Photon detector
Photon detector
Hello everyone,
I would like to calculate dose (in units of Gy/s) in Serpent that will be equivalent to MCNP.
In MCNP, I define the tally as follows:
f4:p 2
fm4 1 1 5 6
(I changed the constant, i.e., the first entry on the fm4 card to 1 since I guess that there is no possibility to multiply the tally in some constant in Serpent).
In Serpent I set the det card as follows:
det 4 p dc 2 dr 25 m1 dr 26 m1
I get two different results. Why is that?
Thank you very much!
I would like to calculate dose (in units of Gy/s) in Serpent that will be equivalent to MCNP.
In MCNP, I define the tally as follows:
f4:p 2
fm4 1 1 5 6
(I changed the constant, i.e., the first entry on the fm4 card to 1 since I guess that there is no possibility to multiply the tally in some constant in Serpent).
In Serpent I set the det card as follows:
det 4 p dc 2 dr 25 m1 dr 26 m1
I get two different results. Why is that?
Thank you very much!

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Re: Photon detector
Hi,
the dr card for Serpent detectors specifies a response function for the detector. If you define multiple response functions, you will get multiple results, one for each response. I would imagine you would want to use one of the responses for the photon dose rate found here: http://serpent.vtt.fi/mediawiki/index.p ... eactions_2
Ville
the dr card for Serpent detectors specifies a response function for the detector. If you define multiple response functions, you will get multiple results, one for each response. I would imagine you would want to use one of the responses for the photon dose rate found here: http://serpent.vtt.fi/mediawiki/index.p ... eactions_2
Ville
Re: Photon detector
Dear Ville,
thank you very much for your answer.
The macroscopic total heating crosssection obtained from Serpent (dr 26) is some orders of magnitude smaller than the one obtained from MCNP. The same is for the energy deposition detector (dr 12). Why is that? What are the units of the energy deposition detector?
Another question regarding source definition: is it possible to define source energy in discrete values?
Thank you very much!
thank you very much for your answer.
The macroscopic total heating crosssection obtained from Serpent (dr 26) is some orders of magnitude smaller than the one obtained from MCNP. The same is for the energy deposition detector (dr 12). Why is that? What are the units of the energy deposition detector?
Another question regarding source definition: is it possible to define source energy in discrete values?
Thank you very much!
 Jaakko Leppänen
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Re: Photon detector
One difference between MCNP and Serpent is that MCNP divides the tally results by volume and Serpent doesn't. Could this explain the difference in the order of magnitude?
You should also check that the results are consistently normalized (use set srcrate 1 to normalize to unit source rate).
You can define a discrete energy spectrum using the sb option of the src card
You should also check that the results are consistently normalized (use set srcrate 1 to normalize to unit source rate).
You can define a discrete energy spectrum using the sb option of the src card
 Jaakko
Re: Photon detector
Dear Jaakko,
thank you very much for your answer.
I set the tallies volume in MCNP to 1, so it should not be the problem.
Here is the tallis setting and the results:
MCNP:
f14:p 3
sd14 1
fm14 1 1 5
Serpent: det 14 p dc 3 dr 25 m1
Results:
MCNP: 5.23955E02 0.0023
Serpent: 5.19428E02 0.0050
MCNP:
f24:p 3
sd24 1
fm24 1 1 6
Serpent: det 24 p dc 3 dr 26 m1
Results:
MCNP: 5.67940E04 0.0024
Serpent: 1.53047E16 0.0051
The problem is with the dr 26.
I can't define a discrete energy spectrum with the sb option since it is required in the first entry (N) to give the number of bins. Therefore, I can only use the sb option for a histogram. Hence, I just defined different src for each energy and gave the relative source weight with the sw option.
I would also like to ask, please, how can I calculate energy deposition for photons (the dr 12 give the same problem as dr 26).
Also, I would like to ask if there is an equivalent detector to tally *f8 of MCNP.
Thank you very much!
thank you very much for your answer.
I set the tallies volume in MCNP to 1, so it should not be the problem.
Here is the tallis setting and the results:
MCNP:
f14:p 3
sd14 1
fm14 1 1 5
Serpent: det 14 p dc 3 dr 25 m1
Results:
MCNP: 5.23955E02 0.0023
Serpent: 5.19428E02 0.0050
MCNP:
f24:p 3
sd24 1
fm24 1 1 6
Serpent: det 24 p dc 3 dr 26 m1
Results:
MCNP: 5.67940E04 0.0024
Serpent: 1.53047E16 0.0051
The problem is with the dr 26.
I can't define a discrete energy spectrum with the sb option since it is required in the first entry (N) to give the number of bins. Therefore, I can only use the sb option for a histogram. Hence, I just defined different src for each energy and gave the relative source weight with the sw option.
I would also like to ask, please, how can I calculate energy deposition for photons (the dr 12 give the same problem as dr 26).
Also, I would like to ask if there is an equivalent detector to tally *f8 of MCNP.
Thank you very much!
 Jaakko Leppänen
 Site Admin
 Posts: 2315
 Joined: Thu Mar 18, 2010 10:43 pm
 Security question 2: 0
 Location: Espoo, Finland
 Contact:
Re: Photon detector
The several orders of magnitude difference probably comes from MeV vs. J, but that doesn't explain it alone. Are the MCNP tallies divided by mass? If so, that could explain the remaining factor of 6 or so difference.
The most recent version of Serpent has the discrete energy line option for the for the source spectrum.
The most recent version of Serpent has the discrete energy line option for the for the source spectrum.
 Jaakko
Re: Photon detector
Dear Jaakko,
thank you very much for your answer.
I understand that that the units of dr 12 and dr 26 is J.
Unfortunately, I didn't succeed to define a discrete energy spectrum with the sb option. The definition of the sb does not allow that ([ sb N INTT E1 WGT1 E2 WGT2 ... ]). It is still giving an error such as: "Probability of first energy point must be zero." Also, the first entry (N) limits the sb just for the histogram energy spectrum. I am using Version 2.1.31. Please let me know how to use the sb option for the discrete energy spectrum.
Thank you very much!
thank you very much for your answer.
I understand that that the units of dr 12 and dr 26 is J.
Unfortunately, I didn't succeed to define a discrete energy spectrum with the sb option. The definition of the sb does not allow that ([ sb N INTT E1 WGT1 E2 WGT2 ... ]). It is still giving an error such as: "Probability of first energy point must be zero." Also, the first entry (N) limits the sb just for the histogram energy spectrum. I am using Version 2.1.31. Please let me know how to use the sb option for the discrete energy spectrum.
Thank you very much!
 Jaakko Leppänen
 Site Admin
 Posts: 2315
 Joined: Thu Mar 18, 2010 10:43 pm
 Security question 2: 0
 Location: Espoo, Finland
 Contact:
Re: Photon detector
The zero bin is included for compatibility with MCNP. For line spectrum you just need to add one more line at the beginning with zero probability.
This is what I get for a simple test input with different values of INTT:
This is what I get for a simple test input with different values of INTT:
Code: Select all
surf 1 sph 0 0 0 1
cell 1 0 air 1
cell 2 0 outside 1
mat air 1E9
1001.03c 1
src 1 sp 0 0 0
sb 5 0
1 0
2 2
3 1
4 3
5 1
set nps 10000000
set srcrate 1
ene 1 2 1000 0 10
det 1 ds 1 1 de 1
 Attachments

 intt2.png (15.12 KiB) Viewed 222 times

 intt1.png (14.31 KiB) Viewed 222 times

 intt0.png (12.4 KiB) Viewed 222 times
 Jaakko
Re: Photon detector
Dear Jaakko, thank you very much for your answer!