Dear FLUKA experts,
I am running a simulation where a proton target and an electron target are placed in separate Vaccum chambers and there is another service chamber. And I have to design a downstream of each target and calculate the prompt ambient dose rates, the neutron ambient dose rates, and the residual ambient dose rates inside the service chamber that is in between the two chambers that contain targets. The input is attached here with please help me that how can I use and add scoring cards.
shielding.inp (8.3 KB)
Dear @muneeb.wajid.r,
I had a look at your input and I see that the geometry is not finished, there is plenty of errors.
I advice you to have a look at the slides from the beginner course, particularly at the lecture about geometry (in order to fix your geometry) and the lecture about scoring (to understand how they work).
Im simulating a geometry where a proton beam of 800GeV and 500kW is runs along z-axis (positive direction) and is 10cm upstream from the target. Also along z-axis but in opposite direction an electron beam of 500MeV, 1MW and 10mA runs along negative z-direction. Both the targets are placed in separate 2cm3 vacuum chambers and there’s a chamber in between those two chambers called service space with 2cm3 volume. My purpose of this simulations os to design a shielding downstream each target to mitigate the prompt ambient dose rates inside the service space.
For the scoring of neutron dose rate I use USRBIN with X-Y-Z and used DOSE-EQ with dimensions of service space and then to score the neutron dose I used AUXSCORE card and select the part. Neutron and the results of USRBIN were multiplied by the beam intensity and 3600E-6 for conversation to uSv/h. The same procedure was done for ambient dose of proton beam. Similarly for residual dose rates I used the RESNUCLE card with Semi-Analogue and for this I activated EVAPORAT. With heavy fragments and COALESCEnce in physics cards. Is it correct? Or I need some other cars for this?
Dear @muneeb.wajid.r,
As pointed out by @amario, it is a difficult to judge from the input file you provided, specifically considering that there the only scoring card present is not properly filled in.
The general approach you have described seems reasonable: you need AUXSCORE if you want the separate contribution of neutrons and protons, while scoring DOSE-EQ with no AUXSCORE associated to the corresponding USRBIN will give you the ambient dose equivalent from all the particles.
Yes, for residual nuclei estimation you should have evaporation and coalescence activated. For residual dose rate calculations the more correct approach would be to treat radioactive nuclei in an analogue way and adding the irradiation profile (and cooling time) as explained for example in the activation lecture.
Please take your time to digest the material and feel free to come back to us in case of further inquiries.
Best,
Davide
shielding 99(1).inp (9.2 KB)
Dear Davide,
I had worked on it and removed the errors in geometry and also run it successfully. The data files were also processed successfully without any error. But when I plot the the results of USRBIN I got the following error
"color axis has cb coord of -1 must be 0 for log scale’
What does it mean and how it can be resolved.
Thank you
Dear Abdul,
you still have some geometry errors (multiple defined regions) which you can easily spot and correct with the Flair. Additionally, the second SPOTPOS and SPOTDIR cards do not have any associated beam spot number (which should be 2 in your case) and RADDECAY should be in Active mode (not Semi-Analogue) since you have an irradiation profile.
Assuming that your beam settings and all the rest is fine, the scoring cards are not properly set. In particular you have to fill WHAT(4) of AUXSCORE with the name of the detector you wish the coefficients are applied to (currently you are setting WHAT(5) only in all the AUXSCORE cards).
Scoring absorbed dose (DOSE) in vacuum (USRBIN on unit 47) will give you zero in any case since there is no energy deposition. Also residual ambient dose equivalent from neutrons only (USRBIN on unit 51 and 47) will give you zero.
As final comment remember that in order to have activity from RESNUCLE scoring, the card must be associated to a DCYSCORE card.
Best,
Davide
Dear Davide,
Thank you for your reply and I apologize for the geometry error. I do not know what is goin when I open the file it gives no error and when someone else open it, it shows up with errors.
Secondly what unit in USRBIN card will be set? How can I know what I should pick? As I had picked 51 what it should be?
I wanted to calculate dose rates of neutrons in the central regional.
Dear Abdul,
as long as you do not mix between output formats and scoring types and select the units that Flair lists as available, there shouldn’t be any preference on the USRBIN unit: you can organize your scorings as you find appropriate.
My main point before was that you will never be able to see residual ambient dose equivalent from neutrons. What you can do is score the prompt ambient dose equivalent from neutrons only (by removing the DCYSCORE cards associated with the USRBINs trying to score ambient dose equivalent from neutrons only) and/or residual ambient dose equivalent (without adding AUXSCORE filters).
The latter will be the residual ambient dose equivalent from the beta and gamma radiation owing to the decay of the residual nuclei produced by activation.
Best,
Davide
Dear Davide,
Thank you for your replies. Probably this one is the last query.
As I mentioned above that I had two beam one of proton and one of electron. And I want to calculate the ambient dose inside the service space. So how can I calculate the Total dose for both beams.?
For a single beam we normalize the results by multiplying with beam intensity. What normalization will be used here?
As per my understanding it’ll be like
number of sources*beam intensity
But the intensity of both beam combined or a single beam?
Thank you
Dear Abdul,
If the proton and electron beam are operated at the same time you can proceed as you were setting up with two beam spots. A simpler approach (considering also the normalization) would also be to make two separate simulations and sum the results before plotting.
Without normalization the simulation results are expressed per primary particle: the prompt ambient dose equivalent would be for example in pSv/primary. If you want the prompt ambient dose equivalent rate you will have to multiply your results by the beam intensity in particles/s.
If you decide to make two separate simulations, the intensity to be used in the normalization is clearly the one of the beam you are simulating. If you instead decide to use the two beam spots I think you should properly set WHAT(3) of SPOTBEAM, for example 1.0 for the protons and equal to (intensity_electron_beam/intensity_proton_beam) for electrons and normalize the final results by the intensity of the proton beam.
Best,
Davide
Thank you for your reply.
What are the steps for two separate simulations and adding there results?
Is there any doc or lecture?
Dear Abdul,
you can follow this simple trick.
You first generate two separate plots (one for protons and one for electrons) via the Flair Plot tab as you would do normally: this will produce two *.dat files, each containing 4 columns (x,y,value,error). Then you can add another 2d plot to combine the *.dat files with the Gnuplot ‘<paste’ command. The files will be joined column-wise: columns 1,2,3,4 for the first file, columns 5,6,7,8 for the second file. So to add two 2d-maps with the same mesh the command to be added in the Flair Plot tab would be something like:
splot '<paste first_file.dat second_file.dat' using 1:2:($3+$7) notitle, 'first.geo.dat' ind 0 us 5:4:(0.) w l ls 1 notit
You can have a try, and come back if you get stuck somewhere.
Best,
Davide