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RIKEN Accel. Próg. Rep. 24 (1990)

V-2-20. Performance Test of Lumped NEG Pump

S.R. In,¹ T. Maruyama,² S Yokouchi, and S.H. Be

In the vacuum system of SPring-8, synchrotron radiation produced in bending magnets is mostly intercepted by crotches and absorbers. To protect other vacuum components from severe inrush of the photo-desorbed particles from the crotches and absorbers, a proper pumping system of sufficient pumping speed and capacity must be prepared. A Lumped NEG Pump (LNP) was manufactured and tested to examine such reąuirement.

Słructure of LNP A proto-type LNPⁿ consists of

LNP

LNP lumped Nc$ P%/np TMP Turbo MotoCutJr Pump OMA Oujdrupok AnaJyicr DACil.i B-iyjrJ Alpen Nade Gjuge A V Mi/iutl Arifle V*l\«

GV M»_w|(uifV VLV Vmjbte Uak VłIvc

Fig. 1. Schematic diagram of the experimentaJ setup for the LNP.

14 St 707 non-evaporable getter (NEG) wafer mod-ules installed concentrically in a cylindrical housing madę of Al-alloy. The inner virtual surface madę by 14 wafer modules forms a strong adsorbing cylindrical channel of which diameter and length are all 250 mm. The diameter of the pumping port is 200 mm, and the total weight of the LNP is about 45 kgf.

Performance test of LNP Figurę 1 shows a schematic diagram of the experimental setup. Figurę 2 indicates the pumping speeds of the LNP for H₂, CO, N₂ and C0₂. CO is morę reactive with the NEG materiał and, conseąuently, has a higher sticking coefficient than H₂. However the pumping

Q (torr.l/cm2)

a)

Q (torr.l/cm2)

Fig. 2. Pumping speeds of the LNP for H₂, CO, N₂, and C0₂ as a function of the sorption amount of each gas.

Fig. 3. Comparison of measured pumping speeds of the LNP for a) H₂ and b) CO with calculated pumping speeds using the data of 1 wafer module experiment.

1

On leave from KAERI, Dajeon, Korea.

2

♦ ¹ Osaka Yacuum Ltd.