Hi everyone! I am a beginner. I want to simulate the detection efficiency of High purity germanium detector. According to the definition of high purity germanium detection efficiency, I need to count the pulses, but the EVENTBIN of FLUKA can only score the energy deposition in HPGe detector. How can I get the pulses of HPGe? Or is there any way that I don’t know to convert energy deposition into pulses?
Each pulse that you read from your detector is caused by an energy deposition event (or, to be more precise, by energy deposition events that occur within a short time that the detector cannot resolve). A higher energy deposition leads to a higher amplitude pulse. Nevertheless, the scaling between deposited energy and signal amplitude, which depends on the particular detector, the gain of the electronics etc., is not needed in order to estimate the efficiency.
There are a few ways to go about this, depending on the level of detail you wish to include. Assuming a simple case in which you are studying the efficiency for different point or extended monoenergetic gamma sources, then using EVENTBIN would tell you what fraction of the gammas from the given source will deposit energy (and therefore generate a pulse) in the detector (and how much), which is the definition of the efficiency. You can also get the energy deposition spectrum with the DETECT card.
Keep in mind that, for HPGe detectors in particular, the efficiency is sensitive not only to the counting geometry and the gamma energy, but also to the window material and thickness, the internal distance between the window and the crystal which is not generally known, the exact crystal shape, the crystal dead layer etc.
It all boils down to the desired level of detail of your study, things can get as complicated as you want.
Thank you for your answer! I just study a simple case. There is a confusion about your answer:
1.As you said that I can use EVENTBIN card to get the efficiency, do you mean that I should count the events of gammas incident the detector by EVENTBIN?
Besides, I download the pdf of FLUKA courses from https://fluka.cern/support/courses-and-events. But I find that there are only a few words about eventbin, I have difficulty learning it. I lack knowledge of EVENTBIN card, can you can tell me some experience of using it？Please accept my best thanks!
Assuming you are defining an isotropic monoenergetic photon source at a certain distance from the crystal, then the EVENTBIN card will tell you what was the energy deposition in the detector for each photon generated in the source. Most photons will lead to an energy deposition equal to zero because of the acceptance of the detector (geometric efficiency), and others will not deposit energy in the crystal even if they enter it (intrinsic efficiency). So, for example, if you create 10^6 photons, you may get a non-zero energy deposition only for 10^3, therefore giving an efficiency of 10^-3. The further away from the detector and the higher the energy (from about 100-200keV onwards), the lower the efficiency will be (decreasing linearly in log-log scale).
Below is an example of the EVENTBIN card. TARGET is the name of the crystal region, to be replaced with yours, and we are asking for ENERGY deposition scoring, printing all values, including zeros.
As previously mentioned, you can also add a DETECT card to obtain the energy deposition spectrum (which you can also obtain by creating a histogram of the values printed in EVENTBIN). You could then get the efficiency by integrating the photo-peak(s).
Once again, keep in mind that especially for photon energies below ~100keV the efficiency becomes very sensitive to the detector window and casing, so you should describe your detector geometry with the necessary level of detail.
Hi, thank you for your answer. Your answer is very important to me, and now I know how to use this card simply.