**From:** Alberto Fasso' (*Alberto.Fasso@cern.ch*)

**Date:** Wed Apr 02 2003 - 01:14:51 CEST

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Indeed, your geometry description is incorrect.

I will try to list a few things which are obviously wrong or

inconsistent, but the main message is that a geometry such as

the one you are trying to describe cannot be done without the use

of the OR operator.

1) Region 1 (blackhole):

7 -2 4 -6

that means "the space inside sphere 7, which is outside cylinder 2, on the

left of plane 4 and on the right of plane 6"

No point can be at the same time on the left of plane 4 and on the right of

plane 6: it is the same as saying that its Z coordinate must be both < -5 and

* > 66. What you probably wanted was:
*

OR 7 -2OR 7 4OR 7 -6

2) Region 2 (vacuum at the beginning):

2 -1 3 -4 6 -5

This would mean: "the space inside the wall of a cylindrical shell contained

between cylinder 2 and cylinder 1, left of plane 3, right of plane 4, left

of plane 6 and right of plane 5"

Again, a point cannot be at the same time be left of plane 3 and right of

plane 5. And it is not clear why you want vacuum only between 2 and 1 and not

also inside 1. In any case, the space inside cyl. 1, left of plane 3 and

right of plane 4 remains undefined. What you probably wanted was:

OR 2 3 -4OR 2 6 -5OR 2 -1 6 -4

Alberto

On Tue, 1 Apr 2003, Christopher Knievel wrote:

*> Dear FLUKA users and authors:
*

*>
*

*> I am having a problem when I run my input with fluka. I am trying to simulate
*

*> an electron beam interacting with a cylindrical aluminum beam stop. The error
*

*> which I receive in the .err file is as follows:
*

*>
*

*> Geofar: Particle in region 3 (cell # 0) in position 5.730835694E+00 9.686117683E+00 3.982049539E+01
*

*> is now causing trouble, requesting a step of 9.549625271E+00 cm
*

*> to direction 1.929431495E-01 7.823632011E-01 5.921830482E-01, error count: 0
*

*> R2: 1.125448149E+01 R3: 4.138037224E+01 cm
*

*> X*U (2D): 8.683787525E+00 X*U (3D): 3.226480986E+01 cm
*

*> X*UOLD(2D): -2.805983023E+00 X*UOLD(3D): 2.332732094E+01 cm
*

*> Kloop: 49, Irsave: 3, Irsav2: 3, error code: -33 Nfrom: 5000
*

*> old direction 4.859413563E-01 -5.772006160E-01 6.562777210E-01, lagain, lstnew, lsense, lsnsct F F F F
*

*> Particle index 7 total energy 7.510855076E-04 GeV Nsurf 0
*

*> Try again to establish the current region moving the particle of a 1.000000000E-06 long step
*

*> We succeeded in saving the particle: current region is n. 3 (cell # 0)
*

*>
*

*> This error continues for many more cycles. In the .out file the error reads as:
*

*>
*

*> 0EXIT BEING CALLED FROM G1, NEXT REGION NOT FOUND.
*

*> IR= 3 XB= 0.57308359E+01 0.96861185E+01 0.39820496E+02 WB= 0.19294315E+00 0.78236320E+00 0.59218305E+00 DIST= 0.48005062E+01
*

*> IRLTGG= 0 SB= 0.57308359E+01 0.96861185E+01 0.39820496E+02 UB= 0.19294315E+00 0.78236320E+00 0.59218305E+00
*

*> PR 10 0.57308359E+01 0.96861185E+01 0.39820496E+02 0.19294315E+00 0.78236320E+00 0.59218305E+00 3
*

*> 3 3 1 -1 1 0 1 54 54 10
*

*> 93 101 1 93 95 4 0 105 10 10
*

*> -0.31547868E+02 0.48005062E+01 0.48005062E+01 0.48005062E+01
*

*>
*

*> I will attach my input file which I used. I understand that the error means
*

*> that the program is having problems tracking the particle from point (x,y,z)
*

*> to point (x',y',z') defined by the directional vectors given above, I just do
*

*> not know what to do to correct the problem. As one can see from my input, the
*

*> beam dump should be 61 cm long and it is enclosed in a cylindrical vacuum
*

*> shell that is 5 cm thick. At least this is what I tried to simulate.
*

*> Transport should also start at the front of the aluminum cylinder, which is
*

*> the coordinate (0,0,0). If anyone could assist me with my problem, it would
*

*> be greatly appreciated.
*

*>
*

*> Sincerely,
*

*>
*

*> Christopher Knievel
*

*> Health, Safety and Environment Assistant
*

*> Canadian Light Source
*

*>
*

*> <<dice.inp.txt>>
*

*>
*

-- Alberto Fassò CERN-EP/AIP, CH-1211 Geneve 23 (Switzerland) Phone: (41 22) 767 2398 Fax: (41 22) 767 9480 Alberto.Fasso@cern.ch

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