Classified abstracts 5446-5453

related to the observed good performance of SF, in circuit breakers. Arc resistance is also measured during the decay phase. (France) J M Cormier et al, J Phys D: Appl F’hys, 15 (3), 1982.451455.

II. Vacuum apparatus and auxiliaries

20. PUMPING SYSTEMS 20

5046. Design, Mpptroctjol) and testing of a auckar-pmnpiag facility at tbe Universitv of Miswuri - Reactor. (USA) An inter& effort to design, construct and test a nuclear-pumping facility (NPF) has been completed at the University of Missouri-Columbia (UMC). The NPF has a flow capability similar to that of the now defunct Brookhaven Chcmonuclear In-Pile Research. Loop, plus the optical capability .to monitor light output from the irradiation chamber. Both features make the UMC NPF a unique research loop usable for a wide variety of projects including radiation chemistry, fluorescence studies, photochemistry, dual media nuclear-pumped lasers and direct nuclear- pumped lasers. Initial tests of the facility induded a demonstration of 40.0 ft” h-i flow rates (pump limited), and a spectral scan of N, and He. The latter test represents a lirst effort in obtaining nuclear-pumped gas spectra from a high-power steady-state reactor such as the University of Missouri Research Reactor (MURR). Results indicate that observed spontaneous emission mainly comes from the first negative spectral series in NT (8% +x*Z.‘) and from He? electronic transitions. Mie&l J &~ws-& al, Rev Sci I&rum, 53 (7). 1982,952-959.

20 g447. Antomatie control of gas w in a vakmm system. (GB) This paper describes the development of a microprocessor based system to be used for the automatic setting of the gas pressure within a vacuum chamber. The requirements of the system have been presented by five modes of operation which are easily set up by thumbwhed and on/off switches on a pand. The microprocessor system automatically balances the rates of the pumping system and gas inlet to set and maintain the requested gas pressure. Thegas inlet needle valve is controlled by either an ac or dc motor. The use of computer software allows the system to be readily adapted for use with the commonly used needle valves, pressure gauges and pumping systems. It allows for non linear transducers and mechanical wear and additional modes of operation may be easily added when required. The system is intended for use as a subsystem of a microprocessor controlled vacuum system for laboratory or industrial use. The technique has been illustrated by controlling the pressure over the range l-20 torr in a conventionally pumped vacuum system. J Lars et al, Vacuum, 32 (5), 1982,257-263.

20 5448. The LLNL tandem mirror experbeat (TMX) upgrade vacuum system. (USA) The tandem- mirror experiment (TMX) upgrade is a large, tandem, magnetic-mirror fusion experimmt with stringent requiranmts on base pressure (10-f torr), low H reflux from the first walis and peak gas pressure (5 x 10“ torr) due to neutral beam gas during plasma operation. The 225 m3 vacuum vessel is initially evacuated by turbopumps. Cryopumps provide a continuous sink for gases other than helium, deuterium and hydrogen. The neutral beam system introduces up to 480 l/s of H or D.The hydrogen isotopes arepumped at very high speed by titanium sublimed onto two cylindrical radially-separated stainless steel quilttd liners with a total surface area of 540 ml. These surfaces (when cooled to about 80 K) provide a pumping speed of 6 x lO’l/s for hydrogen. The titanium getter system is programmable and is used for heating as well as gettering. The itmer plasma liner can be operated at elevated temperatures to mhance migration of gases away from the surfaces dose to the plasma. Glow discharge cleaning is part of the pumpdown procedure. The design features are discussed in conjunction with the operating procedures developed to manage the dynamic vacuum conditions. W L Pie&s et al, J Voc Sci kchnd, 20 (4), 1982, 1177-l 181.

20 5449. D&sip @d falwication of tbe vacutmt v&s4 for tk toksnmk Won mt teactor. (USA) The design parametm, special features and certain fabrication and test aspects of the TFTR.vacuum ‘vessel are described. The vessel is a single walled, stainless steel toroidal shell, designed for a base pressure of lo-* torr. The design basis includes the electromagnetic loads resulting

from the disruption of a 3 MA plasma in a 5.2 T magnetic field. The vessel is configured to permit maximum access for neutral beam injection and diagnostic equipment. In addition, it is designed so that a segment of the machine can be removed and replaced using remote maintenance techniques. During the fabrication special processes were used to ensure cleanliness, achieve dimmsional control and perform in-process vacuum tests. W G Raldan, J Vat Sci 7irchnol, 20 (4), 1985 1173-1176.

20 5450. A triti nmumsgatibk high-vaenmn gmnplng system. (USA) Large magnetic-fusion power reactors will require vacuum pumps with greater speeds and capacities for hydrogen and helium isotopes than any now available. Present fusion mgineering efforts concentrate on DT- burning tokamaks, so pumps of these systems must perform reliably during prolonged exposure to radioactive tritium gas. A mechanical pumping train that exposes only tritium-compatible metals to the vacuum medium has been assembled. Tbc system comprises a reciprocating metal- bellows compressor, a bellows-sealed, spiral-cavity, positivedisplacemmt blower, and a canned-motor, magneti&earing turbopump. These pumps feature hermetic drives, and their pumping chambers contain no liquid metals, plastics, elastomers, or lubricants. The pumping system achieves vacuums as low as 1 mPa without cryogenics, and its pumping speed increases from 51s-’ at atmospheric pressure to 5001 s-i below 100 mPa Systems with ultimate pumping speeds of 5000 I s-’ can be assembled using larger pumps of the same design as those tested. Doa 0. Coflht, J Vat Sci Technol, #) (S), 1982, 1126-1131.

20 5451. Tanpera~ vamumeeBamltwouagegampingsystem for laau-b&teai m and ahmwgtba stadiea of UF,. (USA) One of the commonly used compounds in uranium processing is gaseous UF6. Laser methods for monitoring UF6 density and pressure have been under investigation at Los Alamos. In order to calibrate these laser probe techniques, an evacuable, temperature-controlled cell was needed for laser-induced fluorescence (LIF) and ultraviolet absorption studies of UF,. It was necessar y to construct the optical cell from materials compatible with UF, and to thermally control the cell. The pumping system had to evacuate the cell and the complete gas-handling system to 5 x lo-” tot-r and also be corrosion resistant. A cell and system were constructed that met and exceeded our requirements. Constant, repeat- able LIF results have been obtained at temperatures of - 30 to 80°C and over the pressure range of 0.005 to 80 torr with this cell. This repeatability is due to the temperature stability of the system (i.e. fO.l”C from -30 to 0°C and *O.OS”C from 0 to 100°C). The well-controlled temperature of the UF, has also allowed us to successfully determine ultraviolet absorption cross sections as functions of temperature over the 0 to 100°C range. By judicious choice of materials&d working fluid, the temperature range of this cell may be extended beyond the - 30 to 100°C range of our present work. R N Shelton et al, J Vuc Sci Technol, 20 (4), 1982, 1114-1117.

21. PUMPS AND PUMP FLUIDS

5452. A eryogenie pump of 20,000 I s-l. (GB) 21

This pump belongs to the vacuum system of GANIL. GANIL is a particle accelerator in construction in Caen, consisting principally of two separated sector cyclotrons. To pump a total surface of about 1000 m2 it has been decided to install a cryogmic pump of 20,000 1 s. This system must be able to maintain a pressure of 2.10b6 Pa (2.10-s tot-r) in the vacuum chamber of the SSC over a period of at least 1 month without regeneration by warm-up. (France) G Rommel, Vmmn, 32 (2), 1982,95-97.

21 5453. Comparison of two pumping speed measllring metbods of oil diffmioa pmn~ GB) This paper presents a comparative study of two pumping speed measurement methods recommmded for oil diffusion pumps. The methods used are the test dome method and the conductance tube method with an auxiliary pumping system which is used at very low pressures when the throughput is below lo-’ Nm s-i. It is found that, in order to obtain the comparative results in the overlapping pressure region on the speed measurement of oil diffusion pumps by these two methods, the conductance tube in the conductance tube method should be located at a height 1.2 D from the pump mouth whm the position of the inlet gauge is at a distance D/2 from the pump flange, i.e. at the same position as

345