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Pumping problems and some solutions adopted in recent linear accelerators for particle beams
Classified
abstracts
387-398
387. The electro-cyclotron wave field in a cylindrical plasma. (Cerml?~$ For cylindrical waves in a hot homogeneous plasma, the dielectric tensor is given and the approximation limits of zero temperature determined. In this approximation the wave field is calculated numerically for a metal cylinder completely filled with plasma. In contrast to the vacuum field a considerable axial component of the E-field arises for the parameter range in question. H Grawe, Euratom Information, 4 (IO), 1966, 1108, Rept (MF) EUR 3108d (in German). 388. Distortion of the electronic energy distribution in an electrostaii: tally pinched discharge. (Germany) The positive column (50 mm diameter) of a low pressure mercury discharge (2.5 x lO-2 torr) was ninched over a length of 10 cm bv a radial &&rostatic field. -Tests with Langmuir probes in the pinch zone showed steep gradients in the potential, density and temperature curves. The energy distribution was determined by the method of Druyvesteyn. The disturbance of the probe characteristic-line by contact potentials varying in time was eliminated by using a new type of equilibrium-heated probe which yields reproducible results. M Troppmann, Euratom Information, 4 (IO), 1966,1108, Rept (MF) EVR 3109d (in German). 32 : 21 389. Pumping problems in isochronous cyclotrons. (France) These cyclotrons require high speed pumping to compensate for the gas flow arising from the internal ion source. Conventional systems use oil diffusion pumps with liquid nitrogen traps and operate at pressures of the order of lO-s N/m2. Experiments involving the acceleration of negative ions, protons or deuterons would require pressures of the order of 10-s N/m2 and means for achieving this lower pressure are discussed. A limiting factor is the poor conductance of the vacuum chamber and this could be improved by use of an external ion source, removing the electromagnetic pole pieces from the centre of the chamber. Nevertheless, improvement in the pumping system is essential and it is considered that the final form will involve the addition of cryopumps located inside the chamber. R Jean and A Dupuis, Le Vide, 21 (124), July-Aug 1966, 273-279 (in French). 32 390. The vacuum in a tritium accelerator. (France) Problems in evacuating a tritium accelerator arise chiefly from the contamination of the pumps and associated equipment by the tritium. The isotope also constitutes a health hazard to personnel. The effects of contamination in the ion source, accelerator tube and pumping system are described and recommendations for improved performance are presented. Conventional pumping systems combine mercury diffusion pumps and rotary vane pumps. The latter are always contaminated by the reactive tritium. It is suggested that the present systems be replaced by an ion pump (100 litres/second) together with an easily rechargeable zeolite pump. J C Oberlin, Le Vide, 21 (124), July-Aug 1966, 279-282 (in French). 391. The accelerator tube in Van de Graaff electrostatic acceleratoi.1 (France) The results of previous research on the vacuum discharge are briefly surveyed and some experimental data obtained during the conditioning of the tube for the Saclay Tandem Accelerator are presented. The tube of this accelerator was able to operate at 7.5 MV maximum and could operate for more than a week at 14.5 MeV. The effects on the tube performance of pressure variation between 5 x 10-Oand 20 x 1Om6 torr and of adsorption processes are discussed. B Delaunay, Le Vide, 21 (124), July-Aug 1966, 291-298 (in French). 32 : 21 392. Observations on the pumping system of the Saturn accelerator. (France) The performance of the pumping system employed in the Saturn accelerator over the period 1959 to 1965 is surveyed with reference to the statistics of pump failure and maintenance for that period. In this proton accelerator, a volume of 7mS is evacuated by an ion pump backed by four pumping groups each consisting of a mechanical pump an oil diffusion pump and a freon refrigerated baffle. The only maintenance required by the oil diffusion pumps over the entire period was 118
replacement of the oil by a silicone DC703 oil in 1963. From the results of the survey the pumping system is evaluated. In a further study, the effect of the oil partial pressure on the particle loss from the accelerator was accounted for by a total pressure of 2 x 10-O torr when the oil used has a partial pressure of 10m9torr. G Rommel, Le Vide, 21 (125), Sept-Ott 1966, 369-374 (in French). 32 : 21 393. Pumping problems and some solutions adoKtad in recent linear accelerators for particle beams. (France) Various aspects of the pumping requirements for linear accelerators are considered leading to the conclusion that conventional mechanical /oil-diffusion combinations are inadequate and recommending the use of ion pumps or turbomolecular pumps. The advantages and disadvantages of each system are summarized with particular reference to the vacuum achieved in the accelerating zones where strong rf fields operate. Two recently constructed accelerators are described and their pumping systems evaluated. G Azam and J Milcamps, Le Vide, 21(125), 1966,380-385 (irl French). 32 : 21 394. Construction of the vacuum chamber for a synchrotron. (France) The most important properties of the vacuum chamber are that it can withstand large radiation doses of the order of IO” rads and that it does not distort the magnetic field. To this end, prototypes in alumina ceramic, glass and stainless steel were investigated and the advantages and disadvantages of each are described together with the appropriate fabrication techniques. None of the three systems are free from fault and the final choice must depend on considerations of economy and safety of the specific application. M J M Lefebvre, Le Vide, 21 (125), Sept-Ott 1966, 386-390 (01 French). 32 : 21 395. Determination of the vacuum system in a large accelerator. (French) The criteria for selection of vacuum pump combinations to meet the demands of large accelerators are described. The availability of ion and turbomolecular pumps facilitates the resolution of many problems. Examples of the application of these criteria are given with respect to an electron synchrotron and a proton synchrotron. G Rommel and R Vienet, Le Vide, 21 (125), Sept-Ott 1966, 391-395 (in French). 32 396. Iron-free one-turn synchrotron type BSB. (USSR) The design of the synchrotron type BSB is described. Its accelerating chamber is pumped by two oil-diffusion pumps with liquid N2 traps to obtain the operational pressure 5 x 1O-6 torr. A relatively large fore-vacuum reservoir chamber with its own liquid N, trap allows to switch the mechanical fore-vacuum pump off for 15 hours during the work. G I Budker et ul, Zh Tekh Fiz, 36 (9), Sept 1966, 1523-1535 (in Russian). 32 397. Probing plasma investigation in thermoemission converters of high caesium pressure. Part 3. (USSR) In this part of the paper results of measurements of the distribution of density, electron temperature and spatial potential in the interelectrode space of thermoemission converters with Cs vapour pressures 0.4 to 2 torr are presented for both diffusion and arc regimes. G A Dyuzhev et al, Zh Tekh Fiz, 36 (9), Sept 1966, 1685-1697 (i/l Russian). JL
398. Vacuum evaporating system with inductive heating to evaporate radioactive metals and metal oxides. (Austria) A vacuum evaporating system is described for the evaporation of radioactive metals and oxides. The evaporating quartz container is demountable and is placed in a glove box. An induction heating coil is placed over an arm container, in which Pu and U are placed as nitrates, W as metal. Pu and U nitrates are converted to oxides by heating. After high-temperature evaporation, the deposits containing U and Pu oxides are converted to dioxides by heating in hydrogen at looo”. W Fiedler et al, Atom-kerenergie, 11, 1966, 257-258 (in German).
abstracts
387-398
387. The electro-cyclotron wave field in a cylindrical plasma. (Cerml?~$ For cylindrical waves in a hot homogeneous plasma, the dielectric tensor is given and the approximation limits of zero temperature determined. In this approximation the wave field is calculated numerically for a metal cylinder completely filled with plasma. In contrast to the vacuum field a considerable axial component of the E-field arises for the parameter range in question. H Grawe, Euratom Information, 4 (IO), 1966, 1108, Rept (MF) EUR 3108d (in German). 388. Distortion of the electronic energy distribution in an electrostaii: tally pinched discharge. (Germany) The positive column (50 mm diameter) of a low pressure mercury discharge (2.5 x lO-2 torr) was ninched over a length of 10 cm bv a radial &&rostatic field. -Tests with Langmuir probes in the pinch zone showed steep gradients in the potential, density and temperature curves. The energy distribution was determined by the method of Druyvesteyn. The disturbance of the probe characteristic-line by contact potentials varying in time was eliminated by using a new type of equilibrium-heated probe which yields reproducible results. M Troppmann, Euratom Information, 4 (IO), 1966,1108, Rept (MF) EVR 3109d (in German). 32 : 21 389. Pumping problems in isochronous cyclotrons. (France) These cyclotrons require high speed pumping to compensate for the gas flow arising from the internal ion source. Conventional systems use oil diffusion pumps with liquid nitrogen traps and operate at pressures of the order of lO-s N/m2. Experiments involving the acceleration of negative ions, protons or deuterons would require pressures of the order of 10-s N/m2 and means for achieving this lower pressure are discussed. A limiting factor is the poor conductance of the vacuum chamber and this could be improved by use of an external ion source, removing the electromagnetic pole pieces from the centre of the chamber. Nevertheless, improvement in the pumping system is essential and it is considered that the final form will involve the addition of cryopumps located inside the chamber. R Jean and A Dupuis, Le Vide, 21 (124), July-Aug 1966, 273-279 (in French). 32 390. The vacuum in a tritium accelerator. (France) Problems in evacuating a tritium accelerator arise chiefly from the contamination of the pumps and associated equipment by the tritium. The isotope also constitutes a health hazard to personnel. The effects of contamination in the ion source, accelerator tube and pumping system are described and recommendations for improved performance are presented. Conventional pumping systems combine mercury diffusion pumps and rotary vane pumps. The latter are always contaminated by the reactive tritium. It is suggested that the present systems be replaced by an ion pump (100 litres/second) together with an easily rechargeable zeolite pump. J C Oberlin, Le Vide, 21 (124), July-Aug 1966, 279-282 (in French). 391. The accelerator tube in Van de Graaff electrostatic acceleratoi.1 (France) The results of previous research on the vacuum discharge are briefly surveyed and some experimental data obtained during the conditioning of the tube for the Saclay Tandem Accelerator are presented. The tube of this accelerator was able to operate at 7.5 MV maximum and could operate for more than a week at 14.5 MeV. The effects on the tube performance of pressure variation between 5 x 10-Oand 20 x 1Om6 torr and of adsorption processes are discussed. B Delaunay, Le Vide, 21 (124), July-Aug 1966, 291-298 (in French). 32 : 21 392. Observations on the pumping system of the Saturn accelerator. (France) The performance of the pumping system employed in the Saturn accelerator over the period 1959 to 1965 is surveyed with reference to the statistics of pump failure and maintenance for that period. In this proton accelerator, a volume of 7mS is evacuated by an ion pump backed by four pumping groups each consisting of a mechanical pump an oil diffusion pump and a freon refrigerated baffle. The only maintenance required by the oil diffusion pumps over the entire period was 118
replacement of the oil by a silicone DC703 oil in 1963. From the results of the survey the pumping system is evaluated. In a further study, the effect of the oil partial pressure on the particle loss from the accelerator was accounted for by a total pressure of 2 x 10-O torr when the oil used has a partial pressure of 10m9torr. G Rommel, Le Vide, 21 (125), Sept-Ott 1966, 369-374 (in French). 32 : 21 393. Pumping problems and some solutions adoKtad in recent linear accelerators for particle beams. (France) Various aspects of the pumping requirements for linear accelerators are considered leading to the conclusion that conventional mechanical /oil-diffusion combinations are inadequate and recommending the use of ion pumps or turbomolecular pumps. The advantages and disadvantages of each system are summarized with particular reference to the vacuum achieved in the accelerating zones where strong rf fields operate. Two recently constructed accelerators are described and their pumping systems evaluated. G Azam and J Milcamps, Le Vide, 21(125), 1966,380-385 (irl French). 32 : 21 394. Construction of the vacuum chamber for a synchrotron. (France) The most important properties of the vacuum chamber are that it can withstand large radiation doses of the order of IO” rads and that it does not distort the magnetic field. To this end, prototypes in alumina ceramic, glass and stainless steel were investigated and the advantages and disadvantages of each are described together with the appropriate fabrication techniques. None of the three systems are free from fault and the final choice must depend on considerations of economy and safety of the specific application. M J M Lefebvre, Le Vide, 21 (125), Sept-Ott 1966, 386-390 (01 French). 32 : 21 395. Determination of the vacuum system in a large accelerator. (French) The criteria for selection of vacuum pump combinations to meet the demands of large accelerators are described. The availability of ion and turbomolecular pumps facilitates the resolution of many problems. Examples of the application of these criteria are given with respect to an electron synchrotron and a proton synchrotron. G Rommel and R Vienet, Le Vide, 21 (125), Sept-Ott 1966, 391-395 (in French). 32 396. Iron-free one-turn synchrotron type BSB. (USSR) The design of the synchrotron type BSB is described. Its accelerating chamber is pumped by two oil-diffusion pumps with liquid N2 traps to obtain the operational pressure 5 x 1O-6 torr. A relatively large fore-vacuum reservoir chamber with its own liquid N, trap allows to switch the mechanical fore-vacuum pump off for 15 hours during the work. G I Budker et ul, Zh Tekh Fiz, 36 (9), Sept 1966, 1523-1535 (in Russian). 32 397. Probing plasma investigation in thermoemission converters of high caesium pressure. Part 3. (USSR) In this part of the paper results of measurements of the distribution of density, electron temperature and spatial potential in the interelectrode space of thermoemission converters with Cs vapour pressures 0.4 to 2 torr are presented for both diffusion and arc regimes. G A Dyuzhev et al, Zh Tekh Fiz, 36 (9), Sept 1966, 1685-1697 (i/l Russian). JL
398. Vacuum evaporating system with inductive heating to evaporate radioactive metals and metal oxides. (Austria) A vacuum evaporating system is described for the evaporation of radioactive metals and oxides. The evaporating quartz container is demountable and is placed in a glove box. An induction heating coil is placed over an arm container, in which Pu and U are placed as nitrates, W as metal. Pu and U nitrates are converted to oxides by heating. After high-temperature evaporation, the deposits containing U and Pu oxides are converted to dioxides by heating in hydrogen at looo”. W Fiedler et al, Atom-kerenergie, 11, 1966, 257-258 (in German).