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Forum: Event and Track Management
Re: Question Energy distribution of source as histogram (GPS) (Suhaili Zakaria)
Date: 02 Mar, 2010
From: Fan Lei <Fan Lei>

On Thu, 25 Feb 2010 03:52:51 GMT, Suhaili Zakaria wrote:
> Hello
> I have referred to and examples in
> /extended/eventgenerator/exgps/, but I still have questions and
> uncertainties on how to use/define energy distribution as histogram
> using GPS.
> 1. I am interested with two of the options that can be used to defined
> energy distribution, i.e. energy (/gsp/ene/type User ), and arbitrary
> point-wise spectrum (/gps/ene/type Arb). However, I am not sure what is
> the difference between this two options, and in what conditions they are
> best used. Can someone please explain it?

User: user defined histogram, i.e. step function like spectrum Arb: point-wise spectrum

> 2. To choose a histogram, the command /gps/hist/type is used. In case of
> energy it should be /gps/hist/type energy and /gps/hist/type arb for
> arbitrary point-wise.
> I suppose you use /gsp/ene/type User with /gps/hist/type energy; and
> (/gps/ene/type Arb) with /gps/hist/type arb. Am I correct?


> 3. Next, /gps/hist/point <X> <Y> command is used to load the histogram,
> where <X> is the energy in MeV and Y is the weight (or area) of the bin.

Correct for the "energy" case. <X> is the lower-edge of the the bin, <Y> is the area of the bin. Please follow test18.g4mac in

> How do I determine the weight in this case?
> Is <Y> the number of particles per energy, but that doesn&#65533;t seem right.

In this case you should use the "Arb and "arb" combination, i.e. point-wise distribution. Please follow test19.g4mac in

> I really appreciate and looking forward to any insights/answers/comments
> on this matter. Many, many thanks

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