The 25 mA continuous-wave surface-plasma source of H{sup −} ions

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

Belchenko, Yu., E-mail: belchenko@inp.nsk.su; Gorbovsky, A.; Sanin, A.

The ion source with the Penning geometry of electrodes producing continuous-wave beam of H{sup −} ions with current up to 25 mA was developed. Several improvements were introduced to increase source intensity, reliability, and lifetime. The collar around the emission aperture increases the electrons filtering. The apertures’ diameters of the ion-optical system electrodes were increased to generate the beam with higher intensity. An optimization of electrodes’ temperature was performed.

Electron cyclotron resonance ion source for high currents of mono- and multicharged ion and general purpose unlimited lifetime application on implantation devices

NASA Astrophysics Data System (ADS)

Bieth, C.; Bouly, J. L.; Curdy, J. C.; Kantas, S.; Sortais, P.; Sole, P.; Vieux-Rochaz, J. L.

2000-02-01

The electron cyclotron resonance (ECR) ion sources were originally developed for high energy physic applications. They are used as injectors on linear accelerators and cyclotrons to further increase the particle energy via high charge state ions. This ECR technology is well suited for sources placed on a high voltage platform where ac power available is limited by insulated transformers. The PANTECHNIK family of ion source with its wide range of ion beam (various charge states with various beam currents) offers new possibilities and perspectives in the field of ion implantation. In addition to all these possibilities, the PANTECHNIK ion sources have many other advantages like: a very long lifetime without maintenance expense, good stability, efficiency of ionization close to 100% (this improves the lifetime of the pumping system and other equipment), the possibility of producing ion beams with different energies, and a very good reproducibility. The main characteristics of sources like Nanogan or SuperNanogan will be recalled. We will especially present the results obtained with the new Microgan 10 GHz source that can be optimized for the production of high currents of monocharged ion, including reactive gas like BF3 (2 mA e of B+) or medium currents of low charge state like 0.5 mA e of Ar4+. The latest results obtained with Microgan 10 GHz show that it is possible to drive the source up to 30 mA e of total current, with an emittance of 150 π mm mrad at 40 kV and also to maintain the production of multicharged ions like Ar8+.

Present limits for the luminosity, the beam current and the beam lifetime in Doris II

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

Nesemann, H.; Sarau, B.

1985-10-01

The e e storage ring DORIS II has been operating for high energy physics experiments in the region of the Y resonances around 2x5 GeV and as a source for synchrotron radiation near 3.7 GeV. A luminosity of nearly 3x10T cm Ssec or more than 1500 (nb) /day has been achieved. For synchrotron radiation e -currents of about 100 mA are stored in 4 bunches (out of 480 buckets). As long as the beam-beam interaction does not limit the luminosity the optimum performance of the ring is obtained for both modes of operation if the currents stored are large, themore » cross section of the beam is small and the lifetime is long. Thus we concentrate the discussion on these subjects.« less

Improvements for extending the time between maintenance periods for the Heidelberg ion beam therapy center (HIT) ion sources.

PubMed

Winkelmann, Tim; Cee, Rainer; Haberer, Thomas; Naas, Bernd; Peters, Andreas; Schreiner, Jochen

2014-02-01

The clinical operation at the Heidelberg Ion Beam Therapy Center (HIT) started in November 2009; since then more than 1600 patients have been treated. In a 24/7 operation scheme two 14.5 GHz electron cyclotron resonance ion sources are routinely used to produce protons and carbon ions. The modification of the low energy beam transport line and the integration of a third ion source into the therapy facility will be shown. In the last year we implemented a new extraction system at all three sources to enhance the lifetime of extraction parts and reduce preventive and corrective maintenance. The new four-electrode-design provides electron suppression as well as lower beam emittance. Unwanted beam sputtering effects which typically lead to contamination of the insulator ceramics and subsequent high-voltage break-downs are minimized by the beam guidance of the new extraction system. By this measure the service interval can be increased significantly. As a side effect, the beam emittance can be reduced allowing a less challenging working point for the ion sources without reducing the effective beam performance. This paper gives also an outlook to further enhancements at the HIT ion source testbench.

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.

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.

Construction of the Helsinki University of Technology (HUT) pulsed positron beam

NASA Astrophysics Data System (ADS)

Fallström, K.; Laine, T.

1999-08-01

We are constructing a pulsed positron beam facility for lifetime measurements in thin surface layers. Our beam system comprises a 22Na positron source and a tungsten foil moderator followed by a prebuncher and a chopper. A double-drift buncher will compress the beam into 120-ps pulses at the target. The end energy of the positron beam can be adjusted between 3 keV and 30 keV by changing the potential of the source end of the beam. The bunching electronics and most of the beam guiding magnets are also floating at the high voltage. The sample is at ground potential to facilitate variable temperature measurements. With a test source of 6 mCi 22Na we get a prebunched beam intensity of 4×10 3 positrons per second in 1.5-ns wide pulses (the bunching frequency is 33.33 MHz). We are currently testing the chopper and the following buncher stages and building the final accelerator/decelerator system.

Program for studying fundamental interactions at the PIK reactor facilities

NASA Astrophysics Data System (ADS)

Serebrov, A. P.; Vassiljev, A. V.; Varlamov, V. E.; Geltenbort, P.; Gridnev, K. A.; Dmitriev, S. P.; Dovator, N. A.; Egorov, A. I.; Ezhov, V. F.; Zherebtsov, O. M.; Zinoviev, V. G.; Ivochkin, V. G.; Ivanov, S. N.; Ivanov, S. A.; Kolomensky, E. A.; Konoplev, K. A.; Krasnoschekova, I. A.; Lasakov, M. S.; Lyamkin, V. A.; Martemyanov, V. P.; Murashkin, A. N.; Neustroev, P. V.; Onegin, M. S.; Petelin, A. L.; Pirozhkov, A. N.; Polyushkin, A. O.; Prudnikov, D. V.; Ryabov, V. L.; Samoylov, R. M.; Sbitnev, S. V.; Fomin, A. K.; Fomichev, A. V.; Zimmer, O.; Cherniy, A. V.; Shoka, I. V.

2016-05-01

A research program aimed at studying fundamental interactions by means of ultracold and polarized cold neutrons at the GEK-4-4' channel of the PIK reactor is presented. The apparatus to be used includes a source of cold neutrons in the heavy-water reflector of the reactor, a source of ultracold neutrons based on superfluid helium and installed in a cold-neutron beam extracted from the GEK-4 channel, and a number of experimental facilities in neutron beams. An experiment devoted to searches for the neutron electric dipole moment and an experiment aimed at a measurement the neutron lifetime with the aid of a large gravitational trap are planned to be performed in a beam of ultracold neutrons. An experiment devoted to measuring neutron-decay asymmetries with the aid of a superconducting solenoid is planned in a beam of cold polarized neutrons from the GEK-4' channel. The second ultracold-neutron source and an experiment aimed at measuring the neutron lifetime with the aid of a magnetic trap are planned in the neutron-guide system of the GEK-3 channel. In the realms of neutrino physics, an experiment intended for sterile-neutrino searches is designed. The state of affairs around the preparation of the experimental equipment for this program is discussed.

Very-low-energy-spread ion sources

NASA Astrophysics Data System (ADS)

Lee, Y.

1997-05-01

Ion beams with low axial energy spread are required in many applications such as ion projection lithography, isobaric separation in radioactive ion beam experiments, and ion beam deposition processes. In an ion source, the spread of the axial ion energy is caused by the nonuniformity of the plasma potential distribution along the source axis. Multicusp ion sources are capable of production positive and negative ions with good beam quality and relatively low energy spread. By intorducing a magnetic filter inside the multicusp source chamber, the axial plasma potential distribution is modified and the energy spread of positive hydrogen ions can be reduced to as low as 1 eV. The energy spread measurements of multicusp sources have been conducted by employing three different techniques: an electrostatic energy analyzer at the source exit; a magnetic deflection spectrometer; and a retarding-field energy analyzer for the accelerated beam. These different measurements confirmed tha! t ! the axial energy spread of positive and negative ions generated in the filter-equipped multicusp sources are small. New ion source configurations are now being investigated at LBNL with the purpose of achieving enen lower energy spread (<1eV) and of maximizing source performance such as reliability and lifetime.

Multiaperture ion beam extraction from gas-dynamic electron cyclotron resonance source of multicharged ions

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

Sidorov, A.; Dorf, M.; Zorin, V.

2008-02-15

Electron cyclotron resonance ion source with quasi-gas-dynamic regime of plasma confinement (ReGIS), constructed at the Institute of Applied Physics, Russia, provides opportunities for extracting intense and high-brightness multicharged ion beams. Despite the short plasma lifetime in a magnetic trap of a ReGIS, the degree of multiple ionization may be significantly enhanced by the increase in power and frequency of the applied microwave radiation. The present work is focused on studying the intense beam quality of this source by the pepper-pot method. A single beamlet emittance measured by the pepper-pot method was found to be {approx}70 {pi} mm mrad, and themore » total extracted beam current obtained at 14 kV extraction voltage was {approx}25 mA. The results of the numerical simulations of ion beam extraction are found to be in good agreement with experimental data.« less

High temperature ion source for an on-line isotope separator

DOEpatents

Mlekodaj, Ronald L.

1979-01-01

A reduced size ion source for on-line use with a cyclotron heavy-ion beam is provided. A sixfold reduction in source volume while operating with similar input power levels results in a 2000.degree. C. operating temperature. A combined target/window normally provides the reaction products for ionization while isolating the ion source plasma from the cyclotron beam line vacuum. A graphite felt catcher stops the recoiling reaction products and releases them into the plasma through diffusion and evaporation. Other target arrangements are also possible. A twenty-four hour lifetime of unattended operation is achieved, and a wider range of elements can be studied than was heretofore possible.

Compact microwave ion source for industrial applications.

PubMed

Cho, Yong-Sub; Kim, Dae-Il; Kim, Han-Sung; Seol, Kyung-Tae; Kwon, Hyeok-Jung; Hong, In-Seok

2012-02-01

A 2.45 GHz microwave ion source for ion implanters has many good properties for industrial application, such as easy maintenance and long lifetime, and it should be compact for budget and space. But, it has a dc current supply for the solenoid and a rf generator for plasma generation. Usually, they are located on high voltage platform because they are electrically connected with beam extraction power supply. Using permanent magnet solenoid and multi-layer dc break, high voltage deck and high voltage isolation transformer can be eliminated, and the dose rate on targets can be controlled by pulse duty control with semiconductor high voltage switch. Because the beam optics does not change, beam transfer components, such as focusing elements and beam shutter, can be eliminated. It has shown the good performances in budget and space for industrial applications of ion beams.

First storage of ion beams in the Double Electrostatic Ion-Ring Experiment: DESIREE.

PubMed

Schmidt, H T; Thomas, R D; Gatchell, M; Rosén, S; Reinhed, P; Löfgren, P; Brännholm, L; Blom, M; Björkhage, M; Bäckström, E; Alexander, J D; Leontein, S; Hanstorp, D; Zettergren, H; Liljeby, L; Källberg, A; Simonsson, A; Hellberg, F; Mannervik, S; Larsson, M; Geppert, W D; Rensfelt, K G; Danared, H; Paál, A; Masuda, M; Halldén, P; Andler, G; Stockett, M H; Chen, T; Källersjö, G; Weimer, J; Hansen, K; Hartman, H; Cederquist, H

2013-05-01

We report on the first storage of ion beams in the Double ElectroStatic Ion Ring ExpEriment, DESIREE, at Stockholm University. We have produced beams of atomic carbon anions and small carbon anion molecules (C(n)(-), n = 1, 2, 3, 4) in a sputter ion source. The ion beams were accelerated to 10 keV kinetic energy and stored in an electrostatic ion storage ring enclosed in a vacuum chamber at 13 K. For 10 keV C2 (-) molecular anions we measure the residual-gas limited beam storage lifetime to be 448 s ± 18 s with two independent detector systems. Using the measured storage lifetimes we estimate that the residual gas pressure is in the 10(-14) mbar range. When high current ion beams are injected, the number of stored particles does not follow a single exponential decay law as would be expected for stored particles lost solely due to electron detachment in collision with the residual-gas. Instead, we observe a faster initial decay rate, which we ascribe to the effect of the space charge of the ion beam on the storage capacity.

A New Electron Source for Laboratory Simulation of the Space Environment

NASA Technical Reports Server (NTRS)

Krause, Linda Habash; Everding, Daniel; Bonner, Mathew; Swan, Brian

2012-01-01

We have developed a new collimated electron source called the Photoelectron Beam Generator (PEBG) for laboratory and spaceflight applications. This technology is needed to replace traditional cathodes because of serious fundamental weaknesses with the present state of the art. Filament cathodes suffer from numerous practical problems, even if expertly designed, including the dependence of electron emission on filament temperature, short lifetimes (approx 100 hours), and relatively high power (approx 10s of W). Other types of cathodes have solved some of these problems, but they are plagued with other difficult problems, such as the Spindt cathode's extreme sensitivity to molecular oxygen. None to date have been able to meet the demand of long lifetime, robust packaging, and precision energy and flux control. This new cathode design avoids many common pitfalls of traditional cathodes. Specifically, there are no fragile parts, no sensitivity to oxygen, no intrinsic emission dependencies on device temperature, and no vacuum requirements for protecting the source from contamination or damage. Recent advances in high-brightness Light Emitting Diodes (LEDs) have provided the key enabling technology for this new electron source. The LEDs are used to photoeject electrons off a target material of a low work-function, and these photoelectrons are subsequently focused into a laminar beam using electrostatic lenses. The PEBG works by illuminating a target material and steering photoelectrons into a laminar beam using electrostatic lenses

A 60 mA DC H- multi cusp ion source developed at TRIUMF

NASA Astrophysics Data System (ADS)

Jayamanna, K.; Ames, F.; Bylinskii, I.; Lovera, M.; Minato, B.

2018-07-01

This paper describes the latest high-current multi cusp type ion source developed at TRIUMF, which is capable of producing a negative hydrogen ion beam (H-) of 60 mA of direct current at 140V and 90A arc. The results achieved to date including emittance measurements and filament lifetime issues are presented. The low current version of this ion source is suitable for medical cyclotrons as well as accelerators and the high current version is intended for producing large neutral hydrogen beams for fusion research. The description of the source magnetic configuration, the electron filter profile and the differential pumping techniques given in the paper will allow the building of an arc discharge H- ion source with similar properties.

Determination of minority-carrier lifetime and surface recombination velocity with high spacial resolution

NASA Technical Reports Server (NTRS)

Watanabe, M.; Actor, G.; Gatos, H. C.

1977-01-01

Quantitative analysis of the electron beam induced current in conjunction with high-resolution scanning makes it possible to evaluate the minority-carrier lifetime three dimensionally in the bulk and the surface recombination velocity two dimensionally, with a high spacial resolution. The analysis is based on the concept of the effective excitation strength of the carriers which takes into consideration all possible recombination sources. Two-dimensional mapping of the surface recombination velocity of phosphorus-diffused silicon diodes is presented as well as a three-dimensional mapping of the changes in the minority-carrier lifetime in ion-implanted silicon.

Challenges/issues of NIS used in particle accelerator facilities

NASA Astrophysics Data System (ADS)

Faircloth, Dan

2013-09-01

High current, high duty cycle negative ion sources are an essential component of many high power particle accelerators. This talk gives an overview of the state-of-the-art sources used around the world. Volume, surface and charge exchange negative ion production processes are detailed. Cesiated magnetron and Penning surface plasma sources are discussed along with surface converter sources. Multicusp volume sources with filament and LaB6 cathodes are described before moving onto RF inductively coupled volume sources with internal and external antennas. The major challenges facing accelerator facilities are detailed. Beam current, source lifetime and reliability are the most pressing. The pros and cons of each source technology is discussed along with their development programs. The uncertainties and unknowns common to these sources are discussed. The dynamics of cesium surface coverage and the causes of source variability are still unknown. Minimizing beam emittance is essential to maximizing the transport of high current beams; space charge effects are very important. The basic physics of negative ion production is still not well understood, theoretical and experimental programs continue to improve this, but there are still many mysteries to be solved.

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.

150 {mu}A 18F{sup -} target and beam port upgrade for the IBA 18/9 cyclotron

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

Stokely, M. H.; Peeples, J. L.; Poorman, M. C.

2012-12-19

A high power ({approx}3 kW) target platform has been developed for the IBA 18/9 cyclotron. New designs for the airlock, collimator and target subsystems have been fabricated and deployed. The primary project goal is reliable commercial production of 18F{sup -} at 150 {mu}A or greater, while secondary goals include improving serviceability and extending service intervals relative to OEM systems. Reliable operation in a production environment has been observed at beam currents up to 140 {mu}A. Challenges include ion source lifetime and localized peaking in the beam intensity distribution.

Neutralization of an ion beam from the end-Hall ion source by a plasma electron source based on a discharge in crossed E × H fields

NASA Astrophysics Data System (ADS)

Dostanko, A. P.; Golosov, D. A.

2009-10-01

The possibility of using a plasma electron source (PES) with a discharge in crossed E × H field for compensating the ion beam from an end-Hall ion source (EHIS) is analyzed. The PES used as a neutralizer is mounted in the immediate vicinity of the EHIS ion generation and acceleration region at 90° to the source axis. The behavior of the discharge and emission parameters of the EHIS is determined for operation with a filament neutralizer and a plasma electron source. It is found that the maximal discharge current from the ion source attains a value of 3.8 A for operation with a PES and 4 A for operation with a filament compensator. It is established that the maximal discharge current for the ion source strongly depends on the working gas flow rate for low flow rates (up to 10 ml/min) in the EHIS; for higher flow rates, the maximum discharge current in the EHIS depends only on the emissivity of the PES. Analysis of the emission parameters of EHISs with filament and plasma neutralizers shows that the ion beam current and the ion current density distribution profile are independent of the type of the electron source and the ion current density can be as high as 0.2 mA/cm2 at a distance of 25 cm from the EHIS anode. The balance of currents in the ion source-electron source system is considered on the basis of analysis of operation of EHISs with various sources of electrons. It is concluded that the neutralization current required for operation of an ion source in the discharge compensation mode must be equal to or larger than the discharge current of the ion source. The use of PES for compensating the ion beam from an end-Hall ion source proved to be effective in processes of ion-assisted deposition of thin films using reactive gases like O2 or N2. The application of the PES technique makes it possible to increase the lifetime of the ion-assisted deposition system by an order of magnitude (the lifetime with a Ti cathode is at least 60 h and is limited by the replacement life of the deposited cathode insertion).

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.

Present status of the low energy linac-based slow positron beam and positronium spectrometer in Saclay

NASA Astrophysics Data System (ADS)

Liszkay, L.; Comini, P.; Corbel, C.; Debu, P.; Grandemange, P.; Pérez, P.; Rey, J.-M.; Reymond, J.-M.; Ruiz, N.; Sacquin, Y.; Vallage, B.

2014-04-01

A new slow positron beamline featuring a large acceptance positronium lifetime spectrometer has been constructed and tested at the linac-based slow positron source at IRFU CEA Saclay, France. The new instrument will be used in the development of a dense positronium target cloud for the GBAR experiment. The GBAR project aims at precise measurement of the gravitational acceleration of antihydrogen in the gravitational field of the Earth. Beyond application in fundamental science, the positron spectrometer will be used in materials research, for testing thin porous films and layers by means of positronium annihilation. The slow positron beamline is being used as a test bench to develop further instrumentation for positron annihilation spectroscopy (Ps time-of-flight, pulsed positron beam). The positron source is built on a low energy linear electron accelerator (linac). The 4.3 MeV electron energy used is well below the photoneutron threshold, making the source a genuine on-off device, without remaining radioactivity. The spectrometer features large BGO (Bismuth Germanate) scintillator detectors, with sufficiently large acceptance to detect all ortho-positronium annihilation lifetime components (annihilation in vacuum and in nanopores).

SNS Proton Beam Window Disposal

NASA Astrophysics Data System (ADS)

Popova, Irina; Gallmeier, Franz X.; Trotter, Steven

2017-09-01

In order to support the disposal of the proton beam window assembly of the Spallation Neutron Source beamline to the target station, waste classification analyses are performed. The window has a limited life-time due to radiation-induced material damage. Analyses include calculation of the radionuclide inventory and shielding analyses for the transport package/container to ensure that the container is compliant with the transportation and waste management regulations. In order to automate this procedure and minimize manual work a script in Perl language was written.

Towards an In-Beam Measurement of the Neutron Lifetime to 1 Second

NASA Astrophysics Data System (ADS)

Mulholland, Jonathan

2014-03-01

A precise value for the neutron lifetime is required for consistency tests of the Standard Model and is an essential parameter in the theory of Big Bang Nucleosynthesis. A new measurement of the neutron lifetime using the in-beam method is planned at the National Institute of Standards and Technology Center for Neutron Research. The systematic effects associated with the in-beam method are markedly different than those found in storage experiments utilizing ultracold neutrons. Experimental improvements, specifically recent advances in the determination of absolute neutron fluence, should permit an overall uncertainty of 1 second on the neutron lifetime. The dependence of the primordial mass fraction on the neutron lifetime, technical improvements of the in-beam technique, and the path toward improving the precision of the new measurement will be discussed.

High flux circularly polarized gamma beam factory: coupling a Fabry-Perot optical cavity with an electron storage ring

PubMed Central

Chaikovska, I.; Cassou, K.; Chiche, R.; Cizeron, R.; Cornebise, P.; Delerue, N.; Jehanno, D.; Labaye, F.; Marie, R.; Martens, A.; Peinaud, Y.; Soskov, V.; Variola, A.; Zomer, F.; Cormier, E.; Lhermite, J.; Dolique, V.; Flaminio, R.; Michel, C.; Pinard, L.; Sassolas, B.; Akagi, T.; Araki, S.; Honda, Y.; Omori, T.; Terunuma, N.; Urakawa, J.; Miyoshi, S.; Takahashi, T.; Yoshitama, H.

2016-01-01

We report and discuss high-flux generation of circularly polarized γ-rays by means of Compton scattering. The γ-ray beam results from the collision of an external-cavity-enhanced infrared laser beam and a low emittance relativistic electron beam. By operating a non-planar bow-tie high-finesse optical Fabry-Perot cavity coupled to a storage ring, we have recorded a flux of up to (3.5 ± 0.3) × 108 photons per second with a mean measured energy of 24 MeV. The γ-ray flux has been sustained for several hours. In particular, we were able to measure a record value of up to 400 γ-rays per collision in a full bandwidth. Moreover, the impact of Compton scattering on the electron beam dynamics could be observed resulting in a reduction of the electron beam lifetime correlated to the laser power stored in the Fabry-Perot cavity. We demonstrate that the electron beam lifetime provides an independent and consistent determination of the γ-ray flux. Furthermore, a reduction of the γ-ray flux due to intrabeam scattering has clearly been identified. These results, obtained on an accelerator test facility, warrant potential scaling and revealed both expected and yet unobserved effects. They set the baseline for further scaling of the future Compton sources under development around the world. PMID:27857146

Slot-Antenna/Permanent-Magnet Device for Generating Plasma

NASA Technical Reports Server (NTRS)

Foster, John E.

2007-01-01

A device that includes a rectangular-waveguide/slot-antenna structure and permanent magnets has been devised as a means of generating a substantially uniform plasma over a relatively large area, using relatively low input power and a low gas flow rate. The device utilizes electron cyclotron resonance (ECR) excited by microwave power to efficiently generate plasma in a manner that is completely electrodeless in the sense that, in principle, there is no electrical contact between the plasma and the antenna. Plasmas generated by devices like this one are suitable for use as sources of ions and/or electrons for diverse material-processing applications (e.g., etching or deposition) and for ion thrusters. The absence of plasma/electrode contact essentially prevents plasma-induced erosion of the antenna, thereby also helping to minimize contamination of the plasma and of objects exposed to the plasma. Consequently, the operational lifetime of the rectangular-waveguide/ slot-antenna structure is long and the lifetime of the plasma source is limited by the lifetime of the associated charged-particle-extraction grid (if used) or the lifetime of the microwave power source. The device includes a series of matched radiating slot pairs that are distributed along the length of a plasma-source discharge chamber (see figure). This arrangement enables the production of plasma in a distributed fashion, thereby giving rise to a uniform plasma profile. A uniform plasma profile is necessary for uniformity in any electron- or ion-extraction electrostatic optics. The slotted configuration of the waveguide/ antenna structure makes the device scalable to larger areas and higher powers. All that is needed for scaling up is the attachment of additional matched radiating slots along the length of the discharge chamber. If it is desired to make the power per slot remain constant in scaling up, then the input microwave power must be increased accordingly. Unlike in prior ECR microwave plasma-generating devices, there is no need for an insulating window on the antenna. Such windows are sources of contamination and gradually become ineffective as they become coated with erosion products over time. These characteristics relegate prior ECR microwave plasma-generating devices to non-ion beam, non-deposition plasma applications. In contrast, the lack of need for an insulating window in the present device makes it possible to use the device in both ion-beam (including deposition) and electron-beam applications. The device is designed so that ECR takes place above each slot and the gradient of the magnetic field at each slot is enough to prevent backflow of plasma.

Progress toward a new beam measurement of the neutron lifetime

NASA Astrophysics Data System (ADS)

Hoogerheide, Shannon Fogwell

2016-09-01

Neutron beta decay is the simplest example of nuclear beta decay. A precise value of the neutron lifetime is important for consistency tests of the Standard Model and Big Bang Nucleosysnthesis models. The beam neutron lifetime method requires the absolute counting of the decay protons in a neutron beam of precisely known flux. Recent work has resulted in improvements in both the neutron and proton detection systems that should permit a significant reduction in systematic uncertainties. A new measurement of the neutron lifetime using the beam method will be performed at the National Institute of Standards and Technology Center for Neutron Research. The projected uncertainty of this new measurement is 1 s. An overview of the measurement and the technical improvements will be discussed.

Helicon plasma generator-assisted surface conversion ion source for the production of H- ion beams at the Los Alamos Neutron Science Centera)

NASA Astrophysics Data System (ADS)

Tarvainen, O.; Rouleau, G.; Keller, R.; Geros, E.; Stelzer, J.; Ferris, J.

2008-02-01

The converter-type negative ion source currently employed at the Los Alamos Neutron Science Center (LANSCE) is based on cesium enhanced surface production of H- ion beams in a filament-driven discharge. In this kind of an ion source the extracted H- beam current is limited by the achievable plasma density which depends primarily on the electron emission current from the filaments. The emission current can be increased by increasing the filament temperature but, unfortunately, this leads not only to shorter filament lifetime but also to an increase in metal evaporation from the filament, which deposits on the H- converter surface and degrades its performance. Therefore, we have started an ion source development project focused on replacing these thermionic cathodes (filaments) of the converter source by a helicon plasma generator capable of producing high-density hydrogen plasmas with low electron energy. In our studies which have so far shown that the plasma density of the surface conversion source can be increased significantly by exciting a helicon wave in the plasma, and we expect to improve the performance of the surface converter H- ion source in terms of beam brightness and time between services. The design of this new source and preliminary results are presented, along with a discussion of physical processes relevant for H- ion beam production with this novel design. Ultimately, we perceive this approach as an interim step towards our long-term goal, combining a helicon plasma generator with an SNS-type main discharge chamber, which will allow us to individually optimize the plasma properties of the plasma cathode (helicon) and H- production (main discharge) in order to further improve the brightness of extracted H- ion beams.

Helicon plasma generator-assisted surface conversion ion source for the production of H(-) ion beams at the Los Alamos Neutron Science Center.

PubMed

Tarvainen, O; Rouleau, G; Keller, R; Geros, E; Stelzer, J; Ferris, J

2008-02-01

The converter-type negative ion source currently employed at the Los Alamos Neutron Science Center (LANSCE) is based on cesium enhanced surface production of H(-) ion beams in a filament-driven discharge. In this kind of an ion source the extracted H(-) beam current is limited by the achievable plasma density which depends primarily on the electron emission current from the filaments. The emission current can be increased by increasing the filament temperature but, unfortunately, this leads not only to shorter filament lifetime but also to an increase in metal evaporation from the filament, which deposits on the H(-) converter surface and degrades its performance. Therefore, we have started an ion source development project focused on replacing these thermionic cathodes (filaments) of the converter source by a helicon plasma generator capable of producing high-density hydrogen plasmas with low electron energy. In our studies which have so far shown that the plasma density of the surface conversion source can be increased significantly by exciting a helicon wave in the plasma, and we expect to improve the performance of the surface converter H(-) ion source in terms of beam brightness and time between services. The design of this new source and preliminary results are presented, along with a discussion of physical processes relevant for H(-) ion beam production with this novel design. Ultimately, we perceive this approach as an interim step towards our long-term goal, combining a helicon plasma generator with an SNS-type main discharge chamber, which will allow us to individually optimize the plasma properties of the plasma cathode (helicon) and H(-) production (main discharge) in order to further improve the brightness of extracted H(-) ion beams.

Test of Time-Reversal Invariance at COSY (TRIC)

NASA Astrophysics Data System (ADS)

Eversheim, D.; Valdau, Yu.; Lorentz, B.

2016-02-01

At the Cooler Synchrotron COSY a novel (P-even, T-odd) null test of time-reversal invariance to an accuracy of 10-6 is planned as an internal target transmission experiment. The parity conserving time-reversal violating observable is the total cross-section asymmetry Ay,xz. This quantity is measured using a polarized proton beam with an energy of 135 MeV and an internal tensor polarized deuteron target from the PAX atomic beam source. The reaction rate will be determined by the lifetime of the beam. Consequently, the accuracy of the current measurement of the circulating proton beam is crucial for this experiment. Thus, the cooler synchroton ring serves as an ideal forward spectrometer, as a detector, and an accelerator.

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.

A liquid hydrocarbon deuteron source for neutron generators

NASA Astrophysics Data System (ADS)

Schwoebel, P. R.

2017-06-01

Experimental studies of a deuteron spark source for neutron generators using hydrogen isotope fusion reactions are reported. The ion source uses a spark discharge between electrodes coated with a deuterated hydrocarbon liquid, here Santovac 5, to inhibit permanent electrode erosion and extend the lifetime of high-output neutron generator spark ion sources. Thompson parabola mass spectra show that principally hydrogen and deuterium ions are extracted from the ion source. Hydrogen is the chief residual gas phase species produced due to source operation in a stainless-steel vacuum chamber. The prominent features of the optical emission spectra of the discharge are C+ lines, the hydrogen Balmer Hα-line, and the C2 Swan bands. Operation of the ion source was studied in a conventional laboratory neutron generator. The source delivered an average deuteron current of ˜0.5 A nominal to the target in a 5 μs duration pulse at 1 Hz with target voltages of -80 to -100 kV. The thickness of the hydrocarbon liquid in the spark gap and the consistency thereof from spark to spark influences the deuteron yield and plays a role in determining the beam-focusing characteristics through the applied voltage necessary to break down the spark gap. Higher breakdown voltages result in larger ion beam spots on the target and vice-versa. Because the liquid self-heals and thereby inhibits permanent electrode erosion, the liquid-based source provides long life, with 104 pulses to date, and without clear evidence that, in principle, the lifetime could not be much longer. Initial experiments suggest that an alternative cylindrical target-type generator design can extract approximately 10 times the deuteron current from the source. Preliminary data using the deuterated source liquid as a neutron-producing target are also presented.

Optimization of the Nonradiative Lifetime of Molecular-Beam-Epitaxy (MBE)-Grown Undoped GaAs/AlGaAs Double Heterostructures (DH)

DTIC Science & Technology

2013-09-01

Optimization of the Nonradiative Lifetime of Molecular- Beam-Epitaxy (MBE)-Grown Undoped GaAs/AlGaAs Double Heterostructures (DH) by P...it to the originator. Army Research Laboratory Adelphi, MD 20783-1197 ARL-TR-6660 September 2013 Optimization of the Nonradiative ...REPORT TYPE Final 3. DATES COVERED (From - To) FY2013 4. TITLE AND SUBTITLE Optimization of the Nonradiative Lifetime of Molecular-Beam-Epitaxy

Status of the BL2 beam measurement of the neutron lifetime

NASA Astrophysics Data System (ADS)

Hoogerheide, Shannon Fogwell; BL2 Collaboration

2017-09-01

Neutron beta decay is the simplest example of nuclear beta decay and a precise value of the neutron lifetime is important for consistency tests of the Standard Model and Big Bang Nucleosynthesis models. A new measurement of the neutron lifetime, utilizing the beam method, is underway at the National Institute of Standards and Technology Center for Neutron Research with a projected uncertainty of 1 s. A review of the beam method and the technical improvements in this experiment will be presented. The status of the experiment, as well as preliminary measurements, beam characteristics, and early data will be discussed.

Progress toward a new beam measurement of the neutron lifetime

NASA Astrophysics Data System (ADS)

Hoogerheide, Shannon Fogwell; BL2 Collaboration

2017-01-01

Neutron beta decay is the simplest example of nuclear beta decay. A precise value of the neutron lifetime is important for consistency tests of the Standard Model and Big Bang Nucleosynthesis models. The beam neutron lifetime method requires the absolute counting of the decay protons in a neutron beam of precisely known flux. Recent work has resulted in improvements in both the neutron and proton detection systems that should permit a significant reduction in systematic uncertainties. A new measurement of the neutron lifetime using the beam method is underway at the National Institute of Standards and Technology Center for Neutron Research. The projected uncertainty of this new measurement is 1 s. An overview of the measurement, its current status, and the technical improvements will be discussed.

Rugged spin-polarized electron sources based on negative electron affinity GaAs photocathode with robust Cs2Te coating

NASA Astrophysics Data System (ADS)

Bae, Jai Kwan; Cultrera, Luca; DiGiacomo, Philip; Bazarov, Ivan

2018-04-01

Photocathodes capable of providing high intensity and highly spin-polarized electron beams with long operational lifetimes are of great interest for the next generation nuclear physics facilities like Electron Ion Colliders. We report on GaAs photocathodes activated by Cs2Te, a material well known for its robustness. GaAs activated by Cs2Te forms Negative Electron Affinity, and the lifetime for extracted charge is improved by a factor of 5 compared to that of GaAs activated by Cs and O2. The spin polarization of photoelectrons was measured using a Mott polarimeter and found to be independent from the activation method, thereby shifting the paradigm on spin-polarized electron sources employing photocathodes with robust coatings.

Low temperature grown GaNAsSb: A promising material for photoconductive switch application

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

Tan, K. H.; Yoon, S. F.; Wicaksono, S.

2013-09-09

We report a photoconductive switch using low temperature grown GaNAsSb as the active material. The GaNAsSb layer was grown at 200 °C by molecular beam epitaxy in conjunction with a radio frequency plasma-assisted nitrogen source and a valved antimony cracker source. The low temperature growth of the GaNAsSb layer increased the dark resistivity of the switch and shortened the carrier lifetime. The switch exhibited a dark resistivity of 10{sup 7} Ω cm, a photo-absorption of up to 2.1 μm, and a carrier lifetime of ∼1.3 ps. These results strongly support the suitability of low temperature grown GaNAsSb in the photoconductivemore » switch application.« less

Development of the front end test stand and vessel for extraction and source plasma analyses negative hydrogen ion sources at the Rutherford Appleton Laboratory.

PubMed

Lawrie, S R; Faircloth, D C; Letchford, A P; Perkins, M; Whitehead, M O; Wood, T; Gabor, C; Back, J

2014-02-01

The ISIS pulsed spallation neutron and muon facility at the Rutherford Appleton Laboratory (RAL) in the UK uses a Penning surface plasma negative hydrogen ion source. Upgrade options for the ISIS accelerator system demand a higher current, lower emittance beam with longer pulse lengths from the injector. The Front End Test Stand is being constructed at RAL to meet the upgrade requirements using a modified ISIS ion source. A new 10% duty cycle 25 kV pulsed extraction power supply has been commissioned and the first meter of 3 MeV radio frequency quadrupole has been delivered. Simultaneously, a Vessel for Extraction and Source Plasma Analyses is under construction in a new laboratory at RAL. The detailed measurements of the plasma and extracted beam characteristics will allow a radical overhaul of the transport optics, potentially yielding a simpler source configuration with greater output and lifetime.

A High-Power Broadband Terahertz Source Enabled by Three-Dimensional Light Confinement in a Plasmonic Nanocavity.

PubMed

Yardimci, Nezih Tolga; Cakmakyapan, Semih; Hemmati, Soroosh; Jarrahi, Mona

2017-06-23

The scope and potential uses of time-domain terahertz imaging and spectroscopy are mainly limited by the low optical-to-terahertz conversion efficiency of photoconductive terahertz sources. State-of-the-art photoconductive sources utilize short-carrier-lifetime semiconductors to recombine carriers that cannot contribute to efficient terahertz generation and cause additional thermal dissipation. Here, we present a novel photoconductive terahertz source that offers a significantly higher efficiency compared with terahertz sources fabricated on short-carrier-lifetime substrates. The key innovative feature of this source is the tight three-dimensional confinement of the optical pump beam around the terahertz nanoantennas that are used as radiating elements. This is achieved by means of a nanocavity formed by plasmonic structures and a distributed Bragg reflector. Consequently, almost all of the photo-generated carriers can be routed to the terahertz nanoantennas within a sub-picosecond time-scale. This results in a very strong, ultrafast current that drives the nanoantennas to produce broadband terahertz radiation. We experimentally demonstrate that this terahertz source can generate 4 mW pulsed terahertz radiation under an optical pump power of 720 mW over the 0.1-4 THz frequency range. This is the highest reported power level for terahertz radiation from a photoconductive terahertz source, representing more than an order of magnitude of enhancement in the optical-to-terahertz conversion efficiency compared with state-of-the-art photoconductive terahertz sources fabricated on short-carrier-lifetime substrates.

A High-Power Broadband Terahertz Source Enabled by Three-Dimensional Light Confinement in a Plasmonic Nanocavity

DOE PAGES

Yardimci, Nezih Tolga; Cakmakyapan, Semih; Hemmati, Soroosh; ...

2017-06-23

The scope and potential uses of time-domain terahertz imaging and spectroscopy are mainly limited by the low optical-to-terahertz conversion efficiency of photoconductive terahertz sources. State-of-theart photoconductive sources utilize short-carrier-lifetime semiconductors to recombine carriers that cannot contribute to efficient terahertz generation and cause additional thermal dissipation. Here, we present a novel photoconductive terahertz source that offers a significantly higher efficiency compared with terahertz sources fabricated on short-carrier-lifetime substrates. The key innovative feature of this source is the tight three-dimensional confinement of the optical pump beam around the terahertz nanoantennas that are used as radiating elements. This is achieved by means ofmore » a nanocavity formed by plasmonic structures and a distributed Bragg reflector. Consequently, almost all of the photo-generated carriers can be routed to the terahertz nanoantennas within a sub-picosecond time-scale. This results in a very strong, ultrafast current that drives the nanoantennas to produce broadband terahertz radiation. We experimentally demonstrate that this terahertz source can generate 4 mW pulsed terahertz radiation under an optical pump power of 720 mW over the 0.1–4 THz frequency range. This is the highest reported power level for terahertz radiation from a photoconductive terahertz source, representing more than an order of magnitude of enhancement in the optical-to-terahertz conversion efficiency compared with state-of-the-art photoconductive terahertz sources fabricated on shortcarrier- lifetime substrates.« less

Barium-Dispenser Thermionic Cathode

NASA Technical Reports Server (NTRS)

Wintucky, Edwin G.; Green, M.; Feinleib, M.

1989-01-01

Improved reservoir cathode serves as intense source of electrons required for high-frequency and often high-output-power, linear-beam tubes, for which long operating lifetime important consideration. High emission-current densities obtained through use of emitting surface of relatively-low effective work function and narrow work-function distribution, consisting of coat of W/Os deposited by sputtering. Lower operating temperatures and enhanced electron emission consequently possible.

Chevron beam dump for ITER edge Thomson scattering system.

PubMed

Yatsuka, E; Hatae, T; Vayakis, G; Bassan, M; Itami, K

2013-10-01

This paper contains the design of the beam dump for the ITER edge Thomson scattering system and mainly concerns its lifetime under the harsh thermal and electromagnetic loads as well as tight space allocation. The lifetime was estimated from the multi-pulse laser-induced damage threshold. In order to extend its lifetime, the structure of the beam dump was optimized. A number of bent sheets aligned parallel in the beam dump form a shape called a chevron which enables it to avoid the concentration of the incident laser pulse energy. The chevron beam dump is expected to withstand thermal loads due to nuclear heating, radiation from the plasma, and numerous incident laser pulses throughout the entire ITER project with a reasonable margin for the peak factor of the beam profile. Structural analysis was also carried out in case of electromagnetic loads during a disruption. Moreover, detailed issues for more accurate assessments of the beam dump's lifetime are clarified. Variation of the bi-directional reflection distribution function (BRDF) due to erosion by or contamination of neutral particles derived from the plasma is one of the most critical issues that needs to be resolved. In this paper, the BRDF was assumed, and the total amount of stray light and the absorbed laser energy profile on the beam dump were evaluated.

Studies in High Current Density Ion Sources for Heavy Ion Fusion Applications

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

Chacon-Golcher, Edwin

This dissertation develops diverse research on small (diameter ~ few mm), high current density (J ~ several tens of mA/cm 2) heavy ion sources. The research has been developed in the context of a programmatic interest within the Heavy Ion Fusion (HIF) Program to explore alternative architectures in the beam injection systems that use the merging of small, bright beams. An ion gun was designed and built for these experiments. Results of average current density yield () at different operating conditions are presented for K + and Cs + contact ionization sources and potassium aluminum silicate sources. Maximum valuesmore » for a K + beam of ~90 mA/cm 2 were observed in 2.3 μs pulses. Measurements of beam intensity profiles and emittances are included. Measurements of neutral particle desorption are presented at different operating conditions which lead to a better understanding of the underlying atomic diffusion processes that determine the lifetime of the emitter. Estimates of diffusion times consistent with measurements are presented, as well as estimates of maximum repetition rates achievable. Diverse studies performed on the composition and preparation of alkali aluminosilicate ion sources are also presented. In addition, this work includes preliminary work carried out exploring the viability of an argon plasma ion source and a bismuth metal vapor vacuum arc (MEVVA) ion source. For the former ion source, fast rise-times (~ 1 μs), high current densities (~ 100 mA/cm +) and low operating pressures (< 2 mtorr) were verified. For the latter, high but acceptable levels of beam emittance were measured (ε n ≤ 0.006 π· mm · mrad) although measured currents differed from the desired ones (I ~ 5mA) by about a factor of 10.« less

The continued development of the Spallation Neutron Source external antenna H- ion sourcea)

NASA Astrophysics Data System (ADS)

Welton, R. F.; Carmichael, J.; Desai, N. J.; Fuga, R.; Goulding, R. H.; Han, B.; Kang, Y.; Lee, S. W.; Murray, S. N.; Pennisi, T.; Potter, K. G.; Santana, M.; Stockli, M. P.

2010-02-01

The U.S. Spallation Neutron Source (SNS) is an accelerator-based, pulsed neutron-scattering facility, currently in the process of ramping up neutron production. In order to ensure that the SNS will meet its operational commitments as well as provide for future facility upgrades with high reliability, we are developing a rf-driven, H- ion source based on a water-cooled, ceramic aluminum nitride (AlN) plasma chamber. To date, early versions of this source have delivered up to 42 mA to the SNS front end and unanalyzed beam currents up to ˜100 mA (60 Hz, 1 ms) to the ion source test stand. This source was operated on the SNS accelerator from February to April 2009 and produced ˜35 mA (beam current required by the ramp up plan) with availability of ˜97%. During this run several ion source failures identified reliability issues, which must be addressed before the source re-enters production: plasma ignition, antenna lifetime, magnet cooling, and cooling jacket integrity. This report discusses these issues, details proposed engineering solutions, and notes progress to date.

How to Reach a Thousand-Second in-Plane Polarization Lifetime with 0.97 - GeV / c Deuterons in a Storage Ring

DOE PAGES

Guidoboni, G.; Stephenson, E.; Andrianov, S.; ...

2016-07-28

Here, we observe a deuteron beam polarization lifetime near 1000 s in the horizontal plane of a magnetic storage ring (COSY). This long spin coherence time is maintained through a combination of beam bunching, electron cooling, sextupole field corrections, and the suppression of collective effects through beam current limits. This record lifetime is required for a storage ring search for an intrinsic electric dipole moment on the deuteron at a statistical sensitivity level approaching 10 -29 $e$ cm.

Measuring The Neutron Lifetime to One Second Using in Beam Techniques

NASA Astrophysics Data System (ADS)

Mulholland, Jonathan; NIST In Beam Lifetime Collaboration

2013-10-01

The decay of the free neutron is the simplest nuclear beta decay and is the prototype for charged current semi-leptonic weak interactions. A precise value for the neutron lifetime is required for consistency tests of the Standard Model and is an essential parameter in the theory of Big Bang Nucleosynthesis. A new measurement of the neutron lifetime using the in-beam method is planned at the National Institute of Standards and Technology Center for Neutron Research. The systematic effects associated with the in-beam method are markedly different than those found in storage experiments utilizing ultracold neutrons. Experimental improvements, specifically recent advances in the determination of absolute neutron fluence, should permit an overall uncertainty of 1 second on the neutron lifetime. The technical improvements in the in-beam technique, and the path toward improving the precision of the new measurement will be discussed.

Measurement of the Neutron Lifetime Using a Proton Trap

NASA Astrophysics Data System (ADS)

Dewey, M. S.; Gilliam, D. M.; Nico, J. S.; Wietfeldt, F. E.; Fei, X.; Snow, W. M.; Greene, G. L.; Pauwels, J.; Eykens, R.; Lamberty, A.; van Gestel, J.

2003-10-01

We report a new measurement of the neutron decay lifetime by the absolute counting of in-beam neutrons and their decay protons. Protons were confined in a quasi-Penning trap and counted with a silicon detector. The neutron beam fluence was measured by capture in a thin 6LiF foil detector with known absolute efficiency. The combination of these simultaneous measurements gives the neu­tron lifetime: τn=(886.8±1.2[stat]±3.2[syst]) s. The systematic uncertainty is dominated by uncertainties in the mass of the 6LiF deposit and the 6Li(n,t) cross section. This is the most precise measurement of the neutron lifetime to date using an in-beam method.

Optimizing integrated luminosity of future hadron colliders

NASA Astrophysics Data System (ADS)

Benedikt, Michael; Schulte, Daniel; Zimmermann, Frank

2015-10-01

The integrated luminosity, a key figure of merit for any particle-physics collider, is closely linked to the peak luminosity and to the beam lifetime. The instantaneous peak luminosity of a collider is constrained by a number of boundary conditions, such as the available beam current, the maximum beam-beam tune shift with acceptable beam stability and reasonable luminosity lifetime (i.e., the empirical "beam-beam limit"), or the event pileup in the physics detectors. The beam lifetime at high-luminosity hadron colliders is largely determined by particle burn off in the collisions. In future highest-energy circular colliders synchrotron radiation provides a natural damping mechanism, which can be exploited for maximizing the integrated luminosity. In this article, we derive analytical expressions describing the optimized integrated luminosity, the corresponding optimum store length, and the time evolution of relevant beam parameters, without or with radiation damping, while respecting a fixed maximum value for the total beam-beam tune shift or for the event pileup in the detector. Our results are illustrated by examples for the proton-proton luminosity of the existing Large Hadron Collider (LHC) at its design parameters, of the High-Luminosity Large Hadron Collider (HL-LHC), and of the Future Circular Collider (FCC-hh).

Carbon Nanotube Bundle Array Cold Cathodes for THz Vacuum Tube Sources

NASA Astrophysics Data System (ADS)

Manohara, Harish M.; Toda, Risaku; Lin, Robert H.; Liao, Anna; Bronikowski, Michael J.; Siegel, Peter H.

2009-12-01

We present high performance cold cathodes composed of arrays of carbon nanotube bundles that routinely produce > 15 A/cm2 at applied fields of 5 to 8 V/µm without any beam focusing. They have exhibited robust operation in poor vacuums of 10-6 to 10-4 Torr- a typically achievable range inside hermetically sealed microcavities. A new double-SOI process was developed to monolithically integrate a gate and additional beam tailoring electrodes. The ability to design the electrodes for specific requirements makes carbon nanotube field emission sources extremely flexible. The lifetime of these cathodes is found to be affected by two effects: a gradual decay of emission due to anode sputtering, and catastrophic failure because of dislodging of CNT bundles at high fields ( > 10 V/µm).

Simulation of Swap-Out Reliability For The Advance Photon Source Upgrade

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

Borland, M.

2017-06-01

The proposed upgrade of the Advanced Photon Source (APS) to a multibend-achromat lattice relies on the use of swap-out injection to accommodate the small dynamic acceptance, allow use of unusual insertion devices, and minimize collective effects at high single-bunch charge. This, combined with the short beam lifetime, will make injector reliability even more important than it is for top-up operation. We used historical data for the APS injector complex to obtain probability distributions for injector up-time and down-time durations. Using these distributions, we simulated several years of swap-out operation for the upgraded lattice for several operatingmodes. The results indicate thatmore » obtaining very high availability of beam in the storage ring will require improvements to injector reliability.« less

Determining the wavelength spectrum of neutrons on the NG6 beam line at NCNR

NASA Astrophysics Data System (ADS)

Ivanov, Juliet

2016-09-01

Historically, in-beam experiments and bottle experiments have been performed to determine the lifetime of a free neutron. However, these two different experimental techniques have provided conflicting results. It is crucial to precisely and accurately elucidate the neutron lifetime for Big Bang Nucleosynthesis calculations and to investigate physics beyond the Standard Model. Therefore, we aimed to understand and minimize systematic errors present in the neutron beam experiment at the NIST Center for Neutron Research (NCNR). In order to reduce the uncertainty related to wavelength dependent corrections present in previous beam experiments, the wavelength spectrum of the NCNR reactor cold neutron beam must be known. We utilized a beam chopper and lithium detector to characterize the wavelength spectrum on the NG6 beam line at the NCNR. The experimental design and techniques employed will be discussed, and our results will be presented. Future plans to utilize our findings to improve the neutron lifetime measurement at NCNR will also be described.

Rod-filter-field optimization of the J-PARC RF-driven H{sup −} ion source

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

Ueno, A., E-mail: akira.ueno@j-parc.jp; Ohkoshi, K.; Ikegami, K.

2015-04-08

In order to satisfy the Japan Proton Accelerator Research Complex (J-PARC) second-stage requirements of an H{sup −} ion beam of 60mA within normalized emittances of 1.5πmm•mrad both horizontally and vertically, a flat top beam duty factor of 1.25% (500μs×25Hz) and a life-time of longer than 1month, the J-PARC cesiated RF-driven H{sup −} ion source was developed by using an internal-antenna developed at the Spallation Neutron Source (SNS). Although rod-filter-field (RFF) is indispensable and one of the most beam performance dominative parameters for the RF-driven H{sup −} ion source with the internal-antenna, the procedure to optimize it is not established. Inmore » order to optimize the RFF and establish the procedure, the beam performances of the J-PARC source with various types of rod-filter-magnets (RFMs) were measured. By changing RFM’s gap length and gap number inside of the region projecting the antenna inner-diameter along the beam axis, the dependence of the H{sup −} ion beam intensity on the net 2MHz-RF power was optimized. Furthermore, the fine-tuning of RFM’s cross-section (magnetmotive force) was indispensable for easy operation with the temperature (T{sub PE}) of the plasma electrode (PE) lower than 70°C, which minimizes the transverse emittances. The 5% reduction of RFM’s cross-section decreased the time-constant to recover the cesium effects after an slightly excessive cesiation on the PE from several 10 minutes to several minutes for T{sub PE} around 60°C.« less

Chevron beam dump for ITER edge Thomson scattering system

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

Yatsuka, E.; Hatae, T.; Bassan, M.

This paper contains the design of the beam dump for the ITER edge Thomson scattering system and mainly concerns its lifetime under the harsh thermal and electromagnetic loads as well as tight space allocation. The lifetime was estimated from the multi-pulse laser-induced damage threshold. In order to extend its lifetime, the structure of the beam dump was optimized. A number of bent sheets aligned parallel in the beam dump form a shape called a chevron which enables it to avoid the concentration of the incident laser pulse energy. The chevron beam dump is expected to withstand thermal loads due tomore » nuclear heating, radiation from the plasma, and numerous incident laser pulses throughout the entire ITER project with a reasonable margin for the peak factor of the beam profile. Structural analysis was also carried out in case of electromagnetic loads during a disruption. Moreover, detailed issues for more accurate assessments of the beam dump's lifetime are clarified. Variation of the bi-directional reflection distribution function (BRDF) due to erosion by or contamination of neutral particles derived from the plasma is one of the most critical issues that needs to be resolved. In this paper, the BRDF was assumed, and the total amount of stray light and the absorbed laser energy profile on the beam dump were evaluated.« less

Implementation of Design Changes Towards a More Reliable, Hands-off Magnetron Ion Source

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

Sosa, A.; Bollinger, D. S.; Karns, P. R.

As the main H- ion source for the accelerator complex, magnetron ion sources have been used at Fermilab since the 1970’s. At the offline test stand, new R&D is carried out to develop and upgrade the present magnetron-type sources of H- ions of up to 80 mA and 35 keV beam energy in the context of the Proton Improvement Plan. The aim of this plan is to provide high-power proton beams for the experiments at FNAL. In order to reduce the amount of tuning and monitoring of these ion sources, a new electronic system consisting of a current-regulated arc dischargemore » modulator allow the ion source to run at a constant arc current for improved beam output and operation. A solenoid-type gas valve feeds H2 gas into the source precisely and independently of ambient temperature. This summary will cover several studies and design changes that have been tested and will eventually be implemented on the operational magnetron sources at Fermilab. Innovative results for this type of ion source include cathode geometries, solenoid gas valves, current controlled arc pulser, cesium boiler redesign, gas mixtures of hydrogen and nitrogen, and duty factor reduction, with the aim to improve source lifetime, stability, and reducing the amount of tuning needed. In this summary, I will highlight the advances made in ion sources at Fermilab and will outline the directions of the continuing R&D effort.« less

Maintenance and operation procedure, and feedback controls of the J-PARC RF-driven H{sup −} ion source

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

Ueno, A., E-mail: akira.ueno@j-parc.jp; Ohkoshi, K.; Ikegami, K.

2015-04-08

In order to satisfy the Japan Proton Accelerator Research Complex (J-PARC) second stage requirements of an H{sup −} ion beam of 60mA within normalized emittances of 1.5πmm•mrad both horizontally and vertically, a flat top beam duty factor of 1.25% (500μs×25Hz) and a life-time of longer than 1month, the J-PARC cesiated RF-driven H{sup −} ion source was developed by using an internal-antenna developed at the Spallation Neutron Source (SNS). The maintenance and operation procedure to minimize the plasma chamber (PCH) replacement time on the beam line, which is very important to maximize the J-PARC beam time especially for an antenna failure,more » is presented in this paper. The PCH preserved by filling argon (Ar) gas inside after pre-conditioning including pre-cesiation to produce the required beam at a test-stand successfully produced the required beam on the beam line with slight addition of cesium (Cs). The methods of the feedback controls of a 2MHz-RF-matching, an H{sup −} ion beam intensity and the addition of Cs are also presented. The RF-matching feedback by using two vacuum variable capacitors (VVCs) and RF-frequency shift produced the almost perfect matching with negligibly small reflected RF-power. The H{sup −} ion beam intensity was controlled within errors of ±0.1mA by the RF-power feedback. The amount of Cs was also controlled by remotely opening a Cs-valve to keep the RF-power lower than a settled value.« 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.

RF-driven ion source with a back-streaming electron dump

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

Kwan, Joe; Ji, Qing

A novel ion source is described having an improved lifetime. The ion source, in one embodiment, is a proton source, including an external RF antenna mounted to an RF window. To prevent backstreaming electrons formed in the beam column from striking the RF window, a back streaming electron dump is provided, which in one embodiment is formed of a cylindrical tube, open at one end to the ion source chamber and capped at its other end by a metal plug. The plug, maintained at the same electrical potential as the source, captures these backstreaming electrons, and thus prevents localized heatingmore » of the window, which due to said heating, might otherwise cause window damage.« less

Progress toward a new measurement of the neutron lifetime

NASA Astrophysics Data System (ADS)

Grammer, Kyle

2015-10-01

Free neutron decay is the simplest nuclear beta decay. A precise value for the neutron lifetime is valuable for standard model consistency tests and Big Bang Nucleosynthesis models. There is a disagreement between the measured neutron lifetime from cold neutron beam experiments and ultracold neutron storage experiments. A new measurement of the neutron lifetime using the beam method is planned at the National Institute of Standards and Technology Center for Neutron Research. Experimental improvements should result in a 1s uncertainty measurement of the neutron lifetime. The technical improvements, recent apparatus tests, and the path towards the new measurement will be discussed. This work is supported by DOE Office of Science, NIST, and NSF.

Progress toward a new measurement of the neutron lifetime

NASA Astrophysics Data System (ADS)

Grammer, Kyle

2015-04-01

Free neutron decay is the simplest nuclear beta decay. A precise value for the neutron lifetime is valuable for standard model consistency tests and Big Bang Nucleosynthesis models. There is a disagreement between the measured neutron lifetime from cold neutron beam experiments and ultracold neutron storage experiments. A new measurement of the neutron lifetime using the beam method is planned at the National Institute of Standards and Technology Center for Neutron Research. Experimental improvements should result in a 1s uncertainty measurement of the neutron lifetime. The technical improvements and the path towards the new measurement will be discussed. This work is supported by DOE Office of Science, NIST, and NSF.

Performance evaluation of PEP

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

Zisman, M.S.

An investigation of collective effects has been undertaken to assess the possibilities for using the low emittance operating mode of the PEP storage ring as a dedicated source of synchrotron radiation. Beam current limitations associated with longitudinal and transverse instabilities, and the expected emittance growth due to intrabeam scattering have been studied as a function of beam energy. Calculations of the beam lifetime due to Touschek and gas scattering are presented, and the growth times of coupled-bunch instabilities are estimated. In general, the results are encouraging, and no fundamental problems have been uncovered. It appears that beam currents up tomore » about 10 mA per bunch should be achievable, and that the emittance growth is not a severe problem at an energy of about 8 GeV. A feedback system to deal with coupled-bunch instabilities is likely to be required. 7 refs., 13 figs.« less

A Polarized Electron RF Photoinjector Using the Plane-Wave-Transformer (PWT) Design

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

Clendenin, James E

Polarized electron beams are now in routine use in particle accelerators for nuclear and high energy physics experiments. These beams are presently produced by dc-biased photoelectron sources combined with rf chopping and bunching systems with inherently high transverse emittances. Low emittances can be produced with an rf gun, but the vacuum environment has until now been considered too harsh to support a negative electron affinity GaAs photocathode. We propose to significantly improve the vacuum conditions by adapting a PWT rf photoinjector to achieve reasonable cathode emission rates and lifetimes. This adaptation can also be combined with special optics that willmore » result in a flat beam with a normalized rms emittance in the narrow dimension that may be as low as 10{sup -8} m.« less

Intra-Beam and Touschek Scattering Computations for Beam with Non-Gaussian Longitudinal Distributions

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

Xiao, A.; Borland, M.

Both intra-beamscattering (IBS) and the Touschek effect become prominent formulti-bend-achromat- (MBA-) based ultra-low-emittance storage rings. To mitigate the transverse emittance degradation and obtain a reasonably long beam lifetime, a higher harmonic rf cavity (HHC) is often proposed to lengthen the bunch. The use of such a cavity results in a non-gaussian longitudinal distribution. However, common methods for computing IBS and Touschek scattering assume Gaussian distributions. Modifications have been made to several simulation codes that are part of the elegant [1] toolkit to allow these computations for arbitrary longitudinal distributions. After describing thesemodifications, we review the results of detailed simulations formore » the proposed hybrid seven-bend-achromat (H7BA) upgrade lattice [2] for the Advanced Photon Source.« less

Emittance measurements for optimum operation of the J-PARC RF-driven H{sup −} ion source

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

Ueno, A., E-mail: akira.ueno@j-parc.jp; Ohkoshi, K.; Ikegami, K.

2015-04-08

In order to satisfy the Japan Proton Accelerator Research Complex (J-PARC) second stage requirements of an H{sup −} ion beam of 60mA within normalized emittances of 1.5πmm•mrad both horizontally and vertically, a flat top beam duty factor of 1.25% (500μs×25Hz) and a life-time of longer than 1month, the J-PARC cesiated RF-driven H{sup −} ion source was developed by using an internal-antenna developed at the Spallation Neutron Source (SNS). The transverse emittances of the source were measured with various conditions to find out the optimum operation conditions minimizing the horizontal and vertical rms normalized emittances. The transverse emittances were most effectivelymore » reduced by operating the source with the plasma electrode temperature lower than 70°C. The optimum value of the cesium (Cs) density around the beam hole of the plasma electrode seems to be proportional to the plasma electrode temperature. The fine control of the Cs density is indispensable, since the emittances seem to increase proportionally to the excessiveness of the Cs density. Furthermore, the source should be operated with the Cs density beyond a threshold value, since the plasma meniscus shape and the ellipse parameters of the transverse emittances seem to be changed step-function-likely on the threshold Cs value.« less

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.

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

Bischoff, Lothar, E-mail: l.bischoff@hzdr.de; Mazarov, Paul, E-mail: Paul.Mazarov@raith.de; Bruchhaus, Lars, E-mail: Lars.Bruchhaus@raith.de

Today, Focused Ion Beam (FIB) processing is nearly exclusively based on gallium Liquid Metal Ion Sources (LMIS). But, many applications in the μm- or nm range could benefit from ion species other than gallium: local ion implantation, ion beam mixing, ion beam synthesis, or Focused Ion Beam Lithography (IBL). Therefore, Liquid Metal Alloy Ion Sources (LMAIS) represent a promising alternative to expand the remarkable application fields for FIB. Especially, the IBL process shows potential advantages over, e.g., electron beam or other lithography techniques: direct, resistless, and three-dimensional patterning, enabling a simultaneous in-situ process control by cross-sectioning and inspection. Taking additionallymore » into account that the used ion species influences significantly the physical and chemical nature of the resulting nanostructures—in particular, the electrical, optical, magnetic, and mechanic properties leading to a large potential application area which can be tuned by choosing a well suited LMAIS. Nearly half of the elements of the periodic table are recently available in the FIB technology as a result of continuous research in this area during the last forty years. Key features of a LMAIS are long life-time, high brightness, and stable ion current. Recent developments could make these sources feasible for nano patterning issues as an alternative technology more in research than in industry. The authors will review existing LMAIS, LMIS other than Ga, and binary and ternary alloys. These physical properties as well as the fabrication technology and prospective domains for modern FIB applications will similarly be reviewed. Other emerging ion sources will be also presented and their performances discussed.« less

Diagnostic for a high-repetition rate electron photo-gun and first measurements

NASA Astrophysics Data System (ADS)

Filippetto, D.; Doolittle, L.; Huang, G.; Norum, E.; Portmann, G.; Qian, H.; Sannibale, F.

2015-05-01

The APEX electron source at LBNL combines the high-repetition-rate with the high beam brightness typical of photoguns, delivering low emittance electron pulses at MHz frequency. Proving the high beam quality of the beam is an essential step for the success of the experiment, opening the doors of the high average power to brightness-hungry applications as X-Ray FELs, MHz ultrafast electron diffraction etc.. As first step, a complete characterization of the beam parameters is foreseen at the Gun beam energy of 750 keV. Diagnostics for low and high current measurements have been installed and tested, and measurements of cathode lifetime and thermal emittance in a RF environment with mA current performed. The recent installation of a double slit system, a deflecting cavity and a high precision spectrometer, allow the exploration of the full 6D phase space. Here we discuss the present layout of the machine and future upgrades, showing the latest results at low and high repetition rate, together with the tools and techniques used.

Multipurpose neutron generators based on the radio frequency quadrupole linear accelerator

NASA Astrophysics Data System (ADS)

Hamm, Robert W.

2000-12-01

Neutron generators based on the Radio Frequency Quadrupole accelerator are now used for a variety of applications. These compact linear accelerators can produce from 108 to more than 1013 neutrons/second using either proton or deuteron beams to bombard beryllium targets. They exhibit long lifetimes at full output, as there is little target or beam degradation. Since they do not use radioactive materials, licensing requirements are less stringent than for isotopic sources or tritium sealed tube generators. The light weight and compact size of these robust systems make them transportable. The low divergence output beam from the RFQ also allows use of a remote target, which can reduce the seize of the shielding and moderator. The RFQ linac can be designed with a wide range of output beam energy and used with other targets such as lithium and deuterium to produce a neutron spectrum tailored to a specific application. These pulsed systems are well-suited for applications requiring a high peak neutron flux, including activation analysis of very short-lived reaction products. They can replace conventional sources in non-destructive testing applications such as thermal or fast neutron radiography, and can also be used for cancer therapy.

Exciton diffusion coefficient measurement in ZnO nanowires under electron beam irradiation.

PubMed

Donatini, Fabrice; Pernot, Julien

2018-03-09

In semiconductor nanowires (NWs) the exciton diffusion coefficient can be determined using a scanning electron microscope fitted with a cathodoluminescence system. High spatial and temporal resolution cathodoluminescence experiments are needed to measure independently the exciton diffusion length and lifetime in single NWs. However, both diffusion length and lifetime can be affected by the electron beam bombardment during observation and measurement. Thus, in this work the exciton lifetime in a ZnO NW is measured versus the electron beam dose (EBD) via a time-resolved cathodoluminescence experiment with a temporal resolution of 50 ps. The behavior of the measured exciton lifetime is consistent with our recent work on the EBD dependence of the exciton diffusion length in similar NWs investigated under comparable SEM conditions. Combining the two results, the exciton diffusion coefficient in ZnO is determined at room temperature and is found constant over the full span of EBD.

Liquid metal ion source and alloy for ion emission of multiple ionic species

DOEpatents

Clark, Jr., William M.; Utlaut, Mark W.; Wysocki, Joseph A.; Storms, Edmund K.; Szklarz, Eugene G.; Behrens, Robert G.; Swanson, Lynwood W.; Bell, Anthony E.

1987-06-02

A liquid metal ion source and alloy for the simultaneous ion evaporation of arsenic and boron, arsenic and phosphorus, or arsenic, boron and phosphorus. The ionic species to be evaporated are contained in palladium-arsenic-boron and palladium-arsenic-boron-phosphorus alloys. The ion source, including an emitter means such as a needle emitter and a source means such as U-shaped heater element, is preferably constructed of rhenium and tungsten, both of which are readily fabricated. The ion sources emit continuous beams of ions having sufficiently high currents of the desired species to be useful in ion implantation of semiconductor wafers for preparing integrated circuit devices. The sources are stable in operation, experience little corrosion during operation, and have long operating lifetimes.

Helium Bubble Injection Solution To The Cavitation Damage At The Spallation Neutron Source

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

Francis, M. W.; Ruggles, A. E.

2009-03-10

The Spallation Neutron Source (SNS) is one of the largest science projects in the United States, with total cost near 1.4 Billion Dollars. The limiting factor of the facility had always been assumed to be the lifetime of the target window due to radiation damage. After further investigation, the lifetime of the target was determined not to be limited by radiation damage but by cavitation damage. The cavitation damage derives from pressure waves caused by the beam energy deposition. Vapor bubbles form when low to negative pressures occur in the mercury near the stainless steel target window due to wavemore » interaction with the structure. Collapse of these bubbles can focus wave energy in small liquid jets that erode the window surface. Compressibility of the mercury can be enhanced to reduce the amplitude of the pressure wave caused by the beam energy deposition. To enhance compressibility, small (10 to 30 micron diameter) gas bubbles could be injected into the bulk of the mercury. Solubility and diffusivity parameters of inert gas in mercury are required for a complete mechanical simulation and engineering of these strategies. Using current theoretical models, one obtains a theoretical Henry coefficient of helium in mercury on the order of 3.9E15 Pa-molHg/molHe at 300 K. This low solubility was confirmed by a direct, offline experimental method. Mercury was charged with helium and any pressure change was recorded. Any pressure change was attributed to gas going into solution. Therefore, with the sensitivity of the experiment, a lower limit of 9E12 Pa-molHg/molHe was placed on the mercury-helium system. These values guarantee a stable bubble lifetime needed within the SNS mercury target to mitigate cavitation issues.« less

50-mJ, 1-kHz Yb:YAG thin-disk regenerative amplifier with 969-nm pulsed pumping

NASA Astrophysics Data System (ADS)

Chyla, Michal; Miura, Taisuke; Smrž, Martin; Severova, Patricie; Novak, Ondrej; Endo, Akira; Mocek, Tomas

2014-02-01

We are developing a 100-mJ Yb:YAG thin-disk regenerative amplifier operating at 1-kHz repetition rate pumped at zero-phonon-line (968.825-nm1) and delivering 1-2 ps pulses for EUV plasma sources applicable in science and industry. Recently we achieved the output energy of nearly 50-mJ from a single laser-head cavity with good beam quality (M2<1.2) as well as stable beam-pointing (<4μrad). Applying pulsed pumping with the pulse duration shorter than the upper state lifetime of Yb:YAG helps to reduce the ASE and thermal loading of the thin-disk.

In situ monitoring of stacking fault formation and its carrier lifetime mediation in p-type 4H-SiC

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

Chen, Bin, E-mail: chenbinmse@gmail.com; Chen, Jun; Yao, Yuanzhao

Using the fine control of an electron beam (e-beam) in scanning electron microscopy with the capabilities of both electrical and optical imaging, the stacking fault (SF) formation together with its tuning of carrier lifetime was in situ monitored and investigated in p-type 4H-SiC homoepitaxial films. The SFs were formed through engineering basal plane dislocations with the energy supplied by the e-beam. The e-beam intensity required for the SF formation in the p-type films was ∼100 times higher than that in the n-type ones. The SFs reduced the minority-carrier lifetime in the p-type films, which was opposite to that observed inmore » the n-type case. The reason for the peculiar SF behavior in the p-type 4H-SiC is discussed with the cathodoluminescence results.« less

Improvements of the target lifetime in the RHIC polarimeter

NASA Astrophysics Data System (ADS)

Steski, D. B.; Huang, H.; Kewisch, J.; Sukhanova, L.; Zelenski, A.

2018-05-01

The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) is the only collider in the world to collide polarized protons. It is critical to the RHIC experimental program that the polarization of the proton beam is measured. This is accomplished with the Coulomb Nuclear Interference (CNI) polarimeter. The targets used in the RHIC CNI polarimeter are 50 nm thick, 25 mm long and <10 µm wide. As the beam intensity in RHIC has increased and the beam size has decreased, the lifetime of these targets has decreased dramatically. During the 2013 polarized proton experimental run, the targets needed to be replaced twice. This resulted in additional work and lost beam time. Before the 2015 experimental run, metal shields were installed around the ends of the targets which greatly improved the target lifetime. The results from the 2015 experimental run and plans for the 2017 experimental run will be discussed.

Plans for a measurement of the neutron lifetime to better than 0.3s using a Penning trap and absolute measurement of neutron fluence

NASA Astrophysics Data System (ADS)

Mulholland, Jonathan; NBL3 Collaboration

2014-09-01

The decay of the free neutron is the prototypical charged current semi-leptonic weak process. A precise value for the neutron lifetime is required for consistency tests of the Standard Model and is needed to predict the primordial He4 abundance from the theory of Big Bang Nucleosynthesis. Plans are being made for an in-beam measurement of the neutron lifetime with an anticipated 0.3s of uncertainty or better. This effort is part of a phased campaign of neutron lifetime measurements based at the NIST Center for Neutron Research, using the Sussex-ILL-NIST technique. Advances in neutron fluence measurement, used in to provide the best existing in-beam determination of the neutron lifetime, as well as new silicon detector technology, in use now at LANSCE, address the two largest contributors to the uncertainty of in-beam measurements-the statistical uncertainty associated with proton counting and the systematic uncertainty in the neutron fluence measurement. The experimental design and projected uncertainties for the 0.3s measurement will be discussed.

Demonstration of miniaturized 20mW CW 280nm and 266nm solid-state UV laser sources

NASA Astrophysics Data System (ADS)

Landru, Nicolas; Georges, Thierry; Beaurepaire, Julien; Le Guen, Bruno; Le Bail, Guy

2015-02-01

Visible 561 nm and 532 nm laser emissions from 14-mm long DPSS monolithic cavities are frequency converted to deep UV 280 nm and 266 nm in 16-mm long monolithic external cavities. Wavelength conversion is fully insensitive to mechanical vibrations and the whole UV laser sources fit in a miniaturized housing. More than 20 mW deep UV laser emission is demonstrated with high power stability, low noise and good beam quality. Aging tests are in progress but long lifetimes are expected thanks to the cavity design. Protein detection and deep UV resonant Raman spectroscopy are applications that could benefit from these laser sources.

Robert R. Wilson Prize I: Intrabeam Scattering and Touschek Effect

NASA Astrophysics Data System (ADS)

Piwinski, Anton

2017-01-01

Intrabeam scattering and the Touschek effect are explained and compared. Especially intrabeam scattering plays an important role in colliders and synchrotron radiation sources where it limits the beam lifetime and the brightness,respectively. A short history of the consequences of both effects in different accelerators is given. An invariant due to intrabeam scattering is discussed which shows that only below transition energy a stable particle distribution is possible whereas above transition energy a stable distribution cannot exist.

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.

Fluorescence lifetime imaging with near-infrared dyes

NASA Astrophysics Data System (ADS)

Becker, Wolfgang; Shcheslavskiy, Vladislav

2013-02-01

Near-infrared (NIR) dyes are used as fluorescence markers in small-animal imaging and in diffuse optical tomography of the human brain. In these applications it is important to know whether the dyes bind to proteins or other tissue constituents, and whether their fluorescence lifetimes depend on the targets they are bound to. Unfortunately, neither the lasers nor the detectors of commonly used confocal and multiphoton laser scanning microscopes allow for excitation and detection of NIR fluorescence. We therefore upgraded existing confocal TCSPC FLIM systems with NIR lasers and NIR sensitive detectors. In multiphoton systems we used the Ti:Sa laser as a one-photon excitation source in combination with an NIR-sensitive detector in the confocal beam path. We tested a number of NIR dyes in biological tissue. Some of them showed clear lifetime changes depending on the tissue structures they are bound to. We therefore believe that NIR FLIM can deliver supplementary information on the tissue constitution and on local biochemical parameters.

Oblate Field-Reversed Configuration Experiments with Neutral Beam Injection

NASA Astrophysics Data System (ADS)

T., II; Gi, K.; Umezawa, T.; Inomoto, M.; Ono, Y.

2011-11-01

The effect of energetic beam ions on oblate Field-Reversed Configurations (FRCs) has been studied experimentally in the TS-4 plasma merging device. In order to examine its kinetic effects, we developed an economical pulsed Neutral Beam Injection (NBI) system by using a washer gun plasma source and finally attained the beam power of 0.6 MW (15 kV, 40 A) for its pulse length of 0.5 ms, longer than the FRC lifetime in TS-4. The Monte Carlo simulation indicates that the tangential NB ions of 15 keV are trapped between the magnetic axis and the separatrix. We found that two merging high-s (s is plasma size normalized by ion gyroradius) hydrogen spheromaks with opposite helicities relaxed into the large scale FRC with poloidal flux as high as 15 mWb under the assistance of the NBI. Without the assistance of NBI, however, they did not relax to an FRC but to another spheromak. These facts suggest some ion kinetic effects such as toroidal ion flow are essential to FRC stability. Recently, two new NB sources with acceleration voltage and current of 15 kV and 20 A were installed on the TS-4 device on the midplane for tangential injection, increasing the beam power over 1 MW. We will start the upgraded FRC experiments using the 1 MW NBI for ion flow control.

Dynamics of Ion Beam Charge Neutralization by Ferroelectric Plasma Sources

NASA Astrophysics Data System (ADS)

Stepanov, Anton D.; Gilson, Erik P.; Grisham, Larry R.; Kaganovich, Igor D.; Davidson, Ronald C.; Ji, Qing; Persaud, Arun; Seidl, Peter A.; Schenkel, Thomas

2016-10-01

Ferroelectric Plasma Sources (FEPSs) can generate plasma that provides effective space-charge neutralization of intense high-perveance ion beams. Here we present experimental results on charge neutralization of a high-perveance 38 keV Ar+ beam by a FEPS plasma. By comparing the measured beam radius with the envelope model for space-charge expansion, it is shown that a charge neutralization fraction of 98% is attainable. The transverse electrostatic potential of the ion beam is reduced from 15 V before neutralization to 0.3 V, implying that the energy of the neutralizing electrons is below 0.3 eV. Near-complete charge neutralization is established 5 μs after the driving pulse is applied to the FEPS, and can last for 35 μs. It is argued that the duration of neutralization is much longer than a reasonable lifetime of the plasma produced in the sub- μs surface discharge. Measurements of current flow in the driving circuit of the FEPS suggest that plasma can be generated for tens of μs after the high voltage pulse is applied. This is confirmed by fast photography of the plasma in the 1-meter long FEPS on NDCX-II, where effective charge neutralization of the beam was achieved with the optimized FEPS timing. This work was supported by the Office of Science of the US Department of Energy under contracts DE-AC0209CH11466 (PPPL) and DE-AC0205CH11231 (LBNL).

Spin-filtering at COSY

NASA Astrophysics Data System (ADS)

Weidemann, Christian; PAX Collaboration

2011-05-01

The Spin Filtering experiments at COSY and AD at CERN within the framework of the Polarized Antiproton EXperiments (PAX) are proposed to determine the spin-dependent cross sections in bar pp scattering by observation of the buildup of polarization of an initially unpolarized stored antiproton beam after multiple passage through an internal polarized gas target. In order to commission the experimental setup for the AD and to understand the relevant machine parameters spin-filtering will first be done with protons at COSY. A first major step toward this goal has been achieved with the installation of the required mini-β section in summer 2009 and it's commissioning in January 2010. The target chamber together with the atomic beam source and the so-called Breit-Rabi polarimeter have been installed and commissioned in summer 2010. In addition an openable storage cell has been used. It provides a target thickness of 5·1013 atoms/cm2. We report on the status of spin-filtering experiments at COSY and the outcome of a recent beam time including studies on beam lifetime limitations like intra-beam scattering and the electron-cooling performance as well as machine acceptance studies.

Surface recombination velocity and diffusion length of minority carriers in heavily doped silicon layers

NASA Technical Reports Server (NTRS)

Gatos, H. C.; Watanabe, M.; Actor, G.

1977-01-01

Quantitative analysis of the electron beam-induced current and the dependence of the effective diffusion length of the minority carriers on the penetration depth of the electron beam were employed for the analysis of the carrier recombination characteristics in heavily doped silicon layers. The analysis is based on the concept of the effective excitation strength of the carriers which takes into consideration all possible recombination sources. Two dimensional mapping of the surface recombination velocity of P-diffused Si layers will be presented together with a three dimensional mapping of minority carrier lifetime in ion implanted Si. Layers heavily doped with As exhibit improved recombination characteristics as compared to those of the layers doped with P.

Geant4 simulations of NIST beam neutron lifetime experiment

NASA Astrophysics Data System (ADS)

Valete, Daniel; Crawford, Bret; BL2 Collaboration Collaboration

2017-09-01

A free neutron is unstable and its decay is described by the Standard Model as the transformation of a down quark into an up quark through the weak interaction. Precise measurements of the neutron lifetime test the validity of the theory of the weak interaction and provide useful information for the predictions of the theory of Big Bang nucleosynthesis of the primordial helium abundance in the universe and the number of different types of light neutrinos Nν. The predominant experimental methods for determination of the neutron lifetime are commonly called `beam' and `bottle' methods, and the most recent uses of each method do not agree with each other within their stated uncertainties. An improved experiment of the beam technique, which uses magnetic and electric fields to trap and guide the decay protons of a beam of cold neutrons to a detector, is in progress at the National Institute of Standards and Technology, Gaithersburg, MD with a precision goal of 0.1. I acknowledge the support of the Cross-Diciplinary Institute at Gettysburg College.

Dynamics of ion beam charge neutralization by ferroelectric plasma sources

DOE PAGES

Stepanov, Anton D.; Gilson, Erik P.; Grisham, Larry R.; ...

2016-04-27

Ferroelectric Plasma Sources (FEPSs) can generate plasma that provides effective space-charge neutralization of intense high-perveance ion beams, as has been demonstrated on the Neutralized Drift Compression Experiment NDCX-I and NDCX-II. This article presents experimental results on charge neutralization of a high-perveance 38 keV Ar + beam by a plasma produced in a FEPS discharge. By comparing the measured beam radius with the envelope model for space-charge expansion, it is shown that a charge neutralization fraction of 98% is attainable with sufficiently dense FEPS plasma. The transverse electrostatic potential of the ion beam is reduced from 15V before neutralization to 0.3more » V, implying that the energy of the neutralizing electrons is below 0.3 eV. Measurements of the time-evolution of beam radius show that near-complete charge neutralization is established similar to –5 μs after the driving pulse is applied to the FEPS and can last for 35 μs. It is argued that the duration of neutralization is much longer than a reasonable lifetime of the plasma produced in the sub-mu s surface discharge. Measurements of current flow in the driving circuit of the FEPS show the existence of electron emission into vacuum, which lasts for tens of mu s after the high voltage pulse is applied. Lastly, it is argued that the beam is neutralized by the plasma produced by this process and not by a surface discharge plasma that is produced at the instant the high-voltage pulse is applied.« less

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.

Feasibility of maintaining in-plane polarization for a storage ring EDM search

NASA Astrophysics Data System (ADS)

Stephenson, Edward; Storage Ring EDM Collaboration

2014-09-01

A search for an electric dipole moment (EDM) on charged particles using a storage ring requires beam polarization lifetimes approaching 1000 s for in-plane polarization. A feasibility study using beam bunching and sextupole field adjustment is underway with a 0.97-GeV/c vector-polarized deuteron beam at COSY. The polarimeter consists of a thick carbon target positioned at the edge of the beam and the EDDA scintillation detectors. The DAQ system assigns a clock time to each polarimeter event. Once calibrated against the RF-cavity, the clock time is used to select events associated with a maximal sideways polarization (precessing at 120 kHz). With this tool, the in-plane polarization magnitude is tracked versus time. Electron cooling reduces the depolarization from finite emittance and second-order momentum spread acting through synchrotron oscillations. Further lifetime improvement to the level of hundreds of seconds is achieved by adjusting sextupole fields located in the COSY ring arcs at places of large transverse beta functions and dispersion. The dependence of the reciprocal of the lifetime on sextupole field strength is nearly linear, permitting an easy location of the best field values. These typically occur near loci of zero chromaticity. A search for an electric dipole moment (EDM) on charged particles using a storage ring requires beam polarization lifetimes approaching 1000 s for in-plane polarization. A feasibility study using beam bunching and sextupole field adjustment is underway with a 0.97-GeV/c vector-polarized deuteron beam at COSY. The polarimeter consists of a thick carbon target positioned at the edge of the beam and the EDDA scintillation detectors. The DAQ system assigns a clock time to each polarimeter event. Once calibrated against the RF-cavity, the clock time is used to select events associated with a maximal sideways polarization (precessing at 120 kHz). With this tool, the in-plane polarization magnitude is tracked versus time. Electron cooling reduces the depolarization from finite emittance and second-order momentum spread acting through synchrotron oscillations. Further lifetime improvement to the level of hundreds of seconds is achieved by adjusting sextupole fields located in the COSY ring arcs at places of large transverse beta functions and dispersion. The dependence of the reciprocal of the lifetime on sextupole field strength is nearly linear, permitting an easy location of the best field values. These typically occur near loci of zero chromaticity. Supported in part by the Forschungszentrum-Juelich and the European Union.

High resolution multiplexed functional imaging in live embryos (Conference Presentation)

NASA Astrophysics Data System (ADS)

Xu, Dongli; Zhou, Weibin; Peng, Leilei

2017-02-01

Fourier multiplexed fluorescence lifetime imaging (FmFLIM) scanning laser optical tomography (FmFLIM-SLOT) combines FmFLIM and Scanning laser optical tomography (SLOT) to perform multiplexed 3D FLIM imaging of live embryos. The system had demonstrate multiplexed functional imaging of zebrafish embryos genetically express Foster Resonant Energy Transfer (FRET) sensors. However, previous system has a 20 micron resolution because the focused Gaussian beam diverges quickly from the focused plane, makes it difficult to achieve high resolution imaging over a long projection depth. Here, we present a high-resolution FmFLIM-SLOT system with achromatic Bessel beam, which achieves 3 micron resolution in 3D deep tissue imaging. In Bessel-FmFLIM-SLOT, multiple laser excitation lines are firstly intensity modulated by a Michelson interferometer with a spinning polygon mirror optical delay line, which enables Fourier multiplexed multi-channel lifetime measurements. Then, a spatial light modulator and a prism are used to transform the modulated Gaussian laser beam to an achromatic Bessel beam. The achromatic Bessel beam scans across the whole specimen with equal angular intervals as sample rotated. After tomography reconstruction and the frequency domain lifetime analysis method, both the 3D intensity and lifetime image of multiple excitation-emission can be obtained. Using Bessel-FmFLIM-SLOT system, we performed cellular-resolution FLIM tomography imaging of live zebrafish embryo. Genetically expressed FRET sensors in these embryo will allow non-invasive observation of multiple biochemical processes in vivo.

Correlation of ion and beam current densities in Kaufman thrusters.

NASA Technical Reports Server (NTRS)

Wilbur, P. J.

1973-01-01

In the absence of direct impingement erosion, electrostatic thruster accelerator grid lifetime is defined by the charge exchange erosion that occurs at peak values of the ion beam current density. In order to maximize the thrust from an engine with a specified grid lifetime, the ion beam current density profile should therefore be as flat as possible. Knauer (1970) has suggested this can be achieved by establishing a radial plasma uniformity within the thruster discharge chamber; his tests with the radial field thruster provide an example of uniform plasma properties within the chamber and a flat ion beam profile occurring together. It is shown that, in particular, the ion density profile within the chamber determines the beam current density profile, and that a uniform ion density profile at the screen grid end of the discharge chamber should lead to a flat beam current density profile.

Fast plasma discharge capillary design as a high power throughput soft x-ray emission source.

PubMed

Wyndham, E S; Favre, M; Valdivia, M P; Valenzuela, J C; Chuaqui, H; Bhuyan, H

2010-09-01

We present the experimental details and results from a low energy but high repetition rate compact plasma capillary source for extreme ultraviolet and soft x-ray research and applications. Two lengths of capillary are mounted in two versions of a closely related design. The discharge operates in 1.6 and 3.2 mm inner diameter alumina capillaries of lengths 21 and 36 mm. The use of water both as dielectric and as coolant simplifies the compact low inductance design with nanosecond discharge periods. The stored electrical energy of the discharge is approximately 0.5 J and is provided by directly charging the capacitor plates from an inexpensive insulated-gate bipolar transistor in 1 μs or less. We present characteristic argon spectra from plasma between 30 and 300 Å as well as temporally resolved x-ray energy fluence in discrete bands on axis. The spectra also allow the level of ablated wall material to be gauged and associated with useful capillary lifetime according to the chosen configuration and energy storage. The connection between the electron beams associated with the transient hollow cathode mechanism, soft x-ray output, capillary geometry, and capillary lifetime is reported. The role of these e-beams and the plasma as measured on-axis is discussed. The relation of the electron temperature and the ionization stages observed is discussed in the context of some model results of ionization in a non-Maxwellian plasma.

Laser Encapsulation of Organic Electronics with Adapted Diode Lasers in Flexible Production Processes

NASA Astrophysics Data System (ADS)

Brosda, Maximilian; Olowinsky, Alexander; Pelzer, Alexander

Flexible organic electronics such as OLPV and OLED modules are highly sensitive against water and oxygen. To protect them against the environment and to ensure a long lifetime visual transparent ultra high barrier films are used for the encapsulation process. These multilayer films usually consist of a polymer substrate on which, depending on the requirements, various functional layers are applied. The organic device is then fully packed in this films. Instead of conventional joining these film with adhesive, a flexible laser based process can be an interesting alternative especially for roll2roll applications. According to a precise spectral analysis and a consideration of the interaction between the laser radiation and the individual layers of the film a suitable laser beam source is selected. With this laser beam source the weldability of the films is investigated. For analysis of the weldseam and the melted volume cross sections and scanning-electron-microscopy-images are prepared. The strength of the weld is determined by T-Peel tensile tests.

Lifetime and g-factor measurements of excited states using Coulomb excitation and alpha transfer reactions

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

Guevara, Z. E., E-mail: zjguevaram@unal.edu.co; Torres, D. A., E-mail: datorresg@unal.edu.co

2016-07-07

In this contribution the challenges in the use of a setup to simultaneously measure lifetimes and g-factor values will be presented. The simultaneous use of the transient field technique and the Doppler Shift Attenuation Method, to measure magnetic moments and lifetimes respectively, allows to obtain a complete characterization of the currents of nucleons and the deformation in excited states close to the ground state. The technique is at the moment limited to Coulomb excitation and alpha-transfer reactions, what opens an interesting perspective to consider this type of experiments with radioactive beams. The use of deep-inelastic and fusion-evaporation reactions will bemore » discussed. An example of a setup that makes use of a beam of {sup 106}Cd to study excited states of {sup 110}Sn and the beam nuclei itself will be presented.« less

Bessel beam fluorescence lifetime tomography of live embryos (Conference Presentation)

NASA Astrophysics Data System (ADS)

Xu, Dongli; Peng, Leilei

2016-03-01

Optical tomography allows isotropic 3D imaging of embryos. Scanning-laser optical tomography (SLOT) has superior light collecting efficiency than wide-field optical tomography, making it ideal for fluorescence imaging of live embryos. We previously reported an imaging system that combines SLOT with a novel Fourier-multiplexed fluorescence lifetime imaging (FmFLIM) technique named FmFLIM-SLOT. FmFLIM-SLOT performs multiplexed FLIM-FRET readout of multiple FRET sensors in live embryos. Here we report a recent effort on improving the spatial resolution of the FmFLIM-SLOT system in order to image complex biochemical processes in live embryos at the cellular level. Optical tomography has to compromise between resolution and the depth of view. In SLOT, the commonly-used focused Gaussian beam diverges quickly from the focal plane, making it impossible to achieve high resolution imaging in a large volume specimen. We thus introduce Bessel beam laser-scanning tomography, which illuminates the sample with a spatial-light-modulator-generated Bessel beam that has an extended focal depth. The Bessel beam is scanned across the whole specimen. Fluorescence projection images are acquired at equal angular intervals as the sample rotates. Reconstruction artifacts due to annular-rings of the Bessel beam are removed by a modified 3D filtered back projection algorithm. Furthermore, in combination of Fourier-multiplexing fluorescence lifetime imaging (FmFLIM) method, the Bessel FmFLIM-SLOT system is capable of perform 3D lifetime imaging of live embryos at cellular resolution. The system is applied to in-vivo imaging of transgenic Zebrafish embryos. Results prove that Bessel FmFLIM-SLOT is a promising imaging method in development biology research.

Rechargeable thin film battery and method for making the same

DOEpatents

Goldner, Ronald B.; Liu, Te-Yang; Goldner, Mark A.; Gerouki, Alexandra; Haas, Terry E.

2006-01-03

A rechargeable, stackable, thin film, solid-state lithium electrochemical cell, thin film lithium battery and method for making the same is disclosed. The cell and battery provide for a variety configurations, voltage and current capacities. An innovative low temperature ion beam assisted deposition method for fabricating thin film, solid-state anodes, cathodes and electrolytes is disclosed wherein a source of energetic ions and evaporants combine to form thin film cell components having preferred crystallinity, structure and orientation. The disclosed batteries are particularly useful as power sources for portable electronic devices and electric vehicle applications where high energy density, high reversible charge capacity, high discharge current and long battery lifetimes are required.

Surface plasma source with saddle antenna radio frequency plasma generator.

PubMed

Dudnikov, V; Johnson, R P; Murray, S; Pennisi, T; Piller, C; Santana, M; Stockli, M; Welton, R

2012-02-01

A prototype RF H(-) surface plasma source (SPS) with saddle (SA) RF antenna is developed which will provide better power efficiency for high pulsed and average current, higher brightness with longer lifetime and higher reliability. Several versions of new plasma generators with small AlN discharge chambers and different antennas and magnetic field configurations were tested in the plasma source test stand. A prototype SA SPS was installed in the Spallation Neutron Source (SNS) ion source test stand with a larger, normal-sized SNS AlN chamber that achieved unanalyzed peak currents of up to 67 mA with an apparent efficiency up to 1.6 mA∕kW. Control experiments with H(-) beam produced by SNS SPS with internal and external antennas were conducted. A new version of the RF triggering plasma gun has been designed. A saddle antenna SPS with water cooling is fabricated for high duty factor testing.

Laser ion source for multi-nucleon transfer reaction products

NASA Astrophysics Data System (ADS)

Hirayama, Y.; Watanabe, Y. X.; Imai, N.; Ishiyama, H.; Jeong, S. C.; Miyatake, H.; Oyaizu, M.; Kimura, S.; Mukai, M.; Kim, Y. H.; Sonoda, T.; Wada, M.; Huyse, M.; Kudryavtsev, Yu.; Van Duppen, P.

2015-06-01

We have developed a laser ion source for the target-like fragments (TLFs) produced in multi-nucleon transfer (MNT) reactions. The operation principle of the source is based on the in-gas laser ionization and spectroscopy (IGLIS) approach. In the source TLFs are thermalized and neutralized in high pressure and high purity argon gas, and are extracted after being selectively re-ionized in a multi-step laser resonance ionization process. The laser ion source has been implemented at the KEK Isotope Separation System (KISS) for β-decay spectroscopy of neutron-rich isotopes with N = 126 of nuclear astrophysical interest. The simulations of gas flow and ion-beam optics have been performed to optimize the gas cell for efficient thermalization and fast transporting the TLFs, and the mass-separator for efficient transport with high mass-resolving power, respectively. To confirm the performances expected at the design stage, off-line experiments have been performed by using 56Fe atoms evaporated from a filament in the gas cell. The gas-transport time of 230 ms in the argon cell and the measured KISS mass-resolving power of 900 are consistent with the designed values. The high purity of the gas-cell system, which is extremely important for efficient and highly-selective production of laser ions, was achieved and confirmed from the mass distribution of the extracted ions. After the off-line tests, on-line experiments were conducted by directly injecting energetic 56Fe beam into the gas cell. After thermalization of the injected 56Fe beam, laser-produced singly-charged 56Fe+ ions were extracted. The extraction efficiency and selectivity of the gas cell in the presence of plasma induced by 56Fe beam injection as well as the time profile of the extracted ions were investigated; extraction efficiency of 0.25%, a beam purity of >99% and an extraction time of 270 ms. It has been confirmed that the performance of the KISS laser ion source is satisfactory to start the measurements of lifetimes of the β-decayed nuclei with N = 126 .

Research on Novel High-Power Microwave/Millimeter Wave Sources and Applications

DTIC Science & Technology

2010-08-28

density with acceptable operating temperature and lifetime. The MIG is optimized with the EGUN code for a cath- ode voltage Vb of 100 kV and a beam...emission suppression. Figure 2 is an EGUN drawing of the MIG configuration/ dimensions and electron trajectories. The design is flexible TABLE I. Predicted...and measured MIG parameters. EGUN prediction smooth cathode Measurement Voltage kV 100.0 100.0 Current A 8.0 8.0 0 1.40 1.40 vz /vz0 3.5% 4.6

Time-resolved experiments in the frequency domain using synchrotron radiation (invited)

NASA Astrophysics Data System (ADS)

De Stasio, Gelsomina; Giusti, A. M.; Parasassi, T.; Ravagnan, G.; Sapora, O.

1992-01-01

PLASTIQUE is the only synchrotron radiation beam line in the world that performs time-resolved fluorescence experiments in frequency domain. These experiments are extremely valuable sources of information on the structure and the dynamics of molecules. This technique measures fluorescence lifetimes with picosecond resolution in the near UV spectral range. Such accurate measurements are rendered possible by taking phase and modulation data, and by the advantages of the cross-correlation technique. A successful experiment demonstrated the radiation damage induced by low doses of radiation on rabbit blood cell membranes.

Lifetimes of relativistic heavy-ion beams in the High Energy Storage Ring of FAIR

NASA Astrophysics Data System (ADS)

Shevelko, V. P.; Litvinov, Yu. A.; Stöhlker, Th.; Tolstikhina, I. Yu.

2018-04-01

The High Energy Storage Ring, HESR, will be constructed at the Facility for Antiproton and Ion Research, FAIR, Darmstadt. For the first time, it will be possible to perform experiments with cooled high-intensity stable and radioactive heavy ions at highly relativistic energies. To design experiments at the HESR, realistic estimations of beam lifetimes are indispensable. Here we report calculated cross sections and lifetimes for typical U88+ , U90+ , U92+ , Sn49+ and Sn50+ ions in the energy range E = 400 MeV/u-5 GeV/u, relevant for the HESR. Interactions with the residual gas and with internal gas-jet targets are also considered.

Low-lying electromagnetic transition strengths in 180Pt

NASA Astrophysics Data System (ADS)

Müller-Gatermann, C.; Dewald, A.; Fransen, C.; Braunroth, T.; Jolie, J.; Litzinger, J.; Régis, J. M.; von Spee, F.; Warr, N.; Zell, K. O.; Grahn, T.; Greenlees, P. T.; Hauschild, K.; Jakobsson, U.; Julin, R.; Juutinen, S.; Ketelhut, S.; Nieminen, P.; Nyman, M.; Peura, P.; Rahkila, P.; Ruotsalainen, P.; Sandzelius, M.; Sarén, J.; Scholey, C.; Sorri, J.; Stolze, S.; Uusitalo, J.; Petkov, P.

2018-02-01

Lifetime measurements have been performed using the 98Mo(86Kr,4 n )180Pt reaction at a beam energy of 380 MeV, and the recoil distance Doppler-shift method. In a second experiment the 168Yb(16O,4 n )180Pt reaction at a beam energy of 88 MeV using the Ge-gated γ -γ fast timing technique was used to determine lifetimes. Lifetimes of the four lowest yrast states of 180Pt have been determined. The experimental data are compared to calculations within the framework of the interacting boson model and the general collective model. Both models predict a deformed ground state and are consistent with all the remaining experimental results.

Development of thick, long-lived carbon stripper foils for PSR of LANL

NASA Astrophysics Data System (ADS)

Sugai, I.; Oyaizu, M.; Kawakami, H.; Ohmori, C.; Hattori, T.; Kawasaki, K.; Borden, M. J.; Macek, R. J.

1995-02-01

Thick carbon stripper foils (multi-layer thickness ≈ 200 μg/cm 2) have been developed for use with 800 MeV, H + ion beam in the Proton Storage Ring (PSR) at Los Alamos National Laboratory. Foils were prepared by means of the modified controlled ACDC arc discharge method (mCADAD). The lifetime measurements of the foils made by different methods were performed using an 800 MeV proton beam of up to 85 μA in the PSR, and a 3.2 MeV Ne + ion beam of 3 μA at Tokyo Institute of Technology. The foils made by the mCADAD method showed very long lifetimes, as compared to other foils tested, for both 800 MeV p and 3.2 MeV Ne + beam bombardments.

Neutron Transport Simulations for NIST Neutron Lifetime Experiment

NASA Astrophysics Data System (ADS)

Li, Fangchen; BL2 Collaboration Collaboration

2016-09-01

Neutrons in stable nuclei can exist forever; a free neutron lasts for about 15 minutes on average before it beta decays to a proton, an electron, and an antineutrino. Precision measurements of the neutron lifetime test the validity of weak interaction theory and provide input into the theory of the evolution of light elements in the early universe. There are two predominant ways of measuring the neutron lifetime: the bottle method and the beam method. The bottle method measures decays of ultracold neutrons that are stored in a bottle. The beam method measures decay protons in a beam of cold neutrons of known flux. An improved beam experiment is being prepared at the National Institute of Science and Technology (Gaithersburg, MD) with the goal of reducing statistical and systematic uncertainties to the level of 1 s. The purpose of my studies was to develop computer simulations of neutron transport to determine the beam collimation and study the neutron distribution's effect on systematic effects for the experiment, such as the solid angle of the neutron flux monitor. The motivation for the experiment and the results of this work will be presented. This work was supported, in part, by a Grant to Gettysburg College from the Howard Hughes Medical Institute through the Precollege and Undergraduate Science Education Program.

Analysis and correction of linear optics errors, and operational improvements in the Indus-2 storage ring

NASA Astrophysics Data System (ADS)

Husain, Riyasat; Ghodke, A. D.

2017-08-01

Estimation and correction of the optics errors in an operational storage ring is always vital to achieve the design performance. To achieve this task, the most suitable and widely used technique, called linear optics from closed orbit (LOCO) is used in almost all storage ring based synchrotron radiation sources. In this technique, based on the response matrix fit, errors in the quadrupole strengths, beam position monitor (BPM) gains, orbit corrector calibration factors etc. can be obtained. For correction of the optics, suitable changes in the quadrupole strengths can be applied through the driving currents of the quadrupole power supplies to achieve the desired optics. The LOCO code has been used at the Indus-2 storage ring for the first time. The estimation of linear beam optics errors and their correction to minimize the distortion of linear beam dynamical parameters by using the installed number of quadrupole power supplies is discussed. After the optics correction, the performance of the storage ring is improved in terms of better beam injection/accumulation, reduced beam loss during energy ramping, and improvement in beam lifetime. It is also useful in controlling the leakage in the orbit bump required for machine studies or for commissioning of new beamlines.

Prostate cancer diagnosis with fluorescence lifetime imaging (Conference Presentation)

NASA Astrophysics Data System (ADS)

Sridharan, Shamira; Gandour-Edwards, Regina F.; Dall'Era, Marc; Marcu, Laura

2017-02-01

More than 1 million men in the United States undergo a prostate biopsy procedure annually and approximately 200,000 men receive a diagnosis of prostate cancer. 5-10% of these men have to undergo a repeat biopsy due to insufficient tissue sampling. We are studying the utility of a multi-spectral time resolved fluorescence spectroscopy (MS-TRFS) technique for real-time prostate cancer diagnosis. The MS-TRFS imaging setup, which includes a fiberoptic set-up with a 355nm excitation light source coupled with a blue (450nm) aiming beam, was used to image ex-vivo prostatectomy specimen. The prostate tissue from 11 patients was sectioned at 2mm thickness and the fluorescence lifetime information was overlaid spatially for histology and thus, diagnostic co-registration. Initial results show that fluorescence lifetime in the 390±40nm channel, which measures collagen and elastin signatures, is longer for glandular regions than in the stromal regions. Additionally, lifetime in the 452±45nm channel, corresponding to NAD redox state, is longer in the cancerous glandular region in comparison with the normal glandular regions. Current work is focused on developing real-time quantitative algorithms to combine the fluorescence signatures from the two channels for performing prostate cancer diagnosis on biopsies.

Ultra-High Sensitivity Techniques for the Determination of 3 He /4 He Abundances in Helium by Accelerator Mass Spectrometry

NASA Astrophysics Data System (ADS)

Mumm, H. P.; Huber, M.; Bauder, W.; Abrams, N.; Deibel, C.; Huffer, C.; Huffman, P.; Schelhammer, K.; Janssens, R.; Jiang, C.; Scott, R.; Pardo, R.; Rehm, K.; Vondrasek, R.; Swank, C.; O'Shaughnessy, C.; Paul, M.; Yang, L.

2017-01-01

We report the development of an Accelerator Mass Spectrometry technique to measure the 3He/4He isotopic ratio using a radio frequency (RF) discharge source and the ATLAS facility at Argonne National Laboratory. Control over 3He/4He ratio in helium several orders of magnitude lower than natural abundance is critical for neutron lifetime and source experiments using liquid helium. Due to low ultimate beam currents, the ATLAS accelerator and beam line were tuned using a succession of species of the same M/q. A unique RF source was developed for the experiment due to large natural 3He backgrounds. Analog H_3 + and DH + molecular ions are eliminated by dissociation via a gold stripper foil near the detector. The stripped ions were dispersed in a magnetic spectrograph and 3He2 + ions counted in the focal plane detector. This technique is sensitive to 3 He /4 He ratios in the regime of 10-12 with backgrounds that appear to be below 10-14. The techniques used to reduce the backgrounds and remaining outstanding problems will be presented along with results from measurements on high purity 4He samples.

Development of Compact Electron Cyclotron Resonance Ion Source with Permanent Magnets for High-Energy Carbon-Ion Therapy

NASA Astrophysics Data System (ADS)

Muramatsu, M.; Kitagawa, A.; Iwata, Y.; Hojo, S.; Sakamoto, Y.; Sato, S.; Ogawa, Hirotsugu; Yamada, S.; Ogawa, Hiroyuki; Yoshida, Y.; Ueda, T.; Miyazaki, H.; Drentje, A. G.

2008-11-01

Heavy-ion cancer treatment is being carried out at the Heavy Ion Medical Accelerator in Chiba (HIMAC) with 140 to 400 MeV/n carbon ions at National Institute of Radiological Sciences (NIRS) since 1994. At NIRS, more than 4,000 patients have been treated, and the clinical efficiency of carbon ion radiotherapy has been demonstrated for many diseases. A more compact accelerator facility for cancer therapy is now being constricted at the Gunma University. In order to reduce the size of the injector (consists of ion source, low-energy beam transport and post-accelerator Linac include these power supply and cooling system), an ion source requires production of highly charged carbon ions, lower electric power for easy installation of the source on a high-voltage platform, long lifetime and easy operation. A compact Electron Cyclotron Resonance Ion Source (ECRIS) with all permanent magnets is one of the best types for this purpose. An ECRIS has advantage for production of highly charged ions. A permanent magnet is suitable for reduce the electric power and cooling system. For this, a 10 GHz compact ECRIS with all permanent magnets (Kei2-source) was developed. The maximum mirror magnetic fields on the beam axis are 0.59 T at the extraction side and 0.87 T at the gas-injection side, while the minimum B strength is 0.25 T. These parameters have been optimized for the production of C4+ based on experience at the 10 GHz NIRS-ECR ion source. The Kei2-source has a diameter of 320 mm and a length of 295 mm. The beam intensity of C4+ was obtained to be 618 eμA under an extraction voltage of 30 kV. Outline of the heavy ion therapy and development of the compact ion source for new facility are described in this paper.

Detecting cavitation in mercury exposed to a high-energy pulsed proton beam

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

Manzi, Nicholas J; Chitnis, Parag V; Holt, Ray G

2010-01-01

The Oak Ridge National Laboratory Spallation Neutron Source employs a high-energy pulsed proton beam incident on a mercury target to generate short bursts of neutrons. Absorption of the proton beam produces rapid heating of the mercury, resulting in the formation of acoustic shock waves and the nucleation of cavitation bubbles. The subsequent collapse of these cavitation bubbles promote erosion of the steel target walls. Preliminary measurements using two passive cavitation detectors (megahertz-frequency focused and unfocused piezoelectric transducers) installed in a mercury test target to monitor cavitation generated by proton beams with charges ranging from 0.041 to 4.1 C will bemore » reported on. Cavitation was initially detected for a beam charge of 0.082 C by the presence of an acoustic emission approximately 250 s after arrival of the incident proton beam. This emission was consistent with an inertial cavitation collapse of a bubble with an estimated maximum bubble radius of 0.19 mm, based on collapse time. The peak pressure in the mercury for the initiation of cavitation was predicted to be 0.6 MPa. For a beam charge of 0.41 C and higher, the lifetimes of the bubbles exceeded the reverberation time of the chamber (~300 s), and distinct windows of cavitation activity were detected, a phenomenon that likely resulted from the interaction of the reverberation in the chamber and the cavitation bubbles.« less

Radiative lifetimes in B I using ultraviolet and vacuum-ultraviolet laser-induced fluorescence

NASA Technical Reports Server (NTRS)

O'Brian, T. R.; Lawler, J. E.

1992-01-01

Radiative lifetimes of the eight lowest even parity levels in the doublet system of B I are measured using time-resolved laser-induced fluorescence in the UV and VUV on an atomic beam of boron. The accurate lifetimes provide a base for improved determination of absolute transition probabilities in B I. The techniques described are broadly applicable to measurement of lifetimes of levels with transitions in the visible, UV, and VUV in almost any element.

High-purity silicon crystal growth investigations

NASA Technical Reports Server (NTRS)

Ciszek, T. F.; Hurd, J. L.; Schuyler, T.

1985-01-01

The study of silicon sheet material requirements for high efficiency solar cells is reported. Research continued on obtaining long lifetime single crystal float zone silicon and on understanding and reducing the mechanisms that limit the achievement of long lifetimes. The mechanisms studied are impurities, thermal history, point defects, and surface effect. The lifetime related crystallographic defects are characterized by X-ray topography and electron beam induced current.

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

A Hybrid Lifetime Extended Directional Approach for WBANs

PubMed Central

Li, Changle; Yuan, Xiaoming; Yang, Li; Song, Yueyang

2015-01-01

Wireless Body Area Networks (WBANs) can provide real-time and reliable health monitoring, attributing to the human-centered and sensor interoperability properties. WBANs have become a key component of the ubiquitous eHealth (electronic health) revolution that prospers on the basis of information and communication technologies. The prime consideration in WBAN is how to maximize the network lifetime with battery-powered sensor nodes in energy constraint. Novel solutions in Medium Access Control (MAC) protocols are imperative to satisfy the particular BAN scenario and the need of excellent energy efficiency in healthcare applications. In this paper, we propose a hybrid Lifetime Extended Directional Approach (LEDA) MAC protocol based on IEEE 802.15.6 to reduce energy consumption and prolong network lifetime. The LEDA MAC protocol takes full advantages of directional superiority in energy saving that employs multi-beam directional mode in Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) and single-beam directional mode in Time Division Multiple Access (TDMA) for alternative in data reservation and transmission according to the traffic varieties. Moreover, the impacts of some inherent problems of directional antennas such as deafness and hidden terminal problem can be decreased owing to that all nodes generate individual beam according to user priorities designated. Furthermore, LEDA MAC employs a Dynamic Polled Allocation Period (DPAP) for burst data transmissions to increase the network reliability and adaptability. Extensive analysis and simulation results show that the proposed LEDA MAC protocol achieves extended network lifetime with improved performance compared with IEEE 802.15.6. PMID:26556357

Beam Energy Scan on Hypertriton Production and Lifetime Measurement at RHIC STAR

NASA Astrophysics Data System (ADS)

Zhu, Yuhui

2013-05-01

We report preliminary results on HΛ3 production in Au + Au collisions at RHIC at s=7.7, 11.5, 19.6, 27, 39, and 200 GeV. The beam energy dependence of strangeness population factor HΛ3/3HeΛ/p is shown and the result indicates that HΛ3/3HeΛ/p has an increasing trend with 1.7σ significance. The hypertriton lifetime combining the above Au + Au collision data set is measured to be 123±2226(stat)±10(sys) ps.

Analog detection for cavity lifetime spectroscopy

DOEpatents

Zare, Richard N.; Harb, Charles C.; Paldus, Barbara A.; Spence, Thomas G.

2001-05-15

An analog detection system for determining a ring-down rate or decay rate 1/.tau. of an exponentially decaying ring-down beam issuing from a lifetime or ring-down cavity during a ring-down phase. Alternatively, the analog detection system determines a build-up rate of an exponentially growing beam issuing from the cavity during a ring-up phase. The analog system can be employed in continuous wave cavity ring-down spectroscopy (CW CRDS) and pulsed CRDS (P CRDS) arrangements utilizing any type of ring-down cavity including ring-cavities and linear cavities.

Analog detection for cavity lifetime spectroscopy

DOEpatents

Zare, Richard N.; Harb, Charles C.; Paldus, Barbara A.; Spence, Thomas G.

2003-01-01

An analog detection system for determining a ring-down rate or decay rate 1/.tau. of an exponentially decaying ring-down beam issuing from a lifetime or ring-down cavity during a ring-down phase. Alternatively, the analog detection system determines a build-up rate of an exponentially growing beam issuing from the cavity during a ring-up phase. The analog system can be employed in continuous wave cavity ring-down spectroscopy (CW CRDS) and pulsed CRDS (P CRDS) arrangements utilizing any type of ring-down cavity including ring-cavities and linear cavities.

Spatial emission distribution of InGaN/GaN light-emitting diodes depending on the pattern structures

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

Lee, Kwanjae; Lee, Hyunjung; Lee, Cheul-Ro

2014-10-15

Highlights: • We study carrier lifetimes of InGaN/GaN LEDs fabricated on different PSS. • Spatial EL distribution was investigated depending on the pattern structure. • The carrier lifetime of the LEDs was compared with the spatial EL distribution. - Abstract: We investigated the emission characteristics of InGaN/GaN light-emitting diodes (LEDs) fabricated on lens-shaped (LS) patterned-sapphire substrates (PSS) by using time-resolved photoluminescence (TRPL) and confocal-scanning-electroluminescence microscopy (CSEM). The carrier lifetimes evaluated from the TRPL spectra for the LEDs on the LS-PSS (LS-LEDs) at 10 K were relatively shorter than those of the LEDs on a conventional planar substrate (C-LED). However, themore » carrier lifetimes for the LS-LEDs were relatively long compared to that of the C-LED at room temperature. In the CSEM images of the LS-LEDs, the emission beam around the center region of the LS pattern was relatively weaker than that of the edge region. In addition, the beam profile for the LS-LEDs showed different shapes according to the pattern structures. The emission beam around the boundary region of the LS pattern showed periodic fluctuation with the peak-to-peak distance of 814 nm.« less

Compact D-D Neutron Source-Driven Subcritical Multiplier and Beam-Shaping Assembly for Boron Neutron Capture Therapy

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

Francesco Ganda; Jasmina Vujic; Ehud Greenspan

2010-12-01

This work assesses the feasibility of using a small, safe, and inexpensive keff 0.98 subcritical fission assembly [subcritical neutron multiplier (SCM)] to amplify the treatment neutron beam intensity attainable from a compact deuterium-deuterium (D-D) fusion neutron source delivering [approximately]1012 n/s. The objective is to reduce the treatment time for deep-seated brain tumors to [approximately]1 h. The paper describes the optimal SCM design and two optimal beam-shaping assemblies (BSAs) - one designed to maximize the dose rate and the other designed to maximize the total dose that can be delivered to a deep-seated tumor. The neutron beam intensity amplification achieved withmore » the optimized SCM and BSA results in an increase in the treatment dose rate by a factor of 18: from 0.56 Gy/h without the SCM to 10.1 Gy/h. The entire SCM is encased in an aluminum structure. The total amount of 20% enriched uranium required for the SCM is 8.5 kg, and the cost (not including fabrication) is estimated to be less than $60,000. The SCM power level is estimated at 400 W when driven by a 1012 n/s D-D neutron source. This translates into consumption of only [approximately]0.6% of the initially loaded 235U atoms during 50 years of continuous operation and implies that the SCM could operate continuously for the entire lifetime of the facility without refueling. Cooling the SCM does not pose a challenge; it may be accomplished by natural circulation as the maximum heat flux is only 0.034 W/cm2.« less

COMPARISON OF NONLINEAR DYNAMICS OPTIMIZATION METHODS FOR APS-U

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

Sun, Y.; Borland, Michael

Many different objectives and genetic algorithms have been proposed for storage ring nonlinear dynamics performance optimization. These optimization objectives include nonlinear chromaticities and driving/detuning terms, on-momentum and off-momentum dynamic acceptance, chromatic detuning, local momentum acceptance, variation of transverse invariant, Touschek lifetime, etc. In this paper, the effectiveness of several different optimization methods and objectives are compared for the nonlinear beam dynamics optimization of the Advanced Photon Source upgrade (APS-U) lattice. The optimized solutions from these different methods are preliminarily compared in terms of the dynamic acceptance, local momentum acceptance, chromatic detuning, and other performance measures.

Optical properties and carrier dynamics of GaAs/GaInAs multiple-quantum-well shell grown on GaAs nanowire by molecular beam epitaxy

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

Park, Kwangwook; Ravindran, Sooraj; Ju, Gun Wu

GaAs/GaInAs multiple-quantum-well (MQW) shells having different GaInAs shell width formed on the surface of self-catalyzed GaAs core nanowires (NWs) are grown on (100) Si substrate using molecular beam epitaxy. The photoluminescence emission from GaAs/GaInAs MQW shells and the carrier lifetime could be varied by changing the width of GaInAs shell. Time-resolved photoluminescence measurements showed that the carrier lifetime had a fast and slow decay owing to the mixing of wurtzite and zinc-blende structures of the NWs. Furthermore, strain relaxation caused the carrier lifetime to decrease beyond a certain thickness of GaInAs quantum well shells.

Preparation and comparative testing of advanced diamond-like carbon foils for tandem accelerators and time-of-flight spectrometers

NASA Astrophysics Data System (ADS)

Liechtenstein, V. Kh.; Ivkova, T. M.; Olshanski, E. D.; Baranov, A. M.; Repnow, R.; Hellborg, R.; Weller, R. A.; Wirth, H. L.

1999-12-01

The sputter preparation technique for thin diamond-like carbon (DLC) foils, advantageously used for ion-beam stripping and timing in accelerator experiments, has been optimized to improve the quality and the performance of the foils. Irradiation lifetimes of 5 μg/cm 2 DLC foils prepared by this technique have been compared with those for foils of approximately the same thickness, prepared by laser plasma ablation and for ethylene cracked foils when bombarded by 11 MeV Cu - - and Au --ion beams of ˜1 μA beam current at the Heidelberg MP-tandem. Standard carbon arc-evaporated foils were used as references. In these experiments, DLC stripper foils appeared to have a mean lifetime approximately two times longer than ethylene-cracked foils regardless of ion species, and compared favorably with foils prepared by laser ablation method. All these foils lasted at least, 10 times longer than standard carbon foils, when irradiated in the MP terminal. Approximately, the same improvement factor was confirmed with 3 μg/cm 2 DLC stripper foils irradiated with 2.3 MeV Ni-beams at the Pelletron accelerator in Lund. Unlike standard carbon foils, most of the advanced lifetime foils exhibited thinning during long irradiation, under clean vacuum. This suggests that sputtering of the foil by the heavy-ion beam might be a dominant process, responsible for the observed failure of these long-lived strippers. Along with specifically corrugated self-supporting DLC beam strippers, we succeeded in the fabrication of very smooth and ultra thin (˜0.5 μg/cm 2) DLC foils, mounted on grids and used as start foils for the ToF spectrometers applied in ion beam analysis.

Nuclear structure studies in highly neutron-deficient (114,116)Xe

NASA Astrophysics Data System (ADS)

Degraaf, James Hendrick

Lifetimes of nuclear states in 114Xe and 116Xe were measured for the first time; these nuclei represent the most neutron-deficient isotopes of xenon for which lifetimes have now been measured. The fusion-evaporation reactions 58Ni(60Ni, 2p)116Xe at 223 MeV beam energy and 58Ni(58Ni, 2p)114Xe at 215 MeV beam energy were used. Lifetimes were measured using the Recoil Distance Method (RDM) with the 8π gamma-ray spectrometer at Chalk River Laboratories. The new measurements of the B(E2;2+/to 0+) strength in these nuclei, coupled with the recent measurements for heavier xenon isotopes, are well described within the framework of the O(6) symmetry limit of the Interacting Boson Approximation. The octupole nature of the negative parity side-band was also studied, and the lifetime measurements indicate a change from a K/approx 3 structure in heavier xenon isotopes to a K/approx 0,/ 1 structure in 114Xe.

Lifetime experimental study of graphite cathode for relativistic backward wave oscillator

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

Wu, Ping; Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi'an 710024; Sun, Jun

2016-07-21

Graphite cathodes are widely used due to their good emission properties, especially their long lifetime. Some previous papers have researched their lifetime under certain conditions and uncovered some important phenomena. This paper is dedicated to research the lifetime of the graphite cathode under higher power. In the lifetime test, the voltage and current amplitudes are about 970 kV and 9.7 kA, respectively. The repetition rate is 20 Hz. An X-band relativistic backward wave oscillator is used to generate high power microwave by utilizing the electron beam energy. The experimental results demonstrate that the emission property of the graphite cathode remains quite stable duringmore » 10{sup 5} pulses, despite some slight deteriorations regarding the beam and microwave parameters. The macroscopic morphology change of the cathode blade due to material evaporation is observed by a laser microscope. The mass loss of the graphite cathode is about 60 μg/C. Meanwhile, the observation by a scanning electron microscope uncovers that the original numerous flaky micro-structures are totally replaced by a relatively smooth surface at the mid region of the cathode blade and a large number of new micro-protrusions at the blade edges during the lifetime test.« less

A long-lived tritiated titanium target for fast neutron production

NASA Astrophysics Data System (ADS)

Hughey, B. J.

1995-03-01

Diagnostic techniques using neutron beams have a broad spectrum of applications in advanced manufacturing, explosives and contraband detection, medicine, and industry. The most suitable nuclear reaction for producing large fluxes of fast neutrons at low bombarding energy is the H(d,n)-3 He-4, i.e. d-T, reaction. The lifetime of currently used d-T neutron generators is limited by the gradual evolution of tritium gas from the target during bombardment. This paper is a report of work in progress to develop a method for inhibiting the replacement of tritium with beam deuterons and thus preventing the evolution of tritium gas leading to reduced neutron yield. It is anticipated that tritiated target lifetime can be increased by at least an order of magnitude by using a range-thin tritiated titanium target mounted on a substrate with a high hydrogen diffusivity, such as niobium. Lifetime can be further enhanced by increasing the deuteron beam bombarding energy from the typical value of 200 keV to 600 keV. The results of experiments demonstrating the effect of hydrogen diffusion coefficient on concentration of implanted beam deuterons in candidate substrate materials (Cu, Pd, and Nb) are presented, and issues relevant to the fabrication of a tritiated titanium target on a niobium substrate are discussed.

Beam Test of a Dielectric Loaded High Pressure RF Cavity for Use in Muon Cooling Channels

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

Freemire, Ben; Bowring, Daniel; Kochemirovskiy, Alexey

2016-06-01

Bright muon sources require six dimensional cooling to achieve acceptable luminosities. Ionization cooling is the only known method able to do so within the muon lifetime. One proposed cooling channel, the Helical Cooling Channel, utilizes gas filled radio frequency cavities to both mitigate RF breakdown in the presence of strong, external magnetic fields, and provide the cooling medium. Engineering constraints on the diameter of the magnets within which these cavities operate dictate the radius of the cavities be decreased at their nominal operating frequency. To accomplish this, one may load the cavities with a larger dielectric material. A 99.5% aluminamore » ring was inserted in a high pressure RF test cell and subjected to an intense proton beam at the MuCool Test Area at Fermilab. The results of the performance of this dielectric loaded high pressure RF cavity will be presented.« less

Invited Article: Refined analysis of synchrotron radiation for NIST's SURF III facility

NASA Astrophysics Data System (ADS)

Shirley, Eric L.; Furst, Mitchell; Arp, Uwe

2018-04-01

We have developed a new method for the exact calculation of synchrotron radiation for the National Institute of Standards and Technology Synchrotron Ultraviolet Radiation Facility, SURF III. Instead of using the Schwinger formula, which is only an approximation, we develop formulae based on Graf's addition theorem for Bessel functions and accurate asymptotic expansions for Hankel functions and Bessel functions. By measuring the radiation intensity profile at two distances from the storage ring, we also confirm an apparent vertical emittance that is consistent with the vertical betatron oscillations that are intentionally introduced to extend beam lifetime by spreading the electron beam spatially. Finally, we determine how much diffraction by beamline apertures enhances the spectral irradiance at an integrating sphere entrance port at the end station. This should eliminate small but treatable components of the uncertainty budget that one should consider when using SURF III or similar synchrotrons as standard, calculable sources of ultraviolet and other radiation.

Perspective of Muon Production Target at J-PARC MLF MUSE

NASA Astrophysics Data System (ADS)

Makimura, Shunsuke; Matoba, Shiro; Kawamura, Naritoshi; Matsuzawa, Yukihiro; Tabe, Masato; Aoyagi, Hiroyuki; Kondo, Hiroto; Kobayashi, Yasuo; Fujimori, Hiroshi; Ikedo, Yutaka; Kadono, Ryosuke; Koda, Akihiro; Kojima, Kenji M.; Miyake, Yasuhiro; Nakamura, Jumpei G.; Oishi, Yu; Okabe, Hirotaka; Shimomura, Koichiro; Strasser, Patrick

A pulsed muon beam with unprecedented intensity will be generated by a 3-GeV 333-microA proton beam on a muon target made of 20-mm thick isotropic graphite at J-PARC MLF MUSE (Muon Science Establishment). The first muon beam was successfully generated on September 26th, 2008. Gradually upgrading the beam intensity, continuous 300-kW proton beam has been operated by a fixed target method without replacements till June of 2014. However, the lifetime of the fixed target was anticipated to be less than 1 year by the proton-irradiation damage of the graphite through 1-MW beam operation. To extend the lifetime, a muon rotating target, in which the radiation damage is distributed to a wider area, was installed in September of 2014, and continuous and stable operation has been successfully performed. Because the muon target becomes highly radioactive by the proton irradiation, the maintenance is conducted by remote handling in the Hot cell. In September of 2015, a scraper No. 1 to collimate the proton beam scattered by the target was replaced for further high-power beam operation. Recently, new developments on monitoring and maintenance of the muon target for higher power operation are in progress. In this article, perspective of muon production target at J-PARC MLF MUSE will be described.

Benchmarking Heavy Ion Transport Codes FLUKA, HETC-HEDS MARS15, MCNPX, and PHITS

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

Ronningen, Reginald Martin; Remec, Igor; Heilbronn, Lawrence H.

Powerful accelerators such as spallation neutron sources, muon-collider/neutrino facilities, and rare isotope beam facilities must be designed with the consideration that they handle the beam power reliably and safely, and they must be optimized to yield maximum performance relative to their design requirements. The simulation codes used for design purposes must produce reliable results. If not, component and facility designs can become costly, have limited lifetime and usefulness, and could even be unsafe. The objective of this proposal is to assess the performance of the currently available codes PHITS, FLUKA, MARS15, MCNPX, and HETC-HEDS that could be used for designmore » simulations involving heavy ion transport. We plan to access their performance by performing simulations and comparing results against experimental data of benchmark quality. Quantitative knowledge of the biases and the uncertainties of the simulations is essential as this potentially impacts the safe, reliable and cost effective design of any future radioactive ion beam facility. Further benchmarking of heavy-ion transport codes was one of the actions recommended in the Report of the 2003 RIA R&D Workshop".« less

Formation of long-lived CDn2+ and CHn2+ dications

NASA Astrophysics Data System (ADS)

Levy, Y.; Bar-David, A.; Ben-Itzhak, I.; Gertner, I.; Rosner, B.

1999-08-01

A systematic study of the formation of CDn2+ and CHn2+ dications in fast charge-stripping collisions with Ar atoms was conducted. The experimental method was based on the detection of the D (or H) fragments of the molecular ion of interest, and thus reducing the effect of the fraction of molecular ions containing the 13C isotope and other beam impurities. We observed long-lived CD22+, CD42+, and CD52+ dications. In the same process neither long-lived CD2+ nor CD32+ were observed. The mean lifetime of CD22+ was determined to be 4.0±1.11.3 µs, and those of CD42+ and CD52+ were longer than 2.1 and 3.3 µs, respectively. The production cross sections of CDn2+ from different CDm+ beams were measured. Long-lived CD22+ was formed from all CDm+ beams (micons/Journals/Common/geq" ALT="geq" ALIGN="TOP"/>2) and also directly from the rf ion source. In contrast, CD42+ and CD52+ were formed only from CD4+ and CD5+, respectively.

Analysis of Methods to Excite Head-Tail Motion Within the Cornell Electron Storage Ring

NASA Astrophysics Data System (ADS)

Gendler, Naomi; Billing, Mike; Shanks, Jim

The main accelerator complex at Cornell consists of two rings around which electrons and positrons move: the synchrotron, where the particles are accelerated to 5 GeV, and the Storage Ring, where the particles circulate a ta Þxed energy, guided by quadrupole and dipole magnets, with a steady energy due to a sinusoidal voltage source. Keeping the beam stable in the Storage Ring is crucial for its lifetime. A long-lasting, invariable beam means more accurate experiments, as well as brighter, more focused X-rays for use in the Cornell High Energy Synchrotron Source (CHESS). The stability of the electron and positron beams in the Cornell Electron Storage Ring (CESR) is important for the development of accelerators and for usage of the beam in X-ray science and accelerator physics. Bunch oscillations tend to enlarge the beam's cross section, making it less stable. We believe that one such oscillation is ``head-tail motion,'' where the bunch rocks back and forth on a pivot located at the central particle. In this project, we write a simulation of the bunch that induces head-tail motion with a vertical driver. We also excite this motion physically in the storage ring, and observe a deÞnite head-tail signal. In the experiment, we saw a deÞnite persistence of the drive-damp signal within a small band around the head-tail frequency, indicating that the head-tail frequency is a natural vertical mode of the bunch that was being excited. The signal seen in the experiment matched the signal seen in the simulation to within an order of magnitude.

Nanoparticle discrimination based on wavelength and lifetime-multiplexed cathodoluminescence microscopy.

PubMed

Garming, Mathijs W H; Weppelman, I Gerward C; de Boer, Pascal; Martínez, Felipe Perona; Schirhagl, Romana; Hoogenboom, Jacob P; Moerland, Robert J

2017-08-31

Nanomaterials can be identified in high-resolution electron microscopy images using spectrally-selective cathodoluminescence. Capabilities for multiplex detection can however be limited, e.g., due to spectral overlap or availability of filters. Also, the available photon flux may be limited due to degradation under electron irradiation. Here, we demonstrate single-pass cathodoluminescence-lifetime based discrimination of different nanoparticles, using a pulsed electron beam. We also show that cathodoluminescence lifetime is a robust parameter even when the nanoparticle cathodoluminescence intensity decays over an order of magnitude. We create lifetime maps, where the lifetime of the cathodoluminescence emission is correlated with the emission intensity and secondary-electron images. The consistency of lifetime-based discrimination is verified by also correlating the emission wavelength and the lifetime of nanoparticles. Our results show how cathodoluminescence lifetime provides an additional channel of information in electron microscopy.

Empirical Constraints on the Origin of Fast Radio Bursts: Volumetric Rates and Host Galaxy Demographics as a Test of Millisecond Magnetar Connection

NASA Astrophysics Data System (ADS)

Nicholl, M.; Williams, P. K. G.; Berger, E.; Villar, V. A.; Alexander, K. D.; Eftekhari, T.; Metzger, B. D.

2017-07-01

The localization of the repeating fast radio burst (FRB) 121102 to a low-metallicity dwarf galaxy at z = 0.193, and its association with a luminous quiescent radio source, suggests the possibility that FRBs originate from magnetars, formed by the unusual supernovae that occur in such galaxies. We investigate this possibility via a comparison of magnetar birth rates, the FRB volumetric rate, and host galaxy demographics. We calculate average volumetric rates of possible millisecond magnetar production channels, such as superluminous supernovae (SLSNe), long and short gamma-ray bursts (GRBs), and general magnetar production via core-collapse supernovae (CCSNe). For each channel, we also explore the expected host galaxy demographics using their known properties. We determine for the first time the number density of FRB emitters (the product of their volumetric birth rate and lifetime), {R}{FRB}τ ≈ {10}4 Gpc-3, assuming that FRBs are predominantly emitted from repetitive sources similar to FRB 121102 and adopting a beaming factor of 0.1. By comparing rates, we find that production via rare channels (SLSNe, GRBs) implies a typical FRB lifetime of ˜30-300 years, in good agreement with other lines of argument. The total energy emitted over this time is consistent with the available energy stored in the magnetic field. On the other hand, any relation to magnetars produced via normal CCSNe leads to a very short lifetime of ˜0.5 years, in conflict with both theory and observation. We demonstrate that due to the diverse host galaxy distributions of the different progenitor channels, many possible sources of FRB birth can be ruled out with ≲ 10 host galaxy identifications. Conversely, targeted searches of galaxies that have previously hosted decades-old SLSNe and GRBs may be a fruitful strategy for discovering new FRBs and related quiescent radio sources, and determining the nature of their progenitors.

Neutron resonance spin-echo upgrade at the three-axis spectrometer FLEXX

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

Groitl, F., E-mail: felix.groitl@psi.ch; Quintero-Castro, D. L.; Habicht, K.

2015-02-15

We describe the upgrade of the neutron resonance spin-echo setup at the cold neutron triple-axis spectrometer FLEXX at the BER II neutron source at the Helmholtz-Zentrum Berlin. The parameters of redesigned key components are discussed, including the radio frequency (RF) spin-flip coils, the magnetic shield, and the zero field coupling coils. The RF-flippers with larger beam windows allow for an improved neutron flux transfer from the source to the sample and further to the analyzer. The larger beam cross sections permit higher coil inclination angles and enable measurements on dispersive excitations with a larger slope of the dispersion. Due tomore » the compact design of the spin-echo units in combination with the increased coil tilt angles, the accessible momentum-range in the Larmor diffraction mode is substantially enlarged. In combination with the redesigned components of the FLEXX spectrometer, including the guide, the S-bender polarizer, the double focusing monochromator, and a Heusler crystal analyzer, the count rate increased by a factor of 15.5, and the neutron beam polarization is enhanced. The improved performance extends the range of feasible experiments, both for inelastic scattering on excitation lifetimes in single crystals, and for high-resolution Larmor diffraction. The experimental characterization of the instrument components demonstrates the reliable performance of the new neutron resonance spin-echo option, now available for the scientific community at FLEXX.« less

Radiological considerations for bulk shielding calculations of national synchrotron light source-II

NASA Astrophysics Data System (ADS)

Job, Panakkal K.; Casey, William R.

2011-12-01

Brookhaven National Laboratory is designing a new electron synchrotron for scientific research using synchrotron radiation. This facility, called the “National Synchrotron Light Source II” (NSLS-II), will provide x-ray radiation of ultra-high brightness and exceptional spatial and energy resolution. It will also provide advanced insertion devices, optics, detectors and robotics, and a suite of scientific instruments designed to maximize the scientific output of the facility. The project scope includes the design, construction, installation, and commissioning of the following accelerators: a 200 MeV linac, a booster synchrotron operating from 200 MeV to 3.0 GeV, and the storage ring which stores a maximum of 500 mA current of electrons at an energy of 3.0 GeV. It is planned to operate the facility primarily in a top-off mode, thereby maintaining the maximum variation in stored beam current to <1%. Because of the very demanding requirements for beam emittance and synchrotron radiation brilliance, the beam life-time is expected to be quite low, on the order of 2 h. Analysis of the bulk shielding for operating this facility and the input parameters used for this analysis have been discussed in this paper. The characteristics of each of the accelerators and their operating modes have been summarized with the input assumptions for the bulk shielding analysis.

A new possibility of low-Z gas stripper for high power uranium beam acceleration alternative to C-foil

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

Okuno, H.; Hershcovitch, A.; Fukunishi, N.

2010-09-27

The RIKEN accelerator complex started feeding the next-generation exotic beam facility RIBF (RadioIsotope Beam Factory) with heavy ion beams from 2007 after the successful commissioning at the end of 2006. Many elaborating improvements increased the intensity of the various heavy ion beams from 2007 to 2010. However, the available beam intensity especially of uranium beam is far below our goal of 1 p{micro}A (6 x 10{sup 12} particle/s). In order to achieve it, upgrade programs are well in progress, including constructions of a new 28 GHz superconducting ECR ion source and a new injector linac. However, the most serious problemmore » of the charge stripper for uranium beam is still open although many elaborating R&D works for the problems. Equilibrium charge state in gas generally is much lower than that in carbon foil due to its density-effect. But gas stripper is free from the problems originated from its lifetime and uniformity in thickness. Such merits pushed us think about low-Z gas stripper to get higher equilibrium charge state even in gas. Electron loss and capture cross section of U ion beams in He gas were measured as a function of their charge state at 11, 14 and 15 MeV/u. The extracted equilibrium charge states from the cross point of the two lines of the cross sections were promisingly higher than those in N{sub 2} gas by more than 10. The plasma window is expected to be a key technology to solve the difficulty in accumulation of such thick as about 1 mg/cm{sup 2} of low-Z gas.« less

Parasitic production of slow RI-beam from a projectile fragment separator by ion guide Laser Ion Source (PALIS)

NASA Astrophysics Data System (ADS)

Sonoda, Tetsu

2009-10-01

The projectile fragment separator BigRIPS of RIBF at RIKEN provides a wide variety of short-lived radioactive isotope (RI) ions without restrictions on their lifetime or chemical properties. A universal slow RI-beam facility (SLOWRI) to decelerate the beams from BigRIPS using an RF-carpet ion guide has been proposed as a principal facility of RIBF. However, beam time at such a modern accelerator facility is always limited and operational costs are high. We therefore propose an additional scheme as a complementary option to SLOWRI to drastically enhance the usability of such an expensive facility. In BigRIPS, a single primary beam produces thousands of isotopes but only one isotope is used for an experiment while the other >99.99% of isotopes are simply dumped in the slits or elsewhere in the fragment separator. We plan to locate a compact gas cell with 1 bar Ar at the slits. The thermalized ions in the cell will be quickly neutralized and transported to the exit by gas flow and resonantly re-ionized by lasers. Such low energy RI-beams will always be provided without any restriction to the main experiment. It will allow us to run parasitic experiments for precision atomic or decay spectroscopy, mass measurements. Furthermore, the resonance ionization in the cell itself can be used for high-sensitive laser spectroscopy, which will expand our knowledge of the ground state property of unstable nuclei.

Defects in mercury-cadmium telluride heteroepitaxial structures grown by molecular-beam epitaxy on silicon substrates

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

Mynbaev, K. D., E-mail: mynkad@mail.ioffe.ru; Zablotsky, S. V.; Shilyaev, A. V.

Defects in mercury-cadmium-telluride heteroepitaxial structures (with 0.3 to 0.4 molar fraction of cadmium telluride) grown by molecular-beam epitaxy on silicon substrates are studied. The low-temperature photoluminescence method reveals that there are comparatively deep levels with energies of 50 to 60 meV and shallower levels with energies of 20 to 30 meV in the band gap. Analysis of the temperature dependence of the minority carrier lifetime demonstrates that this lifetime is controlled by energy levels with an energy of ∼30 meV. The possible relationship between energy states and crystal-structure defects is discussed.

Measurement of the lifetime and the proportion of 12C3+ ions in stored relativistic ion beams as a preparation for laser cooling experiments at the CSRe

NASA Astrophysics Data System (ADS)

Wang, H. B.; Wen, W. Q.; Huang, Z. K.; Zhang, D. C.; Hai, B.; Zhu, X. L.; Zhao, D. M.; Yang, J.; Li, J.; Li, X. N.; Mao, L. J.; Mao, R. S.; Wu, J. X.; Yang, J. C.; Yuan, Y. J.; Eidam, L.; Winters, D.; Beck, T.; Kiefer, D.; Rein, B.; Walther, Th.; Loeser, M.; Schramm, U.; Siebold, M.; Bussmann, M.; Ma, X.

2017-10-01

We report on an experiment that was conducted in preparation of laser cooling experiments at the heavy-ion storage ring CSRe. The lifetimes of ion beams made up of 12C3+ and 16O4+ ions stored at an energy of 122 MeV/u in the CSRe were determined by two independent methods, firstly via a DC current transformer (DCCT) and secondly via a Schottky resonator. Using electron-cooling, the signals of the 12C3+ and 16O4+ ions could be separated and clearly observed in the Schottky spectrum. The obtained individual lifetimes of the 12C3+ and 16O4+ components were 23.6 s and 17.8 s, respectively. The proportion of 12C3+ ions in the stored ion beam was measured to be more than 70% at the beginning of the injection and increasing as a function of time. In addition to these measurements, the operation and remote control of a pulsed laser system placed directly next to the storage ring was tested in a setup similar to the one envisaged for future laser experiments.

Alternate operating scenarios for NDCX-II

NASA Astrophysics Data System (ADS)

Sharp, W. M.; Friedman, A.; Grote, D. P.; Cohen, R. H.; Lund, S. M.; Vay, J.-L.; Waldron, W. L.

2014-01-01

NDCX-II is a newly completed accelerator facility at LBNL, built to study ion-heated warm dense matter, as well as aspects of ion-driven targets and intense-beam dynamics for inertial-fusion energy. The baseline design calls for using 12 induction cells to accelerate 30-50 nC of Li+ ions to 1.2 MeV. During commissioning, though, we plan to extend the source lifetime by extracting less total charge. Over time, we expect that NDCX-II will be upgraded to substantially higher energies, necessitating the use of heavier ions to keep a suitable deposition range in targets. For operational flexibility, the option of using a helium plasma source is also being investigated. Each of these options requires development of an alternate acceleration schedule. The schedules here are worked out with a fast-running 1-D particle-in-cell code ASP.

Fluorescence lifetime measurements in flow cytometry

NASA Astrophysics Data System (ADS)

Beisker, Wolfgang; Klocke, Axel

1997-05-01

Fluorescence lifetime measurements provide insights int eh dynamic and structural properties of dyes and their micro- environment. The implementation of fluorescence lifetime measurements in flow cytometric systems allows to monitor large cell and particle populations with high statistical significance. In our system, a modulated laser beam is used for excitation and the phase shift of the fluorescence signal recorded with a fast computer controlled digital oscilloscope is processed digitally to determine the phase shift with respect to a reference beam by fast fourier transform. Total fluorescence intensity as well as other parameters can be determined simultaneously from the same fluorescence signal. We use the epi-illumination design to allow the use of high numerical apertures to collect as much light as possible to ensure detection of even weak fluorescence. Data storage and processing is done comparable to slit-scan flow cytometric data using data analysis system. The results are stored, displayed, combined with other parameters and analyzed as normal listmode data. In our report we discuss carefully the signal to noise ratio for analog and digital processed lifetime signals to evaluate the theoretical minimum fluorescence intensity for lifetime measurements. Applications to be presented include DNA staining, parameters of cell functions as well as different applications in non-mammalian cells such as algae.

Online SEOP polarization of Large Area Neutron Spin Filters

NASA Astrophysics Data System (ADS)

Babcock, Earl; Salhi, Zahir; Ioffe, Alexander

2015-04-01

The Juelich Center for neutron Science has a program to use SEOP polarized 3He Neutron Spin Filters (3He NSF) on many neutron scattering instruments. The main applications are for polarization analysis of the scattered beam. As such, the devices must operate in close proximity to the neutron sample and sample environment which can include complicated cryostats, humidity and pressure cells, and high field magnets. Thus we have developed novel magnetic cavities to house the 3He NSF cells which allow for simultaneous optical pumping on the instruments. Further we continually develop and redevelop the laser sources which must be relatively narrow band and have long term (i.e. months) stability and robust operation. The first fully operational polarizer has been used continuously for over 2, 60-day reactor cycles at the FRM2. This device uses a 12.5 cm I.D. 3He cell, and has a 3He storage lifetime, including the cells lifetime, in excess of 200 hours with the cell about 60 cm from the sample position inside a 1.2 T electromagnet, and has achieved over 75% 3He polarisation when fully optimized. This talk will describe the magnetic cavities, and laser sources as well as provide a description of the completed 3He polarizer devices.

Improved Determination of the Neutron Lifetime

NASA Astrophysics Data System (ADS)

Yue, A.

2013-10-01

The most precise determination of the neutron lifetime using the beam method reported a result of τn = (886 . 3 +/- 3 . 4) s. The dominant uncertainties were attributed to the absolute determination of the fluence of the neutron beam (2.7 s). The fluence was determined with a monitor that counted the neutron-induced charged particles from absorption in a thin, well-characterized 6Li deposit. The detection efficiency of the monitor was calculated from the areal density of the deposit, the detector solid angle, and the ENDF/B-VI 6Li(n,t)4He thermal neutron cross section. We have used a second, totally-absorbing neutron detector to directly measure the detection efficiency of the monitor on a monochromatic neutron beam of precisely known wavelength. This method does not rely on the 6Li(n,t)4He cross section or any other nuclear data. The monitor detection efficiency was measured to an uncertainty of 0.06%, which represents a five-fold improvement in uncertainty. We have verified the temporal stability of the monitor with ancillary measurements, and the measured neutron monitor efficiency has been used to improve the fluence determination in the past lifetime experiment. An updated neutron lifetime based on the improved fluence determination will be presented. Work done in collaboration with M. Dewey, D. Gilliam, J. Nico, National Institute of Standards and Technology; G. Greene, University of Tennessee / Oak Ridge National Laboratory; A. Laptev, Los Alamos National Laboratory; W. Snow, Indiana University; and F. Wietfeldt, Tulane University.

Radiative lifetimes and transition probabilities for electric-dipole delta n equals zero transitions in highly stripped sulfur ions

NASA Technical Reports Server (NTRS)

Pegg, D. J.; Elston, S. B.; Griffin, P. M.; Forester, J. P.; Thoe, R. S.; Peterson, R. S.; Sellin, I. A.; Hayden, H. C.

1976-01-01

The beam-foil time-of-flight method has been used to investigate radiative lifetimes and transition rates involving allowed intrashell transitions within the L shell of highly ionized sulfur. The results for these transitions, which can be particularly correlation-sensitive, are compared with current calculations based upon multiconfigurational models.

Optima HD Imax: Molecular Implant

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

Tieger, D. R.; Splinter, P. R.; Hsieh, T. J.

2008-11-03

Molecular implantation offers semiconductor device manufacturers multiple advantages over traditional high current ion implanters. The dose multiplication due to implanting more than one atom per molecule and the transport of beams at higher energies relative to the effective particle energies result in significant throughput enhancements without risk of energy contamination. The Optima HD Imax is introduced with molecular implant capability and the ability to reach up to 4.2 keV effective {sup 11}B from octadecaborane (B{sub 18}H{sub 22}). The ion source and beamline are optimized for molecular species ionization and transport. The beamline is coupled to the Optima HD mechanically scannedmore » endstation. The use of spot beam technology with ionized molecules maximizes the throughput potential and produces uniform implants with fast setup time and with superior angle control. The implanter architecture is designed to run multiple molecular species; for example, in addition to B{sub 18}H{sub 22} the system is capable of implanting carbon molecules for strain engineering and shallow junction engineering. Source lifetime data and typical operating conditions are described both for high dose, memory applications such as dual poly gate as well as lower energy implants for source drain extension and contact implants. Throughputs have been achieved in excess of 50 wafers per hour at doses up to 1x10{sup 16} ions/cm{sup 2} and for energies as low as 1 keV.« less

Converting an AEG Cyclotron to H- Acceleration and Extraction

NASA Astrophysics Data System (ADS)

Ramsey, Fred; Carroll, Lewis; Rathmann, Tom; Huenges, Ernst; Bechtold, Matthias Mentler Volker

2009-03-01

Clinical Trials are under way to evaluate agents labeled with the nuclide 225Ac and its decay product 213Bi, in targeted alpha-immuno-therapy [1]. 225Ac can be produced on a medium-energy cyclotron via the nuclear reaction 226Ra(p,n)225Ac. To demonstrate proof-of-principle, a vintage AEG cyclotron, Model E33 [2], with an internal target, had been employed in a pilot production program at the Technical University of Munich (TUM). To enhance production capability and further support the clinical studies, the TUM facility has recently been refurbished and upgraded, adding a new external beam-line, automated target irradiation and transport systems, new laboratories, hot cells, etc. [3]. An improved high-power rotating target has been built and installed [4]. The AEG cyclotron itself has also been modified and upgraded to accelerate and extract H- ions. We have designed, built, and tested a new axial Penning-type ion source which is optimized for the production of H- ions. The ion source has continued to evolve through experiment and experience. Steady improvements in materials and mechanics have led to enhanced source stability, life-time, and H- production. We have also designed and built a precision H- charge-exchange beam-extraction system which is equipped with a vacuum lock. To fit within the tight mechanical constraint imposed by the narrow magnet gap, the system incorporates a novel chain-drive foil holder and foil-changer mechanism. The reconfigured cyclotron system has now been in operation for more than 1 year. Three long-duration target irradiations have been conducted. The most recent bombardment ran 160 continuous hours at a beam on target of ˜80 microamperes for a total yield of ˜70 milli-curies of 225Ac.

Accelerator based fusion reactor

NASA Astrophysics Data System (ADS)

Liu, Keh-Fei; Chao, Alexander Wu

2017-08-01

A feasibility study of fusion reactors based on accelerators is carried out. We consider a novel scheme where a beam from the accelerator hits the target plasma on the resonance of the fusion reaction and establish characteristic criteria for a workable reactor. We consider the reactions d+t\\to n+α,d+{{}3}{{H}\\text{e}}\\to p+α , and p+{{}11}B\\to 3α in this study. The critical temperature of the plasma is determined from overcoming the stopping power of the beam with the fusion energy gain. The needed plasma lifetime is determined from the width of the resonance, the beam velocity and the plasma density. We estimate the critical beam flux by balancing the energy of fusion production against the plasma thermo-energy and the loss due to stopping power for the case of an inert plasma. The product of critical flux and plasma lifetime is independent of plasma density and has a weak dependence on temperature. Even though the critical temperatures for these reactions are lower than those for the thermonuclear reactors, the critical flux is in the range of {{10}22}-{{10}24}~\\text{c}{{\\text{m}}-2}~{{\\text{s}}-1} for the plasma density {ρt}={{10}15}~\\text{c}{{\\text{m}}-3} in the case of an inert plasma. Several approaches to control the growth of the two-stream instability are discussed. We have also considered several scenarios for practical implementation which will require further studies. Finally, we consider the case where the injected beam at the resonance energy maintains the plasma temperature and prolongs its lifetime to reach a steady state. The equations for power balance and particle number conservation are given for this case.

Numerical Analysis of Parasitic Crossing Compensation with Wires in DA$$\\Phi$$NE

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

Valishev, A.; Shatilov, D.; Milardi, C.

2015-06-24

Current-bearing wire compensators were successfully used in the 2005-2006 run of the DAΦNE collider to mitigate the detrimental effects of parasitic beam-beam interactions. A marked improvement of the positron beam lifetime was observed in machine operation with the KLOE detector. In view of the possible application of wire beam-beam compensators for the High Luminosity LHC upgrade, we revisit the DAΦNE experiments. We use an improved model of the accelerator with the goal to validate the modern simulation tools and provide valuable input for the LHC upgrade project.

Effects of hydrogen on majority carrier transport and minority carrier lifetimes in long wavelength infrared HgCdTe on Si

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

Boieriu, P.; Grein, C.H.; Velicu, S.

2006-02-06

We present the results of using an electron cyclotron resonance (ECR) plasma to incorporate hydrogen into long wavelength infrared HgCdTe layers grown by molecular beam epitaxy. Both as-grown and annealed layers doped in situ with indium were hydrogenated. Secondary ion mass spectroscopy confirmed the incorporation of hydrogen. Hall and photoconductive lifetime measurements were used to assess the effects of the hydrogenation. Increases in the electron mobilities and minority carrier lifetimes were observed for almost all ECR conditions.

Lifetime and Relative g Factor Measurements in 104,106,108Pd

NASA Astrophysics Data System (ADS)

Ilie, G.; Werner, V.; Radeck, D.; Ahn, T.; Bettermann, L.; Casperson, R. J.; Chevrier, R.; Cooper, N. M.; Heinz, A.; Holland, E.; McCarthy, D.; Smith, M. K.; Terry, J. R.; Williams, E.; Beausang, C. W.; Bonniwell, T. C.; Pauertein, B.

2013-03-01

The lifetimes and the relative g factors of the first excited states in 104,106,108Pd are reported here. The first 2+1 state in these Pd isotopes were excited by inverse kinematics Coulomb excitation on a 24Mg target and the lifetime was measured by the Recoil Distance Doppler Shift with the New Yale Plunger Device combined with the SPEEDY array of Clover detectors. The results show the feasibility of the new method, which should be applicable to experiments with radioactive ion beams.

Improved determination of the neutron lifetime.

PubMed

Yue, A T; Dewey, M S; Gilliam, D M; Greene, G L; Laptev, A B; Nico, J S; Snow, W M; Wietfeldt, F E

2013-11-27

The most precise determination of the neutron lifetime using the beam method was completed in 2005 and reported a result of τ(n)=(886.3±1.2[stat]±3.2[syst]) s. The dominant uncertainties were attributed to the absolute determination of the fluence of the neutron beam (2.7 s). The fluence was measured with a neutron monitor that counted the neutron-induced charged particles from absorption in a thin, well-characterized 6Li deposit. The detection efficiency of the monitor was calculated from the areal density of the deposit, the detector solid angle, and the evaluated nuclear data file, ENDF/B-VI 6Li(n,t)4He thermal neutron cross section. In the current work, we measure the detection efficiency of the same monitor used in the neutron lifetime measurement with a second, totally absorbing neutron detector. This direct approach does not rely on the 6Li(n,t)4He cross section or any other nuclear data. The detection efficiency is consistent with the value used in 2005 but is measured with a precision of 0.057%, which represents a fivefold improvement in the uncertainty. We verify the temporal stability of the neutron monitor through ancillary measurements, allowing us to apply the measured neutron monitor efficiency to the lifetime result from the 2005 experiment. The updated lifetime is τ(n)=(887.7±1.2[stat]±1.9[syst]) s.

Three-dimensional online surface reconstruction of augmented fluorescence lifetime maps using photometric stereo (Conference Presentation)

NASA Astrophysics Data System (ADS)

Unger, Jakob; Lagarto, Joao; Phipps, Jennifer; Ma, Dinglong; Bec, Julien; Sorger, Jonathan; Farwell, Gregory; Bold, Richard; Marcu, Laura

2017-02-01

Multi-Spectral Time-Resolved Fluorescence Spectroscopy (ms-TRFS) can provide label-free real-time feedback on tissue composition and pathology during surgical procedures by resolving the fluorescence decay dynamics of the tissue. Recently, an ms-TRFS system has been developed in our group, allowing for either point-spectroscopy fluorescence lifetime measurements or dynamic raster tissue scanning by merging a 450 nm aiming beam with the pulsed fluorescence excitation light in a single fiber collection. In order to facilitate an augmented real-time display of fluorescence decay parameters, the lifetime values are back projected to the white light video. The goal of this study is to develop a 3D real-time surface reconstruction aiming for a comprehensive visualization of the decay parameters and providing an enhanced navigation for the surgeon. Using a stereo camera setup, we use a combination of image feature matching and aiming beam stereo segmentation to establish a 3D surface model of the decay parameters. After camera calibration, texture-related features are extracted for both camera images and matched providing a rough estimation of the surface. During the raster scanning, the rough estimation is successively refined in real-time by tracking the aiming beam positions using an advanced segmentation algorithm. The method is evaluated for excised breast tissue specimens showing a high precision and running in real-time with approximately 20 frames per second. The proposed method shows promising potential for intraoperative navigation, i.e. tumor margin assessment. Furthermore, it provides the basis for registering the fluorescence lifetime maps to the tissue surface adapting it to possible tissue deformations.

A 5000-hour test of a grid-translation beam-deflection system for a 5-cm diameter Kaufman thruster

NASA Technical Reports Server (NTRS)

Lathem, W. C.

1973-01-01

A grid-translation type beam deflection system was tested on a 5-cm diameter mercury ion thruster for 5000 hours at a thrust level of about 0.36 mlb. During the first 2000 hours the beam was vectored 10 degrees in one direction. No erosion damage attributable to beam deflection was detected. Results indicate a possible lifetime of 15,000 to 20,000 hours. An optimized neutralizer position was used which eliminated the sputter erosion groove observed on the SERT 2 thrusters.

A 25kW fiber-coupled diode laser for pumping applications

NASA Astrophysics Data System (ADS)

Malchus, Joerg; Krause, Volker; Koesters, Arnd; Matthews, David G.

2014-03-01

In this paper we report the development of a new fiber-coupled diode laser for pumping applications capable of generating 25 kW with four wavelengths. The delivery fiber has 2.0 mm core diameter and 0.22 NA resulting in a Beam Parameter Product (BPP) of 220 mm mrad. To achieve the specifications mentioned above a novel beam transformation technique has been developed combining two high power laser stacks in one common module. After fast axis collimation and beam reformatting a beam with a BPP of 200 mm mrad x 40 mm mrad in the slow and fast-axis is generated. Based on this architecture a customer-specific pump laser with 25 kW optical output power has been developed, in which two modules are polarization multiplexed for each wavelength (980nm, 1020nm, 1040m and 1060nm). After slow-axis collimation these wavelengths are combined using dense wavelength coupling before focusing onto the fiber endface. This new laser is based on a turn-key platform, allowing straight-forward integration into any pump application. The complete system has a footprint of less than 1.4m² and a height of less than 1.8m. The laser diodes are water cooled, achieve a wall-plug efficiency of up to 60%, and have a proven lifetime of <30,000 hours. The new beam transformation techniques open up prospects for the development of pump sources with more than 100kW of optical output power.

Lifetime measurements using the recoil distance method—achievements and perspectives

NASA Astrophysics Data System (ADS)

Krücken, R.

2001-07-01

The recoil distance method (RDM) for measuring pico-second nuclear level lifetimes and its use in nuclear structure studies is reviewed and perspectives for the future are presented. High precision measurements in the mass-130 region, studies of multi-phonon states in rare earth nuclei, the investigation of shape coexistence and the recently discovered phenomenon of "magnetic rotation" are reviewed. Prospects for lifetime measurements in exotic regions of nuclei such as the measurement of lifetimes in neutron rich nuclei populated via spontaneous and heavy-ion induced fission are discussed. Other prospects include the use of the RDM technique in conjunction with recoil separators. The relevance of these techniques for experiments with radioactive ion beams will be discussed.

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.

Infrared detector device inspection system

DOEpatents

Soehnel, Grant; Bender, Daniel A.

2016-08-09

Methods and apparatuses for identifying carrier lifetimes are disclosed herein. In a general embodiment, a beam of light is sent to a group of locations on a material for an optical device. Photons emitted from the material are detected at each of the group of locations. A carrier lifetime is identified for each of the group of locations based on the photons detected from each of the group of locations.

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

Guarnieri, C.R.; Ramanathan, K.V.; Yee, D.S.

When Kaufman ion sources are used with pure oxygen at high discharge powers, their operational lifetime is limited to minutes. The lifetime of the source can be significantly increased by using thoria-coated filaments for the cathodes. In addition, the lifetime can be increased further by coating the anode with a conductive oxide such as IrO/sub 2/. This coating is deposited by sputter deposition. With these improvements the operational lifetime can be increased by a factor of 100.

Intra-Beam Scattering, Impedance, and Instabilities in Ultimate Storage Rings

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

Bane, Karl; /SLAC

We have investigated collective effects in an ultimate storage ring, i.e. one with diffraction limited emittances in both planes, using PEP-X as an example. In an ultimate ring intra-beam scattering (IBS) sets the limit of current that can be stored. In PEP-X, a 4.5 GeV ring running round beams at 200 mA in 3300 bunches, IBS doubles the emittances to 11.5 pm at the design current. The Touschek lifetime is 11 hours. Impedance driven collective effects tend not to be important since the beam current is relatively low. We have investigated collective effects in PEP-X, an ultimate storage ring, i.e.more » one with diffraction limited emittances (at one angstrom wavelength) in both planes. In an ultimate ring intra-beam scattering (IBS) sets the limit of current that can be stored. In PEP-X, IBS doubles the emittances to 11.5 pm at the design current of 200 mA, assuming round beams. The Touschek lifetime is quite large in PEP-X, 11.6 hours, and - near the operating point - increases with decreasing emittance. It is, however, a very sensitive function of momentum acceptance. In an ultimate ring like PEP-X impedance driven collective effects tend not to be important since the beam current is relatively low. Before ultimate PEP-X can be realized, the question of how to run a machine with round beams needs serious study. For example, in this report we assumed that the vertical emittance is coupling dominated. It may turn out that using vertical dispersion is a preferable way to generate round beams. The choice will affect IBS and the Touschek effect.« less

Recoil distance lifetime measurements in 122,124Xe

NASA Astrophysics Data System (ADS)

Govil, I. M.; Kumar, A.; Iyer, H.; Li, H.; Garg, U.; Ghugre, S. S.; Johnson, T.; Kaczarowski, R.; Kharraja, B.; Naguleswaran, S.; Walpe, J. C.

1998-02-01

Lifetimes of the lower-excited states in 122,124Xe are measured using the recoil-distance Doppler-shift technique. The reactions 110Pd(16O,4n)122Xe and 110Pd(18O,4n)124Xe at a beam energy of 66 MeV were used for this experiment. The lifetimes of the 2+, 4+, 6+, and 8+ states of the ground state band were extracted using the computer code LIFETIME including the corrections due to the side feeding and the nuclear deorientation effects. The lifetime of the 2+ state in 122Xe agrees with the recoil distance method (RDM) measurements but for the 124Xe it does not agree with the RDM measurements but agrees with the Coulomb-excitation experiment. The measured B(E2) values for both the nuclei are compared with the standard algebraic and the multishell models.

Design of a tokamak fusion reactor first wall armor against neutral beam impingement

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

Myers, R.A.

1977-12-01

The maximum temperatures and thermal stresses are calculated for various first wall design proposals, using both analytical solutions and the TRUMP and SAP IV Computer Codes. Beam parameters, such as pulse time, cycle time, and beam power, are varied. It is found that uncooled plates should be adequate for near-term devices, while cooled protection will be necessary for fusion power reactors. Graphite and tungsten are selected for analysis because of their desirable characteristics. Graphite allows for higher heat fluxes compared to tungsten for similar pulse times. Anticipated erosion (due to surface effects) and plasma impurity fraction are estimated. Neutron irradiationmore » damage is also discussed. Neutron irradiation damage (rather than erosion, fatigue, or creep) is estimated to be the lifetime-limiting factor on the lifetime of the component in fusion power reactors. It is found that the use of tungsten in fusion power reactors, when directly exposed to the plasma, will cause serious plasma impurity problems; graphite should not present such an impurity problem.« less

Measurements and predictions of the 6s6p{sup 1,3}P{sub 1} lifetimes in the Hg isoelectronic sequence

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

Curtis, L. J.; Irving, R. E.; Henderson, M.

2001-04-01

Experimental and theoretical values for the lifetimes of the 6s6p{sup 1}P{sub 1} and {sup 3}P{sub 1} levels in the Hg isoelectronic sequence are examined in the context of a data-based isoelectronic systematization. New beam-foil measurements for lifetimes in Pb III and Bi IV are reported and included in a critical evaluation of the available database. These results are combined with ab initio theoretical calculations and linearizing parametrizations to make predictive extrapolations for ions with 84{<=}Z{le}92.

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.

High yield neutron generators using the DD reaction

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

Vainionpaa, J. H.; Harris, J. L.; Piestrup, M. A.

2013-04-19

A product line of high yield neutron generators has been developed at Adelphi technology inc. The generators use the D-D fusion reaction and are driven by an ion beam supplied by a microwave ion source. Yields of up to 5 Multiplication-Sign 10{sup 9} n/s have been achieved, which are comparable to those obtained using the more efficient D-T reaction. The microwave-driven plasma uses the electron cyclotron resonance (ECR) to produce a high plasma density for high current and high atomic ion species. These generators have an actively pumped vacuum system that allows operation at reduced pressure in the target chamber,more » increasing the overall system reliability. Since no radioactive tritium is used, the generators can be easily serviced, and components can be easily replaced, providing essentially an unlimited lifetime. Fast neutron source size can be adjusted by selecting the aperture and target geometries according to customer specifications. Pulsed and continuous operation has been demonstrated. Minimum pulse lengths of 50 {mu}s have been achieved. Since the generators are easily serviceable, they offer a long lifetime neutron generator for laboratories and commercial systems requiring continuous operation. Several of the generators have been enclosed in radiation shielding/moderator structures designed for customer specifications. These generators have been proven to be useful for prompt gamma neutron activation analysis (PGNAA), neutron activation analysis (NAA) and fast neutron radiography. Thus these generators make excellent fast, epithermal and thermal neutron sources for laboratories and industrial applications that require neutrons with safe operation, small footprint, low cost and small regulatory burden.« less

High yield neutron generators using the DD reaction

NASA Astrophysics Data System (ADS)

Vainionpaa, J. H.; Harris, J. L.; Piestrup, M. A.; Gary, C. K.; Williams, D. L.; Apodaca, M. D.; Cremer, J. T.; Ji, Qing; Ludewigt, B. A.; Jones, G.

2013-04-01

A product line of high yield neutron generators has been developed at Adelphi technology inc. The generators use the D-D fusion reaction and are driven by an ion beam supplied by a microwave ion source. Yields of up to 5 × 109 n/s have been achieved, which are comparable to those obtained using the more efficient D-T reaction. The microwave-driven plasma uses the electron cyclotron resonance (ECR) to produce a high plasma density for high current and high atomic ion species. These generators have an actively pumped vacuum system that allows operation at reduced pressure in the target chamber, increasing the overall system reliability. Since no radioactive tritium is used, the generators can be easily serviced, and components can be easily replaced, providing essentially an unlimited lifetime. Fast neutron source size can be adjusted by selecting the aperture and target geometries according to customer specifications. Pulsed and continuous operation has been demonstrated. Minimum pulse lengths of 50 μs have been achieved. Since the generators are easily serviceable, they offer a long lifetime neutron generator for laboratories and commercial systems requiring continuous operation. Several of the generators have been enclosed in radiation shielding/moderator structures designed for customer specifications. These generators have been proven to be useful for prompt gamma neutron activation analysis (PGNAA), neutron activation analysis (NAA) and fast neutron radiography. Thus these generators make excellent fast, epithermal and thermal neutron sources for laboratories and industrial applications that require neutrons with safe operation, small footprint, low cost and small regulatory burden.

Recoil distance method lifetime measurements at TRIUMF-ISAC using the TIGRESS Integrated Plunger

NASA Astrophysics Data System (ADS)

Chester, A.; Ball, G. C.; Bernier, N.; Cross, D. S.; Domingo, T.; Drake, T. E.; Evitts, L. J.; Garcia, F. H.; Garnsworthy, A. B.; Hackman, G.; Hallam, S.; Henderson, J.; Henderson, R.; Krücken, R.; MacConnachie, E.; Moukaddam, M.; Padilla-Rodal, E.; Paetkau, O.; Pore, J. L.; Rizwan, U.; Ruotsalainen, P.; Shoults, J.; Smallcombe, J.; Smith, J. K.; Starosta, K.; Svensson, C. E.; Van Wieren, K.; Williams, J.; Williams, M.

2018-02-01

The TIGRESS Integrated Plunger device (TIP) has been developed for recoil distance method (RDM) lifetime measurements using the TIGRESS array of HPGe γ-ray detectors at TRIUMF's ISAC-II facility. A commissioning experiment was conducted utilizing a 250 MeV 84Kr beam at ≈ 2 × 108 particles per second. The 84Kr beam was Coulomb excited to the 21+ state on a movable 27Al target. A thin Cu foil fixed downstream from the target was used as a degrader. Excited nuclei emerged from the target and decayed by γ-ray emission at a distance determined by their velocity and the lifetime of the 21+ state. The ratio of decays which occur between the target and degrader to those occurring after traversing the degrader changes as a function of the target-degrader separation distance. Gamma-ray spectra at 13 target-degrader separation distances were measured and compared to simulated lineshapes to extract the lifetime. The result of τ = 5 . 541 ± 0 . 013(stat.) ± 0 . 063(sys.) ps is shorter than the literature value of 5 . 84 ± 0 . 18 ps with a reduction in uncertainty by a factor of approximately two. The TIP plunger device, experimental technique, analysis tools, and result are discussed.

Materials characterization of free volume and void properties by two-dimensional positron annihilation lifetime spectroscopy

NASA Astrophysics Data System (ADS)

Chen, Hongmin; Van Horn, J. David; Jean, Y. C.; Hung, Wei-Song; Lee, Kueir-Rarn

2013-04-01

Positron annihilation lifetime spectroscopy (PALS) has been widely used to determine the free volume and void properties in polymeric materials. Recently, a two dimensional positron annihilation lifetime spectroscopy (2DPALS) system has been developed for membrane applications. The system measures the coincident signals between the lifetime and the energy which could separate the 2γ and 3γ annihilations and improve the accuracy in the determination of the free volume and void properties. When 2D-PALS is used in coupling with a variable mono-energy slow positron beam, it could be applied to a variety of material characterization. Results of free volumes and voids properties in a multi-layer polymer membrane characterized using 2D-PALS are presented.

Measurement of the Neutron Beta Decay Lifetime using Magnetically Trapped Ultracold Neutrons

NASA Astrophysics Data System (ADS)

Adamek, Evan Robert

The neutron lifetime is an important parameter in the Standard Model of particle physics, with influences on the electroweak interaction and on Big Bang nucleosynthesis. Measurements of this quantity in cold beam experiments and in experiments using ultracold neutrons (UCN) disagree; this discrepancy may indicate that these measurements possess unaccounted-for systematic errors. The UCNtau experiment at Los Alamos Neutron Science Center (LANSCe) utilizes an asymmetrical magneto-gravitational storage volume with an in-situ vanadium detector. This setup is designed to either avoid or control many of the weaknesses that reduce systematic precision in other UCN lifetime experiments. Controlling for the many measurable errors requires detailed calculation and simulation, aided, for example, by the Geant4 Monte Carlo particle transport toolkit, which has been used to create a high fidelity model of the UCNtau experiment for modeling UCN transport, storage, and detection. Through the course of running the experiment, improvements in knowledge of particle measurement have led to improvements to the transport and to the detectors used in various parts of the experiment. With the experimental setup optimized to account for the subtleties of the measurement, the 2014-2015 beam period at LANSCe generated 85 measurement runs from which we could calculate the storage lifetime. Careful analysis of the effects of background on the vanadium detector assembly allowed for elimination of undesired signal and allowed for the extraction of a preliminary value for the neutron lifetime and the determination of areas to improve for the following run cycle.

Growth and Characterization of In(1-x)Ga(x)As(y)P(1-y) and GaAs Using Molecular Beam Epitaxy.

DTIC Science & Technology

1980-03-01

incident beams of As and P, respectively. The high vapor pressure , group V elements have a very short lifetime on the heated substrate unless there is...oven loaded with a high vapor pressure , group V element such as arsenic and phosphorous. An error analysis of Equation 5 reveals that incremental

Dynamics of submicron aerosol droplets in a robust optical trap formed by multiple Bessel beams

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

Thanopulos, Ioannis; Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, Athens 11635; Luckhaus, David

In this paper, we model the three-dimensional escape dynamics of single submicron-sized aerosol droplets in optical multiple Bessel beam traps. Trapping in counter-propagating Bessel beams (CPBBs) is compared with a newly proposed quadruple Bessel beam (QBB) trap, which consists of two perpendicularly arranged CPBB traps. Calculations are performed for perfectly and imperfectly aligned traps. Mie-theory and finite-difference time-domain methods are used to calculate the optical forces. The droplet escape kinetics are obtained from the solution of the Langevin equation using a Verlet algorithm. Provided the traps are perfectly aligned, the calculations indicate very long lifetimes for droplets trapped either inmore » the CPBB or in the QBB trap. However, minor misalignments that are hard to control experimentally already severely diminish the stability of the CPBB trap. By contrast, such minor misalignments hardly affect the extended droplet lifetimes in a QBB trap. The QBB trap is found to be a stable, robust optical trap, which should enable the experimental investigation of submicron droplets with radii down to 100 nm. Optical binding between two droplets and its potential role in preventing coagulation when loading a CPBB trap is briefly addressed.« less

Relation between electron- and photon-caused oxidation in EUVL optics

NASA Astrophysics Data System (ADS)

Malinowski, Michael E.; Steinhaus, Charles A.; Meeker, Donald E.; Clift, W. Miles; Klebanoff, Leonard E.; Bajt, Sasa

2003-06-01

Extreme ultraviolet (EUV)-induced oxidation of silicon-capped, [Mo/Si] multilayer mirrors in the presence of background levels of water vapor is recognized as one of the most serious threats to multilayer lifetime since oxidation of the top silicon layer is an irreversible process. The current work directly compares the oxidation on a silicon-capped, [Mo/Si] multilayers caused by EUV photons with the oxidation caused by 1 keV electrons in the presence of the same water vapor environment (2 x 10-6 Torr). Similar, 4 nm, silicon-capped, [Mo/Si] multilayer mirror samples were exposed to photons (95.3 eV) + water vapor at the ALS, LBNL, and also to a 1 keV electron beam + water vapor in separate experimental systems. The results of this work showed that the oxidation produced by ~1 µA of e-beam current was found to be equivalent to that produced by ~1 mW of EUV exposure. These results will help allow the use of 1 keV electrons beams, instead of EUV photons, to perform environmental testing of multilayers in a low-pressure water environment and to more accurately determine projected mirror lifetimes based on the electron beam exposures.

Relation between electron- and photon-caused oxidation in EUVL optics

NASA Astrophysics Data System (ADS)

Malinowski, Michael E.; Steinhaus, Charles A.; Meeker, Donald E.; Clift, W. Miles; Klebanoff, Leonard E.; Bajt, Sasa

2003-06-01

Extreme ultraviolet (EUV)-induced oxidation of silicon-capped, [Mo/Si] multilayer mirrors in the presence of background levels of water vapor is recognized as one of the most serious threats to multilayer lifetime since oxidation of the top silicon layer is an irreversible process. The current work directly compares the oxidation on a silicon-capped, [Mo/Si] multilayers caused by EUV photons with the oxidation caused by 1 keV electrons in the presence of the same water vapor environment (2 x 10-6 Torr). Similar, 4 nm, silicon-capped, [Mo/Si] multilayer mirror samples were exposed to photons (95.3 eV) + water vapor at the ALS, LBNL, and also to a 1 keV electron beam + water vapor in separate experimental systems. The results of this work showed that the oxidation produced by ~1 ´A of e-beam current was found to be equivalent to that produced by ~1 mW of EUV exposure. These results will help allow the use of 1 keV electrons beams, instead of EUV photons, to perform environmental testing of multilayers in a low-pressure water environment and to more accurately determine projected mirror lifetimes based on the electron beam exposures.

Pinhole shifting lifetime imaging microscopy

PubMed Central

Ramshesh, Venkat K.; Lemasters, John J.

2009-01-01

Lifetime imaging microscopy is a powerful tool to probe biological phenomena independent of luminescence intensity and fluorophore concentration. We describe time-resolved imaging of long-lifetime luminescence with an unmodified commercial laser scanning confocal/multiphoton microscope. The principle of the measurement is displacement of the detection pinhole to collect delayed luminescence from a position lagging the rasting laser beam. As proof of principle, luminescence from microspheres containing europium (Eu3+), a red emitting probe, was compared to that of short-lifetime green-fluorescing microspheres and/or fluorescein and rhodamine in solution. Using 720-nm two-photon excitation and a pinhole diameter of 1 Airy unit, the short-lifetime fluorescence of fluorescein, rhodamine and green microspheres disappeared much more rapidly than the long-lifetime phosphorescence of Eu3+ microspheres as the pinhole was repositioned in the lagging direction. In contrast, repositioning of the pinhole in the leading and orthogonal directions caused equal loss of short- and long-lifetime luminescence. From measurements at different lag pinhole positions, a lifetime of 270 μs was estimated for the Eu3+ microspheres, consistent with independent measurements. This simple adaptation is the basis for quantitative 3-D lifetime imaging microscopy. PMID:19123648

Precision Lifetime Measurements in Molecular Hydrogen

NASA Astrophysics Data System (ADS)

Ray, Mark D.

1995-01-01

We have measured the lifetimes of three rovibrational levels--g ^3Sigma_sp {g}{+}(v = 1,N = 2), i ^3{rm II}_sp{g} {-}(v = 0,N = 1), and j ^3Delta_sp{g}{-}(v = 1,N = 3)--in the n = 3 complex of para H _2 with a precision of 2%. The lifetimes are 8.66 +/- 0.16 ns for i ^3{rm II}_sp{g }{-}(v = 0, N = 1), 6.05+/- 0.11 ns for g ^3Sigma_sp {g}{+}(v = 1,N = 2), and 12.77 +/- 0.30 ns for j ^3 Delta_sp{g}{-}(v = 1,N = 3). On the basis of the first two measurements, we suggest that a previously neglected decay channel should be included in theoretical treatments and may have played an important role in an earlier experiment. Our value for the lifetime of j ^3Delta _sp{g}{-}(v = 1,N = 3) agrees well with the earlier experiment; the best theoretical estimate lies almost 50% higher. The measurements are done in a molecular beam via laser photoionization. An intense beam of metastable (2p) c ^3{rm II}_sp {u}{-} levels is created by electron bombardment. Downstream, a specific rotational -vibrational level of an n = 3 electronic state is excited by a resonant laser. After a delay, the remaining population is photoionized by a second laser. By measuring the photoionization yield as a function of the delay between the exciting and photoionizing lasers, we are able to determine the lifetime of the excited level. With a few modifications to the experimental apparatus, we believe it is possible to measure lifetimes at the 0.5% level of precision. We also propose the use of muti-channel quantum defect theory to obtain accurate ab initio decay rates for some of the branches involved.

Digitally synthesized beat frequency-multiplexed fluorescence lifetime spectroscopy

PubMed Central

Chan, Jacky C. K.; Diebold, Eric D.; Buckley, Brandon W.; Mao, Sien; Akbari, Najva; Jalali, Bahram

2014-01-01

Frequency domain fluorescence lifetime imaging is a powerful technique that enables the observation of subtle changes in the molecular environment of a fluorescent probe. This technique works by measuring the phase delay between the optical emission and excitation of fluorophores as a function of modulation frequency. However, high-resolution measurements are time consuming, as the excitation modulation frequency must be swept, and faster low-resolution measurements at a single frequency are prone to large errors. Here, we present a low cost optical system for applications in real-time confocal lifetime imaging, which measures the phase vs. frequency spectrum without sweeping. Deemed Lifetime Imaging using Frequency-multiplexed Excitation (LIFE), this technique uses a digitally-synthesized radio frequency comb to drive an acousto-optic deflector, operated in a cat’s-eye configuration, to produce a single laser excitation beam modulated at multiple beat frequencies. We demonstrate simultaneous fluorescence lifetime measurements at 10 frequencies over a bandwidth of 48 MHz, enabling high speed frequency domain lifetime analysis of single- and multi-component sample mixtures. PMID:25574449

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

Development of a Muon Rotating Target for J-PARC/MUSE

NASA Astrophysics Data System (ADS)

Makimura, Shunsuke; Kobayashi, Yasuo; Miyake, Yasuhiro; Kawamura, Naritoshi; Strasser, Patrick; Koda, Akihiro; Shimomura, Koichiro; Fujimori, Hiroshi; Nishiyama, Kusuo; Kato, Mineo; Kojima, Kenji; Higemoto, Wataru; Ito, Takashi; Shimizu, Ryou; Kadono, Ryosuke

At the J-PARC muon science facility (J-PARC/MUSE), a graphite target with a thickness of 20 mm has been used in vacuum to obtain an intense pulsed muon beam from the RCS 3-GeV proton beam [1], [2]. In the current design, the target frame is constructed using copper with a stainless steel tube embedded for water cooling. The energy deposited by the proton beam at 1 MW is evaluated to be 3.3 kW on the graphite target and 600 W on the copper frame by a Monte-Carlo simulation code, PHITS [3]. Graphite materials are known to lose their crystal structure and can be shrunk under intense proton beam irradiation. Consequently, the lifetime of the muon target is essentially determined by the radiation damage in graphite, and is evaluated to be half a year [4]. Hence, we are planning to distribute the radiation damage by rotating a graphite wheel. Although the lifetime of graphite in this case will be more than 10 years, the design of the bearing must be carefully considered. Because the bearing in JPARC/MUSE is utilized in vacuum, under high radiation, and at high temperature, an inorganic and solid lubricant must be applied to the bearing. Simultaneously, the temperature of the bearing must also be decreased to extend the lifetime. In 2009, a mock-up of the Muon Rotating Target, which could heat up and rotate a graphite wheel, was fabricated. Then several tests were started to select the lubricant and to determine the structure of the Muon Rotating Target, the control system and so on. In this report, the present status of the Muon Rotating Target for J-PARC/MUSE, especially the development of a rotation system in vacuum, is described.

Cathodoluminescent UV-radiation sources

NASA Astrophysics Data System (ADS)

Vereschagina, N. Y.; Danilkin, M. I.; Kazaryan, M. A.; Ozol, D. I.; Sheshin, E. P.; Spassky, D. A.

2018-04-01

Mercury-free UV-radiation sources are described. An electron beam similar to cathode-ray tubes (CRT) excites a luminescent material in a vacuum bulb. A high density of excitation requires the cathode and the luminescent material to be resistant for that and provide the extended lifetime of the UV-radiation source. Carbon fibre and nano-carbon based field-emission cathodes produce long lasting stable emission with a high current density (up to 0.3-0.5 A/cm2 ). Li2B4O7:Cu and Li2B4O7:Ag luminescent ceramics survive under high radiation doses and provide UV luminescence bands peaked at 360-370 nm and 270 nm, respectively. The luminescence band at 360-370 nm has a good overlap with the fundamental absorption edge of TiO2, which is known as a photo-catalyst in air and water cleaning systems. The luminescence band at 270 nm overlaps with DNA absorption and provides a direct disinfection effect. We suggest the structure of complex luminescence centres and energy transfer mechanisms. The electron structure of lithium tetraborate and the contribution of impurities are also discussed in paper.

Ultrastructure Processing and Environmental Stability of Advanced Structural and Electronic Materials.

DTIC Science & Technology

1983-03-01

network dissolution, electron beam simulated desorption, electron signal decay, oxidation, oxide layer , growth kinetics, silicon carbide, assivation...surface layers on silicate glasses are reviewed. A type IIIB glass surface is proposed. The mechanisms of hydrothermal attack of two phase lithia...method to make reliable lifetime predictions. Use of electron beam techniques is essential for understanding surface layers formed on glasses (Section III

A Microwave Driven Ion Source for Continuous-Flow AMS (Abstract)

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

Wills, J.; Schneider, R.J.; Reden, K.F. von

2005-03-15

A microwave-driven, gas-fed ion source originally developed as a high-current positive ion injector for a Tandem accelerator at Chalk River has been the subject of a three-year development program at the Woods Hole Oceanographic Institution NOSAMS facility. Off-line tests have demonstrated positive carbon currents of 1 mA and negative carbon currents of 80 {mu}A from CO2 gas feed. This source and a magnesium charge-exchange canal were coupled to the recombinator of the NOSAMS Tandetron for on-line tests, with the source fed with reference gasses and a combustion device.The promising results obtained have prompted the redesign of the microwave source formore » use as an on-line, continuous-flow injector for a new AMS facility under construction at NOSAMS. The new design is optimized for best transmission of the extracted positive-ion beam through the charge-exchange canal and for reliable operation at 40 kV extraction voltage. Other goals of the re-design include improved lifetime of the microwave window and the elimination of dead volumes in the plasma generator that increase sample hold-up time.This talk will include a summary of results obtained to date at NOSAMS with the Chalk River source and a detailed description of the new design.« less

A New Method for Studying the Atom: Optical spectra for multiply ionized atoms are produced by means of nuclear-physics techniques.

PubMed

Bashkin, S

1965-05-21

The new spectroscopy is in its infancy, and many fascinating aspects are yet to be studied. The properties of thin films may be studied by means of the excitation they induce in a given kind of beam. The production of ions with but a single electron offers a means of carefully mapping the nuclear charge distribution without the complications introduced by the normal complement of electrons. The study of high-purity, multiply ionized particles should make for better temperature determinations in hot plasmas. Possibly the data on lifetimes and modes of decay of excited energy levels may assist in the quantitative assignment of element abundances in the stars. One can even attempt to use the glowing beams as sources for absorption spectroscopy. The method seems to permit study of every stage of excitation for every stage of ionization for every element in the periodic table. Practical problems may interfere with so complete a study, but a major extension of our knowledge of atomic structure seems to be at hand.

Measuring radiative capture rates at DRAGON

NASA Astrophysics Data System (ADS)

Hager, U.; Davids, B.; Fallis, J.; Greife, U.; Hutcheon, D. A.; Rojas, A.; Ruiz, C.

2013-04-01

The DRAGON recoil separator facility is located at the ISAC facility at TRIUMF, Vancouver. It is designed to measure radiative alpha and proton capture reactions of astrophysical importance in inverse kinematics. The Supernanogan ion source at ISAC provides stable beams of high intensities. The DRAGON collaboration has taken advantage of this over the last years by measuring several reactions requiring high-intensity stable oxygen beams. In particular,the ^17O(p,γ) and ^16O(α,γ) reaction rates were recently measured. The former reaction is part of the hot CNO cycle, and strongly influences the abundance of ^18F in classical novae. Because of its relatively long lifetime, ^18F is a possible target for satellite-based gamma-ray spectroscopy. The ^16O(α,γ) reaction plays a role in steady-state helium burning in massive stars, where it follows the ^12C(α,γ) reaction. At astrophysically relevant energies, the reaction proceeds exclusively via direct capture, resulting in a low rate. In both cases, the unique capabilities of DRAGON enabled determination not only of the total reaction rates, but also of decay branching ratios. Results from both experiments will be presented.

Thermal analysis and cooling structure design of the primary collimator in CSNS/RCS

NASA Astrophysics Data System (ADS)

Zou, Yi-Qing; Wang, Na; Kang, Ling; Qu, Hua-Min; He, Zhe-Xi; Yu, Jie-Bing

2013-05-01

The rapid cycling synchrotron (RCS) of the China Spallation Neutron Source (CSNS) is a high intensity proton ring with beam power of 100 kW. In order to control the residual activation to meet the requirements of hands-on maintenance, a two-stage collimation system has been designed for the RCS. The collimation system consists of one primary collimator made of thin metal to scatter the beam and four secondary collimators as absorbers. Thermal analysis is an important aspect in evaluating the reliability of the collimation system. The calculation of the temperature distribution and thermal stress of the primary collimator with different materials is carried out by using ANSYS code. In order to control the temperature rise and thermal stress of the primary collimator to a reasonable level, an air cooling structure is intended to be used. The mechanical design of the cooling structure is presented, and the cooling efficiency with different chin numbers and wind velocity is also analyzed. Finally, the fatigue lifetime of the collimator under thermal shocks is estimated.

Lifetime measurements of the first 2 + states in 104,106Zr: Evolution of ground-state deformations

DOE PAGES

Browne, F.; Bruce, A. M.; Sumikama, T.; ...

2015-09-25

In this study, the first fast-timing measurements from nuclides produced via the in-flight fission mechanism are reported. The lifetimes of the first 2 + states in 104,106Zr nuclei have been measured via β-delayed γ-ray timing of stopped radioactive isotope beams. An improved precision for the lifetime of the 2 + 1 in 104Zr was obtained, τ(2 + 1) = 2.90 +25 –20, as well as a first measurement of the 2 + 1 state in 106Zr, τ(2 + 1) = 2.60 +20 –15 ns, with corresponding reduced transition probabilities.

Minority carrier lifetime in iodine-doped molecular beam epitaxy-grown HgCdTe

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

Madni, I.; Umana-Membreno, G. A.; Lei, W.

2015-11-02

The minority carrier lifetime in molecular beam epitaxy grown layers of iodine-doped Hg{sub 1−x}Cd{sub x}Te (x ∼ 0.3) on CdZnTe substrates has been studied. The samples demonstrated extrinsic donor behavior for carrier concentrations in the range from 2 × 10{sup 16} cm{sup −3} to 6 × 10{sup 17} cm{sup −3} without any post-growth annealing. At a temperature of 77 K, the electron mobility was found to vary from 10{sup 4} cm{sup 2}/V s to 7 × 10{sup 3} cm{sup 2}/V s and minority carrier lifetime from 1.6 μs to 790 ns, respectively, as the carrier concentration was increased from 2 × 10{sup 16} cm{supmore » −3} to 6 × 10{sup 17} cm{sup −3}. The diffusion of iodine is much lower than that of indium and hence a better alternative in heterostructures such as nBn devices. The influence of carrier concentration and temperature on the minority carrier lifetime was studied in order to characterize the carrier recombination mechanisms. Measured lifetimes were also analyzed and compared with the theoretical models of the various recombination processes occurring in these materials, indicating that Auger-1 recombination was predominant at higher doping levels. An increase in deep-level generation-recombination centers was observed with increasing doping level, which suggests that the increase in deep-level trap density is associated with the incorporation of higher concentrations of iodine into the HgCdTe.« less

The X-beam as a deployable boom for the space station

NASA Technical Reports Server (NTRS)

Adams, Louis R.

1988-01-01

Extension of antennas and thrust modules from the primary structure of the space station will require deployable beams of high stiffness and strength, as well as low mass and package volume. A square boom cross section is desirable for interface reasons. These requirements and others are satisfied by the X-beam. The X-beam folds by simple geometry, using single-degree-of-freedom hinges at simple angles, with no strain during deployment. Strut members are of large diameter with unidirectional graphite fibers for maximum beam performance. Fittings are aluminum with phosphor bronze bushings so that compliance is low and joint lifetime is high. The several beam types required for different applications on the space station will use the same basic design, with changes in strut cross section where necessary. Deployment is by a BI-STEM which pushes the beam out; retraction is by cables which cause initial folding and pull the beam in.

Solid-State Thyratron Replacement. Final Report

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

Roth, Ian

2017-12-12

Under this SBIR, DTI developed a solid-state switch as an alternative to legacy thyratron equipment. Our Phase II objective was to make a solid-state thyratron replacement that would provide equivalent or better performance, much higher reliability (at least a 20 year lifetime, compared to a thyratron’s two-year lifetime) and would sell for ~3x the cost of a thyratron, or less than $40k. We were successful in building a solid-state switch which could reliably function as a thyratron replacement. The unit was designed to directly replace the thyratrons currently being used at SLAC’s Linac Coherent Light Source (LCLS), and was builtmore » in a tank that was small enough to fit into the existing thyratron cabinet, providing a true form-fit-function replacement path. We tested the switch at the full operating specifications: 48 kV, 6.3 kA, and 1 µs risetime. We also demonstrated a peak-to-peak pulse jitter of 1.5 ns, which is five times shorter than is typical for thyratrons. This lower jitter would improve the performance of the LCLS beam. The predicted reliability is more than 80 years, which is 40 times greater than a thyratron.« less

The Generalized Centroid Difference method for lifetime measurements via γ-γ coincidences using large fast-timing arrays

NASA Astrophysics Data System (ADS)

Régis, J.-M.; Jolie, J.; Mach, H.; Simpson, G. S.; Blazhev, A.; Pascovici, G.; Pfeiffer, M.; Rudigier, M.; Saed-Samii, N.; Warr, N.; Blanc, A.; de France, G.; Jentschel, M.; Köster, U.; Mutti, P.; Soldner, T.; Ur, C. A.; Urban, W.; Bruce, A. M.; Drouet, F.; Fraile, L. M.; Ilieva, S.; Korten, W.; Kröll, T.; Lalkovski, S.; Mărginean, S.; Paziy, V.; Podolyák, Zs.; Regan, P. H.; Stezowski, O.; Vancraeyenest, A.

2015-05-01

A novel method for direct electronic "fast-timing" lifetime measurements of nuclear excited states via γ-γ coincidences using an array equipped with N very fast high-resolution LaBr3(Ce) scintillator detectors is presented. The generalized centroid difference method provides two independent "start" and "stop" time spectra obtained without any correction by a superposition of the N(N - 1)/2 calibrated γ-γ time difference spectra of the N detector fast-timing system. The two fast-timing array time spectra correspond to a forward and reverse gating of a specific γ-γ cascade and the centroid difference as the time shift between the centroids of the two time spectra provides a picosecond-sensitive mirror-symmetric observable of the set-up. The energydependent mean prompt response difference between the start and stop events is calibrated and used as a single correction for lifetime determination. These combined fast-timing array mean γ-γ zero-time responses can be determined for 40 keV < Eγ < 1.4 MeV with a precision better than 10 ps using a 152Eu γ-ray source. The new method is described with examples of (n,γ) and (n,f,γ) experiments performed at the intense cold-neutron beam facility PF1B of the Institut Laue-Langevin in Grenoble, France, using 16 LaBr3(Ce) detectors within the EXILL&FATIMA campaign in 2013. The results are discussed with respect to possible systematic errors induced by background contributions.

Single-crystal phosphors for high-brightness white LEDs/LDs

NASA Astrophysics Data System (ADS)

Víllora, Encarnación G.; Arjoca, Stelian; Inomata, Daisuke; Shimamura, Kiyoshi

2016-03-01

White light-emitting diodes (wLEDs) are the new environmental friendly sources for general lighting purposes. For applications requiring a high-brightness, current wLEDs present overheating problems, which drastically decrease their emission efficiency, color quality and lifetime. This work gives an overview of the recent investigations on single-crystal phosphors (SCPs), which are proposed as novel alternative to conventional ceramic powder phosphors (CPPs). This totally new approach takes advantage of the superior properties of single-crystals in comparison with ceramic materials. SCPs exhibit an outstanding conversion efficiency and thermal stability up to 300°C. Furthermore, compared with encapsulated CPPs, SCPs possess a superior thermal conductivity, so that generated heat can be released efficiently. The conjunction of all these characteristics results in a low temperature rise of SCPs even under high blue irradiances, where conventional CPPs are overheated or even burned. Therefore, SCPs represent the ideal, long-demanded all-inorganic phosphors for high-brightness white light sources, especially those involving the use of high-density laser-diode beams.

Top-up injection schemes for future circular lepton collider

NASA Astrophysics Data System (ADS)

Aiba, M.; Goddard, B.; Oide, K.; Papaphilippou, Y.; Saá Hernández, Á.; Shwartz, D.; White, S.; Zimmermann, F.

2018-02-01

Top-up injection is an essential ingredient for the future circular lepton collider (FCC-ee) to maximize the integrated luminosity and it determines the design performance. In ttbar operation mode, with a beam energy of 175 GeV, the design lifetime of ∼1 h is the shortest of the four anticipated operational modes, and the beam lifetime may be even shorter in actual operation. A highly robust top-up injection scheme is consequently imperative. Various top-up methods are investigated and a number of suitable schemes are considered in developing alternative designs for the injection straight section of the collider ring. For the first time, we consider multipole-kicker off-energy injection, for minimizing detector background in top-up operation, and the use of a thin wire septum in a lepton storage ring, for maximizing the luminosity.

Online multispectral fluorescence lifetime values estimation and overlay onto tissue white-light video frames

NASA Astrophysics Data System (ADS)

Gorpas, Dimitris; Ma, Dinglong; Bec, Julien; Yankelevich, Diego R.; Marcu, Laura

2016-03-01

Fluorescence lifetime imaging has been shown to be a robust technique for biochemical and functional characterization of tissues and to present great potential for intraoperative tissue diagnosis and guidance of surgical procedures. We report a technique for real-time mapping of fluorescence parameters (i.e. lifetime values) onto the location from where the fluorescence measurements were taken. This is achieved by merging a 450 nm aiming beam generated by a diode laser with the excitation light in a single delivery/collection fiber and by continuously imaging the region of interest with a color CMOS camera. The interrogated locations are then extracted from the acquired frames via color-based segmentation of the aiming beam. Assuming a Gaussian profile of the imaged aiming beam, the segmentation results are fitted to ellipses that are dynamically scaled at the full width of three automatically estimated thresholds (50%, 75%, 90%) of the Gaussian distribution's maximum value. This enables the dynamic augmentation of the white-light video frames with the corresponding fluorescence decay parameters. A fluorescence phantom and fresh tissue samples were used to evaluate this method with motorized and hand-held scanning measurements. At 640x512 pixels resolution the area of interest augmented with fluorescence decay parameters can be imaged at an average 34 frames per second. The developed method has the potential to become a valuable tool for real-time display of optical spectroscopy data during continuous scanning applications that subsequently can be used for tissue characterization and diagnosis.

Local re-acceleration and a modified thick target model of solar flare electrons

NASA Astrophysics Data System (ADS)

Brown, J. C.; Turkmani, R.; Kontar, E. P.; MacKinnon, A. L.; Vlahos, L.

2009-12-01

Context: The collisional thick target model (CTTM) of solar hard X-ray (HXR) bursts has become an almost “standard model” of flare impulsive phase energy transport and radiation. However, it faces various problems in the light of recent data, particularly the high electron beam density and anisotropy it involves. Aims: We consider how photon yield per electron can be increased, and hence fast electron beam intensity requirements reduced, by local re-acceleration of fast electrons throughout the HXR source itself, after injection. Methods: We show parametrically that, if net re-acceleration rates due to e.g. waves or local current sheet electric (E) fields are a significant fraction of collisional loss rates, electron lifetimes, and hence the net radiative HXR output per electron can be substantially increased over the CTTM values. In this local re-acceleration thick target model (LRTTM) fast electron number requirements and anisotropy are thus reduced. One specific possible scenario involving such re-acceleration is discussed, viz, a current sheet cascade (CSC) in a randomly stressed magnetic loop. Results: Combined MHD and test particle simulations show that local E fields in CSCs can efficiently accelerate electrons in the corona and and re-accelerate them after injection into the chromosphere. In this HXR source scenario, rapid synchronisation and variability of impulsive footpoint emissions can still occur since primary electron acceleration is in the high Alfvén speed corona with fast re-acceleration in chromospheric CSCs. It is also consistent with the energy-dependent time-of-flight delays in HXR features. Conclusions: Including electron re-acceleration in the HXR source allows an LRTTM modification of the CTTM in which beam density and anisotropy are much reduced, and alleviates theoretical problems with the CTTM, while making it more compatible with radio and interplanetary electron numbers. The LRTTM is, however, different in some respects such as spatial distribution of atmospheric heating by fast electrons.

Cobalt-60 Machines and Medical Linear Accelerators: Competing Technologies for External Beam Radiotherapy.

PubMed

Healy, B J; van der Merwe, D; Christaki, K E; Meghzifene, A

2017-02-01

Medical linear accelerators (linacs) and cobalt-60 machines are both mature technologies for external beam radiotherapy. A comparison is made between these two technologies in terms of infrastructure and maintenance, dosimetry, shielding requirements, staffing, costs, security, patient throughput and clinical use. Infrastructure and maintenance are more demanding for linacs due to the complex electric componentry. In dosimetry, a higher beam energy, modulated dose rate and smaller focal spot size mean that it is easier to create an optimised treatment with a linac for conformal dose coverage of the tumour while sparing healthy organs at risk. In shielding, the requirements for a concrete bunker are similar for cobalt-60 machines and linacs but extra shielding and protection from neutrons are required for linacs. Staffing levels can be higher for linacs and more staff training is required for linacs. Life cycle costs are higher for linacs, especially multi-energy linacs. Security is more complex for cobalt-60 machines because of the high activity radioactive source. Patient throughput can be affected by source decay for cobalt-60 machines but poor maintenance and breakdowns can severely affect patient throughput for linacs. In clinical use, more complex treatment techniques are easier to achieve with linacs, and the availability of electron beams on high-energy linacs can be useful for certain treatments. In summary, there is no simple answer to the question of the choice of either cobalt-60 machines or linacs for radiotherapy in low- and middle-income countries. In fact a radiotherapy department with a combination of technologies, including orthovoltage X-ray units, may be an option. Local needs, conditions and resources will have to be factored into any decision on technology taking into account the characteristics of both forms of teletherapy, with the primary goal being the sustainability of the radiotherapy service over the useful lifetime of the equipment. Copyright © 2016 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

Accurate determination of electronic transport properties of silicon wafers by nonlinear photocarrier radiometry with multiple pump beam sizes

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

Wang, Qian; University of the Chinese Academy of Sciences, Beijing 100039; Li, Bincheng, E-mail: bcli@uestc.ac.cn

2015-12-07

In this paper, photocarrier radiometry (PCR) technique with multiple pump beam sizes is employed to determine simultaneously the electronic transport parameters (the carrier lifetime, the carrier diffusion coefficient, and the front surface recombination velocity) of silicon wafers. By employing the multiple pump beam sizes, the influence of instrumental frequency response on the multi-parameter estimation is totally eliminated. A nonlinear PCR model is developed to interpret the PCR signal. Theoretical simulations are performed to investigate the uncertainties of the estimated parameter values by investigating the dependence of a mean square variance on the corresponding transport parameters and compared to that obtainedmore » by the conventional frequency-scan method, in which only the frequency dependences of the PCR amplitude and phase are recorded at single pump beam size. Simulation results show that the proposed multiple-pump-beam-size method can improve significantly the accuracy of the determination of the electronic transport parameters. Comparative experiments with a p-type silicon wafer with resistivity 0.1–0.2 Ω·cm are performed, and the electronic transport properties are determined simultaneously. The estimated uncertainties of the carrier lifetime, diffusion coefficient, and front surface recombination velocity are approximately ±10.7%, ±8.6%, and ±35.4% by the proposed multiple-pump-beam-size method, which is much improved than ±15.9%, ±29.1%, and >±50% by the conventional frequency-scan method. The transport parameters determined by the proposed multiple-pump-beam-size PCR method are in good agreement with that obtained by a steady-state PCR imaging technique.« less

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.

Fabrication of 94Zr thin target for recoil distance doppler shift method of lifetime measurement

NASA Astrophysics Data System (ADS)

Gupta, C. K.; Rohilla, Aman; Abhilash, S. R.; Kabiraj, D.; Singh, R. P.; Mehta, D.; Chamoli, S. K.

2014-11-01

A thin isotopic 94Zr target of thickness 520 μg /cm2 has been prepared for recoil distance Doppler shift method (RDM) lifetime measurement by using an electron beam deposition method on tantalum backing of 3.5 mg/cm2 thickness at Inter University Accelerator Center (IUAC), New Delhi. To meet the special requirement of smoothness of surface for RDM lifetime measurement and also to protect the outer layer of 94Zr from peeling off, a very thin layer of gold has been evaporated on a 94Zr target on a specially designed substrate holder. In all, 143 mg of 99.6% enriched 94Zr target material was utilized for the fabrication of 94Zr targets. The target has been successfully used in a recent RDM lifetime measurement experiment at IUAC.

Long lifetime, low intensity light source for use in nighttime viewing of equipment maps and other writings

DOEpatents

Frank, Alan M.; Edwards, William R.

1983-01-01

A long-lifetime light source with sufficiently low intensity to be used for reading a map or other writing at nighttime, while not obscuring the user's normal night vision. This light source includes a diode electrically connected in series with a small power source and a lens properly positioned to focus at least a portion of the light produced by the diode.

Focused electron and ion beam systems

DOEpatents

Leung, Ka-Ngo; Reijonen, Jani; Persaud, Arun; Ji, Qing; Jiang, Ximan

2004-07-27

An electron beam system is based on a plasma generator in a plasma ion source with an accelerator column. The electrons are extracted from a plasma cathode in a plasma ion source, e.g. a multicusp plasma ion source. The beam can be scanned in both the x and y directions, and the system can be operated with multiple beamlets. A compact focused ion or electron beam system has a plasma ion source and an all-electrostatic beam acceleration and focusing column. The ion source is a small chamber with the plasma produced by radio-frequency (RF) induction discharge. The RF antenna is wound outside the chamber and connected to an RF supply. Ions or electrons can be extracted from the source. A multi-beam system has several sources of different species and an electron beam source.

An Acoustic Charge Transport Imager for High Definition Television Applications: Reliability Modeling and Parametric Yield Prediction of GaAs Multiple Quantum Well Avalanche Photodiodes. Degree awarded Oct. 1997

NASA Technical Reports Server (NTRS)

Hunt, W. D.; Brennan, K. F.; Summers, C. J.; Yun, Ilgu

1994-01-01

Reliability modeling and parametric yield prediction of GaAs/AlGaAs multiple quantum well (MQW) avalanche photodiodes (APDs), which are of interest as an ultra-low noise image capture mechanism for high definition systems, have been investigated. First, the effect of various doping methods on the reliability of GaAs/AlGaAs multiple quantum well (MQW) avalanche photodiode (APD) structures fabricated by molecular beam epitaxy is investigated. Reliability is examined by accelerated life tests by monitoring dark current and breakdown voltage. Median device lifetime and the activation energy of the degradation mechanism are computed for undoped, doped-barrier, and doped-well APD structures. Lifetimes for each device structure are examined via a statistically designed experiment. Analysis of variance shows that dark-current is affected primarily by device diameter, temperature and stressing time, and breakdown voltage depends on the diameter, stressing time and APD type. It is concluded that the undoped APD has the highest reliability, followed by the doped well and doped barrier devices, respectively. To determine the source of the degradation mechanism for each device structure, failure analysis using the electron-beam induced current method is performed. This analysis reveals some degree of device degradation caused by ionic impurities in the passivation layer, and energy-dispersive spectrometry subsequently verified the presence of ionic sodium as the primary contaminant. However, since all device structures are similarly passivated, sodium contamination alone does not account for the observed variation between the differently doped APDs. This effect is explained by the dopant migration during stressing, which is verified by free carrier concentration measurements using the capacitance-voltage technique.

RDM lifetime measurements in 107Cd

NASA Astrophysics Data System (ADS)

Andgren, K.; Ashley, S. F.; Regan, P. H.; McCutchan, E. A.; Zamfir, N. V.; Amon, L.; Cakirli, R. B.; Casten, R. F.; Clark, R. M.; Gürdal, G.; Keyes, K. L.; Meyer, D. A.; Erduran, M. N.; Papenberg, A.; Pietralla, N.; Plettner, C.; Rainovski, G.; Ribas, R. V.; Thomas, N. J.; Vinson, J.; Warner, D. D.; Werner, V.; Williams, E.

2005-10-01

Lifetimes for decays linking near-yrast states in 107Cd have been measured using the recoil distance method (RDM). The nucleus of interest was populated via the 98Mo(12C,3n)107Cd fusion-evaporation reaction at an incident beam energy of 60 MeV. From the measured lifetimes, transition probabilities have been deduced and compared with the theoretical B(E2) values for limiting cases of harmonic vibrational and axially deformed rotational systems. Our initial results suggest a rotor-like behaviour for the structure based on the unnatural-parity, h11/2 orbital in 107Cd, providing further evidence for the role of this 'shape-polarizing' orbital in stabilizing the nuclear deformation in the A ~ 100 transitional region.

Effect of 1.5 MeV electron irradiation on β-Ga2O3 carrier lifetime and diffusion length

NASA Astrophysics Data System (ADS)

Lee, Jonathan; Flitsiyan, Elena; Chernyak, Leonid; Yang, Jiancheng; Ren, Fan; Pearton, Stephen J.; Meyler, Boris; Salzman, Y. Joseph

2018-02-01

The influence of 1.5 MeV electron irradiation on minority transport properties of Si doped β-Ga2O3 vertical Schottky rectifiers was observed for fluences up to 1.43 × 1016 cm-2. The Electron Beam-Induced Current technique was used to determine the minority hole diffusion length as a function of temperature for each irradiation dose. This revealed activation energies related to shallow donors at 40.9 meV and radiation-induced defects with energies at 18.1 and 13.6 meV. Time-resolved cathodoluminescence measurements showed an ultrafast 210 ps decay lifetime and reduction in carrier lifetime with increased irradiation.

Landau Damping of Beam Instabilities by Electron Lenses

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

Shiltsev, V.; Alexahin, Yuri; Burov, A.

2017-06-26

Modern and future particle accelerators employ increasingly higher intensity and brighter beams of charged particles and become operationally limited by coherent beam instabilities. Usual methods to control the instabilities, such as octupole magnets, beam feedback dampers and use of chromatic effects, become less effective and insufficient. We show that, in contrast, Lorentz forces of a low-energy, a magnetically stabilized electron beam, or "electron lens", easily introduces transverse nonlinear focusing sufficient for Landau damping of transverse beam instabilities in accelerators. It is also important that, unlike other nonlinear elements, the electron lens provides the frequency spread mainly at the beam core,more » thus allowing much higher frequency spread without lifetime degradation. For the parameters of the Future Circular Collider, a single conventional electron lens a few meters long would provide stabilization superior to tens of thousands of superconducting octupole magnets.« less

Landau Damping of Beam Instabilities by Electron Lenses

DOE PAGES

Shiltsev, V.; Alexahin, Yuri; Burov, A.; ...

2017-09-27

Modern and future particle accelerators employ increasingly higher intensity and brighter beams of charged particles and become operationally limited by coherent beam instabilities. Usual methods to control the instabilities, such as octupole magnets, beam feedback dampers, and use of chromatic effects, become less effective and insufficient. Here, we show that, in contrast, Lorentz forces of a low-energy, magnetically stabilized electron beam, or “electron lens,” easily introduce transverse nonlinear focusing sufficient for Landau damping of transverse beam instabilities in accelerators. It is also important to note that, unlike other nonlinear elements, the electron lens provides the frequency spread mainly at themore » beam core, thus allowing much higher frequency spread without lifetime degradation. For the parameters of the Future Circular Collider, a single conventional electron lens a few meters long would provide stabilization superior to tens of thousands of superconducting octupole magnets.« less

High-energy surface and volume plasmons in nanopatterned sub-10 nm aluminum nanostructures

DOE PAGES

Hobbs, Richard G.; Manfrinato, Vitor R.; Yang, Yujia; ...

2016-06-13

In this paper, we use electron energy-loss spectroscopy to map the complete plasmonic spectrum of aluminum nanodisks with diameters ranging from 3 to 120 nm fabricated by high-resolution electron-beam lithography. Our nanopatterning approach allows us to produce localized surface plasmon resonances across a wide spectral range spanning 2–8 eV. Electromagnetic simulations using the finite element method support the existence of dipolar, quadrupolar, and hexapolar surface plasmon modes as well as centrosymmetric breathing modes depending on the location of the electron-beam excitation. In addition, we have developed an approach using nanolithography that is capable of meV control over the energy andmore » attosecond control over the lifetime of volume plasmons in these nanodisks. The precise measurement of volume plasmon lifetime may also provide an opportunity to probe and control the DC electrical conductivity of highly confined metallic nanostructures. Lastly, we show the strong influence of the nanodisk boundary in determining both the energy and lifetime of surface plasmons and volume plasmons locally across individual aluminum nanodisks, and we have compared these observations to similar effects produced by scaling the nanodisk diameter.« less

Search for new physics with long-lived particles decaying to photons and missing energy in pp collisions at $$ \\sqrt{s}=7 $$ TeV

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

Chatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.

A search is performed for long-lived neutral particles decaying into a photon and invisible particles. An example of such a signature is the decay of the lightest neutralino with nonzero lifetime into a gravitino and a photon in gauge-mediated supersymmetry, with the neutralino as the next-to-lightest supersymmetric particle and the gravitino as the lightest. The search uses events containing photons, missing transverse energy, and jets. The impact parameter of the photon relative to the beam-beam collision point can be reconstructed using converted photons. The method is sensitive to lifetimes of the order of 0.1 to 1 ns. The data samplemore » corresponds to an integrated luminosity of 2.23 inverse femtobarns in pp collisions at sqrt(s) = 7 TeV, recorded in the first part of 2011 by the CMS experiment at the LHC. Cross-section limits are presented on pair production for such particles, each of which decays into a photon and invisible particles. The observed 95% confidence level limits vary between 0.11 and 0.21 pb, depending on the neutral particle lifetime.« less

Transient diffraction grating measurements of molecular diffusion in the undergraduate laboratory

NASA Astrophysics Data System (ADS)

Spiegel, Daniel R.; Tuli, Santona

2011-07-01

Diffusion is a central process in many biological, chemical, and physical systems. We describe an experiment that employs the interference of laser beams to allow the measurement of molecular diffusion on submillimeter length scales. The interference fringes of two intersecting pump beams within a dye solution create a sinusoidal distribution of long-lived molecular excited states. A third probe beam is incident at a wavelength at which the indices of refraction of the ground and excited states are different, so the probe beam diffracts from the spatially periodic excited-state pattern. After the pump beams are switched off, the excited-state periodicity washes out as the system diffuses back to equilibrium. The molecular diffusion constant is obtained from the rate constant of the exponential decay of the diffracted beam. It is also possible to measure the excited-state lifetime.

Development of Next Generation Lifetime PSP Imaging Systems

NASA Technical Reports Server (NTRS)

Watkins, A. Neal; Jordan, Jeffrey D.; Leighty, Bradley D.; Ingram, JoAnne L.; Oglesby, Donald M.

2002-01-01

This paper describes a lifetime PSP system that has recently been developed using pulsed light-emitting diode (LED) lamps and a new interline transfer CCD camera technology. This system alleviates noise sources associated with lifetime PSP systems that use either flash-lamp or laser excitation sources and intensified CCD cameras for detection. Calibration curves have been acquired for a variety of PSP formulations using this system, and a validation test was recently completed in the Subsonic Aerodynamic Research Laboratory (SARL) at Wright-Patterson Air Force Base (WPAFB). In this test, global surface pressure distributions were recovered using both a standard intensity-based method and the new lifetime system. Results from the lifetime system agree both qualitatively and quantitatively with those measured using the intensity-based method. Finally, an advanced lifetime imaging technique capable of measuring temperature and pressure simultaneously is introduced and initial results are presented.

Quantum efficiency temporal response and lifetime of a GaAs cathode in SRF electron gun

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

Wang, E.; Ben-Zvi, I.; Kewisch, J.

2010-05-23

RF electron guns with a strained super lattice GaAs cathode can generate polarized electron beam of higher brightness and lower emittance than do DC guns, due to their higher field gradient at the cathode's surface. In a normal conducting RF gun, the extremely high vaccum required by these cathodes can not be met. We report on an experiment with a superconducting SRF gun, which can maintain a vacuum of nearly 10-12 torr because of cryo-pumping at the temperature of 4.2K. With conventional activation, we obtained a QE of 3% at 532 nm, with lifetime of nearly 3 days in themore » preparation chamber. We plan to use this cathode in a 1.3 GHz 1/2 cell SRF gun to study its performance. In addition, we studied the multipacting at the location of cathode. A new model based on the Forkker-Planck equation which can estimate the bunch length of the electron beam is discussed in this paper. Future particle accelerators such as eRHIC and ILC require high brightness, high current polarized electrons Recently, using a superlattice crystal, the maximum polarization of 95% was reached. Activation with Cs,O lowers the electron affinity and makes it energetically possible for all the electrons excited in to the conduction band and reach the surface to escape into the vacuum. Presently the polarized electron sources are based on DC gun, such as that at the CEBAF at Jlab. In these devices, the life time of the cathode is extended due to the reduced back bombardment in their UHV conditions. However, the low accelerating gradient of the DC guns lead to poor longitudinal emittance. The higher accelerating gradient of the RF gun generates low emittance beams. Superconducting RF guns combine the excellent vacuum conditions of the DC guns with the higher accelerating gradients of the RF guns and provide potentially a long lived cathode with very low transverse and longitudinal emittance. In our work at BNL, we successfully activated the GaAs. The quantum efficient is 3% at 532 nm and is expected to improve further. In addition, we studied the multipacting at the location of cathode. A new model based on the Forkker-Planck equation which can estimate the bunch length of the electron beam is discussed in this paper.« less

A novel approach to prepare optically active ion doped luminescent materials via electron beam evaporation into ionic liquids

DOE PAGES

Richter, K.; Lorbeer, C.; Mudring, A. -V.

2014-11-10

A novel approach to prepare luminescent materials via electron-beam evaporation into ionic liquids is presented which even allows doping of host lattices with ions that have a strong size mismatch. Thus, to prove this, MgF 2 nanoparticles doped with Eu 3+ were fabricated. The obtained nanoparticles featured an unusually high luminescence lifetime and the obtained material showed a high potential for application.

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

Gaubas, E., E-mail: eugenijus.gaubas@ff.vu.lt; Ceponis, T.; Jasiunas, A.

Evolution of the microwave-probed photoconductivity transients and of the proton induced luminescence has simultaneously been examined in polycrystalline CdS layers evaporated in vacuum during exposure to a 1.6 MeV proton beam. The decrease of the intensity of luminescence peaked at 510 and 709 nm wavelengths and of values of the effective carrier lifetime has been correlated in dependence of proton irradiation fluence. The defect introduction rate has been evaluated by the comparative analysis of the laser and proton beam induced luminescence. The difference of a carrier pair generation mechanism inherent for light and for a proton beam has been revealed.

Between-cycle laser system for depressurization and resealing of modified design nuclear fuel assemblies

DOEpatents

Bradley, John G.

1982-01-01

A laser beam is used to puncture fuel cladding for release of contained pressurized fission gas from plenum sections or irradiated fuel pins. Exhausted fission gases are collected and trapped for safe disposal. The laser beam, adjusted to welding mode, is subsequently used to reseal the puncture holes. The fuel assembly is returned to additional irradiation or, if at end of reactivity lifetime, is routed to reprocess. The fuel assembly design provides graded cladding lengths, by rows or arrays, such that the cladding of each component fuel element of the assembly is accessible to laser beam reception.

Ion Storage Tests with the High Performance Antimatter Trap (HiPAT)

NASA Technical Reports Server (NTRS)

Martin, James J.; Lewis, Raymond A.; Chakrabarti, Suman; Pearson, Boise; Schafer, Charles (Technical Monitor)

2002-01-01

The NASA/Marshall Space Flight Centers (NASA/MSFC) Propulsion Research Center (PRC) is evaluating an antiproton storage system, referred to as the High Performance Antiproton Trap (HiPAT). This interest stems from the sheer energy represented by matter/antimatter annihilation process with has an energy density approximately 10 order of magnitude above that of chemical propellants. In other terms, one gram of antiprotons contains the equivalent energy of approximately 23 space shuttle external tanks or ET's (each ET contains roughly 740,000 kgs of fuel and oxidizer). This incredible source of stored energy, if harnessed, would be an enabling technology for deep space mission where both spacecraft weight and propulsion performance are key to satisfying aggressive mission requirements. The HiPAT hardware consists of a 4 Tesla superconductor system, an ultra high vacuum test section (vacuum approaching 10(exp -12) torr), and a high voltage confinement electrode system (up to 20 kvolts operation). The current laboratory layout is illustrated. The HiPAT designed objectives included storage of up to 1 trillion antiprotons with corresponding lifetimes approaching 18 days. To date, testing has centered on the storage of positive hydrogen ions produced in situ by a stream of high-energy electrons that passes through the trapping region. However, due to space charge issues and electron beam compression as it passes through the HiPAT central field, current ion production is limited to less then 50,000 ions. Ion lifetime was determined by counting particle populations at the end of various storage time intervals. Particle detection was accomplished by destructively expelling the ions against a micro-channel plate located just outside the traps magnetic field. The effect of radio frequency (RF) stabilization on the lifetime of trapped particles was also examined. This technique, referred to as a rotating wall, made use of a segmented electrode located near the center of the trap on which various phases of a particular frequency were applied. Various experiments were performed illustrating the ability of an RF drive to both prolong and reduced the lifetimes of various ion species depending on the selected frequency. HiPAT is now being reconfigured for testing with an ion source that will provide both positive and negative hydrogen ions from an external source. This ion system shall provide higher fill capacity (order of million of ions per shot), stacking of multiple shots, and injection schemes typical of a realistic antiproton delivery system.

Long lifetime, low intensity light source for use in nighttime viewing of equipment maps and other writings

DOEpatents

Frank, A.M.; Edwards, W.R.

1983-10-11

A long-lifetime light source with sufficiently low intensity to be used for reading a map or other writing at nighttime, while not obscuring the user's normal night vision is disclosed. This light source includes a diode electrically connected in series with a small power source and a lens properly positioned to focus at least a portion of the light produced by the diode. 1 fig.

Long lifetime, low intensity light source for use in nighttime viewing of equipment maps and other writings

DOEpatents

Frank, A.M.; Edwards, W.R.

1982-03-23

A long-lifetime light source is discussed with sufficiently low intensity to be used for reading a map or other writing at nightime, while not obscuring the user's normal night vision. This light source includes a diode electrically connected in series with a small power source and a lens properly positioned to focus at least a portion of the light produced by the diode.

Cathode performance during two beam operation of the high current high polarization electron gun for eRHIC

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

Rahman, O.; Ben-Zvi, I.; Degen, C.

Two electron beams from two activated bulk GaAs photocathodes were successfully combined during the recent beam test of the High Current High Polarization Electron gun for eRHIC. The beam test took place in Stangenes Industries in Palo Alto, CA, where the cathodes were placed in diagonally opposite locations inside the high voltage shroud. No significant cross talking between the cathodes was found for the pertinent vacuum and low average current operation, which is very promising towards combining multiple beams for higher average current. This paper describes the cathode preparation, transport and cathode performance in the gun for the combining test,more » including the QE and lifetimes of the photocathodes at various steps of the experiment.« less

Defining Threshold Values of Encapsulant and Backsheet Adhesion for PV Module Reliability

DOE PAGES

Bosco, Nick; Eafanti, Joshua; Kurtz, Sarah; ...

2017-10-04

The width-tapered cantilever beam method is used to quantify the debond energy (adhesion) of encapsulant and backsheet structures of 32 modules collected from the field. The collected population of modules contains both those that have remained intact and those with instances of either or both encapsulant and backsheet delamination. From this survey, initial threshold values (an adhesion value above which a module should remain intact throughout its lifetime) for encapsulant and backsheet interfaces are proposed. For encapsulants this value is ~ 160J/m 2 and for backsheets ~ 10J/m 2. Here, it is expected that these values will continue to bemore » refined and evolve as the width-tapered cantilever beam method gets adopted by the PV industry, and that they may aid in the future improvement of accelerated lifetime tests and the development of new, low-cost materials.« less

Passivation effect on optical and electrical properties of molecular beam epitaxy-grown HgCdTe/CdTe/Si layers

NASA Astrophysics Data System (ADS)

Kiran, Rajni; Mallick, Shubhrangshu; Hahn, Suk-Ryong; Lee, T. S.; Sivananthan, Sivalingam; Ghosh, Siddhartha; Wijewarnasuriya, P. S.

2006-06-01

The effects of passivation with two different passivants, ZnS and CdTe, and two different passivation techniques, physical vapor deposition (PVD) and molecular beam epitaxy (MBE), were quantified in terms of the minority carrier lifetime and extracted surface recombination velocity on both MBE-grown medium-wavelength ir (MWIR) and long-wavelength ir HgCdTe samples. A gradual increment of the minority carrier lifetime was reported as the passivation technique was changed from PVD ZnS to PVD CdTe, and finally to MBE CdTe, especially at low temperatures. A corresponding reduction in the extracted surface recombination velocity in the same order was also reported for the first time. Initial data on the 1/ f noise values of as-grown MWIR samples showed a reduction of two orders of noise power after 1200-Å ZnS deposition.

Defining Threshold Values of Encapsulant and Backsheet Adhesion for PV Module Reliability: Preprint

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

Bosco, Nicholas S; Kurtz, Sarah; Eafanti, Joshua

2017-08-28

The width-tapered cantilever beam method is used to quantify the debond energy (adhesion) of encapsulant and backsheet structures of 27 modules collected from the field. The collected population of modules contains both those that have remained in-tact and those with instances of either or both encapsulant and backsheet delamination. From this survey, initial threshold values (an adhesion value above which a module should remain intact throughout its lifetime) for encapsulant and backsheet interfaces are proposed. For encapsulants this value is about 60 J/m2 and for backsheets about 20 J/m2. It is expected that these values will continue to be refinedmore » and evolve as the width-tapered cantilever beam method becomes adopted by the PV industry, and that they may aid in the future improvement of accelerated lifetime tests and the development of new, low-cost materials.« less

Generalized expression for optical source fields

NASA Astrophysics Data System (ADS)

Kamacıoğlu, Canan; Baykal, Yahya

2012-09-01

A generalized optical beam expression is developed that presents the majority of the existing optical source fields such as Bessel, Laguerre-Gaussian, dark hollow, bottle, super Gaussian, Lorentz, super-Lorentz, flat-topped, Hermite-sinusoidal-Gaussian, sinusoidal-Gaussian, annular, Gauss-Legendre, vortex, also their higher order modes with their truncated, elegant and elliptical versions. Source intensity profiles derived from the generalized optical source beam fields are checked to match the intensity profiles of many individual known beam types. Source intensities for several interesting beam combinations are presented. Our generalized optical source beam field expression can be used to examine both the source characteristics and the propagation properties of many different optical beams in a single formulation.

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.

Fast lifetime measurements of stored e/sup +//e/sup -/ single bunches in PETRA and DORIS II utilizing the ac-signals of simple beam current transformers

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

Radloff, W.; Kriens, W.

1983-08-01

A monitor for fast lifetime measurements has been developed and successfully tested. The monitor pick-up consists of a standard broadband transformer device in a ring position with equidistant bunch spacing. It has an upper cut-off frequency of about 4 MHz which allows to measure simultaneously the lifetimes of up to 8 individual bunches in PETRA (2 in DORIS II). In the electronic section the ac-signals are separated, baseline-restored, stretched and finally digitized in a highly stable 16 bit ad-converter. The output data are fed then into a microprocessor that computes the average currents and their time derivatives. As a resultmore » lifetimes of up to 5X10/sup 4/ s can be measured in less than 2 seconds. Some measurements are reported.« less

Grid-translation beam deflection systems for 5-cm and 30-cm diameter Kaufman thrusters.

NASA Technical Reports Server (NTRS)

Lathem, W. C.

1972-01-01

A 5-cm grid translation mechanism has been developed capable of 10-deg beam deflection. A 2026-hour endurance test was run at a preset 10-deg deflection angle, and an extrapolated lifetime of better than 10,000 hours was obtained. Response time data for grid translation are presented. Preliminary results for a 30-cm diameter system are given, and results of a theoretical analysis of a dished grid system are discussed.

Grid-translation beam deflection systems for 5-cm and 30-cm diameter Kaufman thrusters

NASA Technical Reports Server (NTRS)

Lathem, W. C.

1972-01-01

A 5-cm grid translation mechanism has been developed capable of 10 deg beam deflection. A 2026-hour endurance test was run at a preset 10 deg deflection angle and an extrapolated lifetime of better than 10,000 hours obtained. Response time data for grid translation are presented. Preliminary results for a 30-cm diameter system are given and results of a theoretical analysis of a dished grid system are discussed.

The intense slow positron beam facility at the PULSTAR reactor and applications in nano-materials study

NASA Astrophysics Data System (ADS)

Liu, Ming; Moxom, Jeremy; Hawari, Ayman I.; Gidley, David W.

2013-04-01

An intense slow positron beam has been established at the PULSTAR nuclear research reactor of North Carolina State University. The slow positrons are generated by pair production in a tungsten moderator from gammarays produced in the reactor core and by neutron capture reactions in cadmium. The moderated positrons are electrostatically extracted and magnetically guided out of the region near the core. Subsequently, the positrons are used in two spectrometers that are capable of performing positron annihilation lifetime spectroscopy (PALS) and positron Doppler broadening spectroscopy (DBS) to probe the defect and free volume properties of materials. One of the spectrometers (e+-PALS) utilizes an rf buncher to produce a pulsed beam and has a timing resolution of 277 ps. The second spectrometer (Ps-PALS) uses a secondary electron timing technique and is dedicated to positronium lifetime measurements with an approximately 1 ns timing resolution. PALS measurements have been conducted in the e+-PALS spectrometer on a series of nano-materials including organic photovoltaic thin films, membranes for filtration, and polymeric fibers. These studies have resulted in understanding some critical issues related to the development of the examined nano-materials.

Rebuilding the Brookhaven high flux beam reactor: A feasibility study

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

Brynda, W.J.; Passell, L.; Rorer, D.C.

1995-01-01

After nearly thirty years of operation, Brookhaven`s High Flux Beam Reactor (HFBR) is still one of the world`s premier steady-state neutron sources. A major center for condensed matter studies, it currently supports fifteen separate beamlines conducting research in fields as diverse as crystallography, solid-state, nuclear and surface physics, polymer physics and structural biology and will very likely be able to do so for perhaps another decade. But beyond that point the HFBR will be running on borrowed time. Unless appropriate remedial action is taken, progressive radiation-induced embrittlement problems will eventually shut it down. Recognizing the HFBR`s value as a nationalmore » scientific resource, members of the Laboratory`s scientific and reactor operations staffs began earlier this year to consider what could be done both to extend its useful life and to assure that it continues to provide state-of-the-art research facilities for the scientific community. This report summarizes the findings of that study. It addresses two basic issues: (i) identification and replacement of lifetime-limiting components and (ii) modifications and additions that could expand and enhance the reactor`s research capabilities.« less

Recent advances in Reltron and Super-Reltron HPM source development

NASA Astrophysics Data System (ADS)

Miller, Robert B.; Muehlenweg, Carl A.; Habiger, Kerry W.; Smith, John R.; Shiffler, Donald A.

1994-05-01

Reltron and super-reltron microwave tubes use post acceleration of a well-modulated beam and multiple output cavity extraction sections to generate high power microwave pulses with excellent efficiency. We have continued our development of these tubes with emphasis being given to four specific topics: (1) Recent experiments with our 1-GHz super-reltron tube have demonstrated operation at a peak power level of 600 MW. With pulse durations of several hundred nanoseconds, the microwave energy per pulse is about 250 J. (2) We have extracted significant power (several tens of megawatts) at the third multiple (3 GHz) of our 1-GHz super-reltron tube using output cavities designed for operation in S-band. (3) We have fielded a small S-band super-reltron tube on our 260 kV modulator. We have obtained lifetime data for this tube under repetitive (20 Hz), long pulse (2 microsecond(s) ec) operating conditions. (4) We have initiated feasibility experiments of the reltron concept by post accelerating the bunched beam produced by a SLAC XK-5 klystron. In this paper we report our experimental results and discuss relevant theoretical considerations related to each of these four topics.

Electron beam physical vapor deposition of thin ruby films for remote temperature sensing

NASA Astrophysics Data System (ADS)

Li, Wei; Coppens, Zachary J.; Greg Walker, D.; Valentine, Jason G.

2013-04-01

Thermographic phosphors (TGPs) possessing temperature-dependent photoluminescence properties have a wide range of uses in thermometry due to their remote access and large temperature sensitivity range. However, in most cases, phosphors are synthesized in powder form, which prevents their use in high resolution micro and nanoscale thermal microscopy. In the present study, we investigate the use of electron beam physical vapor deposition to fabricate thin films of chromium-doped aluminum oxide (Cr-Al2O3, ruby) thermographic phosphors. Although as-deposited films were amorphous and exhibited weak photoluminescence, the films regained the stoichiometry and α-Al2O3 crystal structure of the combustion synthesized source powder after thermal annealing. As a consequence, the annealed films exhibit both strong photoluminescence and a temperature-dependent lifetime that decreases from 2.9 ms at 298 K to 2.1 ms at 370 K. Ruby films were also deposited on multiple substrates. To ensure a continuous film with smooth surface morphology and strong photoluminescence, we use a sapphire substrate, which is thermal expansion coefficient and lattice matched to the film. These thin ruby films can potentially be used as remote temperature sensors for probing the local temperatures of micro and nanoscale structures.

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

Kwan, J.W.; Arbelaez, D.; Bieniosek, F.M.

The Heavy Ion Fusion Science Virtual National Laboratory in the USA is constructing a new Neutralized Drift Compression eXperiment (NDCX-II) at LBNL. This facility is being developed for high energy density physics and inertial fusion energy research. The 12 m long induction linac in NDCX-II will produce a Li{sup +} beam pulse, at energies of 1.2-3 MeV, to heat target material to the warm dense matter regime ({approx} 1 eV). By making use of special acceleration voltage waveforms, 2.5T solenoid focusing, and neutralized drift compression, 20 - 50 nC of beam charge from the ion source will be compressed longitudinallymore » and radially to achieve a subnanosecond pulse length and mm-scale target spot size. The original Neutralized Drift Compression Experiment (NDCX-I) has successfully demonstrated simultaneous radial and longitudinal compression by imparting a velocity ramp to the ion beam, which then drifts in a neutralizing plasma to and through the final focussing solenoid and onto the target. At higher kinetic energy and current, NDCX-II will offer more than 100 times the peak energy fluence on target of NDCX-I. NDCX-II makes use of many parts from the decommissioned Advanced Test Accelerator (ATA) at LLNL. It includes 27 lattice periods between the injector and the neutralized drift compression section (Figure 1). There are 12 energized induction cells, 9 inactive cells which provide drift space, and 6 diagnostic cells which provide beam diagnostics and pumping. Custom pulsed power systems generate ramped waveforms for the first 7 induction cells, so as to quickly compress the beam from 600 ns at the injector down to 70 ns. After this compression, the high voltages of the ATA Blumleins are then used to rapidly add energy to the beam. The Blumleins were designed to match the ferrite core volt-seconds with pulses up to 250 kV and a fixed FWHM of 70 ns. The machine is limited to a pulse repetition rate of once every 20 seconds due to cooling requirements. The NDCX-II beam is highly space-charge dominated. The 1-D ASP code was used to synthesize high voltage waveform for acceleration, while the 3-D Warp particle-in-cell code was used for detailed design of the lattice. The Li{sup +} ion was chosen because its Bragg Peak energy (at {approx} 2 MeV) coincides with the NDCX-II beam energy. The 130 keV injector will have a 10.9 cm diameter ion source. Testing of small (0.64 cm diameter) lithium doped alumino-silicate ion sources has demonstrated the current density ({approx} 1 mA/cm{sup 2}) used in the design, with acceptable lifetime. A 7.6 cm diameter source has been successfully produced to verify that the coating method can be applied to such a large emitting area. The ion source will operate at {approx} 1275 C; thus a significant effort was made in the design to manage the 4 kW heating power and the associated cooling requirements. In modifying the ATA induction cells for NDCX-II, the low-field DC solenoids were replaced with 2.5 T pulsed solenoids. The beam pipe diameter was decreased in order to reduce the axial extent of the solenoid fringe fields and to make room for water cooling. In addition, an outer copper cylinder (water-cooled) was used to exclude the solenoid magnetic flux from the ferrite cores. Precise alignment is essential because the beam has a large energy spread due to the rapid pulse compression, such that misalignments lead to corkscrew deformation of the beam and reduced intensity at focus. A novel pulsed-wire measurement method is used to align the pulsed solenoid magnets. Alignment accuracy has been demonstrated to within 100 {micro}m of the induction cell axis. The neutralized drift compression region after the last induction cell is approximately 1.2 m long and includes ferroelectric plasma sources (FEPS) fabricated by PPPL similar to those successfully operating in NDCX-I. The 8-T final focus pulsed solenoid, filtered cathodic arc plasma sources (FCAPS), and target chamber from NDCX-I are to be relocated to NDCX-II. The NDCX-II project started in July 2009 and is expected to complete in fall of 2011. As future funds become available, additional induction cells and pulsed power systems will be added to increase the beam energy.« less

Mass spectrometer with electron source for reducing space charge effects in sample beam

DOEpatents

Houk, Robert S.; Praphairaksit, Narong

2003-10-14

A mass spectrometer includes an ion source which generates a beam including positive ions, a sampling interface which extracts a portion of the beam from the ion source to form a sample beam that travels along a path and has an excess of positive ions over at least part of the path, thereby causing space charge effects to occur in the sample beam due to the excess of positive ions in the sample beam, an electron source which adds electrons to the sample beam to reduce space charge repulsion between the positive ions in the sample beam, thereby reducing the space charge effects in the sample beam and producing a sample beam having reduced space charge effects, and a mass analyzer which analyzes the sample beam having reduced space charge effects.

Shifts in the fluorescence lifetime of EGFP during bacterial phagocytosis measured by phase-sensitive flow cytometry

NASA Astrophysics Data System (ADS)

Li, Wenyan; Houston, Kevin D.; Houston, Jessica P.

2017-01-01

Phase-sensitive flow cytometry (PSFC) is a technique in which fluorescence excited state decay times are measured as fluorescently labeled cells rapidly transit a finely focused, frequency-modulated laser beam. With PSFC the fluorescence lifetime is taken as a cytometric parameter to differentiate intracellular events that are challenging to distinguish with standard flow cytometry. For example PSFC can report changes in protein conformation, expression, interactions, and movement, as well as differences in intracellular microenvironments. This contribution focuses on the latter case by taking PSFC measurements of macrophage cells when inoculated with enhanced green fluorescent protein (EGFP)-expressing E. coli. During progressive internalization of EGFP-E. coli, fluorescence lifetimes were acquired and compared to control groups. It was hypothesized that fluorescence lifetimes would correlate well with phagocytosis because phagosomes become acidified and the average fluorescence lifetime of EGFP is known to be affected by pH. We confirmed that average EGFP lifetimes consistently decreased (3 to 2 ns) with inoculation time. The broad significance of this work is the demonstration of how high-throughput fluorescence lifetime measurements correlate well to changes that are not easily tracked by intensity-only cytometry, which is affected by heterogeneous protein expression, cell-to-cell differences in phagosome formation, and number of bacterium engulfed.

Low-frequency wide-field fluorescence lifetime imaging using a high-power near-infrared light-emitting diode light source

PubMed Central

Gioux, Sylvain; Lomnes, Stephen J.; Choi, Hak Soo; Frangioni, John V.

2010-01-01

Fluorescence lifetime imaging (FLi) could potentially improve exogenous near-infrared (NIR) fluorescence imaging, because it offers the capability of discriminating a signal of interest from background, provides real-time monitoring of a chemical environment, and permits the use of several different fluorescent dyes having the same emission wavelength. We present a high-power, LED-based, NIR light source for the clinical translation of wide-field (larger than 5 cm in diameter) FLi at frequencies up to 35 MHz. Lifetime imaging of indocyanine green (ICG), IRDye 800-CW, and 3,3′-diethylthiatricarbocyanine iodide (DTTCI) was performed over a large field of view (10 cm by 7.5 cm) using the LED light source. For comparison, a laser diode light source was employed as a gold standard. Experiments were performed both on the bench by diluting the fluorescent dyes in various chemical environments in Eppendorf tubes, and in vivo by injecting the fluorescent dyes mixed in Matrigel subcutaneously into CD-1 mice. Last, measured fluorescence lifetimes obtained using the LED and the laser diode sources were compared with those obtained using a state-of-the-art time-domain imaging system and with those previously described in the literature. On average, lifetime values obtained using the LED and the laser diode light sources were consistent, exhibiting a mean difference of 3% from the expected values and a coefficient of variation of 12%. Taken together, our study offers an alternative to laser diodes for clinical translation of FLi and explores the use of relatively low frequency modulation for in vivo imaging. PMID:20459250

Low-energy beam transport studies supporting the spallation neutron source 1-MW beam operation.

PubMed

Han, B X; Kalvas, T; Tarvainen, O; Welton, R F; Murray, S N; Pennisi, T R; Santana, M; Stockli, M P

2012-02-01

The H(-) injector consisting of a cesium enhanced RF-driven ion source and a 2-lens electrostatic low-energy beam transport (LEBT) system supports the spallation neutron source 1 MW beam operation with ∼38 mA beam current in the linac at 60 Hz with a pulse length of up to ∼1.0 ms. In this work, two important issues associated with the low-energy beam transport are discussed: (1) inconsistent dependence of the post-radio frequency quadrupole accelerator beam current on the ion source tilt angle and (2) high power beam losses on the LEBT electrodes under some off-nominal conditions compromising their reliability.

Defect characterization of silicon dendritic web ribbons

NASA Technical Reports Server (NTRS)

Cheng, L. J.

1985-01-01

Progress made in the study of defect characterization of silicon dendritic web ribbon is presented. Chemical etching is used combined with optical microscopy, as well as the electron beam induced current (EBIC) technique. Thermal annealing effect on carrier lifetime is examined.

Sensitivity of 30-cm mercury bombardment ion thruster characteristics to accelerator grid design

NASA Technical Reports Server (NTRS)

Rawlin, V. K.

1978-01-01

The design of ion optics for bombardment thrusters strongly influences overall performance and lifetime. The operation of a 30 cm thruster with accelerator grid open area fractions ranging from 43 to 24 percent, was evaluated and compared with experimental and theoretical results. Ion optics properties measured included the beam current extraction capability, the minimum accelerator grid voltage to prevent backstreaming, ion beamlet diameter as a function of radial position on the grid and accelerator grid hole diameter, and the high energy, high angle ion beam edge location. Discharge chamber properties evaluated were propellant utilization efficiency, minimum discharge power per beam amp, and minimum discharge voltage.

A STED-FLIM microscope applied to imaging the natural killer cell immune synapse

NASA Astrophysics Data System (ADS)

Lenz, M. O.; Brown, A. C. N.; Auksorius, E.; Davis, D. M.; Dunsby, C.; Neil, M. A. A.; French, P. M. W.

2011-03-01

We present a stimulated emission depletion (STED) fluorescence lifetime imaging (FLIM) microscope, excited by a microstructured optical fibre supercontinuum source that is pumped by a femtosecond Ti:Sapphire-laser, which is also used for depletion. Implemented using a piezo-scanning stage on a laser scanning confocal fluorescence microscope system with FLIM realised using time correlated single photon counting (TCSPC), this provides convenient switching between confocal and STED-FLIM with spatial resolution down to below 60 nm. We will present our design considerations to make a robust instrument for biological applications including a comparison between fixed phase plate and spatial light modulator (SLM) approaches to shape the STED beam and the correlation of STED and confocal FLIM microscopy. Following our previous application of FLIM-FRET to study intercellular signalling at the immunological synapse (IS), we are employing STED microscopy to characterize the spatial distribution of cellular molecules with subdiffraction resolution at the IS. In particular, we are imaging cytoskeletal structure at the Natural Killer cell activated immune synapse. We will also present our progress towards multilabel STED microscopy to determine how relative spatial molecular organization, previously undetectable by conventional microscopy techniques, is important for NK cell cytotoxic function. Keywords: STED, Stimulated Emission Depletion Microscopy, Natural Killer (NK) cell, Fluorescence lifetime imaging, FLIM, Super resolution microscopy.

Scintillation analysis of truncated Bessel beams via numerical turbulence propagation simulation.

PubMed

Eyyuboğlu, Halil T; Voelz, David; Xiao, Xifeng

2013-11-20

Scintillation aspects of truncated Bessel beams propagated through atmospheric turbulence are investigated using a numerical wave optics random phase screen simulation method. On-axis, aperture averaged scintillation and scintillation relative to a classical Gaussian beam of equal source power and scintillation per unit received power are evaluated. It is found that in almost all circumstances studied, the zeroth-order Bessel beam will deliver the lowest scintillation. Low aperture averaged scintillation levels are also observed for the fourth-order Bessel beam truncated by a narrower source window. When assessed relative to the scintillation of a Gaussian beam of equal source power, Bessel beams generally have less scintillation, particularly at small receiver aperture sizes and small beam orders. Upon including in this relative performance measure the criteria of per unit received power, this advantageous position of Bessel beams mostly disappears, but zeroth- and first-order Bessel beams continue to offer some advantage for relatively smaller aperture sizes, larger source powers, larger source plane dimensions, and intermediate propagation lengths.

Optimal Model-Based Fault Estimation and Correction for Particle Accelerators and Industrial Plants Using Combined Support Vector Machines and First Principles Models

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

Sayyar-Rodsari, Bijan; Schweiger, Carl; /SLAC /Pavilion Technologies, Inc., Austin, TX

2010-08-25

Timely estimation of deviations from optimal performance in complex systems and the ability to identify corrective measures in response to the estimated parameter deviations has been the subject of extensive research over the past four decades. The implications in terms of lost revenue from costly industrial processes, operation of large-scale public works projects and the volume of the published literature on this topic clearly indicates the significance of the problem. Applications range from manufacturing industries (integrated circuits, automotive, etc.), to large-scale chemical plants, pharmaceutical production, power distribution grids, and avionics. In this project we investigated a new framework for buildingmore » parsimonious models that are suited for diagnosis and fault estimation of complex technical systems. We used Support Vector Machines (SVMs) to model potentially time-varying parameters of a First-Principles (FP) description of the process. The combined SVM & FP model was built (i.e. model parameters were trained) using constrained optimization techniques. We used the trained models to estimate faults affecting simulated beam lifetime. In the case where a large number of process inputs are required for model-based fault estimation, the proposed framework performs an optimal nonlinear principal component analysis of the large-scale input space, and creates a lower dimension feature space in which fault estimation results can be effectively presented to the operation personnel. To fulfill the main technical objectives of the Phase I research, our Phase I efforts have focused on: (1) SVM Training in a Combined Model Structure - We developed the software for the constrained training of the SVMs in a combined model structure, and successfully modeled the parameters of a first-principles model for beam lifetime with support vectors. (2) Higher-order Fidelity of the Combined Model - We used constrained training to ensure that the output of the SVM (i.e. the parameters of the beam lifetime model) are physically meaningful. (3) Numerical Efficiency of the Training - We investigated the numerical efficiency of the SVM training. More specifically, for the primal formulation of the training, we have developed a problem formulation that avoids the linear increase in the number of the constraints as a function of the number of data points. (4) Flexibility of Software Architecture - The software framework for the training of the support vector machines was designed to enable experimentation with different solvers. We experimented with two commonly used nonlinear solvers for our simulations. The primary application of interest for this project has been the sustained optimal operation of particle accelerators at the Stanford Linear Accelerator Center (SLAC). Particle storage rings are used for a variety of applications ranging from 'colliding beam' systems for high-energy physics research to highly collimated x-ray generators for synchrotron radiation science. Linear accelerators are also used for collider research such as International Linear Collider (ILC), as well as for free electron lasers, such as the Linear Coherent Light Source (LCLS) at SLAC. One common theme in the operation of storage rings and linear accelerators is the need to precisely control the particle beams over long periods of time with minimum beam loss and stable, yet challenging, beam parameters. We strongly believe that beyond applications in particle accelerators, the high fidelity and cost benefits of a combined model-based fault estimation/correction system will attract customers from a wide variety of commercial and scientific industries. Even though the acquisition of Pavilion Technologies, Inc. by Rockwell Automation Inc. in 2007 has altered the small business status of the Pavilion and it no longer qualifies for a Phase II funding, our findings in the course of the Phase I research have convinced us that further research will render a workable model-based fault estimation and correction for particle accelerators and industrial plants feasible.« less

Wave-Kinetic Simulations of the Nonlinear Generation of Electromagnetic VLF Waves through Velocity Ring Instabilities

NASA Astrophysics Data System (ADS)

Ganguli, G.; Crabtree, C. E.; Rudakov, L.; Mithaiwala, M.

2014-12-01

Velocity ring instabilities are a common naturally occuring magnetospheric phenomenon that can also be generated by man made ionospheric experiments. These instabilities are known to generate lower-hybrid waves, which generally cannot propagte out of the source region. However, nonlinear wave physics can convert these linearly driven electrostatic lower-hybrid waves into electromagnetic waves that can escape the source region. These nonlinearly generated waves can be an important source of VLF turbulence that controls the trapped electron lifetime in the radiation belts. We develop numerical solutions to the wave-kinetic equation in a periodic box including the effects of nonlinear (NL) scattering (nonlinear Landau damping) of Lower-hybrid waves giving the evolution of the wave-spectra in wavenumber space. Simultaneously we solve the particle diffusion equation of both the background plasma particles and the ring ions, due to both linear and nonlinear Landau resonances. At initial times for cold ring ions, an electrostatic beam mode is excited, while the kinetic mode is stable. As the instability progresses the ring ions heat, the beam mode is stabilized, and the kinetic mode destabilizes. When the amplitude of the waves becomes sufficient the lower-hybrid waves are scattered (by either nearly unmagnetized ions or magnetized electrons) into electromagnetic magnetosonic waves [Ganguli et al 2010]. The effect of NL scattering is to limit the amplitude of the waves, slowing down the quasilinear relaxation time and ultimately allowing more energy from the ring to be liberated into waves [Mithaiwala et al. 2011]. The effects of convection out of the instability region are modeled, additionally limiting the amplitude of the waves, allowing further energy to be liberated from the ring [Scales et al., 2012]. Results are compared to recent 3D PIC simulations [Winske and Duaghton 2012].

Electromagnetic Modeling of Distributed-Source-Excitation of Coplanar Waveguides: Applications to Traveling-Wave Photomixers

NASA Technical Reports Server (NTRS)

Pasqualini, Davide; Neto, Andrea; Wyss, Rolf A.

2001-01-01

In this work an electromagnetic model and subsequent design is presented for a traveling-wave, coplanar waveguide (CPW) based source that will operate in the THz frequency regime. The radio frequency (RF) driving current is a result of photoexcitation of a thin GaAs membrane using two frequency-offset lasers. The GaAs film is grown by molecular-beam-epitaxy (MBE) and displays sub-ps carrier lifetimes which enable the material conductivity to be modulated at a very high rate. The RF current flows between electrodes deposited on the GaAs membrane which are biased with a DC voltage source. The electrodes form a CPW and are terminated with a double slot antenna that couples the power to a quasi-optical system. The membrane is suspended above a metallic reflector to launch all radiation in one direction. The theoretical investigation and consequent design is performed in two steps. The first step consists of a direct evaluation of the magnetic current distribution on an infinitely extended coplanar waveguide excited by an impressed electric current distributed over a finite area. The result of the analysis is the difference between the incident angle of the laser beams and the length of the excited area that maximizes the RF power coupled to the CPW. The optimal values for both parameters are found as functions of the CPW and membrane dimensions as well as the dielectric constants of the layers. In the second step, a design is presented of a double slot antenna that matches the CPW characteristic impedance and gives good overall performance. The design is presently being implemented and measurements will soon be available.

Self consistent hydrodynamic description of the plasma wake field excitation induced by a relativistic charged-particle beam in an unmagnetized plasma

NASA Astrophysics Data System (ADS)

Jovanović, Dušan; Fedele, Renato; De Nicola, Sergio; Akhter, Tamina; Belić, Milivoj

2017-12-01

A self-consistent nonlinear hydrodynamic theory is presented of the propagation of a long and thin relativistic electron beam, for a typical plasma wake field acceleration configuration in an unmagnetized and overdense plasma. The random component of the trajectories of the beam particles as well as of their velocity spread is modelled by an anisotropic temperature, allowing the beam dynamics to be approximated as a 3D adiabatic expansion/compression. It is shown that even in the absence of the nonlinear plasma wake force, the localisation of the beam in the transverse direction can be achieved owing to the nonlinearity associated with the adiabatic compression/rarefaction and a coherent stationary state is constructed. Numerical calculations reveal the possibility of the beam focussing and defocussing, but the lifetime of the beam can be significantly extended by the appropriate adjustments, so that transverse oscillations are observed, similar to those predicted within the thermal wave and Vlasov kinetic models.

A portable time-domain LED fluorimeter for nanosecond fluorescence lifetime measurements

NASA Astrophysics Data System (ADS)

Wang, Hongtao; Qi, Ying; Mountziaris, T. J.; Salthouse, Christopher D.

2014-05-01

Fluorescence lifetime measurements are becoming increasingly important in chemical and biological research. Time-domain lifetime measurements offer fluorescence multiplexing and improved handling of interferers compared with the frequency-domain technique. In this paper, an all solid-state, filterless, and highly portable light-emitting-diode based time-domain fluorimeter (LED TDF) is reported for the measurement of nanosecond fluorescence lifetimes. LED based excitation provides more wavelengths options compared to laser diode based excitation, but the excitation is less effective due to the uncollimated beam, less optical power, and longer latency in state transition. Pulse triggering and pre-bias techniques were implemented in our LED TDF to improve the peak optical power to over 100 mW. The proposed pulsing circuit achieved an excitation light fall time of less than 2 ns. Electrical resetting technique realized a time-gated photo-detector to remove the interference of the excitation light with fluorescence. These techniques allow the LED fluorimeter to accurately measure the fluorescence lifetime of fluorescein down to concentration of 0.5 μM. In addition, all filters required in traditional instruments are eliminated for the non-attenuated excitation/emission light power. These achievements make the reported device attractive to biochemical laboratories seeking for highly portable lifetime detection devices for developing sensors based on fluorescence lifetime changes. The device was initially validated by measuring the lifetimes of three commercial fluorophores and comparing them with reported lifetime data. It was subsequently used to characterize a ZnSe quantum dot based DNA sensor.

Neutron Lifetime and Axial Coupling Connection

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

Czarnecki, Andrzej; Marciano, William J.; Sirlin, Alberto

Here, experimental studies of neutron decay, n→pe¯ν, exhibit two anomalies. The first is a 8.6(2.1) s, roughly 4σ difference between the average beam measured neutron lifetime, τ beam n = 888.0(2.0) s, and the more precise average trapped ultracold neutron determination, τ trap n = 879.4(6) s. The second is a 5σ difference between the pre2002 average axial coupling, gA, as measured in neutron decay asymmetries g pre2002 A = 1.2637(21), and the more recent, post2002, average g post2002 A = 1.2755(11), where, following the UCNA Collaboration division, experiments are classified by the date of their most recent result. Inmore » this Letter, we correlate those τ n and g A values using a (slightly) updated relation τ n(1+3g 2 A) = 5172.0(1.1) s. Consistency with that relation and better precision suggest τ favored n = 879.4(6) s and g favored A = 1.2755(11) as preferred values for those parameters. Comparisons of g favored A with recent lattice QCD and muonic hydrogen capture results are made. A general constraint on exotic neutron decay branching ratios, <0.27%, is discussed and applied to a recently proposed solution to the neutron lifetime puzzle.« less

Lifetime and relative g factor measurements in 104 , 106 , 108Pd isotopes

NASA Astrophysics Data System (ADS)

Ilie, G.; Werner, V.; Radeck, D.; Ahn, T.; Beausang, C. W.; Bettermann, L.; Casperson, R. J.; Chevrier, R.; Cooper, N.; Bonniwell, T. C.; Heinz, A.; Holland, E.; McCarthy, D.; Pauerstein, B.; Smith, M. K.; Terry, J. R.; Williams, E.

2011-10-01

The purpose of this research was the proof-of-principle for the new g-plunger technique to measure the deorientation and the lifetime of a state after an inverse kinematics reaction. The deorientation effect is due to the hyperfine interaction between the nuclear spin and the surrounding electron configurations. The attenuation of γ-ray angular distributions has been measured for the 21+ and 41+ states of 104Pd, 106Pd and 108Pd. The beams with energies of 324 MeV, 330 MeV and 336 MeV, respectively, were Coulomb excited into their 21+ state on a 24Mg target. Forward scattered Mg was detected after passing a Cu foil, which served as a stopper for the beam. We measured the time-dependence of the attenuation as a function of distance, in parallel to measuring the lifetimes of the 21+ and 41+ states. This attenuation is used to measure the g factor of the decaying states relative to each other. In this work, hyperfine parameters have been calibrated for the Pd isotopes. The results of this work and a discussion of the parameterization used to fit the data in this work will be presented. Research was supported by the U.S. Department of Energy under Grant No. DE-FG02-91ER-40609.

Neutron Lifetime and Axial Coupling Connection

DOE PAGES

Czarnecki, Andrzej; Marciano, William J.; Sirlin, Alberto

2018-05-16

Here, experimental studies of neutron decay, n→pe¯ν, exhibit two anomalies. The first is a 8.6(2.1) s, roughly 4σ difference between the average beam measured neutron lifetime, τ beam n = 888.0(2.0) s, and the more precise average trapped ultracold neutron determination, τ trap n = 879.4(6) s. The second is a 5σ difference between the pre2002 average axial coupling, gA, as measured in neutron decay asymmetries g pre2002 A = 1.2637(21), and the more recent, post2002, average g post2002 A = 1.2755(11), where, following the UCNA Collaboration division, experiments are classified by the date of their most recent result. Inmore » this Letter, we correlate those τ n and g A values using a (slightly) updated relation τ n(1+3g 2 A) = 5172.0(1.1) s. Consistency with that relation and better precision suggest τ favored n = 879.4(6) s and g favored A = 1.2755(11) as preferred values for those parameters. Comparisons of g favored A with recent lattice QCD and muonic hydrogen capture results are made. A general constraint on exotic neutron decay branching ratios, <0.27%, is discussed and applied to a recently proposed solution to the neutron lifetime puzzle.« less

Reliability assessment of multiple quantum well avalanche photodiodes

NASA Technical Reports Server (NTRS)

Yun, Ilgu; Menkara, Hicham M.; Wang, Yang; Oguzman, Isamil H.; Kolnik, Jan; Brennan, Kevin F.; May, Gray S.; Wagner, Brent K.; Summers, Christopher J.

1995-01-01

The reliability of doped-barrier AlGaAs/GsAs multi-quantum well avalanche photodiodes fabricated by molecular beam epitaxy is investigated via accelerated life tests. Dark current and breakdown voltage were the parameters monitored. The activation energy of the degradation mechanism and median device lifetime were determined. Device failure probability as a function of time was computed using the lognormal model. Analysis using the electron beam induced current method revealed the degradation to be caused by ionic impurities or contamination in the passivation layer.

Beam property measurement of a 300-kV ion source test stand for a 1-MV electrostatic accelerator

NASA Astrophysics Data System (ADS)

Park, Sae-Hoon; Kim, Dae-Il; Kim, Yu-Seok

2016-09-01

The KOMAC (Korea Multi-purpose Accelerator Complex) has been developing a 300-kV ion source test stand for a 1-MV electrostatic accelerator for industrial purposes. A RF ion source was operated at 200 MHz with its matching circuit. The beam profile and emittance were measured behind an accelerating column to confirm the beam property from the RF ion source. The beam profile was measured at the end of the accelerating tube and at the beam dump by using a beam profile monitor (BPM) and wire scanner. An Allison-type emittance scanner was installed behind the beam profile monitor (BPM) to measure the beam density in phase space. The measurement results for the beam profile and emittance are presented in this paper.

Beam wander of dark hollow, flat-topped and annular beams

NASA Astrophysics Data System (ADS)

Eyyuboğlu, H. T.; Çil, C. Z.

2008-11-01

Benefiting from the earlier derivations for the Gaussian beam, we formulate beam wander for dark hollow (DH) and flat-topped (FT) beams, also covering the annular Gaussian (AG) beam as a special case. Via graphical illustrations, beam wander variations of these beams are analyzed and compared among themselves and to the fundamental Gaussian beam against changes in propagation length, amplitude factor, source size, wavelength of operation, inner and outer scales of turbulence. These comparisons show that in relation to the fundamental Gaussian beam, DH and FT beams will exhibit less beam wander, particularly at small primary beam source sizes, lower amplitude factors of the secondary beam and higher beam orders. Furthermore, DH and FT beams will continue to preserve this advantageous position all throughout the considered range of wavelengths, inner and outer scales of turbulence. FT beams, in particular, are observed to have the smallest beam wander values among all, up to certain source sizes.

Nonradiative Decay Dynamics of METHYL-4-HYDROXYCINNAMATE and its Monohydrated Complex Revealed by Picosecond Pump-Probe Spectroscopy

NASA Astrophysics Data System (ADS)

Ebata, T.; Shimada, D.; Kusaka, R.; Inokuchi, Y.; Ehara, M.

2012-06-01

The lifetimes of methyl 4-hydroxycinnamate (OMpCA) and its mono-hydrated complex (OMpCA-H_2O) in the S_1 state have been measured by picosecond pump-probe spectroscopy in a supersonic beam. For OMpCA, the lifetime of the S_1 - S_0 origin is 8 - 9 ps. On the other hand, the lifetime of OMpCA-H_2O complex at the origin is 930 ps, which is 100 times longer than that. Furthermore, in the complex the S_1 lifetime shows rapid decrease at an energy of 200 cm-1 above the origin and becomes as short as 9 ps at 500 cm-1. Theoretical calculations with symmetry-adapted cluster-configuration interaction (SAC-CI) method suggest that in OMpCA, the trans - cis isomerization occurs smoothly without a barrier on the S_1surface, while in OMpCA-H_2O complex, there exists a barrier along the isomerization coordinate. The calculated barrier height of OMpCA-H_2O is in good agreement with that estimated from the lifetime measurements.

Fluorescence lifetime as a new parameter in analytical cytology measurements

NASA Astrophysics Data System (ADS)

Steinkamp, John A.; Deka, Chiranjit; Lehnert, Bruce E.; Crissman, Harry A.

1996-05-01

A phase-sensitive flow cytometer has been developed to quantify fluorescence decay lifetimes on fluorochrome-labeled cells/particles. This instrument combines flow cytometry (FCM) and frequency-domain fluorescence spectroscopy measurement principles to provide unique capabilities for making phase-resolved lifetime measurements, while preserving conventional FCM capabilities. Cells are analyzed as they intersect a high-frequency, intensity-modulated (sine wave) laser excitation beam. Fluorescence signals are processed by conventional and phase-sensitive signal detection electronics and displayed as frequency distribution histograms. In this study we describe results of fluorescence intensity and lifetime measurements on fluorescently labeled particles, cells, and chromosomes. Examples of measurements on intrinsic cellular autofluorescence, cells labeled with immunofluorescence markers for cell- surface antigens, mitochondria stains, and on cellular DNA and protein binding fluorochromes will be presented to illustrate unique differences in measured lifetimes and changes caused by fluorescence quenching. This innovative technology will be used to probe fluorochrome/molecular interactions in the microenvironment of cells/chromosomes as a new parameter and thus expand the researchers' understanding of biochemical processes and structural features at the cellular and molecular level.

An adaptable dual species effusive source and Zeeman slower design demonstrated with Rb and Li

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

Bowden, William, E-mail: william.bowden@physics.ox.ac.uk; Gunton, Will; Semczuk, Mariusz

2016-04-15

We present a dual-species effusive source and Zeeman slower designed to produce slow atomic beams of two elements with a large mass difference and with very different oven temperature requirements. We demonstrate this design for the case of {sup 6}Li and {sup 85}Rb and achieve magneto-optical trap (MOT) loading rates equivalent to that reported in prior work on dual species (Rb+Li) Zeeman slowers operating at the same oven temperatures. Key design choices, including thermally separating the effusive sources and using a segmented coil design to enable computer control of the magnetic field profile, ensure that the apparatus can be easilymore » modified to slow other atomic species. By performing the final slowing using the quadrupole magnetic field of the MOT, we are able to shorten our Zeeman slower length making for a more compact system without compromising performance. We outline the construction and analyze the emission properties of our effusive sources. We also verify the performance of the source and slower, and we observe sequential loading rates of 12 × 10{sup 8} atoms/s for a Rb oven temperature of 140 °C and 1.1 × 10{sup 8} atoms/s for a Li reservoir at 460 °C, corresponding to reservoir lifetimes for continuous operation of 10 and 4 years, respectively.« less

Characterisation of the properties of a negative hydrogen ion beam by several beam diagnostic techniques

NASA Astrophysics Data System (ADS)

Maurizio, R.; Fantz, U.; Bonomo, F.; Serianni, G.

2016-06-01

The beam properties of the BATMAN negative ion source, which is the prototype of one module of the source for the ITER neutral beam injection system, are characterised by means of three diagnostic techniques: beam emission spectroscopy (BES), the experimental calorimeter mini-STRIKE and a copper calorimeter. The main beam parameters—beam divergence, homogeneity and top-bottom asymmetries—are studied in different operational scenarios: with different magnetic filter field setups, source settings and with different gases (hydrogen or deuterium). Among all dependences, the influence of the magnetic field configuration on the beam and the evolution of the beam features during some conditioning days are investigated in detail. Data show that the stronger the filter field in the beam region, the higher the beam top-bottom asymmetry—likely a v× B effect. During the conditioning of the source, such vertical beam asymmetry increases as well, suggesting an inhomogeneous H -production at the first grid of the extraction system.

Positive and negative ion beam merging system for neutral beam production

DOEpatents

Leung, Ka-Ngo; Reijonen, Jani

2005-12-13

The positive and negative ion beam merging system extracts positive and negative ions of the same species and of the same energy from two separate ion sources. The positive and negative ions from both sources pass through a bending magnetic field region between the pole faces of an electromagnet. Since the positive and negative ions come from mirror image positions on opposite sides of a beam axis, and the positive and negative ions are identical, the trajectories will be symmetrical and the positive and negative ion beams will merge into a single neutral beam as they leave the pole face of the electromagnet. The ion sources are preferably multicusp plasma ion sources. The ion sources may include a multi-aperture extraction system for increasing ion current from the sources.

Scintillation screen applications in a vacuum arc ion source with composite hydride cathode

NASA Astrophysics Data System (ADS)

Wang, X. H.; Tuo, X. G.; Yang, Z.; Peng, Y. F.; Li, J.; Lv, H. Y.; Li, J. H.; Long, J. D.

2018-05-01

Vacuum arc ion source with composite hydride cathode was developed to produce intense ion beams which can be applied in particle accelerator injections. Beam profile and beam composition are two fundamental parameters of the beam for the vacuum arc ion source in such specific applications. An aluminum-coated scintillation screen with an ICCD camera readout was used to show the space-time distribution of the beam directly. A simple magnetic analysis assembly with the scintillation screen shows the beam composition information of this kind ion source. Some physical and technical issues are discussed and analyzed in the text.

Effect of beam types on the scintillations: a review

NASA Astrophysics Data System (ADS)

Baykal, Yahya; Eyyuboglu, Halil T.; Cai, Yangjian

2009-02-01

When different incidences are launched in atmospheric turbulence, it is known that the intensity fluctuations exhibit different characteristics. In this paper we review our work done in the evaluations of the scintillation index of general beam types when such optical beams propagate in horizontal atmospheric links in the weak fluctuations regime. Variation of scintillation indices versus the source and medium parameters are examined for flat-topped-Gaussian, cosh- Gaussian, cos-Gaussian, annular, elliptical Gaussian, circular (i.e., stigmatic) and elliptical (i.e., astigmatic) dark hollow, lowest order Bessel-Gaussian and laser array beams. For flat-topped-Gaussian beam, scintillation is larger than the single Gaussian beam scintillation, when the source sizes are much less than the Fresnel zone but becomes smaller for source sizes much larger than the Fresnel zone. Cosh-Gaussian beam has lower on-axis scintillations at smaller source sizes and longer propagation distances as compared to Gaussian beams where focusing imposes more reduction on the cosh- Gaussian beam scintillations than that of the Gaussian beam. Intensity fluctuations of a cos-Gaussian beam show favorable behaviour against a Gaussian beam at lower propagation lengths. At longer propagation lengths, annular beam becomes advantageous. In focused cases, the scintillation index of annular beam is lower than the scintillation index of Gaussian and cos-Gaussian beams starting at earlier propagation distances. Cos-Gaussian beams are advantages at relatively large source sizes while the reverse is valid for annular beams. Scintillations of a stigmatic or astigmatic dark hollow beam can be smaller when compared to stigmatic or astigmatic Gaussian, annular and flat-topped beams under conditions that are closely related to the beam parameters. Intensity fluctuation of an elliptical Gaussian beam can also be smaller than a circular Gaussian beam depending on the propagation length and the ratio of the beam waist size along the long axis to that along the short axis (i.e., astigmatism). Comparing against the fundamental Gaussian beam on equal source size and equal power basis, it is observed that the scintillation index of the lowest order Bessel-Gaussian beam is lower at large source sizes and large width parameters. However, for excessively large width parameters and beyond certain propagation lengths, the advantage of the lowest order Bessel-Gaussian beam seems to be lost. Compared to Gaussian beam, laser array beam exhibits less scintillations at long propagation ranges and at some midrange radial displacement parameters. When compared among themselves, laser array beams tend to have reduced scintillations for larger number of beamlets, longer wavelengths, midrange radial displacement parameters, intermediate Gaussian source sizes, larger inner scales and smaller outer scales of turbulence. The number of beamlets used does not seem to be so effective in this improvement of the scintillations.

RDM Lifetime measurements in ^191Hg using the Gammasphere Plunger

NASA Astrophysics Data System (ADS)

Jin, H.; Kharraja, B.; Garg, U.; Ghugre, S. S.; Carpenter, M. P.; Fischer, S.; Janssens, R. V. F.; Khoo, T. L.; Lauritsen, T.; Nisius, D.; Kaczarowski, R.; Govil, I. M.; Kruecken, R.; Machiavelli, A.; MacLeod, R.

1998-10-01

Recoil Distance Lifetime Measurements have been performed for the nucleus ^191Hg at Gammasphere with a view to further investigate the prolate non-collective structure (ɛ2 = 0.1 - 0.15, γ ~= - 120^circ) reported several years ago by D. Ye et al. (D. Ye et al.,) Phys. Lett. B236, 7 (1990) The ^174Yb(^22Ne, 5n) reaction was employed at a beam energy of 120 MeV. In this experiment the new Gammasphere Plunger was used for the first time. Data were collected at 7 distances ranging from 50 μm to 1070 μm. The extracted lifetimes for the level sequence of interest are in the range of ~ 7 ps to 120 ps, leading to transition probabilities that indeed correspond to a non-collective nature.

High brilliance negative ion and neutral beam source

DOEpatents

Compton, Robert N.

1991-01-01

A high brilliance mass selected (Z-selected) negative ion and neutral beam source having good energy resolution. The source is based upon laser resonance ionization of atoms or molecules in a small gaseous medium followed by charge exchange through an alkali oven. The source is capable of producing microampere beams of an extremely wide variety of negative ions, and milliampere beams when operated in the pulsed mode.

Continuous all-optical deceleration of molecular beams

NASA Astrophysics Data System (ADS)

Jayich, Andrew; Chen, Gary; Long, Xueping; Wang, Anna; Campbell, Wesley

2014-05-01

A significant impediment to generating ultracold molecules is slowing a molecular beam to velocities where the molecules can be cooled and trapped. We report on progress toward addressing this issue with a general optical deceleration technique for molecular and atomic beams. We propose addressing the molecular beam with a pump and dump pulse sequence from a mode-locked laser. The pump pulse counter-propagates with respect to the beam and drives the molecules to the excited state. The dump pulse co-propagates and stimulates emission, driving the molecules back to the ground state. This cycle transfers 2 ℏk of momentum and can generate very large optical forces, not limited by the spontaneous emission lifetime of the molecule or atom. Importantly, avoiding spontaneous emission limits the branching to dark states. This technique can later be augmented with cooling and trapping. We are working towards demonstrating this optical force by accelerating a cold atomic sample.

Final muon cooling for a muon collider

NASA Astrophysics Data System (ADS)

Acosta Castillo, John Gabriel

To explore the new energy frontier, a new generation of particle accelerators is needed. Muon colliders are a promising alternative if muon cooling can be made to work. Muons are 200 times heavier than electrons, so they produce less synchrotron radiation, and they behave like point particles. However, they have a short lifetime of 2.2 mus and the beam is more difficult to cool than an electron beam. The Muon Accelerator Program (MAP) was created to develop concepts and technologies required by a muon collider. An important effort has been made in the program to design and optimize a muon beam cooling system. The goal is to achieve the small beam emittance required by a muon collider. This work explores a final ionization cooling system using magnetic quadrupole lattices with a low enough beta* region to cool the beam to the required limit with available low Z absorbers.

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

Acosta Castillo, John Gabriel

To explore the new energy frontier, a new generation of particle accelerators is needed. Muon colliders are a promising alternative, if muon cooling can be made to work. Muons are 200 times heavier than electrons, so they produce less synchrotron radiation, and they behave like point particles. However, they have a short lifetime of 2.2more » $$\\mathrm{\\mu s}$$ and the beam is more difficult to cool than an electron beam. The Muon Accelerator Program (MAP) was created to develop concepts and technologies required by a muon collider. An important effort has been made in the program to design and optimize a muon beam cooling system. The goal is to achieve the small beam emittance required by a muon collider. This work explores a final ionization cooling system using magnetic quadrupole lattices with a low enough $$\\beta^{\\star} $$ region to cool the beam to the required limit with available low Z absorbers.« less

Cold and intense OH radical beam sources

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

Ploenes, Ludger; Meerakker, Sebastiaan Y. T. van de; Haas, Dominik

2016-05-15

We present the design and performance of two supersonic radical beam sources: a conventional pinhole-discharge source and a dielectric barrier discharge (DBD) source, both based on the Nijmegen pulsed valve. Both designs have been characterized by discharging water molecules seeded in the rare gases Ar, Kr, or Xe. The resulting OH radicals have been detected by laser-induced fluorescence. The measured OH densities are (3.0 ± 0.6) × 10{sup 11} cm{sup -3} and (1.0 ± 0.5) × 10{sup 11} cm{sup -3} for the pinhole-discharge and DBD sources, respectively. The beam profiles for both radical sources show a relative longitudinal velocity spreadmore » of about 10%. The absolute rotational ground state population of the OH beam generated from the pinhole-discharge source has been determined to be more than 98%. The DBD source even produces a rotationally colder OH beam with a population of the ground state exceeding 99%. For the DBD source, addition of O{sub 2} molecules to the gas mixture increases the OH beam density by a factor of about 2.5, improves the DBD valve stability, and allows to tune the mean velocity of the radical beam.« less

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

Taylor, J.A.; Brasseur, G.P.; Zimmerman, P.R.

Using the hydroxyl radical field calibrated to the methyl chloroform observations, the globally averaged release of methane and its spatial and temporal distribution were investigated. Two source function models of the spatial and temporal distribution of the flux of methane to the atmosphere were developed. The first model was based on the assumption that methane is emitted as a proportion of net primary productivity (NPP). With the average hydroxyl radical concentration fixed, the methane source term was computed as {approximately}623 Tg CH{sub 4}, giving an atmospheric lifetime for methane {approximately}8.3 years. The second model identified source regions for methane frommore » rice paddies, wetlands, enteric fermentation, termites, and biomass burning based on high-resolution land use data. This methane source distribution resulted in an estimate of the global total methane source of {approximately}611 Tg CH{sub 4}, giving an atmospheric lifetime for methane {approximately}8.5 years. The most significant difference between the two models were predictions of methane fluxes over China and South East Asia, the location of most of the world's rice paddies. Using a recent measurement of the reaction rate of hydroxyl radical and methane leads to estimates of the global total methane source for SF1 of {approximately}524 Tg CH{sub 4} giving an atmospheric lifetime of {approximately}10.0 years and for SF2{approximately}514 Tg CH{sub 4} yielding a lifetime of {approximately}10.2 years.« less

Ion Beam Propulsion Study

NASA Technical Reports Server (NTRS)

2008-01-01

The Ion Beam Propulsion Study was a joint high-level study between the Applied Physics Laboratory operated by NASA and ASRC Aerospace at Kennedy Space Center, Florida, and Berkeley Scientific, Berkeley, California. The results were promising and suggested that work should continue if future funding becomes available. The application of ion thrusters for spacecraft propulsion is limited to quite modest ion sources with similarly modest ion beam parameters because of the mass penalty associated with the ion source and its power supply system. Also, the ion source technology has not been able to provide very high-power ion beams. Small ion beam propulsion systems were used with considerable success. Ion propulsion systems brought into practice use an onboard ion source to form an energetic ion beam, typically Xe+ ions, as the propellant. Such systems were used for steering and correction of telecommunication satellites and as the main thruster for the Deep Space 1 demonstration mission. In recent years, "giant" ion sources were developed for the controlled-fusion research effort worldwide, with beam parameters many orders of magnitude greater than the tiny ones of conventional space thruster application. The advent of such huge ion beam sources and the need for advanced propulsion systems for exploration of the solar system suggest a fresh look at ion beam propulsion, now with the giant fusion sources in mind.

Mapping quadrupole collectivity in the Cd isotopes: The breakdown of harmonic vibrational motion

NASA Astrophysics Data System (ADS)

Garrett, P. E.; Green, K. L.; Bangay, J.; Varela, A. Diaz; Sumithrarachchi, C. S.; Austin, R. A. E.; Ball, G. C.; Bandyopadhyay, D. S.; Bianco, L.; Colosimo, S.; Cross, D. S.; Demand, G. A.; Finlay, P.; Garnsworthy, A. B.; Grinyer, G. F.; Hackman, G.; Kulp, W. D.; Leach, K. G.; Morton, A. C.; Orce, J. N.; Pearson, C. J.; Phillips, A. A.; Schumaker, M. A.; Svensson, C. E.; Triambak, S.; Wong, J.; Wood, J. L.; Yates, S. W.

2011-10-01

The stable Cd isotopes have long been used as paradigms for spherical vibrational motion. Extensive investigations with in-beam γ spectroscopy have resulted in very-well-established level schemes, including many lifetimes or lifetime limits. A programme has been initiated to complement these studies with very-high-statistics β decay using the 8π spectrometer at the TRIUMF radioactive beam facility. The decays of 112In and 112Ag have been studied with an emphasis on the observation of, or the placement of stringent limits on, low-energy branches between potential multi-phonon levels. A lack of suitable 0+ or 2+ three-phonon candidates has been revealed. Further, the sum of the B(E2) strength from spin 0+ and 2+ states up to 3 MeV in excitation energy to the assigned two-phonon levels falls far short of the harmonic-vibrational expectations. This lack of strength points to the failing of collective models based on vibrational phonon structures.

A high speed multifocal multiphoton fluorescence lifetime imaging microscope for live-cell FRET imaging

PubMed Central

Poland, Simon P.; Krstajić, Nikola; Monypenny, James; Coelho, Simao; Tyndall, David; Walker, Richard J.; Devauges, Viviane; Richardson, Justin; Dutton, Neale; Barber, Paul; Li, David Day-Uei; Suhling, Klaus; Ng, Tony; Henderson, Robert K.; Ameer-Beg, Simon M.

2015-01-01

We demonstrate diffraction limited multiphoton imaging in a massively parallel, fully addressable time-resolved multi-beam multiphoton microscope capable of producing fluorescence lifetime images with sub-50ps temporal resolution. This imaging platform offers a significant improvement in acquisition speed over single-beam laser scanning FLIM by a factor of 64 without compromising in either the temporal or spatial resolutions of the system. We demonstrate FLIM acquisition at 500 ms with live cells expressing green fluorescent protein. The applicability of the technique to imaging protein-protein interactions in live cells is exemplified by observation of time-dependent FRET between the epidermal growth factor receptor (EGFR) and the adapter protein Grb2 following stimulation with the receptor ligand. Furthermore, ligand-dependent association of HER2-HER3 receptor tyrosine kinases was observed on a similar timescale and involved the internalisation and accumulation or receptor heterodimers within endosomes. These data demonstrate the broad applicability of this novel FLIM technique to the spatio-temporal dynamics of protein-protein interaction. PMID:25780724

Scalable focused ion beam creation of nearly lifetime-limited single quantum emitters in diamond nanostructures

PubMed Central

Schröder, Tim; Trusheim, Matthew E.; Walsh, Michael; Li, Luozhou; Zheng, Jiabao; Schukraft, Marco; Sipahigil, Alp; Evans, Ruffin E.; Sukachev, Denis D.; Nguyen, Christian T.; Pacheco, Jose L.; Camacho, Ryan M.; Bielejec, Edward S.; Lukin, Mikhail D.; Englund, Dirk

2017-01-01

The controlled creation of defect centre—nanocavity systems is one of the outstanding challenges for efficiently interfacing spin quantum memories with photons for photon-based entanglement operations in a quantum network. Here we demonstrate direct, maskless creation of atom-like single silicon vacancy (SiV) centres in diamond nanostructures via focused ion beam implantation with ∼32 nm lateral precision and <50 nm positioning accuracy relative to a nanocavity. We determine the Si+ ion to SiV centre conversion yield to be ∼2.5% and observe a 10-fold conversion yield increase by additional electron irradiation. Low-temperature spectroscopy reveals inhomogeneously broadened ensemble emission linewidths of ∼51 GHz and close to lifetime-limited single-emitter transition linewidths down to 126±13 MHz corresponding to ∼1.4 times the natural linewidth. This method for the targeted generation of nearly transform-limited quantum emitters should facilitate the development of scalable solid-state quantum information processors. PMID:28548097

Scalable focused ion beam creation of nearly lifetime-limited single quantum emitters in diamond nanostructures

DOE PAGES

Schroder, Tim; Trusheim, Matthew E.; Walsh, Michael; ...

2017-05-26

The controlled creation of defect centre—nanocavity systems is one of the outstanding challenges for efficiently interfacing spin quantum memories with photons for photon-based entanglement operations in a quantum network. Here we demonstrate direct, maskless creation of atom-like single silicon vacancy (SiV) centres in diamond nanostructures via focused ion beam implantation with ~32 nm lateral precision and <50 nm positioning accuracy relative to a nanocavity. We determine the Si+ ion to SiV centre conversion yield to be ~2.5% and observe a 10-fold conversion yield increase by additional electron irradiation. Low-temperature spectroscopy reveals inhomogeneously broadened ensemble emission linewidths of ~51 GHz andmore » close to lifetime-limited single-emitter transition linewidths down to 126±13 MHz corresponding to ~1.4 times the natural linewidth. Furthermore, this method for the targeted generation of nearly transform-limited quantum emitters should facilitate the development of scalable solid-state quantum information processors.« less

Scalable focused ion beam creation of nearly lifetime-limited single quantum emitters in diamond nanostructures

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

Schroder, Tim; Trusheim, Matthew E.; Walsh, Michael

The controlled creation of defect centre—nanocavity systems is one of the outstanding challenges for efficiently interfacing spin quantum memories with photons for photon-based entanglement operations in a quantum network. Here we demonstrate direct, maskless creation of atom-like single silicon vacancy (SiV) centres in diamond nanostructures via focused ion beam implantation with ~32 nm lateral precision and <50 nm positioning accuracy relative to a nanocavity. We determine the Si+ ion to SiV centre conversion yield to be ~2.5% and observe a 10-fold conversion yield increase by additional electron irradiation. Low-temperature spectroscopy reveals inhomogeneously broadened ensemble emission linewidths of ~51 GHz andmore » close to lifetime-limited single-emitter transition linewidths down to 126±13 MHz corresponding to ~1.4 times the natural linewidth. Furthermore, this method for the targeted generation of nearly transform-limited quantum emitters should facilitate the development of scalable solid-state quantum information processors.« less

Positronium formation in SiO2 films grown on Si substrates studied by monoenergetic positron beams

NASA Astrophysics Data System (ADS)

Uedono, A.; Wei, L.; Tanigawa, S.; Suzuki, R.; Ohgaki, H.; Mikado, T.; Kawano, T.; Ohji, Y.

1994-04-01

The annihilation characteristics of positrons in SiO2 films grown on Si substrates were studied by using monoenergetic positron beams. Doppler broadening profiles of the annihilation radiation and lifetime spectra of positrons were measured as a function of incident positron energy for SiO2 (166 nm)/Si specimens fabricated by thermal oxidation. From the measurements, it was found that about 90% of positrons implanted into the SiO2 film annihilate from positronium (Ps) states. This fact was due to the trapping of positrons by open-space defects and a resultant enhanced formation of Ps in such regions. For the SiO2 film grown at 650 °C, the lifetime of ortho-Ps was found to be shorter than that in the film grown at 1000 °C. This result suggests that the volume of open-space defects in the SiO2 film decreased with decreasing the growth rate of the SiO2 film.

A new front-face optical cell for measuring weak fluorescent emissions with time resolution in the picosecond time scale.

PubMed

Gryczynski, Z; Bucci, E

1993-11-01

Recent developments of ultrafast fluorimeters allow measuring time-resolved fluorescence on the picosecond time scale. This implies one is able to monitor lifetimes and anisotropy decays of highly quenched systems and of systems that contain fluorophores having lifetimes in the subnanosecond range; both systems that emit weak signals. The combination of weak signals and very short lifetimes makes the measurements prone to distortions which are negligible in standard fluorescence experiments. To cope with these difficulties, we have designed a new optical cell for front-face optics which offers to the excitation beam a horizontal free liquid surface in the absence of interactions with optical windows. The new cell has been tested with probes of known lifetimes and anisotropies. It proved very useful in detecting tryptophan fluorescence in hemoglobin. If only diluted samples are available, which cannot be used in front-face optics, regular square geometry can still be utilized by inserting light absorbers into a cuvette of 1 cm path length.

Multiple-predators-based capture process on complex networks

NASA Astrophysics Data System (ADS)

Ramiz Sharafat, Rajput; Pu, Cunlai; Li, Jie; Chen, Rongbin; Xu, Zhongqi

2017-03-01

The predator/prey (capture) problem is a prototype of many network-related applications. We study the capture process on complex networks by considering multiple predators from multiple sources. In our model, some lions start from multiple sources simultaneously to capture the lamb by biased random walks, which are controlled with a free parameter $\\alpha$. We derive the distribution of the lamb's lifetime and the expected lifetime $\\left\\langle T\\right\\rangle $. Through simulation, we find that the expected lifetime drops substantially with the increasing number of lions. We also study how the underlying topological structure affects the capture process, and obtain that locating on small-degree nodes is better than large-degree nodes to prolong the lifetime of the lamb. Moreover, dense or homogeneous network structures are against the survival of the lamb.

Microsecond Electron Beam Source with Electron Energy Up to 400 Kev and Plasma Anode

NASA Astrophysics Data System (ADS)

Abdullin, É. N.; Basov, G. F.; Shershnev, S.

2017-12-01

A new high-power source of electrons with plasma anode for producing high-current microsecond electron beams with electron energy up to 400 keV has been developed, manufactured, and put in operation. To increase the cross section and pulse current duration of the beam, a multipoint explosive emission cathode is used in the electron beam source, and the beam is formed in an applied external guiding magnetic field. The Marx generator with vacuum insulation is used as a high-voltage source. Electron beams with electron energy up to 300-400 keV, current of 5-15 kA, duration of 1.5-3 μs, energy up to 4 kJ, and cross section up to 150 cm2 have been produced. The operating modes of the electron beam source are realized in which the applied voltage is influenced weakly on the current. The possibility of source application for melting of metal surfaces is demonstrated.

128Xe Lifetime Measurement Using the Coulex-Plunger Technique in Inverse Kinematics

NASA Astrophysics Data System (ADS)

Konstantinopoulos, T.; Lagoyannis, A.; Harissopulos, S.; Dewald, A.; Rother, W.; Ilie, G.; Jones, P.; Rakhila, P.; Greenlees, P.; Grahn, T.; Julin, R.; Balabanski, D. L.

2008-05-01

The lifetimes of the lowest collective yrast and non-yrast states in 128Xe were measured in a Coulomb excitation experiment using the recoil distance method (RDM) in inverse kinematics. Hereby, the Cologne plunger apparatus was employed together with the JUROGAM spectrometer. Excited states in 128Xe were populated using a 128Xe beam impinging on a natFe target with E(128Xe)~525 MeV. Recoils were detected by means of an array of solar cells placed at forward angles. Recoil-gated γ-spectra were measured at different plunger distances.

Dose control in electron beam processing: Comparison of results from a graphite charge collector, routine dosimeters and the ISS alanine-based dosimeter

NASA Astrophysics Data System (ADS)

Fuochi, P. G.; Onori, S.; Casali, F.; Chirco, P.

1993-10-01

A 12 MeV linear accelerator is currently used for electron beam processing of power semiconductor devices for lifetime control and, on an experimental basis, for food irradiation, sludge treatment etc. In order to control the irradiation process a simple, quick and reliable method for a direct evaluation of dose and fluence in a broad electron beam has been developed. This paper presents the results obtained using a "charge collector" which measures the charge absorbed in a graphite target exposed in air. Calibration of the system with super-Fricke dosimeter and comparison of absorbed dose results obtained with plastic dosimeters and alanine pellets are discussed.

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

Observed circuit limits to time resolution in correlation measurements with Si-on-sapphire, GaAs, and InP picosecond photoconductors

NASA Astrophysics Data System (ADS)

Hammond, R. B.; Paulter, N. G.; Wagner, R. S.

1984-08-01

Cross-correlation measurements of the response of photoconductor pulsers and sampling gates excited by a femtosecond laser are reported. The photoconductors were fabricated in microstrip transmission line structures on Si-on-sapphire, semiinsulating GaAs, and semiinsulating InP wafers. The photoconductor sampling gates were ion beam-damaged to produce short carrier lifetimes (less than 3 ps in one case). Damage was introduced with 6 MeV Ne-20 on the Si-on-sapphire, 2 MeV H-2 on the GaAs, and 2 MeV He-4 on the InP. Doses in the range 10 to the 12th - 10 to the 15th were used. Results show circuit limits to the time resolution in correlation measurements from two sources: (1) RC time constants due to photoconductor gap capacitance and transmission line characteristic impedance and (2) dispersion in microstrip transmission lines.

Macroscopic erosion of divertor and first wall armour in future tokamaks

NASA Astrophysics Data System (ADS)

Würz, H.; Bazylev, B.; Landman, I.; Pestchanyi, S.; Safronov, V.

2002-12-01

Sputtering, evaporation and macroscopic erosion determine the lifetime of the 'in vessel' armour materials CFC, tungsten and beryllium presently under discussion for future tokamaks. For CFC armour macroscopic erosion means brittle destruction and dust formation whereas for metallic armour melt layer erosion by melt motion and droplet splashing. Available results on macroscopic erosion from hot plasma and e-beam simulation experiments and from tokamaks are critically evaluated and a comprehensive discussion of experimental and numerical macroscopic erosion and its extrapolation to future tokamaks is given. Shielding of divertor armour materials by their own vapor exists during plasma disruptions. The evolving plasma shield protects the armour from high heat loads, absorbs the incoming energy and reradiates it volumetrically thus reducing drastically the deposited energy. As a result, vertical target erosion by vaporization turns out to be of the order of a few microns per disruption event and macroscopic erosion becomes the dominant erosion source.

Degradation of Nylon 6,6 Fire-Suppression Casing from Plutonium Glove Boxes Under Alpha and Neutron Irradiation

DOE PAGES

Millsap, Donald W.; Cournoyer, Michael E.; Landsberger, Sheldon; ...

2015-04-23

Nylon 6,6 tensile specimens, conforming to the casing for self-contained fire extinguisher systems, have been irradiated using both an accelerator He ++ ion beam and a 5-Ci PuBe neutron source to model the radiation damage these systems would likely incur over a lifetime of operation within glove boxes. Following irradiation, these samples were mechanically tested using standard practices as described in ASTM D638. The results of the He ++ study indicate that the tensile strength of the nylon specimens undergoes some slight (<10%) degradation while other properties of the samples, such as elongation and tangent modulus, appear to fluctuate withmore » increasing dose levels. The He ++-irradiated specimens also have a noticeable level of discoloration corresponding to increasing levels of dose. The neutron-irradiated samples show a higher degree of mechanical degradation than the He ++-irradiated samples.« less

Two-photon microscopy using fiber-based nanosecond excitation.

PubMed

Karpf, Sebastian; Eibl, Matthias; Sauer, Benjamin; Reinholz, Fred; Hüttmann, Gereon; Huber, Robert

2016-07-01

Two-photon excitation fluorescence (TPEF) microscopy is a powerful technique for sensitive tissue imaging at depths of up to 1000 micrometers. However, due to the shallow penetration, for in vivo imaging of internal organs in patients beam delivery by an endoscope is crucial. Until today, this is hindered by linear and non-linear pulse broadening of the femtosecond pulses in the optical fibers of the endoscopes. Here we present an endoscope-ready, fiber-based TPEF microscope, using nanosecond pulses at low repetition rates instead of femtosecond pulses. These nanosecond pulses lack most of the problems connected with femtosecond pulses but are equally suited for TPEF imaging. We derive and demonstrate that at given cw-power the TPEF signal only depends on the duty cycle of the laser source. Due to the higher pulse energy at the same peak power we can also demonstrate single shot two-photon fluorescence lifetime measurements.

A portable time-domain LED fluorimeter for nanosecond fluorescence lifetime measurements

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

Wang, Hongtao; Salthouse, Christopher D., E-mail: salthouse@ecs.umass.edu; Center for Personalized Health Monitoring, University of Massachusetts, Amherst, Massachusetts 01003

2014-05-15

Fluorescence lifetime measurements are becoming increasingly important in chemical and biological research. Time-domain lifetime measurements offer fluorescence multiplexing and improved handling of interferers compared with the frequency-domain technique. In this paper, an all solid-state, filterless, and highly portable light-emitting-diode based time-domain fluorimeter (LED TDF) is reported for the measurement of nanosecond fluorescence lifetimes. LED based excitation provides more wavelengths options compared to laser diode based excitation, but the excitation is less effective due to the uncollimated beam, less optical power, and longer latency in state transition. Pulse triggering and pre-bias techniques were implemented in our LED TDF to improve themore » peak optical power to over 100 mW. The proposed pulsing circuit achieved an excitation light fall time of less than 2 ns. Electrical resetting technique realized a time-gated photo-detector to remove the interference of the excitation light with fluorescence. These techniques allow the LED fluorimeter to accurately measure the fluorescence lifetime of fluorescein down to concentration of 0.5 μM. In addition, all filters required in traditional instruments are eliminated for the non-attenuated excitation/emission light power. These achievements make the reported device attractive to biochemical laboratories seeking for highly portable lifetime detection devices for developing sensors based on fluorescence lifetime changes. The device was initially validated by measuring the lifetimes of three commercial fluorophores and comparing them with reported lifetime data. It was subsequently used to characterize a ZnSe quantum dot based DNA sensor.« less

Direct measurements of the lifetime of medium-heavy hypernuclei

NASA Astrophysics Data System (ADS)

Qiu, X.; Tang, L.; Chen, C.; Margaryan, A.; Wood, S. A.; Achenbach, P.; Ahmidouch, A.; Albayrak, I.; Androic, D.; Asaturyan, A.; Asaturyan, R.; Ates, O.; Badui, R.; Baturin, P.; Boeglin, W.; Bono, J.; Brash, E.; Carter, P.; Chen, X.; Chiba, A.; Christy, M. E.; Dalton, M. M.; Danagoulian, S.; De Leo, R.; Doi, D.; Elaasar, M.; Ent, R.; Fenker, H.; Fujii, Y.; Furic, M.; Gabrielyan, M.; Gan, L.; Garibaldi, F.; Gaskell, D.; Gasparian, A.; Gogami, T.; Hashimoto, O.; Horn, T.; Hu, B.; Hungerford, Ed V.; Jones, M.; Kanda, H.; Kaneta, M.; Kawama, D.; Khanal, H.; Kohl, M.; Liyanage, A.; Luo, W.; Maeda, K.; Markowitz, P.; Marikyan, G.; Maruta, T.; Matsumura, A.; Maxwell, V.; Mkrtchyan, A.; Mkrtchyan, H.; Nagao, S.; Nakamura, S. N.; Narayan, A.; Neville, C.; Niculescu, G.; Niculescu, M. I.; Nunez, A.; Nuruzzaman; Okayasu, Y.; Petkovic, T.; Pochodzalla, J.; Reinhold, J.; Rodriguez, V. M.; Samanta, C.; Sawatzky, B.; Seva, T.; Shichijo, A.; Tadevosyan, V.; Taniya, N.; Tsukada, K.; Veilleux, M.; Vulcan, W.; Wesselmann, F. R.; Yamamoto, T.; Ye, Z.; Yokota, K.; Yuan, L.; Zhamkochyan, S.; Zhu, L.; HKS (JLab E02-017) Collaboration

2018-05-01

The lifetime of a Λ particle embedded in a nucleus (hypernucleus) decreases from that of free Λ decay mainly due to the opening of the ΛN → NN weak decay channel. However, it is generally believed that the lifetime of a hypernucleus attains a constant value (saturation) for medium to heavy hypernuclear masses, yet this hypothesis has been difficult to verify. This paper presents a direct measurement of the lifetime of medium-heavy hypernuclei that were hyper-fragments produced by fission or break-up from heavy hypernuclei initially produced with a 2.34 GeV photon-beam incident on thin Fe, Cu, Ag, and Bi target foils. For each event, fragments were detected in coincident pairs by a low-pressure multi-wire proportional chamber system. The lifetime was extracted from decay time spectrum formed by the difference of the time zeros between the pairs. The measured lifetime from each target is actually a statistical average over a range of mass with mean about 1/2 of the target mass and appears to be a constant of about 200 ps. Although this result cannot exclude unexpected shorter or longer lifetimes for some specific hypernuclei or hypernuclear states, it shows that a systematic decrease in lifetime as hypernuclear mass increases is not a general feature for hypernuclei with mean mass up to A ≈ 130. On the other hand, the success of this experiment and its technique shows that the time delayed fissions observed and used by all the lifetime measurements done so far on heavy hypernuclei could likely have originated from hyper-fragments lighter than the assumed masses.

Investigations of the emittance and brightness of ion beams from an electron beam ion source of the Dresden EBIS type.

PubMed

Silze, Alexandra; Ritter, Erik; Zschornack, Günter; Schwan, Andreas; Ullmann, Falk

2010-02-01

We have characterized ion beams extracted from the Dresden EBIS-A, a compact room-temperature electron beam ion source (EBIS) with a permanent magnet system for electron beam compression, using a pepper-pot emittance meter. The EBIS-A is the precursor to the Dresden EBIS-SC in which the permanent magnets have been replaced by superconducting solenoids for the use of the source in high-ion-current applications such as heavy-ion cancer therapy. Beam emittance and brightness values were calculated from data sets acquired for a variety of source parameters, in leaky as well as pulsed ion extraction mode. With box shaped pulses of C(4+) ions at an energy of 39 keV root mean square emittances of 1-4 mm mrad and a brightness of 10 nA mm(-2) mrad(-2) were achieved. The results meet the expectations for high quality ion beams generated by an electron beam ion source.

Low-z gas stripper as an alternative to carbon foils for the acceleration of high-power uranium beams

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

Okuno, H.; Hershcovitch, A.; Fukunishi, N.

2011-04-23

The RIKEN accelerator complex started feeding the next-generation exotic beam facility radioisotope beam factory (RIBF) with heavy-ion beams from 2007 after the successful commissioning of RIBF at the end of 2006. Many improvements made from 2007 to 2010 were instrumental in increasing the intensity of various heavy-ion beams. However, the available beam intensity of very heavy ion beams, especially uranium beams, is far below our goal of 1 p{mu}A (6 x 10{sup 12} particles/s). In order to achieve this goal, upgrade programs are already in progress; the programs include the construction of a new 28-GHz superconducting electron cyclotron resonance ionmore » source and a new injector linac. However, the most serious problem, that of a charge stripper for high-power uranium beams, still remains unsolved, despite extensive research and development work using large foils mounted on a rotating cylinder and a N{sup 2} gas stripper. A gas stripper is free from problems related to lifetime, though the equilibrium charge state in this stripper is considerably lower than that in a carbon foil, owing to the absence of the density effect. Nevertheless, the merits of gas strippers motivated us to develop a low-Z gas stripper to achieve a higher equilibrium charge state even in gases. We measured the electron-loss and electron-capture cross sections of uranium ions in He gas as a function of their charge state at 11, 14, and 15 MeV/nucleon. The equilibrium charge states extracted from the intersection of the lines of the two cross sections were promisingly higher than those in N{sub 2} gas by more than 10. Simple simulations of charge development along the stripper thickness were performed by assuming the measured cross sections. The simulation results show that about 1 mg/cm{sup 2} of He gas should be accumulated to achieve a charge state higher than that of N{sub 2} gas, notwithstanding the difficulty in accumulation of this helium amount owing to its fast dispersion. However, we now believe that the following two solutions can overcome this difficulty: a gas cell with a very large differential pumping system and a gas cell with a plasma window. Their merits and demerits are discussed in the paper.« less

A combined thermal dissociation and electron impact ionization source for radioactive ion beam generation{sup a}

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

Alton, G.D.; Williams, C.

1996-04-01

The probability for simultaneously dissociating and efficiently ionizing the individual atomic constituents of molecular feed materials with conventional, hot-cathode, electron-impact ion sources is low and consequently, the ion beams from these sources often appear as mixtures of several molecular sideband beams. This fragmentation process leads to dilution of the intensity of the species of interest for radioactive ion beam (RIB) applications where beam intensity is at a premium. We have conceived an ion source that combines the excellent molecular dissociation properties of a thermal dissociator and the high ionization efficiency characteristics of an electron impact ionization source that will, inmore » principle, overcome this handicap. The source concept will be evaluated as a potential candidate for use for RIB generation at the Holifield Radioactive Ion Beam Facility, now under construction at the Oak Ridge National Laboratory. The design features and principles of operation of the source are described in this article. {copyright} {ital 1996 American Institute of Physics.}« less

A combined thermal dissociation and electron impact ionization source for radioactive ion beam generation (abstract){sup a}

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

Alton, G.D.; Williams, C.

1996-03-01

The probability for simultaneously dissociating and efficiently ionizing the individual atomic constituents of molecular feed materials with conventional, hot-cathode, electron-impact ion sources is low and consequently, the ion beams from these sources often appear as mixtures of several molecular sideband beams. This fragmentation process leads to dilution of the intensity of the species of interest for radioactive ion beam (RIB) applications where beam intensity is at a premium. We have conceived an ion source that combines the excellent molecular dissociation properties of a thermal dissociator and the high ionization efficiency characteristics of an electron impact ionization source that will, inmore » principle, overcome this handicap. The source concept will be evaluated as a potential candidate for use for RIB generation at the Holifield Radioactive Ion Beam Facility, now under construction at the Oak Ridge National Laboratory. The design features and principles of operation of the source are described in this article. {copyright} {ital 1996 American Institute of Physics.}« less

High resolution stationary digital breast tomosynthesis using distributed carbon nanotube x-ray source array.

PubMed

Qian, Xin; Tucker, Andrew; Gidcumb, Emily; Shan, Jing; Yang, Guang; Calderon-Colon, Xiomara; Sultana, Shabana; Lu, Jianping; Zhou, Otto; Spronk, Derrek; Sprenger, Frank; Zhang, Yiheng; Kennedy, Don; Farbizio, Tom; Jing, Zhenxue

2012-04-01

The purpose of this study is to investigate the feasibility of increasing the system spatial resolution and scanning speed of Hologic Selenia Dimensions digital breast tomosynthesis (DBT) scanner by replacing the rotating mammography x-ray tube with a specially designed carbon nanotube (CNT) x-ray source array, which generates all the projection images needed for tomosynthesis reconstruction by electronically activating individual x-ray sources without any mechanical motion. The stationary digital breast tomosynthesis (s-DBT) design aims to (i) increase the system spatial resolution by eliminating image blurring due to x-ray tube motion and (ii) reduce the scanning time. Low spatial resolution and long scanning time are the two main technical limitations of current DBT technology. A CNT x-ray source array was designed and evaluated against a set of targeted system performance parameters. Simulations were performed to determine the maximum anode heat load at the desired focal spot size and to design the electron focusing optics. Field emission current from CNT cathode was measured for an extended period of time to determine the stable life time of CNT cathode for an expected clinical operation scenario. The source array was manufactured, tested, and integrated with a Selenia scanner. An electronic control unit was developed to interface the source array with the detection system and to scan and regulate x-ray beams. The performance of the s-DBT system was evaluated using physical phantoms. The spatially distributed CNT x-ray source array comprised 31 individually addressable x-ray sources covering a 30 angular span with 1 pitch and an isotropic focal spot size of 0.6 mm at full width at half-maximum. Stable operation at 28 kV(peak) anode voltage and 38 mA tube current was demonstrated with extended lifetime and good source-to-source consistency. For the standard imaging protocol of 15 views over 14, 100 mAs dose, and 2 × 2 detector binning, the projection resolution along the scanning direction increased from 4.0 cycles/mm [at 10% modulation-transfer-function (MTF)] in DBT to 5.1 cycles/mm in s-DBT at magnification factor of 1.08. The improvement is more pronounced for faster scanning speeds, wider angular coverage, and smaller detector pixel sizes. The scanning speed depends on the detector, the number of views, and the imaging dose. With 240 ms detector readout time, the s-DBT system scanning time is 6.3 s for a 15-view, 100 mAs scan regardless of the angular coverage. The scanning speed can be reduced to less than 4 s when detectors become faster. Initial phantom studies showed good quality reconstructed images. A prototype s-DBT scanner has been developed and evaluated by retrofitting the Selenia rotating gantry DBT scanner with a spatially distributed CNT x-ray source array. Preliminary results show that it improves system spatial resolution substantially by eliminating image blur due to x-ray focal spot motion. The scanner speed of s-DBT system is independent of angular coverage and can be increased with faster detector without image degration. The accelerated lifetime measurement demonstrated the long term stability of CNT x-ray source array with typical clinical operation lifetime over 3 years.

Production, formation, and transport of high-brightness atomic hydrogen beam studies for the relativistic heavy ion collider polarized source upgrade.

PubMed

Kolmogorov, A; Atoian, G; Davydenko, V; Ivanov, A; Ritter, J; Stupishin, N; Zelenski, A

2014-02-01

The RHIC polarized H(-) ion source had been successfully upgraded to higher intensity and polarization by using a very high brightness fast atomic beam source developed at BINP, Novosibirsk. In this source the proton beam is extracted by a four-grid multi-aperture ion optical system and neutralized in the H2 gas cell downstream from the grids. The proton beam is extracted from plasma emitter with a low transverse ion temperature of ∼0.2 eV which is formed by plasma jet expansion from the arc plasma generator. The multi-hole grids are spherically shaped to produce "geometrical" beam focusing. Proton beam formation and transport of atomic beam were experimentally studied at test bench.

Influence of vacuum chamber impurities on the lifetime of organic light-emitting diodes

PubMed Central

Fujimoto, Hiroshi; Suekane, Takashi; Imanishi, Katsuya; Yukiwaki, Satoshi; Wei, Hong; Nagayoshi, Kaori; Yahiro, Masayuki; Adachi, Chihaya

2016-01-01

We evaluated the influence of impurities in the vacuum chamber used for the fabrication of organic light-emitting diodes on the lifetime of the fabricated devices and found a correlation between lifetime and the device fabrication time. The contact angle of the ITO substrates stored the chamber under vacuum were used to evaluate chamber cleanliness. Liquid chromatography-mass spectrometry was performed on Si wafers stored in the vacuum chamber before device fabrication to examine the impurities in the chamber. Surprisingly, despite the chamber and evaporation sources being at room temperature, a variety of materials were detected, including previously deposited materials and plasticizers from the vacuum chamber components. We show that the impurities, and not differences in water content, in the chamber were the source of lifetime variations even when the duration of exposure to impurities only varied before and after deposition of the emitter layer. These results suggest that the impurities floating in the vacuum chamber significantly impact lifetime values and reproducibility. PMID:27958304

Influence of vacuum chamber impurities on the lifetime of organic light-emitting diodes

NASA Astrophysics Data System (ADS)

Fujimoto, Hiroshi; Suekane, Takashi; Imanishi, Katsuya; Yukiwaki, Satoshi; Wei, Hong; Nagayoshi, Kaori; Yahiro, Masayuki; Adachi, Chihaya

2016-12-01

We evaluated the influence of impurities in the vacuum chamber used for the fabrication of organic light-emitting diodes on the lifetime of the fabricated devices and found a correlation between lifetime and the device fabrication time. The contact angle of the ITO substrates stored the chamber under vacuum were used to evaluate chamber cleanliness. Liquid chromatography-mass spectrometry was performed on Si wafers stored in the vacuum chamber before device fabrication to examine the impurities in the chamber. Surprisingly, despite the chamber and evaporation sources being at room temperature, a variety of materials were detected, including previously deposited materials and plasticizers from the vacuum chamber components. We show that the impurities, and not differences in water content, in the chamber were the source of lifetime variations even when the duration of exposure to impurities only varied before and after deposition of the emitter layer. These results suggest that the impurities floating in the vacuum chamber significantly impact lifetime values and reproducibility.

A Multicusp Ion Source for Radioactive Ion Beams

NASA Astrophysics Data System (ADS)

Wutte, D.; Freedman, S.; Gough, R.; Lee, Y.; Leitner, M.; Leung, K. N.; Lyneis, C.; Picard, D. S.; Sun, L.; Williams, M. D.; Xie, Z. Q.

1997-05-01

In order to produce a radioactive ion beam of (14)O+, a 10-cm-diameter, 13.56 MHz radio frequency (rf) driven multicusp ion source is now being developed at Lawrence Berkeley National Laboratory. In this paper we describe the specific ion source design and the basic ion source characteristics using Ar, Xe and a 90types of measurements have been performed: extractable ion current, ion species distributions, gas efficiency, axial energy spread and ion beam emittance measurements. The source can generate ion current densities of approximately 60 mA/cm2 . In addition the design of the ion beam extraction/transport system for the actual experimental setup for the radioactive beam line will be presented.

Temperature-sensitive optrode

DOEpatents

Hirschfeld, T.B.

1985-09-24

Method and apparatus are provided for measuring temperature and for generating optical signals related to temperature. Light from a fiber optic is directed to a material whose fluorescent response varies with ambient temperature. The same fiber optic delivering the excitation beam also collects a portion of the fluorescent emission for analysis. Signal collection efficiency of the fiber optic is enhanced by requiring that the fluorescent probe material be in the shape of an oblong parabolically tapered solid. Reproducibility is enhanced by using Raman backscatter to monitor excitation beam fluctuations, and by using measurements of fluorescence lifetime. 10 figs.

Electronic Desorption of gas from metals

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

Molvik, A W; Kollmus, H; Mahner, E

During heavy ion operation in several particle accelerators world-wide, dynamic pressure rises of orders of magnitude were triggered by lost beam ions that bombarded the vacuum chamber walls. This ion-induced molecular desorption, observed at CERN, GSI, and BNL, can seriously limit the ion beam lifetime and intensity of the accelerator. From dedicated test stand experiments we have discovered that heavy-ion induced gas desorption scales with the electronic energy loss (dE{sub e}/dx) of the ions slowing down in matter; but it varies only little with the ion impact angle, unlike electronic sputtering.

Temperature-sensitive optrode

DOEpatents

Hirschfeld, Tomas B.

1985-01-01

Method and apparatus are provided for measuring temperature and for generating optical signals related to temperature. Light from a fiber optic is directed to a material whose fluorescent response varies with ambient temperature. The same fiber optic delivering the excitation beam also collects a portion of the fluorescent emission for analysis. Signal collection efficiency of the fiber optic is enhanced by requiring that the fluorescent probe material be in the shape of an oblong parabolically tapered solid. Reproducibility is enhanced by using Raman backscatter to monitor excitation beam fluctuations, and by using measurements of fluorescence lifetime.

Producing carbon stripper foils containing boron

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

Stoner, J. O. Jr.

2012-12-19

Parameters being actively tested by the accelerator community for the purpose of extending carbon stripper foil lifetimes in fast ion beams include methods of deposition, parting agents, mounting techniques, support (fork) materials, and inclusion of alloying elements, particularly boron. Specialized production apparatus is required for either sequential deposition or co-deposition of boron in carbon foils. A dual-use vacuum evaporator for arc evaporation of carbon and electron-beam evaporation of boron and other materials has been built for such development. Production of both carbon and boron foils has begun and improvements are in progress.

Towards Polarised Antiprotons: Machine Developments for Spin-Filtering Studies

NASA Astrophysics Data System (ADS)

Lenisa, Paolo

2016-02-01

We address the commissioning of the experimental equipment and the machine studies required for the first spin-filtering experiment with protons at the COSY ring in Jülich (Germany) at a beam kinetic energy of 49.3 MeV. The implementation of a low-beta insertion made it possible to achieve beam lifetimes of 8000 s in the presence of a dense polarized hydrogen storage cell target. The developed techniques can be directly applied to antiproton machines and allow for the determination of the spin-dependent pbar-p cross sections via spin-filtering.

Use of Segregation Indices, Townsend Index, and Air Toxics Data to Assess Lifetime Cancer Risk Disparities in Metropolitan Charleston, South Carolina, USA

PubMed Central

Rice, LaShanta J.; Jiang, Chengsheng; Wilson, Sacoby M.; Burwell-Naney, Kristen; Samantapudi, Ashok; Zhang, Hongmei

2014-01-01

Background: Studies have demonstrated a relationship between segregation and level of education, occupational opportunities, and risk behaviors, yet a paucity of research has elucidated the association between racial residential segregation, socioeconomic deprivation, and lifetime cancer risk. Objectives: We examined estimated lifetime cancer risk from air toxics by racial composition, segregation, and deprivation in census tracts in Metropolitan Charleston. Methods: Segregation indices were used to measure the distribution of groups of people from different races within neighborhoods. The Townsend Index was used to measure economic deprivation in the study area. Poisson multivariate regressions were applied to assess the association of lifetime cancer risk with segregation indices and Townsend Index along with several sociodemographic measures. Results: Lifetime cancer risk from all pollution sources was 28 persons/million for half of the census tracts in Metropolitan Charleston. Isolation Index and Townsend Index both showed significant correlation with lifetime cancer risk from different sources. This significance still holds after adjusting for other sociodemographic measures in a Poisson regression, and these two indices have stronger effect on lifetime cancer risk compared to the effects of sociodemographic measures. Conclusions: We found that material deprivation, measured by the Townsend Index and segregation measured by the Isolation index, introduced high impact on lifetime cancer risk by air toxics at the census tract level. PMID:24852759

Technology assessment of high pulse energy CO(2) lasers for remote sensing from satellites

NASA Technical Reports Server (NTRS)

Hess, R. V.; Brockman, P.; Schryer, D. R.; Miller, I. M.; Bair, C. H.; Sidney, B. D.; Wood, G. M.; Upchurch, B. T.; Brown, K. G.

1985-01-01

Developments and needs for research to extend the lifetime and optimize the configuration of CO2 laser systems for satellite based on remote sensing of atmospheric wind velocities and trace gases are reviewed. The CO2 laser systems for operational satellite application will require lifetimes which exceed 1 year. Progress in the development of efficient low temperature catalysts and gas mixture modifications for extending the lifetime of high pulse energy closed cycle common and rare isotope CO2 lasers and of sealed CW CO2 lasers is reviewed. Several CO2 laser configurations are under development to meet the requirements including: unstable resonators, master oscillator power amplifiers and telescopic stable resonators, using UV or E-beam preionization. Progress in the systems is reviewed and tradeoffs in the system parameters are discussed.

Lifetimes of excited states in triaxially deformed 107Tc and 109,111,113Rh

NASA Astrophysics Data System (ADS)

Hagen, T. W.; Görgen, A.; Korten, W.; Grente, L.; Salsac, M.-D.; Farget, F.; Braunroth, T.; Bruyneel, B.; Celikovic, I.; Clément, E.; de France, G.; Delaune, O.; Dewald, A.; Dijon, A.; Hackstein, M.; Jacquot, B.; Litzinger, J.; Ljungvall, J.; Louchart, C.; Michelagnoli, C.; Napoli, D. R.; Recchia, F.; Rother, W.; Sahin, E.; Siem, S.; Sulignano, B.; Theisen, Ch.; Valiente-Dobon, J. J.

2018-03-01

Lifetimes of excited states in 107Tc, 109Rh, 111Rh, and 113Rh were measured at GANIL using the Recoil-Distance Doppler Shift method. The neutron-rich nuclei were produced in fission reactions in inverse kinematics with a 238U beam impinging on a 9Be target. Fission fragments were identified event-by-event in the ray-tracing spectrometer VAMOS++ and correlated with prompt γ rays observed around the target position with the EXOGAM Ge detector array. Several lifetimes were obtained for states in the positive-parity yrast bands in the four nuclei and compared to triaxial particle-rotor calculations. The results clarify the configuration for the strongest positive-parity band in 107Tc and suggest a gradual increase of triaxial deformation with atomic number Z, reaching almost maximum triaxiality for the neutron-rich Rh nuclei.

New Horizon in Nuclear Physics and Astrophysics Using Radioactive Nuclear Beams

NASA Astrophysics Data System (ADS)

Tanihata, Isao

Beams of β- radioactive nuclei, having a lifetime as short as 1 ms have been used for studies of the nuclear structure and reaction relevant to nucleosynthesis in the universe. In nuclear-structure studies, decoupling of the proton and neutron distributions in nuclei has been discovered. The decoupling appeared as neutron halos and neutron skins on the surface of neutron-rich unstable nuclei. In astrophysics, reaction cross sections have been determined for many key reactions of nucleosynthesis involving short-lived nuclei in the initial and final states. One such important reaction, 13N+p → 14O +γ, has been studied using beams of unstable 13N nuclei. Such studies became possible after the invention of beams of radioactive nuclei in the mid-80's. Before that, the available ion beams were restricted to ions of stable nuclei for obvious reasons. In the next section the production method of radioactive beams is presented, then a few selected studies using radioactive beams are discussed in the following sections. In the last section, some useful properties of radioactive nuclei for other applications is shown.

Ion related problems for the XLS ring

NASA Astrophysics Data System (ADS)

Bozoki, Eva S.; Halama, Henry

1991-10-01

The electron beam in a storage ring collides with the residual gas in the vacuum chamber. As a consequence, low velocity positive ions are produced and trapped in the potential well of the electron beam. They perform stable or unstable oscillations around the beam under the repetitive Coulomb force of the bunches. If not cleared, the captured ions can lead to partial or total neutralization of the beam, causing both a decrease of lifetime and a change in the vertical tunes as well as an increase in the tune spread. It can also cause coherent and incoherent transverse instabilities. An electrostatic clearing electrodes system was designed to keep the neutralization below a desired limit. The location and the geometry of the clearing electrodes as well as the applied clearing voltage is based on the study of the ion production rate, longitudinal velocity of ions in field-free regions and in the dipoles, beam self-electric field, beam potential, critical mass for ion capture in the bunched beam and the bounce frequencies of the ions, tune shift and pressure rise due to trapped ions.

Free-electron laser power beaming to satellites at China Lake, California

NASA Astrophysics Data System (ADS)

Bennett, Harold E.; Rather, John D.; Montgomery, Edward E.

1994-05-01

Laser power beaming of energy through the atmosphere to a satellite can extend its lifetime by maintaining the satellite batteries in operating condition. An alternate propulsion system utilizing power beaming will also significantly reduce the initial insertion cost of these satellites, which now are as high as $72,000/lb for geosynchronous orbit. Elements of the power beaming system are a high-power laser, a large diameter telescope to reduce diffractive losses, an adaptive optic beam conditioning system and possibly a balloon or aerostat carrying a large mirror to redirect the laser beam to low earth orbit satellites after it has traversed most of the earth's atmosphere vertically. China Lake, California has excellent seeing, averages 260 cloud-free days/year, has the second largest geothermal plant in the United States nearby for power, groundwater from the lake for cooling water, and is at the center of one of the largest restricted airspaces in the United States. It is an ideal site for such a laser power beaming system. Technological challenges in building such a system and installing it at China Lake are discussed.

Free-electron laser power beaming to satellites at China Lake, California

NASA Astrophysics Data System (ADS)

Bennett, Harold E.; Rather, John D.; Montgomery, Edward E.

1994-05-01

Laser power beaming of energy through the atmosphere to a satellite can extend its lifetime by maintaining the satellite batteries in operating condition. An alternate propulsion system utilizing power beaming will also significantly reduce the initial insertion cost of these satellites, which now are as high as $DLR72,000/lb for geosynchronous orbit. Elements of the power beaming system are a high-power laser, a large diameter telescope to reduce diffractive losses, an adaptive optic beam conditioning system and possibly a balloon or aerostat carrying a large mirror to redirect the laser beam to low earth orbit satellites after it has traversed most of the earth's atmosphere vertically. China Lake, California has excellent seeing, averages 260 cloud-free days/year, has the second largest geothermal plant in the United States nearby for power, groundwater from the lake for cooling water, and is at the center of one of the largest restricted airspaces in the United States. It is an ideal site for such a laser power beaming system. Technological challenges in building such a system and installing it at China Lake will be discussed.

Polarized negative ions

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

Haeberli, W.

1981-04-01

This paper presents a survey of methods, commonly in use or under development, to produce beams of polarized negative ions for injection into accelerators. A short summary recalls how the hyperfine interaction is used to obtain nuclear polarization in beams of atoms. Atomic-beam sources for light ions are discussed. If the best presently known techniques are incorporated in all stages of the source, polarized H/sup -/ and D/sup -/ beams in excess of 10 ..mu..A can probably be achieved. Production of polarized ions from fast (keV) beams of polarized atoms is treated separately for atoms in the H(25) excited statemore » (Lamb-Shift source) and atoms in the H(1S) ground state. The negative ion beam from Lamb-Shift sources has reached a plateau just above 1 ..mu..A, but this beam current is adequate for many applications and the somewhat lower beam current is compensated by other desirable characteristics. Sources using fast polarized ground state atoms are in a stage of intense development. The next sections summarize production of polarized heavy ions by the atomic beam method, which is well established, and by optical pumping, which has recently been demonstrated to yield very large nuclear polarization. A short discussion of proposed ion sources for polarized /sup 3/He/sup -/ ions is followed by some concluding remarks.« less

New ion source for KSTAR neutral beam injection system.

PubMed

Kim, Tae-Seong; Jeong, Seung Ho; In, Sang-Ryul

2012-02-01

The neutral beam injection system (NBI-1) of the KSTAR tokamak can accommodate three ion sources; however, it is currently equipped with only one prototype ion source. In the 2010 and 2011 KSTAR campaigns, this ion source supplied deuterium neutral beam power of 0.7-1.6 MW to the KSTAR plasma with a beam energy of 70-100 keV. A new ion source will be prepared for the 2012 KSTAR campaign with a much advanced performance compared with the previous one. The newly designed ion source has a very large transparency (∼56%) without deteriorating the beam optics, which is designed to deliver a 2 MW injection power of deuterium beams at 100 keV. The plasma generator of the ion source is of a horizontally cusped bucket type, and the whole inner wall, except the cathode filaments and plasma grid side, functions as an anode. The accelerator assembly consists of four multi-circular aperture grids made of copper and four electrode flanges made of aluminum alloy. The electrodes are insulated using PEEK. The ion source will be completed and tested in 2011.

Applications of beam-foil spectroscopy to atomic collisions in solids

NASA Technical Reports Server (NTRS)

Sellin, I. A.

1976-01-01

Some selected papers presented at the Fourth International Conference on Beam-Foil Spectroscopy, whose results are of particular pertinence to ionic collision phenomena in solids, are reviewed. The topics discussed include solid target effects and means of surmounting them in the measurement of excited projectile ion lifetimes for low-energy heavy element ions; the electron emission accompanying the passage of heavy particles through solid targets; the collision broadening of X rays emitted from 100 keV ions moving in solids; residual K-shell excitation in chlorine ions penetrating carbon; comparison between 40 MeV Si on gaseous SiH4 targets at 300 mtorr and 40 MeV Si on Al; and the emergent surface interaction in beam-foil spectroscopy. A distinct overlap of interests between the sciences of beam-foil spectroscopy and atomic collisions in solids is pointed out.

Emission dynamics of hybrid plasmonic gold/organic GaN nanorods

NASA Astrophysics Data System (ADS)

Mohammadi, F.; Schmitzer, H.; Kunert, G.; Hommel, D.; Ge, J.; Duscher, G.; Langbein, W.; Wagner, H. P.

2017-12-01

We studied the emission of bare and aluminum quinoline (Alq3)/gold coated wurtzite GaN nanorods by temperature- and intensity-dependent time-integrated and time-resolved photoluminescence (PL). The GaN nanorods of ˜1.5 μm length and ˜250 nm diameter were grown by plasma-assisted molecular beam epitaxy. Gold/Alq3 coated GaN nanorods were synthesized by organic molecular beam deposition. The near band-edge and donor-acceptor pair luminescence was investigated in bare GaN nanorods and compared with multilevel model calculations providing the dynamical parameters for electron-hole pairs, excitons, impurity bound excitons, donors and acceptors. Subsequently, the influence of a 10 nm gold coating without and with an Alq3 spacer layer was studied and the experimental results were analyzed with the multilevel model. Without a spacer layer, a significant PL quenching and lifetime reduction of the near band-edge emission is found. The behavior is attributed to surface band-bending and Förster energy transfer from excitons to surface plasmons in the gold layer. Inserting a 5 nm Alq3 spacer layer reduces the PL quenching and lifetime reduction which is consistent with a reduced band-bending and Förster energy transfer. Increasing the spacer layer to 30 nm results in lifetimes which are similar to uncoated structures, showing a significantly decreased influence of the gold coating on the excitonic dynamics.

Emission dynamics of hybrid plasmonic gold/organic GaN nanorods.

PubMed

Mohammadi, F; Schmitzer, H; Kunert, G; Hommel, D; Ge, J; Duscher, G; Langbein, W; Wagner, H P

2017-12-15

We studied the emission of bare and aluminum quinoline (Alq 3 )/gold coated wurtzite GaN nanorods by temperature- and intensity-dependent time-integrated and time-resolved photoluminescence (PL). The GaN nanorods of ∼1.5 μm length and ∼250 nm diameter were grown by plasma-assisted molecular beam epitaxy. Gold/Alq 3 coated GaN nanorods were synthesized by organic molecular beam deposition. The near band-edge and donor-acceptor pair luminescence was investigated in bare GaN nanorods and compared with multilevel model calculations providing the dynamical parameters for electron-hole pairs, excitons, impurity bound excitons, donors and acceptors. Subsequently, the influence of a 10 nm gold coating without and with an Alq 3 spacer layer was studied and the experimental results were analyzed with the multilevel model. Without a spacer layer, a significant PL quenching and lifetime reduction of the near band-edge emission is found. The behavior is attributed to surface band-bending and Förster energy transfer from excitons to surface plasmons in the gold layer. Inserting a 5 nm Alq 3 spacer layer reduces the PL quenching and lifetime reduction which is consistent with a reduced band-bending and Förster energy transfer. Increasing the spacer layer to 30 nm results in lifetimes which are similar to uncoated structures, showing a significantly decreased influence of the gold coating on the excitonic dynamics.

Positron annihilation in SiO 2-Si studied by a pulsed slow positron beam

NASA Astrophysics Data System (ADS)

Suzuki, R.; Ohdaira, T.; Uedono, A.; Kobayashi, Y.

2002-06-01

Positron and positronium (Ps) behavior in SiO 2-Si have been studied by means of positron annihilation lifetime spectroscopy (PALS) and age-momentum correlation (AMOC) spectroscopy with a pulsed slow positron beam. The PALS study of SiO 2-Si samples, which were prepared by a dry-oxygen thermal process, revealed that the positrons implanted in the Si substrate and diffused back to the interface do not contribute to the ortho-Ps long-lived component, and the lifetime spectrum of the interface has at least two components. From the AMOC study, the momentum distribution of the ortho-Ps pick-off annihilation in SiO 2, which shows broader momentum distribution than that of crystalline Si, was found to be almost the same as that of free positron annihilation in SiO 2. A varied interface model was proposed to interpret the results of the metal-oxide-semiconductor (MOS) experiments. The narrow momentum distribution found in the n-type MOS with a negative gate bias voltage could be attributed to Ps formation and rapid spin exchange in the SiO 2-Si interface. We have developed a two-dimensional positron lifetime technique, which measures annihilation time and pulse height of the scintillation gamma-ray detector for each event. Using this technique, the positronium behavior in a porous SiO 2 film, grown by a sputtering method, has been studied.

Development of a rotating graphite carbon disk stripper

NASA Astrophysics Data System (ADS)

Hasebe, Hiroo; Okuno, Hiroki; Tatami, Atsushi; Tachibana, Masamitsu; Murakami, Mutsuaki; Kuboki, Hironori; Imao, Hiroshi; Fukunishi, Nobuhisa; Kase, Masayuki; Kamigaito, Osamu

2018-05-01

Highly oriented graphite carbon sheets (GCSs) were successfully used as disk strippers. An irradiation test conducted in 2015 showed that GCS strippers have the longest lifetime and exhibit improved stripping and transmission efficiencies. The problem of disk deformation in previously used Be-disk was solved even with higher beam intensity.

High-Reliability Pump Module for Non-Planar Ring Oscillator Laser

NASA Technical Reports Server (NTRS)

Liu, Duncan T.; Qiu, Yueming; Wilson, Daniel W.; Dubovitsky, Serge; Forouhar, Siamak

2007-01-01

We propose and have demonstrated a prototype high-reliability pump module for pumping a Non-Planar Ring Oscillator (NPRO) laser suitable for space missions. The pump module consists of multiple fiber-coupled single-mode laser diodes and a fiber array micro-lens array based fiber combiner. The reported Single-Mode laser diode combiner laser pump module (LPM) provides a higher normalized brightness at the combined beam than multimode laser diode based LPMs. A higher brightness from the pump source is essential for efficient NPRO laser pumping and leads to higher reliability because higher efficiency requires a lower operating power for the laser diodes, which in turn increases the reliability and lifetime of the laser diodes. Single-mode laser diodes with Fiber Bragg Grating (FBG) stabilized wavelength permit the pump module to be operated without a thermal electric cooler (TEC) and this further improves the overall reliability of the pump module. The single-mode laser diode LPM is scalable in terms of the number of pump diodes and is capable of combining hundreds of fiber-coupled laser diodes. In the proof-of-concept demonstration, an e-beam written diffractive micro lens array, a custom fiber array, commercial 808nm single mode laser diodes, and a custom NPRO laser head are used. The reliability of the proposed LPM is discussed.

β-delayed p-decay of proton-rich nuclei ^23Al and ^31Cl and explosive H-burning in novae

NASA Astrophysics Data System (ADS)

Trache, L.; Banu, A.; Hardy, J. C.; McCleskey, M.; Simmons, E.; Tabacaru, G.; Tribble, R. E.; Aysto, J.; Jokinen, A.; Saastamoinen, A.; Davinson, T.; Woods, P. J.; Achouri, L.; Roeder, B.

2008-10-01

We developed a technique to measure β-delayed proton-decay of proton-rich nuclei produced and separated with MARS at TAMU. In particular, we studied the decay of ^23Al and ^31Cl, both important for understanding explosive H-burning in novae. We have pulsed the beam, implanting the source nuclei moving at about 40 MeV/u in a thin Si strip detector, and then measured β-p and β-γ coincidences simultaneously. The states populated above the proton threshold in ^23Mg and ^31S, respectively, may proton decay. They are resonances in the reaction ^22Na(p,γ)^23Mg (crucial for the depletion of ^22Na in ONe novae) and in ^30P(p,γ)^31S (critical point in explosive H-burning in novae), but the protons emitted have very low energies, starting at about 200 keV, an experimental challenge. The setup and the results are described. The β-decay schemes were established for both nuclei, and IAS identified. The technique has shown a remarkable selectivity to β-delayed charged particle emission and shown to work even at radioactive beam rates of a few pps, for rare isotopes with lifetimes as low as 10s msec.

Studies on Beam Formation in an Atomic Beam Source

NASA Astrophysics Data System (ADS)

Nass, A.; Stancari, M.; Steffens, E.

2009-08-01

Atomic beam sources (ABS) are widely used workhorses producing polarized atomic beams for polarized gas targets and polarized ion sources. Although they have been used for decades the understanding of the beam formation processes is crude. Models were used more or less successfully to describe the measured intensity and beam parameters. ABS's are also foreseen for future experiments, such as PAX [1]. An increase of intensity at a high polarization would be beneficial. A direct simulation Monte-Carlo method (DSMC) [2] was used to describe the beam formation of a hydrogen or deuterium beam in an ABS. For the first time a simulation of a supersonic gas expansion on a molecular level for this application was performed. Beam profile and Time-of-Flight measurements confirmed the simulation results. Furthermore a new method of beam formation was tested, the Carrier Jet method [3], based on an expanded beam surrounded by an over-expanded carrier jet.

Planned Experiments on the Princeton Advanced Test Stand

NASA Astrophysics Data System (ADS)

Stepanov, A.; Gilson, E. P.; Grisham, L.; Kaganovich, I.; Davidson, R. C.

2010-11-01

The Princeton Advanced Test Stand (PATS) device is an experimental facility based on the STS-100 high voltage test stand transferred from LBNL. It consists of a multicusp RF ion source, a pulsed extraction system capable of forming high-perveance 100keV ion beams, and a large six-foot-long vacuum with convenient access for beam diagnostics. This results in a flexible system for studying high perveance ion beams relevant to NDCX-I/II, including experiments on beam neutralization by ferroelectric plasma sources (FEPS) being developed at PPPL. Research on PATS will concern the basic physics of beam-plasma interactions, such as the effects of volume neutralization on beam emittance, as well as optimizing technology of the FEPS. PATS combines the advantage of an ion beam source and a large-volume plasma source in a chamber with ample access for diagnostics, resulting in a robust setup for investigating and improving relevant aspects of neutralized drift. There are also plans for running the ion source with strongly electro-negative gases such as chlorine, making it possible to extract positive or negative ion beams.

Experimental Analysis of Pseudospark Sourced Electron Beam

NASA Astrophysics Data System (ADS)

Kumar, Niraj; Pal, U. N.; Verma, D. K.; Prajapati, J.; Kumar, M.; Meena, B. L.; Tyagi, M. S.; Srivastava, V.

2011-12-01

The pseudospark (PS) discharge has been shown to be a promising source of high brightness, high intensity electron beam pulses. The PS discharge sourced electron beam has potential applications in plasma filled microwave sources where normal material cathode cannot be used. Analysis of the electron beam profile has been done experimentally for different applied voltages. The investigation has been carried out at different axial and radial location inside the drift space in argon atmosphere. This paper represents experimentally found axial and radial variation of the beam current inside the drift tube of PS discharge based plasma cathode electron (PCE) gun. With the help of current density estimation the focusing and defocusing point of electron beam in axial direction can be analyzed.

Tunable pulsed narrow bandwidth light source

DOEpatents

Powers, Peter E.; Kulp, Thomas J.

2002-01-01

A tunable pulsed narrow bandwidth light source and a method of operating a light source are provided. The light source includes a pump laser, first and second non-linear optical crystals, a tunable filter, and light pulse directing optics. The method includes the steps of operating the pump laser to generate a pulsed pump beam characterized by a nanosecond pulse duration and arranging the light pulse directing optics so as to (i) split the pulsed pump beam into primary and secondary pump beams; (ii) direct the primary pump beam through an input face of the first non-linear optical crystal such that a primary output beam exits from an output face of the first non-linear optical crystal; (iii) direct the primary output beam through the tunable filter to generate a sculpted seed beam; and direct the sculpted seed beam and the secondary pump beam through an input face of the second non-linear optical crystal such that a secondary output beam characterized by at least one spectral bandwidth on the order of about 0.1 cm.sup.-1 and below exits from an output face of the second non-linear optical crystal.

Vacuum isostatic micro/macro molding of PTFE materials for laser beam shaping in environmental applications: large scale UV laser water purification

NASA Astrophysics Data System (ADS)

Lizotte, Todd; Ohar, Orest

2009-08-01

Accessibility to fresh clean water has determined the location and survival of civilizations throughout the ages [1]. The tangible economic value of water is demonstrated by industry's need for water in fields such as semiconductor, food and pharmaceutical manufacturing. Economic stability for all sectors of industry depends on access to reliable volumes of good quality water. As can be seen on television a nation's economy is seriously affected by water shortages through drought or mismanagement and as such those water resources must therefore be managed both for the public interest and the economic future. For over 50 years ultraviolet water purification has been the mainstay technology for water treatment, killing potential microbiological agents in water for leisure activities such as swimming pools to large scale waste water treatment facilities where the UV light photo-oxidizes various pollutants and contaminants. Well tailored to the task, UV provides a cost effective way to reduce the use of chemicals in sanitization and anti-biological applications. Predominantly based on low pressure Hg UV discharge lamps, the system is plagued with lifetime issues (~1 year normal operation), the last ten years has shown that the technology continues to advance and larger scale systems are turning to more advanced lamp designs and evaluating solidstate UV light sources and more powerful laser sources. One of the issues facing the treatment of water with UV lasers is an appropriate means of delivering laser light efficiently over larger volumes or cross sections of water. This paper examines the potential advantages of laser beam shaping components made from isostatically micro molding microstructured PTFE materials for integration into large scale water purification and sterilization systems, for both lamps and laser sources. Applying a unique patented fabrication method engineers can form micro and macro scale diffractive, holographic and faceted reflective structures into fused and semi-fused PTFE materials and compounds for use in UV Reactors. The materials unique attributes provide an unusual but effective hybrid element, by combining Lambertian diffusion and spectral reflective attributes. This paper will provide examples of the applications where this technology could be applied and typical constructions. An overview of UV sources commonly used in water treatment, including high power UV lasers and solid state UV light sources will be discussed. The paper will summarize how beam shaping elements produced in PTFE materials would provide further benefits to the emerging water disinfection or treatment market.

Review of the High Performance Antiproton Trap (HiPAT) Experiment at the Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

Pearson, J. B.; Sims, Herb; Martin, James; Chakrabarti, Suman; Lewis, Raymond; Fant, Wallace

2003-01-01

The significant energy density of matter-antimatter annihilation is attractive to the designers of future space propulsion systems, with the potential to offer a highly compact source of power. Many propulsion concepts exist that could take advantage of matter-antimatter reactions, and current antiproton production rates are sufficient to support basic proof-of-principle evaluation of technology associated with antimatter- derived propulsion. One enabling technology for such experiments is portable storage of low energy antiprotons, allowing antiprotons to be trapped, stored, and transported for use at an experimental facility. To address this need, the Marshall Space Flight Center's Propulsion Research Center is developing a storage system referred to as the High Performance Antiproton Trap (HiPAT) with a design goal of containing 10(exp 12) particles for up to 18 days. The HiPAT makes use of an electromagnetic system (Penning- Malmberg design) consisting of a 4 Telsa superconductor, high voltage electrode structure, radio frequency (RF) network, and ultra high vacuum system. To evaluate the system normal matter sources (both electron guns and ion sources) are used to generate charged particles. The electron beams ionize gas within the trapping region producing ions in situ, whereas the ion sources produce the particles external to the trapping region and required dynamic capture. A wide range of experiments has been performed examining factors such as ion storage lifetimes, effect of RF energy on storage lifetime, and ability to routinely perform dynamic ion capture. Current efforts have been focused on improving the FW rotating wall system to permit longer storage times and non-destructive diagnostics of stored ions. Typical particle detection is performed by extracting trapped ions from HiPAT and destructively colliding them with a micro-channel plate detector (providing number and energy information). This improved RF system has been used to detect various plasma modes for both electron and ion plasmas in the two traps at MSFC, including axial, cyclotron, and diocotron modes. New diagnostics are also being added to HiPAT to measure the axial density distribution of the trapped cloud to match measured RF plasma modes to plasma conditions.

Large area multiarc ion beam source {open_quote}MAIS{close_quote}

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

Engelko, V.; Giese, H.; Schalk, S.

1996-12-31

A pulsed large area intense ion beam source is described, in which the ion emitting plasma is built up by an array of individual discharge units, homogeneously distributed over the surface of a common discharge electrode. A particularly advantageous feature of the source is that for plasma generation and subsequent acceleration of the ions only one common energy supply is necessary. This allows to simplify the source design and provides inherent synchronization of plasma production and ion extraction. The homogeneity of the plasma density was found to be superior to plasma sources using plasma expanders. Originally conceived for the productionmore » of proton beams, the source can easily be modified for the production of beams composed of carbon and metal ions or mixed ion species. Results of investigations of the source performance for the production of a proton beam are presented. The maximum beam current achieved to date is of the order of 100 A, with a particle kinetic energy of 15 - 30 keV and a pulse length in the range of 10 {mu}s.« less

Beam brilliance investigation of high current ion beams at GSI heavy ion accelerator facility.

PubMed

Adonin, A A; Hollinger, R

2014-02-01

In this work the emittance measurements of high current Ta-beam provided by VARIS (Vacuum Arc Ion Source) ion source are presented. Beam brilliance as a function of beam aperture at various extraction conditions is investigated. Influence of electrostatic ion beam compression in post acceleration gap on the beam quality is discussed. Use of different extraction systems (single aperture, 7 holes, and 13 holes) in order to achieve more peaked beam core is considered. The possible ways to increase the beam brilliance are discussed.

Spectroscopy of Dipolar Fermions in Layered Two-Dimensional and Three-Dimensional Lattices

DTIC Science & Technology

2011-09-06

Moreover, we consider other sources of spectral broadening: interaction-induced quasiparticle lifetimes and the different polarizabilities of the...and study Cooper pair binding [7,8], polaron quasiparticle residue [9], and pseudogap behavior of ultracold fermions across the BEC/BCS crossover [10...imaginary part of this energy is the quasiparticle lifetime, and the only source of quasiparticle decay is the p-wave particle loss. Thus the cloud

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

Cai, Yunhai

Similar to a super B-factory, a circular Higgs factory (CHF) will require strong focusing systems near the interaction points and a low-emittance lattice in the arcs to achieve a factory luminosity. At electron beam energy of 125 GeV, beamstrahlung effects during the collision pose an additional challenge to the collider design. In particular, a large momentum acceptance at the 2% level is necessary to retain an adequate beam lifetime. This turns out to be the most challenging aspect in the design of a CHF. In this paper, an example will be provided to illustrate the beam dynamics in a CHF,more » emphasizing the chromatic optics. Basic optical modules and advanced analysis will be presented. Most importantly, we will show that 2% momentum aperture is achievable.« less

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

Cai, Yunhai

Similar to a super B-factory, a circular Higgs factory will require strong focusing systems near the interaction points and a low-emittance lattice in arcs to achieve a factory luminosity. At electron beam energy of 120 GeV, beamstrahlung effects during the collision pose an additional challenge to the collider design. In particular, a large momentum acceptance at 2 percent level is necessary to retain an adequate beam lifetime. This turns out to be the most challenging aspect in the design of circular Higgs factory. In this paper, an example will be provided to illustrate the beam dynamics in circular Higgs factory,more » emphasizing on the chromatic optics. Basic optical modules and advanced analysis will be presented. Most important, we will show that 2% momentum aperture is achievable« less

Ion shaking in the 200 MeV XLS-ring

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

Bozoki, E.; Kramer, S.L.

1992-12-31

It has been shown that ions, trapped inside the beam`s potential, can be removed by the clearing electrodes when the amplitude of the ion oscillation is increased by vertically shaking the ions. We will report on a similar experiment in the 200 Mev XLS ring. The design of the ion clearing system for the ring and the first results obtained, were already reported. In the present series of experiments, RF voltage was applied on a pair of vertical strip-lines. The frequency was scanned in the range of the ion (from H{sub 2} to CO{sub 2}) bounce frequencies in the ringmore » (1--10 MHz). The response of the beam size, vertical betatron tune and lifetime was studied.« less

Desired lifetime and end-of-life desires across adulthood from 20 to 90: a dual-source information model.

PubMed

Lang, Frieder R; Baltes, Paul B; Wagner, Gert G

2007-09-01

How long do people want to live, and how does scientific research on aging affect such desires? A dual-source information model proposes that aging expectations and desires are informed differently by two sources: personal experiences on the one hand, and scientific and societal influences on the other. Two studies with independent German national samples explored desires regarding length of life and end of life among adults between the ages of 20 and 90. FINDINGS ARE: First, desired lifetime is consistent at around 85 years with few age differences. Second, experimental induction of good or bad news from research on aging has little effect in Study 1. Third, interest in science has moderating effects on desired lifetime in Study 2. Fourth, there is a high prevalence of a strong desire to control the "when and how" of one's death, although only 11% of the individuals completed a living will. Findings are consistent with the dual-source information model.

Studies of the beam extraction system of the GTS-LHC electron cyclotron resonance ion source at CERN

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

Toivanen, V., E-mail: ville.aleksi.toivanen@cern.ch; Küchler, D.

2016-02-15

The 14.5 GHz GTS-LHC Electron Cyclotron Resonance Ion Source (ECRIS) provides multiply charged heavy ion beams for the CERN experimental program. The GTS-LHC beam formation has been studied extensively with lead, argon, and xenon beams with varied beam extraction conditions using the ion optical code IBSimu. The simulation model predicts self-consistently the formation of triangular and hollow beam structures which are often associated with ECRIS ion beams, as well as beam loss patterns which match the observed beam induced markings in the extraction region. These studies provide a better understanding of the properties of the extracted beams and a waymore » to diagnose the extraction system performance and limitations, which is otherwise challenging due to the lack of direct diagnostics in this region and the limited availability of the ion source for development work.« less

Studies of the beam extraction system of the GTS-LHC electron cyclotron resonance ion source at CERN.

PubMed

Toivanen, V; Küchler, D

2016-02-01

The 14.5 GHz GTS-LHC Electron Cyclotron Resonance Ion Source (ECRIS) provides multiply charged heavy ion beams for the CERN experimental program. The GTS-LHC beam formation has been studied extensively with lead, argon, and xenon beams with varied beam extraction conditions using the ion optical code IBSimu. The simulation model predicts self-consistently the formation of triangular and hollow beam structures which are often associated with ECRIS ion beams, as well as beam loss patterns which match the observed beam induced markings in the extraction region. These studies provide a better understanding of the properties of the extracted beams and a way to diagnose the extraction system performance and limitations, which is otherwise challenging due to the lack of direct diagnostics in this region and the limited availability of the ion source for development work.

Status of the 1 MeV Accelerator Design for ITER NBI

NASA Astrophysics Data System (ADS)

Kuriyama, M.; Boilson, D.; Hemsworth, R.; Svensson, L.; Graceffa, J.; Schunke, B.; Decamps, H.; Tanaka, M.; Bonicelli, T.; Masiello, A.; Bigi, M.; Chitarin, G.; Luchetta, A.; Marcuzzi, D.; Pasqualotto, R.; Pomaro, N.; Serianni, G.; Sonato, P.; Toigo, V.; Zaccaria, P.; Kraus, W.; Franzen, P.; Heinemann, B.; Inoue, T.; Watanabe, K.; Kashiwagi, M.; Taniguchi, M.; Tobari, H.; De Esch, H.

2011-09-01

The beam source of neutral beam heating/current drive system for ITER is needed to accelerate the negative ion beam of 40A with D- at 1 MeV for 3600 sec. In order to realize the beam source, design and R&D works are being developed in many institutions under the coordination of ITER organization. The development of the key issues of the ion source including source plasma uniformity, suppression of co-extracted electron in D beam operation and also after the long beam duration time of over a few 100 sec, is progressed mainly in IPP with the facilities of BATMAN, MANITU and RADI. In the near future, ELISE, that will be tested the half size of the ITER ion source, will start the operation in 2011, and then SPIDER, which demonstrates negative ion production and extraction with the same size and same structure as the ITER ion source, will start the operation in 2014 as part of the NBTF. The development of the accelerator is progressed mainly in JAEA with the MeV test facility, and also the computer simulation of beam optics also developed in JAEA, CEA and RFX. The full ITER heating and current drive beam performance will be demonstrated in MITICA, which will start operation in 2016 as part of the NBTF.

Correlated Optical Spectroscopy and Transmission Electron Microscopy of Individual Hollow Nanoparticles and their Dimers

PubMed Central

Yang, Linglu; Yan, Bo; Reinhard, Björn M.

2009-01-01

The optical spectra of individual Ag-Au alloy hollow particles were correlated with the particles’ structures obtained by transmission electron microscopy (TEM). The TEM provided direct experimental access to the dimension of the cavity, thickness of the metal shell, and the interparticle distance of hollow particle dimers with high spatial resolution. The analysis of correlated spectral and structural information enabled the quantification of the influence of the core-shell structure on the resonance energy, plasmon lifetime, and plasmon coupling efficiency. Electron beam exposure during TEM inspection was observed to affect plasmon wavelength and lifetime, making optical inspection prior to structural characterization mandatory. PMID:19768108

High-intensity polarized H- ion source for the RHIC SPIN physics

NASA Astrophysics Data System (ADS)

Zelenski, A.; Atoian, G.; Raparia, D.; Ritter, J.; Kolmogorov, A.; Davydenko, V.

2017-08-01

A novel polarization technique had been successfully implemented for the RHIC polarized H- ion source upgrade to higher intensity and polarization. In this technique a proton beam inside the high magnetic field solenoid is produced by ionization of the atomic hydrogen beam (from external source) in the He-gas ionizer cell. Further proton polarization is produced in the process of polarized electron capture from the optically-pumped Rb vapour. The use of high-brightness primary beam and large cross-sections of charge-exchange cross-sections resulted in production of high intensity H- ion beam of 85% polarization. High beam brightness and polarization resulted in 75% polarization at 23 GeV out of AGS and 60-65% beam polarization at 100-250 GeV colliding beams in RHIC. The status of un-polarized magnetron type (Cs-vapour loaded) BNL source is also discussed.

Design and characterization of electron beam focusing for X-ray generation in novel medical imaging architecturea

PubMed Central

Bogdan Neculaes, V.; Zou, Yun; Zavodszky, Peter; Inzinna, Louis; Zhang, Xi; Conway, Kenneth; Caiafa, Antonio; Frutschy, Kristopher; Waters, William; De Man, Bruno

2014-01-01

A novel electron beam focusing scheme for medical X-ray sources is described in this paper. Most vacuum based medical X-ray sources today employ a tungsten filament operated in temperature limited regime, with electrostatic focusing tabs for limited range beam optics. This paper presents the electron beam optics designed for the first distributed X-ray source in the world for Computed Tomography (CT) applications. This distributed source includes 32 electron beamlets in a common vacuum chamber, with 32 circular dispenser cathodes operated in space charge limited regime, where the initial circular beam is transformed into an elliptical beam before being collected at the anode. The electron beam optics designed and validated here are at the heart of the first Inverse Geometry CT system, with potential benefits in terms of improved image quality and dramatic X-ray dose reduction for the patient. PMID:24826066

Efficient nanosecond photoluminescence from infrared PbS quantum dots coupled to plasmonic nanoantennas

DOE PAGES

Akselrod, Gleb M.; Weidman, Mark C.; Li, Ying; ...

2016-09-13

Infrared (IR) light sources with high modulation rates are critical components for on-chip optical communications. Lead-based colloidal quantum dots are promising nonepitaxial materials for use in IR light-emitting diodes, but their slow photoluminescence lifetime is a serious limitation. Here we demonstrate coupling of PbS quantum dots to colloidal plasmonic nanoantennas based on film-coupled metal nanocubes, resulting in a dramatic 1300-fold reduction in the emission lifetime from the microsecond to the nanosecond regime. This lifetime reduction is primarily due to a 1100-fold increase in the radiative decay rate owing to the high quantum yield (65%) of the antenna. The short emissionmore » lifetime is accompanied by high antenna quantum efficiency and directionality. Lastly, this nonepitaxial platform points toward GHz frequency, electrically modulated, telecommunication wavelength light-emitting diodes and single-photon sources.« less

Development of an optically-pumped cesium standard at the Aerospace Corporation

NASA Technical Reports Server (NTRS)

Chan, Yat C.

1992-01-01

We have initiated a research program to study the performance of compact optically-pumped cesium (Cs) frequency standards, which have potential for future timekeeping applications in space. A Cs beam clock apparatus has been assembled. Basic functions of the frequency standard have been demonstrated. Clock signals are observed with optical pumping schemes using one or two lasers. With two laser pumping, we are able to selectively place up to 80 percent of the atomic population into one of the clock transition states. The observed pattern of clock signal indicates that the velocity distribution of the Cs atoms contributing to the microwave signal is beam-Maxwellian. Thus, in the optically-pumped Cs frequency standards, the entire Cs population in the atomic beam could be utilized to generate the clock signals. This is in contrast to the conventional Cs beam standards where only approx. 1 percent of the atoms in the beam are used. More efficient Cs consumption can lead to improved reliability and increased useful lifetime of the clock.

Inductively generated streaming plasma ion source

DOEpatents

Glidden, Steven C.; Sanders, Howard D.; Greenly, John B.

2006-07-25

A novel pulsed, neutralized ion beam source is provided. The source uses pulsed inductive breakdown of neutral gas, and magnetic acceleration and control of the resulting plasma, to form a beam. The beam supplies ions for applications requiring excellent control of ion species, low remittance, high current density, and spatial uniformity.

Beam experiments with the Grenoble test electron cyclotron resonance ion source at iThemba LABS.

PubMed

Thomae, R; Conradie, J; Fourie, D; Mira, J; Nemulodi, F; Kuechler, D; Toivanen, V

2016-02-01

At iThemba Laboratory for Accelerator Based Sciences (iThemba LABS) an electron cyclotron ion source was installed and commissioned. This source is a copy of the Grenoble Test Source (GTS) for the production of highly charged ions. The source is similar to the GTS-LHC at CERN and named GTS2. A collaboration between the Accelerators and Beam Physics Group of CERN and the Accelerator and Engineering Department of iThemba LABS was proposed in which the development of high intensity argon and xenon beams is envisaged. In this paper, we present beam experiments with the GTS2 at iThemba LABS, in which the results of continuous wave and afterglow operation of xenon ion beams with oxygen as supporting gases are presented.

CANCELLED Microwave Ion Source and Beam Injection for anAccelerator-Driven Neut ron Source

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

Vainionpaa, J.H.; Gough, R.; Hoff, M.

2007-02-27

An over-dense microwave driven ion source capable of producing deuterium (or hydrogen) beams at 100-200 mA/cm{sup 2} and with atomic fraction > 90% was designed and tested with an electrostatic low energy beam transport section (LEBT). This ion source was incorporated into the design of an Accelerator Driven Neutron Source (ADNS). The other key components in the ADNS include a 6 MeV RFQ accelerator, a beam bending and scanning system, and a deuterium gas target. In this design a 40 mA D{sup +} beam is produced from a 6 mm diameter aperture using a 60 kV extraction voltage. The LEBTmore » section consists of 5 electrodes arranged to form 2 Einzel lenses that focus the beam into the RFQ entrance. To create the ECR condition, 2 induction coils are used to create {approx} 875 Gauss on axis inside the source chamber. To prevent HV breakdown in the LEBT a magnetic field clamp is necessary to minimize the field in this region. Matching of the microwave power from the waveguide to the plasma is done by an autotuner. They observed significant improvement of the beam quality after installing a boron nitride liner inside the ion source. The measured emittance data are compared with PBGUNS simulations.« less

Plasma formed ion beam projection lithography system

DOEpatents

Leung, Ka-Ngo; Lee, Yung-Hee Yvette; Ngo, Vinh; Zahir, Nastaran

2002-01-01

A plasma-formed ion-beam projection lithography (IPL) system eliminates the acceleration stage between the ion source and stencil mask of a conventional IPL system. Instead a much thicker mask is used as a beam forming or extraction electrode, positioned next to the plasma in the ion source. Thus the entire beam forming electrode or mask is illuminated uniformly with the source plasma. The extracted beam passes through an acceleration and reduction stage onto the resist coated wafer. Low energy ions, about 30 eV, pass through the mask, minimizing heating, scattering, and sputtering.

Lifetimes of excited states in 196, 198Pt; Application of interacting boson approximation model to even Pt isotopes systematics

NASA Astrophysics Data System (ADS)

Bolotin, H. H.; Stuchbery, A. E.; Morrison, I.; Kennedy, D. L.; Ryan, C. G.; Sie, S. H.

1981-11-01

The lifetimes and lifetime limits of the low-lying excited states up to and including the 6 1+ levels in 196, 198Pt were determined by the recoil-distance method (RDM). Gamma-ray angular distributions in 198Pt were also measured. These states were populated by multiple Coulomb excitation using 220 MeV 58Ni ion beams and the measurements were carried out in coincidence with back-scattered projectiles. The measured mean lives of the states and B(E2) values inferred for the transitions between levels are presented. These specific findings, and the observed structure systematics obtained from the combination of the present results and those of prior workers for the even 194-198Pt isotopes, are critically compared with our structure calculations employing the interacting boson approximation (IBA) model incorporating a symmetry-breaking quadrupole force; evaluative comparisons are also made with boson expansion theory (BET) calculations.

Propagation properties of cylindrical sinc Gaussian beam

NASA Astrophysics Data System (ADS)

Eyyuboğlu, Halil T.; Bayraktar, Mert

2016-09-01

We investigate the propagation properties of cylindrical sinc Gaussian beam in turbulent atmosphere. Since an analytic solution is hardly derivable, the study is carried out with the aid of random phase screens. Evolutions of the beam intensity profile, beam size and kurtosis parameter are analysed. It is found that on the source plane, cylindrical sinc Gaussian beam has a dark hollow appearance, where the side lobes also start to emerge with increase in width parameter and Gaussian source size. During propagation, beams with small width and Gaussian source size exhibit off-axis behaviour, losing the dark hollow shape, accumulating the intensity asymmetrically on one side, whereas those with large width and Gaussian source size retain dark hollow appearance even at long propagation distances. It is seen that the beams with large widths expand more in beam size than the ones with small widths. The structure constant values chosen do not seem to alter this situation. The kurtosis parameters of the beams having small widths are seen to be larger than the ones with the small widths. Again the choice of the structure constant does not change this trend.

Production of high current proton beams using complex H-rich molecules at GSI

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

Adonin, A., E-mail: a.adonin@gsi.de; Barth, W.; Heymach, F.

2016-02-15

In this contribution, the concept of production of intense proton beams using molecular heavy ion beams from an ion source is described, as well as the indisputable advantages of this technique for operation of the GSI linear accelerator. The results of experimental investigations, including mass-spectra analysis and beam emittance measurements, with different ion beams (CH{sub 3}{sup +},C{sub 2}H{sub 4}{sup +},C{sub 3}H{sub 7}{sup +}) using various gaseous and liquid substances (methane, ethane, propane, isobutane, and iodoethane) at the ion source are summarized. Further steps to improve the ion source and injector performance with molecular beams are depicted.

Exotic X-ray Sources from Intermediate Energy Electron Beams

NASA Astrophysics Data System (ADS)

Chouffani, K.; Wells, D.; Harmon, F.; Jones, J. L.; Lancaster, G.

2003-08-01

High intensity x-ray beams are used in a wide variety of applications in solid-state physics, medicine, biology and material sciences. Synchrotron radiation (SR) is currently the primary, high-quality x-ray source that satisfies both brilliance and tunability. The high cost, large size and low x-ray energies of SR facilities, however, are serious limitations. Alternatively, "novel" x-ray sources are now possible due to new small linear accelerator (LINAC) technology, such as improved beam emittance, low background, sub-Picosecond beam pulses, high beam stability and higher repetition rate. These sources all stem from processes that produce Radiation from relativistic Electron beams in (crystalline) Periodic Structures (REPS), or the periodic "structure" of laser light. REPS x-ray sources are serious candidates for bright, compact, portable, monochromatic, and tunable x-ray sources with varying degrees of polarization and coherence. Despite the discovery and early research into these sources over the past 25 years, these sources are still in their infancy. Experimental and theoretical research are still urgently needed to answer fundamental questions about the practical and ultimate limits of their brightness, mono-chromaticity etc. We present experimental results and theoretical comparisons for three exotic REPS sources. These are Laser-Compton Scattering (LCS), Channeling Radiation (CR) and Parametric X-Radiation (PXR).

Polarization Studies for the eRHIC Electron Storage Ring

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

Gianfelice-Wendt, Eliana; Tepikian, S.

A hadron/lepton collider with polarized beams has been under consideration by the scientific community since some years, in the U.S. and Europe. Among the various proposals, those by JLAB and BNL with polarized electron and proton beams are currently under closer study in the U.S. Experimenters call for the simultaneous storage of electron bunches with both spin helicity. In the BNL based Ring-Ring design, electrons are stored at top energy in a ring to be accommodated in the existing RHIC tunnel. The transversely polarized electron beam is injected into the storage ring at variable energies, between 5 and 18 GeV.more » Polarization is brought into the longitudinal direction at the IP by a couple of spin rotators. In this paper results of first studies of the attainable beam polarization level and lifetime in the storage ring at 18 GeV are presented.« less

SIN accelerator, operational experience and improvement programs

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

Joho, W.; Olivo, M.; Stammbach, T.

1977-06-01

The SIN meson facility, in operation since 1974, consists of a 590 MeV ring cyclotron for protons and a 72 MeV injector cyclotron. The average beam current on target is presently about 50 ..mu..A, the peak being 112 ..mu..A. Extraction efficiency, once considered a severe handicap for cyclotrons, is now 99.6 to 99.9% for the ring cyclotron and about 90% for the injector. Many improvements in both accelerators allow single turn extraction in the ring cyclotron. The present current limit is given by the injector, while the ring itself could accept now a 600 ..mu..A beam, with 2 to 4more » mA as an ultimate limit. Some muon experiments require a pulsed beam with on-off times in the order of the lifetime of the muon. First trials with beam pulse frequencies of 200 and 400 kHz and a 50% duty cycle have been successful.« less

The experimental program for high pressure gas filled radio frequency cavities for muon cooling channels

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

Freemire, B.; Chung, M.; Hanlet, P. M.

An intense beam of muons is needed to provide a luminosity on the order of 10 34 cm -2s -1 for a multi-TeV collider. Because muons produced by colliding a multi-MW proton beam with a target made of carbon or mercury have a large phase space, significant six dimensional cooling is required. Through ionization cooling—the only cooling method that works within the lifetime of the muon—and emittance exchange, the desired emittances for a Higgs Factory or higher energy collider are attainable. A cooling channel utilizing gas filled radio frequency cavities has been designed to deliver the requisite cool muon beam.more » Technology development of these RF cavities has progressed from breakdown studies, through beam tests, to dielectric loaded and reentrant cavity designs. The results of these experiments are summarized.« less

The experimental program for high pressure gas filled radio frequency cavities for muon cooling channels

DOE PAGES

Freemire, B.; Chung, M.; Hanlet, P. M.; ...

2018-01-30

An intense beam of muons is needed to provide a luminosity on the order of 10 34 cm -2s -1 for a multi-TeV collider. Because muons produced by colliding a multi-MW proton beam with a target made of carbon or mercury have a large phase space, significant six dimensional cooling is required. Through ionization cooling—the only cooling method that works within the lifetime of the muon—and emittance exchange, the desired emittances for a Higgs Factory or higher energy collider are attainable. A cooling channel utilizing gas filled radio frequency cavities has been designed to deliver the requisite cool muon beam.more » Technology development of these RF cavities has progressed from breakdown studies, through beam tests, to dielectric loaded and reentrant cavity designs. The results of these experiments are summarized.« less

Pulsed ion beam source

DOEpatents

Greenly, John B.

1997-01-01

An improved pulsed ion beam source having a new biasing circuit for the fast magnetic field. This circuit provides for an initial negative bias for the field created by the fast coils in the ion beam source which pre-ionize the gas in the source, ionize the gas and deliver the gas to the proper position in the accelerating gap between the anode and cathode assemblies in the ion beam source. The initial negative bias improves the interaction between the location of the nulls in the composite magnetic field in the ion beam source and the position of the gas for pre-ionization and ionization into the plasma as well as final positioning of the plasma in the accelerating gap. Improvements to the construction of the flux excluders in the anode assembly are also accomplished by fabricating them as layered structures with a high melting point, low conductivity material on the outsides with a high conductivity material in the center.

Development of a hybrid molecular beam epitaxy deposition system for in situ surface x-ray studies

NASA Astrophysics Data System (ADS)

Andersen, Tassie K.; Cook, Seyoung; Benda, Erika; Hong, Hawoong; Marks, Laurence D.; Fong, Dillon D.

2018-03-01

A portable metalorganic gas delivery system designed and constructed to interface with an existing molecular beam epitaxy chamber at beamline 33-ID-E of the Advanced Photon Source is described. This system offers the ability to perform in situ X-ray measurements of complex oxide growth via hybrid molecular beam epitaxy. The performance of the hybrid molecular beam epitaxy system while delivering metalorganic source materials is described. The high-energy X-ray scattering capabilities of the hybrid molecular beam epitaxy system are demonstrated both on oxide films grown solely from the metalorganic source and ABO3 oxide perovskites containing elements from both the metalorganic source and a traditional effusion cell.

Negative ion source development at the cooler synchrotron COSY/Jülich

NASA Astrophysics Data System (ADS)

Felden, O.; Gebel, R.; Maier, R.; Prasuhn, D.

2013-02-01

The Nuclear Physics Institute at the Forschungszentrum Jülich, a member of the Helmholtz Association, conducts experimental and theoretical basic research in the field of hadron, particle, and nuclear physics. It operates the cooler synchrotron COSY, an accelerator and storage ring, which provides unpolarized and polarized proton and deuteron beams with beam momenta of up to 3.7 GeV/c. Main activities of the accelerator division are the design and construction of the high energy storage ring HESR, a synchrotron and part of the international FAIR project, and the operation and development of COSY with injector cyclotron and ion sources. Filament driven volume sources and a charge exchange colliding beams source, based on a nuclear polarized atomic beam source, provide unpolarized and polarized H- or D- routinely for more than 6500 hours/year. Within the Helmholtz Association's initiative Accelerator Research and Development, ARD, the existing sources at COSY, as well as new sources for future programs, are investigated and developed. The paper reports about these plans, improved pulsed beams from the volume sources and the preparation of a source for the ELENA project at CERN.

ION SOURCE WITH SPACE CHARGE NEUTRALIZATION

DOEpatents

Flowers, J.W.; Luce, J.S.; Stirling, W.L.

1963-01-22

This patent relates to a space charge neutralized ion source in which a refluxing gas-fed arc discharge is provided between a cathode and a gas-fed anode to provide ions. An electron gun directs a controlled, monoenergetic electron beam through the discharge. A space charge neutralization is effected in the ion source and accelerating gap by oscillating low energy electrons, and a space charge neutralization of the source exit beam is effected by the monoenergetic electron beam beyond the source exit end. The neutralized beam may be accelerated to any desired energy at densities well above the limitation imposed by Langmuir-Child' s law. (AEC)

Novel cryogenic sources for liquid droplet and solid filament beams

NASA Astrophysics Data System (ADS)

Grams, Michael P.

Two novel atomic and molecular beam sources have been created and tested consisting first of a superfluid helium liquid jet, and secondly a solid filament of argon. The superfluid helium apparatus is the second of its kind in the world and uses a modified liquid helium cryostat to inject a cylindrical stream of superfluid helium into vacuum through glass capillary nozzles with diameters on the order of one micron created on-site at Arizona State University. The superfluid beam is an entirely new way to study superfluid behavior, and has many new applications such as superfluid beam-surface scattering, beam-beam scattering, and boundary-free study of superfluidity. The solid beam of argon is another novel beam source created by flowing argon gas through a capillary 50 microns in diameter which is clamped by a small copper plate to a copper block kept at liquid nitrogen temperature. The gas subsequently cools and solidifies plugging the capillary. Upon heating, the solid plug melts and liquid argon exits the capillary and immediately freezes by evaporative cooling. The solid filaments may find application as wall-less cryogenic matrices, or targets for laser plasma sources of extreme UV and soft x-ray sources.

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.

Isomer beam elastic scattering: 26mAl(p, p) for astrophysics

NASA Astrophysics Data System (ADS)

Kahl, D.; Shimizu, H.; Yamaguchi, H.; Abe, K.; Beliuskina, O.; Cha, S. M.; Chae, K. Y.; Chen, A. A.; Ge, Z.; Hayakawa, S.; Imai, N.; Iwasa, N.; Kim, A.; Kim, D. H.; Kim, M. J.; Kubono, S.; Kwag, M. S.; Liang, J.; Moon, J. Y.; Nishimura, S.; Oka, S.; Park, S. Y.; Psaltis, A.; Teranishi, T.; Ueno, Y.; Yang, L.

2018-01-01

The advent of radioactive ground-state beams some three decades ago ultimately sparked a revolution in our understanding of nuclear physics. However, studies with radioactive isomer beams are sparse and have often required sophisticated apparatuses coupled with the technologies of ground-state beams due to typical mass differences on the order of hundreds of keV and vastly different lifetimes for isomers. We present an application of a isomeric beam of 26mAl to one of the most famous observables in nuclear astrophysics: galactic 26Al. The characteristic decay of 26Al in the Galaxy was the first such specific radioactivity to be observed originating from outside the Earth some four decades ago. We present a newly-developed, novel technique to probe the structure of low-spin states in 27Si. Using the Center for Nuclear Study low-energy radioisotope beam separator (CRIB), we report on the measurement of 26mAl proton resonant elastic scattering conducted with a thick target in inverse kinematics. The preliminary results of this on-going study are presented.

Global Source-Receptor Relationships for Mercury Deposition Under Present-Day and 2050 Emissions Scenarios

PubMed Central

Corbitt, Elizabeth S.; Jacob, Daniel J.; Holmes, Christopher D.; Streets, David G.; Sunderland, Elsie M.

2011-01-01

Global policies regulating anthropogenic mercury require an understanding of the relationship between emitted and deposited mercury on intercontinental scales. Here we examine source-receptor relationships for present-day conditions and for four 2050 IPCC scenarios encompassing a range of economic development and environmental regulation projections. We use the GEOS-Chem global model to track mercury from its point of emission through rapid cycling in surface ocean and land reservoirs to its accumulation in longer-lived ocean and soil pools. Deposited mercury has a local component (emitted HgII, lifetime of 3.7 days against deposition) and a global component (emitted Hg0, lifetime of 6 months against deposition). Fast recycling of deposited mercury through photoreduction of HgII and re-emission of Hg0 from surface reservoirs (ice, land, surface ocean) increases the effective lifetime of anthropogenic mercury to 9 months against loss to legacy reservoirs (soil pools and the subsurface ocean). This lifetime is still sufficiently short that source-receptor relationships have a strong hemispheric signature. Asian emissions are the largest source of anthropogenic deposition to all ocean basins, though there is also regional source influence from upwind continents. Current anthropogenic emissions account for only about one-third of mercury deposition to the global ocean with the remainder from natural and legacy sources. However, controls on anthropogenic emissions would have the added benefit of reducing the legacy mercury re-emitted to the atmosphere. Better understanding is needed of the timescales for transfer of mercury from active pools to stable geochemical reservoirs. PMID:22050654

Interferometric source of multi-color, multi-beam entangled photons with mirror and mixer

DOEpatents

Dress, William B.; Kisner, Roger A.; Richards, Roger K.

2004-06-01

53 Systems and methods are described for an interferometric source of multi-color, multi-beam entangled photons. An apparatus includes: a multi-refringent device optically coupled to a source of coherent energy, the multi-refringent device providing a beam of multi-color entangled photons; a condenser device optically coupled to the multi-refringent device, the condenser device i) including a mirror and a mixer and ii) converging two spatially resolved portions of the beam of multi-color entangled photons into a converged multi-color entangled photon beam; a tunable phase adjuster optically coupled to the condenser device, the tunable phase adjuster changing a phase of at least a portion of the converged multi-color entangled photon beam to generate a first interferometeric multi-color entangled photon beam; and a beam splitter optically coupled to the condenser device, the beam splitter combining the first interferometeric multi-color entangled photon beam with a second interferometric multi-color entangled photon beam.

The effects of detergents DDM and beta-OG on the singlet excited state lifetime of the chlorophyll a in cytochrome b6f complex from spinach chloroplasts.

PubMed

Chen, XiaoBo; Zhao, XiaoHui; Zhang, JianPing; Li, LiangBi; Kuang, TingYun

2007-08-01

The singlet excited state lifetime of the chlorophyll a (Chl a) in cytochrome b(6)f (Cyt b(6)f) complex was reported to be shorter than that of free Chl a in methanol, but the value was different for Cyt b(6)f complexes from different sources ( approximately 200 and approximately 600 ps are the two measured results). The present study demonstrated that the singlet excited state lifetime is associated with the detergents n-dodecyl-beta-D-maltoside (DDM) and n-octyl-beta-D-glucopyranoside (beta-OG), but has nothing to do with the different sources of Cyt b(6)f complexes. Compared with the Cyt b(6)f dissolved in beta-OG, the Cyt b(6)f in DDM had a lower fluorescence yield, a lower photodegradation rate of Chl a, and a shorter lifetime of Chl a excited state. In short, the singlet excited state lifetime, approximately 200 ps, of the Chl a in Cyt b(6)f complex in DDM is closer to the true in vivo.

Relative magnetic moments in ^106,108Pd from the new g-plunger technique

NASA Astrophysics Data System (ADS)

Ilie, G.; Werner, V.; Terry, J. R.; Radeck, D.; Ahn, T.; Bettermann, L.; Casperson, R. J.; Chevrier, R.; Cooper, N.; Heinz, A.; Holland, E.; McCarthy, D.; Smith, M. K.; Williams, E.; Beausang, C.; Bonniwell, T. C.; Pauerstein, B.

2010-11-01

The aim of the present work was the proof-of-principle for the new g-plunger technique to measure the deorientation and the lifetime of a state after an inverse kinematics reaction. The deorientation effect, observed in nuclei recoiling from thin targets into vacuum, is due to the hyperfine interactions between the nuclear spin and the surrounding electron configurations. The attenuation of γ-ray angular distributions has been measured for the 2^+1 states in ^106Pd and ^108Pd. ^106,108Pd beams with energies of 330 MeV and 336 MeV, respectively, were Coulomb excited into their 2^+1 state on a ^24Mg target. Forward scattered Mg was detected, passing a Cu foil which served as a stopper for the beam. We measured the time-dependence of the attenuation as a function of distance, in parallel to measuring the lifetimes of the 2^+1 states via RDDS method. This the attenuation is used to measure the g factor of the decaying states relative to each other. The results of this work will be presented.

Extended hot carrier lifetimes observed in bulk In{sub 0.265±0.02}Ga{sub 0.735}N under high-density photoexcitation

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

Zhang, Yi; Tayebjee, Murad J. Y.; Smyth, Suntrana

2016-03-28

We have investigated the ultrafast carrier dynamics in a 1 μm bulk In{sub 0.265}Ga{sub 0.735}N thin film grown using energetic neutral atom-beam lithography/epitaxy molecular beam epitaxy. Cathodoluminescence and X-ray diffraction experiments are used to observe the existence of indium-rich domains in the sample. These domains give rise to a second carrier population and bi-exponential carrier cooling is observed with characteristic lifetimes of 1.6 and 14 ps at a carrier density of 1.3 × 10{sup 16 }cm{sup −3}. A combination of band-filling, screening, and hot-phonon effects gives rise to a two-fold enhanced mono-exponential cooling rate of 28 ps at a carrier density of 8.4 × 10{sup 18 }cm{sup −3}. Thismore » is the longest carrier thermalization time observed in bulk InGaN alloys to date.« less

Estimate of the shielding effect on secondary cancer risk due to cone-beam CT in image-guided radiotherapy

NASA Astrophysics Data System (ADS)

Sung, Jiwon; Baek, Tae Seong; Yoon, Myonggeun; Kim, Dong Wook; Kim, Dong Hyun

2014-09-01

This study evaluated the effect of a simple shielding method using a thin lead sheet on the imaging dose caused by cone-beam computed tomography (CBCT) in image-guided radiation therapy (IGRT). Reduction of secondary doses from CBCT was measured using a radio-photoluminescence glass dosimeter (RPLGD) placed inside an anthropomorphic phantom. The entire body, except for the region scanned by using CBCT, was shielded by wrapping it with a 2-mm lead sheet. Changes in secondary cancer risk due to shielding were calculated using BEIR VII models. Doses to out-of-field organs for head-and-neck, chest, and pelvis scans were decreased 15 ~ 100%, 23 ~ 90%, and 23 ~ 98%, respectively, and the average reductions in lifetime secondary cancer risk due to the 2-mm lead shielding were 1.6, 11.5, and 12.7 persons per 100,000, respectively. These findings suggest that a simple, thin-lead-sheet-based shielding method can effectively decrease secondary doses to out-of-field regions for CBCT, which reduces the lifetime cancer risk on average by 9 per 100,000 patients.

Generation of tunable radially polarized array beams by controllable coherence

NASA Astrophysics Data System (ADS)

Wang, Jing; Zhang, Jipeng; Zhu, Shijun; Li, Zhenhua

2017-05-01

In this paper, a new method for converting a single radial polarization beam into an arbitrary radially polarized array (RPA) beam such as a radial or rectangular symmetry array in the focal plane by modulating a periodic correlation structure is introduced. The realizability conditions for such source and the beam condition for radiation generated by such source are derived. It is illustrated that both the amplitude and the polarization are controllable by means of initial correlation structure and coherence parameter. Furthermore, by designing the source correlation structure, a tunable NUST-shaped RPA beam is demonstrated, which can find widespread applications in micro-nano engineering. Such a method for generation of arbitrary vector array beams is useful in beam shaping and optical tweezers.

Deuteron Beam Source Based on Mather Type Plasma Focus

NASA Astrophysics Data System (ADS)

Lim, L. K.; Yap, S. L.; Wong, C. S.; Zakaullah, M.

2013-04-01

A 3 kJ Mather type plasma focus system filled with deuterium gas is operated at pressure lower than 1 mbar. Operating the plasma focus in a low pressure regime gives a consistent ion beam which can make the plasma focus a reliable ion beam source. In our case, this makes a good deuteron beam source, which can be utilized for neutron generation by coupling a suitable target. This paper reports ion beam measurements obtained at the filling pressure of 0.05-0.5 mbar. Deuteron beam energy is measured by time of flight technique using three biased ion collectors. The ion beam energy variation with the filling pressure is investigated. Deuteron beam of up to 170 keV are obtained with the strongest deuteron beam measured at 0.1 mbar, with an average energy of 80 keV. The total number of deuterons per shot is in the order of 1018 cm-2.

Polarized 3He Spin Filters for Slow Neutron Physics

PubMed Central

Gentile, T. R.; Chen, W. C.; Jones, G. L.; Babcock, E.; Walker, T. G.

2005-01-01

Polarized 3He spin filters are needed for a variety of experiments with slow neutrons. Their demonstrated utility for highly accurate determination of neutron polarization are critical to the next generation of betadecay correlation coefficient measurements. In addition, they are broadband devices that can polarize large area and high divergence neutron beams with little gamma-ray background, and allow for an additional spin-flip for systematic tests. These attributes are relevant to all neutron sources, but are particularly well-matched to time of flight analysis at spallation sources. There are several issues in the practical use of 3He spin filters for slow neutron physics. Besides the essential goal of maximizing the 3He polarization, we also seek to decrease the constraints on cell lifetimes and magnetic field homogeneity. In addition, cells with highly uniform gas thickness are required to produce the spatially uniform neutron polarization needed for beta-decay correlation coefficient experiments. We are currently employing spin-exchange (SE) and metastability-exchange (ME) optical pumping to polarize 3He, but will focus on SE. We will discuss the recent demonstration of 75 % 3He polarization, temperature-dependent relaxation mechanism of unknown origin, cell development, spectrally narrowed lasers, and hybrid spin-exchange optical pumping. PMID:27308140

Nanophotonic enhanced quantum emitters

NASA Astrophysics Data System (ADS)

Li, Xin; Zhou, Zhang-Kai; Yu, Ying; Gather, Malte; Di Falco, Andrea

2017-08-01

Quantum dots are excellent solid-state quantum sources, because of their stability, their narrow spectral linewidth, and radiative lifetime in the range of 1ns. Most importantly, they can be integrated into more complex nanophononics devices, to realize high quality quantum emitters of single photons or entangled photon sources. Recent progress in nanotechnology materials and devices has opened a number of opportunities to increase, optimize and ultimately control the emission property of single quantum dot. In this work, we present an approach that combines the properties of quantum dots with the flexibility of light control offered by nanoplasmonics and metamaterials structuring. Specifically, we show the nanophotonic enhancement of two types of quantum dots devices. The quantum dots are inserted into optical-positioned micropillar cavities, or decorated on the facets of core-shell GaAs/AlGaAs nanowires, fabricated with a bottom-up approach. In both cases, the metallic nanofeatures, which are designed to control the emission and the polarization state of the emitted light, are realized via direct electron-beam-induced deposition. This approach permits to create three-dimensional features with nanometric resolution and positional accuracy, and does not require wet lithographic steps and previous knowledge of the exact spatial arrangement of the quantum devices.

Polarized (3) He Spin Filters for Slow Neutron Physics.

PubMed

Gentile, T R; Chen, W C; Jones, G L; Babcock, E; Walker, T G

2005-01-01

Polarized (3)He spin filters are needed for a variety of experiments with slow neutrons. Their demonstrated utility for highly accurate determination of neutron polarization are critical to the next generation of betadecay correlation coefficient measurements. In addition, they are broadband devices that can polarize large area and high divergence neutron beams with little gamma-ray background, and allow for an additional spin-flip for systematic tests. These attributes are relevant to all neutron sources, but are particularly well-matched to time of flight analysis at spallation sources. There are several issues in the practical use of (3)He spin filters for slow neutron physics. Besides the essential goal of maximizing the (3)He polarization, we also seek to decrease the constraints on cell lifetimes and magnetic field homogeneity. In addition, cells with highly uniform gas thickness are required to produce the spatially uniform neutron polarization needed for beta-decay correlation coefficient experiments. We are currently employing spin-exchange (SE) and metastability-exchange (ME) optical pumping to polarize (3)He, but will focus on SE. We will discuss the recent demonstration of 75 % (3)He polarization, temperature-dependent relaxation mechanism of unknown origin, cell development, spectrally narrowed lasers, and hybrid spin-exchange optical pumping.

In-situ structural integrity evaluation for high-power pulsed spallation neutron source - Effects of cavitation damage on structural vibration

NASA Astrophysics Data System (ADS)

Wan, Tao; Naoe, Takashi; Futakawa, Masatoshi

2016-01-01

A double-wall structure mercury target will be installed at the high-power pulsed spallation neutron source in the Japan Proton Accelerator Research Complex (J-PARC). Cavitation damage on the inner wall is an important factor governing the lifetime of the target-vessel. To monitor the structural integrity of the target vessel, displacement velocity at a point on the outer surface of the target vessel is measured using a laser Doppler vibrometer (LDV). The measured signals can be used for evaluating the damage inside the target vessel because of cyclic loading and cavitation bubble collapse caused by pulsed-beam induced pressure waves. The wavelet differential analysis (WDA) was applied to reveal the effects of the damage on vibrational cycling. To reduce the effects of noise superimposed on the vibration signals on the WDA results, analysis of variance (ANOVA) and analysis of covariance (ANCOVA), statistical methods were applied. Results from laboratory experiments, numerical simulation results with random noise added, and target vessel field data were analyzed by the WDA and the statistical methods. The analyses demonstrated that the established in-situ diagnostic technique can be used to effectively evaluate the structural response of the target vessel.

Heavy-ion induced electronic desorption of gas from metals

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

Molvik, A W; Kollmus, H; Mahner, E

During heavy ion operation in several particle accelerators world-wide, dynamic pressure rises of orders of magnitude were triggered by lost beam ions that bombarded the vacuum chamber walls. This ion-induced molecular desorption, observed at CERN, GSI, and BNL, can seriously limit the ion beam lifetime and intensity of the accelerator. From dedicated test stand experiments we have discovered that heavy-ion induced gas desorption scales with the electronic energy loss (dE{sub e}/d/dx) of the ions slowing down in matter; but it varies only little with the ion impact angle, unlike electronic sputtering.

The (n,γ) campaigns at EXILL

NASA Astrophysics Data System (ADS)

Jolie, J.; Régis, J.-M.; Wilmsen, D.; Ahmed, S.; Pfeiffer, M.; Saed-Samii, N.; Warr, N.; Blanc, A.; Jentschel, M.; Köster, U.; Mutti, P.; Soldner, T.; Simpson, G.; De France, G.; Urban, W.; Drouet, F.; Vancraeyenest, A.; Baczyk, P.; Czerwinski, M.; Korgul, A.; Mazzocchi, C.; Rzaca-Urban, T.; Bruce, A.; Roberts, O. J.; Fraile, L. M.; Mach, H.; Paziy, V.; Ignatov, A.; Ilieva, S.; Kröll, Th.; Scheck, M.; Thürauf, M.; Ivanova, D.; Kisyov, S.; Lalkovski, S.; Podolyák, Zs.; Regan, P. H.; Korten, W.; Zielinska, M.; Salsac, M. D.; Habs, D.; Thirolf, P. G.; Ur, C. A.; Bernards, C.; Casten, R. F.; Cooper, N.; Werner, V.; Cakirli, R. B.; Leoni, S.; Benzoni, G.; Bocchi, G.; Bottoni, S.; Crespi, F. C. L.; Fornal, B.; Cieplicka, N.; Szpak, B.; Petrache, C. M.; Leguillon, R.; John, R.; Lorenz, C.; Massarczyk, R.; Schwengner, R.; Curien, D.; Lozeva, R.; Sengele, L.; Marginean, N.; Lica, R.

2015-05-01

At the PF1B cold neutron beam line at the Institut Laue Langevin, the EXILL array consisting of EXOGAM, GASP and ILL-Clover detectors was used to perform (n,γ) measurements at very high coincidence rates. About ten different reactions were measured in autumn 2012 using a highly collimated cold neutron beam. In spring 2013, the EXOGAM array was combined with 16 LaBr3(Ce) scintillators in the EXILL&FATIMA campaign for the measurement of lifetimes using the generalised centroid difference method. We report on the properties of the set-ups and present first results from both campaigns.

Room-temperature healing of a thermosetting polymer using the Diels-Alder reaction.

PubMed

Peterson, Amy M; Jensen, Robert E; Palmese, Giuseppe R

2010-04-01

Self-healing materials are particularly desirable for load-bearing applications because they offer the potential for increased safety and material lifetimes. A furan-functionalized polymer network was designed that can heal via covalent bonding across the crack surface with the use of a healing agent consisting of a bismaleimide in solution. Average healing efficiencies of approximately 70% were observed. The healing ability of fiber-reinforced composite specimens was investigated with flexural, short beam shear, and double cantilever beam specimens. It was found that solvent amount and maleimide concentration play key roles in determining healing efficiency.

Achieving a long-lived high-beta plasma state by energetic beam injection

NASA Astrophysics Data System (ADS)

Guo, H. Y.; Binderbauer, M. W.; Tajima, T.; Milroy, R. D.; Steinhauer, L. C.; Yang, X.; Garate, E. G.; Gota, H.; Korepanov, S.; Necas, A.; Roche, T.; Smirnov, A.; Trask, E.

2015-04-01

Developing a stable plasma state with high-beta (ratio of plasma to magnetic pressures) is of critical importance for an economic magnetic fusion reactor. At the forefront of this endeavour is the field-reversed configuration. Here we demonstrate the kinetic stabilizing effect of fast ions on a disruptive magneto-hydrodynamic instability, known as a tilt mode, which poses a central obstacle to further field-reversed configuration development, by energetic beam injection. This technique, combined with the synergistic effect of active plasma boundary control, enables a fully stable ultra-high-beta (approaching 100%) plasma with a long lifetime.

Simulation of a beam rotation system for a spallation source

NASA Astrophysics Data System (ADS)

Reiss, Tibor; Reggiani, Davide; Seidel, Mike; Talanov, Vadim; Wohlmuther, Michael

2015-04-01

With a nominal beam power of nearly 1 MW on target, the Swiss Spallation Neutron Source (SINQ), ranks among the world's most powerful spallation neutron sources. The proton beam transport to the SINQ target is carried out exclusively by means of linear magnetic elements. In the transport line to SINQ the beam is scattered in two meson production targets and as a consequence, at the SINQ target entrance the beam shape can be described by Gaussian distributions in transverse x and y directions with tails cut short by collimators. This leads to a highly nonuniform power distribution inside the SINQ target, giving rise to thermal and mechanical stresses. In view of a future proton beam intensity upgrade, the possibility of homogenizing the beam distribution by means of a fast beam rotation system is currently under investigation. Important aspects which need to be studied are the impact of a rotating proton beam on the resulting neutron spectra, spatial flux distributions and additional—previously not present—proton losses causing unwanted activation of accelerator components. Hence a new source description method was developed for the radiation transport code MCNPX. This new feature makes direct use of the results from the proton beam optics code TURTLE. Its advantage to existing MCNPX source options is that all phase space information and correlations of each primary beam particle computed with TURTLE are preserved and transferred to MCNPX. Simulations of the different beam distributions together with their consequences in terms of neutron production are presented in this publication. Additionally, a detailed description of the coupling method between TURTLE and MCNPX is provided.

Design of the low energy beam transport line for the China spallation neutron source

NASA Astrophysics Data System (ADS)

Li, Jin-Hai; Ouyang, Hua-Fu; Fu, Shi-Nian; Zhang, Hua-Shun; He, Wei

2008-03-01

The design of the China Spallation Neutron Source (CSNS) low-energy beam transport (LEBT) line, which locates between the ion source and the radio-frequency quadrupole (RFQ), has been completed with the TRACE3D code. The design aims at perfect matching, primary chopping, a small emittance growth and sufficient space for beam diagnostics. The line consists of three solenoids, three vacuum chambers, two steering magnets and a pre-chopper. The total length of LEBT is about 1.74 m. This LEBT is designed to transfer 20 mA of H-pulsed beam from the ion source to the RFQ. An induction cavity is adopted as the pre-chopper. The electrostatic octupole steerer is discussed as a candidate. A four-quadrant aperture for beam scraping and beam position monitoring is designed.

Electromagnetic sinc Schell-model beams and their statistical properties.

PubMed

Mei, Zhangrong; Mao, Yonghua

2014-09-22

A class of electromagnetic sources with sinc Schell-model correlations is introduced. The conditions on source parameters guaranteeing that the source generates a physical beam are derived. The evolution behaviors of statistical properties for the electromagnetic stochastic beams generated by this new source on propagating in free space and in atmosphere turbulence are investigated with the help of the weighted superposition method and by numerical simulations. It is demonstrated that the intensity distributions of such beams exhibit unique features on propagating in free space and produce a double-layer flat-top profile of being shape-invariant in the far field. This feature makes this new beam particularly suitable for some special laser processing applications. The influences of the atmosphere turbulence with a non-Kolmogorov power spectrum on statistical properties of the new beams are analyzed in detail.

Improved design of proton source and low energy beam transport line for European Spallation Source

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

Neri, L., E-mail: neri@lns.infn.it; Celona, L.; Gammino, S.

2014-02-15

The design update of the European Spallation Source (ESS) accelerator is almost complete and the construction of the prototype of the microwave discharge ion source able to provide a proton beam current larger than 70 mA to the 3.6 MeV Radio Frequency Quadrupole (RFQ) started. The source named PS-ESS (Proton Source for ESS) was designed with a flexible magnetic system and an extraction system able to merge conservative solutions with significant advances. The ESS injector has taken advantage of recent theoretical updates and new plasma diagnostics tools developed at INFN-LNS (Laboratori Nazionali del Sud, Istituto Nazionale di Fisica Nucleare). Themore » design strategy considers the PS-ESS and the low energy beam transport line as a whole, where the proton beam behaves like an almost neutralized non-thermalized plasma. Innovative solutions have been used as hereinafter described. Thermo-mechanical optimization has been performed to withstand the chopped beam and the misaligned focused beam over the RFQ input collimator; the results are reported here.« less

The supercontinuum laser as a flexible source for quasi-steady state and time resolved fluorescence studies

NASA Astrophysics Data System (ADS)

Fenske, Roger; Näther, Dirk U.; Dennis, Richard B.; Smith, S. Desmond

2010-02-01

Commercial Fluorescence Lifetime Spectrometers have long suffered from the lack of a simple, compact and relatively inexpensive broad spectral band light source that can be flexibly employed for both quasi-steady state and time resolved measurements (using Time Correlated Single Photon Counting [TCSPC]). This paper reports the integration of an optically pumped photonic crystal fibre, supercontinuum source1 (Fianium model SC400PP) as a light source in Fluorescence Lifetime Spectrometers (Edinburgh Instruments FLS920 and Lifespec II), with single photon counting detectors (micro-channel plate photomultiplier and a near-infrared photomultiplier) covering the UV to NIR range. An innovative method of spectral selection of the supercontinuum source involving wedge interference filters is also discussed.

Beam experiments with the Grenoble test electron cyclotron resonance ion source at iThemba LABS

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

Thomae, R., E-mail: rthomae@tlabs.ac.za; Conradie, J.; Fourie, D.

2016-02-15

At iThemba Laboratory for Accelerator Based Sciences (iThemba LABS) an electron cyclotron ion source was installed and commissioned. This source is a copy of the Grenoble Test Source (GTS) for the production of highly charged ions. The source is similar to the GTS-LHC at CERN and named GTS2. A collaboration between the Accelerators and Beam Physics Group of CERN and the Accelerator and Engineering Department of iThemba LABS was proposed in which the development of high intensity argon and xenon beams is envisaged. In this paper, we present beam experiments with the GTS2 at iThemba LABS, in which the resultsmore » of continuous wave and afterglow operation of xenon ion beams with oxygen as supporting gases are presented.« less

Performance of the LANSCE H^- Source and Low Energy Transport at Higher Peak Current

NASA Astrophysics Data System (ADS)

Pillai, Chandra; Stevens, Ralph; Fitzgerald, Daniel; Garnett, Robert; Ingllas, William; Merrill, Frank; Rybarcyk, Larry; Sander, Oscar

1997-05-01

The Los Alamos Neutron Science Center (LANSCE) 800 MeV linac facility uses a multicusp field, surface ion source to produce H^- beam for delivery to the Proton Storage Ring (PSR) and to the Weapon Neutron Research (WNR) areas. The source typically operates at a duty factor of 9.4% delivering a peak current of about 14 mA into the 750 keV LEBT. Each beam macropulse is chopped to create a sequence of 360 ns pulse, each with a 100 ns ``extraction notch'' for injection into PSR. The average current delivered to the short-pulse spallation target is nominally 70μA. One goal of the present PSR upgrade projects is an increase in the average beam current to 200μA. This will be accomplished by a combination of increased repetition rate (to 30 Hz), upgraded PSR bunchers, and a brighter H^- ion source that will produce higher peak current with lower beam emittance. The present ion source and injector system was studied to investigate the beam qualities of the source and the performance of the low energy transpot. The performance of the ion source at higher currents and the change in beam parameters in the low energy transport compared to those in the standard source conditions will be presented.

Electron beam ion source and electron beam ion trap (invited).

PubMed

Becker, Reinard; Kester, Oliver

2010-02-01

The electron beam ion source (EBIS) and its trap variant [electron beam ion trap (EBIT)] celebrated their 40th and 20th anniversary, respectively, at the EBIS/T Symposium 2007 in Heidelberg. These technologically challenging sources of highly charged ions have seen a broad development in many countries over the last decades. In contrast to most other ion sources the recipe of improvement was not "sorcery" but a clear understanding of the physical laws and obeying the technological constraints. This review will report important achievements of the past as well as promising developments in the future.

Intense steady state electron beam generator

DOEpatents

Hershcovitch, A.; Kovarik, V.J.; Prelec, K.

1990-07-17

An intense, steady state, low emittance electron beam generator is formed by operating a hollow cathode discharge plasma source at critical levels in combination with an extraction electrode and a target electrode that are operable to extract a beam of fast primary electrons from the plasma source through a negatively biased grid that is critically operated to repel bulk electrons toward the plasma source while allowing the fast primary electrons to move toward the target in the desired beam that can be successfully transported for relatively large distances, such as one or more meters away from the plasma source. 2 figs.

Intense steady state electron beam generator

DOEpatents

Hershcovitch, Ady; Kovarik, Vincent J.; Prelec, Krsto

1990-01-01

An intense, steady state, low emittance electron beam generator is formed by operating a hollow cathode discharge plasma source at critical levels in combination with an extraction electrode and a target electrode that are operable to extract a beam of fast primary electrons from the plasma source through a negatively biased grid that is critically operated to repel bulk electrons toward the plasma source while allowing the fast primary electrons to move toward the target in the desired beam that can be successfully transported for relatively large distances, such as one or more meters away from the plasma source.

Review on high current 2.45 GHz electron cyclotron resonance sources (invited).

PubMed

Gammino, S; Celona, L; Ciavola, G; Maimone, F; Mascali, D

2010-02-01

The suitable source for the production of intense beams for high power accelerators must obey to the request of high brightness, stability, and reliability. The 2.45 GHz off-resonance microwave discharge sources are the ideal device to generate the requested beams, as they produce multimilliampere beams of protons, deuterons, and monocharged ions, remaining stable for several weeks without maintenance. A description of different technical designs will be given, analyzing their strength, and weakness, with regard to the extraction system and low energy beam transport line, as the presence of beam halo is detrimental for the accelerator.

Development of the TFTR neutral beam injection system

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

Prichard, Jr., B. A.

1977-01-01

The TFTR Neutral Beam Lines are designed to inject 20 MW of 120 keV neutral deuterium atoms into the plasma. This is accomplished using 12 sources, 65 amperes each, mounted in 4 beam lines. The 120 kV sources and a prototype beam line are being developed. The implementation of these beam lines has required the development of several associated pieces of hardware. 200 kV switch tubes for the power supplies are being developed for modulation and regulation of the accelerating supplies. A 90 cm metallic seal gate valve capable of sealing against atmosphere in either direction is being developed formore » separating the torus and beam line vacuum systems. A 70 x 80 cm fast shutter valve is also being developed to limit tritium migration from the torus into the beam line. Internal to the beam line a calorimeter, ion dump and deflection magnet have been designed to handle three beams, and optical diagnostics utilizing the doppler broadening and doppler shift of light emitted from the accelerated beam are being developed. The control and monitoring of the 12 sources will be done via the TFTR computer control system (CICADA) as will other parts of the machine, and software is being developed to condition and operate the sources automatically. The prototype beam line is scheduled to begin operation in the fall of 1978 and all four production beam lines on TFTR in 1982.« less

UV fatigue investigations with non-destructive tools in silica

NASA Astrophysics Data System (ADS)

Natoli, Jean-Yves; Beaudier, Alexandre; Wagner, Frank R.

2017-08-01

A fatigue effect is often observed under multiple laser irradiations, overall in UV. This decrease of LIDT, is a critical parameter for laser sources with high repetition rates and with a need of long-term life, as in spatial applications at 355nm. A challenge is also to replace excimer lasers by solid laser sources, this challenge requires to improve drastically the lifetime of optical materials at 266nm. Main applications of these sources are devoted to material surface nanostructuration, spectroscopy and medical surgeries. In this work we focus on the understanding of the laser matter interaction at 266nm in silica in order to predict the lifetime of components and study parameters links to these lifetimes to give keys of improvement for material suppliers. In order to study the mechanism involved in the case of multiple irradiations, an interesting approach is to involve the evolution of fluorescence, in order to observe the first stages of material changes just before breakdown. We will show that it is sometime possible to estimate the lifetime of component only with the fluorescence measurement, saving time and materials. Moreover, the data from the diagnostics give relevant informations to highlight "defects" induced by multiple laser irradiations.

Development of a hybrid molecular beam epitaxy deposition system for in situ surface x-ray studies

DOE PAGES

Andersen, Tassie K.; Cook, Seyoung; Benda, Erika; ...

2018-03-08

A portable metalorganic gas delivery system designed and constructed to interface with an existing molecular beam epitaxy chamber at beamline 33-ID-E of the Advanced Photon Source is described. This system offers the ability to perform in situ X-ray measurements of complex oxide growth via hybrid molecular beam epitaxy. The performance of the hybrid molecular beam epitaxy system while delivering metalorganic source materials is described. In conclusion, the high-energy X-ray scattering capabilities of the hybrid molecular beam epitaxy system are demonstrated both on oxide films grown solely from the metalorganic source and ABO 3 oxide perovskites containing elements from both themore » metalorganic source and a traditional effusion cell.« less

Development of a hybrid molecular beam epitaxy deposition system for in situ surface x-ray studies

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

Andersen, Tassie K.; Cook, Seyoung; Benda, Erika

A portable metalorganic gas delivery system designed and constructed to interface with an existing molecular beam epitaxy chamber at beamline 33-ID-E of the Advanced Photon Source is described. This system offers the ability to perform in situ X-ray measurements of complex oxide growth via hybrid molecular beam epitaxy. The performance of the hybrid molecular beam epitaxy system while delivering metalorganic source materials is described. In conclusion, the high-energy X-ray scattering capabilities of the hybrid molecular beam epitaxy system are demonstrated both on oxide films grown solely from the metalorganic source and ABO 3 oxide perovskites containing elements from both themore » metalorganic source and a traditional effusion cell.« less

Influence of Bondcoat Spray Process on Lifetime of Suspension Plasma-Sprayed Thermal Barrier Coatings

NASA Astrophysics Data System (ADS)

Gupta, M.; Markocsan, N.; Li, X.-H.; Östergren, L.

2017-12-01

Development of thermal barrier coatings (TBCs) manufactured by suspension plasma spraying (SPS) is of high commercial interest as SPS has been shown capable of producing highly porous columnar microstructures similar to the conventionally used electron beam-physical vapor deposition. However, lifetime of SPS coatings needs to be improved further to be used in commercial applications. The bondcoat microstructure as well as topcoat-bondcoat interface topography affects the TBC lifetime significantly. The objective of this work was to investigate the influence of different bondcoat deposition processes for SPS topcoats. In this work, a NiCoCrAlY bondcoat deposited by high velocity air fuel (HVAF) was compared to commercial vacuum plasma-sprayed NiCoCrAlY and PtAl diffusion bondcoats. All bondcoat variations were prepared with and without grit blasting the bondcoat surface. SPS was used to deposit the topcoats on all samples using the same spray parameters. Lifetime of these samples was examined by thermal cyclic fatigue testing. Isothermal heat treatment was performed to study bondcoat oxidation over time. The effect of bondcoat deposition process and interface topography on lifetime in each case has been discussed. The results show that HVAF could be a suitable process for bondcoat deposition in SPS TBCs.

Influence of Bondcoat Spray Process on Lifetime of Suspension Plasma-Sprayed Thermal Barrier Coatings

NASA Astrophysics Data System (ADS)

Gupta, M.; Markocsan, N.; Li, X.-H.; Östergren, L.

2018-01-01

Development of thermal barrier coatings (TBCs) manufactured by suspension plasma spraying (SPS) is of high commercial interest as SPS has been shown capable of producing highly porous columnar microstructures similar to the conventionally used electron beam-physical vapor deposition. However, lifetime of SPS coatings needs to be improved further to be used in commercial applications. The bondcoat microstructure as well as topcoat-bondcoat interface topography affects the TBC lifetime significantly. The objective of this work was to investigate the influence of different bondcoat deposition processes for SPS topcoats. In this work, a NiCoCrAlY bondcoat deposited by high velocity air fuel (HVAF) was compared to commercial vacuum plasma-sprayed NiCoCrAlY and PtAl diffusion bondcoats. All bondcoat variations were prepared with and without grit blasting the bondcoat surface. SPS was used to deposit the topcoats on all samples using the same spray parameters. Lifetime of these samples was examined by thermal cyclic fatigue testing. Isothermal heat treatment was performed to study bondcoat oxidation over time. The effect of bondcoat deposition process and interface topography on lifetime in each case has been discussed. The results show that HVAF could be a suitable process for bondcoat deposition in SPS TBCs.

An ion source module for the Beijing Radioactive Ion-beam Facility

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

Cui, B., E-mail: cui@ciae.ac.cn; Huang, Q.; Tang, B.

2014-02-15

An ion source module is developed for Beijing Radioactive Ion-beam Facility. The ion source module is designed to meet the requirements of remote handling. The connection and disconnection of the electricity, cooling and vacuum between the module and peripheral units can be executed without on-site manual work. The primary test of the target ion source has been carried out and a Li{sup +} beam has been extracted. Details of the ion source module and its primary test results are described.

Recoil Distance Method lifetime measurements via gamma-ray and charged-particle spectroscopy at NSCL

NASA Astrophysics Data System (ADS)

Voss, Philip Jonathan

The Recoil Distance Method (RDM) is a well-established technique for measuring lifetimes of electromagnetic transitions. Transition matrix elements derived from the lifetimes provide valuable insight into nuclear structure. Recent RDM investigations at NSCL present a powerful new model-independent tool for the spectroscopy of nuclei with extreme proton-to-neutron ratios that exhibit surprising behavior. Neutron-rich 18C is one such example, where a small B(E2; 2+1 → 0+gs) represented a dramatic shift from the expected inverse relationship between the B(E2) and 2+1 excitation energy. To shed light on the nature of this quadrupole excitation, the RDM lifetime technique was applied with the Koln/NSCL plunger. States in 18C were populated by the one-proton knockout reaction of a 19N secondary beam. De-excitation gamma rays were detected with the Segmented Germanium Array in coincidence with reaction residues at the focal plane of the S800 Magnetic Spectrometer. The deduced B(E2) and excitation energy were both well described by ab initio no-core shell model calculations. In addition, a novel extension of RDM lifetime measurements via charged-particle spectroscopy of exotic proton emitters has been investigated. Substituting the reaction residue degrader of the Koln/NSCL plunger with a thin silicon detector permits the study of short-lived nuclei beyond the proton dripline. A proof of concept measurement of the mean lifetime of the two-proton emitter 19Mg was conducted. The results indicated a sub-picosecond lifetime, one order of magnitude smaller than the published results, and validate this new technique for lifetime measurements of charged-particle emitters.

Characterizing the Performance of the Princeton Advanced Test Stand Ion Source

NASA Astrophysics Data System (ADS)

Stepanov, A.; Gilson, E. P.; Grisham, L.; Kaganovich, I.; Davidson, R. C.

2012-10-01

The Princeton Advanced Test Stand (PATS) is a compact experimental facility for studying the physics of intense beam-plasma interactions relevant to the Neutralized Drift Compression Experiment - II (NDCX-II). The PATS facility consists of a multicusp RF ion source mounted on a 2 m-long vacuum chamber with numerous ports for diagnostic access. Ar+ beams are extracted from the source plasma with three-electrode (accel-decel) extraction optics. The RF power and extraction voltage (30 - 100 kV) are pulsed to produce 100 μsec duration beams at 0.5 Hz with excellent shot-to-shot repeatability. Diagnostics include Faraday cups, a double-slit emittance scanner, and scintillator imaging. This work reports measurements of beam parameters for a range of beam energies (30 - 50 keV) and currents to characterize the behavior of the ion source and extraction optics. Emittance scanner data is used to calculate the beam trace-space distribution and corresponding transverse emittance. If the plasma density is changing during a beam pulse, time-resolved emittance scanner data has been taken to study the corresponding evolution of the beam trace-space distribution.

Beam characterization at BATMAN for variation of the Cs evaporation asymmetry and comparing two driver geometries

NASA Astrophysics Data System (ADS)

Aza, E.; Schiesko, L.; Wimmer, C.; Wünderlich, D.; Fantz, U.

2017-08-01

The properties of the negative hydrogen ion beam produced by the scaled prototype ITER NBI source at the BATMAN testbed were investigated by means of two beam diagnostics: Beam Emission Spectroscopy (BES) and a calorimeter. Two modifications to the prototype were applied. The first was the installation of a second Cs oven at the bottom part of the backplate in addition to the standard one at the upper part of the backplate varying the Cs evaporation asymmetry inside the source. The second consisted in the replacement of the cylindrical driver with a larger racetrack-shaped RF driver and placing a single Cs oven in a central position at the backplate of the driver. The resulting beam characteristics are discussed and compared with those obtained with the previous source design. The position of the Cs oven and the different driver size and geometry appear not to influence the beam profile and the beam deflection for a well-conditioned source.

Fast Ion Mesurements in LAPD

NASA Astrophysics Data System (ADS)

Zhao, L.; Boehmer, H.; Edrich, D.; Heidbrink, W.; McWilliams, R.; Zimmerman, D.; Leneman, D.

2003-10-01

To study fast-ion transport, a 3-cm diameter, 17 MHZ, ˜80W, ˜3 mA argon source launches ˜500 eV ions in the LArge Plasma Device (LAPD). The beam is diagnosed with a gridded analyzer and, on a test stand at Irvine, laser-induced fluorescence (LIF). Neutral scattering is important near the source. The measured beam energy can be more than 100 eV larger than the accelerating voltage applied to the extraction grids. In LAPD the profile of the pulsed ion beam is measured at various axial locations between z=0.3-6.0 m from the source. When the beam velocity is parallel to the solenoidal field (0^o) evidence of peristaltic focusing, beam attenuation, and radial scattering is observed. At an angle of 22^o with respect to the field the beam follows the expected helical trajectory. Three meters axially from the source strong attenuation and elongation of the beam in the direction of the gyro-angle are observed. The data are compared with classical Coulomb and neutral scattering theory.

Space environment simulation and sensor calibration facility

NASA Astrophysics Data System (ADS)

Engelhart, Daniel P.; Patton, James; Plis, Elena; Cooper, Russell; Hoffmann, Ryan; Ferguson, Dale; Hilmer, Robert V.; McGarity, John; Holeman, Ernest

2018-02-01

The Mumbo space environment simulation chamber discussed here comprises a set of tools to calibrate a variety of low flux, low energy electron and ion detectors used in satellite-mounted particle sensors. The chamber features electron and ion beam sources, a Lyman-alpha ultraviolet lamp, a gimbal table sensor mounting system, cryogenic sample mount and chamber shroud, and beam characterization hardware and software. The design of the electron and ion sources presented here offers a number of unique capabilities for space weather sensor calibration. Both sources create particle beams with narrow, well-characterized energetic and angular distributions with beam diameters that are larger than most space sensor apertures. The electron and ion sources can produce consistently low fluxes that are representative of quiescent space conditions. The particle beams are characterized by 2D beam mapping with several co-located pinhole aperture electron multipliers to capture relative variation in beam intensity and a large aperture Faraday cup to measure absolute current density.

Space environment simulation and sensor calibration facility.

PubMed

Engelhart, Daniel P; Patton, James; Plis, Elena; Cooper, Russell; Hoffmann, Ryan; Ferguson, Dale; Hilmer, Robert V; McGarity, John; Holeman, Ernest

2018-02-01

The Mumbo space environment simulation chamber discussed here comprises a set of tools to calibrate a variety of low flux, low energy electron and ion detectors used in satellite-mounted particle sensors. The chamber features electron and ion beam sources, a Lyman-alpha ultraviolet lamp, a gimbal table sensor mounting system, cryogenic sample mount and chamber shroud, and beam characterization hardware and software. The design of the electron and ion sources presented here offers a number of unique capabilities for space weather sensor calibration. Both sources create particle beams with narrow, well-characterized energetic and angular distributions with beam diameters that are larger than most space sensor apertures. The electron and ion sources can produce consistently low fluxes that are representative of quiescent space conditions. The particle beams are characterized by 2D beam mapping with several co-located pinhole aperture electron multipliers to capture relative variation in beam intensity and a large aperture Faraday cup to measure absolute current density.

BATMAN beam properties characterization by the beam emission spectroscopy diagnostic

NASA Astrophysics Data System (ADS)

Bonomo, F.; Ruf, B.; Barbisan, M.; Cristofaro, S.; Schiesko, L.; Fantz, U.; Franzen, P.; Pasqualotto, R.; Riedl, R.; Serianni, G.; Wünderlich, D.

2015-04-01

The ITER neutral beam heating systems are based on the production and acceleration of negative ions (H/D) up to 1 MV. The requirements for the beam properties are strict: a low core beam divergence (< 0.4 °) together with a low source pressure (≤ 0.3 Pa) would permit to reduce the ion losses along the beamline, keeping the stripping particle losses below 30%. However, the attainment of such beam properties is not straightforward. At IPP, the negative ion source testbed BATMAN (BAvarian Test MAchine for Negative ions) allows for deepening the knowledge of the determination of the beam properties. One of the diagnostics routinely used to this purpose is the Beam Emission Spectroscopy (BES): the Hα light emitted in the beam is detected and the corresponding spectra are evaluated to estimate the beam divergence and the stripping losses. The BES number of lines of sight in BATMAN has been recently increased: five horizontal lines of sight providing a vertical profile of the beam permit to characterize the negative ion beam properties in relation to the source parameters. Different methods of Hα spectra analysis are here taken into account and compared for the estimation of the beam divergence and the amount of stripping. In particular, to thoroughly study the effect of the space charge compensation on the beam divergence, an additional hydrogen injection line has been added in the tank, which allows for setting different background pressure values (one order of magnitude, from about 0.04 Pa up to the source pressure) in the beam drift region.

Compact quasi-monoenergetic photon sources from laser-plasma accelerators for nuclear detection and characterization

NASA Astrophysics Data System (ADS)

Geddes, Cameron G. R.; Rykovanov, Sergey; Matlis, Nicholas H.; Steinke, Sven; Vay, Jean-Luc; Esarey, Eric H.; Ludewigt, Bernhard; Nakamura, Kei; Quiter, Brian J.; Schroeder, Carl B.; Toth, Csaba; Leemans, Wim P.

2015-05-01

Near-monoenergetic photon sources at MeV energies offer improved sensitivity at greatly reduced dose for active interrogation, and new capabilities in treaty verification, nondestructive assay of spent nuclear fuel and emergency response. Thomson (also referred to as Compton) scattering sources are an established method to produce appropriate photon beams. Applications are however restricted by the size of the required high-energy electron linac, scattering (photon production) system, and shielding for disposal of the high energy electron beam. Laser-plasma accelerators (LPAs) produce GeV electron beams in centimeters, using the plasma wave driven by the radiation pressure of an intense laser. Recent LPA experiments are presented which have greatly improved beam quality and efficiency, rendering them appropriate for compact high-quality photon sources based on Thomson scattering. Designs for MeV photon sources utilizing the unique properties of LPAs are presented. It is shown that control of the scattering laser, including plasma guiding, can increase photon production efficiency. This reduces scattering laser size and/or electron beam current requirements to scale compatible with the LPA. Lastly, the plasma structure can decelerate the electron beam after photon production, reducing the size of shielding required for beam disposal. Together, these techniques provide a path to a compact photon source system.

Status of the NIST Penning-Trap Neutron Lifetime Measurement

NASA Astrophysics Data System (ADS)

Snow, W. M.; Fei, X.; Chowdhuri, Z.; Dewey, M. S.; Gilliam, D.; Nico, J. S.; Greene, G. L.

1998-10-01

The decay rate of the free neutron is important input for Big-Bang Nucleosynthesis calculations of the primordial ^4He abundance in the universe(T. P. Walker et al, Astrophys. J. 376, 51 (1991).) and for tests of the electroweak model in the charged-current sector(I. S. Towner, Nucl. Phys. A540, 478 (1992).). We will describe an experiment in progress at NIST to measure the neutron decay rate. The technique uses a Penning trap to trap and count protons from in-beam neutron decay(J. Byrne et al., Phys. Rev. Lett. 65, 289 (1990).) and an absolutely calibrated beam monitor to measure the neutron density in the beam(R. D. Scott et al., Nucl. Inst. Meth. A362, 151 (1995).). We will present data taken in the spring and summer of 1998.

RF System for the MICE Demonstration of Ionisation Cooling

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

Ronald, K.; et al.

2017-04-01

Muon accelerators offer an attractive option for a range of future particle physics experiments. They can enable high energy (TeV+) high energy lepton colliders whilst mitigating the difficulty of synchrotron losses, and can provide intense beams of neutrinos for fundamental physics experiments investigating the physics of flavor. The method of production of muon beams results in high beam emittance which must be reduced for efficient acceleration. Conventional emittance control schemes take too long, given the very short (2.2 microsecond) rest lifetime of the muon. Ionisation cooling offers a much faster approach to reducing particle emittance, and the international MICE collaborationmore » aims to demonstrate this technique for the first time. This paper will present the MICE RF system and its role in the context of the overall experiment.« less

Electron beam pumped semiconductor laser

NASA Technical Reports Server (NTRS)

Hug, William F. (Inventor); Reid, Ray D. (Inventor)

2009-01-01

Electron-beam-pumped semiconductor ultra-violet optical sources (ESUVOSs) are disclosed that use ballistic electron pumped wide bandgap semiconductor materials. The sources may produce incoherent radiation and take the form of electron-beam-pumped light emitting triodes (ELETs). The sources may produce coherent radiation and take the form of electron-beam-pumped laser triodes (ELTs). The ELTs may take the form of electron-beam-pumped vertical cavity surface emitting lasers (EVCSEL) or edge emitting electron-beam-pumped lasers (EEELs). The semiconductor medium may take the form of an aluminum gallium nitride alloy that has a mole fraction of aluminum selected to give a desired emission wavelength, diamond, or diamond-like carbon (DLC). The sources may be produced from discrete components that are assembled after their individual formation or they may be produced using batch MEMS-type or semiconductor-type processing techniques to build them up in a whole or partial monolithic manner, or combination thereof.

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

Nigg, D.W.; Mitchell, H.E.; Harker, Y.D.

Therapeutically-useful epithermal-neutron beams for BNCT are currently generated by nuclear reactors. Various accelerator-based neutron sources for BNCT have been proposed and some low intensity prototypes of such sources, generally featuring the use of proton beams and beryllium or lithium targets have been constructed. This paper describes an alternate approach to the realization of a clinically useful accelerator-based source of epithermal neutrons for BNCT that reconciles the often conflicting objectives of target cooling, neutron beam intensity, and neutron beam spectral purity via a two stage photoneutron production process.

An evaluation of differences due to changing source directivity in room acoustic computer modeling

NASA Astrophysics Data System (ADS)

Vigeant, Michelle C.; Wang, Lily M.

2004-05-01

This project examines the effects of changing source directivity in room acoustic computer models on objective parameters and subjective perception. Acoustic parameters and auralizations calculated from omnidirectional versus directional sources were compared. Three realistic directional sources were used, measured in a limited number of octave bands from a piano, singing voice, and violin. A highly directional source that beams only within a sixteenth-tant of a sphere was also tested. Objectively, there were differences of 5% or more in reverberation time (RT) between the realistic directional and omnidirectional sources. Between the beaming directional and omnidirectional sources, differences in clarity were close to the just-noticeable-difference (jnd) criterion of 1 dB. Subjectively, participants had great difficulty distinguishing between the realistic and omnidirectional sources; very few could discern the differences in RTs. However, a larger percentage (32% vs 20%) could differentiate between the beaming and omnidirectional sources, as well as the respective differences in clarity. Further studies of the objective results from different beaming sources have been pursued. The direction of the beaming source in the room is changed, as well as the beamwidth. The objective results are analyzed to determine if differences fall within the jnd of sound-pressure level, RT, and clarity.

Autofluorescence lifetime imaging during transoral robotic surgery: a clinical validation study of tumor detection (Conference Presentation)

NASA Astrophysics Data System (ADS)

Lagarto, João. L.; Phipps, Jennifer E.; Unger, Jakob; Faller, Leta M.; Gorpas, Dimitris; Ma, Dinglong M.; Bec, Julien; Moore, Michael G.; Bewley, Arnaud F.; Yankelevich, Diego R.; Sorger, Jonathan M.; Farwell, Gregory D.; Marcu, Laura

2017-02-01

Autofluorescence lifetime spectroscopy is a promising non-invasive label-free tool for characterization of biological tissues and shows potential to report structural and biochemical alterations in tissue owing to pathological transformations. In particular, when combined with fiber-optic based instruments, autofluorescence lifetime measurements can enhance intraoperative diagnosis and provide guidance in surgical procedures. We investigate the potential of a fiber-optic based multi-spectral time-resolved fluorescence spectroscopy instrument to characterize the autofluorescence fingerprint associated with histologic, morphologic and metabolic changes in tissue that can provide real-time contrast between healthy and tumor regions in vivo and guide clinicians during resection of diseased areas during transoral robotic surgery. To provide immediate feedback to the surgeons, we employ tracking of an aiming beam that co-registers our point measurements with the robot camera images and allows visualization of the surgical area augmented with autofluorescence lifetime data in the surgeon's console in real-time. For each patient, autofluorescence lifetime measurements were acquired from normal, diseased and surgically altered tissue, both in vivo (pre- and post-resection) and ex vivo. Initial results indicate tumor and normal regions can be distinguished based on changes in lifetime parameters measured in vivo, when the tumor is located superficially. In particular, results show that autofluorescence lifetime of tumor is shorter than that of normal tissue (p < 0.05, n = 3). If clinical diagnostic efficacy is demonstrated throughout this on-going study, we believe that this method has the potential to become a valuable tool for real-time intraoperative diagnosis and guidance during transoral robot assisted cancer removal interventions.

Progress in the development of an H{sup −} ion source for cyclotrons

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

Etoh, H., E-mail: Hrh-Etoh@shi.co.jp; Aoki, Y.; Mitsubori, H.

2015-04-08

A multi-cusp DC H{sup −} ion source has been developed for cyclotrons in medical use. Beam optics of the H{sup −} ion beam is studied using a 2D beam trajectory code. The simulation results are compared with the experimental results obtained in the Mark I source, which has produced up to 16 mA H{sup −} ion beams. The optimum extraction voltages show good agreement between the calculation and the experimental results. A new ion source, Mark II source, is designed to achieve the next goal of producing an H{sup −} beam of 20 mA. The magnetic field configurations and the plasma electrodemore » design are optimized for Cs-seeded operation. Primary electron trajectory simulation shows that primary electrons are confined well and the magnetic filter prevents the primary electrons from entering into the extraction region.« less

Kinetic energy offsets for multicharged ions from an electron beam ion source.

PubMed

Kulkarni, D D; Ahl, C D; Shore, A M; Miller, A J; Harriss, J E; Sosolik, C E; Marler, J P

2017-08-01

Using a retarding field analyzer, we have measured offsets between the nominal and measured kinetic energy of multicharged ions extracted from an electron beam ion source (EBIS). By varying source parameters, a shift in ion kinetic energy was attributed to the trapping potential produced by the space charge of the electron beam within the EBIS. The space charge of the electron beam depends on its charge density, which in turn depends on the amount of negative charge (electron beam current) and its velocity (electron beam energy). The electron beam current and electron beam energy were both varied to obtain electron beams of varying space charge and these were related to the observed kinetic energy offsets for Ar 4+ and Ar 8+ ion beams. Knowledge of these offsets is important for studies that seek to utilize slow, i.e., low kinetic energy, multicharged ions to exploit their high potential energies for processes such as surface modification. In addition, we show that these offsets can be utilized to estimate the effective radius of the electron beam inside the trap.

Optimization of Compton Source Performance through Electron Beam Shaping

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

Malyzhenkov, Alexander; Yampolsky, Nikolai

2016-09-26

We investigate a novel scheme for significantly increasing the brightness of x-ray light sources based on inverse Compton scattering (ICS) - scattering laser pulses off relativistic electron beams. The brightness of ICS sources is limited by the electron beam quality since electrons traveling at different angles, and/or having different energies, produce photons with different energies. Therefore, the spectral brightness of the source is defined by the 6d electron phase space shape and size, as well as laser beam parameters. The peak brightness of the ICS source can be maximized then if the electron phase space is transformed in a waymore » so that all electrons scatter off the x-ray photons of same frequency in the same direction, arriving to the observer at the same time. We describe the x-ray photon beam quality through the Wigner function (6d photon phase space distribution) and derive it for the ICS source when the electron and laser rms matrices are arbitrary.« less

Pulsed ion beam source

DOEpatents

Greenly, J.B.

1997-08-12

An improved pulsed ion beam source is disclosed having a new biasing circuit for the fast magnetic field. This circuit provides for an initial negative bias for the field created by the fast coils in the ion beam source which pre-ionize the gas in the source, ionize the gas and deliver the gas to the proper position in the accelerating gap between the anode and cathode assemblies in the ion beam source. The initial negative bias improves the interaction between the location of the nulls in the composite magnetic field in the ion beam source and the position of the gas for pre-ionization and ionization into the plasma as well as final positioning of the plasma in the accelerating gap. Improvements to the construction of the flux excluders in the anode assembly are also accomplished by fabricating them as layered structures with a high melting point, low conductivity material on the outsides with a high conductivity material in the center. 12 figs.

Conceptual design of hollow electron lenses for beam halo control in the Large Hadron Collider

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

Stancari, Giulio; Previtali, Valentina; Valishev, Alexander

Collimation with hollow electron beams is a technique for halo control in high-power hadron beams. It is based on an electron beam (possibly pulsed or modulated in intensity) guided by strong axial magnetic fields which overlaps with the circulating beam in a short section of the ring. The concept was tested experimentally at the Fermilab Tevatron collider using a hollow electron gun installed in one of the Tevatron electron lenses. We are proposing a conceptual design for applying this technique to the Large Hadron Collider at CERN. A prototype hollow electron gun for the LHC was built and tested. Themore » expected performance of the hollow electron beam collimator was based on Tevatron experiments and on numerical tracking simulations. Halo removal rates and enhancements of halo diffusivity were estimated as a function of beam and lattice parameters. Proton beam core lifetimes and emittance growth rates were checked to ensure that undesired effects were suppressed. Hardware specifications were based on the Tevatron devices and on preliminary engineering integration studies in the LHC machine. Required resources and a possible timeline were also outlined, together with a brief discussion of alternative halo-removal schemes and of other possible uses of electron lenses to improve the performance of the LHC.« less

Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station

DOE PAGES

Gallmeier, F. X.; Lu, W.; Riemer, B. W.; ...

2016-06-14

We identified candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) using a global optimizer framework built around the MCNPX particle transport code. Neutron brightness metrics were selected as the figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate at 1.3 GeV proton energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate that the peak brightness can be increased by a factor of 5 and 2.5 on a per proton pulse basis compared tomore » the SNS first target station for both coupled and decoupled para-hydrogen moderators, respectively. Additional increases by factors of 3 and 2 were demonstrated for coupled and decoupled moderators, respectively, by reducing the area of neutron emission from 100 × 100 mm 2 to 20 × 20 mm 2. Furthermore, this increase in brightness has the potential to translate to an increase of beam intensity at the instruments’ sample positions even though the total neutron emission of the smaller moderator is less than that of the larger. This is especially true for instruments with small samples (beam dimensions). The increased fluxes in the STS moderators come at accelerated poison and de-coupler burnout and higher radiation-induced material damage rates per unit power, which overall translate into lower moderator lifetimes. Our first effort decoupled group moderators into a cluster collectively positioning them at the peak neutron production zone in the target and having a three-port neutron emission scheme that complements that of a cylindrical coupled moderator.« less

Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station

NASA Astrophysics Data System (ADS)

Gallmeier, F. X.; Lu, W.; Riemer, B. W.; Zhao, J. K.; Herwig, K. W.; Robertson, J. L.

2016-06-01

Candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) have been identified using a global optimizer framework built around the MCNPX particle transport code. Neutron brightness metrics were selected as the figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate at 1.3 GeV proton energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate that the peak brightness can be increased by a factor of 5 and 2.5 on a per proton pulse basis compared to the SNS first target station for both coupled and decoupled para-hydrogen moderators, respectively. Additional increases by factors of 3 and 2 were demonstrated for coupled and decoupled moderators, respectively, by reducing the area of neutron emission from 100 × 100 mm2 to 20 × 20 mm2. This increase in brightness has the potential to translate to an increase of beam intensity at the instruments' sample positions even though the total neutron emission of the smaller moderator is less than that of the larger. This is especially true for instruments with small samples (beam dimensions). The increased fluxes in the STS moderators come at accelerated poison and de-coupler burnout and higher radiation-induced material damage rates per unit power, which overall translate into lower moderator lifetimes. A first effort was undertaken to group decoupled moderators into a cluster collectively positioning them at the peak neutron production zone in the target and having a three-port neutron emission scheme that complements that of a cylindrical coupled moderator.

Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station

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

Gallmeier, F. X.; Lu, W.; Riemer, B. W.

We identified candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) using a global optimizer framework built around the MCNPX particle transport code. Neutron brightness metrics were selected as the figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate at 1.3 GeV proton energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate that the peak brightness can be increased by a factor of 5 and 2.5 on a per proton pulse basis compared tomore » the SNS first target station for both coupled and decoupled para-hydrogen moderators, respectively. Additional increases by factors of 3 and 2 were demonstrated for coupled and decoupled moderators, respectively, by reducing the area of neutron emission from 100 × 100 mm 2 to 20 × 20 mm 2. Furthermore, this increase in brightness has the potential to translate to an increase of beam intensity at the instruments’ sample positions even though the total neutron emission of the smaller moderator is less than that of the larger. This is especially true for instruments with small samples (beam dimensions). The increased fluxes in the STS moderators come at accelerated poison and de-coupler burnout and higher radiation-induced material damage rates per unit power, which overall translate into lower moderator lifetimes. Our first effort decoupled group moderators into a cluster collectively positioning them at the peak neutron production zone in the target and having a three-port neutron emission scheme that complements that of a cylindrical coupled moderator.« less

Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station

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

Gallmeier, F. X., E-mail: gallmeierfz@ornl.gov; Lu, W.; Riemer, B. W.

Candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) have been identified using a global optimizer framework built around the MCNPX particle transport code. Neutron brightness metrics were selected as the figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate at 1.3 GeV proton energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate that the peak brightness can be increased by a factor of 5 and 2.5 on a per proton pulse basis comparedmore » to the SNS first target station for both coupled and decoupled para-hydrogen moderators, respectively. Additional increases by factors of 3 and 2 were demonstrated for coupled and decoupled moderators, respectively, by reducing the area of neutron emission from 100 × 100 mm{sup 2} to 20 × 20 mm{sup 2}. This increase in brightness has the potential to translate to an increase of beam intensity at the instruments’ sample positions even though the total neutron emission of the smaller moderator is less than that of the larger. This is especially true for instruments with small samples (beam dimensions). The increased fluxes in the STS moderators come at accelerated poison and de-coupler burnout and higher radiation-induced material damage rates per unit power, which overall translate into lower moderator lifetimes. A first effort was undertaken to group decoupled moderators into a cluster collectively positioning them at the peak neutron production zone in the target and having a three-port neutron emission scheme that complements that of a cylindrical coupled moderator.« less

High spatial resolution and high brightness ion beam probe for in-situ elemental and isotopic analysis

NASA Astrophysics Data System (ADS)

Long, Tao; Clement, Stephen W. J.; Bao, Zemin; Wang, Peizhi; Tian, Di; Liu, Dunyi

2018-03-01

A high spatial resolution and high brightness ion beam from a cold cathode duoplasmatron source and primary ion optics are presented and applied to in-situ analysis of micro-scale geological material with complex structural and chemical features. The magnetic field in the source as well as the influence of relative permeability of magnetic materials on source performance was simulated using COMSOL to confirm the magnetic field strength of the source. Based on SIMION simulation, a high brightness and high spatial resolution negative ion optical system has been developed to achieve Critical (Gaussian) illumination mode. The ion source and primary column are installed on a new Time-of-Flight secondary ion mass spectrometer for analysis of geological samples. The diameter of the ion beam was measured by the knife-edge method and a scanning electron microscope (SEM). Results show that an O2- beam of ca. 5 μm diameter with a beam intensity of ∼5 nA and an O- beam of ca. 5 μm diameter with a beam intensity of ∼50 nA were obtained, respectively. This design will open new possibilities for in-situ elemental and isotopic analysis in geological studies.

Energy balance in the core of the Saturn plasma sheet: H2O chemistry

NASA Astrophysics Data System (ADS)

Shemansky, D. E.; Yoshii, J.; Liu, X.

2011-10-01

A model of the weakly ionized plasma at Saturn has been developed to investigate the properties of the system. Energy balance is a critical consideration. The present model is based on two sources of mass, H2O, and HI. H2O is a variable. HI is a significant volume of gas flowing through the plasma imposed by the source at Saturn [1,2,3]. The energy sources are solar radiation and heterogeneous magnetosphere electrons. The model calculations produce energy rates, species partitioning, and relaxation lifetimes. For the first time the state of the ambient plasma sheet electrons is directly connected to the energy forcing functions. Within limits of knowledge, the predicted state of the core region of the plasma sheet in neutral and ionized gas corresponds satisfactorily to observation. The dominant ions in these calculations are H2O+ and H3O+ with lifetimes of several days. The lifetime of H2O is roughly 60 days. In calculations carried out so far the predicted source rate for H2O is lower than the rates quoted from the Enceladus encounters.

Lasing characteristics of gas mixtures involving UFG: Application to nuclear pumping of lasers

NASA Technical Reports Server (NTRS)

Verdeyen, J. T.; Eden, J. G.

1980-01-01

Intense blue-green fluorescence from a structured band centered at lambda approximately 484 nm was observed from Ar, CF3I and NF3 gas mixtures excited by an electron beam. This emission was tentatively assigned to the E yields A transition of the iodine monofluoride (IF) molecule. The fluorescence efficiency of the IF(E yields A) band and the IF (E) state radiative lifetime were estimated to be approximately 6% and 15 ns, respectively. The emission band structure, the short IF(E) radiative lifetime and the Franck-Condon shift between the E and A states suggest that IF is an attractive candidate for a blue-green laser.

Short beam shear tests of polymeric laminates and unidirectional composites

NASA Technical Reports Server (NTRS)

Stinchcomb, W. W.; Henneke, E. G.

1980-01-01

The application of advanced composite materials in aerospace, ground transportation, and sporting industries are discussed. Failure theories for the design and mechanical behavior of composite materials are emphasized. Methods for detecting specific types of flaws are outlined. The effect of detected flaws on mechanical properties such as stiffness, strength, fatigue lifetime, or residual strength is described.

rf improvements for Spallation Neutron Source H- ion source.

PubMed

Kang, Y W; Fuja, R; Goulding, R H; Hardek, T; Lee, S-W; McCarthy, M P; Piller, M C; Shin, K; Stockli, M P; Welton, R F

2010-02-01

The Spallation Neutron Source at Oak Ridge National Laboratory is ramping up the accelerated proton beam power to 1.4 MW and just reached 1 MW. The rf-driven multicusp ion source that originates from the Lawrence Berkeley National Laboratory has been delivering approximately 38 mA H(-) beam in the linac at 60 Hz, 0.9 ms. To improve availability, a rf-driven external antenna multicusp ion source with a water-cooled ceramic aluminum nitride (AlN) plasma chamber is developed. Computer modeling and simulations have been made to analyze and optimize the rf performance of the new ion source. Operational statistics and test runs with up to 56 mA medium energy beam transport beam current identify the 2 MHz rf system as a limiting factor in the system availability and beam production. Plasma ignition system is under development by using a separate 13 MHz system. To improve the availability of the rf power system with easier maintenance, we tested a 70 kV isolation transformer for the 80 kW, 6% duty cycle 2 MHz amplifier to power the ion source from a grounded solid-state amplifier.

Source of polarized ions for the JINR accelerator complex

NASA Astrophysics Data System (ADS)

Belov, A. S.; Donets, D. E.; Fimushkin, V. V.; Kovalenko, A. D.; Kutuzova, L. V.; Prokofichev, Yu V.; Shutov, V. B.; Turbabin, A. V.; Zubets, V. N.

2017-12-01

The JINR atomic beam type polarized ion source is described. Results of tests of the plasma ionizer with a storage cell and of tuning of high frequency transition units are presented. The source was installed in a linac injector hall of NUCLOTRON in May 2016. The source has been commissioned and used in the NUCLOTRON runs in 2016 and February - March 2017. Polarized and unpolarized deuteron beams were produced as well as polarized protons for acceleration in the NUCLOTRON. Polarized deuteron beam with pulsed current up to 2 mA has been produced. Deuteron beam polarization of 0.6-0.9 of theoretical values for different modes of high frequency transition units operation has been measured with the NUCLOTRON ring internal polarimeter for the accelerated deuteron and proton beams.

Charge neutralization apparatus for ion implantation system

DOEpatents

Leung, Ka-Ngo; Kunkel, Wulf B.; Williams, Malcom D.; McKenna, Charles M.

1992-01-01

Methods and apparatus for neutralization of a workpiece such as a semiconductor wafer in a system wherein a beam of positive ions is applied to the workpiece. The apparatus includes an electron source for generating an electron beam and a magnetic assembly for generating a magnetic field for guiding the electron beam to the workpiece. The electron beam path preferably includes a first section between the electron source and the ion beam and a second section which is coincident with the ion beam. The magnetic assembly generates an axial component of magnetic field along the electron beam path. The magnetic assembly also generates a transverse component of the magnetic field in an elbow region between the first and second sections of the electron beam path. The electron source preferably includes a large area lanthanum hexaboride cathode and an extraction grid positioned in close proximity to the cathode. The apparatus provides a high current, low energy electron beam for neutralizing charge buildup on the workpiece.

Evaluation of beam divergence of a negative hydrogen ion beam using Doppler shift spectroscopy diagnostics

NASA Astrophysics Data System (ADS)

Deka, A. J.; Bharathi, P.; Pandya, K.; Bandyopadhyay, M.; Bhuyan, M.; Yadav, R. K.; Tyagi, H.; Gahlaut, A.; Chakraborty, A.

2018-01-01

The Doppler Shift Spectroscopy (DSS) diagnostic is in the conceptual stage to estimate beam divergence, stripping losses, and beam uniformity of the 100 keV hydrogen Diagnostics Neutral Beam of International Thermonuclear Experimental Reactor. This DSS diagnostic is used to measure the above-mentioned parameters with an error of less than 10%. To aid the design calculations and to establish a methodology for estimation of the beam divergence, DSS measurements were carried out on the existing prototype ion source RF Operated Beam Source in India for Negative ion Research. Emissions of the fast-excited neutrals that are generated from the extracted negative ions were collected in the target tank, and the line broadening of these emissions were used for estimating beam divergence. The observed broadening is a convolution of broadenings due to beam divergence, collection optics, voltage ripple, beam focusing, and instrumental broadening. Hence, for estimating the beam divergence from the observed line broadening, a systematic line profile analysis was performed. To minimize the error in the divergence measurements, a study on error propagation in the beam divergence measurements was carried out and the error was estimated. The measurements of beam divergence were done at a constant RF power of 50 kW and a source pressure of 0.6 Pa by varying the extraction voltage from 4 kV to10 kV and the acceleration voltage from 10 kV to 15 kV. These measurements were then compared with the calorimetric divergence, and the results seemed to agree within 10%. A minimum beam divergence of ˜3° was obtained when the source was operated at an extraction voltage of ˜5 kV and at a ˜10 kV acceleration voltage, i.e., at a total applied voltage of 15 kV. This is in agreement with the values reported in experiments carried out on similar sources elsewhere.

The R&D progress of 4 MW EAST-NBI high current ion source.

PubMed

Xie, Yahong; Hu, Chundong; Liu, Sheng; Xu, Yongjian; Liang, Lizhen; Xie, Yuanlai; Sheng, Peng; Jiang, Caichao; Liu, Zhimin

2014-02-01

A high current ion source, which consists of the multi-cusp bucket plasma generator and tetrode accelerator with multi-slot apertures, is developed and tested for the Experimental Advanced Superconducting Tokamak neutral beam injector. Three ion sources are tested on the test bed with arc power of 80 kW, beam voltage of 80 keV, and beam power of 4 MW. The arc regulation technology with Langmuir probes is employed for the long pulse operation of ion source, and the long pulse beam of 50 keV @ 15.5 A @ 100 s and 80 keV @ 52A @ 1s are extracted, respectively.

Design of a compact all-permanent magnet ECR ion source injector for ReA at the MSU NSCL

NASA Astrophysics Data System (ADS)

Pham, Alfonse N.; Leitner, Daniela; Glennon, Patrick; Ottarson, Jack; Lawton, Don; Portillo, Mauricio; Machicoane, Guillaume; Wenstrom, John; Lajoie, Andrew

2016-06-01

The design of a compact all-permanent magnet electron cyclotron resonance (ECR) ion source injector for the ReAccelerator Facility (ReA) at the Michigan State University (MSU) National Superconducting Cyclotron Laboratory (NSCL) is currently being carried out. The ECR ion source injector will complement the electron beam ion trap (EBIT) charge breeder as an off-line stable ion beam injector for the ReA linac. The objective of the ECR ion source injector is to provide continuous-wave beams of heavy ions from hydrogen to masses up to 136Xe within the ReA charge-to-mass ratio (Q / A) operational range from 0.2 to 0.5. The ECR ion source will be mounted on a high-voltage platform that can be adjusted to obtain the required 12 keV/u injection energy into a room temperature radio-frequency quadrupole (RFQ) for further acceleration. The beam line consists of a 30 kV tetrode extraction system, mass analyzing section, and optical matching section for injection into the existing ReA low energy beam transport (LEBT) line. The design of the ECR ion source and the associated beam line are discussed.

Preliminary result of rapid solenoid for controlling heavy-ion beam parameters of laser ion source

DOE PAGES

Okamura, M.; Sekine, M.; Ikeda, S.; ...

2015-03-13

To realize a heavy ion inertial fusion driver, we have studied a possibility of laser ion source (LIS). A LIS can provide high current high brightness heavy ion beams, however it was difficult to manipulate the beam parameters. To overcome the issue, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The rapid ramping magnetic field could enhance limited time slice of the current and simultaneously the beam emittance changed accordingly. This approach may also useful to realize an ion source for HIF power plant.

Alignment reference device

DOEpatents

Patton, Gail Y.; Torgerson, Darrel D.

1987-01-01

An alignment reference device provides a collimated laser beam that minimizes angular deviations therein. A laser beam source outputs the beam into a single mode optical fiber. The output end of the optical fiber acts as a source of radiant energy and is positioned at the focal point of a lens system where the focal point is positioned within the lens. The output beam reflects off a mirror back to the lens that produces a collimated beam.

RF Plasma Source for Heavy Ion Beam Charge Neutralization

NASA Astrophysics Data System (ADS)

Efthimion, P. C.; Gilson, E.; Grisham, L.; Davidson, R. C.

2003-10-01

Highly ionized plasmas are being employed as a medium for charge neutralizing heavy ion beams in order to focus to a small spot size. Calculations suggest that plasma at a density of 1 - 100 times the ion beam density and at a length 0.1-0.5 m would be suitable for achieving a high level of charge neutralization. An ECR source has been built at the Princeton Plasma Physics Laboratory (PPPL) in support of the joint Neutralized Transport Experiment (NTX) at the Lawrence Berkeley National Laboratory (LBNL) to study ion beam neutralization with plasma. The ECR source operates at 13.6 MHz and with solenoid magnetic fields of 0-10 gauss. The goal is to operate the source at pressures 10-5 Torr at full ionization. The initial operation of the source has been at pressures of 10-4 - 10-1 Torr. Electron densities in the range of 10^8 - 10^11 cm-3 have been achieved. Recently, pulsed operation of the source has enabled operation at pressures in the 10-6 Torr range with densities of 10^11 cm-3. Near 100% ionization has been achieved. The source has been integrated with NTX and is being used in the experiments. The plasma is approximately 10 cm in length in the direction of the beam propagation. Modifications to the source will be presented that increase its length in the direction of beam propagation.

A combined thermal dissociation and electron impact ionization source for RIB generation

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

Alton, G.D.; Williams, C.

1995-12-31

The probability for simultaneously dissociating and efficiently ionizing the individual atomic constituents of molecular feed materials with conventional, hot-cathode, electron-impact ion sources is low and consequently, the ion beams from these sources often appear as mixtures of several molecular sideband beams. This fragmentation process leads to dilution of the intensity of the species of interest for RIB applications where beam intensity is at a premium. We have conceived an ion source that combines the excellent molecular dissociation properties of a thermal dissociator and the high ionization efficiency characteristics of an electron impact ionization source that will, in principle, overcome thismore » handicap. The source concept will be evaluated as a potential candidate for use for RIB generation at the Holifield Radioactive Ion Beam Facility (HRIBF), now under construction at the Oak Ridge National Laboratory. The design features and principles of operation of the source are described in this article.« less

Dianion diagnostics in DESIREE: High-sensitivity detection of Cn2 - from a sputter ion source

NASA Astrophysics Data System (ADS)

Chartkunchand, K. C.; Stockett, M. H.; Anderson, E. K.; Eklund, G.; Kristiansson, M. K.; Kamińska, M.; de Ruette, N.; Blom, M.; Björkhage, M.; Källberg, A.; Löfgren, P.; Reinhed, P.; Rosén, S.; Simonsson, A.; Zettergren, H.; Schmidt, H. T.; Cederquist, H.

2018-03-01

A sputter ion source with a solid graphite target has been used to produce dianions with a focus on carbon cluster dianions, Cn2 -, with n = 7-24. Singly and doubly charged anions from the source were accelerated together to kinetic energies of 10 keV per atomic unit of charge and injected into one of the cryogenic (13 K) ion-beam storage rings of the Double ElectroStatic Ion Ring Experiment facility at Stockholm University. Spontaneous decay of internally hot Cn2 - dianions injected into the ring yielded Cn- anions with kinetic energies of 20 keV, which were counted with a microchannel plate detector. Mass spectra produced by scanning the magnetic field of a 90° analyzing magnet on the ion injection line reflect the production of internally hot C72 - - C242 - dianions with lifetimes in the range of tens of microseconds to milliseconds. In spite of the high sensitivity of this method, no conclusive evidence of C62 - was found while there was a clear C72 - signal with the expected isotopic distribution. This is consistent with earlier experimental studies and with theoretical predictions. An upper limit is deduced for a C62 - signal that is two orders-of-magnitude smaller than that for C72 -. In addition, CnO2- and CnCu2- dianions were detected.

A Penning sputter ion source with very low energy spread

NASA Astrophysics Data System (ADS)

Nouri, Z.; Li, R.; Holt, R. A.; Rosner, S. D.

2010-03-01

We have developed a version of the Frankfurt Penning ion source that produces ion beams with very low energy spreads of ˜3 eV, while operating in a new discharge mode characterized by very high pressure, low voltage, and high current. The extracted ions also comprise substantial metastable and doubly charged species. Detailed studies of the operating parameters of the source showed that careful adjustment of the magnetic field and gas pressure is critical to achieving optimum performance. We used a laser-fluorescence method of energy analysis to characterize the properties of the extracted ion beam with a resolving power of 1×10 4, and to measure the absolute ion beam energy to an accuracy of 4 eV in order to provide some insight into the distribution of plasma potential within the ion source. This characterization method is widely applicable to accelerator beams, though not universal. The low energy spread, coupled with the ability to produce intense ion beams from almost any gas or conducting solid, make this source very useful for high-resolution spectroscopic measurements on fast-ion beams.

Optical profile determining apparatus and associated methods including the use of a plurality of wavelengths in the reference beam and a plurality of wavelengths in a reflective transit beam

NASA Technical Reports Server (NTRS)

Montgomery, Robert M. (Inventor)

2006-01-01

An optical profile determining apparatus includes an optical detector and an optical source. The optical source generates a transmit beam including a plurality of wavelengths, and generates a reference beam including the plurality of wavelengths. Optical elements direct the transmit beam to a target, direct a resulting reflected transmit beam back from the target to the optical detector, and combine the reference beam with the reflected transmit beam so that a profile of the target is based upon fringe contrast produced by the plurality of wavelengths in the reference beam and the plurality of wavelengths in the reflected transmit beam.

Operating characteristics of a new ion source for KSTAR neutral beam injection system.

PubMed

Kim, Tae-Seong; Jeong, Seung Ho; Chang, Doo-Hee; Lee, Kwang Won; In, Sang-Ryul

2014-02-01

A new positive ion source for the Korea Superconducting Tokamak Advanced Research neutral beam injection (KSTAR NBI-1) system was designed, fabricated, and assembled in 2011. The characteristics of the arc discharge and beam extraction were investigated using hydrogen and helium gas to find the optimum operating parameters of the arc power, filament voltage, gas pressure, extracting voltage, accelerating voltage, and decelerating voltage at the neutral beam test stand at the Korea Atomic Energy Research Institute in 2012. Based on the optimum operating condition, the new ion source was then conditioned, and performance tests were primarily finished. The accelerator system with enlarged apertures can extract a maximum 65 A ion beam with a beam energy of 100 keV. The arc efficiency and optimum beam perveance, at which the beam divergence is at a minimum, are estimated to be 1.0 A/kW and 2.5 uP, respectively. The beam extraction tests show that the design goal of delivering a 2 MW deuterium neutral beam into the KSTAR Tokamak plasma is achievable.

Method to Detect the Cellular Source of Over-Activated NADPH Oxidases Using NAD(P)H Fluorescence Lifetime Imaging.

PubMed

Bremer, Daniel; Leben, Ruth; Mothes, Ronja; Radbruch, Helena; Niesner, Raluca

2017-04-03

Fluorescence-lifetime imaging microscopy (FLIM) is a technique to generate images, in which the contrast is obtained by the excited-state lifetime of fluorescent molecules instead of their intensity and emission spectrum. The ubiquitous coenzymes NADH and NADPH, hereafter NAD(P)H, in cells show a short fluorescence lifetime ≈400 psec in the free-state and a longer fluorescence lifetime when bound to enzymes. The fluorescence lifetime of NAD(P)H in this state depends on the binding-site on the specific enzyme. In the case of NADPH bound to members of the NADPH oxidases family we measured a fluorescence lifetime of 3650 psec as compared to enzymes typically active in cells, in which case fluorescence lifetimes of ∼2000 psec are measured. Here we present a robust protocol based on NAD(P)H fluorescence lifetime imaging in isolated cells to distinguish between normally active enzymes and NADPH oxidases, mainly responsible for oxidative stress. © 2017 by John Wiley & Sons, Inc. Copyright © 2017 John Wiley & Sons, Inc.

The rational design of a Au(I) precursor for focused electron beam induced deposition

PubMed Central

Marashdeh, Ali; Tiesma, Thiadrik; van Velzen, Niels J C; Harder, Sjoerd; Havenith, Remco W A; De Hosson, Jeff T M

2017-01-01

Au(I) complexes are studied as precursors for focused electron beam induced processing (FEBIP). FEBIP is an advanced direct-write technique for nanometer-scale chemical synthesis. The stability and volatility of the complexes are characterized to design an improved precursor for pure Au deposition. Aurophilic interactions are found to play a key role. The short lifetime of ClAuCO in vacuum is explained by strong, destabilizing Au–Au interactions in the solid phase. While aurophilic interactions do not affect the stability of ClAuPMe3, they leave the complex non-volatile. Comparison of crystal structures of ClAuPMe3 and MeAuPMe3 shows that Au–Au interactions are much weaker or partially even absent for the latter structure. This explains its high volatility. However, MeAuPMe3 dissociates unfavorably during FEBIP, making it an unsuitable precursor. The study shows that Me groups reduce aurophilic interactions, compared to Cl groups, which we attribute to electronic rather than steric effects. Therefore we propose MeAuCO as a potential FEBIP precursor. It is expected to have weak Au–Au interactions, making it volatile. It is stable enough to act as a volatile source for Au deposition, being stabilized by 6.5 kcal/mol. Finally, MeAuCO is likely to dissociate in a single step to pure Au. PMID:29354346

VizieR Online Data Catalog: AGB stars with GALEX observations (Montez+, 2017)

NASA Astrophysics Data System (ADS)

Montez, R.; Ramstedt, S.; Kastner, J. H.; Vlemmings, W.; Sanchez, E.

2018-01-01

Our sample of AGB stars is derived from numerous AGB samples found in the literature and was originally compiled by Ramstedt+ (2012A&A...543A.147R) to search for X-ray detections associated with AGB stars. The GALEX mission performed a two-band survey of the UV sky. Using a dichromatic beam splitter, GALEX simultaneously observed far-UV (FUV; λeff~1528Å; 1344-1786Å) and near-UV (NUV; λeff~2310Å; 1771-2831Å) in surveys with different depths. The spatial resolution is 4.3" in FUV and 5.3" in NUV. As described in further detail in Morrissey+ (2007ApJS..173..682M), spectroscopic observations place a grism into the converging beam of the telescope to simultaneously disperse all sources onto the detector plane. According to Morrissey+ (2007), the usable ranges of the grism spectra are 1300-1820Å and 1820-3000Å in the FUV and NUV, with average resolutions of 8Å and 20Å, respectively. To supplement our study of the GALEX observations of AGB stars, we collected photometric data from across the electromagnetic spectrum for all the AGB stars considered using SIMBAD and VizieR tools. We aslo collected AAVSO light curves that span the GALEX mission lifetime (2003 May 28 to 2013 June 28) from the AAVSO International Database. (3 data files).

The rational design of a Au(I) precursor for focused electron beam induced deposition.

PubMed

Marashdeh, Ali; Tiesma, Thiadrik; van Velzen, Niels J C; Harder, Sjoerd; Havenith, Remco W A; De Hosson, Jeff T M; van Dorp, Willem F

2017-01-01

Au(I) complexes are studied as precursors for focused electron beam induced processing (FEBIP). FEBIP is an advanced direct-write technique for nanometer-scale chemical synthesis. The stability and volatility of the complexes are characterized to design an improved precursor for pure Au deposition. Aurophilic interactions are found to play a key role. The short lifetime of ClAuCO in vacuum is explained by strong, destabilizing Au-Au interactions in the solid phase. While aurophilic interactions do not affect the stability of ClAuPMe 3 , they leave the complex non-volatile. Comparison of crystal structures of ClAuPMe 3 and MeAuPMe 3 shows that Au-Au interactions are much weaker or partially even absent for the latter structure. This explains its high volatility. However, MeAuPMe 3 dissociates unfavorably during FEBIP, making it an unsuitable precursor. The study shows that Me groups reduce aurophilic interactions, compared to Cl groups, which we attribute to electronic rather than steric effects. Therefore we propose MeAuCO as a potential FEBIP precursor. It is expected to have weak Au-Au interactions, making it volatile. It is stable enough to act as a volatile source for Au deposition, being stabilized by 6.5 kcal/mol. Finally, MeAuCO is likely to dissociate in a single step to pure Au.

Modeling of a Compact Terahertz Source based on the Two-Stream Instability

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

Svimonishvili, Tengiz

2016-05-17

THz radiation straddles the microwave and infrared bands of the electromagnetic spectrum, thus combining the penetrating power of lower-frequency waves and imaging capabilities of higher-energy infrared radiation. THz radiation is employed in various elds such as cancer research, biology, agriculture, homeland security, and environmental monitoring. Conventional vacuum electronic sources of THz radiation (e.g., fast- and slow-wave devices) either require very small structures or are bulky and expensive to operate. Optical sources necessitate cryogenic cooling and are presently capable of producing milliwatt levels of power at THz frequencies. We propose a millimeter and sub-millimeter wave source based on a well-known phenomenonmore » called the two-stream instability. The two-beam source relies on lowenergy and low-current electron beams for operation. Also, it is compact, simple in design, and does not contain expensive parts that require complex machining and precise alignment. In this dissertation, we perform 2-D particle-in-cell (PIC) simulations of the interaction region of the two-beam source. The interaction region consists of a beam pipe of radius ra and two electron beams of radius rb co-propagating and interacting inside the pipe. The simulations involve the interaction of unmodulated (no initial energy modulation) and modulated (energy-modulated, seeded at a given frequency) electron beams. In addition, both cold (monoenergetic) and warm (Gaussian) beams are treated.« less

Negative ion beam injection apparatus with magnetic shield and electron removal means

DOEpatents

Anderson, Oscar A.; Chan, Chun F.; Leung, Ka-Ngo

1994-01-01

A negative ion source is constructed to produce H.sup.- ions without using Cesium. A high percentage of secondary electrons that typically accompany the extracted H.sup.- are trapped and eliminated from the beam by permanent magnets in the initial stage of acceleration. Penetration of the magnetic field from the permanent magnets into the ion source is minimized. This reduces the destructive effect the magnetic field could have on negative ion production and extraction from the source. A beam expansion section in the extractor results in a strongly converged final beam.

High throughput laser processing

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

Harley, Gabriel; Pass, Thomas; Cousins, Peter John

A solar cell is formed using a solar cell ablation system. The ablation system includes a single laser source and several laser scanners. The laser scanners include a master laser scanner, with the rest of the laser scanners being slaved to the master laser scanner. A laser beam from the laser source is split into several laser beams, with the laser beams being scanned onto corresponding wafers using the laser scanners in accordance with one or more patterns. The laser beams may be scanned on the wafers using the same or different power levels of the laser source.

Inverse compton light source: a compact design proposal

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

Deitrick, Kirsten Elizabeth

In the last decade, there has been an increasing demand for a compact Inverse Compton Light Source (ICLS) which is capable of producing high-quality X-rays by colliding an electron beam and a high-quality laser. It is only in recent years when both SRF and laser technology have advanced enough that compact sources can approach the quality found at large installations such as the Advanced Photon Source at Argonne National Laboratory. Previously, X-ray sources were either high flux and brilliance at a large facility or many orders of magnitude lesser when produced by a bremsstrahlung source. A recent compact source wasmore » constructed by Lyncean Technologies using a storage ring to produce the electron beam used to scatter the incident laser beam. By instead using a linear accelerator system for the electron beam, a significant increase in X-ray beam quality is possible, though even subsequent designs also featuring a storage ring offer improvement. Preceding the linear accelerator with an SRF reentrant gun allows for an extremely small transverse emittance, increasing the brilliance of the resulting X-ray source. In order to achieve sufficiently small emittances, optimization was done regarding both the geometry of the gun and the initial electron bunch distribution produced off the cathode. Using double-spoke SRF cavities to comprise the linear accelerator allows for an electron beam of reasonable size to be focused at the interaction point, while preserving the low emittance that was generated by the gun. An aggressive final focusing section following the electron beam's exit from the accelerator produces the small spot size at the interaction point which results in an X-ray beam of high flux and brilliance. Taking all of these advancements together, a world class compact X-ray source has been designed. It is anticipated that this source would far outperform the conventional bremsstrahlung and many other compact ICLSs, while coming closer to performing at the levels found at large facilities than ever before. The design process, including the development between subsequent iterations, is presented here in detail, with the simulation results for this groundbreaking X-ray source.« less

Concept of a tunable source of coherent THz radiation driven by a plasma modulated electron beam

NASA Astrophysics Data System (ADS)

Zhang, H.; Konoplev, I. V.; Doucas, G.; Smith, J.

2018-04-01

We have carried out numerical studies which consider the modulation of a picosecond long relativistic electron beam in a plasma channel and the generation of a micro-bunched train. The subsequent propagation of the micro-bunched beam in the vacuum area was also investigated. The same numerical model was then used to simulate the radiation arising from the interaction of the micro-bunched beam with a metallic grating. The dependence of the radiation spectrum on the parameters of the micro-bunched beam has been studied and the tunability of the radiation by the variation of the micro-bunch spacing has been demonstrated. The micro-bunch spacing can be changed easily by altering the plasma density without changing the beam energy or current. Using the results of these studies, we develop a conceptual design of a tunable source of coherent terahertz (THz) radiation driven by a plasma modulated beam. Such a source would be a potential and useful alternative to conventional vacuum THz tubes and THz free-electron laser sources.

Improved alternating gradient transport and focusing of neutral molecules

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

Kalnins, Juris; Lambertson, Glen; Gould, Harvey

2001-12-02

Polar molecules, in strong-field seeking states, can be transported and focused by an alternating sequence of electric field gradients that focus in one transverse direction while defocusing in the other. We show by calculation and numerical simulation, how one may greatly improve the alternating gradient transport and focusing of molecules. We use a new optimized multipole lens design, a FODO lattice beam transport line, and lenses to match the beam transport line to the beam source and the final focus. We derive analytic expressions for the potentials, fields, and gradients that may be used to design these lenses. We describemore » a simple lens optimization procedure and derive the equations of motion for tracking molecules through a beam transport line. As an example, we model a straight beamline that transports a 560 m/s jet-source beam of methyl fluoride molecules 15 m from its source and focuses it to 2 mm diameter. We calculate the beam transport line acceptance and transmission, for a beam with velocity spread, and estimate the transmitted intensity for specified source conditions. Possible applications are discussed.« less

Optimization of ion-atomic beam source for deposition of GaN ultrathin films.

PubMed

Mach, Jindřich; Šamořil, Tomáš; Kolíbal, Miroslav; Zlámal, Jakub; Voborny, Stanislav; Bartošík, Miroslav; Šikola, Tomáš

2014-08-01

We describe the optimization and application of an ion-atomic beam source for ion-beam-assisted deposition of ultrathin films in ultrahigh vacuum. The device combines an effusion cell and electron-impact ion beam source to produce ultra-low energy (20-200 eV) ion beams and thermal atomic beams simultaneously. The source was equipped with a focusing system of electrostatic electrodes increasing the maximum nitrogen ion current density in the beam of a diameter of ≈15 mm by one order of magnitude (j ≈ 1000 nA/cm(2)). Hence, a successful growth of GaN ultrathin films on Si(111) 7 × 7 substrate surfaces at reasonable times and temperatures significantly lower (RT, 300 °C) than in conventional metalorganic chemical vapor deposition technologies (≈1000 °C) was achieved. The chemical composition of these films was characterized in situ by X-ray Photoelectron Spectroscopy and morphology ex situ using Scanning Electron Microscopy. It has been shown that the morphology of GaN layers strongly depends on the relative Ga-N bond concentration in the layers.

Physics and applications of positron beams in an integrated PET/MR.

PubMed

Watson, Charles C; Eriksson, Lars; Kolb, Armin

2013-02-07

In PET/MR systems having the PET component within the uniform magnetic field interior to the MR, positron beams can be injected into the PET field of view (FOV) from unshielded emission sources external to it, as a consequence of the action of the Lorentz force on the transverse components of the positron's velocity. Such beams may be as small as a few millimeters in diameter, but extend 50 cm or more axially without appreciable divergence. Larger beams form 'phantoms' of annihilations in air that can be easily imaged, and that are essentially free of γ-ray attenuation and scatter effects, providing a unique tool for characterizing PET systems and reconstruction algorithms. Thin targets intersecting these beams can produce intense annihilation sources having the thickness of a sheet of paper, which are very useful for high resolution measurements, and difficult to achieve with conventional sources. Targeted beams can provide other point, line and surface sources for various applications, all without the need to have radioactivity within the FOV. In this paper we discuss the physical characteristics of positron beams in air and present examples of their applications.

Negative ion source with low temperature transverse divergence optical system

DOEpatents

Whealton, John H.; Stirling, William L.

1986-01-01

A negative ion source is provided which has extremely low transverse divergence as a result of a unique ion focusing system in which the focal line of an ion beam emanating from an elongated, concave converter surface is outside of the ion exit slit of the source and the path of the exiting ions. The beam source operates with a minimum ion temperature which makes possible a sharply focused (extremely low transverse divergence) ribbon like negative ion beam.

Negative ion source with low temperature transverse divergence optical system

DOEpatents

Whealton, J.H.; Stirling, W.L.

1985-03-04

A negative ion source is provided which has extremely low transverse divergence as a result of a unique ion focusing system in which the focal line of an ion beam emanating from an elongated, concave converter surface is outside of the ion exit slit of the source and the path of the exiting ions. The beam source operates with a minimum ion temperature which makes possible a sharply focused (extremely low transverse divergence) ribbon like negative ion beam.

Measurements of beam halo diffusion and population density in the Tevatron and in the Large Hadron Collider

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

Stancari, Giulio

2015-03-01

Halo dynamics influences global accelerator performance: beam lifetimes, emittance growth, dynamic aperture, and collimation efficiency. Halo monitoring and control are also critical for the operation of high-power machines. For instance, in the high-luminosity upgrade of the LHC, the energy stored in the beam tails may reach several megajoules. Fast losses can result in superconducting magnet quenches, magnet damage, or even collimator deformation. The need arises to measure the beam halo and to remove it at controllable rates. In the Tevatron and in the LHC, halo population densities and diffusivities were measured with collimator scans by observing the time evolution ofmore » losses following small inward or outward collimator steps, under different experimental conditions: with single beams and in collision, and, in the case of the Tevatron, with a hollow electron lens acting on a subset of bunches. After the LHC resumes operations, it is planned to compare measured diffusivities with the known strength of transverse damper excitations. New proposals for nondestructive halo population density measurements are also briefly discussed.« less

High-power and 2.5 kW advanced-technology ion thruster

NASA Technical Reports Server (NTRS)

Poeschel, R. L.

1977-01-01

Investigations for improving ion thruster components in the 30 cm engineering model thruster (EMT) resulted in the demonstration of useful techniques for grid short removal and discharge chamber erosion monitoring, establishment of relationships between double ion production and thruster operating parameters, verification of satisfactory specifications on porous tungsten vaporizer material and barium impregnated porous tungsten inserts, demonstration of a new hollow cathode configuration, and specification of magnetic circuit requirements for reproducing desired magnetic mappings. The capacity of a 30 cm EMT to operate at higher beam voltages and currents (higher power) was determined. Operation at 2 A beam current and higher beam voltage is shown to be essentially equivalent to operation at 1.1 kV with regard to efficiency, lifetime and operating conditions. The only additional requirement is an improvement in high voltage insulation and propellant isolator capacity. Operation at minimum voltage and higher beam currents is shown to increase thruster discharge chamber erosion in proportion to beam current. Studies to find alternatives to molybdenum for manufacturing ion optics grids are also reported.

Boron ion beam generation utilizing lanthanum hexaboride cathodes: Comparison of vacuum arc and planar magnetron glow

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

Nikolaev, A. G.; Vizir, A. V.; Yushkov, G. Yu., E-mail: gyushkov@mail.ru

Boron ion beams are widely used for semiconductor ion implantation and for surface modification for improving the operating parameters and increasing the lifetime of machine parts and tools. For the latter application, the purity requirements of boron ion beams are not as stringent as for semiconductor technology, and a composite cathode of lanthanum hexaboride may be suitable for the production of boron ions. We have explored the use of two different approaches to boron plasma production: vacuum arc and planar high power impulse magnetron in self-sputtering mode. For the arc discharge, the boron plasma is generated at cathode spots, whereasmore » for the magnetron discharge, the main process is sputtering of cathode material. We present here the results of comparative test experiments for both kinds of discharge, aimed at determining the optimal discharge parameters for maximum yield of boron ions. For both discharges, the extracted ion beam current reaches hundreds of milliamps and the fraction of boron ions in the total extracted ion beam is as high as 80%.« less

Test of the SO(6) selection rule in 196Pt using cold-neutron capture

NASA Astrophysics Data System (ADS)

Jolie, J.; Régis, J.-M.; Wilmsen, D.; Saed-Samii, N.; Pfeiffer, M.; Warr, N.; Blanc, A.; Jentschel, M.; Köster, U.; Mutti, P.; Soldner, T.; Simpson, G. S.; De France, G.; Urban, W.; Drouet, F.; Vancraeyenest, A.; Bruce, A. M.; Roberts, O. J.; Fraile, L. M.; Paziy, V.; Ignatov, A.; Kröll, Th.; Ivanova, D.; Kisyov, S.; Lalkovski, S.; Podolyak, Zs.; Regan, P. H.; Wilson, E.; Korten, W.; Ur, C. A.; Lica, R.; Marginean, N.

2015-02-01

At the PF1B cold-neutron beam line of the Institut Laue Langevin, the EXILL&FATIMA array, consisting of EXOGAM Ge detectors and fast LaBr3(Ce) scintillators, was used to perform fast electronic timing measurements after the 195Pt(n, γ) reaction using a highly collimated cold-neutron beam. An upper lifetime limit was obtained for the third 0+ state in 196Pt. As this state is the lowest state of the σ = N - 2 set of SO(6) states, the selection rule which forbids E2 transitions to the lower lying σ = N could be tested.

Abort Gap Cleaning for LHC Run 2

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

Uythoven, Jan; Boccardi, Andrea; Bravin, Enrico

2014-07-01

To minimize the beam losses at the moment of an LHC beam dump the 3 μs long abort gap should contain as few particles as possible. Its population can be minimised by abort gap cleaning using the LHC transverse damper system. The LHC Run 1 experience is briefly recalled; changes foreseen for the LHC Run 2 are presented. They include improvements in the observation of the abort gap population and the mechanism to decide if cleaning is required, changes to the hardware of the transverse dampers to reduce the detrimental effect on the luminosity lifetime and proposed changes to themore » applied cleaning algorithms.« less

Toward polarized antiprotons: Machine development for spin-filtering experiments

NASA Astrophysics Data System (ADS)

Weidemann, C.; Rathmann, F.; Stein, H. J.; Lorentz, B.; Bagdasarian, Z.; Barion, L.; Barsov, S.; Bechstedt, U.; Bertelli, S.; Chiladze, D.; Ciullo, G.; Contalbrigo, M.; Dymov, S.; Engels, R.; Gaisser, M.; Gebel, R.; Goslawski, P.; Grigoriev, K.; Guidoboni, G.; Kacharava, A.; Kamerdzhiev, V.; Khoukaz, A.; Kulikov, A.; Lehrach, A.; Lenisa, P.; Lomidze, N.; Macharashvili, G.; Maier, R.; Martin, S.; Mchedlishvili, D.; Meyer, H. O.; Merzliakov, S.; Mielke, M.; Mikirtychiants, M.; Mikirtychiants, S.; Nass, A.; Nikolaev, N. N.; Oellers, D.; Papenbrock, M.; Pesce, A.; Prasuhn, D.; Retzlaff, M.; Schleichert, R.; Schröer, D.; Seyfarth, H.; Soltner, H.; Statera, M.; Steffens, E.; Stockhorst, H.; Ströher, H.; Tabidze, M.; Tagliente, G.; Engblom, P. Thörngren; Trusov, S.; Valdau, Yu.; Vasiliev, A.; Wüstner, P.

2015-02-01

The paper describes the commissioning of the experimental equipment and the machine studies required for the first spin-filtering experiment with protons at a beam kinetic energy of 49.3 MeV in COSY. The implementation of a low-β insertion made it possible to achieve beam lifetimes of τb=8000 s in the presence of a dense polarized hydrogen storage-cell target of areal density dt=(5.5 ±0.2 )×1 013 atoms /cm2 . The developed techniques can be directly applied to antiproton machines and allow the determination of the spin-dependent p ¯p cross sections via spin filtering.

High-flux beam source of fast neutral helium.

PubMed

Fahey, D W; Schearer, L D; Parks, W F

1978-04-01

A high-flux beam source of fast neutral helium has been constructed by extending the designs of previous authors. The source is a dc or pulsed electric discharge in an expanding gas nozzle. The beam produced has a flux on the order of 10(15) atoms/s sr and a mean velocity on the order of 10(7) cm/s. The composition of the beam has been determined by the use of particle detectors and by the observation of the excitation of certain target gases. An upper bound of 3.7 x 10(-5) has been estimated for the He(2(3)S(1))/He((1)S(0))beam density ratio and a value of 0.2 found for the He(+)/He(1(1)S(0)) beam density ratio.

Compensating the electron beam energy spread by the natural transverse gradient of laser undulator in all-optical x-ray light sources.

PubMed

Zhang, Tong; Feng, Chao; Deng, Haixiao; Wang, Dong; Dai, Zhimin; Zhao, Zhentang

2014-06-02

All-optical ideas provide a potential to dramatically cut off the size and cost of x-ray light sources to the university-laboratory scale, with the combination of the laser-plasma accelerator and the laser undulator. However, the large longitudinal energy spread of the electron beam from laser-plasma accelerator may hinder the way to high brightness of these all-optical light sources. In this paper, the beam energy spread effect is proposed to be significantly compensated by the natural transverse gradient of a laser undulator when properly transverse-dispersing the electron beam. Theoretical analysis and numerical simulations on conventional laser-Compton scattering sources and high-gain all-optical x-ray free-electron lasers with the electron beams from laser-plasma accelerators are presented.

Electrical shielding box measurement of the negative hydrogen beam from Penning ion gauge ion source.

PubMed

Wang, T; Yang, Z; Dong, P; long, J D; He, X Z; Wang, X; Zhang, K Z; Zhang, L W

2012-06-01

The cold-cathode Penning ion gauge (PIG) type ion source has been used for generation of negative hydrogen (H(-)) ions as the internal ion source of a compact cyclotron. A novel method called electrical shielding box dc beam measurement is described in this paper, and the beam intensity was measured under dc extraction inside an electrical shielding box. The results of the trajectory simulation and dc H(-) beam extraction measurement were presented. The effect of gas flow rate, magnetic field strength, arc current, and extraction voltage were also discussed. In conclusion, the dc H(-) beam current of about 4 mA from the PIG ion source with the puller voltage of 40 kV and arc current of 1.31 A was extrapolated from the measurement at low extraction dc voltages.

Rapid Optical Shutter, Chopper, Modulator and Deflector

NASA Technical Reports Server (NTRS)

Danehy, Paul M. (Inventor)

2017-01-01

An optical device with a light source and a detector is provided. A digital micromirror device positioned between the detector and the light source may deflect light beams projected from the light source. An aperture in front of the detector may block an incoming light beam from the detector when the incoming light beam is incident on the detector outside of a passable incident range and including an aperture opening configured to pass the incoming light beam to the detector when the incoming light beam is incident on the detector within a passable incident range. The digital micromirror device may rotate between a first position causing the light beam to pass through the aperture opening and a second position causing the light beam to be blocked by the aperture. The optical device may be configured to operate as a shutter, chopper, modulator and/or deflector.

Bessel-Gauss beams as rigorous solutions of the Helmholtz equation.

PubMed

April, Alexandre

2011-10-01

The study of the nonparaxial propagation of optical beams has received considerable attention. In particular, the so-called complex-source/sink model can be used to describe strongly focused beams near the beam waist, but this method has not yet been applied to the Bessel-Gauss (BG) beam. In this paper, the complex-source/sink solution for the nonparaxial BG beam is expressed as a superposition of nonparaxial elegant Laguerre-Gaussian beams. This provides a direct way to write the explicit expression for a tightly focused BG beam that is an exact solution of the Helmholtz equation. It reduces correctly to the paraxial BG beam, the nonparaxial Gaussian beam, and the Bessel beam in the appropriate limits. The analytical expression can be used to calculate the field of a BG beam near its waist, and it may be useful in investigating the features of BG beams under tight focusing conditions.

Design study of primary ion provider for relativistic heavy ion collider electron beam ion source.

PubMed

Kondo, K; Kanesue, T; Tamura, J; Okamura, M

2010-02-01

Brookhaven National Laboratory has developed the new preinjector system, electron beam ion source (EBIS) for relativistic heavy ion collider (RHIC) and National Aeronautics and Space Administration Space Radiation Laboratory. Design of primary ion provider is an essential problem since it is required to supply beams with different ion species to multiple users simultaneously. The laser ion source with a defocused laser can provide a low charge state and low emittance ion beam, and is a candidate for the primary ion source for RHIC-EBIS. We show a suitable design with appropriate drift length and solenoid, which helps to keep sufficient total charge number with longer pulse length. The whole design of primary ion source, as well as optics arrangement, solid targets configuration and heating about target, is presented.

Beam commission of the high intensity proton source developed at INFN-LNS for the European Spallation Source

NASA Astrophysics Data System (ADS)

Neri, L.; Celona, L.; Gammino, S.; Miraglia, A.; Leonardi, O.; Castro, G.; Torrisi, G.; Mascali, D.; Mazzaglia, M.; Allegra, L.; Amato, A.; Calabrese, G.; Caruso, A.; Chines, F.; Gallo, G.; Longhitano, A.; Manno, G.; Marletta, S.; Maugeri, A.; Passarello, S.; Pastore, G.; Seminara, A.; Spartà, A.; Vinciguerra, S.

2017-07-01

At the Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali del Sud (INFN-LNS) the beam commissioning of the high intensity Proton Source for the European Spallation Source (PS-ESS) started in November 2016. Beam stability at high current intensity is one of the most important parameter for the first steps of the ongoing commissioning. Promising results were obtained since the first source start with a 6 mm diameter extraction hole. The increase of the extraction hole to 8 mm allowed improving PS-ESS performances and obtaining the values required by the ESS accelerator. In this work, extracted beam current characteristics together with Doppler shift and emittance measurements are presented, as well as the description of the next phases before the installation at ESS in Lund.

Compact Gamma-Beam Source for Nuclear Security Technologies

NASA Astrophysics Data System (ADS)

Gladkikh, P.; Urakawa, J.

2015-10-01

A compact gamma-beam source dedicated to the development of the nuclear security technologies by use of the nuclear resonance fluorescence is described. Besides, such source is a very promising tool for novel technologies of the express cargoes inspection to prevent nuclear terrorism. Gamma-beam with the quanta energies from 0.3MeV to 7.2MeV is generated in the Compton scattering of the "green" laser photons on the electron beam with energies from 90MeV to 430MeV. The characteristic property of the proposed gammabeam source is a narrow spectrum (less than 1%) at high average gamma-yield (of 1013γ/s) due to special operation mode.

Modeling of an Adjustable Beam Solid State Light Project

NASA Technical Reports Server (NTRS)

Clark, Toni

2015-01-01

This proposal is for the development of a computational model of a prototype variable beam light source using optical modeling software, Zemax Optics Studio. The variable beam light source would be designed to generate flood, spot, and directional beam patterns, while maintaining the same average power usage. The optical model would demonstrate the possibility of such a light source and its ability to address several issues: commonality of design, human task variability, and light source design process improvements. An adaptive lighting solution that utilizes the same electronics footprint and power constraints while addressing variability of lighting needed for the range of exploration tasks can save costs and allow for the development of common avionics for lighting controls.

A Compact, High-Flux Cold Atom Beam Source

NASA Technical Reports Server (NTRS)

Kellogg, James R.; Kohel, James M.; Thompson, Robert J.; Aveline, David C.; Yu, Nan; Schlippert, Dennis

2012-01-01

The performance of cold atom experiments relying on three-dimensional magneto-optical trap techniques can be greatly enhanced by employing a highflux cold atom beam to obtain high atom loading rates while maintaining low background pressures in the UHV MOT (ultra-high vacuum magneto-optical trap) regions. Several techniques exist for generating slow beams of cold atoms. However, one of the technically simplest approaches is a two-dimensional (2D) MOT. Such an atom source typically employs at least two orthogonal trapping beams, plus an additional longitudinal "push" beam to yield maximum atomic flux. A 2D atom source was created with angled trapping collimators that not only traps atoms in two orthogonal directions, but also provides a longitudinal pushing component that eliminates the need for an additional push beam. This development reduces the overall package size, which in turn, makes the 2D trap simpler, and requires less total optical power. The atom source is more compact than a previously published effort, and has greater than an order of magnitude improved loading performance.

Photoacoustic effect generated by moving optical sources: Motion in one dimension

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

Bai, Wenyu; Diebold, Gerald J.

2016-03-28

Although the photoacoustic effect is typically generated by pulsed or amplitude modulated optical beams, it is clear from examination of the wave equation for pressure that motion of an optical source in space will result in the production of sound as well. Here, the properties of the photoacoustic effect generated by moving sources in one dimension are investigated. The cases of a moving Gaussian beam, an oscillating delta function source, and an accelerating Gaussian optical sources are reported. The salient feature of one-dimensional sources in the linear acoustic limit is that the amplitude of the beam increases in time withoutmore » bound.« less

Laser ion source for high brightness heavy ion beam

DOE PAGES

Okamura, M.

2016-09-01

A laser ion source is known as a high current high charge state heavy ion source. But, we place great emphasis on the capability to realize a high brightness ion source. A laser ion source has a pinpoint small volume where materials are ionized and can achieve quite uniform low temperature ion beam. Those features may enable us to realize very small emittance beams. Furthermore, a low charge state high brightness laser ion source was successfully commissioned in Brookhaven National Laboratory in 2014. Now most of all the solid based heavy ions are being provided from the laser ion sourcemore » for regular operation.« less

Application of complex geometrical optics to determination of thermal, transport, and optical parameters of thin films by the photothermal beam deflection technique.

PubMed

Korte, Dorota; Franko, Mladen

2015-01-01

In this work, complex geometrical optics is, for what we believe is the first time, applied instead of geometrical or wave optics to describe the probe beam interaction with the field of the thermal wave in photothermal beam deflection (photothermal deflection spectroscopy) experiments on thin films. On the basis of this approach the thermal (thermal diffusivity and conductivity), optical (energy band gap), and transport (carrier lifetime) parameters of the semiconductor thin films (pure TiO2, N- and C-doped TiO2, or TiO2/SiO2 composites deposited on a glass or aluminum support) were determined with better accuracy and simultaneously during one measurement. The results are in good agreement with results obtained by the use of other methods and reported in the literature.

Review of the High Performance Antiproton Trap (HiPAT) Experiment

NASA Technical Reports Server (NTRS)

Martin, James J.; Lewis, Raymond A.; Pearson, J. Boise; Sims, W. Herb; Chakrabarti, Suman; Fant, Wallace E.; McDonald, Stan

2003-01-01

Many space propulsion concepts exist that use matter-antimatter reactions. Current antiproton production rates are enough to conduct proof-of-principle evaluation of these concepts. One enabling technology for such experiments is portable storage of low energy antiprotons, to transport antiprotons to experimental facilities. To address this need, HiPAT is being developed, with a design goal of containing 10(exp 12) particles for up to 18 days. HiPAT is a Penning-Malmberg trap with a 4 Tesla superconductor, 20kV electrodes, radio frequency (RF) network, and 10(exp -13) Torr vacuum. 'Normal' matter is being used to evaluate the system. An electron beam ionizes background gas in situ, and particle beams are captured dynamically. The experiment examines ion storage lifetimes, RF plasma diagnostics, charge exchange with background gases, and dynamic ion beam capture.

Search for unbound nuclides and beam/fragment optics with the MoNA/LISA segmented target at NSCL

NASA Astrophysics Data System (ADS)

Gueye, Paul; Frank, Nathan; Thoennessen, Michael; Redpath, Thomas; MoNA Collaboration

2017-09-01

A multi-layered Si/Be segmented target consisting of three 700 mg/cm2 thick Be9 slabs and four 140 microns Si detectors was used by the MoNA Collaboration at the National Superconducting Cyclotron Laboratory of Michigan State University to study the O26 lifetime. This target provides unprecedented information on the incident beams and fragments (energy loss and position), thus allowing for better determination of the incident and outgoing energies and momenta of the detected particles compare to previous experiments conducted at this facility. With the availability of a newly developed Geant4 Monte Carlo simulation of the full N2 vault, we will present and discuss the performances of this target. Search for unbound nuclides and beam/fragment optics with the MoNA/LISA segmented target at NSCL.

Continuous-wave organic dye lasers and methods

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

Shapira, Ofer; Chua, Song-Liang; Zhen, Bo

2014-09-16

An organic dye laser produces a continuous-wave (cw) output without any moving parts (e.g., without using flowing dye streams or spinning discs of solid-state dye media to prevent photobleaching) and with a pump beam that is stationary with respect to the organic dye medium. The laser's resonant cavity, organic dye medium, and pump beam are configured to excite a lasing transition over a time scale longer than the associated decay lifetimes in the organic dye medium without photobleaching the organic dye medium. Because the organic dye medium does not photobleach when operating in this manner, it may be pumped continuouslymore » so as to emit a cw output beam. In some examples, operation in this manner lowers the lasing threshold (e.g., to only a few Watts per square centimeter), thereby facilitating electrical pumping for cw operation.« less

Gamma-ray Transition Matrix Elements in ^21Na: First TIGRESS Radioactive Beam Experiment

NASA Astrophysics Data System (ADS)

Hackman, Greg

2007-04-01

Modern shell model calculations should be expected to reliably reproduce the properties of the deformed five-particle nucleus ^21Na. However the lowest-lying B(E2) value deduced from lifetime and mixing ratio measurements disagrees with models by an unacceptably large factor of two. To measure the B(E2) values directly, a beam of ^21Na at 1.7 MeV/u from the TRIUMF ISAC facility was directed upon a 0.5 mg/cm^2 ^natTi target. Gamma-ray yield in coincidence with inelastically scattered heavy ions was measured with two TIGRESS high energy- and position-resolution germanium detector units and the BAMBINO highly segmented silicon detector system. The result resolves the discrepancy between the shell model and prior measurements. This represents the first radioactive in-beam experiment with TIGRESS.

Analysis of spectra of 3s-3p and 3p-3d transitions of highly-charged copper ions

NASA Astrophysics Data System (ADS)

Su, M. G.; Min, Q.; He, S. Q.; Wu, L.; Sun, R.; Ding, X. B.; Sun, D. X.

2017-08-01

Beam-foil excited spectra in the range of 160-360 Å from highly charged copper ions were identified with the aid of the National Institute of Standards and Technology Atomic Spectra Database and theoretical calculations with Cowan and Flexible Atomic Code (FAC) calculations. Spectra arising from 3s-3p and 3p-3d transitions of Cu13+-Cu22+ ions were considered. The ion fraction at an ion beam energy of 110 MeV was estimated from the equilibrium charge distribution of the fast ion beams after passing through the solid. The corresponding simulated spectra were in good agreement with the experimental result. Our Cowan and FAC calculation results should be useful for further spectral identification and lifetime measurements of highly charged copper ions.

rf improvements for Spallation Neutron Source H- ion sourcea)

NASA Astrophysics Data System (ADS)

Kang, Y. W.; Fuja, R.; Goulding, R. H.; Hardek, T.; Lee, S.-W.; McCarthy, M. P.; Piller, M. C.; Shin, K.; Stockli, M. P.; Welton, R. F.

2010-02-01

The Spallation Neutron Source at Oak Ridge National Laboratory is ramping up the accelerated proton beam power to 1.4 MW and just reached 1 MW. The rf-driven multicusp ion source that originates from the Lawrence Berkeley National Laboratory has been delivering ˜38 mA H- beam in the linac at 60 Hz, 0.9 ms. To improve availability, a rf-driven external antenna multicusp ion source with a water-cooled ceramic aluminum nitride (AlN) plasma chamber is developed. Computer modeling and simulations have been made to analyze and optimize the rf performance of the new ion source. Operational statistics and test runs with up to 56 mA medium energy beam transport beam current identify the 2 MHz rf system as a limiting factor in the system availability and beam production. Plasma ignition system is under development by using a separate 13 MHz system. To improve the availability of the rf power system with easier maintenance, we tested a 70 kV isolation transformer for the 80 kW, 6% duty cycle 2 MHz amplifier to power the ion source from a grounded solid-state amplifier.

Long-range transport of black carbon to the Pacific Ocean and its dependence on aging timescale

NASA Astrophysics Data System (ADS)

Zhang, J.; Liu, J.; Tao, S.; Ban-Weiss, G. A.

2015-06-01

Improving the ability of global models to predict concentrations of black carbon (BC) over the Pacific Ocean is essential to evaluate the impact of BC on marine climate. In this study, we tag BC tracers from 13 source regions around the globe in a global chemical transport model MOZART-4. Numerous sensitivity simulations are carried out varying the aging timescale of BC emitted from each source region. The aging timescale for each source region is optimized by minimizing errors in vertical profiles of BC mass mixing ratios between simulations and HIAPER Pole-to-Pole Observations (HIPPO). For most HIPPO deployments, in the Northern Hemisphere, optimized aging timescales are less than half a day for BC emitted from tropical and mid-latitude source regions, and about 1 week for BC emitted from high latitude regions in all seasons except summer. We find that East Asian emissions contribute most to the BC loading over the North Pacific, while South American, African and Australian emissions dominate BC loadings over the South Pacific. Dominant source regions contributing to BC loadings in other parts of the globe are also assessed. The lifetime of BC originating from East Asia (i.e., the world's largest BC emitter) is found to be only 2.2 days, much shorter than the global average lifetime of 4.9 days, making East Asia's contribution to global burden only 36 % of BC from the second largest emitter, Africa. Thus, evaluating only relative emission rates without accounting for differences in aging timescales and deposition rates is not predictive of the contribution of a given source region to climate impacts. Our simulations indicate that lifetime of BC increases nearly linearly with aging timescale for all source regions. When aging rate is fast, the lifetime of BC is largely determined by factors that control local deposition rates (e.g. precipitation). The sensitivity of lifetime to aging timescale depends strongly on the initial hygroscopicity of freshly emitted BC. Our findings suggest that the aging timescale of BC varies significantly by region and season, and can strongly influence the contribution of source regions to BC burdens around the globe. Improving parameterizations of the aging process for BC is important for enhancing the predictive skill of air quality and climate models. Future observations that investigate the evolution of hygroscopicity of BC as it ages from different source regions to the remote atmosphere are urgently needed.

Long-range transport of black carbon to the Pacific Ocean and its dependence on aging timescale

NASA Astrophysics Data System (ADS)

Zhang, J.; Liu, J.; Tao, S.; Ban-Weiss, G. A.

2015-10-01

Improving the ability of global models to predict concentrations of black carbon (BC) over the Pacific Ocean is essential to evaluate the impact of BC on marine climate. In this study, we tag BC tracers from 13 source regions around the globe in a global chemical transport model, Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4). Numerous sensitivity simulations are carried out varying the aging timescale of BC emitted from each source region. The aging timescale for each source region is optimized by minimizing errors in vertical profiles of BC mass mixing ratios between simulations and HIAPER Pole-to-Pole Observations (HIPPO). For most HIPPO deployments, in the Northern Hemisphere, optimized aging timescales are less than half a day for BC emitted from tropical and midlatitude source regions and about 1 week for BC emitted from high-latitude regions in all seasons except summer. We find that East Asian emissions contribute most to the BC loading over the North Pacific, while South American, African and Australian emissions dominate BC loadings over the South Pacific. Dominant source regions contributing to BC loadings in other parts of the globe are also assessed. The lifetime of BC originating from East Asia (i.e., the world's largest BC emitter) is found to be only 2.2 days, much shorter than the global average lifetime of 4.9 days, making the contribution from East Asia to the global BC burden only 36 % of that from the second largest emitter, Africa. Thus, evaluating only relative emission rates without accounting for differences in aging timescales and deposition rates is not predictive of the contribution of a given source region to climate impacts. Our simulations indicate that the lifetime of BC increases nearly linearly with aging timescale for all source regions. When the aging rate is fast, the lifetime of BC is largely determined by factors that control local deposition rates (e.g., precipitation). The sensitivity of lifetime to aging timescale depends strongly on the initial hygroscopicity of freshly emitted BC. Our findings suggest that the aging timescale of BC varies significantly by region and season and can strongly influence the contribution of source regions to BC burdens around the globe. Therefore, improving parameterizations of the aging process for BC is important for enhancing the predictive skill of global models. Future observations that investigate the evolution of the hygroscopicity of BC as it ages from different source regions to the remote atmosphere are urgently needed.

Status of intense permanent magnet proton source for China-accelerator driven sub-critical system Linac.

PubMed

Wu, Q; Ma, H Y; Yang, Y; Sun, L T; Zhang, X Z; Zhang, Z M; Zhao, H Y; He, Y; Zhao, H W

2016-02-01

Two compact intense 2.45 GHz permanent magnet proton sources and their corresponding low energy beam transport (LEBT) system were developed successfully for China accelerator driven sub-critical system in 2014. Both the proton sources operate at 35 kV potential. The beams extracted from the ion source are transported by the LEBT, which is composed of two identical solenoids, to the 2.1 MeV Radio-Frequency Quadrupole (RFQ). In order to ensure the safety of the superconducting cavities during commissioning, an electrostatic-chopper has been designed and installed in the LEBT line that can chop the continuous wave beam into a pulsed one. The minimum width of the pulse is less than 10 μs and the fall/rise time of the chopper is about 20 ns. The performance of the proton source and the LEBT, such as beam current, beam profile, emittance and the impact to RFQ injection will be presented.

Status of intense permanent magnet proton source for China-accelerator driven sub-critical system Linac

NASA Astrophysics Data System (ADS)

Wu, Q.; Ma, H. Y.; Yang, Y.; Sun, L. T.; Zhang, X. Z.; Zhang, Z. M.; Zhao, H. Y.; He, Y.; Zhao, H. W.

2016-02-01

Two compact intense 2.45 GHz permanent magnet proton sources and their corresponding low energy beam transport (LEBT) system were developed successfully for China accelerator driven sub-critical system in 2014. Both the proton sources operate at 35 kV potential. The beams extracted from the ion source are transported by the LEBT, which is composed of two identical solenoids, to the 2.1 MeV Radio-Frequency Quadrupole (RFQ). In order to ensure the safety of the superconducting cavities during commissioning, an electrostatic-chopper has been designed and installed in the LEBT line that can chop the continuous wave beam into a pulsed one. The minimum width of the pulse is less than 10 μs and the fall/rise time of the chopper is about 20 ns. The performance of the proton source and the LEBT, such as beam current, beam profile, emittance and the impact to RFQ injection will be presented.

An all permanent magnet electron cyclotron resonance ion source for heavy ion therapy.

PubMed

Cao, Yun; Li, Jia Qing; Sun, Liang Ting; Zhang, Xue Zhen; Feng, Yu Cheng; Wang, Hui; Ma, Bao Hua; Li, Xi Xia

2014-02-01

A high charge state all permanent Electron Cyclotron Resonance ion source, Lanzhou All Permanent ECR ion source no. 3-LAPECR3, has been successfully built at IMP in 2012, which will serve as the ion injector of the Heavy Ion Medical Machine (HIMM) project. As a commercial device, LAPECR3 features a compact structure, small size, and low cost. According to HIMM scenario more than 100 eμA of C(5+) ion beam should be extracted from the ion source, and the beam emittance better than 75 π*mm*mrad. In recent commissioning, about 120 eμA of C(5+) ion beam was got when work gas was CH4 while about 262 eμA of C(5+) ion beam was obtained when work gas was C2H2 gas. The design and construction of the ion source and its low-energy transportation beam line, and the preliminary commissioning results will be presented in detail in this paper.

Thermocathode radio-frequency gun for the Budker Institute of Nuclear Physics free-electron laser

NASA Astrophysics Data System (ADS)

Volkov, V.; Getmanov, Ya.; Kenjebulatov, E.; Kolobanov, E.; Krutikhin, S.; Kurkin, G.; Ovchar, V.; Petrov, V. M.; Sedlyarov, I.

2016-12-01

A radio-frequency (RF) gun for a race-track microtron-recuperator injector driving the free-electron laser (FEL) (Budker Institute of Nuclear Physics) is being tested at a special stand. Electron bunches of the RF gun have an energy of up to 300 keV and a repetition rate of up to 90 MHz. The average electro-beam current can reach 100 mA in the continuous operation regime. The advantages of the new injector are as follows: long lifetime of the cathode for high average beam current; simple scheme of longitudinal beam bunching, which does not require an additional bunching resonator in the injector; absence of dark-current contamination of the injector beam; and comfortable RF gun operation due to the absence of a high potential of 300 kV at the cathode control circuits. In this study we describe the RF gun design, present the main characteristics of the injector with the RF gun, and give the results of testing.

Giant nonlinear interaction between two optical beams via a quantum dot embedded in a photonic wire

NASA Astrophysics Data System (ADS)

Nguyen, H. A.; Grange, T.; Reznychenko, B.; Yeo, I.; de Assis, P.-L.; Tumanov, D.; Fratini, F.; Malik, N. S.; Dupuy, E.; Gregersen, N.; Auffèves, A.; Gérard, J.-M.; Claudon, J.; Poizat, J.-Ph.

2018-05-01

Optical nonlinearities usually appear for large intensities, but discrete transitions allow for giant nonlinearities operating at the single-photon level. This has been demonstrated in the last decade for a single optical mode with cold atomic gases, or single two-level systems coupled to light via a tailored photonic environment. Here, we demonstrate a two-mode giant nonlinearity with a single semiconductor quantum dot (QD) embedded in a photonic wire antenna. We exploit two detuned optical transitions associated with the exciton-biexciton QD level scheme. Owing to the broadband waveguide antenna, the two transitions are efficiently interfaced with two free-space laser beams. The reflection of one laser beam is then controlled by the other beam, with a threshold power as low as 10 photons per exciton lifetime (1.6 nW ). Such a two-color nonlinearity opens appealing perspectives for the realization of ultralow-power logical gates and optical quantum gates, and could also be implemented in an integrated photonic circuit based on planar waveguides.

Magnetic Frequency Response of HL-LHC Beam Screens

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

Morrone, M.; Martino, M.; De Maria, R.

Magnetic fields used to control particle beams in accelerators are usually controlled by regulating the electrical current of the power converters. In order to minimize lifetime degradation and ultimately luminosity loss in circular colliders, current-noise is a highly critical figure of merit of power converters, in particular for magnets located in areas with high beta-function, like the High Luminosity Large Hadron Collider (HL-LHC) insertions. However, what is directly acting upon the beam is the magnetic field and not the current of the power converter, which undergoes several frequency-dependent transformations until the desired magnetic field, seen by the beam, is obtained.more » Beam screens are very rarely considered when assessing or specifying the noise figure of merit, but their magnetic frequency response is such that they realize relatively effective low pass filtering of the magnetic field produced by the system magnet-power converter. This work aims at filling this gap by quantifying the expected impact of different beam screen layouts for the most relevant HL-LHC insertion magnets. A welldefined post-processing technique is used to derive the frequency response of the different multipoles from multi-physics Finite Element Method (FEM) simulation results. In addition, a well approximated analytical formula for the low-frequency range of multi-layered beam screens is presented.« less

ECR Plasma Source for Heavy Ion Beam Charge Neutralization

NASA Astrophysics Data System (ADS)

Efthimion, P. C.; Gilson, E.; Grishman, L.; Kolchin, P.; Davidson, R. C.

2002-01-01

Highly ionized plasmas are being considered as a medium for charge neutralizing heavy ion beams in order to focus beyond the space-charge limit. Calculations suggest that plasma at a density of 1 - 100 times the ion beam density and at a length of approximately 0.1-2 m would be suitable for achieving a high level of charge neutralization. An ECR source has been built at the Princeton Plasma Physics Laboratory (PPPL) to support a joint Neutralized Transport Experiment (NTX) at the Lawrence Berkeley National Laboratory (LBNL) to study ion beam neutralization with plasma. The ECR source operates at 13.6 MHz and with solenoid magnetic fields of 1-10 gauss. The goal is to operate the source at pressures of approximately 10-6 torr at full ionization. The initial operation of the source has been at pressures of 10-4 - 10-1. Electron densities in the range of 108 - 1011 per cubic centimeter have been achieved. Low-pressure operation is important to reduce ion beam ionization. A cusp magnetic field has been installed to improve radial confinement and reduce the field strength on the beam axis. In addition, axial confinement is believed to be important to achieve lower-pressure operation. To further improve breakdown at low pressure, a weak electron source will be placed near the end of the ECR source.

Level Lifetime Measurements in ^150Sm

NASA Astrophysics Data System (ADS)

Barton, C. J.; Krücken, R.; Beausang, C. W.; Caprio, M. A.; Casten, R. F.; Cooper, J. R.; Hecht, A. A.; Newman, H.; Novak, J. R.; Pietralla, N.; Wolf, A.; Zyromski, K. E.; Zamfir, N. V.; Börner, H. G.

2000-10-01

Shape/phase coexistence and the evolution of structure in the region around ^152Sm have recently been of great interest. Experiments performed at WNSL, Yale University, measured the lifetime of low spin states in a target of ^150Sm with the recoil distance method (RDM) and the Doppler-shift attenuation method (DSAM). The low spin states, both yrast and non-yrast, were populated via Coulomb excitation with a beam of ^16O. The experiments were performed with the NYPD plunger in conjunction with the SPEEDY γ-ray array. The SCARY array of solar cells was used to detect backward scattered projectiles, selecting forward flying Coulomb excited target nuclei. The measured lifetimes yield, for example, B(E2) values for transitions such as the 2^+2 arrow 2^+1 and the 2^+3 arrow 0^+_1. Data from the RDM measurment and the DSAM experiment will be presented. This work was supported by the US DOE under grants DE-FG02-91ER-40609 and DE-FG02-88ER-40417.

Recoil distance method lifetime measurement of the 21+ state in 94Sr and implications for the structure of neutron-rich Sr isotopes

NASA Astrophysics Data System (ADS)

Chester, A.; Ball, G. C.; Caballero-Folch, R.; Cross, D. S.; Cruz, S.; Domingo, T.; Drake, T. E.; Garnsworthy, A. B.; Hackman, G.; Hallam, S.; Henderson, J.; Henderson, R.; Korten, W.; Krücken, R.; Moukaddam, M.; Olaizola, B.; Ruotsalainen, P.; Smallcombe, J.; Starosta, K.; Svensson, C. E.; Williams, J.; Wimmer, K.

2017-07-01

A high precision lifetime measurement of the 21+ state in 94Sr was performed at TRIUMF's ISAC-II facility by coupling the recoil distance method implemented via the TIGRESS integrated plunger with unsafe Coulomb excitation in inverse kinematics. Due to limited statistics imposed by the use of a radioactive 94Sr beam, a likelihood ratio χ2 method was derived and used to compare experimental data to Geant4 simulations. The B (E 2 ;21+→01+) value extracted from the lifetime measurement of 7 .80-0.40+0.50(stat.)±0.07 (sys.) ps is approximately 25% larger than previously reported while the relative error has been reduced by a factor of approximately 8. A baseline deformation has been established for Sr isotopes with N ≤58 which is a necessary condition for the quantum phase transition interpretation of the onset of deformation in this region. A comparison to existing theoretical models is presented.

Emittance studies of the 2.45 GHz permanent magnet ECR ion source

NASA Astrophysics Data System (ADS)

Zelenak, A.; Bogomolov, S. L.; Yazvitsky, N. Yu.

2004-05-01

During the past several years different types of permanent magnet 2.45 GHz (electron cyclotron resonance) ion sources were developed for production of singly charged ions. Ion sources of this type are used in the first stage of DRIBs project, and are planned to be used in the MASHA mass separator. The emittance of the beam provided by the source is one of the important parameters for these applications. An emittance scanner composed from a set of parallel slits and rotary wire beam profile monitor was used for the studying of the beam emittance characteristics. The emittance of helium and argon ion beams was measured with different shapes of the plasma electrode for several ion source parameters: microwave power, source potential, plasma aperture-puller aperture gap distance, gas pressure. The results of measurements are compared with previous simulations of ion optics.

Spatial light modulators for full cross-connections in optical networks

NASA Technical Reports Server (NTRS)

Juday, Richard D. (Inventor)

2004-01-01

A polarization-independent optical switch is disclosed for switching at least one incoming beam from at least one input source to at least one output drain. The switch includes a polarizing beam splitter to split each of the at least one incoming beam into a first input beam and a second input beam, wherein the first input beam and the second input beams are independently polarized; a wave plate optically coupled to the second input beam for converting the polarization of the second input beam to an appropriately polarized second input beam; a beam combiner optically coupled to the first input beam and the modified second input beam, wherein the beam combiner accepts the first input beam and the modified second input beam to produce a combined beam; the combined beam is invariant to the polarization state of the input source's polarization; and a controllable spatial light modulator optically coupled to the combined beam, wherein the combined beam is diffracted by the controllable spatial light modulator to place light at a plurality of output locations.

The modification at CSNS ion source

NASA Astrophysics Data System (ADS)

Liu, S.; Ouyang, H.; Huang, T.; Xiao, Y.; Cao, X.; Lv, Y.; Xue, K.; Chen, W.

2017-08-01

The commissioning of CSNS front end has been finished. Above 15 mA beam intensity is obtained at the end of RFQ. For CSNS ion source, it is a type of penning surface plasma ion source, similar to ISIS ion source. To improve the operation stability and reduce spark rate, some modifications have been performed, including Penning field, extraction optics and post acceleration. PBGUNS is applied to optimize beam extraction. The co-extraction electrons are considered at PBGUNS simulation and various extracted structure are simulated aiming to make the beam through the extracted electrode without loss. The stability of ion source is improved further.

Tandem-Mirror Ion Source

NASA Technical Reports Server (NTRS)

Biddle, A.; Stone, N.; Reasoner, D.; Chisholm, W.; Reynolds, J.

1986-01-01

Improved ion source produces beam of ions at any kinetic energy from 1 to 1,000 eV, with little spread in energy or angle. Such ion beams useful in studies of surface properties of materials, surface etching, deposition, and development of plasma-diagnostic instrumentation. Tandemmirror ion source uses electrostatic and magnetic fields to keep electrons in ionization chamber and assure uniform output ion beam having low divergence in energy and angle.

Virtual source for a Mathieu-Gauss beam

NASA Astrophysics Data System (ADS)

Dan, Li; Zhijun, Ren; Suyu, Deng

2017-05-01

We introduce a group of virtual sources for generating 2nth-order even Mathieu-Gauss beams based on the beam superposition. Integral and differential representations are derived for a 2nth-order even Mathieu-Gauss wave and the solution yields a corresponding 2nth-order even paraxial Mathieu-Gauss beam in an appropriate limit. The first three orders of nonparaxial corrections for the on-axis field of the 2nth-order even paraxial Mathieu-Gauss beam are obtained using the integral representation.

SU-F-T-336: A Quick Auto-Planning (QAP) Method for Patient Intensity Modulated Radiotherapy (IMRT)

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

Peng, J; Zhang, Z; Wang, J

2016-06-15

Purpose: The aim of this study is to develop a quick auto-planning system that permits fast patient IMRT planning with conformal dose to the target without manual field alignment and time-consuming dose distribution optimization. Methods: The planning target volume (PTV) of the source and the target patient were projected to the iso-center plane in certain beameye- view directions to derive the 2D projected shapes. Assuming the target interior was isotropic for each beam direction boundary analysis under polar coordinate was performed to map the source shape boundary to the target shape boundary to derive the source-to-target shape mapping function. Themore » derived shape mapping function was used to morph the source beam aperture to the target beam aperture over all segments in each beam direction. The target beam weights were re-calculated to deliver the same dose to the reference point (iso-center) as the source beam did in the source plan. The approach was tested on two rectum patients (one source patient and one target patient). Results: The IMRT planning time by QAP was 5 seconds on a laptop computer. The dose volume histograms and the dose distribution showed the target patient had the similar PTV dose coverage and OAR dose sparing with the source patient. Conclusion: The QAP system can instantly and automatically finish the IMRT planning without dose optimization.« less

T he Faint Drifting Decameter Radio Bursts From The Solar Corona

NASA Astrophysics Data System (ADS)

Briand, C.; Zaslavsky, A.; Lecacheux, A.; Zarka, P.; Maksimovic, M.; Mangeney, A.

2007-01-01

The radio observations of solar corona at decameter wavelengths reveal the presence of numerous faint, frequency drifting structures. We analyse observations performed on July 13th , 2002 with the DSP wideband spectrometer instrument implemented at the UTR-2 radiote- lescope. The main characteristics of these structures are statistically studied. Three populations of bursts are iden- tifies. The largest one presents negative frequency drifts of about -0.89 MHz.s-1 and a lifetime extending up to 11 sec (median value 2.72 sec). A second one shows positive frequency drifts of about +0.95 MHz.s-1 and a life- time extending up to 3 sec. The last population consists in structures with very small frequency drifts of about -0.1 MHz.s-1 and a shorter lifetime (about 1 sec). Assuming that those emissions are the signature of elec- tron beams propagating through the solar corona, we deduce that they have a velocity of about 3-5 times the electron thermal velocity. A new mechanism is proposed to explain the formation of plasma waves with such low beam velocity: spatially localized, temporal fluctuations of the electron distribution function width (heating).

Exciton Emission from Bare and Alq3/Gold Coated GaN Nanorods

NASA Astrophysics Data System (ADS)

Mohammadi, Fatemesadat; Kuhnert, Gerd; Hommel, Detlef; Schmitzer, Heidrun; Wagner, Hans-Peter

We study the excitonic and impurity related emission in bare and aluminum quinoline (Alq3)/gold coated wurtzite GaN nanorods by temperature-dependent time-integrated (TI) and time-resolved (TR) photoluminescence (PL). The GaN nanorods were grown by molecular beam epitaxy. Alq3 as well as Alq3/gold covered nanorods were synthesized by organic molecular beam deposition. In the near-band edge region a donor-bound-exciton (D0X) emission is observed at 3.473 eV. Another emission band at 3.275 eV reveals LO-phonon replica and is attributed to a donor-acceptor-pair (DAP) luminescence. TR PL traces at 20 K show a nearly biexponential decay for the D0X with lifetimes of approximately 180 and 800 ps for both bare and Alq3 coated nanorods. In GaN nanorods which were coated with an Alq3 film and subsequently with a 10 nm thick gold layer we observe a PL quenching of D0X and DAP band and the lifetimes of the D0X transition shorten. The quenching behaviour is partially attributed to the energy-transfer from free excitons and donor-bound-excitons to plasmon oscillations in the gold layer.

Optical damage performance of conductive widegap semiconductors: spatial, temporal, and lifetime modeling

DOE PAGES

Elhadj, Selim; Yoo, Jae-hyuck; Negres, Raluca A.; ...

2016-12-19

The optical damage performance of electrically conductive gallium nitride (GaN) and indium tin oxide (ITO) films is addressed using large area, high power laser beam exposures at 1064 nm sub-bandgap wavelength. Analysis of the laser damage process assumes that onset of damage (threshold) is determined by the absorption and heating of a nanoscale region of a characteristic size reaching a critical temperature. We use this model to rationalize semi-quantitatively the pulse width scaling of the damage threshold from picosecond to nanosecond timescales, along with the pulse width dependence of the damage threshold probability derived by fitting large beam damage densitymore » data. Multi-shot exposures were used to address lifetime performance degradation described by an empirical expression based on the single exposure damage model. A damage threshold degradation of at least 50% was observed for both materials. Overall, the GaN films tested had 5-10 × higher optical damage thresholds than the ITO films tested for comparable transmission and electrical conductivity. This route to optically robust, large aperture transparent electrodes and power optoelectronics may thus involve use of next generation widegap semiconductors such as GaN.« less