From: Alberto Fasso' (fasso@SLAC.Stanford.EDU)
Date: Tue Dec 12 2006 - 17:42:00 CET
Thank you, but yesterday, because I was focusing on finding the cause of the
error, I overlooked a more obvious and elegant way to do what you want.
Primary particles can be distinguished by their generation number.
Therefore you could change the test to:
IF (ICODE.EQ.101 .AND. LTRACK.EQ.1) THEN
LTRACK is an integer and you can safely test for equality.
Alberto
On Tue, 12 Dec 2006, me@marychin.org wrote:
> You are absolutely right. Thanks a million Alberto!
>
> Alberto Fasso' wrote:
> > The reason is probably in your test
> > ETRACK.EQ.PBEAM
> > both ETRACK and PBEAM are real (actually double precision) quantities, and
> > it is well known that comparisons of such quantities should be done only
> > by .LE. .LT. .GE. or .GT. Equality can be spoiled by rounding errors.
> > Suppose for instance that PBEAM has been input as 21.5, but ETRACK
> > for some reason is 24.99999999999999D0. For computing purposes it is the same
> > thing, but the test of equality would fail. I suggest that you change your test
> > into:
> > IF (ICODE.EQ.101 .AND. ETRACK.GE.PBEAM*ONEMNS) THEN
> > (ONEMNS is predefined in FLUKA as 0.999999999999999D+00)
> >
> > Alberto
> >
> >
> > On Mon, 11 Dec 2006, me@marychin.org wrote:
> >
> >
> >>Dear FLUKA friends,
> >>
> >>I started monoenergetic photons in homogeneous lead. Simulations were
> >>repeated for different incident energy, ranging from 7.5 to 29.5 MeV. My
> >>USDRAW in mgdraw.f has:
> >> IF (ICODE.EQ.101 .AND. ETRACK.EQ.PBEAM) THEN
> >> J = 0
> >> DO I = 1, Np
> >> IF (Kpart(I)==8) THEN
> >> J = J + 1
> >> END IF
> >> END DO
> >> WRITE (IODRAW) J
> >> END IF
> >>so that only photons at incident energy undergoing inelastic
> >>interactions scores. Slowing down photons were not allowed to score. I
> >>basically mean to count the number of (g,n), (g,2n) and (g,3n) events.
> >>When the count is plotted against the incident energy, I expect
> >>the plot to resemble the photoneutron cross section. Generally results
> >>appear as expected except that at incident energies 21.5, 25.5 and 29.5
> >>MeV, I miraculously get zero counts. Zero counts were obtained at
> >>exactly the same three energies when the simulation was repeated with
> >>carbon and calcium. I can't understand the abrupt zero and the
> >>discontinuity. Could someone please help. Have I missed something?
> >>
> >>My results for lead is as follows. Please note the region of interest I
> >>have zoomed into between 21 and 22 MeV. 21.4, 21.49 and 21.6 all
> >>produced non-zero counts while 21.499 and 21.5 produced zero.
> >>MeV (g,0n) (g,n) (g,2n) (g,3n)
> >>7.5 709 1747 0 0
> >>8.5 0 11923 0 0
> >>9.5 0 37225 0 0
> >>10.5 0 85953 0 0
> >>11.5 0 181338 0 0
> >>12.5 0 266842 0 0
> >>13.5 1 328983 0 0
> >>14.5 0 242696 17314 0
> >>15.5 1 90913 76994 0
> >>16.5 0 20916 80017 0
> >>17.5 2 5257 65996 0
> >>18.5 4 1634 52304 0
> >>19.5 8 572 35742 0
> >>20.5 9 235 21941 0
> >>21 13 188 18131 0
> >>21.1 10 190 17868 0
> >>21.2 16 148 17409 0
> >>21.3 10 169 17280 0
> >>21.4 10 155 17156 0
> >>21.49 12 157 17694 0
> >>21.499 0 0 0 0
> >>21.5 0 0 0 0
> >>21.6 12 175 17529 0
> >>21.7 11 158 17700 0
> >>21.8 18 162 18257 1
> >>21.9 13 154 18703 9
> >>22 18 152 19278 18
> >>22.5 20 161 22008 210
> >>23.5 40 168 22886 2608
> >>24.5 32 118 12426 5929
> >>25.5 0 0 0 0
> >>26.5 20 75 2865 9170
> >>27.5 19 94 1715 10760
> >>28.5 32 85 951 9397
> >>29.5 0 0 0 0
> >>
> >>Attached inp file, as well as photoneutron cross sections for lead. The
> >>cross section doesn't seem to explain the trend. Calcium, carbon and
> >>lead are unlikely to have absolute-zero valleys at exactly the same 3
> >>energies anyway?
> >>
> >>Thanks very much.
> >>
> >>mary
> >>
> >>
> >>
> >
> >
>
-- Alberto Fassò SLAC-RP, MS 48, 2575 Sand Hill Road, Menlo Park CA 94025 Phone: (1 650) 926 4762 Fax: (1 650) 926 3569 fasso@slac.stanford.edu
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