optimising photomultiplier performance at low power

1
optimising photomultiplier performance at low
power

• Tony Wright, Electron Tubes Ltd

VLVnT2 Catania 8 - 11 November 2005
2
optimising photomultiplier performance at low
power

• battery operated
• solar powered ( Auger, satellite)
• under-water and under-ice experiments

heat generation is never a good thing!

• two considerations
• consuming the power (voltage divider)
• providing the power (power supply)

3
voltage divider considerations

• Requirement
• establish maintain a set of fixed dynode
  potentials
• Two types available
• resistor type
• active divider (FET)
• The all-resistor divider always fails the
  requirement but why and how
• badly?

4
all-resistor divider
5
(No Transcript)
6
two possibilities

• light source is absolutely constant
• mean anode current Ia does not change

problem goes away

• light source varies with time constant greater
  than that of the voltage divider

gain will shift as Ia changes
7
solutions

• increase ID0 by decreasing all R values
• or
• reduce R(dn-a) only
• use either a fully or partially active divider
  based on emitter follower action
• capacitors for pulsed signals

8
active divider networks
9
power supplies

• CW type with n individual socket outputs
• Active divider with n individual outputs
• Low power dc-dc converter with single output
• Industrial dc-dc converter with single output

10
power supply outlines
PS1800/PS1806
PS2010
PS2001
11
(No Transcript)
12
(No Transcript)
13
power supplies
14
Multichannel high voltage and control system for
photomultipliersHVSys
illustrating the system configuration for the
control and supply of up to 254 pmts. Only a
single 12V supply is required with the HV
generated by the individual power bases
15
functional diagram of 1 channel. The hardware
shown is integrated within each power base
enclosure
16
illustrating the superior performance of an
active divider compared with conventional
resistor types. One of the basic requirements of
any detector is that its gain should remain
constant and independent of input signal
17
(No Transcript)
18
current per channel as a function of mean anode
current with 12 V supply. The inset illustrates
the low power consumption for multiple channels
19
specification
(1)   at 1 kV, per power base (2)   100 k? //5 pF
load (3)   to within 1 (4)   to 40 V output
20
summary and features   eliminates expensive and
bulky HV cable and connectors one PCI card can
control up to 254 individual power bases
system expansion is possible via additional
RS485 cards programmable options for setting
and monitoring parameters utilises up to 16
preset voltage settings low power consumption
per power base exceptional dc and pulse
linearity facility for monitoring temperature
or other transducers high voltages are
restricted to the power supply and
photomultiplier this reduces the electrical
shock hazard associated with traditional
multi- channel power supplies graphical
display of parameters easy maintenance
21
Simplistic explanation g a Vn
dg n dV .(1)

g V but dV ? Ia R where Ia is the
mean anode current, n ? 10 and V 1000 volts low
power consumption dividers typically use 1 M?
resistors and draw 100 ?A divider current, so  
dg 10 (10-6 x 106) g
1000   1 per ?A of Ia