The ET Enterprises' range of fast photomultipliers has a focus electrode that can be biased negative with respect to the photocathode to cut off the photoelectron input to the multiplier section.

This is essential to avoid saturation of the photomultiplier output and processing electronics in applications such as fluorescence lifetime measurements and LIDAR.

Photomultiplier types with focus electrodes.

9214 9372 9426 9427 9813 9814
9817 9821 9822 9823 9921 9939
9954          

Circuits

Two complimentary versions are available to gate ON or gate OFF a photomultiplier normally in the opposite state:

  • GB1A switches OFF a normally ON photomultiplier
  • GB1A/DC can be switched OFF indefinitely
  • GB1B switches ON a normally OFF photomultiplier

Gating parameters, referred to in the table below, are defined in the diagrams below.

  GB1A GB1A/DC GB1B
 pmt voltage (max) 2500V 2500V 2500V
 gate level amplitude
 (max)
5V, 50 mA 5V, 50 mA 5V, 50 mA
 gate pulse width
 Gw  (min)
2 µs n/a1) 2 µs
 gate delay d1 0.5 µs n/a1) 0.5 µs
 gate delay d2 0.7 to 7 µs2) n/a1) 0.7 to 7 µs2)
 gated pmt output
 width Ga (min)
5 µs 1 ms 5 µs
 gated output
 width (max)
1 ms   1 ms
 period (min) 1000 x Gw n/a 1000 x Gw
 t off 0.2 µs n/a1) 0.2 µs
 t on 1.0 µs n/a1) 1.0 µs
 cut-off ratio (typ) 1000:1 1000:1 1000:1

Diagrams

Gating diagram 1

Gating diagram 2, sample trace.

1) DC gating board is not recommended for use in pulsed mode. The 5 V gate input should be switched manually, or from computer control.

2) Gating boards are powered from the voltage divider; the voltage divider resistances determine the recharging time. Generally, higher current dividers have shorter gate delay d2.

© ET Enterprises Limited 2011-2015
ET Enterprises is a trading name of ET Enterprises Limited. Registered in England & Wales, company number 06081468.