A precise measurement of the cosmic-ray antiprotons in the solar minimum period and a study of their origin

我们用BESS光谱仪进行了四次气球观测。有效载荷是在加拿大的林恩湖发射的，那里的地磁截止刚度很低。1997年是太阳活动最平静的时期，之后逐渐增强。据报道，2000年太阳磁极发生了变化。在本项目期间收集到的数百个宇宙线反质子以及质子和氦核，为研究反质子的起源、星系传播和太阳调制机制提供了宝贵的数据。我们在反质子谱中观测到了2 GeV左右的峰值，这是次级反质子的特征，并确定了大部分宇宙线反质子是初级宇宙线与星际介质相互作用的次级产物。我们还在高山上测量了宇宙线，以研究其在大气中的发展。为了进行上述研究，我们升级了BESS光谱仪;提高了飞行时间分辨率，安装了气凝胶切伦科夫计数器和淋浴计数器，并升级了数据采集系统。

We have carried out four balloon observations using the BESS spectrometer. The payload was launched at Lynn Lake, Canada, where the geomagnetic cut-off rigidity is low. The solar activity was at the most quiet phase in 1997 and then it gradually increased. It has been reported that the solar magnetic polarity has been changed in 2000. Hundreds of cosmic ray antiprotons together with protons and helium nuclei collected during the term of this project have provided valuable data to study the origin of antiprotons and the mechanism of galactic propagation and solar modulation. We have observed a peak in the antiproton spectrum at around 2 GeV, characteristic of the secondary antiprotons, and established that the majority of cosmic ray antiprotons are the secondary products of the interaction between primary cosmic rays and the interstellar medium.We have also measured cosmic rays at a mountain altitude to study the development in the atmosphere. In order to perform the above studies, we have upgraded the BESS spectrometer ; improvement in the time-of-flight resolution, installation of an aerogel Cherenkov counter and shower counters and upgrade of the data acquisition system.