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Photomultiplier - Cherenkov detector success! - soldering questions

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jmelson:
You can get pins for AMP connectors where a wire is crimped to a box-style contact which is then inserted into a housing.
These are made for .025" square posts, but there may be other sizes.  Also, there are DB-25 style connectors where wires are crimped
to the contact and then inserted into the connector.  These would fit slightly larger pins.  So,measure the pins on the tube and
then find a suitable contact for that diameter.

Jon

jmelson:

--- Quote from: ChristofferB on February 08, 2020, 04:47:10 pm ---Oops, C5 is also supposed to be 10n. My bad.

The capacitors across the final stages is how I've seen it done in litterally all examples, see below, so I just copied that over.


https://scionix.nl/voltage-dividers/#tab-id-1



Maybe I should remove the output parallel RC circuit completely, and rely on cables/external termination as needed, making it more open for experiments.

My first worry is to fry the PMT by overcurrent/voltages, so I'm happy that side of things look good.

--Chris

--- End quote ---
Note that thes positive HV arrangement requires a very high voltage coupling capacitor, which MUST not fail!  If it does, you will have the HV goign right into whatever is receiving the PMT signal.

The negative HV arrangement has the anode at ground, so is a bit safer.

Jon

Kleinstein:
To be on the safe side for the PMT, one can start with a lower voltage, so that the gain is lower.  One point is to avoid higher intensity light.
For use with a scintillator one would later use a relatively high voltage to get high gain.  There are usually 3 regimes:  low gain for linear operation of the PMT,  high gain for pulse analysis like with a scintillator and very high gain for photon counting.

richnormand:
Have a look at this link for proper design and usage of PMTs and base wiring according to intended usage:
https://psec.uchicago.edu/links/Photomultiplier_Handbook.pdf
It is a copy of the venerable RCA classic about photomultipiers. It has pretty much most of the the answers to your questions.
Well worth a complete read, even if you are familiar with PMTs.

Avoid UV light (fluorescent or white LEDs) as dark current might be high for a few days. For low intensity (photon counting) I alway wear gloves to avoid oil from my hands that could create a leakage path on the base/electronics.

ChristofferB:

--- Quote from: jmelson on February 08, 2020, 06:12:06 pm ---
--- Quote from: ChristofferB on February 08, 2020, 04:47:10 pm ---Oops, C5 is also supposed to be 10n. My bad.

The capacitors across the final stages is how I've seen it done in litterally all examples, see below, so I just copied that over.


https://scionix.nl/voltage-dividers/#tab-id-1



Maybe I should remove the output parallel RC circuit completely, and rely on cables/external termination as needed, making it more open for experiments.

My first worry is to fry the PMT by overcurrent/voltages, so I'm happy that side of things look good.

--Chris

--- End quote ---
Note that thes positive HV arrangement requires a very high voltage coupling capacitor, which MUST not fail!  If it does, you will have the HV goign right into whatever is receiving the PMT signal.

The negative HV arrangement has the anode at ground, so is a bit safer.

Jon

--- End quote ---


I was actually planning on using two DC blocking caps in series for that eventuality.

The problem with negative HV is that anything earthed or conductive MUST be kept physically away from the tube, especially the window. Since scintillation crystals usually come in aluminum cans this is impractical for these.



--- Quote from: Kleinstein on February 08, 2020, 08:01:20 pm ---To be on the safe side for the PMT, one can start with a lower voltage, so that the gain is lower.  One point is to avoid higher intensity light.
For use with a scintillator one would later use a relatively high voltage to get high gain.  There are usually 3 regimes:  low gain for linear operation of the PMT,  high gain for pulse analysis like with a scintillator and very high gain for photon counting.

--- End quote ---


The standard procedure for powering up any HV particle detector is to ramp it up slowly until the count rate stabilizes, I've heard, so it might be worth it to keep it at half voltage for a while to see how it acts.

For the first probe I'm just going to wrap the pmt and scintillator (optical coupling grease between? not solved yet) completely in self-vulcanizing tape.

Once I've verified operation, I'll get some 100x100mm aluminium tubing and make a proper probe with everything wrapped in foam.


--- Quote from: richnormand on February 08, 2020, 09:07:12 pm ---Have a look at this link for proper design and usage of PMTs and base wiring according to intended usage:
https://psec.uchicago.edu/links/Photomultiplier_Handbook.pdf
It is a copy of the venerable RCA classic about photomultipiers. It has pretty much most of the the answers to your questions.
Well worth a complete read, even if you are familiar with PMTs.

Avoid UV light (fluorescent or white LEDs) as dark current might be high for a few days. For low intensity (photon counting) I alway wear gloves to avoid oil from my hands that could create a leakage path on the base/electronics.


--- End quote ---

I did come across it myself, but yeah, it's a pretty great reference! Thanks!

--Chris

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