# [fluka-discuss]: Asymmetrical results and high error percentage

From: Jyoti <jyoti.grg_at_britatom.gov.in>
Date: Sat, 30 Apr 2022 14:20:40 +0530 (IST)

Dear FLUKA Experts,

In the attached input file, I want to score Dose-Eq. at z=56 (top surface) of the geometry. I used four USRBIN cards:

x-y-z, z= 56 to 57, y = -0.5 to 0.5, x = -59.5 to 59.5 (119 bins), Volume of one bin: 1cc
x-y-z, z= 56 to 58, y = -1 to 1, x = -59 to 59 (59 bins), Volume of one bin: 8cc
x-y-z, z= 56 to 57, x = -0.5 to 0.5,y = -59.5 to 59.5 (119 bins), Volume of one bin: 1cc
x-y-z, z= 56 to 58, x = -1 to 1,y = -59 to 59 (59 bins), Volume of one bin: 8cc

The dose-eq. values near the air gap (i.e., x = 32.5 to 32.7 and x = -32.5 to -32.7) have increased suddenly to very large value (e.g, from 0.00026mR/h to 0.00268mR/h). Also, the values at x = -32.6 are not same as the values at x = 32.6 even when the geometry is symmetrical.

First, I kept 25 source pencils (odd number), the values were different at x = 32.6 and -32.6. So, I kept 40 pencils (even number), then also values are different. I even tried increasing the NPS from 5E07 to 2E08, but values are still different. Why is it so?

What can I do to improve the values (I already tried increasing bin volume and NPS)?
Am I doing something wrong in biasing? Or is there any other method of biasing which may improve my results?

With regards,
Jyoti

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Received on Sat Apr 30 2022 - 13:02:44 CEST

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