[ Identification | Description | Input parameters | Output parameters | Links ]

The Source_gen Component

Circular/squared neutron source with flat or Maxwellian energy/wavelength spectrum (possibly spatially gaussian)

Identification

Description

This routine is a neutron source (rectangular or circular), which aims at
a square target centered at the beam (in order to improve MC-acceptance
rate). The angular divergence is then given by the dimensions of the
target.
The neutron energy/wavelength is distributed between Emin=E0-dE and
Emax=E0+dE or Lmin=Lambda0-dLambda and Lmax=Lambda0+dLambda. The I1 may
be either arbitrary (I1=0), or specified in neutrons per steradian per
square cm per Angstrom. A Maxwellian spectra may be selected if you give
the source temperatures (up to 3).
The source shape is defined by its radius, or can alternatively be squared
if you specify non-zero h and w parameters.
The beam is spatially uniform, but becomes gaussian if one of the source
dimensions (radius, h or w) is negative, or you set the gaussian flag.
Divergence profiles are triangular.
The source may have a thickness, which will broaden the default zero time
distribution.
For the Maxwellian spectra, the generated intensity is dPhi/dLambda (n/s/AA)
For flat spectra, the generated intensity is Phi (n/s).

Usage example:
  Source_gen(radius=0.1,Lambda0=2.36,dLambda=0.16, T1=20, T2=38, I1=1e13)
  Source_gen(h=0.1,w=0.1,Emin=1,Emax=3, I1=1e13, verbose=1, gaussian=1)
  EXTEND
  %{
     t = rand0max(1e-3); // set time from 0 to 1 ms for TOF instruments.
  %}

Some sources parameters:
PSI cold source T1=150.42,I1=3.67e11 T2=38.74,I2=3.64e11
                T3=14.84,I3=0.95e11
ILL VCS cold source T1=216.8,I1=1.24e+13,T2=33.9,I2=1.02e+13
       (H1)         T3=16.7 ,I3=3.0423e+12
ILL HCS cold source T1=413.5,I1=10.22e12,T2=145.8,I2=3.44e13
       (H5)         T3=40.1 ,I3=2.78e13
ILL Thermal tube    T1=683.7,I1=0.5874e+13,T2=257.7,I2=2.5099e+13
       (H12)        T3=16.7 ,I3=1.0343e+12
ILL Hot source      T1=1695,I1=1.74e13,T2=708,I2=3.9e12

%VALIDATION
Feb 2005: output cross-checked for 3 Maxwellians against VITESS source
          I(lambda), I(hor_div), I(vert_div) identical in shape and absolute values
Validated by: K. Lieutenant

Input parameters

Parameters in boldface are required; the others are optional.
Name Unit Description Default
radius m Radius of circle in (x,y,0) plane where neutrons are generated. You may also use 'h' and 'w' for a square source 0.0
dist m Distance to target along z axis. 57.296
xw m Width(x) of target. If dist=0.0, xw = horz. div in deg 0
yh m Height(y) of target. If dist=0.0, yh = vert. div in deg 0
E0 meV Mean energy of neutrons. You may also use Lambda0. 14.68
dE meV Energy spread of neutrons, half width. 0
Lambda0 AA Mean wavelength of neutrons. 2.36
dLambda AA Wavelength spread of neutrons,half width 0.1627
I1 1/(cm**2*st*AA) Source flux per solid angle, area and Angstrom 0
h m Source y-height, then does not use radius parameter 0
w m Source x-width, then does not use radius parameter 0
gaussian 0/1 Use gaussian beam, normal distributions 0
verbose 0/1 display info about the source. -1 unactivate source. 0
T1 K Temperature of the Maxwellian source, 0=none 0
Lmin AA Minimum wavelength of neutrons 0
Lmax AA Maximum wavelength of neutrons 0
Emin meV Minimum energy of neutrons 0
Emax meV Maximum energy of neutrons 0
T2 K Second Maxwellian source Temperature, 0=none 0
I2 1/(cm**2*st*AA) Second Maxwellian Source flux 0
T3 K Third Maxwellian source Temperature, 0=none 0
I3 1/(cm**2*st*AA) Third Maxwellian Source flux 0
length m Source z-length, not anymore flat 0

Output parameters

Name Unit Description Default
p_in  
lambda0  
lambda02  
L2P  
lambda_0  
d_lambda  
lambda0b  
lambda02b  
L2Pb  
lambda0c  
lambda02c  
L2Pc  

Links


[ Identification | Description | Input parameters | Output parameters | Links ]

Generated automatically by McDoc, Peter Willendrup <peter.willendrup@risoe.dk> / Tue Sep 30 19:37:37 2008