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

From: Saurabh Mukherjee <>
Date: Tue, 28 Jun 2016 10:23:07 +0530

Thank you for the reply, nikhil. I was under the impression that one
routinely does that in MCNP. I will try a detailed target.

On Mon, Jun 27, 2016 at 2:16 PM, nikhil shetty <>

> 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.
> Cheers,
> Nikhil
> On Sun, Jun 26, 2016 at 7:01 PM, Saurabh Mukherjee <>
> wrote:
>> 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 Tue Jun 28 2016 - 08:34:58 CEST

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