Re: [fluka-discuss]: Neutron Yield from Be Target

From: Emilio Ciuffoli <>
Date: Tue, 3 May 2016 16:33:29 +0800

Dear Vittorio,

thank you for your answer, and I apologize for the late reply.

> In your case about 11% of the secondaries generated in the inelastic
> interaction are be Deuterons which are not handled by FLUKA at such low
> energies.
Just to be sure: you mean that 11% of all the particle generated (n, p
alpha, D, etc..) should be deuterons, right? Not that in the 11% of the
case, the reaction Be+p produce deuteron...

In any case, I don;t think the deuterium can change significantly the total
neutron yield. Using RESNUCLEi to score the amount of deuteron produced, I
found a rate D/p=4% (compared to a rate n/p of 7%) In order to get the
missing 3% n/p, every 4 deuterons, 3 neutrons should be produced (= rate
n/D=75%). However, the neutron yield from deuterons at 60-70 MeV on Be
target is n/D=10%-15% (see here
<>, for
example): the deuterons can contribuite to n/p for less 0.5% (actually,
much less: this was assuming that all D were created at 62 MeV).

I found out that, if I decativated the COALESCEnce card, the neutron yields
go up from 7% to 9%, which is much more in agreement to the experimental
results (and the deuterium goes from 4% to 2%).

I am a bit confused: I thought that the COALESCEnce card should always be
activated, if possible (this was written also here
<> by
Francesco Cerrutti, for example, and it also what was written by Alfredo
Ferrari yesterday). However without it I found a much better agreement with
the experimental results.

Am I right if I say that the correct proceure, in this case, is to activate
the COALESCEnce card? Or is there a reason for NOT activate it in the study
of the neutron yield?

Thank you again for your time and help
Best Regards

Emilio Ciuffoli

2016-04-27 6:53 GMT+08:00 Vittorio Boccone <>:


> Hi Emilio,
> as already mentioned from Mario back in November, this number might be
underestimated for different reasons. You could also more easily score the*
neu-bala* with a USRBIN (per region scored at point) which will give you in
this case directly the neutron balance for the region.
> In your case about 11% of the secondaries generated in the inelastic
interaction are be Deuterons which are not handled by FLUKA at such low
> Not sure if this is sufficient to explain a 30% mismatch....
> Best,
> Vittorio
> On Tue, Apr 26, 2016 at 3:30 PM, Emilio Ciuffoli <>


>> Dear FLUKA experts,
>> I am studying the neutron yield from a Be target hitten by a proton beam.
>> I am trying to reproduce the experimental results reported in this paper:
>> They used a cylindrical target (diameter: 3.5 cm, lenght: 3 cm) and 62
MeV proton beam, they reported a neutron/proton ratio of 9.87% +/- 0.53%
(syst). However from my simulation I obtain a neutron yield of only 6.88%
+/- 0.002% (stat).
>> Could you please take a look at my input card and tell me if I made some
mystake? Please find in the attached files also the output of the USRYIELD
card I used to score the neutron yield
>> Thank you very much for your help
>> Best Regards
>> Emilio Ciuffoli

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Received on Tue May 03 2016 - 12:14:52 CEST

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