IniFial trapping process of ultra slow antiprotons

目前的研究项目主要计划在两年内与科学研究补助金相结合，以建造一条超慢反质子传输光束线。然而，该项目只获得了第一年的批准，这使得整个项目的一致性很难保持。该项目的目的是为安装在欧洲核子研究中心LEAR(低能反质子环)的Penning陷阱中提取的超慢反质子准备一条传输光束线，这使得首次能够研究在单一碰撞条件下反质子进入原子轨道的初始捕获过程。由于时间有限，我们在第一阶段试图找到一种有效冷却被捕获反质子的方法，然后优化从陷阱中提取慢反质子的条件。在测量陷阱中反质子的湮没速率时，人们可以估计反质子在剩余气体的原子轨道中的俘获截面，这被认为与反质子的速度成反比，即湮灭速率保持不变。然而，我们的实验表明，俘获截面在冷却开始时增加，然后开始减小，这清楚地表明俘获截面在低速区饱和，甚至随着速度的降低而减小。目前的项目进展令人满意，除了加速器故障造成的一些延误外，没有任何严重的问题。现在我们相信，我们已经准备好在下一财政年度成功完成拟议试验的主要部分，即从4月到9月几乎每天都分配波束时间，将波束线发送到欧洲核子研究中心，等等。然而，需要指出的是，要求继续支持访问欧洲核子研究中心的提议已被拒绝。

The present research project were primarily planned for two years combined with Grant-in-Aid for Scientific Research to construct a transport beamline for ultra slow antiprotons. However, the project was approved only for the first year, which makes it very difficult to keep the consistency over the whole project.The purpose of the project has been to prepare a transport beamline for ultra slow antiprotons extracted from a Penning trap which is installed at LEAR (low energy antiproton ring) of CERN,which enables, for the first time, to investigate the initial trapping processes of antiprotons into atomic orbitals under single collision conditions.Because of the limited time, we have, in the first stage, tried to find a way of cooling trapped antiprotons efectively, and then to optimize the extraction condition of slow antiprotons from the trap. In measuring the annihilation rate of antiprotons in the trap, one can estimate the capture cross section of antiprotons into atomic orbitals of the residual gas, which has been believed to be inversely proportional to the velocity of antiprotons, i.e., the annihilation rate stays constant. However, our experiment shows that the rate increases at the beginning of the cooling, and then start to decrease, which is a clear indication that the capture cross section saturates in the low velocity region or even decreases when the velocity decreases. The present project proceeds satisfactorily without any serious problem except for some delay originating in accelerator troubles. Now we believe that we are ready to make the major part of the proposed experiment successfully for the coming fiscal year, i.e., the beamtime is allocated almost every day from April to September, the beamline is sent out to CERN,etc. It is noted however, that the proposal asking continuation of the support to visit CERN has been rejected.