Ion Feedback Noise in Channel Multipliers

Abstract

This chapter focuses on ion-feedback noise in channel multipliers. Experimental measurements were made of the pulse-height distribution of an array of channel multipliers, which was subjected to sequential, single-electron input events. The presence of ionic feedback was found to be very prominent. The output pulse-height distribution of the channel multiplier array is shown for two different electric-field conditions in the input region in front of the array. The lower curve was obtained when an electron-retarding field was established between the electrode adjacent to the array and the input surface of the array so that ions emanating from the input surface of the array impacted upon this adjacent electrode. However, the resulting low-energy secondary electrons were unable to enter the array, so that the output was small. Based on preliminary results, it is felt that ionic feedback is a major factor affecting the average gain, the noise, and the operating lifetime of channel multipliers. Imaging devices using channel plates should preferably be constructed using the concentric, spherical electron optics in the input region. Additional electrodes may improve focusing and trap or deflect the hydrogen ions emanating from the channel plate.