Dose calculation for oscilloscope

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Discussion Overview

The discussion revolves around the feasibility of calculating dose from the output voltage pulse recorded by an oscilloscope when using various types of radiation detectors. It explores the implications of different detector types and their responses to pulse measurements, focusing on the technical aspects of dose measurement in the context of radiation detection.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • Some participants propose that for an ion chamber, the total charge transferred could be calculated from the area under the curve of the oscilloscope trace or the height of the pulse, depending on the circumstances.
  • Others argue that a Geiger counter tube would not be suitable for this purpose, while some other detectors might work but could present challenges in interpretation.
  • A participant questions the effectiveness of commercial PMT/scintillator combinations, suggesting that they may not function well due to design limitations that could lead to saturation.
  • Concerns are raised about the potential dangers of reinventing instrumentation for high-power devices, indicating a need for caution.
  • Another participant highlights that an ion chamber and a digital voltmeter (DVM) are standard for measuring dose from x/gamma radiation, questioning the necessity of using an oscilloscope.
  • There is a discussion about the response time of ion chambers, with one participant expressing skepticism about their ability to measure nanosecond pulse doses due to their microsecond response time.
  • It is noted that ion recombination could be an issue for nanosecond pulses, and a solid-state detector might be a viable alternative, provided it is calibrated appropriately.

Areas of Agreement / Disagreement

Participants express differing views on the suitability of various detectors for measuring dose from pulse outputs, with no consensus reached on the best approach or the effectiveness of specific detectors.

Contextual Notes

Limitations include the dependence on the type of detector used, the specific characteristics of the pulse being measured, and the potential for nonlinear effects at high power levels. The discussion also highlights unresolved questions regarding the calibration of solid-state detectors compared to ion chambers.

Salman Khan
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If pulse source output is recorded by a detector on oscilloscope, is it possible to calculate dose from this output voltage pulse?
 
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That depends on the detector and any amplifier. For an ion chamber it would be the total charge transferred, which would be the area under the curve on an oscilloscope trace under some circumstances, or the height of the pulse in others.

A Geiger counter tube would not work. Some other forms of detector might work, but interpreting the result might be challenging.
 
Alex A said:
That depends on the detector and any amplifier. For an ion chamber it would be the total charge transferred, which would be the area under the curve on an oscilloscope trace under some circumstances, or the height of the pulse in others.

A Geiger counter tube would not work. Some other forms of detector might work, but interpreting the result might be challenging.
In case of PMT or other solid state detector?
 
A commercial PMT/Scintillator would probably fail to work. Counters are usually designed with high value resistor chains to save power and with small value capacitors close to the anode. These saturate easily. Spectroscopy grade combinations would probably damage themselves at fairly low exposures.

If you are measuring the dose within the beam I would expect a strong pulse of light from the scintillator. Much more than would be a good fit for a PMT.

A reverse biased diode would probably give a signal, but at these power levels there may be a lot of nonlinear effects. A scintillator connected to a photodiode by a light pipe or fiber optic cable might work well.

I'm bothered that you seem to be trying to reinvent the wheel for instrumentation for a very dangerous device.
 
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Dear Alex, very thanks for sharing your experience.
 
Why use an oscilloscope? An ion chamber and a DVM works and is standard for dose measurement of x/gamma radiation.
 
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So far as I know ion chamber is gaseous detector having response tim in micro second, how is it possible to measure a pulse dose of nano second pulse using ion chamber ??
 
You didn't say nanoseconds. It works for microseconds for sure. The problem with nsec. pulses is ion recombination. A solid-state detector can be used, I think, instead of an IC, but can be calibrated with a longer pulse width beam relative to an IC.

Just found this for ICs https://www.drct.com/Ion_Chambers/TBM-IC-Pulse-X.html
 
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