[fluka-discuss]: Angular distribution of usryield

From: YANG Tao <yangt_at_ihep.ac.cn>
Date: Sat, 20 Oct 2018 00:28:44 +0800 (GMT+08:00)

Hellow, everyone!

        Recently I simulate the angular distribution of secondary ions from (n,B) reaction, I using USRYIELD card to obtain this. However, I cannot interpret the results.

① I set the first quantity polar angle θ (polar angle in the c.m.s. frame, relative to the primary beam direction)and second E, I get a similar isotropic distribution over the polar θ,indeed, I know this distribution is isotropic, but it corresponds to the solid angle Ω not the polar angle θ(i.e.,dΩ=2πsinθdθ). Suppose dN/dΩ=A(some constant),thus,dN/dθ=2Aπsinθ,so at the angle near 0° , we should get a minimal value, and get a maximal value near 90° (I think it is some counterintuitive). Maybe I misunderstand the output of USRYIELD card, so could anyone interpret the meaning of USRYIELD setting. I read the manual, it states:

"In the case of polar angle quantities (| ie| or | ia| = 14, 15, 17, 18, 24, 25) the differential yield is always referred to solid angle in steradian, although input is specified in radian or degrees."

Does it mean the results shown in figure1 is only dN/dΩ? I'm very confused about this, if it is the result of dN/dΩ, then how to obtain dN/dθ?


② Besides, I find the total response of 32BIN unit of the input file is 0.2155161(gem_32_sum.lis), which I think is the total yield of α particle leaving from the layer since it is integrated over two quantities, but the value doesn't match the total response of 25BIN((gem_25_sum.lis)) result which is 4.3065209E-04(gem_25_sum.lis,this value seems to be the true yield basing on the reaction cross section ), do the two responding values have different meaning?

Any help is appreciate!

Best regards!

Yang





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Received on Fri Oct 19 2018 - 20:33:10 CEST