I am new to FLUKA and have recently started learning how to use it for neutron detector simulations. I have successfully installed FLUKA and Flair, and I have built the geometry of my neutron rem counter (Anderson–Braun type).
My goal is to simulate the detector response and calculate the neutron fluence so that I can compare it with the standard fluence-to-ambient dose equivalent H*(10) conversion curve.
At this stage, I am unsure about the following points:
Which scoring card should be used to correctly calculate neutron fluence inside the detector (USRTRACK, USRBIN, or another option)?
How can I obtain the fluence-to-dose equivalent H*(10) curve for my neutron rem counter?
What is the recommended step-by-step procedure to perform this type of simulation (monoenergetic runs, scoring method, normalization, etc.)?
I would be very grateful if you could guide me through the proper methodology to perform this simulation correctly in FLUKA.
I am not very familiar with what you are trying to do, but if I understand correctly you want to measure the response of the rem counter and compare it to the conversion coefficients h*(10). The response R(E) of an ideal rem counter, defined as the number of detected events given a unit fluence on its surface of a specified energy E, should approximate well the conversion coefficients h(E).
To answer your first question, about scoring neutron fluence, you may use USRTRACK if you want the energy-dependent fluence, and USRBIN if you would like to have the energy-integrated one. In either case, you should score NEUTRONs. While not directly relevant to your question, you can also score DOSE_EQ, which will provide you with H*(10) converted dose equivalent.
However, your question is about simulating the response of the REM counter which should approximate (within reason) the conversion curve. To do so, the procedure is as follows
Steps:
you want to create a monoenergetic neutron field, and scan across a variety of energies. This can be just a simple narrow beam, or a broader beam. For best results, use a beam broad enough to cover the entire area of the detector
you can score the fluence crossing the surface of the device by using, for example, a USRBDX card. if you are using the same beam shape every time, and you ignore attenuation before the sphere, the normalization by fluence amounts to a correction proportional to the area and identical in all points, so it is not strictly needed as the shape of the response vs energy will be unaffected.
then, you need to somehow simulate the detector interacting with the neutrons. The best way to do this is by using a DETECT card, with a threshold that allows you to see the neutron interactions. (In your first question you mentioned scoring a fluence. this is also possible, if you wish by scoring only the thermal neutron fluence inside of the detector, multiplying it with the macroscopic cross section, to get a reaction rate, but more complicated and less accurate)
For each beam energy, you can then take your count rate and divide it by the fluence. This should provide you with a detector response as a function of the neutron energy. If everything is done correctly the response approximates the conversion coefficients