Base for 64APMT

1
Base for 64A-PMT

• Why an active base ?

• Very large currents are expected (230µA on the
  hottest PMT) with the present design of the
  electronics (see Stephanes talk).
• Even if we suppose a reduction of the gain of a
  factor 10, there are still currents larger than
  the maximum average current specified by
  HAMAMATSU for his resistive base 18µA.
• Furthermore, we observed overlinearities even
  with Ilt18µA .
• Anyway, an active base is needed for the ageing
  tests.
• A transistor base is being studied.

2

• Why a transistor base ?

Two requirements

• Need of a compact circuit with few components .
• Simplicity only 3 components must be added (1
  resistor and 2 transistors on the two last
  stages).

Such a base has been simulated and the
results were satisfactory. (see M. Crouaus talk
may 2002)
3

• Here is a diagram for both the passive and the
  active base under study.

The resistor values distribution is, for the time
being, the HAMAMATSU one. The inter-dynode
voltages at the two last stages are given by the
resistor values the two transistors compensate
the dynode current variation.
4

• First prototype of the base

• The prototype will be tested and used with the
  VFE board installed on the PMT Clermont test
  bench.
• The constraints are
• Mechanical structure (in development)
• the inter-pin spacing of the naked PMT (2.3 mm)
  is not the inter-pin spacing set on the VFE
  board prototype (2.54mm)!

5

• Photographs of the prototype of the base

Lets notice that what is performed here is not
suitable for a large production .
Connector for 2.3/2.54 adaptation It is awful !!
The resistors are on supports to change them
easily in the optimisation procedure.
6

• Perspective

• Complete the design of the base by setting
  properly the resistor values to maximise
  linearity on our test bench. (see Stephanes
  talk)
• Add the transistors and test the functionality of
  the base - still on our test bench.
• Use the final design to perform the ageing tests.

7

• A solution for the mechanical design of next
  prototype for VFE board.
• The 64-anodes connector will be at the 2.3 mm
  inter-pin spacing.
• We have to think about the support of the active
  base in the experiment conditions.
• A simple solution is represented on this
  drawing the shaded region supports the
  components of the base.