Re: Re: [fluka-discuss]: Re: [fluka-discuss]: Re: [fluka-discuss]: Comparisons of different methods to obtain γ-rays of Cobalt-60 in FLUKA !

From: YANG Tao <yangt_at_ihep.ac.cn>
Date: Wed, 7 Dec 2016 12:44:36 +0800 (GMT+08:00)

Dear Nikhi,
Thanks for your answer. Your suggestions are very useful for me.


Best,
Yang.


-----原始邮件-----
发件人: "nikhil shetty" <nikhil.nitk_at_gmail.com>
发送时间: 2016年12月5日 星期一
收件人: "YANG Tao" <yangt_at_ihep.ac.cn>
抄送: fluka-discuss <fluka-discuss_at_fluka.org>
主题: Re: [fluka-discuss]: Re: [fluka-discuss]: Re: [fluka-discuss]: Comparisons of different methods to obtain γ-rays of Cobalt-60 in FLUKA !


Dear Yang,


here is a thread explaining "weight": http://www.fluka.org/FLUKA/web_archive/earchive/new-fluka-discuss/0325.html


In most of the cases, weight simply means particle.


And this line ("WEIPRI = WEIPRI + WTFLK (NPFLKA)") is counting primary particles or decay events. In method 2, this line is executed twice, therefore wrongly counting the number of primary particles.



Cheers,

Nikhil








On Sat, Dec 3, 2016 at 7:33 AM, YANG Tao <yangt_at_ihep.ac.cn> wrote:


Dear Nikhil,

    Thanks for your suggestions, I run method 2 successfully, and get the expected 2 PHOTONS/primary. However, I don't well understand the reasons to do like this though you explained it in detail. Could you send me some references or links to understand it, especially the term "weight" ?

Best,

Yang.




-----原始邮件-----
发件人: "nikhil shetty" <nikhil.nitk_at_gmail.com>
发送时间: 2016年12月2日 星期五
收件人: "YANG Tao" <yangt_at_ihep.ac.cn>
抄送: fluka-discuss <fluka-discuss_at_fluka.org>
主题: [fluka-discuss]: Re: [fluka-discuss]: Re: [fluka-discuss]: Comparisons of different methods to obtain γ-rays of Cobalt-60 in FLUKA !



Dear Yang,


the problem is in the source routine of method 3. Because the weight summing is happening inside the loop, the weight of each gamma is added to the sum. That is, each gamma emission is treated as an independent decay event.

In the end, fluka gives you the results divided by the total weight accumulated and the weight is counted twice. In other words, it appears as though only one photon is emitted per primary.


The simplest solution is to edit the source routine and move this line "WEIPRI = WEIPRI + WTFLK (NPFLKA)" outside of the loop.


Cheers,

Nikhil







On Thu, Dec 1, 2016 at 5:38 PM, YANG Tao <yangt_at_ihep.ac.cn> wrote:


Dear Nikhil,

    Thanks for your reply. Attachments are the relevant input files and the source routines. I think there may be some problems in the source routine of method 2, so please point out them.

Best regards,

Yang




-----原始邮件-----
发件人: "nikhil shetty" <nikhil.nitk_at_gmail.com>
发送时间: 2016年12月1日 星期四
收件人: "YANG Tao" <yangt_at_ihep.ac.cn>
抄送: fluka-discuss <fluka-discuss_at_fluka.org>
主题: [fluka-discuss]: Re: [fluka-discuss]: Comparisons of different methods to obtain γ-rays of Cobalt-60 in FLUKA !



Hello,


Irrespective of method 1 and 2, it seems that there is a physical problem in method 3. In reality, the two gamma rays are emitted simultaneously and both with almost 100 % probability. The way it is implemented in method 3, the gammas are sampled independently, however it is not true.


Well, regarding your actual question, it helps if you post the source routines so that someone can debug them.


Cheers,

Nikhil






On Thu, Dec 1, 2016 at 11:59 AM, YANG Tao <yangt_at_ihep.ac.cn> wrote:


Dear FLUKA users,

    Recently I have simulated the dose given by cobalt-60 source and I have some confusions. As is known, two γ-rays with energy of 1.17 MeV and 1.33 MeV are emitted in the decay process. To obtain the beam of two energies, I try to finish it in three different ways.

1. Set the BEAM card to ISOTOPE, and then define Co-60 with the HI-PROPE and RADDECAYcards.

2. Write a user routine to define the source, which is mainly relied on method by Giuseppe( http://www.fluka.org/web_archive/earchive/new-fluka-discuss/2860.html). I also declare a array titled Egamma(N) and inject two photons in a DO loop.

3. A similar user routine with method 2, but I don't define an array of photon energy, but a sampling method as follows:

    IF (FLRNDM(XDUMMY) .LE. 0.5) THEN

         TKEFLK (NPFLKA) = 0.001333

      ELSE

         TKEFLK (NPFLKA) = 0.001173

      END IF

    Then I compare the different results. Method 1 seems to give the correct results compared to the experiments. Results of method 2 and 3 are almost the same with each other and only about one half of the one given by method 1. I guess only one PHOTON/primary is emitted in method 2 and 3, so I define a region to wrap the Co-60 source region and score the photons from source using the USRBDX card, and the results confirm the guess, method 1 gives 2 particles/primar, while method 2 and 3 both gives 1 particles/primary.
   
    Result of method 1 is correct since it simulates the real isotope decay process and emits two photons for each event by the internal setting of FLUKA. Method 3 emits one PHOTON each event also doesn't puzzle me since I use a sampling method and it selects one photon energy by the random number each time. However, method 2 as the explanation of Giuseppe will inject two PHOTONS for each event, why does it give the results like one PHOTON each time? I guess method 2 and 3 may indeed only emit one PHOTON/primary each time and I should multiply the result by 2 to obtain the real value, if that is the case, what is the difference of method 2 and 3?

Any help is appreciated.

T. Yang

CAS







 






--
杨涛
中科院高能所东莞分部(东莞中子科学中心)加速器技术部      
地址:东莞市大朗镇中子源路1号中国散裂中子源A2栋606室
E-mail:yangt_at_ihep.ac.cn
电话:0769-38944239
邮编:523803
__________________________________________________________________________
You can manage unsubscription from this mailing list at https://www.fluka.org/fluka.php?id=acc_info
Received on Wed Dec 07 2016 - 07:29:05 CET

This archive was generated by hypermail 2.3.0 : Wed Dec 07 2016 - 07:29:11 CET