# Re: Geometry problems

From: Alberto Fasso' <fasso_at_slac.stanford.edu>
Date: Sun, 19 Apr 2009 14:49:06 -0700 (PDT)

Dear Francesca,

it is never a good idea to ask many different questions in the same
mail. Somebody can know an easy answer about one question, but will not
answer because he doesn't know about the other ones or doesn't have
the time to look at them....:-)

Anyway, I will answer your first question and leave to somebody else
A cone with one base of radius zero is not a _truncated_ cone but just a cone.
(In TRC, T stands for truncated).
There are good reasons why Combinatorial Geometry has truncated cones
but not just cones. The solution of the 2nd degree equation providing
the intersection of a straight line with a conical surface has a
singularity at the cone vertex. In addition, a conical surface has
two "nappes" (in your and my language, "due falde"), and the vertex
belongs to both (or to neither, as you prefer): sticking to a truncated
cone makes sure that we don't have to worry about solution belonging to
the other nappe.

Alberto

On Fri, 17 Apr 2009, francesca.belloni_at_ts.infn.it wrote:

> Dear FLUKA users.
> I'm trying to score energy deposition as a function of the angle
> between the z-axis and the direction of the generated particle. In order
> to define different angular regions around the z axis,truncated cylinders
> (TRC) were drawn.
> These TRC, in my intentions, should have the same height parallel to
> the z-axis, the same coordinates of the centre of the major circular base
> (and hence the same vertice), but different major radii.
> As a first step, in order to debug my geometry I begun with
> "macroscopic" bodies (for example, the target thickness was set equal to 1
> cm instead than equal to 4.2689E-5) and just 2 cones. My input file
> (235U_old.inp) gave a geometry error, which I can't see.
>
>
> **** Geometry debugging requested and activated ****
> from X= 0.000000000E+00 to X= 1.000000000E+01 in step dX= 1.000000000E-01
> from Y= 0.000000000E+00 to Y= 1.000000000E+01 in step dY= 1.000000000E-01
> from Z= 0.000000000E+00 to Z= 1.000000000E+01 in step dZ= 1.000000000E-01
>
> **** Lookdb: Geometry error found ****
> **** The point: 1.1 1.1 1.1 ****
> **** is contained in more than 1 region ****
> **** (regions: 5 Reg.#5 7 Reg.#7 ) ****
>
> **** Lookdb: Geometry error found ****
> **** The point: 1.4 1.4 1.4 ****
> **** is contained in more than 1 region ****
> **** (regions: 5 Reg.#5 7 Reg.#7 ) ****
>
> **** Lookdb: Geometry error found ****
> **** The point: 1.7 1.7 1.7 ****
> **** is contained in more than 1 region ****
> **** (regions: 5 Reg.#5 7 Reg.#7 ) ****
>
> **** Lookdb: Geometry error found ****
> **** The point: 2. 2. 2. ****
> **** is contained in more than 1 region ****
> **** (regions: 5 Reg.#5 7 Reg.#7 ) ****
>
>
> I modified the geometry in 2 different ways:
> 1. setting the minor radii to a number different from 0 (235U_radii.inp)
> 2. subtracting every time all inner cones (thought I thought it was not
> necessary) (235U_subtracting.inp)
>
> In both cases the debugging gives no mistake anymore.
> Could someone tell me what was wrong in my first input file, please?
>
> As a second step, I came back to the real sizes and scored energy
> deposition in the whole gas around the target (235U.inp), with no
> attention to angles. Then I scored energy deposition in the whole gas
> again, but dividing the gas in 2 regions according to angles
> (235U_mic_trc.inp). I expected that the sum of 2 histograms of energy
> deposition (in region #4 and #5 of the 235U_mic_trc.inp) had to be equal
> to the energy deposited in region #4 of the file 235U.inp. But I obtain
> something different ("Results.ps").
> Thinking this could be due to some energy cut, I changed 235U_mic_trc.inp
> into 235U_mic_trc_OR.inp. In this file the region #4 and #5 of
> 235U_mic_trc.inp are unified in one region using "OR".
> The histogram of the deposited energy in region #4 of 235U.inp and of
> 235U_mic_trc_OR.inp are exactly the same now. Is the difference (in the
> deposited energy) between the results given by 235U.inp and
> 235U_mic_trc.inp really given by energy cuts, or do I make a geometry
>
> Thanks.
> Best regards,
> Francesca Belloni
>
>
> P.S.
> As for my previous message, thanks for help!
> As for sampling only in forward direction,excuse me: I had to speak
> I meant that FFs are emitted on 4pi, but the gas is situated only in
> the forward direction with respect to the U3O8 target. Since I score
> energy deposition only inside the gas, I'm scoring it in the forward
> direction.
>

```--
Alberto Fasso`
SLAC-RP, MS 48, 2575 Sand Hill Road, Menlo Park CA 94025
Phone: (1 650) 926 4762   Fax: (1 650) 926 3569
fasso_at_slac.stanford.edu
```
Received on Mon Apr 20 2009 - 10:25:47 CEST

This archive was generated by hypermail 2.2.0 : Mon Apr 20 2009 - 10:25:50 CEST