It is not necessary to have a well matched 50
1
load to preserve pulser lifetime, but we
recommend the load should present a dc resistive load to the pulser in the range of approx 25
to 100 ohms.
If it is necessary to monitor or characterise the pulse output then suitable attenuators must be
used.
The 12kV and 45kV pulse outputs from this unit are capable of destroying most
types of power attenuators and terminators including most of the high pulse power
types
.
The pulser was characterised at the factory using two methods:-
a) For the 12kV outputs a x2 Kentech suicide T attenuator was followed by two x10 Barth
142-NMFP-20 attenuators then two radial x10 attenuators. These outputs unit will destroy the
Barth 142 if used without the T.
b) For the 45kV output a special x10 Kentech resistive attenuator was used followed by two
x10 Barth 142-NMFP-20 attenuators then two radial x10 attenuators.
See the photographs enclosed in this manual.
The output may be observed with a high bandwidth oscilloscope. This may either be a fast
(>3GHz) single shot type or a sampling type.
If the output of the pulser is to be used directly or via any passive network it is essential that
cable lengths are kept as short as possible and that only high quality cable is used. This will
enable the fast rising edge generated by the unit to reach the load without serious degradation.
The PBG7 is controlled by the microprocessor unit with LCD display and four button keypad.
On power up, the trigger input of the avalanche stack is disabled, note that it is always
necessary to issue commands to the microprocessor unit via the keyboard or the RS232
interface to enable the trigger circuit and make the pulser run normally. Please see the software
section below.
The µP unit includes a self test routine. This should be run at least once a day at power up, or at
any change of configuration and any faults noted, see sections on stack faults and comms faults
below. Otherwise there is no regular maintenance required. There is some redundancy in the
unit by virtue of its design, and the unit may continue to operate at slightly reduced amplitude
