E3730A OPERATING INSTRUCTIONS
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damage by arcing is accumulated to a particular part of electrodes. As the E3730A klystron
produces very high output power, the PFN energy is dangerously high enough to give serious
damage to the electron gun electrodes with a very small number of successive arcing.
To prevent the electrodes from the serious damage, the modulator system must provide a
fast, pulse-to-pulse basis, interlock system that detects the arcing in the electron gun, and
immediately cuts off the HV, or more conveniently turns off the triggering of the main switching
device, usually thyratron. Measuring device based on the average quantity measurement is not
suitable for this purpose unless the pulse repetition rate is quite low. There are some possible
ideas to detect arcing of the electron gun; peak current detection of shunt circuit of the PFN, or
peak inverse current detection is recommended.
Before resuming operation after arcing, be sure the ion pump current has been less than or
equal to the steady state level. It is recommended to reduce the HV to a certain extent and
gradually raise the HV for the prescribed value for secure start up.
6.2.2. Normal operation
When the station waveguide or dummy load is new or exposed to air, the waveguide
conditioning operation must be taken. When the tube has been used recently or when it has
already been put through the conditioning period described in the preceding paragraph, starting of
the tube can be very fast, even instantaneous. The klystron can be operated after one hour of
cathode heat up. However, gradual increase of the high voltage and drive power is recommended.
It is far better for the tube to keep the reliability, especially for the klystron output window.
6.2.3. Protective device operation
In case of protective device operation, that means some fault occurred, certain additional
precautions should be taken, as outlined in the following table.
Interlock
Precautions
Ion pump current
Check the focus-coil currents and tube cooling are correct.
Make sure that the ion pump current has returned to the
normal value.
Tube water flow
Make sure there is no leakage in the circuit.
Heater current
Make sure there is no open or short circuit.
Electromagnet water flow
Make sure there is no leakage in the circuit.
Electromagnet currents
Make sure there is no open or short circuit.
Waveguide pressure
Check that evacuating system is in normal operation. Make
sure that the pressure has returned normal level.
In case of SF
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pressurization, check the gas pressure level
is in the proper range.
Beam current
Make sure the ion pump current has returned to the normal
level. Check the applied high voltage is in the normal
operation range.
VSWR in waveguide
Check that evacuating system is in normal operation. Make
sure that the pressure has returned normal level.