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北京谱仪升级后 (BESⅢ )的飞行时间计数器 (TOF)将使用精细网型光电倍增管 (PMT) .本工作对日本浜松 (Hamamatsu)公司生产的精细网型光电倍增管R5 92 4 (FM )的性能在强磁场下进行了测试 .测量了PMT在顺、逆磁场方向时相对增益随磁场强度的变化 ,在 1T时 ,与 0磁场相比 ,相对增益下降约 5 0余倍 .测量了不同磁场强度 (0 ,0 .5 ,1T)下 ,PMT的相对增益随工作电压的变化 ,在相当宽的工作电压范围内 ,相对增益随工作电压的变化具有指数关系 .通过不同磁场强度下PMT相对增益随工作电压变化趋势的比较 ,表明PMT打拿极精细网型的特殊构造使二次电子发射系数δ中的因子k小于一般值 ,且随磁场强度的增强而变小 ,这是造成强磁场下PMT增益下降的重要原因 .
Fine mesh photomultiplier tube (PMT) will be used for the time-of-flight counter (TOF) of BESIII after the upgrade of Beijing spectrometer.This work was conducted on Hamamatsu’s fine mesh photomultiplier tube R5 92 4 (FM) The performance of the PMT was tested in a strong magnetic field.The relative gain of the PMT with the direction of the forward and reverse magnetic fields was measured with the magnetic field strength change, the relative gain decreased by about 50 times at 1T compared with 0 magnetic field. Under the magnetic field strength (0, 0.5, 1T), the relative gain of PMT varies with the operating voltage, and the relative gain varies exponentially with the operating voltage over a wide operating voltage range. By comparing the PMT with different magnetic field strengths The comparison of the gain with the trend of the operating voltage shows that the special structure of PMT dynode makes the factor k in the secondary electron emission coefficient δ smaller than the normal value and decreases with the increase of the magnetic field strength, An important reason for the decrease of PMT gain.