RE: [fluka-discuss]: magnetic field in vacuum

From: REDDELL, BRANDON D. (JSC-EV511) <"REDDELL,>
Date: Fri, 14 Feb 2014 23:23:22 +0000

Hi Francesco,

Thanks for your reply and I thought I had the FLUKA discussion on the last email (it should be included on this one).

I have a rather large geometry and I am using the SFLOOD routine to emit GCR protons from a spherical surface just large enough to encompass the large cylindrical shell containing the magnetic field (defined previously). I am performing uniform sampling over the whole energy range and have run 2e10 primaries to produce the attached plot. This is particle-magnetic field interaction is hard to visualize given the isotropic nature of the source and the energy range. I am sure there are some particle tracks that are turned toward my detector surface. I used USRYIELD to produce the flux across a spherical surface (centered at the origin) having a radius of ~30cm. All materials are assigned a vacuum to eliminate secondary particle generation.

Attached is a plot that shows near the peak of the cosmic ray spectrum that the 1 Tesla field reduces the flux somewhat and the 10 Tesla, just a little more. What is surprising is that the low energy side all matches the free space spectrum (i.e. the source spectrum). Given the magnetic cutoff, I would expect increasingly less flux on the lower energy side of the spectrum peak working down to lower energy. However, there are some particles entering in from the ends of the cylindrical field as well. Is it possible to recover the full low energy spectrum for this simulation?

Brandon

-----Original Message-----
From: Francesco Cerutti [mailto:Francesco.Cerutti_at_cern.ch]
Sent: Friday, February 14, 2014 2:38 PM
To: REDDELL, BRANDON D. (JSC-EV511)
Cc: Dr. Vittorio Boccone; FLUKA discussion
Subject: RE: [fluka-discuss]: magnetic field in vacuum


Dear Brandon

please keep the discussion on the list, considering the huge interest captured by magnetic field, as proved in parallel by Mina's stimulating posts.

As previously stated, your MGNFIELD card, coupled to ASSIGNMA, is perfectly working without any additional magfld.f routine. You can realize it yourself by plotting the field through the Flair geometry plot referring for instance to the Geoviewer horizontal cut (green), as I just did. Moreover, if you send in the field a particle with appropriate momentum, you will be able to appreciate its trajectory bending by displaying a USRBIN fluence scoring.
The coordinates of the magnetic regions are totally immaterial, since in MGNFIELD you are defining a vector which is applied in all points of those regions.

The fact that you cannot see any difference depends on the combination of your particle direction/momentum with your field direction/intensity and on the position/geometry of your detector.

Best

Francesco

**************************************************
Francesco Cerutti
CERN-EN/STI
CH-1211 Geneva 23
Switzerland
tel. ++41 22 7678962
fax ++41 22 7668854

On Fri, 14 Feb 2014, REDDELL, BRANDON D. (JSC-EV511) wrote:

> Francesco,
>
> I used the following CARDs (cut out from my inp file) to define a uniform 1 Tesla field (and also a second run of 10 Tesla) and noticed no difference in the flux across the surface of a sphere at the origin as compared to the same run with the field turned off. So, if the region where the field is supposed to be is not on the coordinate axes, do I need to use magfld.f?
>
> Brandon
>
>
>
> MGNFIELD 20.0 0.2 0.10 0.0 0.0 1.0
> STEPSIZE 0.5 0.0 VAC2 0.0 0.0 0.0
> EMF EMF-OFF
> *---o---- ----o---- ----o---- ----o---- ----o---- ----o---- ----o---- ----o----
> GEOBEGIN COMBNAME
> 0 0 Targets
> SPH BLKH 0.0 0.0 0.0 5.D4
> SPH SPCE 0.0 0.0 0.0 2.5D4
> * BField Region
> RCC B1 0.0 0.0 -1000.0 0.0 0.0 2000.0 1030.0 RCC B2 0.0 0.0 -1000.0
> 0.0 0.0 2000.0 400.0
> * Det 1
> SPH D01a 0.0 0.0 0.0 28.2095
> SPH D01b 0.0 0.0 0.0 27.2095
> *
> END
> BH 5 +BLKH -SPCE
> VAC1 5 +SPCE -B1
> VAC2 5 +B1 -B2
> VAC3 5 +B2 -D01a
> D01 5 +D01a -D01b
> *
> .
> .
> *---o---- ----o---- ----o---- ----o---- ----o---- ----o---- ----o---- ----o----
> ASSIGNMA BLCKHOLE BH
> ASSIGNMA VACUUM VAC1
> ASSIGNMA VACUUM VAC2 1.0
> ASSIGNMA VACUUM D01
> .
> .
> .
>
> -----Original Message-----
> From: Francesco Cerutti [mailto:Francesco.Cerutti_at_cern.ch]
> Sent: Friday, February 14, 2014 3:58 AM
> To: Dr. Vittorio Boccone
> Cc: REDDELL, BRANDON D. (JSC-EV511); FLUKA discussion
> Subject: Re: [fluka-discuss]: magnetic field in vacuum
>
>
> Hallo,
>
> actually, in case of constant magnetic field in all magnetic regions,
> the MGNFIELD card is enough (as stated in the manual). It will
> automatically feed the default magfld routine (the one provided in
> usermvax, where in fact the comment
> * 2 Tesla uniform field along +z:
> does not apply) and you do NOT need to link the latter into a customized executable, unless you want to modify it, since it is already in the standard FLUKA library and linked in the standard executable.
>
> Cheers
>
> Francesco
>
> **************************************************
> Francesco Cerutti
> CERN-EN/STI
> CH-1211 Geneva 23
> Switzerland
> tel. ++41 22 7678962
> fax ++41 22 7668854
>
> On Thu, 13 Feb 2014, Dr. Vittorio Boccone wrote:
>
>> No you should still include and link the default magfld routine which
>> is configured for a uniform magnetic field, as explained in the
>> lecture and the tutorial.
>> Best
>> V.
>> Sent from my iPad
>>
>> On 13/feb/2014, at 22:42, "REDDELL, BRANDON D. (JSC-EV511)"
>> <brandon.d.reddell_at_nasa.gov> wrote:
>>
>> Thanks Vittorio.
>>
>> So in my simple problem, I am not using the magfld.f routine,
>> just only the MGNFIELD card. So, could you confirm if these
>> cards should work:
>>
>> MGNFIELD        20.0       0.2      0.10       0.0      
>> 0.0       1.0
>> STEPSIZE         0.5       0.0      VAC2       0.0      
>> 0.0       0.0
>> EMF                                                                  
>> EMF-OFF
>> .
>> .
>> .
>> ASSIGNMA      VACUUM      VAC2                           1.0
>> (the 1 here is at WHAT(5)
>>
>> Thanks.
>>
>> Brandon
>>
>>
>>
>> ____________________________________________________________________________
>> From: Vittorio Boccone [dr.vittorio.boccone_at_ieee.org]
>> Sent: Thursday, February 13, 2014 2:47 PM
>> To: REDDELL, BRANDON D. (JSC-EV511); fluka-discuss_at_fluka.org
>> Subject: Re: [fluka-discuss]: magnetic field in vacuum
>>
>> Sure, check out the magnetic field exercise (solution) on the
>> advanced
>> course:
>> http://www.fluka.org/fluka.php?id=course&sub=program&navig=2&which=tr
>> i
>> umf20
>> 12
>> Best
>> V.
>>
>> On 2/13/2014 8:47 PM, REDDELL, BRANDON D. (JSC-EV511) wrote:
>>
>> FLUKA Users/Experts,
>>
>>  
>>
>> Do the magnetic field settings in a region (using MGNFIELD
>> card along with WHAT card 5 in ASSIGNMA Card) work if the
>> region of the B field is a vacuum?
>>
>>  
>>
>> Brandon
>>
>>
>>
>>
>



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Received on Sat Feb 15 2014 - 02:33:19 CET

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