Re: [fluka-discuss]: pair production in tungsten- reduced yield with higher density

From: nikhil shetty <>
Date: Mon, 27 Jun 2016 10:46:47 +0200

Hello Saurabh,

the simulation results seem plausible to me as there is lower "absorption"
of positrons inside the low-density tungsten which could contribute to
higher track-lengths. Exactly because of this, lowering the density to
compensate for a hollow material might not be a good way for simulation.

I would model a hollow tungsten as it is.


On Sun, Jun 26, 2016 at 7:01 PM, Saurabh Mukherjee <>

> Hello,
> I am trying to estimate pair production induced positron flux. The
> target is hollow tungsten and beam is ~3 MeV gamma. I am estimating the
> number of positrons produced using USRTRACK.
> Since my target will be hollow tungsten, I have simulated the target in
> FLUKA with a density of 1 gm/cc instead of the usual 19 gm/cc for tungsten
> ( The target is a disk of thickness 2.5 cm and dia 20 cm). To achieve this
> reduced density, I defined a material called 'tung' with rho=1 and then
> defined a compound card containing 100% by vol Tungsten. I initially wanted
> to define two materials in the compound card- tungsten and void. But Fluka
> does not allow void in the materials, it seems.
> The question that I have is that I get (slightly) higher yield of
> positrons when the density is low and vice versa. I was thinking that with
> lower density the pair production will be less but simulations seem to
> suggest different. Can someone please suggest me if I am doing something
> wrong? Is this a good way to simulate a hollow tungsten?
> I am attaching the yield for density= 10 and 1 gm/cc.
> thank you
> saurabh

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Received on Mon Jun 27 2016 - 12:25:55 CEST

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