- Email: [email protected]
416. The mechanism of electrical clean-up of gas in the hot cathode ionization gauge
158
Classified Abstracts 412--421
then the mercury column of the gauge adjusts itself, always to the same height in the gauge independently of the prevailing barometric pressure. (in German) (Author) G. Peche, Vakuum-Technik, 11 (5), July 1962, 148-149. 22 412. The measurement of very low pressures with the BayardAipert modulator gauge. Germany. For the measurement of very low pressures ( < 10 ~0 torr) a Bayard-Alpert ionization gauge with a modulator has been used. As shown by Redhead, this gauge allows elimination of the residual current ir caused by X-rays. The method as described by Redhead is based on ir : constant, when the potential of the modulator is changed from the ion collector potential to the potential of the grid. It was found, however, that the current ir in our gauge did alter by about fifteen per cent in spite of constant emission current. This alteration is due to a change in intensity or radiation on the collector electrode, for which a solid angle effect seems to be responsible. The intensity alteration has been calculated approximately and is of the same order of magnitude as the current alteration obtained by our measurements. In conclusion the article shows how the method as described by Redhead has to be modified in order to take into consideration the alteration of the residual current. It is quite possible that, depending on the particular design, the alteration of i, in some Bayard-Alpert gauges has no measurable effect. (in German) (Author) G. Appelt, Vakuum-Technik, 11 (6), Sept. 1962, 174-177. 22 413. Comparative measurements between omegatron and BayardAlpert gauge. Germany. Depending on the experimental conditions, the sum of partial pressures measured with an omegatron does not always agree well with the total pressure measured with a BayardAlpert gauge. The discrepancy can become very important in the ultra-high vacuum range of pressures. A number of typical measurements are presented and their interpretation discussed. They include the following effects : insufficient gauge outgassing, "' CO p o i s o n i n g " of gauge, outgassing of gauge cathode, ion pumping and a peculiar effect arising when pure CO is released by electron bombardment. Experience shows that in most cases the omegatron readings are more reliable than those obtained with a Bayard-Alpert gauge, particularly at pressures below 10 -8 torr. (in German) (Author) L.A. P6termann, Vakuum-Tecnhik, 11 (7), Oct. 1962, 200-204. 22 414. Monitoring fast changing processes by means of a mass filler partial pressure analyser. Germany. Details are given of a mass filter partial pressure analyser which features a specially designed h.f. generator and a suitable d.c. amplifier, so that the registration of fast changing processes is possible at comparatively little expense. A wobblingtime of only 2 sec is required for monitoring the total mass range of the instrument, i.e., m = 2--120, whereby the maximum resolving power, m/Am, is between 50 and 100. Sensitivity and noise level are such that partial pressures in 10 -9 torr range can be detected ; the partial pressure sensitivity is between 10 -s and 10-~. A few practical examples demonstrate the properties of the instrument and its potentialities for a variety of applications. (in German) (Authors) H. B6hm and K. G. Gunther, Vakuum-Technik, I1 (8), Dec. 1962, 240-243. 22 415. Vacuum gauges employing radioactive materials. France. Gauges of this type are commercially available under the name of alphatrons. They depend on measuring the ionization produced by the particles emitted by a Ra 226 source and possess two great advantages : (1) a large pressure range can be covered
by one instrument (atmospheric-10 4 torr) ; (2) the gauge is very robust and easily used. Their main disadvantage is radiation danger unless proper precautions are taken. This applies especially to the radon emitted by Ra 226 which necessitates discharging all the pumped gas into the outer atmosphere when alphatron gauges are attached to vacuum systems, a procedure which complicates the use of these instruments. In order to obviate this danger, and simplify the installation the author recommends the use of an equilibrium mixture of RaD and RaE, which source does not emit radon. Unfortunately its ~ emission is complicated by 13 and 7 emission. Whilst the former can easily be filtered out the 7 radiation is difficult to shield and care has to be taken when handling the instrument. The author gives details for the construction of such a gauge employing a source of the order of 200/zc. It is hoped that pure ~ emitters such as Nd 144 or Sm 147 will become commercially available in due course. This would remove the last objection to the general use of gauges of this type. w.J.s. J. Moreau, Le Vide, 17 (99), May/June 1962, 222-226. 22 : 33 416. The mechanism of electrical clean-up of gas in the hot cathode ionization gauge. Great Britain. The author explains electrical gas clean-up in the hot cathode ionization gauge in terms of ion neutralization at the solid surface, followed by penetration of the solid lattice by the atom. The resulting lattice damage or disorder is regarded as instrumental in subsequent escape or recovery by a diffusion controlled process. Long term gas removal is due to annealing out of bombardment damage. These conclusions are consistent with the known fact that argon in bombardment removes surface contamination but damages the solid lattice. F. A. Baker, Le Vide, 17 (99), May/June, 256-265. 22 Influence of sorption on pressure measurements carried out in ultra-high vacuum. See Abstr. No. 374.
23.
Plumbing 23
417. Liquid gas lines. Anon., Nucl. Enging., 7, Dec. 1962, 500. 23
418. Metal joining service for industry. Anon., Nucl. Power, 7, June 1962, 48. 23 419. Sealing Pyrex glass to stainless steel and ll~conel. S. O. Colgate and E. C. Whitehead, Rev. Sci. Instrum., 33 (10), Oct. 1962, 1122-1124. 23
420. High-voltage vacuum lead through. W. E. Bron et. al.. Rev. Sci. Instrum., 33 (11), Nov. 1962, 1287. 25.
Baffles, Traps, and R e f r i g e r a t i o n E q u i p m e n t 25:21 421. The ion baffle in conjunction with an air-cooled oil diffusion pump. Liechtenstein. The mechanisms of four different types of ion baffle, mounted on an air-cooled oil diffusion pump, were investigated in the high vacuum pressure vacuum range with the aid of a mass spectrometer. It was found that in the 10 -6 torr pressure range the ion baffle considerably reduced all components present in the residual gas. The magnetron-type ion baffle with chevron shaped titanium cathodes was the most effective. (in German) (Author, modified) R. A. Haefer, Vakuum-Technik, 11 (2), March 1962,141-44.
Classified Abstracts 412--421
then the mercury column of the gauge adjusts itself, always to the same height in the gauge independently of the prevailing barometric pressure. (in German) (Author) G. Peche, Vakuum-Technik, 11 (5), July 1962, 148-149. 22 412. The measurement of very low pressures with the BayardAipert modulator gauge. Germany. For the measurement of very low pressures ( < 10 ~0 torr) a Bayard-Alpert ionization gauge with a modulator has been used. As shown by Redhead, this gauge allows elimination of the residual current ir caused by X-rays. The method as described by Redhead is based on ir : constant, when the potential of the modulator is changed from the ion collector potential to the potential of the grid. It was found, however, that the current ir in our gauge did alter by about fifteen per cent in spite of constant emission current. This alteration is due to a change in intensity or radiation on the collector electrode, for which a solid angle effect seems to be responsible. The intensity alteration has been calculated approximately and is of the same order of magnitude as the current alteration obtained by our measurements. In conclusion the article shows how the method as described by Redhead has to be modified in order to take into consideration the alteration of the residual current. It is quite possible that, depending on the particular design, the alteration of i, in some Bayard-Alpert gauges has no measurable effect. (in German) (Author) G. Appelt, Vakuum-Technik, 11 (6), Sept. 1962, 174-177. 22 413. Comparative measurements between omegatron and BayardAlpert gauge. Germany. Depending on the experimental conditions, the sum of partial pressures measured with an omegatron does not always agree well with the total pressure measured with a BayardAlpert gauge. The discrepancy can become very important in the ultra-high vacuum range of pressures. A number of typical measurements are presented and their interpretation discussed. They include the following effects : insufficient gauge outgassing, "' CO p o i s o n i n g " of gauge, outgassing of gauge cathode, ion pumping and a peculiar effect arising when pure CO is released by electron bombardment. Experience shows that in most cases the omegatron readings are more reliable than those obtained with a Bayard-Alpert gauge, particularly at pressures below 10 -8 torr. (in German) (Author) L.A. P6termann, Vakuum-Tecnhik, 11 (7), Oct. 1962, 200-204. 22 414. Monitoring fast changing processes by means of a mass filler partial pressure analyser. Germany. Details are given of a mass filter partial pressure analyser which features a specially designed h.f. generator and a suitable d.c. amplifier, so that the registration of fast changing processes is possible at comparatively little expense. A wobblingtime of only 2 sec is required for monitoring the total mass range of the instrument, i.e., m = 2--120, whereby the maximum resolving power, m/Am, is between 50 and 100. Sensitivity and noise level are such that partial pressures in 10 -9 torr range can be detected ; the partial pressure sensitivity is between 10 -s and 10-~. A few practical examples demonstrate the properties of the instrument and its potentialities for a variety of applications. (in German) (Authors) H. B6hm and K. G. Gunther, Vakuum-Technik, I1 (8), Dec. 1962, 240-243. 22 415. Vacuum gauges employing radioactive materials. France. Gauges of this type are commercially available under the name of alphatrons. They depend on measuring the ionization produced by the particles emitted by a Ra 226 source and possess two great advantages : (1) a large pressure range can be covered
by one instrument (atmospheric-10 4 torr) ; (2) the gauge is very robust and easily used. Their main disadvantage is radiation danger unless proper precautions are taken. This applies especially to the radon emitted by Ra 226 which necessitates discharging all the pumped gas into the outer atmosphere when alphatron gauges are attached to vacuum systems, a procedure which complicates the use of these instruments. In order to obviate this danger, and simplify the installation the author recommends the use of an equilibrium mixture of RaD and RaE, which source does not emit radon. Unfortunately its ~ emission is complicated by 13 and 7 emission. Whilst the former can easily be filtered out the 7 radiation is difficult to shield and care has to be taken when handling the instrument. The author gives details for the construction of such a gauge employing a source of the order of 200/zc. It is hoped that pure ~ emitters such as Nd 144 or Sm 147 will become commercially available in due course. This would remove the last objection to the general use of gauges of this type. w.J.s. J. Moreau, Le Vide, 17 (99), May/June 1962, 222-226. 22 : 33 416. The mechanism of electrical clean-up of gas in the hot cathode ionization gauge. Great Britain. The author explains electrical gas clean-up in the hot cathode ionization gauge in terms of ion neutralization at the solid surface, followed by penetration of the solid lattice by the atom. The resulting lattice damage or disorder is regarded as instrumental in subsequent escape or recovery by a diffusion controlled process. Long term gas removal is due to annealing out of bombardment damage. These conclusions are consistent with the known fact that argon in bombardment removes surface contamination but damages the solid lattice. F. A. Baker, Le Vide, 17 (99), May/June, 256-265. 22 Influence of sorption on pressure measurements carried out in ultra-high vacuum. See Abstr. No. 374.
23.
Plumbing 23
417. Liquid gas lines. Anon., Nucl. Enging., 7, Dec. 1962, 500. 23
418. Metal joining service for industry. Anon., Nucl. Power, 7, June 1962, 48. 23 419. Sealing Pyrex glass to stainless steel and ll~conel. S. O. Colgate and E. C. Whitehead, Rev. Sci. Instrum., 33 (10), Oct. 1962, 1122-1124. 23
420. High-voltage vacuum lead through. W. E. Bron et. al.. Rev. Sci. Instrum., 33 (11), Nov. 1962, 1287. 25.
Baffles, Traps, and R e f r i g e r a t i o n E q u i p m e n t 25:21 421. The ion baffle in conjunction with an air-cooled oil diffusion pump. Liechtenstein. The mechanisms of four different types of ion baffle, mounted on an air-cooled oil diffusion pump, were investigated in the high vacuum pressure vacuum range with the aid of a mass spectrometer. It was found that in the 10 -6 torr pressure range the ion baffle considerably reduced all components present in the residual gas. The magnetron-type ion baffle with chevron shaped titanium cathodes was the most effective. (in German) (Author, modified) R. A. Haefer, Vakuum-Technik, 11 (2), March 1962,141-44.