Development of a crystal installing SQUID's for the detection of charged particles

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A weak magnetic field follows a moving charged particle and the strength of the field increases with the velocity of the particle. Accoridng to our calculation using the theory of special relativity, it is predicted that the strength of the magnetic field induced by a charged prticle moving with a relativistic speed have an order of magnitude detectable by a SQUID. This fact opens a possibility of detecting a charged particle without directly "touching". As a first step we develop a crystal for the installation of the SQUID which should be operated at the helium temperature. The crystal is characterized with a hole through which charged particles can come and go.Thinking of the future development, we decided to use FRP material instead of metal such as stainless steel. The type of the FRP was examined in order to survive the low temperature and to achieve good magnetic character. For the liquid and the vacuum seal, a screw system has been tested and developed, which makes the assembling and the deassembling easy. In a preliminary test we succeeded in sealing the liquid nitrogen and also the liquid helium. The prototype crystal could keep the liquid nitrogen for a while, but it was not possible to reach the stage of keeping the liquid helium. The cause of the leakage was detected and we hope we can keep them after the improvement progressing now.