一、引言我们在实验中观察到所用的光电倍加管在某些取向时,由于地磁场的影响其增益显著下降.文献[1—4]中也曾定性地指出地磁场对光电倍加管增益的影响有时是不可忽略的。因为在实验过程中常常需要改变光电倍加管的取向,为了保证测量的精确度就必须了解这种影响的大小,并设法消除它。为此本文研究了我们常用的几支。ФЭУ-19、ФЭУ-33和ФЭУ-36型 I. INTRODUCTION We observed in experiments that the gain of a photomultiplier tube used in some orientations decreases significantly due to the effect of the geomagnetic field. References [1-4] have also qualitatively pointed out the influence of the geomagnetic field on the photomultiplier tube gain Impact sometimes can not be ignored. Because it is often necessary to change the orientation of the photomultiplier tubes during the experiment, it is important to understand the magnitude of this effect and try to eliminate it in order to ensure the accuracy of the measurement. This article studies several of our commonly used. ФЭУ-19, ФЭУ-33 and ФЭУ-36