A miniature extractor gauge for the UHV (in particle storage rings)

An extractor type ionization gauge has been developed for flange mounting in a 15.7 mm diam. aperture. The gauge electrodes are aligned by ceramic plates. A cylindrical anode grid of 9 mm diam. and 12.5 mm length is formed of photo-etched W-sheet. A thoria coated W-filament is employed made from two semicircular loops mounted outside and concentric with the anode grid. The two halves of the filament are connected in parallel. The height of the electrodes from the top of the anode grid to the base of the hemispherical collector is 18.9 mm. The gauge design is a compromise between obtaining a low X-ray or pressure limit, high sensitivity and high electron emission current. The foregoing, given in the same order, were respectively 5*10/sup -12 / torr; 5 torr/sup -1/ for N/sub 2/ at 10 mA emission current and 6 torr/sup -1/ at below 5 mA; and an emission current of between 5-10 mA which gave the high anode current density required to maintain a clean grid. (15 refs)