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Gas field Detectors.

  1. Mar 24, 2012 #1
    Hi, I would appreciate it if someone could explain these expressions to me.
    I was reading about Gas field detectors from " Radiation Detection and Measurements" for "Knoll" and paticulary in chapter five
    "The gas field detectors are commonly used in dose measurements. In this case, the
    detector response should be directed toured the conversion of radiation interactions to detector response in dose scale"

    but what I didn't understand what exactly he mean by :

    "electron-balance-compensation in the measurement of gamma ray
    exposure." ?
    and what's the difference between
    "free air ionization chamber (for up to 250 keV)" ?
    "wide range ionization chamber (cavity chamber)" ?
    I couldn't find anything on Google and the book didn't explain very well.
    Thanks in advance.
  2. jcsd
  3. Mar 24, 2012 #2
    You might have more luck googling for gas FILLED detectors.

    Basically, ionization of some detection gas is turned into an electronic signal that is then interpreted to find the dose.

    The type of gas determines what kind of radiation you are sensitive to
  4. Mar 24, 2012 #3
    yeah I know "filled" and "field" , I made copy and paste for the paragraph above , I thought field would mean something different, not sure of a misspelling.
    I thought the same at the first place , if we have two detectors have the same gas and the same volume , one is detecting a high energy gamma-rays and the other for gamma-rays up to 250 kev , what's the different in the design? this might be a better question ..
    I think there's could be some collectors from gamma rays inside the detector works somehow to collect gamma-rays or the other particles that produced from the interaction between the gamma-rays and the collector material as indication for the presence of gamma-ray ,
    and if we have a small volume detector comparing with the range of gamma-rays how possible that detector could give us good measurements about the dose , I guess all these are design parameters....? if you have any idea about this I would appreciate it.
  5. Mar 24, 2012 #4
    One thing that might be different is the gas pressure, the next is the geometry of the electrodes and the voltage across them.

    Ionization chambers operate with constant electric fields that just collect the charges generated by the radiation.

    Geiger counters operate with much higher fields such that the primary charges get accellerated to the point where they themselves ionize gas and generate more charges (a charge avalanche), thus amplifying the signal, but loosing energy resolution...

    There are many different types of gas filled detectors that work with different field geometries and voltages/electric fields strengths. And that is just gas filled detectors. You also have scintillators, semiconductor based detectors, ...
  6. Mar 24, 2012 #5
    Thank you.. :)
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