- Email: [email protected]
A convenient method for the measurement of species composition from an intense neutral beam
Classified
abstracts
4540-4547
J111+‘11 where
J and 4 are the elemental impingement rates and thermal sticking probabilities, respectively. At any value of r investigated, a value of V, could be found such that for negative substrate biases greater than this value, the films were single phase. No preferential resputtering was observed for V, up to 250 V in films in which JsbQsb = J,,,$,,,. Thus, the range of r and T$ values over which single-phase stoichiometric films could be deposited from the vapour phase was extended by low energy ion bombardment of the growing film.
A H Eltoukhy
et al, J Vuc Sci Technol,
16 (2),
500 eV e- impacting on SS (304) samples (- 1000 cm* surface area) prepared by : (i) a degrease treatment; (ii) an acid cleaning (l/3 HF, l/3 HNO,, l/3 H,Ol, (iii) concentrated HF. Three separate samples were analysed for the first two treatments allowing the sample-tosample variation to be determined (10’&20:/; yield variations). The unit yield energy E0 (electron energy for which the total secondary electron emission is 1.0) has also been measured for each of the above treatments.
D Edwards,
J Vat Sci Technol,
16 (2), 1979, 758-760.
1979, 321-323 4544. Synchrotron-radiation-induced storage ring vacuum system. (USA)
32.
EVACUATION
AND
SEALING
32 4540.
Ion-acceleration mechanisms in vacuum diodes. (USA) A study of proton acceleration in a Lute diode has been carried out. Measurements of beam-neutralization times, electron and ion energy distributions, and induced radioactivity have been made. These measurements show that the effective potential-well depth at the beam head is less than the electron-accelerating voltage. Also, the relative activity of Mylar and copper foils indicates that ion energy increases with mass for Z = 1 particles. Both of these observations are consistent with ion acceleration resulting from a moving potential well. R J Adler and J A Nation, J Appl Phys, 50 (7), 1979, 5025-5027.
33.
NUCLEONICS
4541. Ultra-high vacuum compatibility materials: K-rami& and ATJ graphite.
of two possible
fusion
33 reactor
(USA) Outgassing characteristics of K-rami (manufactured by Kaman Nuclear) and ATJ graphite were evaluated under various treatments. For K-ramic,O total outgassing rates of 2 x 10m9 torr I s-’ cm-’ unbaked and 7 x IO-” torr Is-’ cme2 baked were measured. Mass spectroscopic measurements showed H, and CO to be the dominant residual gases. For ATJ, graphite the treatment consisted of repeated heatings in CCICI,O to 1250 K as well as repeated exposures to atmosphere. Residual gas analysis measured the time dependence of desorbed quantities of H2, H,O, CO,, CO and CH,. During the initial heating, the maximum species atom to lattice atom ratios were obtained yielding values of 2.6 >: IO-” for Hz, 3.4 x 10e5 for HZO, 1.6 x 10ms for CO,, 7.6 Y 10e6 for CO, and 5.2 x 10e6 for CHa. The total outgassed material from the graphite sample decreased by a factor of 10” after successive heatings.
R Moore,
J Vat Sci Technol,
16 (2), 1979, 748-751. 33
4542. Observations of changes in residual with discharge cleaning in PLT. (USA)
gas and surface
composition
Hydrogen discharge cleaning of the PLT vacuum vessel has been studied by mass spectroscopy of desorbed gases and surface analysis of exposed samples. Several modes of vessel conditioning have been studied to date: (I) a high-power discharge cleaning (PDC) mode, with a peak power density lo the vessel wall P, -0.6 W cm-* and a peak electron temperature T, - 100 eV: (2) low-power (Taylor-type) discharge cleaning (TDC) with P, -0.05 W cm-’ and T, < 5 eV. The predominant residual gases produced during PDC are CH, v IO-’ torr), whereas TDC pro(l-5 x 10e6 torr) and CO (I-IO duced primarily Hz0 (l-2 x 10e6 torr) and CH, (I-IO :.’ IO-’ torr). The transient behaviour of the residual gases is not simply related to pumping time constants, and provides evidence for the role of surface chemical reactions and diffusion on the formation of these gases. In situ surface analysis of hydrocarbon-covered stainless steel has shown significant decreases in carbon coverage occurring after 103lo4 pulses of either cleaning mode. Observed changes in oxygen coverage are more difficult to interpret because of the presence of the passivation oxide layer on the stainless-steel substrates.
H F Dylla
et al, J Vuc Sci Technol,
4543. Ion and electron steel (304). (USA)
desorption
16 (2). 1979.752-757. of neutral
The vacuum performance of both electron (as well as certain types of fusion reactors) to the desorption of neutral molecules wall by -keV charged particles. In this of Hz, CO, CO* and CH, are reported
molecules
from
33 stainless
and proton storage rings is expected to be sensitive from the vacuum chamber study the desorption yields from 1000 eV Ar+ and
heating
effects
in
the
33 PEP
The advent of large high-energy storage rings has facilitated the need for more detailed analysis of synchrotron radiation interactions and related thermal effects. In the PEP storage ring, a maximum of 5 MW of synchrotron radiation with a critical energy of 44 keV will interact with 2200 m of vacuum hardware. A Monte Carlo based computer code, EGS, was employed to follow electromagnetic reactions of the synchrotron radiation through various computerized models of the vacuum system. The computer simulated structures with hundreds of discrete rkgions and varying materials. Results showed that typically 70”/, of the svnchrotron power was absorbed in incident surfaces and 204/, was scattered outside the vacuum vessel. The remaining power was deposited in varied vacuum components. Sensitive PEP ring components, particularly distributed ion pumps, were subsequently designed to minimize power absorption and to maximize cooling effects. Other thermal calculations were employed to design for minimal wall temperatures in areas of direct synchrotron radiation incidence.
T W Martin,
J Yuc Sci Techttol.
16 (2), 1979, 761-762. 33
4545.
Residual
gas analysis
in the ISX-A
tokamak.
(USA) A computer-controlled mass analyser was utilized to observe the residual gases in the ISX-A tokamak. This residual gas analysis (RCA) system enabled time resolved measurements of preselected m/e peak heights to be made during and after tokamak discharges. Routine mass scans were also made and displayed in the form of semilogarithmic plots of partial pressure (torr) vs m/e. Wall conditioning of the stainless steel torus consisted of hydrogen discharge cleaning and titanium gettering. which ultimately produced gauge pressures on the order of IO-’ and 10e9 torr, respectively. The dominant plasma impurities, carbon and oxygen, were observed by the RCA as light hydrocarbons and water vapour. Entrapment of deuterium by the walls was investigated by monitoring the residual Dz content after the working gas was changed lo Hz. The effective nuclear charge (Z.,,) was found to be proportional lo the residual contaminants measured by the RGA immediately following a discharge.
J E Simpkins
et al, J Vat Sci Techtrol,
4546.
impurity
16 (2). 1979, 763-765. 33
Surface
studies
in the ISX-A
tokamak.
(USA)
The Impurity Study Experiment (ISX-A) was a tokamak designed to study impurity sources, plasma wall interactions, impurity behaviour within the plasma, and related phenomena. An Auger electron spectrometer, attached to the tokamak by means of a uhv sample transfer system. has been the primary tool used for surface studies of the first wall. Stainless steel samples positioned at the wall edge were used to follow the progressive ‘clean-up’ of the torus wall. Cleaning consisted of low energy hydrogen discharge plasmas, and later titanium gettering. The principal contaminants initially were carbon, oxygen and sulphur. As cleaning proceeded, the surface oxide layers were reduced to substoichiometric levels, and the carbon deposits appeared to be converted to metallic carbides. The sulphur was largely removed. A decrease in the effective nuclear charge of the plasma could be correlated with these surface changes. Discharge cleaning reduced Zcrr from -4 to 1.6 over a period of several months while titanium gettering produced values approaching 1.0.
L C Emerson
et al, J Vuc Sci Technol,
16 (2). 1979, 766-768. 33
4547. A convenient method for the measurement from an intense neutral beam. (USA)
of species composition
We present a method to infer the approximate species mixture neutral beam sources which accelerate positive hydrogen ions. idealized neutral beam is specified by the accelerating voltage, neutralizer thickness (molecules of hydrogen per cm*), and
of An the the 349
Classified
abstracts
4548-4556
currents of extracted H+, Hz+ and H3+. These currents define two independent ratios which lie within a narrow parameter region and which can be determined by two independent measurements downstream from the source. The two suitable parameters are: (I) the ratio of neutral beam to total beam power; and (2) the ratio of hydrogen produced by the neutral beam in the target volume to the hydrogen produced by the total beam. We give experimental results from the 10 x 10 cm2 120 keV test stand at the Lawrence Berkeley Laboratory. R R Smith and J W Steams, Rev. Sci Imrrrrm, 50 (9). 1979, 1070-1073.
33 4548. Vacuum photodiode detector ip a tokamak plasma. (USA)
array
for broadband
uv detection
An array of vacuum photodiode detectors has been used to monitor discharge equilibrium, stability and cleanliness in the Macrotor tokamak. These detectors use the photoelectric effect on small tungsten plates to measure uv emission in the band h -200-1200 8, and so are sensitive mainly to impurity line radiation in Macrotor. The response of this system to controlled impurity contamination experiments and lo disruptions is described. The design, construction and background problems associated with these detectors are discussed in detail.
S J Zweben
et al, Rev Sci Itnrrwn,
50 (S), 1979, 972-978. 33
4549.
Fast ion beam-plasma
interaction
system.
(USA) A device has been constructed for the study of the interaction between a fast ion beam and a target plasma of separately controllable parameters. The beam of either hydrogen or helium ions has an energy of l-4 keV and a total current of OS-2 A. The beam energy and beam current can be varied separately. The ion source plasma is created by a pulsed (0.2-10 ms pulse length) discharge in neutral gas at up to 3 x 1O-3 torr. The neutrals are pulsed into the source chamber, allowing the neutral pressure in the target region lo remain less than 5 x 10m5 torr at a 2 Hz repetition rate. The creation of the source plasma can be described by a simple set of equations which predict optimum source design parameters. The target plasma is also produced by a pulsed discharge. Between the target and source chambers the beam is neutralized by electrons drawn from a set of hot filaments. Currently under study is an unstable wave in a field-free plasma excited when the beam velocity is nearly equal to the target electron thermal velocity uhcJ,,, e 3.5 x IO’ cm s-‘. r, = 0.5 eV).
R A Breun
and J R Ferron,
34. ELECTRONICS TECHNOLOGY
AND
Reu Sci Imrrrtm,
HIGH
50 (7),
1979, 862-866.
ALTITUDE
PHYSICS
AND
34 4550. Vacuum ultra-violet spectroscopic apparatus for space- and timeresolved measurements on a single tokamak plasma discharge. (GB) We describe the vacuum ultra-violet spectroscopic apparatus developed for the TFR-600 tokamak and operating between IO and 220 nm. By use of a rotating mirror working at grazing incidence, several spatial profiles (between five and ten, depending on plasma lifetime and mirror rotation speed) of two impurity lines are obtained during a single plasma discharge. (France)
C Breton
et al, J P/IY~ E; Scim/
Im/rrwl,
4551. Microwave discharge source atom and free radical beams. (GB)
for
12 (9),
1979. 894-898.
the production
34 of supersonic
This paper describes the design and construction of a microwave discharge source which operates with a dilute mixture of oxygen molecules in excess helium or neon buffer gas at high pressure (below about 2.6 x 10” Pa, 200 torr). Seeded supersonic beams of oxygen atoms are produced with Mach numbers M 7 5 and translational energies E = 33.6 kJ mol-’ for helium buffer gas and E = 13.5 kJ mol-’ for neon. Oxygen atom beam fluxes of around 5 x IO” atoms/srI s- ’ are obtained using helium buffer gas, and slightly lower fluxes of about I x 10” atom.+-’ s-’ with neon. A supersonic beam of chlorine atoms with similar characteristics has been produced by discharge of a dilute mixture of chlorine molecules in helium buffer gas.
P A Gerry 860. 350
and R Grice,
J Phys E: Scimf
hfrtrm,
12 (9), 1979, 857-
4552. study
Improved version of an electron image tube designs. (GB)
optical
demountable
system
34 to
The study of electron optical characteristics in high-resolution vacuum devices like image converters and intensifiers plays an important part in improving the performance of such devices. The work reported has been carried out using an experimental electron optical demountable system. The paper describes the constructional aspects and the technology involved in developing the system. Some of the salient features such as vacuum engineering details, fabrication of gold photocathode resolution patterns and establishment of essential tolerances in the tube electrode positions are described. Finally, the mode of analysis of image tube designs in this system is mentioned. (India)
L M Rangarajan
et al, J Whys E: Scienf
htrwn,
12 (9), 1979, 845-848. 34
4553. Effect of diffusion pump oil contamination efficiency in the vuv spectral region. (USA)
on diffraction
grating
The efficiency of a concave grating contaminated with diffusion pump oil has been measured and compared with that of an uncontaminated sister grating. At 1216 8, and 4000 A, the contamination has little effect on the efficiency, but at intermediate wavelengths the loss in efIiciency is large. Vapour degreasing provided a partial restoration, and overcoating with gold, a complete restoration of efficiency.
W R Hunter
and D W Angel,
Appl
Opt,
18 (20),
1979, 3506-3509. 34
4554.
Pioneer
Venus
large
probe
neutral
mass spectrometer.
(USA)
A neutral particle mass spectrometer has been constructed to measure the composition and abundance of the atmospheric gases of the planet Venus. This instrument is being flown on the Pioneer Venus Multiprobe and will sample the planet’s atmosphere from an attitude of 67 km to its surface. The mass spectrometer is a single focusing magnetic sector field instrument capable of scanning the mass range from l-208 amu with a sensitivity of better than 1 ppm relative to the dominant gas, CO,. It possesses a unique inlet system which is capable of sampling gases from an environment of 770 K and 100 atm. Operation of the instrument is under the control of a microprocessor. Through this powerful device, a highly efficient peak stepping and data compression program is effected permitting transmission to earth of the entire mass spectral output in only 64 s at a data rate of 40 bits s-’ resulting in an excellent altitude resolution of variations of atmospheric composition. An isotope ratio measurement cell purges an atmospheric sample of active gases yielding an enriched rare gas sample for isotopic ratio analysis. To maintain an ultra-clean vacuum in the mass analyser tube, a combination of ion pumping and chemical gettering is employed. Instrument weight is 11 kg, volume is 10.650 cm’ and power is 14 W. J H Hoffman et al, J Vuc Sci Tm/uro/, 16 (21, 1979, 692-694.
35.
PROCESSING
OF
MATERIALS
4555. Stoichiometry measurements backscattering. (USA)
of GaAs by means of 15 MeV
35 He+ +
The stoichiometry of heat-treated GaAs crystals was measured over the region about 1 pm below the surface by means of 15 MeV He++ backscattering. Samples were annealed for 1 h at various temperatures between 200 and 900°C. The annealing-temperature dependence of the concentration ratio of As to Ga in the above-mentioned region shows abrupt change at around 250°C and at around 800°C. For annealing at 300-700°C. this ratio (0.81 & 0.05) is almost independent of the annealing temperature. (Japan) H Kudo et al, J Appl fhys, 50 (7). 1979, 5034-5035.
4556. Microfabrication prepared by reactive
and evaluation of diffractive sputter etching. (USA)
optical
35 filters
Single or linearly superimposed square-wave surface-relief patterns in a transparent plate yield optical transmission characteristics similar to those of interference filters. Reactive sputter etching of fused quartz in CHF3 using Shipley 1350 H photoresist as an etch mask offers a well-controlled method to produce these complex structures. Gratings with periodicities of 1-2 pm and depths of up to 3 pm are fabricated with dimensional tolerances of +0.02 pm using laser interferometric
abstracts
4540-4547
J111+‘11 where
J and 4 are the elemental impingement rates and thermal sticking probabilities, respectively. At any value of r investigated, a value of V, could be found such that for negative substrate biases greater than this value, the films were single phase. No preferential resputtering was observed for V, up to 250 V in films in which JsbQsb = J,,,$,,,. Thus, the range of r and T$ values over which single-phase stoichiometric films could be deposited from the vapour phase was extended by low energy ion bombardment of the growing film.
A H Eltoukhy
et al, J Vuc Sci Technol,
16 (2),
500 eV e- impacting on SS (304) samples (- 1000 cm* surface area) prepared by : (i) a degrease treatment; (ii) an acid cleaning (l/3 HF, l/3 HNO,, l/3 H,Ol, (iii) concentrated HF. Three separate samples were analysed for the first two treatments allowing the sample-tosample variation to be determined (10’&20:/; yield variations). The unit yield energy E0 (electron energy for which the total secondary electron emission is 1.0) has also been measured for each of the above treatments.
D Edwards,
J Vat Sci Technol,
16 (2), 1979, 758-760.
1979, 321-323 4544. Synchrotron-radiation-induced storage ring vacuum system. (USA)
32.
EVACUATION
AND
SEALING
32 4540.
Ion-acceleration mechanisms in vacuum diodes. (USA) A study of proton acceleration in a Lute diode has been carried out. Measurements of beam-neutralization times, electron and ion energy distributions, and induced radioactivity have been made. These measurements show that the effective potential-well depth at the beam head is less than the electron-accelerating voltage. Also, the relative activity of Mylar and copper foils indicates that ion energy increases with mass for Z = 1 particles. Both of these observations are consistent with ion acceleration resulting from a moving potential well. R J Adler and J A Nation, J Appl Phys, 50 (7), 1979, 5025-5027.
33.
NUCLEONICS
4541. Ultra-high vacuum compatibility materials: K-rami& and ATJ graphite.
of two possible
fusion
33 reactor
(USA) Outgassing characteristics of K-rami (manufactured by Kaman Nuclear) and ATJ graphite were evaluated under various treatments. For K-ramic,O total outgassing rates of 2 x 10m9 torr I s-’ cm-’ unbaked and 7 x IO-” torr Is-’ cme2 baked were measured. Mass spectroscopic measurements showed H, and CO to be the dominant residual gases. For ATJ, graphite the treatment consisted of repeated heatings in CCICI,O to 1250 K as well as repeated exposures to atmosphere. Residual gas analysis measured the time dependence of desorbed quantities of H2, H,O, CO,, CO and CH,. During the initial heating, the maximum species atom to lattice atom ratios were obtained yielding values of 2.6 >: IO-” for Hz, 3.4 x 10e5 for HZO, 1.6 x 10ms for CO,, 7.6 Y 10e6 for CO, and 5.2 x 10e6 for CHa. The total outgassed material from the graphite sample decreased by a factor of 10” after successive heatings.
R Moore,
J Vat Sci Technol,
16 (2), 1979, 748-751. 33
4542. Observations of changes in residual with discharge cleaning in PLT. (USA)
gas and surface
composition
Hydrogen discharge cleaning of the PLT vacuum vessel has been studied by mass spectroscopy of desorbed gases and surface analysis of exposed samples. Several modes of vessel conditioning have been studied to date: (I) a high-power discharge cleaning (PDC) mode, with a peak power density lo the vessel wall P, -0.6 W cm-* and a peak electron temperature T, - 100 eV: (2) low-power (Taylor-type) discharge cleaning (TDC) with P, -0.05 W cm-’ and T, < 5 eV. The predominant residual gases produced during PDC are CH, v IO-’ torr), whereas TDC pro(l-5 x 10e6 torr) and CO (I-IO duced primarily Hz0 (l-2 x 10e6 torr) and CH, (I-IO :.’ IO-’ torr). The transient behaviour of the residual gases is not simply related to pumping time constants, and provides evidence for the role of surface chemical reactions and diffusion on the formation of these gases. In situ surface analysis of hydrocarbon-covered stainless steel has shown significant decreases in carbon coverage occurring after 103lo4 pulses of either cleaning mode. Observed changes in oxygen coverage are more difficult to interpret because of the presence of the passivation oxide layer on the stainless-steel substrates.
H F Dylla
et al, J Vuc Sci Technol,
4543. Ion and electron steel (304). (USA)
desorption
16 (2). 1979.752-757. of neutral
The vacuum performance of both electron (as well as certain types of fusion reactors) to the desorption of neutral molecules wall by -keV charged particles. In this of Hz, CO, CO* and CH, are reported
molecules
from
33 stainless
and proton storage rings is expected to be sensitive from the vacuum chamber study the desorption yields from 1000 eV Ar+ and
heating
effects
in
the
33 PEP
The advent of large high-energy storage rings has facilitated the need for more detailed analysis of synchrotron radiation interactions and related thermal effects. In the PEP storage ring, a maximum of 5 MW of synchrotron radiation with a critical energy of 44 keV will interact with 2200 m of vacuum hardware. A Monte Carlo based computer code, EGS, was employed to follow electromagnetic reactions of the synchrotron radiation through various computerized models of the vacuum system. The computer simulated structures with hundreds of discrete rkgions and varying materials. Results showed that typically 70”/, of the svnchrotron power was absorbed in incident surfaces and 204/, was scattered outside the vacuum vessel. The remaining power was deposited in varied vacuum components. Sensitive PEP ring components, particularly distributed ion pumps, were subsequently designed to minimize power absorption and to maximize cooling effects. Other thermal calculations were employed to design for minimal wall temperatures in areas of direct synchrotron radiation incidence.
T W Martin,
J Yuc Sci Techttol.
16 (2), 1979, 761-762. 33
4545.
Residual
gas analysis
in the ISX-A
tokamak.
(USA) A computer-controlled mass analyser was utilized to observe the residual gases in the ISX-A tokamak. This residual gas analysis (RCA) system enabled time resolved measurements of preselected m/e peak heights to be made during and after tokamak discharges. Routine mass scans were also made and displayed in the form of semilogarithmic plots of partial pressure (torr) vs m/e. Wall conditioning of the stainless steel torus consisted of hydrogen discharge cleaning and titanium gettering. which ultimately produced gauge pressures on the order of IO-’ and 10e9 torr, respectively. The dominant plasma impurities, carbon and oxygen, were observed by the RCA as light hydrocarbons and water vapour. Entrapment of deuterium by the walls was investigated by monitoring the residual Dz content after the working gas was changed lo Hz. The effective nuclear charge (Z.,,) was found to be proportional lo the residual contaminants measured by the RGA immediately following a discharge.
J E Simpkins
et al, J Vat Sci Techtrol,
4546.
impurity
16 (2). 1979, 763-765. 33
Surface
studies
in the ISX-A
tokamak.
(USA)
The Impurity Study Experiment (ISX-A) was a tokamak designed to study impurity sources, plasma wall interactions, impurity behaviour within the plasma, and related phenomena. An Auger electron spectrometer, attached to the tokamak by means of a uhv sample transfer system. has been the primary tool used for surface studies of the first wall. Stainless steel samples positioned at the wall edge were used to follow the progressive ‘clean-up’ of the torus wall. Cleaning consisted of low energy hydrogen discharge plasmas, and later titanium gettering. The principal contaminants initially were carbon, oxygen and sulphur. As cleaning proceeded, the surface oxide layers were reduced to substoichiometric levels, and the carbon deposits appeared to be converted to metallic carbides. The sulphur was largely removed. A decrease in the effective nuclear charge of the plasma could be correlated with these surface changes. Discharge cleaning reduced Zcrr from -4 to 1.6 over a period of several months while titanium gettering produced values approaching 1.0.
L C Emerson
et al, J Vuc Sci Technol,
16 (2). 1979, 766-768. 33
4547. A convenient method for the measurement from an intense neutral beam. (USA)
of species composition
We present a method to infer the approximate species mixture neutral beam sources which accelerate positive hydrogen ions. idealized neutral beam is specified by the accelerating voltage, neutralizer thickness (molecules of hydrogen per cm*), and
of An the the 349
Classified
abstracts
4548-4556
currents of extracted H+, Hz+ and H3+. These currents define two independent ratios which lie within a narrow parameter region and which can be determined by two independent measurements downstream from the source. The two suitable parameters are: (I) the ratio of neutral beam to total beam power; and (2) the ratio of hydrogen produced by the neutral beam in the target volume to the hydrogen produced by the total beam. We give experimental results from the 10 x 10 cm2 120 keV test stand at the Lawrence Berkeley Laboratory. R R Smith and J W Steams, Rev. Sci Imrrrrm, 50 (9). 1979, 1070-1073.
33 4548. Vacuum photodiode detector ip a tokamak plasma. (USA)
array
for broadband
uv detection
An array of vacuum photodiode detectors has been used to monitor discharge equilibrium, stability and cleanliness in the Macrotor tokamak. These detectors use the photoelectric effect on small tungsten plates to measure uv emission in the band h -200-1200 8, and so are sensitive mainly to impurity line radiation in Macrotor. The response of this system to controlled impurity contamination experiments and lo disruptions is described. The design, construction and background problems associated with these detectors are discussed in detail.
S J Zweben
et al, Rev Sci Itnrrwn,
50 (S), 1979, 972-978. 33
4549.
Fast ion beam-plasma
interaction
system.
(USA) A device has been constructed for the study of the interaction between a fast ion beam and a target plasma of separately controllable parameters. The beam of either hydrogen or helium ions has an energy of l-4 keV and a total current of OS-2 A. The beam energy and beam current can be varied separately. The ion source plasma is created by a pulsed (0.2-10 ms pulse length) discharge in neutral gas at up to 3 x 1O-3 torr. The neutrals are pulsed into the source chamber, allowing the neutral pressure in the target region lo remain less than 5 x 10m5 torr at a 2 Hz repetition rate. The creation of the source plasma can be described by a simple set of equations which predict optimum source design parameters. The target plasma is also produced by a pulsed discharge. Between the target and source chambers the beam is neutralized by electrons drawn from a set of hot filaments. Currently under study is an unstable wave in a field-free plasma excited when the beam velocity is nearly equal to the target electron thermal velocity uhcJ,,, e 3.5 x IO’ cm s-‘. r, = 0.5 eV).
R A Breun
and J R Ferron,
34. ELECTRONICS TECHNOLOGY
AND
Reu Sci Imrrrtm,
HIGH
50 (7),
1979, 862-866.
ALTITUDE
PHYSICS
AND
34 4550. Vacuum ultra-violet spectroscopic apparatus for space- and timeresolved measurements on a single tokamak plasma discharge. (GB) We describe the vacuum ultra-violet spectroscopic apparatus developed for the TFR-600 tokamak and operating between IO and 220 nm. By use of a rotating mirror working at grazing incidence, several spatial profiles (between five and ten, depending on plasma lifetime and mirror rotation speed) of two impurity lines are obtained during a single plasma discharge. (France)
C Breton
et al, J P/IY~ E; Scim/
Im/rrwl,
4551. Microwave discharge source atom and free radical beams. (GB)
for
12 (9),
1979. 894-898.
the production
34 of supersonic
This paper describes the design and construction of a microwave discharge source which operates with a dilute mixture of oxygen molecules in excess helium or neon buffer gas at high pressure (below about 2.6 x 10” Pa, 200 torr). Seeded supersonic beams of oxygen atoms are produced with Mach numbers M 7 5 and translational energies E = 33.6 kJ mol-’ for helium buffer gas and E = 13.5 kJ mol-’ for neon. Oxygen atom beam fluxes of around 5 x IO” atoms/srI s- ’ are obtained using helium buffer gas, and slightly lower fluxes of about I x 10” atom.+-’ s-’ with neon. A supersonic beam of chlorine atoms with similar characteristics has been produced by discharge of a dilute mixture of chlorine molecules in helium buffer gas.
P A Gerry 860. 350
and R Grice,
J Phys E: Scimf
hfrtrm,
12 (9), 1979, 857-
4552. study
Improved version of an electron image tube designs. (GB)
optical
demountable
system
34 to
The study of electron optical characteristics in high-resolution vacuum devices like image converters and intensifiers plays an important part in improving the performance of such devices. The work reported has been carried out using an experimental electron optical demountable system. The paper describes the constructional aspects and the technology involved in developing the system. Some of the salient features such as vacuum engineering details, fabrication of gold photocathode resolution patterns and establishment of essential tolerances in the tube electrode positions are described. Finally, the mode of analysis of image tube designs in this system is mentioned. (India)
L M Rangarajan
et al, J Whys E: Scienf
htrwn,
12 (9), 1979, 845-848. 34
4553. Effect of diffusion pump oil contamination efficiency in the vuv spectral region. (USA)
on diffraction
grating
The efficiency of a concave grating contaminated with diffusion pump oil has been measured and compared with that of an uncontaminated sister grating. At 1216 8, and 4000 A, the contamination has little effect on the efficiency, but at intermediate wavelengths the loss in efIiciency is large. Vapour degreasing provided a partial restoration, and overcoating with gold, a complete restoration of efficiency.
W R Hunter
and D W Angel,
Appl
Opt,
18 (20),
1979, 3506-3509. 34
4554.
Pioneer
Venus
large
probe
neutral
mass spectrometer.
(USA)
A neutral particle mass spectrometer has been constructed to measure the composition and abundance of the atmospheric gases of the planet Venus. This instrument is being flown on the Pioneer Venus Multiprobe and will sample the planet’s atmosphere from an attitude of 67 km to its surface. The mass spectrometer is a single focusing magnetic sector field instrument capable of scanning the mass range from l-208 amu with a sensitivity of better than 1 ppm relative to the dominant gas, CO,. It possesses a unique inlet system which is capable of sampling gases from an environment of 770 K and 100 atm. Operation of the instrument is under the control of a microprocessor. Through this powerful device, a highly efficient peak stepping and data compression program is effected permitting transmission to earth of the entire mass spectral output in only 64 s at a data rate of 40 bits s-’ resulting in an excellent altitude resolution of variations of atmospheric composition. An isotope ratio measurement cell purges an atmospheric sample of active gases yielding an enriched rare gas sample for isotopic ratio analysis. To maintain an ultra-clean vacuum in the mass analyser tube, a combination of ion pumping and chemical gettering is employed. Instrument weight is 11 kg, volume is 10.650 cm’ and power is 14 W. J H Hoffman et al, J Vuc Sci Tm/uro/, 16 (21, 1979, 692-694.
35.
PROCESSING
OF
MATERIALS
4555. Stoichiometry measurements backscattering. (USA)
of GaAs by means of 15 MeV
35 He+ +
The stoichiometry of heat-treated GaAs crystals was measured over the region about 1 pm below the surface by means of 15 MeV He++ backscattering. Samples were annealed for 1 h at various temperatures between 200 and 900°C. The annealing-temperature dependence of the concentration ratio of As to Ga in the above-mentioned region shows abrupt change at around 250°C and at around 800°C. For annealing at 300-700°C. this ratio (0.81 & 0.05) is almost independent of the annealing temperature. (Japan) H Kudo et al, J Appl fhys, 50 (7). 1979, 5034-5035.
4556. Microfabrication prepared by reactive
and evaluation of diffractive sputter etching. (USA)
optical
35 filters
Single or linearly superimposed square-wave surface-relief patterns in a transparent plate yield optical transmission characteristics similar to those of interference filters. Reactive sputter etching of fused quartz in CHF3 using Shipley 1350 H photoresist as an etch mask offers a well-controlled method to produce these complex structures. Gratings with periodicities of 1-2 pm and depths of up to 3 pm are fabricated with dimensional tolerances of +0.02 pm using laser interferometric