Re: USRYIELD and heavy ions

From: Francesco Cerutti <>
Date: Mon Jun 09 2008 - 18:08:31 CEST

Hi Joel,

for your purposes the USRYIELD scoring you implemented is the good choice,
but it requires not negligible corrections. You select HEAVYION
(WHAT(2) of the first card) and score as a function of their unrestricted
LET (given in keV/(um g/cm3)) and charge (through the code 2223.0 in
WHAT(1) of the first card, implying multiple LET bins and only one
charge bin). However, you have to specify in WHAT(6) of the continuation
card which quantity you want (plain double differential YIELD in your
case) and the material to which LET is referred (which has to be assigned
to a geometry region) -> 3+100*WATER=2803.0 (WATER is the material #28 in
your input).
Moreover, you limit (of course not intentionally) the ion charge interval
to 0<=Z<26 so loosing iron nuclei, and also cobalt nuclei which can in
principle be produced by the interaction of the iron beam with hydrogen in
polyethylene. As WHAT(4-5) of the continuation card, you may simply
put e.g. 100.5 and 0.5, respectively, to not cut any nucleus (this way
you ask from hydrogen to fermium - though you will not have anything
beyond cobalt - ). Since charge has only integer values, by half-integer
limits you are sure about what is included and what is not.
Since water has density 1g/cm3, if you want 1 keV/um bins you have to
choose the number of LET bins according to the requested range (200 bins
from 0 to 200 keV/um or 195 bins from 5 to 200 keV/um).
To apply the proper normalization, remember that the results are divided
by the LET bin width (1 keV/um) and by the charge interval width (100
according to my suggestion). To get surface density, you have to divide
in addition by the area of the scoring surface (16cm2), which can be
directly incorporated as WHAT(6) of the first card. Take finally into
account that FLUKA results are normalized per primary ion and, since you
have a 10cmx10cm square beam and a 4cmx4cm detector, as a first
approximation (neglecting divergence and beam/secondary lateral
scattering) 84% of the simulated beam is not seen by your detector ->
scored values are accordingly scaled down.



Francesco Cerutti
CH-1211 Geneva 23
tel. ++41 22 7678962
fax ++41 22 7668854
Received on Mon Jun 9 23:08:13 2008

This archive was generated by hypermail 2.1.8 : Mon Jun 09 2008 - 23:08:15 CEST