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Sample records for rf-driven negative hydrogen

  1. Plasma And Beam Homogeneity Of The RF-Driven Negative Hydrogen Ion Source For ITER NBI

    SciTech Connect

    Fantz, U.; Franzen, P.; Kraus, W.; Wuenderlich, D.; Gutser, R.; Berger, M.

    2009-03-12

    The neutral beam injection (NBI) system of ITER is based on a large RF driven negative hydrogen ion source. For good beam transmission ITER requires a beam homogeneity of better than 10%. The plasma uniformity and the correlation with the beam homogeneity are being investigated at the prototype ion sources at IPP. Detailed studies are carried out at the long pulse test facility MANITU with a source of roughly 1/8 of the ITER source size. The plasma homogeneity close to plasma grid is measured by optical emission spectroscopy and by fixed Langmuir probes working in the ion saturation region. The beam homogeneity is measured with a spatially resolved H{sub {alpha}} Doppler-shifted beam spectroscopy system. The plasma top-to-bottom symmetry improves with increasing RF power and increasing bias voltage which is applied to suppress the co-extracted electron current. The symmetry is better in deuterium than in hydrogen. The boundary layer near the plasma grid determines the plasma symmetry. At high ion currents with a low amount of co-extracted electrons the plasma is symmetrical and the beam homogeneity is typically 5-10%(RMS). The size scaling and the influence of the magnetic field strength of the filter field created by a plasma grid current is studied at the test facility RADI (roughly a 1/2 size ITER source) at ITER relevant RF power levels. In volume operation in deuterium (non-cesiated source), the plasma illumination of the grid is satisfying.

  2. Operation of RF driven negative ion source in a pure-hydrogen mode

    NASA Astrophysics Data System (ADS)

    Abdrashitov, G.; Belchenko, Yu.; Ivanov, A. A.; Gusev, I.; Senkov, D.; Sanin, A.; Shikhovtsev, I.; Sotnikov, O.; Kondakov, A.

    2015-04-01

    The production of negative hydrogen ions in the radio-frequency driven long-pulsed source with external antenna is studied. RF drivers with various geometry of external antenna, Faraday shield and magnets at the rear flange were examined. H- beam extraction through the single emission aperture was performed in the source pure-hydrogen mode with no external seed of alkali additives. H- beam with ion emission current density up to 5 mA/cm2 and energy up to 75 keV was regularly obtained in the 1 s pulses of the pure-hydrogen mode. The regular temporal increase of H- ion production due to deposition of impurities on the plasma grid surface was recorded. The H- emission current density increased up to 9 mA/cm2 in this case.

  3. Operation of RF driven negative ion source in a pure-hydrogen mode

    SciTech Connect

    Abdrashitov, G.; Belchenko, Yu. Gusev, I.; Senkov, D.; Sanin, A.; Shikhovtsev, I.; Kondakov, A.; Ivanov, A. A.; Sotnikov, O.

    2015-04-08

    The production of negative hydrogen ions in the radio-frequency driven long-pulsed source with external antenna is studied. RF drivers with various geometry of external antenna, Faraday shield and magnets at the rear flange were examined. H- beam extraction through the single emission aperture was performed in the source pure-hydrogen mode with no external seed of alkali additives. H- beam with ion emission current density up to 5 mA/cm{sup 2} and energy up to 75 keV was regularly obtained in the 1 s pulses of the pure-hydrogen mode. The regular temporal increase of H- ion production due to deposition of impurities on the plasma grid surface was recorded. The H- emission current density increased up to 9 mA/cm{sup 2} in this case.

  4. Simulation of cesium injection and distribution in rf-driven ion sources for negative hydrogen ion generation

    SciTech Connect

    Gutser, R.; Wuenderlich, D.; Fantz, U.

    2010-02-15

    Cesium seeded sources for surface generated negative hydrogen ions are major components of neutral beam injection systems in future large-scale fusion experiments such as ITER. Stability and delivered current density depend highly on the cesium conditions during plasma-on and plasma-off phases of the ion source. The Monte Carlo code CSFLOW3D was used to study the transport of neutral and ionic cesium in both phases. Homogeneous and intense flows were obtained from two cesium sources in the expansion region of the ion source and from a dispenser array, which is located 10 cm in front of the converter surface.

  5. Efficient cesiation in RF driven surface plasma negative ion source

    NASA Astrophysics Data System (ADS)

    Belchenko, Yu.; Ivanov, A.; Konstantinov, S.; Sanin, A.; Sotnikov, O.

    2016-02-01

    Experiments on hydrogen negative ions production in the large radio-frequency negative ion source with cesium seed are described. The system of directed cesium deposition to the plasma grid periphery was used. The small cesium seed (˜0.5 G) provides an enhanced H- production during a 2 month long experimental cycle. The gradual increase of negative ion yield during the long-term source runs was observed after cesium addition to the source. The degraded H- production was recorded after air filling to the source or after the cesium washing away from the driver and plasma chamber walls. The following source conditioning by beam shots produces the gradual recovery of H- yield to the high value. The effect of H- yield recovery after cesium coverage passivation by air fill was studied. The concept of cesium coverage replenishment and of H- yield recovery due to sputtering of cesium from the deteriorated layers is discussed.

  6. Efficient cesiation in RF driven surface plasma negative ion source.

    PubMed

    Belchenko, Yu; Ivanov, A; Konstantinov, S; Sanin, A; Sotnikov, O

    2016-02-01

    Experiments on hydrogen negative ions production in the large radio-frequency negative ion source with cesium seed are described. The system of directed cesium deposition to the plasma grid periphery was used. The small cesium seed (∼0.5 G) provides an enhanced H(-) production during a 2 month long experimental cycle. The gradual increase of negative ion yield during the long-term source runs was observed after cesium addition to the source. The degraded H(-) production was recorded after air filling to the source or after the cesium washing away from the driver and plasma chamber walls. The following source conditioning by beam shots produces the gradual recovery of H(-) yield to the high value. The effect of H(-) yield recovery after cesium coverage passivation by air fill was studied. The concept of cesium coverage replenishment and of H(-) yield recovery due to sputtering of cesium from the deteriorated layers is discussed. PMID:26932015

  7. Optical emission spectroscopy at the large RF driven negative ion test facility ELISE: Instrumental setup and first results

    SciTech Connect

    Wünderlich, D.; Fantz, U.; Franzen, P.; Riedl, R.; Bonomo, F.

    2013-09-15

    One of the main topics to be investigated at the recently launched large (A{sub source}= 1.0 × 0.9 m{sup 2}) ITER relevant RF driven negative ion test facility ELISE (Extraction from a Large Ion Source Experiment) is the connection between the homogeneity of the plasma parameters close to the extraction system and the homogeneity of the extracted negative hydrogen ion beam. While several diagnostics techniques are available for measuring the beam homogeneity, the plasma parameters are determined by optical emission spectroscopy (OES) solely. First OES measurements close to the extraction system show that without magnetic filter field the vertical profile of the plasma emission is more or less symmetric, with maxima of the emission representing the projection of the plasma generation volumes, and a distinct minimum in between. The profile changes with the strength of the magnetic filter field but under all circumstances the plasma emission in ELISE is much more homogeneous compared to the smaller IPP prototype sources. Planned after this successful demonstration of the ELISE OES system is to combine OES with tomography in order to determine locally resolved values for the plasma parameters.

  8. Optical emission spectroscopy at the large RF driven negative ion test facility ELISE: Instrumental setup and first results

    NASA Astrophysics Data System (ADS)

    Wünderlich, D.; Fantz, U.; Franzen, P.; Riedl, R.; Bonomo, F.

    2013-09-01

    One of the main topics to be investigated at the recently launched large (Asource = 1.0 × 0.9 m2) ITER relevant RF driven negative ion test facility ELISE (Extraction from a Large Ion Source Experiment) is the connection between the homogeneity of the plasma parameters close to the extraction system and the homogeneity of the extracted negative hydrogen ion beam. While several diagnostics techniques are available for measuring the beam homogeneity, the plasma parameters are determined by optical emission spectroscopy (OES) solely. First OES measurements close to the extraction system show that without magnetic filter field the vertical profile of the plasma emission is more or less symmetric, with maxima of the emission representing the projection of the plasma generation volumes, and a distinct minimum in between. The profile changes with the strength of the magnetic filter field but under all circumstances the plasma emission in ELISE is much more homogeneous compared to the smaller IPP prototype sources. Planned after this successful demonstration of the ELISE OES system is to combine OES with tomography in order to determine locally resolved values for the plasma parameters.

  9. Operation of a cw rf driven ion source with hydrogen and deuterium gas{sup a}

    SciTech Connect

    Melnychuk, S.T.; Debiak, T.W.; Sredniawski, J.J.

    1996-04-01

    We will describe the operation of a cw rf driven multicusp ion source designed for extraction of high current hydrogen and deuterium beams. The source is driven at 2 MHz by a 2.5 turn induction antenna immersed in the plasma. Bare stainless-steel and porcelain-coated Cu antennas have been used. The plasma load is matched to the rf generator by a variable tap {ital N}:1 transformer isolated to 46 kV, and an LC network on the secondary. With H{sub 2} gas the source can be operated at pressures between 5 and 60 mT with power reflection coefficients {lt}0.01. The extracted ion current density with a porcelain-coated antenna is approximately given by 35 mA/cm{sup 2}/kW with an 80 G dipole filter field for input powers from 3.5 to 6.6 kW. The current density remained constant for operation with a 6 and an 8 mm aperture. The source has been operated for 260 h at 3.6 kW with a single-porcelain-coated antenna. Mass spectrometer measurements of the extracted beam at this power show a species mix for H{sup +}:H{sup +}{sub 2}:H{sup +}{sub 3}:OH{sup +} of 0.49: 0.04: 0.42: 0.04. The calculated beam divergence using the IGUN code is compared with the measured divergence from an electrostatic sweep emittance scanner designed for high-power cw beam diagnostics. Phase space measurements at 40 kV and 23 mA beam current result in a normalized rms emittance of 0.09 {pi}mmmrad. {copyright} {ital 1996 American Institute of Physics.}

  10. Operation of a cw rf driven ion source with hydrogen and deuterium gas (abstract){sup a}

    SciTech Connect

    Melnychuk, S.T.; Debiak, T.W.; Sredniawski, J.J.

    1996-03-01

    We will describe the operation of a cw rf driven multicusp ion source designed for extraction of high current hydrogen and deuterium beams. The source is driven at 2 MHz by a 2.5 turn induction antenna immersed in the plasma. Bare stainless-steel and porcelain-coated Cu antennas have been used. The plasma load is matched to the rf generator by a variable tap {ital N}:1 transformer isolated to 46 kV, and an LC network on the secondary. With H{sub 2} gas the source can be operated at pressures between 5 and 60 mT with power reflection coefficients {lt}0.01. The extracted ion current density with a porcelain-coated antenna is approximately given by 35 mA/cm{sup 2}/kW with an 80 G dipole filter field for input powers from 3.5 to 6.6 kW. The current density remained constant for operation with a 6 and an 8 mm aperture. The source has been operated for 260 h at 3.6 kW with a single-porcelain-coated antenna. Mass spectrometer measurements of the extracted beam at this power show a species mix for H{sup +}:H{sup +}{sub 2}:H{sup +}{sub 3}:OH{sup +} of 0.49: 0.04: 0.42: 0.04. The calculated beam divergence using the IGUN code is compared with the measured divergence from an electrostatic sweep emittance scanner designed for high-power cw beam diagnostics. Phase space measurements at 40 kV and 23 mA beam current result in a normalized rms emittance of 0.09 {pi}mmmrad. {copyright} {ital 1996 American Institute of Physics.}

  11. Effect of plasma grid bias on extracted currents in the RF driven surface-plasma negative ion source.

    PubMed

    Belchenko, Yu; Ivanov, A; Sanin, A; Sotnikov, O; Shikhovtsev, I

    2016-02-01

    Extraction of negative ions from the large inductively driven surface-plasma negative ion source was studied. The dependencies of the extracted currents vs plasma grid (PG) bias potential were measured for two modifications of radio-frequency driver with and without Faraday screen, for different hydrogen feeds and for different levels of cesium conditioning. The maximal PG current was independent of driver modification and it was lower in the case of inhibited cesium. The maximal extracted negative ion current depends on the potential difference between the near-PG plasma and the PG bias potentials, while the absolute value of plasma potential in the driver and in the PG area is less important for the negative ion production. The last conclusion confirms the main mechanism of negative ion production through the surface conversion of fast atoms. PMID:26932001

  12. Effect of plasma grid bias on extracted currents in the RF driven surface-plasma negative ion source

    NASA Astrophysics Data System (ADS)

    Belchenko, Yu.; Ivanov, A.; Sanin, A.; Sotnikov, O.; Shikhovtsev, I.

    2016-02-01

    Extraction of negative ions from the large inductively driven surface-plasma negative ion source was studied. The dependencies of the extracted currents vs plasma grid (PG) bias potential were measured for two modifications of radio-frequency driver with and without Faraday screen, for different hydrogen feeds and for different levels of cesium conditioning. The maximal PG current was independent of driver modification and it was lower in the case of inhibited cesium. The maximal extracted negative ion current depends on the potential difference between the near-PG plasma and the PG bias potentials, while the absolute value of plasma potential in the driver and in the PG area is less important for the negative ion production. The last conclusion confirms the main mechanism of negative ion production through the surface conversion of fast atoms.

  13. rf-driven ion sources for industrial applications (invited) (abstract)

    SciTech Connect

    Leung, Ka-Ngo

    2008-02-15

    The Plasma and Ion Source Technology Group at the Lawrence Berkeley National Laboratory have been developing rf-driven ion sources for the last two decades. These sources are being used to generate both positive and negative ion beams. Some of these sources are operating in particle accelerators such as the Spallation Neutron Source (SNS) at Oak Ridge, while others are being employed in various industrial ion beam systems. There are four areas where the rf-driven ion sources are commonly used in industry. (1) In semiconductor manufacturing, rf-driven sources have found important applications in plasma etching, ion beam implantation, and ion beam lithography. (2) In material analysis and surface modification, miniature rf-ion sources can be found in focused ion beam systems. They can provide ion beams of essentially any element in the Periodic Table. The newly developed combined rf ion-electron beam unit improves greatly the performance of the secondary ion mass spectrometry tool. (3) For neutron production, rf ion source is a major component of compact, high flux D-D, D-T, or T-T neutron generators. These neutron sources are now being employed in boron neutron capture therapy (BNCT) as well as in neutron imaging and material interrogation. (4) Large area rf-driven ion source will be used in an industrial design neutral beam diagnostic system for probing fusion plasmas. Such sources can be easily scaled to provide large ion beam current for future fusion reactor applications.

  14. Status of the RF-driven H- ion source for J-PARC linac

    NASA Astrophysics Data System (ADS)

    Oguri, H.; Ohkoshi, K.; Ikegami, K.; Takagi, A.; Asano, H.; Ueno, A.; Shibata, T.

    2016-02-01

    For the upgrade of the Japan Proton Accelerator Research Complex linac beam current, a cesiated RF-driven negative hydrogen ion source was installed during the 2014 summer shutdown period, with subsequent operations commencing on September 29, 2014. The ion source has been successfully operating with a beam current and duty factor of 33 mA and 1.25% (500 μs and 25 Hz), respectively. The result of recent beam operation has demonstrated that the ion source is capable of continuous operation for approximately 1100 h. The spark rate at the beam extractor was observed to be at a frequency of less than once a day, which is an acceptable level for user operation. Although an antenna failure occurred during operation on October 26, 2014, no subsequent serious issues have occurred since then.

  15. Status of the RF-driven H⁻ ion source for J-PARC linac.

    PubMed

    Oguri, H; Ohkoshi, K; Ikegami, K; Takagi, A; Asano, H; Ueno, A; Shibata, T

    2016-02-01

    For the upgrade of the Japan Proton Accelerator Research Complex linac beam current, a cesiated RF-driven negative hydrogen ion source was installed during the 2014 summer shutdown period, with subsequent operations commencing on September 29, 2014. The ion source has been successfully operating with a beam current and duty factor of 33 mA and 1.25% (500 μs and 25 Hz), respectively. The result of recent beam operation has demonstrated that the ion source is capable of continuous operation for approximately 1100 h. The spark rate at the beam extractor was observed to be at a frequency of less than once a day, which is an acceptable level for user operation. Although an antenna failure occurred during operation on October 26, 2014, no subsequent serious issues have occurred since then. PMID:26932020

  16. Mini RF-driven ion source for focused ion beam system

    SciTech Connect

    Jiang, X.; Ji, Q.; Chang, A.; Leung, K.N.

    2002-08-02

    Mini RF-driven ion sources with 1.2 cm and 1.5 cm inner chamber diameter have been developed at Lawrence Berkeley National Laboratory. Several gas species have been tested including argon, krypton and hydrogen. These mini ion sources operate in inductively coupled mode and are capable of generating high current density ion beams at tens of watts. Since the plasma potential is relatively low in the plasma chamber, these mini ion sources can function reliably without any perceptible sputtering damage. The mini RF-driven ion sources will be combined with electrostatic focusing columns, and are capable of producing nano focused ion beams for micro machining and semiconductor fabrications.

  17. RF Driven Multicusp H- Ion Source

    SciTech Connect

    Leung, K.N.; DeVries, G.J.; DiVergilio, W.F.; Hamm, R.W.; Hauck, C.A.; Kunkel, W.B.; McDonald, D.S.; Williams, M.D.

    1990-06-01

    An rf driven multicusp source capable of generating 1-ms H{sup -} beam pulses with a repetition rate as high as 150 Hz has been developed. This source can be operated with a filament or other types of starter. There is almost no lifetime limitation and a clean plasma can be maintained for a long period of operation. It is demonstrated that rf power as high as 25 kW could be coupled inductively to the plasma via a glass-coated copper-coil antenna. The extracted H{sup -} current density achieved is about 200 mA/cm{sup 2}.

  18. Negative hydrogen ion production mechanisms

    SciTech Connect

    Bacal, M.; Wada, M.

    2015-06-15

    Negative hydrogen/deuterium ions can be formed by processes occurring in the plasma volume and on surfaces facing the plasma. The principal mechanisms leading to the formation of these negative ions are dissociative electron attachment to ro-vibrationally excited hydrogen/deuterium molecules when the reaction takes place in the plasma volume, and the direct electron transfer from the low work function metal surface to the hydrogen/deuterium atoms when formation occurs on the surface. The existing theoretical models and reported experimental results on these two mechanisms are summarized. Performance of the negative hydrogen/deuterium ion sources that emerged from studies of these mechanisms is reviewed. Contemporary negative ion sources do not have negative ion production electrodes of original surface type sources but are operated with caesium with their structures nearly identical to volume production type sources. Reasons for enhanced negative ion current due to caesium addition to these sources are discussed.

  19. rf-driven ion sources for industrial applications (invited) (abstract)a)

    NASA Astrophysics Data System (ADS)

    Leung, Ka-Ngo

    2008-02-01

    The Plasma and Ion Source Technology Group at the Lawrence Berkeley National Laboratory have been developing rf-driven ion sources for the last two decades. These sources are being used to generate both positive and negative ion beams. Some of these sources are operating in particle accelerators such as the Spallation Neutron Source (SNS) at Oak Ridge, while others are being employed in various industrial ion beam systems. There are four areas where the rf-driven ion sources are commonly used in industry. (1) In semiconductor manufacturing, rf-driven sources have found important applications in plasma etching, ion beam implantation, and ion beam lithography. (2) In material analysis and surface modification, miniature rf-ion sources can be found in focused ion beam systems. They can provide ion beams of essentially any element in the Periodic Table. The newly developed combined rf ion-electron beam unit improves greatly the performance of the secondary ion mass spectrometry tool. (3) For neutron production, rf ion source is a major component of compact, high flux D-D, D-T, or T-T neutron generators. These neutron sources are now being employed in boron neutron capture therapy (BNCT) as well as in neutron imaging and material interrogation. (4) Large area rf-driven ion source will be used in an industrial design neutral beam diagnostic system for probing fusion plasmas. Such sources can be easily scaled to provide large ion beam current for future fusion reactor applications.

  20. Size scaling of negative hydrogen ion sources for fusion

    NASA Astrophysics Data System (ADS)

    Fantz, U.; Franzen, P.; Kraus, W.; Schiesko, L.; Wimmer, C.; Wünderlich, D.

    2015-04-01

    The RF-driven negative hydrogen ion source (H-, D-) for the international fusion experiment ITER has a width of 0.9 m and a height of 1.9 m and is based on a ⅛ scale prototype source being in operation at the IPP test facilities BATMAN and MANITU for many years. Among the challenges to meet the required parameters in a caesiated source at a source pressure of 0.3 Pa or less is the challenge in size scaling of a factor of eight. As an intermediate step a ½ scale ITER source went into operation at the IPP test facility ELISE with the first plasma in February 2013. The experience and results gained so far at ELISE allowed a size scaling study from the prototype source towards the ITER relevant size at ELISE, in which operational issues, physical aspects and the source performance is addressed, highlighting differences as well as similarities. The most ITER relevant results are: low pressure operation down to 0.2 Pa is possible without problems; the magnetic filter field created by a current in the plasma grid is sufficient to reduce the electron temperature below the target value of 1 eV and to reduce together with the bias applied between the differently shaped bias plate and the plasma grid the amount of co-extracted electrons. An asymmetry of the co-extracted electron currents in the two grid segments is measured, varying strongly with filter field and bias. Contrary to the prototype source, a dedicated plasma drift in vertical direction is not observed. As in the prototype source, the performance in deuterium is limited by the amount of co-extracted electrons in short as well as in long pulse operation. Caesium conditioning is much harder in deuterium than in hydrogen for which fast and reproducible conditioning is achieved. First estimates reveal a caesium consumption comparable to the one in the prototype source despite the large size.

  1. Long pulse H- beam extraction with a rf driven ion source on a high power level.

    PubMed

    Kraus, W; Fantz, U; Franzen, P

    2010-02-01

    IPP Garching is investigating the applicability of rf driven negative ion sources for the neutral beam injection of International Thermonuclear Experimental Reactor. The setup of the tested source was improved to enable long pulses up to 100 kW rf power. The efficiency of negative ion production decreases at high power. The extracted H(-) currents as well as the symmetry of the plasma density close to the plasma grid and of the beam divergence depend on the magnetic filter field. The pulse duration is limited by the increase in coextracted electrons, which depends on the rf power and the caesium conditions on the plasma grid. PMID:20192417

  2. Tunable negative Poisson's ratio in hydrogenated graphene.

    PubMed

    Jiang, Jin-Wu; Chang, Tienchong; Guo, Xingming

    2016-09-21

    We perform molecular dynamics simulations to investigate the effect of hydrogenation on the Poisson's ratio of graphene. It is found that the value of the Poisson's ratio of graphene can be effectively tuned from positive to negative by varying the percentage of hydrogenation. Specifically, the Poisson's ratio decreases with an increase in the percentage of hydrogenation, and reaches a minimum value of -0.04 when the percentage of hydrogenation is about 50%. The Poisson's ratio starts to increase upon a further increase of the percentage of hydrogenation. The appearance of a minimum negative Poisson's ratio in the hydrogenated graphene is attributed to the suppression of the hydrogenation-induced ripples during the stretching of graphene. Our results demonstrate that hydrogenation is a valuable approach for tuning the Poisson's ratio from positive to negative in graphene. PMID:27536878

  3. Size scaling of negative hydrogen ion sources for fusion

    SciTech Connect

    Fantz, U. Franzen, P.; Kraus, W.; Schiesko, L.; Wimmer, C.; Wünderlich, D.

    2015-04-08

    The RF-driven negative hydrogen ion source (H{sup −}, D{sup −}) for the international fusion experiment ITER has a width of 0.9 m and a height of 1.9 m and is based on a ⅛ scale prototype source being in operation at the IPP test facilities BATMAN and MANITU for many years. Among the challenges to meet the required parameters in a caesiated source at a source pressure of 0.3 Pa or less is the challenge in size scaling of a factor of eight. As an intermediate step a ½ scale ITER source went into operation at the IPP test facility ELISE with the first plasma in February 2013. The experience and results gained so far at ELISE allowed a size scaling study from the prototype source towards the ITER relevant size at ELISE, in which operational issues, physical aspects and the source performance is addressed, highlighting differences as well as similarities. The most ITER relevant results are: low pressure operation down to 0.2 Pa is possible without problems; the magnetic filter field created by a current in the plasma grid is sufficient to reduce the electron temperature below the target value of 1 eV and to reduce together with the bias applied between the differently shaped bias plate and the plasma grid the amount of co-extracted electrons. An asymmetry of the co-extracted electron currents in the two grid segments is measured, varying strongly with filter field and bias. Contrary to the prototype source, a dedicated plasma drift in vertical direction is not observed. As in the prototype source, the performance in deuterium is limited by the amount of co-extracted electrons in short as well as in long pulse operation. Caesium conditioning is much harder in deuterium than in hydrogen for which fast and reproducible conditioning is achieved. First estimates reveal a caesium consumption comparable to the one in the prototype source despite the large size.

  4. An advanced negative hydrogen ion source.

    PubMed

    Goncharov, Alexey A; Dobrovolsky, Andrey N; Goretskii, Victor P

    2016-02-01

    The results of investigation of emission productivity of negative particles source with cesiated combined discharge are presented. A cylindrical beam of negative hydrogen ions with density about 2 A/cm(2) in low noise mode on source emission aperture is obtained. The total beam current values are up to 200 mA for negative hydrogen ions and up to 1.5 A for all negative particles with high divergence after source. The source has simple design and can produce stable discharge with low level of oscillation. PMID:26931996

  5. Ground state of the hydrogen negative ion

    NASA Astrophysics Data System (ADS)

    Obreshkov, Boyan

    2009-03-01

    Based on recently developed variational many-body Schr"odinger equation for electrons with Coulomb interactions [1], we provide first numerical results for the ground state electron structure of the hydrogen negative ion. It is shown that Fermi-Teller promotion effect together with non-adiabatic screening effects due to the Pauli's exclusion principle are responsible for the weak binding of the anion. The calculated ionization potential J=-1/2 - 2 λ+ <1/r12> of the hydrogen negative ion is compared with the experiment, where λ is the mean binding energy per one electron in the ground state.[0pt] [1] B. D. Obreshkov , Phys. Rev. A 78, 032503 (2008).

  6. Above-threshold ionization of negative hydrogen

    NASA Astrophysics Data System (ADS)

    Nikolopoulos, L. A. A.; Lambropoulos, P.

    1997-10-01

    We present detailed calculations for two-and three-photon above-threshold ionization of the negative hydrogen ion. In addition to calculated values for partial wave amplitudes and phase shifts pertaining to recent experimental results [Xin Miao Zhao et al., Phys. Rev. Lett. 78, 1656 (1997)], we also address the question of the asymmetry of photoelectron angular distributions in ionization under elliptically polarized radiation, which has been studied experimentally in other negative ions [C. Blondel and C. Delsart, Laser Phys. 3, 3 (1993); Nucl. Instrum. Methods Phys. Res. B 79, 156 (1993); F. Dulieu, C. Blondel, and C. Delsart, J. Phys. B 28, 3861 (1995)].

  7. Negative hydrogen ion yields at plasma grid surface in a negative hydrogen ion source

    SciTech Connect

    Wada, M.; Kenmotsu, T.; Sasao, M.

    2015-04-08

    Negative hydrogen (H{sup −}) ion yield from the plasma grid due to incident hydrogen ions and neutrals has been evaluated with the surface collision cascade model, ACAT (Atomic Collision in Amorphous Target) coupled to a negative surface ionization models. Dependence of negative ion fractions upon the velocity component normal to the surface largely affect the calculation results of the final energy and angular distributions of the H{sup −} ions. The influence is particularly large for H{sup −} ions desorbed from the surface due to less than several eV hydrogen particle implact. The present calculation predicts that H{sup −} ion yield can be maximized by setting the incident angle of hydrogen ions and neutrals to be 65 degree. The Cs thickness on the plasma grid should also affect the yields and mean energies of surface produced H{sup −} ions by back scattering and ion induced desorption processes.

  8. Compression effects in inductively coupled, high-power radio-frequency discharges for negative hydrogen ion production

    NASA Astrophysics Data System (ADS)

    Wilhelm, Rolf

    2003-02-01

    In the paper we present a simplified model description of inductively coupled plasma discharges operating at a rather high radio-frequency (rf) power. In this case the induced high plasma currents can cause periodic compressions over a substantial radial distance. Such conditions are obviously given in rf driven 1 MHz/150 kW plasma sources developed at the Institute for Plasma Physics Garching for negative (hydrogen) ion production in future neutral beam injection (NBI) systems for nuclear fusion research, such as the 1 MeV/50 MW NBI system for the International Thermonuclear Experimental Reactor [T. Inoue, R. Hemsworth, V. Kulygin, and Y. Okumura, Fusion Eng. Design 55, 291 (2001)]. The given model describes quite well the compression and other features of the discharge. The results include the Ohmic power input (i.e., electron heating), the resulting density build-up, and—as a new feature—periodical plasma compressions, leading to a direct energy input also into the plasma ions. The model also explains the strange effect of small argon admixtures, which improve the negative ion yield in rf sources by a factor of up to 2-3 (but which have no effect in conventional dc arc sources). With the calculated dependencies from external parameters (e.g., rf-power and frequency, gas pressure, ion mass or the specific geometry), the modeling may help for the further optimization of the rf source.

  9. Negative ion extraction from hydrogen plasma bulk

    SciTech Connect

    Oudini, N.; Taccogna, F.; Minelli, P.

    2013-10-15

    A two-dimensional particle-in-cell/Monte Carlo collision model has been developed and used to study low electronegative magnetized hydrogen plasma. A configuration characterized by four electrodes is used: the left electrode is biased at V{sub l} = −100 V, the right electrode is grounded, while the upper and lower transversal electrodes are biased at an intermediate voltage V{sub ud} between 0 and −100 V. A constant and homogeneous magnetic field is applied parallel to the lateral (left/right) electrodes. It is shown that in the magnetized case, the bulk plasma potential is close to the transversal electrodes bias inducing then a reversed sheath in front of the right electrode. The potential drop within the reversed sheath is controlled by the transversal electrodes bias allowing extraction of negative ions with a significant reduction of co-extracted electron current. Furthermore, introducing plasma electrodes, between the transversal electrodes and the right electrode, biased with a voltage just above the plasma bulk potential, increases the negative ion extracted current and decreases significantly the co-extracted electron current. The physical mechanism on basis of this phenomenon has been discussed.

  10. Production of negative hydrogen ions on metal grids

    SciTech Connect

    Oohara, W.; Maetani, Y.; Takeda, Takashi; Takeda, Toshiaki; Yokoyama, H.; Kawata, K.

    2015-03-15

    Negative hydrogen ions are produced on a nickel grid with positive-ion irradiation. In order to investigate the production mechanism, a copper grid without the chemisorption of hydrogen atoms and positive helium ions without negative ionization are used for comparison. Positive hydrogen ions reflected on the metal surface obtain two electrons from the surface and become negatively ionized. It is found that the production yield of negative ions by desorption ionization of chemisorbed hydrogen atoms seems to be small, and the production is a minor mechanism.

  11. Particle balance in long duration RF driven plasmas on QUEST

    NASA Astrophysics Data System (ADS)

    Hanada, K.; Zushi, H.; Yoshida, N.; Yugami, N.; Honda, T.; Hasegawa, M.; Mishra, K.; Kuzmin, A.; Nakamura, K.; Fujisawa, A.; Idei, H.; Nagashima, Y.; Watanabe, O.; Onchi, T.; Watanabe, H.; Tokunaga, K.; Higashijima, A.; Kawasaki, S.; Nakashima, H.; Takase, Y.; Fukuyama, A.; Mitarai, O.; Peng, Y. K. M.

    2015-08-01

    Global particle balance in non-inductive long-duration plasma on QUEST has been investigated. Approximately 70% of the fuel hydrogen (H) was retained in the wall and then was almost exhausted just after the discharge. The global recycling ratio (Rg), defined as the ratio of the evacuated H2 flux to that injected, was found to gradually increase during discharges and subsequently rose rapidly. To study the growth of Rg, the thermal desorption spectra after deuterium implantation in a specimen exposed to QUEST plasma was analyzed with a model which includes reflection, diffusion, solution, recombination, trapping, and plasma-induced desorption in the re-deposition layer. The model reconstructs the growth of Rg during a long-duration plasma and indicates solution plays a dominant role in the growth.

  12. Hydrogen Plasmas for Negative Ion Production

    SciTech Connect

    Pagano, D.; Gorse, C.; Capitelli, M.

    2005-05-16

    We have improved a zero-dimensional model, built to simulate the operating conditions in the excitation ('driver') region of a multicusp ion source optimized for negative ion production of great interest in thermonuclear applications. The new approach to couple heavy particle and electron kinetics is discussed.

  13. Study on space charge compensation in negative hydrogen ion beam

    NASA Astrophysics Data System (ADS)

    Zhang, A. L.; Peng, S. X.; Ren, H. T.; Zhang, T.; Zhang, J. F.; Xu, Y.; Guo, Z. Y.; Chen, J. E.

    2016-02-01

    Negative hydrogen ion beam can be compensated by the trapping of ions into the beam potential. When the beam propagates through a neutral gas, these ions arise due to gas ionization by the beam ions. However, the high neutral gas pressure may cause serious negative hydrogen ion beam loss, while low neutral gas pressure may lead to ion-ion instability and decompensation. To better understand the space charge compensation processes within a negative hydrogen beam, experimental study and numerical simulation were carried out at Peking University (PKU). The simulation code for negative hydrogen ion beam is improved from a 2D particle-in-cell-Monte Carlo collision code which has been successfully applied to H+ beam compensated with Ar gas. Impacts among ions, electrons, and neutral gases in negative hydrogen beam compensation processes are carefully treated. The results of the beam simulations were compared with current and emittance measurements of an H- beam from a 2.45 GHz microwave driven H- ion source in PKU. Compensation gas was injected directly into the beam transport region to modify the space charge compensation degree. The experimental results were in good agreement with the simulation results.

  14. Study on space charge compensation in negative hydrogen ion beam.

    PubMed

    Zhang, A L; Peng, S X; Ren, H T; Zhang, T; Zhang, J F; Xu, Y; Guo, Z Y; Chen, J E

    2016-02-01

    Negative hydrogen ion beam can be compensated by the trapping of ions into the beam potential. When the beam propagates through a neutral gas, these ions arise due to gas ionization by the beam ions. However, the high neutral gas pressure may cause serious negative hydrogen ion beam loss, while low neutral gas pressure may lead to ion-ion instability and decompensation. To better understand the space charge compensation processes within a negative hydrogen beam, experimental study and numerical simulation were carried out at Peking University (PKU). The simulation code for negative hydrogen ion beam is improved from a 2D particle-in-cell-Monte Carlo collision code which has been successfully applied to H(+) beam compensated with Ar gas. Impacts among ions, electrons, and neutral gases in negative hydrogen beam compensation processes are carefully treated. The results of the beam simulations were compared with current and emittance measurements of an H(-) beam from a 2.45 GHz microwave driven H(-) ion source in PKU. Compensation gas was injected directly into the beam transport region to modify the space charge compensation degree. The experimental results were in good agreement with the simulation results. PMID:26932087

  15. Linac4 low energy beam measurements with negative hydrogen ions

    SciTech Connect

    Scrivens, R. Bellodi, G.; Crettiez, O.; Dimov, V.; Gerard, D.; Granemann Souza, E.; Guida, R.; Hansen, J.; Lallement, J.-B.; Lettry, J.; Lombardi, A.; Midttun, Ø.; Pasquino, C.; Raich, U.; Riffaud, B.; Roncarolo, F.; Valerio-Lizarraga, C. A.; Wallner, J.; Yarmohammadi Satri, M.; Zickler, T.

    2014-02-15

    Linac4, a 160 MeV normal-conducting H{sup −} linear accelerator, is the first step in the upgrade of the beam intensity available from the LHC proton injectors at CERN. The Linac4 Low Energy Beam Transport (LEBT) line from the pulsed 2 MHz RF driven ion source, to the 352 MHz RFQ (Radiofrequency Quadrupole) has been built and installed at a test stand, and has been used to transport and match to the RFQ a pulsed 14 mA H{sup −} beam at 45 keV. A temporary slit-and-grid emittance measurement system has been put in place to characterize the beam delivered to the RFQ. In this paper a description of the LEBT and its beam diagnostics is given, and the results of beam emittance measurements and beam transmission measurements through the RFQ are compared with the expectation from simulations.

  16. Fine-tuning to minimize emittances of J-PARC RF-driven H- ion source

    NASA Astrophysics Data System (ADS)

    Ueno, A.; Ohkoshi, K.; Ikegami, K.; Takagi, A.; Asano, H.; Oguri, H.

    2016-02-01

    The Japan Proton Accelerator Research Complex (J-PARC) cesiated RF-driven H- ion source has been successfully operated for about one year. By the world's brightest level beam, the J-PARC design beam power of 1 MW was successfully demonstrated. In order to minimize the transverse emittances, the rod-filter-field (RFF) was optimized by changing the triple-gap-lengths of each of pairing five piece rod-filter-magnets. The larger emittance degradation seems to be caused by impurity-gases than the RFF. The smaller beam-hole-diameter of the extraction electrode caused the more than expected improvements on not only the emittances but also the peak beam intensity.

  17. Fine-tuning to minimize emittances of J-PARC RF-driven H⁻ ion source.

    PubMed

    Ueno, A; Ohkoshi, K; Ikegami, K; Takagi, A; Asano, H; Oguri, H

    2016-02-01

    The Japan Proton Accelerator Research Complex (J-PARC) cesiated RF-driven H(-) ion source has been successfully operated for about one year. By the world's brightest level beam, the J-PARC design beam power of 1 MW was successfully demonstrated. In order to minimize the transverse emittances, the rod-filter-field (RFF) was optimized by changing the triple-gap-lengths of each of pairing five piece rod-filter-magnets. The larger emittance degradation seems to be caused by impurity-gases than the RFF. The smaller beam-hole-diameter of the extraction electrode caused the more than expected improvements on not only the emittances but also the peak beam intensity. PMID:26932012

  18. The mobility of negative charges in liquid hydrogen

    NASA Astrophysics Data System (ADS)

    Lerner, P. B.; Sokolov, I. M.

    1994-06-01

    There is a great difference in behavior of e- in liquid hydrogen and helium despite the fact that the adopted theories of the mobility are quite similar. Recently, Levchenko and Mezhov-Deglin (Journal of Low Temperature Physics, 89, 457 (1992)) reported large discrepancies of the mobility of the electrons in liquid hydrogen from estimates based on the theory that the electrons are trapped in bubbles forming atomlike structures (“bubblonium”). They properly suggested that these deviations are related to the existence in liquid hydrogen of another, metastable type of negative charge carrier. The subject of the current paper is the physical explanation of the existence of two types of carriers in liquid hydrogen. We attribute the second type of carriers to the cluster ion H - ( H 2 ) x , which is created by the formation of solid hydrogen around a bound state of a hydride ion. We provide estimates for the radius and the kinetics of degradation of the “snowball” formed around the H - ion on the basis of energy diagrams for a hydride ion submerged in liquid hydrogen.

  19. Production of intense negative hydrogen beams with polarized nuclei by selective neutralization of cold negative ions

    DOEpatents

    Hershcovitch, A.

    1984-02-13

    A process for selectively neutralizing H/sup -/ ions in a magnetic field to produce an intense negative hydrogen ion beam with spin polarized protons. Characteristic features of the process include providing a multi-ampere beam of H/sup -/ ions that are

  20. Deactivating bacteria with RF Driven Hollow Slot Microplasmas in Open Air at Atmospheric Pressure

    NASA Astrophysics Data System (ADS)

    Yu, Zengqi; Pruden, Amy; Sharma, Ashish; Collins, George

    2003-10-01

    A hollow slot discharge operating in open air at atmospheric pressure has demonstrated its ability to deactivate bacterial growth on nearby surfaces exposed to the RF driven plasma. The cold plasma exits from a hollow slot with a width of 0.2 mm and variable length of 1-35 cm. An internal electrode was powered by 13.56 MHz radio-frequency power at a voltage below 200 V. External electrically grounded slots face the work piece. The plasma plume extends millimeters to centimeter beyond the hollow slot toward the work piece to be irradiated. Argon-Oxygen gas mixtures, at 33 liters per minute flow, were passed through the electrodes and the downstream plasma was employed for the process, with treatment exposure time varied from 0.06 to 0.18 seconds. Bacterial cultures were fixed to 0.22 micron cellulose filter membranes and passed under the plasma at a controlled rate at a distance of about 5-10 millimeters from the grounded slot electrode. Preliminary studies on the effectiveness of the plasma for sterilization were carried out on E. coli. Cultures were grown overnight on the membranes after exposure and the resulting colony forming units (cfu) were determined in treated and untreated groups. In the plasma treated group, a 98.2% kill rate was observed with the lowest exposure time, and increased to 99.8% when the exposure time was tripled. These studies clearly demonstrate the ability of the RF-driven hollow slot atmospheric plasma to inhibit bacterial growth on surfaces.

  1. Rod-filter-field optimization of the J-PARC RF-driven H- ion source

    NASA Astrophysics Data System (ADS)

    Ueno, A.; Ohkoshi, K.; Ikegami, K.; Takagi, A.; Yamazaki, S.; Oguri, H.

    2015-04-01

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

  2. Negative hydrogen ion source for TOKAMAK neutral beam injector (invited)

    NASA Astrophysics Data System (ADS)

    Okumura, Y.; Fujiwara, Y.; Kashiwagi, M.; Kitagawa, T.; Miyamoto, K.; Morishita, T.; Hanada, M.; Takayanagi, T.; Taniguchi, M.; Watanabe, K.

    2000-02-01

    Intense negative ion source producing multimegawatt hydrogen/deuterium negative ion beams has been developed for the neutral beam injector (NBI) in TOKAMAK thermonuclear fusion machines. Negative ions are produced in a cesium seeded multi-cusp plasma generator via volume and surface processes, and accelerated with a multistage electrostatic accelerator. The negative ion source for JT-60U has produced 18.5 A/360 keV (6.7 MW) H- and 14.3 A/380 keV (5.4 MW) D- ion beams at average current densities of 11 mA/cm2 (H-) and 8.5 mA/cm2 (D-). A high energy negative ion source has been developed for the next generation TOKAMAK such as the International Thermonuclear Experimental Reactor (ITER). The source has demonstrated to accelerate negative ions up to 1 MeV, the energy required for ITER. Higher negative ion current density of more than 20 mA/cm2 was obtained in the ITER concept sources. It was confirmed that the consumption rate of cesium is small enough to operate the source for a half year in ITER-NBI without maintenance.

  3. Negative hydrogen ion production in a helicon plasma source

    SciTech Connect

    Santoso, J. Corr, C. S.; Manoharan, R.; O'Byrne, S.

    2015-09-15

    In order to develop very high energy (>1 MeV) neutral beam injection systems for applications, such as plasma heating in fusion devices, it is necessary first to develop high throughput negative ion sources. For the ITER reference source, this will be realised using caesiated inductively coupled plasma devices, containing either hydrogen or deuterium discharges, operated with high rf input powers (up to 90 kW per driver). It has been suggested that due to their high power coupling efficiency, helicon devices may be able to reduce power requirements and potentially obviate the need for caesiation due to the high plasma densities achievable. Here, we present measurements of negative ion densities in a hydrogen discharge produced by a helicon device, with externally applied DC magnetic fields ranging from 0 to 8.5 mT at 5 and 10 mTorr fill pressures. These measurements were taken in the magnetised plasma interaction experiment at the Australian National University and were performed using the probe-based laser photodetachment technique, modified for the use in the afterglow of the plasma discharge. A peak in the electron density is observed at ∼3 mT and is correlated with changes in the rf power transfer efficiency. With increasing magnetic field, an increase in the negative ion fraction from 0.04 to 0.10 and negative ion densities from 8 × 10{sup 14 }m{sup −3} to 7 × 10{sup 15 }m{sup −3} is observed. It is also shown that the negative ion densities can be increased by a factor of 8 with the application of an external DC magnetic field.

  4. Hydrogen atom temperature measured with wavelength-modulated laser absorption spectroscopy in large scale filament arc negative hydrogen ion source

    SciTech Connect

    Nakano, H. Goto, M.; Tsumori, K.; Kisaki, M.; Ikeda, K.; Nagaoka, K.; Osakabe, M.; Takeiri, Y.; Kaneko, O.; Nishiyama, S.; Sasaki, K.

    2015-04-08

    The velocity distribution function of hydrogen atoms is one of the useful parameters to understand particle dynamics from negative hydrogen production to extraction in a negative hydrogen ion source. Hydrogen atom temperature is one of the indicators of the velocity distribution function. To find a feasibility of hydrogen atom temperature measurement in large scale filament arc negative hydrogen ion source for fusion, a model calculation of wavelength-modulated laser absorption spectroscopy of the hydrogen Balmer alpha line was performed. By utilizing a wide range tunable diode laser, we successfully obtained the hydrogen atom temperature of ∼3000 K in the vicinity of the plasma grid electrode. The hydrogen atom temperature increases as well as the arc power, and becomes constant after decreasing with the filling of hydrogen gas pressure.

  5. A future, intense source of negative hydrogen ions

    NASA Technical Reports Server (NTRS)

    Siefken, Hugh; Stein, Charles

    1994-01-01

    By directly heating lithium hydride in a vacuum, up to 18 micro-A/sq cm of negative hydrogen has been obtained from the crystal lattice. The amount of ion current extracted and analyzed is closely related to the temperature of the sample and to the rate at which the temperature is changed. The ion current appears to be emission limited and saturates with extraction voltage. For a fixed extraction voltage, the ion current could be maximized by placing a grid between the sample surface and the extraction electrode. Electrons accompanying the negative ions were removed by a magnetic trap. A Wein velocity filter was designed and built to provide definitive mass analysis of the extracted ion species. This technique when applied to other alkali hydrides may produce even higher intensity beams possessing low values of emittance.

  6. Emittance measurements for optimum operation of the J-PARC RF-driven H- ion source

    NASA Astrophysics Data System (ADS)

    Ueno, A.; Ohkoshi, K.; Ikegami, K.; Takagi, A.; Yamazaki, S.; Oguri, H.

    2015-04-01

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

  7. A new hybrid scheme for simulations of highly collisional RF-driven plasmas

    NASA Astrophysics Data System (ADS)

    Eremin, Denis; Hemke, Torben; Mussenbrock, Thomas

    2016-02-01

    This work describes a new 1D hybrid approach for modeling atmospheric pressure discharges featuring complex chemistry. In this approach electrons are described fully kinetically using particle-in-cell/Monte-Carlo (PIC/MCC) scheme, whereas the heavy species are modeled within a fluid description. Validity of the popular drift-diffusion approximation is verified against a ‘full’ fluid model accounting for the ion inertia and a fully kinetic PIC/MCC code for ions as well as electrons. The fluid models require knowledge of the momentum exchange frequency and dependence of the ion mobilities on the electric field when the ions are in equilibrium with the latter. To this end an auxiliary Monte-Carlo scheme is constructed. It is demonstrated that the drift-diffusion approximation can overestimate ion transport in simulations of RF-driven discharges with heavy ion species operated in the γ mode at the atmospheric pressure or in all discharge simulations for lower pressures. This can lead to exaggerated plasma densities and incorrect profiles provided by the drift-diffusion models. Therefore, the hybrid code version featuring the full ion fluid model should be favored against the more popular drift-diffusion model, noting that the suggested numerical scheme for the former model implies only a small additional computational cost.

  8. Development of a novel radio-frequency negative hydrogen ion source in conically converging configuration.

    PubMed

    Jung, B K; Dang, J J; An, Y H; Chung, K J; Hwang, Y S

    2014-02-01

    Volume-produced negative ion source still requires enhancement of current density with lower input RF (radio-frequency) power in lower operating pressure for various applications. To confirm recent observation of efficient negative ion production with a short cylindrical chamber with smaller effective plasma size, the RF-driven transformer-coupled plasma H(-) ion source at Seoul National University is modified by adopting a newly designed quartz RF window to reduce the chamber length. Experiments with the reduced chamber length show a few times enhancement of H(-) ion beam current compared to that extracted from the previous chamber design, which is consistent with the measured H(-) ion population. Nevertheless, decrease in H(-) ion beam current observed in low pressure regime below ∼5 mTorr owing to insufficient filtering of high energy electrons in the extraction region needs to be resolved to address the usefulness of electron temperature control by the change of geometrical configuration of the discharge chamber. A new discharge chamber with conically converging configuration has been developed, in which the chamber diameter decreases as approaching to the extraction region away from the planar RF antenna such that stronger filter magnetic field can be utilized to prohibit high energy electrons from transporting to the extraction region. First experimental results for the H(-) ion beam extraction with this configuration show that higher magnetic filter field makes peak negative beam currents happen in lower operating pressure. However, overall decrease in H(-) ion beam current due to the change of chamber geometry still requires further study of geometrical effect on particle transport and optimization of magnetic field in this novel configuration. PMID:24593552

  9. Experimental studies of the Negative Ion of Hydrogen. Final Report

    SciTech Connect

    Bryant, Howard C.

    1999-06-30

    This document presents an overview of the results of the DOE'S support of experimental research into the structure and interactions of the negative ion of hydrogen conducted by the Department of Physics and Astronomy of the University of New Mexico at the Los Alamos National Laboratory. The work involves many collaborations with scientists from both institutions, as well as others. Although official DOE support for this work began in 1977, the experiment that led to it was done in 1971, near the time the 800 MeV linear accelerator at Los Alamos (LAMPF) first came on line. Until the mid nineties, the work was performed using the relativistic beam at LAMFF. The most recent results were obtained using the 35 keV injector beam for the Ground Test Accelerator at Los Alamos. A list of all published results from this work is presented.

  10. Perfectly matched pulsed 2MHz RF network and CW 30MHz RF matching network for the J-PARC RF-driven H- ion source

    NASA Astrophysics Data System (ADS)

    Ueno, A.; Namekawa, Y.; Yamazaki, S.; Ohkoshi, K.; Koizumi, I.; Ikegami, K.; Takagi, A.; Oguri, H.

    2013-02-01

    In order to satisfy the Japan Proton Accelerator Research Complex (J-PARC) 2nd stage requirements of an H- ion beam current of 60mA within normalized emittances of 1.5πmmṡmrad both horizontally and vertically, a flat top beam duty factor of 1.25% (500μs×25Hz) and a life-time of more than 50days, a cesiated RF-driven H- ion source using a internal-antenna developed at the Spallation Neutron Source (SNS) was developed. As similar as the SNS ion source, the 60kW pulsed 2MHz-RF and 200W CW 30MHz-RF systems are used in order to produce pulsed high-temperature 2MHz-RF plasma and CW low-temperature 30MHz-RF plasma. Each matching network for each system is composed of two vacuum variable condensers (VVCs). In order to supply pulsed 60kW-2MHz-RF power from the power supply (PS) on the ground level, a one-turn isolation transformer using FINEMET cores is installed between the PS and the J-PARC ion source. By comprehending the matching networks with the LTspice IV simulations and high- and low- power experiments and setting the parameters properly, the pulsed 2MHz-RF power up to 46 kW is successfully input to the hydrogen plasma without any misfire and with almost no reflected power.

  11. Cavity Ring-Down System for Density Measurement of Negative Hydrogen Ion on Negative Ion Source

    SciTech Connect

    Nakano, Haruhisa; Tsumori, Katsuyoshi; Nagaoka, Kenichi; Shibuya, Masayuki; Kisaki, Masashi; Ikeda, Katsunori; Osakabe, Masaki; Kaneko, Osamu; Asano, Eiji; Kondo, Tomoki; Sato, Mamoru; Komada, Seiji; Sekiguchi, Haruo; Takeiri, Yasuhiko; Fantz, Ursel

    2011-09-26

    A Cavity Ring-Down (CRD) system was applied to measure the density of negative hydrogen ion (H{sup -}) in vicinity of extraction surface in the H{sup -} source for the development of neutral beam injector on Large Helical Device (LHD). The density measurement with sampling time of 50 ms was carried out. The measured density with the CRD system is relatively good agreement with the density evaluated from extracted beam-current with applying a similar relation of positive ion sources. In cesium seeded into ion-source plasma, the linearity between an arc power of the discharge and the measured density with the CRD system was observed. Additionally, the measured density was proportional to the extracted beam current. These characteristics indicate the CRD system worked well for H{sup -} density measurement in the region of H{sup -} and extraction.

  12. Production of intense negative hydrogen beams with polarized nuclei by selective neutralization of negative ions

    DOEpatents

    Hershcovitch, Ady

    1987-01-01

    A process for selectively neutralizing H.sup.- ions in a magnetic field to produce an intense negative hydrogen ion beam with spin polarized protons. Characteristic features of the process include providing a multi-ampere beam of H.sup.- ions that are intersected by a beam of laser light. Photodetachment is effected in a uniform magnetic field that is provided around the beam of H.sup.- ions to spin polarize the H.sup.- ions and produce first and second populations or groups of ions, having their respective proton spin aligned either with the magnetic field or opposite to it. The intersecting beam of laser light is directed to selectively neutralize a majority of the ions in only one population, or given spin polarized group of H.sup.- ions, without neutralizing the ions in the other group thereby forming a population of H.sup.- ions each of which has its proton spin down, and a second group or population of H.sup.o atoms having proton spin up. Finally, the two groups of ions are separated from each other by magnetically bending the group of H.sup.- ions away from the group of neutralized ions, thereby to form an intense H.sup.- ion beam that is directed toward a predetermined objective.

  13. Vibrational States of Hydrogen Molecules in One Third LHD Negative Ion Source

    SciTech Connect

    Nishiura, M.; Tsumori, K.; Matsumoto, Y.; Wada, M.; Inoue, T.

    2011-09-26

    The effect of the cesium on hydrogen negative ions is discussed using the vacuum ultraviolet emissions (VUV) from vibrational states of hydrogen molecules. The VUV spectrum from 90 to 165 nm is related to the H{sup -} production from the dissociative attachment of electrons to hydrogen molecules. The VUV spectra in hydrogen plasmas are measured in the extraction region of a negative ion source for neutral beam injector. Under the pure hydrogen discharge, the cesium vapor is introduced into the ion source to enhance the hydrogen negative ion density. When the same arc power of {approx}99 kW is applied in both with and without cesium admixture cases, the ratio of the observed VUV spectrum without to with cesium is not changed clearly. Therefore the production process of H{sup -} related to the wall/electrode surface would be enhanced rather than the volume production process.

  14. Production of intense beams of polarized negative hydrogen ions by double charge exchange in alkali vapour

    NASA Astrophysics Data System (ADS)

    Gruëbler, W.; Schmelzbach, P. A.

    1983-07-01

    The intensity of the polarized negative hydrogen ion beam of the ETHZ atomic beam polarized ion source has been substantially improved by a new double charge exchange device. Increasing the diameter of the charge exchange canal to 1.4 cm results in a beam output of the source of 6 μA of polarized negative hydrogen ions. Further improvements of the charge exchanger are proposed and discussed. With an updated design of the atomic beam apparatus, beams of 0.5 mA polarized negative hydrogen ions may be obtained from such a source.

  15. An RF driven H{sup {minus}} source and a low energy beam injection system for RFQ operation

    SciTech Connect

    Leung, K.N.; Bachman, D.A.; Chan, C.F.; McDonald, D.S.

    1992-12-31

    An RF driven H{sup {minus}} source has been developed at LBL for use in the Superconducting Super Collider (SSC). To date, an H{sup {minus}} current of {approx}40 mA can be obtained from a 5.6-cm-diam aperture with the source operated at a pressure of about 12 m Torr and 50 kW of RF power. In order to match the accelerated H{sup {minus}} beam into the SSC RFQ, a low-energy H{sup {minus}} injection system has been designed. This injector produces an outgoing H{sup {minus}} beam free of electron contamination, with small radius, large convergent angle and small projectional emittance.

  16. Pre-conditioning procedure suitable for internal-RF-antenna of J-PARC RF-driven H- ion source

    NASA Astrophysics Data System (ADS)

    Ueno, A.; Ohkoshi, K.; Ikegami, K.; Takagi, A.; Asano, H.; Oguri, H.

    2016-02-01

    The Japan Proton Accelerator Research Complex (J-PARC) cesiated RF-driven H- ion source has been successfully operated for about 1 yr. By the world brightest level beam, the J-PARC design beam power of 1 MW was successfully demonstrated. Although no internal-RF-antenna failure, except for the once caused by an excess cesium due to a misoperation, occurred in the operation, many antennas failed in pre-conditionings for the first hundred days. The antenna failure rate was drastically decreased by using an antenna with coating thicker than a standard value and the pre-conditioning procedure repeating 15 min 25 kW RF-power operation and impurity-gas evacuation a few times, before the full power (50 kW) operation.

  17. Pre-conditioning procedure suitable for internal-RF-antenna of J-PARC RF-driven H⁻ ion source.

    PubMed

    Ueno, A; Ohkoshi, K; Ikegami, K; Takagi, A; Asano, H; Oguri, H

    2016-02-01

    The Japan Proton Accelerator Research Complex (J-PARC) cesiated RF-driven H(-) ion source has been successfully operated for about 1 yr. By the world brightest level beam, the J-PARC design beam power of 1 MW was successfully demonstrated. Although no internal-RF-antenna failure, except for the once caused by an excess cesium due to a misoperation, occurred in the operation, many antennas failed in pre-conditionings for the first hundred days. The antenna failure rate was drastically decreased by using an antenna with coating thicker than a standard value and the pre-conditioning procedure repeating 15 min 25 kW RF-power operation and impurity-gas evacuation a few times, before the full power (50 kW) operation. PMID:26932011

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

    SciTech Connect

    Ueno, A. Ohkoshi, K.; Ikegami, K.; Takagi, A.; Yamazaki, S.; Oguri, H.

    2015-04-08

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

  19. RF-driven Proton Source with a Back-streaming Electron Dump

    SciTech Connect

    Ji, Q.; Sy, A.; Kwan, J.W.

    2009-09-20

    This article describes an RF ion source with a back-streaming electron dump. A quartz tube, brazed to a metal plug at one end, is fused in the center of a flat quartz plate. RF power (at 13.6 MHz) is coupled to generate hydrogen plasma using a planar external antenna bonded to the window. Bonding the water-cooled rf antenna to the quartz window significantly lowers its temperature. The water-cooled metal plug serves as the backstreaming electron dump. At 1800W, the current density of extracted hydrogen ions reaches approximately 125 mA/cm{sup 2}.

  20. Laser photodetachment diagnostics of a 1/3-size negative hydrogen ion source for NBI

    SciTech Connect

    Geng, S.; Tsumori, K.; Nakano, H.; Kisaki, M.; Ikeda, K.; Takeiri, Y.; Osakabe, M.; Nagaoka, K.; Kaneko, O.

    2015-04-08

    To investigate the flows of charged particles in front of the plasma grid (PG) in a negative hydrogen ion source, the information of the local densities of electrons and negative hydrogen ions (H-) are necessary. For this purpose, the laser photodetachment is applied for pure hydrogen plasmas and Cs-seeded plasma in a 1/3-size negative hydrogen ion source in NIFS-NBI test stand. The H- density obtained by photodetachment is calibrated by the results from cavity ring-down (CRD). The pressure dependence and PG bias dependence of the local H- density are presented and discussed. The results show that H- density increases significantly by seeding Cs into the plasma. In Cs-seeded plasma, relativity exists between the H- ion density and plasma potential.

  1. Cavity Ringdown Technique for negative-hydrogen-ion measurement in ion source for neutral beam injector

    NASA Astrophysics Data System (ADS)

    Nakano, H.; Tsumori, K.; Shibuya, M.; Geng, S.; Kisaki, M.; Ikeda, K.; Nagaoka, K.; Osakabe, M.; Takeiri, Y.; Kaneko, O.

    2016-03-01

    The Cavity Ringdown Technique (CRD) is applied for negative hydrogen ion (H-) density measurement in H- source for the neutral beam injector. The CRD is one of the laser absorption techniques. Nd:YAG pulse laser was utilized for negative-hydrogen-ion photodetachment. The H- density related to extracted H- beam was successfully observed by a fixed position CRD. A two-dimensional movable CRD has been developed to measure the H- density profile. Measured profiles were consistent with expected profiles from the H- production area in pure hydrogen and cesium seeded plasmas. By applying absorption saturation in the optical cavity, negative hydrogen ion temperature was evaluated and was confirmed as being a similar value measured with other diagnostics.

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

    PubMed

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

    2014-02-01

    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(-) 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(-) ion production as long as low electron temperatures are maintained in the extraction region in volume-produced negative hydrogen ion sources. PMID:24593559

  3. 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.

  4. Development of a volume production type hydrogen negative ion source by using sheet plasma

    NASA Astrophysics Data System (ADS)

    Matsumoto, Satoki; Iijima, Takaaki; Tonegawa, Akira; Sato, Kohnosuke; Kawamura, Kazutaka

    2014-10-01

    Stationary production of negative ions are important to play an essential role in Neutral beam injection (NBI). Cesium seeded Surface-production of negative ion sources are used for NBI. However, Cesium seeded surface- production of negative ion sources are not desirable from the point of view of operating steady state ion sources. We carried out the development of negative ion sources by volume-production in hydrogen sheet plasma. Production of hydrogen negative ions through volume processes needs both high energy electron region and low energy electron region. The sheet plasma is suitable for the production of negative ions, because the electron temperature in the central region of the plasma as high as 10-15 eV, whereas in the periphery of the plasma, a low temperature of a few eV of obtained. The hydrogen negative ions density were detected using an omegatron mass analyzer, while the electron density and temperature were measured using a Langmuir probe. Negative ions current extracted from the grid are measured by Faraday-cup.

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

    SciTech Connect

    Ueno, A. Ohkoshi, K.; Ikegami, K.; Takagi, A.; Yamazaki, S.; Oguri, H.

    2015-04-08

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

  6. Development of cesium-free negative hydrogen ion source by using sheet plasma

    NASA Astrophysics Data System (ADS)

    Hase, Takuya; Iijima, Takaaki; Tanaka, Yuta; Takimoto, Tosikio; Tonegawa, Akira; Sato, Kohnosuke; Kawamura, Kazutaka

    2015-09-01

    We demonstrated the production of hydrogen negative ions in cesium-free discharge by using the magnetized sheet plasma. Plasma crossed with a vertical gas flow system and extracting H- beams from the sheet plasma. Under a secondary hydrogen gas entering the hydrogen plasma, the peak position of the hydrogen plasma is localized in the periphery of the sheet plasma. The maximum negative ion beam is successfully extracted using grids located in the periphery of the sheet plasma. The extraction current density is about 8 mA/cm2 at extraction voltage is 2 kV and discharge current of 30 A. The extraction negative ion current density is saturated at the extraction voltage is 2 kV for the limit of the negative ion density in the periphery region of the sheet plasma. On the other hand, the extraction current is saturated (3 mA/cm2) with increasing extraction voltage and the negative ions are not detected without the secondary gas flow (0 sccm). This curve depends on the electrons present. Therefore, it is considered that the negative ion current against the extraction current is around 60% from the ratio of the extraction current and the extraction electron current.

  7. Optimum plasma grid bias for a negative hydrogen ion source operation with Cs

    NASA Astrophysics Data System (ADS)

    Bacal, Marthe; Sasao, Mamiko; Wada, Motoi; McAdams, Roy

    2016-02-01

    The functions of a biased plasma grid of a negative hydrogen (H-) ion source for both pure volume and Cs seeded operations are reexamined. Proper control of the plasma grid bias in pure volume sources yields: enhancement of the extracted negative ion current, reduction of the co-extracted electron current, flattening of the spatial distribution of plasma potential across the filter magnetic field, change in recycling from hydrogen atomic/molecular ions to atomic/molecular neutrals, and enhanced concentration of H- ions near the plasma grid. These functions are maintained in the sources seeded with Cs with additional direct emission of negative ions under positive ion and neutral hydrogen bombardment onto the plasma electrode.

  8. Design and Start-to-End Simulation of an X-Band RF Driven Hard X-Ray FEL with LCLS Injector

    SciTech Connect

    Sun, Yipeng; /SLAC

    2012-08-20

    In this note, it is briefly discussed the accelerator design and start-to-end 3D macro particles simulation (using ELEGANT and GENESIS) of an X-band RF driven hard X-ray FEL with LCLS injector. A preliminary design and LiTrack 1D simulation studies were presented before in an older publication [1]. In numerical simulations this X-band RF driven hard X-ray FEL achieves/exceeds LCLS-like performance in a much shorter overall length of 350 m, compared with 1200 m in the LCLS case. One key feature of this design is that it may achieve a higher final beam current of 5 kA plus a uniform energy profile, mainly due to the employment of stronger longitudinal wake fields in the last X-band RF linac [2].

  9. Effect of nickel grid parameters on production of negative hydrogen ions

    SciTech Connect

    Oohara, W.; Yokoyama, H.; Takeda, Toshiaki; Maetani, Y.; Takeda, Takashi; Kawata, K.

    2014-06-15

    Negative hydrogen ions are produced by plasma-assisted catalytic ionization using a nickel grid. When positive ions passing through the grid are decelerated by an electric field, the extraction current density of passing positive ions is sharply reduced by neutralization and negative ionization of the ions. This phenomenon is found to depend on the specific surface area of the grid and the current density.

  10. Maintenance and operation procedure, and feedback controls of the J-PARC RF-driven H- ion source

    NASA Astrophysics Data System (ADS)

    Ueno, A.; Ohkoshi, K.; Ikegami, K.; Takagi, A.; Yamazaki, S.; Oguri, H.

    2015-04-01

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

  11. Measurement of Gas Temperature in Negative Hydrogen Ion Source by Wavelength-Modulated Laser Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Nishiyama, S.; Sasaki, K.; Nakano, H.; Goto, M.; Kisaki, M.; Tsumori, K.; NIFS-NBI Team

    2014-10-01

    Measurement of the energy distribution of hydrogen atom is important and essential to understand the production mechanism of its negative ion (H-) in cesium-seeded negative ion sources. In this work, we evaluated the temperature of atomic hydrogen in the large-scale arc-discharge negative hydrogen ion source in NIFS by wavelength-modulated laser absorption spectroscopy. The laser beam was passed through the adjacent region to the grid electrode for extracting negative ions. The frequency of the laser was scanned slowly over the whole range of the Doppler width (100 GHz in 1s). A sinusoidal frequency modulation at 600 Hz with a width of 30 GHz was superposed onto the slow modulation. The transmitted laser was detected using a photodiode, and its second harmonic component of the sinusoidal modulation was amplified using a lock-in amplifier. The obtained spectrum was in good agreement with an expected spectrum of the Doppler-broadened Balmer- α line. The estimated temperature of atomic hydrogen was approximately 3000 K. The absorption increased with the arc-discharge power, while the temperature was roughly independent of the power. This work is supported by the NIFS Collaboration Research Program NIFS13KLER021.

  12. Roles of a plasma grid in a negative hydrogen ion source

    NASA Astrophysics Data System (ADS)

    Bacal, M.; Sasao, M.; Wada, M.; McAdams, R.

    2015-04-01

    The plasma grid is electrically biased with respect to other parts of source chamber wall in both volume sources and sources seeded with alkali metals. The roles of the plasma grid in these two kinds of sources will be described. The main functions of the plasma grid in volume sources are: optimizing the extracted negative ion current, reducing the co-extracted electron current, controlling the axial plasma potential profile, recycling the hydrogen atoms to molecules, concentrating the negative ions near its surface and, when biased positive, depleting the electron population near its surface. These functions are maintained in the sources seeded with alkali metals. However an additional function appears in the Cs seeded sources, namely direct emission of negative ions under positive ion and neutral hydrogen bombardment.

  13. Roles of a plasma grid in a negative hydrogen ion source

    SciTech Connect

    Bacal, M.; Sasao, M.; Wada, M.; McAdams, R.

    2015-04-08

    The plasma grid is electrically biased with respect to other parts of source chamber wall in both volume sources and sources seeded with alkali metals. The roles of the plasma grid in these two kinds of sources will be described. The main functions of the plasma grid in volume sources are: optimizing the extracted negative ion current, reducing the co-extracted electron current, controlling the axial plasma potential profile, recycling the hydrogen atoms to molecules, concentrating the negative ions near its surface and, when biased positive, depleting the electron population near its surface. These functions are maintained in the sources seeded with alkali metals. However an additional function appears in the Cs seeded sources, namely direct emission of negative ions under positive ion and neutral hydrogen bombardment.

  14. Comparison of measured and modelled negative hydrogen ion densities at the ECR-discharge HOMER

    NASA Astrophysics Data System (ADS)

    Rauner, D.; Kurutz, U.; Fantz, U.

    2015-04-01

    As the negative hydrogen ion density nH- is a key parameter for the investigation of negative ion sources, its diagnostic quantification is essential in source development and operation as well as for fundamental research. By utilizing the photodetachment process of negative ions, generally two different diagnostic methods can be applied: via laser photodetachment, the density of negative ions is measured locally, but only relatively to the electron density. To obtain absolute densities, the electron density has to be measured additionally, which induces further uncertainties. Via cavity ring-down spectroscopy (CRDS), the absolute density of H- is measured directly, however LOS-averaged over the plasma length. At the ECR-discharge HOMER, where H- is produced in the plasma volume, laser photodetachment is applied as the standard method to measure nH-. The additional application of CRDS provides the possibility to directly obtain absolute values of nH-, thereby successfully bench-marking the laser photodetachment system as both diagnostics are in good agreement. In the investigated pressure range from 0.3 to 3 Pa, the measured negative hydrogen ion density shows a maximum at 1 to 1.5 Pa and an approximately linear response to increasing input microwave powers from 200 up to 500 W. Additionally, the volume production of negative ions is 0-dimensionally modelled by balancing H- production and destruction processes. The modelled densities are adapted to the absolute measurements of nH- via CRDS, allowing to identify collisions of H- with hydrogen atoms (associative and non-associative detachment) to be the dominant loss process of H- in the plasma volume at HOMER. Furthermore, the characteristic peak of nH- observed at 1 to 1.5 Pa is identified to be caused by a comparable behaviour of the electron density with varying pressure, as ne determines the volume production rate via dissociative electron attachment to vibrationally excited hydrogen molecules.

  15. Experimental Evaluation of a Negative Ion Source for a Heavy Ion Fusion Negative Ion Driver

    SciTech Connect

    Grisham, L. R.; Hahto, S. K.; Hahto, S. T.; Kwan, J. W.; Leung, K. N.

    2004-06-16

    Negative halogen ions have recently been proposed as a possible alternative to positive ions for heavy ion fusion drivers because electron accumulation would not be a problem in the accelerator, and if desired, the beams could be photo-detached to neutrals. To test the ability to make suitable quality beams, an experiment was conducted at Lawrence Berkeley National Laboratory using chlorine in an RF-driven ion source. Without introducing any cesium (which is required to enhance negative ion production in hydrogen ion sources) a negative chlorine current density of 45 mA/cm{sup 2} was obtained under the same conditions that gave 57 45 mA/cm{sup 2} of positive chlorine, suggesting the presence of nearly as many negative ions as positive ions in the plasma near the extraction plane. The negative ion spectrum was 99.5% atomic chlorine ions, with only 0.5% molecular chlorine, and essentially no impurities. Although this experiment did not incorporate the type of electron suppression technology that i s used in negative hydrogen beam extraction, the ratio of co-extracted electrons to Cl{sup -} was as low as 7 to 1, many times lower than the ratio of their mobilities, suggesting that few electrons are present in the near-extractor plasma. This, along with the near-equivalence of the positive and negative ion currents, suggests that the plasma in this region was mostly an ion-ion plasma. The negative chlorine current density was relatively insensitive to pressure, and scaled linearly with RF power. If this linear scaling continues to hold at higher RF powers, it should permit current densities of 100 45 mA/cm{sup 2}, sufficient for present heavy ion fusion injector concepts. The effective ion temperatures of the positive and negative ions appeared to be similar and relatively low for a plasma source.

  16. Experimental evaluation of a negative ion source for a heavy ionfusion negative ion driver

    SciTech Connect

    Grisham, L.R.; Hahto, S.K.; Hahto, S.T.; Kwan, J.W.; Leung, K.N.

    2005-01-18

    Negative halogen ions have recently been proposed as a possible alternative to positive ions for heavy ion fusion drivers because electron accumulation would not be a problem in the accelerator, and if desired, the beams could be photodetached to neutrals [1,2,3]. To test the ability to make suitable quality beams, an experiment was conducted at Lawrence Berkeley National Laboratory using chlorine in an RF-driven ion source. Without introducing any cesium (which is required to enhance negative ion production in hydrogen ion sources) a negative chlorine current density of 45 mA/cm{sup 2} was obtained under the same conditions that gave 57 mA/cm{sup 2} of positive chlorine, suggesting the presence of nearly as many negative ions as positive ions in the plasma near the extraction plane. The negative ion spectrum was 99.5% atomic chlorine ions, with only 0.5% molecular chlorine, and essentially no impurities. Although this experiment did not incorporate the type of electron suppression technology that is used in negative hydrogen beam extraction, the ratio of co-extracted electrons to Cl{sup -} was as low as 7 to 1, many times lower than the ratio of their mobilities, suggesting that few electrons are present in the near-extractor plasma. This, along with the near-equivalence of the positive and negative ion currents, suggests that the plasma in this region was mostly an ion-ion plasma. The negative chlorine current density was relatively insensitive to pressure, and scaled linearly with RF power. If this linear scaling continues to hold at higher RF powers, it should permit current densities of 100 mA/cm{sup 2}, sufficient for present heavy ion fusion injector concepts. The effective ion temperatures of the positive and negative ions appeared to be similar and relatively low for a plasma source.

  17. Ways to improve the efficiency and reliability of radio frequency driven negative ion sources for fusion

    SciTech Connect

    Kraus, W.; Briefi, S.; Fantz, U.; Gutmann, P.; Doerfler, J.

    2014-02-15

    Large RF driven negative hydrogen ion sources are being developed at IPP Garching for the future neutral beam injection system of ITER. The overall power efficiency of these sources is low, because for the RF power supply self-excited generators are utilized and the plasma is generated in small cylindrical sources (“drivers”) and expands into the source main volume. At IPP experiments to reduce the primary power and the RF power required for the plasma production are performed in two ways: The oscillator generator of the prototype source has been replaced by a transistorized RF transmitter and two alternative driver concepts, a spiral coil, in which the field is concentrated by ferrites, which omits the losses by plasma expansion and a helicon source are being tested.

  18. Hydrogen evolution at the negative electrode of the all-vanadium redox flow batteries

    NASA Astrophysics Data System (ADS)

    Sun, Che-Nan; Delnick, Frank M.; Baggetto, Loïc; Veith, Gabriel M.; Zawodzinski, Thomas A.

    2014-02-01

    This work demonstrates a quantitative method to determine the hydrogen evolution rate occurring at the negative carbon electrode of the all vanadium redox flow battery (VRFB). Two carbon papers examined by buoyancy measurements yield distinct hydrogen formation rates (0.170 and 0.005 μmol min-1 g-1). The carbon papers have been characterized using electron microscopy, nitrogen gas adsorption, capacitance measurement by electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS). We find that the specific electrochemical surface area (ECSA) of the carbon material has a strong influence on the hydrogen generation rate. This is discussed in light of the use of high surface area material to obtain high reaction rates in the VRFB.

  19. Magnetic ordering temperature of nanocrystalline Gd: enhancement of magnetic interactions via hydrogenation-induced "negative" pressure.

    PubMed

    Tereshina, E A; Khmelevskyi, S; Politova, G; Kaminskaya, T; Drulis, H; Tereshina, I S

    2016-01-01

    Gadolinium is a nearly ideal soft-magnetic material. However, one cannot take advantage of its properties at temperatures higher than the room temperature where Gd loses the ferromagnetic ordering. By using high-purity bulk samples with grains ~200 nm in size, we present proof-of-concept measurements of an increased Curie point (TC) and spontaneous magnetization in Gd due to hydrogenation. From first-principles we explain increase of TC in pure Gd due to the addition of hydrogen. We show that the interplay of the characteristic features in the electronic structure of the conduction band at the Fermi level in the high-temperature paramagnetic phase of Gd and "negative" pressure exerted by hydrogen are responsible for the observed effect. PMID:26931775

  20. Cesium dynamics in long pulse operation of negative hydrogen ion sources for fusiona)

    NASA Astrophysics Data System (ADS)

    Fantz, U.; Wimmer, C.

    2012-02-01

    Large scale negative hydrogen ion sources operating stable for 1 h (cw mode) are required for the neutral beam heating system of the fusion experiment ITER. The formation of negative hydrogen ions relies on the surface effect for which cesium is evaporated into the source. In order to monitor the cesium dynamics the laser absorption spectroscopy technique is applied to the long pulse test facility MANITU. In the vacuum phase, without plasma operation the evaporation of cesium and the built-up of the cesium in the source are measured. Typical neutral cesium densities are 1015 m-3. During plasma operation and after the plasma phase a high cesium dynamics is observed, showing also depletion of cesium during long pulses with low cesium amount. The co-extracted electron current decreases with the cesium amount to a certain level whereas the ion current indicates an optimum density range.

  1. Cesium dynamics in long pulse operation of negative hydrogen ion sources for fusion

    SciTech Connect

    Fantz, U.; Wimmer, C.

    2012-02-15

    Large scale negative hydrogen ion sources operating stable for 1 h (cw mode) are required for the neutral beam heating system of the fusion experiment ITER. The formation of negative hydrogen ions relies on the surface effect for which cesium is evaporated into the source. In order to monitor the cesium dynamics the laser absorption spectroscopy technique is applied to the long pulse test facility MANITU. In the vacuum phase, without plasma operation the evaporation of cesium and the built-up of the cesium in the source are measured. Typical neutral cesium densities are 10{sup 15} m{sup -3}. During plasma operation and after the plasma phase a high cesium dynamics is observed, showing also depletion of cesium during long pulses with low cesium amount. The co-extracted electron current decreases with the cesium amount to a certain level whereas the ion current indicates an optimum density range.

  2. Development of spectrally selective imaging system for negative hydrogen ion source

    SciTech Connect

    Ikeda, K. Nakano, H.; Tsumori, K.; Kisaki, M.; Nagaoka, K.; Osakabe, M.; Takeiri, Y.; Kaneko, O.

    2014-02-15

    A spectrally selective imaging system has been developed to obtain a distribution of H{sub α} emissions at the extraction region in a hydrogen negative ion source. The diagnostic system consisted of an aspherical lens, optical filters, a fiber image conduit, and a charge coupled device detector was installed on the 1/3-scaled hydrogen negative ion source in the National Institute for Fusion Science. The center of sight line passes beside the plasma grid (PG) surface with the distance of 11 mm, and the viewing angle has coverage 35 mm from the PG surface. Two dimensional H{sub α} distribution in the range up to 20 mm from the PG surface was clearly observed. The reduction area for H{sub α} emission caused by beam extraction was widely distributed in the extraction region near the PG surface.

  3. The First Observation of Intra Beam Stripping of Negative Hydrogen in a Superconducting Linear Accelerator

    SciTech Connect

    Aleksandrov, Alexander V; Plum, Michael A; Shishlo, Andrei P; Galambos, John D

    2012-01-01

    We report on an experiment in which a negative hydrogen ions beam in the Spallation Neutron Source (SNS) linear accelerator was replaced with a beam of protons with similar size and dynamics. Beam loss in the superconducting part of the SNS accelerator was at least an order of magnitude lower for the proton beam. Also beam loss has a stronger dependence on intensity with H- than with proton beams. These measurements verify a recent theoretical explanation of unexpected beam losses in the SNS superconducting linear accelerator based on an intra beam stripping mechanism for negative hydrogen ions. An identification of the new physics mechanism for beam loss is important for the design of new high current linear ion accelerators and the performance improvement of existing machines

  4. First Observation of Intrabeam Stripping of Negative Hydrogen in a Superconducting Linear Accelerator

    NASA Astrophysics Data System (ADS)

    Shishlo, A.; Galambos, J.; Aleksandrov, A.; Lebedev, V.; Plum, M.

    2012-03-01

    We report on an experiment in which a negative hydrogen ion beam in the Spallation Neutron Source (SNS) linear accelerator was replaced with a beam of protons with similar size and dynamics. Fractional beam loss in the superconducting part of the SNS accelerator was measured to be at least 2×10-5 for the H- beam, and it was an order of magnitude lower for the protons. Also beam loss has a stronger dependence on intensity with H- than with proton beams. These measurements verify a recent theoretical explanation of unexpected beam losses in the SNS superconducting linear accelerator based on an intrabeam stripping mechanism for negative hydrogen ions. This previously unidentified mechanism for beam loss is important for the design of new high current linear ion accelerators and the performance improvement of existing machines.

  5. Research progress on ionic plasmas generated in an intense hydrogen negative ion source

    SciTech Connect

    Takeiri, Y. Tsumori, K.; Nagaoka, K.; Kaneko, O.; Ikeda, K.; Nakano, H.; Kisaki, M.; Tokuzawa, T.; Osakabe, M.; Kondo, T.; Sato, M.; Shibuya, M.; Komada, S.; Sekiguchi, H.; Geng, S.

    2015-04-08

    Characteristics of ionic plasmas, observed in a high-density hydrogen negative ion source, are investigated with a multi-diagnostics system. The ionic plasma, which consists of hydrogen positive- and negative-ions with a significantly low-density of electrons, is generated in the ion extraction region, from which the negative ions are extracted through the plasma grid. The negative ion density, i.e., the ionic plasma density, as high as the order of 1×10{sup 17}m{sup −3}, is measured with cavity ring-down spectroscopy, while the electron density is lower than 1×10{sup 16}m{sup −3}, which is confirmed with millimeter-wave interferometer. Reduction of the negative ion density is observed at the negative ion extraction, and at that time the electron flow into the ionic plasma region is observed to conserve the charge neutrality. Distribution of the plasma potential is measured in the extraction region in the direction normal to the plasma grid surface with a Langmuir probe, and the results suggest that the sheath is formed at the plasma boundary to the plasma grid to which the bias voltage is applied. The beam extraction should drive the negative ion transport in the ionic plasma across the sheath formed on the extraction surface. Larger reduction of the negative ions at the beam extraction is observed in a region above the extraction aperture on the plasma grid, which is confirmed with 2D image measurement of the Hα emission and cavity ring-down spectroscopy. The electron distribution is also measured near the plasma grid surface. These various properties observed in the ionic plasma are discussed.

  6. Negative hydrogen ion beam extraction from an AC heated cathode driven Bernas-type ion source

    NASA Astrophysics Data System (ADS)

    Okano, Y.; Miyamoto, N.; Kasuya, T.; Wada, M.

    2015-04-01

    A plasma grid structure was installed to a Bernas-type ion source used for ion implantation equipment. A negative hydrogen (H-) ion beam was extracted by an AC driven ion source by adjusting the bias to the plasma grid. The extracted electron current was reduced by positively biasing the plasma grid, while an optimum plasma grid bias voltage for negative ion beam extraction was found to be positive 3 V with respect to the arc chamber. Source operations with AC cathode heating show extraction characteristics almost identical to that with DC cathode heating, except a minute increase in H- current at higher frequency of cathode heating current.

  7. Doubly excited states of the hydrogen negative ion and helium atom in astrophysical plasmas

    SciTech Connect

    Jiang Pinghui; Kar, Sabyasachi; Zhou, Y.

    2013-01-15

    The nonthermal effects on the doubly excited resonance states of the hydrogen negative ion and helium atom are investigated in Lorentzian astrophysical plasma environments using highly correlated Hylleraas-type wave functions in the framework of the stabilization method. Resonance parameters (resonance position and width) are reported for the first time as functions of the spectral index and plasma parameter. The screening effects are more pronounced in the stronger screening region.

  8. A collisional radiative model of hydrogen plasmas developed for diagnostic purposes of negative ion sources

    NASA Astrophysics Data System (ADS)

    Iordanova, Snejana; Paunska, Tsvetelina

    2016-02-01

    A collisional radiative model of low-pressure hydrogen plasmas is elaborated and applied in optical emission spectroscopy diagnostics of a single element of a matrix source of negative hydrogen ions. The model accounts for the main processes determining both the population densities of the first ten states of the hydrogen atom and the densities of the positive hydrogen ions H+, H2+, and H3+. In the calculations, the electron density and electron temperature are varied whereas the atomic and molecular temperatures are included as experimentally obtained external parameters. The ratio of the Hα to Hβ line intensities is calculated from the numerical results for the excited state population densities, obtained as a solution of the set of the steady-state rate balance equations. The comparison of measured and theoretically obtained ratios of line intensities yields the values of the electron density and temperature as well as of the degree of dissociation, i.e., of the parameters which have a crucial role for the volume production of the negative ions.

  9. First experiments with Cs doped Mo as surface converter for negative hydrogen ion sources

    SciTech Connect

    Schiesko, L. Hopf, C.; Höschen, T.; Meisl, G.; Encke, O.; Heinemann, B.; Fantz, U.; Cartry, G.; Amsalem, P.; Achkasov, K.

    2015-08-21

    A study was conducted on the properties of molybdenum implanted with caesium as an approach to reduce the Cs consumption of negative hydrogen ion sources based on evaporated Cs. The depth profiles of the implanted Cs were simulated by SDTrimSP and experimentally determined by X-ray photoelectron spectroscopy depth profiling. In particular, one year after implantation, the depth profiles showed no signs of Cs diffusion into the molybdenum, suggesting long term stability of the implanted Cs atoms. The H{sup −} surface generation mechanisms on the implanted samples in hydrogen plasma were investigated, and the stability of the H{sup −} yield during four hours low power hydrogen plasma discharges was demonstrated. An estimation of the work function reduction (−0.8 eV) by the Cs implantation was performed, and a comparison of the relative negative ion yields between the implanted samples and highly oriented pyrolitic graphite showed that the Cs doped Mo negative ion yield was larger.

  10. Comparison of measured and modelled negative hydrogen ion densities at the ECR-discharge HOMER

    SciTech Connect

    Rauner, D.; Kurutz, U.; Fantz, U.

    2015-04-08

    As the negative hydrogen ion density n{sub H{sup −}} is a key parameter for the investigation of negative ion sources, its diagnostic quantification is essential in source development and operation as well as for fundamental research. By utilizing the photodetachment process of negative ions, generally two different diagnostic methods can be applied: via laser photodetachment, the density of negative ions is measured locally, but only relatively to the electron density. To obtain absolute densities, the electron density has to be measured additionally, which induces further uncertainties. Via cavity ring-down spectroscopy (CRDS), the absolute density of H{sup −} is measured directly, however LOS-averaged over the plasma length. At the ECR-discharge HOMER, where H{sup −} is produced in the plasma volume, laser photodetachment is applied as the standard method to measure n{sub H{sup −}}. The additional application of CRDS provides the possibility to directly obtain absolute values of n{sub H{sup −}}, thereby successfully bench-marking the laser photodetachment system as both diagnostics are in good agreement. In the investigated pressure range from 0.3 to 3 Pa, the measured negative hydrogen ion density shows a maximum at 1 to 1.5 Pa and an approximately linear response to increasing input microwave powers from 200 up to 500 W. Additionally, the volume production of negative ions is 0-dimensionally modelled by balancing H{sup −} production and destruction processes. The modelled densities are adapted to the absolute measurements of n{sub H{sup −}} via CRDS, allowing to identify collisions of H{sup −} with hydrogen atoms (associative and non-associative detachment) to be the dominant loss process of H{sup −} in the plasma volume at HOMER. Furthermore, the characteristic peak of n{sub H{sup −}} observed at 1 to 1.5 Pa is identified to be caused by a comparable behaviour of the electron density with varying pressure, as n{sub e} determines

  11. Triple Guest Occupancy and Negative Compressibility in Hydrogen-Loaded β-Hydroquinone Clathrate.

    PubMed

    Rozsa, Viktor F; Strobel, Timothy A

    2014-06-01

    The molecular interactions and structural behavior of a previously unexplored clathrate system, hydrogen-loaded β-hydroquinone (β-HQ+H2), were investigated under high pressure with synchrotron X-ray diffraction and Raman/infrared spectroscopies. The β-HQ+H2 system exhibits coupling of two independently rare phenomena: multiple occupancy and negative compressibility. The number of H2 molecules per cavity increases from one to three, causing unit cell volume increase by way of unique crystallographic interstitial guest positioning. We anticipate these occupancy-derived trends may be general to a range of inclusion compounds and may aid the chemical and crystallographic design of both high-occupancy hydrogen storage clathrates and novel, variable-composition materials with tunable mechanical properties. PMID:26273868

  12. Space charge compensation in the Linac4 low energy beam transport line with negative hydrogen ions

    SciTech Connect

    Valerio-Lizarraga, Cristhian A.; Lallement, Jean-Baptiste; Lettry, Jacques; Scrivens, Richard; Leon-Monzon, Ildefonso; Midttun, Øystein

    2014-02-15

    The space charge effect of low energy, unbunched ion beams can be compensated by the trapping of ions or electrons into the beam potential. This has been studied for the 45 keV negative hydrogen ion beam in the CERN Linac4 Low Energy Beam Transport using the package IBSimu [T. Kalvas et al., Rev. Sci. Instrum. 81, 02B703 (2010)], which allows the space charge calculation of the particle trajectories. The results of the beam simulations will be compared to emittance measurements of an H{sup −} beam at the CERN Linac4 3 MeV test stand, where the injection of hydrogen gas directly into the beam transport region has been used to modify the space charge compensation degree.

  13. Formation of silicon hydride using hyperthermal negative hydrogen ions (H -) extracted from an argon-seeded hydrogen sheet plasma source

    NASA Astrophysics Data System (ADS)

    Fernandez, Marcedon S.; Blantocas, Gene Q.; Ramos, Henry J.

    2008-12-01

    An E × B probe (a modified Wien filter) is constructed to function both as a mass spectrometer and ion implanter. The device, given the acronym EXBII selects negative hydrogen ions (H -) from a premixed 10% argon-seeded hydrogen sheet plasma. With a vacuum background of 1.0 × 10 -6 Torr, H - extraction ensues at a total gas feed of 1.8 mTorr, 0.5 A plasma discharge. The EXBII is positioned 3 cm distance from the sheet core as this is the region densely populated by cold electrons ( Te ˜ 2 eV, Ne ˜ 3.4 × 10 11 cm -3) best suited for H - formation. The extracted H - ions of flux density ˜0.26 A/m 2 are segregated, accelerated to hyperthermal range (<100 eV) and subsequently deposited into a palladium-coated 1.1 × 1.1 cm 2, n-type Si (1 0 0) substrate held at the rear end of the EXBII, placed in lieu of its Faraday cup. The palladium membrane plays the role of a catalyst initiating the reaction between Si atoms and H - ions simultaneously capping the sample from oxidation and other undesirable adsorbents. AFM and FTIR characterization tests confirm the formation of SiH 2. Absorbance peaks between 900-970 cm -1 (bending modes) and 2050-2260 cm -1 (stretching modes) are observed in the FTIR spectra of the processed samples. It is found that varying hydrogen exposure time results in the shifting of wavenumbers which may be interpreted as changes in the frequencies of vibration for SiH 2. These are manifestations of chemical changes accompanying alterations in the force constant of the molecule. The sample with longer exposure time exhibits an additional peak at 2036 cm -1 which are hydrides of nano-crystalline silicon.

  14. Extraction of negative hydrogen ions from a compact 14 GHz microwave ion source

    SciTech Connect

    Wada, M.; Kasuya, T.; Nishida, T.; Kenmotsu, T.; Maeno, S.; Nishiura, M.; Shinto, K.; Yamaoka, H.

    2012-02-15

    A pair of permanent magnets has formed enough intensity to realize electron cyclotron resonance condition for a 14 GHz microwave in a 2 cm diameter 9 cm long alumina discharge chamber. A three-electrode extraction system assembled in a magnetic shielding has formed a stable beam of negative hydrogen ions (H{sup -}) in a direction perpendicular to the magnetic field. The measured H{sup -} current density was about 1 mA/cm{sup 2} with only 50 W of discharge power, but the beam intensity had shown saturation against further increase in microwave power. The beam current decreased monotonically against increasing pressure.

  15. Negative hydrogen ion beam extraction from an AC heated cathode driven Bernas-type ion source

    SciTech Connect

    Okano, Y.; Miyamoto, N.; Kasuya, T.; Wada, M.

    2015-04-08

    A plasma grid structure was installed to a Bernas-type ion source used for ion implantation equipment. A negative hydrogen (H{sup −}) ion beam was extracted by an AC driven ion source by adjusting the bias to the plasma grid. The extracted electron current was reduced by positively biasing the plasma grid, while an optimum plasma grid bias voltage for negative ion beam extraction was found to be positive 3 V with respect to the arc chamber. Source operations with AC cathode heating show extraction characteristics almost identical to that with DC cathode heating, except a minute increase in H{sup −} current at higher frequency of cathode heating current.

  16. Plasma transfer process in hydrogen negative ions source based on reflective discharge

    SciTech Connect

    Goretsky, V.P.; Ryabtsev, A.V.; Soloshenko, I.A.; Tarasenko, A.F.; Schedrin, A.I.

    1996-07-01

    The results of theoretical and experimental studies of stationary volume source of hydrogen negative ions based on reflective discharge are presented in the report. Measurements of plasma parameters and emission characteristics are accomplished, and the optimization of ion source geometry is provided. The best parameters of ion beam extracted from the source across a magnetic field are the following: current 40 mA, current density 80 mA/cm{sup 2}, emittance along a magnetic field 3{center_dot}10{sup {minus}5} cm{center_dot}rad, emittance across a magnetic field 1{center_dot}10{sup {minus}5} cm{center_dot}rad. The calculation of beam basic properties is performed by numeric solving of Boltzman equation for electrons, balance equations for more than 300 elementary processes in gas discharge plasma, and equations of ions and electrons motion. Calculated dependencies of hydrogen negative ions current density in a plane of emission slit on the gas pressure and the discharge current are found to be in a good agreement with the experimental data. {copyright} {ital 1996 American Institute of Physics.}

  17. Behavior of Negative Hydrogen Ion and its Beam by Bias and Beam Extraction Voltages

    NASA Astrophysics Data System (ADS)

    Nakano, Haruhisa; Tsumori, Katsuyoshi; Kisaki, Masashi; Ikeda, Katsunori; Geng, Shaofei; Nagaoka, Kenichi; Osakabe, Masaki; Takeiri, Yasuhiko; Kaneko, Osamu; Serianni, Gianluigi; Agostinetti, Piero; Sartori, Emanuele; Brombin, Matteo; Wimmer, Christian

    2015-09-01

    Negative hydrogen ion (H-) dynamics from production to beam extraction in H- source for fusion have not been enough understood in cesium-seeded negative-hydrogen-ion sources. This dynamics understanding contributes constructions of higher performance ion sources. The H- is produced on and emitted from plasma grid electrode (PG) which is boundary electrode between source plasma and beam. The H- density in the vicinity of the PG decreased with bias voltage (between PG and arc chamber) by suppression of H- emission and/or yield. The H- density decrement was observed in H- beam extraction phase and penetrated to 30 mm depth from PG. The depth and H- beam current decreased with bias voltage. One of the possibilities which explain it is extracted H- coming from space in the vicinity of the PG. An object made of ceramic was inserted above the PG aperture. The H- beam intensity decreased if the object was set 9 mm from PG. This does not conflict with the possibility. This work is supported by NIFS Research Programs NIFS13ULRR008 and NIFS13ULRR702, and JSPS KAKENHI Grant Numbers 25800307 and 25249134.

  18. Multiplying probe for accurate power measurements on an RF driven atmospheric pressure plasma jet applied to the COST reference microplasma jet

    NASA Astrophysics Data System (ADS)

    Beijer, P. A. C.; Sobota, A.; van Veldhuizen, E. M.; Kroesen, G. M. W.

    2016-03-01

    In this paper a new multiplying probe for measuring the power dissipated in a miniature capacitively coupled, RF driven, atmospheric pressure plasma jet (μAPPJ—COST Reference Microplasma Jet—COST RMJ) is presented. The approach aims for substantially higher accuracy than provided by traditionally applied methods using bi-directional power meters or commercially available voltage and current probes in conjunction with digitizing oscilloscopes. The probe is placed on a miniature PCB and designed to minimize losses, influence of unknown elements, crosstalk and variations in temperature. The probe is designed to measure powers of the order of magnitude of 0.1-10 W. It is estimated that it measures power with less than 2% deviation from the real value in the tested power range. The design was applied to measure power dissipated in COST-RMJ running in helium with a small addition of oxygen.

  19. A Negative Hydrogen-Ion Source for SNS Using a Helicon Plasma Generator

    SciTech Connect

    Goulding, R. H.; Welton, R. F.; Baity, F. W.; Crisp, D. W.; Fadnek, A.; Kang, Y.; Murray, S. N.; Sparks, D. O.; Stockli, M. P.

    2007-09-28

    The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory is a world-class facility for materials research based on neutron scattering. It consists of a negative hydrogen (H-) ion source, linear accelerator, proton accumulator ring, and liquid Hg target. A power upgrade is planned for the device, which will require significant improvements in the negative ion source, including the production of H-beam currents of 70-95 mA ({approx}2xthe present SNS source value), with a pulse length of 1 ms and duty factor of {approx}7%. No H-sources currently in existence meet these combined requirements. A proof-of-principle experiment is being constructed in which the rf inductive plasma generator in the present source is replaced by a helicon plasma generator. This is expected to produce a factor of three or better increase in the maximum source plasma density at a reduced rf power level, resulting in significantly increased negative ion current with reduced heat removal requirements.

  20. A Negative Hydrogen-Ion Source for SNS Using a Helicon Plasma Generator

    SciTech Connect

    Goulding, Richard Howell; Welton, Robert F; Baity Jr, F Wallace; Crisp, Danny W; Fadnek, Andy; Kang, Yoon W; Murray Jr, S N; Sparks, Dennis O; Stockli, Martin P

    2007-01-01

    The Spallation Neutron Source (SNS) at Oak Ridge National Labo ratory is a world-class facility for materials research based on neutron scattering. It consists of a negative hydrogen (H-) ion source, linear accelerator, proton accumulator ring, and liquid Hg target. A power up grade is planned for the device, which will require significant improvements in the negative ion source, including the production of H- beam currents of 70-95 mA (~2 the present SNS source value), with a pulse length of 1 ms and duty factor of ~ 7%. No H- sources currently in existence meet these combined requirements. A proof-of-principle experiment is being constructed in which the rf inductive plasma generator in the present source is replaced by a helicon plasma generator. This is expected to produce a factor of three or better in crease in the maximum source plasma density at a reduced rf power level, resulting in significantly increased negative ion current with reduced heat removal requirements.

  1. A collisional radiative model for caesium and its application to an RF source for negative hydrogen ions

    SciTech Connect

    Wünderlich, D. Wimmer, C.; Friedl, R.

    2015-04-08

    A collisional radiative (CR) model for caesium atoms in low-temperature, low-pressure hydrogen-caesium plasmas is introduced. This model includes the caesium ground state, 14 excited states, the singly charged caesium ion and the negative hydrogen ion. The reaction probabilities needed as input are based on data from the literature, using some scaling and extrapolations. Additionally, new cross sections for electron collision ionization and three-body recombination have been calculated. The relevance of mutual neutralization of positive caesium ions and negative hydrogen ions is highlighted: depending on the densities of the involved particle species, this excitation channel can have a significant influence on the population densities of excited states in the caesium atom. This strong influence is successfully verified by optical emission spectroscopy measurements performed at the IPP prototype negative hydrogen ion source for ITER NBI. As a consequence, population models for caesium in electronegative low-temperature, low-pressure hydrogen-caesium plasmas need to take into account the mutual neutralization process. The present CR model is an example for such models and represents an important prerequisite for deducing the total caesium density in surface production based negative hydrogen ion sources.

  2. Dependence of beam emittance on plasma electrode temperature and rf-power, and filter-field tuning with center-gapped rod-filter magnets in J-PARC rf-driven H- ion source

    NASA Astrophysics Data System (ADS)

    Ueno, A.; Koizumi, I.; Ohkoshi, K.; Ikegami, K.; Takagi, A.; Yamazaki, S.; Oguri, H.

    2014-02-01

    The prototype rf-driven H- ion-source with a nickel plated oxygen-free-copper (OFC) plasma chamber, which satisfies the Japan Proton Accelerator Research Complex (J-PARC) 2nd stage requirements of a H- ion beam current of 60 mA within normalized emittances of 1.5 π mm mrad both horizontally and vertically, a flat top beam duty factor of 1.25% (500 μs × 25 Hz) and a life-time of more than 50 days, was reported at the 3rd international symposium on negative ions, beams, and sources (NIBS2012). The experimental results of the J-PARC ion source with a plasma chamber made of stainless-steel, instead of nickel plated OFC used in the prototype source, are presented in this paper. By comparing these two sources, the following two important results were acquired. One was that the about 20% lower emittance was produced by the rather low plasma electrode (PE) temperature (TPE) of about 120 °C compared with the typically used TPE of about 200 °C to maximize the beam current for the plasma with the abundant cesium (Cs). The other was that by using the rod-filter magnets with a gap at each center and tuning the gap-lengths, the filter-field was optimized and the rf-power necessary to produce the J-PARC required H- ion beam current was reduced typically 18%. The lower rf-power also decreases the emittances.

  3. Dependence of beam emittance on plasma electrode temperature and rf-power, and filter-field tuning with center-gapped rod-filter magnets in J-PARC rf-driven H{sup −} ion source

    SciTech Connect

    Ueno, A. Koizumi, I.; Ohkoshi, K.; Ikegami, K.; Takagi, A.; Yamazaki, S.; Oguri, H.

    2014-02-15

    The prototype rf-driven H{sup −} ion-source with a nickel plated oxygen-free-copper (OFC) plasma chamber, which satisfies the Japan Proton Accelerator Research Complex (J-PARC) 2nd stage requirements of a H{sup −} ion beam current of 60 mA within normalized emittances of 1.5 π mm mrad both horizontally and vertically, a flat top beam duty factor of 1.25% (500 μs × 25 Hz) and a life-time of more than 50 days, was reported at the 3rd international symposium on negative ions, beams, and sources (NIBS2012). The experimental results of the J-PARC ion source with a plasma chamber made of stainless-steel, instead of nickel plated OFC used in the prototype source, are presented in this paper. By comparing these two sources, the following two important results were acquired. One was that the about 20% lower emittance was produced by the rather low plasma electrode (PE) temperature (T{sub PE}) of about 120 °C compared with the typically used T{sub PE} of about 200 °C to maximize the beam current for the plasma with the abundant cesium (Cs). The other was that by using the rod-filter magnets with a gap at each center and tuning the gap-lengths, the filter-field was optimized and the rf-power necessary to produce the J-PARC required H{sup −} ion beam current was reduced typically 18%. The lower rf-power also decreases the emittances.

  4. The negative hydrogen Penning ion gauge ion source for KIRAMS-13 cyclotron

    SciTech Connect

    An, D. H.; Jung, I. S.; Kang, J.; Chang, H. S.; Hong, B. H.; Hong, S.; Lee, M. Y.; Kim, Y.; Yang, T. K.; Chai, J. S.

    2008-02-15

    The cold-cathode-type Penning ion gauge (PIG) ion source for the internal ion source of KIRAMS-13 cyclotron has been used for generation of negative hydrogen ions. The dc H-beam current of 650 {mu}A from the PIG ion source with the Dee voltage of 40 kV and arc current of 1.0 A is extrapolated from the measured dc extraction beam currents at the low extraction dc voltages. The output optimization of PIG ion source in the cyclotron has been carried out by using various chimneys with different sizes of the expansion gap between the plasma boundary and the chimney wall. This paper presents the results of the dc H-extraction measurement and the expansion gap experiment.

  5. Monitoring Surface Condition of Plasma Grid of a Negative Hydrogen Ion Source

    SciTech Connect

    Wada, M.; Kasuya, T.; Tokushige, S.; Kenmotsu, T.

    2011-09-26

    Surface condition of a plasma grid in a negative hydrogen ion source is controlled so as to maximize the beam current under a discharge operation with introducing Cs into the ion source. Photoelectric current induced by laser beams incident on the plasma grid can produce a signal to monitor the surface condition, but the signal detection can be easily hindered by plasma noise. Reduction in size of a detection electrode embedded in the plasma grid can improve signal-to-noise ratio of the photoelectric current from the electrode. To evaluate the feasibility of monitoring surface condition of a plasma gird by utilizing photoelectric effect, a small experimental setup capable of determining quantum yields of a surface in a cesiated plasma environment is being assembled. Some preliminary test results of the apparatus utilizing oxide cathodes are reported.

  6. Over-the-barrier electron detachment in the hydrogen negative ion

    NASA Astrophysics Data System (ADS)

    Milošević, M. Z.; Simonović, N. S.

    2016-09-01

    The electron detachment from the hydrogen negative ion in strong fields is studied using the two-electron and different single-electron models within the quasistatic approximation. Special attention is payed to over-the-barrier regime where the Stark saddle is suppressed below the lowest energy level. It is demonstrated that the single-electron description of the lowest state of the ion, that is a good approximation for weak fields, fails in this and partially in the tunnelling regime. The exact lowest state energies and detachment rates for the ion at different strengths of the applied field are determined by solving the eigenvalue problem of the full two-electron Hamiltonian. A simple formula for the rate, which is valid in both regimes, is determined by fitting the exact data to the expression estimated using single-electron descriptions.

  7. Capture of negative muons by hydrogen atoms at low collision energies

    SciTech Connect

    Sakimoto, Kazuhiro

    2010-01-15

    A rigorous quantum mechanical calculation is carried out for negative muon capture by atomic hydrogen (mu{sup -}+H->mu{sup -}p+e) by using the R-matrix method. The total and final-state selected capture cross sections are calculated at low collision energies ranging from 0.001 to 1 eV. The total capture cross section can, on average, be explained in terms of a previously obtained empirical formula [K. Sakimoto, Phys. Rev. A 66, 032506 (2002)]. However, the present result exhibits additional undulation and cusp structures, which stem from quantum phenomena. The muons are predominantly captured into the highest energetically possible state of mu{sup -}p in the present energy region. However, the mu{sup -}p products having high angular momenta cannot be formed unless the collision energy becomes high.

  8. 3D self-consistent modeling of a matrix source of negative hydrogen ions.

    PubMed

    Tarnev, Kh; Demerdjiev, A; Shivarova, A; Lishev, St

    2016-02-01

    The paper is in the scope of studies on the rf driving of a matrix source of negative hydrogen ions: a matrix of small radius discharges with planar-coil inductive driving and single aperture extraction from each discharge. The results from a three-dimensional model, in which plasma description is coupled to electrodynamics, confirm former conclusion that a single coil driving of the whole matrix by a zigzag coil with an omega-shaped conductor on the bottom of each discharge tube ensures efficient rf power deposition to the plasma. The latter is due to similarities with the rf driving of a single discharge by a single planar coil, shown by the obtained induced current and spatial distribution of the plasma parameters. Distinctions associated with the coil configuration as a single coil for the whole matrix are also discussed. PMID:26932005

  9. Study on a negative hydrogen ion source with hot cathode arc discharge

    SciTech Connect

    Lin, S. H. Fang, X.; Zhang, H. J.; Qian, C.; Ma, B. H.; Wang, H.; Li, X. X.; Zhang, X. Z.; Sun, L. T.; Zhang, Z. M.; Yuan, P.; Zhao, H. W.

    2014-02-15

    A negative hydrogen (H{sup −}) ion source with hot cathode arc discharge was designed and fabricated as a primary injector for a 10 MeV PET cyclotron at IMP. 1 mA dc H{sup −} beam with ε {sub N,} {sub RMS} = 0.08 π mm mrad was extracted at 25 kV. Halbach hexapole was adopted to confine the plasma. The state of arc discharge, the parameters including filament current, arc current, gas pressure, plasma electrode bias, and the ratio of I{sub e{sup −}}/I{sub H{sup −}} were experimentally studied. The discussion on the result, and opinions to improve the source were given.

  10. Electrical shielding box measurement of the negative hydrogen beam from Penning ion gauge ion source

    SciTech Connect

    Wang, T.; Yang, Z.; Dong, P.; Long, J. D.; He, X. Z.; Zhang, K. Z.; Zhang, L. W.; Wang, X.

    2012-06-15

    The cold-cathode Penning ion gauge (PIG) type ion source has been used for generation of negative hydrogen (H{sup -}) ions as the internal ion source of a compact cyclotron. A novel method called electrical shielding box dc beam measurement is described in this paper, and the beam intensity was measured under dc extraction inside an electrical shielding box. The results of the trajectory simulation and dc H{sup -} beam extraction measurement were presented. The effect of gas flow rate, magnetic field strength, arc current, and extraction voltage were also discussed. In conclusion, the dc H{sup -} beam current of about 4 mA from the PIG ion source with the puller voltage of 40 kV and arc current of 1.31 A was extrapolated from the measurement at low extraction dc voltages.

  11. Negative hydrogen ion beam extracted from a Bernas-type ion source

    SciTech Connect

    Miyamoto, N.; Wada, M.

    2011-09-26

    Negative hydrogen (H{sup -}) ion beam was produced without cesium seeding by a Bernas-type ion source with a coaxial hot cathode. The amount of H{sup -} ion beam current extracted from an original Bernas-type ion source using a hairpin shape filament as a hot cathode was 1 {mu}A with the 0.4 A arc current, while that 300 eV beam energy. In the other hand, H{sup -} ion beam current using the Bernas-type ion source with a coaxial hot cathode reached 4 {mu}A under the same condition. Production efficiency was enhanced by the focused plasma produced by a coaxial hot cathode.

  12. Electrical shielding box measurement of the negative hydrogen beam from Penning ion gauge ion source

    NASA Astrophysics Data System (ADS)

    Wang, T.; Yang, Z.; Dong, P.; long, J. D.; He, X. Z.; Wang, X.; Zhang, K. Z.; Zhang, L. W.

    2012-06-01

    The cold-cathode Penning ion gauge (PIG) type ion source has been used for generation of negative hydrogen (H-) ions as the internal ion source of a compact cyclotron. A novel method called electrical shielding box dc beam measurement is described in this paper, and the beam intensity was measured under dc extraction inside an electrical shielding box. The results of the trajectory simulation and dc H- beam extraction measurement were presented. The effect of gas flow rate, magnetic field strength, arc current, and extraction voltage were also discussed. In conclusion, the dc H- beam current of about 4 mA from the PIG ion source with the puller voltage of 40 kV and arc current of 1.31 A was extrapolated from the measurement at low extraction dc voltages.

  13. Electron cyclotron resonance heating by magnetic filter field in a negative hydrogen ion source.

    PubMed

    Kim, June Young; Cho, Won-Hwi; Dang, Jeong-Jeung; Chung, Kyoung-Jae; Hwang, Y S

    2016-02-01

    The influence of magnetic filter field on plasma properties in the heating region has been investigated in a planar-type inductively coupled radio-frequency (RF) H(-) ion source. Besides filtering high energy electrons near the extraction region, the magnetic filter field is clearly observed to increase the electron temperature in the heating region at low pressure discharge. With increasing the operating pressure, enhancement of electron temperature in the heating region is reduced. The possibility of electron cyclotron resonance (ECR) heating in the heating region due to stray magnetic field generated by a filter magnet located at the extraction region is examined. It is found that ECR heating by RF wave field in the discharge region, where the strength of an axial magnetic field is approximately ∼4.8 G, can effectively heat low energy electrons. Depletion of low energy electrons in the electron energy distribution function measured at the heating region supports the occurrence of ECR heating. The present study suggests that addition of axial magnetic field as small as several G by an external electromagnet or permanent magnets can greatly increase the generation of highly ro-vibrationally excited hydrogen molecules in the heating region, thus improving the performance of H(-) ion generation in volume-produced negative hydrogen ion sources. PMID:26931999

  14. Electron cyclotron resonance heating by magnetic filter field in a negative hydrogen ion source

    NASA Astrophysics Data System (ADS)

    Kim, June Young; Cho, Won-Hwi; Dang, Jeong-Jeung; Chung, Kyoung-Jae; Hwang, Y. S.

    2016-02-01

    The influence of magnetic filter field on plasma properties in the heating region has been investigated in a planar-type inductively coupled radio-frequency (RF) H- ion source. Besides filtering high energy electrons near the extraction region, the magnetic filter field is clearly observed to increase the electron temperature in the heating region at low pressure discharge. With increasing the operating pressure, enhancement of electron temperature in the heating region is reduced. The possibility of electron cyclotron resonance (ECR) heating in the heating region due to stray magnetic field generated by a filter magnet located at the extraction region is examined. It is found that ECR heating by RF wave field in the discharge region, where the strength of an axial magnetic field is approximately ˜4.8 G, can effectively heat low energy electrons. Depletion of low energy electrons in the electron energy distribution function measured at the heating region supports the occurrence of ECR heating. The present study suggests that addition of axial magnetic field as small as several G by an external electromagnet or permanent magnets can greatly increase the generation of highly ro-vibrationally excited hydrogen molecules in the heating region, thus improving the performance of H- ion generation in volume-produced negative hydrogen ion sources.

  15. Progress on producing polarized negative hydrogen ions by the ETHZ polarized ion source using the atomic beam method

    NASA Astrophysics Data System (ADS)

    Schmelzbach, P. A.; Grüebler, W.

    1983-03-01

    The progress on the ETHZ polarized negative hydrogen ion source, based on the atomic beam method, is described. Particular improvements have been made in the double charge exchange from positive to negative hydrogen ions. At present the source produces over 100 μA H+ ions, which yields 5-6 μA polarized negative hydrogen ions. These ions have been accelerated, in a EN tandem accelerator. A record current of 2-3 μA of polarized deuterons with 89% polarization could be focused through a 3 mm diameter collimator on a target. Further improvements incorporating presently available techniques are discussed. It is shown that 50-100 μA of polarized H- and D- ions can be produced with this type of source.

  16. Negative Linear Compressibility in Organic Mineral Ammonium Oxalate Monohydrate with Hydrogen Bonding Wine-Rack Motifs.

    PubMed

    Qiao, Yuancun; Wang, Kai; Yuan, Hongsheng; Yang, Ke; Zou, Bo

    2015-07-16

    Negative linear compressibility (NLC) is a relatively uncommon phenomenon and rarely studied in organic systems. Here we provide the direct evidence of the persistent NLC in organic mineral ammonium oxalate monohydrate under high pressure using synchrotron X-ray powder diffraction, Raman spectroscopy and density functional theory (DFT) calculation. Synchrotron X-ray powder diffraction measurement reveals that ammonium oxalate monohydrate shows both positive and negative linear compressibility along b-axis before 11.5 GPa. The red shift of the external Raman modes and abnormal changes of several selected internal modes in high-pressure Raman spectra further confirmed the NLC. DFT calculations demonstrate that the N-H···O hydrogen bonding "wine-rack" motifs result in the NLC along b-axis in ammonium oxalate monohydrate. We anticipate the high-pressure study of ammonium oxalate monohydrate may represent a promising strategy for accelerating the pace of exploitation and improvement of NLC materials especially in organic systems. PMID:26266859

  17. Single discharge of the matrix source of negative hydrogen ions: Influence of the neutral particle dynamics

    SciTech Connect

    Paunska, Ts.; Todorov, D. Shivarova, A.; Tarnev, Kh.

    2015-04-08

    The study presents two-dimensional (2D) fluid-plasma-model description of a planar-coil inductively-driven discharge, considered as a single element of a matrix source of volume-produced negative hydrogen ions. Whereas the models developed up to now have been directed towards description of the charged particle behavior in the discharge, including that of the negative ions, this model stresses on the role of the neutral particle dynamics and of the surface processes in the formation of the discharge structure. The latter is discussed based on comparison of results obtained for discharges in a flowing gas and at a constant gas pressure as well as for different values of the coefficient of atom recombination on the walls. The conclusions are that the main plasma parameters – electron density and temperature and plasma potential – determining the gas discharge regime stay stable, regardless of changes in the redistribution of the densities of the neutral particles and of the positive ions. With regards to the volume production of the ions, which requires high density of (vibrationally excited) molecules, the impact on the degree of dissociation of the coefficient of atom recombination on the wall is discussed.

  18. Studies of negative ions by collision-induced decomposition and hydrogen-deuterium exchange techniques.

    PubMed Central

    Hunt, D F; Sethi, S K; Shabanowitz, J

    1980-01-01

    Development of two new techniques for studying the gas phase chemistry of negative ions is reported. Collision induced dissociation (CID) of (M-1)- ions has been accomplished in a newly constructed triple stage quadrupole mass spectrometer. This instrument was assembled by adding two additional Finnigan quadrupole mass filters to a Finnigan Model 3200 CI mass spectrometer. Generation of (M-1)- ions is accomplished by allowing OH- and sample to react under CI conditions in the ion source. The first quadrupole mass filter, Q1, is then employed to selectively pass the (M-1)- ion into a second quadrupole filter containing argon or neon at 10(-3) torr. On collision with the inert gas the (M-1)- ions dissociate into fragments which are then mass analyzed in the third quadrupole filter, CID spectra of (M-1)- ions from twelve carbonyl compounds are presented in this paper. Ion molecule isotope exchange reactions in the CI ion source can be used to count the number of hydrogen atoms in many different chemical environments. Collisions between sample (M-1)- ions and deuterium-labeled reagent gases (ND3, D2O, EtOD) facilitate incorporation of deuterium into the negative ion if the basicities of the sample and reagent anions are similar. Thus it is possible to selectively incorporate deuterium into many organic samples by controlling the exothermicity of the acid base, ion-molecule chemistry. PMID:7428745

  19. Measurement of the negative hydrogen ions temperature by using an omegatron mass analyzer in the sheet plasma

    NASA Astrophysics Data System (ADS)

    Takimoto, Toshikio; Iijima, Takaaki; Tanaka, Yuta; Hase, Takuya; Tonegawa, Akira; Sato, Kohnosuke; Kawamura, Kazutaka

    2015-09-01

    The production mechanisms of negative ions in hydrogen plasma are not easily understood because of the complex phenomena of atomic and molecular reactions. A mainstream measurement of H- is a laser photodetachment technique. We had measured negative ions using a laser photodetachment technique. Consequently, under a secondary hydrogen gas supply entering into the plasma, the H- is distributed in the periphery of the sheet plasma. In addition, it has been reported that the negative hydrogen ions transport velocity evaluated by the relaxation time of optically released electron current. Nevertheless, this technique a laser photodetachment cannot be used as a mass analyzer. In this paper, we have measured the temperature of the negative hydrogen ions TH- by using an omegatron mass analyzer in the sheet plasma. The TH- is determined by measuring the collection ion currents IH- as a function of the ion repeller voltage VG2 by using an omegatron mass analyzer. From the fitting an exponential region of the measured I-V characteristics curve, TH- is around 1.40 eV at the gas pressure of 0.23 Pa in the periphery region of the sheet plasma.

  20. The study of discharge characteristic of the cold-cathode negative hydrogen PIG-type ion source

    NASA Astrophysics Data System (ADS)

    Yang, Z.; Dong, P.; Long, J. D.; Wang, T.; Lan, C. H.; Peng, Y. F.; Wei, T.; He, X. Z.; Zhang, K. Z.; Shi, J. S.

    2012-09-01

    The cold-cathode Penning ion gage (PIG)-type ion source is designed for the internal ion source of the compact cyclotron. This kind of ion source has been used for generation of the negative hydrogen (H-) ions for many decades. The discharge characteristics of the ion source are investigated systematically for hydrogen operation at different discharge currents, gas flow rates and magnetic fields, respectively. In this paper, optical emission spectroscopy measurement is carried out to diagnose the parameters of the hydrogen plasma in the ion source. The preliminary optimization of the H- formation with the gas flow rates is discussed and analyzed. Current experimental results can provide useful information for the design and operation of the negative ion source.

  1. Quantification Of Cesium In Negative Hydrogen Ion Sources By Laser Absorption Spectroscopy

    SciTech Connect

    Fantz, U.; Wimmer, Ch.

    2011-09-26

    The use of cesium in negative hydrogen ion sources and the resulting cesium dynamics caused by the evaporation and redistribution in the vacuum and plasma phase makes a reliable and on-line monitoring of the cesium amount in the source highly desirable. For that purpose, a robust and compact laser absorption setup suitable for the ion source environment has been developed utilizing the Cs D{sub 2} resonance line at 852.1 nm. First measurements are taken in a small laboratory plasma chamber with cesium evaporation. A detection limit of {approx_equal}5x10{sup 13} m{sup -3} at a typical path length of 15 cm has been obtained with a dynamic range of more than three orders of magnitude, limited by line saturation at high densities. For on-line monitoring an automatic data analysis is established achieving a temporal resolution of 100 ms. The setup has then been applied to the ITER prototype ion sources developed at IPP. It is been shown that the method is well suited for routine measurements revealing a new insight into the cesium dynamics during source operation and cesium conditioning.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  3. Operation Status of the J-PARC Negative Hydrogen Ion Source

    SciTech Connect

    Oguri, H.; Ikegami, K.; Ohkoshi, K.; Namekawa, Y.; Ueno, A.

    2011-09-26

    A cesium-free negative hydrogen ion source driven with a lanthanum hexaboride (LaB{sub 6}) filament is being operated without any serious trouble for approximately four years in J-PARC. Although the ion source is capable of producing an H{sup -} ion current of more than 30 mA, the current is routinely restricted to approximately 16 mA at present for the stable operation of the RFQ linac which has serious discharge problem from September 2008. The beam run is performed during 1 month cycle, which consisted of a 4-5 weeks beam operation and a few days down-period interval. At the recent beam run, approximately 700 h continuous operation was achieved. At every runs, the beam interruption time due to the ion source failure is a few hours, which correspond to the ion source availability of more than 99%. The R and D work is being performed in parallel with the operation in order to enhance the further beam current. As a result, the H{sup -} ion current of 61 mA with normalized rms emittance of 0.26 {pi}mm.mrad was obtained by adding a cesium seeding system to a J-PARC test ion source which has the almost same structure with the present J-PARC ion source.

  4. Effects of roughness and temperature on low-energy hydrogen positive and negative ion reflection from silicon and carbon surfaces

    SciTech Connect

    Tanaka, N.; Kato, S.; Miyamoto, T.; Wada, M.; Nishiura, M.; Tsumori, K.; Matsumoto, Y.; Kenmotsu, T.; Okamoto, A.; Kitajima, S.; Sasao, M.; Yamaoka, H.

    2014-02-15

    Angle-resolved energy distribution functions of positive and negative hydrogen ions produced from a rough-finished Si surface under 1 keV proton irradiation have been measured. The corresponding distribution from a crystalline surface and a carbon surface are also measured for comparison. Intensities of positive and negative ions from the rough-finished Si are substantially smaller than those from crystalline Si. The angular distributions of these species are broader for rough surface than the crystalline surface. No significant temperature dependence for positive and negative ion intensities is observed for all samples in the temperature range from 300 to 400 K.

  5. Chaos, noise, and tails on the I-V curve steps of rf-driven Josephson junctions

    NASA Astrophysics Data System (ADS)

    Cronemeyer, D. C.; Chi, C. C.; Davidson, A.; Pedersen, N. F.

    1985-03-01

    We report the first experiments and digital and analog simulations which demonstrate the existence of chaotic regions in the I-V curves of dc- and rf-current-biased Josephson junctions. These junctions were formed of crossed Pb strips and were shunted with Au resistors. Chaos appears as negatively going tails on the trailing edges of the rf-induced steps; these tails, which may be as large as 50% of the voltage step width, have not previously been reported. The parameters for the occurrence of these tails center at βc=4, Ω=ω/ωp=0.15, irf=Irf/Ic=1.04, Ic=3×105 A/m2 at 4.2 K. The thermal noise of the shunting resistor was emulated by a Gaussian spectrum. The presence of such noise dramatically alters the substeps, spikes, and bifurcations predicted for zero temperature. With only small amounts of noise, such complexities disappear, and are replaced by a smooth tail on the step accompanied by broadband noise. There is good agreement between the experiments on a real junction, simulations with a phase-locked loop, and numerical calculations with a digital computer.

  6. Design of long pulse/steady state negative hydrogen ion sources for fusion applications

    SciTech Connect

    Prelec, K.

    1980-01-01

    By using parameters of ion sources when operating in a pulsed mode and without cooling (pulse length < 0.1 s), requirements have been determined for a long pulse (several seconds) or steady state operating mode and two sources have been designed and fabricated. First of the two is a penning source, designed for a steady state operation with a cathode power density of 1 kW/cm/sup 2/. For the range of cathode power densities between 0.2 kW/cm/sup 2/ and 1 Kw/cm/sup 2/, nucleated boiling has to be used for heat removal; below 0.2 kW/cm/sup 2/ water flow cooling suffices. Although this source should deliver 0.3 to 0.5 A of H/sup -/ ions in a steady state operation and at full power, the other source, which has a magnetron geometry, is more promising. The latter incorporates two new features compared to first designs, geometrical focusing of fast, primary negative hydrogen ions from the cathode into the extraction slit, and a wider discharge gap in the back of the source. These two changes have resulted in an improvement of the power and gas efficiencies by a factor of 3 to 4 and in a reduction of the cathode power density by an order of magnitude. The source has water cooling for all the electrodes, because maximum power densities will not be higher than 0.2 kW/cm/sup 2/. Very recently a modification of this magnetron source is being considered; it consists of plasma injection into the source from a hollow cathode discharge.

  7. Spatial and temporal evolution of negative ions in a pulsed inductively coupled hydrogen plasma source across a magnetic filter

    NASA Astrophysics Data System (ADS)

    Nulty, Stuart; Corr, Cormac

    2015-09-01

    Low-temperature electronegative plasmas have important applications in high-energy sources for fusion energy, plasma thrusters and materials processing. Neutral beam injection systems and space thruster technology such as the PEGASUS propulsion system rely on efficiently producing extractable negative ions. In this work we investigate the production of hydrogen negative ions in a pulsed inductively coupled plasma across a magnetic filter. The electron energy distribution function, plasma density and electron temperature are determined using an RF compensated Langmuir probe, and time-resolved laser photo-detachment is used to measure the negative ion fraction. The spatial and temporal evolution of these plasma parameters within the plasma source will be presented. Using a pulsed plasma and a magnetic filter, the electron temperature can be efficiently controlled and a higher density of negative ions compared to electrons can be obtained at certain locations within the source.

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

    SciTech Connect

    Ueno, A. Ohkoshi, K.; Ikegami, K.; Takagi, A.; Yamazaki, S.; Oguri, H.

    2015-04-08

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

  9. Hydrogen negative-ion surface production on diamond materials in low-pressure H2 plasmas

    NASA Astrophysics Data System (ADS)

    Cartry, Gilles; Achkasov, Kostiantyn; Pardanaud, Cédric; Layet, Jean-Marc; Simonin, Alain; Gicquel, Alix; PIIM Collaboration; IRFM Collaboration; LSPM Collaboration

    2014-10-01

    Negative-ion sources producing H-current density of ~200 A/m2 are required for the heating of the fusion plasma of the international project ITER. The only up-to-date solution to reach such a high H-negative-ion current is the use of cesium (Cs). Deposition of Cs on the negative-ion source walls lowers the material work function and allows for high electron-capture efficiency by incident particles and thus, high negative ion yields. However, severe drawbacks to the use of Cs have been identified and its elimination from the fusion negative-ion sources would be highly valuable. Volume production is not efficient enough at low-pressure to reach the high current required. Therefore, we are working on alternative solutions to produce high yield of H-negative-ions on surfaces in Cs-free H2 plasmas. In this communication, we will detail the methodology employed to study negative-ion surface production. In particular we will describe how the negative-ions are extracted from the plasma, and how we can obtain information on surface production mechanisms from the measurement of the H-energy distribution functions. We will present some results obtained on diamond surfaces and show that diamond is a promising candidate as a negative-ion enhancer material in low-pressure H2 plasmas. EFDA, FR-FCM, ANR, PACA are acknowledged for their support.

  10. Partially hydrogenated and fluorinated graphene: Structure, roughness, and negative thermal expansion

    NASA Astrophysics Data System (ADS)

    Neek-Amal, M.; Peeters, F. M.

    2015-10-01

    The structural properties of partially hydrogenated and fluorinated graphene with different percentages of H/F atoms are investigated using molecular dynamics simulations based on reactive force field (ReaxFF) potentials. We found that the roughness of graphene varies with the percentage (p ) of H or F and in both cases is maximal around p =50 % . Similar results were obtained for partially oxidized graphene. The two-dimensional area size of partially fluorinated and hydrogenated graphene exhibits a local minimum around p =35 % coverage. The lattice thermal contraction in partially functionalized graphene is found to be one order of magnitude larger than that of fully covered graphene. We also show that the armchair structure for graphene oxide (similar to the structure of fully hydrogenated and fluorinated graphene) is unstable. Our results show that the structure of partially functionalized graphene changes nontrivially with the C : H and C : F ratio as well as with temperature.

  11. An unexpected negative influence of light intensity on hydrogen production by dark fermentative bacteria Clostridium beijerinckii.

    PubMed

    Zagrodnik, R; Laniecki, M

    2016-01-01

    The role of light intensity on biohydrogen production from glucose by Clostridium beijerinckii, Clostridium acetobutylicum, and Rhodobacter sphaeroides was studied to evaluate the performance and possible application in co-culture fermentation system. The applied source of light had spectrum similar to the solar radiation. The influence of light intensity on hydrogen production in dark process by C. acetobutylicum was negligible. In contrast, dark fermentation by C. beijerinckii bacteria showed a significant decrease (83%) in produced hydrogen at light intensity of 540W/m(2). Here, the redirection of metabolism from acetic and butyric acid formation towards lactic acid was observed. This not yet reported effect was probably caused by irradiation of these bacteria by light within UVA range, which is an important component of the solar radiation. The excessive illumination with light of intensity higher than 200W/m(2) resulted in decrease in hydrogen production with photofermentative bacteria as well. PMID:26602144

  12. Capacitively Coupled Radio Frequency Discharge Plasmas In Hydrogen: Particle Modeling and Negative Ion Kinetics

    SciTech Connect

    Diomede, P.; Longo, S.; Capitelli, M.

    2005-05-16

    We present a 1D(r)2D(v) particle code for capacitively coupled radio frequency discharge plasmas in hydrogen, which includes a rigorous kinetic modeling of ion transport and several solutions to speed up the convergence. In a test case the effect of surface atom recombination and molecule vibrational deactivation on H- concentration is investigated.

  13. Hydrogen Peroxide Linked to Lysine Oxidase Activity Facilitates Biofilm Differentiation and Dispersal in Several Gram-Negative Bacteria▿

    PubMed Central

    Mai-Prochnow, Anne; Lucas-Elio, Patricia; Egan, Suhelen; Thomas, Torsten; Webb, Jeremy S.; Sanchez-Amat, Antonio; Kjelleberg, Staffan

    2008-01-01

    The marine bacterium Pseudoalteromonas tunicata produces an antibacterial and autolytic protein, AlpP, which causes death of a subpopulation of cells during biofilm formation and mediates differentiation, dispersal, and phenotypic variation among dispersal cells. The AlpP homologue (LodA) in the marine bacterium Marinomonas mediterranea was recently identified as a lysine oxidase which mediates cell death through the production of hydrogen peroxide. Here we show that AlpP in P. tunicata also acts as a lysine oxidase and that the hydrogen peroxide generated is responsible for cell death within microcolonies during biofilm development in both M. mediterranea and P. tunicata. LodA-mediated biofilm cell death is shown to be linked to the generation of phenotypic variation in growth and biofilm formation among M. mediterranea biofilm dispersal cells. Moreover, AlpP homologues also occur in several other gram-negative bacteria from diverse environments. Our results show that subpopulations of cells in microcolonies also die during biofilm formation in two of these organisms, Chromobacterium violaceum and Caulobacter crescentus. In all organisms, hydrogen peroxide was implicated in biofilm cell death, because it could be detected at the same time as the killing occurred, and the addition of catalase significantly reduced biofilm killing. In C. violaceum the AlpP-homologue was clearly linked to biofilm cell death events since an isogenic mutant (CVMUR1) does not undergo biofilm cell death. We propose that biofilm killing through hydrogen peroxide can be linked to AlpP homologue activity and plays an important role in dispersal and colonization across a range of gram-negative bacteria. PMID:18502869

  14. Study of negative hydrogen ion beam optics using the 3D3V PIC model

    NASA Astrophysics Data System (ADS)

    Miyamoto, K.; Nishioka, S.; Goto, I.; Hatayama, A.; Hanada, M.; Kojima, A.

    2015-04-01

    The mechanism of negative ion extraction under real conditions with the complex magnetic field is studied by using the 3D PIC simulation code. The extraction region of the negative ion source for the negative ion based neutral beam injection system in fusion reactors is modelled. It is shown that the E x B drift of electrons is caused by the magnetic filter and the electron suppression magnetic field, and the resultant asymmetry of the plasma meniscus. Furthermore, it is indicated that that the asymmetry of the plasma meniscus results in the asymmetry of negative ion beam profile including the beam halo. It could be demonstrated theoretically that the E x B drift is not significantly weakened by the elastic collisions of the electrons with neutral particles.

  15. Study of negative hydrogen ion beam optics using the 3D3V PIC model

    SciTech Connect

    Miyamoto, K.; Nishioka, S.; Goto, I.; Hatayama, A.; Hanada, M.; Kojima, A.

    2015-04-08

    The mechanism of negative ion extraction under real conditions with the complex magnetic field is studied by using the 3D PIC simulation code. The extraction region of the negative ion source for the negative ion based neutral beam injection system in fusion reactors is modelled. It is shown that the E x B drift of electrons is caused by the magnetic filter and the electron suppression magnetic field, and the resultant asymmetry of the plasma meniscus. Furthermore, it is indicated that that the asymmetry of the plasma meniscus results in the asymmetry of negative ion beam profile including the beam halo. It could be demonstrated theoretically that the E x B drift is not significantly weakened by the elastic collisions of the electrons with neutral particles.

  16. Hydrogen Bonding and Binding of Polybasic Residues with Negatively Charged Mixed Lipid Monolayers

    SciTech Connect

    Lorenz, C.; Feraudo, J.; Travesset, A.

    2008-01-23

    Phosphoinositides, phosphorylated products of phosphatidylinositol, are a family of phospholipids present in tiny amounts (1% or less) in the cytosolic surface of cell membranes, yet they play an astonishingly rich regulatory role, particularly in signaling processes. In this letter, we use molecular dynamics simulations on a model system of mixed lipid monolayers to investigate the interaction of phosphatidylinositol 4,5-bisphosphate (PIP{sub 2}), the most common of the phosphoinositides, with a polybasic peptide consisting of 13 lysines. Our results show that the polybasic peptide sequesters three PIP{sub 2} molecules, forming a complex stabilized by the formation of multiple hydrogen bonds between PIP{sub 2} and the Lys residues. We also show that the polybasic peptide does not sequester other charged phospholipids such as phosphatidylserine because of the inability to form long-lived stable hydrogen bonds.

  17. Tests on the extracted current density of negative hydrogen ions from a single element of the matrix source

    SciTech Connect

    Lishev, St.; Yordanov, D. Shivarova, A.

    2015-04-08

    Concepts for the extraction of volume-produced negative hydrogen ions from a rf matrix source (a matrix of small-radius discharges with a planar-coil inductive driving) are presented and discussed based on experimental results for the current densities of the extracted ions and the co-extracted electrons. The experiment has been carried out in a single discharge of the source: a rf discharge with a radius of 2.25 cm inductively driven by a 3.5-turn planar coil. The length of the discharge tube, the area of the reference electrode inserted in the discharge volume, the discharge modes, the magnetic filter and its position along the discharge length, the position of the permanent magnets for the separation of the co-extracted electrons from the extracted ions in the extraction device and the bias applied to its first electrode are considered as factors influencing the extracted currents of negative ions.

  18. VUV Absorption Spectroscopy of a Penning Surface - Negative Hydrogen Ion Source

    NASA Astrophysics Data System (ADS)

    Pitcher, Eric John

    The demand for energetic, high-current H ^- beams is ever-growing. Because H ^- is efficiently neutralized at high energies, these beams are ideally suited to applications where energetic neutral beams of particles are required to propagate across magnetic fields. Prime examples are neutral-beam heating of magnetic fusion plasmas and directed-energy weapons for ballistic missile defense. Such applications place demanding requirements on sources of H^ - ions, particularly with respect to the parameters of beam current, brightness, quiescence, reliability, and duty-factor. A class of sources that holds great promise for meeting these stringent requirements is the surface-plasma source (SPS), and in particular, the Penning type of SPS. It has long been conjectured that atomic hydrogen plays an important role in both H^- formation and transport in these sources. Understanding the interdependence of atomic hydrogen properties and those of H^ -, and how this relationship might be exploited to improve source performance is the motivation for this research. An overview of SPS's is presented. Previous measurements on the discharge are reviewed. Absorption spectroscopy, the diagnostic technique used to gather all of the data presented here, is discussed. Techniques that may potentially be used to measure the properties of H^ - in the discharge are discussed. The two absorption spectrometers used in this experiment are described. Measurements of ground-state atomic hydrogen density and temperature in a Penning SPS are presented. These measurements are the first of this kind for this type of discharge. An upper limit on the H^- density in the extraction region of the source is measured by the application of a novel diagnostic technique: the hydrogen atom density following H^- photodetachment by a Nd:YAG beam is measured and compared to the equilibrium atomic density. A simple model is derived that describes the dependence of the atomic temperature on the externally

  19. Volume generation of negative ions in high density hydrogen discharges. Revision 1

    SciTech Connect

    Hiskes, J.R.; Karo, A.M.

    1983-11-11

    An optimized tandem two-chamber negative-ion source system is discussed. In the first chamber high energy (E > 20 eV) electron collisions provide for H/sub 2/ vibrational excitation, while in the second chamber negative ions are formed by dissociative attachment. The gas density, electron density, and system scale length are varied as independent parameters. The extracted negative ion current density passes through a maximum as electron and gas densities are varied. This maximum scales inversely with system scale length, R. The optimum extracted current densities occur for electron densities near nR = 10/sup 13/ electrons cm/sup -2/ and for gas densities, N/sub 2/R, in the range 10/sup 14/ to 10/sup 15/ molecules cm/sup -2/. The extracted current densities are sensitive to the atomic concentration in the discharge. The atomic concentration is parametrized by the wall recombination coefficient, ..gamma.., and scale length, R. As ..gamma.. ranges from 0.1 to 1.0 and for system scale lengths of one centimeter, extracted current densities range from 8.0 to 80. mA cm/sup -2/.

  20. Characteristics of Hydrogen Negative Ion Source with FET based RF System

    SciTech Connect

    Ando, A.; Matsuno, T.; Funaoi, T.; Tanaka, N.; Tsumori, K.; Takeiri, Y.

    2011-09-26

    Characteristics of radio frequency (RF) plasma production were investigated using a FET inverter power supply as a RF generator. High density hydrogen plasma was obtained using an external coil wound a cylindrical ceramic tube (driver region) with RF frequency of lower than 0.5 MHz. When an axial magnetic field around 10 mT was applied to the driver region, an electron density increased drastically and attained to over 10{sup 19} m{sup -3} in the driver region. Effect of the axial magnetic field in driver and expansion region was examined. Lower gas pressure operation below 0.5 Pa was possible with higher RF frequency. H{sup -} density in the expansion region was measured by using laser photo-detachment system. It decreased as the axial magnetic field applied, which was caused by the increase of energetic electron from the driver.

  1. Analysis of Discharge Initiation in a RF Hydrogen Negative Ion Source

    SciTech Connect

    Hayami, T.; Yoshinari, S.; Terasaki, R.; Hatayama, A.; Fukano, A.

    2011-09-26

    The maintenance free RF ion source is expected to be one of the most promising candidates for the negative ion sources of plasma heating for fusion reactors. In order to make clear the condition for the discharge initiation of the RF source, we are developing an electromagnetic PIC model. The numerical result shows that a positive potential built-up with respect to the wall. As a result, the electron wall loss decreases and the electron density increases. The positive potential plays a key role for the suppression of wall loss and the electron confinement. The electromagnetic-PIC model developed is useful for the analysis of discharge initiation of the RF source.

  2. Mesic molecular effects in the capture of negative pions stopped in gaseous hydrogen isotopes

    NASA Astrophysics Data System (ADS)

    Aniol, K. A.; Measday, D. F.; Hasinoff, M. D.; Roser, H. W.; Bagheri, A.; Entezami, F.; Virtue, C.; Stadlbauer, J. M.; Horváth, D.; Salomon, M.; Robertson, B. C.

    1983-11-01

    The influence of molecular structure on the nuclear capture probability of stopped negative pions has been observed by comparing the π0 gamma-ray spectrum from π- mesons stopped in HD gas to that from a mixture of equal amounts of H2 plus D2. The fraction of stopped pions that are captured by a proton in the H2+D2 mixture is fH2D2=0.417+/-0.004, while for HD it is fHD=0.338+/-0.008, independent of the gas pressure between 6 and 90 atm. The ratio, fH2D2fHD, of the fractions is 1.23+/-0.03.

  3. Transport properties of bare and hydrogenated zigzag silicene nanoribbons: Negative differential resistances and perfect spin-filtering effects

    SciTech Connect

    Yang, X. F.; Liu, Y. S. Feng, J. F.; Wang, X. F.; Zhang, C. W.; Chi, F.

    2014-09-28

    Ab initio calculations are performed to investigate the spin-polarized transport properties of the bare and hydrogenated zigzag silicene nanoribbons (ZSiNRs). The results show that the ZSiNRs with symmetric (asymmetric) edges prefer the ferromagnetic (antiferromagnetic) as their ground states with the semiconductor properties, while the accordingly antiferromagnetic (ferromagnetic) states exhibit the metallic behaviors. These facts result in a giant magnetoresistance behavior between the ferromagnetic and antiferromagnetic states in the low bias-voltage regime. Moreover, in the ferromagnetic ZSiNRs with asymmetric edges, a perfect spin-filtering effect with 100% positive electric current polarization can be achieved by altering the bias voltage. In addition, we also find that the negative differential resistances prefer the metastable states. The findings here indicate that the asymmetric and symmetric ZSiNRs are promising materials for spintronic applications.

  4. Measurements of Lyman Alpha Radiation from Collisions, 100 EV to 4000EV, of Negative Hydrogen Ions on Various Target Gases and Positive Hydrogen Ions on Xenon

    NASA Astrophysics Data System (ADS)

    Greenland, Glenn Blair

    This study reports measurements of cross sections for the production of Lyman alpha radiation from processes in which an ion is incident on a neutral target gas. Two kinds of processes were measured: the stripping of the extra electron from a negative hydro- gen ion leaving an excited neutral and the capture of an electron by a proton also leaving an excited neutral. In each case, radiation from the 2p state of the neutral hydrogen was detected. The projectile struck the static gas target with a kinetic energy between 100 and 4000 electron volts. The measurements used the ultraviolet absorption properties of molecular oxygen to isolate the Lyman alpha line. Cross sections for emission of Lyman alpha perpendicular to the incident beam were determined. The targets used in the stripping experiments were the atomic gases: helium, neon, argon, krypton and xenon, and the molecular gases: hydrogen, nitrogen and methane. The cross sections are rela- tively flat over the energy range investigated. All are slightly below 10('-16) cm('2) at 1000 eV. Only with the neon target does the cross section fall below 2 x 10('0-17) cm('2) at 100 electron volts. While the data appear to support the modeling of stripping with excitation as a two step process, this modeling may not be valid for excitation above 2p. Only a xenon target was used in the capture experiments. Careful measurements did not substantiate an earlier report of unusual structure('1) in this cross section. ('1)P. J. Martin, Ph.D. Dissertation, Univ. of Nebraska, 1975.

  5. Aharonov-Bohm Effect in the Photodetachment Microscopy of Hydrogen Negative Ions in an Electric Field

    NASA Astrophysics Data System (ADS)

    Wang, Dehua

    2014-09-01

    The Aharonov-Bohm (AB) effect in the photodetachment microscopy of the H- ions in an electric field has been studied on the basis of the semiclassical theory. After the H- ion is irradiated by a laser light, they provide a coherent electron source. When the detached electron is accelerated by a uniform electric field, two trajectories of a detached electron which run from the source to the same point on the detector, will interfere with each other and lead to an interference pattern in the photodetachment microscopy. After the solenoid is electrified beside the H- ion, even though no Lorentz force acts on the electron outside the solenoid, the photodetachment microscopy interference pattern on the detector is changed with the variation in the magnetic flux enclosed by the solenoid. This is caused by the AB effect. Under certain conditions, the interference pattern reaches the macroscopic dimensions and could be observed in a direct AB effect experiment. Our study can provide some predictions for the future experimental study of the AB effect in the photodetachment microscopy of negative ions.

  6. Development of a Negative Hydrogen Ion Source for Spatial Beam Profile Measurement of a High Intensity Positive Ion Beam

    SciTech Connect

    Shinto, Katsuhiro; Wada, Motoi; Nishida, Tomoaki; Demura, Yasuhiro; Sasaki, Daichi; Tsumori, Katsuyoshi; Nishiura, Masaki; Kaneko, Osamu; Kisaki, Masashi; Sasao, Mamiko

    2011-09-26

    We have been developing a negative hydrogen ion (H{sup -} ion) source for a spatial beam profile monitor of a high intensity positive ion beam as a new diagnostic tool. In case of a high intensity continuous-wave (CW) deuteron (D{sup +}) beam for the International Fusion Materials Irradiation Facility (IFMIF), it is difficult to measure the beam qualities in the severe high radiation environment during about one-year cyclic operation period. Conventional techniques are next to unusable for diagnostics in the operation period of about eleven months and for maintenance in the one-month shutdown period. Therefore, we have proposed an active beam probe system by using a negative ion beam and started an experimental study for the proof-of-principle (PoP) of the new spatial beam profile monitoring tool. In this paper, we present the status of development of the H{sup -} ion source as a probe beam source for the PoP experiment.

  7. Global model analysis of negative ion generation in low-pressure inductively coupled hydrogen plasmas with bi-Maxwellian electron energy distributions

    SciTech Connect

    Huh, Sung-Ryul; Kim, Nam-Kyun; Jung, Bong-Ki; Chung, Kyoung-Jae; Hwang, Yong-Seok; Kim, Gon-Ho

    2015-03-15

    A global model was developed to investigate the densities of negative ions and the other species in a low-pressure inductively coupled hydrogen plasma with a bi-Maxwellian electron energy distribution. Compared to a Maxwellian plasma, bi-Maxwellian plasmas have higher populations of low-energy electrons and highly vibrationally excited hydrogen molecules that are generated efficiently by high-energy electrons. This leads to a higher reaction rate of the dissociative electron attachment responsible for negative ion production. The model indicated that the bi-Maxwellian electron energy distribution at low pressures is favorable for the creation of negative ions. In addition, the electron temperature, electron density, and negative ion density calculated using the model were compared with the experimental data. In the low-pressure regime, the model results of the bi-Maxwellian electron energy distributions agreed well quantitatively with the experimental measurements, unlike those of the assumed Maxwellian electron energy distributions that had discrepancies.

  8. Optimization of plasma parameters with magnetic filter field and pressure to maximize H- ion density in a negative hydrogen ion source

    NASA Astrophysics Data System (ADS)

    Cho, Won-Hwi; Dang, Jeong-Jeung; Kim, June Young; Chung, Kyoung-Jae; Hwang, Y. S.

    2016-02-01

    Transverse magnetic filter field as well as operating pressure is considered to be an important control knob to enhance negative hydrogen ion production via plasma parameter optimization in volume-produced negative hydrogen ion sources. Stronger filter field to reduce electron temperature sufficiently in the extraction region is favorable, but generally known to be limited by electron density drop near the extraction region. In this study, unexpected electron density increase instead of density drop is observed in front of the extraction region when the applied transverse filter field increases monotonically toward the extraction aperture. Measurements of plasma parameters with a movable Langmuir probe indicate that the increased electron density may be caused by low energy electron accumulation in the filter region decreasing perpendicular diffusion coefficients across the increasing filter field. Negative hydrogen ion populations are estimated from the measured profiles of electron temperatures and densities and confirmed to be consistent with laser photo-detachment measurements of the H- populations for various filter field strengths and pressures. Enhanced H- population near the extraction region due to the increased low energy electrons in the filter region may be utilized to increase negative hydrogen beam currents by moving the extraction position accordingly. This new finding can be used to design efficient H- sources with an optimal filtering system by maximizing high energy electron filtering while keeping low energy electrons available in the extraction region.

  9. Optimization of plasma parameters with magnetic filter field and pressure to maximize H⁻ ion density in a negative hydrogen ion source.

    PubMed

    Cho, Won-Hwi; Dang, Jeong-Jeung; Kim, June Young; Chung, Kyoung-Jae; Hwang, Y S

    2016-02-01

    Transverse magnetic filter field as well as operating pressure is considered to be an important control knob to enhance negative hydrogen ion production via plasma parameter optimization in volume-produced negative hydrogen ion sources. Stronger filter field to reduce electron temperature sufficiently in the extraction region is favorable, but generally known to be limited by electron density drop near the extraction region. In this study, unexpected electron density increase instead of density drop is observed in front of the extraction region when the applied transverse filter field increases monotonically toward the extraction aperture. Measurements of plasma parameters with a movable Langmuir probe indicate that the increased electron density may be caused by low energy electron accumulation in the filter region decreasing perpendicular diffusion coefficients across the increasing filter field. Negative hydrogen ion populations are estimated from the measured profiles of electron temperatures and densities and confirmed to be consistent with laser photo-detachment measurements of the H(-) populations for various filter field strengths and pressures. Enhanced H(-) population near the extraction region due to the increased low energy electrons in the filter region may be utilized to increase negative hydrogen beam currents by moving the extraction position accordingly. This new finding can be used to design efficient H(-) sources with an optimal filtering system by maximizing high energy electron filtering while keeping low energy electrons available in the extraction region. PMID:26932018

  10. Negative-ion surface production in hydrogen plasmas: Determination of the negative-ion energy and angle distribution function using mass spectrometry

    NASA Astrophysics Data System (ADS)

    Dubois, J. P. J.; Achkasov, K.; Kogut, D.; Ahmad, A.; Layet, J. M.; Simonin, A.; Cartry, G.

    2016-05-01

    This work focuses on the understanding of the production mechanism of negative-ions on surface in low pressure plasmas of H2/D2. The negative ions are produced on a Highly Oriented Pyrolytic Graphite sample negatively biased with respect to plasma potential. The negative ions created under the positive ion bombardment are accelerated towards the plasma, self-extracted, and detected according to their energy and mass by a mass spectrometer placed in front of the sample. The shape of the measured Negative-Ion Energy Distribution Function (NIEDF) strongly differs from the NIEDF of the ions emitted by the sample because of the limited acceptance angle of the mass spectrometer. To get information on the production mechanisms, we propose a method to obtain the distribution functions in energy and angle (NIEADFs) of the negative-ions emitted by the sample. It is based on an a priori determination of the NIEADF and on an a posteriori validation of the choice by comparison of the modelled and experimental NIEDFs.

  11. Endothelial nitric oxide synthase negatively regulates hydrogen peroxide-stimulated AMP-activated protein kinase in endothelial cells

    PubMed Central

    Jin, Benjamin Y.; Sartoretto, Juliano L.; Gladyshev, Vadim N.; Michel, Thomas

    2009-01-01

    Hydrogen peroxide and other reactive oxygen species are intimately involved in endothelial cell signaling. In many cell types, the AMP-activated protein kinase (AMPK) has been implicated in the control of metabolic responses, but the role of endothelial cell redox signaling in the modulation of AMPK remains to be completely defined. We used RNA interference and pharmacological methods to establish that H2O2 is a critical activator of AMPK in cultured bovine aortic endothelial cells (BAECs). H2O2 treatment of BAECs rapidly and significantly increases the phosphorylation of AMPK. The EC50 for H2O2-promoted phosphorylation of AMPK is 65 ± 15 μM, within the physiological range of cellular H2O2 concentrations. The Ca2+/calmodulin-dependent protein kinase kinase-β (CaMKKβ) inhibitor STO-609 abolishes H2O2-dependent AMPK activation, whereas eNOS inhibitors enhance AMPK activation. Similarly, siRNA-mediated knockdown of CaMKKβ abrogates AMPK activation, whereas siRNA-mediated knockdown of eNOS leads to a striking increase in AMPK phosphorylation. Cellular imaging studies using the H2O2 biosensor HyPer show that siRNA-mediated eNOS knockdown leads to a marked increase in intracellular H2O2 generation, which is blocked by PEG-catalase. eNOS−/− mice show a marked increase in AMPK phosphorylation in liver and lung compared to wild-type mice. Lung endothelial cells from eNOS−/− mice also show a significant increase in AMPK phosphorylation. Taken together, these results establish that CaMKKβ is critically involved in mediating the phosphorylation of AMPK promoted by H2O2 in endothelial cells, and document that eNOS is an important negative regulator of AMPK phosphorylation and intracellular H2O2 generation in endothelial cells. PMID:19805165

  12. Endothelial nitric oxide synthase negatively regulates hydrogen peroxide-stimulated AMP-activated protein kinase in endothelial cells.

    PubMed

    Jin, Benjamin Y; Sartoretto, Juliano L; Gladyshev, Vadim N; Michel, Thomas

    2009-10-13

    Hydrogen peroxide and other reactive oxygen species are intimately involved in endothelial cell signaling. In many cell types, the AMP-activated protein kinase (AMPK) has been implicated in the control of metabolic responses, but the role of endothelial cell redox signaling in the modulation of AMPK remains to be completely defined. We used RNA interference and pharmacological methods to establish that H(2)O(2) is a critical activator of AMPK in cultured bovine aortic endothelial cells (BAECs). H(2)O(2) treatment of BAECs rapidly and significantly increases the phosphorylation of AMPK. The EC(50) for H(2)O(2)-promoted phosphorylation of AMPK is 65 + or - 15 microM, within the physiological range of cellular H(2)O(2) concentrations. The Ca(2+)/calmodulin-dependent protein kinase kinase-beta (CaMKKbeta) inhibitor STO-609 abolishes H(2)O(2)-dependent AMPK activation, whereas eNOS inhibitors enhance AMPK activation. Similarly, siRNA-mediated knockdown of CaMKKbeta abrogates AMPK activation, whereas siRNA-mediated knockdown of eNOS leads to a striking increase in AMPK phosphorylation. Cellular imaging studies using the H(2)O(2) biosensor HyPer show that siRNA-mediated eNOS knockdown leads to a marked increase in intracellular H(2)O(2) generation, which is blocked by PEG-catalase. eNOS(-/-) mice show a marked increase in AMPK phosphorylation in liver and lung compared to wild-type mice. Lung endothelial cells from eNOS(-/-) mice also show a significant increase in AMPK phosphorylation. Taken together, these results establish that CaMKKbeta is critically involved in mediating the phosphorylation of AMPK promoted by H(2)O(2) in endothelial cells, and document that eNOS is an important negative regulator of AMPK phosphorylation and intracellular H(2)O(2) generation in endothelial cells. PMID:19805165

  13. Angle-resolved intensity and energy distributions of positive and negative hydrogen ions released from tungsten surface by molecular hydrogen ion impact

    NASA Astrophysics Data System (ADS)

    Kato, S.; Tanaka, N.; Sasao, M.; Kisaki, M.; Tsumori, K.; Nishiura, M.; Matsumoto, Y.; Kenmotsu, T.; Wada, M.; Yamaoka, H.

    2015-08-01

    Hydrogen ion reflection properties have been investigated following the injection of H+, H2+ and H3+ ions onto a polycrystalline W surface. Angle- and energy-resolved intensity distributions of both scattered H+ and H- ions are measured by a magnetic momentum analyzer. We have detected atomic hydrogen ions reflected from the surface, while molecular hydrogen ions are unobserved within our detection limit. The reflected hydrogen ion energy is approximately less than one-third of the incident beam energy for H3+ ion injection and less than a half of that for H2+ ion injection. Other reflection properties are very similar to those of monoatomic H+ ion injection. Experimental results are compared to the classical trajectory simulations using the ACAT code based on the binary collision approximation.

  14. Negative ion source development for fusion application (invited).

    PubMed

    Takeiri, Yasuhiko

    2010-02-01

    Giant negative ion sources, producing high-current of several tens amps with high energy of several hundreds keV to 1 MeV, are required for a neutral beam injector (NBI) in a fusion device. The giant negative ion sources are cesium-seeded plasma sources, in which the negative ions are produced on the cesium-covered surface. Their characteristic features are discussed with the views of large-volume plasma production, large-area beam acceleration, and high-voltage dc holding. The international thermonuclear experimental reactor NBI employs a 1 MeV-40 A of deuterium negative ion source, and intensive development programs for the rf-driven source plasma production and the multistage electrostatic acceleration are in progress, including the long pulse operation for 3600 s. Present status of the development, as well as the achievements of the giant negative ion sources in the working injectors, is also summarized. PMID:20192420

  15. Negative ion source development for fusion application (invited)

    SciTech Connect

    Takeiri, Yasuhiko

    2010-02-15

    Giant negative ion sources, producing high-current of several tens amps with high energy of several hundreds keV to 1 MeV, are required for a neutral beam injector (NBI) in a fusion device. The giant negative ion sources are cesium-seeded plasma sources, in which the negative ions are produced on the cesium-covered surface. Their characteristic features are discussed with the views of large-volume plasma production, large-area beam acceleration, and high-voltage dc holding. The international thermonuclear experimental reactor NBI employs a 1 MeV-40 A of deuterium negative ion source, and intensive development programs for the rf-driven source plasma production and the multistage electrostatic acceleration are in progress, including the long pulse operation for 3600 s. Present status of the development, as well as the achievements of the giant negative ion sources in the working injectors, is also summarized.

  16. Recombination and dissociative recombination of H/sub 2//sup +/ and H/sub 3//sup +/ ions on surfaces with application to hydrogen negative ion sources

    SciTech Connect

    Hiskes, J.R.; Karo, A.M.

    1988-12-01

    A four-step model for recombination and dissociative recombination of H/sub 2//sup +/ and H/sub 3//sup +/ ions on metal surfaces is discussed. Vibrationally excited molecules, H/sub 2/(v''), from H/sub 3//sup +/ recombination are produced in a broad spectrum that enhances the excited level distribution. The application of this latter process to hydrogen negative ion discharges is discussed. 5 refs., 3 figs., 1 tab.

  17. Femtosecond Hydrogen Bond Dynamics of Bulk-like and Bound Water at Positively and Negatively Charged Lipid Interfaces Revealed by 2D HD-VSFG Spectroscopy.

    PubMed

    Singh, Prashant Chandra; Inoue, Ken-Ichi; Nihonyanagi, Satoshi; Yamaguchi, Shoichi; Tahara, Tahei

    2016-08-26

    Interfacial water in the vicinity of lipids plays an important role in many biological processes, such as drug delivery, ion transportation, and lipid fusion. Hence, molecular-level elucidation of the properties of water at lipid interfaces is of the utmost importance. We report the two-dimensional heterodyne-detected vibrational sum frequency generation (2D HD-VSFG) study of the OH stretch of HOD at charged lipid interfaces, which shows that the hydrogen bond dynamics of interfacial water differ drastically, depending on the lipids. The data indicate that the spectral diffusion of the OH stretch at a positively charged lipid interface is dominated by the ultrafast (<∼100 fs) component, followed by the minor sub-picosecond slow dynamics, while the dynamics at a negatively charged lipid interface exhibit sub-picosecond dynamics almost exclusively, implying that fast hydrogen bond fluctuation is prohibited. These results reveal that the ultrafast hydrogen bond dynamics at the positively charged lipid-water interface are attributable to the bulk-like property of interfacial water, whereas the slow dynamics at the negatively charged lipid interface are due to bound water, which is hydrogen-bonded to the hydrophilic head group. PMID:27482947

  18. On the meniscus formation and the negative hydrogen ion extraction from ITER neutral beam injection relevant ion source

    NASA Astrophysics Data System (ADS)

    Mochalskyy, S.; Wünderlich, D.; Ruf, B.; Fantz, U.; Franzen, P.; Minea, T.

    2014-10-01

    The development of a large area (Asource,ITER = 0.9 × 2 m2) hydrogen negative ion (NI) source constitutes a crucial step in construction of the neutral beam injectors of the international fusion reactor ITER. To understand the plasma behaviour in the boundary layer close to the extraction system the 3D PIC MCC code ONIX is exploited. Direct cross checked analysis of the simulation and experimental results from the ITER-relevant BATMAN source testbed with a smaller area (Asource,BATMAN ≈ 0.32 × 0.59 m2) has been conducted for a low perveance beam, but for a full set of plasma parameters available. ONIX has been partially benchmarked by comparison to the results obtained using the commercial particle tracing code for positive ion extraction KOBRA3D. Very good agreement has been found in terms of meniscus position and its shape for simulations of different plasma densities. The influence of the initial plasma composition on the final meniscus structure was then investigated for NIs. As expected from the Child-Langmuir law, the results show that not only does the extraction potential play a crucial role on the meniscus formation, but also the initial plasma density and its electronegativity. For the given parameters, the calculated meniscus locates a few mm downstream of the plasma grid aperture provoking a direct NI extraction. Most of the surface produced NIs do not reach the plasma bulk, but move directly towards the extraction grid guided by the extraction field. Even for artificially increased electronegativity of the bulk plasma the extracted NI current from this region is low. This observation indicates a high relevance of the direct NI extraction. These calculations show that the extracted NI current from the bulk region is low even if a complete ion-ion plasma is assumed, meaning that direct extraction from surface produced ions should be present in order to obtain sufficiently high extracted NI current density. The calculated extracted currents, both ions

  19. Negative ion-driven associated particle neutron generator

    SciTech Connect

    Antolak, A. J.; Leung, K. N.; Morse, D. H.; Donovan, D. C.; Chames, J. M.; Whaley, J. A.; Buchenauer, D. A.; Chen, A. X.; Hausladen, P. A.; Liang, F.

    2015-10-09

    We describe an associated particle neutron generator that employs a negative ion source to produce high neutron flux from a small source size. Furthermore, negative ions produced in an rf-driven plasma source are extracted through a small aperture to form a beam which bombards a positively biased, high voltage target electrode. Electrons co-extracted with the negative ions are removed by a permanent magnet electron filter. The use of negative ions enables high neutron output (100% atomic ion beam), high quality imaging (small neutron source size), and reliable operation (no high voltage breakdowns). Finally, the neutron generator can operate in either pulsed or continuous-wave (cw) mode and has been demonstrated to produce 106 D-D n/s (equivalent to similar to 108 D-T n/s) from a 1 mm-diameter neutron source size to facilitate high fidelity associated particle imaging.

  20. Negative ion-driven associated particle neutron generator

    DOE PAGESBeta

    Antolak, A. J.; Leung, K. N.; Morse, D. H.; Donovan, D. C.; Chames, J. M.; Whaley, J. A.; Buchenauer, D. A.; Chen, A. X.; Hausladen, P. A.; Liang, F.

    2015-10-09

    We describe an associated particle neutron generator that employs a negative ion source to produce high neutron flux from a small source size. Furthermore, negative ions produced in an rf-driven plasma source are extracted through a small aperture to form a beam which bombards a positively biased, high voltage target electrode. Electrons co-extracted with the negative ions are removed by a permanent magnet electron filter. The use of negative ions enables high neutron output (100% atomic ion beam), high quality imaging (small neutron source size), and reliable operation (no high voltage breakdowns). Finally, the neutron generator can operate in eithermore » pulsed or continuous-wave (cw) mode and has been demonstrated to produce 106 D-D n/s (equivalent to similar to 108 D-T n/s) from a 1 mm-diameter neutron source size to facilitate high fidelity associated particle imaging.« less

  1. Negative ion-driven associated particle neutron generator

    NASA Astrophysics Data System (ADS)

    Antolak, A. J.; Leung, K. N.; Morse, D. H.; Donovan, D. C.; Chames, J. M.; Whaley, J. A.; Buchenauer, D. A.; Chen, A. X.; Hausladen, P. A.; Liang, F.

    2016-01-01

    An associated particle neutron generator is described that employs a negative ion source to produce high neutron flux from a small source size. Negative ions produced in an rf-driven plasma source are extracted through a small aperture to form a beam which bombards a positively biased, high voltage target electrode. Electrons co-extracted with the negative ions are removed by a permanent magnet electron filter. The use of negative ions enables high neutron output (100% atomic ion beam), high quality imaging (small neutron source size), and reliable operation (no high voltage breakdowns). The neutron generator can operate in either pulsed or continuous-wave (cw) mode and has been demonstrated to produce 106 D-D n/s (equivalent to ~108 D-T n/s) from a 1 mm-diameter neutron source size to facilitate high fidelity associated particle imaging.

  2. Small radio frequency driven multicusp ion source for positive hydrogen ion beam production

    SciTech Connect

    Perkins, L.T.; Herz, P.R.; Leung, K.N.; Pickard, D.S. )

    1994-04-01

    A compact, 2.5 cm diam rf-driven multicusp ion source has been developed and tested for H[sup +] ion production in pulse mode operation. The source is optimized for atomic hydrogen ion species and extractable current. It is found that hydrogen ion beam current densities in excess of 650 mA/cm[sup 2] can be achieved with H[sup +] species above 80%. The geometry and position of the porcelain-coated copper antenna were found to be of great significance in relation to the efficiency of the ion source.

  3. A spin-Seebeck diode with a negative differential spin-Seebeck effect in a hydrogen-terminated zigzag silicene nanoribbon heterojunction.

    PubMed

    Fu, Hua-Hua; Gu, Lei; Wu, Dan-Dan

    2016-05-14

    The spin-Seebeck effect (SSE), the central topic of spin caloritronics, provides a new direction for future low power consumption technology. To realize device applications of SSE, a spin-Seebeck diode (SSD) with a negative differential SSE is very desirable. To this end, we constructed a spin caloritronics device that was composed of a ferromagnetic double-single-hydrogen-terminated zigzag silicene nanoribbon (ZSiNR-H2-H) and an antiferromagnetic double-double-hydrogen-terminated zigzag silicene nanoribbon (ZSiNR-H2-H2). By using ab initio calculations combined with nonequilibrium Green's function technique, we found that thermally driven spin current through the heterojunction featured the SSD effect and negative differential SSE. The former originates from the asymmetrical thermal-driven conducting electrons and holes, and the latter ascribes to the thermal spin compensation effect. Their physical mechanisms are much different from the previous ones mainly relying on the spin-wave excitations in the interface between metals and magnetic insulators, supporting our study that puts forward a new route to realize the SSD with a negative differential SSE. PMID:27098900

  4. Negative-ion production on carbon materials in hydrogen plasma: influence of the carbon hybridization state and the hydrogen content on H- yield

    NASA Astrophysics Data System (ADS)

    Ahmad, Ahmad; Pardanaud, Cédric; Carrère, Marcel; Layet, Jean-Marc; Gicquel, Alix; Kumar, Pravin; Eon, David; Jaoul, Cédric; Engeln, Richard; Cartry, Gilles

    2014-02-01

    Highly oriented polycrystalline graphite (HOPG), boron-doped diamond (BDD), nanocrystalline diamond, ultra-nanocrystalline diamond and diamond-like carbon surfaces are exposed to low-pressure hydrogen plasma in a 13.56 MHz plasma reactor. Relative yields of surface-produced H- ions due to bombardment of positive ions from the plasma are measured by an energy analyser cum quadrupole mass spectrometer. Irrespective of plasma conditions (0.2 and 2 Pa), HOPG surfaces show the highest yield at room temperature (RT), while at high temperature (HT), the highest yield (˜3-5 times compared to HOPG surface at RT) is observed on BDD surfaces. The shapes of ion distribution functions are compared at RT and HT to demonstrate the mechanism of ion generation at the surface. Raman spectroscopy analyses of the plasma-exposed samples reveal surface modifications influencing H- production yields, while further analyses strongly suggest that the hydrogen content of the material and the sp3/sp2 ratio are the key parameters in driving the surface ionization efficiency of carbon materials under the chosen plasma conditions.

  5. Doppler shift measurement of Balmer-alpha line spectrum emission from a plasma in a negative hydrogen ion source

    SciTech Connect

    Wada, M. Doi, K.; Kisaki, M.; Nakano, H.; Tsumori, K.; Nishiura, M.

    2015-04-08

    Balmer-α light emission from the extraction region of the LHD one-third ion source has shown a characteristic Doppler broadening in the wavelength spectrum detected by a high resolution spectrometer. The spectrum resembles Gaussian distribution near the wavelength of the intensity peak, while it has an additional component of a broader foot. The measured broadening near the wavelength of the intensity peak corresponds to 0.6 eV hydrogen atom temperature. The spectrum exhibits a larger expansion in the blue wing which becomes smaller when the line of sight is tilted toward the driver region from the original observation axis parallel to the plasma grid. A surface collision simulation model predicts the possibility of hydrogen reflection at the plasma grid surface to form a broad Balmer-α light emission spectrum.

  6. Negative ion production by backscattering from alkali-metal surfaces bombarded by ions of hydrogen and deuterium

    SciTech Connect

    Schneider, P.J.

    1980-03-01

    Measurements have been made of the total backscattered D/sup -/ and H/sup -/ yields from thick, clean targets of Cs, Rb, K, Na, and Li, bombarded with H/sub 2//sup +/, H/sub 3//sup +/, D/sub 2//sup +/, and D/sub 3//sup +/ with incident energies from 0.15 to 4.0 keV/nucleus. All of the measurements were made at background pressures less than 10/sup -9/ Torr and the alkali-metal targets were evaporated onto a cold substrate (T = 77K) in situ to assure thick, uncontaminated targets. Measurements of the H/sup -/ yield from various transition metal targets with thin coverages of alkali-metals have also been made as a function of the surface work function. The negative ion yields are discussed in terms of the probabilities of reflection of the incident particles, of formation of the negative ion at the surface and of the survival of the negative ion leaving the surface. For each thick alkali-metal target, the negative ion yield measurements have been used in a least squares fit to determine two parameters in a theoretically derived expression for the negative ion yield. The parameters obtained from a thick Na target have been used to calculate the yield from a Cu target with thin coverage of Na (such that the surface work function is equal to thick Na).

  7. Doubly excited {sup 1,3}P{sup e} resonance states of helium and the hydrogen negative ion interacting with Coulomb and screened Coulomb potentials

    SciTech Connect

    Kar, Sabyasachi; Ho, Y. K.

    2011-04-15

    We have investigated the doubly excited {sup 1,3}P{sup e} resonance states of helium and the hydrogen negative ion interacting with Coulomb and screened Coulomb potentials using exponential correlated wave functions. In the pure Coulomb case, calculations have been carried out by using the complex-coordinate rotation and the stabilization method. The {sup 1}P{sup e} resonance states of He below the N= 3, 4, and 5 thresholds of He{sup +}, and the {sup 3}P{sup e} resonance states of He below the N= 3 thresholds of He{sup +}, are reported. The 5p{sup 2} {sup 3}P{sup e} state, which has attracted recent interest, is also reported and discussed. In the screened Coulomb case, we have used the stabilization method to obtain two different series (3pnp and 3dnd) of resonance states below the N= 3 He{sup +} threshold as a function of the screening parameters. Resonance widths for the 3dnd series show some interesting behaviors. The resonance parameters (position and width) for helium and the hydrogen negation ion as functions of the screening parameters are reported.

  8. Negative-ion yield in low-pressure radio frequency discharges in hydrogen: Particle modeling and vibrational kinetics

    SciTech Connect

    Diomede, P.; Longo, S.; Capitelli, M.

    2006-03-15

    A theoretical study of the complex interplay between the vibrational kinetics and the plasma dynamics in low-pressure hydrogen plasmas produced by radio frequency discharges is performed. The study is realized by means of a one-dimensional particle model with five species (e, H{sup +}, H{sub 2}{sup +}, H{sub 3}{sup +}, and H{sup -}) while the vibrational/dissociation kinetics is based on a continuum model and the two are self-consistently coupled. In particular, we analyze the influence of pressure.

  9. H{sup -} beam extraction from a cesium seeded field effect transistor based radio frequency negative hydrogen ion source

    SciTech Connect

    Ando, A.; Matsuno, T.; Funaoi, T.; Tanaka, N.; Tsumori, K.; Takeiri, Y.

    2012-02-15

    H{sup -} beam was successfully extracted from a cesium seeded ion source operated using a field effect transistor inverter power supply as a radio frequency (RF) wave source. High density hydrogen plasma more than 10{sup 19} m{sup -3} was obtained using an external type antenna with RF frequency of lower than 0.5 MHz. The source was isolated by an isolation transformer and H{sup -} ion beam was extracted from a single aperture. Acceleration current and extraction current increased with the increase of extraction voltage. Addition of a small amount of cesium vapor into the source enhanced the currents.

  10. Negative ion surface production on carbon materials in hydrogen plasma: a thermodesorption analysis of carbon surface states

    NASA Astrophysics Data System (ADS)

    Cartry, Gilles; Achkasov, Kostiantyn; Pardanaud, Cédric; Layet, Jean-Marc; Simonin, Alain; Gicquel, Alix; Saidi, Othmen; Bisson, Régis; Angot, Thierry; PIIM Collaboration; IRFM Collaboration; LSPM Collaboration

    2014-10-01

    Negative ion surface production in plasmas has been studied in the context of fusion where H-surface production in cesium-seeded plasmas is of a primary interest for neutral beam injection devices. Although surface production is much lower in Cs-free plasmas, it may be non-negligible. Indeed it has been observed that significant numbers of H-ions can be created on a graphite surface upon positive ion bombardment in H2 plasmas. Graphite material has been compared to a large variety of diamond layers, in particular poly-crystalline boron-doped and non-doped diamond thin films. It has been shown an enhancement of the negative-ion yield by a factor 5 for diamond materials at high temperature, while the yield continuously decreases for graphite. The difference is due to the different properties of the pristine materials but also to the modifications bring by the plasma to the materials during exposure. In order to study in detail these modifications, plasma exposed samples have been analyzed by Raman spectroscopy and Temperature Programmed Desorption (TPD). These diagnostics helped to trace the surface state changes of the materials and identify the reasons for the elevated negative ion production at high temperature on diamonds.

  11. Preparation of hydrogenated diamond-like carbon films by reactive Ar/CH4 high power impulse magnetron sputtering with negative pulse voltage

    NASA Astrophysics Data System (ADS)

    Kimura, Takashi; Kamata, Hikaru

    2015-09-01

    High power impulse magnetron sputtering (HiPIMS) has been attracted, because sputtered target species are highly ionized. High densities of active species such as radical ions and neutral radicals can be also achieved owing to high density reactive HiPIMS plasmas. We investigate properties of hydrogenated diamond-like carbon films prepared by reactive HiPIMS of Ar/CH4 gas mixture. The properties of the films strongly depend on the plasma compositions and the kinetic energy of the carbon-containing ions which can enter into the films. The film preparation is performed at an average power of 60 W and a repetition frequency of 110 Hz, changing CH4 fraction up to 15%. Total pressure ranges between 0.3 and 2 Pa. The maximum of instantaneous power is about 20-25 kW, and the magnitude of the current is 36 A. A negative pulse voltage is applied to the substrates for about 10 μs after the target voltage changed from about -600 V to 0 V. The structural properties are characterized by Raman spectroscopy and nano-indentation method. Film hardness strongly depends on the magnitude of negative pulse voltage. By adjusting the magnitude of negative voltage, the film hardness ranges between about 10 and 22 GPa. This work is partially supported by JSPS KAKENHI Grant Number 26420230.

  12. Hydrogen negative ion production in a 14 GHz electron cyclotron resonance compact ion source with a cone-shaped magnetic filter.

    PubMed

    Ichikawa, T; Kasuya, T; Kenmotsu, T; Maeno, S; Nishiura, M; Shimozuma, T; Yamaoka, H; Wada, M

    2014-02-01

    The plasma electrode structure of a 14 GHz ECR ion source was modified to enlarge the plasma volume of low electron temperature region. The result shows that the extracted beam current reached about 0.6 mA/cm(2) with about 40 W microwave power. To investigate the correlation between the volume of the low electron temperature region and the H(-) current, a vacuum ultraviolet (VUV) spectrometer had been installed to observe light emission in the VUV wavelength range from the plasma. From the results of the negative ion beam current and that from VUV spectrometry, production rate of vibrationally excited hydrogen molecule seems to be enhanced by increasing the volume of low electron temperature region. PMID:24593572

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

    SciTech Connect

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

    2014-02-15

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

  14. Hydrogen negative ion production in a 14 GHz electron cyclotron resonance compact ion source with a cone-shaped magnetic filter

    SciTech Connect

    Ichikawa, T.; Kasuya, T.; Wada, M.; Kenmotsu, T.; Maeno, S.; Nishiura, M.; Shimozuma, T.; Yamaoka, H.

    2014-02-15

    The plasma electrode structure of a 14 GHz ECR ion source was modified to enlarge the plasma volume of low electron temperature region. The result shows that the extracted beam current reached about 0.6 mA/cm{sup 2} with about 40 W microwave power. To investigate the correlation between the volume of the low electron temperature region and the H{sup −} current, a vacuum ultraviolet (VUV) spectrometer had been installed to observe light emission in the VUV wavelength range from the plasma. From the results of the negative ion beam current and that from VUV spectrometry, production rate of vibrationally excited hydrogen molecule seems to be enhanced by increasing the volume of low electron temperature region.

  15. Negative ion source with external RF antenna

    DOEpatents

    Leung, Ka-Ngo; Hahto, Sami K.; Hahto, Sari T.

    2007-02-13

    A radio frequency (RF) driven plasma ion source has an external RF antenna, i.e. the RF antenna is positioned outside the plasma generating chamber rather than inside. The RF antenna is typically formed of a small diameter metal tube coated with an insulator. An external RF antenna assembly is used to mount the external RF antenna to the ion source. The RF antenna tubing is wound around the external RF antenna assembly to form a coil. The external RF antenna assembly is formed of a material, e.g. quartz, which is essentially transparent to the RF waves. The external RF antenna assembly is attached to and forms a part of the plasma source chamber so that the RF waves emitted by the RF antenna enter into the inside of the plasma chamber and ionize a gas contained therein. The plasma ion source is typically a multi-cusp ion source. A converter can be included in the ion source to produce negative ions.

  16. Influence of electrolyte composition and temperature on behaviour of AB5 hydrogen storage alloy used as negative electrode in Ni-MH batteries

    NASA Astrophysics Data System (ADS)

    Karwowska, Malgorzata; Jaron, Tomasz; Fijalkowski, Karol J.; Leszczynski, Piotr J.; Rogulski, Zbigniew; Czerwinski, Andrzej

    2014-10-01

    The AB5-type metal alloy (Mm-Ni4.1Al0.2Mn0.4Co0.45) has been investigated in different electrolytes (LiOH, NaOH, KOH, RbOH, CsOH). All of the electrochemical measurements have been performed using limited volume electrode technique (LVE). Thickness of the working electrode is nearly equal to the diameter of the grain (ca. 50 μm). Hydrogen diffusion coefficient has been determined using chronoamperometry. Hydrogen diffusion coefficient calculated for 100% state of charge reaches maximum value in KOH (DH = 4.65·10-10 cm2 s-1). We have obtained the highest value of capacity for the electrode in KOH and the lowest - in CsOH. The temperature influence on alloy capacity has been also tested. The alloy has been also characterised with SEM coupled with EDS, TGA/DSC and powder XRD. The unit cell of MmNi4.1Al0.2Mn0.4Co0.45 have been refined in the Cu5.4Yb0.8 structure type (a modified LaNi5 structure); the structure is unaffected by the electrochemical treatment.

  17. Negative mass

    NASA Astrophysics Data System (ADS)

    Hammond, Richard T.

    2015-03-01

    Some physical aspects of negative mass are examined. Several unusual properties, such as the ability of negative mass to penetrate any armor, are analysed. Other surprising effects include the bizarre system of negative mass chasing positive mass, naked singularities and the violation of cosmic censorship, wormholes, and quantum mechanical results as well. In addition, a brief look into the implications for strings is given.

  18. Sensitivity of RF-driven Plasma Filaments to Trace Gases

    NASA Astrophysics Data System (ADS)

    Burin, M. J.; Czarnocki, C. J.; Czarnocki, K.; Zweben, S. J.; Zwicker, A.

    2011-10-01

    Filamentary structures have been observed in many types of plasma discharges in both natural (e.g. lightning) and industrial systems (e.g. dielectric barrier discharges). Recent progress has been made in characterizing these structures, though various aspects of their essential physics remain unclear. A common example of this phenomenon can be found within a toy plasma globe (or plasma ball), wherein a primarily neon gas mixture near atmospheric pressure clearly and aesthetically displays filamentation. Recent work has provided the first characterization of these plasma globe filaments [Campanell et al., Physics of Plasmas 2010], where it was noticed that discharges of pure gases tend not to produce filaments. We have extended this initial work to investigate in greater detail the dependence of trace gases on filamentation within a primarily Neon discharge. Our preliminary results using a custom globe apparatus will be presented, along with some discussion of voltage dependencies. Newly supported by the NSF/DOE Partnership in Basic Plasma Science and Engineering.

  19. Negative Electron Affinity Mechanism for Diamond Surfaces

    NASA Technical Reports Server (NTRS)

    Krainsky, I. L.; Asnin, V. M.

    1998-01-01

    The energy distribution of the secondary electrons for chemical vacuum deposited diamond films with Negative Electron Affinity (NEA) was investigated. It was found that while for completely hydrogenated diamond surfaces the negative electron affinity peak in the energy spectrum of the secondary electrons is present for any energy of the primary electrons, for partially hydrogenated diamond surfaces there is a critical energy above which the peak is present in the spectrum. This critical energy increases sharply when hydrogen coverage of the diamond surface diminishes. This effect was explained by the change of the NEA from the true type for the completely hydrogenated surface to the effective type for the partially hydrogenated surfaces.

  20. Improvements of the magnetic field design for SPIDER and MITICA negative ion beam sources

    NASA Astrophysics Data System (ADS)

    Chitarin, G.; Agostinetti, P.; Aprile, D.; Marconato, N.; Veltri, P.

    2015-04-01

    The design of the magnetic field configuration in the SPIDER and MITICA negative ion beam sources has evolved considerably during the past four years. This evolution was driven by three factors: 1) the experimental results of the large RF-driven ion sources at IPP, which have provided valuable indications on the optimal magnetic configurations for reliable RF plasma source operation and for large negative ion current extraction, 2) the comprehensive beam optics and heat load simulations, which showed that the magnetic field configuration in the accelerator is crucial for keeping the heat load due to electrons on the accelerator grids within tolerable limits, without compromising the optics of the negative ion beam in the foreseen operating scenarios, 3) the progress of the detailed mechanical design of the accelerator, which stimulated the evaluation of different solutions for the correction of beamlet deflections of various origin and for beamlet aiming. On this basis, new requirements and solution concepts for the magnetic field configuration in the SPIDER and MITICA beam sources have been progressively introduced and updated until the design converged. The paper presents how these concepts have been integrated into a final design solution based on a horizontal "long-range" field (few mT) in combination with a "local" vertical field of some tens of mT on the acceleration grids.

  1. Improvements of the magnetic field design for SPIDER and MITICA negative ion beam sources

    SciTech Connect

    Chitarin, G.; Agostinetti, P.; Aprile, D.; Marconato, N.; Veltri, P.

    2015-04-08

    The design of the magnetic field configuration in the SPIDER and MITICA negative ion beam sources has evolved considerably during the past four years. This evolution was driven by three factors: 1) the experimental results of the large RF-driven ion sources at IPP, which have provided valuable indications on the optimal magnetic configurations for reliable RF plasma source operation and for large negative ion current extraction, 2) the comprehensive beam optics and heat load simulations, which showed that the magnetic field configuration in the accelerator is crucial for keeping the heat load due to electrons on the accelerator grids within tolerable limits, without compromising the optics of the negative ion beam in the foreseen operating scenarios, 3) the progress of the detailed mechanical design of the accelerator, which stimulated the evaluation of different solutions for the correction of beamlet deflections of various origin and for beamlet aiming. On this basis, new requirements and solution concepts for the magnetic field configuration in the SPIDER and MITICA beam sources have been progressively introduced and updated until the design converged. The paper presents how these concepts have been integrated into a final design solution based on a horizontal “long-range” field (few mT) in combination with a “local” vertical field of some tens of mT on the acceleration grids.

  2. Negative hydrogen ion sources for accelerators

    SciTech Connect

    Moehs, D.P.; Peters, J.; Sherman, J.; /Los Alamos

    2005-08-01

    A variety of H{sup -} ion sources are in use at accelerator laboratories around the world. A list of these ion sources includes surface plasma sources with magnetron, Penning and surface converter geometries as well as magnetic-multipole volume sources with and without cesium. Just as varied is the means of igniting and maintaining magnetically confined plasmas. Hot and cold cathodes, radio frequency, and microwave power are all in use, as well as electron tandem source ignition. The extraction systems of accelerator H{sup -} ion sources are highly specialized utilizing magnetic and electric fields in their low energy beam transport systems to produce direct current, as well as pulsed and/or chopped beams with a variety of time structures. Within this paper, specific ion sources utilized at accelerator laboratories shall be reviewed along with the physics of surface and volume H{sup -} production in regard to source emittance. Current research trends including aperture modeling, thermal modeling, surface conditioning, and laser diagnostics will also be discussed.

  3. Cesium in hydrogen negative-ion sources

    SciTech Connect

    Belchenko, Yu.I.; Davydenko, V.I.

    2006-03-15

    Experimental data on the dynamics of cesium particles in the pulsed magnetron and Penning surface-plasma ion sources are presented. Cesium escape from the source emission apertures and the cesium ion current to discharge electrodes was measured. The low value of cesium flux from the source was detected. An intense cesium ion current to the cathode (up to 0.8 A/cm{sup 2}) was measured. The high value of cesium ion current to surface-plasma source cathode confirms the cesium circulation near the cathode.

  4. Hydrogen production

    NASA Technical Reports Server (NTRS)

    England, C.; Chirivella, J. E.; Fujita, T.; Jeffe, R. E.; Lawson, D.; Manvi, R.

    1975-01-01

    The state of hydrogen production technology is evaluated. Specific areas discussed include: hydrogen production fossil fuels; coal gasification processes; electrolysis of water; thermochemical production of hydrogen; production of hydrogen by solar energy; and biological production of hydrogen. Supply options are considered along with costs of hydrogen production.

  5. An experimental study of waveguide coupled microwave heating with conventional multicusp negative ion sources

    SciTech Connect

    Komppula, J.; Kalvas, T.; Koivisto, H.; Laulainen, J.; Tarvainen, O.

    2015-04-08

    Negative ion production with conventional multicusp plasma chambers utilizing 2.45 GHz microwave heating is demonstrated. The experimental results were obtained with the multicusp plasma chambers and extraction systems of the RF-driven RADIS ion source and the filament driven arc discharge ion source LIISA. A waveguide microwave coupling system, which is almost similar to the one used with the SILHI ion source, was used. The results demonstrate that at least one third of negative ion beam obtained with inductive RF-coupling (RADIS) or arc discharge (LIISA) can be achieved with 1 kW of 2.45 GHz microwave power in CW mode without any modification of the plasma chamber. The co-extracted electron to H{sup −} ratio and the optimum pressure range were observed to be similar for both heating methods. The behaviour of the plasma implies that the energy transfer from the microwaves to the plasma electrons is mainly an off-resonance process.

  6. Hydrogen sensor

    DOEpatents

    Duan, Yixiang; Jia, Quanxi; Cao, Wenqing

    2010-11-23

    A hydrogen sensor for detecting/quantitating hydrogen and hydrogen isotopes includes a sampling line and a microplasma generator that excites hydrogen from a gas sample and produces light emission from excited hydrogen. A power supply provides power to the microplasma generator, and a spectrometer generates an emission spectrum from the light emission. A programmable computer is adapted for determining whether or not the gas sample includes hydrogen, and for quantitating the amount of hydrogen and/or hydrogen isotopes are present in the gas sample.

  7. Hydrogenation apparatus

    DOEpatents

    Friedman, Joseph [Encino, CA; Oberg, Carl L [Canoga Park, CA; Russell, Larry H [Agoura, CA

    1981-01-01

    Hydrogenation reaction apparatus comprising a housing having walls which define a reaction zone and conduits for introducing streams of hydrogen and oxygen into the reaction zone, the oxygen being introduced into a central portion of the hydrogen stream to maintain a boundary layer of hydrogen along the walls of the reaction zone. A portion of the hydrogen and all of the oxygen react to produce a heated gas stream having a temperature within the range of from 1100.degree. to 1900.degree. C., while the boundary layer of hydrogen maintains the wall temperature at a substantially lower temperature. The heated gas stream is introduced into a hydrogenation reaction zone and provides the source of heat and hydrogen for a hydrogenation reaction. There also is provided means for quenching the products of the hydrogenation reaction. The present invention is particularly suitable for the hydrogenation of low-value solid carbonaceous materials to provide high yields of more valuable liquid and gaseous products.

  8. Hydrogen trapping and the interaction of hydrogen with metals

    NASA Technical Reports Server (NTRS)

    Danford, Merlin D.

    1987-01-01

    A method has been developed for the determination of trapped hydrogen in metal alloys, involving the determination of mobile hydrogen using the electrochemical method and the determination of total hydrogen with the fusion method, the difference in hydrogen concentrations being due to trapped hydrogen. It has been found that hydrogen enters body-centered cubic structures through the grain bodies rather than through the grain boundaries. Hydrogen also diffuses much more rapidly in body-centered cubic structures on charging than in face-centered cubic structures, the hydrogen distribution being more uniform in nature. The energy necessary to cause hydrogen embrittlement is postulated to arise from the changes in crystal lattice energies brought about through interaction of hydrogen with atoms in the metal lattice. The total energy change is more negative for body-centered cubic structures, believed to be the cause of a greater tendency toward hydrogen embrittlement. Finally, the agreement of hydrogen concentrations obtained at 25 C by the electrochemical method with those obtained by the fusion method are taken as a strong indication of the power and validity of the electrochemical method.

  9. Hydrogen Production

    SciTech Connect

    2014-09-01

    This 2-page fact sheet provides a brief introduction to hydrogen production technologies. Intended for a non-technical audience, it explains how different resources and processes can be used to produce hydrogen. It includes an overview of research goals as well as “quick facts” about hydrogen energy resources and production technologies.

  10. Hydrogenation apparatus

    DOEpatents

    Friedman, J.; Oberg, C. L.; Russell, L. H.

    1981-06-23

    Hydrogenation reaction apparatus is described comprising a housing having walls which define a reaction zone and conduits for introducing streams of hydrogen and oxygen into the reaction zone, the oxygen being introduced into a central portion of the hydrogen stream to maintain a boundary layer of hydrogen along the walls of the reaction zone. A portion of the hydrogen and all of the oxygen react to produce a heated gas stream having a temperature within the range of from 1,100 to 1,900 C, while the boundary layer of hydrogen maintains the wall temperature at a substantially lower temperature. The heated gas stream is introduced into a hydrogenation reaction zone and provides the source of heat and hydrogen for a hydrogenation reaction. There also is provided means for quenching the products of the hydrogenation reaction. The present invention is particularly suitable for the hydrogenation of low-value solid carbonaceous materials to provide high yields of more valuable liquid and gaseous products. 2 figs.

  11. Hydrogen Generator

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Another spinoff from spacecraft fuel cell technology is the portable hydrogen generator shown. Developed by General Electric Company, it is an aid to safer operation of systems that use hydrogen-for example, gas chromatographs, used in laboratory analysis of gases. or flame ionization detectors used as $ollution monitors. The generator eliminates the need for high-pressure hydrogen storage bottles, which can be a safety hazard, in laboratories, hospitals and industrial plants. The unit supplies high-purity hydrogen by means of an electrochemical process which separates the hydrogen and oxygen in distilled water. The oxygen is vented away and the hydrogen gas is stored within the unit for use as needed. GE's Aircraft Equipment Division is producing about 1,000 of the generators annually.

  12. Meningitis - gram-negative

    MedlinePlus

    Gram-negative meningitis ... Acute bacterial meningitis can be caused by Gram-negative bacteria. Meningococcal and H. influenzae meningitis are caused by Gram-negative bacteria and are covered in detail in other articles. This article ...

  13. Cesium injection system for negative ion duoplasmatrons

    DOEpatents

    Kobayashi, Maasaki; Prelec, Krsto; Sluyters, Theodorus J

    1978-01-01

    Longitudinally extending, foraminous cartridge means having a cylindrical side wall forming one flat, circular, tip end surface and an opposite end; an open-ended cavity, and uniformly spaced orifices for venting the cavity through the side wall in the annulus of a plasma ring for uniformly ejecting cesium for coating the flat, circular, surface. To this end, the cavity is filled with a cesium containing substance and attached to a heater in a hollow-discharge duoplasmatron. By coating the flat circular surface with a uniform monolayer of cesium and locating it in an electrical potential well at the end of a hollow-discharge, ion duoplasmatron source of an annular hydrogen plasma ring, the negative hydrogen production from the duoplasmatron is increased. The negative hydrogen is produced on the flat surface of the cartridge and extracted by the electrical potential well along a trajectory coaxial with the axis of the plasma ring.

  14. Hydrogen Bibliography

    SciTech Connect

    Not Available

    1991-12-01

    The Hydrogen Bibliography is a compilation of research reports that are the result of research funded over the last fifteen years. In addition, other documents have been added. All cited reports are contained in the National Renewable Energy Laboratory (NREL) Hydrogen Program Library.

  15. Hydrogen energy.

    PubMed

    Edwards, P P; Kuznetsov, V L; David, W I F

    2007-04-15

    The problem of anthropogenically driven climate change and its inextricable link to our global society's present and future energy needs are arguably the greatest challenge facing our planet. Hydrogen is now widely regarded as one key element of a potential energy solution for the twenty-first century, capable of assisting in issues of environmental emissions, sustainability and energy security. Hydrogen has the potential to provide for energy in transportation, distributed heat and power generation and energy storage systems with little or no impact on the environment, both locally and globally. However, any transition from a carbon-based (fossil fuel) energy system to a hydrogen-based economy involves significant scientific, technological and socio-economic barriers. This brief report aims to outline the basis of the growing worldwide interest in hydrogen energy and examines some of the important issues relating to the future development of hydrogen as an energy vector. PMID:17272235

  16. Atomic wall recombination and volume negative ion production

    SciTech Connect

    Pagano, Damiano; Gorse, Claudine; Capitelli, Mario

    2006-03-15

    The development of a numerical code for the modeling of negative ion sources requires the knowledge of a lot of processes occurring both in the gas phase and at the surface. The present work concerns the effect of surface processes (in particular atomic wall recombination) on the kinetics of production/destruction of negative ions. Especially in the pressure regimes useful to produce negative hydrogen ions for thermonuclear applications, wall processes can strongly affect the negative ion production acting on the vibrational distribution of molecular hydrogen.

  17. Hydrogen Effect against Hydrogen Embrittlement

    NASA Astrophysics Data System (ADS)

    Murakami, Yukitaka; Kanezaki, Toshihiko; Mine, Yoji

    2010-10-01

    The well-known term “hydrogen embrittlement” (HE) expresses undesirable effects due to hydrogen such as loss of ductility, decreased fracture toughness, and degradation of fatigue properties of metals. However, this article shows, surprisingly, that hydrogen can have an effect against HE. A dramatic phenomenon was found in which charging a supersaturated level of hydrogen into specimens of austenitic stainless steels of types 304 and 316L drastically improved the fatigue crack growth resistance, rather than accelerating fatigue crack growth rates. Although this mysterious phenomenon has not previously been observed in the history of HE research, its mechanism can be understood as an interaction between hydrogen and dislocations. Hydrogen can play two roles in terms of dislocation mobility: pinning (or dragging) and enhancement of mobility. Competition between these two roles determines whether the resulting phenomenon is damaging or, unexpectedly, desirable. This finding will, not only be the crucial key factor to elucidate the mechanism of HE, but also be a trigger to review all existing theories on HE in which hydrogen is regarded as a dangerous culprit.

  18. Negative-ion states

    SciTech Connect

    Compton, R.N.

    1982-01-01

    In this brief review, we discuss some of the properties of atomic and molecular negative ions and their excited states. Experiments involving photon reactions with negative ions and polar dissociation are summarized. 116 references, 14 figures.

  19. Volume production of negative ions in the reflex-type ion source

    SciTech Connect

    Jimbo, K.

    1982-06-01

    The production of negative hydrogen ions is investigated in the reflex-type negative ion source. The extracted negative hydrogen currents of 9.7 mA (100 mA/cm/sup 2/) for H/sup -/ and of 4.1 mA(42 mA/cm/sup 2/) for D/sup -/ are obtained continuously. The impurity is less than 1%. An isotope effect of negative ion production is observed.

  20. Negative ion generator

    DOEpatents

    Stinnett, R.W.

    1984-05-08

    A negative ion generator is formed from a magnetically insulated transmission line having a coating of graphite on the cathode for producing negative ions and a plurality of apertures on the opposed anode for the release of negative ions. Magnetic insulation keeps electrons from flowing from the cathode to the anode. A transverse magnetic field removes electrons which do escape through the apertures from the trajectory of the negative ions. 8 figs.

  1. Negative ion generator

    DOEpatents

    Stinnett, Regan W.

    1984-01-01

    A negative ion generator is formed from a magnetically insulated transmission line having a coating of graphite on the cathode for producing negative ions and a plurality of apertures on the opposed anode for the release of negative ions. Magnetic insulation keeps electrons from flowing from the cathode to the anode. A transverse magnetic field removes electrons which do escape through the apertures from the trajectory of the negative ions.

  2. [Negative symptoms: which antipsychotics?].

    PubMed

    Maurel, M; Belzeaux, R; Adida, M; Azorin, J-M

    2015-12-01

    Treating negative symptoms of schizophrenia is a major issue and a challenge for the functional and social prognosis of the disease, to which they are closely linked. First- and second-generation antipsychotics allow a reduction of all negative symptoms. The hope of acting directly on primary negative symptoms with any antipsychotic is not supported by the literature. However, the effectiveness of first- and second-generation antipsychotics is demonstrated on secondary negative symptoms. PMID:26776390

  3. Storing Hydrogen

    SciTech Connect

    Kim, Hyun Jeong; Karkamkar, Abhijeet J.; Autrey, Thomas; Chupas, Peter; Proffen, Thomas E.

    2010-05-31

    Researchers have been studying mesoporous materials for almost two decades with a view to using them as hosts for small molecules and scaffolds for molding organic compounds into new hybrid materials and nanoparticles. Their use as potential storage systems for large quantities of hydrogen has also been mooted. Such systems that might hold large quantities of hydrogen safely and in a very compact volume would have enormous potential for powering fuel cell vehicles, for instance. A sponge-like form of silicon dioxide, the stuff of sand particles and computer chips, can soak up and store other compounds including hydrogen. Studies carried out at the XOR/BESSRC 11-ID-B beamline at the APS have revealed that the nanoscopic properties of the hydrogenrich compound ammonia borane help it store hydrogen more efficiently than usual. The material may have potential for addressing the storage issues associated with a future hydrogen economy. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  4. Sentential Negation in English

    ERIC Educational Resources Information Center

    Mowarin, Macaulay

    2009-01-01

    This paper undertakes a detailed analysis of sentential negation in the English language with Chomsky's Government-Binding theory of Transformational Grammar as theoretical model. It distinguishes between constituent and sentential negation in English. The essay identifies the exact position of Negation phrase in an English clause structure. It…

  5. Hydrogen program overview

    SciTech Connect

    Gronich, S.

    1997-12-31

    This paper consists of viewgraphs which summarize the following: Hydrogen program structure; Goals for hydrogen production research; Goals for hydrogen storage and utilization research; Technology validation; DOE technology validation activities supporting hydrogen pathways; Near-term opportunities for hydrogen; Market for hydrogen; and List of solicitation awards. It is concluded that a full transition toward a hydrogen economy can begin in the next decade.

  6. Hydrogen chloride

    Integrated Risk Information System (IRIS)

    Hydrogen chloride ; CASRN 7647 - 01 - 0 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogeni

  7. Hydrogen sulfide

    Integrated Risk Information System (IRIS)

    Hydrogen sulfide ; 7783 - 06 - 4 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effec

  8. Electrochemical Hydrogen Peroxide Generator

    NASA Technical Reports Server (NTRS)

    Tennakoon, Charles L. K.; Singh, Waheguru; Anderson, Kelvin C.

    2010-01-01

    Two-electron reduction of oxygen to produce hydrogen peroxide is a much researched topic. Most of the work has been done in the production of hydrogen peroxide in basic media, in order to address the needs of the pulp and paper industry. However, peroxides under alkaline conditions show poor stabilities and are not useful in disinfection applications. There is a need to design electrocatalysts that are stable and provide good current and energy efficiencies to produce hydrogen peroxide under acidic conditions. The innovation focuses on the in situ generation of hydrogen peroxide using an electrochemical cell having a gas diffusion electrode as the cathode (electrode connected to the negative pole of the power supply) and a platinized titanium anode. The cathode and anode compartments are separated by a readily available cation-exchange membrane (Nafion 117). The anode compartment is fed with deionized water. Generation of oxygen is the anode reaction. Protons from the anode compartment are transferred across the cation-exchange membrane to the cathode compartment by electrostatic attraction towards the negatively charged electrode. The cathode compartment is fed with oxygen. Here, hydrogen peroxide is generated by the reduction of oxygen. Water may also be generated in the cathode. A small amount of water is also transported across the membrane along with hydrated protons transported across the membrane. Generally, each proton is hydrated with 3-5 molecules. The process is unique because hydrogen peroxide is formed as a high-purity aqueous solution. Since there are no hazardous chemicals or liquids used in the process, the disinfection product can be applied directly to water, before entering a water filtration unit to disinfect the incoming water and to prevent the build up of heterotrophic bacteria, for example, in carbon based filters. The competitive advantages of this process are: 1. No consumable chemicals are needed in the process. The only raw materials

  9. Metallic Hydrogen

    NASA Astrophysics Data System (ADS)

    Silvera, Isaac; Zaghoo, Mohamed; Salamat, Ashkan

    2015-03-01

    Hydrogen is the simplest and most abundant element in the Universe. At high pressure it is predicted to transform to a metal with remarkable properties: room temperature superconductivity, a metastable metal at ambient conditions, and a revolutionary rocket propellant. Both theory and experiment have been challenged for almost 80 years to determine its condensed matter phase diagram, in particular the insulator-metal transition. Hydrogen is predicted to dissociate to a liquid atomic metal at multi-megabar pressures and T =0 K, or at megabar pressures and very high temperatures. Thus, its predicted phase diagram has a broad field of liquid metallic hydrogen at high pressure, with temperatures ranging from thousands of degrees to zero Kelvin. In a bench top experiment using static compression in a diamond anvil cell and pulsed laser heating, we have conducted measurements on dense hydrogen in the region of 1.1-1.7 Mbar and up to 2200 K. We observe a first-order phase transition in the liquid phase, as well as sharp changes in optical transmission and reflectivity when this phase is entered. The optical signature is that of a metal. The mapping of the phase line of this transition is in excellent agreement with recent theoretical predictions for the long-sought plasma phase transition to metallic hydrogen. Research supported by the NSF, Grant DMR-1308641, the DOE Stockpile Stewardship Academic Alliance Program, Grant DE-FG52-10NA29656, and NASA Earth and Space Science Fellowship Program, Award NNX14AP17H.

  10. Negative Ion Density Fronts

    SciTech Connect

    Igor Kaganovich

    2000-12-18

    Negative ions tend to stratify in electronegative plasmas with hot electrons (electron temperature Te much larger than ion temperature Ti, Te > Ti ). The boundary separating a plasma containing negative ions, and a plasma, without negative ions, is usually thin, so that the negative ion density falls rapidly to zero-forming a negative ion density front. We review theoretical, experimental and numerical results giving the spatio-temporal evolution of negative ion density fronts during plasma ignition, the steady state, and extinction (afterglow). During plasma ignition, negative ion fronts are the result of the break of smooth plasma density profiles during nonlinear convection. In a steady-state plasma, the fronts are boundary layers with steepening of ion density profiles due to nonlinear convection also. But during plasma extinction, the ion fronts are of a completely different nature. Negative ions diffuse freely in the plasma core (no convection), whereas the negative ion front propagates towards the chamber walls with a nearly constant velocity. The concept of fronts turns out to be very effective in analysis of plasma density profile evolution in strongly non-isothermal plasmas.

  11. Hydrogen environment embrittlement.

    NASA Technical Reports Server (NTRS)

    Gray, H. R.

    1972-01-01

    Hydrogen embrittlement is classified into three types: internal reversible hydrogen embrittlement, hydrogen reaction embrittlement, and hydrogen environment embrittlement. Characteristics of and materials embrittled by these types of hydrogen embrittlement are discussed. Hydrogen environment embrittlement is reviewed in detail. Factors involved in standardizing test methods for detecting the occurrence of and evaluating the severity of hydrogen environment embrittlement are considered. The effects of test technique, hydrogen pressure, purity, strain rate, stress concentration factor, and test temperature are discussed.

  12. The addiction to negativity.

    PubMed

    Lane, R C; Hull, J W; Foehrenbach, L M

    1991-01-01

    In this paper, we have described a type of resistance that has attracted increasing psychoanalytic attention in recent years. Patients exposed to intense negativity during early life may develop an addiction to negative experience as adolescents and adults, and this may constitute a central organizing feature of their personality. In almost all patients, however, some moments of negativity may be observed. We have traced the developmental origins of an attachment to negativity, drawing especially on psychoanalytic investigations of preoedipal pathology. Manifestations and derivatives of early negativity include anhedonia, attachment to physical pain, fear of success, masochism, deprivation of self and others, and negative voyeurism. In discussing the dynamic functions of negativity, we place particular emphasis on two motives: the patient's desires for revenge against early objects that have been a source of deprivation and frustration; and the defensive function of negativity in helping to express as well as ward off dangerous wishes to merge with the object. Deviant forms of autoerotism are likely to be used by these patients to deal with the reactivation of early experiences of neglect and rejection. When negativity is used as a defense or method of relating to others it can lead to a severe disruption of the psychotherapeutic relationship. We have reviewed suggestions for the management of extreme negativity in treatment. Resolution of the therapist's countertransference reactions, especially induced feelings of frustration, rage, and helplessness, is crucial. Emphasis also has been placed on the patient's desires for revenge against self and object, and the manner in which these may be understood and eventually resolved. Only when patient and therapist begin to investigate the adaptive functions of extreme negativity can this pathological symptom be resolved and the patient's awareness of self and sense of autonomy be enhanced. PMID:1763149

  13. The Evolution of Negation.

    ERIC Educational Resources Information Center

    Croft, William

    1991-01-01

    Discusses a method for extrapolation of diachronic processes from synchronic states, the dynamicization of synchronic typologies, to propose a hitherto unobserved historical source for markers of verbal negation, namely irregular negative existential predicate forms. Explanations are proposed for the occurrence of the attested processes in this…

  14. Learning from Negative Morality.

    ERIC Educational Resources Information Center

    Oser, Fritz K.

    1996-01-01

    Identifies and discusses the elements and applications of learning from negative morality. Negative morality refers to the experience of learning from mistakes thereby creating a body of personal knowledge about "what not to do." This knowledge not only protects individuals but steers them to the right behavior. (MJP)

  15. Hydrogen scavengers

    SciTech Connect

    Carroll, David W.; Salazar, Kenneth V.; Trkula, Mitchell; Sandoval, Cynthia W.

    2002-01-01

    There has been invented a codeposition process for fabricating hydrogen scavengers. First, a .pi.-bonded allylic organometallic complex is prepared by reacting an allylic transition metal halide with an organic ligand complexed with an alkali metal; and then, in a second step, a vapor of the .pi.-bonded allylic organometallic complex is combined with the vapor of an acetylenic compound, irradiated with UV light, and codeposited on a substrate.

  16. On Negative Mass

    NASA Astrophysics Data System (ADS)

    Belletête, Jonathan; Paranjape, M. B.

    2013-06-01

    The Schwarzschild solution to the matter free, spherically symmetric Einstein equations has one free parameter, the mass. But the mass can be of any sign. What is the meaning of the negative mass solutions? The answer to this question for the case of a pure Schwarzschild negative mass black solution is still elusive, however, in this essay, we will consider negative mass solutions within a Schwarzschild-de Sitter geometry. We show that there exist reasonable configurations of matter, bubbles of distributions of matter, that satisfy the dominant energy condition everywhere, that are nonsingular and well behaved everywhere, but correspond to the negative mass Schwarzschild-de Sitter geometry outside the matter distribution. These negative mass bubbles could occur as the end state of a quantum tunneling transition.

  17. Hydrogen environment embrittlement

    NASA Technical Reports Server (NTRS)

    Gray, H. R.

    1972-01-01

    Hydrogen embrittlement is classified into three types: internal reversible hydrogen embrittlement, hydrogen reaction embrittlement, and hydrogen environment embrittlement. Characteristics of and materials embrittled by these types of hydrogen embrittlement are discussed. Hydrogen environment embrittlement is reviewed in detail. Factors involved in standardizing test methods for detecting the occurrence of and evaluating the severity of hydrogen environment embrittlement are considered. The effect of test technique, hydrogen pressure, purity, strain rate, stress concentration factor, and test temperature are discussed. Additional research is required to determine whether hydrogen environment embrittlement and internal reversible hydrogen embrittlement are similar or distinct types of embrittlement.

  18. The injection of microorganisms into an atmospheric pressure rf-driven microplasma

    NASA Astrophysics Data System (ADS)

    Maguire, P. D.; Mahony, C. M. O.; Diver, D.; Mariotti, D.; Bennet, E.; Potts, H.; McDowell, D. A.

    2013-09-01

    The introduction of living organisms, such as bacteria, into atmospheric pressure microplasmas offers a unique means to study certain physical mechanisms in individual microorganisms and also help understand the impact of macroscopic entities and liquid droplets on plasma characteristics. We present the characterization of an RF-APD operating at 13.56 MHz and containing microorganisms in liquid droplets emitted from a nebulizer, with the spray entrained in a gas flow by a gas shroud and passed into the plasma source. We report successful microorganism injection and transmission through the plasma with stable plasma operation of at least one hour. Diagnostics include RF electrical characterization, optical emission spectrometry and electrostatic deflection to investigate microorganism charging. A close-coupled Impedans Octiv VI probe indicates source efficiencies of 10 to 15%. The introduction of the droplets/microorganisms results in increased plasma conductivity and reduced capacitance, due to their impact on electron density and temperature. An electrical model will be presented based on diagnostic data and deflection studies with input from simulations of charged aerosol diffusion and evaporation. Engineering and Physical Sciences Research Council EP/K006088, EP/K006142.

  19. Application of a pulsed, RF-driven, multicusp source for low energy plasma immersion ion implantation

    SciTech Connect

    Wengrow, A.B.; Leung, K.N.; Perkins, L.T.; Pickard, D.S.; Rickard, M.; Williams, M.D.; Tucker, M.

    1996-06-01

    The multicusp ion source can produce large volumes of uniform, quiescent, high density plasmas. A plasma chamber suited for plasma immersion ion implantation (PIII) was readily made. Conventional PIII pulses the bias voltage applied to the substrate which is immersed in a CW mode plasma. Here, a method by which the plasma itself is pulsed was developed. Typically pulse lengths of 500 {mu}s are used and are much shorter than that of the substrate voltage pulse (5-15 ms). This approach, together with low gas pressures and low bias voltages, permits the constant energy implantation of an entire wafer simultaneously without glow discharge. Results show that this process can yield implant currents of up to 2.5 mA/cm{sup 2}; thus very short implant times can be achieved. Uniformity of the ion flux is also discussed. As this method can be scaled to any dimension, it can be made to handle any size wafer.

  20. Simulations of the GEC rf-driven plasma reactor with He

    SciTech Connect

    Riley, M.E.; Drallos, P.; McGrath, R.

    1992-12-01

    The authors have developed a model of the electronic processes occuring in a He plasma entailing 12 electronic transitions, 5 levels (some composite), and trapped radiative decay of certain states. Along with surface scattering conditions, momentum transfer, charge transfer, and diffusion, these processes are incorporated into a 1D-2V electron Boltzmann equation (BE) code with time evolution alternating between BE and fluid equations (FE) dynamics. The FE electronic rates are obtained periodically from the BE. The ions and neutrals are completely FE. The BE-FE hybrid works well, enabling a study of the plasma and reaction kinetics to near steady state of the actual laboratory system.

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

    DOEpatents

    Kwan, Joe; Ji, Qing

    2014-05-20

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

  2. RF driven sulfur lamp having driving electrodes which face each other

    DOEpatents

    Gabor, G.; Orr, T.R.; Greene, C.M.; Crawford, D.G.; Berman, S.M.

    1999-06-22

    A high intensity discharge lamp without mercury is disclosed radiating a selected spectrum of which can be almost entirely in the visible range from an envelope that contains a sulfur containing substance. The lamp utilizes a signal source that generates an excitation signal that is externally coupled to the exterior surface of the envelope to excite the enclosed sulfur containing substance. Various embodiments of the lamp use electrodes adjacent the envelope to couple the excitation signal thereto with the face of the electrodes shaped to complement the shape of the exterior surface of the envelope. Two shapes discussed are spherical and cylindrical. To minimize filamentary discharges each envelope may include an elongated stem affixed to the exterior thereof whereby a rotational subsystem spins the envelope. In yet another embodiment the envelope has a Dewar configuration with two electrodes, one positioned near the external curved side surface of the body, and a second to the inner surface of the hole through the envelope. Further, the envelope may contain a backfill of a selected inert gas to assist in the excitation of lamp with that backfill at a pressure of less than 1 atmosphere, wherein the backfill pressure is directly related to the increase or decrease of peak output and inversely related to the increase and decrease of the emitted spectrum from the envelope. The emitting fill can be less than 6 mg/cc, or at least 2 mg/cc of the envelope of a sulfur containing substance. 17 figs.

  3. RF driven sulfur lamp having driving electrodes arranged to cool the lamp

    DOEpatents

    Gabor, G.; Orr, T.R.; Greene, C.M.; Crawford, D.G.; Berman, S.M.

    1998-10-20

    A high intensity discharge lamp without mercury is disclosed radiating a selected spectrum of which can be almost entirely in the visible range from an envelope that contains a sulfur containing substance. The lamp utilizes a signal source that generates an excitation signal that is externally coupled to the exterior surface of the envelope to excite the enclosed sulfur containing substance. Various embodiments of the lamp use electrodes adjacent the envelope to couple the excitation signal thereto with the face of the electrodes shaped to complement the shape of the exterior surface of the envelope. Two shapes discussed are spherical and cylindrical. To minimize filamentary discharges each envelope may include an elongated stem affixed to the exterior thereof whereby a rotational subsystem spins the envelope. In yet another embodiment the envelope has a Dewar configuration with two electrodes, one positioned near the external curved side surface of the body, and a second to the inner surface of the hole through the envelope. Further, the envelope may contain a backfill of a selected inert gas to assist in the excitation of lamp with that backfill at a pressure of less than 1 atmosphere, wherein the backfill pressure is directly related to the increase or decrease of peak output and inversely related to the increase and decrease of the emitted spectrum from the envelope. The emitting fill can be less than 6 mg/cc, or at least 2 mg/cc of the envelope of a sulfur containing substance. 17 figs.

  4. RF driven sulfur lamp having driving electrodes which face each other

    DOEpatents

    Gabor, George; Orr, Thomas Robert; Greene, Charles Maurice; Crawford, Douglas Gordon; Berman, Samuel Maurice

    1999-01-01

    A high intensity discharge lamp without mercury is disclosed radiating a selected spectrum of which can be almost entirely in the visible range from an envelope that contains a sulfur containing substance. The lamp utilizes a signal source that generates an excitation signal that is externally coupled to the exterior surface of the envelope to excite the enclosed sulfur containing substance. Various embodiments of the lamp use electrodes adjacent the envelope to couple the excitation signal thereto with the face of the electrodes shaped to complement the shape of the exterior surface of the envelope. Two shapes discussed are spherical and cylindrical. To minimize filamentary discharges each envelope may include an elongated stem affixed to the exterior thereof whereby a rotational subsystem spins the envelope. In yet another embodiment the envelope has a Dewar configuration with two electrodes, one positioned near the external curved side surface of the body, and a second to the inner surface of the hole through the envelope. Further, the envelope may contain a backfill of a selected inert gas to assist in the excitation of lamp with that backfill at a pressure of less than 1 atmosphere, wherein the backfill pressure is directly related to the increase or decrease of peak output and inversely related to the increase and decrease of the emitted spectrum from the envelope. The emitting fill can be less than 6 mg/cc, or at least 2 mg/cc of the envelope of a sulfur containing substance.

  5. RF driven sulfur lamp having driving electrodes arranged to cool the lamp

    DOEpatents

    Gabor, George; Orr, Thomas Robert; Greene, Charles Maurice; Crawford, Douglas Gordon; Berman, Samuel Maurice

    1998-01-01

    A high intensity discharge lamp without mercury is disclosed radiating a selected spectrum of which can be almost entirely in the visible range from an envelope that contains a sulfur containing substance. The lamp utilizes a signal source that generates an excitation signal that is externally coupled to the exterior surface of the envelope to excite the enclosed sulfur containing substance. Various embodiments of the lamp use electrodes adjacent the envelope to couple the excitation signal thereto with the face of the electrodes shaped to complement the shape of the exterior surface of the envelope. Two shapes discussed are spherical and cylindrical. To minimize filamentary discharges each envelope may include an elongated stem affixed to the exterior thereof whereby a rotational subsystem spins the envelope. In yet another embodiment the envelope has a Dewar configuration with two electrodes, one positioned near the external curved side surface of the body, and a second to the inner surface of the hole through the envelope. Further, the envelope may contain a backfill of a selected inert gas to assist in the excitation of lamp with that backfill at a pressure of less than 1 atmosphere, wherein the backfill pressure is directly related to the increase or decrease of peak output and inversely related to the increase and decrease of the emitted spectrum from the envelope. The emitting fill can be less than 6 mg/cc, or at least 2 mg/cc of the envelope of a sulfur containing substance.

  6. RUI: Structure and Behavior of RF-Driven Plasma Filaments in High-Pressure Gases

    SciTech Connect

    Burin, Michael

    2014-11-18

    The filamentary discharge seen within commercial plasma globes is commonly enjoyed, yet not well understood. We investigate filament properties in a plasma globe using a variable high voltage amplifier. Results from the 3-year grant period and their physics are discussed.

  7. ADX: A high Power Density, Advanced RF-Driven Divertor Test Tokamak for PMI studies

    NASA Astrophysics Data System (ADS)

    Whyte, Dennis; ADX Team

    2015-11-01

    The MIT PSFC and collaborators are proposing an advanced divertor experiment, ADX; a divertor test tokamak dedicated to address critical gaps in plasma-material interactions (PMI) science, and the world fusion research program, on the pathway to FNSF/DEMO. Basic ADX design features are motivated and discussed. In order to assess the widest range of advanced divertor concepts, a large fraction (>50%) of the toroidal field volume is purpose-built with innovative magnetic topology control and flexibility for assessing different surfaces, including liquids. ADX features high B-field (>6 Tesla) and high global power density (P/S ~ 1.5 MW/m2) in order to access the full range of parallel heat flux and divertor plasma pressures foreseen for reactors, while simultaneously assessing the effect of highly dissipative divertors on core plasma/pedestal. Various options for efficiently achieving high field are being assessed including the use of Alcator technology (cryogenic cooled copper) and high-temperature superconductors. The experimental platform would also explore advanced lower hybrid current drive and ion-cyclotron range of frequency actuators located at the high-field side; a location which is predicted to greatly reduce the PMI effects on the launcher while minimally perturbing the core plasma. The synergistic effects of high-field launchers with high total B on current and flow drive can thus be studied in reactor-relevant boundary plasmas.

  8. Kriging without negative weights

    SciTech Connect

    Szidarovszky, F.; Baafi, E.Y.; Kim, Y.C.

    1987-08-01

    Under a constant drift, the linear kriging estimator is considered as a weighted average of n available sample values. Kriging weights are determined such that the estimator is unbiased and optimal. To meet these requirements, negative kriging weights are sometimes found. Use of negative weights can produce negative block grades, which makes no practical sense. In some applications, all kriging weights may be required to be nonnegative. In this paper, a derivation of a set of nonlinear equations with the nonnegative constraint is presented. A numerical algorithm also is developed for the solution of the new set of kriging equations.

  9. Negative birefringent polyimide films

    NASA Technical Reports Server (NTRS)

    Harris, Frank W. (Inventor); Cheng, Stephen Z. D. (Inventor)

    1994-01-01

    A negative birefringent film, useful in liquid crystal displays, and a method for controlling the negative birefringence of a polyimide film is disclosed which allows the matching of an application to a targeted amount of birefringence by controlling the degree of in-plane orientation of the polyimide by the selection of functional groups within both the diamine and dianhydride segments of the polyimide which affect the polyimide backbone chain rigidity, linearity, and symmetry. The higher the rigidity, linearity and symmetry of the polyimide backbone, the larger the value of the negative birefringence of the polyimide film.

  10. Evaluation of negative ion distribution changes by image processing diagnostic

    SciTech Connect

    Ikeda, K. Nakano, H.; Tsumori, K.; Kisaki, M.; Nagaoka, K.; Tokuzawa, T.; Osakabe, M.; Takeiri, Y.; Kaneko, O.; Geng, S.

    2015-04-08

    Distributions of hydrogen Balmer-α (H{sub α}) intensity and its reduction behavior close to a plasma grid (PG) surface have been observed by a spectrally selective imaging system in an arc discharge type negative hydrogen ion source in National Institute for Fusion Science. H{sub α} reduction indicates a reduction of negative hydrogen ions because the mutual neutralization process between H{sup +} and H{sup −} ions causes the dominant excitation process for H{sub α} emission in the rich H{sup −} condition such as in ionic plasma. We observed a significant change in H{sub α} reduction distribution due to change in the bias voltage, which is used to suppress the electron influx. Small H{sub α} reduction in higher bias is likely because the production of negative ions is suppressed by the potential difference between the plasma and PG surface.

  11. Negative electrode composition

    DOEpatents

    Kaun, Thomas D.; Chilenskas, Albert A.

    1982-01-01

    A secondary electrochemical cell and a negative electrode composition for use therewith comprising a positive electrode containing an active material of a chalcogen or a transiton metal chalcogenide, a negative electrode containing a lithium-aluminum alloy and an amount of a ternary alloy sufficient to provide at least about 5 percent overcharge capacity relative to a negative electrode solely of the lithium-aluminum alloy, the ternary alloy comprising lithium, aluminum, and iron or cobalt, and an electrolyte containing lithium ions in contact with both of the positive and the negative electrodes. The ternary alloy is present in the electrode in the range of from about 5 percent to about 50 percent by weight of the electrode composition and may include lithium-aluminum-nickel alloy in combination with either the ternary iron or cobalt alloys. A plurality of series connected cells having overcharge capacity can be equalized on the discharge side without expensive electrical equipment.

  12. Logo and Negative Numbers.

    ERIC Educational Resources Information Center

    Strawn, Candace A.

    1998-01-01

    Describes LOGO's turtle graphics capabilities based on a sixth-grade classroom's activities with negative numbers and Logo programming. A sidebar explains LOGO and offers suggestions to teachers for using LOGO effectively. (LRW)

  13. Atomic negative ions

    SciTech Connect

    Brage, T.

    1991-01-01

    We review some of the recent progress in the studies of alkaline-earth, negative ions. Computations of autodetachment rates, electron affinities and transition wavelengths are discussed and some new and improved results are given.

  14. Atomic negative ions

    SciTech Connect

    Brage, T.

    1991-12-31

    We review some of the recent progress in the studies of alkaline-earth, negative ions. Computations of autodetachment rates, electron affinities and transition wavelengths are discussed and some new and improved results are given.

  15. Hydrogen detector

    DOEpatents

    Kanegae, Naomichi; Ikemoto, Ichiro

    1980-01-01

    A hydrogen detector of the type in which the interior of the detector is partitioned by a metal membrane into a fluid section and a vacuum section. Two units of the metal membrane are provided and vacuum pipes are provided independently in connection to the respective units of the metal membrane. One of the vacuum pipes is connected to a vacuum gauge for static equilibrium operation while the other vacuum pipe is connected to an ion pump or a set of an ion pump and a vacuum gauge both designed for dynamic equilibrium operation.

  16. Negative affixes in medical English.

    PubMed

    Dzuganova, B

    2006-01-01

    Many medical terms have negative meaning expressed by means of a negative prefix or suffix. The most frequently used negative prefixes are: a-, dis-, in-, non-, and un-. There is only one negative suffix -less (Ref. 15). PMID:17125069

  17. Mechanochemical hydrogenation of coal

    DOEpatents

    Yang, Ralph T.; Smol, Robert; Farber, Gerald; Naphtali, Leonard M.

    1981-01-01

    Hydrogenation of coal is improved through the use of a mechanical force to reduce the size of the particulate coal simultaneously with the introduction of gaseous hydrogen, or other hydrogen donor composition. Such hydrogen in the presence of elemental tin during this one-step size reduction-hydrogenation further improves the yield of the liquid hydrocarbon product.

  18. Negative Halogen Ions for Fusion Applications

    SciTech Connect

    Grisham, L.R.; Kwan, J.W.; Hahto, S.K.; Hahto, S.T.; Leung, K.N.; Westenskow, G.

    2006-01-01

    Over the past quarter century, advances in hydrogen negative ion sources have extended the usable range of hydrogen isotope neutral beams to energies suitable for large magnetically confined fusion devices. Recently, drawing upon this experience, negative halogen ions have been proposed as an alternative to positive ions for heavy ion fusion drivers in inertial confinement fusion, because electron accumulation would be prevented in negative ion beams, and if desired, the beams could be photo-detached to neutrals. This paper reports the results of an experiment comparing the current density and beam emittance of Cl+ and Cl- extracted from substantially ion-ion plasmas with that of Ar+ extracted from an ordinary electron-ion plasma, all using the same source, extractor, and emittance scanner. At similar discharge conditions, the Cl- current was typically 85 – 90% of the positive chlorine current, with an e-/ Cl- ratio as low as seven without grid magnets. The Cl- was as much as 76% of the Ar+ current from a discharge with the same RF drive. The minimum normalized beam emittance and inferred ion temperatures of Cl+, Cl-, and Ar+ were all similar, so the current density and optical quality of Cl- appear as suitable for heavy ion fusion driver applications as a positive noble gas ion of similar mass. Since F, I, and Br should all behave similarly in an ion source, they should also be suitable as driver beams.

  19. Hydrogen peroxide poisoning

    MedlinePlus

    ... peroxide is used in these products: Hydrogen peroxide Hair bleach Some contact lens cleaners Note: Household hydrogen peroxide ... it contains 97% water and 3% hydrogen peroxide. Hair bleaches are stronger. They usually have a concentration of ...

  20. Negative pressure wound therapy.

    PubMed

    Thompson, James T; Marks, Malcolm W

    2007-10-01

    Negative pressure wound therapy has become an increasingly important part of wound management. Over the last decade, numerous uses for this method of wound management have been reported, ranging from acute and chronic wounds, to closure of open sternal and abdominal wounds, to assistance with skin grafts. The biophysics behind the success of this treatment largely have focused on increased wound blood flow, increased granulation tissue formation, decreased bacterial counts, and stimulation of wound healing pathways through shear stress mechanisms. The overall success of negative pressure wound therapy has led to a multitude of clinical applications, which are discussed in this article. PMID:17967622

  1. Extracted current saturation in negative ion sources

    SciTech Connect

    Mochalskyy, S.; Lifschitz, A. F.; Minea, T.

    2012-06-01

    The extraction of negatively charged particles from a negative ion source is one of the crucial issues in the development of the neutral beam injector system for future experimental reactor ITER. Full 3D electrostatic particle-in-cell Monte Carlo collision code - ONIX [S. Mochalskyy et al., Nucl. Fusion 50, 105011 (2010)] - is used to simulate the hydrogen plasma behaviour and the extracted particle features in the vicinity of the plasma grid, both sides of the aperture. It is found that the contribution to the extracted negative ion current of ions born in the volume is small compared with that of ions created at the plasma grid walls. The parametric study with respect to the rate of negative ions released from the walls shows an optimum rate. Beyond this optimum, a double layer builds-up by the negative ion charge density close to the grid aperture surface reducing thus extraction probability, and therefore the extracted current. The effect of the extraction potential and magnetic field magnitudes on the extraction is also discussed. Results are in good agreement with available experimental data.

  2. Charged particle flows in the beam extraction region of a negative ion source for NBI.

    PubMed

    Geng, S; Tsumori, K; Nakano, H; Kisaki, M; Ikeda, K; Osakabe, M; Nagaoka, K; Takeiri, Y; Shibuya, M; Kaneko, O

    2016-02-01

    Experiments by a four-pin probe and photodetachment technique were carried out to investigate the charged particle flows in the beam extraction region of a negative hydrogen ion source for neutral beam injector. Electron and positive ion flows were obtained from the polar distribution of the probe saturation current. Negative hydrogen ion flow velocity and temperature were obtained by comparing the recovery times of the photodetachment signals at opposite probe tips. Electron and positive ions flows are dominated by crossed field drift and ambipolar diffusion. Negative hydrogen ion temperature is evaluated to be 0.12 eV. PMID:26931985

  3. Charged particle flows in the beam extraction region of a negative ion source for NBI

    NASA Astrophysics Data System (ADS)

    Geng, S.; Tsumori, K.; Nakano, H.; Kisaki, M.; Ikeda, K.; Osakabe, M.; Nagaoka, K.; Takeiri, Y.; Shibuya, M.; Kaneko, O.

    2016-02-01

    Experiments by a four-pin probe and photodetachment technique were carried out to investigate the charged particle flows in the beam extraction region of a negative hydrogen ion source for neutral beam injector. Electron and positive ion flows were obtained from the polar distribution of the probe saturation current. Negative hydrogen ion flow velocity and temperature were obtained by comparing the recovery times of the photodetachment signals at opposite probe tips. Electron and positive ions flows are dominated by crossed field drift and ambipolar diffusion. Negative hydrogen ion temperature is evaluated to be 0.12 eV.

  4. Hydrogen Permeation Barrier Coatings

    SciTech Connect

    Henager, Charles H.

    2008-01-01

    Gaseous hydrogen, H2, has many physical properties that allow it to move rapidly into and through materials, which causes problems in keeping hydrogen from materials that are sensitive to hydrogen-induced degradation. Hydrogen molecules are the smallest diatomic molecules, with a molecular radius of about 37 x 10-12 m and the hydrogen atom is smaller still. Since it is small and light it is easily transported within materials by diffusion processes. The process of hydrogen entering and transporting through a materials is generally known as permeation and this section reviews the development of hydrogen permeation barriers and barrier coatings for the upcoming hydrogen economy.

  5. The Negative Repetition Effect

    ERIC Educational Resources Information Center

    Mulligan, Neil W.; Peterson, Daniel J.

    2013-01-01

    A fundamental property of human memory is that repetition enhances memory. Peterson and Mulligan (2012) recently documented a surprising "negative repetition effect," in which participants who studied a list of cue-target pairs twice recalled fewer targets than a group who studied the pairs only once. Words within a pair rhymed, and…

  6. [Chemotherapies of negative schizophrenia].

    PubMed

    Petit, M; Dollfus, S

    1991-01-01

    Five years ago, Goldberg claimed that negative symptoms of schizophrenia do respond to neuroleptics. This apparent discovery is, in fact, a very common way of thinking for European schools of psychiatry, specially the French one guided by Delay and Deniker. Initially focused on reserpine and some alerting phenothiazines such as thioproperazine, this opinion has been extended to benzamides in the 1970s. The analysis of the publications devoted to this point indicates that several drugs are actually considered as potent disinhibitors (i.e. active on negative symptoms of schizophrenia): Phenothiazines: As shown in the controlled studies by Itil (1971), Poirier-Littré (1988), fluphenazine and pipotiazine improve the BPRS anergia factor and the SANS score. Butyrophenones: The first description of the "imipramine like" effect of trifluperidol by Janssen (1959) initiated the studies by Gallant (1960), Fox (1963). They compared trifluperidol at low doses versus haloperidol and chlorpromazine at medium and high doses, BPRS anergia factor improved only at low doses. Diphenylbutylpiperidines (DPBP): Meltzer's review (1986) concluded to the efficacy of such drugs on negative symptoms appearing as a specific biochemical relationship effect. A definite analysis about doses leads to a very different interpretation: DPBP low doses and only low doses improved negative symptoms as much as some low doses of phenothiazines. On the opposite, DPBP, phenothiazines and butyrophenones high doses are inefficient.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1683624

  7. Hydrogen embrittlement in nickel-hydrogen cells

    NASA Technical Reports Server (NTRS)

    Gross, Sidney

    1989-01-01

    It was long known that many strong metals can become weakened and brittle as the result of the accumulation of hydrogen within the metal. When the metal is stretched, it does not show normal ductile properties, but fractures prematurely. This problem can occur as the result of a hydrogen evolution reaction such as corrosion or electroplating, or due to hydrogen in the environment at the metal surface. High strength alloys such as steels are especially susceptible to hydrogen embrittlement. Nickel-hydrogen cells commonly use Inconel 718 alloy for the pressure container, and this also is susceptible to hydrogen embrittlement. Metals differ in their susceptibility to embrittlement. Hydrogen embrittlement in nickel-hydrogen cells is analyzed and the reasons why it may or may not occur are discussed. Although Inconel 718 can display hydrogen embrittlement, experience has not identified any problem with nickel-hydrogen cells. No hydrogen embrittlement problem is expected with the 718 alloy pressure container used in nickel-hydrogen cells.

  8. Think (Gram) negative!

    PubMed Central

    2010-01-01

    The increasing prevalence of multiresistant Gram-negative bacteria of the Enterobacteriaceae family in Europe is a worrisome phenomenon. Extended spectrum betalactamase-producing Escherichia coli strains are widespread in the community and are frequently imported into the hospital. Of even more concern is the spread of carbapenem-resistant strains of Klebsiella spp. from regions where they are already endemic. Antibiotic use is a main driver of antibiotic resistance, which again increases broad spectrum antibiotic use, resulting in a vicious circle that is difficult to interrupt. The present commentary highlights important findings of a surveillance study of antimicrobial use and resistance in German ICUs over 8 years with a focus on Gram-negative resistance. PMID:20587087

  9. Negative refraction and superconductivity

    NASA Astrophysics Data System (ADS)

    Amariti, Antonio; Forcella, Davide; Mariotti, Alberto; Siani, Massimo

    2011-10-01

    We discuss exotic properties of charged hydrodynamical systems, in the broken superconducting phase, probed by electromagnetic waves. Motivated by general arguments from hydrodynamics, we observe that negative refraction, namely the propagation in opposite directions of the phase velocities and of the energy flux, is expected for low enough frequencies. We corroborate this general idea by analyzing a holographic superconductor in the AdS/CFT correspondence, where the response functions can be explicitly computed. We study the dual gravitational theory both in the probe and in the backreacted case. We find that, while in the first case the refractive index is positive at every frequency, in the second case there is negative refraction at low enough frequencies. This is in agreement with hydrodynamic considerations.

  10. Negative Emissions Technology

    NASA Astrophysics Data System (ADS)

    Day, Danny

    2006-04-01

    Although `negative emissions' of carbon dioxide need not, in principle, involve use of biological processes to draw carbon out of the atmosphere, such `agricultural' sequestration' is the only known way to remove carbon from the atmosphere on time scales comparable to the time scale for anthropogenic increases in carbon emissions. In order to maintain the `negative emissions' the biomass must be used in such a way that the resulting carbon dioxide is separated and permanently sequestered. Two options for sequestration are in the topsoil and via geologic carbon sequestration. The former has multiple benefits, but the latter also is needed. Thus, although geologic carbon sequestration is viewed skeptically by some environmentalists as simply a way to keep using fossil fuels---it may be a key part of reversing accelerating climate forcing if rapid climate change is beginning to occur. I will first review the general approach of agricultural sequestration combined with use of resulting biofuels in a way that permits carbon separation and then geologic sequestration as a negative emissions technology. Then I discuss the process that is the focus of my company---the EPRIDA cycle. If deployed at a sufficiently large scale, it could reverse the increase in CO2 concentrations. I also estimate of benefits --carbon and other---of large scale deployment of negative emissions technologies. For example, using the EPRIDA cycle by planting and soil sequestering carbon in an area abut In 3X the size of Texas would remove the amount of carbon that is being accumulated worldwide each year. In addition to the atmospheric carbon removal, the EPRIDA approach also counters the depletion of carbon in the soil---increasing topsoil and its fertility; reduces the excess nitrogen in the water by eliminating the need for ammonium nitrate fertilizer and reduces fossil fuel reliance by providing biofuel and avoiding natural gas based fertilizer production.