Two questions regarding PMTs

Discussion in 'General Electronics Chat' started by Hypatia's Protege, Apr 15, 2016.

  1. Hypatia's Protege

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    OP On post #2 -- Thanks!
     
  2. Hypatia's Protege

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    FWIW: Inasmuch as OPs (at Post #1) are non-editable and in reasonable anticipation that a post of this 'complexity' may require edits --- I chose to place the 'OP' here -- Thanks!

    Kind friends:


    I have recently purchased several PMT devices to the end of construction of an X-Ray scintillometer.

    Although I have been unable to locate 'data' for said units, I feel (hope) the fact that each unit is complete with a 'divider'/amplifier assembly may obviate the necessity for same.

    Please see the images/comments below:

    My questions are as follows:

    1) What is a reasonably 'safe' starting point for potential applied to the 'HV' lead? (Please see below)

    2) In the reader's opinion, is it indeed likely/possible that the PMT window is so designed as to serve as the scintillation 'crystal'?


    Please note -- My 'inventory' is sufficient that I can afford to sacrifice a few of these in the name of 'higher knowledge':cool: -- Any insight, even 'wild guesses' will be greatly appreciated!!! -- Note also that I have very little practical knowledge/experience with PMTs -- so please don't assume that 'I've already thought of/know' anything!:oops::)


    Accompanying each unit is a manufacturer-supplied 'test data' slip.
    As may be seen, the devices were 'certified' prior to packaging -- Curiously, the 'crystal' material (i.e. 'phosphor') is not specified (is it possible that the window functions as an 'integral 'crystal'?) --- Note that the test source (Co57) is a gamma emitter of, principally, PEs commensurate with those of certain medical radiography equipment (most notably 122keV and 139keV) --- The pulse height of 82mV exhibiting a resolution of ≈ 10% is likewise auspicious!:)

    [​IMG]


    Three leads emerge from the EMF divider/Amp assembly the PCB designations are as follows:

    Black lead - "K" (Cathode?)
    Orange lead - "HV" (High Voltage?) -- Such makes perfect sense save for the 'magnet-wire' grade insulation with which said lead is clad:confused:
    Green lead - "SO" (Signal output?)

    Image of Divider/Amp module at base of PMT:
    [​IMG]


    Image of the PMT window -- Again, considering the enclosed 'test-data' -- I'm tempted to guess that the window glass is so treated/composed as to function as an integral scintillator crystal? --- Thoughts?
    [​IMG]


    Side view images of PMT unit:


    [​IMG]

    [​IMG]

    Very best regards
    HP:)
     
    Last edited: Apr 16, 2016
  3. bertus

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    Hello,

    You might want to know the attached PDF.

    Bertus
     
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  4. Hypatia's Protege

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    Thanks, Bertus! --- General background material is always handy!:) --- That said, it seems I've a complete 'system' here (i.e. tube and support electronics) - and a strange beast at that!:confused::)

    Very best regards
    HP:)
     
  5. KeepItSimpleStupid

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    Interesting.

    Where I worked we had essentially a "home made" x-ray diffraction setup, at least the electronics. The diffraction set up was built in like 1942 by Phillips. It was upgraded inexpensively to stepper control and acquisition (A commercial piece). It also had the filament xformer replaced/upgraded (Dual filament) because the voltages were not the normal X-ray source.

    The last time I worked on it, I did a rebuild of the X-ray power supply (100 kV at 0.1 A max) . I was told it was quieter than it every has been.

    Cooling was provided by a water circulator.

    We used a NIM (Nuclear Instrumentation Module) and either Phillips or Ortec parts. I forget what they were,. One, of course, was a HV power supply (3 kV max) if I remember.

    Ortec and Phillips might be a good place to start:

    See https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0ahUKEwiSpoL135DMAhUBVD4KHXZNAnsQFggtMAE&url=http://www.ortec-online.com/download/Preamplifier-Introduction.pdf&usg=AFQjCNGm5oZ4VUWdiITKcaTtiqT-a1w4Mw

    I think we used the Databox http://www.materialsdata.com/products.htm

    I think there was an AMP and a Pulse height analyzer.
     
    Last edited: Apr 15, 2016
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  6. GopherT

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    I really doubt it. That would make a complex mess of any UV/X-ray aborptions and broaden the intensity vs. time response of the tube.
    I think the glass appears yellow because there is likely an anti-reflective coating on the glass - anti-reflective for blue and UV where most of these tubes are used (scintillators for X-Ray are usually in the near UV). Anti-reflective coatings decrease losses (improve yield of photons penetrating the window).

    Many organic compounds are yellow to amber color in white light because absorptions with peaks in the UV have tails that trail into the visible blue region of the spectrum. Lack of blue means the emitted light will appear yellow. In your case, more blue penetrating the glass means white inncident light will reflect as a yellow.
     
    Last edited: Apr 15, 2016
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  7. MrChips

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    Judging from the hexagonal shape of the tube it was most likely manufactured to be used in an Anger camera with the tubes stacked in a honeycomb arrangement.

    600V is usually a good starting point.

    Agreed with GopherT. NaI scintillator cystal is commonly employed.
     
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  8. Hypatia's Protege

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    @KeepItSImpleStupid

    Thanks! -- I have bookmarked references will explore them ASAP:):):)

    As an aside:
    That surprises me!:cool: -- I was unaware of an application for 'dual focus' as regards diffractometry...

    100kVp applied to diffractometry? -- The (admittedly few) units I've seen operated at PEs in the 'Mammo' range (i.e. 25keV -- 40keV) - Now I'm curious -- without wishing to sound a 'busybody' are you at liberty to share details of said application?:)

    Was that based upon a mains-operated transformer or a (so called) "high frequency generator"?

    With genuine interest
    Very best regards
    HP:)
     
  9. Hypatia's Protege

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    That would have been asking too much;) -- So, it seems the test material's designation = #2011?

    Thanks for that:) -- I assumed it was merely the (deposited) photo-cathode material:oops:

    I hope that doesn't mean the envelope is fashioned of silica (as is frequently the case where UV-lucency is required)? Inasmuch as said substance is prey of He permeation - Then so goes the APTS:(:(:(

    Very best regards
    HP:)
     
    Last edited: Apr 15, 2016
  10. GopherT

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    I am guessing the #2011 is the lot number of any liquid scintillator or serial number of any solid scintillator used along with the serial number of the specific source they used to do the quality check.
     
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  11. GopherT

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    See pages 6 - 8 of this PDF (PDF numbering) or p34-36 per numbering printed on each page for likely window materials.
    https://www.hamamatsu.com/resources/pdf/etd/PMT_handbook_v3aE-Chapter4.pdf
     
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  12. Hypatia's Protege

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    At ≈ $12k per pixel that makes for a rather 'dear' camera:eek:

    Many thanks!:) 'Stay at home magic smoke' is the best sort!:cool:

    So 'scintillator #2011' = sodium iodide? --- Thanks! I'll see what I can find:):):)

    Very best regards
    HP:)
     
  13. Hypatia's Protege

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    As per the linked resource - It seems silica's thermal characteristics mandate special construction (Spec a 'graded seal') -- That the tubes under discussion seem to lack said feature taken with your remark (in an earlier post) that the intended crystal's 'output' likely falls within the near-UV 'band', it seems reasonable to assume that the tubes are fashioned of either borosilicate or 'UV-transmitting' glass - I'd sure like to think so!:):):)

    Best regards and many thanks
    HP:)
     
  14. Hypatia's Protege

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    Ok then - what I'm looking for is a NaI crystal -- Interestingly, a number of polymer 'crystals' are available:confused::confused::confused:

    Best regards
    HP:)
     
  15. MrChips

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    That's not how the camera works. I've work on a number of gamma cameras. I think one had about 57 PMTs.
    They sum the signals from all the PMTs and then determine the position from relative voltages. From this you can get about 256 x 256 image.

    Here is the last Ohio Nuclear camera I worked on.


    Anger camera.jpg
     
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  16. KeepItSimpleStupid

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    The power supply was "RATED" for 100 kV at 0.1 A. It was probably operated at about 1/2 that. Since I wasn't an operator, I forget the actual details. The power supply was basically a VARIAC connected to a huge fluid filled transformer. A round box about 2' diameter x2'x2'. The fluid was replaced, but I was not involved.

    These http://www.toshiba-tetd.co.jp/tetd/eng/product/prden.php?type=cat&search=100200300000 are showing about 60 kV aand 40 mA which I think was about right.

    My rebuild basically consisted of putting Locktite 222 on the screws, checking connections and replacing a few parts.

    I did the same for an electron beam evaporator power supply ( 0-15 kV at 1 Amp) Tube series regulator. About 15 KW. Input was 50 A, 208 VAC, 3 phase. The other one I rebuilt was 90 A, 208 V 3 phase.

    Filament
    It was my understanding at the x-ray sources http://pd.chem.ucl.ac.uk/pdnn/inst1/xtube.htm and http://www.toshiba-tetd.co.jp/tetd/eng/product/prden.php?type=cat&search=100200300000. Somehow on this diffraction set-up the filament transformer had to be changed. It had two XLR connectors that you could move to set the filament voltages. That fix was done some 25 to 30 years ago.

    The power supply was basically "open frame". The back was never in place and all of the X-ray power source was built onto a 2 foot x 19" panel.
    It contained a few relays for interlocks and the indicator, a Variac and a filiment current meter. Nothing fancy - Old school, like 1942.

    A simplistic view of an X-ray source: https://xraykamarul.files.wordpress.com/2011/11/lecture10.pdf

    The diffractomer had essentially upgrades rather than repairs. The last repair was basically a worn spot on the filament rheostat and loose connections.

    Aside:
    The darn arc lamp power supply was another story. 40 kV to start. 22 V at 40 A to run. The idiots that designed the power supply used a 10 amp rectifier. They fixed it for free. I should say rebuilt it. New transformer and rectifier.

    The prior one was so bad they discounted the replacement.

    I made changes in the external ignitor wiring until they effectively made the ignitor external and did the modifications for free. We had about a 6 week down time. The spark gap had to be replaced periodically. The lamp could explode if operated upside down; fingerprints were verboten; and the lamp was pressurized to 15 atmospheres.
     
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  17. GopherT

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    Do me a favor and try putting your source in a plastic beer bottle. The kind sold at major sporting events - I am not sure if they are a ail able at the local duluth or Superior liquor stores. Those bottles are made with layer of polyethylene naphalenate (PEN), essentially a high performance (low oxygen permeable) version of the common PET. It is said to be the superior polymer scintillator and no doping or additives are needed.
     
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  18. Hypatia's Protege

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    Inasmuch as my 'sources' are Coolidge tubes, placing same inside the container is not an option;) -- That said - I'll be happy to irradiate the latter!:cool: FWIW; I neither store nor use (licensable) radioisotope/radionuclide sources in my home labs (owing to myriad safety, legal, and liability concerns --- to say nothing of something remotely akin to iophobia:eek::oops:) -- That said, I have a few 'red' (actually orange) Fiestaware platters 'kicking around':D

    So -- as regards the proposed experiment -- a few questions please:

    Roughly speaking:
    -What is the optimal excitation spectra range (i.e. the PE or λ range to which PEN exhibits greatest 'sensitivity')?
    -Where is the scintillation spectra range?
    -Is the PEN layer applied to both walls of the container? -- If no - which wall is coated/layered?

    Additionally:
    Is the presence of PEN in such containers reflected by the RIC code?

    Very best regards
    HP:)
     
  19. Hypatia's Protege

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    That's interesting in that it is rather similar to an NM 'gamma camera' (i.e. Anger ['tracer chasers'], etc... but more 'robust') -- What was the application of the pictured device?

    Very best regards
    HP:)
     
  20. Hypatia's Protege

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    Probably just as well! 'round here (USA) excessive Cl content (last I checked >50 ppm as PCBs) in the old dielectric oil - no matter how 'compliantly' handled/disposed of = fines all around - including attending employees of the owner!:mad: --- Seems organic chlorides are pure evil everywhere - with the exception coffee and breakfast cereal:rolleyes:

    I find it interesting that even so precise an application as diffractometry tolerates pulsating anode EMF (and, hence, a 'swept' bremstralung 'band'):confused: -- Seems I've some studying to do:oops:

    Very best regards
    HP:)
     
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