Particle detector for Tristan electron-positron collision experiment

Many of the elemental processes following an electron-positron collision involve the production of unstable paired particles. To investigate the elemental and secondary processes accompanying a collision, it is necessary to make a simultaneous observation of a large number of various high-energy particles. The system for the experiment comprises a magnetic spectrometer and a shower counter. The spectrometer consists of a large tracking chamber and a superconducting solenoid. The chamber is placed in a static magnetic field to detect a charged particle passing various detection points. The set of points where the particle is detected represents its path. A drift chamber is adopted which is designed taking into account the following three processes: (1) formation of ionizing electrons along the particle path (track generation), (2) forced transfer of electrons due to static magnetic field (electron drift) and (3) electron amplification by local strong electric field after the transfer (signal generation). If the drift rate is known, a point where the particle passes can be determined from the drift time from (1) to (3). A high-energy particle produces shower after entering a high-density material. The energy of the particle can be estimated from the amount of the shower, which is represented by, for example, the total number of secondary particles produced. (Nogami, K.)