We have exposed an emulsion chamber with full use of screen-type X-ray film at a level of 11.7g/cm^2 for∿20h. Our chamber consists of a sandwith of stainless target (500μm thickness each) and sensitive materials such as Fuji #200-type X-ray film (non screen type), nuclear emulsion plate and screen-type X-ray film (Fuji Grenex HR_8+Fuji RXO_H film). Since electromagnetic calorimeter layer is removed, it makes possible to construct large size emulsion chamber with light weight. We discuss the possibility of a screen-type X-ray film for the observation of heavy cosmic ray primaries, and report preliminary results obtained by this observation, particularly on an interesting event showing an extremely penetrative nature in the atmosphere with high effective charge, Z=36∿40.
『軽量型エマルションチェンバーによる重一次宇宙線観測』
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