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Sample records for 2d ion chamber

  1. Dosimetric verification of gated delivery of electron beams using a 2D ion chamber array

    PubMed Central

    Yoganathan, S. A.; Das, K. J. Maria; Raj, D. Gowtham; Kumar, Shaleen

    2015-01-01

    The purpose of this study was to compare the dosimetric characteristics; such as beam output, symmetry and flatness between gated and non-gated electron beams. Dosimetric verification of gated delivery was carried for all electron beams available on Varian CL 2100CD medical linear accelerator. Measurements were conducted for three dose rates (100 MU/min, 300 MU/min and 600 MU/min) and two respiratory motions (breathing period of 4s and 8s). Real-time position management (RPM) system was used for the gated deliveries. Flatness and symmetry values were measured using Imatrixx 2D ion chamber array device and the beam output was measured using plane parallel ion chamber. These detector systems were placed over QUASAR motion platform which was programmed to simulate the respiratory motion of target. The dosimetric characteristics of gated deliveries were compared with non-gated deliveries. The flatness and symmetry of all the evaluated electron energies did not differ by more than 0.7 % with respect to corresponding non-gated deliveries. The beam output variation of gated electron beam was less than 0.6 % for all electron energies except for 16 MeV (1.4 %). Based on the results of this study, it can be concluded that Varian CL2100 CD is well suitable for gated delivery of non-dynamic electron beams. PMID:26170552

  2. Dosimetric verification of gated delivery of electron beams using a 2D ion chamber array.

    PubMed

    Yoganathan, S A; Das, K J Maria; Raj, D Gowtham; Kumar, Shaleen

    2015-01-01

    The purpose of this study was to compare the dosimetric characteristics; such as beam output, symmetry and flatness between gated and non-gated electron beams. Dosimetric verification of gated delivery was carried for all electron beams available on Varian CL 2100CD medical linear accelerator. Measurements were conducted for three dose rates (100 MU/min, 300 MU/min and 600 MU/min) and two respiratory motions (breathing period of 4s and 8s). Real-time position management (RPM) system was used for the gated deliveries. Flatness and symmetry values were measured using Imatrixx 2D ion chamber array device and the beam output was measured using plane parallel ion chamber. These detector systems were placed over QUASAR motion platform which was programmed to simulate the respiratory motion of target. The dosimetric characteristics of gated deliveries were compared with non-gated deliveries. The flatness and symmetry of all the evaluated electron energies did not differ by more than 0.7 % with respect to corresponding non-gated deliveries. The beam output variation of gated electron beam was less than 0.6 % for all electron energies except for 16 MeV (1.4 %). Based on the results of this study, it can be concluded that Varian CL2100 CD is well suitable for gated delivery of non-dynamic electron beams.

  3. Verification measurements of an eMC algorithm using a 2D ion chamber array.

    PubMed

    Wanklyn, Mark D; Kidane, Ghirmay; Crees, Liz

    2016-01-01

    The aim of this study was to assess the suitability of the Im'RT MatriXX 2D ion chamber array for performing verification measurements on the Varian Eclipse electron Monte Carlo (eMC) algorithm for a range of clinical energies (6, 12, and 20 MeV) on a Varian 2100iX linear accelerator. Firstly, the suitability of the MatriXX for measuring percentage depth doses (PDD) in water was assessed, including characterization of the inherent buildup found in the MatriXX. Secondly the suitability of the MatriXX for measuring dose distributions in homogeneous and heterogeneous phantoms was assessed using gamma analysis at 3%/3 mm. It was found that after adjusting the PDD curves for the inherent buildup, that the position of R50,D measured using the MatriXX agreed to within 1 mm to the PDDs generated using the eMC algorithm for all energies used in this study. Gamma analysis at 3%/3mm showed very good agreement (> 95%) for all cases in both homogeneous and heterogeneous phantoms. It was concluded that the Im'RT MatriXX is a suitable device for performing eMC verification and could potentially be used for routine energy checks of electron beams. PMID:27685111

  4. The Octavius1500 2D ion chamber array and its associated phantoms: Dosimetric characterization of a new prototype

    SciTech Connect

    Van Esch, Ann Huyskens, Dominique P.; Basta, Katarzyna; Evrard, Marie; Ghislain, Michel; Sergent, Francois

    2014-09-15

    Purpose: The purpose of the study is to characterize the prototype of the new Octavius1500 (PTW, Freiburg, Germany) 2D ion chamber array, covering its use in different phantom setups, from the most basic solid water sandwich setup to the more complex cylindrical Octavius{sup ®} 4D (Oct4D) (PTW) phantom/detector combination. The new detector houses nearly twice the amount of ion chambers as its predecessors (Seven29 and Octavius729), thereby tackling one of the most important limitations of ion chamber (or diode) arrays, namely the limited detector density. The 0.06 cm{sup 3} cubic ion chambers are now arranged in a checkerboard pattern, leaving no lines (neither longitudinally nor laterally) without detectors. Methods: All measurements were performed on a dual energy (6 MV and 18 MV) iX Clinac (Varian Medical Systems, Palo Alto, CA) and all calculations were done in the Eclipse treatment planning system (Varian) with the Anisotropic Analytical Algorithm. First, the basic characteristics of the 2D array, such as measurement stability, dose rate dependence and dose linearity were investigated in the solid water sandwich setup. Second, the directional dependence was assessed to allow the evaluation of the new Octavius2D phantom (Oct2D{sup 1500}) for planar verification measurements of composite plans. Third, measurements were performed in the Oct4D phantom to evaluate the impact of the increased detector density on the accuracy of the volumetric dose reconstruction. Results: While showing equally good dose linearity and dose rate independence, the Octavius1500 outperforms the previous models because of its instantaneous measurement stability and its twofold active area coverage. Orthogonal field-by-field measurements immediately benefit from the increased detector density. The 3.9 cm wide compensation cavity in the new Oct2D{sup 1500} phantom prototype adequately corrects for directional dependence from the rear, resulting in good agreement within the target dose

  5. A 2D ion chamber array audit of wedged and asymmetric fields in an inhomogeneous lung phantom

    SciTech Connect

    Lye, Jessica; Dunn, Leon Alves, Andrew; Kenny, John; Lehmann, Joerg; Williams, Ivan; Kron, Tomas; Cole, Andrew

    2014-10-15

    Purpose: The Australian Clinical Dosimetry Service (ACDS) has implemented a new method of a nonreference condition Level II type dosimetric audit of radiotherapy services to increase measurement accuracy and patient safety within Australia. The aim of this work is to describe the methodology, tolerances, and outcomes from the new audit. Methods: The ACDS Level II audit measures the dose delivered in 2D planes using an ionization chamber based array positioned at multiple depths. Measurements are made in rectilinear homogeneous and inhomogeneous phantoms composed of slabs of solid water and lung. Computer generated computed tomography data sets of the rectilinear phantoms are supplied to the facility prior to audit for planning of a range of cases including reference fields, asymmetric fields, and wedged fields. The audit assesses 3D planning with 6 MV photons with a static (zero degree) gantry. Scoring is performed using local dose differences between the planned and measured dose within 80% of the field width. The overall audit result is determined by the maximum dose difference over all scoring points, cases, and planes. Pass (Optimal Level) is defined as maximum dose difference ≤3.3%, Pass (Action Level) is ≤5.0%, and Fail (Out of Tolerance) is >5.0%. Results: At close of 2013, the ACDS had performed 24 Level II audits. 63% of the audits passed, 33% failed, and the remaining audit was not assessable. Of the 15 audits that passed, 3 were at Pass (Action Level). The high fail rate is largely due to a systemic issue with modeling asymmetric 60° wedges which caused a delivered overdose of 5%–8%. Conclusions: The ACDS has implemented a nonreference condition Level II type audit, based on ion chamber 2D array measurements in an inhomogeneous slab phantom. The powerful diagnostic ability of this audit has allowed the ACDS to rigorously test the treatment planning systems implemented in Australian radiotherapy facilities. Recommendations from audits have led to

  6. On-line quality assurance of rotational radiotherapy treatment delivery by means of a 2D ion chamber array and the Octavius phantom

    SciTech Connect

    Esch, Ann van; Clermont, Christian; Devillers, Magali; Iori, Mauro; Huyskens, Dominique P.

    2007-10-15

    For routine pretreatment verification of innovative treatment techniques such as (intensity modulated) dynamic arc therapy and helical TomoTherapy, an on-line and reliable method would be highly desirable. The present solution proposed by TomoTherapy, Inc. (Madison, WI) relies on film dosimetry in combination with up to two simultaneous ion chamber point dose measurements. A new method is proposed using a 2D ion chamber array (Seven29, PTW, Freiburg, Germany) inserted in a dedicated octagonal phantom, called Octavius. The octagonal shape allows easy positioning for measurements in multiple planes. The directional dependence of the response of the detector was primarily investigated on a dual energy (6 and 18 MV) Clinac 21EX (Varian Medical Systems, Palo Alto, CA) as no fixed angle incidences can be calculated in the Hi-Art TPS of TomoTherapy. The array was irradiated from different gantry angles and with different arc deliveries, and the dose distributions at the level of the detector were calculated with the AAA (Analytical Anisotropic Algorithm) photon dose calculation algorithm implemented in Eclipse (Varian). For validation on the 6 MV TomoTherapy unit, rotational treatments were generated, and dose distributions were calculated with the Hi-Art TPS. Multiple cylindrical ion chamber measurements were used to cross-check the dose calculation and dose delivery in Octavius in the absence of the 2D array. To compensate for the directional dependence of the 2D array, additional prototypes of Octavius were manufactured with built-in cylindrically symmetric compensation cavities. When using the Octavius phantom with a 2 cm compensation cavity, measurements with an accuracy comparable to that of single ion chambers can be achieved. The complete Octavius solution for quality assurance of rotational treatments consists of: The 2D array, two octagonal phantoms (with and without compensation layer), an insert for nine cylindrical ion chambers, and a set of inserts of

  7. SU-D-BRE-04: Evaluating the Dose Accuracy of a 2D Ion Chamber Array in High Dose Rate Pencil Beam Scanning Proton Beam

    SciTech Connect

    Perles, L; Mascia, A; Piskulich, F; Lepage, R; Zhang, Y; Giebeler, A; Dong, L

    2014-06-01

    Purpose: To evaluate the absolute dose accuracy of the PTW Octavius 729 XDR 2D ion chamber array at a high dose rate pencil beam scanning proton therapy facility. Methods: A set of 18 plans were created in our treatment planning system, each of which comprising a unique combination of field sizes (FS), length of spread out of Bragg peaks (SOBP) and depths. The parameters used were: FS of 5×5cm{sup 2}, 10×10cm{sup 2} and 15×15cm{sup 2}; flat SOBP of 5cm and 10cm; and isocenter depths of 10cm, 15cm and 20cm, which coincides with the center of the SOBP. The 2D array detector was positioned at the machine isocenter and the appropriate amount of solid water was used to match the planned depths of 10, 15 and 20 cm water equivalent depth. Subsequently, we measured the absolute dose at isocenter using a CC04 ion chamber in a 1D water tank. Both 2D array and CC04 were previously cross calibrated. We also collected the MU rates used by our proton machine from the log files. Results: The relative differences between the CC04 and the 2D array can be summarized into two groups, one with 5 cm SOBP and another with 10 cm SOBP. Plotting these datasets against FS shows that the 2D array response for high dose rate fields (FS of 5×5cm{sup 2} and 5cm SOBP) can be up to 2% lower. Similarly, plotting them against isocenter depths reveals the detector's response can be up to 2% lower for higher energy beams (about 200MeV nominal). The MU rate found in the machine log files for 5cm SOBP's were as high as twice the MU rate for the 10cm SOBP. Conclusion: The 2D array dose response showed a dose rate effect in scanning pencil beam delivery, which needs to be corrected to achieve a better dose accuracy.

  8. TH-C-19A-01: Analytic Design Method to Make a 2D Planar, Segmented Ion Chamber Water-Equivalent for Proton Dose Measurements

    SciTech Connect

    Harris, W; Hollebeek, R; Teo, B; Maughan, R; Dolney, D

    2014-06-15

    Purpose: Quality Assurance (QA) measurements of proton therapy fields must accurately measure steep longitudinal dose gradients as well as characterize the dose distribution laterally. Currently, available devices for two-dimensional field measurements perturb the dose distribution such that routine QA measurements performed at multiple depths require multiple field deliveries and are time consuming. Methods: A design procedure for a two-dimensional detector array is introduced whereby the proton energy loss and scatter are adjusted so that the downstream dose distribution is maintained to be equivalent to that which would occur in uniform water. Starting with the design for an existing, functional two-dimensional segmented ion chamber prototype, a compensating material is introduced downstream of the detector to simultaneously equate the energy loss and lateral scatter in the detector assembly to the values in water. An analytic formalism and procedure is demonstrated to calculate the properties of the compensating material in the general case of multiple layers of arbitrary material. The resulting design is validated with Monte Carlo simulations. Results: With respect to the specific prototype design considered, the results indicate that a graphite compensating layer of the proper dimensions can yield proton beam range perturbation less than 0.1mm and beam sigma perturbation less than 2% across the energy range of therapeutic proton beams. Conclusion: We have shown that, for a 2D gas-filled detector array, a graphite-compensating layer can balance the energy loss and multiple Coulomb scattering relative to uniform water. We have demonstrated an analytic formalism and procedure to determine a compensating material in the general case of multiple layers of arbitrary material. This work was supported by the US Army Medical Research and Materiel Command under Contract Agreement No. DAMD17-W81XWH-04-2-0022. Opinions, interpretations, conclusions and recommendations

  9. Tumor-tracking radiotherapy of moving targets; verification using 3D polymer gel, 2D ion-chamber array and biplanar diode array

    NASA Astrophysics Data System (ADS)

    Ceberg, Sofie; Falk, Marianne; Rosenschöld, Per Munck Af; Cattell, Herbert; Gustafsson, Helen; Keall, Paul; Korreman, Stine S.; Medin, Joakim; Nordström, Fredrik; Persson, Gitte; Sawant, Amit; Svatos, Michelle; Zimmerman, Jens; Bäck, Sven ÅJ

    2010-11-01

    The aim of this study was to carry out a dosimetric verification of a dynamic multileaf collimator (DMLC)-based tumor-tracking delivery during respiratory-like motion. The advantage of tumor-tracking radiation delivery is the ability to allow a tighter margin around the target by continuously following and adapting the dose delivery to its motion. However, there are geometric and dosimetric uncertainties associated with beam delivery system constraints and output variations, and several investigations have to be accomplished before a clinical integration of this tracking technique. Two types of delivery were investigated in this study I) a single beam perpendicular to a target with a one dimensional motion parallel to the MLC moving direction, and II) an intensity modulated arc delivery (RapidArc®) with a target motion diagonal to the MLC moving direction. The feasibility study (I) was made using an 2D ionisation chamber array and a true 3D polymer gel. The arc delivery (II) was verified using polymer gel and a biplanar diode array. Good agreement in absorbed dose was found between delivery to a static target and to a moving target with DMLC tracking using all three detector systems. However, due to the limited spatial resolution of the 2D array a detailed comparison was not possible. The RapidArc® plan delivery was successfully verified using the biplanar diode array and true 3D polymer gel, and both detector systems could verify that the DMLC-based tumor-tracking delivery system has a very good ability to account for respiratory target motion.

  10. Three chamber negative ion source

    DOEpatents

    Leung, Ka-Ngo; Ehlers, Kenneth W.; Hiskes, John R.

    1985-01-01

    A negative ion vessel is divided into an excitation chamber, a negative ionization chamber and an extraction chamber by two magnetic filters. Input means introduces neutral molecules into a first chamber where a first electron discharge means vibrationally excites the molecules which migrate to a second chamber. In the second chamber a second electron discharge means ionizes the molecules, producing negative ions which are extracted into or by a third chamber. A first magnetic filter prevents high energy electrons from entering the negative ionization chamber from the excitation chamber. A second magnetic filter prevents high energy electrons from entering the extraction chamber from the negative ionizing chamber. An extraction grid at the end of the negative ion vessel attracts negative ions into the third chamber and accelerates them. Another grid, located adjacent to the extraction grid, carries a small positive voltage in order to inhibit positive ions from migrating into the extraction chamber and contour the plasma potential. Additional electrons can be suppressed from the output flux using ExB forces provided by magnetic field means and the extractor grid electric potential.

  11. Ion chamber based neutron detectors

    DOEpatents

    Derzon, Mark S; Galambos, Paul C; Renzi, Ronald F

    2014-12-16

    A neutron detector with monolithically integrated readout circuitry, including: a bonded semiconductor die; an ion chamber formed in the bonded semiconductor die; a first electrode and a second electrode formed in the ion chamber; a neutron absorbing material filling the ion chamber; and the readout circuitry which is electrically coupled to the first and second electrodes. The bonded semiconductor die includes an etched semiconductor substrate bonded to an active semiconductor substrate. The readout circuitry is formed in a portion of the active semiconductor substrate. The ion chamber has a substantially planar first surface on which the first electrode is formed and a substantially planar second surface, parallel to the first surface, on which the second electrode is formed. The distance between the first electrode and the second electrode may be equal to or less than the 50% attenuation length for neutrons in the neutron absorbing material filling the ion chamber.

  12. Compact ion chamber based neutron detector

    DOEpatents

    Derzon, Mark S.; Galambos, Paul C.; Renzi, Ronald F.

    2015-10-27

    A directional neutron detector has an ion chamber formed in a dielectric material; a signal electrode and a ground electrode formed in the ion chamber; a neutron absorbing material filling the ion chamber; readout circuitry which is electrically coupled to the signal and ground electrodes; and a signal processor electrically coupled to the readout circuitry. The ion chamber has a pair of substantially planar electrode surfaces. The chamber pressure of the neutron absorbing material is selected such that the reaction particle ion trail length for neutrons absorbed by the neutron absorbing material is equal to or less than the distance between the electrode surfaces. The signal processor is adapted to determine a path angle for each absorbed neutron based on the rise time of the corresponding pulse in a time-varying detector signal.

  13. Chamber propagation physics for heavy ion fusion

    SciTech Connect

    Callahan, D.A.

    1995-09-01

    Chamber transport is an important area of study for heavy ion fusion. Final focus and chamber-transport are high leverage areas providing opportunities to significantly decrease the cost of electricity from a heavy ion fusion power plant. Chamber transport in two basic regimes is under consideration. In the low chamber density regime ({approx_lt}0.003 torr), ballistic or nearly-ballistic transport is used. Partial beam neutralization has been studied to offset the effects of beam stripping. In the high chamber density regime ({approx_gt}.1 torr), two transport modes (pinched transport and channel transport) are under investigation. Both involve focusing the beam outside the chamber then transporting it at small radius ({approx} 2 mm). Both high chamber density modes relax the constraints on the beam quality needed from the accelerator which will reduce the driver cost and the cost of electricity.

  14. Chamber transport for heavy ion fusion

    NASA Astrophysics Data System (ADS)

    Olson, Craig L.

    2014-01-01

    A brief review is given of research on chamber transport for HIF (heavy ion fusion) dating from the first HIF Workshop in 1976 to the present. Chamber transport modes are categorized into ballistic transport modes and channel-like modes. Four major HIF reactor studies are summarized (HIBALL-II, HYLIFE-II, Prometheus-H, OSIRIS), with emphasis on the chamber transport environment. In general, many beams are used to provide the required symmetry and to permit focusing to the required small spots. Target parameters are then discussed, with a summary of the individual heavy ion beam parameters required for HIF. The beam parameters are then classified as to their line charge density and perveance, with special emphasis on the perveance limits for radial space charge spreading, for the space charge limiting current, and for the magnetic (Alfven) limiting current. The major experiments on ballistic transport (SFFE, Sabre beamlets, GAMBLE II, NTX, NDCX) are summarized, with specific reference to the axial electron trapping limit for charge neutralization. The major experiments on channel-like transport (GAMBLE II channel, GAMBLE II self-pinch, LBNL channels, GSI channels) are discussed. The status of current research on HIF chamber transport is summarized, and the value of future NDCX-II transport experiments for the future of HIF is noted.

  15. Quantum Simulation with 2D Arrays of Trapped Ions

    NASA Astrophysics Data System (ADS)

    Richerme, Philip

    2016-05-01

    The computational difficulty of solving fully quantum many-body spin problems is a significant obstacle to understanding the behavior of strongly correlated quantum matter. This work proposes the design and construction of a 2D quantum spin simulator to investigate the physics of frustrated materials, highly entangled states, mechanisms potentially underpinning high-temperature superconductivity, and other topics inaccessible to current 1D systems. The effective quantum spins will be encoded within the well-isolated electronic levels of trapped ions, confined in a two-dimensional planar geometry, and made to interact using phonon-mediated optical dipole forces. The system will be scalable to 100+ quantum particles, far beyond the realm of classical intractability, while maintaining individual-ion control, long quantum coherence times, and site-resolved projective spin measurements. Once constructed, the two-dimensional quantum simulator will implement a broad range of spin models on a variety of reconfigurable lattices and characterize their behavior through measurements of spin-spin correlations and entanglement. This versatile tool will serve as an important experimental resource for exploring difficult quantum many-body problems in a regime where classical methods fail.

  16. Quantitative Verification of Dynamic Wedge Dose Distribution Using a 2D Ionization Chamber Array.

    PubMed

    Sahnoun, Tarek; Farhat, Leila; Mtibaa, Anis; Besbes, Mounir; Daoud, Jamel

    2015-10-01

    The accuracy of two calculation algorithms of the Eclipse 8.9 treatment planning system (TPS)--the anisotropic analytic algorithm (AAA) and pencil-beam convolution (PBC)--in modeling the enhanced dynamic wedge (EDW) was investigated. Measurements were carried out for 6 and 18 MV photon beams using a 2D ionization chamber array. Accuracy of the TPS was evaluated using a gamma index analysis with the following acceptance criteria for dose differences (DD) and distance to agreement (DTA): 3%/3 mm and 2%/2 mm. The TPS models the dose distribution accurately except for 20×20 cm(2) field size, 60 (°) and 45 (°) wedge angles using PBC at 6 MV photon energy. For these latter fields, the pass rate and the mean value of gamma were less than 90% and more than 0.5, respectively at the (3%/3 mm) acceptance criteria. In addition, an accuracy level of (2%/2 mm) was achieved using AAA with better agreement for 18 MV photon energy.

  17. Ion chambers simplify absolute intensity measurements in the vacuum ultraviolet

    NASA Technical Reports Server (NTRS)

    Sampson, J. A. R.

    1966-01-01

    Single or double ion chamber technique measures absolute radiation intensities in the extreme vacuum ultraviolet region of the spectrum. The ion chambers use rare gases as the ion carrier. Photon absorbed by the gas creates one ion pair so a measure of these is a measure of the number of incident photons.

  18. Recombination characteristics of therapeutic ion beams on ion chamber dosimetry

    NASA Astrophysics Data System (ADS)

    Matsufuji, Naruhiro; Matsuyama, Tetsuharu; Sato, Shinji; Kohno, Toshiyuki

    2016-09-01

    In heavy ion radiotherapy, ionization chambers are regarded as a standard for determining the absorbed dose given to patients. In ion dosimetry, it is necessary to correct the radiation quality, which depends on the initial recombination effect. This study reveals for the radiation quality dependence of the initial recombination in air in ion dosimetry. Ionization charge was measured for the beams of protons at 40-160 MeV, carbon at 21-400 MeV/n, and iron at 23.5-500 MeV/n using two identical parallel-plate ionization chambers placed in series along the beam axis. The downstream chamber was used as a monitor operated with a constant applied voltage, while the other chamber was used for recombination measurement by changing the voltage. The ratio of the ionization charge measured by the two ionization chambers showed a linear relationship with the inverse of the voltage in the high-voltage region. The initial recombination factor was estimated by extrapolating the obtained linear relationship to infinite voltage. The extent of the initial recombination was found to increase with decreasing incident energy or increasing atomic number of the beam. This behavior can be explained with an amorphous track structure model: the increase of ionization density in the core region of the track due to decreasing kinetic energy or increasing atomic number leads to denser initial ion production and results in a higher recombination probability. For therapeutic carbon ion beams, the extent of the initial recombination was not constant but changed by 0.6% even in the target region. This tendency was quantitatively well reproduced with the track-structure based on the initial recombination model; however, the transitional change in the track structure is considered to play an important role in further understanding of the characteristics of the initial recombination.

  19. Vacuum chamber for ion manipulation device

    DOEpatents

    Chen, Tsung-Chi; Tang, Keqi; Ibrahim, Yehia M; Smith, Richard D; Anderson, Gordon A; Baker, Erin M

    2014-12-09

    An ion manipulation method and device is disclosed. The device includes a pair of substantially parallel surfaces. An array of inner electrodes is contained within, and extends substantially along the length of, each parallel surface. The device includes a first outer array of electrodes and a second outer array of electrodes. Each outer array of electrodes is positioned on either side of the inner electrodes, and is contained within and extends substantially along the length of each parallel surface. A DC voltage is applied to the first and second outer array of electrodes. A RF voltage, with a superimposed electric field, is applied to the inner electrodes by applying the DC voltages to each electrode. Ions either move between the parallel surfaces within an ion confinement area or along paths in the direction of the electric field, or can be trapped in the ion confinement area. A predetermined number of pairs of surfaces are disposed in one or more chambers, forming a multiple-layer ion mobility cyclotron device.

  20. SU-E-P-35: Real-Time Patient Transit Dose Verification of Volumetric Modulated Arc Radiotherapy by a 2D Ionization Chamber Array

    SciTech Connect

    Liu, X

    2015-06-15

    Purpose: To explore the real-time dose verification method in volumetric modulated arc radiotherapy (VMAT) with a 2D array ion chamber array. Methods: The 2D ion chamber array was fixed on the panel of electronic portal imaging device (EPID). Source-detector distance (SDD)was 140cm. 8mm RW3 solid water was added to the detector panel to achieve maximum readings.The patient plans for esophageal, prostate and liver cancers were selected to deliver on the cylindrical Cheese phantom 5 times in order to validate the reproducibility of doses. Real-time patient transit dose measurements were performed at each fraction. Dose distributions wereevaluated using gamma index criteria of 3mm DTA and 3% dose difference referred to the firsttime Result. Results: The gamma index pass rate in the Cheese phantom were about 98%; The gamma index pass rate for esophageal, liver and prostate cancer patient were about 92%,94%, and 92%, respectively; Gamma pass rate for all single fraction were more than 90%. Conclusion: The 2D array is capable of monitoring the real time transit doses during VMAT delivery. It is helpful to improve the treatment accuracy.

  1. 2D accelerator design for SITEX negative ion source

    SciTech Connect

    Whealton, J.H.; Raridon, R.J.; McGaffey, R.W.; McCollough, D.H.; Stirling, W.L.; Dagenhart, W.K.

    1983-01-01

    Solving the Poisson-Vlasov equations where the magnetic field, B, is assumed constant, we optimize the optical system of a SITEX negative ion source in infinite slot geometry. Algorithms designed to solve the above equations were modified to include the curved emitter boundary data appropriate to a negative ion source. Other configurations relevant to negative ion sources are examined.

  2. Ion acoustic wave collapse via two-ion wave decay: 2D Vlasov simulation and theory

    NASA Astrophysics Data System (ADS)

    Chapman, Thomas; Berger, Richard; Banks, Jeffrey; Brunner, Stephan

    2015-11-01

    The decay of ion acoustic waves (IAWs) via two-ion wave decay may transfer energy from the electric field of the IAWs to the particles, resulting in a significant heating of resonant particles. This process has previously been shown in numerical simulations to decrease the plasma reflectivity due to stimulated Brillouin scattering. Two-ion wave decay is a fundamental property of ion acoustic waves that occurs over most if not all of the parameter space of relevance to inertial confinement fusion experiments, and can lead to a sudden collapse of IAWs. The treatment of all species kinetically, and in particular the electrons, is required to describe the decay process correctly. We present fully kinetic 2D+2V Vlasov simulations of IAWs undergoing decay to a highly nonlinear turbulent state using the code LOKI. The scaling of the decay rate with characteristic plasma parameters and wave amplitude is shown. A new theory describing two-ion wave decay in 2D, that incorporates key kinetic properties of the electrons, is presented and used to explain quantitatively for the first time the observed decay of IAWs. Work performed under auspices of U.S. DoE by LLNL, Contract DE-AC52-07NA2734. Funded by LDRD 15-ERD-038 and supported by LLNL Grand Challenge allocation.

  3. Dosimetric characteristics of the novel 2D ionization chamber array OCTAVIUS Detector 1500

    SciTech Connect

    Stelljes, T. S. Looe, H. K.; Chofor, N.; Poppe, B.; Harmeyer, A.; Reuter, J.; Harder, D.

    2015-04-15

    Purpose: The dosimetric properties of the OCTAVIUS Detector 1500 (OD1500) ionization chamber array (PTW-Freiburg, Freiburg, Germany) have been investigated. A comparative study was carried out with the OCTAVIUS Detector 729 and OCTAVIUS Detector 1000 SRS arrays. Methods: The OD1500 array is an air vented ionization chamber array with 1405 detectors in a 27 × 27 cm{sup 2} measurement area arranged in a checkerboard pattern with a chamber-to-chamber distance of 10 mm in each row. A sampling step width of 5 mm can be achieved by merging two measurements shifted by 5 mm, thus fulfilling the Nyquist theorem for intensity modulated dose distributions. The stability, linearity, and dose per pulse dependence were investigated using a Semiflex 31013 chamber (PTW-Freiburg, Freiburg, Germany) as a reference detector. The effective depth of measurement was determined by measuring TPR curves with the array and a Roos chamber type 31004 (PTW-Freiburg, Freiburg, Germany). Comparative output factor measurements were performed with the array, the Semiflex 31010 ionization chamber and the Diode 60012 (both PTW-Freiburg, Freiburg, Germany). The energy dependence of the OD1500 was measured by comparing the array’s readings to those of a Semiflex 31010 ionization chamber for varying mean photon energies at the depth of measurement, applying to the Semiflex chamber readings the correction factor k{sub NR} for nonreference conditions. The Gaussian lateral dose response function of a single array detector was determined by searching the convolution kernel suitable to convert the slit beam profiles measured with a Diode 60012 into those measured with the array’s central chamber. An intensity modulated dose distribution measured with the array was verified by comparing a OD1500 measurement to TPS calculations and film measurements. Results: The stability and interchamber sensitivity variation of the OD1500 array were within ±0.2% and ±0.58%, respectively. Dose linearity was within 1

  4. 2D electron density profile measurement in tokamak by laser-accelerated ion-beam probea)

    NASA Astrophysics Data System (ADS)

    Chen, Y. H.; Yang, X. Y.; Lin, C.; Wang, L.; Xu, M.; Wang, X. G.; Xiao, C. J.

    2014-11-01

    A new concept of Heavy Ion Beam Probe (HIBP) diagnostic has been proposed, of which the key is to replace the electrostatic accelerator of traditional HIBP by a laser-driven ion accelerator. Due to the large energy spread of ions, the laser-accelerated HIBP can measure the two-dimensional (2D) electron density profile of tokamak plasma. In a preliminary simulation, a 2D density profile was reconstructed with a spatial resolution of about 2 cm, and with the error below 15% in the core region. Diagnostics of 2D density fluctuation is also discussed.

  5. 2D electron density profile measurement in tokamak by laser-accelerated ion-beam probe.

    PubMed

    Chen, Y H; Yang, X Y; Lin, C; Wang, L; Xu, M; Wang, X G; Xiao, C J

    2014-11-01

    A new concept of Heavy Ion Beam Probe (HIBP) diagnostic has been proposed, of which the key is to replace the electrostatic accelerator of traditional HIBP by a laser-driven ion accelerator. Due to the large energy spread of ions, the laser-accelerated HIBP can measure the two-dimensional (2D) electron density profile of tokamak plasma. In a preliminary simulation, a 2D density profile was reconstructed with a spatial resolution of about 2 cm, and with the error below 15% in the core region. Diagnostics of 2D density fluctuation is also discussed.

  6. 2D electron density profile measurement in tokamak by laser-accelerated ion-beam probe

    SciTech Connect

    Chen, Y. H.; Yang, X. Y.; Lin, C. E-mail: cjxiao@pku.edu.cn; Wang, X. G.; Xiao, C. J. E-mail: cjxiao@pku.edu.cn; Wang, L.; Xu, M.

    2014-11-15

    A new concept of Heavy Ion Beam Probe (HIBP) diagnostic has been proposed, of which the key is to replace the electrostatic accelerator of traditional HIBP by a laser-driven ion accelerator. Due to the large energy spread of ions, the laser-accelerated HIBP can measure the two-dimensional (2D) electron density profile of tokamak plasma. In a preliminary simulation, a 2D density profile was reconstructed with a spatial resolution of about 2 cm, and with the error below 15% in the core region. Diagnostics of 2D density fluctuation is also discussed.

  7. Monte Carlo modeling of ion chamber performance using MCNP.

    PubMed

    Wallace, J D

    2012-12-01

    Ion Chambers have a generally flat energy response with some deviations at very low (<100 keV) and very high (>2 MeV) energies. Some improvements in the low energy response can be achieved through use of high atomic number gases, such as argon and xenon, and higher chamber pressures. This work looks at the energy response of high pressure xenon-filled ion chambers using the MCNP Monte Carlo package to develop geometric models of a commercially available high pressure ion chamber (HPIC). The use of the F6 tally as an estimator of the energy deposited in a region of interest per unit mass, and the underlying assumptions associated with its use are described. The effect of gas composition, chamber gas pressure, chamber wall thickness, and chamber holder wall thicknesses on energy response are investigated and reported. The predicted energy response curve for the HPIC was found to be similar to that reported by other investigators. These investigations indicate that improvements to flatten the overall energy response of the HPIC down to 70 keV could be achieved through use of 3 mm-thick stainless steel walls for the ion chamber.

  8. SIMULATION OF CHAMBER TRANSPORT FOR HEAVY-ION FUSION DRIVERS

    SciTech Connect

    Sharp, W M; Callahan, D A; Tabak, M; Yu, S S; Peterson, P F; Rose, D V; Welch, D R

    2004-05-20

    The heavy-ion fusion (HIF) community recently developed a power-plant design that meets the various requirements of accelerators, final focus, chamber transport, and targets. The point design is intended to minimize physics risk and is certainly not optimal for the cost of electricity. Recent chamber-transport simulations, however, indicate that changes in the beam ion species, the convergence angle, and the emittance might allow more-economical designs.

  9. Understanding the interaction between energetic ions and freestanding graphene towards practical 2D perforation

    NASA Astrophysics Data System (ADS)

    Buchheim, Jakob; Wyss, Roman M.; Shorubalko, Ivan; Park, Hyung Gyu

    2016-04-01

    We report experimentally and theoretically the behavior of freestanding graphene subjected to bombardment of energetic ions, investigating the capability of large-scale patterning of freestanding graphene with nanometer sized features by focused ion beam technology. A precise control over the He+ and Ga+ irradiation offered by focused ion beam techniques enables investigating the interaction of the energetic particles and graphene suspended with no support and allows determining sputter yields of the 2D lattice. We found a strong dependency of the 2D sputter yield on the species and kinetic energy of the incident ion beams. Freestanding graphene shows material semi-transparency to He+ at high energies (10-30 keV) allowing the passage of >97% He+ particles without creating destructive lattice vacancy. Large Ga+ ions (5-30 keV), in contrast, collide far more often with the graphene lattice to impart a significantly higher sputter yield of ~50%. Binary collision theory applied to monolayer and few-layer graphene can successfully elucidate this collision mechanism, in great agreement with experiments. Raman spectroscopy analysis corroborates the passage of a large fraction of He+ ions across graphene without much damaging the lattice whereas several colliding ions create single vacancy defects. Physical understanding of the interaction between energetic particles and suspended graphene can practically lead to reproducible and efficient pattern generation of unprecedentedly small features on 2D materials by design, manifested by our perforation of sub-5 nm pore arrays. This capability of nanometer-scale precision patterning of freestanding 2D lattices shows the practical applicability of focused ion beam technology to 2D material processing for device fabrication and integration.We report experimentally and theoretically the behavior of freestanding graphene subjected to bombardment of energetic ions, investigating the capability of large-scale patterning of

  10. Understanding the interaction between energetic ions and freestanding graphene towards practical 2D perforation.

    PubMed

    Buchheim, Jakob; Wyss, Roman M; Shorubalko, Ivan; Park, Hyung Gyu

    2016-04-21

    We report experimentally and theoretically the behavior of freestanding graphene subjected to bombardment of energetic ions, investigating the capability of large-scale patterning of freestanding graphene with nanometer sized features by focused ion beam technology. A precise control over the He(+) and Ga(+) irradiation offered by focused ion beam techniques enables investigating the interaction of the energetic particles and graphene suspended with no support and allows determining sputter yields of the 2D lattice. We found a strong dependency of the 2D sputter yield on the species and kinetic energy of the incident ion beams. Freestanding graphene shows material semi-transparency to He(+) at high energies (10-30 keV) allowing the passage of >97% He(+) particles without creating destructive lattice vacancy. Large Ga(+) ions (5-30 keV), in contrast, collide far more often with the graphene lattice to impart a significantly higher sputter yield of ∼50%. Binary collision theory applied to monolayer and few-layer graphene can successfully elucidate this collision mechanism, in great agreement with experiments. Raman spectroscopy analysis corroborates the passage of a large fraction of He(+) ions across graphene without much damaging the lattice whereas several colliding ions create single vacancy defects. Physical understanding of the interaction between energetic particles and suspended graphene can practically lead to reproducible and efficient pattern generation of unprecedentedly small features on 2D materials by design, manifested by our perforation of sub-5 nm pore arrays. This capability of nanometer-scale precision patterning of freestanding 2D lattices shows the practical applicability of focused ion beam technology to 2D material processing for device fabrication and integration.

  11. Chamber transport of ''foot'' pulses for heavy-ion fusion

    SciTech Connect

    Sharp, W.M.; Callahan-Miller, D.A.; Tabak, M.; Yu, S.S.; Peterson, P.F.

    2002-02-20

    Indirect-drive targets for heavy-ion fusion must initially be heated by ''foot'' pulses that precede the main heating pulses by tens of nanoseconds. These pulses typically have a lower energy and perveance than the main pulses, and the fusion-chamber environment is different from that seen by later pulses. The preliminary particle-in-cell simulations of foot pulses here examine the sensitivity of the beam focusing to ion-beam perveance, background-gas density, and pre-neutralization by a plasma near the chamber entry port.

  12. Development of ultra-fast 2D ion Doppler tomography using image intensified CMOS fast camera

    NASA Astrophysics Data System (ADS)

    Tanabe, Hiroshi; Kuwahata, Akihiro; Yamanaka, Haruki; Inomoto, Michiaki; Ono, Yasushi; TS-group Team

    2015-11-01

    The world fastest novel time-resolved 2D ion Doppler tomography diagnostics has been developed using fast camera with high-speed gated image intensifier (frame rate: 200kfps. phosphor decay time: ~ 1 μ s). Time evolution of line-integrated spectra are diffracted from a f=1m, F/8.3 and g=2400L/mm Czerny-Turner polychromator, whose output is intensified and recorded to a high-speed camera with spectral resolution of ~0.005nm/pixel. The system can accommodate up to 36 (9 ×4) spatial points recorded at 5 μs time resolution, tomographic reconstruction is applied for the line-integrated spectra, time-resolved (5 μs/frame) local 2D ion temperature measurement has been achieved without any assumption of shot repeatability. Ion heating during intermittent reconnection event which tends to happen during high guide field merging tokamak was measured around diffusion region in UTST. The measured 2D profile shows ion heating inside the acceleration channel of reconnection outflow jet, stagnation point and downstream region where reconnected field forms thick closed flux surface as in MAST. Achieved maximum ion temperature increases as a function of Brec2 and shows good fit with MAST experiment, demonstrating promising CS-less startup scenario for spherical tokamak. This work is supported by JSPS KAKENHI Grant Number 15H05750 and 15K20921.

  13. Modeling Chamber Transport for Heavy-Ion Fusion

    SciTech Connect

    Sharp, W M; Niller, D A C; Tabak, M; Yu, S S; Peterson, P F; Welch, D R; Rose, D V; Olson, C L

    2002-08-02

    In a typical thick-liquid-wall scenario for heavy-ion fusion (HIF), between seventy and two hundred high-current beams enter the target chamber through ports and propagate about three meters to the target. Since molten-salt jets are planned to protect the chamber wall, the beams move through vapor from the jets, and collisions between beam ions and this background gas both strip the ions and ionize the gas molecules. Radiation from the preheated target causes further beam stripping and gas ionization. Due to this stripping, beams for heavy-ion fusion are expected to require substantial neutralization in a target chamber. Much recent research has, therefore, focused on beam neutralization by electron sources that were neglected in earlier simulations, including emission from walls and the target, photoionization by the target radiation, and pre-neutralization by a plasma generated along the beam path. When these effects are included in simulations with practicable beam and chamber parameters, the resulting focal spot is approximately the size required by a distributed radiator target.

  14. Modeling chamber transport for heavy-ion fusion

    SciTech Connect

    Sharp, W.M.; Callahan, D.A.; Tabak, M.; Yu, S.S.; Peterson, P.F.; Welch, D.R.; Rose, D.V.; Olson, C.L.

    2002-10-01

    In a typical thick-liquid-wall scenario for heavy-ion fusion (HIF), between seventy and two hundred high-current beams enter the target chamber through ports and propagate about three meters to the target. Since molten-salt jets are planned to protect the chamber wall, the beams move through vapor from the jets, and collisions between beam ions and this background gas both strip the ions and ionize the gas molecules. Radiation from the preheated target causes further beam stripping and gas ionization. Due to this stripping, beams for heavy-ion fusion are expected to require substantial neutralization in a target chamber. Much recent research has, therefore, focused on beam neutralization by electron sources that were neglected in earlier simulations, including emission from walls and the target, photoionization by the target radiation, and pre-neutralization by a plasma generated along the beam path. When these effects are included in simulations with practicable beam and chamber parameters, the resulting focal spot is approximately the size required by a distributed radiator target.

  15. Ion microprobe analysis of bone surface elements: Effects of 1,25(OH)2D3

    SciTech Connect

    Bushinsky, D.A.; Chabala, J.M.; Levi-Setti, R. )

    1989-12-01

    When neonatal mouse calvariae are incubated with 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) there is net calcium efflux from the bone into the medium. The effect of this enhanced cell-mediated Ca efflux on the relative concentrations of mineral 23Na, 39K, and 40Ca has not previously been studied. We used an imaging scanning ion microprobe, utilizing secondary ion mass spectrometry, to compare the relative ion concentrations of Na, K, and Ca on the surface, subsurface, and cross-section of cultured bone incubated in the presence of 1,25(OH)2D3 with the ion concentrations in similar regions of bone incubated in unaltered control medium. Changes in mineral ion concentration were correlated with net fluxes of Na, K, and Ca relative to bone. Calvariae incubated in control medium (24 h at pH approximately 7.40) have abundant surface Na and K relative to Ca (Na/Ca, 85 and K/Ca, 68), whereas the subsurface has less Na/Ca (21) and K/Ca (23), and on cross section the ratios of both Na/Ca (2.0) and K/Ca (1.9) decrease further. After incubation with 10(-8) M 1,25(OH)2D3, there is a significant increase in bone surface Na/Ca (154) and K/Ca (141) without a change in these ratios on the subsurface and a small fall in both ratios on cross section. The linear relationship between Na/Ca and K/Ca across the three regions of bone observed in control calvariae did not change with 1,25(OH)2D3 treatment. As determined by flux measurements there is a net efflux of Ca but not Na or K from bone.

  16. 2D fluorescence spectroscopy for monitoring ion-exchange membrane based technologies - Reverse electrodialysis (RED).

    PubMed

    Pawlowski, Sylwin; Galinha, Claudia F; Crespo, João G; Velizarov, Svetlozar

    2016-01-01

    Reverse electrodialysis (RED) is one of the emerging, membrane-based technologies for harvesting salinity gradient energy. In RED process, fouling is an undesirable operation constraint since it leads to a decrease of the obtainable net power density due to increasing stack electric resistance and pressure drop. Therefore, early fouling detection is one of the main challenges for successful RED technology implementation. In the present study, two-dimensional (2D) fluorescence spectroscopy was used, for the first time, as a tool for fouling monitoring in RED. Fluorescence excitation-emission matrices (EEMs) of ion-exchange membrane surfaces and of natural aqueous streams were acquired during one month of a RED stack operation. Fouling evolvement on the ion-exchange membrane surfaces was successfully followed by 2D fluorescence spectroscopy and quantified using principal components analysis (PCA). Additionally, the efficiency of cleaning strategy was assessed by measuring the membrane fluorescence emission intensity before and after cleaning. The anion-exchange membrane (AEM) surface in contact with river water showed to be significantly affected due to fouling by humic compounds, which were found to cross through the membrane from the lower salinity (river water) to higher salinity (sea water) stream. The results obtained show that the combined approach of using 2D fluorescence spectroscopy and PCA has a high potential for studying fouling development and membrane cleaning efficiency in ion exchange membrane processes.

  17. 2D PIC simulations for an EN discharge with magnetized electrons and unmagnetized ions

    NASA Astrophysics Data System (ADS)

    Lieberman, Michael A.; Kawamura, Emi; Lichtenberg, Allan J.

    2009-10-01

    We conducted 2D particle-in-cell (PIC) simulations for an electronegative (EN) discharge with magnetized electrons and unmagnetized ions, and compared the results to a previously developed 1D (radial) analytical model of an EN plasma with strongly magnetized electrons and weakly magnetized ions [1]. In both cases, there is a static uniform applied magnetic field in the axial direction. The 1D radial model mimics the wall losses of the particles in the axial direction by introducing a bulk loss frequency term νL. A special (desired) solution was found in which only positive and negative ions but no electrons escaped radially. The 2D PIC results show good agreement with the 1D model over a range of parameters and indicate that the analytical form of νL employed in [1] is reasonably accurate. However, for the PIC simulations, there is always a finite flux of electrons to the radial wall which is about 10 to 30% of the negative ion flux.[4pt] [1] G. Leray, P. Chabert, A.J. Lichtenberg and M.A. Lieberman, J. Phys. D, accepted for publication 2009.

  18. Commissioning of a large segmented ion chamber for the FMA

    SciTech Connect

    Lister, C.J.; Davids, C.N.; Blumenthal, D.J.

    1995-08-01

    A large-area sectored ion chamber was built by a Yale-Daresbury (U.K.) - ANL collaboration to allow extensions of studies of N = Z (T = 0) nuclei. The ion chamber is a conventional DE-DE-E detector which is 20-cm deep, but each anode is segmented into eight pads to allow high count-rate capability and ray-trace reconstruction. With suitable electronics, the detector can become eight close-packed ion chambers, considerably reducing the count rate in each. A position-wire plane allows further raytracing which should permit the rejection of anomalous trajectories and improve Z-separation. A brief test run was scheduled shortly after delivery. Performance appeared promising, but issues of gain matching and cross talk need further exploration. We will study these features {open_quotes}off line{close_quotes} and hope to perform a full experiment on selenium isotopes in the summer. This detector appears to have many uses and is potentially more useful than previous detectors of its type. Similar detectors are being built for the HHRF at Oak Ridge and for Texas A&M University.

  19. Charge exchange of metastable 2D oxygen ions with molecular oxygen - A new source of thermospheric O2/+/ ions

    NASA Technical Reports Server (NTRS)

    Torr, D. G.; Torr, M. R.; Rusch, D. W.; Nier, A. O.; Kayser, D.; Hanson, W. B.; Hoffman, J. H.; Donahue, K.

    1979-01-01

    Reactions involving metastable ions are difficult to study in the laboratory. Much new information on these reactions has been derived from satellite measurements of aeronomic parameters. In this paper, Atmosphere Explorer D data are used to study charge exchange of metastable O(+)(2D) ions with O2. Using direct measurements of the O2 at 200 km to compute O2 densities at 300 km and supporting ionic concentrations and temperature observations, we find the rate coefficient for this reaction to be 1 + or - 0.6 times 10 to the minus 9th cu cm/sec. The process constitutes a significant source of O2(+) ions in the F2 layer at times when the N2 and O2 densities are enhanced. This finding leads to the conclusion that charge exchange with O2 must be a major sink for O(+)(2D) and an important source of O2(+) ions in the E region, because of the increase in the O2 concentration/N2 concentration ratio with decreasing altitude. The results imply that 80% of all O(+) ions formed in the E region are converted to O2(+) and that only about 20% of the metastable O(+) ions are converted into N2(+) through charge exchange with N2.

  20. Ultrafast state detection and 2D ion crystals in a Paul trap

    NASA Astrophysics Data System (ADS)

    Ip, Michael; Ransford, Anthony; Campbell, Wesley

    2016-05-01

    Projective readout of quantum information stored in atomic qubits typically uses state-dependent CW laser-induced fluorescence. This method requires an often sophisticated imaging system to spatially filter out the background CW laser light. We present an alternative approach that instead uses simple pulse sequences from a mode-locked laser to affect the same state-dependent excitations in less than 1 ns. The resulting atomic fluorescence occurs in the dark, allowing the placement of non-imaging detectors right next to the atom to improve the qubit state detection efficiency and speed. We also study 2D Coulomb crystals of atomic ions in an oblate Paul trap. We find that crystals with hundreds of ions can be held in the trap, potentially offering an alternative to the use of Penning traps for the quantum simulation of 2D lattice spin models. We discuss the classical physics of these crystals and the metastable states that are supported in 2D. This work is supported by the US Army Research Office.

  1. Models Ion Trajectories in 2D and 3D Electrostatic and Magnetic Fields

    2000-02-21

    SIMION3D7.0REV is a C based ion optics simulation program that can model complex problems using Laplace equation solutions for potential fields. The program uses an ion optics workbench that can hold up to 200 2D and/or 3D electrostatic/magnetic potential arrays. Arrays can have up to 50,000,000 points. SIMION3D7.0''s 32 bit virtual Graphics User Interface provides a highly interactive advanced user environment. All potential arrays are visualized as 3D objects that the user can cut awaymore » to inspect ion trajectories and potential energy surfaces. User programs allow the user to customize the program for specific simulations. A geometry file option supports the definition of highly complex array geometry. Algorithm modifications have improved this version''s computational speed and accuracy.« less

  2. Quantum information experiments with 2D arrays of hundreds of trapped ions

    NASA Astrophysics Data System (ADS)

    Gilmore, Kevin; Bohnet, Justin; Sawyer, Brian; Britton, Joseph; Wall, Michael; Foss-Feig, Michael; Rey, Ana Maria; Bollinger, John

    2016-05-01

    We summarize recent experimental work with 2D arrays of hundreds of trapped 9 Be+ ions stored in a Penning trap. Penning traps utilize static magnetic and electric fields to confine ions, and enable the trapping and laser cooling of ion crystals larger than typically possible in RF ion traps. We work with single-plane ion crystals where the ions form a triangular lattice through minimization of their Coulomb potential energy. The crystals rotate, and we present numerical studies that determine optimal operating parameters for producing low temperature, stable 2-dimensional crystals with Doppler laser cooling and a rotating wall potential. Our qubit is the electron spin-flip transition in the ground state of 9 Be+ and is sensitive to magnetic field fluctuations. Through mitigation of part-per-billion, vibration-induced magnetic field fluctuations we demonstrate T2 coherence times longer than 50 ms. We engineer long-range Ising interactions with spin-dependent optical dipole forces, and summarize recent measurements that characterize the entanglement generated through single-axis twisting. Supported by: JILA-NSF-PFC-1125844, NSF-PHY-1521080, ARO, AFOSR, AFOSR-MURI.

  3. Origin of energetic ions observed in the terrestrial ion foreshock : 2D full-particle simulations

    NASA Astrophysics Data System (ADS)

    Savoini, Philippe; Lembege, bertrand

    2016-04-01

    Collisionless shocks are well-known structures in astrophysical environments which dissipate bulk flow kinetic energy and accelerate large fraction of particle. Spacecrafts have firmly established the existence of the so-called terrestrial foreshock region magnetically connected to the shock and filled by two distinct populations in the quasi-perpendicular shock region (i.e. for 45r{ } ≤ quad θ Bn quad ≤ 90r{ }, where θ Bn is the angle between the shock normal and the upstream magnetic field) : (i) the field-aligned ion beams or `` FAB '' characterized by a gyrotropic distributionsout{,} and (ii) the gyro-phase bunched ions or `` GPB '' characterized by a NON gyrotropic distribution. The present work is based on the use of two dimensional PIC simulation of a curved shock and associated foreshock region where full curvature effects, time of flight effects and both electrons and ions dynamics are fully described by a self consistent approach. Our previous analysis (Savoini et Lembège, 2015) has evidenced that these two types of backstreaming populations can originate from the shock front itself without invoking any local diffusion by ion beam instabilities. Present results are focussed on individual ion trajectories and evidence that "FAB" population is injected into the foreshock mainly along the shock front whereas the "GPB" population penetrates more deeply the shock front. Such differences explain why the "FAB" population loses their gyro-phase coherency and become gyrotropic which is not the case for the "GPB". The impact of these different injection features on the energy gain for each ion population will be presented in détails. Savoini, P. and B. Lembège (2015), `` Production of nongyrotropic and gyrotropic backstreaming ion distributions in the quasi-perpendicular ion foreshock région '', J. Geophys. Res., 120, pp 7154-7171, doi = 10.1002/2015JA021018.

  4. MEASUREMENT OF SURFACE ALPHA CONTAMINATION USING ELECTRET ION CHAMBERS

    SciTech Connect

    M.A. Ebadian, Ph.D.

    1999-01-01

    Electret ion chambers (EICs) are known to be inexpensive, reliable, passive, integrating devices used for measurement of ionizing radiation. Their application for measurement of alpha contamination on surfaces was recently realized. This two-year project deals with the evaluation of electret ion chambers with different types of electrets and chambers for measurement of surface alpha contamination, their demonstration at U.S. Department of Energy (DOE) sites, a cost-benefit comparison with the existing methods, and the potential deployment at DOE sites. During the first year (FY98) of the project, evaluation of the EICS was completed. It was observed that EICS could be used for measurement of free release level of alpha contamination for transuranics (100 dpm/100 cm{sup 2} fixed). DOE sites, where demonstration of EIC technology for surface alpha contamination measurements could be performed, were also identified. During FY99, demonstration and deployment of EICS at DOE sites are planned. A cost-benefit analysis of the EIC for surface alpha contamination measurement will also be performed.

  5. 2D He+ pickup ion velocity distribution functions: STEREO PLASTIC observations

    NASA Astrophysics Data System (ADS)

    Drews, C.; Berger, L.; Taut, A.; Peleikis, T.; Wimmer-Schweingruber, R. F.

    2015-03-01

    Context. He+ pickup ions are either born from the ionization of interstellar neutral helium inside our heliosphere, the so-called interstellar pickup ions, or through the interaction of solar wind ions with small dust particles, the so-called inner source of pickup ions. Until now, most observations of pickup ions were limited to reduced 1D velocity spectra, which are insufficient to study certain characteristics of the He+ velocity distribution function (VDF). Aims: It is generally assumed that rapid pitch-angle scattering of freshly created pickup ions quickly leads to a fully isotropic He+ VDF. In light of recent observations, this assumption has found to be oversimplified and needs to be reinvestigated. Methods: Using He+ pickup ion data from the PLASTIC instrument on board the STEREO A spacecraft, we reconstruct a reduced form of the He+ VDF in two dimensions. This allows us to study relative changes of the 2D He+ VDF as a function of the configuration of the heliospheric magnetic field. Results: Our observations show that the He+ VDF is highly anisotropic and even indicates that, at least for certain configurations of B, it is not fully gyrotropic. Our results further suggest, that the observed velocity and pitch angle of He+ depends strongly on the local solar magnetic field vector, B, the ecliptic longitude, λ, the solar wind speed, vsw, and the global distribution of B. Conclusions: We found two distinct signatures that systematically change as a function of the alignment of B: (1) a ring beam distribution that is most pronounced at wsw> 0.5 and likely attributed to interstellar He+; (2) a beam signature aligned parallel to B that is most pronounced at wsw < 0.5 and attributed to inner-source He+. The strong anisotropy and the aforementioned dependencies of the He+ VDF also imply that observations of 1D velocity spectra of He+ pickup ions are potentially deceiving.

  6. 2-D Three Fluid Simulation of Upstreaming Ions Above Auroral Precipitation

    NASA Astrophysics Data System (ADS)

    Danielides, M. A.; Lummerzheim, D.; Otto, A.; Stevens, R. J.

    2006-12-01

    The ionosphere is a rich reservoir of charged particles from which a variable fraction is transported to the magnetosphere. An important transport phenomena is the formation of upward ion flow above auroral structure. A primary region of the outflow is not known, but contributions come from polar cap, dayside cusp/cleft region, auroral oval, or even from mid-latitudes. In the past global magnetospheric models and fluid codes were used to simulate large scale ion outflow above, e.g., the polar-cap aurora. However, satellites orbiting at low- altitudes have repeatingly detected localized ion outflow above the auroral oval. Ionosphere-magnetosphere coupling simulations gave first insides into the small-scale dynamics of aurora. The aim of this study is the investigation of coupled plasma and neutral dynamics in smaller scale aurora to explain the generation, structure, and dynamics of vertical ion upstream. We consider auroral electron precipitation at ionospheric heights in a 2-D three fluid ionospheric-magnetospheric coupling code (Otto and Zhu, 2003). Specially we examine the effects of the electron precipitation, heat conduction and heating in field- aligned current through coulomb collisions or turbulence causing: i) electron heating, ii) electron pressure gradients, and iii) upstreaming of ions through a resulting ambipolar electric field. Our first case studies are performed for different boundary conditions and for different auroral electron precipitation parameters (variation in characteristic auroral energy, auroral energy flux and horizontal scale). The results shall clarify how auroral precipitation can drive ions upwards. Finally we discuss the effect of ion drag and the interaction of the upstreaming ions with a stable neutral constituent. Otto, O. and H. Zhu, Fluid plasma simulation of coupled systems: Ionosphere and magnetosphere, Space Plasma Simulation. Edited by J. Buechner, C. Dum, and M. Scholer., Lecture Notes in Physics, vol. 615, p.193

  7. Radon exhalation rates from building materials using electret ion chamber radon monitors in accumulators.

    PubMed

    Kotrappa, Payasada; Stieff, Frederick

    2009-08-01

    An electret ion chamber (EIC) radon monitor in a sealed accumulator measures the integrated average radon concentration at the end of the accumulation duration. Theoretical equations have been derived to relate such radon concentrations (Bq m(-3) ) to the radon emanation rate (Bq d(-1)) from building materials enclosed in the accumulator. As an illustration, a 4-L sealable glass jar has been used as an accumulator to calculate the radon emanation rate from different granite samples. The radon emanation rate was converted into radon flux (Bq mm(-2) d(-1)) by dividing the emanation rate by surface area of the sample. Fluxes measured on typical, commercially available granites ranged from 20-30 Bq m(-2) d(-1). These results are similar to the results reported in the literature. The lower limit of detection for a 2-d measurement works out to be 7 Bq m(-2) d(-1). Equations derived can also be used for other sealable accumulators and other integrating detectors, such as alpha track detectors.

  8. The stability of freely-propagating ion acoustic waves in 2D systems

    NASA Astrophysics Data System (ADS)

    Chapman, Thomas; Berger, Richard; Banks, Jeffrey; Brunner, Stephan

    2014-10-01

    The stability of a freely-propagating ion acoustic wave (IAW) is a basic science problem that is made difficult by the need to resolve electron kinetic effects over a timescale that greatly exceeds the IAW period during numerical simulation. Recent results examining IAW stability using a 1D+1V Vlasov-Poisson solver indicate that instability is a fundamental property of IAWs that occurs over most if not all of the parameter space of relevance to ICF experiments. We present here new results addressing the fundamental question of IAW stability across a broad range of plasma conditions in a 2D+2V system using LOKI, ranging from a regime of relatively weak to a regime of relatively strong ion kinetic effects. Work performed under the auspices of the U.S. DOE by LLNL (DE-AC52-07NA27344) and funded by the LDRD Program at LLNL (12-ERD-061).

  9. Indirect check of the stability of the reference ion chamber used for accelerator output calibration

    NASA Astrophysics Data System (ADS)

    Kang, Sei-Kwon; Yoon, Jai-Woong; Park, Soah; Hwang, Taejin; Cheong, Kwang-Ho; Han, Tae Jin; Kim, Haeyoung; Lee, Me-Yeon; Kim, Kyoung Ju; Bae, Hoonsik

    2014-11-01

    A linear accelerator's output is periodically checked by using a reference ion chamber which is also periodically calibrated at the accredited standard dosimetry laboratories. We suggest a simple procedure for checking the chamber's stability between calibrations by comparison with another ion chamber. To identify the long-term stability of chambers, we collected and assessed the dose-to-water conversion factors provided by standard laboratories for three chambers during a period of four years. To develop the chamber constancy check program, we used one Farmer-type reference ion chamber FC65-G, two ion chambers (CC13a and CC13b) and one CC01 ion chamber (IBA). Under the accelerator, each chamber was placed inside the solid phantom and irradiated; the experimental configurations were identical. To check the variation in charge collection of the reference chamber, we monitored the ratios of the FC65-G values over each chamber reading. Based on the error propagation of the two chamber ratios, we estimated the uncertainty of the output calibration from the chamber variation. The calibration factors provided for the three chambers showed 0.04 ˜ 0.12% standard deviations during four years. For procedure development, the reading ratios of FC65-G over CCxx showed very good stability; the ratios of FC65-G over CC13a, CC13b and CC01 varied less than 0.059, 0.087 and 0.248%, respectively, over five measurements. By ascribing possible uncertainties of the ratio to the reference chamber alone, we could conservatively check the stability of the reference chamber for treatment safety. An extension of the chamber calibration period was also evaluated. In conclusion, we designed a stability check procedure for the reference chamber based on a reading ratio of two chambers. This could help the user assess the chamber stability between periodic chamber calibration, and the associated patient treatment could be carried out with enhanced safety.

  10. Phantom dosimetric study of nondivergent aluminum tissue compensator using ion chamber, TLD, and gafchromic film.

    PubMed

    Kinhikar, Rajesh A; Tambe, Chandrashekhar M; Upreti, Ritu R; Patkar, Sachin; Patil, Kalpana; Deshpande, Deepak D

    2008-01-01

    Anatomic contour irregularity and tissue inhomogeneity in head-and-neck radiotherapy can lead to significant dose inhomogeneity due to the presence of hot and cold spots across the treatment volumes. Missing tissue compensators (TCs) can overcome this dose inhomogeneity. The current study examines the capacity of 2-dimensional (2D) custom aluminum TCs fabricated at our hospital to improve the dose homogeneity across the treatment volume. The dosimetry of the 2D custom TCs was carried out in a specially designed head-and-neck phantom for anterior-posterior (AP) and posterior-anterior (PA) fields with an ion chamber, thermoluminscence dosimeters (TLDs), and film. The results were compared for compensated and uncompensated plans generated from the Eclipse treatment planning system. On average, open-field plans contained peak doses of 117%, optimally wedged-plans contained peak doses of 113%, and custom-compensated plans contained peak doses of 105%. The dose variation between prescribed and measured dose at midplane of the phantom was observed as high as 17%, which was reduced to 3.2% for the customized TC during ionometric measurements. It was further confirmed with TLDs, in a sagittal plane, that the high-dose region of 13.3% was reduced to 2.3%. The measurements carried out with the ion chamber, TLDs, and film were found in good agreement with each other and with Eclipse. Thus, a custom-made 2D TC is capable of reducing hot spots to improve overall dose homogeneity across the treatment volume.

  11. Phantom Dosimetric Study of Nondivergent Aluminum Tissue Compensator Using Ion Chamber, TLD, and Gafchromic Film

    SciTech Connect

    Kinhikar, Rajesh A. Tambe, Chandrashekhar M.; Upreti, Ritu R.; Patkar, Sachin; Patil, Kalpana; Deshpande, Deepak D.

    2008-01-01

    Anatomic contour irregularity and tissue inhomogeneity in head-and-neck radiotherapy can lead to significant dose inhomogeneity due to the presence of hot and cold spots across the treatment volumes. Missing tissue compensators (TCs) can overcome this dose inhomogeneity. The current study examines the capacity of 2-dimensional (2D) custom aluminum TCs fabricated at our hospital to improve the dose homogeneity across the treatment volume. The dosimetry of the 2D custom TCs was carried out in a specially designed head-and-neck phantom for anterior-posterior (AP) and posterior-anterior (PA) fields with an ion chamber, thermoluminscence dosimeters (TLDs), and film. The results were compared for compensated and uncompensated plans generated from the Eclipse treatment planning system. On average, open-field plans contained peak doses of 117%, optimally wedged-plans contained peak doses of 113%, and custom-compensated plans contained peak doses of 105%. The dose variation between prescribed and measured dose at midplane of the phantom was observed as high as 17%, which was reduced to 3.2% for the customized TC during ionometric measurements. It was further confirmed with TLDs, in a sagittal plane, that the high-dose region of 13.3% was reduced to 2.3%. The measurements carried out with the ion chamber, TLDs, and film were found in good agreement with each other and with Eclipse. Thus, a custom-made 2D TC is capable of reducing hot spots to improve overall dose homogeneity across the treatment volume.

  12. Response of air-filled ion chambers to high-intensity radiation pulses

    SciTech Connect

    Plum, M.; Brown, D.

    1993-06-01

    Ion chambers are one of the most popular types of detectors used for beam loss-monitor systems. To provide a foundation for the development of future loss-monitor systems, and to fully characterize the ion chambers in use at LAMPF, we have studied the response of air-filled cylindrical ion chambers to high-intensity, short-duration radiation pulses. The most intense pulses were about 180 rad in 250 ns (the equivalent steady-state dose rate was about 700 Mrad/h). We filled our chambers with nitrogen gas at 760 Torr and air at 600 Torr. The ion chambers were driven into extreme nonlinear response. We hope these data will be used to design loss-monitor systems based on air-filled ion chambers, thus eliminating the need for gas-flow systems and/or airtight ion chambers.

  13. Response of air-filled ion chambers to high-intensity radiation pulses

    SciTech Connect

    Plum, M.; Brown, D.

    1993-01-01

    Ion chambers are one of the most popular types of detectors used for beam loss-monitor systems. To provide a foundation for the development of future loss-monitor systems, and to fully characterize the ion chambers in use at LAMPF, we have studied the response of air-filled cylindrical ion chambers to high-intensity, short-duration radiation pulses. The most intense pulses were about 180 rad in 250 ns (the equivalent steady-state dose rate was about 700 Mrad/h). We filled our chambers with nitrogen gas at 760 Torr and air at 600 Torr. The ion chambers were driven into extreme nonlinear response. We hope these data will be used to design loss-monitor systems based on air-filled ion chambers, thus eliminating the need for gas-flow systems and/or airtight ion chambers.

  14. Towards Simulating the Transverse Ising Model in a 2D Array of Trapped Ions

    NASA Astrophysics Data System (ADS)

    Sawyer, Brian

    2013-05-01

    Two-dimensional Coulomb crystals provide a useful platform for large-scale quantum simulation. Penning traps enable confinement of large numbers of ions (>100) and allow for the tunable-range spin-spin interactions demonstrated in linear ion strings, facilitating simulation of quantum magnetism at a scale that is currently intractable on classical computers. We readily confine hundreds of Doppler laser-cooled 9Be+ within a Penning trap, producing a planar array of ions with self-assembled triangular order. The transverse ``drumhead'' modes of our 2D crystal along with the valence electron spin of Be+ serve as a resource for generating spin-motion and spin-spin entanglement. Applying a spin-dependent optical dipole force (ODF) to the ion array, we perform spectroscopy and thermometry of individual drumhead modes. This ODF also allows us to engineer long-range Ising spin couplings of either ferromagnetic or anti-ferromagnetic character whose approximate power-law scaling with inter-ion distance, d, may be varied continuously from 1 /d0 to 1 /d3. An effective transverse magnetic field is applied via microwave radiation at the ~124-GHz spin-flip frequency, and ground states of the effective Ising Hamiltonian may in principle be prepared adiabatically by slowly decreasing this transverse field in the presence of the induced Ising coupling. Long-range anti-ferromagnetic interactions are of particular interest due to their inherent spin frustration and resulting large, near-degenerate manifold of ground states. We acknowledge support from NIST and the DARPA-OLE program.

  15. Hall-Effect Thruster Simulations with 2-D Electron Transport and Hydrodynamic Ions

    NASA Technical Reports Server (NTRS)

    Mikellides, Ioannis G.; Katz, Ira; Hofer, Richard H.; Goebel, Dan M.

    2009-01-01

    A computational approach that has been used extensively in the last two decades for Hall thruster simulations is to solve a diffusion equation and energy conservation law for the electrons in a direction that is perpendicular to the magnetic field, and use discrete-particle methods for the heavy species. This "hybrid" approach has allowed for the capture of bulk plasma phenomena inside these thrusters within reasonable computational times. Regions of the thruster with complex magnetic field arrangements (such as those near eroded walls and magnets) and/or reduced Hall parameter (such as those near the anode and the cathode plume) challenge the validity of the quasi-one-dimensional assumption for the electrons. This paper reports on the development of a computer code that solves numerically the 2-D axisymmetric vector form of Ohm's law, with no assumptions regarding the rate of electron transport in the parallel and perpendicular directions. The numerical challenges related to the large disparity of the transport coefficients in the two directions are met by solving the equations in a computational mesh that is aligned with the magnetic field. The fully-2D approach allows for a large physical domain that extends more than five times the thruster channel length in the axial direction, and encompasses the cathode boundary. Ions are treated as an isothermal, cold (relative to the electrons) fluid, accounting for charge-exchange and multiple-ionization collisions in the momentum equations. A first series of simulations of two Hall thrusters, namely the BPT-4000 and a 6-kW laboratory thruster, quantifies the significance of ion diffusion in the anode region and the importance of the extended physical domain on studies related to the impact of the transport coefficients on the electron flow field.

  16. Plasma generation near an Ion thruster disharge chamber hollow cathode

    NASA Technical Reports Server (NTRS)

    Katz, Ira; Anderson, John R.; Goebel, Dan M.; Wirz, Richard; Sengupta, Anita

    2003-01-01

    In gridded electrostatic thrusters, ions are produced by electron bombardment in the discharge chamber. In most of these thrusters, a single, centrally located hollow cathode supplies the ionizing electrons. An applied magnetic field in the discharge chamber restricts the electrons leaving the hollow cathode to a very narrow channel. In this channel, the high electron current density ionizes both propellant gas flowing from the hollow cathode, and other neutrals from the main propellant flow from the plenum. The processes that occur just past the hollow cathode exit are very important. In recent engine tests, several cases of discharge cathode orifice place and keeper erosion have been reported. In this paper we present results from a new 1-D, variable area model of the plasma processes in the magnetized channel just downstream of the hollow cathode keeper. The model predicts plasma densities, and temperatures consistent with those reported in the literature for the NSTAR engine, and preliminary results from the model show a potential maximum just downstream of the cathode.

  17. Extraction characteristics of a low-energy ion beam system with a remote plasma chamber

    NASA Astrophysics Data System (ADS)

    Vasquez, M. R.; Wada, M.

    2016-02-01

    Low-energy argon beams were extracted from a dual-chamber ion source system. The first chamber is a quartz cylinder where dense inductively coupled plasmas were produced using 13.56 MHz radio frequency (rf) power. The discharge was driven into an adjacent chamber which acts as a reservoir for ion beam extraction using a dual-electrode extractor configuration. Extraction of ions from the second chamber with energies in the 100 eV range was achieved while minimizing fluctuations induced by the rf signal. A custom-built retarding potential analyzer was used to analyze the effectiveness of ion beam transport using the remote plasma chamber. Well-defined beams were extracted between 60 and 100 V extraction potentials at 50-100 W rf powers. An increase in rf power resulted in an increase in average ion energy, increase in ion current density while the energy spread remains constant.

  18. Post-flight Analysis of the Argon Filled Ion Chamber

    NASA Technical Reports Server (NTRS)

    Tai, H.; Goldhagen, P.; Jones, I. W.; Wilson, J. W.; Maiden, D. L.; Shinn, J. L.

    2003-01-01

    Atmospheric ionizing radiation is a complex mixture of primary galactic and solar cosmic rays and a multitude of secondary particles produced in collision with air nuclei. The first series of Atmospheric Ionizing Radiation (AIR) measurement flights on the NASA research aircraft ER-2 took place in June 1997. The ER-2 flight package consisted of fifteen instruments from six countries and were chosen to provide varying sensitivity to specific components. These AIR ER-2 flight measurements are to characterize the AIR environment during solar minimum to allow the continued development of environmental models of this complex mixture of ionizing radiation. This will enable scientists to study the ionizing radiation health hazard associated with the high-altitude operation of a commercial supersonic transport and to allow estimates of single event upsets for advanced avionics systems design. The argon filled ion chamber representing about 40 percent of the contributions to radiation risks are analyzed herein and model discrepancies for solar minimum environment are on the order of 5 percent and less. Other biologically significant components remain to be analyzed.

  19. Characterization of a multi-axis ion chamber array

    SciTech Connect

    Simon, Thomas A.; Kozelka, Jakub; Simon, William E.; Kahler, Darren; Li, Jonathan; Liu, Chihray

    2010-11-15

    Purpose: The aim of this work was to characterize a multi-axis ion chamber array (IC PROFILER; Sun Nuclear Corporation, Melbourne, FL USA) that has the potential to simplify the acquisition of LINAC beam data. Methods: The IC PROFILER (or panel) measurement response was characterized with respect to radiation beam properties, including dose, dose per pulse, pulse rate frequency (PRF), and energy. Panel properties were also studied, including detector-calibration stability, power-on time, backscatter dependence, and the panel's agreement with water tank measurements [profiles, fractional depth dose (FDD), and output factors]. Results: The panel's relative deviation was typically within ({+-}) 1% of an independent (or nominal) response for all properties that were tested. Notable results were (a) a detectable relative field shape change of {approx}1% with linear accelerator PRF changes; (b) a large range in backscatter thickness had a minimal effect on the measured dose distribution (typically less than 1%); (c) the error spread in profile comparison between the panel and scanning water tank (Blue Phantom, CC13; IBA Schwarzenbruck, DE) was approximately ({+-}) 0.75%. Conclusions: The ability of the panel to accurately reproduce water tank profiles, FDDs, and output factors is an indication of its abilities as a dosimetry system. The benefits of using the panel versus a scanning water tank are less setup time and less error susceptibility. The same measurements (including device setup and breakdown) for both systems took 180 min with the water tank versus 30 min with the panel. The time-savings increase as the measurement load is increased.

  20. Development of ion chambers for the measurement of low energy synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Mahant, A. K.; Singh, Sunil Kumar; Panyam, Vinatha S.

    2009-04-01

    Measurement of radiation fields due to low energy synchrotron radiation (SR) needs special considerations. The photoelectric interactions, which are mainly responsible for signal generation in this case, result in electron emission in a direction nearly perpendicular to the direction of incident photon. A free air ionisation chamber was designed and used for measurement of intensity of SR in the beam line and a methodology has been developed to measure SR fields away from the beam line using large volume ion chambers. Studies with spherical and cylindrical ion chambers in X-ray beams obtained at a tube potential of 15 kV (3 mm Be inherent filtration) showed that the chamber sensitivity at low energy strongly depended on curvature of the chamber wall especially in thick walled chambers. Our studies further showed that large volume thin and plane walled (0.01 mm thick aluminium wall) chambers could be used for measurement of SR fields away from the beam lines, with reasonably good accuracy (±10%) by calibrating them against the free air ion chamber through a similar chamber of smaller dimensions.

  1. Binary and ternary recombination of H2D(+) and HD2(+) ions with electrons at 80 K.

    PubMed

    Dohnal, Petr; Kálosi, Ábel; Plašil, Radek; Roučka, Štěpán; Kovalenko, Artem; Rednyk, Serhiy; Johnsen, Rainer; Glosík, Juraj

    2016-08-24

    The recombination of deuterated trihydrogen cations with electrons has been studied in afterglow plasmas containing mixtures of helium, argon, hydrogen and deuterium. By monitoring the fractional abundances of H3(+), H2D(+), HD2(+) and D3(+) as a function of the [D2]/[H2] ratio using infrared absorption observed in a cavity ring down absorption spectrometer (CRDS), it was possible to deduce effective recombination rate coefficients for H2D(+) and HD2(+) ions at a temperature of 80 K. From pressure dependences of the measured effective recombination rate coefficients the binary and the ternary recombination rate coefficients for both ions have been determined. The inferred binary and ternary recombination rate coefficients are: αbinH2D(80 K) = (7.1 ± 4.2) × 10(-8) cm(3) s(-1), αbinHD2(80 K) = (8.7 ± 2.5) × 10(-8) cm(3) s(-1), KH2D(80 K) = (1.1 ± 0.6) × 10(-25) cm(6) s(-1) and KHD2(80 K) = (1.5 ± 0.4) × 10(-25) cm(6) s(-1). PMID:27506912

  2. Reactions of State-Selected Atomic Oxygen Ions O(+)((4)S, (2)D, (2)P) with Methane.

    PubMed

    Cunha de Miranda, Barbara; Romanzin, Claire; Chefdeville, Simon; Vuitton, Véronique; Žabka, Jan; Polášek, Miroslav; Alcaraz, Christian

    2015-06-11

    An experimental study has been carried out on the reactions of state selected O(+)((4)S, (2)D, (2)P) ions with methane with the aims of characterizing the effects of both the parent ion internal energy and collision energy on the reaction dynamics and determining the fate of oxygen species in complex media, in particular the Titan ionosphere. Absolute cross sections and product velocity distributions have been determined for the reactions of (16)O(+) or (18)O(+) ions with CH4 or CD4 from thermal to 5 eV collision energies by using the guided ion beam (GIB) technique. Dissociative photoionization of O2 with vacuum ultraviolet (VUV) synchrotron radiation delivered by the DESIRS beamline at the SOLEIL storage ring and the threshold photoion photoelectron coincidence (TPEPICO) technique are used for the preparation of purely state-selected O(+)((4)S, (2)D, (2)P) ions. A complete inversion of the product branching ratio between CH4(+) and CH3(+) ions in favor of the latter is observed for excitation of O(+) ions from the (4)S ground state to either the (2)D or the (2)P metastable state. CH4(+) and CH3(+) ions, which are by far the major products for the reaction of ground state and excited states, are strongly backward scattered in the center of mass frame relative to O(+) parent ions. For the reaction of O(+)((4)S), CH3(+) production also rises with increasing collision energy but with much less efficiency than with O(+) excitation. We found that a mechanism of dissociative charge transfer, mediated by an initial charge transfer step, can account very well for all the observations, indicating that CH3(+) production is associated with the formation of H and O atoms (CH3(+) + H + O) rather than with OH formation by an hydride transfer process (CH3(+) + OH). Therefore, as the CH4(+) production by charge transfer is also associated with O atoms, the fate of oxygen species in these reactions is essentially the O production, except for the reaction of O(+)((4)S), which also

  3. Reactions of State-Selected Atomic Oxygen Ions O(+)((4)S, (2)D, (2)P) with Methane.

    PubMed

    Cunha de Miranda, Barbara; Romanzin, Claire; Chefdeville, Simon; Vuitton, Véronique; Žabka, Jan; Polášek, Miroslav; Alcaraz, Christian

    2015-06-11

    An experimental study has been carried out on the reactions of state selected O(+)((4)S, (2)D, (2)P) ions with methane with the aims of characterizing the effects of both the parent ion internal energy and collision energy on the reaction dynamics and determining the fate of oxygen species in complex media, in particular the Titan ionosphere. Absolute cross sections and product velocity distributions have been determined for the reactions of (16)O(+) or (18)O(+) ions with CH4 or CD4 from thermal to 5 eV collision energies by using the guided ion beam (GIB) technique. Dissociative photoionization of O2 with vacuum ultraviolet (VUV) synchrotron radiation delivered by the DESIRS beamline at the SOLEIL storage ring and the threshold photoion photoelectron coincidence (TPEPICO) technique are used for the preparation of purely state-selected O(+)((4)S, (2)D, (2)P) ions. A complete inversion of the product branching ratio between CH4(+) and CH3(+) ions in favor of the latter is observed for excitation of O(+) ions from the (4)S ground state to either the (2)D or the (2)P metastable state. CH4(+) and CH3(+) ions, which are by far the major products for the reaction of ground state and excited states, are strongly backward scattered in the center of mass frame relative to O(+) parent ions. For the reaction of O(+)((4)S), CH3(+) production also rises with increasing collision energy but with much less efficiency than with O(+) excitation. We found that a mechanism of dissociative charge transfer, mediated by an initial charge transfer step, can account very well for all the observations, indicating that CH3(+) production is associated with the formation of H and O atoms (CH3(+) + H + O) rather than with OH formation by an hydride transfer process (CH3(+) + OH). Therefore, as the CH4(+) production by charge transfer is also associated with O atoms, the fate of oxygen species in these reactions is essentially the O production, except for the reaction of O(+)((4)S), which also

  4. 2D profile of poloidal magnetic field diagnosed by a laser-driven ion-beam trace probe (LITP)

    NASA Astrophysics Data System (ADS)

    Yang, Xiaoyi; Xiao, Chijie; Chen, Yihang; Xu, Tianchao; Lin, Chen; Wang, Long; Xu, Min; Yu, Yi

    2016-11-01

    Based on large energy spread of laser-driven ion beam (LIB), a new method, the Laser-driven Ion-beam Trace Probe (LITP), was suggested recently to diagnose the poloidal magnetic field (Bp) and radial electric field (Er) in toroidal devices. Based on another property of LIB, a wide angular distribution, here we suggested that LITP could be extended to get 2D Bp profile or 1D profile of both poloidal and radial magnetic fields at the same time. In this paper, we show the basic principle, some preliminary simulation results, and experimental preparation to test the basic principle of LITP.

  5. A 2D Particle in Cell model for ion extraction and focusing in electrostatic accelerators.

    PubMed

    Veltri, P; Cavenago, M; Serianni, G

    2014-02-01

    Negative ions are fundamental to produce intense and high energy neutral beams used to heat the plasma in fusion devices. The processes regulating the ion extraction involve the formation of a sheath on a scale comparable to the Debye length of the plasma. On the other hand, the ion acceleration as a beam is obtained on distances greater than λD. The paper presents a model for both the phases of ion extraction and acceleration of the ions and its implementation in a numerical code. The space charge of particles is deposited following usual Particle in Cell codes technique, while the field is solved with finite element methods. Some hypotheses on the beam plasma transition are described, allowing to model both regions at the same time. The code was tested with the geometry of the NIO1 negative ions source, and the results are compared with existing ray tracing codes and discussed.

  6. A 2D Particle in Cell model for ion extraction and focusing in electrostatic accelerators

    SciTech Connect

    Veltri, P. Serianni, G.; Cavenago, M.

    2014-02-15

    Negative ions are fundamental to produce intense and high energy neutral beams used to heat the plasma in fusion devices. The processes regulating the ion extraction involve the formation of a sheath on a scale comparable to the Debye length of the plasma. On the other hand, the ion acceleration as a beam is obtained on distances greater than λ{sub D}. The paper presents a model for both the phases of ion extraction and acceleration of the ions and its implementation in a numerical code. The space charge of particles is deposited following usual Particle in Cell codes technique, while the field is solved with finite element methods. Some hypotheses on the beam plasma transition are described, allowing to model both regions at the same time. The code was tested with the geometry of the NIO1 negative ions source, and the results are compared with existing ray tracing codes and discussed.

  7. A 2D Particle in Cell model for ion extraction and focusing in electrostatic accelerators

    NASA Astrophysics Data System (ADS)

    Veltri, P.; Cavenago, M.; Serianni, G.

    2014-02-01

    Negative ions are fundamental to produce intense and high energy neutral beams used to heat the plasma in fusion devices. The processes regulating the ion extraction involve the formation of a sheath on a scale comparable to the Debye length of the plasma. On the other hand, the ion acceleration as a beam is obtained on distances greater than λD. The paper presents a model for both the phases of ion extraction and acceleration of the ions and its implementation in a numerical code. The space charge of particles is deposited following usual Particle in Cell codes technique, while the field is solved with finite element methods. Some hypotheses on the beam plasma transition are described, allowing to model both regions at the same time. The code was tested with the geometry of the NIO1 negative ions source, and the results are compared with existing ray tracing codes and discussed.

  8. Hybrid plan verification for intensity-modulated radiation therapy (IMRT) using the 2D ionization chamber array I'mRT MatriXX--a feasibility study.

    PubMed

    Dobler, Barbara; Streck, Natalia; Klein, Elisabeth; Loeschel, Rainer; Haertl, Petra; Koelbl, Oliver

    2010-01-21

    The 2D ionization chamber array I'mRT MatriXX (IBA, Schwarzenbruck, Germany) has been developed for absolute 2D dosimetry and verification of intensity-modulated radiation therapy (IMRT) for perpendicular beam incidence. The aim of this study is to evaluate the applicability of I'mRT MatriXX for oblique beam incidence and hybrid plan verification of IMRT with original gantry angles. For the assessment of angular dependence, open fields with gantry angles in steps of 10 degrees were calculated on a CT scan of I'mRT MatriXX. For hybrid plan verification, 17 clinical IMRT plans and one rotational plan were used. Calculations were performed with pencil beam (PB), collapsed cone (CC) and Monte Carlo (MC) methods, which had been previously validated. Measurements were conducted on an Elekta SynergyS linear accelerator. To assess the potential and limitations of the system, gamma evaluation was performed with different dose tolerances and distances to agreement. Hybrid plan verification passed the gamma test with 4% dose tolerance and 3 mm distance to agreement in all cases, in 82-88% of the cases for tolerances of 3%/3 mm, and in 59-76% of the cases if 3%/2 mm were used. Separate evaluation of the low dose and high dose regions showed that I'mRT MatriXX can be used for hybrid plan verification of IMRT plans within 3% dose tolerance and 3 mm distance to agreement with a relaxed dose tolerance of 4% in the low dose region outside the multileaf collimator (MLC).

  9. Determination of relative ion chamber calibration coefficients from depth-ionization measurements in clinical electron beams.

    PubMed

    Muir, B R; McEwen, M R; Rogers, D W O

    2014-10-01

    A method is presented to obtain ion chamber calibration coefficients relative to secondary standard reference chambers in electron beams using depth-ionization measurements. Results are obtained as a function of depth and average electron energy at depth in 4, 8, 12 and 18 MeV electron beams from the NRC Elekta Precise linac. The PTW Roos, Scanditronix NACP-02, PTW Advanced Markus and NE 2571 ion chambers are investigated. The challenges and limitations of the method are discussed. The proposed method produces useful data at shallow depths. At depths past the reference depth, small shifts in positioning or drifts in the incident beam energy affect the results, thereby providing a built-in test of incident electron energy drifts and/or chamber set-up. Polarity corrections for ion chambers as a function of average electron energy at depth agree with literature data. The proposed method produces results consistent with those obtained using the conventional calibration procedure while gaining much more information about the behavior of the ion chamber with similar data acquisition time. Measurement uncertainties in calibration coefficients obtained with this method are estimated to be less than 0.5%. These results open up the possibility of using depth-ionization measurements to yield chamber ratios which may be suitable for primary standards-level dissemination.

  10. Determination of relative ion chamber calibration coefficients from depth-ionization measurements in clinical electron beams

    NASA Astrophysics Data System (ADS)

    Muir, B. R.; McEwen, M. R.; Rogers, D. W. O.

    2014-10-01

    A method is presented to obtain ion chamber calibration coefficients relative to secondary standard reference chambers in electron beams using depth-ionization measurements. Results are obtained as a function of depth and average electron energy at depth in 4, 8, 12 and 18 MeV electron beams from the NRC Elekta Precise linac. The PTW Roos, Scanditronix NACP-02, PTW Advanced Markus and NE 2571 ion chambers are investigated. The challenges and limitations of the method are discussed. The proposed method produces useful data at shallow depths. At depths past the reference depth, small shifts in positioning or drifts in the incident beam energy affect the results, thereby providing a built-in test of incident electron energy drifts and/or chamber set-up. Polarity corrections for ion chambers as a function of average electron energy at depth agree with literature data. The proposed method produces results consistent with those obtained using the conventional calibration procedure while gaining much more information about the behavior of the ion chamber with similar data acquisition time. Measurement uncertainties in calibration coefficients obtained with this method are estimated to be less than 0.5%. These results open up the possibility of using depth-ionization measurements to yield chamber ratios which may be suitable for primary standards-level dissemination.

  11. Ion Dynamics at a Rippled Quasi-parallel Shock: 2D Hybrid Simulations

    NASA Astrophysics Data System (ADS)

    Hao, Yufei; Lu, Quanming; Gao, Xinliang; Wang, Shui

    2016-05-01

    In this paper, two-dimensional hybrid simulations are performed to investigate ion dynamics at a rippled quasi-parallel shock. The results show that the ripples around the shock front are inherent structures of a quasi-parallel shock, and the re-formation of the shock is not synchronous along the surface of the shock front. By following the trajectories of the upstream ions, we find that these ions behave differently when they interact with the shock front at different positions along the shock surface. The upstream particles are transmitted more easily through the upper part of a ripple, and the corresponding bulk velocity downstream is larger, where a high-speed jet is formed. In the lower part of the ripple, the upstream particles tend to be reflected by the shock. Ions reflected by the shock may suffer multiple-stage acceleration when moving along the shock surface or trapped between the upstream waves and the shock front. Finally, these ions may escape further upstream or move downstream; therefore, superthermal ions can be found both upstream and downstream.

  12. Imaging with a multiplane multiwire proportional chamber using heavy ion beams

    SciTech Connect

    Chu, W.T.; Alonso, J.R.; Tobias, C.A.

    1982-01-01

    A 16-plane multiwire proportional chamber has been developed to accurately map intensity profiles of heavy ion beams at the Bevalac. The imaging capability of the system has been tested for reconstruction of 3-dimensional representation of a canine thorax region using heavy ion beams.

  13. Imaging With A Multiplane Multiwire Proportional Chamber Using Heavy Ion Beams

    NASA Astrophysics Data System (ADS)

    Chu, W. T.; Alonso, J. R.; Tobias, C. A...

    1982-11-01

    A 16-plane multiwire proportional chamber has been developed to accurately map intensity pro files of heavy ion beams at the Bevalac. The imaging capability of the system has been tested for reconstruction of 3-dimensional representation of a canine thorax region using heavy ion beams.

  14. Imaging with a multiplane multiwire proportional chamber using heavy-ion beams

    NASA Astrophysics Data System (ADS)

    Chu, W. T.; Alonso, J. R.; Tobias, C. A.

    A 16 plane multiwire proportional chamber was developed to accurately map intensity profiles of heavy ion beams at the Bevalac. The imaging capability of the system was tested for reconstruction of 3 dimensional representation of a canine thorax region using heavy ion beams.

  15. Heavy ion beam studies and imaging with a multiplane multiwire proportional chamber

    NASA Astrophysics Data System (ADS)

    Chu, W. T.; Alonso, J. R.; Tobias, C.

    1981-03-01

    A 16-plane multiwire proportional chamber was used to accurately measure intensity profiles of heavy ion beams at the Bevalac. An imaging capability was developed for the system, allowing for reconstruction of three dimensional representation of radiological objects using heavy ion beams.

  16. Implementing a New Ion Chamber Design for Neutron Spin Rotation

    NASA Astrophysics Data System (ADS)

    Gardiner, Hannah; Anderson, Eamon; Fry, Jason; Holley, Adam; Snow, Mike

    2012-10-01

    The quark-quark weak interaction is difficult to measure due to the presence of the strong force. However, low energy neutrons passing through liquid Helium-4 can be used to probe the nucleon-nucleon weak interaction, which is induced by the quark-quark weak interaction. The neutron spin rotation experiment seeks to measure the spin rotation angle of neutrons due to their weak interaction with Helium-4 nuclei. This rotation angle is translated into a neutron flux asymmetry with a neutron polarizer/analyzer pair. A segmented Helium-3 gas ionization chamber was developed to measure the resultant neutron flux. We report on the design and initial tests of that ionization chamber. This work is supported by the National Science Foundation REU program and NSF grant #PHY-0969490.

  17. Shielding analysis for a heavy ion beam chamber with plasma channels for ion transport

    SciTech Connect

    Sawan, M.E.; Peterson, R.R.; Yu, S.

    2000-06-28

    Neutronics analysis has been performed to assess the shielding requirements for the insulators and final focusing magnets in a modified HYLIFE-II target chamber that utilizes pre-formed plasma channels for heavy ion beam transport. Using 65 cm thick Flibe jet assemblies provides adequate shielding for the electrical insulator units. Additional shielding is needed in front of the final focusing superconducting quadrupole magnets. A shield with a thickness varying between 45 and 90 cm needs to be provided in front of the quadrupole unit. The final laser mirrors located along the channel axis are in the direct line-of-sight of source neutrons. Neutronics calculations were performed to determine the constraints on the placement of these mirrors to be lifetime components.

  18. Effects of discharge chamber length on the negative ion generation in volume-produced negative hydrogen ion source

    SciTech Connect

    Chung, Kyoung-Jae; Jung, Bong-Ki; An, YoungHwa; Dang, Jeong-Jeung; Hwang, Y. S.

    2014-02-15

    In a volume-produced negative hydrogen ion source, control of electron temperature is essential due to its close correlation with the generation of highly vibrationally excited hydrogen molecules in the heating region as well as the generation of negative hydrogen ions by dissociative attachment in the extraction region. In this study, geometric effects of the cylindrical discharge chamber on negative ion generation via electron temperature changes are investigated in two discharge chambers with different lengths of 7.5 cm and 11 cm. Measurements with a radio-frequency-compensated Langmuir probe show that the electron temperature in the heating region is significantly increased by reducing the length of the discharge chamber due to the reduced effective plasma size. A particle balance model which is modified to consider the effects of discharge chamber configuration on the plasma parameters explains the variation of the electron temperature with the chamber geometry and gas pressure quite well. Accordingly, H{sup −} ion density measurement with laser photo-detachment in the short chamber shows a few times increase compared to the longer one at the same heating power depending on gas pressure. However, the increase drops significantly as operating gas pressure decreases, indicating increased electron temperatures in the extraction region degrade dissociative attachment significantly especially in the low pressure regime. It is concluded that the increase of electron temperature by adjusting the discharge chamber geometry is efficient to increase H{sup −} ion production as long as low electron temperatures are maintained in the extraction region in volume-produced negative hydrogen ion sources.

  19. Dynamics of Ion-Gating 2D Crystals Using a Solid Polymer Electrolyte

    NASA Astrophysics Data System (ADS)

    Li, Hua-Min; Bourdon, Buchanan; Lin, Yu-Chuan; Robinson, Joshua; Seabaugh, Alan; Fullerton, Susan; CenterLow Energy Systems Technology (Least) Team

    2015-03-01

    Ion-gating can significantly increase the static carrier density of graphene due to the formation of an electric double layer (EDL); however, the dynamics of ion-gating have not been extensively reported. A comprehensive understanding of ion dynamics is important because it establishes the timescales required to achieve EDL equilibrium, and directly affects the operating speed of devices and circuits employing electrolytic gates. Here, ion dynamics are measured on epitaxial graphene Hall-bar devices that are electrolytically gated with polyethylene oxide and lithium perchlorate. The time constants for EDL formation and dissipation are measured as a function of temperature. The measured formation time is slower than the dissipation time, because ion diffusion resulting from a concentration gradient must be opposed during EDL formation. These results quantitatively agree with COMSOL multiphysics simulations. EDL dissipation follows a stretched exponential decay described by the Kohlrausch-Williams-Watts (KWW) equation. The temperature-dependent relaxation times extracted from the KWW fit follow the Vogel-Fulcher-Tammann (VFT) temperature dependence. At temperatures approaching the glass transition temperature of the electrolyte, the relaxation times exceed several hours, demonstrating the long timescales over which the EDL can persist in the absence of a gate bias.

  20. Convert Ten Foot Environmental Test Chamber into an Ion Engine Test Chamber

    NASA Technical Reports Server (NTRS)

    VanVelzer, Paul

    2006-01-01

    The 10 Foot Space Simulator at the Jet Propulsion Laboratory has been used for the last 40 years to test numerous spacecraft, including the Ranger series, several Mariner class, among many others and finally, the Spirit and Opportunity Mars Rovers. The request was made to convert this facility to an Ion Engine test facility, with a possible long term life test. The Ion engine was to propel the Prometheus spacecraft to Jupiter's moons. This paper discusses the challenges that were met, both from a procedural and physical standpoint. The converted facility must operate unattended, support a 30 Kw Ion Engine, operate economically, and be easily converted back to former operation as a spacecraft test facility.

  1. An EGSnrc investigation of correction factors for ion chamber dosimetry

    NASA Astrophysics Data System (ADS)

    Buckley, Lesley A.

    Radiation dosimetry is used to quantify the dose delivered during radiation therapy by using ionization chambers with several correction factors. Knowledge of these factors is needed at well below the 1% level in order to maintain the overall uncertainty on the reference dosimetry near 1-2%. The small magnitude of the corrections renders measurements very difficult. Monte Carlo calculations are widely used for this purpose, however they require very low statistical uncertainties. A new user-code, CSnrc, for the EGSnrc Monte Carlo system is described. CSnrc uses a correlated sampling variance reduction technique to reduce the uncertainty for dose ratio calculations. Compared to an existing EGSnrc user-code from which it was developed, CSnrc shows gains in efficiency of up to a factor of 64 and achieves much lower statistical uncertainties on correction factors than previously published. CSnrc is used to compute the central electrode correction factor, Pcel, in a broader range of beams than previously used and at the depths relevant to modern protocols. For photon beams, the CSnrc values compare well with the values used in dosimetry protocols whereas for electron beams, CSnrc shows up to a 0.2% correction for a graphite electrode, a correction currently ignored by dosimetry protocols. The difference from currently used values is slightly less for an aluminum electrode. CSnrc is also used to compute the wall correction factor, P wall. For cylindrical chambers in photon beams, the CSnrc calculations are compared to the currently used Almond-Svensson formalism and differ from this formalism by as much as 0.8%. The CSnrc values are used to explain some previously published experiments showing problems with Pwall . For electron beams, where dosimetry protocols assume a Pwall of unity, CSnrc calculations show a correction as large as 0.6%. For parallel-plate chambers, there is little information available regarding Pwall in photon beams. CSnrc shows corrections of over 2

  2. The 2-D Ion Chromatography Development and Application: Determination of Sulfate in Formation Water at Pre-Salt Region

    NASA Astrophysics Data System (ADS)

    Tonietto, G. B.; Godoy, J. M.; Almeida, A. C.; Mendes, D.; Soluri, D.; Leite, R. S.; Chalom, M. Y.

    2015-12-01

    Formation water is the naturally-occurring water which is contained within the geological formation itself. The quantity and quality of the formation water can both be problematic. Over time, the water volume should decrease as the gas volumes increase. Formation water has been found to contain high levels of Cl, As, Fe, Ba, Mn, PAHs and may even contain naturally occurring radioactive materials. Chlorides in some cases have been found to be in excess of four-five times the level of concentrations found in the ocean. Within the management of well operation, there is sulfate between the analytes of greatest importance due to the potential for hydrogen sulphide formation and consequent corrosion of pipelines. As the concentration of sulfate in these waters can be less than n times that of chloride, a quantitative determination, using the technique of ion chromatography, constitutes an analytical challenge. This work aimed to develop and validate a method for the determination of sulphate ions in hyper-saline waters coming from the oil wells of the pre-salt, using 2D IC. In 2D IC the first column can be understood as a separating column, in which the species with retention times outside a preset range are discarded, while those belonging to this range are retained in a pre-concentrator column to further injecting a second column, the second dimension in which occurs the separation and quantification of the analytes of interest. As the chloride ions have a retention time lower than that of sulfate, a method was developed a for determining sulfate in very low range (mg L-1) by 2D IC, applicable to hypersaline waters, wherein the first dimension is used to the elimination of the matrix, ie, chloride ions, and the second dimension utilized in determining sulfate. For sulphate in a concentration range from 1.00 mg L-1 was obtained an accuracy of 1.0%. The accuracy of the method was tested by the standard addition method different samples of formation water in the pre

  3. Construction and Commissioning of a New Scattering Chamber at the Union College Ion Beam Analysis Laboratory

    NASA Astrophysics Data System (ADS)

    Turley, Colin; Moore, Robert; Johnson, Christopher; Battaglia, Maria; Vineyard, Michael; Labrake, Scott

    2011-10-01

    We have constructed a new scattering chamber in the Union College Ion Beam Analysis Laboratory to improve our experimental capabilities. The new chamber was constructed from a ten-inch, conflat, multi-way cross. We fitted the chamber with an eight-inch, Leybold turbomolecular pump so that it can be evacuated quickly. A target manipulator with stepper motors that provide x, y, and z-positioning of the target with micron precision is mounted atop the chamber. A target ladder was constructed for the manipulator that allows us to analyze multiple samples without breaking the vacuum. The chamber has a door with an O-ring seal mounted on one of the ten-inch ports that provides easy access to the interior of the chamber. An Amptek silicon-drift X-ray detector is mounted close to the target ladder, inside the vacuum so that low-energy X-rays can be detected. A new Faraday cup was also installed to provide more accurate current measurements. Finally, a new collimator system was developed and installed in the beam-line to the scattering chamber to provide a well-defined beam spot. A proton induced X-ray emission analysis of aerosol samples has been performed as the commissioning experiment for the chamber. Here, we report on the construction and commissioning of this new chamber.

  4. Impact of beam transport method on chamber and driver design for heavy ion inertial fusion energy

    SciTech Connect

    Rose, D.V.; Welch, D.R.; Olson, C.L.; Yu, S.S.; Neff, S.; Sharp, W.M.

    2002-12-01

    In heavy ion inertial fusion energy systems, intense beams of ions must be transported from the exit of the final focus magnet system through the target chamber to hit millimeter spot sizes on the target. In this paper, we examine three different modes of beam propagation: neutralized ballistic transport, assisted pinched transport, and self-pinched transport. The status of our understanding of these three modes is summarized, and the constraints imposed by beam propagation upon the chamber environment, as well as their compatibility with various chamber and target concepts, are considered. We conclude that, on the basis of our present understanding, there is a reasonable range of parameter space where beams can propagate in thick-liquid wall, wetted-wall, and dry-wall chambers.

  5. Computational Model Tracking Primary Electrons, Secondary Electrons, and Ions in the Discharge Chamber of an Ion Engine

    NASA Technical Reports Server (NTRS)

    Mahalingam, Sudhakar; Menart, James A.

    2005-01-01

    Computational modeling of the plasma located in the discharge chamber of an ion engine is an important activity so that the development and design of the next generation of ion engines may be enhanced. In this work a computational tool called XOOPIC is used to model the primary electrons, secondary electrons, and ions inside the discharge chamber. The details of this computational tool are discussed in this paper. Preliminary results from XOOPIC are presented. The results presented include particle number density distributions for the primary electrons, the secondary electrons, and the ions. In addition the total number of a particular particle in the discharge chamber as a function of time, electric potential maps and magnetic field maps are presented. A primary electron number density plot from PRIMA is given in this paper so that the results of XOOPIC can be compared to it. PRIMA is a computer code that the present investigators have used in much of their previous work that provides results that compare well to experimental results. PRIMA only models the primary electrons in the discharge chamber. Modeling ions and secondary electrons, as well as the primary electrons, will greatly increase our ability to predict different characteristics of the plasma discharge used in an ion engine.

  6. Distributed drift chamber design for rare particle detection in relativistic heavy ion collisions

    SciTech Connect

    Bellwied, R.; Bennett, M.J.; Bernardo, V.; Caines, H.; Christie, W.; Costa, S.; Crawford, H.J.; Cronqvist, M.; Debbe, R.; Dinnwiddie, R.; Engelage, J.; Flores, I.; Fuzesy, R.; Greiner, L.; Hallman, T.; Hoffmann, G.; Huang, H.Z.; Jensen, P.; Judd, E.G.; Kainz, K.; Kaplan, M.; Kelly, S.; Lindstrom, P.J; Llope, W.J.; LoCurto, G.; Longacre, R.; Milosevich, Z.; Mitchell, J.T.; Mitchell, J.W.; Mogavero, E.; Mutchler, G.; Paganis, S.; Platner, E.; Potenza, R.; Rotondo, F.; Russ, D.; Sakrejda, I.; Saulys, A.; Schambach, J.; Sheen, J.; Smirnoff, N.; Stokeley, C.; Tang, J.; Trattner, A.L.; Trentalange, S.; Visser, G.; Whitfield, J.P.; Witharm, F.; Witharm, R.; Wright, M.

    2001-10-02

    This report describes a multi-plane drift chamber that was designed and constructed to function as a topological detector for the BNL AGSE896 rare particle experiment. The chamber was optimized for good spatial resolution, two track separation, and a high uniform efficiency while operating in a 1.6 Tesla magnetic field and subjected to long term exposure from a 11.6 GeV/nucleon beam of 10**6 Au ions per second.

  7. Ring cusp/hollow cathode discharge chamber performance studies. [ion propulsion

    NASA Technical Reports Server (NTRS)

    Vaughn, J. A.; Wilbur, Paul J.

    1988-01-01

    An experimental study was performed to determine the effects of hollow cathode position, anode position, and ring cusp magnetic field configuration and strength on discharge chamber performance. The results are presented in terms of comparative plasma ion energy cost, extracted ion fraction, and beam profile data. Such comparisons are used to demonstrate whether changes in performance are caused by changes in the loss rate of primary electrons to the anode or the loss rate of ions to discharge chamber walls or cathode and anode surfaces. Results show: (1) the rate of primary electron loss to the anode decreases as the anode is moved downstream of the ring cusp toward the screen grid; (2) the loss rate of ions to hollow cathode surfaces are excessive if the cathode is located upstream of a point of peak magnetic flux density at the discharge chamber centerline; and (3) the fraction of the ions produced that are lost to discharge chamber walls and ring magnet surfaces is reduced by positioning of the magnet rings so the plasma density is uniform over the grid surface, and adjusting their strength to a level where it is sufficient to prevent excessive ion losses by Bohm diffusion.

  8. Monte Carlo calculations of electron beam quality conversion factors for several ion chamber types

    SciTech Connect

    Muir, B. R.; Rogers, D. W. O.

    2014-11-01

    Purpose: To provide a comprehensive investigation of electron beam reference dosimetry using Monte Carlo simulations of the response of 10 plane-parallel and 18 cylindrical ion chamber types. Specific emphasis is placed on the determination of the optimal shift of the chambers’ effective point of measurement (EPOM) and beam quality conversion factors. Methods: The EGSnrc system is used for calculations of the absorbed dose to gas in ion chamber models and the absorbed dose to water as a function of depth in a water phantom on which cobalt-60 and several electron beam source models are incident. The optimal EPOM shifts of the ion chambers are determined by comparing calculations of R{sub 50} converted from I{sub 50} (calculated using ion chamber simulations in phantom) to R{sub 50} calculated using simulations of the absorbed dose to water vs depth in water. Beam quality conversion factors are determined as the calculated ratio of the absorbed dose to water to the absorbed dose to air in the ion chamber at the reference depth in a cobalt-60 beam to that in electron beams. Results: For most plane-parallel chambers, the optimal EPOM shift is inside of the active cavity but different from the shift determined with water-equivalent scaling of the front window of the chamber. These optimal shifts for plane-parallel chambers also reduce the scatter of beam quality conversion factors, k{sub Q}, as a function of R{sub 50}. The optimal shift of cylindrical chambers is found to be less than the 0.5 r{sub cav} recommended by current dosimetry protocols. In most cases, the values of the optimal shift are close to 0.3 r{sub cav}. Values of k{sub ecal} are calculated and compared to those from the TG-51 protocol and differences are explained using accurate individual correction factors for a subset of ion chambers investigated. High-precision fits to beam quality conversion factors normalized to unity in a beam with R{sub 50} = 7.5 cm (k{sub Q}{sup ′}) are provided. These

  9. Retention of Sputtered Molybdenum on Ion Engine Discharge Chamber Surfaces

    NASA Technical Reports Server (NTRS)

    Sovey, James S.; Dever, Joyce A.; Power, John L.

    2001-01-01

    Grit-blasted anode surfaces are commonly used in ion engines to ensure adherence of sputtered coatings. Next generation ion engines will require higher power levels, longer operating times, and thus there will likely be thicker sputtered coatings on their anode surfaces than observed to date on 2.3 kW-class xenon ion engines. The thickness of coatings on the anode of a 10 kW, 40-centimeter diameter thruster, for example, may be 22 micrometers or more after extended operation. Grit-blasted wire mesh, titanium, and aluminum coupons were coated with molybdenum at accelerated rates to establish coating stability after the deposition process and after thermal cycling tests. These accelerated deposition rates are roughly three orders of magnitude more rapid than the rates at which the screen grid is sputtered in a 2.3 kW-class, 30-centimeter diameter ion engine. Using both RF and DC sputtering processes, the molybdenum coating thicknesses ranged from 8 to 130 micrometers, and deposition rates from 1.8 micrometers per hour to 5.1 micrometers per hour. In all cases, the molybdenum coatings were stable after the deposition process, and there was no evidence of spalling of the coatings after 20 cycles from about -60 to +320 C. The stable, 130 micrometer molybdenum coating on wire mesh is 26 times thicker than the thickest coating found on the anode of a 2.3 kW, xenon ion engine that was tested for 8200 hr. Additionally, this coating on wire mesh coupon is estimated to be a factor of greater than 4 thicker than one would expect to obtain on the anode of the next generation ion engine which may have xenon throughputs as high as 550 kg.

  10. Fast 2D fluid-analytical simulation of ion energy distributions and electromagnetic effects in multi-frequency capacitive discharges

    NASA Astrophysics Data System (ADS)

    Kawamura, E.; Lieberman, M. A.; Graves, D. B.

    2014-12-01

    A fast 2D axisymmetric fluid-analytical plasma reactor model using the finite elements simulation tool COMSOL is interfaced with a 1D particle-in-cell (PIC) code to study ion energy distributions (IEDs) in multi-frequency capacitive argon discharges. A bulk fluid plasma model, which solves the time-dependent plasma fluid equations for the ion continuity and electron energy balance, is coupled with an analytical sheath model, which solves for the sheath parameters. The time-independent Helmholtz equation is used to solve for the fields and a gas flow model solves for the steady-state pressure, temperature and velocity of the neutrals. The results of the fluid-analytical model are used as inputs to a PIC simulation of the sheath region of the discharge to obtain the IEDs at the target electrode. Each 2D fluid-analytical-PIC simulation on a moderate 2.2 GHz CPU workstation with 8 GB of memory took about 15-20 min. The multi-frequency 2D fluid-analytical model was compared to 1D PIC simulations of a symmetric parallel-plate discharge, showing good agreement. We also conducted fluid-analytical simulations of a multi-frequency argon capacitively coupled plasma (CCP) with a typical asymmetric reactor geometry at 2/60/162 MHz. The low frequency 2 MHz power controlled the sheath width and sheath voltage while the high frequencies controlled the plasma production. A standing wave was observable at the highest frequency of 162 MHz. We noticed that adding 2 MHz power to a 60 MHz discharge or 162 MHz to a dual frequency 2 MHz/60 MHz discharge can enhance the plasma uniformity. We found that multiple frequencies were not only useful for controlling IEDs but also plasma uniformity in CCP reactors.

  11. Fast Ion Induced Shearing of 2D Alfven Eigenmodes Measured by Electron Cyclotron Emission Imaging

    SciTech Connect

    Tobias, Ben; Classen, I.G.J.; Domier, C. W.; Heidbrink, W.; Luhmann, N.C.; Nazikian, Raffi; Park, H.K.; Spong, Donald A; Van Zeeland, Michael

    2011-01-01

    Two-dimensional images of electron temperature perturbations are obtained with electron cyclotron emission imaging (ECEI) on the DIII-D tokamak and compared to Alfven eigenmode structures obtained by numerical modeling using both ideal MHD and hybrid MHD-gyrofluid codes. While many features of the observations are found to be in excellent agreement with simulations using an ideal MHD code (NOVA), other characteristics distinctly reveal the influence of fast ions on the mode structures. These features are found to be well described by the nonperturbative hybrid MHD-gyrofluid model TAEFL.

  12. Characterization of a two-dimensional liquid-filled ion chamber detector array used for verification of the treatments in radiotherapy

    SciTech Connect

    Markovic, Miljenko Stathakis, Sotirios; Mavroidis, Panayiotis; Jurkovic, Ines-Ana; Papanikolaou, Nikos

    2014-05-15

    Purpose: The purpose of the study is to investigate the characteristics of a two-dimensional (2D) liquid-filled ion chamber detector array, which is used for the verification of radiotherapy treatment plans that use small field sizes of up to 10 × 10 cm. Methods: The device used in this study was Octavius 1000 SRS model (PTW, Freiburg, Germany). Its 2D array of detectors consists of 977 liquid-filled ion chambers arranged over an area of 11 × 11 cm. The size of the detectors is 2.3 × 2.3 × 0.5 mm (volume of 0.003 cm{sup 3}) and their spacing in the inner area of 5.5 × 5.5 cm is 2.5 mm center-to-center, whereas in the outer area it is 5 mm center-to-center. The detector reproducibility, dose linearity, and sensitivity to positional changes of the collimator were tested. Also, the output factors of field sizes ranging from 0.5 × 0.5 to 10 × 10 cm{sup 2} both for open and wedged fields have been measured and compared against those measured by a pin-point ionization chamber, liquid filled microchamber, SRS diode, and EDR2 film. Results: Its short-term reproducibility was within 0.2% and its medium and long-term reproducibility was within 0.5% (verified with air ionization chamber absolute dose measurements), which is an excellent result taking into account the daily fluctuation of the linear accelerator and the errors in the device setup reproducibility. The dose linearity and dose rate dependence were measured in the range of 0.5–85 Gy and 0.5–10 Gy min{sup −1}, respectively, and were verified with air ionization chamber absolute dose measurements was within 3%. The measurements of the sensitivity showed that the 2D Array could detect millimetric collimator positional changes. The measured output factors showed an agreement of better than 0.3% with the pinpoint chamber and microliquid filled chamber for the field sizes between 3 × 3 and 10 × 10 cm{sup 2}. For field sizes down to 1 × 1 cm{sup 2}, the agreement with SRS diode and microliquid filled

  13. Lithium-ion capacitors with 2D Nb2CTx (MXene) - carbon nanotube electrodes

    NASA Astrophysics Data System (ADS)

    Byeon, Ayeong; Glushenkov, Alexey M.; Anasori, Babak; Urbankowski, Patrick; Li, Jingwen; Byles, Bryan W.; Blake, Brian; Van Aken, Katherine L.; Kota, Sankalp; Pomerantseva, Ekaterina; Lee, Jae W.; Chen, Ying; Gogotsi, Yury

    2016-09-01

    There is a growing interest to hybrid energy storage devices, such as lithium-ion capacitors, in which battery-type electrodes are combined with capacitor-type ones. It is anticipated that the energy density (either gravimetric or volumetric) of lithium-ion capacitors is improved if pseudocapacitive or fast insertion materials are used instead of conventional activated carbon (AC) in the capacitor-type electrode. MXenes, a new family of two-dimensional transition metal carbides, demonstrate metallic conductivity and fast charge-discharge behavior that make them suitable for this application. In this study, we move beyond single electrodes, half-cell studies and demonstrate three types of hybrid cells using Nb2CTx-carbon nanotube (CNT) films. It is shown that lithiated graphite/Nb2CTx-CNT, Nb2CTx-CNT/LiFePO4 and lithiated Nb2CTx-CNT/Nb2CTx-CNT cells are all able to operate within 3 V voltage windows and deliver capacities of 43, 24 and 36 mAh/g (per total weight of two electrodes), respectively. Moreover, the polarity of the electrodes can be reversed in the symmetric Nb2CTx-CNT cells from providing a positive potential between 0 and 3 V to a negative one from -3 to 0 V. It is shown that the volumetric energy density (50-70 Wh/L) of our first-generation devices with MXene electrodes exceeds that of a lithium titanate/AC capacitor.

  14. Efficiency improvements for ion chamber calculations in high energy photon beams

    SciTech Connect

    Wulff, J.; Zink, K.; Kawrakow, I.

    2008-04-15

    This article presents the implementation of several variance reduction techniques that dramatically improve the simulation efficiency of ion chamber dose and perturbation factor calculations. The cavity user code for the EGSnrc Monte Carlo code system is extended by photon cross-section enhancement (XCSE), an intermediate phase-space storage (IPSS) technique, and a correlated sampling (CS) scheme. XCSE increases the density of photon interaction sites inside and in the vicinity of the chamber and results - in combination with a Russian Roulette game for electrons that cannot reach the cavity volume - in an increased efficiency of up to a factor of 350 for calculating dose in a Farmer type chamber placed at 10 cm depth in a water phantom. In combination with the IPSS and CS techniques, the efficiency for the calculation of the central electrode perturbation factor P{sub cel} can be increased by up to three orders of magnitude for a single chamber location and by nearly four orders of magnitude when considering the P{sub cel} variation with depth or with distance from the central axis in a large field photon beam. The intermediate storage of the phase-space properties of particles entering a volume that contains many possible chamber locations leads to efficiency improvements by a factor larger than 500 when computing a profile of chamber doses in the field of a linear accelerator photon beam. All techniques are combined in a new EGSnrc user code egs{sub c}hamber. Optimum settings for the variance reduction parameters are investigated and are reported for a Farmer type ion chamber. A few example calculations illustrating the capabilities of the egs{sub c}hamber code are presented.

  15. SU-E-T-35: An Investigation of the Accuracy of Cervical IMRT Dose Distribution Using 2D/3D Ionization Chamber Arrays System and Monte Carlo Simulation

    SciTech Connect

    Zhang, Y; Yang, J; Liu, H; Liu, D

    2014-06-01

    Purpose: The purpose of this work is to compare the verification results of three solutions (2D/3D ionization chamber arrays measurement and Monte Carlo simulation), the results will help make a clinical decision as how to do our cervical IMRT verification. Methods: Seven cervical cases were planned with Pinnacle 8.0m to meet the clinical acceptance criteria. The plans were recalculated in the Matrixx and Delta4 phantom with the accurate plans parameters. The plans were also recalculated by Monte Carlo using leaf sequences and MUs for individual plans of every patient, Matrixx and Delta4 phantom. All plans of Matrixx and Delta4 phantom were delivered and measured. The dose distribution of iso slice, dose profiles, gamma maps of every beam were used to evaluate the agreement. Dose-volume histograms were also compared. Results: The dose distribution of iso slice and dose profiles from Pinnacle calculation were in agreement with the Monte Carlo simulation, Matrixx and Delta4 measurement. A 95.2%/91.3% gamma pass ratio was obtained between the Matrixx/Delta4 measurement and Pinnacle distributions within 3mm/3% gamma criteria. A 96.4%/95.6% gamma pass ratio was obtained between the Matrixx/Delta4 measurement and Monte Carlo simulation within 2mm/2% gamma criteria, almost 100% gamma pass ratio within 3mm/3% gamma criteria. The DVH plot have slightly differences between Pinnacle and Delta4 measurement as well as Pinnacle and Monte Carlo simulation, but have excellent agreement between Delta4 measurement and Monte Carlo simulation. Conclusion: It was shown that Matrixx/Delta4 and Monte Carlo simulation can be used very efficiently to verify cervical IMRT delivery. In terms of Gamma value the pass ratio of Matrixx was little higher, however, Delta4 showed more problem fields. The primary advantage of Delta4 is the fact it can measure true 3D dosimetry while Monte Carlo can simulate in patients CT images but not in phantom.

  16. High-resolution ion pulse ionization chamber with air filling for the 222Rn decays detection

    NASA Astrophysics Data System (ADS)

    Gavrilyuk, Yu. M.; Gangapshev, A. M.; Gezhaev, A. M.; Etezov, R. A.; Kazalov, V. V.; Kuzminov, V. V.; Panasenko, S. I.; Ratkevich, S. S.; Tekueva, D. A.; Yakimenko, S. P.

    2015-11-01

    The construction and characteristics of the cylindrical ion pulse ionization chamber (CIPIC) with a working volume of 3.2 L are described. The chamber is intended to register α-particles from the 222Rn and its daughter's decays in the filled air sample. The detector is less sensitive to electromagnetic pick-ups and mechanical noises. The digital pulse processing method is proposed to improve the energy resolution of the ion pulse ionization chamber. An energy resolution of 1.6% has been achieved for the 5.49 MeV α-line. The dependence of the energy resolution on high voltage and working media pressure has been investigated and the results are presented.

  17. Design and development of a wide range ion chamber for reactor instrumentation

    NASA Astrophysics Data System (ADS)

    Dighe, P. M.; Mukhopadhyay, P. K.

    2010-03-01

    An innovative design small size ion chamber has been developed that is capable of measuring gamma radiation below 100 mR/h and reaches saturation current even at less than 200 V operating voltage for 25,900 R/h gamma background. This wide ranging capability was achieved with a special combination of electrode arrangement and guard rings placed together with the support of radiation-resistant poly ether ether ketone (PEEK) spacers. The use of machinable PEEK material removed the dead spaces and accurately defined the sensitive volume to achieve nearly ideal performance. The ion chamber is made of stainless steel with 64 cm 3 sensitive volume and has 8.2 pA/100 mR/h gamma sensitivity. The chamber has been designed for reactor applications and therefore has been made rugged by separating and anchoring both the electrodes on both the ends to reduce any cantilever type vibrations with reduced noise pickup.

  18. Determination of ion recombination correction factors for a liquid ionization chamber in megavoltage photon beams

    NASA Astrophysics Data System (ADS)

    Choi, Sang Hyoun; Kim, Kum-Bae; Ji, Young Hoon; Kim, Chan Hyeong; Kim, Seonghoon; Huh, Hyun Do

    2015-05-01

    The aim of this study is to determine the ion recombination correction factor for a liquid ionization chamber in a high energy photon beam by using our experimental method. The ion recombination correction factors were determined by using our experimental method and were compared with theoretical and experimental methods proposed by using the theoretical method (Greening, Johansson) and the two-dose rate method in a cobalt beam and a high energy photon beam. In order to apply the liquid ionization chamber in a reference and small field dosimetry, we acquired the absorbed dose to water correction coefficient, the beam quality correction factor, and the influence quantities for the microLion chamber according to the TRS-398 protocol and applied the results to a high energy photon beam used in clinical fields. As a result, our experimental method for ion recombination in a cobalt beam agreed with the results from the heoretical method (Greening theory) better than it did with the results from the two-dose rate method. For high energy photon beams, the two-dose rate and our experimental methods were in good agreement, less than 2% deviation, while the theoretical general collection efficiency (Johansson et al.) deviated greatly from the experimental values. When we applied the factors for the absorbed dose to water measurement, the absorbed dose to water for the microLion chamber was in good agreement, within 1%, compared with the values for the PTW 30013 chamber in 6 and 10 MV Clinac iX and 6 and 15 MV Oncor impression. With these results, not only can the microLion ionization chamber be used to measure the absorbed dose to water in a reference condition, it can also be used to a the chamber for small, non-standard field dosimetry.

  19. Plasma Emission Characteristics from a High Current Hollow Cathode in an Ion Thruster Discharge Chamber

    NASA Technical Reports Server (NTRS)

    Foster, John E.; Patterson, Michael J.

    2002-01-01

    The presence of energetic ions produced by a hollow cathodes operating at high emission currents (greater than 5A) has been documented in the literature. In order to further elucidate these findings, an investigation of a high current cathode operating in an ion thruster discharge chamber has been undertaken. Using Langmuir probes, a low energy charged particle analyzer and emission spectroscopy, the behavior of the near-cathode plasma and the emitted ion energy distribution was characterized. The presence of energetic ions was confirmed. It was observed that these ions had energies in excess of the discharge voltage and thus cannot be simply explained by ions falling out of plasma through a potential difference of this order. Additionally, evidence provided by Langmuir probes suggests the existence of a double layer essentially separating the hollow cathode plasma column from the main discharge. The radial potential difference associated with this double layer was measured to be of order the ionization potential.

  20. PVA:LiClO4: a robust, high Tg polymer electrolyte for adjustable ion gating of 2D materials

    NASA Astrophysics Data System (ADS)

    Kinder, Erich; Fullerton, Susan; CenterLow Energy Systems Technology Team

    2015-03-01

    Polymer electrolytes are an effective way to gate organic semiconductors and nanomaterials, such as nanotubes and 2D materials, by establishing an electrostatic double layer with large capacitance. Widely used solid electrolytes, such as those based on polyethylene oxide, have a glass transition temperature below room temperature. This permits relatively fast ion mobility at T = 23 °C, but requires a constant applied field to maintain a doping profile. Moreover, PEO-based electrolytes cannot withstand a variety of solvents, limiting its use. Here, we demonstrate a polymer electrolyte using polyvinyl alcohol (PVA) with Tg >23 °C, through which a doping profile can be defined by a potential applied when the polymer is heated above Tg, then ``locked-in'' by cooling the electrolyte to room temperature (ion mobility. Current-voltage measurements of a graphene field effect transistor verify the ``lock-in'' process, showing constant drain current regardless of the applied electrolyte gate bias. Hall bar measurements are used to quantify the charge carrier density. Owing to PVA's chemical stability, photolithography can be performed directly on the polymer electrolyte, which allows for the deposition of a patterned, metal gate directly on the electrolyte, as well as the ability to pattern the electrolyte itself. This work was supported in part by the Center for Low Energy Systems Technology (LEAST), one of the six SRC STARnet Centers, sponsored by MARCO and DARPA.

  1. Detection and measurement of delay in the yield of negative ions from the ionization chamber of a mass spectrometer

    NASA Astrophysics Data System (ADS)

    Lukin, V. G.; Khvostenko, O. G.; Tuimedov, G. M.

    2016-02-01

    The times of extraction of negative ions from the ionization chamber of a mass spectrometer have been measured. The obtained values amount to several dozen microseconds or above—that is, significantly exceed the time of free ion escape from the chamber. It is established that ions are retained in the ionization chamber because of their adsorption on the inner surface. This leads to distortion of the experimentally measured lifetimes of negative ions that become unstable with respect to autodetachment of the excess electron.

  2. Detector Characterization Report, Response Related to Linear Movement and Radiation Levels for an Oak Ridge National Laboratory (ORNL)-Developed Ion Chamber and a Commercial Ion Chamber

    SciTech Connect

    Chiaro, P.J.

    2001-01-11

    Recent activities regarding the safeguarding of radioactive material have indicated there is a need to use radiation sensors to monitor intentional or unintentional material movement. Existing radiation detection systems were not typically designed for this type of operation since most of their use accounted for monitoring material while the material is stationary. To ensure that a radiation monitoring system is capable of detecting the movement of radioactive material, a series of tests were needed. These tests would need to be performed in known radiological conditions, under controlled environmental conditions, and at known movement speeds. The Radiation Effects Facility (REF), located at the Radiation Calibration Laboratory, provided the necessary capabilities to perform these tests. This report provides a compilation of the results from a characterization of two different sensors--a simple, air ionization chamber-based sensor developed at ORNL that consists of an ion chamber connected to a separate amplifier, and an Eberline model RO-7-LD. The RO-7-LD is also an air ionization chamber-based sensor, but the electronics are in the same physical package.

  3. Dosimetric comparisons of carbon ion treatment plans for 1D and 2D ripple filters with variable thicknesses

    NASA Astrophysics Data System (ADS)

    Printz Ringbæk, Toke; Weber, Uli; Santiago, Alina; Simeonov, Yuri; Fritz, Peter; Krämer, Michael; Wittig, Andrea; Bassler, Niels; Engenhart-Cabillic, Rita; Zink, Klemens

    2016-06-01

    A ripple filter (RiFi)—also called mini-ridge filter—is a passive energy modulator used in particle beam treatments that broadens the Bragg peak (BP) as a function of its maximum thickness. The number of different energies requested from the accelerator can thus be reduced, which significantly reduces the treatment time. A new second generation RiFi with 2D groove shapes was developed using rapid prototyping, which optimizes the beam-modulating material and enables RiFi thicknesses of up to 6 mm. Carbon ion treatment plans were calculated using the standard 1D 3 mm thick RiFi and the new 4 and 6 mm 2D RiFis for spherical planning target volumes (PTVs) in water, eight stage I non-small cell lung cancer cases, four skull base chordoma cases and three prostate cancer cases. TRiP98 was used for treatment planning with facility-specific base data calculated with the Monte Carlo code SHIELD-HIT12A. Dose-volume-histograms, spatial dose distributions and dosimetric indexes were used for plan evaluation. Plan homogeneity and conformity of thinner RiFis were slightly superior to thicker RiFis but satisfactory results were obtained for all RiFis investigated. For the 6 mm RiFi, fine structures in the dose distribution caused by the larger energy steps were observed at the PTV edges, in particular for superficial and/or very small PTVs but performances for all RiFis increased with penetration depth due to straggling and scattering effects. Plans with the new RiFi design yielded for the studied cases comparable dosimetric results to the standard RiFi while the 4 and 6 mm RiFis lowered the irradiation time by 25–30% and 45–49%, respectively.

  4. Dosimetric comparisons of carbon ion treatment plans for 1D and 2D ripple filters with variable thicknesses.

    PubMed

    Ringbæk, Toke Printz; Weber, Uli; Santiago, Alina; Simeonov, Yuri; Fritz, Peter; Krämer, Michael; Wittig, Andrea; Bassler, Niels; Engenhart-Cabillic, Rita; Zink, Klemens

    2016-06-01

    A ripple filter (RiFi)-also called mini-ridge filter-is a passive energy modulator used in particle beam treatments that broadens the Bragg peak (BP) as a function of its maximum thickness. The number of different energies requested from the accelerator can thus be reduced, which significantly reduces the treatment time. A new second generation RiFi with 2D groove shapes was developed using rapid prototyping, which optimizes the beam-modulating material and enables RiFi thicknesses of up to 6 mm. Carbon ion treatment plans were calculated using the standard 1D 3 mm thick RiFi and the new 4 and 6 mm 2D RiFis for spherical planning target volumes (PTVs) in water, eight stage I non-small cell lung cancer cases, four skull base chordoma cases and three prostate cancer cases. TRiP98 was used for treatment planning with facility-specific base data calculated with the Monte Carlo code SHIELD-HIT12A. Dose-volume-histograms, spatial dose distributions and dosimetric indexes were used for plan evaluation. Plan homogeneity and conformity of thinner RiFis were slightly superior to thicker RiFis but satisfactory results were obtained for all RiFis investigated. For the 6 mm RiFi, fine structures in the dose distribution caused by the larger energy steps were observed at the PTV edges, in particular for superficial and/or very small PTVs but performances for all RiFis increased with penetration depth due to straggling and scattering effects. Plans with the new RiFi design yielded for the studied cases comparable dosimetric results to the standard RiFi while the 4 and 6 mm RiFis lowered the irradiation time by 25-30% and 45-49%, respectively. PMID:27203127

  5. Dosimetric comparisons of carbon ion treatment plans for 1D and 2D ripple filters with variable thicknesses

    NASA Astrophysics Data System (ADS)

    Printz Ringbæk, Toke; Weber, Uli; Santiago, Alina; Simeonov, Yuri; Fritz, Peter; Krämer, Michael; Wittig, Andrea; Bassler, Niels; Engenhart-Cabillic, Rita; Zink, Klemens

    2016-06-01

    A ripple filter (RiFi)—also called mini-ridge filter—is a passive energy modulator used in particle beam treatments that broadens the Bragg peak (BP) as a function of its maximum thickness. The number of different energies requested from the accelerator can thus be reduced, which significantly reduces the treatment time. A new second generation RiFi with 2D groove shapes was developed using rapid prototyping, which optimizes the beam-modulating material and enables RiFi thicknesses of up to 6 mm. Carbon ion treatment plans were calculated using the standard 1D 3 mm thick RiFi and the new 4 and 6 mm 2D RiFis for spherical planning target volumes (PTVs) in water, eight stage I non-small cell lung cancer cases, four skull base chordoma cases and three prostate cancer cases. TRiP98 was used for treatment planning with facility-specific base data calculated with the Monte Carlo code SHIELD-HIT12A. Dose-volume-histograms, spatial dose distributions and dosimetric indexes were used for plan evaluation. Plan homogeneity and conformity of thinner RiFis were slightly superior to thicker RiFis but satisfactory results were obtained for all RiFis investigated. For the 6 mm RiFi, fine structures in the dose distribution caused by the larger energy steps were observed at the PTV edges, in particular for superficial and/or very small PTVs but performances for all RiFis increased with penetration depth due to straggling and scattering effects. Plans with the new RiFi design yielded for the studied cases comparable dosimetric results to the standard RiFi while the 4 and 6 mm RiFis lowered the irradiation time by 25-30% and 45-49%, respectively.

  6. Dosimetric comparisons of carbon ion treatment plans for 1D and 2D ripple filters with variable thicknesses.

    PubMed

    Ringbæk, Toke Printz; Weber, Uli; Santiago, Alina; Simeonov, Yuri; Fritz, Peter; Krämer, Michael; Wittig, Andrea; Bassler, Niels; Engenhart-Cabillic, Rita; Zink, Klemens

    2016-06-01

    A ripple filter (RiFi)-also called mini-ridge filter-is a passive energy modulator used in particle beam treatments that broadens the Bragg peak (BP) as a function of its maximum thickness. The number of different energies requested from the accelerator can thus be reduced, which significantly reduces the treatment time. A new second generation RiFi with 2D groove shapes was developed using rapid prototyping, which optimizes the beam-modulating material and enables RiFi thicknesses of up to 6 mm. Carbon ion treatment plans were calculated using the standard 1D 3 mm thick RiFi and the new 4 and 6 mm 2D RiFis for spherical planning target volumes (PTVs) in water, eight stage I non-small cell lung cancer cases, four skull base chordoma cases and three prostate cancer cases. TRiP98 was used for treatment planning with facility-specific base data calculated with the Monte Carlo code SHIELD-HIT12A. Dose-volume-histograms, spatial dose distributions and dosimetric indexes were used for plan evaluation. Plan homogeneity and conformity of thinner RiFis were slightly superior to thicker RiFis but satisfactory results were obtained for all RiFis investigated. For the 6 mm RiFi, fine structures in the dose distribution caused by the larger energy steps were observed at the PTV edges, in particular for superficial and/or very small PTVs but performances for all RiFis increased with penetration depth due to straggling and scattering effects. Plans with the new RiFi design yielded for the studied cases comparable dosimetric results to the standard RiFi while the 4 and 6 mm RiFis lowered the irradiation time by 25-30% and 45-49%, respectively.

  7. Computational Study of Primary Electrons in the Cusp Region of an Ion Engine's Discharge Chamber

    NASA Technical Reports Server (NTRS)

    Stueber, Thomas J. (Technical Monitor); Deshpande, Shirin S.; Mahalingam, Sudhakar; Menart, James A.

    2004-01-01

    In this work a computer code called PRIMA is used to study the motion of primary electrons in the magnetic cusp region of the discharge chamber of an ion engine. Even though the amount of wall area covered by the cusps is very small, the cusp regions are important because prior computational analyses have indicated that most primary electrons leave the discharge chamber through the cusps. The analysis presented here focuses on the cusp region only. The affects of the shape and size of the cusp region on primary electron travel are studied as well as the angle and location at which the electron enters the cusp region. These affects are quantified using the confinement length and the number density distributions of the primary electrons. In addition to these results comparisons of the results from PRIMA are made to experimental results for a cylindrical discharge chamber with two magnetic rings. These comparisons indicate the validity of the computer code called PRIMA.

  8. A new approach for the evaluation of the effective electrode spacing in spherical ion chambers

    NASA Astrophysics Data System (ADS)

    Maghraby, Ahmed M.; Shqair, Mohammed

    2016-10-01

    Proper determination of the effective electrode spacing (deff) of an ion chamber ensures proper determination of its collection efficiency either in continuous or in pulsed radiation in addition to the proper evaluation of the transit time. Boag's method for the determination of deff assumes the spherical shape of the internal electrode of the spherical ion chambers which is not always true, except for some cases, its common shape is cylindrical. Current work provides a new approach for the evaluation of the effective electrode spacing in spherical ion chambers considering the cylindrical shape of the internal electrode. Results indicated that deff values obtained through current work are less than those obtained using Boag's method by factors ranging from 12.1% to 26.9%. Current method also impacts the numerically evaluated collection efficiency (f) where values obtained differ by factors up to 3% at low potential (V) values while at high V values minor differences were noticed. Additionally, impacts on the evaluation of the transit time (τi) were obtained. It is concluded that approximating the internal electrode as a sphere may result in false values of deff, f, and τi.

  9. Methods and apparatus for cleaning objects in a chamber of an optical instrument by generating reactive ions using photon radiation

    SciTech Connect

    Klebanoff, Leonard E.; Delgado, Gildardo R.; Hollenshead, Jeromy T.; Umstadter, Karl R.; Starodub, Elena; Zhuang, Guorong V.

    2015-10-13

    An optical instrument, including a chamber, an object exposed to an interior of the chamber, a source of low-pressure gas, the gas comprising at least one of low-pressure molecular hydrogen gas, low-pressure molecular oxygen and a low-pressure noble gas, the source of low pressure gas being fluidly coupled to the chamber, a low voltage source electrically coupled between the object and a remaining portion of the instrument that is exposed to the interior of the chamber so as to maintain the object at a low voltage relative to the remaining portion, and an EUV/VUV light source adapted to direct EUV/VUV light through the low pressure gas in the chamber onto the object. In such a system, when the EUV/VUV light source is activated ions of the low-pressure gas are formed and directed to the object. The ions may be ions of Hydrogen, Oxygen or a noble gas.

  10. Evaluation of the applicability of pinpoint ion chambers for SRS dosimetric quality assurance

    NASA Astrophysics Data System (ADS)

    Baek, Jong Geun; Jang, Hyun Soo; Kim, Eng Chan; Lee, Yong Hee; Oh, Young Kee; Kim, Sung Kyu

    2015-06-01

    The aim of the present study was to evaluate the applicability of a Pinpoint ion chamber for the measurement of the absolute dose for dosimetric quality assurance (QA) under the same conditions as are used for actual stereotactic radiosurgery (SRS). A PTW 31014 Pinpoint chamber with a active volume of 0.015 cm3 was used to measure the absolute doses of small beams. The PTW 60003 natural diamond detector was used as a reference dosimeter. A custom-made cylindrical acrylic phantom (15 cm diameter, 15 cm long) was produced to obtain measurements, and a noncoplanar arc plan was devised to deliver a prescription dose (15-25 Gy) to 80% of the maximum dose to the target in a single fraction by using the BrainLAB planning system. All irradiations were performed by using a Varian Clinac IX 6 MV equipped with a micro-multileaf-collimators (m3) designed by BrainLAB. The acceptability criterion used was a dose difference of less than 3%. The diameter of the target volume was considered the standard parameter in the present study and was used to divide the cases into two groups, that is, a ≤ 10 mm target diameter group (10 cases) and a > 10 mm target diameter group (13 cases). For the Pinpoint chamber and target diameters of ≤ 10 mm, dosimetric uncertainties of > 3% were seen in 4 of the 10 cases, and differences ranged widely from 0.7% to 4.85%. On the other hand, for the Pinpoint chamber and target diameters of > 10 mm all dose differences were less than 1.6%, and the mean discrepancy was 0.81%. A highly significant, but moderate, correlation between dosimetric uncertainties and all target diameters was observed for the Pinpoint chamber (R2 = 0.483, p 0.001). This result indicates that Pinpoint chambers exhibit a field-size dependency when used for SRS dosimetric QA. Based on the results of the present study, we conclude that the use of a Pinpoint chamber for verification of SRS dosimetric QA is unsuitable for all field sizes, but that it can be used to verify the

  11. Ag(nic)2 (nic = nicotinate): a spin-canted quasi-2D antiferromagnet composed of square-planar S = 1/2 Ag(II) ions.

    PubMed

    Manson, Jamie L; Woods, Toby J; Lapidus, Saul H; Stephens, Peter W; Southerland, Heather I; Zapf, Vivien S; Singleton, John; Goddard, Paul A; Lancaster, Tom; Steele, Andrew J; Blundell, Stephen J

    2012-02-20

    Square-planar S = 1/2 Ag(II) ions in polymeric Ag(nic)(2) are linked by bridging nic monoanions to yield 2D corrugated sheets. Long-range magnetic order occurs below T(N) = 11.8(2) K due to interlayer couplings that are estimated to be about 30 times weaker than the intralayer exchange interaction.

  12. Monte Carlo calculations for reference dosimetry of electron beams with the PTW Roos and NE2571 ion chambers

    SciTech Connect

    Muir, B. R. Rogers, D. W. O.

    2013-12-15

    Purpose: To investigate recommendations for reference dosimetry of electron beams and gradient effects for the NE2571 chamber and to provide beam quality conversion factors using Monte Carlo simulations of the PTW Roos and NE2571 ion chambers. Methods: The EGSnrc code system is used to calculate the absorbed dose-to-water and the dose to the gas in fully modeled ion chambers as a function of depth in water. Electron beams are modeled using realistic accelerator simulations as well as beams modeled as collimated point sources from realistic electron beam spectra or monoenergetic electrons. Beam quality conversion factors are calculated with ratios of the doses to water and to the air in the ion chamber in electron beams and a cobalt-60 reference field. The overall ion chamber correction factor is studied using calculations of water-to-air stopping power ratios. Results: The use of an effective point of measurement shift of 1.55 mm from the front face of the PTW Roos chamber, which places the point of measurement inside the chamber cavity, minimizes the difference betweenR{sub 50}, the beam quality specifier, calculated from chamber simulations compared to that obtained using depth-dose calculations in water. A similar shift minimizes the variation of the overall ion chamber correction factor with depth to the practical range and reduces the root-mean-square deviation of a fit to calculated beam quality conversion factors at the reference depth as a function of R{sub 50}. Similarly, an upstream shift of 0.34 r{sub cav} allows a more accurate determination of R{sub 50} from NE2571 chamber calculations and reduces the variation of the overall ion chamber correction factor with depth. The determination of the gradient correction using a shift of 0.22 r{sub cav} optimizes the root-mean-square deviation of a fit to calculated beam quality conversion factors if all beams investigated are considered. However, if only clinical beams are considered, a good fit to results for

  13. Burst size distributions in the digitized data of the ion chambers t Mt. Norikura and sea level stations

    NASA Technical Reports Server (NTRS)

    Kusunose, M.; Wada, M.; Kudo, S.; Chuang, L. S.

    1985-01-01

    A practical and simple method for burst rejection is applied to the digitized data of cosmic ray ion chambers at Mt. Norikura, Tokyo and Kochi. As a result of burst rejection, the burst size frequency distributions in the digitized data at mountain altitude and sea level ion chambers is obtained. Results show that there are no significant differences between the digital and analog data processing in burst rejection.

  14. Evaluation of the ability of a 2D ionisation chamber array and an EPID to detect systematic delivery errors in IMRT plans

    NASA Astrophysics Data System (ADS)

    Bawazeer, Omemh; Gray, Alison; Arumugam, Sankar; Vial, Philip; Thwaites, David; Descallar, Joseph; Holloway, Lois

    2014-03-01

    Two clinical intensity modulated radiotherapy plans were selected. Eleven plan variations were created with systematic errors introduced: Multi-Leaf Collimator (MLC) positional errors with all leaf pairs shifted in the same or the opposite direction, and collimator rotation offsets. Plans were measured using an Electronic Portal Imaging Device (EPID) and an ionisation chamber array. The plans were evaluated using gamma analysis with different criteria. The gamma pass rates remained around 95% or higher for most cases with MLC positional errors of 1 mm and 2 mm with 3%/3mm criteria. The ability of both devices to detect delivery errors was similar.

  15. Measurement of a 2D fast-ion velocity distribution function by tomographic inversion of fast-ion D-alpha spectra

    NASA Astrophysics Data System (ADS)

    Salewski, M.; Geiger, B.; Jacobsen, A. S.; García-Muñoz, M.; Heidbrink, W. W.; Korsholm, S. B.; Leipold, F.; Madsen, J.; Moseev, D.; Nielsen, S. K.; Rasmussen, J.; Stejner, M.; Tardini, G.; Weiland, M.; the ASDEX Upgrade Team

    2014-02-01

    We present the first measurement of a local fast-ion 2D velocity distribution function f(v‖, v⊥). To this end, we heated a plasma in ASDEX Upgrade by neutral beam injection and measured spectra of fast-ion Dα (FIDA) light from the plasma centre in three views simultaneously. The measured spectra agree very well with synthetic spectra calculated from a TRANSP/NUBEAM simulation. Based on the measured FIDA spectra alone, we infer f(v‖, v⊥) by tomographic inversion. Salient features of our measurement of f(v‖, v⊥) agree reasonably well with the simulation: the measured as well as the simulated f(v‖, v⊥) are lopsided towards negative velocities parallel to the magnetic field, and they have similar shapes. Further, the peaks in the simulation of f(v‖, v⊥) at full and half injection energies of the neutral beam also appear in the measurement at similar velocity-space locations. We expect that we can measure spectra in up to seven views simultaneously in the next ASDEX Upgrade campaign which would further improve measurements of f(v‖, v⊥) by tomographic inversion.

  16. New reaction chamber for transient field g-factor measurements with radioactive ion beams

    NASA Astrophysics Data System (ADS)

    Illana, A.; Perea, A.; Nácher, E.; Orlandi, R.; Jungclaus, A.

    2015-06-01

    A new reaction chamber has been designed and constructed to measure g-factors of short-lived excited states using the Transient Field technique in combination with Coulomb excitation in inverse kinematics. In this paper we will discuss several important aspects which have to be considered in order to successfully carry out this type of measurement with radioactive ion beams, instead of the stable beams used in a wide range of experiments in the past. The technical solutions to the problems arising from the use of such radioactive beams will be exposed in detail and the first successful experiment using the new chamber in combination with MINIBALL cluster detectors at REX-ISOLDE (CERN) will be reported on.

  17. Solutions for discharge chamber sputtering and anode deposit spalling in small mercury ion thrusters

    NASA Technical Reports Server (NTRS)

    Power, J. L.; Hiznay, D. J.

    1975-01-01

    Proposed solutions to the problems of sputter erosion and sputtered material spalling in the discharge chamber of small mercury ion thrusters are presented. The accelerated life test evaluated three such proposed solutions: (1) the use of tantalum as a single low sputter yield material for the exposed surfaces of the discharge chamber components subject to sputtering, (2) the use of a severely roughened anode surface to improve the adhesion of the sputter-deposited coating, and (3) the use of a wire cloth anode surface in order to limit the size of any coating flakes which might spall from it. Because of the promising results obtained in the accelerated life test with anode surfaces roughened by grit-blasting, experiments were carried out to optimize the grit-blasting procedure. The experimental results and an optimal grit-blasting procedure are presented.

  18. Experimental Investigation of the 2D Ion Beam Profile Generated by an ESI Octopole-QMS System

    NASA Astrophysics Data System (ADS)

    Syed, Sarfaraz U. A. H.; Eijkel, Gert B.; Kistemaker, Piet; Ellis, Shane; Maher, Simon; Smith, Donald F.; Heeren, Ron M. A.

    2014-10-01

    In this paper, we have employed an ion imaging approach to investigate the behavior of ions exiting from a quadrupole mass spectrometer (QMS) system that employs a radio frequency octopole ion guide before the QMS. An in-vacuum active pixel detector (Timepix) is employed at the exit of the QMS to image the ion patterns. The detector assembly simultaneously records the ion impact position and number of ions per pixel in every measurement frame. The transmission characteristics of the ion beam exiting the QMS are studied using this imaging detector under different operating conditions. Experimental results confirm that the ion spatial distribution exiting the QMS is heavily influenced by ion injection conditions. Furthermore, ion images from Timepix measurements of protein standards demonstrate the capability to enhance the quality of the mass spectral information and provide a detailed insight in the spatial distribution of different charge states (and hence different m/z) ions exiting the QMS.

  19. Ion-chamber-based loss monitor system for the Los Alamos Meson Physics Facility

    SciTech Connect

    Plum, M.A.; Brown, D.; Browman, A.; Macek, R.J.

    1995-05-01

    A new loss monitor system has been designed and installed at the Los Alamos Meson Physics Facility (LAMPF). The detectors are ion chambers filled with N{sub 2} gas. The electronics modules have a threshold range of 1:100, and they can resolve changes in beam loss of about 2% of the threshold settings. They can generate a trip signal in 2 {mu}s if the beam loss is large enough; if the response time of the Fast Protect System is included the beam will be shut off in about 37 {mu}s.

  20. Sputtering phenomena of discharge chamber components in a 30-cm diameter Hg ion thruster

    NASA Technical Reports Server (NTRS)

    Mantenieks, M. A.; Rawlin, V. K.

    1976-01-01

    Sputtering and deposition rates were measured for discharge chamber components of a 30-cm diameter mercury ion thruster. It was found that sputtering rates of the screen grid and cathode baffle were strongly affected by geometry of the baffle holder. Sputtering rates of the baffle and screen grid were reduced to 80 and 125 A/hr, respectively, by combination of appropriate geometry and materials selections. Sputtering rates such as these are commensurate with thruster lifetimes of 15,000 hours or more. A semiempirical sputtering model showed good agreement with the measured values.

  1. Interplay of Ion-Water and Water-Water Interactions within the Hydration Shells of Nitrate and Carbonate Directly Probed with 2D IR Spectroscopy.

    PubMed

    Fournier, Joseph A; Carpenter, William; De Marco, Luigi; Tokmakoff, Andrei

    2016-08-01

    The long-range influence of ions in solution on the water hydrogen-bond (H-bond) network remains a topic of vigorous debate. Recent spectroscopic and theoretical studies have, for the most part, reached the consensus that weakly coordinating ions only affect water molecules in the first hydration shell. Here, we apply ultrafast broadband two-dimensional infrared (2D IR) spectroscopy to aqueous nitrate and carbonate in neat H2O to study the solvation structure and dynamics of ions on opposite ends of the Hofmeister series. By exciting both the water OH stretches and ion stretches and probing the associated cross-peaks between them, we are afforded a comprehensive view into the complex nature of ion hydration. We show in aqueous nitrate that weak ion-water H-bonding leads to water-water interactions in the ion solvation shells dominating the dynamics. In contrast, the carbonate CO stretches show significant mixing with the water OH stretches due to strong ion-water H-bonding such that the water and ion modes are intimately correlated. Further, the excitonic nature of vibrations in neat H2O, which spans multiple water molecules, is an important factor in describing ion hydration. We attribute these complex dynamics to the likely presence of intermediate-range effects influenced by waters beyond the first solvation shell. PMID:27404015

  2. Two-chamber configuration of Bio-Nano electron cyclotron resonance ion source for fullerene modification

    NASA Astrophysics Data System (ADS)

    Uchida, T.; Rácz, R.; Muramatsu, M.; Kato, Y.; Kitagawa, A.; Biri, S.; Yoshida, Y.

    2016-02-01

    We report on the modification of fullerenes with iron and chlorine using two individually controllable plasmas in the Bio-Nano electron cyclotron resonance ion source (ECRIS). One of the plasmas is composed of fullerene and the other one is composed of iron and chlorine. The online ion beam analysis allows one to investigate the rate of the vapor-phase collisional modification process in the ECRIS, while the offline analyses (e.g., liquid chromatography-mass spectrometry) of the materials deposited on the plasma chamber can give information on the surface-type process. Both analytical methods show the presence of modified fullerenes such as fullerene-chlorine, fullerene-iron, and fullerene-chlorine-iron.

  3. Characterization of Ion-Acoustic Wave Reflection Off A Plasma Chamber Wall

    NASA Astrophysics Data System (ADS)

    Berumen, Jorge; Chu, Feng; Hood, Ryan; Mattingly, Sean; Rogers, Anthony; Skiff, Fred

    2015-11-01

    We present an experimental characterization of the ion acoustic wave reflection coefficient off a plasma chamber wall. The experiment is performed in a cylindrical, magnetized, singly-ionized Argon inductively-coupled gas discharge plasma that is weakly collisional with typical conditions: n ~ 1010cm-3 Te ~ 3 eV and B ~ 1 kG. The main diagnostics are laser-induced fluorescence and Langmuir probe measurements. A survey of the ion velocity distribution function's zeroth and first order as well as density fluctuations at different wave excitation frequencies is obtained. Analysis of the reflection coefficient's dependence on the phase velocity and frequency of the wave is done through the characterization of waves utilizing Case-Van Kampen modes and the use of Morrison's G-transform. This research is supported by the Department of Energy under grant No. DOE DE-FG02-99ER54543.

  4. Formation of metal nanoparticles by short-distance sputter deposition in a reactive ion etching chamber

    SciTech Connect

    Nie Min; Meng, Dennis Desheng; Sun Kai

    2009-09-01

    A new method is reported to form metal nanoparticles by sputter deposition inside a reactive ion etching chamber with a very short target-substrate distance. The distribution and morphology of nanoparticles are found to be affected by the distance, the ion concentration, and the sputtering time. Densely distributed nanoparticles of various compositions were fabricated on the substrates that were kept at a distance of 130 mum or smaller from the target. When the distance was increased to 510 mum, island structures were formed, indicating the tendency to form continuous thin film with longer distance. The observed trend for nanoparticle formation is opposite to the previously reported mechanism for the formation of nanoparticles by sputtering. A new mechanism based on the seeding effect of the substrate is proposed to interpret the experimental results.

  5. A multiple sampling ionization chamber (MUSIC) for measuring the charge of relativistic heavy ions

    NASA Astrophysics Data System (ADS)

    Christie, W. B.; Romero, J. L.; Brady, F. P.; Tull, C. E.; Castaneda, C. M.; Barasch, E. F.; Webb, M. L.; Drummond, J. R.; Crawford, H. J.; Flores, I.; Greiner, D. E.; Lindstrom, P. J.; Sann, H.; Young, J. C.

    1987-04-01

    A large area (1 m × 2 m) multiple sampling ionization chamber (MUSIC) has been constructed and tested. The MUSIC detector makes multiple measurements of energy "loss", d E/d x, for a relativistic heavy ion. Given the velocity, the charge of the ion can be extracted from the energy loss distributions. The widths of the distributions we observe are much narrower than predicted by Vavilov's theory for energy loss while agreeing well with the theory of Badhwar which deals with the energy deposited. The versatile design of MUSIC allows a variety of anode configurations which results in a large dynamic range of charge. In our tests to date we have observed charge resolutions of 0.25e fwhm for 727 MeV/nucleon40A and 0.30e fwhm for 1.08 GeV/nucleon139La and139La fragments. Vertical position and multiple track determination are obtained by using time projection chamber electronics. Preliminary tests indicate that the position resolution is also very good with α ≅ 100 μm.

  6. High-resolution high-sensitivity elemental imaging by secondary ion mass spectrometry: from traditional 2D and 3D imaging to correlative microscopy

    NASA Astrophysics Data System (ADS)

    Wirtz, T.; Philipp, P.; Audinot, J.-N.; Dowsett, D.; Eswara, S.

    2015-10-01

    Secondary ion mass spectrometry (SIMS) constitutes an extremely sensitive technique for imaging surfaces in 2D and 3D. Apart from its excellent sensitivity and high lateral resolution (50 nm on state-of-the-art SIMS instruments), advantages of SIMS include high dynamic range and the ability to differentiate between isotopes. This paper first reviews the underlying principles of SIMS as well as the performance and applications of 2D and 3D SIMS elemental imaging. The prospects for further improving the capabilities of SIMS imaging are discussed. The lateral resolution in SIMS imaging when using the microprobe mode is limited by (i) the ion probe size, which is dependent on the brightness of the primary ion source, the quality of the optics of the primary ion column and the electric fields in the near sample region used to extract secondary ions; (ii) the sensitivity of the analysis as a reasonable secondary ion signal, which must be detected from very tiny voxel sizes and thus from a very limited number of sputtered atoms; and (iii) the physical dimensions of the collision cascade determining the origin of the sputtered ions with respect to the impact site of the incident primary ion probe. One interesting prospect is the use of SIMS-based correlative microscopy. In this approach SIMS is combined with various high-resolution microscopy techniques, so that elemental/chemical information at the highest sensitivity can be obtained with SIMS, while excellent spatial resolution is provided by overlaying the SIMS images with high-resolution images obtained by these microscopy techniques. Examples of this approach are given by presenting in situ combinations of SIMS with transmission electron microscopy (TEM), helium ion microscopy (HIM) and scanning probe microscopy (SPM).

  7. 1-Aza-15-Crown-5 Functionalized Graphene Oxide for 2D Graphene-Based Li⁺-ion Conductor.

    PubMed

    Banerjee, Moutusi; Gupta, Abhisek; Saha, Shyamal K; Chakravorty, Dipankar

    2015-07-01

    Attachment of Li(+) ion on graphene surface to realize Li(+)-ion conductor is a real challenge because of the weak interaction between the ions and the functional groups of graphene oxide; although, a large number of theoretical results are already available in the literature. To overcome this problem, graphene oxide is functionalized by 1-aza-15-crown-5, the cage-like structure containing four oxygens that can bind Li(+) ion through electrostatic interaction. Li(+) migration on graphene surface has been investigated using ac relaxation mechanism. Perfect Debye-type relaxation behavior with β (relaxation exponent) value ≈1 resulting from single ion is observed. The activation energy of Li(+) migration arising due to cation-π interaction is found to be 0.37 eV, which agrees well with recently reported theoretical value. It is believed that this study will help to design isolated ion conductors for Li(+)-ion battery.

  8. Ion chamber absorbed dose calibration coefficients, N{sub D,w}, measured at ADCLs: Distribution analysis and stability

    SciTech Connect

    Muir, B. R.

    2015-04-15

    Purpose: To analyze absorbed dose calibration coefficients, N{sub D,w}, measured at accredited dosimetry calibration laboratories (ADCLs) for client ionization chambers to study (i) variability among N{sub D,w} coefficients for chambers of the same type calibrated at each ADCL to investigate ion chamber volume fluctuations and chamber manufacturing tolerances; (ii) equivalency of ion chamber calibration coefficients measured at different ADCLs by intercomparing N{sub D,w} coefficients for chambers of the same type; and (iii) the long-term stability of N{sub D,w} coefficients for different chamber types by investigating repeated chamber calibrations. Methods: Large samples of N{sub D,w} coefficients for several chamber types measured over the time period between 1998 and 2014 were obtained from the three ADCLs operating in the United States. These are analyzed using various graphical and numerical statistical tests for the four chamber types with the largest samples of calibration coefficients to investigate (i) and (ii) above. Ratios of calibration coefficients for the same chamber, typically obtained two years apart, are calculated to investigate (iii) above and chambers with standard deviations of old/new ratios less than 0.3% meet stability requirements for accurate reference dosimetry recommended in dosimetry protocols. Results: It is found that N{sub D,w} coefficients for a given chamber type compared among different ADCLs may arise from differing probability distributions potentially due to slight differences in calibration procedures and/or the transfer of the primary standard. However, average N{sub D,w} coefficients from different ADCLs for given chamber types are very close with percent differences generally less than 0.2% for Farmer-type chambers and are well within reported uncertainties. Conclusions: The close agreement among calibrations performed at different ADCLs reaffirms the Calibration Laboratory Accreditation Subcommittee process of ensuring

  9. Frequency measurement of the 2S(1/2)-2D(3/2) electric quadrupole transition in a single 171Yb+ ion.

    PubMed

    Webster, Stephen; Godun, Rachel; King, Steven; Huang, Guilong; Walton, Barney; Tsatourian, Veronika; Margolis, Helen; Lea, Stephen; Gill, Patrick

    2010-03-01

    We report on precision laser spectroscopy of the 2S(1/2)(F = 0)-2D(3/2) (F = 2, m(F) = 0) clock transition in a single ion of 171Yb+. The absolute value of the transition frequency, determined using an optical frequency comb referenced to a hydrogen maser, is 688358979309310 +/- 9 Hz. This corresponds to a fractional frequency uncertainty of 1.3 x 10(-14).

  10. A multiple-cathode, high-power, rectangular ion thruster discharge chamber of increasing thruster lifetime

    NASA Astrophysics Data System (ADS)

    Rovey, Joshua Lucas

    Ion thrusters are high-efficiency, high-specific impulse space propulsion systems proposed for deep space missions requiring thruster operational lifetimes of 7--14 years. One of the primary ion thruster components is the discharge cathode assembly (DCA). The DCA initiates and sustains ion thruster operation. Contemporary ion thrusters utilize one molybdenum keeper DCA that lasts only ˜30,000 hours (˜3 years), so single-DCA ion thrusters are incapable of satisfying the mission requirements. The aim of this work is to develop an ion thruster that sequentially operates multiple DCAs to increase thruster lifetime. If a single-DCA ion thruster can operate 3 years, then perhaps a triple-DCA thruster can operate 9 years. Initially, a multiple-cathode discharge chamber (MCDC) is designed and fabricated. Performance curves and grid-plane current uniformity indicate operation similar to other thrusters. Specifically, the configuration that balances both performance and uniformity provides a production cost of 194 W/A at 89% propellant efficiency with a flatness parameter of 0.55. One of the primary MCDC concerns is the effect an operating DCA has on the two dormant cathodes. Multiple experiments are conducted to determine plasma properties throughout the MCDC and near the dormant cathodes, including using "dummy" cathodes outfitted with plasma diagnostics and internal plasma property mapping. Results are utilized in an erosion analysis that suggests dormant cathodes suffer a maximum pre-operation erosion rate of 5--15 mum/khr (active DCA maximum erosion is 70 mum/khr). Lifetime predictions indicate that triple-DCA MCDC lifetime is approximately 2.5 times longer than a single-DCA thruster. Also, utilization of new keeper materials, such as carbon graphite, may significantly decrease both active and dormant cathode erosion, leading to a further increase in thruster lifetime. Finally, a theory based on the near-DCA plasma potential structure and propellant flow rate effects

  11. Time-resolved dosimetric verification of respiratory-gated radiotherapy exposures using a high-resolution 2D ionisation chamber array.

    PubMed

    King, R B; Agnew, C E; O'Connell, B F; Prise, K M; Hounsell, A R; McGarry, C K

    2016-08-01

    The aim of this work was to track and verify the delivery of respiratory-gated irradiations, performed with three versions of TrueBeam linac, using a novel phantom arrangement that combined the OCTAVIUS(®) SRS 1000 array with a moving platform. The platform was programmed to generate sinusoidal motion of the array. This motion was tracked using the real-time position management (RPM) system and four amplitude gating options were employed to interrupt MV beam delivery when the platform was not located within set limits. Time-resolved spatial information extracted from analysis of x-ray fluences measured by the array was compared to the programmed motion of the platform and to the trace recorded by the RPM system during the delivery of the x-ray field. Temporal data recorded by the phantom and the RPM system were validated against trajectory log files, recorded by the linac during the irradiation, as well as oscilloscope waveforms recorded from the linac target signal. Gamma analysis was employed to compare time-integrated 2D x-ray dose fluences with theoretical fluences derived from the probability density function for each of the gating settings applied, where gamma criteria of 2%/2 mm, 1%/1 mm and 0.5%/0.5 mm were used to evaluate the limitations of the RPM system. Excellent agreement was observed in the analysis of spatial information extracted from the SRS 1000 array measurements. Comparisons of the average platform position with the expected position indicated absolute deviations of  <0.5 mm for all four gating settings. Differences were observed when comparing time-resolved beam-on data stored in the RPM files and trajectory logs to the true target signal waveforms. Trajectory log files underestimated the cycle time between consecutive beam-on windows by 10.0  ±  0.8 ms. All measured fluences achieved 100% pass-rates using gamma criteria of 2%/2 mm and 50% of the fluences achieved pass-rates  >90% when criteria of 0.5%/0.5

  12. Time-resolved dosimetric verification of respiratory-gated radiotherapy exposures using a high-resolution 2D ionisation chamber array.

    PubMed

    King, R B; Agnew, C E; O'Connell, B F; Prise, K M; Hounsell, A R; McGarry, C K

    2016-08-01

    The aim of this work was to track and verify the delivery of respiratory-gated irradiations, performed with three versions of TrueBeam linac, using a novel phantom arrangement that combined the OCTAVIUS(®) SRS 1000 array with a moving platform. The platform was programmed to generate sinusoidal motion of the array. This motion was tracked using the real-time position management (RPM) system and four amplitude gating options were employed to interrupt MV beam delivery when the platform was not located within set limits. Time-resolved spatial information extracted from analysis of x-ray fluences measured by the array was compared to the programmed motion of the platform and to the trace recorded by the RPM system during the delivery of the x-ray field. Temporal data recorded by the phantom and the RPM system were validated against trajectory log files, recorded by the linac during the irradiation, as well as oscilloscope waveforms recorded from the linac target signal. Gamma analysis was employed to compare time-integrated 2D x-ray dose fluences with theoretical fluences derived from the probability density function for each of the gating settings applied, where gamma criteria of 2%/2 mm, 1%/1 mm and 0.5%/0.5 mm were used to evaluate the limitations of the RPM system. Excellent agreement was observed in the analysis of spatial information extracted from the SRS 1000 array measurements. Comparisons of the average platform position with the expected position indicated absolute deviations of  <0.5 mm for all four gating settings. Differences were observed when comparing time-resolved beam-on data stored in the RPM files and trajectory logs to the true target signal waveforms. Trajectory log files underestimated the cycle time between consecutive beam-on windows by 10.0  ±  0.8 ms. All measured fluences achieved 100% pass-rates using gamma criteria of 2%/2 mm and 50% of the fluences achieved pass-rates  >90% when criteria of 0.5%/0.5

  13. Time-resolved dosimetric verification of respiratory-gated radiotherapy exposures using a high-resolution 2D ionisation chamber array

    NASA Astrophysics Data System (ADS)

    King, R. B.; Agnew, C. E.; O'Connell, B. F.; Prise, K. M.; Hounsell, A. R.; McGarry, C. K.

    2016-08-01

    The aim of this work was to track and verify the delivery of respiratory-gated irradiations, performed with three versions of TrueBeam linac, using a novel phantom arrangement that combined the OCTAVIUS® SRS 1000 array with a moving platform. The platform was programmed to generate sinusoidal motion of the array. This motion was tracked using the real-time position management (RPM) system and four amplitude gating options were employed to interrupt MV beam delivery when the platform was not located within set limits. Time-resolved spatial information extracted from analysis of x-ray fluences measured by the array was compared to the programmed motion of the platform and to the trace recorded by the RPM system during the delivery of the x-ray field. Temporal data recorded by the phantom and the RPM system were validated against trajectory log files, recorded by the linac during the irradiation, as well as oscilloscope waveforms recorded from the linac target signal. Gamma analysis was employed to compare time-integrated 2D x-ray dose fluences with theoretical fluences derived from the probability density function for each of the gating settings applied, where gamma criteria of 2%/2 mm, 1%/1 mm and 0.5%/0.5 mm were used to evaluate the limitations of the RPM system. Excellent agreement was observed in the analysis of spatial information extracted from the SRS 1000 array measurements. Comparisons of the average platform position with the expected position indicated absolute deviations of  <0.5 mm for all four gating settings. Differences were observed when comparing time-resolved beam-on data stored in the RPM files and trajectory logs to the true target signal waveforms. Trajectory log files underestimated the cycle time between consecutive beam-on windows by 10.0  ±  0.8 ms. All measured fluences achieved 100% pass-rates using gamma criteria of 2%/2 mm and 50% of the fluences achieved pass-rates  >90% when criteria of 0.5%/0.5 mm were

  14. Performance evaluation of multi sampling ionization chamber for heavy ion beams by comparison with GEANT4 simulation

    NASA Astrophysics Data System (ADS)

    Kanke, Yuki; Himac H093 Collaboration

    2014-09-01

    In high-energy heavy-ion accelerator facilities, multi sampling ionization chambers are often used for the identification of the atomic number Z by detecting the energy deposit in it. In the study at GSI, the picture of the escape of secondary electrons, δ rays, from the ionization chamber explains the experimental data of pulse-height resolution. If this picture is correct, the pulse-height resolution should depend on the effective area of the ionization chamber. The experiment have been performed at NIRS-HIMAC. The pulse-height resolutions of two ionization chambers with different effective area were compared by using a 400-MeV/u Ni beam and their fragments. The difference in the pulse-height resolutions was observed. By comparison with the GEANT4 simulation including the δ-rays emission, the performance of the ionization chamber have been evaluated.

  15. Molecular desorption of stainless steel vacuum chambers irradiated with 4.2 MeV/u lead ions

    NASA Astrophysics Data System (ADS)

    Mahner, E.; Hansen, J.; Laurent, J.-M.; Madsen, N.

    2003-01-01

    In preparation for the heavy ion program of the Large Hadron Collider at CERN, accumulation and cooling tests with lead ion beams have been performed in the Low Energy Antiproton Ring. These tests have revealed that due to the unexpected large outgassing of the vacuum system, the dynamic pressure of the ring could not be maintained low enough to reach the required beam intensities. To determine the actions necessary to lower the dynamic pressure rise, an experimental program has been initiated for measuring the molecular desorption yields of stainless steel vacuum chambers by the impact of 4.2 MeV/u lead ions with the charge states +27 and +53. The test chambers were exposed either at grazing or at perpendicular incidence. Different surface treatments (glow discharges, nonevaporable getter coating) are reported in terms of the molecular desorption yields for H2, CH4, CO, Ar, and CO2. Unexpected large values of molecular yields per incident ion up to 2×104 molecules/ion have been observed. The reduction of the ion-induced desorption yield due to continuous bombardment with lead ions (beam cleaning) has been investigated for five different stainless steel vacuum chambers. The implications of these results for the vacuum system of the future Low Energy Ion Ring and possible remedies to reduce the vacuum degradation are discussed.

  16. Photoelectron Track Length Distributions Measured in a Negative Ion Time Projection Chamber

    NASA Astrophysics Data System (ADS)

    Prieskorn, Z. R.; Hill, J. E.; Kaaret, P. E.; Black, J. K.

    2014-04-01

    We report photoelectron track length distributions between 3 and 8 keV in gas mixtures of Ne+CO2+CH3NO2 (260:80:10 Torr) and CO2+CH3NO2 (197.5: 15 Torr). The measurements were made using a negative ion time projection chamber (NITPC) at the National Synchrotron Light Source (NSLS) at the Brookhaven National Laboratory (BNL). We report the first quantitative analysis of photoelectron track length distributions in a gas. The distribution of track lengths at a given energy is best fit by a lognormal distribution. A powerlaw distribution of the form, f(E)=a(E/Eo)n, is found to fit the relationship between mean track length and energy. We find n=1.29 +/- 0.07 for Ne+CO2+CH3NO2 and n=1.20 +/- 0.09 for CO2+CH3NO2. Understanding the distribution of photoelectron track lengths in proportional counter gases is important for optimizing the pixel size and the dimensions of the active region in electron-drift time projection chambers (TPCs) and NITPC X-ray polarimeters.

  17. Performance of single chamber biocatalyzed electrolysis with different types of ion exchange membranes.

    PubMed

    Rozendal, René A; Hamelers, Hubertus V M; Molenkamp, Redmar J; Buisman, Cees J N

    2007-05-01

    In this paper hydrogen production through biocatalyzed electrolysis was studied for the first time in a single chamber configuration. Single chamber biocatalyzed electrolysis was tested in two configurations: (i) with a cation exchange membrane (CEM) and (ii) with an anion exchange membrane (AEM). Both configurations performed comparably and produced over 0.3 m3 H2/m3 reactor liquid volume/day at 1.0 V applied voltage (overall hydrogen efficiencies around 23%). Analysis of the water that permeated through the membrane revealed that a large part of potential losses in the system were associated with a pH gradient across the membrane (CEM DeltapH=6.4; AEM DeltapH=4.4). These pH gradient associated potential losses were lower in the AEM configuration (CEM 0.38 V; AEM 0.26 V) as a result of its alternative ion transport properties. This benefit of the AEM, however, was counteracted by the higher cathode overpotentials occurring in the AEM configuration (CEM 0.12 V at 2.39 A/m2; AEM 0.27 V at 2.15 A/m2) as a result of a less effective electroless plating method for the AEM membrane electrode assembly (MEA).

  18. New recoil transfer chamber for thermalization of heavy ions produced in fusion-evaporation reactions

    NASA Astrophysics Data System (ADS)

    Alfonso, M. C.; Tereshatov, E. E.; DeVanzo, M. J.; Sefcik, J. A.; Bennett, M. E.; Mayorov, D. A.; Werke, T. A.; Folden, C. M.

    2015-10-01

    A new Recoil Transfer Chamber (RTC) has been designed, fabricated, and characterized at the Cyclotron Institute at Texas A&M University. The design is based on a gas stopper that was previously in routine use at the National Superconducting Cyclotron Laboratory. This new RTC uses He gas to stop ions, and a combination of a static electric field and gas flow to maximize the extraction efficiency. In offline experiments, a 228Th source was used to produce 216Po which was successfully extracted even though it has a short half-life. In online experiments using the products of the 118Sn(40Ar, 6n)152Er reaction, an efficiency of several tens of percent was measured.

  19. A new multi-strip ionization chamber used as online beam monitor for heavy ion therapy

    NASA Astrophysics Data System (ADS)

    Xu, Zhiguo; Mao, Ruishi; Duan, Limin; She, Qianshun; Hu, Zhengguo; Li, He; Lu, Ziwei; Zhao, Qiecheng; Yang, Herun; Su, Hong; Lu, Chengui; Hu, Rongjiang; Zhang, Junwei

    2013-11-01

    A multi-strip ionization chamber has been built for precise and fast monitoring of the carbon beam spatial distribution at Heavy Ion Researched Facility of Lanzhou Cooling Storing Ring (HIRFL-CSR). All the detector's anode, cathode and sealed windows are made by 2 μm aluminized Mylar film in order to minimize the beam lateral deflection. The sensitive area of the detector is (100×100) mm2, with the anode segmented in 100 strips, and specialized front-end electronics has been developed for simplifying the data acquisition and quick feedback of the relevant parameters to beam control system. It can complete one single beam profile in 200 μs.

  20. A New Cell-Centered Implicit Numerical Scheme for Ions in the 2-D Axisymmetric Code Hall2de

    NASA Technical Reports Server (NTRS)

    Lopez Ortega, Alejandro; Mikellides, Ioannis G.

    2014-01-01

    We present a new algorithm in the Hall2De code to simulate the ion hydrodynamics in the acceleration channel and near plume regions of Hall-effect thrusters. This implementation constitutes an upgrade of the capabilities built in the Hall2De code. The equations of mass conservation and momentum for unmagnetized ions are solved using a conservative, finite-volume, cell-centered scheme on a magnetic-field-aligned grid. Major computational savings are achieved by making use of an implicit predictor/multi-corrector algorithm for time evolution. Inaccuracies in the prediction of the motion of low-energy ions in the near plume in hydrodynamics approaches are addressed by implementing a multi-fluid algorithm that tracks ions of different energies separately. A wide range of comparisons with measurements are performed to validate the new ion algorithms. Several numerical experiments with the location and value of the anomalous collision frequency are also presented. Differences in the plasma properties in the near-plume between the single fluid and multi-fluid approaches are discussed. We complete our validation by comparing predicted erosion rates at the channel walls of the thruster with measurements. Erosion rates predicted by the plasma properties obtained from simulations replicate accurately measured rates of erosion within the uncertainty range of the sputtering models employed.

  1. Influence of pressurized anode chamber on ion transports and power generation of UF membrane microbial fuel cells (UF-MFCs)

    NASA Astrophysics Data System (ADS)

    Kim, Kyoung-Yeol; Chae, Kyu-Jung; Yang, Euntae; Lee, Mi-Young; Kim, In S.

    2015-04-01

    Ultrafiltration membrane integrated microbial fuel cell (UF-MFC) has developed to produce high-quality effluents by integrating the membrane filtration process into the MFC system. During UF-MFC operation, however, unexpected power reductions were observed under different pressures that were applied in the anode chamber (22.0% and 25.5% at 0.7 bar and 2.1 bar, respectively). It was hypothesized that those of power reductions might occur due to the limitation of ion transport across the UF membrane- which could be caused by the pressurized anode chamber to filter the anode solution through the UF membrane. A test with a NaCl concentrated cathode solution showed few dissolved ions being transported from the cathode to anode chamber while the pressure was being applied in the anode chamber. This result clearly indicates that the limitation of ion transport from the cathode to the pressurized anode chamber is a significant factor affecting the power density of UF-MFCs, even more so than water permeation through the UF membrane.

  2. Micro-patterning of ionic reservoirs within a double bilayer lipid membrane to fabricate a 2D array of ion-channel switch based electrochemical biosensors

    SciTech Connect

    Sansinena, J. M.; Yee, C. K.; Sapuri, A.; Swanson, Basil I.; Redondo, A.; Parikh, A. N.

    2004-01-01

    We present a simple approach for the design of ionic reservoir arrays within a double phospholipid bilayer to ultimately develop a 2D array of ion-channel switch based electrochemical biosensors. As a first step, a primary bilayer lipid membrane is deposited onto an array of electrodes patterned onto a substrate surface. Subsequently, an array of microvoids is created within the bilayer by a wet photolithographic patterning of phospholipid bilayers using a deep UV light source and a quartz/chrome photomask. To ensure registry, the photomask used to pattern bilayers is designed to match up the microvoids within the primary bilayer with the array of electrodes on the substrate surface. The deposition of a secondary bilayer lipid membrane onto the primary bilayer that spans across the patterned microvoids leads to the formation of the array of ionic reservoirs within the double phospholipid bilayer. This is accomplished using giant unilamellar vesicles and by exploiting membrane electrostatics. The use of ion-channels incorporated into the secondary bilayer that covers the individual ionic reservoirs allows the construction of a 2D array of ion-channel switch based electrochemical biosensors that are able to recognize different target-agents simultaneously.

  3. Chamber wall materials response to pulsed ions at power-plant level fluences

    NASA Astrophysics Data System (ADS)

    Renk, T. J.; Provencio, P. P.; Tanaka, T. J.; Olson, C. L.; Peterson, R. R.; Stolp, J. E.; Schroen, D. G.; Knowles, T. R.

    2005-12-01

    Candidate dry-wall materials for the reactor chambers of future laser-driven Inertial Fusion Energy (IFE) power plants have been exposed to ion pulses from RHEPP-1, located at Sandia National Laboratories. These pulses simulate the MeV-level ion pulses with fluences of up to 20 J/cm 2 that can be expected to impinge on the first wall of such future plants. Various forms of tungsten and tungsten alloy were subjected to up to 1600 pulses, usually while being heated to 600 °C. Other metals were exposed as well. Thresholds for roughening and material removal, and evolution of surface morphology were measured and compared with code predictions for materials response. Powder-metallurgy (PM) tungsten is observed to undergo surface roughening and subsurface crack formation that evolves over hundreds of pulses, and which can occur both below and above the melt threshold. This roughening is worse than for other metals, and worse than for either tungsten alloyed with rhenium (W25Re), or for CVD and single-crystal forms of tungsten. Carbon, particularly the form used in composite material, appears to suffer material loss well below its sublimation point. Some engineered materials were also investigated. It appears that some modification to PM tungsten is required for its successful use in a reactor environment.

  4. Heavy ion beam propagation through a gas-filled chamber for inertial confinement fusion

    SciTech Connect

    Barboza, N.O.

    1996-10-01

    The work presented here evaluates the dynamics of a beam of heavy ions propagating through a chamber filled with gas. The motivation for this research stems from the possibility of using heavy ion beams as a driver in inertial confinement fusion reactors for the purpose of generating electricity. Such a study is important in determining the constraints on the beam which limit its focus to the small radius necessary for the ignition of thermonuclear microexplosions which are the source of fusion energy. Nuclear fusion is the process of combining light nuclei to form heavier ones. One possible fusion reaction combines two isotopes of hydrogen, deuterium and tritium, to form an alpha particle and a neutron, with an accompanying release of {approximately}17.6 MeV of energy. Generating electricity from fusion requires that we create such reactions in an efficient and controlled fashion, and harness the resulting energy. In the inertial confinement fusion (ICF) approach to energy production, a small spherical target, a few millimeters in radius, of deuterium and tritium fuel is compressed so that the density and temperature of the fuel are high enough, {approximately}200 g/cm{sup 3} and {approximately}20 keV, that a substantial number of fusion reactions occur; the pellet microexplosion typically releases {approximately}350 MJ of energy in optimized power plant scenarios.

  5. Integration of a broad beam ion source with a high-temperature x-ray diffraction vacuum chamber

    NASA Astrophysics Data System (ADS)

    Manova, D.; Bergmann, A.; Mändl, S.; Neumann, H.; Rauschenbach, B.

    2012-11-01

    Here, the integration of a low energy, linearly variable ion beam current density, mechanically in situ adjustable broad beam ion source with a high-temperature x-ray diffraction (XRD) vacuum chamber is reported. This allows in situ XRD investigation of phase formation and evolution processes induced by low energy ion implantation. Special care has been taken to an independent adjustment of the ion beam for geometrical directing towards the substrate, a 15 mm small ion source exit aperture to avoid a secondary sputter process of the chamber walls, linearly variable ion current density by using a pulse length modulation (PLM) for the accelerating voltages without changing the ion beam density profile, nearly homogeneous ion beam distribution over the x-ray footprint, together with easily replaceable Kapton® windows for x-rays entry and exit. By combining a position sensitive x-ray detector with this PLM-modulated ion beam, a fast and efficient time resolved investigation of low energy implantation processes is obtained in a compact experimental setup.

  6. Integration of a broad beam ion source with a high-temperature x-ray diffraction vacuum chamber

    SciTech Connect

    Manova, D.; Bergmann, A.; Maendl, S.; Neumann, H.; Rauschenbach, B.

    2012-11-15

    Here, the integration of a low energy, linearly variable ion beam current density, mechanically in situ adjustable broad beam ion source with a high-temperature x-ray diffraction (XRD) vacuum chamber is reported. This allows in situ XRD investigation of phase formation and evolution processes induced by low energy ion implantation. Special care has been taken to an independent adjustment of the ion beam for geometrical directing towards the substrate, a 15 mm small ion source exit aperture to avoid a secondary sputter process of the chamber walls, linearly variable ion current density by using a pulse length modulation (PLM) for the accelerating voltages without changing the ion beam density profile, nearly homogeneous ion beam distribution over the x-ray footprint, together with easily replaceable Kapton{sup Registered-Sign} windows for x-rays entry and exit. By combining a position sensitive x-ray detector with this PLM-modulated ion beam, a fast and efficient time resolved investigation of low energy implantation processes is obtained in a compact experimental setup.

  7. The diurnal variation of NO, N( sup 2 D), and ions in the thermosphere: A comparison of satellite measurements to a model

    SciTech Connect

    Rusch, D.W. ); Gerard, J.C. ); Fesen, C.G. )

    1991-07-01

    A data base derived from Atmosphere Explorer C measurements of parameters important to the understanding of the diurnal variation of odd-nitrogen and ions in the thermosphere near equinox, at low latitudes, and for quiet geomagnetic conditions is presented. The data were taken during the period from August to September 1974, when perigee was near the equator and reached an altitude of about 135 km. The data base contains profiles of the odd-nitrogen species NO, and N({sup 2}D); the ions NO{sup +}, O{sub 2}{sup +}, O{sup +}, N{sub 2}{sup +}, and N{sup +}; the total ion density; O an N{sub 2}; and the neutral, ion, and electron temperatures. The measured time-dependent variations of NO, N({sup 2}D), O{sub 2}{sup +}, and NO{sup +} compare favorably to the results of a time dependent, photochemical, diffusion model for odd-nitrogen and ion chemistry. In particular, the model reproduces the rapid increase in NO density in the morning hours, the mid-afternoon maximum, and the late afternoon decrease. The model also predicts the measured absolute densities for NO to within 20% over most of the diurnal cycle but falls below the measured density by as much as a factor of 2 in the late afternoon. The agreement between the data and the model indicates that the most important chemical processes for the production and loss of odd-nitrogen in the Earth's thermosphere are induced in the model.

  8. An Ion Chamber Dedicated to Carbon NEXAFS: Removal of High-Order X-Rays and Reliable Flux Measurement

    SciTech Connect

    Fan, L.-J.; Yang, Y.-W.; Lee, Kaidee

    2007-02-02

    The difficulty of performing a reliable carbon NEXAFS measurement for thin films and adsorbate systems has long been recognized. The difficulty is typically related to lower S/B, carbon buildup in beamline optics, dirty mesh, presence of the high-order x-rays, etc. To alleviate the experimental difficulty, we have constructed an intensity-monitoring ion chamber situated between the beamline and sample chamber. The ion chamber is filled with argon up to a working pressure of 10-3 Torr and terminated with 0.1 {mu}m thick Ti foils at both ends. Titanium foils and the filled argon gas effectively remove the high-order x-rays. Consequently, the data are acquired with predominant 1st-order x-rays and thus free of the aforementioned interference, leading to a more reliable data analysis.

  9. An experimental and computational investigation of the standard temperature-pressure correction factor for ion chambers in kilovoltage x rays

    SciTech Connect

    La Russa, Daniel J.; McEwen, Malcolm; Rogers, D. W. O.

    2007-12-15

    For ion chambers with cavities open to the surrounding atmosphere, the response measured at a given temperature and pressure must be corrected using the standard temperature-pressure correction factor (P{sub TP}). A previous paper based solely on Monte Carlo simulations [D. J. La Russa and D. W. O. Rogers, Med. Phys. 33, 4590-4599 (2006)] pointed out the shortcomings of the P{sub TP} correction factor when used to correct the response of non-air-equivalent chambers for low-energy x-ray beams. This work presents the results of several experiments that corroborate these calculations for a number of ion chambers. Monte Carlo simulations of the experimental setup revealed additional insight into the various factors affecting the extent of the breakdown of P{sub TP}, including the effect of impurities and the sensitivity to chamber dimensions. For an unfiltered 60 kV beam, the P{sub TP}-corrected response of an NE 2571 ion chamber measured at 0.7 atm was 2.5% below the response measured at reference conditions. In general, Monte Carlo simulations of the experimental setup using EGSnrc were within 0.5% of measured values. EGSnrc-calculated values of air kerma calibration coefficients (N{sub K}) at low x-ray energies are also provided as a means of estimating the level of impurities in the chambers investigated. Calculated values of N{sub K} normalized to the value measured for a 250 kV beam were obtained for three chambers and were within 1% of experiment with one exception, the Exradin A12 in a 50 kV beam.

  10. Development and characterization of a 2D scintillation detector for quality assurance in scanned carbon ion beams

    NASA Astrophysics Data System (ADS)

    Tamborini, A.; Raffaele, L.; Mirandola, A.; Molinelli, S.; Viviani, C.; Spampinato, S.; Ciocca, M.

    2016-04-01

    At the Centro Nazionale di Adroterapia Oncologica (CNAO Foundation), a two-dimensional high resolution scintillating dosimetry system has been developed and tested for daily Quality Assurance measurements (QA) in carbon ion radiotherapy with active scanning technique, for both single pencil beams and scanned fields produced by a synchrotron accelerator. The detector consists of a thin plane organic scintillator (25×25 cm2, 2 mm thick) coupled with a high spatial resolution CCD camera (0.25 mm) in a light-tight box. A dedicated Labview software was developed for image acquisition triggered with the beam extraction, data post-processing and analysis. The scintillator system was preliminary characterized in terms of short-term reproducibility (found to be within±0.5%), linearity with the number of particles (linear fit χ2 = 0.996) and dependence on particle flux (measured to be < 1.5 %). The detector was then tested for single beam spot measurements (Full Width at Half Maximum and position) and for 6×6 cm2 reference scanned field (determination of homogeneity) for carbon ions with energy from 115 MeV/u up to 400 MeV/u. No major differences in the investigated beam parameters measured with scintillator system and the radiochromic EBT3 reference films were observed. The system allows therefore real-time monitoring of the carbon ion beam relevant parameters, with a significant daily time saving with respect to films currently used. The results of this study show the suitability of the scintillation detector for daily QA in a carbon ion facility with an active beam delivery system.

  11. Subkilohertz comparison of the single-ion optical-clock 2S1/2-2D5/2 transition in two 88Sr+ traps

    NASA Astrophysics Data System (ADS)

    Barwood, G. P.; Huang, G.; Klein, H. A.; Gill, P.; Clarke, R. B. M.

    1999-05-01

    A simultaneous observation of the optical-clock 2S1/2-2D5/2 transition at 674 nm, in two separately trapped single 88Sr+ ions, is reported. Two nominally identical miniature rf Paul traps were used together with a 674-nm sideband-injection-locked extended-cavity diode laser. This ``slave'' laser was optically phase locked about 650 MHz away from a ``master'' diode laser, which was itself locked to a high-finesse, ultra-low-expansion (ULE) cavity. The ULE cavity was temperature-stabilized and suspended in an evacuated enclosure, and provided an ``optical flywheel'' reference standard with a relative drift rate of better than 1 part in 1011 per hour. The difference between center frequencies of the single 88Sr+-ion 674-nm (445-THz) transition multiplet in two traps was 120(90) Hz (one standard uncertainty). Thus the two trap center frequencies agree to 3 parts in 1013.

  12. Novel control modes to improve the performance of rectilinear ion trap mass spectrometer with dual pressure chambers

    NASA Astrophysics Data System (ADS)

    Huo, Xinming; Tang, Fei; Zhang, Xiaohua; Chen, Jin; Zhang, Yan; Guo, Cheng'an; Wang, Xiaohao

    2016-10-01

    The rectilinear ion trap (RIT) has gradually become one of the preferred mass analyzers for portable mass spectrometers because of its simple configuration. In order to enhance the performance, including sensitivity, quantitation capability, throughput, and resolution, a novel RIT mass spectrometer with dual pressure chambers was designed and characterized. The studied system constituted a quadrupole linear ion trap (QLIT) in the first chamber and a RIT in the second chamber. Two control modes are hereby proposed: Storage Quadrupole Linear Ion Trap-Rectilinear Ion Trap (SQLIT-RIT) mode, in which the QLIT was used at high pressure for ion storage and isolation, and the RIT was used for analysis; and Analysis Quadrupole Linear Ion Trap-Rectilinear Ion Trap (AQLIT-RIT) mode, in which the QLIT was used for ion storage and cooling. Subsequently, synchronous scanning and analysis were carried out by QLIT and RIT. In SQLIT-RIT mode, signal intensity was improved by a factor of 30; the limit of quantitation was reduced more than tenfold to 50 ng mL-1, and an optimal duty cycle of 96.4% was achieved. In AQLIT-RIT mode, the number of ions coexisting in the RIT was reduced, which weakened the space-charge effect and reduced the mass shift. Furthermore, the mass resolution was enhanced by a factor of 3. The results indicate that the novel control modes achieve satisfactory performance without adding any system complexity, which provides a viable pathway to guarantee good analytical performance in miniaturization of the mass spectrometer.

  13. Full-particle 2-D Simulations of the Ion Foreshock associated to a Supercritical Quasi-perpendicular Curved Collisionless Shock : Origin of Backstreaming Energetic Particles

    NASA Astrophysics Data System (ADS)

    Savoini, P.; Lembege, B.

    2014-12-01

    The ion foreshock located upstream of the Earth's bow shock is populated with ions reflected back by the shock front. In-situ spacecraft measurements have clearly established the existence of two distinct populations in the upstream of the quasi-perpendicular shock region (i.e. for 45o ≤ ΘBn≤ 90o, where ΘBn is the angle between the shock normal and the upstream magnetostatic field): (i) field-aligned ion beams (or 'FAB') characterized by a gyrotropic distribution, and (ii) gyro-phase bunched ions (or 'GPB') characterized by a NON gyrotropic distribution, which exhibits a non-vanishing perpendicular bulk velocity. The use of 2D PIC simulations where full curvature effects, time of flight effects and both electrons and ions dynamics are fully described, has evidenced that the shock front itself can be the possible source of these two characteristic populations. A recent analysis has evidenced that both populations can be discriminated in terms of interaction time (Δtinter) with the shock front. 'GPB' and 'FAB' populations are characterized by a short (Δtinter ~ 1 τci) and much larger (Δtinter ≥ 2 τci) interaction time respectively, where τci is the ion upstream gyroperiod. In addition, present statistical results evidence that: (i) backstreaming ions are splitted into 'FAB' and 'GPB' populations depending on their injection angle when hitting the shock front (defined between the local normal to the shock front and the gyration velocity vector). (ii) As a consequence, ion trajectories strongly differ between the 'FAB' and 'GPB' populations at the shock front. In particular, 'FAB' ions suffer multi-bounces along the curved front whereas 'GPB' ions make only one bounce. Such differences may explain why the 'FAB' population loses their gyro-phase coherency and become gyrotropic which is not the case for the 'GPB'. Then, the differences observed between 'FAB' and 'GPB' populations do not involve some distinct reflection processes as often claimed in the

  14. 2D wax-printed paper substrates with extended solvent supply capabilities allow enhanced ion signal in paper spray ionization.

    PubMed

    Damon, Deidre E; Maher, Yosef S; Yin, Mengzhen; Jjunju, Fred P M; Young, Iain S; Taylor, Stephen; Maher, Simon; Badu-Tawiah, Abraham K

    2016-06-21

    Paper-based microfluidic channels were created from solid wax printing, and the resultant 2D wax-printed paper substrates were used for paper spray (PS) mass spectrometry (MS) analysis of small organic compounds. Controlling fluid flow at the tip of the wax-printed paper triangles enabled the use of lower spray voltages (0.5-1 kV) and extended signal lifetime (10 minutes) in PS-MS. High sensitivity (sub ng mL(-1) levels) and quantitation precision (<10% RSD) have been achieved in the analysis of illicit drugs in 4 μL of raw urine (fresh and dry), as well as corrosion inhibitors and pesticides in water samples. The reported study encourages the future development of disposable 3D microfluidic paper-based analytical devices, which function with simple operation but capable of on-chip analyte detection by MS; such a device can replace the traditional complex laboratory procedures for MS analysis to enable on-site in situ sampling with portable mass spectrometers.

  15. Fast ion induced shearing of 2D Alfvén eigenmodes measured by electron cyclotron emission imaging.

    PubMed

    Tobias, B J; Classen, I G J; Domier, C W; Heidbrink, W W; Luhmann, N C; Nazikian, R; Park, H K; Spong, D A; Van Zeeland, M A

    2011-02-18

    Two-dimensional images of electron temperature perturbations are obtained with electron cyclotron emission imaging (ECEI) on the DIII-D tokamak and compared to Alfvén eigenmode structures obtained by numerical modeling using both ideal MHD and hybrid MHD-gyrofluid codes. While many features of the observations are found to be in excellent agreement with simulations using an ideal MHD code (NOVA), other characteristics distinctly reveal the influence of fast ions on the mode structures. These features are found to be well described by the nonperturbative hybrid MHD-gyrofluid model TAEFL.

  16. Dynamics of neutralizing electrons during the focusing of intense heavy ions beams inside a HIF reactor chamber

    NASA Astrophysics Data System (ADS)

    Lifschitz, A. F.; Maynard, G.; Vay, J.-L.; Lenglet, A.

    2006-06-01

    The efficiency of a Heavy Ion Fusion reactor heavily depends on the maximum value for the density of energy (DoE) that can be deposited by the ion beams. In order to reduce the final radius, and thus to increase the DoE inside the target, the beam spatial charge has to be neutralized. Therefore the dynamics of the neutralizing electrons (DNE) play a central role in optimizing the DoE deposited in solid targets by high current of high energy heavy ion beams. We present results on some aspects of the DNE, which was performed using the Monte-Carlo 2D1/2 PIC code BPIC.

  17. Sodium ion effect on silk fibroin conformation characterized by solid-state NMR and generalized 2D NMR NMR correlation

    NASA Astrophysics Data System (ADS)

    Ruan, Qing-Xia; Zhou, Ping

    2008-07-01

    In the present work, we investigated Na + ion effect on the silk fibroin (SF) conformation. Samples are Na +-involved regenerated silk fibroin films. 13C CP-MAS NMR demonstrates that as added [Na +] increases, partial silk fibroin conformation transit from helix-form to β-form at certain Na + ion concentration which is much higher than that in Bombyx mori silkworm gland. The generalized two-dimensional NMR-NMR correlation analysis reveals that silk fibroin undergoes several intermediate states during its conformation transition process as [Na +] increase. The appearance order of the intermediates is followed as: helix and/or random coil → helix-like → β-sheet-like → β-sheet, which is the same as that produced by pH decrease from 6.8 to 4.8 in the resultant regenerated silk fibroin films. The binding sites of Na + to silk fibroin might involve the carbonyl oxygen atom of certain amino acids sequence which could promote the formation of β-sheet conformation. Since the Na +sbnd O bond is weak, the ability of Na + inducing the secondary structure transition is weaker than those of Ca 2+, Cu 2+ and even K +. It is maybe a reason why the sodium content is much lower than potassium in the silkworm gland.

  18. Development of a Novel Contamination Resistant Ion Chamber for Process Tritium Measurement and Use in the JET First Trace Tritium Experiment

    SciTech Connect

    Worth, L.B.C.; Pearce, R.J.H.; Bruce, J.; Banks, J.; Scales, S.

    2005-07-15

    The accuracy of process measurements of tritium with conventional ion chambers is often affected by surface tritium contamination. The measurement of tritium in the exhaust of the JET torus is particularly difficult due to surface contamination with highly tritiated hydrocarbons. JET's first unsuccessful attempt to overcome the contamination problem was to use an ion chamber, with a heating element as the chamber wall so that it could be periodically decontaminated by baking. The newly developed ion chamber works on the principle of minimising the surface area within the boundary of the anode and cathode.This paper details the design of the ion chamber, which utilises a grid of 50-micron tungsten wire to define the ion chamber wall and the collector electrode. The effective surface area which, by contamination, is able to effect the measurement of tritium within the process gas has been reduced by a factor of {approx}200 over a conventional ion chamber. It is concluded that the new process ion chamber enables sensitive accurate tritium measurements free from contamination issues. It will be a powerful new tool for future tritium experiments both to improve tritium tracking and to help in the understanding of tritium retention issues.

  19. Experimental validation of a versatile system of CT dosimetry using a conventional ion chamber: Beyond CTDI{sub 100}

    SciTech Connect

    Dixon, Robert L.; Ballard, Adam C.

    2007-08-15

    This article is an experimental demonstration and authentication of a new method of computed tomography dosimetry [R. L. Dixon, Med. Phys. 30, 1272-1280 (2003)], which utilizes a short, conventional ion chamber rather than a pencil chamber, and which is more versatile than the latter. The value of CTDI{sub 100} correctly predicts the accumulated dose only for a total scan length L equal to 100 mm and underestimates the limiting equilibrium dose approached for longer, clinically relevant body scan lengths [R. L. Dixon, Med. Phys. 30, 1272-1280 (2003); K. D. Nakonechny, B. G. Fallone, and S. Rathee, Med. Phys. 32, 98-109 (2005); S. Mori, M. Endo, K. Nishizawa, T. Tsunoo, T. Aoyama, H. Fujiwara, and K. Murase, Med. Phys. 32, 1061-1069 (2005); R. L. Dixon, M. T. Munley, and E. Bayram, Med. Phys. 32, 3712-3728 (2005); R. L. Dixon, Med. Phys. 33, 3973-3976 (2006)]. Dixon [Med. Phys. 30, 1272-1280 (2003)] originally proposed an alternative using a short ion chamber and a helical scan acquisition to collect the same integral for any scan length L (and not limited 100 mm). The primary purpose of this work is to demonstrate experimentally the implementation, robustness, and versatility of this small ion chamber method in measuring the accumulated dose in the body phantom for any desired scan length L (up to the available phantom length) including the limiting equilibrium dose (symbolically CTDI{sub {infinity}}), and validation of the method against the pencil chamber methodology. Additionally, a simple and robust method for independently verifying the active length of a pencil chamber is described. The results of measurements made in a 400 mm long, 32 cm diameter polymethylmethacrylate body phantom using a small Farmer-type ion chamber and two pencil chambers of lengths l=100 and 150 mm confirm that the two methodologies provide the same dose values at the corresponding scan lengths L=l. The measured equilibrium doses obtained for GE MDCT scanners at 120 kVp are CTDI

  20. Monte Carlo calculated correction factors for diodes and ion chambers in small photon fields.

    PubMed

    Czarnecki, D; Zink, K

    2013-04-21

    The application of small photon fields in modern radiotherapy requires the determination of total scatter factors Scp or field factors Ω(f(clin), f(msr))(Q(clin), Q(msr)) with high precision. Both quantities require the knowledge of the field-size-dependent and detector-dependent correction factor k(f(clin), f(msr))(Q(clin), Q(msr)). The aim of this study is the determination of the correction factor k(f(clin), f(msr))(Q(clin), Q(msr)) for different types of detectors in a clinical 6 MV photon beam of a Siemens KD linear accelerator. The EGSnrc Monte Carlo code was used to calculate the dose to water and the dose to different detectors to determine the field factor as well as the mentioned correction factor for different small square field sizes. Besides this, the mean water to air stopping power ratio as well as the ratio of the mean energy absorption coefficients for the relevant materials was calculated for different small field sizes. As the beam source, a Monte Carlo based model of a Siemens KD linear accelerator was used. The results show that in the case of ionization chambers the detector volume has the largest impact on the correction factor k(f(clin), f(msr))(Q(clin), Q(msr)); this perturbation may contribute up to 50% to the correction factor. Field-dependent changes in stopping-power ratios are negligible. The magnitude of k(f(clin), f(msr))(Q(clin), Q(msr)) is of the order of 1.2 at a field size of 1 × 1 cm(2) for the large volume ion chamber PTW31010 and is still in the range of 1.05-1.07 for the PinPoint chambers PTW31014 and PTW31016. For the diode detectors included in this study (PTW60016, PTW 60017), the correction factor deviates no more than 2% from unity in field sizes between 10 × 10 and 1 × 1 cm(2), but below this field size there is a steep decrease of k(f(clin), f(msr))(Q(clin), Q(msr)) below unity, i.e. a strong overestimation of dose. Besides the field size and detector dependence, the results reveal a clear dependence of the

  1. Testing of multigap Resistive Plate Chambers for Electron Ion Collider Detector Development

    NASA Astrophysics Data System (ADS)

    Hamilton, Hannah; Phenix Collaboration

    2015-10-01

    Despite decades of research on the subject, some details of the spin structure of the nucleon continues to be unknown. To improve our knowledge of the nucleon spin structure, the construction of a new collider is needed. This is one of the primary goals of the proposed Electron Ion Collider (EIC). Planned EIC spectrometers will require good particle identification. This can be provided by time of flight (TOF) detectors with excellent timing resolutions of 10 ps. A potential TOF detector that could meet this requirement is a glass multigap resistive plate chamber (mRPC). These mRPCs can provide excellent timing resolution at a low cost. The current glass mRPC prototypes have a total of twenty 0.1 mm thick gas gaps. In order to test the feasibility of this design, a cosmic test stand was assembled. This stand used the coincidence of scintillators as a trigger, and contains fast electronics. The construction, the method of testing, and the test results of the mRPCs will be presented.

  2. Enhanced thermal emittance of space radiators by ion-discharge chamber texturing

    NASA Technical Reports Server (NTRS)

    Mirtich, Michael J.; Kussmaul, Michael T.

    1987-01-01

    The discharge chamber of a 30-cm argon ion source was successfully used to texture potential space radiator materials for the purpose of obtaining values of thermal emittance greater than 0.85 at 700 and 900 K. Some samples were also treated in acid prior to texturing. To evaluate the durability of the textured materials to atomic oxygen, samples were exposed to an RF air plasma environment. The spectral emittance between 2.0 anf 15.0 microns was measured before and after the textured materials were exposed to the plasma asher. The results indicate that copper with extremely high values of emittance after texturing (0.978 and 0.983) at 700 and 900 K, respectively,did not change its values of emittance after ashing, whereas the emittance of stainless steel fell below 0.85 after ashing. These data, along with scanning electron photomicrographs, and the results of texturing and ashing titanium and Nb(1)Zr are presented .

  3. 2D Space-Confined Synthesis of Few-Layer MoS2 Anchored on Carbon Nanosheet for Lithium-Ion Battery Anode.

    PubMed

    Zhou, Jingwen; Qin, Jian; Zhang, Xiang; Shi, Chunsheng; Liu, Enzuo; Li, Jiajun; Zhao, Naiqin; He, Chunnian

    2015-04-28

    A facile and scalable 2D spatial confinement strategy is developed for in situ synthesizing highly crystalline MoS2 nanosheets with few layers (≤5 layers) anchored on 3D porous carbon nanosheet networks (3D FL-MoS2@PCNNs) as lithium-ion battery anode. During the synthesis, 3D self-assembly of cubic NaCl particles is adopted to not only serve as a template to direct the growth of 3D porous carbon nanosheet networks, but also create a 2D-confined space to achieve the construction of few-layer MoS2 nanosheets robustly lain on the surface of carbon nanosheet walls. In the resulting 3D architecture, the intimate contact between the surfaces of MoS2 and carbon nanosheets can effectively avoid the aggregation and restacking of MoS2 as well as remarkably enhance the structural integrity of the electrode, while the conductive matrix of 3D porous carbon nanosheet networks can ensure fast transport of both electrons and ions in the whole electrode. As a result, this unique 3D architecture manifests an outstanding long-life cycling capability at high rates, namely, a specific capacity as large as 709 mAh g(-1) is delivered at 2 A g(-1) and maintains ∼95.2% even after 520 deep charge/discharge cycles. Apart from promising lithium-ion battery anode, this 3D FL-MoS2@PCNN composite also has immense potential for applications in other areas such as supercapacitor, catalysis, and sensors.

  4. Long term changes in cosmic ray diurnal variations observed by ion chambers in Hong Kong and Japan

    NASA Technical Reports Server (NTRS)

    Chuang, L. S.; Kusunose, M.; Wada, M.

    1985-01-01

    Yearly average solar diurnal variations of cosmic ray ion chamber data are inspected from a view point of the eleven and the 22 year solar activity cycle modulations. Ion chamber data and neutron data from various stations are added. From an inspection of observed data, a simple approximation that the 11 year and the 22 year variations of the solar diurnal variation are along 18-hour and 12-hour axes, respectively is proposed. The 18-hour component of diurnal variation in the 11 year cycle increases toward the solar active years. The 12-hour component is enhanced when the solar general magnetic field is parallel to the rotation vector, and is almost zero for the other state. The transition occurs when the amplitude of the 18-hour component is greater owing to the transition of the field during the maximum phase of solar activity. The 22 year shift is consistent with the drift modulation model in heliosphere.

  5. Characterization of Downstream Ion Energy Distributions From a High Current Hollow Cathode in a Ring Cusp Discharge Chamber

    NASA Technical Reports Server (NTRS)

    Foster, John E.; Patterson, Michael J.

    2003-01-01

    The presence of energetic ions produced by a hollow cathodes operating at high emission currents (greater than 10 Angstroms) has been documented in the literature. As part of an ongoing effort to uncover the underlying physics of the formation of these ions, ion efflux from a high current hollow cathode operating in an ion thruster discharge chamber was investigated. Using a spherical sector electrostatic energy analyzer located downstream of the discharge cathode, the ion energy distribution over a 0 to 60 eV energy range was measured. The sensitivity of the ion energy distribution function to zenith angle was also assessed at 3 different positions: 0, 15, and 25 degrees. The measurements suggest that the majority of the ion current at the measuring point falls into the analyzer with an energy approximately equal to the discharge voltage. The ion distribution, however, was found to be quite broad. The high energy tail of the distribution function tended to grow with increasing discharge current. Sensitivity of the profiles to flow rate at fixed discharge current was also investigated. A simple model is presented that provides a potential mechanism for the production of ions with energies above the discharge voltage.

  6. Dose verification in carcinoma of uterine cervix patients undergoing 3D conformal radiotherapy with Farmer type ion chamber

    PubMed Central

    Srinivas, Challapalli; Kumar, P Suman; Ravichandran, Ramamoorthy; Banerjee, S; Saxena, P.U; Kumar, E.S Arun; Pai, Dinesh K.

    2014-01-01

    External beam radiotherapy (EBRT) for carcinoma of uterine cervix is a basic line of treatment with three dimensional conformal radiotherapy (3DCRT) in large number of patients. There is need for an established method for verification dosimetry. We tried to document absorbed doses in a group of carcinoma cervix patients by inserting a 0.6 cc Farmer type ion chamber in the vaginal cavity. A special long perspex sleeve cap is designed to cover the chamber for using in the patient's body. Response of ionization chamber is checked earlier in water phantom with and without cap. Treatment planning was carried out with X-ray computed tomography (CT) scan and with the chamber along with cap in inserted position, and with the images Xio treatment planning system. Three measurements on 3 days at 5-6 fraction intervals were recorded in 12 patients. Electrometer measured charges are converted to absorbed dose at the chamber center, in vivo. Our results show good agreement with planned dose within 3% against prescribed dose. This study, is a refinement over our previous studies with transmission dosimetry and chemicals in ampules. This preliminary work shows promise that this can be followed as a routine dose check with special relevance to new protocols in the treatment of carcinoma cervix with EBRT. PMID:25525313

  7. On-board monitoring of 2-D spatially-resolved temperatures in cylindrical lithium-ion batteries: Part I. Low-order thermal modelling

    NASA Astrophysics Data System (ADS)

    Richardson, Robert R.; Zhao, Shi; Howey, David A.

    2016-09-01

    Estimating the temperature distribution within Li-ion batteries during operation is critical for safety and control purposes. Although existing control-oriented thermal models - such as thermal equivalent circuits (TEC) - are computationally efficient, they only predict average temperatures, and are unable to predict the spatially resolved temperature distribution throughout the cell. We present a low-order 2D thermal model of a cylindrical battery based on a Chebyshev spectral-Galerkin (SG) method, capable of predicting the full temperature distribution with a similar efficiency to a TEC. The model accounts for transient heat generation, anisotropic heat conduction, and non-homogeneous convection boundary conditions. The accuracy of the model is validated through comparison with finite element simulations, which show that the 2-D temperature field (r, z) of a large format (64 mm diameter) cell can be accurately modelled with as few as 4 states. Furthermore, the performance of the model for a range of Biot numbers is investigated via frequency analysis. For larger cells or highly transient thermal dynamics, the model order can be increased for improved accuracy. The incorporation of this model in a state estimation scheme with experimental validation against thermocouple measurements is presented in the companion contribution (http://www.sciencedirect.com/science/article/pii/S0378775316308163)

  8. On-board monitoring of 2-D spatially-resolved temperatures in cylindrical lithium-ion batteries: Part II. State estimation via impedance-based temperature sensing

    NASA Astrophysics Data System (ADS)

    Richardson, Robert R.; Zhao, Shi; Howey, David A.

    2016-09-01

    Impedance-based temperature detection (ITD) is a promising approach for rapid estimation of internal cell temperature based on the correlation between temperature and electrochemical impedance. Previously, ITD was used as part of an Extended Kalman Filter (EKF) state-estimator in conjunction with a thermal model to enable estimation of the 1-D temperature distribution of a cylindrical lithium-ion battery. Here, we extend this method to enable estimation of the 2-D temperature field of a battery with temperature gradients in both the radial and axial directions. An EKF using a parameterised 2-D spectral-Galerkin model with ITD measurement input (the imaginary part of the impedance at 215 Hz) is shown to accurately predict the core temperature and multiple surface temperatures of a 32,113 LiFePO4 cell, using current excitation profiles based on an Artemis HEV drive cycle. The method is validated experimentally on a cell fitted with a heat sink and asymmetrically cooled via forced air convection. A novel approach to impedance-temperature calibration is also presented, which uses data from a single drive cycle, rather than measurements at multiple uniform cell temperatures as in previous studies. This greatly reduces the time required for calibration, since it overcomes the need for repeated cell thermal equalization.

  9. Guided ion beam and theoretical study of the reactions of Hf{sup +} with H{sub 2}, D{sub 2}, and HD

    SciTech Connect

    Hinton, Christopher S.; Armentrout, P. B.

    2010-09-28

    The kinetic energy dependences of reactions of the third-row transition metal cation Hf{sup +} with H{sub 2}, D{sub 2}, and HD were determined using a guided ion beam tandem mass spectrometer. A flow tube ion source produces Hf{sup +} in its {sup 2}D (6s{sup 2}5d{sup 1}) electronic ground state level. Corresponding state-specific reaction cross sections are obtained. The kinetic energy dependences of the cross sections for the endothermic formation of HfH{sup +} and HfD{sup +} are analyzed to give a 0 K bond dissociation energy of D{sub 0}(Hf{sup +}-H)=2.11{+-}0.08 eV. Quantum chemical calculations at several levels of theory performed here generally overestimate the experimental bond energy but results obtained using the Becke-half-and-half-LYP functional show good agreement. Theory also provides the electronic structures of these species and the reactive potential energy surfaces. Results from the reactions with HD provide insight into the reaction mechanisms and indicates that Hf{sup +} reacts via a statistical mechanism. We also compare this third-row transition metal system with the first-row and second-row congeners, Ti{sup +} and Zr{sup +}, and find that Hf{sup +} has a weaker M{sup +}-H bond. As most third-row transition metal hydride cation bonds exceed their lighter congeners, this trend is unusual but can be understood using promotion energy arguments.

  10. Input/output characteristics of a matrix ion-chamber electronic portal imaging device.

    PubMed

    Yin, F F; Schell, M C; Rubin, P

    1994-09-01

    The input/output characteristics of a matrix liquid ion-chamber electronic portal imaging device (EPID) are investigated to elucidate the imaging properties of EPIDs. The radiation input to the detector, represented by dose rate, and the pixel value output from the device are related by a characteristic curve. Various incident radiation intensities are obtained by changing the source-to-detector distance (SDD). For each incident radiation intensity, an electronic portal image is obtained using a field size of 5 x 5 cm2. The output pixel value of the EPID is represented by the average pixel value of a region of interest of 9 x 9 pixels centered at a selected point. The effects of various accelerator settings, such as the repetition-rate setting and photon energy, gantry angle, field size, SDD, and acquisition mode of the EPID on characteristic curves are investigated at the central axis. The off-axis response of the detector is also examined. The derivative of the pixel value with respect to the input dose rate is used to analyze the detector contrast. Results indicate that the output pixel value is not a linear function of the incident radiation intensity. The detector contrast is comparable between photon energies of 10 and 6 MV and increases at low dose rates. The response of the imaging device varies substantially with acquisition mode, but is less sensitive to the SDD used for calibration. Characteristic curves are consistent for different gantry angles at the central axis and with the off-axis locations when the gantry angle is used for imaging and calibration, but vary with off-axis locations when the gantry angle is not at the calibration direction. Characteristic curves are also found to vary with different field sizes, but are similar in shape.

  11. Physical and chemical analysis of lithium-ion battery cell-to-cell failure events inside custom fire chamber

    NASA Astrophysics Data System (ADS)

    Spinner, Neil S.; Field, Christopher R.; Hammond, Mark H.; Williams, Bradley A.; Myers, Kristina M.; Lubrano, Adam L.; Rose-Pehrsson, Susan L.; Tuttle, Steven G.

    2015-04-01

    A 5-cubic meter decompression chamber was re-purposed as a fire test chamber to conduct failure and abuse experiments on lithium-ion batteries. Various modifications were performed to enable remote control and monitoring of chamber functions, along with collection of data from instrumentation during tests including high speed and infrared cameras, a Fourier transform infrared spectrometer, real-time gas analyzers, and compact reconfigurable input and output devices. Single- and multi-cell packages of LiCoO2 chemistry 18650 lithium-ion batteries were constructed and data was obtained and analyzed for abuse and failure tests. Surrogate 18650 cells were designed and fabricated for multi-cell packages that mimicked the thermal behavior of real cells without using any active components, enabling internal temperature monitoring of cells adjacent to the active cell undergoing failure. Heat propagation and video recordings before, during, and after energetic failure events revealed a high degree of heterogeneity; some batteries exhibited short burst of sparks while others experienced a longer, sustained flame during failure. Carbon monoxide, carbon dioxide, methane, dimethyl carbonate, and ethylene carbonate were detected via gas analysis, and the presence of these species was consistent throughout all failure events. These results highlight the inherent danger in large format lithium-ion battery packs with regards to cell-to-cell failure, and illustrate the need for effective safety features.

  12. Monte Carlo-based correction factors for ion chamber dosimetry in heterogeneous phantoms for megavoltage photon beams.

    PubMed

    Araki, Fujio

    2012-11-21

    The purpose of this study was to investigate the perturbation correction factors and inhomogeneity correction factors (ICFs) for a thin-walled cylindrical ion chamber in a heterogeneous phantom including solid water, lung and bone plastic materials. The perturbation factors due to the replacement of the air cavity, non-water equivalence of the wall and the stem, non-air equivalence of the central electrode and the overall perturbation factor, P(Q), for a cylindrical chamber, in the heterogeneous phantom were calculated with the EGSnrc/Cavity Monte Carlo code for 6 and 15 MV photon beams. The PTW31010 (0.125 cm(3)) chamber was modeled with Monte Carlo simulations, and was used for measurements and calculations of percentage depth ionization (PDI) or percentage depth dose (PDD). ICFs were calculated from the ratio of the product of the stopping power ratios (SPRs) and P(Q) of lung or bone to solid water. Finally, the measured PDIs were converted to PDDs by using ICFs and were compared with those calculated by the Monte Carlo method. The perturbation effect for the ion chamber in lung material is insignificant at 5 × 5 and 10 × 10 cm(2) fields, but the effect needs to be considered under conditions of lateral electron disequilibrium with a 3 × 3 cm(2) field. ICFs in lung varied up to 2% and 4% depending on the field size for 6 and 15 MV, respectively. For bone material, the perturbation effects due to the chamber wall and the stem were more significant at up to 3.5% and 1.6% for 6 MV, respectively. ICFs for bone material were approximately 0.945 and 0.940 for 6 and 15 MV, respectively. The converted PDDs by using ICFs were in good agreement with Monte Carlo calculated PDDs. The chamber perturbation correction and SPRs should strictly be considered for ion chamber dosimetry in heterogeneous media. This is more important for small field dosimetry in lung and bone materials. PMID:23103477

  13. Measurement of electron temperature and density in the DIII-D neutral beam ion source arc chamber

    SciTech Connect

    Kellman, D.H.; Busath, J.; Hong, R.

    1993-10-01

    A swept-bias Langmuir probe diagnostic was employed with the DIII-D neutral beam ion source in an effort to study the effects of filament temperature, arc power, and backstreaming energetic electrons on the electron temperature and density of the arc discharge inside the ion source arc chamber. The arc chamber contains six Langmuir probes biased with a negative dc voltage. These probes provide a feedback signal for regulation of the arc power supply, and give a relative indication of plasma uniformity within the arc chamber. For this study, one probe was reconnected to a voltage-sweeping power supply, and probe current versus voltage characteristics were generated. These characteristics provided the information necessary to calculate electron temperature and density. With arc discharge only, the results demonstrated that an filament temperature increases, so does electron density. Electron temperature decreases at a faster rate, however, as required to maintain constant ion maturation current (regulated by the arc power supply). The results also demonstrated that increasing arc power (through control of the arc power supply) results in higher electron temperature and density. Experiments were also performed with probe voltage sweeps during beam extraction, at various accelerator voltage levels and at different delay times after beam turn-on with a fixed acceleration voltage. These results indicated an increase in electron temperature and density as acceleration voltage is increased. However, nearly identical trends result when arc discharges are produced at the same parameter settings as during these beams, but without beam extraction. This indicates minimal influence of backstreaming energetic electrons on electron temperature and density in the arc chamber. Temperature and density also remain fairly constant over time during a long beam pulse.

  14. Technical Note: Influence of Compton currents on profile measurements in small-volume ion chambers

    SciTech Connect

    Tanny, Sean; Sperling, Nicholas; Parsai, E. Ishmael; Holmes, Shannon

    2015-10-15

    Purpose: This work is to evaluate the effects of Compton current generation in three small-volume ionization chambers on measured beam characteristics for electron fields. Methods: Beam scans were performed using Exradin A16, A26, and PTW 31014 microchambers. Scans with varying chamber components shielded were performed. Static point measurements, output factors, and cable only irradiations were performed to determine the contribution of Compton currents to various components of the chamber. Monte Carlo simulations were performed to evaluate why one microchamber showed a significant reduction in Compton current generation. Results: Beam profiles demonstrated significant distortion for two of the three chambers when scanned parallel to the chamber axis, produced by electron deposition within the wire. Measurements of ionization produced within the cable identified Compton current generation as the cause of these distortions. The size of the central collecting wire was found to have the greatest influence on the magnitude of Compton current generation. Conclusions: Microchambers can demonstrate significant (>5%) deviations from properties as measured with larger volume chambers (0.125 cm{sup 3} and above). These deviations can be substantially reduced by averaging measurements conducted at opposite polarities.

  15. Chamber-confined silicon-carbon nanofiber composites for prolonged cycling life of Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Fu, Kun; Lu, Yao; Dirican, Mahmut; Chen, Chen; Yanilmaz, Meltem; Shi, Quan; Bradford, Philip D.; Zhang, Xiangwu

    2014-06-01

    Silicon is a promising high capacity (4200 mA h g-1) anode material for lithium ion batteries but the significant volume change (over 300%) of silicon during lithiation/delithiation remains a challenge in terms of silicon pulverization and solid-electrolyte-interphase (SEI) accumulation in the silicon composite electrode. To alleviate the volumetric change of silicon, we built a flexible and self-supporting carbon-enhanced carbon nanofiber (CNF) structure with vacant chamber to encapsulate Si nanoparticles (vacant Si@CNF@C). This composite was tested directly without any polymer and current collector. The confined vacant chamber allowed the increasing volume of silicon and SEI accumulates to be well retained for a long cycle life. This chamber-confined silicon-carbon nanofiber composite exhibited an improved performance in terms of good cycling performance (620 mA h g-1), high coulombic efficiency (99%), and good capacity retention (80%) after 200 cycles. This self-supported silicon-carbon nanofiber structure showed high flexibility and good electrochemical performance for the potential as flexible electrode for lithium-ion batteries.

  16. Chamber-confined silicon-carbon nanofiber composites for prolonged cycling life of Li-ion batteries.

    PubMed

    Fu, Kun; Lu, Yao; Dirican, Mahmut; Chen, Chen; Yanilmaz, Meltem; Shi, Quan; Bradford, Philip D; Zhang, Xiangwu

    2014-07-01

    Silicon is a promising high capacity (4200 mA h g(-1)) anode material for lithium ion batteries but the significant volume change (over 300%) of silicon during lithiation/delithiation remains a challenge in terms of silicon pulverization and solid-electrolyte-interphase (SEI) accumulation in the silicon composite electrode. To alleviate the volumetric change of silicon, we built a flexible and self-supporting carbon-enhanced carbon nanofiber (CNF) structure with vacant chamber to encapsulate Si nanoparticles (vacant Si@CNF@C). This composite was tested directly without any polymer and current collector. The confined vacant chamber allowed the increasing volume of silicon and SEI accumulates to be well retained for a long cycle life. This chamber-confined silicon-carbon nanofiber composite exhibited an improved performance in terms of good cycling performance (620 mA h g(-1)), high coulombic efficiency (99%), and good capacity retention (80%) after 200 cycles. This self-supported silicon-carbon nanofiber structure showed high flexibility and good electrochemical performance for the potential as flexible electrode for lithium-ion batteries.

  17. A combined segmented anode gas ionization chamber and time-of-flight detector for heavy ion elastic recoil detection analysis

    NASA Astrophysics Data System (ADS)

    Ström, Petter; Petersson, Per; Rubel, Marek; Possnert, Göran

    2016-10-01

    A dedicated detector system for heavy ion elastic recoil detection analysis at the Tandem Laboratory of Uppsala University is presented. Benefits of combining a time-of-flight measurement with a segmented anode gas ionization chamber are demonstrated. The capability of ion species identification is improved with the present system, compared to that obtained when using a single solid state silicon detector for the full ion energy signal. The system enables separation of light elements, up to Neon, based on atomic number while signals from heavy elements such as molybdenum and tungsten are separated based on mass, to a sample depth on the order of 1 μm. The performance of the system is discussed and a selection of material analysis applications is given. Plasma-facing materials from fusion experiments, in particular metal mirrors, are used as a main example for the discussion. Marker experiments using nitrogen-15 or oxygen-18 are specific cases for which the described improved species separation and sensitivity are required. Resilience to radiation damage and significantly improved energy resolution for heavy elements at low energies are additional benefits of the gas ionization chamber over a solid state detector based system.

  18. Guided ion beam and theoretical study of the reactions of Os{sup +} with H{sub 2}, D{sub 2}, and HD

    SciTech Connect

    Hinton, Christopher S.; Citir, Murat; Armentrout, P. B.

    2011-12-21

    Reactions of the third-row transition metal cation Os{sup +} with H{sub 2}, D{sub 2}, and HD to form OsH{sup +} (OsD{sup +}) were studied using a guided ion beam tandem mass spectrometer. A flow tube ion source produces Os{sup +} in its {sup 6}D (6s{sup 1}5d{sup 6}) electronic ground state level. Corresponding state-specific reaction cross sections are obtained. The kinetic energy dependences of the cross sections for the endothermic formation of OsH{sup +} and OsD{sup +} are analyzed to give a 0 K bond dissociation energy of D{sub 0}(Os{sup +}-H) = 2.45 {+-} 0.10 eV. Quantum chemical calculations are performed here at several levels of theory, with B3LYP approaches generally overestimating the experimental bond energy whereas results obtained using BHLYP and CCSD(T), coupled-cluster with single, double, and perturbative triple excitations, levels show good agreement. Theory also provides the electronic structures of these species and the potential energy surfaces for reaction. Results from the reactions with HD provide insight into the reaction mechanism and indicate that Os{sup +} reacts via a direct reaction. We also compare this third-row transition metal system with the first-row and second-row congeners, Fe{sup +} and Ru{sup +}, and find that Os{sup +} reacts more efficiently with dihydrogen, forming a stronger M{sup +}-H bond. These differences can be attributed to the lanthanide contraction and relativistic effects.

  19. Characterization of responses of 2d array seven29 detector and its combined use with octavius phantom for the patient-specific quality assurance in rapidarc treatment delivery

    SciTech Connect

    Syamkumar, S.A.; Padmanabhan, Sriram; Sukumar, Prabakar; Nagarajan, Vivekanandan

    2012-04-01

    A commercial 2D array seven29 detector has been characterized and its performance has been evaluated. 2D array ionization chamber equipped with 729 ionization chambers uniformly arranged in a 27 Multiplication-Sign 27 matrix with an active area of 27 Multiplication-Sign 27 cm{sup 2} was used for the study. An octagon-shaped phantom (Octavius Phantom) with a central cavity is used to insert the 2D ion chamber array. All measurements were done with a linear accelerator. The detector dose linearity, reproducibility, output factors, dose rate, source to surface distance (SSD), and directional dependency has been studied. The performance of the 2D array, when measuring clinical dose maps, was also investigated. For pretreatment quality assurance, 10 different RapidArc plans conforming to the clinical standards were selected. The 2D array demonstrates an excellent short-term output reproducibility. The long-term reproducibility was found to be within {+-}1% over a period of 5 months. Output factor measurements for the central chamber of the array showed no considerable deviation from ion chamber measurements. We found that the 2D array exhibits directional dependency for static fields. Measurement of beam profiles and wedge-modulated fields with the 2D array matched very well with the ion chamber measurements in the water phantom. The study shows that 2D array seven29 is a reliable and accurate dosimeter and a useful tool for quality assurance. The combination of the 2D array with the Octavius phantom proved to be a fast and reliable method for pretreatment verification of rotational treatments.

  20. Peripheral nerve regeneration through a silicone chamber implanted with negative carbon ions: Possibility to clinical application

    NASA Astrophysics Data System (ADS)

    Ikeguchi, Ryosuke; Kakinoki, Ryosuke; Tsuji, Hiroshi; Yasuda, Tadashi; Matsuda, Shuichi

    2014-08-01

    We investigated whether a tube with its inner surface implanted with negative-charged carbon ions (C- ions) would enable axons to extend over a distance greater than 10 mm. The tube was found to support nerves regenerating across a 15-mm-long inter-stump gap. We also investigated whether a C- ion-implanted tube pretreated with basic fibroblast growth factor (bFGF) promotes peripheral nerve regeneration. The C- ion implanted tube accelerated nerve regeneration, and this effect was enhanced by bFGF. Silicone treated with C- ions showed increased hydrophilic properties and cellular affinity, and axon regeneration was promoted with this increased biocompatibility.

  1. Determination of the ground state energies of the H{2/+}, D{2/+} and H{2/+} molecular ions taking into account relativistic corrections

    NASA Astrophysics Data System (ADS)

    Dineykhan, M.; Zhaugasheva, S. A.; Bekbaev, A. K.; Ishmukhamedov, I. S.

    2012-12-01

    On the basis of determination of the asymptotic behavior of correlation functions of the corresponding field currents with the corresponding quantum numbers an analytic method for determination of the energy spectrum of three-body Coulomb system is suggested. Our results show that the constituent masses of particles, which we have defined as masses of particles in a bound state, differ from masses of particles in a free-state. The constituent mass to the free state mass relation for the electron is greater than the same mass relation for the proton, deuteron and triton. It was also found that this constituent electron mass has different values in each systems, i.e. in H{2/+}, D{2/+} and T{2/+} hydrogen molecular ions. The contributions of exchange and self-energy diagrams were taken into account in the determination of the energy spectrum of the three-body Coulomb system. Our results show that the self-energy diagram contribution is inversely proportional to the square of the constituent mass of particles. This contribution is sufficient for the electron and is negligible for the proton, deuteron and triton. When defining the energy and the wave function (WF), it is necessary to take into account the contributions of both the exchange and self-energy diagrams.

  2. Reactions of Th(+) + H2, D2, and HD Studied by Guided Ion Beam Tandem Mass Spectrometry and Quantum Chemical Calculations.

    PubMed

    Cox, Richard M; Armentrout, P B; de Jong, Wibe A

    2016-03-01

    Kinetic energy dependent reactions of Th(+) with H2, D2, and HD were studied using a guided ion beam tandem mass spectrometer. Formation of ThH(+) and ThD(+) is endothermic in all cases with similar thresholds. Branching ratio results for the reaction with HD indicate that Th(+) reacts via a statistical mechanism, similar to Hf(+). The kinetic energy dependent cross sections for formation of ThH(+) and ThD(+) were evaluated to determine a 0 K bond dissociation energy (BDE) of D0(Th(+)-H) = 2.45 ± 0.07 eV. This value is in good agreement with a previous result obtained from analysis of the Th(+) + CH4 reaction. D0(Th(+)-H) is observed to be larger than its transition metal congeners, TiH(+), ZrH(+), and HfH(+), believed to be a result of lanthanide contraction. The reactions with H2 were also explored using quantum chemical calculations that include a semiempirical estimation and explicit calculation of spin-orbit contributions. These calculations agree nicely and indicate that ThH(+) most likely has a (3)Δ1 ground level with a low-lying (1)Σ(+) excited state. Theory also provides the reaction potential energy surfaces and BDEs that are in reasonable agreement with experiment.

  3. Reactions of Th(+) + H2, D2, and HD Studied by Guided Ion Beam Tandem Mass Spectrometry and Quantum Chemical Calculations.

    PubMed

    Cox, Richard M; Armentrout, P B; de Jong, Wibe A

    2016-03-01

    Kinetic energy dependent reactions of Th(+) with H2, D2, and HD were studied using a guided ion beam tandem mass spectrometer. Formation of ThH(+) and ThD(+) is endothermic in all cases with similar thresholds. Branching ratio results for the reaction with HD indicate that Th(+) reacts via a statistical mechanism, similar to Hf(+). The kinetic energy dependent cross sections for formation of ThH(+) and ThD(+) were evaluated to determine a 0 K bond dissociation energy (BDE) of D0(Th(+)-H) = 2.45 ± 0.07 eV. This value is in good agreement with a previous result obtained from analysis of the Th(+) + CH4 reaction. D0(Th(+)-H) is observed to be larger than its transition metal congeners, TiH(+), ZrH(+), and HfH(+), believed to be a result of lanthanide contraction. The reactions with H2 were also explored using quantum chemical calculations that include a semiempirical estimation and explicit calculation of spin-orbit contributions. These calculations agree nicely and indicate that ThH(+) most likely has a (3)Δ1 ground level with a low-lying (1)Σ(+) excited state. Theory also provides the reaction potential energy surfaces and BDEs that are in reasonable agreement with experiment. PMID:26414691

  4. The replacement correction factor for the BIPM flat cavity ion chamber and the value of W/e

    SciTech Connect

    Wang, L. L. W.; Rogers, D. W. O.

    2008-10-15

    A graphite flat cavity ionization chamber is used at the BIPM in France to determine the absorbed dose to graphite in a {sup 60}Co photon beam and thereby used to determine the product of the value of W/e, the average energy required to produce an ion pair in dry air, and the value of (L{sub {Delta}}/{rho}){sub a}{sup C}, the mean restricted mass collision stopping-power ratio for graphite to air in a {sup 60}Co beam. The accuracy of the (W/e) (L{sub {Delta}}/{rho}){sub a}{sup C} value thus determined depends upon the accuracy of the perturbation correction factors adopted for this chamber. The perturbation effect of this chamber was accounted for by the replacement correction factor whose value was calculated by an analytical method and confirmed by an EGS4 Monte Carlo calculation. The purpose of this study is to investigate the validity of the analytical and the EGS4 calculations by using recently established methods and the EGSnrc Monte Carlo code, a much improved version of EGS4, to calculate the replacement correction factors for the graphite chamber. It is found that the replacement correction factors used for the BIPM chamber are not correct: the values used are smaller than they should be by about 1%. This leads to a 1% overestimation of the (W/e) (L{sub {Delta}}/{rho}){sub a}{sup C} value determined by using this chamber. This implies that {sup 60}Co air kerma standards that are directly proportional to this product need to be reduced by 1%. Based on the values of the replacement correction factors calculated in this study, and on the value of (L{sub {Delta}}/{rho}){sub a}{sup C} evaluated from ICRU Report No. 37 stopping power for graphite, the value of W/e determined by using the BIPM chamber should be 33.61{+-}0.08 J/C. If a more recent value of mean excitation energy for graphite (86.8 eV) and grain density are used to evaluate the graphite stopping power, then the value obtained for W/e is 34.15{+-}0.08 J/C.

  5. A telescope with microstrip gas chambers for the detection of charged products in heavy-ion reactions

    NASA Astrophysics Data System (ADS)

    Gramegna, F.; Abbondanno, U.; Andreano, A.; Bassini, R.; Bonutti, F.; Bruno, M.; Casini, G.; D'Agostino, M.; Manzin, G.; Margagliotti, G. V.; Mastinu, P. F.; Milazzo, P. M.; Moroni, A.; Squarcini, M.; Tonetto, F.; Vannini, G.; Vannucci, L.

    1997-02-01

    Prototypes of a ΔE-E telescope, designed to detect and identify with low-energy threshold both light charged particles and heavy fragments, are described. They are based on a gas drift chamber which conveys primary ionization electrons on gas microstrip devices where multiplication occurs and the energy loss signals are generated. Silicon detectors or CsI(T1) crystals operate as residual energy detectors. The prototypes were tested both with a source and heavy ion beams. Performances, mainly related to energy resolution, charge identification and angle resolution, are reported.

  6. Modeling of life limiting phenomena in the discharge chamber of an electron bombardment ion thruster

    NASA Technical Reports Server (NTRS)

    Handoo, Arvind K.; Ray, Pradosh K.

    1991-01-01

    An experimental facility to study the low energy sputtering of metal surfaces with ions produced by an ion gun is described. The energy of the ions ranged from 10 to 500 eV. Cesium ions with energies from 100 to 500 eV were used initially to characterize the operation of the ion gun. Next, argon and xenon ions were used to measure the sputtering yields of cobalt (Co), Cadmium (Cd), and Chromium (Cr) at an operating temperature of 2x10(exp -5) Torr. The ion current ranged from 0.0135 micro-A at 500 eV. The targets were electroplated on a copper substrate. The surface density of the electroplated material was approx. 50 micro-g/sq cm. The sputtered atoms were collected on an aluminum foil surrounding the target. Radioactive tracers were used to measure the sputtering yields. The sputtering yields of Cr were found to be much higher than those of Co and Cd. The yields of Co and Cd were comparable, with Co providing the higher yields. Co and Cd targets were observed to sputter at energies as low as 10 eV for both argon and xenon ions. The Cr yields could not be measured below 20 eV for argon ions and 15 eV for xenon ions. On a linear scale the yield energy curves near the threshold energies exhibit a concave nature.

  7. Signal generator exciting an electromagnetic field for ion beam transport to the vacuum chamber of a mass spectrometer

    NASA Astrophysics Data System (ADS)

    Tubol'tsev, Yu. V.; Kogan, V. T.; Bogdanov, A. A.; Chichagov, Yu. V.; Antonov, A. S.

    2015-02-01

    A high-voltage high-frequency signal generator is described that excites an electric field for ion beam transport from an ion source to the vacuum chamber of a mass spectrometer. Excitation signals to the number of two are high-frequency sine-wave out-of-phase signals with the same amplitudes. The amplitude and phase of the signals vary from 20 to 100 V and from 10 kHz to 1 MHz, respectively. The generator also produces a controlled bias voltage in the interval 50-200 V. The frequency and amplitude of the signals, as well as the bias voltage, are computer-controlled via the USB interface.

  8. SU-E-T-172: Evaluation of the Exradin A26 Ion Chamber in Megavoltage Photon Beams as a Reference Class Instrument

    SciTech Connect

    McEwen, M

    2014-06-01

    Purpose: The Exradin A26 is a new design of micro-ionization ion chamber that externally resembles the Exradin A16 model but has significant internal changes to address measurement issues reported in the literature for the A16. This project involved the characterization of two versions of the A26 chamber in high energy x-rays with particular reference to the performance specification laid out in the imminent Addendum to TG-51. Methods: The Exradin A26 was investigated in a range of megavoltage photon beams (6–25 MV). Investigations looked at chamber settling, ion recombination and polarity. Since it has been previously shown that non-ideal performance is most easily identified through ion recombination measurements, the focus was on the determination of Pion. Results: i) Chamber settling - the chamber response stabilizes very quickly (within 3 minutes), even after a large change in the polarizing voltage.ii) The polarity correction was found to be small (within 0.2% of unity)iii) The chamber showed linear behavior for a Jaffe plot (1/reading vs 1/polarizing voltage) for applied voltages ≤ 200 V.iv) The recombination correction showed a linear variation with the doseper- pulse, was not significantly dependent on the polarity of the collecting voltage and was consistent with the chamber dimensions (i.e. agreed with Boag theory). Conclusion: An initial investigation of the Exradin A26 micro chamber suggests that although its performance exceeds the AAPM specification for a reference-class ion chamber for use in megavoltage photon beams it is a significant improvement over the previous A16 design. Further work is required to evaluate long-term stability and determine kQ factors.

  9. Ion Chambers for Monitoring the NuMI Neutrino Beam at Fermilab

    SciTech Connect

    Indurthy, Dharmaraj; Keisler, Ryan; Kopp, Sacha; Mendoza, Steven; Proga, Marek; Pavlovich, Zarko; Zwaska, Robert; Harris, Deborah; Marchionni, Alberto; Morfin, Jorge; Erwin, Albert; Ping Huicana; Velissaris, Christos; Naples, Donna; Northacker, Dave; McDonald, Jeff; Diwan, Milind; Viren, Brett

    2004-11-10

    The Neutrinos at the Main Injector (NuMI) beamline will deliver an intense muon neutrino beam by focusing a beam of mesons into a long evacuated decay volume. The beam must be steered with 1-mRad angular accuracy toward the Soudan Underground Laboratory in northern Minnesota. We have built 4 arrays of ionization chambers to monitor the neutrino beam direction and quality. The arrays are located at 4 stations downstream of the decay volume, and measure the remnant hadron beam and tertiary muons produced along with neutrinos in meson decays. We review how the monitors will be used to make beam quality measurements, and as well review chamber construction details, radiation damage testing, calibration, and test beam results.

  10. Pressurized ion chamber monitoring system for environmental radiation measurements utilizing a wide-range temperature-compensated electrometer

    NASA Astrophysics Data System (ADS)

    van Steveninck, William

    1994-08-01

    The performance of a complete pressurized ion chamber (PIC) radiation monitoring system is described. The design incorporates an improved temperature-compensated electrometer which is stable to +/- 3 center-dot 10(sup - 16) A over the environmental range of temperature (- 40 to + 40 C). Using a single 10(sup 11) Omega feed-back resistor, the electrometer accurately measures currents over a range from 3 center-dot 10(sup - 15) A to 3 center-dot 10(sup - 11) A. While retaining the sensitivity of the original PIC system (the instrument responds readily to small background fluctuations on the order of 0.1 mu R h(sup - 1)), the new system measures radiation levels up to the point where the collection efficiency of the ion chamber begins to drop off, typically approximately 27 pA at 1 mR h(sup - 1). A data recorder and system controller was designed using the Tattletale(sup TM) Model 4A computer. Digital data is stored on removable solid-state, credit-card style memory cards.

  11. The response of a Fermilab-designed ion chamber in pulsed photon fields

    SciTech Connect

    Freeman, W.S.; Hartman, B.; Krueger, F.; Larson, J.

    1988-01-26

    This note reports measurements of the response of a Fermilab-designed area monitor ionization chamber used in Chipmunk and Scarecrow detectors to pulsed photon fields of various intensities and durations. The measurements were made to better define the operating limits of the instruments and to understand the possible effects of recombination and space charge on the dose measured by the instruments in pulsed fields. 2 refs., 13 figs., 1 tab.

  12. Measurement of changes in linear accelerator photon energy through flatness variation using an ion chamber array

    SciTech Connect

    Gao Song; Balter, Peter A.; Rose, Mark; Simon, William E.

    2013-04-15

    Purpose: To compare the use of flatness versus percent depth dose (PDD) for determining changes in photon beam energy for a megavoltage linear accelerator. Methods: Energy changes were accomplished by adjusting the bending magnet current by up to {+-}15% in 5% increments away from the value used clinically. Two metrics for flatness, relative flatness in the central 80% of the field (Flat) and average maximum dose along the diagonals normalized by central axis dose (F{sub DN}), were measured using a commercially available planner ionization chamber array. PDD was measured in water at depths of 5 and 10 cm in 3 Multiplication-Sign 3 cm{sup 2} and 10 Multiplication-Sign 10 cm{sup 2} fields using a cylindrical chamber. Results: PDD was more sensitive to changes in energy when the beam energy was increased than when it was decreased. For the 18-MV beam in particular, PDD was not sensitive to energy reductions below the nominal energy. The value of Flat was found to be more sensitive to decreases in energy than to increases, with little sensitivity to energy increases above the nominal energy for 18-MV beams. F{sub DN} was the only metric that was found to be sensitive to both increases and reductions of energy for both the 6- and 18-MV beams. Conclusions: Flatness based metrics were found to be more sensitive to energy changes than PDD, In particular, F{sub DN} was found to be the most sensitive metric to energy changes for photon beams of 6 and 18 MV. The ionization chamber array allows this metric to be conveniently measured as part of routine accelerator quality assurance.

  13. Sputter erosion and deposition in the discharge chamber of a small mercury ion thruster

    NASA Technical Reports Server (NTRS)

    Power, J. L.

    1973-01-01

    A 5 cm diameter mercury ion thruster similar to one tested for 9715 hours was operated approximately 400 hrs each at discharge voltages of 36.6, 39.6, and 42.6 V, with corresponding discharge propellant utilizations of 58, 68, and 70 percent. The observed sputter erosion rates of the internal thruster parts and the anode weight gain rate all rose rapidly with discharge voltage and were roughly in the ratio of 1:3:5 for the three voltages. The combined weight loss of the internal thruster parts nearly balanced the anode weight gain. Hg(+2) ion apparently caused most of the observed erosion.

  14. 3D chiral and 2D achiral cobalt(ii) compounds constructed from a 4-(benzimidazole-1-yl)benzoic ligand exhibiting field-induced single-ion-magnet-type slow magnetic relaxation.

    PubMed

    Wang, Yu-Ling; Chen, Lin; Liu, Cai-Ming; Du, Zi-Yi; Chen, Li-Li; Liu, Qing-Yan

    2016-05-01

    Organizing magnetically isolated 3d transition metal ions, which behave as single-ion magnet (SIM) units, in a coordination network is a promising approach to design novel single-molecule magnets (SMMs). Herein 3D chiral and 2D achiral cobalt(ii) coordination compounds based on single metal nodes with a 4-(benzimidazole-1-yl)benzoic acid (Hbmzbc) ligand, namely, [Co(bmzbc)2(1,2-etdio)]n () (1,2-etdio = 1,2-ethanediol) and [Co(bmzbc)2(Hbmzbc)]n (), have been synthesized and structurally characterized. The 3D chiral structure with 2-fold interpenetrating qtz topological nets consisting of totally achiral components was obtained via spontaneous resolution, while the achiral structure is a 2D (4,4) net. In both structures, individual cobalt(ii) ions are spatially well separated by the long organic ligands in the well-defined networks. Magnetic measurements on and showed field-induced slow magnetic relaxation resulting from single-ion anisotropy of the individual Co(ii) ions. Analysis of the dynamic ac susceptibilities with the Arrhenius law afforded an anisotropy energy barrier of 16.8(3) and 31.3(2) K under a 2 kOe static magnetic field for and , respectively. The distinct coordination environments of the Co(ii) ions in and lead to the different anisotropic energy barriers. PMID:27054774

  15. An ion thruster internal discharge chamber electrostatic probe diagnostic technique using a high-speed probe positioning system

    SciTech Connect

    Herman, Daniel A.; Gallimore, Alec D.

    2008-01-15

    Extensive resources have been allocated to diagnose and minimize lifetime-limiting factors in gridded ion thrusters. While most of this effort has focused on grid erosion, results from wear tests indicate that discharge cathode erosion may also play an important role in limiting the lifetime of ring-cusp ion thrusters proposed for future large flagship missions. The detailed characterization of the near-cathode discharge plasma is essential for mitigating discharge cathode erosion. However, severe difficulty is encountered when attempting to measure internal discharge plasma parameters during thruster operation with conventional probing techniques. These difficulties stem from the high-voltage, high-density discharge cathode plume, which is a hostile environment for probes. A method for interrogating the discharge chamber plasma of a working ion thruster over a two-dimensional grid is demonstrated. The high-speed axial reciprocating probe positioning system is used to minimize thruster perturbation during probe insertion and to reduce heating of the probe. Electrostatic probe measurements from a symmetric double Langmuir probe are presented over a two-dimensional spatial array in the near-discharge cathode assembly region of a 30-cm-diameter ring-cusp ion thruster. Electron temperatures, 2-5 eV, and number density contours, with a maximum of 8x10{sup 12} cm{sup -3} on centerline, are measured. These data provide detailed electron temperature and number density contours which, when combined with plasma potential measurements, may shed light on discharge cathode erosion processes and the effect of thruster operating conditions on erosion rates.

  16. Thermal characteristics of air flow cooling in the lithium ion batteries experimental chamber

    SciTech Connect

    Lukhanin A.; Rohatgi U.; Belyaev, A.; Fedorchenko, D.; Khazhmuradov, M.; Lukhanin, O; Rudychev, I.

    2012-07-08

    A battery pack prototype has been designed and built to evaluate various air cooling concepts for the thermal management of Li-ion batteries. The heat generation from the Li-Ion batteries was simulated with electrical heat generation devices with the same dimensions as the Li-Ion battery (200 mm x 150 mm x 12 mm). Each battery simulator generates up to 15W of heat. There are 20 temperature probes placed uniformly on the surface of the battery simulator, which can measure temperatures in the range from -40 C to +120 C. The prototype for the pack has up to 100 battery simulators and temperature probes are recorder using a PC based DAQ system. We can measure the average surface temperature of the simulator, temperature distribution on each surface and temperature distributions in the pack. The pack which holds the battery simulators is built as a crate, with adjustable gap (varies from 2mm to 5mm) between the simulators for air flow channel studies. The total system flow rate and the inlet flow temperature are controlled during the test. The cooling channel with various heat transfer enhancing devices can be installed between the simulators to investigate the cooling performance. The prototype was designed to configure the number of cooling channels from one to hundred Li-ion battery simulators. The pack is thermally isolated which prevents heat transfer from the pack to the surroundings. The flow device can provide the air flow rate in the gap of up to 5m/s velocity and air temperature in the range from -30 C to +50 C. Test results are compared with computational modeling of the test configurations. The present test set up will be used for future tests for developing and validating new cooling concepts such as surface conditions or heat pipes.

  17. The Prototype Active-Target Time-Projection Chamber used with TwinSol radioactive-ion beams

    NASA Astrophysics Data System (ADS)

    Ahn, T.; Bardayan, D. W.; Bazin, D.; Beceiro Novo, S.; Becchetti, F. D.; Bradt, J.; Brodeur, M.; Carpenter, L.; Chajecki, Z.; Cortesi, M.; Fritsch, A.; Hall, M. R.; Hall, O.; Jensen, L.; Kolata, J. J.; Lynch, W.; Mittig, W.; O'Malley, P.; Suzuki, D.

    2016-06-01

    The study of low-energy reactions with radioactive-ion beams has been greatly enhanced by the recent use of active-target detectors, which have high efficiency and low thresholds to detect low-energy charged-particle decays. Both of these features have been used in experiments with the Prototype Active-Target Time-Projection Chamber to study α -cluster structure in unstable nuclei and 3-body charged-particle decays after implantation. Predicted α -cluster structures in 14 C were probed using resonant α scattering and the nature of the 3- α breakup of the 02+ Hoyle state in 12 C after the beta decay of 12 N and 12 B was studied. These experiments used in-flight radioactive-ion beams that were produced using the dual superconducting solenoid magnets TwinSol at the University of Notre Dame. Preliminary results from these experiments as well as the development of future radioactive beams to be used in conjunction with the PAT-TPC are presented.

  18. Insulated Conducting Cantilevered Nanotips and Two-Chamber Recording System for High Resolution Ion Sensing AFM

    NASA Astrophysics Data System (ADS)

    Meckes, Brian; Arce, Fernando Teran; Connelly, Laura S.; Lal, Ratnesh

    2014-03-01

    Biological membranes contain ion channels, which are nanoscale pores allowing controlled ionic transport and mediating key biological functions underlying normal/abnormal living. Synthetic membranes with defined pores are being developed to control various processes, including filtration of pollutants, charge transport for energy storage, and separation of fluids and molecules. Although ionic transport (currents) can be measured with single channel resolution, imaging their structure and ionic currents simultaneously is difficult. Atomic force microscopy enables high resolution imaging of nanoscale structures and can be modified to measure ionic currents simultaneously. Moreover, the ionic currents can also be used to image structures. A simple method for fabricating conducting AFM cantilevers to image pore structures at high resolution is reported. Tungsten microwires with nanoscale tips are insulated except at the apex. This allows simultaneous imaging via cantilever deflections in normal AFM force feedback mode as well as measuring localized ionic currents. These novel probes measure ionic currents as small as picoampere while providing nanoscale spatial resolution surface topography and is suitable for measuring ionic currents and conductance of biological ion channels.

  19. Discharge Chamber Plasma Structure of a 30-cm NSTAR-Type Ion Engine

    NASA Technical Reports Server (NTRS)

    Herman, Daniel A.; Gallimore, Alec D.

    2006-01-01

    Single Langmuir probe measurements are presented over a two-dimensional array of locations in the near Discharge Cathode Assembly (DCA) region of a 30-cm diameter ring cusp ion thruster over a range of thruster operating conditions encompassing the high-power half of the NASA throttling table. The Langmuir probe data were analyzed with two separate methods. All data were analyzed initially assuming an electron population consisting of Maxwellian electrons only. The on-axis data were then analyzed assuming both Maxwellian and primary electrons. Discharge plasma data taken with beam extraction exhibit a broadening of the higher electron temperature plume boundary compared to similar discharge conditions without beam extraction. The opposite effect is evident with the electron/ion number density as the data without began, extraction appears to be more collimated than the corresponding data with beam extraction. Primary electron energy and number densities are presented for one operating condition giving an order of magnitude of their value and the error associated with this calculation.

  20. Insulated Conducting Cantilevered Nanotips and Two-Chamber Recording System for High Resolution Ion Sensing AFM

    PubMed Central

    Meckes, Brian; Arce, Fernando Teran; Connelly, Laura S.; Lal, Ratnesh

    2014-01-01

    Biological membranes contain ion channels, which are nanoscale pores allowing controlled ionic transport and mediating key biological functions underlying normal/abnormal living. Synthetic membranes with defined pores are being developed to control various processes, including filtration of pollutants, charge transport for energy storage, and separation of fluids and molecules. Although ionic transport (currents) can be measured with single channel resolution, imaging their structure and ionic currents simultaneously is difficult. Atomic force microscopy enables high resolution imaging of nanoscale structures and can be modified to measure ionic currents simultaneously. Moreover, the ionic currents can also be used to image structures. A simple method for fabricating conducting AFM cantilevers to image pore structures at high resolution is reported. Tungsten microwires with nanoscale tips are insulated except at the apex. This allows simultaneous imaging via cantilever deflections in normal AFM force feedback mode as well as measuring localized ionic currents. These novel probes measure ionic currents as small as picoampere while providing nanoscale spatial resolution surface topography and is suitable for measuring ionic currents and conductance of biological ion channels. PMID:24663394

  1. Ion-driver fast ignition: Reducing heavy-ion fusion driver energy and cost, simplifying chamber design, target fab, tritium fueling and power conversion

    SciTech Connect

    Logan, G.; Callahan-Miller, D.; Perkins, J.; Caporaso, G.; Tabak, M.; Moir, R.; Meier, W.; Bangerter, Roger; Lee, Ed

    1998-04-01

    Ion fast ignition, like laser fast ignition, can potentially reduce driver energy for high target gain by an order of magnitude, while reducing fuel capsule implosion velocity, convergence ratio, and required precisions in target fabrication and illumination symmetry, all of which should further improve and simplify IFE power plants. From fast-ignition target requirements, we determine requirements for ion beam acceleration, pulse-compression, and final focus for advanced accelerators that must be developed for much shorter pulses and higher voltage gradients than today's accelerators, to deliver the petawatt peak powers and small focal spots ({approx}100 {micro}m) required. Although such peak powers and small focal spots are available today with lasers, development of such advanced accelerators is motivated by the greater likely efficiency of deep ion penetration and deposition into pre-compressed 1000x liquid density DT cores. Ion ignitor beam parameters for acceleration, pulse compression, and final focus are estimated for two examples based on a Dielectric Wall Accelerator; (1) a small target with {rho}r {approx} 2 g/cm{sup 2} for a small demo/pilot plant producing {approx}40 MJ of fusion yield per target, and (2) a large target with {rho}r {approx} 10 g/cm{sup 2} producing {approx}1 GJ yield for multi-unit electricity/hydrogen plants, allowing internal T-breeding with low T/D ratios, >75 % of the total fusion yield captured for plasma direct conversion, and simple liquid-protected chambers with gravity clearing. Key enabling development needs for ion fast ignition are found to be (1) ''Close-coupled'' target designs for single-ended illumination of both compressor and ignitor beams; (2) Development of high gradient (>25 MV/m) linacs with high charge-state (q {approx} 26) ion sources for short ({approx}5 ns) accelerator output pulses; (3) Small mm-scale laser-driven plasma lens of {approx}10 MG fields to provide steep focusing angles close-in to the target

  2. Heavy ion beam degradation from stripping in near vacuum reactor chambers

    SciTech Connect

    Barletta, W.A.

    1981-07-21

    With the use of a particle simulation code we have investigated the ballistic transport of heavy ion beams through a gas-filled reactor for inertial confinement fusion. The background gas pressure has been taken to be 10/sup -4/ torr - 10/sup -3/ torr of Lithium vapor as is appropriate to the HYLIFE reactor concept. During transport to the pellet, Coulomb collisions of beam particles with the background gas will convert a fraction of the beam to charges states higher than the initial value. Collisons will also produce an associated swarm of knock-on electrons. As the beam approaches the pellet, anharmonic components of the space charges forces will lead to a distortion of the phase space of the beam and a consequent degradation of the focal properties of the beam. This degradation can be described in terms of an increase in the rms emittance of the beam. The degree of emittance growth depends sensitivity upon the initial spatial distribution of particles in the beam. For this study we have modified a single-disk particle simulation code, DESTIN (2), to follow two species of particles, the number of which varies in a prescribed fashion dependent upon reactor temperature as the beam converges toward the pellet.

  3. SU-E-T-382: Influence of Compton Currents On Profile Measurements in Small- Volume Ion Chambers

    SciTech Connect

    Tanny, S; Parsai, E; Holmes, S

    2014-06-01

    Purpose: Ionization chambers in electron radiation fields are known to exhibit polarity effects due to Compton currents. Previously we have presented a unique manifestation of this effect observed with a microionization chamber. We have expanded that investigation to include three micro-ionization chambers commonly used in radiation therapy. The purpose of this project is to determine what factors influence this polarity effect for micro-chambers and how it might be mitigated. Methods: Three chambers were utilized: a PTW 31016, an Exradin A-16, and an Exradin A- 26. Beam profile scans were obtained on a Varian TrueBeam linear accelerator in combination with a Wellhofer water phantom for 6, 9, and 12 MeV electrons. Profiles were obtained parallel and perpendicular to the chamber's long axis, with both positive and negative collecting bias. Profiles were obtained with various chamber components shielded by 5 mm of Pb at 6 MeV to determine their relative contributions to this polarity effect. Results: The polarity effect was observed for all three chambers, and the ratio of the polarity effect for the Exradin chambers is proportional to the ratio of chamber volumes. Shielding the stem of both Exradin chambers diminished, but did not remove the polarity effect. However, they demonstrated no out-of-field effect when the cable was shielded with Pb. The PTW chamber demonstrated a significantly reduced polarity effect without any shielding despite its comparable volume with the A-26. Conclusions: The sensitive volume of these micro-chambers is relatively insensitive to collecting polarity. However, charge deposition within the cable can dramatically alter measured ionization profiles. This is demonstrated by the removal of the out-of-field ionization when the cable is shielded for the Exradin chambers. We strongly recommend analyzing any polarity dependence for small-volume chambers used in characterization of electron fields.

  4. The use of multi-gap resistive plate chambers for in-beam PET in proton and carbon ion therapy

    PubMed Central

    Watts, David; Borghi, Giacomo; Sauli, Fabio; Amaldi, Ugo

    2013-01-01

    On-line verification of the delivered dose during proton and carbon ion radiotherapy is currently a very desirable goal for quality assurance of hadron therapy treatment plans. In-beam positron emission tomography (ibPET), which can provide an image of the β+ activity induced in the patient during irradiation, which in turn is correlated to the range of the ion beam, is one of the modalities for achieving this goal. Application to hadron therapy requires that the scanner geometry be modified from that which is used in nuclear medicine. In particular, PET detectors that allow a sub-nanosecond time-of-flight (TOF) registration of the collinear photons have been proposed. Inclusion of the TOF information in PET data leads to more effective PET sensitivity. Considering the challenges inherent in the ibPET technique, namely limited β+ activity and the effect of biological washout due to blood flow, TOF-PET technologies are very attractive. In this context, the TERA Foundation is investigating the use of resistive plate chambers (RPC) for an ibPET application because of their excellent timing properties and low cost. In this paper we present a novel compact multi-gap RPC (MRPC) module design and construction method, which considering the large number of modules that would be needed to practically implement a high-sensitivity RPC-PET scanner, could be advantageous. Moreover, we give an overview of the efficiency and timing measurements that have been obtained in the laboratory using such single-gap and multi-gap RPC modules. PMID:23824118

  5. The application of Ussing chambers for determining the impact of microbes and probiotics on intestinal ion transport.

    PubMed

    Lomasney, Kevin W; Hyland, Niall P

    2013-09-01

    Host-microbe interactions have gained considerable attention in recent years with regards to their role in various organic disorders and diseases. In particular, research efforts have focused on the intestinal microbiota, where the largest and most diverse populations not only co-exist with the host, but also directly influence the state and function of the gastrointestinal (GI) tract. Moreover, both human and animal studies alike are now beginning to show a positive influence of probiotic bacteria on GI disorders associated with diarrhoea or constipation. Diarrheagenic GI diseases, such as those caused by Vibreo cholera or enterpathogenic Eschericia coli, have well-characterised interactions with the host that explain much of the observed symptoms, in particular severe diarrhoea. However, the mechanisms of action of nonpathogenic bacteria or probiotics on host physiology are less clearly understood. In the context of defining the mechanisms of action of probiotics in vitro, the Ussing chamber has proven to be a particularly useful tool. Here, we will present data from several studies that have defined molecular targets for microbes and putative probiotics in the regulation of intestinal secretory and absorptive function, and we will discuss these in the context of their application in pathogen- or inflammation-induced alterations in intestinal ion transport.

  6. Fusion studies with low-intensity radioactive ion beams using an active-target time projection chamber

    NASA Astrophysics Data System (ADS)

    Kolata, J. J.; Howard, A. M.; Mittig, W.; Ahn, T.; Bazin, D.; Becchetti, F. D.; Beceiro-Novo, S.; Chajecki, Z.; Febbrarro, M.; Fritsch, A.; Lynch, W. G.; Roberts, A.; Shore, A.; Torres-Isea, R. O.

    2016-09-01

    The total fusion excitation function for 10Be+40Ar has been measured over the center-of-momentum (c.m.) energy range from 12 to 24 MeV using a time-projection chamber (TPC). The main purpose of this experiment, which was carried out in a single run of duration 90 h using a ≈100 particle per second (pps) 10Be beam, was to demonstrate the capability of an active-target TPC to determine fusion excitation functions for extremely weak radioactive ion beams. Cross sections as low as 12 mb were measured with acceptable (50%) statistical accuracy. It also proved to be possible to separate events in which charged particles were emitted from the fusion residue from those in which only neutrons were evaporated. The method permits simultaneous measurement of incomplete fusion, break-up, scattering, and transfer reactions, and therefore fully exploits the opportunities presented by the very exotic beams that will be available from the new generation of radioactive beam facilities.

  7. Microwave spectrum of the H/sub 2/D/sup +/ ion: The 2/sub 20/ reverse arrow 2/sub 21/ transition

    SciTech Connect

    Saito, S.; Kawaguchi, K.; Hirota, E.

    1985-01-01

    The 2/sub 20/ reverse arrow 2/sub 21/ transition of H/sub 2/D/sup +/ was detected by using a dc discharge in a mixture of H/sub 2/ and D/sub 2/ with a hollow cathode cooled to liquid nitrogen temperature. The assignment was made on the basis of chemistry for production, the observed linewidth, and the lowering of the spectral intensity by the external magnetic field. The transition frequency was determined to be 155 987.185 +- 0.037 MHz.

  8. h-BN Nanosheets as 2D Substrates to Load 0D Fe3O4 Nanoparticles: A Hybrid Anode Material for Lithium-Ion Batteries.

    PubMed

    Duan, Zhi-Qiang; Liu, Yi-Tao; Xie, Xu-Ming; Ye, Xiong-Ying; Zhu, Xiao-Dong

    2016-03-18

    h-BN, as an isoelectronic analogue of graphene, has improved thermal mechanical properties. Moreover, the liquid-phase production of h-BN is greener since harmful oxidants/reductants are unnecessary. Here we report a novel hybrid architecture by employing h-BN nanosheets as 2D substrates to load 0D Fe3O4 nanoparticles, followed by phenol/formol carbonization to form a carbon coating. The resulting carbon-encapsulated h-BN@Fe3O4 hybrid architecture exhibits synergistic interactions: 1) The h-BN nanosheets act as flexible 2D substrates to accommodate the volume change of the Fe3O4 nanoparticles; 2) The Fe3O4 nanoparticles serve as active materials to contribute to a high specific capacity; and 3) The carbon coating not only protects the hybrid architecture from deformation but also keeps the whole electrode highly conductive. The synergistic interactions translate into significantly enhanced electrochemical performances, laying a basis for the development of superior hybrid anode materials. PMID:26833884

  9. Chamber propagation

    SciTech Connect

    Langdon, B.

    1991-01-16

    Propagation of a heavy ion beam to the target appears possible under conditions thought to be realizable by several reactor designs. Beam quality at the lens is believed to provide adequate intensity at the target -- but the beam must pass through chamber debris and its self fields along the way. This paper reviews present consensus on propagation modes and presents recent results on the effects of photoionization of the beam ions by thermal x-rays from the heated target. Ballistic propagation through very low densities is a conservative mode. The more-speculative self-pinched mode, at 1 to 10 Torr, offers reactor advantages and is being re-examined by others. 13 refs.

  10. Chamber transport

    SciTech Connect

    OLSON,CRAIG L.

    2000-05-17

    Heavy ion beam transport through the containment chamber plays a crucial role in all heavy ion fusion (HIF) scenarios. Here, several parameters are used to characterize the operating space for HIF beams; transport modes are assessed in relation to evolving target/accelerator requirements; results of recent relevant experiments and simulations of HIF transport are summarized; and relevant instabilities are reviewed. All transport options still exist, including (1) vacuum ballistic transport, (2) neutralized ballistic transport, and (3) channel-like transport. Presently, the European HIF program favors vacuum ballistic transport, while the US HIF program favors neutralized ballistic transport with channel-like transport as an alternate approach. Further transport research is needed to clearly guide selection of the most attractive, integrated HIF system.

  11. SU-E-T-562: Scanned Percent Depth Dose Curve Discrepancy for Photon Beams with Physical Wedge in Place (Varian IX) Using Different Sensitive Volume Ion Chambers

    SciTech Connect

    Zhao, H; Sarkar, V; Rassiah-Szegedi, P; Huang, Y; Szegedi, M; Huang, L; Salter, B

    2014-06-01

    Purpose: To investigate and report the discrepancy of scanned percent depth dose (PDD) for photon beams with physical wedge in place when using ion chambers with different sensitive volumes. Methods/Materials: PDD curves of open fields and physical wedged fields (15, 30, 45, and 60 degree wedge) were scanned for photon beams (6MV and 10MV, Varian iX) with field size of 5x5 and 10x10 cm using three common scanning chambers with different sensitive volumes - PTW30013 (0.6cm3), PTW23323 (0.1cm3) and Exradin A16 (0.007cm3). The scanning system software used was OmniPro version 6.2, and the scanning water tank was the Scanditronix Wellhoffer RFA 300.The PDD curves from the three chambers were compared. Results: Scanned PDD curves of the same energy beams for open fields were almost identical between three chambers, but the wedged fields showed non-trivial differences. The largest differences were observed between chamber PTW30013 and Exradin A16. The differences increased as physical wedge angle increased. The differences also increased with depth, and were more pronounced for 6MV beam. Similar patterns were shown for both 5x5 and 10x10 cm field sizes. For open fields, all PDD values agreed with each other within 1% at 10cm depth and within 1.62% at 20 cm depth. For wedged fields, the difference of PDD values between PTW30013 and A16 reached 4.09% at 10cm depth, and 5.97% at 20 cm depth for 6MV with 60 degree physical wedge. Conclusion: We observed a significant difference in scanned PDD curves of photon beams with physical wedge in place obtained when using different sensitive volume ion chambers. The PDD curves scanned with the smallest sensitive volume ion chamber showed significant difference from larger chamber results, beyond 10cm depth. We believe this to be caused by varying response to beam hardening by the wedges.

  12. Origin of the Ion Foreshock in a Quasi-perpendicular Curved Collisionless Shock: Particles Trajectory Analysis in 2D PIC Simulations

    NASA Astrophysics Data System (ADS)

    Savoini, P.; Lembege, B.

    2015-12-01

    The ion foreshock located upstream of the Earth's shock wave is populated with ions having interacted with the shock, and then, reflected back with an high energy gain. Spacecrafts have clearly established the existence of two distinct populations in the quasi-perpendicular shock region (i.e. for 45° ≤ ΘBn ≤ 90°, where ΘBn is the angle between the shock normal and the upstream magnetic field) : (i) field-aligned ion beams or « FAB » characterized by a gyrotropic distribution, and (ii) gyro-phase bunched ions or « GPB » characterized by a NON gyrotropic distribution. One of the important unresolved problem is the exact origin of the particles contributing to these two populations. To our knowledge, it was the first time that full-particle simulations have been performed including self-consistently the shock front curvature and nonstationarity, and the time-of-flight effects. Our analysis evidences that these two backstreaming populations may be reflected by the front itself and can be differentiated both in terms of interaction time and trajectory within the shock front. In particular, simulations evidence that "GPB" population is characterized by a short interaction time (ΔTinter = 1 to 2 τci) while the "FAB" population corresponds to a much larger time range (from 1 τci to 10 τci), where tci is the upstream ion gyroperiod. Present individual ion trajectories evidence that "FAB" population shows a strong perpendicular drift at the shock front (i.e. strong dependence of the pitch angle to the perpendicular velocity) whereas the "GPB" population shows no perpendicular drift (i.e. its pitch angle is mainly driven by the parallel velocity). Such differences explain why the "FAB" population loses their gyro-phase coherency and become gyrotropic which is not the case for the "GPB". This important result was not expected and greatly simplifies the question of their origin.

  13. Ion-stimulated gas desorption yields of electropolished, chemically etched, and coated (Au, Ag, Pd, TiZrV) stainless steel vacuum chambers and St707 getter strips irradiated with 4.2 MeV/u lead ions

    NASA Astrophysics Data System (ADS)

    Mahner, E.; Hansen, J.; Küchler, D.; Malabaila, M.; Taborelli, M.

    2005-05-01

    The ion-induced desorption experiment, installed in the CERN Heavy-Ion Accelerator LINAC 3, has been used to measure molecular desorption yields for 4.2 MeV/u lead ions impacting under grazing incidence on different accelerator-type vacuum chambers. Desorption yields for H2, CH4, CO, and CO2, which are of fundamental interest for future accelerator applications, are reported for different stainless steel surface treatments. In order to study the effect of the surface oxide layer on the gas desorption, gold-, silver-, palladium-, and getter-coated 316 LN stainless steel chambers and similarly prepared samples were tested for desorption at LINAC 3 and analyzed for chemical composition by x-ray photoemission spectroscopy. The large effective desorption yield of 2×104 molecules /Pb53+ ion, previously measured for uncoated, vacuum fired stainless steel, was reduced after noble-metal coating by up to 2 orders of magnitude. In addition, pressure rise measurements, the effectiveness of beam scrubbing with lead ions, and the consequence of a subsequent venting on the desorption yields of a beam-scrubbed vacuum chamber are described. Practical consequences for the vacuum system of the future Low Energy Ion Ring are discussed.

  14. Aniso2D

    2005-07-01

    Aniso2d is a two-dimensional seismic forward modeling code. The earth is parameterized by an X-Z plane in which the seismic properties Can have monoclinic with x-z plane symmetry. The program uses a user define time-domain wavelet to produce synthetic seismograms anrwhere within the two-dimensional media.

  15. Towards 2D nanocomposites

    NASA Astrophysics Data System (ADS)

    Jang, Hyun-Sook; Yu, Changqian; Hayes, Robert; Granick, Steve

    2015-03-01

    Polymer vesicles (``polymersomes'') are an intriguing class of soft materials, commonly used to encapsulate small molecules or particles. Here we reveal they can also effectively incorporate nanoparticles inside their polymer membrane, leading to novel ``2D nanocomposites.'' The embedded nanoparticles alter the capacity of the polymersomes to bend and to stretch upon external stimuli.

  16. Bakeout Chamber Within Vacuum Chamber

    NASA Technical Reports Server (NTRS)

    Taylor, Daniel M.; Soules, David M.; Barengoltz, Jack B.

    1995-01-01

    Vacuum-bakeout apparatus for decontaminating and measuring outgassing from pieces of equipment constructed by mounting bakeout chamber within conventional vacuum chamber. Upgrade cost effective: fabrication and installation of bakeout chamber simple, installation performed quickly and without major changes in older vacuum chamber, and provides quantitative data on outgassing from pieces of equipment placed in bakeout chamber.

  17. Robotic radiosurgery system patient-specific QA for extracranial treatments using the planar ion chamber array and the cylindrical diode array.

    PubMed

    Lin, Mu-Han; Veltchev, Iavor; Koren, Sion; Ma, Charlie; Li, Jinsgeng

    2015-07-08

    Robotic radiosurgery system has been increasingly employed for extracranial treatments. This work is aimed to study the feasibility of a cylindrical diode array and a planar ion chamber array for patient-specific QA with this robotic radiosurgery system and compare their performance. Fiducial markers were implanted in both systems to enable image-based setup. An in-house program was developed to postprocess the movie file of the measurements and apply the beam-by-beam angular corrections for both systems. The impact of noncoplanar delivery was then assessed by evaluating the angles created by the incident beams with respect to the two detector arrangements and cross-comparing the planned dose distribution to the measured ones with/without the angular corrections. The sensitivity of detecting the translational (1-3 mm) and the rotational (1°-3°) delivery errors were also evaluated for both systems. Six extracranial patient plans (PTV 7-137 cm³) were measured with these two systems and compared with the calculated doses. The plan dose distributions were calculated with ray-tracing and the Monte Carlo (MC) method, respectively. With 0.8 by 0.8 mm² diodes, the output factors measured with the cylindrical diode array agree better with the commissioning data. The maximum angular correction for a given beam is 8.2% for the planar ion chamber array and 2.4% for the cylindrical diode array. The two systems demonstrate a comparable sensitivity of detecting the translational targeting errors, while the cylindrical diode array is more sensitive to the rotational targeting error. The MC method is necessary for dose calculations in the cylindrical diode array phantom because the ray-tracing algorithm fails to handle the high-Z diodes and the acrylic phantom. For all the patient plans, the cylindrical diode array/ planar ion chamber array demonstrate 100% / > 92% (3%/3 mm) and > 96% / ~ 80% (2%/2 mm) passing rates. The feasibility of using both systems for robotic

  18. SU-E-T-242: Monte Carlo Simulations Used to Test the Perturbation of a Reference Ion Chamber Prototype Used for Small Fields

    SciTech Connect

    Vazquez Quino, L; Calvo, O; Huerta, C; DeWeese, M

    2014-06-01

    Purpose: To study the perturbation due to the use of a novel Reference Ion Chamber designed to measure small field dosimetry (KermaX Plus C by IBA). Methods: Using the Phase-space files for TrueBeam photon beams available by Varian in IAEA-compliant format for 6 and 15 MV. Monte Carlo simulations were performed using BEAMnrc and DOSXYZnrc to investigate the perturbation introduced by a reference chamber into the PDDs and profiles measured in water tank. Field sizes ranging from 1×1, 2×2,3×3, 5×5 cm2 were simulated for both energies with and without a 0.5 mm foil of Aluminum which is equivalent to the attenuation equivalent of the reference chamber specifications in a water phantom of 30×30×30 cm3 and a pixel resolution of 2 mm. The PDDs, profiles, and gamma analysis of the simulations were performed as well as a energy spectrum analysis of the phase-space files generated during the simulation. Results: Examination of the energy spectrum analysis performed shown a very small increment of the energy spectrum at the build-up region but no difference is appreciated after dmax. The PDD, profiles and gamma analysis had shown a very good agreement among the simulations with and without the Al foil, with a gamma analysis with a criterion of 2% and 2mm resulting in 99.9% of the points passing this criterion. Conclusion: This work indicates the potential benefits of using the KermaX Plus C as reference chamber in the measurement of PDD and Profiles for small fields since the perturbation due to in the presence of the chamber the perturbation is minimal and the chamber can be considered transparent to the photon beam.

  19. Mesh2d

    2011-12-31

    Mesh2d is a Fortran90 program designed to generate two-dimensional structured grids of the form [x(i),y(i,j)] where [x,y] are grid coordinates identified by indices (i,j). The x(i) coordinates alone can be used to specify a one-dimensional grid. Because the x-coordinates vary only with the i index, a two-dimensional grid is composed in part of straight vertical lines. However, the nominally horizontal y(i,j0) coordinates along index i are permitted to undulate or otherwise vary. Mesh2d also assignsmore » an integer material type to each grid cell, mtyp(i,j), in a user-specified manner. The complete grid is specified through three separate input files defining the x(i), y(i,j), and mtyp(i,j) variations.« less

  20. 2D potential measurements by applying automatic beam adjustment system to heavy ion beam probe diagnostic on the Large Helical Devicea)

    NASA Astrophysics Data System (ADS)

    Shimizu, A.; Ido, T.; Kurachi, M.; Makino, R.; Nishiura, M.; Kato, S.; Nishizawa, A.; Hamada, Y.

    2014-11-01

    Two-dimensional potential profiles in the Large Helical Device (LHD) were measured with heavy ion beam probe (HIBP). To measure the two-dimensional profile, the probe beam energy has to be changed. However, this task is not easy, because the beam transport line of LHD-HIBP system is very long (˜20 m), and the required beam adjustment consumes much time. To reduce the probe beam energy adjustment time, an automatic beam adjustment system has been developed. Using this system, required time to change the probe beam energy is dramatically reduced, such that two-dimensional potential profiles were able to be successfully measured with HIBP by changing the probe beam energy shot to shot.

  1. 2D potential measurements by applying automatic beam adjustment system to heavy ion beam probe diagnostic on the Large Helical Device

    SciTech Connect

    Shimizu, A. Ido, T.; Kato, S.; Hamada, Y.; Kurachi, M.; Makino, R.; Nishiura, M.; Nishizawa, A.

    2014-11-15

    Two-dimensional potential profiles in the Large Helical Device (LHD) were measured with heavy ion beam probe (HIBP). To measure the two-dimensional profile, the probe beam energy has to be changed. However, this task is not easy, because the beam transport line of LHD-HIBP system is very long (∼20 m), and the required beam adjustment consumes much time. To reduce the probe beam energy adjustment time, an automatic beam adjustment system has been developed. Using this system, required time to change the probe beam energy is dramatically reduced, such that two-dimensional potential profiles were able to be successfully measured with HIBP by changing the probe beam energy shot to shot.

  2. Phase-change enabled 2D Li3V2(PO4)3/C submicron sheets for advanced lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Cheng, Yi; Ni, Xiao; Feng, Kai; Zhang, Hongzhang; Li, Xianfeng; Zhang, Huamin

    2016-09-01

    The exploration of cathode materials with high capacity and power, fast charge/discharge rate, long lifespan and broad temperature adaptability is a challenge for the practical application of lithium ion batteries. Here, submicro-sheet Li3V2(PO4)3/C (LVP/C) cathode materials have been successfully synthesized via a simple and universal phase-change method. This designed melting process increases the crystallinity and decreases the Li+ diffusion distance, which effectively enhances the cycling stability and rate performances of the LVP/C cathode materials. The LVP/C cathode materials exhibit high discharge specific capacity of 130 mAh g-1 in the first cycle. The capacity retention is almost 100% after 100 cycles. In addition, at 10 C, more than 80% of initial discharge capacity is retained after 800 cycles, indicating excellent cycle performance at high rate. Moreover, the synthesized LVP/C materials perform excellent low-temperature properties. At -20 °C, the specific capacity can reach 105 mAh g-1 at 0.5 C. This study provides a novel template-free synthesis method for nano/micro materials.

  3. Detection of Amines and Ammonia with an Ambient Pressure Mass Spectrometer using a Corona Discharge Ion Source, in an Urban Atmosphere and in a Teflon Film Chamber

    NASA Astrophysics Data System (ADS)

    Alves, M.; Hanson, D. R.; Grieves, C.; Ortega, J. V.

    2015-12-01

    Amines and ammonia are an important group of molecules that can greatly affect atmospheric particle formation that can go on to impact cloud formation and their scattering of thermal and solar radiation, and as a result human health and ecosystems. In this study, an Ambient Pressure Mass Spectrometer (AmPMS) that is selective and sensitive to molecules with a high proton affinity, such as amines, was coupled with a newly built corona discharge ion source. AmPMS was used to monitor many different nitrogenous compound that are found in an urban atmosphere (July 2015, Minneapolis), down to the single digit pmol/mol level. Simultaneous to this, a proton transfer mass spectrometer also sampled the atmosphere through an inlet within 20 m of the AmPMS inlet. In another set of studies, a similar AmPMS was attached to a large Teflon film chamber at the Atmospheric Chemistry Division at NCAR (August 2015, Boulder). Exploratory studies are planned on the sticking of amines to the chamber walls as well as oxidizing the amine and monitoring products. Depending on the success of these studies, results will be presented on the reversability of amine partitioning and mass balance for these species in the chamber.

  4. Exposure chamber

    DOEpatents

    Moss, Owen R.; Briant, James K.

    1983-01-01

    An exposure chamber includes an imperforate casing having a fluid inlet at the top and an outlet at the bottom. A single vertical series of imperforate trays is provided. Each tray is spaced on all sides from the chamber walls. Baffles adjacent some of the trays restrict and direct the flow to give partial flow back and forth across the chambers and downward flow past the lowermost pan adjacent a central plane of the chamber.

  5. Magnetospheric modulation effects on solar cosmic rays from simultaneous OGO 1 and 3 ion chamber data in 1968 and 1969

    NASA Technical Reports Server (NTRS)

    Hofmann, D. J.

    1973-01-01

    Simultaneous observations by identical ionization chambers aboard the satellites OGO-1 and OGO-3 are utilized to investigate spatial variations in particle intensity near and inside the magnetosphere during the solar cosmic ray events of September 1966. Cross-correlation of the absolute proton flux computed from the chamber rate during three solar particle events shows good agreement with the measurements by the IMP-F Solar Proton Monitor during the same events. The chamber has a dynamic range of over six orders of magnitude. Before launch it was calibrated in the laboratory with radiation dosages in the range 1 R/hr-6000 R/hr. The OGO-1 and OGO-3 chambers, which were normalized in the laboratory prior to the launch, are found to maintain their normalization within approximately equal to 1 per cent during their flight. The high sensitivity and absolute inter-comparability of the instruments allow small intensity differences to be detected and it is established that the observed differences can be explained by a magnetospheric screening effect when an anisotropic beam of particles is present in space. Evidence is presented to show that the screening is at times complete for a duration of as much as 110 min in the tail of the magnetosphere so that during this period the solar cosmic rays (E approximately equal to 15 MeV) have virtually no access to that region of the magnetosphere. Small intensity fluctuations of a temporal nature observed and found to be subjected to a damping effect inside the magnetosphere.

  6. Effect of a metal-dielectric structure introduced in the plasma chamber of the Frankfurt 14 GHz electron cyclotron resonance ion source

    NASA Astrophysics Data System (ADS)

    Schächter, L.; Stiebing, K. E.; Dobrescu, S.; Badescu-Singureanu, Al. I.; Schmidt, L.; Hohn, O.; Runkel, S.

    1999-02-01

    A new approach of the possibility to significantly increase the high charge state ion beams delivered by electron cyclotron resonance (ECR) ion sources by using metal-dielectric (MD) structures characterized by high secondary electron emission properties is presented. The intensities of argon ion beams extracted from the 14 GHz electron cyclotron resonance ion source of the Institut für Kernphysik (IKF) der Johann Wolfgang Goethe-Universität in Frankfurt/Main were measured when a 26 mm diam disk of a specially treated MD structure (Al-Al2O3) was introduced axially close to the ECR plasma. The Ar beam intensities and charge-state distributions obtained with this disk are compared to measurements with disks of iron and pure aluminum at the same position relative to the plasma. All measurements were performed with the disk at the plasma chamber potential. The results with the MD structure show a net shift of the beam intensity towards higher charge states as compared with the other disk materials. Enhancement factors of the beam current of up to 10 (for Ar12+) when using a MD disk compared to the output when using an aluminum disk and up to 40 (for Ar11+) when using an iron disk were measured.

  7. Exposure chamber

    DOEpatents

    Moss, Owen R.

    1980-01-01

    A chamber for exposing animals, plants, or materials to air containing gases or aerosols is so constructed that catch pans for animal excrement, for example, serve to aid the uniform distribution of air throughout the chamber instead of constituting obstacles as has been the case in prior animal exposure chambers. The chamber comprises the usual imperforate top, bottom and side walls. Within the chamber, cages and their associated pans are arranged in two columns. The pans are spaced horizontally from the walls of the chamber in all directions. Corresponding pans of the two columns are also spaced horizontally from each other. Preferably the pans of one column are also spaced vertically from corresponding pans of the other column. Air is introduced into the top of the chamber and withdrawn from the bottom. The general flow of air is therefore vertical. The effect of the horizontal pans is based on the fact that a gas flowing past the edge of a flat plate that is perpendicular to the flow forms a wave on the upstream side of the plate. Air flows downwardly between the chamber walls and the outer edges of the pan. It also flows downwardly between the inner edges of the pans of the two columns. It has been found that when the air carries aerosol particles, these particles are substantially uniformly distributed throughout the chamber.

  8. A smog chamber study coupling a photoionization aerosol electron/ion spectrometer to VUV synchrotron radiation: organic and inorganic-organic mixed aerosol analysis

    NASA Astrophysics Data System (ADS)

    Baeza-Romero, María Teresa; Gaie-Levrel, Francois; Mahjoub, Ahmed; López-Arza, Vicente; Garcia, Gustavo A.; Nahon, Laurent

    2016-07-01

    A reaction chamber was coupled to a photoionization aerosol time-of-flight mass spectrometer based on an electron/ion coincidence scheme and applied for on-line analysis of organic and inorganic-organic mixed aerosols using synchrotron tunable vacuum ultraviolet (VUV) photons as the ionization source. In this proof of principle study, both aerosol and gas phase were detected simultaneously but could be differentiated. Present results and perspectives for improvement for this set-up are shown in the study of ozonolysis ([O3] = 0.13-3 ppm) of α-pinene (2-3 ppm), and the uptake of glyoxal upon ammonium sulphate. In this work the ozone concentration was monitored in real time, together with the particle size distributions and chemical composition, the latter taking advantage of the coincidence spectrometer and the tuneability of the synchrotron radiation as a soft VUV ionization source.

  9. High divergent 2D grating

    NASA Astrophysics Data System (ADS)

    Wang, Jin; Ma, Jianyong; Zhou, Changhe

    2014-11-01

    A 3×3 high divergent 2D-grating with period of 3.842μm at wavelength of 850nm under normal incidence is designed and fabricated in this paper. This high divergent 2D-grating is designed by the vector theory. The Rigorous Coupled Wave Analysis (RCWA) in association with the simulated annealing (SA) is adopted to calculate and optimize this 2D-grating.The properties of this grating are also investigated by the RCWA. The diffraction angles are more than 10 degrees in the whole wavelength band, which are bigger than the traditional 2D-grating. In addition, the small period of grating increases the difficulties of fabrication. So we fabricate the 2D-gratings by direct laser writing (DLW) instead of traditional manufacturing method. Then the method of ICP etching is used to obtain the high divergent 2D-grating.

  10. Wire chamber

    DOEpatents

    Atac, Muzaffer

    1989-01-01

    A wire chamber or proportional counter device, such as Geiger-Mueller tube or drift chamber, improved with a gas mixture providing a stable drift velocity while eliminating wire aging caused by prior art gas mixtures. The new gas mixture is comprised of equal parts argon and ethane gas and having approximately 0.25% isopropyl alcohol vapor.

  11. Chamber dynamic research with pulsed power

    SciTech Connect

    PETERSON,ROBERT R.; OLSON,CRAIG L.; RENK,TIMOTHY J.; ROCHAU,GARY E.; SWEENEY,MARY ANN

    2000-05-15

    In Inertial Fusion Energy (IFE), Target Chamber Dynamics (TCD) is an integral part of the target chamber design and performance. TCD includes target output deposition of target x-rays, ions and neutrons in target chamber gases and structures, vaporization and melting of target chamber materials, radiation-hydrodynamics in target chamber vapors and gases, and chamber conditions at the time of target and beam injections. Pulsed power provides a unique environment for IFE-TCD validation experiments in two important ways: they do not require the very clean conditions which lasers need and they currently provide large x-ray and ion energies.

  12. Monte Carlo computed machine-specific correction factors for reference dosimetry of TomoTherapy static beam for several ion chambers

    SciTech Connect

    Sterpin, E.; Mackie, T. R.; Vynckier, S.

    2012-07-15

    Purpose: To determine k{sub Q{sub m{sub s{sub r,Q{sub o}{sup f{sub m}{sub s}{sub r},f{sub o}}}}}} correction factors for machine-specific reference (msr) conditions by Monte Carlo (MC) simulations for reference dosimetry of TomoTherapy static beams for ion chambers Exradin A1SL, A12; PTW 30006, 31010 Semiflex, 31014 PinPoint, 31018 microLion; NE 2571. Methods: For the calibration of TomoTherapy units, reference conditions specified in current codes of practice like IAEA/TRS-398 and AAPM/TG-51 cannot be realized. To cope with this issue, Alfonso et al. [Med. Phys. 35, 5179-5186 (2008)] described a new formalism introducing msr factors k{sub Q{sub m{sub s{sub r,Q{sub o}{sup f{sub m}{sub s}{sub r},f{sub o}}}}}} for reference dosimetry, applicable to static TomoTherapy beams. In this study, those factors were computed directly using MC simulations for Q{sub 0} corresponding to a simplified {sup 60}Co beam in TRS-398 reference conditions (at 10 cm depth). The msr conditions were a 10 Multiplication-Sign 5 cm{sup 2} TomoTherapy beam, source-surface distance of 85 cm and 10 cm depth. The chambers were modeled according to technical drawings using the egs++ package and the MC simulations were run with the egs{sub c}hamber user code. Phase-space files used as the source input were produced using PENELOPE after simulation of a simplified {sup 60}Co beam and the TomoTherapy treatment head modeled according to technical drawings. Correlated sampling, intermediate phase-space storage, and photon cross-section enhancement variance reduction techniques were used. The simulations were stopped when the combined standard uncertainty was below 0.2%. Results: Computed k{sub Q{sub m{sub s{sub r,Q{sub o}{sup f{sub m}{sub s}{sub r},f{sub o}}}}}} values were all close to one, in a range from 0.991 for the PinPoint chamber to 1.000 for the Exradin A12 with a statistical uncertainty below 0.2%. Considering a beam quality Q defined as the TPR{sub 20,10} for a 6 MV Elekta photon beam (0

  13. Influence of chamber dimensions on the performance of a conduction micropump

    NASA Astrophysics Data System (ADS)

    Feng, Junyuan; Wan, Zhenping; Wen, Wanyu; Li, Yaochao; Tang, Yong

    2016-05-01

    An electrohydrodynamic (EHD) conduction micropump with symmetric planar electrodes is developed to investigate the effect of micropump chamber dimensions on static pressure and flow rate. The interdigitated electrodes are created on an FR-4 CCL (copper clad laminate) using photolithography. The micropump consists of an electrode plate, chamber plate, top and bottom end cover. A 2D numerical simulation study is conducted to provide details about the ion distribution and fluid flow behaviors within a local domain of micropumps with different chamber height. Experimental results show that, by increasing chamber height, the static pressure and flow rate rise with a big slope under a chamber height of 0.2 mm, and henceforth decrease dramatically. The variation trends of static pressure and flow rate with an increase in chamber height are determined by the combination of ion concentration distribution and fluidic circulation formed between the two electrodes. Additionally, the effect of the chamber width and length is experimentally analyzed for optimum pressure and output flow rate.

  14. IONIZATION CHAMBER

    DOEpatents

    Redman, W.C.; Shonka, F.R.

    1958-02-18

    This patent describes a novel ionization chamber which is well suited to measuring the radioactivity of the various portions of a wire as the wire is moved at a uniform speed, in order to produce the neutron flux traverse pattern of a reactor in which the wire was previously exposed to neutron radiation. The ionization chamber of the present invention is characterized by the construction wherein the wire is passed through a tubular, straight electrode and radiation shielding material is disposed along the wire except at an intermediate, narrow area where the second electrode of the chamber is located.

  15. IFE Chamber Technology - Status and Future Challenges

    SciTech Connect

    Meier, W R; Raffrary, A R; Abdel-Khalik, S; Kulcinski, G; Latkowski, J F; Najmabadi, F; Olson, C L; Peterson, P F; Ying, A; Yoda, M

    2002-11-15

    Significant progress has been made on addressing critical issues for inertial fusion energy (IFE) chambers for heavy-ion, laser and Z-pinch drivers. A variety of chamber concepts are being investigated including dry-wall (currently favored for laser IFE), wetted-wall (applicable to both laser and ion drivers), and thick-liquid-wall favored by heavy ion and z-pinch drivers. Recent progress and remaining challenges in developing IFE chambers are reviewed.

  16. Ultrafast 2D IR microscopy

    PubMed Central

    Baiz, Carlos R.; Schach, Denise; Tokmakoff, Andrei

    2014-01-01

    We describe a microscope for measuring two-dimensional infrared (2D IR) spectra of heterogeneous samples with μm-scale spatial resolution, sub-picosecond time resolution, and the molecular structure information of 2D IR, enabling the measurement of vibrational dynamics through correlations in frequency, time, and space. The setup is based on a fully collinear “one beam” geometry in which all pulses propagate along the same optics. Polarization, chopping, and phase cycling are used to isolate the 2D IR signals of interest. In addition, we demonstrate the use of vibrational lifetime as a contrast agent for imaging microscopic variations in molecular environments. PMID:25089490

  17. AnisWave 2D

    2004-08-01

    AnisWave2D is a 2D finite-difference code for a simulating seismic wave propagation in fully anisotropic materials. The code is implemented to run in parallel over multiple processors and is fully portable. A mesh refinement algorithm has been utilized to allow the grid-spacing to be tailored to the velocity model, avoiding the over-sampling of high-velocity materials that usually occurs in fixed-grid schemes.

  18. Active osmoregulatory ion uptake across the pleopods of the isopod Idotea baltica (Pallas): electrophysiological measurements on isolated split endo- and exopodites mounted in a micro-ussing chamber.

    PubMed

    Postel, U; Becker, W; Brandt, A; Luck-Kopp, S; Riestenpatt, S; Weihrauch, D; Siebers, D

    2000-04-01

    The mechanism of active, osmoregulatory ion uptake was investigated in the pleopods of the marine isopod Idotea baltica (Pallas). Using isolated split half-podites of isopods acclimated to brackish water (20 salinity) mounted in a micro-Ussing chamber and symmetrically superfused with identical haemolymph-like salines, a mean short-circuit current I(sc) of -445 microA cm(-)(2) was measured in endopodites 3-5, corresponding to an inwardly directed transcellular movement of negative charge. Application of ouabain (5 mmol l(-)(1)) to the basolateral superfusate resulted in the almost total abolition of the I(sc) (reduced from -531 to -47 microA cm(-)(2)), suggesting that the Na(+)/K(+)-ATPase is the driving force for active, electrogenic uptake of NaCl. In contrast, mean I(sc) values close to zero were found in preparations of all exopodites and in endopodites 1 and 2. The specific activities of Na(+)/K(+)-ATPase corresponded with these results. Specific activities were highest in posterior endopodites 3-5 and depended on ambient salinity. In all other rami, the activities were much lower and independent of ambient salinity. Activities in posterior endopodites 3-5 were lowest in isopods acclimated to 30 salinity (2-4 micromol P(i )mg(-)(1 )protein h(-)(1)), increased in individuals kept in 20 salinity (8.4 micromol P(i )mg(-)(1 )protein h(-)(1)) and were highest in isopods acclimated to 15 salinity (18.2 micromol P(i )mg(-)(1 )protein h(-)(1)). When specimens were transferred from 30 to 40 salinity, Na(+)/K(+)-ATPase activity increased in the posterior endopodites. The electrophysiological and Na(+)/K(+)-ATPase activity measurements show that active electrogenic ion transport in this species occurs almost exclusively in posterior endopodites 3-5. The endopodite of the fifth pleopod of I. baltica exhibited a microscopic structure remarkably similar to that described for the lamellae of the phyllobranchiae of brachyurans. It is composed of two opposed epithelial

  19. Ionization chamber

    DOEpatents

    Walenta, Albert H.

    1981-01-01

    An ionization chamber has separate drift and detection regions electrically isolated from each other by a fine wire grid. A relatively weak electric field can be maintained in the drift region when the grid and another electrode in the chamber are connected to a high voltage source. A much stronger electric field can be provided in the detection region by connecting wire electrodes therein to another high voltage source. The detection region can thus be operated in a proportional mode when a suitable gas is contained in the chamber. High resolution output pulse waveforms are provided across a resistor connected to the detection region anode, after ionizing radiation enters the drift region and ionize the gas.

  20. Ionization chamber

    DOEpatents

    Walenta, A.H.

    An ionization chamber is described which has separate drift and detection regions electrically isolated from each other by a fine wire grid. A relatively weak electric field can be maintained in the drift region when the grid and another electrode in the chamber are connected to a high voltage source. A much stronger electric field can be provided in the detection region by connecting wire electrodes therein to another high voltage source. The detection region can thus be operated in a proportional mode when a suitable gas is contained in the chamber. High resolution output pulse waveforms are provided across a resistor connected to the detection region anode, after ionizing radiation enters the drift region and ionizes the gas.

  1. SU-E-T-65: Characterization of a 2D Array for QA and Pretreatment Plan Verification

    SciTech Connect

    Anvari, A; Aghamiri, S; Mahdavi, S; Alaei, P

    2014-06-01

    Purpose: The OCTAVIUS detector729 is a 2D array of 729 air vented cubic plane parallel ion chambers used for pretreatment verification and QA. In this study we investigated dosimetric characteristics of this system for clinical photon beam dosimetry. Methods: Detector performance evaluation included determination of the location of the effective point of measurement (EPM), sensitivity, linearity, and reproducibility of detector response, as well as output factor, dose rate, and source to surface distance (SSD) dependence. Finally, assessment of wedge modulated fields was carried out. All the evaluations were performed five times for low and high photon energies. For reference measurements, a 0.6 cc ionization chamber was used. Data analysis and comparison of the OCTAVIUS detector with reference ion chamber data was performed using the VeriSoft patient plan verification software. Results: The reproducibility and stability of the measurements are excellent, the detector showed same signal with a maximum deviation of less than 0.5% in short and long term. Results of sensitivity test showed same signal with a maximum deviation of approximately 0.1%. As the detector 729 response is linear with dose and dose rate, it can be used for the measurement at regions of high dose gradient effectively. The detector agrees with the ionization chamber measurement to within 1% for SSD range of 75 to 125 cm. Also, its measured wedge modulated profiles matched very well with ion chamber dose profiles acquired in a water tank. Conclusions: As the response of the detector 729 is linear with dose and dose rate, it can be used for the measurements in the areas of dose gradients effectively. Based on the measurements and comparisons performed, this system is a reliable and accurate dosimeter for QA and pretreatment plan verification in radiotherapy.

  2. Cost-effective pediatric head and body phantoms for computed tomography dosimetry and its evaluation using pencil ion chamber and CT dose profiler.

    PubMed

    Saravanakumar, A; Vaideki, K; Govindarajan, K N; Jayakumar, S; Devanand, B

    2015-01-01

    In the present work, a pediatric head and body phantom was fabricated using polymethyl methacrylate (PMMA) at a low cost when compared to commercially available phantoms for the purpose of computed tomography (CT) dosimetry. The dimensions of head and body phantoms were 10 cm diameter, 15 cm length and 16 cm diameter, 15 cm length, respectively. The dose from a 128-slice CT machine received by the head and body phantom at the center and periphery were measured using a 100 mm pencil ion chamber and 150 mm CT dose profiler (CTDP). Using these values, the weighted computed tomography dose index (CTDIw) and in turn the volumetric CTDI (CTDIv) were calculated for various combinations of tube voltage and current-time product. A similar study was carried out using standard calibrated phantom and the results have been compared with the fabricated ones to ascertain that the performance of the latter is equivalent to that of the former. Finally, CTDIv measured using fabricated and standard phantoms were compared with respective values displayed on the console. The difference between the values was well within the limits specified by Atomic Energy Regulatory Board (AERB), India. These results indicate that the cost-effective pediatric phantom can be employed for CT dosimetry.

  3. Cost-effective pediatric head and body phantoms for computed tomography dosimetry and its evaluation using pencil ion chamber and CT dose profiler

    PubMed Central

    Saravanakumar, A.; Vaideki, K.; Govindarajan, K. N.; Jayakumar, S.; Devanand, B.

    2015-01-01

    In the present work, a pediatric head and body phantom was fabricated using polymethyl methacrylate (PMMA) at a low cost when compared to commercially available phantoms for the purpose of computed tomography (CT) dosimetry. The dimensions of head and body phantoms were 10 cm diameter, 15 cm length and 16 cm diameter, 15 cm length, respectively. The dose from a 128-slice CT machine received by the head and body phantom at the center and periphery were measured using a 100 mm pencil ion chamber and 150 mm CT dose profiler (CTDP). Using these values, the weighted computed tomography dose index (CTDIw) and in turn the volumetric CTDI (CTDIv) were calculated for various combinations of tube voltage and current-time product. A similar study was carried out using standard calibrated phantom and the results have been compared with the fabricated ones to ascertain that the performance of the latter is equivalent to that of the former. Finally, CTDIv measured using fabricated and standard phantoms were compared with respective values displayed on the console. The difference between the values was well within the limits specified by Atomic Energy Regulatory Board (AERB), India. These results indicate that the cost-effective pediatric phantom can be employed for CT dosimetry. PMID:26500404

  4. Commissioning a small-field biological irradiator using point, 2D, and 3D dosimetry techniques

    PubMed Central

    Newton, Joseph; Oldham, Mark; Thomas, Andrew; Li, Yifan; Adamovics, John; Kirsch, David G.; Das, Shiva

    2011-01-01

    Purpose: To commission a small-field biological irradiator, the XRad225Cx from Precision x-Ray, Inc., for research use. The system produces a 225 kVp x-ray beam and is equipped with collimating cones that produce both square and circular radiation fields ranging in size from 1 to 40 mm. This work incorporates point, 2D, and 3D measurements to determine output factors (OF), percent-depth-dose (PDD) and dose profiles at multiple depths. Methods: Three independent dosimetry systems were used: ion-chambers (a farmer chamber and a micro-ionisation chamber), 2D EBT2 radiochromic film, and a novel 3D dosimetry system (DLOS/PRESAGE®). Reference point dose rates and output factors were determined from in-air ionization chamber measurements for fields down to ∼13 mm using the formalism of TG61. PDD, profiles, and output factors at three separate depths (0, 0.5, and 2 cm), were determined for all field sizes from EBT2 film measurements in solid water. Several film PDD curves required a scaling correction, reflecting the challenge of accurate film alignment in very small fields. PDDs, profiles, and output factors were also determined with the 3D DLOS/PRESAGE® system which generated isotropic 0.2 mm data, in scan times of 20 min. Results: Surface output factors determined by ion-chamber were observed to gradually drop by ∼9% when the field size was reduced from 40 to 13 mm. More dramatic drops were observed for the smallest fields as determined by EBT∼18% and ∼42% for the 2.5 mm and 1 mm fields, respectively. PRESAGE® and film output factors agreed well for fields <20 mm (where 3D data were available) with mean deviation of 2.2% (range 1%–4%). PDD values at 2 cm depth varied from ∼72% for the 40 mm field, down to ∼55% for the 1 mm field. EBT and PRESAGE® PDDs agreed within ∼3% in the typical therapy region (1–4 cm). At deeper depths the EBT curves were slightly steeper (2.5% at 5 cm). These results indicate good overall consistency between ion-chamber, EBT

  5. SU-E-T-448: On the Perturbation Factor P-cav of the Markus Parallel Plate Ion Chambers in Clinical Electron Beams, Monte Carlo Based Reintegration of An Historical Experiment

    SciTech Connect

    Voigts-Rhetz, P von; Zink, K

    2014-06-01

    Purpose: All present dosimetry protocols recommend well-guarded parallel-plate ion chambers for electron dosimetry. For the guard-less Markus chamber an energy dependent fluence perturbation correction pcav is given. This perturbation correction was experimentally determined by van der Plaetsen by comparison of the read-out of a Markus and a NACP chamber, which was assumed to be “perturbation-free”. Aim of the present study is a Monte Carlo based reiteration of this experiment. Methods: Detailed models of four parallel-plate chambers (Roos, Markus, NACP and Advanced Markus) were designed using the Monte Carlo code EGSnrc and placed in a water phantom. For all chambers the dose to the active volume filled with low density water was calculated for 13 clinical electron spectra (E{sub 0}=6-21 MeV) at the depth of maximum and at the reference depth under reference conditions. In all cases the chamber's reference point was positioned at the depth of measurement. Moreover, the dose to water DW was calculated in a small water voxel positioned at the same depth. Results: The calculated dose ratio D{sub NACP}/D{sub Markus}, which according to van der Plaetsen reflects the fluence perturbation correction of the Markus chamber, deviates less from unity than the values given by van der Plaetsen's but exhibits a similar energy dependence. The same holds for the dose ratios of the other well guarded chambers. But, in comparison to water, the Markus chamber reveals the smallest overall perturbation correction which is nearly energy independent at both investigated depths. Conclusion: The simulations principally confirm the energy dependence of the dose ratio D{sub NACP}/D{sub Markus} as published by van der Plaetsen. But, as shown by our simulations of the ratio D{sub W}/D{sub Markus}, the conclusion drawn in all dosimetry protocols is questionable: in contrast to all well-guarded chambers the guard-less Markus chamber reveals the smallest overall perturbation correction and

  6. DYNA2D96. Explicit 2-D Hydrodynamic FEM Program

    SciTech Connect

    Whirley, R.G.

    1992-04-01

    DYNA2D is a vectorized, explicit, two-dimensional, axisymmetric and plane strain finite element program for analyzing the large deformation dynamic and hydrodynamic response of inelastic solids. DYNA2D contains 13 material models and 9 equations of state (EOS) to cover a wide range of material behavior. The material models implemented in all machine versions are: elastic, orthotropic elastic, kinematic/isotropic elastic plasticity, thermoelastoplastic, soil and crushable foam, linear viscoelastic, rubber, high explosive burn, isotropic elastic-plastic, temperature-dependent elastic-plastic. The isotropic and temperature-dependent elastic-plastic models determine only the deviatoric stresses. Pressure is determined by one of 9 equations of state including linear polynomial, JWL high explosive, Sack Tuesday high explosive, Gruneisen, ratio of polynomials, linear polynomial with energy deposition, ignition and growth of reaction in HE, tabulated compaction, and tabulated.

  7. SU-C-304-01: Investigation of Various Detector Response Functions and Their Geometry Dependence in a Novel Method to Address Ion Chamber Volume Averaging Effect

    SciTech Connect

    Barraclough, B; Lebron, S; Li, J; Fan, Qiyong; Liu, C; Yan, G

    2015-06-15

    Purpose: A novel convolution-based approach has been proposed to address ion chamber (IC) volume averaging effect (VAE) for the commissioning of commercial treatment planning systems (TPS). We investigate the use of various convolution kernels and its impact on the accuracy of beam models. Methods: Our approach simulates the VAE by iteratively convolving the calculated beam profiles with a detector response function (DRF) while optimizing the beam model. At convergence, the convolved profiles match the measured profiles, indicating the calculated profiles match the “true” beam profiles. To validate the approach, beam profiles of an Elekta LINAC were repeatedly collected with ICs of various volumes (CC04, CC13 and SNC 125) to obtain clinically acceptable beam models. The TPS-calculated profiles were convolved externally with the DRF of respective IC. The beam model parameters were reoptimized using Nelder-Mead method by forcing the convolved profiles to match the measured profiles. We evaluated three types of DRFs (Gaussian, Lorentzian, and parabolic) and the impact of kernel dependence on field geometry (depth and field size). The profiles calculated with beam models were compared with SNC EDGE diode-measured profiles. Results: The method was successfully implemented with Pinnacle Scripting and Matlab. The reoptimization converged in ∼10 minutes. For all tested ICs and DRFs, penumbra widths of the TPS-calculated profiles and diode-measured profiles were within 1.0 mm. Gaussian function had the best performance with mean penumbra width difference within 0.5 mm. The use of geometry dependent DRFs showed marginal improvement, reducing the penumbra width differences to less than 0.3 mm. Significant increase in IMRT QA passing rates was achieved with the optimized beam model. Conclusion: The proposed approach significantly improved the accuracy of the TPS beam model. Gaussian functions as the convolution kernel performed consistently better than Lorentzian and

  8. Liquid Wall Chambers

    SciTech Connect

    Meier, W R

    2011-02-24

    The key feature of liquid wall chambers is the use of a renewable liquid layer to protect chamber structures from target emissions. Two primary options have been proposed and studied: wetted wall chambers and thick liquid wall (TLW) chambers. With wetted wall designs, a thin layer of liquid shields the structural first wall from short ranged target emissions (x-rays, ions and debris) but not neutrons. Various schemes have been proposed to establish and renew the liquid layer between shots including flow-guiding porous fabrics (e.g., Osiris, HIBALL), porous rigid structures (Prometheus) and thin film flows (KOYO). The thin liquid layer can be the tritium breeding material (e.g., flibe, PbLi, or Li) or another liquid metal such as Pb. TLWs use liquid jets injected by stationary or oscillating nozzles to form a neutronically thick layer (typically with an effective thickness of {approx}50 cm) of liquid between the target and first structural wall. In addition to absorbing short ranged emissions, the thick liquid layer degrades the neutron flux and energy reaching the first wall, typically by {approx}10 x x, so that steel walls can survive for the life of the plant ({approx}30-60 yrs). The thick liquid serves as the primary coolant and tritium breeding material (most recent designs use flibe, but the earliest concepts used Li). In essence, the TLW places the fusion blanket inside the first wall instead of behind the first wall.

  9. MOSS2D V1

    2001-01-31

    This software reduces the data from two-dimensional kSA MOS program, k-Space Associates, Ann Arbor, MI. Initial MOS data is recorded without headers in 38 columns, with one row of data per acquisition per lase beam tracked. The final MOSS 2d data file is reduced, graphed, and saved in a tab-delimited column format with headers that can be plotted in any graphing software.

  10. Ionization chamber dosimeter

    DOEpatents

    Renner, Tim R.; Nyman, Mark A.; Stradtner, Ronald

    1991-01-01

    A method for fabricating an ion chamber dosimeter collecting array of the type utilizing plural discrete elements formed on a uniform collecting surface which includes forming a thin insulating layer over an aperture in a frame having surfaces, forming a predetermined pattern of through holes in the layer, plating both surfaces of the layer and simultaneously tilting and rotating the frame for uniform plate-through of the holes between surfaces. Aligned masking and patterned etching of the surfaces provides interconnects between the through holes and copper leads provided to external circuitry.

  11. Double resonance rotational spectroscopy of CH2D+

    NASA Astrophysics Data System (ADS)

    Töpfer, Matthias; Jusko, Pavol; Schlemmer, Stephan; Asvany, Oskar

    2016-09-01

    Context. Deuterated forms of CH are thought to be responsible for deuterium enrichment in lukewarm astronomical environments. There is no unambiguous detection of CH2D+ in space to date. Aims: Four submillimetre rotational lines of CH2D+ are documented in the literature. Our aim is to present a complete dataset of highly resolved rotational lines, including millimetre (mm) lines needed for a potential detection. Methods: We used a low-temperature ion trap and applied a novel IR-mm-wave double resonance method to measure the rotational lines of CH2D+. Results: We measured 21 low-lying (J ≤ 4) rotational transitions of CH2D+ between 23 GHz and 1.1 THz with accuracies close to 2 ppb.

  12. Chamber Clearing First Principles Modeling

    SciTech Connect

    Loosmore, G

    2009-06-09

    LIFE fusion is designed to generate 37.5 MJ of energy per shot, at 13.3 Hz, for a total average fusion power of 500 MW. The energy from each shot is partitioned among neutrons ({approx}78%), x-rays ({approx}12%), and ions ({approx}10%). First wall heating is dominated by x-rays and debris because the neutron mean free path is much longer than the wall thickness. Ion implantation in the first wall also causes damage such as blistering if not prevented. To moderate the peak-pulse heating, the LIFE fusion chamber is filled with a gas (such as xenon) to reduce the peak-pulse heat load. The debris ions and majority of the x-rays stop in the gas, which re-radiates this energy over a longer timescale (allowing time for heat conduction to cool the first wall sufficiently to avoid damage). After a shot, because of the x-ray and ion deposition, the chamber fill gas is hot and turbulent and contains debris ions. The debris needs to be removed. The ions increase the gas density, may cluster or form aerosols, and can interfere with the propagation of the laser beams to the target for the next shot. Moreover, the tritium and high-Z hohlraum debris needs to be recovered for reuse. Additionally, the cryogenic target needs to survive transport through the gas mixture to the chamber center. Hence, it will be necessary to clear the chamber of the hot contaminated gas mixture and refill it with a cool, clean gas between shots. The refilling process may create density gradients that could interfere with beam propagation, so the fluid dynamics must be studied carefully. This paper describes an analytic modeling effort to study the clearing and refilling process for the LIFE fusion chamber. The models used here are derived from first principles and balances of mass and energy, with the intent of providing a first estimate of clearing rates, clearing times, fractional removal of ions, equilibrated chamber temperatures, and equilibrated ion concentrations for the chamber. These can be used

  13. Unparticle example in 2D.

    PubMed

    Georgi, Howard; Kats, Yevgeny

    2008-09-26

    We discuss what can be learned about unparticle physics by studying simple quantum field theories in one space and one time dimension. We argue that the exactly soluble 2D theory of a massless fermion coupled to a massive vector boson, the Sommerfield model, is an interesting analog of a Banks-Zaks model, approaching a free theory at high energies and a scale-invariant theory with nontrivial anomalous dimensions at low energies. We construct a toy standard model coupling to the fermions in the Sommerfield model and study how the transition from unparticle behavior at low energies to free particle behavior at high energies manifests itself in interactions with the toy standard model particles.

  14. Beam charge and current neutralization of high-charge-state heavy ions

    SciTech Connect

    Logan, B.G.; Callahan, D.A.

    1997-10-29

    High-charge-state heavy-ions may reduce the accelerator voltage and cost of heavy-ion inertial fusion drivers, if ways can be found to neutralize the space charge of the highly charged beam ions as they are focused to a target in a fusion chamber. Using 2-D Particle-In- Cell simulations, we have evaluated the effectiveness of two different methods of beam neutralization: (1) by redistribution of beam charge in a larger diameter, preformed plasma in the chamber, and (2), by introducing a cold-electron-emitting source within the beam channel at the beam entrance into the chamber. We find the latter method to be much more effective for high-charge-state ions.

  15. Metrology for graphene and 2D materials

    NASA Astrophysics Data System (ADS)

    Pollard, Andrew J.

    2016-09-01

    The application of graphene, a one atom-thick honeycomb lattice of carbon atoms with superlative properties, such as electrical conductivity, thermal conductivity and strength, has already shown that it can be used to benefit metrology itself as a new quantum standard for resistance. However, there are many application areas where graphene and other 2D materials, such as molybdenum disulphide (MoS2) and hexagonal boron nitride (h-BN), may be disruptive, areas such as flexible electronics, nanocomposites, sensing and energy storage. Applying metrology to the area of graphene is now critical to enable the new, emerging global graphene commercial world and bridge the gap between academia and industry. Measurement capabilities and expertise in a wide range of scientific areas are required to address this challenge. The combined and complementary approach of varied characterisation methods for structural, chemical, electrical and other properties, will allow the real-world issues of commercialising graphene and other 2D materials to be addressed. Here, examples of metrology challenges that have been overcome through a multi-technique or new approach are discussed. Firstly, the structural characterisation of defects in both graphene and MoS2 via Raman spectroscopy is described, and how nanoscale mapping of vacancy defects in graphene is also possible using tip-enhanced Raman spectroscopy (TERS). Furthermore, the chemical characterisation and removal of polymer residue on chemical vapour deposition (CVD) grown graphene via secondary ion mass spectrometry (SIMS) is detailed, as well as the chemical characterisation of iron films used to grow large domain single-layer h-BN through CVD growth, revealing how contamination of the substrate itself plays a role in the resulting h-BN layer. In addition, the role of international standardisation in this area is described, outlining the current work ongoing in both the International Organization of Standardization (ISO) and the

  16. Effect of nebulizer/spray chamber interfaces on simultaneous, axial view inductively coupled plasma optical emission spectrometry for the direct determination of As and Se species separated by ion exchange high-performance liquid chromatography

    NASA Astrophysics Data System (ADS)

    Gettar, Raquel T.; Smichowski, Patricia; Garavaglia, Ricardo N.; Farías, Silvia; Batistoni, Daniel A.

    2005-06-01

    Different nebulizer/expansion chamber combinations were evaluated to assess their performance for sample introduction in the direct coupling with an axial view inductively coupled plasma multielement spectrometer for on-line determination of As and Se species previously separated by ion exchange-high performance liquid chromatography. The column effluents were injected into the plasma without prior derivatization. The instrument operation software was adapted for data acquisition and processing to allow multi-wavelength recording of the transient chromatographic peaks. After optimization of the chromatographic operating conditions, separation of mixtures of inorganic As and Se species, and of inorganic and two organic As species (monomethylarsonic and dimethylarsinic acids), was achieved with excellent resolution. Species discrimination from mixtures of As and Se oxyanions was further improved by the simultaneous element detection at specific analytical wavelengths. Three nebulizers and three spray chambers, employed in seven combinations, were tested as interfaces. Concentric nebulizers associated to a glass cyclonic chamber appear most suitable regarding sensitivity and signal to noise ratio. Measured element detection limits (3 σ) were around 10 ng ml - 1 for all the species considered, making the method a viable alternative to similar procedures that employ volatile hydride generation previous to sample injection into the plasma. Analytical recoveries both for inorganic and organic species ranged between 92 and 107%. The method was demonstrated to be apt for the analysis of surface waters potentially subjected to natural contamination with arsenic.

  17. In vivo photodynamic effects of phthalocyanines in a skin-fold observation chamber model: role of central metal ion and degree of sulfonation.

    PubMed

    van Leengoed, H L; van der Veen, N; Versteeg, A A; Ouellet, R; van Lier, J E; Star, W M

    1993-10-01

    Six sulfonated metallophthalocyanines, chelated with either aluminum or zinc and sulfonated to different degrees, were studied in vivo for their photodynamic activity in a rat skin-fold chamber model. The chamber, located on the back of female WAG/Rij rats, contained a syngeneic mammary carcinoma implanted into a layer of subcutaneous tissue. Twenty-four hours after intravenous administration of 2.5 mumol/kg of one of the dyes, the chambers received a treatment light dose of 600 J/cm2 with monochromatic light of 675 nm at a power density of 100 mW/cm2. During light delivery and up to a period of 7 days after treatment, vascular effects of tumor and normal tissue were scored. Tumor cell viability was determined by histology and by reimplantation of the chamber contents into the skin of the same animal, either 2 h after treatment or after the 7 day observation period. Vascular effects of both tumor and subcutaneous tissue were strongest with dyes with the lowest degree of sulfonation and decreased with increasing degree of sulfonation. Tumor regrowth did not occur with aluminum phthalocyanine mono- and disulfonate and with zinc phthalocyanine monosulfonate. With the protocol that was used, complete necrosis without recovery was only observed when reimplantation took place at the end of the 7 day follow-up period. Reimplantation 2 h after treatment always resulted in tumor regrowth. At this interval, the presence of viable tumor cells was confirmed histologically. In general tumor tissue vasculature was more susceptible to photodynamic damage than vasculature of the normal tissue. The effect on the circulation of both tumor and normal tissue increased with decreasing degree of sulfonation.(ABSTRACT TRUNCATED AT 250 WORDS)

  18. Portable Hyperbaric Chamber

    NASA Technical Reports Server (NTRS)

    Schneider, William C. (Inventor); Locke, James P. (Inventor); DeLaFuente, Horacio (Inventor)

    2001-01-01

    A portable, collapsible hyperbaric chamber was developed. A toroidal inflatable skeleton provides initial structural support for the chamber, allowing the attendant and/or patient to enter the chamber. Oval hatches mate against bulkhead rings, and the hyperbaric chamber is pressurized. The hatches seal against an o-ring, and the internal pressure of the chamber provides the required pressure against the hatch to maintain an airtight seal. In the preferred embodiment, the hyperbaric chamber has an airlock to allow the attendant to enter and exit the patient chamber during treatment. Visual communication is provided through portholes in the patient and/or airlock chamber. Life monitoring and support systems are in communication with the interior of the hyperbaric chamber and/or airlock chamber through conduits and/or sealed feed-through connectors into the hyperbaric chamber.

  19. Diogene pictorial drift chamber

    SciTech Connect

    Gosset, J.

    1984-01-01

    A pictorial drift chamber, called DIOGENE, has been installed at Saturne in order to study central collisions of high energy heavy ions. It has been adapted from the JADE internal detector, with two major differences to be taken into account. First, the center-of-mass of these collisions is not identical to the laboratory reference frame. Second, the energy loss and the momentum ranges of the particles to be detected are different from the ones in JADE. It was also tried to keep the cost as small as possible, hence the choice of minimum size and minimum number of sensitive wires. Moreover the wire planes are shifted from the beam axis: this trick helps very much to quickly reject the bad tracks caused by the ambiguity of measuring drift distances (positive or negative) through times (always positive).

  20. Diogene pictorial drift chamber

    NASA Astrophysics Data System (ADS)

    Gosset, J.

    1984-02-01

    A pictorial drift chamber, called DIOGENE, has been installed at Saturne in order to study central collisions of high energy heavy ions. It has been adapted from the JADE internal detector, with two major differences to be taken into account. First, the center-of-mass of these collisions is not identical to the laboratory reference frame. Second, the energy loss and the momentum ranges of the particles to be detected are different from the ones in JADE. It was also tried to keep the cost as small as possible, hence the choice of minimum size and minimum number of sensitive wires. Moreover the wire planes are shifted from the beam axis: this trick helps very much to quickly reject the bad tracks caused by the ambiguity of measuring drift distances (positive or negative) through times (always positive).

  1. Characterization of a homemade ionization chamber for radiotherapy beams.

    PubMed

    Neves, Lucio P; Perini, Ana P; dos Santos, Gelson P; Xavier, Marcos; Khoury, Helen J; Caldas, Linda V E

    2012-07-01

    A homemade cylindrical ionization chamber was studied for routine use in therapy beams of (60)Co and X-rays. Several characterization tests were performed: leakage current, saturation, ion collection efficiency, polarity effect, stability, stabilization time, chamber orientation and energy dependence. All results obtained were within international recommendations. Therefore the homemade ionization chamber presents usefulness for routine dosimetric procedures in radiotherapy beams.

  2. ION SOURCE

    DOEpatents

    Bell, W.A. Jr.; Love, L.O.; Prater, W.K.

    1958-01-28

    An ion source is presented capable of producing ions of elements which vaporize only at exceedingly high temperatures, i.e.,--1500 degrees to 3000 deg C. The ion source utilizes beams of electrons focused into a first chamber housing the material to be ionized to heat the material and thereby cause it to vaporize. An adjacent second chamber receives the vaporized material through an interconnecting passage, and ionization of the vaporized material occurs in this chamber. The ionization action is produced by an arc discharge sustained between a second clectron emitting filament and the walls of the chamber which are at different potentials. The resultant ionized material egresses from a passageway in the second chamber. Using this device, materials which in the past could not be processed in mass spectometers may be satisfactorily ionized for such applications.

  3. Positron beam optics for the 2D-ACAR spectrometer at the NEPOMUC beamline

    NASA Astrophysics Data System (ADS)

    Ceeh, H.; Weber, J. A.; Hugenschmidt, C.; Leitner, M.; Boni, P.

    2014-04-01

    In the last year a conventional 2D-ACAR spectrometer has been set up and brought to operation at TUM. Once the NEPOMUC beamline is extended to the new experimental hall at the research reactor FRM-II the conventional 2D-ACAR spectrometer will be upgraded with a second sample chamber in order to be integrated to the NEPOMUC beamline facility. This spectrometer will add a complete new quality to 2D-ACAR experiments as it allows to track the evolution of the electronic structure from the surface to the bulk. We present the design features of the positron beam optics and the sample environment.

  4. Perspectives for spintronics in 2D materials

    NASA Astrophysics Data System (ADS)

    Han, Wei

    2016-03-01

    The past decade has been especially creative for spintronics since the (re)discovery of various two dimensional (2D) materials. Due to the unusual physical characteristics, 2D materials have provided new platforms to probe the spin interaction with other degrees of freedom for electrons, as well as to be used for novel spintronics applications. This review briefly presents the most important recent and ongoing research for spintronics in 2D materials.

  5. Quantitative 2D liquid-state NMR.

    PubMed

    Giraudeau, Patrick

    2014-06-01

    Two-dimensional (2D) liquid-state NMR has a very high potential to simultaneously determine the absolute concentration of small molecules in complex mixtures, thanks to its capacity to separate overlapping resonances. However, it suffers from two main drawbacks that probably explain its relatively late development. First, the 2D NMR signal is strongly molecule-dependent and site-dependent; second, the long duration of 2D NMR experiments prevents its general use for high-throughput quantitative applications and affects its quantitative performance. Fortunately, the last 10 years has witnessed an increasing number of contributions where quantitative approaches based on 2D NMR were developed and applied to solve real analytical issues. This review aims at presenting these recent efforts to reach a high trueness and precision in quantitative measurements by 2D NMR. After highlighting the interest of 2D NMR for quantitative analysis, the different strategies to determine the absolute concentrations from 2D NMR spectra are described and illustrated by recent applications. The last part of the manuscript concerns the recent development of fast quantitative 2D NMR approaches, aiming at reducing the experiment duration while preserving - or even increasing - the analytical performance. We hope that this comprehensive review will help readers to apprehend the current landscape of quantitative 2D NMR, as well as the perspectives that may arise from it.

  6. Charge exchange molecular ion source

    DOEpatents

    Vella, Michael C.

    2003-06-03

    Ions, particularly molecular ions with multiple dopant nucleons per ion, are produced by charge exchange. An ion source contains a minimum of two regions separated by a physical barrier and utilizes charge exchange to enhance production of a desired ion species. The essential elements are a plasma chamber for production of ions of a first species, a physical separator, and a charge transfer chamber where ions of the first species from the plasma chamber undergo charge exchange or transfer with the reactant atom or molecules to produce ions of a second species. Molecular ions may be produced which are useful for ion implantation.

  7. Staring 2-D hadamard transform spectral imager

    DOEpatents

    Gentry, Stephen M.; Wehlburg, Christine M.; Wehlburg, Joseph C.; Smith, Mark W.; Smith, Jody L.

    2006-02-07

    A staring imaging system inputs a 2D spatial image containing multi-frequency spectral information. This image is encoded in one dimension of the image with a cyclic Hadamarid S-matrix. The resulting image is detecting with a spatial 2D detector; and a computer applies a Hadamard transform to recover the encoded image.

  8. CONTINUOUS ROTATION SCATTERING CHAMBER

    DOEpatents

    Verba, J.W.; Hawrylak, R.A.

    1963-08-01

    An evacuated scattering chamber for use in observing nuclear reaction products produced therein over a wide range of scattering angles from an incoming horizontal beam that bombards a target in the chamber is described. A helically moving member that couples the chamber to a detector permits a rapid and broad change of observation angles without breaching the vacuum in the chamber. Also, small inlet and outlet openings are provided whose size remains substantially constant. (auth)

  9. 2D materials for nanophotonic devices

    NASA Astrophysics Data System (ADS)

    Xu, Renjing; Yang, Jiong; Zhang, Shuang; Pei, Jiajie; Lu, Yuerui

    2015-12-01

    Two-dimensional (2D) materials have become very important building blocks for electronic, photonic, and phononic devices. The 2D material family has four key members, including the metallic graphene, transition metal dichalcogenide (TMD) layered semiconductors, semiconducting black phosphorous, and the insulating h-BN. Owing to the strong quantum confinements and defect-free surfaces, these atomically thin layers have offered us perfect platforms to investigate the interactions among photons, electrons and phonons. The unique interactions in these 2D materials are very important for both scientific research and application engineering. In this talk, I would like to briefly summarize and highlight the key findings, opportunities and challenges in this field. Next, I will introduce/highlight our recent achievements. We demonstrated atomically thin micro-lens and gratings using 2D MoS2, which is the thinnest optical component around the world. These devices are based on our discovery that the elastic light-matter interactions in highindex 2D materials is very strong. Also, I would like to introduce a new two-dimensional material phosphorene. Phosphorene has strongly anisotropic optical response, which creates 1D excitons in a 2D system. The strong confinement in phosphorene also enables the ultra-high trion (charged exciton) binding energies, which have been successfully measured in our experiments. Finally, I will briefly talk about the potential applications of 2D materials in energy harvesting.

  10. Internal Photoemission Spectroscopy of 2-D Materials

    NASA Astrophysics Data System (ADS)

    Nguyen, Nhan; Li, Mingda; Vishwanath, Suresh; Yan, Rusen; Xiao, Shudong; Xing, Huili; Cheng, Guangjun; Hight Walker, Angela; Zhang, Qin

    Recent research has shown the great benefits of using 2-D materials in the tunnel field-effect transistor (TFET), which is considered a promising candidate for the beyond-CMOS technology. The on-state current of TFET can be enhanced by engineering the band alignment of different 2D-2D or 2D-3D heterostructures. Here we present the internal photoemission spectroscopy (IPE) approach to determine the band alignments of various 2-D materials, in particular SnSe2 and WSe2, which have been proposed for new TFET designs. The metal-oxide-2-D semiconductor test structures are fabricated and characterized by IPE, where the band offsets from the 2-D semiconductor to the oxide conduction band minimum are determined by the threshold of the cube root of IPE yields as a function of photon energy. In particular, we find that SnSe2 has a larger electron affinity than most semiconductors and can be combined with other semiconductors to form near broken-gap heterojunctions with low barrier heights which can produce a higher on-state current. The details of data analysis of IPE and the results from Raman spectroscopy and spectroscopic ellipsometry measurements will also be presented and discussed.

  11. Two chamber reaction furnace

    DOEpatents

    Blaugher, R.D.

    1998-05-05

    A vertical two chamber reaction furnace is described. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium-copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700 C and 800 C) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800 to 950 C to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product. 2 figs.

  12. Two chamber reaction furnace

    DOEpatents

    Blaugher, Richard D.

    1998-05-05

    A vertical two chamber reaction furnace. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium-copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700.degree. and 800.degree. C.) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800.degree. to 950.degree. C. to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product.

  13. In vivo fluorescence kinetics of phthalocyanines in a skin-fold observation chamber model: role of central metal ion and degree of sulfonation.

    PubMed

    van Leengoed, H L; van der Veen, N; Versteeg, A A; Ouellet, R; van Lier, J E; Star, W M

    1993-08-01

    The fluorescence pharmacokinetics of a series of metallosulfophthalocyanines, chelated with either aluminum or zinc and sulfonated to different degrees, was studied by fluorescence measurements in vivo. Dyes were administered systemically to female WAG/RIJ rats with an isogeneic mammary carcinoma transplanted into the subcutis in a transparent observation chamber located on their backs. Following an intravenous injection of 2.5 mumol/kg of the dye, fluorescence dynamics was observed up to 7 h postinjection. The phthalocyanines were excited at 610 nm with a power density of 0.1 mW/cm2 without causing photodynamic damage to the vasculature. Fluorescence was detected above 665 nm using a fluorescence imaging system based on an image intensifier. Dye retention in the blood vessels and tumor tissue was expressed as ratios relative to the fluorescence signal of the surrounding subcutaneous tissue. Phthalocyanines chelated with aluminum gave the highest fluorescence signal with tumor-over-subcutis ratios of up to a value of 4. The zinc complexes exhibited the highest vascular-over-subcutis ratios with maximum values exceeding a value of 6. They also displayed the longest retention times in the vascular system of well over 7 h. Overall, decreasing the degree of sulfonation of the metallophthalocyanines results in lower tumor-over-normal tissue fluorescence ratios, and furthermore aluminum-based dyes seem superior tumor localizers over zinc-based dyes. The advantages of phthalocyanines over porphyrins with respect to tumor localization and photodynamic therapy are discussed.

  14. 2D materials: to graphene and beyond.

    PubMed

    Mas-Ballesté, Rubén; Gómez-Navarro, Cristina; Gómez-Herrero, Julio; Zamora, Félix

    2011-01-01

    This review is an attempt to illustrate the different alternatives in the field of 2D materials. Graphene seems to be just the tip of the iceberg and we show how the discovery of alternative 2D materials is starting to show the rest of this iceberg. The review comprises the current state-of-the-art of the vast literature in concepts and methods already known for isolation and characterization of graphene, and rationalizes the quite disperse literature in other 2D materials such as metal oxides, hydroxides and chalcogenides, and metal-organic frameworks.

  15. 2D-2D tunneling field-effect transistors using WSe2/SnSe2 heterostructures

    NASA Astrophysics Data System (ADS)

    Roy, Tania; Tosun, Mahmut; Hettick, Mark; Ahn, Geun Ho; Hu, Chenming; Javey, Ali

    2016-02-01

    Two-dimensional materials present a versatile platform for developing steep transistors due to their uniform thickness and sharp band edges. We demonstrate 2D-2D tunneling in a WSe2/SnSe2 van der Waals vertical heterojunction device, where WSe2 is used as the gate controlled p-layer and SnSe2 is the degenerately n-type layer. The van der Waals gap facilitates the regulation of band alignment at the heterojunction, without the necessity of a tunneling barrier. ZrO2 is used as the gate dielectric, allowing the scaling of gate oxide to improve device subthreshold swing. Efficient gate control and clean interfaces yield a subthreshold swing of ˜100 mV/dec for >2 decades of drain current at room temperature, hitherto unobserved in 2D-2D tunneling devices. The subthreshold swing is independent of temperature, which is a clear signature of band-to-band tunneling at the heterojunction. A maximum switching ratio ION/IOFF of 107 is obtained. Negative differential resistance in the forward bias characteristics is observed at 77 K. This work bodes well for the possibilities of two-dimensional materials for the realization of energy-efficient future-generation electronics.

  16. 2-d Finite Element Code Postprocessor

    1996-07-15

    ORION is an interactive program that serves as a postprocessor for the analysis programs NIKE2D, DYNA2D, TOPAZ2D, and CHEMICAL TOPAZ2D. ORION reads binary plot files generated by the two-dimensional finite element codes currently used by the Methods Development Group at LLNL. Contour and color fringe plots of a large number of quantities may be displayed on meshes consisting of triangular and quadrilateral elements. ORION can compute strain measures, interface pressures along slide lines, reaction forcesmore » along constrained boundaries, and momentum. ORION has been applied to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.« less

  17. Matrix models of 2d gravity

    SciTech Connect

    Ginsparg, P.

    1991-01-01

    These are introductory lectures for a general audience that give an overview of the subject of matrix models and their application to random surfaces, 2d gravity, and string theory. They are intentionally 1.5 years out of date.

  18. Matrix models of 2d gravity

    SciTech Connect

    Ginsparg, P.

    1991-12-31

    These are introductory lectures for a general audience that give an overview of the subject of matrix models and their application to random surfaces, 2d gravity, and string theory. They are intentionally 1.5 years out of date.

  19. Brittle damage models in DYNA2D

    SciTech Connect

    Faux, D.R.

    1997-09-01

    DYNA2D is an explicit Lagrangian finite element code used to model dynamic events where stress wave interactions influence the overall response of the system. DYNA2D is often used to model penetration problems involving ductile-to-ductile impacts; however, with the advent of the use of ceramics in the armor-anti-armor community and the need to model damage to laser optics components, good brittle damage models are now needed in DYNA2D. This report will detail the implementation of four brittle damage models in DYNA2D, three scalar damage models and one tensor damage model. These new brittle damage models are then used to predict experimental results from three distinctly different glass damage problems.

  20. Gas Electron Multiplier (GEM) Chamber Characteristics Test

    SciTech Connect

    Yu, Jaehoon; White, Andy; Park, Seongtae; Hahn, Changhie; Baldeloma, Edwin; Tran, Nam; McIntire, Austin; Soha, Aria; /Fermilab

    2011-01-11

    Gas Electron Multipliers (GEMs) have been used in many HEP experiments as tracking detectors. They are sensitive to X-rays which allows use beyond that of HEP. The UTA High Energy group has been working on using GEMs as the sensitive gap detector in a DHCAL for the ILC. The physics goals at the ILC put a stringent requirement on detector performance. Especially the precision required for jet mass and positions demands an unprecedented jet energy resolution to hadronic calorimeters. A solution to meet this requirement is using the Particle Flow Algorithm (PFA). In order for PFA to work well, high calorimeter granularity is necessary. Previous studies based on GEANT simulations using GEM DHCAL gave confidence on the performance of GEM in the sensitive gap in a sampling calorimeter and its use as a DHCAL in PFA. The UTA HEP team has built several GEM prototype chambers, including the current 30cm x 30cm chamber integrated with the SLAC-developed 64 channel kPiX analog readout chip. This chamber has been tested on the bench using radioactive sources and cosmic ray muons. In order to have fuller understanding of various chamber characteristics, the experiments plan to expose 1-3 GEM chambers of dimension 35cm x 35cm x 5cm with 1cm x 1cm pad granularity with 64 channel 2-D simultaneous readout using the kPiX chip. In this experiment the experiments pan to measure MiP signal height, chamber absolute efficiencies, chamber gain versus high voltage across the GEM gap, the uniformity of the chamber across the 8cm x 8cm area, cross talk and its distance dependence to the triggered pad, chamber rate capabilities, and the maximum pad occupancy rate.

  1. Chemical Approaches to 2D Materials.

    PubMed

    Samorì, Paolo; Palermo, Vincenzo; Feng, Xinliang

    2016-08-01

    Chemistry plays an ever-increasing role in the production, functionalization, processing and applications of graphene and other 2D materials. This special issue highlights a selection of enlightening chemical approaches to 2D materials, which nicely reflect the breadth of the field and convey the excitement of the individuals involved in it, who are trying to translate graphene and related materials from the laboratory into a real, high-impact technology. PMID:27478083

  2. Chemical Approaches to 2D Materials.

    PubMed

    Samorì, Paolo; Palermo, Vincenzo; Feng, Xinliang

    2016-08-01

    Chemistry plays an ever-increasing role in the production, functionalization, processing and applications of graphene and other 2D materials. This special issue highlights a selection of enlightening chemical approaches to 2D materials, which nicely reflect the breadth of the field and convey the excitement of the individuals involved in it, who are trying to translate graphene and related materials from the laboratory into a real, high-impact technology.

  3. Stove with multiple chambers

    SciTech Connect

    Black, A.

    1987-04-21

    A stove is described for burning a solid fuel such as wood. The wall means defines a main air inlet, a combustion gas outlet, and four chambers through which gas passes sequentially from the main air inlet to the combustion gas outlet. The chambers comprises a pre-heat plenum chamber into which the main air inlet opens. A main combustion chamber contains solid fuel to be burned into which gas passes from the pre-heat plenum chamber, a second combustion chamber which is downstream of the main combustion chamber with respect to the flow of gas from the main air inlet to the combustion gas outlet, and a third combustion chamber from which the combustion gas outlet opens. The stove also comprises a plate having a restricted opening for providing communication between the second and third combustion chambers. And a catalytic converter comprises a body of solid material formed with passageways, the body of solid material being fitted in the restricted opening so that gas passes from the second combustion chamber to the third combustion chamber by way of the passageways in the body.

  4. Glitter in a 2D monolayer.

    PubMed

    Yang, Li-Ming; Dornfeld, Matthew; Frauenheim, Thomas; Ganz, Eric

    2015-10-21

    We predict a highly stable and robust atomically thin gold monolayer with a hexagonal close packed lattice stabilized by metallic bonding with contributions from strong relativistic effects and aurophilic interactions. We have shown that the framework of the Au monolayer can survive 10 ps MD annealing simulations up to 1400 K. The framework is also able to survive large motions out of the plane. Due to the smaller number of bonds per atom in the 2D layer compared to the 3D bulk we observe significantly enhanced energy per bond (0.94 vs. 0.52 eV per bond). This is similar to the increase in bond strength going from 3D diamond to 2D graphene. It is a non-magnetic metal, and was found to be the global minima in the 2D space. Phonon dispersion calculations demonstrate high kinetic stability with no negative modes. This 2D gold monolayer corresponds to the top monolayer of the bulk Au(111) face-centered cubic lattice. The close-packed lattice maximizes the aurophilic interactions. We find that the electrons are completely delocalized in the plane and behave as 2D nearly free electron gas. We hope that the present work can inspire the experimental fabrication of novel free standing 2D metal systems.

  5. 2d index and surface operators

    NASA Astrophysics Data System (ADS)

    Gadde, Abhijit; Gukov, Sergei

    2014-03-01

    In this paper we compute the superconformal index of 2d (2, 2) supersymmetric gauge theories. The 2d superconformal index, a.k.a. flavored elliptic genus, is computed by a unitary matrix integral much like the matrix integral that computes the 4d superconformal index. We compute the 2d index explicitly for a number of examples. In the case of abelian gauge theories we see that the index is invariant under flop transition and under CY-LG correspondence. The index also provides a powerful check of the Seiberg-type duality for non-abelian gauge theories discovered by Hori and Tong. In the later half of the paper, we study half-BPS surface operators in = 2 super-conformal gauge theories. They are engineered by coupling the 2d (2, 2) supersymmetric gauge theory living on the support of the surface operator to the 4d = 2 theory, so that different realizations of the same surface operator with a given Levi type are related by a 2d analogue of the Seiberg duality. The index of this coupled system is computed by using the tools developed in the first half of the paper. The superconformal index in the presence of surface defect is expected to be invariant under generalized S-duality. We demonstrate that it is indeed the case. In doing so the Seiberg-type duality of the 2d theory plays an important role.

  6. ION SOURCE

    DOEpatents

    Leland, W.T.

    1960-01-01

    The ion source described essentially eliminater the problem of deposits of nonconducting materials forming on parts of the ion source by certain corrosive gases. This problem is met by removing both filament and trap from the ion chamber, spacing them apart and outside the chamber end walls, placing a focusing cylinder about the filament tip to form a thin collimated electron stream, aligning the cylinder, slits in the walls, and trap so that the electron stream does not bombard any part in the source, and heating the trap, which is bombarded by electrons, to a temperature hotter than that in the ion chamber, so that the tendency to build up a deposit caused by electron bombardment is offset by the extra heating supplied only to the trap.

  7. Small SRS photon field profile dosimetry performed using a PinPoint air ion chamber, a diamond detector, a novel silicon-diode array (DOSI), and polymer gel dosimetry. Analysis and intercomparison.

    PubMed

    Pappas, E; Maris, T G; Zacharopoulou, F; Papadakis, A; Manolopoulos, S; Green, S; Wojnecki, C

    2008-10-01

    Small photon fields are increasingly used in modern radiotherapy and especially in IMRT and SRS/SRT treatments. The uncertainties related to small field profile measurements can introduce significant systematic errors to the overall treatment process. These measurements are challenging mainly due to the absence of charged particle equilibrium conditions, detector size and composition effects, and positioning problems. In this work four different dosimetric methods have been used to measure the profiles of three small 6 MV circular fields having diameters of 7.5, 15.0, and 30.0 mm: a small sensitive volume air ion chamber, a diamond detector, a novel silicon-diode array (DOSI), and vinyl-pyrrolidone based polymer gel dosimeter. The results of this work support the validity of previous findings, suggesting that (a) air ion chambers are not suitable for small field dosimetry since they result in penumbra broadening and require significant corrections due to severe charged particle transport alterations; (b) diamond detectors provide high resolution and rather accurate small field profile measurements, as long as positioning problems can be addressed and the necessary dose rate corrections are correctly applied; and (c) the novel silicon-diode array (DOSI) used in this study seems to be adequate for small field profile measurements overcoming positioning problems. Polymer gel data were assumed as reference data to which the other measurement data were compared both qualitatively and quantitatively using the gamma-index concept. Polymer gels are both phantom and dosimeter, hence there are no beam perturbation effects. In addition, polymer gels are tissue equivalent and can provide high-spatial density and high-spatial resolution measurements without positioning problems, which makes them useful for small field dosimetry measurements. This work emphasizes the need to perform beam profile measurements of small fields (for acceptance, commissioning, treatment planning

  8. Orthotropic Piezoelectricity in 2D Nanocellulose

    NASA Astrophysics Data System (ADS)

    García, Y.; Ruiz-Blanco, Yasser B.; Marrero-Ponce, Yovani; Sotomayor-Torres, C. M.

    2016-10-01

    The control of electromechanical responses within bonding regions is essential to face frontier challenges in nanotechnologies, such as molecular electronics and biotechnology. Here, we present Iβ-nanocellulose as a potentially new orthotropic 2D piezoelectric crystal. The predicted in-layer piezoelectricity is originated on a sui-generis hydrogen bonds pattern. Upon this fact and by using a combination of ab-initio and ad-hoc models, we introduce a description of electrical profiles along chemical bonds. Such developments lead to obtain a rationale for modelling the extended piezoelectric effect originated within bond scales. The order of magnitude estimated for the 2D Iβ-nanocellulose piezoelectric response, ~pm V‑1, ranks this material at the level of currently used piezoelectric energy generators and new artificial 2D designs. Such finding would be crucial for developing alternative materials to drive emerging nanotechnologies.

  9. Orthotropic Piezoelectricity in 2D Nanocellulose

    PubMed Central

    García, Y.; Ruiz-Blanco, Yasser B.; Marrero-Ponce, Yovani; Sotomayor-Torres, C. M.

    2016-01-01

    The control of electromechanical responses within bonding regions is essential to face frontier challenges in nanotechnologies, such as molecular electronics and biotechnology. Here, we present Iβ-nanocellulose as a potentially new orthotropic 2D piezoelectric crystal. The predicted in-layer piezoelectricity is originated on a sui-generis hydrogen bonds pattern. Upon this fact and by using a combination of ab-initio and ad-hoc models, we introduce a description of electrical profiles along chemical bonds. Such developments lead to obtain a rationale for modelling the extended piezoelectric effect originated within bond scales. The order of magnitude estimated for the 2D Iβ-nanocellulose piezoelectric response, ~pm V−1, ranks this material at the level of currently used piezoelectric energy generators and new artificial 2D designs. Such finding would be crucial for developing alternative materials to drive emerging nanotechnologies. PMID:27708364

  10. 2D microwave imaging reflectometer electronics

    SciTech Connect

    Spear, A. G.; Domier, C. W. Hu, X.; Muscatello, C. M.; Ren, X.; Luhmann, N. C.; Tobias, B. J.

    2014-11-15

    A 2D microwave imaging reflectometer system has been developed to visualize electron density fluctuations on the DIII-D tokamak. Simultaneously illuminated at four probe frequencies, large aperture optics image reflections from four density-dependent cutoff surfaces in the plasma over an extended region of the DIII-D plasma. Localized density fluctuations in the vicinity of the plasma cutoff surfaces modulate the plasma reflections, yielding a 2D image of electron density fluctuations. Details are presented of the receiver down conversion electronics that generate the in-phase (I) and quadrature (Q) reflectometer signals from which 2D density fluctuation data are obtained. Also presented are details on the control system and backplane used to manage the electronics as well as an introduction to the computer based control program.

  11. Optical modulators with 2D layered materials

    NASA Astrophysics Data System (ADS)

    Sun, Zhipei; Martinez, Amos; Wang, Feng

    2016-04-01

    Light modulation is an essential operation in photonics and optoelectronics. With existing and emerging technologies increasingly demanding compact, efficient, fast and broadband optical modulators, high-performance light modulation solutions are becoming indispensable. The recent realization that 2D layered materials could modulate light with superior performance has prompted intense research and significant advances, paving the way for realistic applications. In this Review, we cover the state of the art of optical modulators based on 2D materials, including graphene, transition metal dichalcogenides and black phosphorus. We discuss recent advances employing hybrid structures, such as 2D heterostructures, plasmonic structures, and silicon and fibre integrated structures. We also take a look at the future perspectives and discuss the potential of yet relatively unexplored mechanisms, such as magneto-optic and acousto-optic modulation.

  12. Effects of ionization chamber construction on dose measurements in a heterogeneity

    SciTech Connect

    Mauceri, T.; Kase, K.

    1987-07-01

    Traditionally, measurements have been made in heterogeneous phantoms to determine the factors which should be applied to dose calculations, when calculating a dose to a heterogeneous medium. Almost all measurements have relied on relatively thin-walled ion chambers, with no attempt to match ion chamber wall material to the measuring medium. The recent AAPM dosimetry protocol has established that a mismatch between ion chamber wall and phantom material can have an effect on dose measurement. To investigate the affect of this mismatch of ion chamber wall material to phantom material, two parallel-plate ion chambers were constructed. One ion chamber from solid water, for measurements in a solid water phantom and the other from plastic lung material, for measurements in a plastic lung material phantom. Correction factors measured by matching ion chamber to media were compared to correction factors measured by using a thin-walled cavity ion chamber with no regard for matching wall and media for cobalt-60, 6-, 10- and 20-MV photon beams. The results demonstrated that the matching of ion chamber to measuring media can be ignored, provided that a small, approximately tissue-equivalent, thin-walled ion chamber is used for measuring the correction factors.

  13. Dual mode ion mobility spectrometer and method for ion mobility spectrometry

    DOEpatents

    Scott, Jill R [Idaho Falls, ID; Dahl, David A [Idaho Falls, ID; Miller, Carla J [Idaho Falls, ID; Tremblay, Paul L [Idaho Falls, ID; McJunkin, Timothy R [Idaho Falls, ID

    2007-08-21

    Ion mobility spectrometer apparatus may include an ion interface that is operable to hold positive and negative ions and to simultaneously release positive and negative ions through respective positive and negative ion ports. A first drift chamber is operatively associated with the positive ion port of the ion interface and encloses an electric field therein. A first ion detector operatively associated with the first drift chamber detects positive ions from the first drift chamber. A second drift chamber is operatively associated with the negative ion port of the ion interface and encloses an electric field therein. A second ion detector operatively associated with the second drift chamber detects negative ions from said second drift chamber.

  14. An Intercomparison of 2-D Models Within a Common Framework

    NASA Technical Reports Server (NTRS)

    Weisenstein, Debra K.; Ko, Malcolm K. W.; Scott, Courtney J.; Jackman, Charles H.; Fleming, Eric L.; Considine, David B.; Kinnison, Douglas E.; Connell, Peter S.; Rotman, Douglas A.; Bhartia, P. K. (Technical Monitor)

    2002-01-01

    A model intercomparison among the Atmospheric and Environmental Research (AER) 2-D model, the Goddard Space Flight Center (GSFC) 2-D model, and the Lawrence Livermore National Laboratory 2-D model allows us to separate differences due to model transport from those due to the model's chemical formulation. This is accomplished by constructing two hybrid models incorporating the transport parameters of the GSFC and LLNL models within the AER model framework. By comparing the results from the native models (AER and e.g. GSFC) with those from the hybrid model (e.g. AER chemistry with GSFC transport), differences due to chemistry and transport can be identified. For the analysis, we examined an inert tracer whose emission pattern is based on emission from a High Speed Civil Transport (HSCT) fleet; distributions of trace species in the 2015 atmosphere; and the response of stratospheric ozone to an HSCT fleet. Differences in NO(y) in the upper stratosphere are found between models with identical transport, implying different model representations of atmospheric chemical processes. The response of O3 concentration to HSCT aircraft emissions differs in the models from both transport-dominated differences in the HSCT-induced perturbations of H2O and NO(y) as well as from differences in the model represent at ions of O3 chemical processes. The model formulations of cold polar processes are found to be the most significant factor in creating large differences in the calculated ozone perturbations

  15. Inkjet printing of 2D layered materials.

    PubMed

    Li, Jiantong; Lemme, Max C; Östling, Mikael

    2014-11-10

    Inkjet printing of 2D layered materials, such as graphene and MoS2, has attracted great interests for emerging electronics. However, incompatible rheology, low concentration, severe aggregation and toxicity of solvents constitute critical challenges which hamper the manufacturing efficiency and product quality. Here, we introduce a simple and general technology concept (distillation-assisted solvent exchange) to efficiently overcome these challenges. By implementing the concept, we have demonstrated excellent jetting performance, ideal printing patterns and a variety of promising applications for inkjet printing of 2D layered materials. PMID:25169938

  16. Inkjet printing of 2D layered materials.

    PubMed

    Li, Jiantong; Lemme, Max C; Östling, Mikael

    2014-11-10

    Inkjet printing of 2D layered materials, such as graphene and MoS2, has attracted great interests for emerging electronics. However, incompatible rheology, low concentration, severe aggregation and toxicity of solvents constitute critical challenges which hamper the manufacturing efficiency and product quality. Here, we introduce a simple and general technology concept (distillation-assisted solvent exchange) to efficiently overcome these challenges. By implementing the concept, we have demonstrated excellent jetting performance, ideal printing patterns and a variety of promising applications for inkjet printing of 2D layered materials.

  17. Parallel stitching of 2D materials

    DOE PAGES

    Ling, Xi; Wu, Lijun; Lin, Yuxuan; Ma, Qiong; Wang, Ziqiang; Song, Yi; Yu, Lili; Huang, Shengxi; Fang, Wenjing; Zhang, Xu; et al

    2016-01-27

    Diverse parallel stitched 2D heterostructures, including metal–semiconductor, semiconductor–semiconductor, and insulator–semiconductor, are synthesized directly through selective “sowing” of aromatic molecules as the seeds in the chemical vapor deposition (CVD) method. Lastly, the methodology enables the large-scale fabrication of lateral heterostructures, which offers tremendous potential for its application in integrated circuits.

  18. Parallel Stitching of 2D Materials.

    PubMed

    Ling, Xi; Lin, Yuxuan; Ma, Qiong; Wang, Ziqiang; Song, Yi; Yu, Lili; Huang, Shengxi; Fang, Wenjing; Zhang, Xu; Hsu, Allen L; Bie, Yaqing; Lee, Yi-Hsien; Zhu, Yimei; Wu, Lijun; Li, Ju; Jarillo-Herrero, Pablo; Dresselhaus, Mildred; Palacios, Tomás; Kong, Jing

    2016-03-23

    Diverse parallel stitched 2D heterostructures, including metal-semiconductor, semiconductor-semiconductor, and insulator-semiconductor, are synthesized directly through selective "sowing" of aromatic molecules as the seeds in the chemical vapor deposition (CVD) method. The methodology enables the large-scale fabrication of lateral heterostructures, which offers tremendous potential for its application in integrated circuits.

  19. Target chambers for gammashpere

    SciTech Connect

    Carpenter, M.P.; Falout, J.W.; Nardi, B.G.

    1995-08-01

    One of our responsibilities for Gammasphere, was designing and constructing two target chambers and associated beamlines to be used with the spectrometer. The first chamber was used with the early implementation phase of Gammasphere, and consisted of two spun-Al hemispheres welded together giving a wall thickness of 0.063 inches and a diameter of 12 inches.

  20. Static diffusion cloud chambers

    NASA Technical Reports Server (NTRS)

    Ayers, G.

    1981-01-01

    The chamber geometry and optical arrangement are described. The supersaturation range is given and consists of readings taken at five fixed points: 0.25%, 0.5%, 0.75%, 1.0%, and 1.25%. The detection system is described including light source, cameras, and photocell detectors. The temperature control and the calibration of the chamber are discussed.

  1. A soundproof pressure chamber.

    PubMed

    Kitahara, M; Kodama, A; Ozawa, H; Inoue, S

    1994-01-01

    For neurotological research we designed a soundproof pressure chamber in which pressure can be adjusted +/- 1000 mmH2O at the rate of less than 100 mmH2O per second. Noise in the chamber can be maintained under 30-35 dB while pressure is kept at a given level.

  2. The Mobile Chamber

    NASA Technical Reports Server (NTRS)

    Scharfstein, Gregory; Cox, Russell

    2012-01-01

    A document discusses a simulation chamber that represents a shift from the thermal-vacuum chamber stereotype. This innovation, currently in development, combines the capabilities of space simulation chambers, the user-friendliness of modern-day electronics, and the modularity of plug-and-play computing. The Mobile Chamber is a customized test chamber that can be deployed with great ease, and is capable of bringing payloads at temperatures down to 20 K, in high vacuum, and with the desired metrology instruments integrated to the systems control. Flexure plans to lease Mobile Chambers, making them affordable for smaller budgets and available to a larger customer base. A key feature of this design will be an Apple iPad-like user interface that allows someone with minimal training to control the environment inside the chamber, and to simulate the required extreme environments. The feedback of thermal, pressure, and other measurements is delivered in a 3D CAD model of the chamber's payload and support hardware. This GUI will provide the user with a better understanding of the payload than any existing thermal-vacuum system.

  3. High resolution drift chambers

    SciTech Connect

    Va'vra, J.

    1985-07-01

    High precision drift chambers capable of achieving less than or equal to 50 ..mu..m resolutions are discussed. In particular, we compare so called cool and hot gases, various charge collection geometries, several timing techniques and we also discuss some systematic problems. We also present what we would consider an ''ultimate'' design of the vertex chamber. 50 refs., 36 figs., 6 tabs.

  4. Measurements of Shear Reduction of 2D Vortex Diffusion.

    NASA Astrophysics Data System (ADS)

    Driscoll, C. F.; Anderegg, F.; Dubin, D. H. E.

    2001-11-01

    Experiments with magnetized ion columns in the 2-dimensional regime demonstrate shear reduction of vortex diffusion, in close correspondence with recent theory.(D.H.E. Dubin, Phys. Lett. A 284), 112 (2001). Here, the ions move in ( r, θ ) as point vortices, and we can accurately control the vorticity ζ (r), fluid rotation Ω (r), and shear S (r) ≡ r ; partial Ω / partial r. Moreover, individual ions can be ``tagged,'' so that the vortex diffusion rate D can be measured directly. For flows with low shear, i.e. S / Ω <= 10-3, the measured diffusion is close to the Taylor-McNamara prediction for a homogeneous gas of N point vortices.(J.B. Taylor and B. McNamara, Phys. Fluids 14), 1492 (1971). As the shear is increased, the measured diffusion decreases by up to 100×, in factor-of-three correspondence with the predicted D ∝ S-1. For very large shear, the ions can no longer be treated as 2D point vortices, since their shear separation is faster than their axial transversal of the trap. In this limit, the measured diffusion agrees quantitatively with the theory of long-range 3D Coulomb collisions.

  5. Ion electric propulsion unit

    DOEpatents

    Light, Max E; Colestock, Patrick L

    2014-01-28

    An electron cyclotron resonance (ECR) thruster is disclosed having a plasma chamber which is electrically biased with a positive voltage. The chamber bias serves to efficiently accelerate and expel the positive ions from the chamber. Electrons follow the exiting ions, serving to provide an electrically neutral exhaust plume. In a further embodiment, a downstream shaping magnetic field serves to further accelerate and/or shape the exhaust plume.

  6. Large-format, high-speed, X-ray pnCCDs combined with electron and ion imaging spectrometers in a multipurpose chamber for experiments at 4th generation light sources

    NASA Astrophysics Data System (ADS)

    Strüder, Lothar; Epp, Sascha; Rolles, Daniel; Hartmann, Robert; Holl, Peter; Lutz, Gerhard; Soltau, Heike; Eckart, Rouven; Reich, Christian; Heinzinger, Klaus; Thamm, Christian; Rudenko, Artem; Krasniqi, Faton; Kühnel, Kai-Uwe; Bauer, Christian; Schröter, Claus-Dieter; Moshammer, Robert; Techert, Simone; Miessner, Danilo; Porro, Matteo; Hälker, Olaf; Meidinger, Norbert; Kimmel, Nils; Andritschke, Robert; Schopper, Florian; Weidenspointner, Georg; Ziegler, Alexander; Pietschner, Daniel; Herrmann, Sven; Pietsch, Ullrich; Walenta, Albert; Leitenberger, Wolfram; Bostedt, Christoph; Möller, Thomas; Rupp, Daniela; Adolph, Marcus; Graafsma, Heinz; Hirsemann, Helmut; Gärtner, Klaus; Richter, Rainer; Foucar, Lutz; Shoeman, Robert L.; Schlichting, Ilme; Ullrich, Joachim

    2010-03-01

    Fourth generation accelerator-based light sources, such as VUV and X-ray Free Electron Lasers (FEL), deliver ultra-brilliant (˜10 12-10 13 photons per bunch) coherent radiation in femtosecond (˜10-100 fs) pulses and, thus, require novel focal plane instrumentation in order to fully exploit their unique capabilities. As an additional challenge for detection devices, existing (FLASH, Hamburg) and future FELs (LCLS, Menlo Park; SCSS, Hyogo and the European XFEL, Hamburg) cover a broad range of photon energies from the EUV to the X-ray regime with significantly different bandwidths and pulse structures reaching up to MHz micro-bunch repetition rates. Moreover, hundreds up to trillions of fragment particles, ions, electrons or scattered photons can emerge when a single light flash impinges on matter with intensities up to 10 22 W/cm 2. In order to meet these challenges, the Max Planck Advanced Study Group (ASG) within the Center for Free Electron Laser Science (CFEL) has designed the CFEL-ASG MultiPurpose (CAMP) chamber. It is equipped with specially developed photon and charged particle detection devices dedicated to cover large solid-angles. A variety of different targets are supported, such as atomic, (aligned) molecular and cluster jets, particle injectors for bio-samples or fixed target arrangements. CAMP houses 4π solid-angle ion and electron momentum imaging spectrometers ("reaction microscope", REMI, or "velocity map imaging", VMI) in a unique combination with novel, large-area, broadband (50 eV-25 keV), high-dynamic-range, single-photon-counting and imaging X-ray detectors based on the pnCCDs. This instrumentation allows a new class of coherent diffraction experiments in which both electron and ion emission from the target may be simultaneously monitored. This permits the investigation of dynamic processes in this new regime of ultra-intense, high-energy radiation—matter interaction. After an introduction into the salient features of the CAMP chamber and

  7. Application of 2D Non-Graphene Materials and 2D Oxide Nanostructures for Biosensing Technology

    PubMed Central

    Shavanova, Kateryna; Bakakina, Yulia; Burkova, Inna; Shtepliuk, Ivan; Viter, Roman; Ubelis, Arnolds; Beni, Valerio; Starodub, Nickolaj; Yakimova, Rositsa; Khranovskyy, Volodymyr

    2016-01-01

    The discovery of graphene and its unique properties has inspired researchers to try to invent other two-dimensional (2D) materials. After considerable research effort, a distinct “beyond graphene” domain has been established, comprising the library of non-graphene 2D materials. It is significant that some 2D non-graphene materials possess solid advantages over their predecessor, such as having a direct band gap, and therefore are highly promising for a number of applications. These applications are not limited to nano- and opto-electronics, but have a strong potential in biosensing technologies, as one example. However, since most of the 2D non-graphene materials have been newly discovered, most of the research efforts are concentrated on material synthesis and the investigation of the properties of the material. Applications of 2D non-graphene materials are still at the embryonic stage, and the integration of 2D non-graphene materials into devices is scarcely reported. However, in recent years, numerous reports have blossomed about 2D material-based biosensors, evidencing the growing potential of 2D non-graphene materials for biosensing applications. This review highlights the recent progress in research on the potential of using 2D non-graphene materials and similar oxide nanostructures for different types of biosensors (optical and electrochemical). A wide range of biological targets, such as glucose, dopamine, cortisol, DNA, IgG, bisphenol, ascorbic acid, cytochrome and estradiol, has been reported to be successfully detected by biosensors with transducers made of 2D non-graphene materials. PMID:26861346

  8. Application of 2D Non-Graphene Materials and 2D Oxide Nanostructures for Biosensing Technology.

    PubMed

    Shavanova, Kateryna; Bakakina, Yulia; Burkova, Inna; Shtepliuk, Ivan; Viter, Roman; Ubelis, Arnolds; Beni, Valerio; Starodub, Nickolaj; Yakimova, Rositsa; Khranovskyy, Volodymyr

    2016-01-01

    The discovery of graphene and its unique properties has inspired researchers to try to invent other two-dimensional (2D) materials. After considerable research effort, a distinct "beyond graphene" domain has been established, comprising the library of non-graphene 2D materials. It is significant that some 2D non-graphene materials possess solid advantages over their predecessor, such as having a direct band gap, and therefore are highly promising for a number of applications. These applications are not limited to nano- and opto-electronics, but have a strong potential in biosensing technologies, as one example. However, since most of the 2D non-graphene materials have been newly discovered, most of the research efforts are concentrated on material synthesis and the investigation of the properties of the material. Applications of 2D non-graphene materials are still at the embryonic stage, and the integration of 2D non-graphene materials into devices is scarcely reported. However, in recent years, numerous reports have blossomed about 2D material-based biosensors, evidencing the growing potential of 2D non-graphene materials for biosensing applications. This review highlights the recent progress in research on the potential of using 2D non-graphene materials and similar oxide nanostructures for different types of biosensors (optical and electrochemical). A wide range of biological targets, such as glucose, dopamine, cortisol, DNA, IgG, bisphenol, ascorbic acid, cytochrome and estradiol, has been reported to be successfully detected by biosensors with transducers made of 2D non-graphene materials.

  9. Ion detector

    DOEpatents

    Tullis, Andrew M.

    1987-01-01

    An improved ion detector device of the ionization detection device chamber ype comprises an ionization chamber having a central electrode therein surrounded by a cylindrical electrode member within the chamber with a collar frictionally fitted around at least one of the electrodes. The collar has electrical contact means carried in an annular groove in an inner bore of the collar to contact the outer surface of the electrode to provide electrical contact between an external terminal and the electrode without the need to solder leads to the electrode.

  10. SU-E-T-77: Comparison of 2D and 3D Gamma Analysis in Patient-Specific QA for Prostate VMAT Plans

    SciTech Connect

    Clemente, F; Perez, C

    2014-06-01

    Purpose: Patient-specific QA procedures for IMRT and VMAT are traditionally performed by comparing TPS calculations with measured single point values and plane dose distributions by means of gamma analysis. New QA devices permit us to calculate 3D dose distributions on patient anatomy as redundant secondary check and reconstruct it from measurements taken with 2D and 3D detector arrays. 3D dose calculations allow us to perform DVH-based comparisons with clinical relevance, as well as 3D gamma analysis. One of these systems (Compass, IBA Dosimetry) combines traditional 2D with new anatomical-based 3D gamma analysis. This work shows the ability of this system by comparing 2D and 3D gamma analysis in pre-treatment QA for several VMAT prostate plans. Methods: Compass is capable of calculating dose as secondary check from DICOM TPS data and reconstructing it from measurements taken by a 2D ion chamber array (MatriXX Evolution, IBA Dosimetry). Both 2D and 3D gamma tests are available to compare calculated and reconstructed dose in Compass with TPS RT Dose. Results: 15 VMAT prostate plans have been measured with Compass. Dose is reconstructed with Compass for these plans. 2D gamma comparisons can be done for any plane from dose matrix. Mean gamma passing rates for isocenter planes (axial, coronal, sagittal) are (99.7±0.2)%, (99.9±0.1)%, (99.9±0.1)% for reconstructed dose planes. 3D mean gamma passing rates are (98.5±1.7)% for PTVs, (99.1±1.5)% for rectum, (100.0±0.0)% for bladder, (99.6±0.7)% for femoral heads and (98.1±4.1)% for penile bulb. Conclusion: Compass is a powerful tool to perform a complete pre-treatment QA analysis, from 2D techniques to 3D DVH-based techniques with clinical relevance. All reported values for VMAT prostate plans are in good agreement with TPS values. This system permits us to ensure the accuracy in the delivery of VMAT treatments completing a full patient-specific QA program.

  11. Investigations on the sensitivity of the computer code TURBO-2D

    NASA Astrophysics Data System (ADS)

    Amon, B.

    1994-12-01

    The two-dimensional computer model TURBO-2D for the calculation of two-phase flow was used to calculate the cold injection of fuel into a model chamber. Investigations of the influence of the input parameter on its sensitivity relative to the obtained results were made. In addition to that calculations were performed and compared using experimental injection pressure data and corresponding averaged injection parameter.

  12. 45. AUXILIARY CHAMBER BETWEEN CHAMBER AND CONCRETE ENCLOSURE (LOCATION DDD), ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    45. AUXILIARY CHAMBER BETWEEN CHAMBER AND CONCRETE ENCLOSURE (LOCATION DDD), VIEW LOOKING EAST. LEAD ENCLOSED PIPING IS DRAIN FROM BOILER CHAMBER No. 1 - Shippingport Atomic Power Station, On Ohio River, 25 miles Northwest of Pittsburgh, Shippingport, Beaver County, PA

  13. Stochastic Inversion of 2D Magnetotelluric Data

    SciTech Connect

    Chen, Jinsong

    2010-07-01

    The algorithm is developed to invert 2D magnetotelluric (MT) data based on sharp boundary parametrization using a Bayesian framework. Within the algorithm, we consider the locations and the resistivity of regions formed by the interfaces are as unknowns. We use a parallel, adaptive finite-element algorithm to forward simulate frequency-domain MT responses of 2D conductivity structure. Those unknown parameters are spatially correlated and are described by a geostatistical model. The joint posterior probability distribution function is explored by Markov Chain Monte Carlo (MCMC) sampling methods. The developed stochastic model is effective for estimating the interface locations and resistivity. Most importantly, it provides details uncertainty information on each unknown parameter. Hardware requirements: PC, Supercomputer, Multi-platform, Workstation; Software requirements C and Fortan; Operation Systems/version is Linux/Unix or Windows

  14. Explicit 2-D Hydrodynamic FEM Program

    1996-08-07

    DYNA2D* is a vectorized, explicit, two-dimensional, axisymmetric and plane strain finite element program for analyzing the large deformation dynamic and hydrodynamic response of inelastic solids. DYNA2D* contains 13 material models and 9 equations of state (EOS) to cover a wide range of material behavior. The material models implemented in all machine versions are: elastic, orthotropic elastic, kinematic/isotropic elastic plasticity, thermoelastoplastic, soil and crushable foam, linear viscoelastic, rubber, high explosive burn, isotropic elastic-plastic, temperature-dependent elastic-plastic. Themore » isotropic and temperature-dependent elastic-plastic models determine only the deviatoric stresses. Pressure is determined by one of 9 equations of state including linear polynomial, JWL high explosive, Sack Tuesday high explosive, Gruneisen, ratio of polynomials, linear polynomial with energy deposition, ignition and growth of reaction in HE, tabulated compaction, and tabulated.« less

  15. Stochastic Inversion of 2D Magnetotelluric Data

    2010-07-01

    The algorithm is developed to invert 2D magnetotelluric (MT) data based on sharp boundary parametrization using a Bayesian framework. Within the algorithm, we consider the locations and the resistivity of regions formed by the interfaces are as unknowns. We use a parallel, adaptive finite-element algorithm to forward simulate frequency-domain MT responses of 2D conductivity structure. Those unknown parameters are spatially correlated and are described by a geostatistical model. The joint posterior probability distribution function ismore » explored by Markov Chain Monte Carlo (MCMC) sampling methods. The developed stochastic model is effective for estimating the interface locations and resistivity. Most importantly, it provides details uncertainty information on each unknown parameter. Hardware requirements: PC, Supercomputer, Multi-platform, Workstation; Software requirements C and Fortan; Operation Systems/version is Linux/Unix or Windows« less

  16. Static & Dynamic Response of 2D Solids

    1996-07-15

    NIKE2D is an implicit finite-element code for analyzing the finite deformation, static and dynamic response of two-dimensional, axisymmetric, plane strain, and plane stress solids. The code is fully vectorized and available on several computing platforms. A number of material models are incorporated to simulate a wide range of material behavior including elasto-placicity, anisotropy, creep, thermal effects, and rate dependence. Slideline algorithms model gaps and sliding along material interfaces, including interface friction, penetration and single surfacemore » contact. Interactive-graphics and rezoning is included for analyses with large mesh distortions. In addition to quasi-Newton and arc-length procedures, adaptive algorithms can be defined to solve the implicit equations using the solution language ISLAND. Each of these capabilities and more make NIKE2D a robust analysis tool.« less

  17. Static & Dynamic Response of 2D Solids

    SciTech Connect

    Lin, Jerry

    1996-07-15

    NIKE2D is an implicit finite-element code for analyzing the finite deformation, static and dynamic response of two-dimensional, axisymmetric, plane strain, and plane stress solids. The code is fully vectorized and available on several computing platforms. A number of material models are incorporated to simulate a wide range of material behavior including elasto-placicity, anisotropy, creep, thermal effects, and rate dependence. Slideline algorithms model gaps and sliding along material interfaces, including interface friction, penetration and single surface contact. Interactive-graphics and rezoning is included for analyses with large mesh distortions. In addition to quasi-Newton and arc-length procedures, adaptive algorithms can be defined to solve the implicit equations using the solution language ISLAND. Each of these capabilities and more make NIKE2D a robust analysis tool.

  18. Explicit 2-D Hydrodynamic FEM Program

    SciTech Connect

    Lin, Jerry

    1996-08-07

    DYNA2D* is a vectorized, explicit, two-dimensional, axisymmetric and plane strain finite element program for analyzing the large deformation dynamic and hydrodynamic response of inelastic solids. DYNA2D* contains 13 material models and 9 equations of state (EOS) to cover a wide range of material behavior. The material models implemented in all machine versions are: elastic, orthotropic elastic, kinematic/isotropic elastic plasticity, thermoelastoplastic, soil and crushable foam, linear viscoelastic, rubber, high explosive burn, isotropic elastic-plastic, temperature-dependent elastic-plastic. The isotropic and temperature-dependent elastic-plastic models determine only the deviatoric stresses. Pressure is determined by one of 9 equations of state including linear polynomial, JWL high explosive, Sack Tuesday high explosive, Gruneisen, ratio of polynomials, linear polynomial with energy deposition, ignition and growth of reaction in HE, tabulated compaction, and tabulated.

  19. 2D photonic-crystal optomechanical nanoresonator.

    PubMed

    Makles, K; Antoni, T; Kuhn, A G; Deléglise, S; Briant, T; Cohadon, P-F; Braive, R; Beaudoin, G; Pinard, L; Michel, C; Dolique, V; Flaminio, R; Cagnoli, G; Robert-Philip, I; Heidmann, A

    2015-01-15

    We present the optical optimization of an optomechanical device based on a suspended InP membrane patterned with a 2D near-wavelength grating (NWG) based on a 2D photonic-crystal geometry. We first identify by numerical simulation a set of geometrical parameters providing a reflectivity higher than 99.8% over a 50-nm span. We then study the limitations induced by the finite value of the optical waist and lateral size of the NWG pattern using different numerical approaches. The NWG grating, pierced in a suspended InP 265-nm thick membrane, is used to form a compact microcavity involving the suspended nanomembrane as an end mirror. The resulting cavity has a waist size smaller than 10 μm and a finesse in the 200 range. It is used to probe the Brownian motion of the mechanical modes of the nanomembrane. PMID:25679837

  20. Compact 2-D graphical representation of DNA

    NASA Astrophysics Data System (ADS)

    Randić, Milan; Vračko, Marjan; Zupan, Jure; Novič, Marjana

    2003-05-01

    We present a novel 2-D graphical representation for DNA sequences which has an important advantage over the existing graphical representations of DNA in being very compact. It is based on: (1) use of binary labels for the four nucleic acid bases, and (2) use of the 'worm' curve as template on which binary codes are placed. The approach is illustrated on DNA sequences of the first exon of human β-globin and gorilla β-globin.

  1. 2D materials: Graphene and others

    NASA Astrophysics Data System (ADS)

    Bansal, Suneev Anil; Singh, Amrinder Pal; Kumar, Suresh

    2016-05-01

    Present report reviews the recent advancements in new atomically thick 2D materials. Materials covered in this review are Graphene, Silicene, Germanene, Boron Nitride (BN) and Transition metal chalcogenides (TMC). These materials show extraordinary mechanical, electronic and optical properties which make them suitable candidates for future applications. Apart from unique properties, tune-ability of highly desirable properties of these materials is also an important area to be emphasized on.

  2. Layer Engineering of 2D Semiconductor Junctions.

    PubMed

    He, Yongmin; Sobhani, Ali; Lei, Sidong; Zhang, Zhuhua; Gong, Yongji; Jin, Zehua; Zhou, Wu; Yang, Yingchao; Zhang, Yuan; Wang, Xifan; Yakobson, Boris; Vajtai, Robert; Halas, Naomi J; Li, Bo; Xie, Erqing; Ajayan, Pulickel

    2016-07-01

    A new concept for junction fabrication by connecting multiple regions with varying layer thicknesses, based on the thickness dependence, is demonstrated. This type of junction is only possible in super-thin-layered 2D materials, and exhibits similar characteristics as p-n junctions. Rectification and photovoltaic effects are observed in chemically homogeneous MoSe2 junctions between domains of different thicknesses. PMID:27136275

  3. Realistic and efficient 2D crack simulation

    NASA Astrophysics Data System (ADS)

    Yadegar, Jacob; Liu, Xiaoqing; Singh, Abhishek

    2010-04-01

    Although numerical algorithms for 2D crack simulation have been studied in Modeling and Simulation (M&S) and computer graphics for decades, realism and computational efficiency are still major challenges. In this paper, we introduce a high-fidelity, scalable, adaptive and efficient/runtime 2D crack/fracture simulation system by applying the mathematically elegant Peano-Cesaro triangular meshing/remeshing technique to model the generation of shards/fragments. The recursive fractal sweep associated with the Peano-Cesaro triangulation provides efficient local multi-resolution refinement to any level-of-detail. The generated binary decomposition tree also provides efficient neighbor retrieval mechanism used for mesh element splitting and merging with minimal memory requirements essential for realistic 2D fragment formation. Upon load impact/contact/penetration, a number of factors including impact angle, impact energy, and material properties are all taken into account to produce the criteria of crack initialization, propagation, and termination leading to realistic fractal-like rubble/fragments formation. The aforementioned parameters are used as variables of probabilistic models of cracks/shards formation, making the proposed solution highly adaptive by allowing machine learning mechanisms learn the optimal values for the variables/parameters based on prior benchmark data generated by off-line physics based simulation solutions that produce accurate fractures/shards though at highly non-real time paste. Crack/fracture simulation has been conducted on various load impacts with different initial locations at various impulse scales. The simulation results demonstrate that the proposed system has the capability to realistically and efficiently simulate 2D crack phenomena (such as window shattering and shards generation) with diverse potentials in military and civil M&S applications such as training and mission planning.

  4. 2D Spinodal Decomposition in Forced Turbulence

    NASA Astrophysics Data System (ADS)

    Fan, Xiang; Diamond, Patrick; Chacon, Luis; Li, Hui

    2015-11-01

    Spinodal decomposition is a second order phase transition for binary fluid mixture, from one thermodynamic phase to form two coexisting phases. The governing equation for this coarsening process below critical temperature, Cahn-Hilliard Equation, is very similar to 2D MHD Equation, especially the conserved quantities have a close correspondence between each other, so theories for MHD turbulence are used to study spinodal decomposition in forced turbulence. Domain size is increased with time along with the inverse cascade, and the length scale can be arrested by a forced turbulence with direct cascade. The two competing mechanisms lead to a stabilized domain size length scale, which can be characterized by Hinze Scale. The 2D spinodal decomposition in forced turbulence is studied by both theory and simulation with ``pixie2d.'' This work focuses on the relation between Hinze scale and spectra and cascades. Similarities and differences between spinodal decomposition and MHD are investigated. Also some transport properties are studied following MHD theories. This work is supported by the Department of Energy under Award Number DE-FG02-04ER54738.

  5. MAGNUM-2D computer code: user's guide

    SciTech Connect

    England, R.L.; Kline, N.W.; Ekblad, K.J.; Baca, R.G.

    1985-01-01

    Information relevant to the general use of the MAGNUM-2D computer code is presented. This computer code was developed for the purpose of modeling (i.e., simulating) the thermal and hydraulic conditions in the vicinity of a waste package emplaced in a deep geologic repository. The MAGNUM-2D computer computes (1) the temperature field surrounding the waste package as a function of the heat generation rate of the nuclear waste and thermal properties of the basalt and (2) the hydraulic head distribution and associated groundwater flow fields as a function of the temperature gradients and hydraulic properties of the basalt. MAGNUM-2D is a two-dimensional numerical model for transient or steady-state analysis of coupled heat transfer and groundwater flow in a fractured porous medium. The governing equations consist of a set of coupled, quasi-linear partial differential equations that are solved using a Galerkin finite-element technique. A Newton-Raphson algorithm is embedded in the Galerkin functional to formulate the problem in terms of the incremental changes in the dependent variables. Both triangular and quadrilateral finite elements are used to represent the continuum portions of the spatial domain. Line elements may be used to represent discrete conduits. 18 refs., 4 figs., 1 tab.

  6. Engineering light outcoupling in 2D materials.

    PubMed

    Lien, Der-Hsien; Kang, Jeong Seuk; Amani, Matin; Chen, Kevin; Tosun, Mahmut; Wang, Hsin-Ping; Roy, Tania; Eggleston, Michael S; Wu, Ming C; Dubey, Madan; Lee, Si-Chen; He, Jr-Hau; Javey, Ali

    2015-02-11

    When light is incident on 2D transition metal dichalcogenides (TMDCs), it engages in multiple reflections within underlying substrates, producing interferences that lead to enhancement or attenuation of the incoming and outgoing strength of light. Here, we report a simple method to engineer the light outcoupling in semiconducting TMDCs by modulating their dielectric surroundings. We show that by modulating the thicknesses of underlying substrates and capping layers, the interference caused by substrate can significantly enhance the light absorption and emission of WSe2, resulting in a ∼11 times increase in Raman signal and a ∼30 times increase in the photoluminescence (PL) intensity of WSe2. On the basis of the interference model, we also propose a strategy to control the photonic and optoelectronic properties of thin-layer WSe2. This work demonstrates the utilization of outcoupling engineering in 2D materials and offers a new route toward the realization of novel optoelectronic devices, such as 2D LEDs and solar cells.

  7. Laboratory measurements of the O+/2D/ + N2 and O+/2D/ + O2 reaction rate coefficients and their ionospheric implications

    NASA Technical Reports Server (NTRS)

    Johnsen, R.; Biondi, M. A.

    1980-01-01

    Rate coefficients which have been measured at thermal energies for the charge transfer reactions of metastable O+/2D/ ions with N2 and O2 are reported. It is found that at an effective temperature of about 550 K, k(n2) = (8 + or - 2) x 10 to the -10 cu cm/sec and k(O2) = (7 + or - 2) x 10 to the -10 cu cm/sec. Drift tube-mass spectrometer measurements employ the reaction He(+) + O2 as the source of metastable O+ ions, showing that the ions produced in this manner are in the 2D state rather than the 2P state, a possible alternative identification. Finally, consideration is given to the ionospheric implications of the laboratory measurements.

  8. Comparison of gated cardiac MRI and 2D echocardiography of intracardiac neoplasms.

    PubMed

    Go, R T; O'Donnell, J K; Underwood, D A; Feiglin, D H; Salcedo, E E; Pantoja, M; MacIntyre, W J; Meaney, T F

    1985-07-01

    The gross diagnostic factors of intracardiac tumor in four patients imaged by two-dimensional echocardiography (2D echo) and magnetic resonance imaging (MRI) were compared. Three cases had left and one had a right atrial tumor, all histologically identified as myxoma. Gated cardiac MRI depicted the size, shape, and surface characteristics of the tumors more clearly than 2D echo, because MRI provides better spatial and contrast resolution. Depiction of tumor attachment was poor to good with both techniques. Both techniques were highly accurate in localizing the tumor and displaying whether it was fixed or mobile. The global field of view provided by MRI allows better definition of tumor prolapse, secondary valvular obstruction, and cardiac chamber size. This study shows that despite its early stage of development, gated cardiac MRI provides superior image quality and is complementary to 2D echo for characterization and diagnosis of intracardiac tumor. PMID:3873848

  9. The GODDESS ionization chamber: developing robust windows

    NASA Astrophysics Data System (ADS)

    Blanchard, Rose; Baugher, Travis; Cizewski, Jolie; Pain, Steven; Ratkiewicz, Andrew; Goddess Collaboration

    2015-10-01

    Reaction studies of nuclei far from stability require high-efficiency arrays of detectors and the ability to identify beam-like particles, especially when the beam is a cocktail beam. The Gammasphere ORRUBA Dual Detectors for Experimental Structure Studies (GODDESS) is made up of the Oak Ridge-Rutgers University Barrel Array (ORRUBA) of silicon detectors for charged particles inside of the gamma-ray detector array Gammasphere. A high-rate ionization chamber is being developed to identify beam-like particles. Consisting of twenty-one alternating anode and cathode grids, the ionization chamber sits downstream of the target chamber and is used to measure the energy loss of recoiling ions. A critical component of the system is a thin and robust mylar window which serves to separate the gas-filled ionization chamber from the vacuum of the target chamber with minimal energy loss. After construction, windows were tested to assure that they would not break below the required pressure, causing harm to the wire grids. This presentation will summarize the status of the ionization chamber and the results of the first tests with beams. This work is supported in part by the U.S. Department of Energy and National Science Foundation.

  10. The PEP Quark Search Proportional Chambers

    NASA Astrophysics Data System (ADS)

    Parker, S. I.; Harris, F.; Karliner, I.; Yount, D.; Ely, R.; Hamilton, R.; Pun, T.; Guryn, W.; Miller, D.; Fries, R.

    1981-04-01

    Proportional chambers are used in the PEP Free Quark Search to identify and remove possible background sources such as particles traversing the edges of counters, to permit geometric corrections to the dE/dx and TOF information from the scintillator and Cerenkov counters, and to look for possible high cross section quarks. The present beam pipe has a thickness of 0.007 interaction lengths (λi) and is followed in both arms (each with 45° <= θ <= 135°. Δphi = 90°) by 5 proportional chambers, each 0.0008 λi thick with 32 channels of pulse height readout, and by 3 thin scintillator planes, each 0.003 λi thick. Following this thin front end, each arm of the detector has 8 layers of scintillator (one with scintillating light pipes) interspersed with 4 proportional chambers and a layer of lucite Cerenkov counters. Both the calculated ion statistics and measurements using He-CH4 gas in a test chamber indicate that the chamber efficiencies should be > 98% for q = 1/3. The Landau spread measured in the test was equal to that observed for normal q = 1 traversals. One scintillator plane and thin chamber in each arm will have an extra set of ADC's with a wide gate bracketing the normal one so timing errors and tails of earlier pulses should not produce fake quarks.

  11. Acoustic-Levitation Chamber

    NASA Technical Reports Server (NTRS)

    Barmatz, M. B.; Granett, D.; Lee, M. C.

    1984-01-01

    Uncontaminated environments for highly-pure material processing provided within completely sealed levitation chamber that suspends particles by acoustic excitation. Technique ideally suited for material processing in low gravity environment of space.

  12. The Mars Chamber

    NASA Video Gallery

    The Mars chamber is a box about the size of a refrigerator that re-creates the temperatures, pressures, and atmosphere of the Martian surface, essentially creating a Mars environment on Earth! Scie...

  13. 2D modeling of electromagnetic waves in cold plasmas

    SciTech Connect

    Crombé, K.; Van Eester, D.; Koch, R.; Kyrytsya, V.

    2014-02-12

    The consequences of sheath (rectified) electric fields, resulting from the different mobility of electrons and ions as a response to radio frequency (RF) fields, are a concern for RF antenna design as it can cause damage to antenna parts, limiters and other in-vessel components. As a first step to a more complete description, the usual cold plasma dielectric description has been adopted, and the density profile was assumed to be known as input. Ultimately, the relevant equations describing the wave-particle interaction both on the fast and slow timescale will need to be tackled but prior to doing so was felt as a necessity to get a feeling of the wave dynamics involved. Maxwell's equations are solved for a cold plasma in a 2D antenna box with strongly varying density profiles crossing also lower hybrid and ion-ion hybrid resonance layers. Numerical modelling quickly becomes demanding on computer power, since a fine grid spacing is required to capture the small wavelengths effects of strongly evanescent modes.

  14. Sleeve reaction chamber system

    DOEpatents

    Northrup, M. Allen; Beeman, Barton V.; Benett, William J.; Hadley, Dean R.; Landre, Phoebe; Lehew, Stacy L.; Krulevitch, Peter A.

    2009-08-25

    A chemical reaction chamber system that combines devices such as doped polysilicon for heating, bulk silicon for convective cooling, and thermoelectric (TE) coolers to augment the heating and cooling rates of the reaction chamber or chambers. In addition the system includes non-silicon-based reaction chambers such as any high thermal conductivity material used in combination with a thermoelectric cooling mechanism (i.e., Peltier device). The heat contained in the thermally conductive part of the system can be used/reused to heat the device, thereby conserving energy and expediting the heating/cooling rates. The system combines a micromachined silicon reaction chamber, for example, with an additional module/device for augmented heating/cooling using the Peltier effect. This additional module is particularly useful in extreme environments (very hot or extremely cold) where augmented heating/cooling would be useful to speed up the thermal cycling rates. The chemical reaction chamber system has various applications for synthesis or processing of organic, inorganic, or biochemical reactions, including the polymerase chain reaction (PCR) and/or other DNA reactions, such as the ligase chain reaction.

  15. GBL-2D Version 1.0: a 2D geometry boolean library.

    SciTech Connect

    McBride, Cory L. (Elemental Technologies, American Fort, UT); Schmidt, Rodney Cannon; Yarberry, Victor R.; Meyers, Ray J.

    2006-11-01

    This report describes version 1.0 of GBL-2D, a geometric Boolean library for 2D objects. The library is written in C++ and consists of a set of classes and routines. The classes primarily represent geometric data and relationships. Classes are provided for 2D points, lines, arcs, edge uses, loops, surfaces and mask sets. The routines contain algorithms for geometric Boolean operations and utility functions. Routines are provided that incorporate the Boolean operations: Union(OR), XOR, Intersection and Difference. A variety of additional analytical geometry routines and routines for importing and exporting the data in various file formats are also provided. The GBL-2D library was originally developed as a geometric modeling engine for use with a separate software tool, called SummitView [1], that manipulates the 2D mask sets created by designers of Micro-Electro-Mechanical Systems (MEMS). However, many other practical applications for this type of software can be envisioned because the need to perform 2D Boolean operations can arise in many contexts.

  16. Human erythrocytes analyzed by generalized 2D Raman correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Wesełucha-Birczyńska, Aleksandra; Kozicki, Mateusz; Czepiel, Jacek; Łabanowska, Maria; Nowak, Piotr; Kowalczyk, Grzegorz; Kurdziel, Magdalena; Birczyńska, Malwina; Biesiada, Grażyna; Mach, Tomasz; Garlicki, Aleksander

    2014-07-01

    The most numerous elements of the blood cells, erythrocytes, consist mainly of two components: homogeneous interior filled with hemoglobin and closure which is the cell membrane. To gain insight into their specific properties we studied the process of disintegration, considering these two constituents, and comparing the natural aging process of human healthy blood cells. MicroRaman spectra of hemoglobin within the single RBC were recorded using 514.5, and 785 nm laser lines. The generalized 2D correlation method was applied to analyze the collected spectra. The time passed from blood donation was regarded as an external perturbation. The time was no more than 40 days according to the current storage limit of blood banks, although, the average RBC life span is 120 days. An analysis of the prominent synchronous and asynchronous cross peaks allow us to get insight into the mechanism of hemoglobin decomposition. Appearing asynchronous cross-peaks point towards globin and heme separation from each other, while synchronous shows already broken globin into individual amino acids. Raman scattering analysis of hemoglobin “wrapping”, i.e. healthy erythrocyte ghosts, allows for the following peculiarity of their behavior. The increasing power of the excitation laser induced alterations in the assemblage of membrane lipids. 2D correlation maps, obtained with increasing laser power recognized as an external perturbation, allows for the consideration of alterations in the erythrocyte membrane structure and composition, which occurs first in the proteins. Cross-peaks were observed indicating an asynchronous correlation between the senescent-cell antigen (SCA) and heme or proteins vibrations. The EPR spectra of the whole blood was analyzed regarding time as an external stimulus. The 2D correlation spectra points towards participation of the selected metal ion centers in the disintegration process.

  17. Periodically sheared 2D Yukawa systems

    SciTech Connect

    Kovács, Anikó Zsuzsa; Hartmann, Peter; Donkó, Zoltán

    2015-10-15

    We present non-equilibrium molecular dynamics simulation studies on the dynamic (complex) shear viscosity of a 2D Yukawa system. We have identified a non-monotonic frequency dependence of the viscosity at high frequencies and shear rates, an energy absorption maximum (local resonance) at the Einstein frequency of the system at medium shear rates, an enhanced collective wave activity, when the excitation is near the plateau frequency of the longitudinal wave dispersion, and the emergence of significant configurational anisotropy at small frequencies and high shear rates.

  18. ENERGY LANDSCAPE OF 2D FLUID FORMS

    SciTech Connect

    Y. JIANG; ET AL

    2000-04-01

    The equilibrium states of 2D non-coarsening fluid foams, which consist of bubbles with fixed areas, correspond to local minima of the total perimeter. (1) The authors find an approximate value of the global minimum, and determine directly from an image how far a foam is from its ground state. (2) For (small) area disorder, small bubbles tend to sort inwards and large bubbles outwards. (3) Topological charges of the same sign repel while charges of opposite sign attract. (4) They discuss boundary conditions and the uniqueness of the pattern for fixed topology.

  19. The development and application of advanced analytical methods to commercial ICF reactor chambers. Final report

    SciTech Connect

    Cousseau, P.; Engelstad, R.; Henderson, D.L.

    1997-10-01

    Progress is summarized in this report for each of the following tasks: (1) multi-dimensional radiation hydrodynamics computer code development; (2) 2D radiation-hydrodynamic code development; (3) ALARA: analytic and Laplacian adaptive radioactivity analysis -- a complete package for analysis of induced activation; (4) structural dynamics modeling of ICF reactor chambers; and (5) analysis of self-consistent target chamber clearing.

  20. Ion beam generating apparatus

    DOEpatents

    Brown, I.G.; Galvin, J.

    1987-12-22

    An ion generating apparatus utilizing a vacuum chamber, a cathode and an anode in the chamber. A source of electrical power produces an arc or discharge between the cathode and anode. The arc is sufficient to vaporize a portion of the cathode to form a plasma. The plasma is directed to an extractor which separates the electrons from the plasma, and accelerates the ions to produce an ion beam. 10 figs.

  1. Development of high intensity ion sources for a Tandem-Electrostatic-Quadrupole facility for Accelerator-Based Boron Neutron Capture Therapy.

    PubMed

    Bergueiro, J; Igarzabal, M; Sandin, J C Suarez; Somacal, H R; Vento, V Thatar; Huck, H; Valda, A A; Repetto, M; Kreiner, A J

    2011-12-01

    Several ion sources have been developed and an ion source test stand has been mounted for the first stage of a Tandem-Electrostatic-Quadrupole facility For Accelerator-Based Boron Neutron Capture Therapy. A first source, designed, fabricated and tested is a dual chamber, filament driven and magnetically compressed volume plasma proton ion source. A 4 mA beam has been accelerated and transported into the suppressed Faraday cup. Extensive simulations of the sources have been performed using both 2D and 3D self-consistent codes.

  2. Discharge Chamber Primary Electron Modeling Activities in Three-Dimensions

    NASA Technical Reports Server (NTRS)

    Steuber, Thomas J.

    2004-01-01

    Designing discharge chambers for ion thrusters involves many geometric configuration decisions. Various decisions will impact discharge chamber performance with respect to propellant utilization efficiency, ion production costs, and grid lifetime. These hardware design decisions can benefit from the assistance of computational modeling. Computational modeling for discharge chambers has been limited to two-dimensional codes that leveraged symmetry for interpretation into three-dimensional analysis. This paper presents model development activities towards a three-dimensional discharge chamber simulation to aid discharge chamber design decisions. Specifically, of the many geometric configuration decisions toward attainment of a worthy discharge chamber, this paper focuses on addressing magnetic circuit considerations with a three-dimensional discharge chamber simulation as a tool. With this tool, candidate discharge chamber magnetic circuit designs can be analyzed computationally to gain insight into factors that may influence discharge chamber performance such as: primary electron loss width in magnetic cusps, cathode tip position with respect to the low magnetic field volume, definition of a low magnetic field region, and maintenance of a low magnetic field region across the grid span. Corroborating experimental data will be obtained from mockup hardware tests. Initially, simulated candidate magnetic circuit designs will resemble previous successful thruster designs. To provide opportunity to improve beyond previous performance benchmarks, off-design modifications will be simulated and experimentally tested.

  3. WFR-2D: an analytical model for PWAS-generated 2D ultrasonic guided wave propagation

    NASA Astrophysics Data System (ADS)

    Shen, Yanfeng; Giurgiutiu, Victor

    2014-03-01

    This paper presents WaveFormRevealer 2-D (WFR-2D), an analytical predictive tool for the simulation of 2-D ultrasonic guided wave propagation and interaction with damage. The design of structural health monitoring (SHM) systems and self-aware smart structures requires the exploration of a wide range of parameters to achieve best detection and quantification of certain types of damage. Such need for parameter exploration on sensor dimension, location, guided wave characteristics (mode type, frequency, wavelength, etc.) can be best satisfied with analytical models which are fast and efficient. The analytical model was constructed based on the exact 2-D Lamb wave solution using Bessel and Hankel functions. Damage effects were inserted in the model by considering the damage as a secondary wave source with complex-valued directivity scattering coefficients containing both amplitude and phase information from wave-damage interaction. The analytical procedure was coded with MATLAB, and a predictive simulation tool called WaveFormRevealer 2-D was developed. The wave-damage interaction coefficients (WDICs) were extracted from harmonic analysis of local finite element model (FEM) with artificial non-reflective boundaries (NRB). The WFR-2D analytical simulation results were compared and verified with full scale multiphysics finite element models and experiments with scanning laser vibrometer. First, Lamb wave propagation in a pristine aluminum plate was simulated with WFR-2D, compared with finite element results, and verified by experiments. Then, an inhomogeneity was machined into the plate to represent damage. Analytical modeling was carried out, and verified by finite element simulation and experiments. This paper finishes with conclusions and suggestions for future work.

  4. Microwave Assisted 2D Materials Exfoliation

    NASA Astrophysics Data System (ADS)

    Wang, Yanbin

    Two-dimensional materials have emerged as extremely important materials with applications ranging from energy and environmental science to electronics and biology. Here we report our discovery of a universal, ultrafast, green, solvo-thermal technology for producing excellent-quality, few-layered nanosheets in liquid phase from well-known 2D materials such as such hexagonal boron nitride (h-BN), graphite, and MoS2. We start by mixing the uniform bulk-layered material with a common organic solvent that matches its surface energy to reduce the van der Waals attractive interactions between the layers; next, the solutions are heated in a commercial microwave oven to overcome the energy barrier between bulk and few-layers states. We discovered the minutes-long rapid exfoliation process is highly temperature dependent, which requires precise thermal management to obtain high-quality inks. We hypothesize a possible mechanism of this proposed solvo-thermal process; our theory confirms the basis of this novel technique for exfoliation of high-quality, layered 2D materials by using an as yet unknown role of the solvent.

  5. Multienzyme Inkjet Printed 2D Arrays.

    PubMed

    Gdor, Efrat; Shemesh, Shay; Magdassi, Shlomo; Mandler, Daniel

    2015-08-19

    The use of printing to produce 2D arrays is well established, and should be relatively facile to adapt for the purpose of printing biomaterials; however, very few studies have been published using enzyme solutions as inks. Among the printing technologies, inkjet printing is highly suitable for printing biomaterials and specifically enzymes, as it offers many advantages. Formulation of the inkjet inks is relatively simple and can be adjusted to a variety of biomaterials, while providing nonharmful environment to the enzymes. Here we demonstrate the applicability of inkjet printing for patterning multiple enzymes in a predefined array in a very straightforward, noncontact method. Specifically, various arrays of the enzymes glucose oxidase (GOx), invertase (INV) and horseradish peroxidase (HP) were printed on aminated glass surfaces, followed by immobilization using glutardialdehyde after printing. Scanning electrochemical microscopy (SECM) was used for imaging the printed patterns and to ascertain the enzyme activity. The successful formation of 2D arrays consisting of enzymes was explored as a means of developing the first surface confined enzyme based logic gates. Principally, XOR and AND gates, each consisting of two enzymes as the Boolean operators, were assembled, and their operation was studied by SECM. PMID:26214072

  6. Preliminary studies of a new monitor ionization chamber.

    PubMed

    Yoshizumi, Maíra T; Vivolo, Vitor; Caldas, Linda V E

    2010-01-01

    A new monitor ionization chamber was developed at Instituto de Pesquisas Energéticas e Nucleares (IPEN) in order to monitor X-ray beams. The main difference of this monitor ionization chamber in relation to other monitor chambers is its geometry, which consists of a ring-shaped sensitive volume. Because of this geometry, the monitor chamber has a central hole through which the direct radiation beam passes. The operational characteristics of the monitor chamber were evaluated: saturation, ion collection efficiency and polarity effect. Besides these tests, the short- and medium-term stabilities of its response were also evaluated. During the tests the leakage current was always negligible. All results showed values within those recommended internationally (IEC, 1997. Medical electrical equipment-dosimeters with ionization chambers and/or semi-conductor detectors as used in X-ray diagnostic imaging. IEC 61674. International Electrotechnical Commission, Genève).

  7. Solar thermal plasma chamber

    NASA Astrophysics Data System (ADS)

    Bonometti, Joseph; Buchele, Donald R.; Castle, Charles H.; Gregory, Don A.

    2001-11-01

    A unique solar thermal chamber has been designed and fabricated to produce the maximum concentration of solar energy and highest temperature possible. Its primary purpose was for solar plasma propulsion experiments and related material specimen testing above 3000 Kelvin. The design not only maximized solar concentration, but also, minimized infrared heat loss. This paper provides the underlining theory and operation of the chamber and initial optical correlation to the actual fabricated hardware. The chamber is placed at the focal point of an existing primary concentrator with a 2.74-meter (9 foot) focal length. A quartz lens focuses a smaller sun image at the inlet hole of the mirrored cavity. The lens focuses two image planes at prescribed positions; the sun at the cavity's entrance hole, and the primary concentrator at the junction plane of two surfaces that form the cavity chamber. The back half is an ellipsoid reflector that produces a 1.27 cm diameter final sun image. The image is 'suspended in space' 7.1cm away from the nearest cavity surface, to minimize thermal and contaminate damage to the mirror surfaces. A hemisphere mirror makes up the front chamber and has its center of curvature at the target image, where rays leaving the target are reflected back upon themselves, minimizing radiation losses.

  8. Improved Rhenium Thrust Chambers

    NASA Technical Reports Server (NTRS)

    O'Dell, John Scott

    2015-01-01

    Radiation-cooled bipropellant thrust chambers are being considered for ascent/ descent engines and reaction control systems on various NASA missions and spacecraft, such as the Mars Sample Return and Orion Multi-Purpose Crew Vehicle (MPCV). Currently, iridium (Ir)-lined rhenium (Re) combustion chambers are the state of the art for in-space engines. NASA's Advanced Materials Bipropellant Rocket (AMBR) engine, a 150-lbf Ir-Re chamber produced by Plasma Processes and Aerojet Rocketdyne, recently set a hydrazine specific impulse record of 333.5 seconds. To withstand the high loads during terrestrial launch, Re chambers with improved mechanical properties are needed. Recent electrochemical forming (EL-Form"TM") results have shown considerable promise for improving Re's mechanical properties by producing a multilayered deposit composed of a tailored microstructure (i.e., Engineered Re). The Engineered Re processing techniques were optimized, and detailed characterization and mechanical properties tests were performed. The most promising techniques were selected and used to produce an Engineered Re AMBR-sized combustion chamber for testing at Aerojet Rocketdyne.

  9. Low frequency 2D Raman-THz spectroscopy of ionic solution: A simulation study

    NASA Astrophysics Data System (ADS)

    Pan, Zhijun; Wu, Tianmin; Jin, Tan; Liu, Yong; Nagata, Yuki; Zhang, Ruiting; Zhuang, Wei

    2015-06-01

    The 2D Raman-THz spectrum of the MgCl2 solution was simulated using the molecular dynamics simulation and the stability matrix method and compared with that of the pure water. The 2D Raman-THz signal provides more information on the ion effects on the collective water motion than the conventional 1D signal. The presence of MgCl2 suppresses the cross peak of water between the hydrogen bond bending and the other intermolecular vibrational mode, which clearly illustrates that the water hydrogen bending motion is affected by the confining effect of the ions. Our theoretical work thus demonstrates that the 2D Raman-THz technique can become a valuable nonlinear vibrational probe for the molecular dynamics in the ionic solutions.

  10. 2-D or not 2-D, that is the question: A Northern California test

    SciTech Connect

    Mayeda, K; Malagnini, L; Phillips, W S; Walter, W R; Dreger, D

    2005-06-06

    Reliable estimates of the seismic source spectrum are necessary for accurate magnitude, yield, and energy estimation. In particular, how seismic radiated energy scales with increasing earthquake size has been the focus of recent debate within the community and has direct implications on earthquake source physics studies as well as hazard mitigation. The 1-D coda methodology of Mayeda et al. has provided the lowest variance estimate of the source spectrum when compared against traditional approaches that use direct S-waves, thus making it ideal for networks that have sparse station distribution. The 1-D coda methodology has been mostly confined to regions of approximately uniform complexity. For larger, more geophysically complicated regions, 2-D path corrections may be required. The complicated tectonics of the northern California region coupled with high quality broadband seismic data provides for an ideal ''apples-to-apples'' test of 1-D and 2-D path assumptions on direct waves and their coda. Using the same station and event distribution, we compared 1-D and 2-D path corrections and observed the following results: (1) 1-D coda results reduced the amplitude variance relative to direct S-waves by roughly a factor of 8 (800%); (2) Applying a 2-D correction to the coda resulted in up to 40% variance reduction from the 1-D coda results; (3) 2-D direct S-wave results, though better than 1-D direct waves, were significantly worse than the 1-D coda. We found that coda-based moment-rate source spectra derived from the 2-D approach were essentially identical to those from the 1-D approach for frequencies less than {approx}0.7-Hz, however for the high frequencies (0.7{le} f {le} 8.0-Hz), the 2-D approach resulted in inter-station scatter that was generally 10-30% smaller. For complex regions where data are plentiful, a 2-D approach can significantly improve upon the simple 1-D assumption. In regions where only 1-D coda correction is available it is still preferable over 2

  11. Bioinspired 2D-Carbon Flakes and Fe3O4 Nanoparticles Composite for Arsenite Removal.

    PubMed

    Venkateswarlu, Sada; Lee, Daeho; Yoon, Minyoung

    2016-09-14

    Development of carbon-based materials has received tremendous attention owing to their multifunctional properties. Biomaterials often serve as an inspiration for the preparation of new carbon materials. Herein, we present a facile synthesis of a new bioinspired graphene oxide-like 2D-carbon flake (CF) using a natural resource, waste onion sheathing (Allium cepa). The 2D-CF was further decorated with crystalline Fe3O4 nanoparticles for applications. Superparamagnetic Fe3O4 nanoparticles (7 nm) were well-dispersed on the surface of the 2D-CF, which was characterized by X-ray diffractometry, X-ray photoelectron spectroscopy, Raman spectrometry, and transmission electron microscopy. Batch As(III) adsorption experiments showed that aqueous arsenic ions strongly adsorbed to the Fe3O4@2D-CF composite. The adsorption capacity of the Fe3O4@2D-CF composite for As(III) was 57.47 mg g(-1). The synergetic effect of both graphene oxide-like 2D-CF and Fe3O4 nanoparticles aided in excellent As(III) adsorption. An As(III) ion adsorption kinetics study showed that adsorption was very fast at the initial stage, and equilibrium was reached within 60 min following a pseudo-second-order rate model. Owing to the excellent superparamagnetic properties (52.6 emu g(-1)), the Fe3O4@2D-CF composite exhibited superb reusability with the shortest recovery time (28 s) among reported materials. This study indicated that Fe3O4@2D-CF composites can be used for practical applications as a global economic material for future generations. PMID:27463424

  12. Canard configured aircraft with 2-D nozzle

    NASA Technical Reports Server (NTRS)

    Child, R. D.; Henderson, W. P.

    1978-01-01

    A closely-coupled canard fighter with vectorable two-dimensional nozzle was designed for enhanced transonic maneuvering. The HiMAT maneuver goal of a sustained 8g turn at a free-stream Mach number of 0.9 and 30,000 feet was the primary design consideration. The aerodynamic design process was initiated with a linear theory optimization minimizing the zero percent suction drag including jet effects and refined with three-dimensional nonlinear potential flow techniques. Allowances were made for mutual interference and viscous effects. The design process to arrive at the resultant configuration is described, and the design of a powered 2-D nozzle model to be tested in the LRC 16-foot Propulsion Wind Tunnel is shown.

  13. 2D Electrostatic Actuation of Microshutter Arrays

    NASA Technical Reports Server (NTRS)

    Burns, Devin E.; Oh, Lance H.; Li, Mary J.; Kelly, Daniel P.; Kutyrev, Alexander S.; Moseley, Samuel H.

    2015-01-01

    Electrostatically actuated microshutter arrays consisting of rotational microshutters (shutters that rotate about a torsion bar) were designed and fabricated through the use of models and experiments. Design iterations focused on minimizing the torsional stiffness of the microshutters, while maintaining their structural integrity. Mechanical and electromechanical test systems were constructed to measure the static and dynamic behavior of the microshutters. The torsional stiffness was reduced by a factor of four over initial designs without sacrificing durability. Analysis of the resonant behavior of the microshutters demonstrates that the first resonant mode is a torsional mode occurring around 3000 Hz. At low vacuum pressures, this resonant mode can be used to significantly reduce the drive voltage necessary for actuation requiring as little as 25V. 2D electrostatic latching and addressing was demonstrated using both a resonant and pulsed addressing scheme.

  14. 2D Electrostatic Actuation of Microshutter Arrays

    NASA Technical Reports Server (NTRS)

    Burns, Devin E.; Oh, Lance H.; Li, Mary J.; Jones, Justin S.; Kelly, Daniel P.; Zheng, Yun; Kutyrev, Alexander S.; Moseley, Samuel H.

    2015-01-01

    An electrostatically actuated microshutter array consisting of rotational microshutters (shutters that rotate about a torsion bar) were designed and fabricated through the use of models and experiments. Design iterations focused on minimizing the torsional stiffness of the microshutters, while maintaining their structural integrity. Mechanical and electromechanical test systems were constructed to measure the static and dynamic behavior of the microshutters. The torsional stiffness was reduced by a factor of four over initial designs without sacrificing durability. Analysis of the resonant behavior of the microshutter arrays demonstrates that the first resonant mode is a torsional mode occurring around 3000 Hz. At low vacuum pressures, this resonant mode can be used to significantly reduce the drive voltage necessary for actuation requiring as little as 25V. 2D electrostatic latching and addressing was demonstrated using both a resonant and pulsed addressing scheme.

  15. 2D quantum gravity from quantum entanglement.

    PubMed

    Gliozzi, F

    2011-01-21

    In quantum systems with many degrees of freedom the replica method is a useful tool to study the entanglement of arbitrary spatial regions. We apply it in a way that allows them to backreact. As a consequence, they become dynamical subsystems whose position, form, and extension are determined by their interaction with the whole system. We analyze, in particular, quantum spin chains described at criticality by a conformal field theory. Its coupling to the Gibbs' ensemble of all possible subsystems is relevant and drives the system into a new fixed point which is argued to be that of the 2D quantum gravity coupled to this system. Numerical experiments on the critical Ising model show that the new critical exponents agree with those predicted by the formula of Knizhnik, Polyakov, and Zamolodchikov.

  16. Graphene suspensions for 2D printing

    NASA Astrophysics Data System (ADS)

    Soots, R. A.; Yakimchuk, E. A.; Nebogatikova, N. A.; Kotin, I. A.; Antonova, I. V.

    2016-04-01

    It is shown that, by processing a graphite suspension in ethanol or water by ultrasound and centrifuging, it is possible to obtain particles with thicknesses within 1-6 nm and, in the most interesting cases, 1-1.5 nm. Analogous treatment of a graphite suspension in organic solvent yields eventually thicker particles (up to 6-10 nm thick) even upon long-term treatment. Using the proposed ink based on graphene and aqueous ethanol with ethylcellulose and terpineol additives for 2D printing, thin (~5 nm thick) films with sheet resistance upon annealing ~30 MΩ/□ were obtained. With the ink based on aqueous graphene suspension, the sheet resistance was ~5-12 kΩ/□ for 6- to 15-nm-thick layers with a carrier mobility of ~30-50 cm2/(V s).

  17. Drift Chamber Experiment

    NASA Astrophysics Data System (ADS)

    Walenta, A. H.; ćonka Nurdan, T.

    2003-07-01

    This paper describes a laboratory course held at ICFA 2002 Regional Instrumentation School in Morelia, Mexico. This course intends to introduce drift chambers, which play an important role in particle physics experiments as tracking detectors. The experimental setup consists of a single-sided, single-cell drift chamber, a plastic scintillator detector and a collimated 90Sr source. The measurements on the drift velocity of electrons, its change as a function of a drift field, gas gain and diffusion are performed at this laboratory course.

  18. Electrostatic Levitator Vacuum Chamber

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Optical ports ring the Electrostatic Levitator (ESL) vacuum chamber to admit light from the heating laser (beam passes through the window at left), positioning lasers (one port is at center), and lamps to allow diagnostic instruments to view the sample. The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  19. Internal combustion chamber

    SciTech Connect

    Schmitz, D.L.

    1988-03-08

    In combination with a high-powered reciprocating piston internal combustion engine, an internal combustion cylinder assembly is described comprising: a cylinder head made of weldable material; a cylinder liner for containing and guiding a reciprocating piston of the engine, a coolant jacket adapted to receive a cooling fluid, mounted on and surrounding the cylinder liner, the jacket being attached to the cylinder head and detachably supported by the cylinder liner, and forming a cooling chamber around the cylinder liner; means to supply the cooling fluid to the cooling chamber and to discharge the cooling fluid therefrom.

  20. Filament wound rocket motor chambers

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The design, analysis, fabrication and testing of a Kevlar-49/HBRF-55A filament wound chamber is reported. The chamber was fabricated and successfully tested to 80% of the design burst pressure. Results of the data reduction and analysis from the hydrotest indicate that the chamber design and fabrication techniques used for the chamber were adequate and the chamber should perform adequately in a static test.

  1. Automated soil gas monitoring chamber

    DOEpatents

    Edwards, Nelson T.; Riggs, Jeffery S.

    2003-07-29

    A chamber for trapping soil gases as they evolve from the soil without disturbance to the soil and to the natural microclimate within the chamber has been invented. The chamber opens between measurements and therefore does not alter the metabolic processes that influence soil gas efflux rates. A multiple chamber system provides for repetitive multi-point sampling, undisturbed metabolic soil processes between sampling, and an essentially airtight sampling chamber operating at ambient pressure.

  2. Chamber, Target and Final Focus Integrated Design

    SciTech Connect

    Moir, R.W

    2000-03-22

    Liquid wall protection, which challenges chamber clearing, has such advantages it's Heavy Ion Fusion's (HIF) main line chamber design. Thin liquid protection from x rays is necessary to avoid erosion of structural surfaces and thick liquid makes structures behind 0.5 m of Flibe (7 mean free paths for 14 MeV neutrons), last the life of the plant. Liquid wall protection holds the promise of greatly increased economic competitiveness. Driver designers require {approx}200 beams to illuminate recent target designs from two sides. The illumination must be compatible with liquid wall protection. The ''best'' values for driver energy, gain, yield and pulse rate comes out of well-known trade-off studies. An integrated chamber design, yet to be made, depends on several key assumptions, which are to be proven before HIF can be shown to be feasible. The chamber R&D needed to reduce the unknowns and risks depend on resolving a few technical issues such as jet surface smoothness and rapid chamber clearing.

  3. Chamber, Target and Final Focus Integrated Design

    SciTech Connect

    Moir, R.W.

    2000-03-03

    Liquid wall protection, which challenges chamber clearing, has such advantages it's Heavy Ion Fusion's (HIF) main line chamber design. Thin liquid protection from x rays is necessary to avoid erosion of structural surfaces and thick liquid makes structures behind 0.5 m of Flibe (7 mean free paths for 14 MeV neutrons), last the life of the plant. Liquid wall protection holds the promise of greatly increased economic competitiveness. Driver designers require {approx}200 beams to illuminate recent target designs from two sides. The illumination must be compatible with liquid wall protection. The ''best'' values for driver energy, gain, yield and pulse rate comes out of well-known trade-off studies. The chamber design is based on several key assumptions, which are to be proven before HIF can be shown to be feasible. The chamber R&D needed to reduce the unknowns and risks depend on resolving a few technical issues such as jet surface smoothness and rapid chamber clearing.

  4. CYP2D6*36 gene arrangements within the cyp2d6 locus: association of CYP2D6*36 with poor metabolizer status.

    PubMed

    Gaedigk, Andrea; Bradford, L Dianne; Alander, Sarah W; Leeder, J Steven

    2006-04-01

    Unexplained cases of CYP2D6 genotype/phenotype discordance continue to be discovered. In previous studies, several African Americans with a poor metabolizer phenotype carried the reduced function CYP2D6*10 allele in combination with a nonfunctional allele. We pursued the possibility that these alleles harbor either a known sequence variation (i.e., CYP2D6*36 carrying a gene conversion in exon 9 along the CYP2D6*10-defining 100C>T single-nucleotide polymorphism) or novel sequences variation(s). Discordant cases were evaluated by long-range polymerase chain reaction (PCR) to test for gene rearrangement events, and a 6.6-kilobase pair PCR product encompassing the CYP2D6 gene was cloned and entirely sequenced. Thereafter, allele frequencies were determined in different study populations comprising whites, African Americans, and Asians. Analyses covering the CYP2D7 to 2D6 gene region established that CYP2D6*36 did not only exist as a gene duplication (CYP2D6*36x2) or in tandem with *10 (CYP2D6*36+*10), as previously reported, but also by itself. This "single" CYP2D6*36 allele was found in nine African Americans and one Asian, but was absent in the whites tested. Ultimately, the presence of CYP2D6*36 resolved genotype/phenotype discordance in three cases. We also discovered an exon 9 conversion-positive CYP2D6*4 gene in a duplication arrangement (CYP2D6*4Nx2) and a CYP2D6*4 allele lacking 100C>T (CYP2D6*4M) in two white subjects. The discovery of an allele that carries only one CYP2D6*36 gene copy provides unequivocal evidence that both CYP2D6*36 and *36x2 are associated with a poor metabolizer phenotype. Given a combined frequency of between 0.5 and 3% in African Americans and Asians, genotyping for CYP2D6*36 should improve the accuracy of genotype-based phenotype prediction in these populations.

  5. Selective ion source

    DOEpatents

    Leung, K.N.

    1996-05-14

    A ion source is described wherein selected ions maybe extracted to the exclusion of unwanted ion species of higher ionization potential. Also described is a method of producing selected ions from a compound, such as P{sup +} from PH{sub 3}. The invention comprises a plasma chamber, an electron source, a means for introducing a gas to be ionized by electrons from the electron source, means for limiting electron energy from the electron source to a value between the ionization energy of the selected ion species and the greater ionization energy of an unwanted ion specie, and means for extracting the target ion specie from the plasma chamber. In one embodiment, the electrons are generated in a plasma cathode chamber immediately adjacent to the plasma chamber. A small extractor draws the electrons from the plasma cathode chamber into the relatively positive plasma chamber. The energy of the electrons extracted in this manner is easily controlled. The invention is particularly useful for doping silicon with P{sup +}, As{sup +}, and B{sup +} without the problematic presence of hydrogen, helium, water, or carbon oxide ions. Doped silicon is important for manufacture of semiconductors and semiconductor devices. 6 figs.

  6. Selective ion source

    DOEpatents

    Leung, Ka-Ngo

    1996-01-01

    A ion source is described wherein selected ions maybe extracted to the exclusion of unwanted ion species of higher ionization potential. Also described is a method of producing selected ions from a compound, such as P.sup.+ from PH.sub.3. The invention comprises a plasma chamber, an electron source, a means for introducing a gas to be ionized by electrons from the electron source, means for limiting electron energy from the electron source to a value between the ionization energy of the selected ion species and the greater ionization energy of an unwanted ion specie, and means for extracting the target ion specie from the plasma chamber. In one embodiment, the electrons are generated in a plasma cathode chamber immediately adjacent to the plasma chamber. A small extractor draws the electrons from the plasma cathode chamber into the relatively positive plasma chamber. The energy of the electrons extracted in this manner is easily controlled. The invention is particularly useful for doping silicon with P.sup.+, AS.sup.+, and B.sup.+ without the problematic presence of hydrogen, helium, water, or carbon oxide ions. Doped silicon is important for manufacture of semiconductors and semiconductor devices.

  7. Ultrasonic Drying Processing Chamber

    NASA Astrophysics Data System (ADS)

    Acosta, V.; Bon, J.; Riera, E.; Pinto, A.

    The design of a high intensity ultrasonic chamber for drying process was investigated. The acoustic pressure distribution in the ultrasonic drying chamber was simulated solving linear elastic models with attenuation for the acoustic-structure interaction. Together with the government equations, the selection of appropriate boundary conditions, mesh refinement, and configuration parameters of the calculation methods, which is of great importance to simulate adequately the process, were considered. Numerical solution, applying the finite element method (FEM), of acoustic-structure interactions involves to couple structural and fluid elements (with different degrees of freedom), whose solution implies several problems of hardware requirements and software configuration, which were solved. To design the drying chamber, the influence of the directivity of the drying open camera and the staggered reflectors over the acoustic pressure distribution was analyzed. Furthermore, to optimize the influence of the acoustic energy on the drying process, the average value of the acoustic energy distribution in the drying chamber was studied. This would determine the adequate position of the food samples to be dried. For this purpose, the acoustic power absorbed by the samples will be analyzed in later studies.

  8. Flame-Test Chamber

    NASA Technical Reports Server (NTRS)

    Bjorklund, R. A.

    1984-01-01

    Experimental chamber provides controlled environment for observation and measurement of flames propagating in expanding plume of flammable air/fuel mixture under atmospheric conditions. Designed to evaluate quenching capability of screen-type flame arresters in atmospheric vents of fuel cargo tanks aboard marine cargo vessels.

  9. Improved wire chamber

    DOEpatents

    Atac, M.

    1987-05-12

    An improved gas mixture for use with proportional counter devices, such as Geiger-Mueller tubes and drift chambers. The improved gas mixture provides a stable drift velocity while eliminating wire aging caused by prior art gas mixtures. The new gas mixture is comprised of equal parts argon and ethane gas and having approximately 0.25% isopropyl alcohol vapor. 2 figs.

  10. Review of straw chambers

    SciTech Connect

    Toki, W.H.

    1990-03-01

    This is a review of straw chambers used in the HRS, MAC, Mark III, CLEO, AMY, and TPC e{sup +}e{sup {minus}} experiments. The straws are 6--8 mm in diameter, operate at 1--4 atmospheres and obtain resolutions of 45--100 microns. The designs and constructions are summarized and possible improvements discussed.

  11. A new method for measuring the response time of the high pressure ionization chamber.

    PubMed

    Wang, Zhentao; Shen, Yixiong; An, Jigang

    2012-08-01

    Time response is an important performance characteristic for gas-pressurized ionization chambers. To study the time response, it is especially crucial to measure the ion drift time in high pressure ionization chambers. In this paper, a new approach is proposed to study the ion drift time in high pressure ionization chambers. It is carried out with a short-pulsed X-ray source and a high-speed digitizer. The ion drift time in the chamber is then determined from the digitized data. By measuring the ion drift time of a 15 atm xenon testing chamber, the method has been proven to be effective in the time response studies of ionization chambers.

  12. A new inversion method for (T2, D) 2D NMR logging and fluid typing

    NASA Astrophysics Data System (ADS)

    Tan, Maojin; Zou, Youlong; Zhou, Cancan

    2013-02-01

    One-dimensional nuclear magnetic resonance (1D NMR) logging technology has some significant limitations in fluid typing. However, not only can two-dimensional nuclear magnetic resonance (2D NMR) provide some accurate porosity parameters, but it can also identify fluids more accurately than 1D NMR. In this paper, based on the relaxation mechanism of (T2, D) 2D NMR in a gradient magnetic field, a hybrid inversion method that combines least-squares-based QR decomposition (LSQR) and truncated singular value decomposition (TSVD) is examined in the 2D NMR inversion of various fluid models. The forward modeling and inversion tests are performed in detail with different acquisition parameters, such as magnetic field gradients (G) and echo spacing (TE) groups. The simulated results are discussed and described in detail, the influence of the above-mentioned observation parameters on the inversion accuracy is investigated and analyzed, and the observation parameters in multi-TE activation are optimized. Furthermore, the hybrid inversion can be applied to quantitatively determine the fluid saturation. To study the effects of noise level on the hybrid method and inversion results, the numerical simulation experiments are performed using different signal-to-noise-ratios (SNRs), and the effect of different SNRs on fluid typing using three fluid models are discussed and analyzed in detail.

  13. Radiofrequency Spectroscopy and Thermodynamics of Fermi Gases in the 2D to Quasi-2D Dimensional Crossover

    NASA Astrophysics Data System (ADS)

    Cheng, Chingyun; Kangara, Jayampathi; Arakelyan, Ilya; Thomas, John

    2016-05-01

    We tune the dimensionality of a strongly interacting degenerate 6 Li Fermi gas from 2D to quasi-2D, by adjusting the radial confinement of pancake-shaped clouds to control the radial chemical potential. In the 2D regime with weak radial confinement, the measured pair binding energies are in agreement with 2D-BCS mean field theory, which predicts dimer pairing energies in the many-body regime. In the qausi-2D regime obtained with increased radial confinement, the measured pairing energy deviates significantly from 2D-BCS theory. In contrast to the pairing energy, the measured radii of the cloud profiles are not fit by 2D-BCS theory in either the 2D or quasi-2D regimes, but are fit in both regimes by a beyond mean field polaron-model of the free energy. Supported by DOE, ARO, NSF, and AFOSR.

  14. Competing coexisting phases in 2D water

    PubMed Central

    Zanotti, Jean-Marc; Judeinstein, Patrick; Dalla-Bernardina, Simona; Creff, Gaëlle; Brubach, Jean-Blaise; Roy, Pascale; Bonetti, Marco; Ollivier, Jacques; Sakellariou, Dimitrios; Bellissent-Funel, Marie-Claire

    2016-01-01

    The properties of bulk water come from a delicate balance of interactions on length scales encompassing several orders of magnitudes: i) the Hydrogen Bond (HBond) at the molecular scale and ii) the extension of this HBond network up to the macroscopic level. Here, we address the physics of water when the three dimensional extension of the HBond network is frustrated, so that the water molecules are forced to organize in only two dimensions. We account for the large scale fluctuating HBond network by an analytical mean-field percolation model. This approach provides a coherent interpretation of the different events experimentally (calorimetry, neutron, NMR, near and far infra-red spectroscopies) detected in interfacial water at 160, 220 and 250 K. Starting from an amorphous state of water at low temperature, these transitions are respectively interpreted as the onset of creation of transient low density patches of 4-HBonded molecules at 160 K, the percolation of these domains at 220 K and finally the total invasion of the surface by them at 250 K. The source of this surprising behaviour in 2D is the frustration of the natural bulk tetrahedral local geometry and the underlying very significant increase in entropy of the interfacial water molecules. PMID:27185018

  15. Phase Engineering of 2D Tin Sulfides.

    PubMed

    Mutlu, Zafer; Wu, Ryan J; Wickramaratne, Darshana; Shahrezaei, Sina; Liu, Chueh; Temiz, Selcuk; Patalano, Andrew; Ozkan, Mihrimah; Lake, Roger K; Mkhoyan, K A; Ozkan, Cengiz S

    2016-06-01

    Tin sulfides can exist in a variety of phases and polytypes due to the different oxidation states of Sn. A subset of these phases and polytypes take the form of layered 2D structures that give rise to a wide host of electronic and optical properties. Hence, achieving control over the phase, polytype, and thickness of tin sulfides is necessary to utilize this wide range of properties exhibited by the compound. This study reports on phase-selective growth of both hexagonal tin (IV) sulfide SnS2 and orthorhombic tin (II) sulfide SnS crystals with diameters of over tens of microns on SiO2 substrates through atmospheric pressure vapor-phase method in a conventional horizontal quartz tube furnace with SnO2 and S powders as the source materials. Detailed characterization of each phase of tin sulfide crystals is performed using various microscopy and spectroscopy methods, and the results are corroborated by ab initio density functional theory calculations. PMID:27099950

  16. Phase Engineering of 2D Tin Sulfides.

    PubMed

    Mutlu, Zafer; Wu, Ryan J; Wickramaratne, Darshana; Shahrezaei, Sina; Liu, Chueh; Temiz, Selcuk; Patalano, Andrew; Ozkan, Mihrimah; Lake, Roger K; Mkhoyan, K A; Ozkan, Cengiz S

    2016-06-01

    Tin sulfides can exist in a variety of phases and polytypes due to the different oxidation states of Sn. A subset of these phases and polytypes take the form of layered 2D structures that give rise to a wide host of electronic and optical properties. Hence, achieving control over the phase, polytype, and thickness of tin sulfides is necessary to utilize this wide range of properties exhibited by the compound. This study reports on phase-selective growth of both hexagonal tin (IV) sulfide SnS2 and orthorhombic tin (II) sulfide SnS crystals with diameters of over tens of microns on SiO2 substrates through atmospheric pressure vapor-phase method in a conventional horizontal quartz tube furnace with SnO2 and S powders as the source materials. Detailed characterization of each phase of tin sulfide crystals is performed using various microscopy and spectroscopy methods, and the results are corroborated by ab initio density functional theory calculations.

  17. Competing coexisting phases in 2D water

    NASA Astrophysics Data System (ADS)

    Zanotti, Jean-Marc; Judeinstein, Patrick; Dalla-Bernardina, Simona; Creff, Gaëlle; Brubach, Jean-Blaise; Roy, Pascale; Bonetti, Marco; Ollivier, Jacques; Sakellariou, Dimitrios; Bellissent-Funel, Marie-Claire

    2016-05-01

    The properties of bulk water come from a delicate balance of interactions on length scales encompassing several orders of magnitudes: i) the Hydrogen Bond (HBond) at the molecular scale and ii) the extension of this HBond network up to the macroscopic level. Here, we address the physics of water when the three dimensional extension of the HBond network is frustrated, so that the water molecules are forced to organize in only two dimensions. We account for the large scale fluctuating HBond network by an analytical mean-field percolation model. This approach provides a coherent interpretation of the different events experimentally (calorimetry, neutron, NMR, near and far infra-red spectroscopies) detected in interfacial water at 160, 220 and 250 K. Starting from an amorphous state of water at low temperature, these transitions are respectively interpreted as the onset of creation of transient low density patches of 4-HBonded molecules at 160 K, the percolation of these domains at 220 K and finally the total invasion of the surface by them at 250 K. The source of this surprising behaviour in 2D is the frustration of the natural bulk tetrahedral local geometry and the underlying very significant increase in entropy of the interfacial water molecules.

  18. Multi-chamber deposition system

    DOEpatents

    Jacobson, Richard L.; Jeffrey, Frank R.; Westerberg, Roger K.

    1989-10-17

    A system for the simultaneous deposition of different coatings onto a thin web within a large volume vacuum chamber is disclosed which chamber is provided with a plurality of deposition chambers in which the different layers are deposited onto the film as its moves from a supply roll to a finished take-up roll of coated web. The deposition chambers provided within the large vacuum chamber are provided with separate seals which minimize back diffusion of any dopant gas from adjacent deposition chambers.

  19. Multi-chamber deposition system

    DOEpatents

    Jacobson, Richard L.; Jeffrey, Frank R.; Westerberg, Roger K.

    1989-06-27

    A system for the simultaneous deposition of different coatings onto a thin web within a large volume vacuum chamber is disclosed which chamber is provided with a plurality of deposition chambers in which the different layers are deposited onto the film as its moves from a supply roll to a finished take-up roll of coated web. The deposition chambers provided within the large vacuum chamber are provided with separate seals which minimize back diffusion of any dopant gas from adjacent deposition chambers.

  20. 44. AUXILIARY CHAMBER BETWEEN CHAMBER AND CONCRETE ENCLOSURE (LOCATION CCC), ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    44. AUXILIARY CHAMBER BETWEEN CHAMBER AND CONCRETE ENCLOSURE (LOCATION CCC), LOOKING NORTHEAST SHOWING DRAIN PIPE FROM SUMP - Shippingport Atomic Power Station, On Ohio River, 25 miles Northwest of Pittsburgh, Shippingport, Beaver County, PA

  1. 61. BOILER CHAMBER No. 2, LOOKING SOUTHWEST BETWEEN CHAMBER AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    61. BOILER CHAMBER No. 2, LOOKING SOUTHWEST BETWEEN CHAMBER AND CONCRETE ENCLOSURE (LOCATION PPP) - Shippingport Atomic Power Station, On Ohio River, 25 miles Northwest of Pittsburgh, Shippingport, Beaver County, PA

  2. 41. AUXILIARY CHAMBER, CONCRETE ENCLOSURE CHAMBER AIR LOCK (EXTERIOR), LOOKING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    41. AUXILIARY CHAMBER, CONCRETE ENCLOSURE CHAMBER AIR LOCK (EXTERIOR), LOOKING NORTHEAST FROM SOUTHWEST CORNER (LOCATION AAA) - Shippingport Atomic Power Station, On Ohio River, 25 miles Northwest of Pittsburgh, Shippingport, Beaver County, PA

  3. 50. BOILER CHAMBER No. 1, LOOKING SOUTHEAST BETWEEN CHAMBER AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    50. BOILER CHAMBER No. 1, LOOKING SOUTHEAST BETWEEN CHAMBER AND ENCLOSURE (LOCATION III) - Shippingport Atomic Power Station, On Ohio River, 25 miles Northwest of Pittsburgh, Shippingport, Beaver County, PA

  4. 72. VISITOR'S CENTER, MODEL OF BOILER CHAMBER, AUXILIARY CHAMBER, REACTOR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    72. VISITOR'S CENTER, MODEL OF BOILER CHAMBER, AUXILIARY CHAMBER, REACTOR AND CANAL (LOCATION T) - Shippingport Atomic Power Station, On Ohio River, 25 miles Northwest of Pittsburgh, Shippingport, Beaver County, PA

  5. The Analysis of Ionization Chambers Used for Detecting Smoke Particles

    NASA Astrophysics Data System (ADS)

    Turlej, Z. (Bish).

    Ionization type cells using a radioactive source of primary ions have been used as fire detectors for many years. They have proven sufficiently sensitive to give an alarm when exposed to the relatively small concentration of smoke particles that occur during the early stages of combustion when control of a fire is still possible. In this work the charging of smoke particles in ionization chambers such as typically employed in ionization smoke detectors are investigated theoretically and experimentally. The ionization chambers investigated in this work have parallel plate and spherical electrode geometries. In the absence of smoke particles, the ionization chambers were operated at some ambient electrode current, which depends upon the ion generation rate, the electrode geometries, the potential difference between the electrodes, and the thermodynamic properties of the gas within the chamber volume. When smoke particles are introduced into the ionization chamber they act as an additional sink for the ions, so that the ion current is reduced. The smoke particles in the experiment performed in this work were transferred from the particle generator to the volume surrounding the ionization chamber and allowed to diffuse inside the ionization chamber. An Aitken nuclei counter was employed to measure the concentration of smoke particles inside the ionization chamber. The electric current flowing through the ionization chamber was recorded as a function of time and concentration of the smoke particles inside the chamber. The current loss due to the particles present inside the chamber was calculated and compared with the experimental results. It was found that at the certain level of ambient electrode current, the current loss due to the smoke particles assumes a maximum value. This optimum operating electrode current was predicted by the mathematical model employed in this work. In the light of this model experimental ionization chambers of both parallel and spherical

  6. 2-D Animation's Not Just for Mickey Mouse.

    ERIC Educational Resources Information Center

    Weinman, Lynda

    1995-01-01

    Discusses characteristics of two-dimensional (2-D) animation; highlights include character animation, painting issues, and motion graphics. Sidebars present Silicon Graphics animations tools and 2-D animation programs for the desktop computer. (DGM)

  7. Generates 2D Input for DYNA NIKE & TOPAZ

    SciTech Connect

    Hallquist, J. O.; Sanford, Larry

    1996-07-15

    MAZE is an interactive program that serves as an input and two-dimensional mesh generator for DYNA2D, NIKE2D, TOPAZ2D, and CHEMICAL TOPAZ2D. MAZE also generates a basic template for ISLAND input. MAZE has been applied to the generation of input data to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.

  8. MAZE96. Generates 2D Input for DYNA NIKE & TOPAZ

    SciTech Connect

    Sanford, L.; Hallquist, J.O.

    1992-02-24

    MAZE is an interactive program that serves as an input and two-dimensional mesh generator for DYNA2D, NIKE2D, TOPAZ2D, and CHEMICAL TOPAZ2D. MAZE also generates a basic template for ISLAND input. MAZE has been applied to the generation of input data to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.

  9. Multiwire proportional chamber development

    NASA Technical Reports Server (NTRS)

    Doolittle, R. F.; Pollvogt, U.; Eskovitz, A. J.

    1973-01-01

    The development of large area multiwire proportional chambers, to be used as high resolution spatial detectors in cosmic ray experiments is described. A readout system was developed which uses a directly coupled, lumped element delay-line whose characteristics are independent of the MWPC design. A complete analysis of the delay-line and the readout electronic system shows that a spatial resolution of about 0.1 mm can be reached with the MWPC operating in the strictly proportional region. This was confirmed by measurements with a small MWPC and Fe-55 X-rays. A simplified analysis was carried out to estimate the theoretical limit of spatial resolution due to delta-rays, spread of the discharge along the anode wire, and inclined trajectories. To calculate the gas gain of MWPC's of different geometrical configurations a method was developed which is based on the knowledge of the first Townsend coefficient of the chamber gas.

  10. CONTINUOUSLY SENSITIVE BUBBLE CHAMBER

    DOEpatents

    Good, R.H.

    1959-08-18

    A radiation detector of the bubble chamber class is described which is continuously sensitive and which does not require the complex pressure cycling equipment characteristic of prior forms of the chamber. The radiation sensitive element is a gas-saturated liquid and means are provided for establishing a thermal gradient across a region of the liquid. The gradient has a temperature range including both the saturation temperature of the liquid and more elevated temperatures. Thus a supersaturated zone is created in which ionizing radiations may give rise to visible gas bubbles indicative of the passage of the radiation through the liquid. Additional means are provided for replenishing the supply of gas-saturated liquid to maintaincontinuous sensitivity.

  11. Electrostatic Levitator Vacuum Chambers

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Optical prots ring the Electrostatic Levitator (ESL) vacuum chamber to admit light from the heating laser (the beam passes through the window at left), poisitioning lasers (one port is at center), and lamps (such as the deuterium arc lamp at right), and to allow diagnostic instruments to view the sample. The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  12. Electrostatic Levitator Vacuum Chamber

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Optical prots ring the Electrostatic Levitator (ESL) vacuum chamber to admit light from the heating laser (the beam passes through the window at left), poisitioning lasers (one port is at center), and lamps (arc lamp at right), and to allow diagnostic instruments to view the sample. The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  13. Electrostatic Levitator Vaccum Chamber

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Optical ports ring the Electrostatic Levitator (ESL) vacuum chamber to admit light from the heating laser (the beam passes through the window at left), positioning lasers (one port is at center), and lamps (such as the deuterium arc lamp at right), and to allow diagnostic instruments to view the sample. The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  14. 2d PDE Linear Symmetric Matrix Solver

    1983-10-01

    ICCG2 (Incomplete Cholesky factorized Conjugate Gradient algorithm for 2d symmetric problems) was developed to solve a linear symmetric matrix system arising from a 9-point discretization of two-dimensional elliptic and parabolic partial differential equations found in plasma physics applications, such as resistive MHD, spatial diffusive transport, and phase space transport (Fokker-Planck equation) problems. These problems share the common feature of being stiff and requiring implicit solution techniques. When these parabolic or elliptic PDE''s are discretized withmore » finite-difference or finite-element methods,the resulting matrix system is frequently of block-tridiagonal form. To use ICCG2, the discretization of the two-dimensional partial differential equation and its boundary conditions must result in a block-tridiagonal supermatrix composed of elementary tridiagonal matrices. The incomplete Cholesky conjugate gradient algorithm is used to solve the linear symmetric matrix equation. Loops are arranged to vectorize on the Cray1 with the CFT compiler, wherever possible. Recursive loops, which cannot be vectorized, are written for optimum scalar speed. For matrices lacking symmetry, ILUCG2 should be used. Similar methods in three dimensions are available in ICCG3 and ILUCG3. A general source containing extensions and macros, which must be processed by a pre-compiler to obtain the standard FORTRAN source, is provided along with the standard FORTRAN source because it is believed to be more readable. The pre-compiler is not included, but pre-compilation may be performed by a text editor as described in the UCRL-88746 Preprint.« less

  15. 2d PDE Linear Asymmetric Matrix Solver

    1983-10-01

    ILUCG2 (Incomplete LU factorized Conjugate Gradient algorithm for 2d problems) was developed to solve a linear asymmetric matrix system arising from a 9-point discretization of two-dimensional elliptic and parabolic partial differential equations found in plasma physics applications, such as plasma diffusion, equilibria, and phase space transport (Fokker-Planck equation) problems. These equations share the common feature of being stiff and requiring implicit solution techniques. When these parabolic or elliptic PDE''s are discretized with finite-difference or finite-elementmore » methods, the resulting matrix system is frequently of block-tridiagonal form. To use ILUCG2, the discretization of the two-dimensional partial differential equation and its boundary conditions must result in a block-tridiagonal supermatrix composed of elementary tridiagonal matrices. A generalization of the incomplete Cholesky conjugate gradient algorithm is used to solve the matrix equation. Loops are arranged to vectorize on the Cray1 with the CFT compiler, wherever possible. Recursive loops, which cannot be vectorized, are written for optimum scalar speed. For problems having a symmetric matrix ICCG2 should be used since it runs up to four times faster and uses approximately 30% less storage. Similar methods in three dimensions are available in ICCG3 and ILUCG3. A general source, containing extensions and macros, which must be processed by a pre-compiler to obtain the standard FORTRAN source, is provided along with the standard FORTRAN source because it is believed to be more readable. The pre-compiler is not included, but pre-compilation may be performed by a text editor as described in the UCRL-88746 Preprint.« less

  16. Position control using 2D-to-2D feature correspondences in vision guided cell micromanipulation.

    PubMed

    Zhang, Yanliang; Han, Mingli; Shee, Cheng Yap; Ang, Wei Tech

    2007-01-01

    Conventional camera calibration that utilizes the extrinsic and intrinsic parameters of the camera and the objects has certain limitations for micro-level cell operations due to the presence of hardware deviations and external disturbances during the experimental process, thereby invalidating the extrinsic parameters. This invalidation is often neglected in macro-world visual servoing and affects the visual image processing quality, causing deviation from the desired position in micro-level cell operations. To increase the success rate of vision guided biological micromanipulations, a novel algorithm monitoring the changing image pattern of the manipulators including the injection micropipette and cell holder is designed and implemented based on 2 dimensional (2D)-to 2D feature correspondences and can adjust the manipulator and perform position control simultaneously. When any deviation is found, the manipulator is retracted to the initial focusing plane before continuing the operation.

  17. A Planar Quantum Transistor Based on 2D-2D Tunneling in Double Quantum Well Heterostructures

    SciTech Connect

    Baca, W.E.; Blount, M.A.; Hafich, M.J.; Lyo, S.K.; Moon, J.S.; Reno, J.L.; Simmons, J.A.; Wendt, J.R.

    1998-12-14

    We report on our work on the double electron layer tunneling transistor (DELTT), based on the gate-control of two-dimensional -- two-dimensional (2D-2D) tunneling in a double quantum well heterostructure. While previous quantum transistors have typically required tiny laterally-defined features, by contrast the DELTT is entirely planar and can be reliably fabricated in large numbers. We use a novel epoxy-bond-and-stop-etch (EBASE) flip-chip process, whereby submicron gating on opposite sides of semiconductor epitaxial layers as thin as 0.24 microns can be achieved. Because both electron layers in the DELTT are 2D, the resonant tunneling features are unusually sharp, and can be easily modulated with one or more surface gates. We demonstrate DELTTs with peak-to-valley ratios in the source-drain I-V curve of order 20:1 below 1 K. Both the height and position of the resonant current peak can be controlled by gate voltage over a wide range. DELTTs with larger subband energy offsets ({approximately} 21 meV) exhibit characteristics that are nearly as good at 77 K, in good agreement with our theoretical calculations. Using these devices, we also demonstrate bistable memories operating at 77 K. Finally, we briefly discuss the prospects for room temperature operation, increases in gain, and high-speed.

  18. 'Brukin2D': a 2D visualization and comparison tool for LC-MS data

    PubMed Central

    Tsagkrasoulis, Dimosthenis; Zerefos, Panagiotis; Loudos, George; Vlahou, Antonia; Baumann, Marc; Kossida, Sophia

    2009-01-01

    Background Liquid Chromatography-Mass Spectrometry (LC-MS) is a commonly used technique to resolve complex protein mixtures. Visualization of large data sets produced from LC-MS, namely the chromatogram and the mass spectra that correspond to its compounds is the focus of this work. Results The in-house developed 'Brukin2D' software, built in Matlab 7.4, which is presented here, uses the compound data that are exported from the Bruker 'DataAnalysis' program, and depicts the mean mass spectra of all the chromatogram compounds from one LC-MS run, in one 2D contour/density plot. Two contour plots from different chromatograph runs can then be viewed in the same window and automatically compared, in order to find their similarities and differences. The results of the comparison can be examined through detailed mass quantification tables, while chromatogram compound statistics are also calculated during the procedure. Conclusion 'Brukin2D' provides a user-friendly platform for quick, easy and integrated view of complex LC-MS data. The software is available at . PMID:19534737

  19. Inhibition of human cytochrome P450 2D6 (CYP2D6) by methadone.

    PubMed Central

    Wu, D; Otton, S V; Sproule, B A; Busto, U; Inaba, T; Kalow, W; Sellers, E M

    1993-01-01

    1. In microsomes prepared from three human livers, methadone competitively inhibited the O-demethylation of dextromethorphan, a marker substrate for CYP2D6. The apparent Ki value of methadone ranged from 2.5 to 5 microM. 2. Two hundred and fifty-two (252) white Caucasians, including 210 unrelated healthy volunteers and 42 opiate abusers undergoing treatment with methadone were phenotyped using dextromethorphan as the marker drug. Although the frequency of poor metabolizers was similar in both groups, the extensive metabolizers among the opiate abusers tended to have higher O-demethylation metabolic ratios and to excrete less of the dose as dextromethorphan metabolites than control extensive metabolizer subjects. These data suggest inhibition of CYP2D6 by methadone in vivo as well. 3. Because methadone is widely used in the treatment of opiate abuse, inhibition of CYP2D6 activity in these patients might contribute to exaggerated response or unexpected toxicity from drugs that are substrates of this enzyme. PMID:8448065

  20. Spectroscopy and Thermometry of Drumhead Modes in a Mesoscopic 2D Coulomb Crystal of ^9Be^+

    NASA Astrophysics Data System (ADS)

    Sawyer, Brian; Britton, Joseph; Teale, Carson; Keith, Adam; Wang, Joseph; Freericks, James; Bollinger, John

    2013-04-01

    We demonstrate spectroscopy and thermometry of individual motional modes in a mesoscopic 2D ion array using entanglement between ion valence electron spins and collective motion. Our system is a ˜400 μm-diameter planar crystal of several hundred ^9Be^+ ions exhibiting complex drumhead modes in the confining potential of a Penning trap. Exploiting precise control over the ^9Be^+ valence electron spins, we apply a homogeneous spin-dependent optical dipole force to excite arbitrary transverse modes with wavelengths ranging from the array diameter to the interparticle spacing of ˜20 μm. In addition to temperature measurements, this spin-motion entanglement induced by the spin-dependent optical dipole force allows for extremely sensitive detection of external forces (˜100 yN) acting on the ion crystal. Characterization of mode frequencies and temperatures is critical for quantum simulation experiments that make use of the ion spins.

  1. Vibrating-chamber levitation systems

    NASA Technical Reports Server (NTRS)

    Barmatz, M. B.; Granett, D.; Lee, M. C. (Inventor)

    1985-01-01

    Systems are described for the acoustic levitation of objects, which enable the use of a sealed rigid chamber to avoid contamination of the levitated object. The apparatus includes a housing forming a substantially closed chamber, and means for vibrating the entire housing at a frequency that produces an acoustic standing wave pattern within the chamber.

  2. Vertical two chamber reaction furnace

    DOEpatents

    Blaugher, Richard D.

    1999-03-16

    A vertical two chamber reaction furnace. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium-copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700.degree. and 800.degree. C.) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800.degree. to 950.degree. C. to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product.

  3. Vertical two chamber reaction furnace

    DOEpatents

    Blaugher, R.D.

    1999-03-16

    A vertical two chamber reaction furnace is disclosed. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700 and 800 C) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800 to 950 C to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product. 2 figs.

  4. Vibrating-chamber levitation systems

    NASA Astrophysics Data System (ADS)

    Barmatz, M. B.; Granett, D.; Lee, M. C.

    1985-10-01

    Systems are described for the acoustic levitation of objects, which enable the use of a sealed rigid chamber to avoid contamination of the levitated object. The apparatus includes a housing forming a substantially closed chamber, and means for vibrating the entire housing at a frequency that produces an acoustic standing wave pattern within the chamber.

  5. Microstrip gas chamber on thin-film Pestov glass and micro gap chamber

    SciTech Connect

    Gong, W.G.; Harris, J.W.; Wieman, H.

    1994-07-01

    The authors report developments of the Microstrip Gas Chamber on thin-film Pestov glass and the Micro Gap Chamber. By coating a thin-layer of low-resistive, electronically-conductive glass on various substrates (including quartz and ceramics), they built MSGCs of high gain stability and low leakage current. They were tested in Ar-CH{sub 4} (10%) and He-C{sub 2}H{sub 6} (50%) gas mixtures. Energy resolutions of 17-20% were measured for 6keV x-rays. This design can make the choice of substrate less important, save the cost of ion-implantation, and use less glass material. Micro Gap Chamber was successfully tested in He-C{sub 2}H{sub 6} (50%) and Ar-C{sub 2}H{sub 6}(50%) gas mixtures. Energy resolutions of about 20% were obtained. Both detectors are expected to have high rate capability.

  6. Segmented ionization chambers for beam monitoring in hadrontherapy

    NASA Astrophysics Data System (ADS)

    Braccini, Saverio; Cirio, Roberto; Donetti, Marco; Marchetto, Flavio; Pittà, Giuseppe; Lavagno, Marco; La Rosa, Vanessa

    2015-05-01

    Segmented ionization chambers represent a good solution to monitor the position, the intensity and the shape of ion beams in hadrontherapy. Pixel and strip chambers have been developed for both passive scattering and active scanning dose delivery systems. In particular, strip chambers are optimal for pencil beam scanning, allowing for spatial and time resolutions below 0.1 mm and 1 ms, respectively. The MATRIX pixel and the Strip Accurate Monitor for Beam Applications (SAMBA) detectors are described in this paper together with the results of several beam tests and industrial developments based on these prototypes.

  7. Correlated Electron Phenomena in 2D Materials

    NASA Astrophysics Data System (ADS)

    Lambert, Joseph G.

    In this thesis, I present experimental results on coherent electron phenomena in layered two-dimensional materials: single layer graphene and van der Waals coupled 2D TiSe2. Graphene is a two-dimensional single-atom thick sheet of carbon atoms first derived from bulk graphite by the mechanical exfoliation technique in 2004. Low-energy charge carriers in graphene behave like massless Dirac fermions, and their density can be easily tuned between electron-rich and hole-rich quasiparticles with electrostatic gating techniques. The sharp interfaces between regions of different carrier densities form barriers with selective transmission, making them behave as partially reflecting mirrors. When two of these interfaces are set at a separation distance within the phase coherence length of the carriers, they form an electronic version of a Fabry-Perot cavity. I present measurements and analysis of multiple Fabry-Perot modes in graphene with parallel electrodes spaced a few hundred nanometers apart. Transition metal dichalcogenide (TMD) TiSe2 is part of the family of materials that coined the term "materials beyond graphene". It contains van der Waals coupled trilayer stacks of Se-Ti-Se. Many TMD materials exhibit a host of interesting correlated electronic phases. In particular, TiSe2 exhibits chiral charge density waves (CDW) below TCDW ˜ 200 K. Upon doping with copper, the CDW state gets suppressed with Cu concentration, and CuxTiSe2 becomes superconducting with critical temperature of T c = 4.15 K. There is still much debate over the mechanisms governing the coexistence of the two correlated electronic phases---CDW and superconductivity. I will present some of the first conductance spectroscopy measurements of proximity coupled superconductor-CDW systems. Measurements reveal a proximity-induced critical current at the Nb-TiSe2 interfaces, suggesting pair correlations in the pure TiSe2. The results indicate that superconducting order is present concurrently with CDW in

  8. 2D-patterning of self-assembled silver nanoisland films.

    PubMed

    Chervinskii, Semen; Reduto, Igor; Kamenskii, Alexander; Mukhin, Ivan S; Lipovskii, Andrey A

    2016-01-01

    The paper is dedicated to the recently developed by the authors technique of silver nanoisland growth, allowing self-arrangement of 2D-patterns of nanoislands. The technique employs silver out-diffusion from ion-exchanged glass in the course of annealing in hydrogen. To modify the silver ion distribution in the exchanged soda-lime glass we included the thermal poling of the ion-exchanged glass with a profiled electrode as an intermediate stage of the process. The resulting consequence consists of three steps: (i) during the ion exchange of the glass in the AgxNa1-xNO3 (x = 0.01-0.15) melt we enrich the subsurface layer of the glass with silver ions; (ii) under the thermal poling, the electric field displaces these ions deeper into the glass under the 2D profiled anodic electrode, the displacement is smaller under the hollows in the electrode where the intensity of the field is minimal; (iii) annealing in a reducing atmosphere of hydrogen results in silver out-diffusion only in the regions corresponding to the electrode hollows, as a result silver forms nanoislands following the shape of the electrode. Varying the electrode and mode of processing allows governing the nanoisland size distribution and self-arrangement of the isolated single nanoislands, pairs, triples or groups of several nanoislands-so-called plasmonic molecules. PMID:26765367

  9. Laboratory studies on N(2D) reactions of relevance to the chemistry of planetary atmospheres

    NASA Astrophysics Data System (ADS)

    Balucani, N.; Casavecchia, P.

    Molecular nitrogen is a very stable molecule, practically inert from a chemical point of view. For a nitrogen chemistry to occur in the planetary atmospheres which contain N2 , it is necessary to transform it into an active form, such as atoms or ions. As far as the production of atomic nitrogen in the upper atmospheres of planets (like Mars) or moons (like Titan) is concerned, several processes - as N2 dissociation induced by electron impact, EUV photolysis (λ <80 nm) and dissociative photoionization, or galactic cosmic ray absorption and N+ dissociative recombination all 2 lead to atomic nitrogen, notably in the ground, 4 S3/2 , and first electronically excited, 2 D3/2,5/2 , states with comparable yields. The radiative lifetimes of the metastable states 2 D3/2 and 2 D5/2 are quite long (12.3 and 48 hours, respectively), because the transition from a doublet to a quartet state is strongly forbidden. In addition, the physical quenching of N(2 D) is often a slow process and in some important cases the main fate of N(2 D) is chemical reaction with other constituents of the planetary atmospheres. The production of N atoms in the 2 D state is an important fact, because N(4 S) atoms exhibit very low reactivity with closed-shell molecules and the probability of collision with an open-shell radical is small. Unfortunately laboratory experiments on the gas-phase reactions of N(2 D) have been lacking until recently, because of serious experimental difficulties in studying these reactive systems. Accurate kinetic data on the reactions of N(2 D) with the some molecules of relevance to the chemistry of planetary atmospheres have finally become available in the late 90's, but a better knowledge of the reactive behavior requires a dynamical investigation of N(2 D) reactions. The capability of generating intense continuous beams of N(2 D) achieved in our laboratory some years ago has opened up the possibility of studying the reactive scattering of this species under single

  10. Spectroscopic investigation of the 3d 2D → nf 2F transitions in lithium

    NASA Astrophysics Data System (ADS)

    Shahzada, S.; Shah, M.; Haq, S. U.; Nawaz, M.; Ahmed, M.; Nadeem, Ali

    2016-05-01

    We report term energies and effective quantum numbers of the odd parity 3d 2D → nf 2F series of lithium using multi-step and multi-photon laser excitation schemes. The experiments were performed using three dye lasers simultaneously pumped by the second harmonic (532 nm) of a Q-switched Nd:YAG laser in conjunction with an atomic beam apparatus and thermionic diode ion detector. The first ionization potential of lithium has been determined as 43,487.13 ± 0.02 cm- 1 from the much extended 3d 2D → nf 2F (17 ≤ n ≤ 70) series. In addition, the oscillator strengths of the 3d 2D → nf 2F (15 ≤ n ≤ 48) transitions have been determined, showing a decreasing trend with the increase in principal quantum number n.

  11. CYP2D7 Sequence Variation Interferes with TaqMan CYP2D6*15 and *35 Genotyping

    PubMed Central

    Riffel, Amanda K.; Dehghani, Mehdi; Hartshorne, Toinette; Floyd, Kristen C.; Leeder, J. Steven; Rosenblatt, Kevin P.; Gaedigk, Andrea

    2016-01-01

    TaqMan™ genotyping assays are widely used to genotype CYP2D6, which encodes a major drug metabolizing enzyme. Assay design for CYP2D6 can be challenging owing to the presence of two pseudogenes, CYP2D7 and CYP2D8, structural and copy number variation and numerous single nucleotide polymorphisms (SNPs) some of which reflect the wild-type sequence of the CYP2D7 pseudogene. The aim of this study was to identify the mechanism causing false-positive CYP2D6*15 calls and remediate those by redesigning and validating alternative TaqMan genotype assays. Among 13,866 DNA samples genotyped by the CompanionDx® lab on the OpenArray platform, 70 samples were identified as heterozygotes for 137Tins, the key SNP of CYP2D6*15. However, only 15 samples were confirmed when tested with the Luminex xTAG CYP2D6 Kit and sequencing of CYP2D6-specific long range (XL)-PCR products. Genotype and gene resequencing of CYP2D6 and CYP2D7-specific XL-PCR products revealed a CC>GT dinucleotide SNP in exon 1 of CYP2D7 that reverts the sequence to CYP2D6 and allows a TaqMan assay PCR primer to bind. Because CYP2D7 also carries a Tins, a false-positive mutation signal is generated. This CYP2D7 SNP was also responsible for generating false-positive signals for rs769258 (CYP2D6*35) which is also located in exon 1. Although alternative CYP2D6*15 and *35 assays resolved the issue, we discovered a novel CYP2D6*15 subvariant in one sample that carries additional SNPs preventing detection with the alternate assay. The frequency of CYP2D6*15 was 0.1% in this ethnically diverse U.S. population sample. In addition, we also discovered linkage between the CYP2D7 CC>GT dinucleotide SNP and the 77G>A (rs28371696) SNP of CYP2D6*43. The frequency of this tentatively functional allele was 0.2%. Taken together, these findings emphasize that regardless of how careful genotyping assays are designed and evaluated before being commercially marketed, rare or unknown SNPs underneath primer and/or probe regions can impact

  12. CYP2D7 Sequence Variation Interferes with TaqMan CYP2D6 (*) 15 and (*) 35 Genotyping.

    PubMed

    Riffel, Amanda K; Dehghani, Mehdi; Hartshorne, Toinette; Floyd, Kristen C; Leeder, J Steven; Rosenblatt, Kevin P; Gaedigk, Andrea

    2015-01-01

    TaqMan™ genotyping assays are widely used to genotype CYP2D6, which encodes a major drug metabolizing enzyme. Assay design for CYP2D6 can be challenging owing to the presence of two pseudogenes, CYP2D7 and CYP2D8, structural and copy number variation and numerous single nucleotide polymorphisms (SNPs) some of which reflect the wild-type sequence of the CYP2D7 pseudogene. The aim of this study was to identify the mechanism causing false-positive CYP2D6 (*) 15 calls and remediate those by redesigning and validating alternative TaqMan genotype assays. Among 13,866 DNA samples genotyped by the CompanionDx® lab on the OpenArray platform, 70 samples were identified as heterozygotes for 137Tins, the key SNP of CYP2D6 (*) 15. However, only 15 samples were confirmed when tested with the Luminex xTAG CYP2D6 Kit and sequencing of CYP2D6-specific long range (XL)-PCR products. Genotype and gene resequencing of CYP2D6 and CYP2D7-specific XL-PCR products revealed a CC>GT dinucleotide SNP in exon 1 of CYP2D7 that reverts the sequence to CYP2D6 and allows a TaqMan assay PCR primer to bind. Because CYP2D7 also carries a Tins, a false-positive mutation signal is generated. This CYP2D7 SNP was also responsible for generating false-positive signals for rs769258 (CYP2D6 (*) 35) which is also located in exon 1. Although alternative CYP2D6 (*) 15 and (*) 35 assays resolved the issue, we discovered a novel CYP2D6 (*) 15 subvariant in one sample that carries additional SNPs preventing detection with the alternate assay. The frequency of CYP2D6 (*) 15 was 0.1% in this ethnically diverse U.S. population sample. In addition, we also discovered linkage between the CYP2D7 CC>GT dinucleotide SNP and the 77G>A (rs28371696) SNP of CYP2D6 (*) 43. The frequency of this tentatively functional allele was 0.2%. Taken together, these findings emphasize that regardless of how careful genotyping assays are designed and evaluated before being commercially marketed, rare or unknown SNPs underneath primer

  13. Multi-anode ionization chamber

    DOEpatents

    Bolotnikov, Aleksey E.; Smith, Graham; Mahler, George J.; Vanier, Peter E.

    2010-12-28

    The present invention includes a high-energy detector having a cathode chamber, a support member, and anode segments. The cathode chamber extends along a longitudinal axis. The support member is fixed within the cathode chamber and extends from the first end of the cathode chamber to the second end of the cathode chamber. The anode segments are supported by the support member and are spaced along the longitudinal surface of the support member. The anode segments are configured to generate at least a first electrical signal in response to electrons impinging thereon.

  14. Synthesis and characterization of 2D molybdenum carbide (MXene)

    DOE PAGES

    Halim, Joseph; Kota, Sankalp; Lukatskaya, Maria R.; Naguib, Michael; Zhao, Meng -Qiang; Moon, Eun Ju; Pitock, Jeremy; Nanda, Jagjit; May, Steven J.; Gogotsi, Yury; et al

    2016-02-17

    Large scale synthesis and delamination of 2D Mo2CT x (where T is a surface termination group) has been achieved by selectively etching gallium from the recently discovered nanolaminated, ternary transition metal carbide Mo2Ga2C. Different synthesis and delamination routes result in different flake morphologies. The resistivity of free-standing Mo2CT x films increases by an order of magnitude as the temperature is reduced from 300 to 10 K, suggesting semiconductor-like behavior of this MXene, in contrast to Ti3C2T x which exhibits metallic behavior. At 10 K, the magnetoresistance is positive. Additionally, changes in electronic transport are observed upon annealing of the films.more » When 2 μm thick films are tested as electrodes in supercapacitors, capacitances as high as 700 F cm–3 in a 1 m sulfuric acid electrolyte and high capacity retention for at least 10,000 cycles at 10 A g–1 are obtained. Free-standing Mo2CT x films, with ≈8 wt% carbon nanotubes, perform well when tested as an electrode material for Li-ions, especially at high rates. In conclusion, at 20 and 131 C cycling rates, stable reversible capacities of 250 and 76 mAh g–1, respectively, are achieved for over 1000 cycles.« less

  15. A versatile interaction chamber for laser-based spectroscopic applications, with the emphasis on Laser-Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Novotný, J.; Brada, M.; Petrilak, M.; Prochazka, D.; Novotný, K.; Hrdička, A.; Kaiser, J.

    2014-11-01

    The technical note describes the interaction chamber developed particularly for the laser spectroscopy technique applications, such as Laser-Induced Breakdown Spectroscopy (LIBS), Raman Spectroscopy and Laser-Induced Fluorescence. The chamber was designed in order to provide advanced possibilities for the research in mentioned fields and to facilitate routine research procedures. Parameters and the main benefits of the chamber are described, such as the built-in module for automatic 2D chemical mapping and the possibility to set different ambient gas conditions (pressure value and gas type). Together with the chamber description, selected LIBS application examples benefiting from chamber properties are described.

  16. Review of wire chamber aging

    SciTech Connect

    Va'Vra, J.

    1986-02-01

    This paper makes an overview of the wire chamber aging problems as a function of various chamber design parameters. It emphasizes the chemistry point of view and many examples are drawn from the plasma chemistry field as a guidance for a possible effort in the wire chamber field. The paper emphasizes the necessity of variable tuning, the importance of purity of the wire chamber environment, as well as it provides a practical list of presently known recommendations. In addition, several models of the wire chamber aging are qualitatively discussed. The paper is based on a summary talk given at the Wire Chamber Aging Workshop held at LBL, Berkeley on January 16-17, 1986. Presented also at Wire Chamber Conference, Vienna, February 25-28, 1986. 74 refs., 18 figs., 11 tabs.

  17. Precision measurement of the 3 d 3/2 2D-state lifetime in a single trapped +40Ca

    NASA Astrophysics Data System (ADS)

    Shao, H.; Huang, Y.; Guan, H.; Qian, Y.; Gao, K.

    2016-10-01

    We present a high-precision measurement of the 3 d 3/2 2D-state lifetime in a single trapped +40Ca. The measurement was performed using a high-efficiency quantum-state detection technique to monitor quantum jumps and a high-precision and highly synchronous measurement sequence for laser control. A feature in our measurement is the pumping rate of the 729-nm laser that was corrected in a real-time way. The 3 d 3/2 2D-state lifetime was obtained through the measurement of the spontaneous decay rate after incoherent shelving of the ion to the 3 d 3/2 2D state with a wait time. Systematic errors, such as collisions with background gases, heating effects, impurity components, the shelving and pumping rates, and state detection, were carefully analyzed and estimated. We determined an improved value of the 3 d 3/2 2D-state lifetime to be τ3 /2=1.195 (8 ) s. Furthermore, the 3 d 3/2 2D →4 s 1/2 2S quadrupole transition matrix element was measured to be Sk i=7.936 (26 ) e a02 , and the ratio between the lifetimes of 3 d 2D3 /2 and 3 d 2D5 /2 was determined to be 1.018(11). Our method can be universally applied to lifetime measurements of other single ions and atoms with a similar structure.

  18. Ion mobility sensor system

    DOEpatents

    Xu, Jun; Watson, David B.; Whitten, William B.

    2013-01-22

    An ion mobility sensor system including an ion mobility spectrometer and a differential mobility spectrometer coupled to the ion mobility spectrometer. The ion mobility spectrometer has a first chamber having first end and a second end extending along a first direction, and a first electrode system that generates a constant electric field parallel to the first direction. The differential mobility spectrometer includes a second chamber having a third end and a fourth end configured such that a fluid may flow in a second direction from the third end to the fourth end, and a second electrode system that generates an asymmetric electric field within an interior of the second chamber. Additionally, the ion mobility spectrometer and the differential mobility spectrometer form an interface region. Also, the first end and the third end are positioned facing one another so that the constant electric field enters the third end and overlaps the fluid flowing in the second direction.

  19. Air ion exposure system for plants

    NASA Technical Reports Server (NTRS)

    Morrow, R. C.; Tibbitts, T. W.

    1987-01-01

    A system was developed for subjecting plants to elevated air ion levels. This system consisted of a rectangular Plexiglas chamber lined with a Faraday cage. Air ions were generated by corona discharge from frayed stainless steel fibers placed at one end of the chamber. This source was capable of producing varying levels of either positive or negative air ions. During plant exposures, environmental conditions were controlled by operating the unit in a growth chamber.

  20. Mechanical characterization of 2D, 2D stitched, and 3D braided/RTM materials

    NASA Technical Reports Server (NTRS)

    Deaton, Jerry W.; Kullerd, Susan M.; Portanova, Marc A.

    1993-01-01

    Braided composite materials have potential for application in aircraft structures. Fuselage frames, floor beams, wing spars, and stiffeners are examples where braided composites could find application if cost effective processing and damage tolerance requirements are met. Another important consideration for braided composites relates to their mechanical properties and how they compare to the properties of composites produced by other textile composite processes being proposed for these applications. Unfortunately, mechanical property data for braided composites do not appear extensively in the literature. Data are presented in this paper on the mechanical characterization of 2D triaxial braid, 2D triaxial braid plus stitching, and 3D (through-the-thickness) braid composite materials. The braided preforms all had the same graphite tow size and the same nominal braid architectures, (+/- 30 deg/0 deg), and were resin transfer molded (RTM) using the same mold for each of two different resin systems. Static data are presented for notched and unnotched tension, notched and unnotched compression, and compression after impact strengths at room temperature. In addition, some static results, after environmental conditioning, are included. Baseline tension and compression fatigue results are also presented, but only for the 3D braided composite material with one of the resin systems.

  1. Phase states of a 2D easy-plane ferromagnet with strong inclined anisotropy

    SciTech Connect

    Fridman, Yu. A. Klevets, F. N.; Gorelikov, G. A.; Meleshko, A. G.

    2012-12-15

    We investigate the spin states of a 2D film exhibiting easy-axis anisotropy and a strong single-ion inclined anisotropy whose axis forms a certain angle with the normal to the film surface. Such a system may have an angular ferromagnetic phase, a spatially inhomogeneous state, and a quadrupole phase, whose realization depends substantially on the inclined anisotropy and the orientation of the wavevector in the film plane.

  2. Computational Screening of 2D Materials for Photocatalysis.

    PubMed

    Singh, Arunima K; Mathew, Kiran; Zhuang, Houlong L; Hennig, Richard G

    2015-03-19

    Two-dimensional (2D) materials exhibit a range of extraordinary electronic, optical, and mechanical properties different from their bulk counterparts with potential applications for 2D materials emerging in energy storage and conversion technologies. In this Perspective, we summarize the recent developments in the field of solar water splitting using 2D materials and review a computational screening approach to rapidly and efficiently discover more 2D materials that possess properties suitable for solar water splitting. Computational tools based on density-functional theory can predict the intrinsic properties of potential photocatalyst such as their electronic properties, optical absorbance, and solubility in aqueous solutions. Computational tools enable the exploration of possible routes to enhance the photocatalytic activity of 2D materials by use of mechanical strain, bias potential, doping, and pH. We discuss future research directions and needed method developments for the computational design and optimization of 2D materials for photocatalysis.

  3. Dynamics of the Rydberg electron in H*+D2-->D*+HD reactive collisions.

    PubMed

    Hayes, Michael Y; Skodje, Rex T

    2007-03-14

    Experimental crossed-beam studies carried out previously have indicated that the dynamics of the Rydberg-atom-molecule reaction H*+D2-->D*+HD are very similar to those of the corresponding ion-molecule reaction H++D2-->D++HD. The equivalence of the cross sections for these related systems would open up a new approach to the experimental study of ion-molecule reactions. However, a recent experimental and theoretical study has brought to light some important qualitative differences between the Rydberg-atom reaction and the ion-molecule reaction; in particular, the experimental cross section for the Rydberg-atom reaction exhibits a higher degree of forward-backward scattering asymmetry than predicted by a quasiclassical trajectory study of the ion-molecule reaction. In this paper, the authors consider the dynamics of the Rydberg-electron over the course of a reactive collision and the implications of these dynamics for the Rydberg-atom-molecule crossed-beam experiment. Using an approach based on perturbation theory, they estimate the attenuation of the experimental signal due to the Rydberg-electron dynamics as a function of the scattering angle. They show that at least part of the experimental asymmetry can be ascribed to this angle dependent attenuation. Their results offer general insight into the practical aspects of the experimental study of ion-molecule reactions by means of their Rydberg-atom counterparts. PMID:17362067

  4. Synthetic Covalent and Non-Covalent 2D Materials.

    PubMed

    Boott, Charlotte E; Nazemi, Ali; Manners, Ian

    2015-11-16

    The creation of synthetic 2D materials represents an attractive challenge that is ultimately driven by their prospective uses in, for example, electronics, biomedicine, catalysis, sensing, and as membranes for separation and filtration. This Review illustrates some recent advances in this diverse field with a focus on covalent and non-covalent 2D polymers and frameworks, and self-assembled 2D materials derived from nanoparticles, homopolymers, and block copolymers.

  5. A Geometric Boolean Library for 2D Objects

    2006-01-05

    The 2D Boolean Library is a collection of C++ classes -- which primarily represent 2D geometric data and relationships, and routines -- which contain algorithms for 2D geometric Boolean operations and utility functions. Classes are provided for 2D points, lines, arcs, edgeuses, loops, surfaces and mask sets. Routines are provided that incorporate the Boolean operations Union(OR), XOR, Intersection and Difference. Various analytical geometry routines and routines for importing and exporting the data in various filemore » formats, are also provided in the library.« less

  6. VizieR Online Data Catalog: The 2dF Galaxy Redshift Survey (2dFGRS) (2dFGRS Team, 1998-2003)

    NASA Astrophysics Data System (ADS)

    Colless, M.; Dalton, G.; Maddox, S.; Sutherland, W.; Norberg, P.; Cole, S.; Bland-Hawthorn, J.; Bridges, T.; Cannon, R.; Collins, C.; Couch, W.; Cross, N.; Deeley, K.; de Propris, R.; Driver, S. P.; Efstathiou, G.; Ellis, R. S.; Frenk, C. S.; Glazebrook, K.; Jackson, C.; Lahav, O.; Lewis, I.; Lumsden, S.; Madgwick, D.; Peacock, J. A.; Peterson, B. A.; Price, I.; Seaborne, M.; Taylor, K.

    2007-11-01

    The 2dF Galaxy Redshift Survey (2dFGRS) is a major spectroscopic survey taking full advantage of the unique capabilities of the 2dF facility built by the Anglo-Australian Observatory. The 2dFGRS is integrated with the 2dF QSO survey (2QZ, Cat. VII/241). The 2dFGRS obtained spectra for 245591 objects, mainly galaxies, brighter than a nominal extinction-corrected magnitude limit of bJ=19.45. Reliable (quality>=3) redshifts were obtained for 221414 galaxies. The galaxies cover an area of approximately 1500 square degrees selected from the extended APM Galaxy Survey in three regions: a North Galactic Pole (NGP) strip, a South Galactic Pole (SGP) strip, and random fields scattered around the SGP strip. Redshifts are measured from spectra covering 3600-8000 Angstroms at a two-pixel resolution of 9.0 Angstrom and a median S/N of 13 per pixel. All redshift identifications are visually checked and assigned a quality parameter Q in the range 1-5; Q>=3 redshifts are 98.4% reliable and have an rms uncertainty of 85 km/s. The overall redshift completeness for Q>=3 redshifts is 91.8% but this varies with magnitude from 99% for the brightest galaxies to 90% for objects at the survey limit. The 2dFGRS data base is available on the World Wide Web at http://www.mso.anu.edu.au/2dFGRS/. (6 data files).

  7. Mush Column Magma Chambers

    NASA Astrophysics Data System (ADS)

    Marsh, B. D.

    2002-12-01

    Magma chambers are a necessary concept in understanding the chemical and physical evolution of magma. The concept may well be similar to a transfer function in circuit or time series analysis. It does what needs to be done to transform source magma into eruptible magma. In gravity and geodetic interpretations the causative body is (usually of necessity) geometrically simple and of limited vertical extent; it is clearly difficult to `see' through the uppermost manifestation of the concentrated magma. The presence of plutons in the upper crust has reinforced the view that magma chambers are large pots of magma, but as in the physical representation of a transfer function, actual magma chambers are clearly distinct from virtual magma chambers. Two key features to understanding magmatic systems are that they are vertically integrated over large distances (e.g., 30-100 km), and that all local magmatic processes are controlled by solidification fronts. Heat transfer considerations show that any viable volcanic system must be supported by a vertically extensive plumbing system. Field and geophysical studies point to a common theme of an interconnected stack of sill-like structures extending to great depth. This is a magmatic Mush Column. The large-scale (10s of km) structure resembles the vertical structure inferred at large volcanic centers like Hawaii (e.g., Ryan et al.), and the fine scale (10s to 100s of m) structure is exemplified by ophiolites and deeply eroded sill complexes like the Ferrar dolerites of the McMurdo Dry Valleys, Antarctica. The local length scales of the sill reservoirs and interconnecting conduits produce a rich spectrum of crystallization environments with distinct solidification time scales. Extensive horizontal and vertical mushy walls provide conditions conducive to specific processes of differentiation from solidification front instability to sidewall porous flow and wall rock slumping. The size, strength, and time series of eruptive behavior

  8. Environmental calibration chamber operations

    NASA Technical Reports Server (NTRS)

    Lester, D. L.

    1988-01-01

    Thermal vacuum capabilities are provided for the development, calibration, and functional operation checks of flight sensors, sources, and laboratory and field instruments. Two systems are available. The first is a 46 cm diameter diffusion pumped vacuum chambler of the bell jar variety. It has an internal thermal shroud, LN2 old trap, two viewing ports, and various electrical and fluid feedthroughs. The other, also an oil diffusion pumped system, consists of a 1.8 m diameter by 2.5 m long stainless steel vacuum tank, associated pumping and control equipment, a liquid nitrogen storage and transfer system and internal IR/visible calibration sources. This is a two story system with the chamber located on one floor and the pumping/cryogenic systems located on the floor below.

  9. Klassifikation von Standardebenen in der 2D-Echokardiographie mittels 2D-3D-Bildregistrierung

    NASA Astrophysics Data System (ADS)

    Bergmeir, Christoph; Subramanian, Navneeth

    Zum Zweck der Entwicklung eines Systems, das einen unerfahrenen Anwender von Ultraschall (US) zur Aufnahme relevanter anatomischer Strukturen leitet, untersuchen wir die Machbarkeit von 2D-US zu 3D-CT Registrierung. Wir verwenden US-Aufnahmen von Standardebenen des Herzens, welche zu einem 3D-CT-Modell registriert werden. Unser Algorithmus unterzieht sowohl die US-Bilder als auch den CT-Datensatz Vorverarbeitungsschritten, welche die Daten durch Segmentierung auf wesentliche Informationen in Form von Labein für Muskel und Blut reduzieren. Anschließend werden diese Label zur Registrierung mittels der Match-Cardinality-Metrik genutzt. Durch mehrmaliges Registrieren mit verschiedenen Initialisierungen ermitteln wir die im US-Bild sichtbare Standardebene. Wir evaluierten die Methode auf sieben US-Bildern von Standardebenen. Fünf davon wurden korrekt zugeordnet.

  10. Epitaxial 2D SnSe2/ 2D WSe2 van der Waals Heterostructures.

    PubMed

    Aretouli, Kleopatra Emmanouil; Tsoutsou, Dimitra; Tsipas, Polychronis; Marquez-Velasco, Jose; Aminalragia Giamini, Sigiava; Kelaidis, Nicolaos; Psycharis, Vassilis; Dimoulas, Athanasios

    2016-09-01

    van der Waals heterostructures of 2D semiconductor materials can be used to realize a number of (opto)electronic devices including tunneling field effect devices (TFETs). It is shown in this work that high quality SnSe2/WSe2 vdW heterostructure can be grown by molecular beam epitaxy on AlN(0001)/Si(111) substrates using a Bi2Se3 buffer layer. A valence band offset of 0.8 eV matches the energy gap of SnSe2 in such a way that the VB edge of WSe2 and the CB edge of SnSe2 are lined up, making this materials combination suitable for (nearly) broken gap TFETs. PMID:27537619

  11. CVMAC 2D Program: A method of converting 3D to 2D

    SciTech Connect

    Lown, J.

    1990-06-20

    This paper presents the user with a method of converting a three- dimensional wire frame model into a technical illustration, detail, or assembly drawing. By using the 2D Program, entities can be mapped from three-dimensional model space into two-dimensional model space, as if they are being traced. Selected entities to be mapped can include circles, arcs, lines, and points. This program prompts the user to digitize the view to be mapped, specify the layers in which the new two-dimensional entities will reside, and select the entities, either by digitizing or windowing. The new two-dimensional entities are displayed in a small view which the program creates in the lower left corner of the drawing. 9 figs.

  12. 2D Four-Channel Perfect Reconstruction Filter Bank Realized with the 2D Lattice Filter Structure

    NASA Astrophysics Data System (ADS)

    Sezen, S.; Ertüzün, A.

    2006-12-01

    A novel orthogonal 2D lattice structure is incorporated into the design of a nonseparable 2D four-channel perfect reconstruction filter bank. The proposed filter bank is obtained by using the polyphase decomposition technique which requires the design of an orthogonal 2D lattice filter. Due to constraint of perfect reconstruction, each stage of this lattice filter bank is simply parameterized by two coefficients. The perfect reconstruction property is satisfied regardless of the actual values of these parameters and of the number of the lattice stages. It is also shown that a separable 2D four-channel perfect reconstruction lattice filter bank can be constructed from the 1D lattice filter and that this is a special case of the proposed 2D lattice filter bank under certain conditions. The perfect reconstruction property of the proposed 2D lattice filter approach is verified by computer simulations.

  13. Herds of methane chambers grazing bubbles

    NASA Astrophysics Data System (ADS)

    Grinham, Alistair; Dunbabin, Matthew

    2014-05-01

    , localised bubbling zones on the water storage were found to produce over 50,000 mg m-2 d-1 and the areal extent ranged from 1.8 to 7% of the total reservoir area. The drivers behind these changes as well as lessons learnt from the system implementation are presented. This system exploits relatively cheap materials, sensing and computing and can be applied to a wide variety of aquatic and terrestrial systems.

  14. Ionization chamber volume determination and quality assurance using micro-CT imaging

    NASA Astrophysics Data System (ADS)

    McNiven, Andrea L.; Umoh, Joseph; Kron, Tomas; Holdsworth, David W.; Battista, Jerry J.

    2008-09-01

    Ion chamber dosimetry requires a high degree of precision, at all steps within the dosimetric process, in order to ensure accurate dose measurements. This work presents a novel technique for ion chamber volume determination and quality assurance, using micro-computed tomography (micro-CT). Four nominally identical Exradin A1SL chambers (0.056 cm3) (Standard Imaging, WI, USA) were imaged using a micro-CT system (GE Locus, GE Healthcare, London, Ontario) and irradiated in a 6 MV x-ray reference field. Air volumes were calculated from the CT datasets using 3D analysis software (Microview 2.1.1, General Electric Healthcare, London, Ontario). Differences in the volumes of each chamber determined using micro-CT images agreed with differences in the ionization response within 1% for each chamber. Calibration coefficients were then compared through cross-calibration with a calibrated ion chamber and from the CT-measured volumes. The average ratio of these values was found to be 0.958 ± 0.009 indicating good correlation. The results demonstrate the promise of using micro-CT imaging for the absolute volumetric characterization of ion chambers. The images have the potential to be an important clinical tool for quality assurance of ion chamber construction and integrity after routine clinical usage.

  15. Investigation of thermal and temporal responses of ionization chambers in radiation dosimetry.

    PubMed

    AlMasri, Hussein; Funyu, Akira; Kakinohana, Yasumasa; Murayama, Sadayuki

    2012-07-01

    The ionization chamber is a primary dosimeter that is used in radiation dosimetry. Generally, the ion chamber response requires temperature/pressure correction according to the ideal gas law. However, this correction does not consider the thermal volume effect of chambers. The temporal and thermal volume effects of various chambers (CC01, CC13, NACP parallel-plate, PTW) with different wall and electrode materials have been studied in a water phantom. Measurements were done after heating the water with a suitable heating system, and chambers were submerged for a sufficient time to allow for temperature equilibrium. Temporal results show that all chambers equilibrate quickly in water. The equilibration time was between 3 and 5 min for all chambers. Thermal results show that all chambers expanded in response to heating except for the PTW, which contracted. This might be explained by the differences in the volumes of all chambers and also by the difference in wall material composition of PTW from the other chambers. It was found that the smallest chamber, CC01, showed the greatest expansion. The magnitude of the expansion was ~1, 0.8, and 0.9% for CC01, CC13, and parallel-plate chambers, respectively, in the temperature range of 295-320 K. The magnitude of the detected contraction was <0.3% for PTW in the same temperature range. For absolute dosimetry, it is necessary to make corrections for the ion chamber response, especially for small ion chambers like the CC01. Otherwise, room and water phantom temperatures should remain within a close range. PMID:22467281

  16. Isotopic exchange processes in cold plasmas of H2/D2 mixtures.

    PubMed

    Jiménez-Redondo, Miguel; Carrasco, Esther; Herrero, Víctor J; Tanarro, Isabel

    2011-05-28

    Isotope exchange in low pressure cold plasmas of H(2)/D(2) mixtures has been investigated by means of mass spectrometric measurements of neutrals and ions, and kinetic model calculations. The measurements, which include also electron temperatures and densities, were performed in a stainless steel hollow cathode reactor for three discharge pressures: 1, 2 and 8 Pa, and for mixture compositions ranging from 100% H(2) to 100% D(2). The data are analyzed in the light of the model calculations, which are in good global agreement with the experiments. Isotope selective effects are found both in the surface recombination and in the gas-phase ionic chemistry. The dissociation of the fuel gas molecules is followed by wall recycling, which regenerates H(2) and D(2) and produces HD. Atomic recombination at the wall is found to proceed through an Eley-Rideal mechanism, with a preference for reaction of the adsorbed atoms with gas phase D atoms. The best fit probabilities for Eley-Rideal abstraction with H and D are: γ(ER H) = 1.5 × 10(-3), γ(ER D) = 2.0 × 10(-3). Concerning ions, at 1 Pa the diatomic species H(2)(+), D(2)(+) and HD(+), formed directly by electron impact, prevail in the distributions, and at 8 Pa, the triatomic ions H(3)(+), H(2)D(+), HD(2)(+) and D(3)(+), produced primarily in reactions of diatomic ions with molecules, dominate the plasma composition. In this higher pressure regime, the formation of the mixed ions H(2)D(+) and HD(2)(+) is favoured in comparison with that of H(3)(+) and D(3)(+), as expected on statistical grounds. The model results predict a very small preference, undetectable within the precision of the measurements, for the generation of triatomic ions with a higher degree of deuteration, which is probably a residual influence at room temperature of the marked zero point energy effects (ZPE), relevant for deuterium fractionation in interstellar space. In contrast, ZPE effects are found to be decisive for the observed distribution of

  17. Production of N.sup.+ ions from a multicusp ion beam apparatus

    DOEpatents

    Leung, Ka-Ngo; Kunkel, Wulf B.; Walther, Steven R.

    1993-01-01

    A method of generating a high purity (at least 98%) N.sup.+ ion beam using a multicusp ion source (10) having a chamber (11) formed by a cylindrical chamber wall (12) surrounded by a plurality of magnets (13), a filament (57) centrally disposed in said chamber, a plasma electrode (36) having an extraction orifice (41) at one end of the chamber, a magnetic filter having two parallel magnets (21, 22) spaced from said plasma electrode (36) and dividing the chamber (11) into arc discharge and extraction regions. The method includes ionizing nitrogen gas in the arc discharge region of the chamber (11), maintaining the chamber wall (12) at a positive voltage relative to the filament (57) and at a magnitude for an optimum percentage of N.sup.+ ions in the extracted ion beams, disposing a hot liner (45) within the chamber and near the chamber wall (12) to limit recombination of N.sup.+ ions into the N.sub.2.sup.+ ions, spacing the magnets (21, 22) of the magnetic filter from each other for optimum percentage of N.sup.3 ions in the extracted ion beams, and maintaining a relatively low pressure downstream of the extraction orifice and of a magnitude (preferably within the range of 3-8.times.10.sup.-4 torr) for an optimum percentage of N.sup.+ ions in the extracted ion beam.

  18. Production of N[sup +] ions from a multicusp ion beam apparatus

    DOEpatents

    Kango Leung; Kunkel, W.B.; Walther, S.R.

    1993-03-30

    A method of generating a high purity (at least 98%) N[sup +] ion beam using a multicusp ion source having a chamber formed by a cylindrical chamber wall surrounded by a plurality of magnets, a filament centrally disposed in said chamber, a plasma electrode having an extraction orifice at one end of the chamber, a magnetic filter having two parallel magnets spaced from said plasma electrode and dividing the chamber into arc discharge and extraction regions. The method includes ionizing nitrogen gas in the arc discharge region of the chamber, maintaining the chamber wall at a positive voltage relative to the filament and at a magnitude for an optimum percentage of N[sup +] ions in the extracted ion beams, disposing a hot liner within the chamber and near the chamber wall to limit recombination of N[sup +] ions into the N[sub 2][sup +] ions, spacing the magnets of the magnetic filter from each other for optimum percentage of N[sup 3] ions in the extracted ion beams, and maintaining a relatively low pressure downstream of the extraction orifice and of a magnitude (preferably within the range of 3-8[times]10[sup [minus]4] torr) for an optimum percentage of N[sup +] ions in the extracted ion beam.

  19. Functional characterization of CYP2D6 enhancer polymorphisms

    PubMed Central

    Wang, Danxin; Papp, Audrey C.; Sun, Xiaochun

    2015-01-01

    CYP2D6 metabolizes nearly 25% of clinically used drugs. Genetic polymorphisms cause large inter-individual variability in CYP2D6 enzyme activity and are currently used as biomarker to predict CYP2D6 metabolizer phenotype. Previously, we had identified a region 115 kb downstream of CYP2D6 as enhancer for CYP2D6, containing two completely linked single nucleotide polymorphisms (SNPs), rs133333 and rs5758550, associated with enhanced transcription. However, the enhancer effect on CYP2D6 expression, and the causative variant, remained to be ascertained. To characterize the CYP2D6 enhancer element, we applied chromatin conformation capture combined with the next-generation sequencing (4C assays) and chromatin immunoprecipitation with P300 antibody, in HepG2 and human primary culture hepatocytes. The results confirmed the role of the previously identified enhancer region in CYP2D6 expression, expanding the number of candidate variants to three highly linked SNPs (rs133333, rs5758550 and rs4822082). Among these, only rs5758550 demonstrated regulating enhancer activity in a reporter gene assay. Use of clustered regularly interspaced short palindromic repeats mediated genome editing in HepG2 cells targeting suspected enhancer regions decreased CYP2D6 mRNA expression by 70%, only upon deletion of the rs5758550 region. These results demonstrate robust effects of both the enhancer element and SNP rs5758550 on CYP2D6 expression, supporting consideration of rs5758550 for CYP2D6 genotyping panels to yield more accurate phenotype prediction. PMID:25381333

  20. An Incompressible 2D Didactic Model with Singularity and Explicit Solutions of the 2D Boussinesq Equations

    NASA Astrophysics Data System (ADS)

    Chae, Dongho; Constantin, Peter; Wu, Jiahong

    2014-09-01

    We give an example of a well posed, finite energy, 2D incompressible active scalar equation with the same scaling as the surface quasi-geostrophic equation and prove that it can produce finite time singularities. In spite of its simplicity, this seems to be the first such example. Further, we construct explicit solutions of the 2D Boussinesq equations whose gradients grow exponentially in time for all time. In addition, we introduce a variant of the 2D Boussinesq equations which is perhaps a more faithful companion of the 3D axisymmetric Euler equations than the usual 2D Boussinesq equations.

  1. HATCH CONNECTING TEMPERED AIR CHAMBER AND HOT AIR CHAMBER OF ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    HATCH CONNECTING TEMPERED AIR CHAMBER AND HOT AIR CHAMBER OF PLENUM WITH ATTACHED DRAFT REGULATOR. - Hot Springs National Park, Bathhouse Row, Superior Bathhouse: Mechanical & Piping Systems, State Highway 7, 1 mile north of U.S. Highway 70, Hot Springs, Garland County, AR

  2. Finite Element Analysis of Reverberation Chambers

    NASA Technical Reports Server (NTRS)

    Bunting, Charles F.; Nguyen, Duc T.

    2000-01-01

    The primary motivating factor behind the initiation of this work was to provide a deterministic means of establishing the validity of the statistical methods that are recommended for the determination of fields that interact in -an avionics system. The application of finite element analysis to reverberation chambers is the initial step required to establish a reasonable course of inquiry in this particularly data-intensive study. The use of computational electromagnetics provides a high degree of control of the "experimental" parameters that can be utilized in a simulation of reverberating structures. As the work evolved there were four primary focus areas they are: 1. The eigenvalue problem for the source free problem. 2. The development of a complex efficient eigensolver. 3. The application of a source for the TE and TM fields for statistical characterization. 4. The examination of shielding effectiveness in a reverberating environment. One early purpose of this work was to establish the utility of finite element techniques in the development of an extended low frequency statistical model for reverberation phenomena. By employing finite element techniques, structures of arbitrary complexity can be analyzed due to the use of triangular shape functions in the spatial discretization. The effects of both frequency stirring and mechanical stirring are presented. It is suggested that for the low frequency operation the typical tuner size is inadequate to provide a sufficiently random field and that frequency stirring should be used. The results of the finite element analysis of the reverberation chamber illustrate io-W the potential utility of a 2D representation for enhancing the basic statistical characteristics of the chamber when operating in a low frequency regime. The basic field statistics are verified for frequency stirring over a wide range of frequencies. Mechanical stirring is shown to provide an effective frequency deviation.

  3. Adaptation algorithms for 2-D feedforward neural networks.

    PubMed

    Kaczorek, T

    1995-01-01

    The generalized weight adaptation algorithms presented by J.G. Kuschewski et al. (1993) and by S.H. Zak and H.J. Sira-Ramirez (1990) are extended for 2-D madaline and 2-D two-layer feedforward neural nets (FNNs).

  4. Integrating Mobile Multimedia into Textbooks: 2D Barcodes

    ERIC Educational Resources Information Center

    Uluyol, Celebi; Agca, R. Kagan

    2012-01-01

    The major goal of this study was to empirically compare text-plus-mobile phone learning using an integrated 2D barcode tag in a printed text with three other conditions described in multimedia learning theory. The method examined in the study involved modifications of the instructional material such that: a 2D barcode was used near the text, the…

  5. Efficient Visible Quasi-2D Perovskite Light-Emitting Diodes.

    PubMed

    Byun, Jinwoo; Cho, Himchan; Wolf, Christoph; Jang, Mi; Sadhanala, Aditya; Friend, Richard H; Yang, Hoichang; Lee, Tae-Woo

    2016-09-01

    Efficient quasi-2D-structure perovskite light-emitting diodes (4.90 cd A(-1) ) are demonstrated by mixing a 3D-structured perovskite material (methyl ammonium lead bromide) and a 2D-structured perovskite material (phenylethyl ammonium lead bromide), which can be ascribed to better film uniformity, enhanced exciton confinement, and reduced trap density. PMID:27334788

  6. CYP2D6: novel genomic structures and alleles

    PubMed Central

    Kramer, Whitney E.; Walker, Denise L.; O’Kane, Dennis J.; Mrazek, David A.; Fisher, Pamela K.; Dukek, Brian A.; Bruflat, Jamie K.; Black, John L.

    2010-01-01

    Objective CYP2D6 is a polymorphic gene. It has been observed to be deleted, to be duplicated and to undergo recombination events involving the CYP2D7 pseudogene and surrounding sequences. The objective of this study was to discover the genomic structure of CYP2D6 recombinants that interfere with clinical genotyping platforms that are available today. Methods Clinical samples containing rare homozygous CYP2D6 alleles, ambiguous readouts, and those with duplication signals and two different alleles were analyzed by long-range PCR amplification of individual genes, PCR fragment analysis, allele-specific primer extension assay, and DNA sequencing to characterize alleles and genomic structure. Results Novel alleles, genomic structures, and the DNA sequence of these structures are described. Interestingly, in 49 of 50 DNA samples that had CYP2D6 gene duplications or multiplications where two alleles were detected, the chromosome containing the duplication or multiplication had identical tandem alleles. Conclusion Several new CYP2D6 alleles and genomic structures are described which will be useful for CYP2D6 genotyping. The findings suggest that the recombination events responsible for CYP2D6 duplications and multiplications are because of mechanisms other than interchromosomal crossover during meiosis. PMID:19741566

  7. Efficient Visible Quasi-2D Perovskite Light-Emitting Diodes.

    PubMed

    Byun, Jinwoo; Cho, Himchan; Wolf, Christoph; Jang, Mi; Sadhanala, Aditya; Friend, Richard H; Yang, Hoichang; Lee, Tae-Woo

    2016-09-01

    Efficient quasi-2D-structure perovskite light-emitting diodes (4.90 cd A(-1) ) are demonstrated by mixing a 3D-structured perovskite material (methyl ammonium lead bromide) and a 2D-structured perovskite material (phenylethyl ammonium lead bromide), which can be ascribed to better film uniformity, enhanced exciton confinement, and reduced trap density.

  8. 2D materials and van der Waals heterostructures.

    PubMed

    Novoselov, K S; Mishchenko, A; Carvalho, A; Castro Neto, A H

    2016-07-29

    The physics of two-dimensional (2D) materials and heterostructures based on such crystals has been developing extremely fast. With these new materials, truly 2D physics has begun to appear (for instance, the absence of long-range order, 2D excitons, commensurate-incommensurate transition, etc.). Novel heterostructure devices--such as tunneling transistors, resonant tunneling diodes, and light-emitting diodes--are also starting to emerge. Composed from individual 2D crystals, such devices use the properties of those materials to create functionalities that are not accessible in other heterostructures. Here we review the properties of novel 2D crystals and examine how their properties are used in new heterostructure devices.

  9. Van der Waals stacked 2D layered materials for optoelectronics

    NASA Astrophysics Data System (ADS)

    Zhang, Wenjing; Wang, Qixing; Chen, Yu; Wang, Zhuo; Wee, Andrew T. S.

    2016-06-01

    The band gaps of many atomically thin 2D layered materials such as graphene, black phosphorus, monolayer semiconducting transition metal dichalcogenides and hBN range from 0 to 6 eV. These isolated atomic planes can be reassembled into hybrid heterostructures made layer by layer in a precisely chosen sequence. Thus, the electronic properties of 2D materials can be engineered by van der Waals stacking, and the interlayer coupling can be tuned, which opens up avenues for creating new material systems with rich functionalities and novel physical properties. Early studies suggest that van der Waals stacked 2D materials work exceptionally well, dramatically enriching the optoelectronics applications of 2D materials. Here we review recent progress in van der Waals stacked 2D materials, and discuss their potential applications in optoelectronics.

  10. KMT2D regulates specific programs in heart development via histone H3 lysine 4 di-methylation.

    PubMed

    Ang, Siang-Yun; Uebersohn, Alec; Spencer, C Ian; Huang, Yu; Lee, Ji-Eun; Ge, Kai; Bruneau, Benoit G

    2016-03-01

    KMT2D, which encodes a histone H3K4 methyltransferase, has been implicated in human congenital heart disease in the context of Kabuki syndrome. However, its role in heart development is not understood. Here, we demonstrate a requirement for KMT2D in cardiac precursors and cardiomyocytes during cardiogenesis in mice. Gene expression analysis revealed downregulation of ion transport and cell cycle genes, leading to altered calcium handling and cell cycle defects. We further determined that myocardial Kmt2d deletion led to decreased H3K4me1 and H3K4me2 at enhancers and promoters. Finally, we identified KMT2D-bound regions in cardiomyocytes, of which a subset was associated with decreased gene expression and decreased H3K4me2 in mutant hearts. This subset included genes related to ion transport, hypoxia-reoxygenation and cell cycle regulation, suggesting that KMT2D is important for these processes. Our findings indicate that KMT2D is essential for regulating cardiac gene expression during heart development primarily via H3K4 di-methylation.

  11. KMT2D regulates specific programs in heart development via histone H3 lysine 4 di-methylation

    PubMed Central

    Ang, Siang-Yun; Uebersohn, Alec; Spencer, C. Ian; Huang, Yu; Lee, Ji-Eun; Ge, Kai; Bruneau, Benoit G.

    2016-01-01

    KMT2D, which encodes a histone H3K4 methyltransferase, has been implicated in human congenital heart disease in the context of Kabuki syndrome. However, its role in heart development is not understood. Here, we demonstrate a requirement for KMT2D in cardiac precursors and cardiomyocytes during cardiogenesis in mice. Gene expression analysis revealed downregulation of ion transport and cell cycle genes, leading to altered calcium handling and cell cycle defects. We further determined that myocardial Kmt2d deletion led to decreased H3K4me1 and H3K4me2 at enhancers and promoters. Finally, we identified KMT2D-bound regions in cardiomyocytes, of which a subset was associated with decreased gene expression and decreased H3K4me2 in mutant hearts. This subset included genes related to ion transport, hypoxia-reoxygenation and cell cycle regulation, suggesting that KMT2D is important for these processes. Our findings indicate that KMT2D is essential for regulating cardiac gene expression during heart development primarily via H3K4 di-methylation. PMID:26932671

  12. KMT2D regulates specific programs in heart development via histone H3 lysine 4 di-methylation.

    PubMed

    Ang, Siang-Yun; Uebersohn, Alec; Spencer, C Ian; Huang, Yu; Lee, Ji-Eun; Ge, Kai; Bruneau, Benoit G

    2016-03-01

    KMT2D, which encodes a histone H3K4 methyltransferase, has been implicated in human congenital heart disease in the context of Kabuki syndrome. However, its role in heart development is not understood. Here, we demonstrate a requirement for KMT2D in cardiac precursors and cardiomyocytes during cardiogenesis in mice. Gene expression analysis revealed downregulation of ion transport and cell cycle genes, leading to altered calcium handling and cell cycle defects. We further determined that myocardial Kmt2d deletion led to decreased H3K4me1 and H3K4me2 at enhancers and promoters. Finally, we identified KMT2D-bound regions in cardiomyocytes, of which a subset was associated with decreased gene expression and decreased H3K4me2 in mutant hearts. This subset included genes related to ion transport, hypoxia-reoxygenation and cell cycle regulation, suggesting that KMT2D is important for these processes. Our findings indicate that KMT2D is essential for regulating cardiac gene expression during heart development primarily via H3K4 di-methylation. PMID:26932671

  13. A multiple sampling ionization chamber for the External Target Facility

    NASA Astrophysics Data System (ADS)

    Zhang, X. H.; Tang, S. W.; Ma, P.; Lu, C. G.; Yang, H. R.; Wang, S. T.; Yu, Y. H.; Yue, K.; Fang, F.; Yan, D.; Zhou, Y.; Wang, Z. M.; Sun, Y.; Sun, Z. Y.; Duan, L. M.; Sun, B. H.

    2015-09-01

    A multiple sampling ionization chamber used as a particle identification device for high energy heavy ions has been developed for the External Target Facility. The performance of this detector was tested with a 239Pu α source and RI beams. A Z resolution (FWHM) of 0.4-0.6 was achieved for nuclear fragments of 18O at 400 AMeV.

  14. Estrogen-Induced Cholestasis Leads to Repressed CYP2D6 Expression in CYP2D6-Humanized Mice

    PubMed Central

    Pan, Xian

    2015-01-01

    Cholestasis activates bile acid receptor farnesoid X receptor (FXR) and subsequently enhances hepatic expression of small heterodimer partner (SHP). We previously demonstrated that SHP represses the transactivation of cytochrome P450 2D6 (CYP2D6) promoter by hepatocyte nuclear factor (HNF) 4α. In this study, we investigated the effects of estrogen-induced cholestasis on CYP2D6 expression. Estrogen-induced cholestasis occurs in subjects receiving estrogen for contraception or hormone replacement, or in susceptible women during pregnancy. In CYP2D6-humanized transgenic (Tg-CYP2D6) mice, cholestasis triggered by administration of 17α-ethinylestradiol (EE2) at a high dose led to 2- to 3-fold decreases in CYP2D6 expression. This was accompanied by increased hepatic SHP expression and subsequent decreases in the recruitment of HNF4α to CYP2D6 promoter. Interestingly, estrogen-induced cholestasis also led to increased recruitment of estrogen receptor (ER) α, but not that of FXR, to Shp promoter, suggesting a predominant role of ERα in transcriptional regulation of SHP in estrogen-induced cholestasis. EE2 at a low dose (that does not cause cholestasis) also increased SHP (by ∼50%) and decreased CYP2D6 expression (by 1.5-fold) in Tg-CYP2D6 mice, the magnitude of differences being much smaller than that shown in EE2-induced cholestasis. Taken together, our data indicate that EE2-induced cholestasis increases SHP and represses CYP2D6 expression in Tg-CYP2D6 mice in part through ERα transactivation of Shp promoter. PMID:25943116

  15. Nanoscale elastic changes in 2D Ti3C2Tx (MXene) pseudocapacitive electrodes

    DOE PAGES

    Come, Jeremy; Xie, Yu; Naguib, Michael; Jesse, Stephen; Kalinin, Sergei V.; Gogotsi, Yury; Kent, Paul R. C.; Balke, Nina

    2016-02-01

    Designing sustainable electrodes for next generation energy storage devices relies on the understanding of their fundamental properties at the nanoscale, including the comprehension of ions insertion into the electrode and their interactions with the active material. One consequence of ion storage is the change in the electrode volume resulting in mechanical strain and stress that can strongly affect the cycle life. Therefore, it is important to understand the changes of dimensions and mechanical properties occurring during electrochemical reactions. While the characterization of mechanical properties via macroscopic measurements is well documented, in-situ characterization of their evolution has never been achieved atmore » the nanoscale. Two dimensional (2D) carbides, known as MXenes, are promising materials for supercapacitors and various kinds of batteries, and understating the coupling between their mechanical and electrochemical properties is therefore necessary. Here we report on in-situ imaging, combined with density functional theory of the elastic changes, of a 2D titanium carbide (Ti3C2Tx) electrode in direction normal to the basal plane during cation intercalation. The results show a strong correlation between the Li+ ions content and the elastic modulus, whereas little effects of K+ ions are observed. Moreover, this strategy enables identifying the preferential intercalation pathways within a single particle.« less

  16. LRL 25-inch Bubble Chamber

    DOE R&D Accomplishments Database

    Alvarez, L. W.; Gow, J. D.; Barrera, F.; Eckman, G.; Shand, J.; Watt, R.; Norgren, D.; Hernandez, H. P.

    1964-07-08

    The recently completed 25-inch hydrogen bubble chamber combines excellent picture quality with a fast operating cycle. The chamber has a unique optical system and is designed to take several pictures each Bevatron pulse, in conjunction with the Bevatron rapid beam ejection system.

  17. Fast-response cloud chamber

    NASA Technical Reports Server (NTRS)

    Fogal, G. L.

    1977-01-01

    Wall structure keeps chambers at constant, uniform temperature, yet allows them to be cooled rapidly if necessary. Wall structure, used in fast-response cloud chamber, has surface heater and coolant shell separated by foam insulation. It is lightweight and requires relatively little power.

  18. Chamber Music: Skills and Teamwork.

    ERIC Educational Resources Information Center

    Villarrubia, Charles

    2000-01-01

    Focuses on the benefits of participating in chamber music ensembles, such as the development of a heightened level of awareness, and considers the role of the music educator/conductor. Provides tools and exercises that teachers can introduce to chamber music players to improve their rehearsals and performances. (CMK)

  19. Slow magnetic relaxation in a hydrogen-bonded 2D array of mononuclear dysprosium(III) oxamates.

    PubMed

    Fortea-Pérez, Francisco R; Vallejo, Julia; Julve, Miguel; Lloret, Francesc; De Munno, Giovanni; Armentano, Donatella; Pardo, Emilio

    2013-05-01

    The reaction of N-(2,6-dimethylphenyl)oxamic acid with dysprosium(III) ions in a controlled basic media afforded the first example of a mononuclear lanthanide oxamate complex exhibiting a field-induced slow magnetic relaxation behavior typical of single-ion magnets (SIMs). The hydrogen-bond-mediated self-assembly of this new bifunctional dysprosium(III) SIM in the solid state provides a unique example of 2D hydrogen-bonded polymer with a herringbone net topology.

  20. National Ignition Facility Target Chamber

    SciTech Connect

    Wavrik, R W; Cox, J R; Fleming, P J

    2000-10-05

    On June 11, 1999 the Department of Energy dedicated the single largest piece of the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) in Livermore, California. The ten (10) meter diameter aluminum target high vacuum chamber will serve as the working end of the largest laser in the world. The output of 192 laser beams will converge at the precise center of the chamber. The laser beams will enter the chamber in two by two arrays to illuminate 10 millimeter long gold cylinders called hohlraums enclosing 2 millimeter capsule containing deuterium, tritium and isotopes of hydrogen. The two isotopes will fuse, thereby creating temperatures and pressures resembling those found only inside stars and in detonated nuclear weapons, but on a minute scale. The NIF Project will serve as an essential facility to insure safety and reliability of our nation's nuclear arsenal as well as demonstrating inertial fusion's contribution to creating electrical power. The paper will discuss the requirements that had to be addressed during the design, fabrication and testing of the target chamber. A team from Sandia National Laboratories (SNL) and LLNL with input from industry performed the configuration and basic design of the target chamber. The method of fabrication and construction of the aluminum target chamber was devised by Pitt-Des Moines, Inc. (PDM). PDM also participated in the design of the chamber in areas such as the Target Chamber Realignment and Adjustment System, which would allow realignment of the sphere laser beams in the event of earth settlement or movement from a seismic event. During the fabrication of the target chamber the sphericity tolerances had to be addressed for the individual plates. Procedures were developed for forming, edge preparation and welding of individual plates. Construction plans were developed to allow the field construction of the target chamber to occur parallel to other NIF construction activities. This was

  1. Targeted fluorescence imaging enhanced by 2D materials: a comparison between 2D MoS2 and graphene oxide.

    PubMed

    Xie, Donghao; Ji, Ding-Kun; Zhang, Yue; Cao, Jun; Zheng, Hu; Liu, Lin; Zang, Yi; Li, Jia; Chen, Guo-Rong; James, Tony D; He, Xiao-Peng

    2016-08-01

    Here we demonstrate that 2D MoS2 can enhance the receptor-targeting and imaging ability of a fluorophore-labelled ligand. The 2D MoS2 has an enhanced working concentration range when compared with graphene oxide, resulting in the improved imaging of both cell and tissue samples.

  2. An extension of ASM2d including pH calculation.

    PubMed

    Serralta, J; Ferrer, J; Borrás, L; Seco, A

    2004-11-01

    This paper presents an extension of the Activated Sludge Model No. 2d (ASM2d) including a chemical model able to calculate the pH value in biological processes. The developed chemical model incorporates the complete set of chemical species affecting the pH value to ASM2d describing non-equilibrium biochemical processes. It considers the system formed by one aqueous phase, in which biochemical processes take place, and one gaseous phase, and is based on the assumptions of instantaneous chemical equilibrium under liquid phase and kinetically governed mass transport between the liquid and gas phase. The ASM2d enlargement comprises the addition of every component affecting the pH value and an ion-balance for the calculation of the pH value and the dissociation species. The significant pH variations observed in a sequencing batch reactor operated for enhanced biological phosphorus removal were used to verify the capability of the extended model for predicting the dynamics of pH jointly with concentrations of acetic acid and phosphate. A pH inhibition function for polyphosphate accumulating bacteria has also been included in the model to simulate the behaviour observed. Experimental data obtained in four different experiments (with different sludge retention time and influent phosphorus concentrations) were accurately reproduced.

  3. Overtone spectroscopy of H2D+ and D2H+ using laser induced reactions

    NASA Astrophysics Data System (ADS)

    Asvany, Oskar; Hugo, Edouard; Müller, Frank; Kühnemann, Frank; Schiller, Stephan; Tennyson, Jonathan; Schlemmer, Stephan

    2007-10-01

    The method of laser induced reaction is used to obtain high-resolution IR spectra of H2D+ and D2H+ in collision with n-H2 at a nominal temperature of 17K. For this purpose three cw-laser systems have been coupled to a 22-pole ion trap apparatus, two commercial diode laser systems in the ranges of 6100-6600cm-1 and 6760-7300cm-1, respectively, and a high-power optical parametric oscillator tunable in the range of 2600-3200cm-1. In total, 27 new overtone and combination transitions have been detected for H2D + and D2H+, as well as a weak line in the ν1 vibrational band of H2D+ (220←101) at 3164.118cm-1. The line positions are compared to high accuracy ab initio calculations, showing small but mode-dependent differences, being largest for three vibrational quanta in the ν2 symmetric bending of H2D+. Within the experimental accuracy, the relative values of the ab initio predicted Einstein B coefficients are confirmed.

  4. Efficient 2D MRI relaxometry using compressed sensing

    NASA Astrophysics Data System (ADS)

    Bai, Ruiliang; Cloninger, Alexander; Czaja, Wojciech; Basser, Peter J.

    2015-06-01

    Potential applications of 2D relaxation spectrum NMR and MRI to characterize complex water dynamics (e.g., compartmental exchange) in biology and other disciplines have increased in recent years. However, the large amount of data and long MR acquisition times required for conventional 2D MR relaxometry limits its applicability for in vivo preclinical and clinical MRI. We present a new MR pipeline for 2D relaxometry that incorporates compressed sensing (CS) as a means to vastly reduce the amount of 2D relaxation data needed for material and tissue characterization without compromising data quality. Unlike the conventional CS reconstruction in the Fourier space (k-space), the proposed CS algorithm is directly applied onto the Laplace space (the joint 2D relaxation data) without compressing k-space to reduce the amount of data required for 2D relaxation spectra. This framework is validated using synthetic data, with NMR data acquired in a well-characterized urea/water phantom, and on fixed porcine spinal cord tissue. The quality of the CS-reconstructed spectra was comparable to that of the conventional 2D relaxation spectra, as assessed using global correlation, local contrast between peaks, peak amplitude and relaxation parameters, etc. This result brings this important type of contrast closer to being realized in preclinical, clinical, and other applications.

  5. Ion thruster performance model

    NASA Technical Reports Server (NTRS)

    Brophy, J. R.

    1984-01-01

    A model of ion thruster performance is developed for high flux density, cusped magnetic field thruster designs. This model is formulated in terms of the average energy required to produce an ion in the discharge chamber plasma and the fraction of these ions that are extracted to form the beam. The direct loss of high energy (primary) electrons from the plasma to the anode is shown to have a major effect on thruster performance. The model provides simple algebraic equations enabling one to calculate the beam ion energy cost, the average discharge chamber plasma ion energy cost, the primary electron density, the primary-to-Maxwellian electron density ratio and the Maxwellian electron temperature. Experiments indicate that the model correctly predicts the variation in plasma ion energy cost for changes in propellant gas (Ar, Kr and Xe), grid transparency to neutral atoms, beam extraction area, discharge voltage, and discharge chamber wall temperature. The model and experiments indicate that thruster performance may be described in terms of only four thruster configuration dependent parameters and two operating parameters. The model also suggests that improved performance should be exhibited by thruster designs which extract a large fraction of the ions produced in the discharge chamber, which have good primary electron and neutral atom containment and which operate at high propellant flow rates.

  6. A two dimensional finite difference time domain analysis of the quiet zone fields of an anechoic chamber

    NASA Technical Reports Server (NTRS)

    Ryan, Deirdre A.; Luebbers, Raymond J.; Nguyen, Truong X.; Kunz, Karl S.; Steich, David J.

    1992-01-01

    Prediction of anechoic chamber performance is a difficult problem. Electromagnetic anechoic chambers exist for a wide range of frequencies but are typically very large when measured in wavelengths. Three dimensional finite difference time domain (FDTD) modeling of anechoic chambers is possible with current computers but at frequencies lower than most chamber design frequencies. However, two dimensional FDTD (2D-FTD) modeling enables much greater detail at higher frequencies and offers significant insight into compact anechoic chamber design and performance. A major subsystem of an anechoic chamber for which computational electromagnetic analyses exist is the reflector. First, an analysis of the quiet zone fields of a low frequency anechoic chamber produced by a uniform source and a reflector in two dimensions using the FDTD method is presented. The 2D-FDTD results are compared with results from a three dimensional corrected physical optics calculation and show good agreement. Next, a directional source is substituted for the uniform radiator. Finally, a two dimensional anechoic chamber geometry, including absorbing materials, is considered, and the 2D-FDTD results for these geometries appear reasonable.

  7. Practical Algorithm For Computing The 2-D Arithmetic Fourier Transform

    NASA Astrophysics Data System (ADS)

    Reed, Irving S.; Choi, Y. Y.; Yu, Xiaoli

    1989-05-01

    Recently, Tufts and Sadasiv [10] exposed a method for computing the coefficients of a Fourier series of a periodic function using the Mobius inversion of series. They called this method of analysis the Arithmetic Fourier Transform(AFT). The advantage of the AFT over the FN 1' is that this method of Fourier analysis needs only addition operations except for multiplications by scale factors at one stage of the computation. The disadvantage of the AFT as they expressed it originally is that it could be used effectively only to compute finite Fourier coefficients of a real even function. To remedy this the AFT developed in [10] is extended in [11] to compute the Fourier coefficients of both the even and odd components of a periodic function. In this paper, the improved AFT [11] is extended to a two-dimensional(2-D) Arithmetic Fourier Transform for calculating the Fourier Transform of two-dimensional discrete signals. This new algorithm is based on both the number-theoretic method of Mobius inversion of double series and the complex conjugate property of Fourier coefficients. The advantage of this algorithm over the conventional 2-D FFT is that the corner-turning problem needed in a conventional 2-D Discrete Fourier Transform(DFT) can be avoided. Therefore, this new 2-D algorithm is readily suitable for VLSI implementation as a parallel architecture. Comparing the operations of 2-D AFT of a MxM 2-D data array with the conventional 2-D FFT, the number of multiplications is significantly reduced from (2log2M)M2 to (9/4)M2. Hence, this new algorithm is faster than the FFT algorithm. Finally, two simulation results of this new 2-D AFT algorithm for 2-D artificial and real images are given in this paper.

  8. ION ACCELERATION SYSTEM

    DOEpatents

    Luce, J.S.; Martin, J.A.

    1960-02-23

    Well focused, intense ion beams are obtained by providing a multi- apertured source grid in front of an ion source chamber and an accelerating multi- apertured grid closely spaced from and in alignment with the source grid. The longest dimensions of the elongated apertures in the grids are normal to the direction of the magnetic field used with the device. Large ion currents may be withdrawn from the source, since they do not pass through any small focal region between the grids.

  9. 2D electron cyclotron emission imaging at ASDEX Upgrade (invited)

    SciTech Connect

    Classen, I. G. J.; Boom, J. E.; Vries, P. C. de; Suttrop, W.; Schmid, E.; Garcia-Munoz, M.; Schneider, P. A.; Tobias, B.; Domier, C. W.; Luhmann, N. C. Jr.; Donne, A. J. H.; Jaspers, R. J. E.; Park, H. K.; Munsat, T.

    2010-10-15

    The newly installed electron cyclotron emission imaging diagnostic on ASDEX Upgrade provides measurements of the 2D electron temperature dynamics with high spatial and temporal resolution. An overview of the technical and experimental properties of the system is presented. These properties are illustrated by the measurements of the edge localized mode and the reversed shear Alfven eigenmode, showing both the advantage of having a two-dimensional (2D) measurement, as well as some of the limitations of electron cyclotron emission measurements. Furthermore, the application of singular value decomposition as a powerful tool for analyzing and filtering 2D data is presented.

  10. Comparison of 2D and 3D gamma analyses

    SciTech Connect

    Pulliam, Kiley B.; Huang, Jessie Y.; Howell, Rebecca M.; Followill, David; Kry, Stephen F.; Bosca, Ryan; O’Daniel, Jennifer

    2014-02-15

    Purpose: As clinics begin to use 3D metrics for intensity-modulated radiation therapy (IMRT) quality assurance, it must be noted that these metrics will often produce results different from those produced by their 2D counterparts. 3D and 2D gamma analyses would be expected to produce different values, in part because of the different search space available. In the present investigation, the authors compared the results of 2D and 3D gamma analysis (where both datasets were generated in the same manner) for clinical treatment plans. Methods: Fifty IMRT plans were selected from the authors’ clinical database, and recalculated using Monte Carlo. Treatment planning system-calculated (“evaluated dose distributions”) and Monte Carlo-recalculated (“reference dose distributions”) dose distributions were compared using 2D and 3D gamma analysis. This analysis was performed using a variety of dose-difference (5%, 3%, 2%, and 1%) and distance-to-agreement (5, 3, 2, and 1 mm) acceptance criteria, low-dose thresholds (5%, 10%, and 15% of the prescription dose), and data grid sizes (1.0, 1.5, and 3.0 mm). Each comparison was evaluated to determine the average 2D and 3D gamma, lower 95th percentile gamma value, and percentage of pixels passing gamma. Results: The average gamma, lower 95th percentile gamma value, and percentage of passing pixels for each acceptance criterion demonstrated better agreement for 3D than for 2D analysis for every plan comparison. The average difference in the percentage of passing pixels between the 2D and 3D analyses with no low-dose threshold ranged from 0.9% to 2.1%. Similarly, using a low-dose threshold resulted in a difference between the mean 2D and 3D results, ranging from 0.8% to 1.5%. The authors observed no appreciable differences in gamma with changes in the data density (constant difference: 0.8% for 2D vs 3D). Conclusions: The authors found that 3D gamma analysis resulted in up to 2.9% more pixels passing than 2D analysis. It must

  11. Recent advances in 2D materials for photocatalysis.

    PubMed

    Luo, Bin; Liu, Gang; Wang, Lianzhou

    2016-04-01

    Two-dimensional (2D) materials have attracted increasing attention for photocatalytic applications because of their unique thickness dependent physical and chemical properties. This review gives a brief overview of the recent developments concerning the chemical synthesis and structural design of 2D materials at the nanoscale and their applications in photocatalytic areas. In particular, recent progress on the emerging strategies for tailoring 2D material-based photocatalysts to improve their photo-activity including elemental doping, heterostructure design and functional architecture assembly is discussed.

  12. Roos and NACP-02 ion chamber perturbations and water-air stopping-power ratios for clinical electron beams for energies from 4 to 22 MeV

    NASA Astrophysics Data System (ADS)

    Bailey, M.; Shipley, D. R.; Manning, J. W.

    2015-02-01

    Empirical fits are developed for depth-compensated wall- and cavity-replacement perturbations in the PTW Roos 34001 and IBA / Scanditronix NACP-02 parallel-plate ionisation chambers, for electron beam qualities from 4 to 22 MeV for depths up to approximately 1.1 × R50,D. These are based on calculations using the Monte Carlo radiation transport code EGSnrc and its user codes with a full simulation of the linac treatment head modelled using BEAMnrc. These fits are used with calculated restricted stopping-power ratios between air and water to match measured depth-dose distributions in water from an Elekta Synergy clinical linear accelerator at the UK National Physical Laboratory. Results compare well with those from recent publications and from the IPEM 2003 electron beam radiotherapy Code of Practice.

  13. DUAL HEATED ION SOURCE STRUCTURE HAVING ARC SHIFTING MEANS

    DOEpatents

    Lawrence, E.O.

    1959-04-14

    An ion source is presented for calutrons, particularly an electrode arrangement for the ion generator of a calutron ion source. The ion source arc chamber is heated and an exit opening with thermally conductive plates defines the margins of the opening. These plates are electrically insulated from the body of the ion source and are connected to a suitable source of voltage to serve as electrodes for shaping the ion beam egressing from the arc chamber.

  14. Starting a High School Chamber Music Group.

    ERIC Educational Resources Information Center

    Rutkowski, Joseph

    2000-01-01

    Presents ideas on how to begin a chamber music ensemble. Discusses how to find time to accomplish chamber music playing in and around the school day. Presents short descriptions of chamber music that can be used with ensembles. Includes chamber music resources and additional chamber works. (CMK)

  15. Development of ``Static'' In-Situ Implanter Chamber Cleaning

    NASA Astrophysics Data System (ADS)

    Yedave, Sharad; Sweeney, Joe; Byl, Oleg; Letaj, Shkelqim; Wodjenski, Mike; Hilgarth, Monica; Marganski, Paul; Bishop, Steve; Eldridge, David; Kaim, Robert

    2008-11-01

    Since the introduction of XeF2 in-situ cleaning, its use in production implanters has been mainly focused on cleaning ion sources by flowing the cleaning vapor through the source arc chamber. This has been called "Dynamic" in-situ cleaning. "Static" in-situ cleaning is a different method under development at ATMI which allows an entire vacuum chamber and its contents to be cleaned. The chamber is filled to a pressure of 1-3 Torr of XeF2 vapor, which reacts with deposited material on all internal surfaces, and the reaction by-products are then pumped away. When applied to the source vacuum chamber, the Static cleaning method allows cleaning vapor to contact components, such as the HV bushing and the manipulator assembly, which may not be adequately cleaned with the Dynamic method. Recently, ATMI has installed a prototype Static in-situ cleaning system on an in-house Ion Source Test Stand in Danbury, CT. This paper will describe the prototype cleaning system and process and its applicability to production implant systems. We will also present experimental data showing removal of various dopant residues and the cleaning effectiveness for different components and surfaces inside the source vacuum chamber.

  16. Formation and properties of a terpyridine-based 2D MOF on the surface of water

    NASA Astrophysics Data System (ADS)

    Koitz, Ralph; Hutter, Jürg; Iannuzzi, Marcella

    2016-06-01

    Two-dimensional networks inspired by graphene are of prime importance in nanoscience. We present a computational study of an infinite molecular sheet confined on a water surface to assess its properties and formation mechanism. Terpyridine-based ligand molecules are interlinked by Zn ions to form an extended 2D metal-organic framework. We show that the network is stable on the water surface, and that the substrate affects the dynamic properties of the sheet, exhibiting a confining effect and flattening the sheet by 30%. We use metadynamics to characterize the process of network formation and breaking and determine an intra-network binding energy of 143 kJ mol‑1. Based on this mechanistic insight we propose that the 2D network strength can be tuned by varying the rigidity of the ligand through its chemical structure.

  17. Topological insulators based on 2D shape-persistent organic ligand complexes.

    PubMed

    Zhou, Qionghua; Wang, Jinlan; Chwee, Tsz Sian; Wu, Gang; Wang, Xiaobai; Ye, Qun; Xu, Jianwei; Yang, Shuo-Wang

    2015-01-14

    Topological insulators (TIs) represent an exciting new class of materials with potential applications in spintronics and quantum computing. In this work, we present a theoretical study on a new family of two dimensional (2D) nanomaterials based on the coordination of shape persistent organic ligands (SPOLs) to heavy transition metal ions such as Pd(2+) and Pt(2+). These 2D structures may be readily fabricated and are expected to be stable under normal atmospheric conditions. From first principles calculations and tight-binding model simulations carried out to characterize the bulk band structures, edge states, spin Chern numbers, and the Z2 topological invariants, we were able to identify candidates with non-trivial topological properties that may serve as topological insulators in real world applications.

  18. Submillimeter laboratory identification of CH{sup +} and CH{sub 2}D{sup +}

    SciTech Connect

    Amano, T.

    2015-01-22

    Laboratory identification of two basic and important interstellar molecular ions is presented. The J = 1 - 0 rotational transition of {sup 12}CH{sup +} together with those of {sup 13}CH{sup +} and {sup 12}CD{sup +} was observed in the laboratory. The newly obtained frequencies were found to be different from those reported previously. Various experimental evidences firmly support the new measurements. In addition, the Zeeman effect and the spin-rotation hyperfine interaction enforce the laboratory identification with no ambiguity. Rotational lines of CH{sub 2}D{sup +} were observed in the submillimeter-wave region. This laboratory observation is consistent with a recent tentative identification of CH{sub 2}D{sup +} toward Ori IRc2.

  19. ION PRODUCING MECHANISM

    DOEpatents

    Backus, J.G.

    1958-08-19

    A novel ion source is described for use in a calutron which has the prime adwantage of reducing the nunnber of unwanted ions in the ion generating mechamism.An important feature of the invention resides In an arc chamber having a lining of the polyisotopic material to be treated In the calutron and bombardment of the linirg with positive ions of a light gas to induce sputtering and ionization of the lining. With the reduction of unwanted ions in the source beam provided by the described source, the calutron operation may be more accurately controlled.

  20. PULSED ION SOURCE

    DOEpatents

    Anderson, C.E.; Ehlers, K.W.

    1958-06-17

    An ion source is described for producing very short high density pulses of ions without bcam scattering. The ions are created by an oscillating electron discharge within a magnetic field. After the ions are drawn from the ionization chamber by an accelerating electrode the ion beam is under the influence of the magnetic field for separation of the ions according to mass and, at the same time, passes between two neutralizing plntes maintained nt equal negative potentials. As the plates are formed of a material having a high ratio of secondary electrons to impinging ions, the ion bombardment of the plntes emits electrons which neutralize the frirge space-charge of the beam and tend to prevent widening of the beam cross section due to the mutual repulsion of the ions.

  1. Alloyed 2D Metal-Semiconductor Atomic Layer Junctions.

    PubMed

    Kim, Ah Ra; Kim, Yonghun; Nam, Jaewook; Chung, Hee-Suk; Kim, Dong Jae; Kwon, Jung-Dae; Park, Sang Won; Park, Jucheol; Choi, Sun Young; Lee, Byoung Hun; Park, Ji Hyeon; Lee, Kyu Hwan; Kim, Dong-Ho; Choi, Sung Mook; Ajayan, Pulickel M; Hahm, Myung Gwan; Cho, Byungjin

    2016-03-01

    Heterostructures of compositionally and electronically variant two-dimensional (2D) atomic layers are viable building blocks for ultrathin optoelectronic devices. We show that the composition of interfacial transition region between semiconducting WSe2 atomic layer channels and metallic NbSe2 contact layers can be engineered through interfacial doping with Nb atoms. WxNb1-xSe2 interfacial regions considerably lower the potential barrier height of the junction, significantly improving the performance of the corresponding WSe2-based field-effect transistor devices. The creation of such alloyed 2D junctions between dissimilar atomic layer domains could be the most important factor in controlling the electronic properties of 2D junctions and the design and fabrication of 2D atomic layer devices.

  2. Emerging and potential opportunities for 2D flexible nanoelectronics

    NASA Astrophysics Data System (ADS)

    Zhu, Weinan; Park, Saungeun; Akinwande, Deji

    2016-05-01

    The last 10 years have seen the emergence of two-dimensional (2D) nanomaterials such as graphene, transition metal dichalcogenides (TMDs), and black phosphorus (BP) among the growing portfolio of layered van der Waals thin films. Graphene, the prototypical 2D material has advanced rapidly in device, circuit and system studies that has resulted in commercial large-area applications. In this work, we provide a perspective of the emerging and potential translational applications of 2D materials including semiconductors, semimetals, and insulators that comprise the basic material set for diverse nanosystems. Applications include RF transceivers, smart systems, the so-called internet of things, and neurotechnology. We will review the DC and RF electronic performance of graphene and BP thin film transistors. 2D materials at sub-um channel length have so far enabled cut-off frequencies from baseband to 100GHz suitable for low-power RF and sub-THz concepts.

  3. 2D hexagonal quaternion Fourier transform in color image processing

    NASA Astrophysics Data System (ADS)

    Grigoryan, Artyom M.; Agaian, Sos S.

    2016-05-01

    In this paper, we present a novel concept of the quaternion discrete Fourier transform on the two-dimensional hexagonal lattice, which we call the two-dimensional hexagonal quaternion discrete Fourier transform (2-D HQDFT). The concept of the right-side 2D HQDFT is described and the left-side 2-D HQDFT is similarly considered. To calculate the transform, the image on the hexagonal lattice is described in the tensor representation when the image is presented by a set of 1-D signals, or splitting-signals which can be separately processed in the frequency domain. The 2-D HQDFT can be calculated by a set of 1-D quaternion discrete Fourier transforms (QDFT) of the splitting-signals.

  4. Technical Review of the UNET2D Hydraulic Model

    SciTech Connect

    Perkins, William A.; Richmond, Marshall C.

    2009-05-18

    The Kansas City District of the US Army Corps of Engineers is engaged in a broad range of river management projects that require knowledge of spatially-varied hydraulic conditions such as velocities and water surface elevations. This information is needed to design new structures, improve existing operations, and assess aquatic habitat. Two-dimensional (2D) depth-averaged numerical hydraulic models are a common tool that can be used to provide velocity and depth information. Kansas City District is currently using a specific 2D model, UNET2D, that has been developed to meet the needs of their river engineering applications. This report documents a tech- nical review of UNET2D.

  5. Alloyed 2D Metal-Semiconductor Atomic Layer Junctions.

    PubMed

    Kim, Ah Ra; Kim, Yonghun; Nam, Jaewook; Chung, Hee-Suk; Kim, Dong Jae; Kwon, Jung-Dae; Park, Sang Won; Park, Jucheol; Choi, Sun Young; Lee, Byoung Hun; Park, Ji Hyeon; Lee, Kyu Hwan; Kim, Dong-Ho; Choi, Sung Mook; Ajayan, Pulickel M; Hahm, Myung Gwan; Cho, Byungjin

    2016-03-01

    Heterostructures of compositionally and electronically variant two-dimensional (2D) atomic layers are viable building blocks for ultrathin optoelectronic devices. We show that the composition of interfacial transition region between semiconducting WSe2 atomic layer channels and metallic NbSe2 contact layers can be engineered through interfacial doping with Nb atoms. WxNb1-xSe2 interfacial regions considerably lower the potential barrier height of the junction, significantly improving the performance of the corresponding WSe2-based field-effect transistor devices. The creation of such alloyed 2D junctions between dissimilar atomic layer domains could be the most important factor in controlling the electronic properties of 2D junctions and the design and fabrication of 2D atomic layer devices. PMID:26839956

  6. ORION96. 2-d Finite Element Code Postprocessor

    SciTech Connect

    Sanford, L.A.; Hallquist, J.O.

    1992-02-02

    ORION is an interactive program that serves as a postprocessor for the analysis programs NIKE2D, DYNA2D, TOPAZ2D, and CHEMICAL TOPAZ2D. ORION reads binary plot files generated by the two-dimensional finite element codes currently used by the Methods Development Group at LLNL. Contour and color fringe plots of a large number of quantities may be displayed on meshes consisting of triangular and quadrilateral elements. ORION can compute strain measures, interface pressures along slide lines, reaction forces along constrained boundaries, and momentum. ORION has been applied to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.

  7. Neutron detection via bubble chambers.

    PubMed

    Jordan, D V; Ely, J H; Peurrung, A J; Bond, L J; Collar, J I; Flake, M; Knopf, M A; Pitts, W K; Shaver, M; Sonnenschein, A; Smart, J E; Todd, L C

    2005-01-01

    Research investigating the application of pressure-cycled bubble chambers to fast neutron detection is described. Experiments with a Halon-filled chamber showed clear sensitivity to an AmBe neutron source and insensitivity to a (137)Cs gamma source. Bubble formation was documented using high-speed photography, and a ceramic piezo-electric transducer element registered the acoustic signature of bubble formation. In a second set of experiments, the bubble nucleation response of a Freon-134a chamber to an AmBe neutron source was documented with high-speed photography.

  8. Phylogenetic tree construction based on 2D graphical representation

    NASA Astrophysics Data System (ADS)

    Liao, Bo; Shan, Xinzhou; Zhu, Wen; Li, Renfa

    2006-04-01

    A new approach based on the two-dimensional (2D) graphical representation of the whole genome sequence [Bo Liao, Chem. Phys. Lett., 401(2005) 196.] is proposed to analyze the phylogenetic relationships of genomes. The evolutionary distances are obtained through measuring the differences among the 2D curves. The fuzzy theory is used to construct phylogenetic tree. The phylogenetic relationships of H5N1 avian influenza virus illustrate the utility of our approach.

  9. Generating a 2D Representation of a Complex Data Structure

    NASA Technical Reports Server (NTRS)

    James, Mark

    2006-01-01

    A computer program, designed to assist in the development and debugging of other software, generates a two-dimensional (2D) representation of a possibly complex n-dimensional (where n is an integer >2) data structure or abstract rank-n object in that other software. The nature of the 2D representation is such that it can be displayed on a non-graphical output device and distributed by non-graphical means.

  10. Anisotropic 2D Materials for Tunable Hyperbolic Plasmonics.

    PubMed

    Nemilentsau, Andrei; Low, Tony; Hanson, George

    2016-02-12

    Motivated by the recent emergence of a new class of anisotropic 2D materials, we examine their electromagnetic modes and demonstrate that a broad class of the materials can host highly directional hyperbolic plasmons. Their propagation direction can be manipulated on the spot by gate doping, enabling hyperbolic beam reflection, refraction, and bending. The realization of these natural 2D hyperbolic media opens up a new avenue in dynamic control of hyperbolic plasmons not possible in the 3D version.

  11. A simultaneous 2D/3D autostereo workstation

    NASA Astrophysics Data System (ADS)

    Chau, Dennis; McGinnis, Bradley; Talandis, Jonas; Leigh, Jason; Peterka, Tom; Knoll, Aaron; Sumer, Aslihan; Papka, Michael; Jellinek, Julius

    2012-03-01

    We present a novel immersive workstation environment that scientists can use for 3D data exploration and as their everyday 2D computer monitor. Our implementation is based on an autostereoscopic dynamic parallax barrier 2D/3D display, interactive input devices, and a software infrastructure that allows client/server software modules to couple the workstation to scientists' visualization applications. This paper describes the hardware construction and calibration, software components, and a demonstration of our system in nanoscale materials science exploration.

  12. QUENCH2D. Two-Dimensional IHCP Code

    SciTech Connect

    Osman, A.; Beck, J.V.

    1995-01-01

    QUENCH2D* is developed for the solution of general, non-linear, two-dimensional inverse heat transfer problems. This program provides estimates for the surface heat flux distribution and/or heat transfer coefficient as a function of time and space by using transient temperature measurements at appropriate interior points inside the quenched body. Two-dimensional planar and axisymmetric geometries such as turnbine disks and blades, clutch packs, and many other problems can be analyzed using QUENCH2D*.

  13. Simulating MEMS Chevron Actuator for Strain Engineering 2D Materials

    NASA Astrophysics Data System (ADS)

    Vutukuru, Mounika; Christopher, Jason; Bishop, David; Swan, Anna

    2D materials pose an exciting paradigm shift in the world of electronics. These crystalline materials have demonstrated high electric and thermal conductivities and tensile strength, showing great potential as the new building blocks of basic electronic circuits. However, strain engineering 2D materials for novel devices remains a difficult experimental feat. We propose the integration of 2D materials with MEMS devices to investigate the strain dependence on material properties such as electrical and thermal conductivity, refractive index, mechanical elasticity, and band gap. MEMS Chevron actuators, provides the most accessible framework to study strain in 2D materials due to their high output force displacements for low input power. Here, we simulate Chevron actuators on COMSOL to optimize actuator design parameters and accurately capture the behavior of the devices while under the external force of a 2D material. Through stationary state analysis, we analyze the response of the device through IV characteristics, displacement and temperature curves. We conclude that the simulation precisely models the real-world device through experimental confirmation, proving that the integration of 2D materials with MEMS is a viable option for constructing novel strain engineered devices. The authors acknowledge support from NSF DMR1411008.

  14. Study of the PTW microLion chamber temperature dependence.

    PubMed

    Gómez, F; González-Castaño, D; Díaz-Botana, P; Pardo-Montero, J

    2014-06-01

    The use of liquid ionization chambers in radiotherapy has grown during the past few years. While for air ionization chambers the k(TP) correction for air mass density due to pressure and temperature variations is well known, less work has been done on the case of liquid ionization chambers, where there is still the need to take into account the influence of temperature in the free ion yield. We have measured the PTW microLion isooctane-filled ionization chamber temperature dependence in a ~ ±10 °C interval around the standard 20 °C room temperature for three operation voltages, including the manufacturer recommended voltage, and two beam qualities, (60)Co and 50 kV x-rays. Within the measured temperature range, the microLion signal exhibits a positive linear dependence, which is around 0.24% K(-1) at 800 V with (60)Co irradiation. This effect is of the same order of magnitude as the T dependence found in air ionization chambers, but its nature is completely different and its sign opposite to that of an air chamber. Onsager theory has been used to model the results and is consistent with this linear behaviour. However, some inconsistencies in the modelling of the 50 kV x-ray results have been found that are attributed to the failure of Onsager's isolated pair assumption for such radiation quality.

  15. IRIS Leaves Thermal Vacuum Chamber

    NASA Video Gallery

    This video shows the transportation of the IRIS observatory from the thermal vacuum chamber back to the clean tent for final testing and preparations for delivery to the launch site at Vandenberg A...

  16. The multigap resistive plate chamber

    SciTech Connect

    Zeballos, E. Cerron; Crotty, I.; Hatzifotiadou, D.; Valverde, J. Lamas; Neupane, S.; Williams, M. C. S.; Zichichi, A.

    2015-02-03

    The paper describes the multigap resistive plate chamber (RPC). This is a variant of the wide gap RPC. However it has much improved time resolution, while keeping all the other advantages of the wide gap RPC design.

  17. Improved ion detector

    DOEpatents

    Tullis, A.M.

    1986-01-30

    An improved ion detector device of the ionization detection device chamber type comprises an ionization chamber having a central electrode therein surrounded by a cylindrical electrode member within the chamber with a collar frictionally fitted around at least one of the electrodes. The collar has electrical contact means carried in an annular groove in an inner bore of the collar to contact the outer surface of the electrode to provide electrical contact between an external terminal and the electrode without the need to solder leads to the electrode.

  18. ECR ion source with electron gun

    DOEpatents

    Xie, Z.Q.; Lyneis, C.M.

    1993-10-26

    An Advanced Electron Cyclotron Resonance ion source having an electron gun for introducing electrons into the plasma chamber of the ion source is described. The ion source has a injection enclosure and a plasma chamber tank. The plasma chamber is defined by a plurality of longitudinal magnets. The electron gun injects electrons axially into the plasma chamber such that ionization within the plasma chamber occurs in the presence of the additional electrons produced by the electron gun. The electron gun has a cathode for emitting electrons therefrom which is heated by current supplied from an AC power supply while bias potential is provided by a bias power supply. A concentric inner conductor and outer conductor carry heating current to a carbon chuck and carbon pusher which hold the cathode in place and also heat the cathode. In the Advanced Electron Cyclotron Resonance ion source, the electron gun replaces the conventional first stage used in prior electron cyclotron resonance ion generators. 5 figures.

  19. Light diffusing fiber optic chamber

    DOEpatents

    Maitland, Duncan J.

    2002-01-01

    A light diffusion system for transmitting light to a target area. The light is transmitted in a direction from a proximal end to a distal end by an optical fiber. A diffusing chamber is operatively connected to the optical fiber for transmitting the light from the proximal end to the distal end and transmitting said light to said target area. A plug is operatively connected to the diffusing chamber for increasing the light that is transmitted to the target area.

  20. Characterization of hollow cathode, ring cusp discharge chambers. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Vaughn, Jason A.

    1989-01-01

    An experimental study into the effects of changes in such physical design parameters as hollow cathode position, anode position and ring cusp magnetic field configuration and strength on discharge chamber performance, is described. The results are presented in terms of comparative plasma ion energy cost, extracted ion fraction and ion beam profile data. Such comparisons are used to demonstrate specific means by which changes in these design parameters induce changes in performance, i.e., through changes in the loss rates of primary electrons to the anode, of ions to discharge chamber walls or of ions to cathode and anode surfaces. Results show: (1) the rate of primary electron loss to the anode decreases as the anode is moved downstream of the ring cusp toward the screen grid, (2) the loss rate of ions to hollow cathode surfaces are excessive if the cathode is located upstream of a point of peak magnetic flux density on the discharge chamber centerline, and (3) the fraction of the ions produced that are lost to discharge chamber walls and ring magnet surfaces is reduced by positioning the magnet rings so the plasma density is uniform over the grid surface and so there are no steep magnetic flux density gradients near the walls through which ions can be lost by Bohm diffusion. The uniformity of the plasma density at the grids can also be improved by moving the point of primary electron injection into the discharge chamber off of the chamber centerline. Other results show the discharge chamber losses decrease when a filament cathode is substituted for a hollow cathode to the extent of the hollow cathode operating power. When plasma ion energy cost is determined in such a way that the cost of operating the hollow cathode is subtracted out, the performance using either electron source is similar.