Xray transformer under oil

Have been busy with the Xray transformer.
It's under oil now, the outgassing with vacuum took some time, lot's of bubbles :)

I tested the transoformer with 10V input, output was about 700V, I expected more, but maybe it's not that linear at low input voltages.

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).

10mm polycarbonate for the 85000V supply

Have been working on the (very small..) saw table today, sawing some polycarbonate sheet for the high voltage supply:

It's big enough for the Xray transformer which is going to be immersed in transformer oil (the real thing, 60kV/mm), to get the air out I will use vacuum, which will create a force of about 2900N on the biggest sides. The sides will be glued together with epoxy, the edges are 45 degrees.

I also got a preview of the circuit board for the neutron counter power supply (eurocircuits.nl):

Circuit board voor HV supply

The SNM-10 and another detector tube need about 1600V.
This is the circuit board:

Designed with Eagle.
The circuit is VERY DANGEROUS, it can deliver a few milliamps at 3kV, the capacitors are charged at 3kV. If you build this thing, make sure that you know what you are doing!
Eagle BRD file
Eagle SCH file

40nF 100kV

For the 85000V supply, a capacitor bank:

The capacitors are 10nF, 20kV, so the 110 capacitors should be 44nF (5x series of 22x parallel).
The cap meter shows 40nF total, only 10% off. The bank will be in oil, and I still need to find the right resistors (5x 200Mohm, 2W, or enough other values make 200Mohm)

85000 volts

Did some measurements on the new XRT transformer.
It's supposed to be 1200W, 85000V @14mA.

And that's not 2x42500V, no, it's really one secondary winding, so with the 4x 80kV diodes I have, I can even make a symmetrical -80kV, 0, +80kV supply!

The DC resistance of the secondary winding is only 78k, so that's only 15W at 14mA, primary resistance is very low, seems like 1200W continious power capability to me :)

more HV supply stuff

Still working on the HV supply, did some test measurements, and designing a pcb in eagle (cadsoft).
The circuit is really working well!
This is the eagle schematic, pcb will follow soon when I have al the parts.

It is working much better than a normal voltage multiplier, and I was wondering how much stages could be added, I tried 11 stages, the circuit still works fine in the simulation, with about 3.6W of output:

The next image shows the "why", the driving voltage peaks are very short spikes, the lower line of capacitors have a very low impedance for these spikes (or in other words, the capacitors form a high-pass filter, but only a very small part of the energy of a delta function is in the lower frequencies)

It should be possible to add a lot more stages without loosing much energy.