Negative HV supply for PMT's

The idea of making a high voltage with a DC-DC converter and a voltage multiplier can also be used to generate a negative supply for PMT's:

There is no need to use a P-channel mosfet, just reversing the diodes in the voltage multiplier reverses the polarity of the output.
The feedback circuit needs to be adapted to a negative output, when the PCB's for the positive supply are in, I will extend the design and make one ciruit board which can generate -3kV...+3kV with jumpers to switch polarity (changing in and out of the voltage multiplier and changing the feedback circuit).