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Question gps gun problem?? 

Keywords: gps, gun, energy, neutrons
Forum: Event and Track Management
Date: 09 Feb, 2006
From: Michael <michael.rinaldi@lmco.com>

Hi,   I'm currently running a simple experiment to familiarize myself with
      the GPS gun.  I'm shooting neutrons into a 5cm cube box filled with
      polySthyrene.  To make sure that GPS was creating the correct neutron 
      energy distribution I did a quick run to compare the input neutron energy
      distribution that I set up using /gps/hist/point with the actual
      neutron distribution that geant generated.  I was surprised to see that 
      the input spectrum is very different from the geant generated spectrum.

Below are the gps commands I used in my macro file and a link to a jpeg of the input/generated spectras.

From a look at my macro can anyone tell me why the geant generated neutron distribution is so far off the mark!!

# using GPS for ambe_spectrum:
# Use a square surface with the same size as the polysthyrene box

/gps/pos/type Plane

/gps/pos/shape Square

/gps/pos/halfx 2.5 cm

/gps/pos/halfy 2.5 cm

/gps/pos/centre 0. 0. -2.5 cm

/gps/direction 0 0 1

#

/gps/particle neutron

#
#

/gps/ene/type Arb

/gps/hist/type arb

/gps/hist/point 0.000 0.000

/gps/hist/point 0.935 0.982

/gps/hist/point 0.996 0.738

/gps/hist/point 1.077 0.679

/gps/hist/point 1.138 0.649

/gps/hist/point 1.219 0.682

/gps/hist/point 1.301 0.732

/gps/hist/point 1.341 0.720

/gps/hist/point 1.422 0.679

/gps/hist/point 1.422 0.644

/gps/hist/point 1.483 0.620

/gps/hist/point 1.504 0.561

/gps/hist/point 1.585 0.608

/gps/hist/point 1.707 0.665

/gps/hist/point 1.809 0.661

/gps/hist/point 1.931 0.673

/gps/hist/point 2.032 0.652

/gps/hist/point 2.134 0.658

/gps/hist/point 2.276 0.646

/gps/hist/point 2.378 0.644

/gps/hist/point 2.439 0.661

/gps/hist/point 2.560 0.723

/gps/hist/point 2.682 0.770

/gps/hist/point 2.764 0.865

/gps/hist/point 2.865 0.923

/gps/hist/point 2.967 1.000

/gps/hist/point 3.150 0.838

/gps/hist/point 3.353 0.787

/gps/hist/point 3.638 0.735

/gps/hist/point 3.800 0.732

/gps/hist/point 3.983 0.741

/gps/hist/point 4.308 0.832

/gps/hist/point 4.410 0.835

/gps/hist/point 4.552 0.817

/gps/hist/point 4.857 0.785

/gps/hist/point 5.121 0.652

/gps/hist/point 5.405 0.525

/gps/hist/point 5.649 0.400

/gps/hist/point 5.934 0.373

/gps/hist/point 6.157 0.511

/gps/hist/point 6.381 0.444

/gps/hist/point 6.645 0.411

/gps/hist/point 6.848 0.449

/gps/hist/point 7.133 0.500

/gps/hist/point 7.377 0.482

/gps/hist/point 7.600 0.435

/gps/hist/point 7.824 0.332

/gps/hist/point 8.047 0.252

/gps/hist/point 8.311 0.152

/gps/hist/point 8.494 0.125

/gps/hist/point 8.718 0.141

/gps/hist/point 8.921 0.176

/gps/hist/point 9.104 0.193

/gps/hist/point 9.348 0.173

/gps/hist/point 9.510 0.135

/gps/hist/point 9.612 0.108

/gps/hist/point 9.714 0.073

/gps/hist/point 9.917 0.046

/gps/hist/point 9.957 0.032

/gps/hist/point 10.079 0.020

/gps/hist/point 10.201 0.011

#

/gps/hist/inter Lin

/run/beamOn 10000

The link to the jpeg showing the input vs generated is: http://www.spasci.com/public/pu239Be.jpg

Thanks for any help, Mike

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1 None: Re: gps gun problem??   (Fan Lei - 16 Feb, 2006)
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