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Question Unexpected results for fluence and TID using Spenvis/GRAS 

Forum: Space Applications
Date: 08 Mar, 2016
From: Svetlana Shasharina <Svetlana Shasharina>

I did the following calculations using Spenvis/GRAS(gdml):

1. Independent runs for two vacuum spheres with r = 19cm and r = 15 cm. Source: Monoenergetic (100MeV) electrons with fluence 100 (1/cm^2 s), sphere with r = 20cm.

SPENVIS calculated fluences 28390 and 17644 for the first and the second spheres. The ratio of fluences/surface_area is constant for these cases (6.24 and 6.26) and is very close to 2pi :-) but is very different from the incident fluence (100).

First confusion: I thought the calculated fluence is normalized to the target's areas. But looks like it is not. Second confusion: after dividing by the surface areas I still have a number very different to the incident environment number (100).

Maybe I do not understand what the incident fluence really mean? How do I get a number that would relate to it?

2. Ta sphere r = 15cm, calculating TID in MeV with the source described. I get 1.6564e+06MeV/s.

If all e were to absorb, I would expect 100(1/cm^2 s)*100MeV*SurfaceArea = 1e+4 MeV/s *2826cm^2 = 2.8e+7 MeV/s.

So about 1/16 of the electrons gets absorbed, I guess? If I change normalization to CURRENT instead of FLUX, I will get 1/4 difference, I assume. Still a big difference. Any intuitive reaction to this difference?

Best regards, Sveta

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1 None: Re: Unexpected results for fluence and TID using Spenvis/GRAS   (Svetlana G. Shasharina - 08 Mar, 2016)
1 None: Re: Unexpected results for fluence and TID using Spenvis/GRAS   (Svetlana Shasharina - 10 Mar, 2016)
2 More: Re: Unexpected results for fluence and TID using Spenvis/GRAS   (Roger Byrd - 02 Apr, 2016)
1 None: Re: Unexpected results for fluence and TID using Spenvis/GRAS   (sveta - 09 Apr, 2016)
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