[ Identification | Description | Input parameters | Links ]

The Source_gen4 Component

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

Identification

• Site:
• Author: Emmanuel Farhi, Kim Lefmann, modified to PSI use by Jonas Okkels Birk
• Origin: ILL/Risoe
• Date: Aug 27, 2001

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). And a high energytail of the shape A/(lambda0-lambda) can also be
specified if you give an A. Finally, a file with the flux as a
function of the wavelength [lambda(AA) flux(n/s/cm^2/st/AA)] may be used
with the 'flux_file' parameter. Format is 2 columns free text.
Additionl distributions for the horizontal and vertical phase spaces
distributions (position-divergence) may be specified with the
'xdiv_file' and 'ydiv_file' parameters. Format is free text, requiring
a comment line '# xylimits: pos_min pos_max div_min div_max' to set
the axis of the distribution matrix. All these files may be generated using
standard monitors (better in McStas/PGPLOT format), e.g.:
Monitor_nD(options="auto lambda per cm2")
Monitor_nD(options="x hdiv, all auto")
Monitor_nD(options="y vdiv, all auto")
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, 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= 296.16, I1=8.5E11, T2=40.68, I2=5.2E11
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
flux_file	str	Name of a two columns [lambda flux] text file that contains the wavelength distribution of the flux in [1/(s*cm**2*st*AA)]. Comments (#) and further columns are ignored. Format is compatible with McStas/PGPLOT wavelength monitor files. When specified, temperature and intensity values are ignored. NO correction for solid-angle is applied, the intensity emitted into the chosen xw x yh rectangle at distance dist.	0
xdiv_file	str	Name of the x-horiz. divergence distribution file, given as a free format text matrix, preceeded with a line '# xylimits: xmin xmax xdiv_min xdiv_max'	0
ydiv_file	str	Name of the y-vert. divergence distribution file, given as a free format text matrix, preceeded with a line '# xylimits: ymin ymax ydiv_min ydiv_max'	0
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.	0
xw	m	Width(x) of target. If dist=0.0, xw = full horz. div in deg	0
yh	m	Height(y) of target. If dist=0.0, yh = full vert. div in deg	0
E0	meV	Mean energy of neutrons.	0
dE	meV	Energy spread of neutrons, half width.	0
Lambda0	AA	Mean wavelength of neutrons.	0
dLambda	AA	Wavelength spread of neutrons,half width	0
I1	1/(cm**2*st)	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 divergence 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
flux_file_perAA	1	When true (1), indicates that flux file data is already per Angstroem. If false, file data is per wavelength bin.	0
flux_file_log	1	When true, will transform the flux table in log scale to improve the sampling. This may also cause	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)	Second Maxwellian Source flux	0
T3	K	Third Maxwellian source Temperature, 0=none	0
I3	1/(cm**2*st)	Third Maxwellian Source flux	0
length	m	Source z-length, not anymore flat	0
phi_init	degrees	Angle abowe the x-z-plan that the source is amied at	0
theta_init	degrees	Angle from the z-axis in the x-z-plan that the source is amied at	0
HEtailA	1/(cm**2*st*AA)	Amplitude of heigh energy tail	0
HEtailL0	AA	Offset of heigh energy tail	0

AT (	,	,		) RELATIVE		Generate
ROTATED (	,	,		) RELATIVE

Links

• Source code for Source_gen4.comp.
• The ILL Yellow book
• P. Ageron, Nucl. Inst. Meth. A 284 (1989) 197

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[ Identification | Description | Input parameters | Links ]

Generated on 2024-01-03 11:47:43

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Last Modified: Tuesday, 17-Sep-2024 05:31:14 CEST