Model 421 Series

The Model 421 Series photomultiplier (PMT) bases incorporating a preamplifier and a high voltage (HV) supply are intended for use with 10-stage PMTs fitted with standard 14-pin sockets. Each unit consists of a resistive divider/preamplifier and bias supply board.

For Models 421 and 421-3, a BNC receptacle (labeled SIGNAL) provides the pre-amplified signal output. The tail-pulse output is a positive-going pulse (Model 421) or negative-going pulse (Model 421-3). For Model 421-1, a BNC receptacle (labeled SIGNAL) provides either AC coupled anode output (negative) or pre-amplified output (positive). 

For all models, the output pulse has an approximately 50 μs tail for connection to a shaping amplifier. The output amplitude may be varied by HV bias adjustment.

Models 421 and 421-3 operate from a 12 Vdc supply only (NIM type 9-pin "D" connector). Model 421-1 operates on 8 - 18 Vdc power supplied either through the NIM compatible plug (9-pin "D") or through a 2.5 x 5.5 mm barrel plug.