Development of compact emulsion spectrometer using a permanent magnet

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We have developed a compact emulsion spectrometer which can be used in places where neither electronic detectors nor electromagnets are available.(1)We designed and constructed a permanent magnetic circuit for the compact emulsion spec-trometer in cooperation with company engineers. Two types of magnetic circuits were examined by calculating magnetic field to be produced. Three-layer-structure Halbach configuration was chosen because it would produce uniform magnetic field inside it.(2)We measured magnetic field inside the magnetic circuit and confirmed that it was almost the same as the designed value.(3)We made a compact emulsion spectrometer by inserting an emulsion chamber which consists of emulsion films and spacers.(4)The compact emulsion spectrometer was exposed to a 180 MeV/u Carbon beam of HIMAC, the National Institute of Radiological Sciences in order to study its performance. The momentum (p/z) of the Carbon beam was successfully measured with a resolution of 12% from the difference between track angles in the most upstream and the most downstream films.(5)It was also exposed to a 158GeV/N Indium beam of SPS, CERN in order to examine its performance on the momentum measurements of pions and Kaons produced in high energy nucleus-nucleus interactions. The analysis is now in progress.