of these stations are briefly described.

Positron annihilation study of the high- Tc (Bi,Pb) 2Sr 2Ca 2Cu 3O x superconductor

NASA Astrophysics Data System (ADS)

Lim, H. J.; Byrne, J. G.

1997-03-01

Positron lifetime spectroscopy (PLS) and positron Doppler-broadening spectroscopy (PDBS) were applied to the high- Tc lead-doped Bi 2Sr 2Ca 2Cu 3O x (BPSCCO 2223) superconductor as a function of temperature. Neither positron lifetimes nor Doppler parameters ( S, W, and{S}/{W}) showed significant change through Tc. This may result from having the highest positron density in the open BiO 2 double layers and no significant positron density in the superconducting CuO 2 layers where positrons, if mainly present, are known to be sensitive to the transition in other high- Tc superconductors. Doppler parameters showed that the probability of positron annihilations with core electrons in the lattice slightly increased and that the probability of positron annihilations with conduction electrons slightly decreased as temperature decreased from ambient temperature to 20 K. The lifetime associated with positron annihilations in the perfect lattice of the sample ( τ1) was 209 ps and, due to the annihilations at internal surfaces or voids in the sample ( τ2) was about 540 ps, independent of temperature. Finally, the mean lifetime for BSCCO 2223 was about 307 ps.

Positron beam studies of solids and surfaces: A summary

NASA Astrophysics Data System (ADS)

Coleman, P. G.

2006-02-01

A personal overview is given of the advances in positron beam studies of solids and surfaces presented at the 10th International Workshop on Positron Beams, held in Doha, Qatar, in March 2005. Solids studied include semiconductors, metals, alloys and insulators, as well as biophysical systems. Surface studies focussed on positron annihilation-induced Auger electron spectroscopy (PAES), but interesting applications of positron-surface interactions in fields as diverse as semiconductor technology and studies of the interstellar medium serve to illustrate once again the breadth of scientific endeavour covered by slow positron beam investigations.

Fast Radio Bursts from the Collapse of Strange Star Crusts

NASA Astrophysics Data System (ADS)

Zhang, Yue; Geng, Jin-Jun; Huang, Yong-Feng

2018-05-01

Fast radio bursts (FRBs) are transient radio sources at cosmological distances. No counterparts in other bands have been observed for non-repeating FRBs. Here we suggest the collapse of strange star (SS) crusts as a possible origin for FRBs. SSs, which are composed of almost equal numbers of u, d, and s quarks, may be encapsulated by a thin crust of normal hadronic matter. When a SS accretes matter from its environment, the crust becomes heavier and heavier. It may finally collapse, leading to the release of a large amount of magnetic energy and plenty of electron/positron pairs on a very short timescale. Electron/positron pairs in the polar cap region of the SS can be accelerated to relativistic velocities, streaming along the magnetic field lines to form a thin shell. FRBs are produced by coherent emission from these electrons when the shell is expanding. Basic characteristics of observed FRBs can be explained in our model.

INTEGRAL/SPI Limits on Electron-Positron Annihilation Radiation from the Galactic Plane

NASA Technical Reports Server (NTRS)

Teegarden, B. J.; Watanabe, K.; Jean, P.; Knoedlseder, J.; Lonjou, V.; Roques, J. P.; Skinner, G. K.; vonBallmoos, P.; Weidenspointner, G.; Bazzano, A.

2005-01-01

The center of our Galaxy is a known strong source of electron-positron 511- keV annihilation radiation. Thus far, however, there have been no reliable detections of annihilation radiation outside of the central radian of our Galaxy. One of the primary objectives of the INTEGRAL (INTErnational Gamma-RAy Astrophysics Laboratory) mission, launched in Oct. 2002, is the detailed study of this radiation. The Spectrometer on INTEGRAL (SPI) is a high resolution coded-aperture gamma-ray telescope with an unprecedented combination of sensitivity, angular resolution and energy resolution. We report results from the first 10 months of observation. During this period a significant fraction of the observing time was spent in or near the Galactic Plane. No positive annihilation flux was detected outside of the central region (|l| greater than 40 degrees) of our Galaxy. In this paper we describe the observations and data analysis methods and give limits on the 511-keV flux.

High-precision γ -ray spectroscopy of the cardiac PET imaging isotope Rb 82 and its impact on dosimetry

DOE PAGES

Nino, M. N.; McCutchan, E. A.; Smith, S. V.; ...

2016-02-01

82Rb is a positron-emitting isotope used in cardiac positron emission tomography (PET) imaging which has been reported to deliver a significantly lower effective radiation dose than analogous imaging isotopes like 201Tl and 99mTc sestamibi. High-quality β-decay data are essential to accurately appraise the total dose received by the patients. A source of 82Sr was produced at the Brookhaven Linac Isotope Producer (BLIP), transported to Argonne National Laboratory, and studied with the Gammasphere facility. Significant revisions have been made to the level scheme of 82Kr including 12 new levels, 50 new γ-ray transitions, and the determination of many new spin assignmentsmore » through angular correlations. Lastly, these new high-quality data allow a precise reappraisal of the β-decay strength function and thus the consequent dose received by patients.« less

Impedance computations and beam-based measurements: A problem of discrepancy

NASA Astrophysics Data System (ADS)

Smaluk, Victor

2018-04-01

High intensity of particle beams is crucial for high-performance operation of modern electron-positron storage rings, both colliders and light sources. The beam intensity is limited by the interaction of the beam with self-induced electromagnetic fields (wake fields) proportional to the vacuum chamber impedance. For a new accelerator project, the total broadband impedance is computed by element-wise wake-field simulations using computer codes. For a machine in operation, the impedance can be measured experimentally using beam-based techniques. In this article, a comparative analysis of impedance computations and beam-based measurements is presented for 15 electron-positron storage rings. The measured data and the predictions based on the computed impedance budgets show a significant discrepancy. Three possible reasons for the discrepancy are discussed: interference of the wake fields excited by a beam in adjacent components of the vacuum chamber, effect of computation mesh size, and effect of insufficient bandwidth of the computed impedance.

Digitized detection of gamma-ray signals concentrated in narrow time windows for transient positron annihilation lifetime spectroscopy

NASA Astrophysics Data System (ADS)

Kinomura, A.; Suzuki, R.; Oshima, N.; O'Rourke, B. E.; Nishijima, T.; Ogawa, H.

2014-12-01

A pulsed slow-positron beam generated by an electron linear accelerator was directly used for positron annihilation lifetime spectroscopy without any positron storage devices. A waveform digitizer was introduced to simultaneously capture multiple gamma-ray signals originating from positron annihilation events during a single accelerator pulse. The positron pulse was chopped and bunched with the chopper signals also sent to the waveform digitizer. Time differences between the annihilation gamma-ray and chopper peaks were calculated and accumulated as lifetime spectra in a computer. The developed technique indicated that positron annihilation lifetime spectroscopy can be performed in a 20 μs time window at a pulse repetition rate synchronous with the linear accelerator. Lifetime spectra of a Kapton sheet and a thermally grown SiO2 layer on Si were successfully measured. Synchronization of positron lifetime measurements with pulsed ion irradiation was demonstrated by this technique.

The Buffer-Gas Positron Accumulator and Resonances in Positron-Molecule Interactions

NASA Technical Reports Server (NTRS)

Surko, C.M.

2007-01-01

This is a personal account of the development of our buffer-gas positron trap and the new generation of cold beams that these traps enabled. Dick Drachman provided much appreciated advice to us from the time we started the project. The physics underlying trap operation is related to resonances (or apparent resonances) in positron-molecule interactions. Amusingly, experiments enabled by the trap allowed us to understand these processes. The positron-resonance "box score" to date is one resounding "yes," namely vibrational Feshbach resonances in positron annihilation on hydrocarbons; a "probably" for positron-impact electronic excitation of CO and NZ;an d a "maybe" for vibrational excitation of selected molecules. Two of these processes enabled the efficient operation of the trap, and one almost killed it in infancy. We conclude with a brief overview of further applications of the trapping technology discussed here, such as "massive" positron storage and beams with meV energy resolution.

Proceedings of Symposium F on New Aspects on the Growth, Characterization and Applications of CdTe and Related Cd Rich Alloys of the 1992 E-MRS Spring Conference held in Strasbourg, France on June 2 - 5, 1992

DTIC Science & Technology

1992-01-01

Bridgman method VI - with (VBZ) and without (VB) a cadmium source can be 1- observed. In VB crystals grown from a slightly tellurium-rich melt the axial...CdTe epilayers will be performed ex 3. Results situ. Light sources are, respectively, a low power HeNe laser emitting at 633 nm and a 75 W xenon lamp for...Positrons can be used as a probe of vacancy-type recorded about 2 x 106 annihilations. After source and defects in semiconductors by studying their

PET monitoring of cancer therapy with 3He and 12C beams: a study with the GEANT4 toolkit.

PubMed

Pshenichnov, Igor; Larionov, Alexei; Mishustin, Igor; Greiner, Walter

2007-12-21

We study the spatial distributions of beta(+)-activity produced by therapeutic beams of (3)He and (12)C ions in various tissue-like materials. The calculations were performed within a Monte Carlo model for heavy-ion therapy (MCHIT) based on the GEANT4 toolkit. The contributions from positron-emitting nuclei with T(1/2) > 10 s, namely (10,11)C, (13)N, (14,15)O, (17,18)F and (30)P, were calculated and compared with experimental data obtained during and after irradiation, where available. Positron-emitting nuclei are created by a (12)C beam in fragmentation reactions of projectile and target nuclei. This leads to a beta(+)-activity profile characterized by a noticeable peak located close to the Bragg peak in the corresponding depth-dose distribution. This can be used for dose monitoring in carbon-ion therapy of cancer. In contrast, as most of the positron-emitting nuclei are produced by a (3)He beam in target fragmentation reactions, the calculated total beta(+)-activity during or soon after the irradiation period is evenly distributed within the projectile range. However, we predict also the presence of (13)N, (14)O, (17,18)F created in charge-transfer reactions by low-energy (3)He ions close to the end of their range in several tissue-like media. The time evolution of beta(+)-activity profiles was investigated for both kinds of beams. We found that due to the production of (18)F nuclides the beta(+)-activity profile measured 2 or 3 h after irradiation with (3)He ions will have a distinct peak correlated with the maximum of depth-dose distribution. We also found certain advantages of low-energy (3)He beams over low-energy proton beams for reliable PET monitoring during particle therapy of shallow-located tumours. In this case the distal edge of beta(+)-activity distribution from (17)F nuclei clearly marks the range of (3)He in tissues.

Apparatus and method for preparing oxygen-15 labeled water H{sub 2}[{sup 15}O] in an injectable form for use in positron emission tomography

DOEpatents

Ferrieri, R.A.; Schlyer, D.J.; Alexoff, D.

1996-01-09

A handling and processing apparatus is revealed for preparing Oxygen-15 labeled water (H{sub 2}[{sup 15}O]) in injectable form for use in Positron Emission Tomography from preferably H{sub 2}[{sup 15}O] produced by irradiating a flowing gas target of nitrogen and hydrogen. The apparatus includes a collector for receiving and directing a gas containing H{sub 2}[{sup 15}O] gas and impurities, mainly ammonia (NH{sub 3}) gas into sterile water to trap the H{sub 2}[{sup 15}O] and form ammonium (NH{sub 4}{sup +}) in the sterile water. A device for displacing the sterile water containing H{sub 2}[{sup 15}O] and NH{sub 4}{sup +} through a cation resin removes NH{sub 4}{sup +} from the sterile water. A device for combining the sterile water containing H{sub 2}[{sup 15}O] with a saline solution produces an injectable solution. Preferably, the apparatus includes a device for delivering the solution to a syringe for injection into a patient. Also, disclosed is a method for preparing H{sub 2}[{sup 15}O] in injectable form for use in Positron Emission Tomography in which the method neither requires isotopic exchange reaction nor application of high temperature. 7 figs.

Advanced Tracers in PET Imaging of Cardiovascular Disease

PubMed Central

Zhang, Wei; Wu, Hua; Liu, Gang

2014-01-01

Cardiovascular disease is the leading cause of death worldwide. Molecular imaging with targeted tracers by positron emission tomography (PET) allows for the noninvasive detection and characterization of biological changes at the molecular level, leading to earlier disease detection, objective monitoring of therapies, and better prognostication of cardiovascular diseases progression. Here we review, the current role of PET in cardiovascular disease, with emphasize on tracers developed for PET imaging of cardiovascular diseases. PMID:25389529

PSMA-Targeted Nano-Conjugates as Dual-Modality (MRI/PET) Imaging Probes for the Non-Invasive Detection of Prostate Cancer

DTIC Science & Technology

2009-10-01

be made. Currently, iodine based compounds are used to enhance contrast of CT which have the limitations of short imaging window due to rapid...number compared to conventionally used iodine compounds . Nanoparticle based CT contrast agents have been demonstrated for vascular imaging, which...constructs with gamma or positron emitting isotopes through a covalent attachment of a bifunctional chelator to the nanoparticles surface. However, in

Accelerator and Fusion Research Division. Annual report, October 1978-September 1979

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1980-03-01

Topics covered include: Super HILAC and Bevalac operations; high intensity uranium beams line item; advanced high charge state ion source; 184-inch synchrocyclotron; VENUS project; positron-electron project; high field superconducting accelerator magnets; beam cooling; accelerator theory; induction linac drivers; RF linacs and storage rings; theory; neutral beam systems development; experimental atomic physics; neutral beam plasma research; plasma theory; and the Tormac project. (GHT)

Galactic cosmic ray composition

NASA Technical Reports Server (NTRS)

Meyer, J. P.

1986-01-01

An assessment is given of the galactic cosmic ray source (GCRS) elemental composition and its correlation with first ionization potential. The isotopic composition of heavy nuclei; spallation cross sections; energy spectra of primary nuclei; electrons; positrons; local galactic reference abundances; comparison of solar energetic particles and solar coronal compositions; the hydrogen; lead; nitrogen; helium; and germanium deficiency problems; and the excess of elements are among the topics covered.

AUSTRALIA TELESCOPE COMPACT ARRAY RADIO CONTINUUM 1384 AND 2368 MHz OBSERVATIONS OF SAGITTARIUS B

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, David I.; Protheroe, Raymond J.; Crocker, Roland M.

2011-03-15

We present images of the Sagittarius (Sgr) B giant molecular cloud at 1384 and 2368 MHz obtained using new, multi-configuration Australia Telescope Compact Array observations. We have combined these observations with archival single-dish observations yielding images at resolutions of 47'' x 14'' and 27'' x 8'' at 1384 and 2368 MHz, respectively. These observations were motivated by our theoretical work indicating the possibility that synchrotron emission from secondary electrons and positrons created in hadronic cosmic ray (CR) collisions with the ambient matter of the Sgr B2 cloud could provide a detectable (and possibly linearly polarized) non-thermal radio signal. We findmore » that the only detectable non-thermal emission from the Sgr B region is from a strong source to the south of Sgr B2, which we label Sgr B2 Southern Complex (SC). We find Sgr B2(SC) integrated flux densities of 1.2 {+-} 0.2 Jy at 1384 MHz and 0.7 {+-} 0.1 Jy at 2368 MHz for a source of FWHM size at 1384 MHz of {approx}54''. Despite its non-thermal nature, the synchrotron emission from this source is unlikely to be dominated due to secondary electrons and positrons. Failing to find clear evidence of non-thermal emission due to secondary electrons and positrons, we use polarization data to place 5{sigma} upper limits on the level of polarized intensity from the Sgr B2 cloud of 3.5 and 3 mJybeam{sup -1} at 1384 and 2368 MHz, respectively. We also use the angular distribution of the total intensity of archival 330 MHz Very Large Array and the total intensity and polarized emission of our new 1384 and 2368 MHz data to constrain the diffusion coefficient for transport of the parent hadronic CRs into the dense core of Sgr B2 to be no larger than about 1% of that in the Galactic disk. Finally, we have also used the data to perform a spectral and morphological study of the features of the Sgr B cloud and compare and contrast these to previous studies.« less

Nondestructive monitoring of fatigue damage evolution in austenitic stainless steel by positron-lifetime measurements

NASA Astrophysics Data System (ADS)

Holzwarth, Uwe; Schaaff, Petra

2004-03-01

Positron-lifetime measurements have been performed on austenitic stainless steel during (i) stress- and (ii) strain-controlled fatigue experiments for different applied stress and strain amplitudes, respectively. For this purpose a generator-detector assembly with a 72Se/72As positron generator [maximum activity 25 μCi (0.9 MBq)] has been mounted on mechanical testing machines in order to measure the positron lifetime without removing the specimens from the load train. The average positron lifetime has been determined by a β+-γ coincidence. The feasibility to use the average positron lifetime for monitoring the evolution of fatigue damage and to predict early failure has been examined. In strain- and stress-controlled experiments the average positron lifetime shows a pronounced increase within the first 10% and 40% of the fatigue life, respectively. In stress-controlled experiments the average positron lifetime at failure depends significantly on the applied stress amplitude. In strain-controlled experiments significantly different positron lifetimes for different applied plastic strain amplitudes are obtained within the first 1.000 fatigue cycles, whereas differences get wiped out during further cycling until failure.

The Correlation Between Dislocations and Vacancy Defects Using Positron Annihilation Spectroscopy

NASA Astrophysics Data System (ADS)

Pang, Jinbiao; Li, Hui; Zhou, Kai; Wang, Zhu

2012-07-01

An analysis program for positron annihilation lifetime spectra is only applicable to isolated defects, but is of no use in the presence of defective correlations. Such limitations have long caused problems for positron researchers in their studies of complicated defective systems. In order to solve this problem, we aim to take a semiconductor material, for example, to achieve a credible average lifetime of single crystal silicon under plastic deformation at different temperatures using positron life time spectroscopy. By establishing reasonable positron trapping models with defective correlations and sorting out four lifetime components with multiple parameters, as well as their respective intensities, information is obtained on the positron trapping centers, such as the positron trapping rates of defects, the density of the dislocation lines and correlation between the dislocation lines, and the vacancy defects, by fitting with the average lifetime with the aid of Matlab software. These results give strong grounds for the existence of dislocation-vacancy correlation in plastically deformed silicon, and lay a theoretical foundation for the analysis of positron lifetime spectra when the positron trapping model involves dislocation-related defects.

Correlation between positron emission tomography and Cerenkov luminescence imaging in vivo and ex vivo using 64Cu-labeled antibodies in a neuroblastoma mouse model.

PubMed

Maier, Florian C; Schmitt, Julia; Maurer, Andreas; Ehrlichmann, Walter; Reischl, Gerald; Nikolaou, Konstantin; Handgretinger, Rupert; Pichler, Bernd J; Thaiss, Wolfgang M

2016-10-11

Antibody-based therapies gain momentum in clinical therapy, thus the need for accurate imaging modalities with respect to target identification and therapy monitoring are of increasing relevance. Cerenkov luminescence imaging (CLI) are a novel method detecting charged particles emitted during radioactive decay with optical imaging. Here, we compare Position Emission Tomography (PET) with CLI in a multimodal imaging study aiming at the fast and efficient screening of monoclonal antibodies (mAb) designated for targeting of the neuroblastoma-characteristic epitope disialoganglioside GD2. Neuroblastoma-bearing SHO mice were injected with a 64Cu-labeled GD2-specific mAb. The tumor uptake was imaged 3 h, 24 h and 48 h after tracer injection with both, PET and CLI, and was compared to the accumulation in GD2-negative control tumors (human embryonic kidney, HEK-293). In addition to an in vivo PET/CLI-correlation over time, we also demonstrate linear correlations of CLI- and γ-counter-based biodistribution analysis. CLI with its comparably short acquisition time can thus be used as an attractive one-stop-shop modality for the longitudinal monitoring of antibody-based tumor targeting and ex vivo biodistribution.These findings suggest CLI as a reliable alternative for PET and biodistribution studies with respect to fast and high-throughput screenings in subcutaneous tumors traced with radiolabeled antibodies. However, in contrast to PET, CLI is not limited to positron-emitting isotopes and can therefore also be used for the visualization of mAb labeled with therapeutic isotopes like electron emitters.

Rational Design, Development, and Stability Assessment of a Macrocyclic Four-Hydroxamate-Bearing Bifunctional Chelating Agent for 89 Zr.

PubMed

Seibold, Uwe; Wängler, Björn; Wängler, Carmen

2017-09-21

Zirconium-89 is a positron-emitting radionuclide of high interest for medical imaging applications with positron emission tomography (PET). For the introduction of this radiometal into biologically active targeting vectors, the chelating agent desferrioxamine B (DFO) is commonly applied. However, DFO is known to form 89 Zr complexes of limited in vivo stability. Herein we describe the rational design and chemical development of a new macrocyclic four-hydroxamate-bearing chelating agent-1,10,19,28-tetrahydroxy-1,5,10,14,19,23,28,32-octaazacyclohexatriacontan-2,6,11,15,20,24,29,33-octaone (CTH36)-for the stable complexation of Zr 4+ . For this purpose, we first performed computational studies to determine the optimal chelator geometry before we developed different synthesis pathways toward the target structures. The best results were obtained using an efficient solution-phase-based synthesis strategy toward the target chelating agent. To enable efficient and chemoselective conjugation to biomolecules, a tetrazine-modified variant of CTH36 was also developed. The excellent conjugation characteristics of the so-functionalized chelator were demonstrated on the example of the model peptide TCO-c(RGDfK). We determined the optimal 89 Zr radiolabeling parameters for CTH36 as well as its bioconjugate, and found that 89 Zr radiolabeling proceeds efficiently under very mild reaction conditions. Finally, we performed comparative complex stability tests for 89 Zr-CHT36-c(RGDfK) and 89 Zr-DFO-c(RGDfK), showing improved complex stability for the newly developed chelator CTH36. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The 12C(n, 2n)11C cross section from threshold to 26.5 MeV

PubMed Central

Eckert, T.; Hartshaw, G.; Padalino, S. J.; Polsin, D. N.; Russ, M.; Simone, A. T.; Brune, C. R.; Massey, T. N.; Parker, C. E.; Fitzgerald, R.; Sangster, T. C.; Regan, S. P.

2018-01-01

The 12C(n, 2n)11C cross section was measured from just below threshold to 26.5 MeV using the Pelletron accelerator at Ohio University. Monoenergetic neutrons, produced via the 3H(d,n)4He reaction, were allowed to strike targets of polyethylene and graphite. Activation of both targets was measured by counting positron annihilations resulting from the β+ decay of 11C. Annihilation gamma rays were detected, both in coincidence and singly, using back-to-back NaI detectors. The incident neutron flux was determined indirectly via 1H(n,p) protons elastically scattered from the polyethylene target. Previous measurements fall into upper and lower bands; the results of the present measurement are consistent with the upper band. PMID:29732443

The 12C(n, 2n)11C cross section from threshold to 26.5 MeV.

PubMed

Yuly, M; Eckert, T; Hartshaw, G; Padalino, S J; Polsin, D N; Russ, M; Simone, A T; Brune, C R; Massey, T N; Parker, C E; Fitzgerald, R; Sangster, T C; Regan, S P

2018-02-01

The 12 C(n, 2n) 11 C cross section was measured from just below threshold to 26.5 MeV using the Pelletron accelerator at Ohio University. Monoenergetic neutrons, produced via the 3 H(d,n) 4 He reaction, were allowed to strike targets of polyethylene and graphite. Activation of both targets was measured by counting positron annihilations resulting from the β + decay of 11 C. Annihilation gamma rays were detected, both in coincidence and singly, using back-to-back NaI detectors. The incident neutron flux was determined indirectly via 1 H(n,p) protons elastically scattered from the polyethylene target. Previous measurements fall into upper and lower bands; the results of the present measurement are consistent with the upper band.

12C(n , 2 n )11C cross section from threshold to 26.5 MeV

NASA Astrophysics Data System (ADS)

Yuly, M.; Eckert, T.; Hartshaw, G.; Padalino, S. J.; Polsin, D. N.; Russ, M.; Simone, A. T.; Brune, C. R.; Massey, T. N.; Parker, C. E.; Fitzgerald, R.; Sangster, T. C.; Regan, S. P.

2018-02-01

The 12C(n ,2 n )11C cross section was measured from just below threshold to 26.5 MeV using the Pelletron accelerator at Ohio University. Monoenergetic neutrons, produced via the 3H(d ,n )4He reaction, were allowed to strike targets of polyethylene and graphite. Activation of both targets was measured by counting positron annihilations resulting from the β+ decay of 11C. Annihilation gamma rays were detected, both in coincidence and singly, using back-to-back NaI detectors. The incident neutron flux was determined indirectly via 1H(n ,p ) protons elastically scattered from the polyethylene target. Previous measurements fall into upper and lower bands; the results of the present measurement are consistent with the upper band.

[Clinical target volume delineation for radiotherapy of the esophagus].

PubMed

Lazarescu, I; Thureau, S; Nkhali, L; Pradier, O; Dubray, B

2013-10-01

The dense lymphatic network of the esophagus facilitates tumour spreading along the cephalo-caudal axis and to locoregional lymph nodes. A better understanding of microscopic invasion by tumour cells, based on histological analysis of surgical specimens and analysis of recurrence sites, has justified a reduction in radiotherapy target volumes. The delineation of the clinical target volume (CTV) depends on tumour characteristics (site, histology) and on its spread as assessed on endoscopic ultrasonography and ((18)F)-fluorodeoxyglucose positron-emission tomography (FDG-PET). We propose that positive and negative predictive values for FDG-PET should be used to adapt the CTV according to the risk of nodal involvement. Copyright © 2013 Société française de radiothérapie oncologique (SFRO). Published by Elsevier SAS. All rights reserved.

Positron Spectroscopy of Hydrothermally Grown Actinide Oxides

DTIC Science & Technology

2014-03-27

POSITRON SPECTROSCOPY OF HYDROTHERMALLY GROWN ACTINIDE OXIDES THESIS Edward C. Schneider...United States Government. AFIT-ENP-14-M-33 POSITRON SPECTROSCOPY OF HYDROTHERMALLY GROWN ACTINIDE OXIDES THESIS...33 POSITRON SPECTROSCOPY OF HYDROTHERMALLY GROWN ACTINIDE OXIDES Edward C. Schneider, BS Captain, USAF Approved

Student research with 400keV beams: {sup 13}N radioisotope production target development

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fru, L. Che; Clymer, J.; Compton, N.

2013-04-19

The AN400 Van de Graaff accelerator at the Minnesota State University, Mankato, Applied Nuclear Science Lab has demonstrated utility as an accessible and versatile platform for student research. Despite the limits of low energy, the research team successfully developed projects with applications to the wider radioisotope production community. A target system has been developed for producing and extracting {sup 13}N by the {sup 12}C(d,n){sup 13}N reaction below 400keV. The system is both reusable and robust, with future applications to higher energy machines producing this important radioisotope for physiological imaging studies with Positron Emission Tomography. Up to 36({+-}1)% of the {supmore » 13}N was extracted from the graphite matrix when 35 A current was externally applied to the graphite target while simultaneously flushing the target chamber with CO{sub 2} gas.« less

Antimatter as an Energy Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jackson, Gerald P.

2009-03-16

Antiprotons and positrons are constantly generated in space, and periodically manufactured by humans here on Earth. Harvesting of these particles in space and forming stable antimatter atoms and molecules would create a significant energy source for power and propulsion. Though dedicated fabrication of these particles on Earth consumes much more energy than could be liberated upon annihilation, manufactured antimatter represents a high-density energy storage mechanism well suited for spacecraft power and propulsion. In this paper the creation, storage, and utilization of antimatter is introduced. Specific examples of electrical energy generation and deep-space propulsion based on antimatter are also reviewed.

Positron Annihilation in Insulating Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Asoka-Kumar, P; Sterne, PA

2002-10-18

We describe positron results from a wide range of insulating materials. We have completed positron experiments on a range of zeolite-y samples, KDP crystals, alkali halides and laser damaged SiO{sub 2}. Present theoretical understanding of positron behavior in insulators is incomplete and our combined theoretical and experimental approach is aimed at developing a predictive understanding of positrons and positronium annihilation characteristics in insulators. Results from alkali halides and alkaline-earth halides show that positrons annihilate with only the halide ions, with no apparent contribution from the alkali or alkaline-earth cations. This contradicts the results of our existing theory for metals, whichmore » predicts roughly equal annihilation contributions from cation and anion. We also present result obtained using Munich positron microprobe on laser damaged SiO{sub 2} samples.« less

Direct Imaging of Radionuclide-Produced Electrons and Positrons with an Ultrathin Phosphor

PubMed Central

Chen, Liying; Gobar, Lisa S.; Knowles, Negar G.; Liu, Zhonglin; Gmitro, Arthur F.; Barrett, Harrison H.

2008-01-01

Current electron detectors are either unable to image in vivo or lack sufficient spatial resolution because of electron scattering in thick detector materials. This study was aimed at developing a sensitive high-resolution system capable of detecting electron-emitting isotopes in vivo. Methods The system uses a lens-coupled charge-coupled-device camera to capture the scintillation light excited by an electron-emitting object near an ultrathin phosphor. The spatial resolution and sensitivity of the system were measured with a 3.7-kBq 90Y/90Sr β-source and a 70-µm resin bead labeled with 99mTc. Finally, we imaged the 99mTc-pertechnetate concentration in the mandibular gland of a mouse in vivo. Results Useful images were obtained with only a few hundred emitted β particles from the 90Y/90Sr source or conversion electrons from the 99mTc bead source. The in vivo image showed a clear profile of the mandibular gland and many fine details with exposures of as low as 30 s. All measurements were consistent with a spatial resolution of about 50 µm, corresponding to 2.5 detector pixels with the current camera. Conclusion Our new electron-imaging system can image electron-emitting isotope distributions at high resolution and sensitivity. The system is useful for in vivo imaging of small animals and small, exposed regions on humans. The ability to image β particles, positrons, and conversion electrons makes the system applicable to most isotopes. PMID:18552136

Digitized detection of gamma-ray signals concentrated in narrow time windows for transient positron annihilation lifetime spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kinomura, A., E-mail: a.kinomura@aist.go.jp; Suzuki, R.; Oshima, N.

2014-12-15

A pulsed slow-positron beam generated by an electron linear accelerator was directly used for positron annihilation lifetime spectroscopy without any positron storage devices. A waveform digitizer was introduced to simultaneously capture multiple gamma-ray signals originating from positron annihilation events during a single accelerator pulse. The positron pulse was chopped and bunched with the chopper signals also sent to the waveform digitizer. Time differences between the annihilation gamma-ray and chopper peaks were calculated and accumulated as lifetime spectra in a computer. The developed technique indicated that positron annihilation lifetime spectroscopy can be performed in a 20 μs time window at amore » pulse repetition rate synchronous with the linear accelerator. Lifetime spectra of a Kapton sheet and a thermally grown SiO{sub 2} layer on Si were successfully measured. Synchronization of positron lifetime measurements with pulsed ion irradiation was demonstrated by this technique.« less

Measurements of defect structures by positron annihilation lifetime spectroscopy of the tellurite glass TeO2-P2O5-ZnO-LiNbO3 doped with ions of rare earth elements: Er3+, Nd3+ and Gd3+

NASA Astrophysics Data System (ADS)

Golis, E.; Yousef, El. S.; Reben, M.; Kotynia, K.; Filipecki, J.

2015-12-01

The objective of the study was the structural analysis of the TeO2-P2O5-ZnO-LiNbO3 tellurite glasses doped with ions of the rare-earth elements: Er3+, Nd3+ and Gd3+ based on the PALS (Positron Annihilation Lifetime Spectroscopy) method of measuring positron lifetimes. Values of positron lifetimes and the corresponding intensities may be connected with the sizes and number of structural defects, such as vacancies, mono-vacancies, dislocations or pores, the sizes of which range from a few angstroms to a few dozen nanometres. Experimental positron lifetime spectrum revealed existence of two positron lifetime components τ1 and τ2. Their interpretation was based on two-state positron trapping model where the physical parameters are the annihilation velocity and positron trapping rate.

Slow positrons in single-crystal samples of Al and Al-AlxOy

NASA Astrophysics Data System (ADS)

Lynn, K. G.; Lutz, H.

1980-11-01

Well-characterized Al(111) and Al(100) samples were studied with monoenergetic positrons before and after exposure to oxygen. Both positronium-formation and positron-emission curves were obtained for various incident positron energies at sample temperatures ranging from 160-900 K. The orthopositronium decay signal provides a unique signature that the positron has emerged from the surface region of a clean metal. In the clean Al crystals part of the positronium formed near the surface is found to be associated with a temperature-activated process described as the thermally activated detrapping of a positron from a surface state. A simple positron diffusion model, including surface and vacancy trapping, is fitted to the positronium data and an estimate of the binding energy of the positron in this trap is made. The positron diffusion constant is found to have a negative temperature dependence before the onset of positron trapping at thermally generated monovacancies (>500 K), in reasonable agreement with theoretical predictions. The depth of the positron surface state is reduced or positronium is formed in the chemisorbed layer as oxygen is adsorbed on both Al sample surfaces, thus increasing the positronium fraction and decreasing the positron emission. At higher oxygen exposures [>500 L (1 L = 10-6 torr sec)] positron or positronium traps are generated in the overlayer and the positronium fraction is reduced. The amorphous-to-crystalline surface transition of AlxOy on Al is observed between 650 and 800 K by the change in the positronium fraction and is interpreted as the removal of trapping centers in the metal-oxide overlayer. At the higher temperatures and incident energies vacancy trapping is observed by the decrease in the positron diffusion length in both the clean and the underlying Al of the oxygen-exposed samples. Similar vacancy formation enthalpies for Al are extracted in both the clean and oxygen-covered samples by a simple model and are in good agreement with those measured by other experimental methods. This technique provides a new experimental means for the study of interfaces and thin films and the vacancy-type defects associated with them.

The PADME calorimeters for missing mass dark photon searches

NASA Astrophysics Data System (ADS)

Ferrarotto, F.

2018-03-01

In this paper we will present the design and expected performance for the Electromagnetic and Small Angle Calorimeters (ECAL, SAC) of the PADME experiment. The design of the calorimeters has been optimized for the detection of the final state γ from the annihilation production (and subsequent "invisible" decay) of a "Dark Photon" produced by a positron beam on a thin, low Z target. Beam tests have been made in 2016 and 2017 at the INFN Frascati National Laboratories Linac Beam Test Facility (BTF) with positron beams of energy 100–400 MeV and results are presented. The PADME experiment will be built at the INFN Frascati National Laboratories by the end of 2017 and will be taking data in 2018 (and possibly also 2019). At the moment the collaboration is composed by the following institutions: INFN Roma and "La Sapienza" University of Roma, INFN Frascati, INFN Lecce and University of Salento, MTA Atomki Debrecen, University of Sofia, Cornell University, U.S. William and Mary College.

Noninvasive imaging of protein-protein interactions in living animals

NASA Astrophysics Data System (ADS)

Luker, Gary D.; Sharma, Vijay; Pica, Christina M.; Dahlheimer, Julie L.; Li, Wei; Ochesky, Joseph; Ryan, Christine E.; Piwnica-Worms, Helen; Piwnica-Worms, David

2002-05-01

Protein-protein interactions control transcription, cell division, and cell proliferation as well as mediate signal transduction, oncogenic transformation, and regulation of cell death. Although a variety of methods have been used to investigate protein interactions in vitro and in cultured cells, none can analyze these interactions in intact, living animals. To enable noninvasive molecular imaging of protein-protein interactions in vivo by positron-emission tomography and fluorescence imaging, we engineered a fusion reporter gene comprising a mutant herpes simplex virus 1 thymidine kinase and green fluorescent protein for readout of a tetracycline-inducible, two-hybrid system in vivo. By using micro-positron-emission tomography, interactions between p53 tumor suppressor and the large T antigen of simian virus 40 were visualized in tumor xenografts of HeLa cells stably transfected with the imaging constructs. Imaging protein-binding partners in vivo will enable functional proteomics in whole animals and provide a tool for screening compounds targeted to specific protein-protein interactions in living animals.

Positron emission tomography/computed tomography imaging and rheumatoid arthritis.

PubMed

Wang, Shi-Cun; Xie, Qiang; Lv, Wei-Fu

2014-03-01

Rheumatoid arthritis (RA) is a phenotypically heterogeneous, chronic, destructive inflammatory disease of the synovial joints. A number of imaging tools are currently available for evaluation of inflammatory conditions. By targeting the upgraded glucose uptake of infiltrating granulocytes and tissue macrophages, positron emission tomography/computed tomography with fluorine-18 fluorodeoxyglucose ((18) F-FDG PET/CT) is available to delineate inflammation with high sensitivity. Recently, several studies have indicated that FDG uptake in affected joints reflects the disease activity of RA. In addition, usage of FDG PET for the sensitive detection and monitoring of the response to treatment has been reported. Combined FDG PET/CT enables the detailed assessment of disease in large joints throughout the whole body. These unique capabilities of FDG PET/CT imaging are also able to detect RA-complicated diseases. Therefore, PET/CT has become an excellent ancillary tool to assess disease activity and prognosis in RA. © 2014 Asia Pacific League of Associations for Rheumatology and Wiley Publishing Asia Pty Ltd.

Positronics of subnanometer atomistic imperfections in solids as a high-informative structure characterization tool.

PubMed

Shpotyuk, Oleh; Filipecki, Jacek; Ingram, Adam; Golovchak, Roman; Vakiv, Mykola; Klym, Halyna; Balitska, Valentyna; Shpotyuk, Mykhaylo; Kozdras, Andrzej

2015-01-01

Methodological possibilities of positron annihilation lifetime (PAL) spectroscopy applied to characterize different types of nanomaterials treated within three-term fitting procedure are critically reconsidered. In contrast to conventional three-term analysis based on admixed positron- and positronium-trapping modes, the process of nanostructurization is considered as substitutional positron-positronium trapping within the same host matrix. Developed formalism allows estimate interfacial void volumes responsible for positron trapping and characteristic bulk positron lifetimes in nanoparticle-affected inhomogeneous media. This algorithm was well justified at the example of thermally induced nanostructurization occurring in 80GeSe2-20Ga2Se3 glass.

Positronics of subnanometer atomistic imperfections in solids as a high-informative structure characterization tool

NASA Astrophysics Data System (ADS)

Shpotyuk, Oleh; Filipecki, Jacek; Ingram, Adam; Golovchak, Roman; Vakiv, Mykola; Klym, Halyna; Balitska, Valentyna; Shpotyuk, Mykhaylo; Kozdras, Andrzej

2015-02-01

Methodological possibilities of positron annihilation lifetime (PAL) spectroscopy applied to characterize different types of nanomaterials treated within three-term fitting procedure are critically reconsidered. In contrast to conventional three-term analysis based on admixed positron- and positronium-trapping modes, the process of nanostructurization is considered as substitutional positron-positronium trapping within the same host matrix. Developed formalism allows estimate interfacial void volumes responsible for positron trapping and characteristic bulk positron lifetimes in nanoparticle-affected inhomogeneous media. This algorithm was well justified at the example of thermally induced nanostructurization occurring in 80GeSe2-20Ga2Se3 glass.

Positron states and annihilation characteristics of surface-trapped positrons at the oxidized Cu(110) surface

NASA Astrophysics Data System (ADS)

Fazleev, N. G.; Olenga, Antoine; Weiss, A. H.

2013-03-01

The process by which oxide layers are formed on metal surfaces is still not well understood. In this work we present the results of theoretical studies of positron states and annihilation characteristics of surface-trapped positrons at the oxidized Cu(110) surface. An ab-initio investigation of stability and associated electronic properties of different adsorption phases of oxygen on Cu(110) has been performed on the basis of density functional theory and using DMOl3 code. The changes in the positron work function and the surface dipole moment when oxygen atoms occupy on-surface and sub-surface sites have been attributed to charge redistribution within the first two layers, buckling effects within each layer and interlayer expansion. The computed positron binding energy, positron surface state wave function, and annihilation probabilities of surface trapped positrons with relevant core electrons demonstrate their sensitivity to oxygen coverage, elemental content, atomic structure of the topmost layers of surfaces, and charge transfer effects. Theoretical results are compared with experimental data obtained from studies of oxidized transition metal surfaces using positron annihilation induced Auger electron spectroscopy. This work was supported in part by the National Science Foundation Grant DMR-0907679.

Positrons in surface physics

NASA Astrophysics Data System (ADS)

Hugenschmidt, Christoph

2016-12-01

Within the last decade powerful methods have been developed to study surfaces using bright low-energy positron beams. These novel analysis tools exploit the unique properties of positron interaction with surfaces, which comprise the absence of exchange interaction, repulsive crystal potential and positron trapping in delocalized surface states at low energies. By applying reflection high-energy positron diffraction (RHEPD) one can benefit from the phenomenon of total reflection below a critical angle that is not present in electron surface diffraction. Therefore, RHEPD allows the determination of the atom positions of (reconstructed) surfaces with outstanding accuracy. The main advantages of positron annihilation induced Auger-electron spectroscopy (PAES) are the missing secondary electron background in the energy region of Auger-transitions and its topmost layer sensitivity for elemental analysis. In order to enable the investigation of the electron polarization at surfaces low-energy spin-polarized positrons are used to probe the outermost electrons of the surface. Furthermore, in fundamental research the preparation of well defined surfaces tailored for the production of bound leptonic systems plays an outstanding role. In this report, it is envisaged to cover both the fundamental aspects of positron surface interaction and the present status of surface studies using modern positron beam techniques.

Positron astrophysics and areas of relation to low-energy positron physics

NASA Astrophysics Data System (ADS)

Guessoum, Nidhal

2014-05-01

I briefly review our general knowledge of positron astrophysics, focusing mostly on the theoretical and modelling aspects. The experimental/observational aspects of the topic have recently been reviewed elsewhere [E. Churazov et al., Mon. Nat. R. Astron. Soc. 411, 1727 (2011); N. Prantazos et al., Rev. Mod. Phys. 83, 1001 (2011)]. In particular, I highlight the interactions and cross sections of the reactions that the positrons undergo in various cosmic media. Indeed, these must be of high interest to both the positron astrophysics community and the low-energy positron physics community in trying to find common areas of potential collaboration for the future or areas of research that will help the astrophysics community make further progress on the problem. The processes undergone by positrons from the moments of their birth to their annihilation (in the interstellar medium or other locations) are thus examined. The physics of the positron interactions with gases and solids (dust grains) and the physical conditions and characteristics of the environments where the processes of energy loss, positronium formation, and annihilation take place, are briefly reviewed. An explanation is given about how all the relevant physical information is taken into account in order to calculate annihilation rates and spectra of the 511 keV emission in the ISM; special attention is paid to positron interactions with dust and with polycyclic aromatic hydrocarbons. In particular, an attempt is made to show to what extent the interactions between positrons and interstellar dust grains are similar to laboratory experiments in which beams of low-energy positrons impinge upon solids and surfaces. Sample results are shown for the effect of dust grains on positron annihilation spectra in some phases of the ISM which, together with high resolution spectra measured by satellites, can be used to infer useful knowledge about the environment where the annihilation is predominantly taking place, and ultimately about the birth place and history of positrons in the Galaxy. The important complementarity between work done by the astrophysical and the positron physics communities is emphasised, and attempts are made to suggest avenues of future research for progress in the two fields. Contribution to the Topical Issue "Electron and Positron Induced Processes", edited by Michael Brunger, Radu Campeanu, Masamitsu Hoshino, Oddur Ingólfsson, Paulo Limão-Vieira, Nigel Mason, Yasuyuki Nagashima and Hajime Tanuma.

77 FR 71802 - Guidance on Investigational New Drug Applications for Positron Emission Tomography Drugs...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-04

...] Guidance on Investigational New Drug Applications for Positron Emission Tomography Drugs; Availability... Positron Emission Tomography (PET) Drugs.'' The guidance is intended to assist manufacturers of PET drugs... ``Investigational New Drug Applications for Positron Emission Tomography (PET) Drugs.'' The guidance summarizes the...

Positron Emission Tomography (PET) and Positron Scanning

Science.gov Websites

National Laboratory 'Positron Emission Tomography ... [is a medical imaging technique that] can track human brain.' Edited excerpts from from Medical Applications of Non-Medical Research: Applications Technical Report, November 1988 High-resolution PET (Positron Emission Tomography) for Medical Science

Positron annihilation induced Auger electron spectroscopy

NASA Technical Reports Server (NTRS)

Weiss, Alex; Koymen, A. R.; Mehl, David; Jensen, K. O.; Lei, Chun; Lee, K. H.

1990-01-01

Recently, Weiss et al. have demonstrated that it is possible to excite Auger transitions by annihilating core electrons using a low energy (less than 30eV) beam of positrons. This mechanism makes possible a new electron spectroscopy, Positron annihilation induced Auger Electron Spectroscopy (PAES). The probability of exciting an Auger transition is proportional to the overlap of the positron wavefunction with atomic core levels. Since the Auger electron energy provides a signature of the atomic species making the transition, PAES makes it possible to determine the overlap of the positron wavefunction with a particular element. PAES may therefore provide a means of detecting positron-atom complexes. Measurements of PAES intensities from clean and adsorbate covered Cu surfaces are presented which indicate that approx. 5 percent of positrons injected into CU at 25eV produce core annihilations that result in Auger transitions.

Positron annihilation in the nuclear outflows of the Milky Way

NASA Astrophysics Data System (ADS)

Panther, Fiona H.; Crocker, Roland M.; Birnboim, Yuval; Seitenzahl, Ivo R.; Ruiter, Ashley J.

2018-02-01

Observations of soft gamma rays emanating from the Milky Way from SPI/INTEGRAL reveal the annihilation of ˜2 × 1043 positrons every second in the Galactic bulge. The origin of these positrons, which annihilate to produce a prominent emission line centred at 511 keV, has remained mysterious since their discovery almost 50 yr ago. A plausible origin for the positrons is in association with the intense star formation ongoing in the Galactic centre. Moreover, there is strong evidence for a nuclear outflow in the Milky Way. We find that advective transport and subsequent annihilation of positrons in such an outflow cannot simultaneously replicate the observed morphology of positron annihilation in the Galactic bulge and satisfy the requirement that 90 per cent of positrons annihilate once the outflow has cooled to 104 K.

Target foil rupture scenario and provision for handling different models of medical cyclotrons used in India

PubMed Central

Shaiju, V. S.; Sharma, S. D.; Kumar, Rajesh; Sarin, B.

2009-01-01

Medical cyclotron is a particle accelerator used in producing short lived radiotracers such as 18F, 11C, 15O, 13N etc. These radiotracers are labeled with suitable pharmaceuticals for use to gather information related to metabolic activity of the cell using Positron Emission Tomography (PET) scan. Target foil rupture is considered one of the major emergency situations during medical cyclotron operations because there is a potential of over exposure to the working personnel. Radiation protection survey of a self-shielded medical cyclotron installation was carried out during normal and emergency conditions. It is found that the induced activity in the target foil increases with its successive usages. As a case study, we have evaluated the emergency handling procedures of GE PETtrace-6 medical cyclotron. Recommendations have also been made to reduce personal exposure while handling the target foil rupture condition such as the use of L-Bench near the target area and participation of experienced personnel. PMID:20098564

The production of [124I]iodine and [86Y]yttrium.

PubMed

Schmitz, Jochen

2011-05-01

The use of paired tracers such as (124)I/(131)I and (86)Y/(90)Y allows pretherapy PET imaging with positron emitting radioisotopes of the same element as used for therapy. Whereas nowadays most therapy nuclides are produced by reactors or generators, the production of the corresponding PET isotopes requires the irradiation of adequate targets using particle accelerators such as cyclotrons. This paper describes the production routes for (124)I and (86)Y.

Optimization via specific fluorescence brightness of a receptor-targeted probe for optical imaging and positron emission tomography of sentinel lymph nodes

PubMed Central

Qin, Zhengtao; Hall, David J.; Liss, Michael A.; Hoh, Carl K.; Kane, Christopher J.; Wallace, Anne M.

2013-01-01

Abstract. The optical properties of a receptor-targeted probe designed for dual-modality mapping of the sentinel lymph node (SLN) was optimized. Specific fluorescence brightness was used as the design criterion, which was defined as the fluorescence brightness per mole of the contrast agent. Adjusting the molar ratio of the coupling reactants, IRDye 800CW-NHS-ester and tilmanocept, enabled us to control the number of fluorescent molecules attached to each tilmanocept, which was quantified by H1 nuclear magnetic resonance spectroscopy. Quantum yields and molar absorptivities were measured for unconjugated IRDye 800CW and IRDye 800CW-tilmanocept (800CW-tilmanocept) preparations at 0.7, 1.5, 2.3, 2.9, and 3.8 dyes per tilmanocept. Specific fluorescence brightness was calculated by multiplication of the quantum yield by the molar absorptivity and the number of dyes per tilmanocept. It predicted that the preparation with 2.3 dyes per tilmanocept would exhibit the brightest signal, which was confirmed by fluorescence intensity measurements using three optical imaging systems. When radiolabeled with Ga68 and injected into the footpads of mice, the probe identified SLNs by both fluorescence and positron emission tomography (PET) while maintaining high percent extraction by the SLN. These studies demonstrated the feasibility of 800CW-tilmanocept for multimodal SLN mapping via fluorescence and PET–computed tomography imaging. PMID:23958947

Study of cluster shapes in a monolithic active pixel detector

NASA Astrophysics Data System (ADS)

Maçzewski, ł.; Adamus, M.; Ciborowski, J.; Grzelak, G.; łużniak, P.; Nieżurawski, P.; Żarnecki, A. F.

2009-11-01

Beamstrahlung will constitute an important source of background in a pixel vertex detector at the future International Linear Collider. Electron and positron tracks of this origin impact the pixel planes at angles generally larger than those of secondary hadrons and the corresponding clusters are elongated. We report studies of cluster characteristics using test beam electron tracks incident at various angles on a MIMOSA-5 monolithic active pixel sensor matrix.

Advanced Photon Source accelerator ultrahigh vacuum guide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, C.; Noonan, J.

1994-03-01

In this document the authors summarize the following: (1) an overview of basic concepts of ultrahigh vacuum needed for the APS project, (2) a description of vacuum design and calculations for major parts of APS, including linac, linac waveguide, low energy undulator test line, positron accumulator ring (PAR), booster synchrotron ring, storage ring, and insertion devices, and (3) cleaning procedures of ultrahigh vacuum (UHV) components presently used at APS.

Summary of the Physics Opportunities Working Group

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Pisin; McDonald, K.T.

The Physics Opportunities Working Group was convened with the rather general mandate to explore physic opportunities that may arise as new accelerator technologies and facilities come into play. Five topics were considered during the workshop: QED at critical field strength, novel positron sources, crystal accelerators, suppression of beamstrahlung, and muon colliders. Of particular interest was the sense that a high energy muon collider might be technically feasible and certainly deserves serious study.

Cognition in the Brain: Investigations Using Positron Emission Tomography

DTIC Science & Technology

1992-07-16

0029 DDIRESS (City. State and ZIP Code) 10. SOURCE Of FUNDING NOS. _____________ .dg. 410 PROGRAM PROJECT TASKC WORK .,%r illing Air Force Base, DC...Bethesda, MD 20892 20. Daniel Bubb, M.D. Department of Neurolinguistics Montreal Neurological Institute 15. Sung-cheng tHuang, Ph.D. 3801 University...Chief of Pediatric Neu- rology Service Director, Center for Morphomet- 24. Terry Allard, Ph.D. ric Analysis Cognitive Science Programs Kennedy 9 Office

Low emittance electron storage rings

NASA Astrophysics Data System (ADS)

Levichev, E. B.

2018-01-01

Low-emittance electron (positron) beams are essential for synchrotron light sources, linear collider damping rings, and circular Crab Waist colliders. In this review, the principles and methods of emittance minimization are discussed, prospects for developing relativistic electron storage rings with small beam phase volume are assessed, and problems related to emittance minimization are examined together with their possible solutions. The special features and engineering implementation aspects of various facilities are briefly reviewed.

DoD Source Selection: Competencies, Deficiencies, and Remedies

DTIC Science & Technology

2014-04-30

University, Ministry of National Defense, Republic of China Strategic Planning and Management in Defense Systems Acquisition Stanley Rosen, Defense... systems procurement officer. He was employed in purchasing management for prime contractors on NASA’s Hubble Space Telescope, DoE’s Positron Electron...was living the good life, “he … was squandering precious tax dollars for, among other things, systems the military didn’t ask for, didn’t need and

Summary of the Physics Opportunities Working Group

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Pisin; McDonald, K.T.

1992-12-01

The Physics Opportunities Working Group was convened with the rather general mandate to explore physic opportunities that may arise as new accelerator technologies and facilities come into play. Five topics were considered during the workshop: QED at critical field strength, novel positron sources, crystal accelerators, suppression of beamstrahlung, and muon colliders. Of particular interest was the sense that a high energy muon collider might be technically feasible and certainly deserves serious study.

A positron emission tomograph based on LSO-APD modules with a sampling ADC read-out system for a students' advanced laboratory course.

PubMed

Schneider, Florian R; Mann, Alexander B; Konorov, Igor; Delso, Gaspar; Paul, Stephan; Ziegler, Sibylle I

2012-06-01

A one-day laboratory course on positron emission tomography (PET) for the education of physics students and PhD students in medical physics has been set up. In the course, the physical background and the principles of a PET scanner are introduced. Course attendees set the system in operation, calibrate it using a (22)Na point source and reconstruct different source geometries filled with (18)F. The PET scanner features an individual channel read-out of 96 lutetium oxyorthosilicate (LSO) scintillator crystals coupled to avalanche photodiodes (APD). The analog data of each APD are digitized by fast sampling analog to digital converters (SADC) and processed within field programmable gate arrays (FPGA) to extract amplitudes and time stamps. All SADCs are continuously sampling with a precise rate of 80MHz, which is synchronous for the whole system. The data is transmitted via USB to a Linux PC, where further processing and the image reconstruction are performed. The course attendees get an insight into detector techniques, modern read-out electronics, data acquisition and PET image reconstruction. In addition, a short introduction to some common software applications used in particle and high energy physics is part of the course. Copyright © 2011. Published by Elsevier GmbH.

Water-sensitive positron trapping modes in nanoporous magnesium aluminate ceramics

NASA Astrophysics Data System (ADS)

Filipecki, J.; Ingram, A.; Klym, H.; Shpotyuk, O.; Vakiv, M.

2007-08-01

The water-sensitive positron trapping modes in nanoporous MgAl2O4 ceramics with a spinel structure are studied. It is shown that water-sorption processes in magnesium aluminate ceramics leads to corresponding increase in positron trapping rates of extended defects located near intergranual boundaries. This catalytic affect has reversible nature, being strongly dependent on sorption water fluxes in ceramics. The fixation of all water-dependent positron trapping inputs allow to refine the most significant changes in positron trapping rate of extended defects.

Positron lifetime beam for defect studies in thin epitaxial semiconductor structures

NASA Astrophysics Data System (ADS)

Laakso, A.; Saarinen, K.; Hautojärvi, P.

2001-12-01

Positron annihilation spectroscopies are methods for direct identification of vacancy-type defects by measuring positron lifetime and Doppler broadening of annihilation radiation and providing information about open volume, concentration and atoms surrounding the defect. Both these techniques are easily applied to bulk samples. Only the Doppler broadening spectroscopy can be employed in thin epitaxial samples by utilizing low-energy positron beams. Here we describe the positron lifetime beam which will provide us with a method to measure lifetime in thin semiconductor layers.

Investigation of Positron Sticking to the Surfaces of Topological Insulators

NASA Astrophysics Data System (ADS)

Shastry, K.; Joglekar, P. V.; Olenga, A. Y.; Fazleev, N. G.; Weiss, A. H.; Barniellini, B.

2013-03-01

We describe experiments aimed at probing the sticking of positrons to the surfaces of topological insulators. In these experiments, a magnetically beam will be used to deposit positrons at the surface of Bi2Te2Se. The energy spectra and intensities of electrons emitted as a result of Positron Annihilation induced Auger electron Spectroscopy (PAES) provides a distinct element specific signal which can be used to determine if positrons can be trapped efficiently into a surface localized bound state. The experiments are aimed at determining the practicality of using positron annihilation to selectively probe the critically important top most layer of topological insulator system. Welch Y1100, NSF DMR 0907679

Positron lifetime spectrometer using a DC positron beam

DOEpatents

Xu, Jun; Moxom, Jeremy

2003-10-21

An entrance grid is positioned in the incident beam path of a DC beam positron lifetime spectrometer. The electrical potential difference between the sample and the entrance grid provides simultaneous acceleration of both the primary positrons and the secondary electrons. The result is a reduction in the time spread induced by the energy distribution of the secondary electrons. In addition, the sample, sample holder, entrance grid, and entrance face of the multichannel plate electron detector assembly are made parallel to each other, and are arranged at a tilt angle to the axis of the positron beam to effectively separate the path of the secondary electrons from the path of the incident positrons.

Studies of Oxidation of the Cu(100) Surface Using Low Energy Positrons

NASA Astrophysics Data System (ADS)

Fazleev, N. G.; Maddox, W. B.; Nadesalingam, M.; Rajeshwar, K.; Weiss, A. H.

2009-03-01

Changes in the surface of an oxidized Cu(100) single crystal resulting from vacuum annealing have been investigated using positron annihilation induced Auger electron spectroscopy (PAES). PAES measurements show a large increase in the intensity of the positron annihilation induced Cu M2,3VV Auger peak as the sample is subjected to a series of isochronal anneals in vacuum up to annealing temperature 300° C. The intensity then decreases monotonically as the annealing temperature is increased to ˜600° C. Experimental PAES results are analyzed by performing calculations of positron surface states and annihilation probabilities of surface-trapped positrons with relevant core electrons taking into account the charge redistribution at the surface, surface reconstructions, and electron-positron correlations effects. Possible explanation for the observed behavior of the intensity of positron annihilation induced Cu M2,3VV Auger peak with changes of the annealing temperature is proposed.

Studies of oxidation of the Cu(100) surface using low energy positrons.

NASA Astrophysics Data System (ADS)

Maddox, W. B.; Fazleev, N. G.; Weiss, A. H.

2009-03-01

Changes in the surface of an oxidized Cu(100) single crystal resulting from vacuum annealing have been investigated using positron annihilation induced Auger electron spectroscopy (PAES). PAES measurements show a large increase in the intensity of the positron annihilation induced Cu M2,3VV Auger peak as the sample is subjected to a series of isochronal anneals in vacuum up to annealing temperature 300^o C. The intensity then decreases monotonically as the annealing temperature is increased to ˜600^o C. Experimental PAES results are analyzed by performing calculations of positron surface states and annihilation probabilities of surface-trapped positrons with relevant core electrons taking into account the charge redistribution at the surface, surface reconstructions, and electron-positron correlations effects. Possible explanation for the observed behavior of the intensity of positron annihilation induced Cu M2,3VV Auger peak with changes of the annealing temperature is proposed.

Improving depth resolutions in positron beam spectroscopy by concurrent ion-beam sputtering

NASA Astrophysics Data System (ADS)

John, Marco; Dalla, Ayham; Ibrahim, Alaa M.; Anwand, Wolfgang; Wagner, Andreas; Böttger, Roman; Krause-Rehberg, Reinhard

2018-05-01

The depth resolution of mono-energetic positron annihilation spectroscopy using a positron beam is shown to improve by concurrently removing the sample surface layer during positron beam spectroscopy. During ion-beam sputtering with argon ions, Doppler-broadening spectroscopy is performed with energies ranging from 3 keV to 5 keV allowing for high-resolution defect studies just below the sputtered surface. With this technique, significantly improved depth resolutions could be obtained even at larger depths when compared to standard positron beam experiments which suffer from extended positron implantation profiles at higher positron energies. Our results show that it is possible to investigate layered structures with a thickness of about 4 microns with significantly improved depth resolution. We demonstrated that a purposely generated ion-beam induced defect profile in a silicon sample could be resolved employing the new technique. A depth resolution of less than 100 nm could be reached.

Radiation Belts of Antiparticles in Planetary Magnetospheres

NASA Astrophysics Data System (ADS)

Pugacheva, G. I.; Gusev, A. A.; Jayanthi, U. B.; Martin, I. M.; Spjeldvik, W. N.

2007-05-01

The Earth's radiation belts could be populated, besides with electrons and protons, also by antiparticles, such as positrons (Basilova et al., 1982) and antiprotons (pbar). Positrons are born in the decay of pions that are directly produced in nuclear reactions of trapped relativistic inner zone protons with the residual atmosphere at altitudes in the range of about 500 to 3000 km over the Earth's surface. Antiprotons are born by high energy (E > 6 GeV) cosmic rays in p+p - p+p+p+ pbar and in p+p - p+p+n+nbar reactions. The trapping and storage of these charged anti-particles in the magnetosphere result in radiation belts similar to the classical Van Allen belts of protons and electrons. We describe the mathematical techniques used for numerical simulation of the trapped positron and antiproton belt fluxes. The pion and antiproton yields were simulated on the basis of the Russian nuclear reaction computer code MSDM, a Multy Stage Dynamical Model, Monte Carlo code, (i.e., Dementyev and Sobolevsky, 1999). For estimates of positron flux there we have accounted for ionisation, bremsstrahlung, and synchrotron energy losses. The resulting numerical estimates show that the positron flux with energy >100 MeV trapped into the radiation belt at L=1.2 is of the order ~1000 m-2 s-1 sr-1, and that it is very sensitive to the shape of the trapped proton spectrum. This confined positron flux is found to be greater than that albedo, not trapped, mixed electron/positron flux of about 50 m-2 s-1 sr-1 produced by CR in the same region at the top of the geomagnetic field line at L=1.2. As we show in report, this albedo flux also consists mostly of positrons. The trapped antiproton fluxes produced by CR in the Earth's upper rarified atmosphere were calculated in the energy range from 10 MeV to several GeV. In the simulations we included a mathematic consideration of the radial diffusion process, both an inner and an outer antiproton source, losses of particles due to ionization process, annihilation, and nuclear interactions with the ambient matter. We have found that the Earth's antiproton belt possesses about 6-60 times larger antiproton fluxes compared to the galactic fluxes in interplanetary space during minimum and maximum solar activity at all energies in confinement zone. The radiation belt antiproton fluxes are spread into a wider L-shell range than its generation location around L=1.2. This is due to diffusion processes, and it demonstrates that radial diffusion as a relatively significant process for antimatter, even in the inner magnetosphere. Antimatter accumulated in the magnetospheres of solar system bodies may be of significance for space travel. It could be used as a propulsion for space missions to the outer planets and beyond. Antimatter has an energy density more than ten orders of magnitude higher than the best chemical propellants currently used in rocket systems. References: Basilova, R. N., A.A. Gusev, G.I. Pugacheva , Geom. and Aeronom. V. 22, p. 671-673, 1982.Chen, J., T. Dementyev, A.V., Sobolevsky, N.M. Radiation Measurements, 30, 553, 1999.

Positron Annihilation Ratio Spectroscopy (PsARS) Applied to Positronium Formation Studies

DTIC Science & Technology

2010-03-01

POSITRON ANNIHILATION RATIO SPECTROSCOPY (PsARS) APPLIED TO POSITRONIUM FORMATION STUDIES THESIS...AFIT/GNE/ENP/10-M07 POSITRON ANNIHILATION RATIO SPECTROSCOPY (PsARS) APPLIED TO POSITRONIUM FORMATION STUDIES ...lifetime studies in local electric field experiments. High local electric fields can polarize a positron -electron pair, which may result in an extended

Positron studies of metal-oxide-semiconductor structures

NASA Astrophysics Data System (ADS)

Au, H. L.; Asoka-Kumar, P.; Nielsen, B.; Lynn, K. G.

1993-03-01

Positron annihilation spectroscopy provides a new probe to study the properties of interface traps in metal-oxide semiconductors (MOS). Using positrons, we have examined the behavior of the interface traps as a function of gate bias. We propose a simple model to explain the positron annihilation spectra from the interface region of a MOS capacitor.

The stationary non-equilibrium plasma of cosmic-ray electrons and positrons

NASA Astrophysics Data System (ADS)

Tomaschitz, Roman

2016-06-01

The statistical properties of the two-component plasma of cosmic-ray electrons and positrons measured by the AMS-02 experiment on the International Space Station and the HESS array of imaging atmospheric Cherenkov telescopes are analyzed. Stationary non-equilibrium distributions defining the relativistic electron-positron plasma are derived semi-empirically by performing spectral fits to the flux data and reconstructing the spectral number densities of the electronic and positronic components in phase space. These distributions are relativistic power-law densities with exponential cutoff, admitting an extensive entropy variable and converging to the Maxwell-Boltzmann or Fermi-Dirac distributions in the non-relativistic limit. Cosmic-ray electrons and positrons constitute a classical (low-density high-temperature) plasma due to the low fugacity in the quantized partition function. The positron fraction is assembled from the flux densities inferred from least-squares fits to the electron and positron spectra and is subjected to test by comparing with the AMS-02 flux ratio measured in the GeV interval. The calculated positron fraction extends to TeV energies, predicting a broad spectral peak at about 1 TeV followed by exponential decay.

Positron annihilation lifetime study of polyvinylpyrrolidone for nanoparticle-stabilizing pharmaceuticals.

PubMed

Shpotyuk, O; Bujňáková, Z; Baláž, P; Ingram, A; Shpotyuk, Y

2016-01-05

Positron annihilation lifetime spectroscopy was applied to characterize free-volume structure of polyvinylpyrrolidone used as nonionic stabilizer in the production of many nanocomposite pharmaceuticals. The polymer samples with an average molecular weight of 40,000 g mol(-1) were pelletized in a single-punch tableting machine under an applied pressure of 0.7 GPa. Strong mixing in channels of positron and positronium trapping were revealed in the polyvinylpyrrolidone pellets. The positron lifetime spectra accumulated under normal measuring statistics were analysed in terms of unconstrained three- and four-term decomposition, the latter being also realized under fixed 0.125 ns lifetime proper to para-positronium self-annihilation in a vacuum. It was shown that average positron lifetime extracted from each decomposition was primary defined by long-lived ortho-positronium component. The positron lifetime spectra treated within unconstrained three-term fitting were in obvious preference, giving third positron lifetime dominated by ortho-positronium pick-off annihilation in a polymer matrix. This fitting procedure was most meaningful, when analysing expected positron trapping sites in polyvinylpyrrolidone-stabilized nanocomposite pharmaceuticals. Copyright © 2015 Elsevier B.V. All rights reserved.

Evidence for a positron bound state on the surface of a topological insulator

NASA Astrophysics Data System (ADS)

Shastry, K.; Weiss, A. H.; Barbiellini, B.; Assaf, B. A.; Lim, Z. H.; Joglekar, P. V.; Heiman, D.

2015-06-01

We describe experiments aimed at probing the sticking of positrons to the surfaces of topological insulators using the Positron Annihilation induced Auger Electron Spectrometer (PAES). A magnetically guided beam was used to deposit positrons at the surface of Bi2Te2Se sample at energy of ∼2eV. Peaks observed in the energy spectra and intensities of electrons emitted as a result of positron annihilation showed peaks at energies corresponding to Auger peaks in Bi, Teand Se providing clear evidence of Auger emission associated with the annihilation of positrons in a surface bound state. Theoretical estimates of the binding energy of this state are compared with estimates obtained by measuring the incident beam energy threshold for secondary electron emission and the temperature dependence positronium(Ps) emission. The experiments provide strong evidence for the existence of a positron bound state at the surface of Bi2Te2Se and indicate the practicality of using positron annihilation to selectively probe the critically important top most layer of topological insulator system.

Studies of the oxidized Cu(100) surface using positron annihilation induced Auger electron spectroscopy

NASA Astrophysics Data System (ADS)

Maddox, W.; Fazleev, N. G.; Nadesalingam, M. P.; Weiss, A. H.

2008-03-01

We discuss recent progress in studies of an oxidized Cu(100) single crystal subjected to vacuum annealing over a temperature range from 293K to 1073K using positron annihilation induced Auger electron spectroscopy (PAES). The PAES measurements show a large monotonic increase in the intensity of the positron annihilation induced Cu M2,3 VV Auger peak as the sample is subjected to a series of isochronal anneals in vacuum up to annealing temperature 573 K. The intensity then decreases monotonically as the annealing temperature is increased to 873 K. Experimental PAES results are analyzed by performing calculations of positron surface states and annihilation probabilities of surface-trapped positrons with relevant core electrons taking into account the charge redistribution at the surface, surface reconstructions, and electron-positron correlations effects. The effects of oxygen adsorption and surface reconstruction on localization of positron surface state wave functions and annihilation characteristics are analyzed. Possible explanations are provided for the observed behavior of the intensity of positron annihilation induced Cu M2,3VV Auger peak with changes of the annealing temperature.

Study of SiO2-Si and metal-oxide-semiconductor structures using positrons

NASA Astrophysics Data System (ADS)

Leung, T. C.; Asoka-Kumar, P.; Nielsen, B.; Lynn, K. G.

1993-01-01

Studies of SiO2-Si and metal-oxide-semiconductor (MOS) structures using positrons are summarized and a concise picture of the present understanding of positrons in these systems is provided. Positron annihilation line-shape S data are presented as a function of the positron incident energy, gate voltage, and annealing, and are described with a diffusion-annihilation equation for positrons. The data are compared with electrical measurements. Distinct annihilation characteristics were observed at the SiO2-Si interface and have been studied as a function of bias voltage and annealing conditions. The shift of the centroid (peak) of γ-ray energy distributions in the depletion region of the MOS structures was studied as a function of positron energy and gate voltage, and the shifts are explained by the corresponding variations in the strength of the electric field and thickness of the depletion layer. The potential role of the positron annihilation technique as a noncontact, nondestructive, and depth-sensitive characterization tool for the technologically important, deeply buried interface is shown.

Proposal for a slow positron facility at Jefferson National Laboratory

NASA Astrophysics Data System (ADS)

Mills, Allen P.

2018-05-01

One goal of the JPos-17 International Workshop on Physics with Positrons was to ascertain whether it would be a good idea to expand the mission of the Thomas Jefferson National Accelerator Facility (JLab) to include science with low energy (i.e. "slow") spin polarized positrons. It is probably true that experimentation with slow positrons would potentially have wide-ranging benefits comparable to those obtained with neutron and x-ray scattering, but it is certain that the full range of these benefits will never be fully available without an infrastructure comparable to that of existing neutron and x-ray facilities. The role for Jefferson Laboratory would therefore be to provide and maintain (1) a dedicated set of machines for making and manipulating high intensity, high brightness beams of polarized slow positrons; (2) a suite of unique and easily used instruments of wide utility that will make efficient use of the positrons; and (3) a group of on-site positron scientists to provide scientific leadership, instrument development, and user support. In this note some examples will be given of the science that might make a serious investment in a positron facility worthwhile. At the same time, the lessons learned from various proposed and successful positron facilities will be presented for consideration.

Oxidation and thermal reduction of the Cu(1 0 0) surface as studied using positron annihilation induced Auger electron spectroscopy (PAES)

NASA Astrophysics Data System (ADS)

Fazleev, N. G.; Nadesalingam, M. P.; Maddox, W.; Mukherjee, S.; Rajeshwar, K.; Weiss, A. H.

2010-01-01

Changes in the surface of an oxidized Cu(1 0 0) single crystal resulting from vacuum annealing have been investigated using positron annihilation induced Auger electron spectroscopy (PAES). PAES measurements show a large increase in the intensity of the annihilation induced Cu M 2,3VV Auger peak as the sample is subjected to a series of isochronal anneals in vacuum up to annealing temperature 300 °C. The intensity then decreases monotonically as the annealing temperature is increased to ˜600 °C. Experimental probabilities of annihilation of surface-trapped positrons with Cu 3p and O 1s core-level electrons are estimated from the measured intensities of the positron annihilation induced Cu M 2,3VV and O KLL Auger transitions. Experimental PAES results are analyzed by performing calculations of positron surface states and annihilation probabilities of surface-trapped positrons with relevant core electrons taking into account the charge redistribution at the surface, surface reconstructions, and electron-positron correlations effects. The effects of oxygen adsorption on localization of positron surface state wave function and annihilation characteristics are also analyzed. Possible explanation is proposed for the observed behavior of the intensity of positron annihilation induced Cu M 2,3VV and O KLL Auger peaks and probabilities of annihilation of surface-trapped positrons with Cu 3p and O 1s core-level electrons with changes of the annealing temperature.