Drift chambers for the observation of multitracks in cosmic ray air showers

Drift chambers have been used to observe multiple tracks in extensive air showers (EAS) produced by ultrahigh energy cosmic rays. Our drift chambers are 80 cm × 80 cm × cm in size with four drift cells. Each cell is 20 cm × 80 cm × 10 cm with five anode wires and the drift length is 10 cm. A spatial resolution of better than 0.3 mm and an angular resolution of better than 0.45° have been obtained for the drift chamber system. As many as 50 particles/m² can be resolved with a minimum separation of 2.8 mm. Two sets of drift chamber systems are now in operation with a conventional array of plastic scintillation detectors for EAS observations. The performance of the drift chambers and the readout system are described.