From: Alfredo Ferrari (alfredo.ferrari@cern.ch)
Date: Mon Dec 19 2005 - 11:16:05 CET
Hi Frances
the 511 keV line is indeed there, but masked by your (toow wide) choice
of bin widhts.
In the attached plot you see:
a) red: the photon spectrum with your USRYIELD cards
b) green: the same with
USRYIELD 2399.0 7.0 -23.0 1.0 2.0 1000.0 PHOTYIELD
USRYIELD 10.0 1.0E-5 120.0 90.0 0.0 3.0 &
where the 511 line is already pretty visible
c) black: the same with
USRYIELD 2399.0 7.0 -23.0 1.0 2.0 1000.0 PHOTYIELD
USRYIELD 10.0 1.0E-5 120.0 90.0 0.0 6.0 &
where now photons are inverse cosine weighted (--> fluence like
and not current like) which is almost surely the right case if the
experiment reports the results in ../cm^2 and "cm^2" are as customary
"per unit NORMAL area" (or per steradian). If you send me the
experiment ref. I can check if this is really the case.
Ciao
Alfredo
On Mon, 12 Dec 2005, Burge, F (Frances) wrote:
> Sorry about the unreadable message - hopefully this will be better.
>
> I am trying to calculate a photon spectrum behind a 2.5cm thick copper
> target, on which a 6GeV electron beam of radius 1cm is incident. Since
> the results required have units of [photons/energy /cm2] I am using the
> USRYIELD card to calculate a plain double differential yield with
> respect to energy as the first quantity and polar angle in degrees as
> the second. I have set limits on the angle between 0 and 90 degrees as I
> guess this includes everything in the 'forward' direction, and score the
> photons crossing from the end of the target region into a detector
> region.
>
> The problem is that my output spectrum doesn't seem to include the peak
> at 0.511MeV for annihilation photons. The peak I get is somewhere
> between 0.1 and 0.2MeV. The published results which I am attempting to
> reproduce show a clear peak at 0.511MeV. I have set transport energy
> cut-offs in the peg file (still using FLUKA2003...) as:
> AP=0.001 UP = 6000
> AE=0.521 UE = 6000.511
>
> I have attached the input file. Can anyone tell me why I don't see the
> 0.511MeV peak? In case the attachment does not make it through, my
> USRYIELD cards are:
>
> *photon double differential yield (per energy per polar angle)
> USRYIELD 2399.0 7.0 -23.0 1.0 2.0 1000.0
> PHOTYIELD
> USRYIELD 6.0 1.0E-5 40.0 90.0 0.0 3.0
> &
>
> Region 1.0 is the copper target and region 2.0 the detector region which
> has the same (1cm) radius as the target and is 3cm long.
>
> many thanks,
>
> Frances
>
> Frances Burge
> Health Physicist
> 01235 778269
> Diamond Light Source Ltd.
> Rutherford Appleton Laboratory
> Chilton
> Didcot
> OX11 0QX
>
>
-- +----------------------------------------------------------------------------+ | Alfredo Ferrari || Tel.: +41.22.767.6119 | | CERN-AB || Fax.: +41.22.767.7555 | | 1211 Geneva 23 || e-mail: Alfredo.Ferrari@cern.ch | | Switzerland || Alfredo.Ferrari@mi.infn.it | +----------------------------------------------------------------------------+
This archive was generated by hypermail 2.1.6 : Mon Dec 19 2005 - 11:47:36 CET