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Fast pulse amplifiers for scintillation output from PMT

Discussion in 'Electronic Basics' started by [email protected], Jan 15, 2006.

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  1. Guest

    Dear all,

    I am doing developing a fast time-resolution scintillation detector for
    a high density focused microbeam (around 10^8cps), directly from the
    PMT output, I've got 2ns wide voltage pulses output. The resolution
    time is fast, but the pulse height is only 6mV, it is not enough to
    directly trigger a Single-Channel-Analyser (usually a minimum threshold
    about 30-50mV),
    a fast, broadband pulse amplifier is need to make an amplification,
    with the time resolution ability still kept good after it.

    So, I am thinking about designing or searching such suitable amplifiers
    for this purpose, anyone has experience can give me advices? Products
    information or home-dsign solutions?
    Maybe an fast Op-Amp can be used for this ?

    Thanks
     
  2. jgreimer

    jgreimer Guest

    Do you have an estimate of the outut impedance of the PMT and the input
    impedance of the Single Channel Analyzer?
     
  3. John  Larkin

    John Larkin Guest

    A fast opamp, an AD8001 or something, should work OK. At these speeds,
    and to keep up linearity, you might go for two stages, with a gain of
    3 or 4 per stage.

    Several people make small wideband amp boxes... names escape me at
    this instant. I'm considering doing some myself, but not this week.

    You could also get a voltage gain of 10 from a single MMIC, maybe a
    low-noise SiGe part, like SGA-3586, but it would be AC coupled, and
    invert.

    John
     
  4. Guest

    I think the impedance macthing is not a problem now, the load resistor
    and signal cable and the anti-reflection resistor behind the PMT are
    all fixed 50ohm, the SNR is good, thus the reason why the pulse height
    is not enough (only 6mV) is mainly physics factors.
    So following work should be enhance the pulse height by two means:
    electronic amplification and increase the photon collection effciency
    of the photomultiplier, while the latter maybe difficult, so the best
    solution should still be fast pulse amplification.
     
  5. Guest

    Thank you John, for the advices on the amplifier, I tried the typical
    spectroscopy amplifier and a charge-sensitive preamplifier
    respectively, both NIM module, but not signal displayed on the
    osciliscope, maybe the frequency ability of these two are far not
    enough for such an fast pulse amplification.
     
  6. nyffeler

    nyffeler Guest

    Becker-Hickl offers amplifier designed for this application (see
    http://www.becker-hickl.com/pdf/dbhfah.pdf )

    However I guess for a reasonable linearity of a poisson distributed pulse
    source up to 10^8cps, as a PMT is, you will need one with a narrower puls than
    2ns or a MCP.
     
  7. Jasen Betts

    Jasen Betts Guest

    how about a trasformer?

    ____------>
    _)
    _)
    _)
    _)
    __)
    |
    .--+--.
    | |
    \ |
    / -----
    \ -----
    / |
    | |
    `--+--'
    __|__
    /////


    Bye.
    Jasen
     
  8. Guest

    oh, maybe it is also a method..I am not familiar with this, but how
    about the time resolution?or the frequency performance ?
     
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