Development of a Two-dimensional Angular-correlation-of-annihilation-radiation Apparatus Using Position Sensitive Photomultiplier Tubes

一种新颖的、新型的二维角相关湮没辐射(2D-ACAR)装置的研制已成功完成，并已投入实际使用。目前，探测器放置在距样品5米的地方。对于尺寸为2 mm的样品，其角分辨率为1.1×10~(-3)；新装置的特点是：(1)它是一种新颖的新型2D-ACAR装置，利用HAMAMATU公司开发的位置敏感光电倍增管。2.2 mm×2.2 mm×15 mm BGO闪烁晶体块阵列与光电倍增管耦合。(2)伽马射线入射位置的检测方法，数据处理系统，探测器的位置控制系统都很简单。(2A)通过CAMAC ADC分析连接到光电倍增管多线阳极的电阻链的8个输出，然后用个人计算机进行处理，简单地确定伽马射线入射位置。(2B)探测器的平移和旋转运动由同一个人计算机控制的单个伺服电机驱动。这样就没有了大臂，否则就不需要让探测器直接面对样品，而不管它们的位置如何。无臂系统使改变探测器布置变得容易。(3)可通过电磁铁将高达-lt；正负2T的可变磁场施加到样品上

The proposed development of an original, new-type two-dimensional angular-correlation-of-annihilation-radiation (2D-ACAR) apparatus has been successfully accomplished.The machine is already in practical use. At present the detectors are placed at 5m away from the sample. The angular resolution for a sample of size 2mm is 1.1x10^<-3>mc.The characteristic features of the new apparatus are as follows :(1) It is an original, new type of 2D-ACAR apparatus, making use of position senseitive photomultiplier tubes developed by HAMAMATSU.Arrays of 2.2mm x 2.2mm x 15mm BGO scintillator crystal blocks are coupled with the photomultiplier tubes.(2) The methods for the detection of the gamma ray incident position, the data processing system, and the detectors position control system are all simple.(2a) The gamma ray incident position is determined simply by analyzing the 8 outputs from the resister chains conected to the multi-wire anodes of the photomultiplier tubes by CAMAC ADC and then processing them by a personal computer.(2b) The translational and rotational motions of the detecters are driven by individual servo-motors controlled by the same personal computer. This gets rid of large arms otherwise necessary to keep the detectors directly face the sample regardless of their positions. The armless system make it easy to change the detector arrangement.(3) A variable magnetic field up to <plus-minus>2T can be applied to the sample by an electromagne