[ Identification | Description | Input parameters | Links ]

The Source_gen Component

Circular/squared neutron source with flat or Maxwellian energy/wavelength spectrum

Identification

• Site:
• Author: Emmanuel Farhi, Kim Lefmann
• 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. However, it may be directly set using the 'focus-aw' and 'focus_ah'
parameters.

The neutron energy/wavelength is distributed uniformly in wavelength 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 per s. A Maxwellian spectra may be selected if you
give the source temperatures (up to 3).

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.

Additional 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 yheight and xwidth parameters.
The beam is divergence uniform,.
The source may have a thickness, which will broaden the default zero time
distribution.

Usage example:
Source_gen(radius=0.1,lambda0=2.36,dlambda=0.16,T1=20,I1=1e13,focus_xw=0.01,focus_yh=0.01)
Source_gen(yheight=0.1,xwidth=0.1,Emin=1,Emax=3,I1=1e13,verbose=1,focus_xw=0.01,focus_yh=0.01)
EXTEND
%{
t = rand0max(1e-3); // set time from 0 to 1 ms for TOF instruments.
%}

Some neutron facility parameters:
PSI cold source     T1=296.2,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, 58 MW)  T3=16.7 ,I3=3.0423e+12
ILL HCS cold source T1=413.5,I1=10.22e12,T2=145.8,I2=3.44e13
(H5, 58 MW)  T3=40.1 ,I3=2.78e13
ILL Thermal tube    T1=683.7,I1=0.5874e+13,T2=257.7,I2=2.5099e+13
(H12, 58 MW) T3=16.7 ,I3=1.0343e+12
ILL Hot source      T1=1695, I1=1.74e13,T2=708,  I2=3.9e12 (58MW)
HZB cold source     T1=43.7 ,I1=1.4e12, T2=137.2,I2=2.08e12,radius=.155 (10MW)
HZB bi-spectral     T1=43.7, I1=1.4e12, T2=137.2,I2=2.08e12,T3=293.0,I3=1.77e12
HZB thermal tube    T1=293.0,I1=2.64e12 (10MW)
FRM2 cold,20MW      T1=35.0, I1=9.38e12,T2=547.5,I2=2.23e12,T3=195.4,I3=1.26e13
FRM2 thermal,20MW   T1=285.6,I1=3.06e13,T2=300.0,I2=1.68e12,T3=429.9,I3=6.77e12
LLB cold,14MW       T1=220,  I1=2.09e12,T2=60,   I2=3.83e12,T3=20,   I3=1.04e12
TRIGA thermal 1MW   T1=300,  I1=3.5e11 (scale by thermal power in MW)

%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 either [1/(s*cm**2*st)] or [1/(s*cm**2*st*AA)] (see flux_file_perAA flag) Comments (#) and further columns are ignored. Format is compatible with McStas/PGPLOT wavelength monitor files. When specified, temperature and intensity values are ignored.	"NULL"
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'	"NULL"
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'	"NULL"
radius	m	Radius of circle in (x,y,0) plane where neutrons are generated. You may also use 'yheight' and 'xwidth' for a square source	0.0
dist	m	Distance to target along z axis.	0
focus_xw	m	Width of target.	0.045
focus_yh	m	Height of target.	0.12
focus_aw	deg	maximal (uniform) horz. width divergence	0
focus_ah	deg	maximal (uniform) vert. height divergence	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*sr)	Source flux per solid angle, area and Angstrom if I1=0, the source emits 1 in 4*PI whole space.	1
yheight	m	Source y-height, then does not use radius parameter	0.1
xwidth	m	Source x-width, then does not use radius parameter	0.1
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 Aangstroem. 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.	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*sr)	Second Maxwellian Source flux	0
T3	K	Third Maxwellian source Temperature, 0=none	0
I3	1/(cm**2*sr)	Third Maxwellian Source flux	0
zdepth	m	Source z-zdepth, not anymore flat	0
target_index	1	relative index of component to focus at, e.g. next is +1 this is used to compute 'dist' automatically.	+1

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

Links

• Source code for Source_gen.comp.
• 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 05:31:15 CEST