Emulsion chamber experiments in People's Republic of China

In People's Republic of China, emulsion chamber experiments were initiated in about 1973, and have been expanded. An emulsion chamber is mainly consists of lead plates and X-ray film manufactured in China. The shower energy of cosmic ray is determined mainly by applying photoelectric densitometry to X-ray films. Reference is prepared and calibrated in advance by comparing the photo-electric density of an X-ray film measured with a micro-photometer, which had been irradiated with an electron accelerator, with the number of electrons at the corresponding position on the film. The first test chamber was exposed at the Yunnan station (3200 m above sea level) in spring of 1974. Its major purpose was to know the performance of X-ray films and general testing conditions. Gamma intensity was (2.20 +- 0.21) x 10-10/cm2. sec. sr. in the energy region above 2 TeV in Yunnan station. The attenuation coefficient of 95 +- 10 g/cm2 was determined from the distribution of zenith angle. In 1976, a small chamber of 0.3 m2 was placed, then the emulsion chamber with 13 ton lead was constructed in August, 1977, on the top of Mt. Kanpara located about 110 km south-west of Lhasa city and 5500 m above sea level. These chambers were dismantled in April, 1978, and the new emulsion chamber was installed at the same time together with 13 ton lead plates. Also in May, 1978, the test chamber was exposed to radiation at the foot of Mt. Chumlamma, 6500 m above sea level. (Wakatsuki, Y.)