RE: [fluka-discuss]: USRBDX and USRYIELD

From: Stefan Roesler <sroesler_at_mail.cern.ch>
Date: Mon, 1 Sep 2014 23:58:30 +0200

Dear Hayley

As you mentioned earlier, in USRYIELD angles are defined with regard to
the beam direction, in USRBDX with regard to the normal of the respective
surface. Of course, beam particles exit the back-plane of your target and
this shouldn't thus matter, nevertheless...

Furthermore, also USRYIELD needs a normalization factor to divide by the
scoring surface (What(6)) if you want to compare to a correctly normalized
USRBDX. Note that due to the definition of the scoring surface to be the
(in theory) entire surface of your MUONTARG, it is not 100cm2 (of course,
again this is not critical since you score BEAMPART).

Your USRBDX-card is a fluence estimator (scoring weighed with
1/cos(theta). Thus, also in USRYIELD you have pick the corresponding
double differential distribution, i.e. ixa = 6 : double differential
fluence yield.

Finally, be careful, your angular bins in USRBDX are equidistant in *solid
angle* and in USRYIELD equidistant in *polar angle*, which does not give
the same binning, i.e. you cannot compare the fluence in individual bins
to each other. btw, note that (to confuse the user ;-)) the USRYIELD
angular bins are normalized by solid angle bin width (see manual).

In the attachement I send you your input with some modifications: I have
entered a dummy scoring plane at the exit of your target, just to compare
scoring on a plane that is normal to the beam direction (see first
comment). Furthermore, I have simplified your USRBDX and USRYIELD cards
such that they score only in a single angular bin, this time of the same
size. Since the USRYIELD distributions are also given per solid angle
(despite its definition in polar angle) it gives, for once, the same
normalization as in USRBDX. If you run and look into the ASCII-output you
can convice yourself that the fluence value is indeed identical...

Hope it helps,

Cheers
Stefan



On Fri, 29 Aug 2014, hayley.smith_at_stfc.ac.uk wrote:

> Thank you Stefan for this clarification and the pointers.
> Initially I thought pseudorapidity was what I required as I am assessing the beam scattering, but know I think scoring the polar angle may be more appropriate.
>
> When scoring polar angle I was hoping to get my USRYIELD and USRBDX results to agree (to convince myself I am using them correctly) but I still haven't been able to, so I think I am misunderstanding something, but still cannot see what I would be doing wrong. When plotted on a log scale the USRYIELD results seem the most believable and vary as I would expect with target thickness and energy. But I cannot seem to get the same behaviour from USRBDX - I have obviously made a mistake somewhere.
>
> Thank you once again, and any further guidance would be much appreciated.
> Hayley
>
>
>
>
> -----Original Message-----
> From: Stefan Roesler [mailto:sroesler_at_mail.cern.ch]
> Sent: 25 August 2014 09:11
> To: Smith, Hayley (STFC,RAL,ISIS)
> Cc: fluka-discuss_at_fluka.org
> Subject: RE: [fluka-discuss]: USRBDX and USRYIELD
>
> Just a minor correction to my below email: it should read "theta being the polar angle" (and not "azimuthal")
>
> cheers
> Stefan
>
>
> On Fri, 22 Aug 2014, Stefan Roesler wrote:
>
>> Dear Hayley
>>
>> USRYIELD/What(6) is an user-defined normalization factor; if you leave
>> it empty it is assumed to be 1. It has nothing to do with What(4) of
>> the continuation card which is the upper scoring limit of the second quantity.
>>
>> Just to be sure: do you indeed what to score USRYIELD in
>> pseudorapidity, which is -ln(tan(theta/2)) (theta being the azimuthal
>> angle)?? It must peak at large values (small theta) for (scattered) beam-particles.
>>
>> USRBDX always scores energy spectra (in your case with one energy bin
>> it is a single value). In case you define several angular bins you get
>> as many "spectra" as angular bins (in your case 100). If you select in
>> Flair 1.x (I recommend to go to Flair 2.x) under "Det" the second option "2 1 scatter 2D"
>> you will see the different values as function of angle.
>>
>> Cheers
>> Stefan
>>
>>
>>
>> On Fri, 22 Aug 2014, hayley.smith_at_stfc.ac.uk wrote:
>>
>>> Thank you very much for your help Stefan, it has been much
>>> appreciated - I am now able to run the deck without it crashing.
>>>
>>> As a follow up, you say it is important to input values for all
>>> WHATs. In this case, are you able to advise what value I should put
>>> for WHAT (6) of the first USRYIELD card? It says in the manual 'normalisation factor'.
>>> Would this be the same as WHAT (4) in the continuation card?
>>>
>>> Also, I am confused by the output I get from the USRYIELD and USRBDX cards.
>>>
>>> I would have thought that to score the angular distribution using
>>> USRYIELD that the maximum angle would be Pi/2. However when I do
>>> this I get strange results. The result seems more sensible for a
>>> maximum angle of 2Pi, but still I would have expected the peak of the
>>> angular distribution to be around 0, rather than around 2Pi? Am I misinterpreting my results?
>>>
>>> With the USRBDX scoring solid angle I understand why the maximum
>>> angle for this would be 2Pi. However, the results I obtain for
>>> angular distribution for a single energy bin are just as confusing to me...
>>>
>>> I have read extensively through the manual and previous posts but
>>> have not been able to find any information.
>>> I understand that a difference between USRBDX and USRYIELD is that
>>> USRBDX calculates the angle with respect to the normal, and USRYIELD
>>> calculates the angle with respect to the beam direction (in my case).
>>> Maybe this is a source of my confusion?
>>>
>>> Are you able to explain:
>>> Why the result of USRYIELD with a maximum angle of 2Pi is centred
>>> around 2Pi?
>>> Why using a maximum angle of Pi/2 in USRYIELD in this case is
>>> seemingly incorrect?
>>> Why I am struggling to get a meaningful result from USRBDX (or
>>> why/how I am misinterpreting the results)?
>>>
>>> My input file and three screenshots showing the resulting graphs I
>>> describe are attached.
>>> Any help is very much appreciated,
>>> Hayley
>>>
>>>
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: Stefan Roesler [mailto:sroesler_at_mail.cern.ch]
>>> Sent: 20 August 2014 09:42
>>> To: Smith, Hayley (STFC,RAL,ISIS)
>>> Cc: fluka-discuss_at_fluka.org
>>> Subject: Re: [fluka-discuss]: USRBDX and USRYIELD
>>>
>>> Dear Hayley
>>>
>>> I recommend to enter input values for all What's in scoring cards.
>>> Some have default values, some don't.
>>>
>>> For example in your case WHAT(4) of the USRYIELD continuation card
>>> (upper limit of the second quantity) has no default (!) which causes
>>> the code to crash (normalization with an undefined value..)
>>>
>>> Furthermore, when the upper energy limit in USRBDX and USRYIELD is
>>> not defined, the code uses the beam energy. However, when scoring
>>> BEAMPART the energy of the particle to be scored is exactly at the
>>> bin limit, and depending on the internal rounding the particle might be scored or not.
>>> Thus, I suggest you define an upper energy limit that is slightly
>>> above the beam energy.
>>>
>>> Cheers
>>> Stefan
>>>
>>>
>>> On Mon, 18 Aug 2014, hayley.smith_at_stfc.ac.uk wrote:
>>>
>>>>
>>>> Dear All
>>>>
>>>>  
>>>>
>>>> I am trying to look at the scattering of a 800 MeV proton beam
>>>> through a carbon target.  (At present the beam distribution and
>>>> target geometry are very much simplified).
>>>>
>>>> I have tried to score the angular distribution of the proton beam in
>>>> two ways, using USRBDX and using USRYIELD.
>>>>
>>>>  
>>>>
>>>> I thought USRYIELD would be the most appropriate since I read
>>>> various threads on the forum, and this one in particular seemed to
>>>> be doing a very similar thing to me,
>>>> http://www.fluka.org/web_archive/earchive/new-fluka-discuss/0568.htm
>>>> l
>>>>
>>>>  
>>>>
>>>> However, when I try to create a USRYIELD card with a single energy
>>>> bin the progress status for the run always ends after the first
>>>> cycle with ?Finished with ERRORS? and  nothing stands out to me from
>>>> the .log, .out or .err files.
>>>>
>>>>  
>>>>
>>>> When I don?t use a USRYIELD card the USRBDX card outputs results,
>>>> however I am unsure how to interpret them in terms of beam
>>>> scattering or divergence.
>>>>
>>>> The relevant files are attached for your information.
>>>>
>>>>  
>>>>
>>>> Is anyone able to advise me on how best to score the beam divergence
>>>> through the target?
>>>>
>>>> Is my approach correct?  What is causing the run to finish with
>>>> errors (that I can?t seem to find in the output files)?
>>>>
>>>>  
>>>>
>>>> Thanks, any assistance is much appreciated,
>>>>
>>>> Hayley
>>>>
>>>>  
>>>>
>>>>  
>>>>
>>>> Hayley Smith
>>>>
>>>>  
>>>>
>>>> Accelerator Physicist
>>>>
>>>> ISIS Facility
>>>>
>>>> Rutherford Appleton Laboratory
>>>>
>>>> Harwell Oxford
>>>>
>>>> OX11 0QX
>>>>
>>>>  
>>>>
>>>> 01235 445524
>>>>
>>>> hayley.smith_at_stfc.ac.uk
>>>>
>>>>  
>>>>
>>>>  
>>>>
>>>>  
>>>>
>>>>  
>>>>
>>>>
>>>> --
>>>> Scanned by iCritical.
>>>>
>>>>
>>>>
>>>>
>>>
>>> --
>>> Scanned by iCritical.
>>
>
> --
> Scanned by iCritical.
>


Received on Tue Sep 02 2014 - 01:12:14 CEST

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