No abstract available

[en] During design and construction of the SLAC polarized LEED (PLEED) system, a search was made for a dependable gear, bearing and lubrication system for the computer-controlled Faraday cup used to measure diffracted beams. Components must be nonmagnetic, bakeable to 250⁰C, and at room temperature must operate at pressures in the 10^-9 to 10^-10 Pa range. A test system was constructed which incorporated a meshed pair of dissimilar pitch diameter spur gears, one of which was confined by bushings to a fixed shaft on which it rotated, while the other gear was driven through a commercial rotary motion feedthrough rotated by a servo motor driven in sine fashion with a direction reversal every six turns and peak speeds of 50 rpm. The criterion for a successful pair was approx. equal to 10⁵ turns, the life rating for the feedthrough. Pairs had actual turn counts from less than 1 to 91 000. Materials for gears included stainless steel, beryllium copper and aluminium alloys. Lubricants used singly and in concert were MoS₂, WS₂, Ag, hard chrome and a MoS₂-graphite-sodium silicate-coated Be-Cu. Subsequent performance in the PLEED system after repeated bakeouts will also be discussed. (orig.)

[en] The beam pipe vacuum system of the HERA proton ring has a length of 6.3 km. During operation of the superconducting magnets the beam pipe is at the temperature of liquid helium over about 5.5 km. There are no detectable leaks within this critical section. The operational pressure is below 10^-12 mbar. The round beam tubes with length up to 10 m are coated with copper of good electrical conductivity from the inside. The remaining 800 m of the system are at ambient temperature. The chambers have different complicated cross sections produced with high precision. Inspite of limited space in certain areas, bakeout up to 300deg C is possible in situ. (orig.)

[en] A new type of driving mechanism suitable for fast U.H.V. valves is presented, based on the electrodynamic forces exerted between closely spaced current carrying conductors. The valve is forced at its maximum throughput within some fractions of a millisecond and it is kept open for some milliseconds, depending on the type of circuit used to excite the coils. A capacitor is used as energy storer and as the source of the fairly large currents required to deliver the necessary acceleration to the sealing needle. Owing to its good timing properties the valve is used for the gas puffing in the Tokamak THOR, while an improved version is under development in order to achieve a faster aperture and a better control of the time the valve stays open

[en] A vacuum post for pumping-out of devices, used for adsorbents investigation, is described. Such vacuum post, generating pure oilless vacuum, is necessary to regenerate adsorbents under investigation. Pure oilless vacuum is produced with the help of two forevacuum pumps with the following pumping-out with highvacuum adsorption and titanium pumps. Adsorption pumps are cooled by liquid nitrogen. It is established in the result of the test of vacuum post with four devices with adsorbents connected with it, that using only adsorbtion pumps for pumping-out the pressure of P = 10^-1 Pa is achieved in devices; after preliminary blowing of all system with dry nitrogen P=10^-2 Pa; during the simultaneous operation of adsorption and titanium pumps at two-hour heating of devices with adsorbents P=6x10^-3 Pa, and at 6-hour heating P=3.2x10^-4 Pa. The limit vacuum, achieved by vacuum post, is equal to 5x10^-5 Pa with devices P=1.2x10^-4 Pa. The devices heating has been carried out at 200 deg C. All post sealings are resin. Described vacuum post permits to accelerate adsorbent regeneration in devices without pollution of studied adsorbent with working substance of pumps

[en] Published in summary form only

[en] A prototype of a cryopump adapted to the operating conditions of the Tokomak Petula has been built and tested. We describe the chosen solutions in order to, obtain a working temperature of 2,16 K and, allow an automatic feeding of cryogenic liquids. We present results of experiments performed in either permanent or pulsed regimes of hydrogen injection. The pumping speed measured on the prototype is 3000 l/s for hydrogen; the pump could absorb more than 10 liters N T P of hydrogen before saturation corresponding to a three month working period for the Tokomak. The liquid helium consumption including transfer losses was 0.9 l/day

[en] A method for mounting thermocouple gauge tubes which eliminates the need for teflon tape wrapping, ring seals, greases, etc., and essentially eliminates all sources of contamination is described

No abstract available

No abstract available