THE OBSERVATION OF PRIMARY COSMIC-RAY BY JAPAN-RUSSIA COORPORATIVE BALLOON EXPERIMENT

为了弄清宇宙线能谱中所谓的“膝”，即谱倾斜度的急剧变化，自1995年以来，我们一直在进行这个实验。从堪察加半岛到伏尔加河的长时间气球飞行于1995年、1996年和1997年分别进行了两次、两次和三次，在9次飞行中有8次成功地观测到宇宙线。通过双方的互访，对回收舱的拆卸、X线胶片和核乳胶的处理、分析方针的讨论和分析数据的比较进行了讨论。这些相互访问的讨论和合作工作对研究的进展是非常有效的。此外，日俄双方开发了一种新的自动测量系统，该系统由显微镜、精密工作台和计算机组成。该系统实现了将级联簇射追溯到核乳胶顶点的繁琐工作的简化，并为长周期观测提供了大量数据分析的能力，我们已完成了1995年的观测数据分析，得到了按化学成分分类的能谱。统计量不够，但在低能区与能谱有较好的一致性。这些结果在1997年于南非Darvan召开的国际宇宙线会议上得到了报道。利用该系统对1996年和1997年的观测资料进行了处理分析，预计今年夏季将得到结果。

This experiment has been carried out amually since I995, for the purpose of making clear so called "knee" in the cosmic-ray energy spectrum which is a rapid change in an inclination of spectrum. Long duration balloon flights from Kamchatka to Volga River were earried out twice in 1995, twice in 1996 and three times in 1997, and 8 flights in total 9 flights were succeeded in the observation of cosmic-ray. The disassembly of recovered chamber, proccessing of x-ray film and nuclear emulsion, the discussion about the policy of analysis and the comparison of analized data were performed through the mutual visit by both side. These discussions and cooperative works through mutual visit were quite effective for the progress in reaserach.Moreover, both side of Japanese and Russian group developed a new auto measuring system which consists of a microscope, precision stage and computer. This system realized the deduction of laborous work in the tracing back of the cascade shower to the vertex point in the nuclear emulsion, and give us a large capacity for the analysis of a large amount of data by the long dulation observation.We have already finished the data analysis for the observation in 1995 and obtained the energy spectra classified by chemical composition. The statistics is not enough but the results shows a good consistency with the energy spectra in low energy region. Convining the methodology as the energy and charge determination, these results were reported in 1997 international cosmic-ray conference held in Darvan, South Africa. The data processing for the 1996 and 1997 observation is under the analysis by use of the above mentioned new system, and the results are expected to be obtained in this summer.