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Simulation of a monopole mass spectrometer with a view to determine operating parameter tolerances
Classified abstracts 3545-3554 to be several orders longer than inferred from earlier work and the polymerization cross-section is found to be comparable to the projected molecular area. Methods are discussed for minimizing contamination build-up on surfaces undergoing ion bombardment. (Australia) E H Hirsch, J Phys D: Appl Phys, 10 (15). 1977, 2069-2076. 12 3545. Emission of electrode vapour resonance radiation at the onset of dc breakdown in vacuum. (USA) Simultaneous time-resolved spectroscopic and current measurements have been made during the early stages of current growth leading to dc breakdown in vacuum between plane-parallel electrodes of dissimilar material. These measurements show that resonance radiation characteristic of anode material is emitted prior to that of cathode material from all regions of the interelectrode gap. Further, the radiation is emitted first from the cathode region of the gap. The results indicate that the initial current growth occurs in anode vapour followed at later times by the appearance of cathode vapour in the gap. D K Davies and M A Biondi, J appl Phys. 48 (IO). 1977, 4229-4233. 4.3
3546. Location of charge centroid in electron-beam-charged polym: films. (USA) The centroid of the charge distribution of electron-beam-charged polymer films electroded on both sides is determined by measurements of the charges on, or currents into, the two electrodes during or after electron-beam injection. Results obtained with 25 nm Teflon FEP films charged with a diffuse monoenergetic beam of 5-40 keV electrons show that the charge centroid is initially located between the average and maximum electron ranges regardless of whether the electrode of injection is floating or grounded (open or short circuit, respectively). During and after charging under open-circuit conditions the centroid moves further into the material beyond the CSDA range. B Gross et al, J appl Phys, 48 (IO), 1977,4303-4306. 12 3547. Thermally assisted field emission near precipitates in p-n junctions (USA) Conductive precipitates imbedded in the space-charge region of a p-n junction give rise to localized high fields near the precipitates. For localized fields of approximately IQ6 V/cm or larger, the dominant current contribution is due to localized Fowler-Nordheim field emission which gives rise to a soft leakage behaviour. By fitting soft leakage currents to a thermally assisted field-emission model, information about the local field enhancement at the precipitates and about the barrier height surrounding the precipitates was obtained. The model predicts that soft leakage currents which are generated in regions of high field enhancement (~10’ V/cm) are almost temperature independent (77-350 K), whereas in regions of moderate field enhancement (-IO6 V/cm) the soft leakage currents are strongly temperature dependent. H H Busta and H A Waggener, J appl Phys, 48 (IO), 1977,43854388. 12 3548. Simulation of a monopole mass spectrometer with a view to determine operating parameter tolerances. (USA) Results from a computer model of the operation of a monopole mass spectrometer are presented and used to illustrate the dependence of peak shape, transmission and resolution upon various waveform and geometric parameters. In addition, the parameter tolerances necessary for highly stable operation are derived and shown to be within the capabilities of present electronic techniques. In particular, for a duty cycle (rectangular waveform operation) or dc-rf ratio (sinusoidal excitation) tolerance of the order of 10 ppm, peak height stability of about 0.1% is seen to be attainable at high resolution and high transmission. This is an order of magnitude better than is possible with a quadrupole mass filter. (Australia) R A Musumeci and J A Richards, J Vat Sri Techno/, 14 (5), 1977, 1180-1185. 12 3549. Reaction energy analysis by plasma diagnostics. (GB) Short-time pulsed plasma diagnostics with Langmuir probes are used to extract information on non-elastic collision processes in weakly ionized gases. (Germany) H D Wok&k and H Bradaczek, J Phys E: Went /nstrum, 10 (IO), 1977, 1077. 198
12 3558. A controllable ion gun with high brightueaa. (GB) A concentric discharge with radial carrier transport is used for obtaining centrally located, dense, non-equilibrium plasmas. The inwardly directed electron beam from an external ring cathode is accelerated over a short distance and traverses the slit of a highenergy ring anode. The electron beam is then decelerated to produce the maximum ionization cross section during irradiation inside the central plasma anode. This results in high drain current from the cathode, low ionization outside the plasma and reflection of plasma ions. The plasma electrons are reflected near the cathode. Thus the plasma produced are confined to the centre and the discharge is not self-maintained but is controllable up to an argon pressure of 10 Pa. Short-time pulsed probe plasma diagnostics have shown an additional contraction of the plasma, caused by unidirectional movement of electrons and positively charged ions which results in a channelling effect. The ion emissivity of the source has reached 6 kA mm2 for argon and hydrogen. (Germany) H D Wokiick, J Phys E: Went Instrum, 10 (lo), 1977, 913a976. 12 3551. Electroluminescence produced by high electric BeIds at the surface of copper cathodes. (GB) Spots of light have been observed on the surface of OFHC copper cathodes following the application of high electric fields. The spectrum of the radiation shows a sharp peak at about 640 nm and its intensity obeys the Alfrey-Taylor relationship for electroluminescence. Within the light-emitting regions, discharges have been seen which it is believed are caused by the breakdown of dielectric inclusions trapped at defects in the crystal structure. Observations are consistent with the inclusions having semiconducting properties and emitting light by recombination of conduction electrons with holes produced by impact ionization within their crystal lattice structure. R E Hurley and P J Dooley, J Phys D: Appl Phys, 10 (15), 1977, Ll95-L201. .e
IL
3552. Penning ionization in doped CO, TEA lasers. (USA) A quantitative model is presented which predicts the behaviour of the discharge of a CO, laser gas mixture with a low-ionization seed gas. The basis of the developed model is the assumption of the so-called Penning ionization mechanism in which metastable nitrogen molecules ionize the seed gas. The developed model will be compared with measurements on an appropriate CO1 laser device. As a result of this study, we describe the successful operation of a simple largeaperture amplifier with a diameter of 12 cm. (Netherlands) B J Reits, J appl Phys, 48 (9), 1977, 3697-3700. 12 3553. Double-discharge stabilization of supersonic CO laser mixtures. (USA) Experiments have been conducted to study the applicability of a cw double-discharge stabilization scheme in conditions appropriate for high-energy lasers in supersonic flows. Steady arc-free volume discharges have been produced in a Mach 3 supersonic flow test cavity using an auxiliary discharge to stabilize the main discharge at lowcurrent densities in NZ and He/CO mixtures. A significant result is the lack of observed plasma E/N changes in response to auxiliary discharge current changes. Also, where glow discharges were obtained, the energy loading achieved was less than the threshold required for laser operation. C Srinivasan and J A Smith, J appl Phys, 48 (9), 1977, 3680-3682.
II.
Vacuum
20. PUMPING
apparatus SYSTEMS
and
auxiliaries
20 3554. A small and economic turbo molecular pump with a pumping speed of 110 I. s for the production of oilfree high and ultrahigh vacuum (Germany) A small turbo molecular pump with a pumping speed of 110 1. s and a weight of only 6 kg is described. The axial length of the pump, which has a suction flange of 100 mm ‘inner diameter, is 200 mm. The ultimate pressure attainable is in the range of 10-r’ mbar. In connection with a small two-stage backing pump very compact fully automatic pumping units can be built. The main applications are
3546. Location of charge centroid in electron-beam-charged polym: films. (USA) The centroid of the charge distribution of electron-beam-charged polymer films electroded on both sides is determined by measurements of the charges on, or currents into, the two electrodes during or after electron-beam injection. Results obtained with 25 nm Teflon FEP films charged with a diffuse monoenergetic beam of 5-40 keV electrons show that the charge centroid is initially located between the average and maximum electron ranges regardless of whether the electrode of injection is floating or grounded (open or short circuit, respectively). During and after charging under open-circuit conditions the centroid moves further into the material beyond the CSDA range. B Gross et al, J appl Phys, 48 (IO), 1977,4303-4306. 12 3547. Thermally assisted field emission near precipitates in p-n junctions (USA) Conductive precipitates imbedded in the space-charge region of a p-n junction give rise to localized high fields near the precipitates. For localized fields of approximately IQ6 V/cm or larger, the dominant current contribution is due to localized Fowler-Nordheim field emission which gives rise to a soft leakage behaviour. By fitting soft leakage currents to a thermally assisted field-emission model, information about the local field enhancement at the precipitates and about the barrier height surrounding the precipitates was obtained. The model predicts that soft leakage currents which are generated in regions of high field enhancement (~10’ V/cm) are almost temperature independent (77-350 K), whereas in regions of moderate field enhancement (-IO6 V/cm) the soft leakage currents are strongly temperature dependent. H H Busta and H A Waggener, J appl Phys, 48 (IO), 1977,43854388. 12 3548. Simulation of a monopole mass spectrometer with a view to determine operating parameter tolerances. (USA) Results from a computer model of the operation of a monopole mass spectrometer are presented and used to illustrate the dependence of peak shape, transmission and resolution upon various waveform and geometric parameters. In addition, the parameter tolerances necessary for highly stable operation are derived and shown to be within the capabilities of present electronic techniques. In particular, for a duty cycle (rectangular waveform operation) or dc-rf ratio (sinusoidal excitation) tolerance of the order of 10 ppm, peak height stability of about 0.1% is seen to be attainable at high resolution and high transmission. This is an order of magnitude better than is possible with a quadrupole mass filter. (Australia) R A Musumeci and J A Richards, J Vat Sri Techno/, 14 (5), 1977, 1180-1185. 12 3549. Reaction energy analysis by plasma diagnostics. (GB) Short-time pulsed plasma diagnostics with Langmuir probes are used to extract information on non-elastic collision processes in weakly ionized gases. (Germany) H D Wok&k and H Bradaczek, J Phys E: Went /nstrum, 10 (IO), 1977, 1077. 198
12 3558. A controllable ion gun with high brightueaa. (GB) A concentric discharge with radial carrier transport is used for obtaining centrally located, dense, non-equilibrium plasmas. The inwardly directed electron beam from an external ring cathode is accelerated over a short distance and traverses the slit of a highenergy ring anode. The electron beam is then decelerated to produce the maximum ionization cross section during irradiation inside the central plasma anode. This results in high drain current from the cathode, low ionization outside the plasma and reflection of plasma ions. The plasma electrons are reflected near the cathode. Thus the plasma produced are confined to the centre and the discharge is not self-maintained but is controllable up to an argon pressure of 10 Pa. Short-time pulsed probe plasma diagnostics have shown an additional contraction of the plasma, caused by unidirectional movement of electrons and positively charged ions which results in a channelling effect. The ion emissivity of the source has reached 6 kA mm2 for argon and hydrogen. (Germany) H D Wokiick, J Phys E: Went Instrum, 10 (lo), 1977, 913a976. 12 3551. Electroluminescence produced by high electric BeIds at the surface of copper cathodes. (GB) Spots of light have been observed on the surface of OFHC copper cathodes following the application of high electric fields. The spectrum of the radiation shows a sharp peak at about 640 nm and its intensity obeys the Alfrey-Taylor relationship for electroluminescence. Within the light-emitting regions, discharges have been seen which it is believed are caused by the breakdown of dielectric inclusions trapped at defects in the crystal structure. Observations are consistent with the inclusions having semiconducting properties and emitting light by recombination of conduction electrons with holes produced by impact ionization within their crystal lattice structure. R E Hurley and P J Dooley, J Phys D: Appl Phys, 10 (15), 1977, Ll95-L201. .e
IL
3552. Penning ionization in doped CO, TEA lasers. (USA) A quantitative model is presented which predicts the behaviour of the discharge of a CO, laser gas mixture with a low-ionization seed gas. The basis of the developed model is the assumption of the so-called Penning ionization mechanism in which metastable nitrogen molecules ionize the seed gas. The developed model will be compared with measurements on an appropriate CO1 laser device. As a result of this study, we describe the successful operation of a simple largeaperture amplifier with a diameter of 12 cm. (Netherlands) B J Reits, J appl Phys, 48 (9), 1977, 3697-3700. 12 3553. Double-discharge stabilization of supersonic CO laser mixtures. (USA) Experiments have been conducted to study the applicability of a cw double-discharge stabilization scheme in conditions appropriate for high-energy lasers in supersonic flows. Steady arc-free volume discharges have been produced in a Mach 3 supersonic flow test cavity using an auxiliary discharge to stabilize the main discharge at lowcurrent densities in NZ and He/CO mixtures. A significant result is the lack of observed plasma E/N changes in response to auxiliary discharge current changes. Also, where glow discharges were obtained, the energy loading achieved was less than the threshold required for laser operation. C Srinivasan and J A Smith, J appl Phys, 48 (9), 1977, 3680-3682.
II.
Vacuum
20. PUMPING
apparatus SYSTEMS
and
auxiliaries
20 3554. A small and economic turbo molecular pump with a pumping speed of 110 I. s for the production of oilfree high and ultrahigh vacuum (Germany) A small turbo molecular pump with a pumping speed of 110 1. s and a weight of only 6 kg is described. The axial length of the pump, which has a suction flange of 100 mm ‘inner diameter, is 200 mm. The ultimate pressure attainable is in the range of 10-r’ mbar. In connection with a small two-stage backing pump very compact fully automatic pumping units can be built. The main applications are