406 



V. M. Zaporozhetz and E. M. Filippov 



absorbent it is possible to rely on the possibility of supporting the necessary 

 vacuum in the tube during a 6-8 hour worldng day. This interval of time 

 is completely sufficient to investigate a bore-hole. Afterwards the absorbing 

 substance can be changed. 



It is completely sufficient to maintain pressures of the order of 10~* mm Hg 

 in an acceleration tube. In order to ensure the absorption of the gas flowing 

 into the tube under this pressure the necessary surface of the absorber 



1 7 X 10"^ ' t— 



should be of an order of — x7.6x 10^x1/2 r^S cm^ . Considering 



60 



the unavoidable contamination of the constituent parts of the tube and 

 also its imperfect hermetic qualities this figure should evidently 

 be increased several times. An absorber possessing such a surface can be 

 used in a bore-hole device. 



It is considered quite desirable to test the use of absorbers. 



4. The use of an ion pump with an absorber 



In order to maintain vacuum in an acceleration tube it is also possible to 

 use an ion pump with an absorber. This is a device in which gas molecules are 

 ionized in an electric field and are directed towards an absorbing surface. 

 However, such a method of maintaining vacuum is evidently only slightly 

 more effective than the use of an absorber by itself (^^). 



5. The use of an ion pump to extract the gas 



Figures 5 and 6 show two types of sealed acceleration tubes. 



Fig. 5. A basic construction scheme of a sealed acceleration tube with different pres- 

 sures at the ion source and the tube. 1 — target; 3 — an electrode extracting the ions; 

 4 — an electrode; 5 — a device ensuring the pressure difference between the chambers 

 6 and 7 ; other notations are the same as in Fig. 4. 



