voltage in the DCC-100 is kept below the critical value. If the H7422 shuts down internally
for whatever reason, it can only be re-activated by cycling the +12 V operating voltage.
Don’t connect or disconnect the signal cable from the detector to the preamplifier when the
detector is switched on. This can destroy the amplifier. Make sure that the +12 V at
connector 2 is switched on. Otherwise the HFAC does not work, and the overload protection
is inactive.
Controlling an R3809U MCP PMT
The Hamamatsu R3809U is the fastest photon counting detector currently available. It uses a
microchannel plate for electron multiplication. In the TCSPC mode a time resolution of less
than 30 ps (fwhm) can be achieved. MCP PMTs are extremely sensitive to overload. Because
the microchannels are continuously destroyed by sputtering the lifetime of the detector is
limited. The degradation effect is not noticeable under normal operating conditions. However,
overloading the detector can rapidly exhaust the residual lifetime. Therefore, MCP PMTs
should always be operated with overload protection, or at least with an overload indicator.
The figure right shows how an R3809U MCP can be
operated with overload protection. An FuG HCN-14-
3500 is used as an high voltage power supply for the
R3809U. The HCN-14 is available with a 0 to 10 V
control input. The high voltage is proportional to the
control voltage. Therefore, the detector operating
voltage can be controlled by the DCC-100 and be shut
down on overload.
For overload detection, the HFAC-26-01 preamplifier
- with an overload threshold of 0.1 µA - is used.
Notice: Please observe the usual safety rules when
working with high voltage. Make sure that there is a
reliable ground connection between the detector and
the HV power supply. Don’t use broken cables, loose
connectors or cables with insufficient insulation.
Don’t connect or disconnect the signal cable from the detector to the preamplifier when the
detector is switched on. This can destroy the amplifier. Make sure that you connected all
ground connections. Missing ground connections can result in high voltage instability or
unreliable overload shutdown.
Make sure that the +12 V at connector 2 is switched on. Otherwise the HFAC does not work,
and the overload protection is inactive.
Controlling PMH-100 detectors
The PMH-100 of bh is an easy to use detector head that
contains a Hamamatsu photosensor module, a
preamplifier, and an optical and acoustical overload
indicator. due to its compact design it has an excellent
noise immunity and a TCSPC time resolution of 140ps to
200ps (fwhm of system response).
Since there is no overload signal available from the PMH-
100 it cannot be automatically shut down on overload. Up
to three detectors can, however, switched on and off via
the DCC-100. By connecting the detectors to a bh SPC
module via a HRT-41 or HRT-81 router the signals of all
