[neutron-mc] Source_Adapt problem

[Aaron M. Percival]

Hello all,

 

I have a question concerning the Source_Adapt component and its energy (or
wavelength) distribution.  My simplified understanding is that this
component initially emits a uniform energy (or wavelength) distribution,
then throughout a simulation adapts this distribution to increase counts in
the adapt_check component.  However, I am having a problem getting an
initial uniform distribution in wavelength, in fact, it seems as though the
distribution models some sort of exponential decay between E0 -dE and E0 +
dE.  In order to test this, I did two things.  I first set up a simulation
where no adaptation in energy was required by creating a simple instrument
with a Source_Adapt, two slits, a collimator and an adapt_check, I've
attached a file showing the wavelength distribution from an L_monitor placed
right after the source (pos1_plot.jpg).   I then added a powder sample to
the previous instrument and moved the adapt_check behind it, but set beta =
1 on the source_adapt (to force the component to distribute all neutrons
uniformly among all bins, i.e. no adaptation).  The wavelength distribution
seen from the source is in pos2_plot.jpg and it the same as the previous.

 

Here is the component definition for the Souce_Adapt in my instrument:

 

COMPONENT source = Source_Adapt(

    N_E = 20, N_xpos = 20, N_xdiv = 20, xmin = -0.005,

    xmax = 0.005, ymin = -0.005, ymax = 0.005, dist = 6.134,

    xw = 0.01, yh = 0.01, E0 =180, dE = 172, alpha = 0.25,

    beta = 0.25)

  AT (0, 0, 0) RELATIVE origin

 

E0 and dE chosen to distribute wavelengths between approximately 0.5AA and
3.2AA.

 

What would like is for the Source_adapt to initially give a uniform
distribution, much like the Source_Simple component.   Is this possible with
my current parameters for E0 and dE?

 

Regards,

 

Aaron

 

*************************************************

Aaron M. Percival

M.Sc. Candidate

Dept. of Physics, Engineering Physics & Astronomy

Queen's University

Kingston, Ontario, Canada, K7L 3N6

Office: 613-533-6000 ext. 74789

Fax: 613-533-6463

*************************************************

 

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