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Stable High Voltage (3kV) Photomultiplier Supply
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sixtimesseven:
Hi

I need a stable 3kv supply for my xray florescence setup to get the best energy resolution from the tube. Unfortunately my current supply is a simple switching converter which has a lot of ripple and is generally unstable.

My first idea was to just add a floating series regulator but then I saw the Agilent handbook on power supplies

http://literature.cdn.keysight.com/litweb/pdf/5952-4020.pdf

Basically they take a unregulated hv supply from a 60Hz transformer, rectifier it via voltage doubler and connect it in series with a series regulated supply.
The supplies which employ that scheme (and I found so far) are the HP6110A and the HP6516A. The 6110A in particular has some rather nice specs with stability in the 0.001% range and ripple of only a few millivolts.

http://apapes.physics.uoc.gr/equipment/documentation/HP_06516-90001.pdf
https://nscainc.com/wp-content/uploads/pdf/A_6110A.pdf

Now the 6110A comes up on ebay from time to time but I'm doubtful about the capacitors in there. Plus I do not really need adjustable. Fixed voltage and current limit would be just fine. So I won't need the high voltage control winding, circuit, low voltage offset and just minimal adjustment circuits. Also, I wondered if I should replace the "voltage input"section with a opamp based design and leave the driver circuit (Q10, Q9) as it is.

I had a look on the transistor they used for the 200V series regulator and there seems to be a recommended replacement, the NTE124

http://www.nteinc.com/specs/100to199/pdf/nte124.pdf

However I had a look at some datasheets and if I happen to interpret the "save operating area" graph correctly this one
https://media.digikey.com/pdf/Data%20Sheets/ST%20Microelectronics%20PDFS/BU208A_508A_508AFI.pdf

Should give me about 30mA dc current @1000V VCE? To bad it's obsolete  :-DD


2000V and 4000V 1uF film capacitors are probably the priciest parts.
https://www.digikey.ch/products/en/capacitors/film-capacitors/62?k=2000v%201uF
https://www.digikey.ch/products/en/capacitors/film-capacitors/62?k=&pkeyword=&sv=0&umin2049=0.1&umax2049=2&rfu2049=%C2%B5F&pv1293=89&pv1293=29&pv1293=171&pv1293=49&pv1293=139&sf=0&FV=ffe0003e&quantity=&ColumnSort=0&page=1&pageSize=25


I would love some feedback, pointers or tips on other HV supplies from HP (didn't find too many) to have a look at.








Yansi:
Why not using a CFPR (Current Fed Parallel Resonant) converter and a voltage multiplier? The CFPR can be also easily regulated for stable voltage. Output will also be fairly clean (less switching mess, as the diodes will operate in soft recovery, due to the sinewave voltages).

I mean, that two-transistor self-oscillating job is more than enough to supply a CRT or photo-multiplier I guess.
Kleinstein:
Do you really need 3 KV for a photo-multiplier ? The ones I know need more like a little below 1000 V to  get pulse hight resolution.

Usually the current is pretty low (e.g.  maybe 1 mA, mainly for the divider).

I would avoid using large capacitor and better use a higher frequency high voltage generation. So more like a 20 kHz resonant converter and than filter caps more in the 20-100 nF range. With voltage doubling rectifier the caps will only see something like half or even less of the voltage.

If one really needs linear regulation this only has to deal with a smaller adjustment range, like 100 V or so. There should be plenty of transistors available, e.g. those made for video CRT drivers in old TVs (e.g. BF869, BF469 - but many similar ones to choose from).
sixtimesseven:

--- Quote from: Kleinstein on February 01, 2019, 11:55:07 am ---Do you really need 3 KV for a photo-multiplier ? The ones I know need more like a little below 1000 V to  get pulse hight resolution.

Usually the current is pretty low (e.g.  maybe 1 mA, mainly for the divider).

I would avoid using large capacitor and better use a higher frequency high voltage generation. So more like a 20 kHz resonant converter and than filter caps more in the 20-100 nF range. With voltage doubling rectifier the caps will only see something like half or even less of the voltage.

If one really needs linear regulation this only has to deal with a smaller adjustment range, like 100 V or so. There should be plenty of transistors available, e.g. those made for video CRT drivers in old TVs (e.g. BF869, BF469 - but many similar ones to choose from).

--- End quote ---

I currently use a small 10-Stage Russian built tube with mixed results.

First idea was a XP2020 which would have taken a max voltage of 3000V. But after some searching today I found a better option.

So next step will probably be a 10-Stage XP2102. It only requires 1000-2000V - Yay. It's affordable and seemed reasonable with the 9.5% resolution.
https://wwwusers.ts.infn.it/~rui/univ/Acquisizione_Dati/Manuals/Philips%20XP2020.pdf
They go on Ebay for about 30 Euros, but under the old phillips brand which now is photonics:
https://www.ebay.ch/itm/Photomultiplier-Tube-XP2412-SQA-Phillips-PH21-pC-PHR-9-20/253087238554?hash=item3aed2cc99a:g:jTUAAOSwRYBZi4xz:rk:1:pf:0



--- Quote ---Why not using a CFPR (Current Fed Parallel Resonant) converter and a voltage multiplier? The CFPR can be also easily regulated for stable voltage. Output will also be fairly clean (less switching mess, as the diodes will operate in soft recovery, due to the sinewave voltages).
--- End quote ---

CFPR seems like an interesting option. Thank you!
David Hess:

--- Quote from: sixtimesseven on February 01, 2019, 10:48:52 am ---Basically they take a unregulated hv supply from a 60Hz transformer, rectifier it via voltage doubler and connect it in series with a series regulated supply.
The supplies which employ that scheme (and I found so far) are the HP6110A and the HP6516A. The 6110A in particular has some rather nice specs with stability in the 0.001% range and ripple of only a few millivolts.
--- End quote ---

Many Tektronix oscilloscopes use that method to tightly regulate the 1 to 3 kilovolt cathode supply to the CRT but the high voltage part comes from a high frequency inverter which makes filtering easier.

At low currents I would consider using a flyback transformer based boost converter to drive a diode-capacitor voltage multiplier and at higher currents a regulated Royer converter which has the advantage of a clean high frequency sine wave output which is easy to filter and a lot of commonality with CCFL making it economical.

Linear Technology application note 118 discusses high voltage low noise DC to DC converters.
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