Development of Time-Zero Detector for PHENIX Expriment at RHIC

第二个原型探测器由1“PMT和细网倍增器电极组成，石英块安装在PMT窗口上，在KEK-PS用π介子束构建和测试。辐射器块的形状被优化为3 cm长的六边形。第三个原型探测器由一个整体组成，最后，对最佳形状的辐射体和改进的光电倍增管阴极-倍增极结构进行了新的设计和测试。结果表明，在磁场作用下，脉冲高度下降了30%，但在磁场强度达到3 kg时，时间分辨率仍保持在50 ps的水平.研究了PHENIX探测器中束/束计数器的蒙特卡罗模拟程序，指出在PHENIX实验的高粒子多城环境下，相邻探测器单元之间的粒子串扰可能会引起一些问题.在BNL-AGS对第三代原型探测器进行了重离子束测试，证明了即使在如此高的粒子多重数下，时间分辨率也可以达到50 ps量级.仿真结果表明，第三代样机的波束/波束计数器将以40 ps的精度提供碰撞时间信息。一个原型探测器已经在15 μ A阳极电流的非常硬的条件下运行了85天，这模拟了一个RHIC年的非常高的计数率的条件，但没有发现任何问题。人们发现一个原型探测器照射后1 MR的伽马射线工作正常，没有任何干扰。8.最后，我们决定采用第三个原型探测器的设计作为PHENIX的最终设计，因为PHENIX实验的所有要求都已经通过了它，我们在1995年开始批量生产它。

1.2nd prototype detector consisting of 1"PMT with fine mesh-dynodes and a Quartz block mounted on the PMT window, was built and tested with a pion beam at KEK-PS.The shape of the radiator block was optimized to be a hexagonal shape with 3 cm long.2.3rd prototype detector which was composed, in one united body, of the optimum shaped radiator and an improved PMT on its cathode-dynode structure was newly designed and tested with the pion beam. It was found that pulse heights in a magnetic field drop by 30%, but timing resolution remains at the same level 50 ps under magnetic fields up to 3 kgauss.3. A Monte Carlo simulation code including the Beam/Beam Counter in the PHENIX detector was studied, and indicated that particle cross talks between neighbor detector elements may cause some problems under high particle multicity environments of the PHENIX experiments.4. The 3rd prototype detector was tested with a heavy ion beam at BNL-AGS,and it proved that even under such a high particle multiplicity, the time resolution of 50 ps level can be achieved.5. The simulation indicates that the Beam/Beam Counter with the 3rd prototype will provide the information of a collision time at the accuracy of 40 ps.6. A prototype detector has been operated for 85 days under a very hard condition of 15 muA anode current, which simulates a condition of very high counting rates for 1 RHIC year, but found no troubles at all.7. It was found a prototype detector after irradiation of 1 MR of gamma-rays works fine without any troubles.8. Finally, we have decided to adopt the design of 3rd prototype detector as the final one for the PHENIX,since every requirement for the PHENIX experiment has been cleared with it. In 1995, we start the mass production of it.