What is Channel Number? (In gamma spectroscopy)

In summary, the Channel Number represents the number of energy bands recorded by the detector. The count rate is the difference in accumulated counts divided by the counting interval. Histograms can be used to plot data without binning, and Gaussian distributions can be used to represent data with histograms.
  • #1
CraigH
222
1
Really quick question.

In a graph like this:
http://en.wikipedia.org/wiki/File:Cs137_Spectrum.PNG

Source

What does the Channel Number represent?

Also, just to make sure, am I right in saying the count rate is [itex]\frac{\delta m}{\delta t}[/itex] ?
where m is the cumulative number of scintillations
and t is time

Edit: I've just noticed the graph says "number of counts" and not "count rate". Some graphs do though, so can I change my second question to: Is a count a single scintillation?
 
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  • #2
Channel number is a band of energy (ΔE). There is a total energy, and one divides that into a number of channels.

A count is one (detection) event or scintillation. The systems captures the counts, and the count rate is simply the difference in accumulated counts divided by the counting interval.
 
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  • #3
Thanks Astronuc. So the scintillation detectors are sensitive to the energy of the flash, but why do we divide this into discrete energy bands instead of just having energy on the horizontal axis?
 
  • #4
Have you ever used histograms before? How else would you plot a set of e.g. 10000 experimentally-measured energy values in a way that shows how they are distributed versus energy?

After you've made a histogram of your data, then you can find a smooth curve that at least approximately "fits" the data, and plot that curve along an energy-axis that doesn't have "bins" or "channels", but that's a somewhat different beast.
 
  • #5
Actually, some systems may record energy.

http://www.iaea.org/OurWork/ST/NE/NEFW/WTS-Networks/IDN/idnfiles/Characterization&Visualization/06-Gamma_Spectrometry.pdf


IAEA-TECDOC-1363 Guidelines for radioelement mapping using gamma ray spectrometry data
http://www-pub.iaea.org/mtcd/publications/pdf/te_1363_web.pdf
 
  • #6
jtbell, ah yeah of course. Sorry I didn't think before posting that question.
 
  • #7
jtbell said:
Have you ever used histograms before? How else would you plot a set of e.g. 10000 experimentally-measured energy values in a way that shows how they are distributed versus energy?
Make a Gaussian distribution out of every measured value, add them up.
It is possible to plot data without histogram bins, it is just impractical in many cases. Unbinned fits use very similar methods.
 

1. What is a channel number in gamma spectroscopy?

A channel number in gamma spectroscopy refers to a discrete energy level that is assigned to a specific gamma ray detected by a gamma-ray detector. Each channel number corresponds to a specific energy level, and the distribution of counts across different channel numbers can provide information about the energy spectrum of the detected radiation.

2. How are channel numbers determined in gamma spectroscopy?

Channel numbers are determined by the electronics of the gamma-ray detector and the associated data acquisition system. The detector converts the energy of the gamma radiation into an electrical signal, which is then amplified and digitized by the data acquisition system. The digitized signal is then sorted into different channel numbers based on its energy level, with higher energy levels corresponding to higher channel numbers.

3. What is the relationship between channel number and energy in gamma spectroscopy?

The relationship between channel number and energy is not linear, as it depends on the type and design of the gamma-ray detector. However, in most cases, the higher the channel number, the higher the energy of the detected gamma ray. The energy range for each channel number can be calibrated using known gamma-ray sources to accurately determine the energy of unknown gamma rays.

4. Can channel numbers be converted to energy units in gamma spectroscopy?

Yes, channel numbers can be calibrated to correspond to energy units such as keV (kiloelectron volts) in gamma spectroscopy. This calibration is typically done using known gamma-ray sources with known energy levels. However, the calibration may vary slightly depending on the type and design of the detector, so it is important to use the appropriate calibration for accurate results.

5. How are channel numbers used in gamma spectroscopy data analysis?

In gamma spectroscopy data analysis, channel numbers are used to create an energy spectrum, which plots the number of counts (or the intensity) of gamma rays at each channel number. This spectrum can then be analyzed to identify the types and energies of the detected gamma rays, providing valuable information about the sample being measured. Additionally, changes in the distribution of counts across different channel numbers can indicate changes in the sample's composition or activity over time.

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