A 70cm STREAMER CHAMBER SYSTEM

Abstract：

In this paper, the design, construction and characteristics of a 70cm streamerchamber system are deseribed. A very fast pulse with rise time 2 ns and duration 10ns has been successfullyobtained by using a four-spark-gap cylindrical Blumlein line with a 25 stage Marxgenerator (up to 600kV) connected to it. The output pulse of the Blumlein line isthen fed to the chamber, via heteromorphic transmission line with pulse shapeminimum distortion. The system are triggered by three-fold large area scintillation counter telescopeto pick up particle of the cosmic ray traversing the sensitive volume of the chamber.The coincidence-counting rate is ～5 particles/min., the resolving time is 10ns, andthe ratio of the true-accidental coincidence is more than 700. The chamber has two 15 cm gaps and is 70 cm long, 50 cm wide, with 30Ω ofcharacteristic impedence. In order to photograph through the electrodes, the central and the ground electrodes towards the cameras are made of 0.2mm diameter beryl-lium-copper wire stands spaced 2 mm apart, with transparency～90%. Pure neon and mixtures of neon-helium gas were used to fill the chamber, oneatmosphere, and a cycling and purifier system were designed to maintain its purity.The gas is passed through type 5A and 13x molecular sieve operated at room andliquid -nitrogen temperature to remove CO₂, H₂O and O₂, N₂, respectively. The im-purities of the chamber gas can be reduced to 0.2% within 2hr., at the gas flow rate500 1/hr. All photographs are taken with one or two oscilloscope cameras on 35mm film of28 DIN. A demagnification 30x and a resolution 30 line pairs/mm at the maximumaperture (f/2) are used. The sizes of the visual streamers were estimated about3 to 4 mm in diameter (view along the E field), and 10 to 15 mm long (view perpen-dicular to the E field). The delay time between the penetration of charged particle and the supply of thehigh voltage pulse on the chamber was ～3.5μs. The system was suggested in June1975. The whole facility began to mount and adjust in January 1979, and the strea-mer tracks were seen on July 26, 1979. We plan to make the performance tests, to reduce the delay time of the system,and to improve the chamber suitable for use in high energy accelerator and cosmic-ray experiments in the near future.