[mcstas-users] Too low I and N
wokaoyan1981
wokaoyan1981 at 126.com
Sun Jul 27 09:49:58 CEST 2008
Hello colleagues,
I've set up a residual stress instrument.The simulation result suggests(Neutron count=109): Neutrons after Fe(211) diffraction are I I_err N=[29927.1 31233.5 3];And neutrons reaching the detector through aperture are I I_err N=[0 0 0]. Both I and N are too low.
I raised horizontal divergences of the first and second collimator but I and N remain too low. What should I do in order to get high I and N on detector?
Here is the code:
/*******************************************************************************
* McStas instrument definition URL=http://www.mcstas.org
*
* Instrument: residual stress instrument
*
* %Identification
* Written by: Tom
* Date:10 Jan 2008
* Origin: institute
* Release: McStas 1.6
* Version: 0.2
* %INSTRUMENT_SITE:thesis
*
* residual stress instrument
*
* %Description
* try to optimize parameters of residual stress instrument. default geometry is
* from blueprints of residual stress instruments at CARR,FRM-II(Germany),E3* (Germany) * and SALSA(France)
* Example: mcrun residual_stress.instr <RV=-1>
*
* %Parameters
* dist: [m] focusing distance from source to SlitIn
* GapM2_G: [m] distance between M2Exit and guide entrance
* xw: [m] width of neutron guide entrance
* yh: [m] height of neutron guide entrance
* l: [m] length of straight neutron guide
* m: [1] m-value of material1.5~3
* CH1: ['] horizontal divergence of the first collimator
* len_C1 [m] length of the first collimator
* L1: [m] distance between exit of first collimator and
* monochromator，0.01~0.3m
* A1: [deg] rotation of mono
* DM: [Angs] d-spacing of monochromator
* NH: [columns] number of slabs horizontal
* NV: [rows] number of slabs vertical
* mosaich： ['] Horisontal mosaic FWHM
* mosaicv: ['] Vertical mosaic FWHM
* RV: [m] Monochromator vertical curvature, 0 for flat, -1 for automatic
* setting(then RV=2*L2*sin(DEG2RAD*A1) )
* RH: [m] Monochromator horizontal curvature, 0 for flat, -1 for automatic
* setting(then RH = 2*L2/sin(DEG2RAD*A1))
* L2: [m] distance between monochromator and sample,1.9~2.2
* CH2: ['] horizontal divergence of the second collimator
* DS: [Angs] d-spacing of sample:default Fe(hkl)
* L3: [m] distance between sample and detector
* %Link
* A reference/HTML link for more information
*
* %End
*******************************************************************************/
/* Change name of instrument and input parameters with default values */
DEFINE INSTRUMENT residual_stress(
dist=2, GapM2_G=0, xw=0.06, yh=0.11, l=6, m=2, CH1=10,
L1=0.3, A1=45, DM=1.0886, len_C1=0.6, NH=1, NV=15, mosaich=30,mosaicv=30,
RV=-1, RH=0, L2=1.9,CH2=30,DS=1.1782,L3=1.0)
/* The DECLARE section allows us to declare variables or small */
/* functions in C syntax. These may be used in the whole instrument. */
DECLARE
%{
double M2Exit_mono; /* distance between M2Exit and monochromator */
double lambda; /*wavelength after diffraction*/
double monow; /*width of mono*/
double A2; /*half of sample take off angle*/
%}
/* The INITIALIZE section is executed when the simulation starts */
/* (C code). You may use them as component parameter values. */
INITIALIZE
%{
M2Exit_mono=GapM2_G+l+len_C1+L1;
lambda=2*DM*sin(DEG2RAD*A1);
if (RV<0) RV=2*L2*sin(DEG2RAD*A1);
if (RH<0) RH = 2*L2/sin(DEG2RAD*A1);
monow=xw/sin(DEG2RAD*A1);
A2=asin(lambda/(2*DS))*RAD2DEG;
printf("\nlambda=%f\tRV=%f\tRH=%f\tmonow=%f\tA2=%f\n",lambda,RV,RH,monow,A2);
%}
/* Here comes the TRACE section, where the actual */
/* instrument is defined as a sequence of components. */
TRACE
/* Progress_bar is an Arm displaying simulation progress.*/
COMPONENT Origin = Progress_bar()
AT (0,0,0) ABSOLUTE
/********************* neutron source********************************/
COMPONENT Source = Source_Maxwell_3(
height = 0.75, width =0.52988 ,
l_low =0.2,l_high =7,
dist = dist,
xw = 0.06, yh = 0.11,
T1 = 320,I1 =9.87E12)
AT (0, 0, 0) RELATIVE Origin
/************channel(Al and Fe) inside reactor, length:4.049m**********/
COMPONENT SlitIn = Slit(
width = 0.06, height = 0.11)
AT (0, 0, 0 ) RELATIVE Source
COMPONENT M2Exit = Slit(
width = 0.06, height = 0.11)
AT (0, 0, 4.049 ) RELATIVE SlitIn
/*************************straight_guide*******************/
COMPONENT straight_guide = Guide(
w1 = xw, h1 = yh, w2 = xw, h2 = yh, l =l, m = m)
AT (0, 0, GapM2_G) RELATIVE M2Exit
/**************************first collimator**************************/
COMPONENT collimator1 = Collimator_linear(
xmin = -xw/2, xmax = xw/2, ymin = -yh/2, ymax = yh/2,
len = len_C1, divergence = CH1)
AT (0, 0, l) RELATIVE straight_guide
/*************************mono_craddle***************************/
COMPONENT mono_craddle = Arm(
)
AT (0, 0, M2Exit_mono) RELATIVE M2Exit
ROTATED (0, A1, 0) RELATIVE Origin
/***************************monochromator Ge(511)****************************/
COMPONENT monochromator = Monochromator_curved(
width=monow, height=0.15, NH=NH, NV=NV,reflect = "0", transmit = "0",
gap = 0.0005, mosaich = mosaich, mosaicv = mosaicv, r0 = 0.7,
t0 = 1.0, RV = RV, RH = RH, DM = DM)
AT (0, 0, 0) RELATIVE mono_craddle
/*********************mono_out*******************/
COMPONENT mono_out = Arm(
)
AT (0, 0, 0) RELATIVE mono_craddle
ROTATED (0, 2*A1, 0) RELATIVE Origin
/********************detectors before second collimator**************************/
COMPONENT LDbeforeC2 = L_monitor(
nchan = 200, filename = "LDbeforeC2", xwidth = 0.15,
yheight = 0.15, Lmin = 0, Lmax = lambda+0.1)
AT (0, 0, 0.8) RELATIVE mono_out
COMPONENT PSDbeforeC2 = PSD_monitor(
filename = "PSDbeforeC2", xwidth = 0.15, yheight = 0.15)
AT (0, 0, 0.8) RELATIVE mono_out
/***********************second collimator***************************/
COMPONENT collimator2 = Collimator_linear(
xmin = -xw/2, xmax = xw/2, ymin = -yh/2, ymax = yh/2, len = 0.4,
divergence = CH2)
AT (0, 0, 0.8) RELATIVE mono_out
/**********************detector after second collimator********************/
COMPONENT PSDafterC2 = PSD_monitor(
filename = "PSDafterC2", xwidth = 0.06, yheight = 0.11)
AT (0, 0, 0.4) RELATIVE collimator2
/**********************aperture before sample*************************/
COMPONENT slit_before = Slit(
width = 0.008, height = 0.008)
AT (0, 0, 1.88) RELATIVE mono_out
/**********************detector behind Slit_before***********************/
COMPONENT PSDafterSlit_before = PSD_monitor(
filename = "PSDafterSlit_before", xwidth = 0.01, yheight = 0.01)
AT (0, 0, 0.01) RELATIVE slit_before
/************************Fe(221) sample****************************/
COMPONENT Sample = PowderN(
reflections = "Fe.laz", radius = 0.004, yheight = 0.8)
AT (0, 0, L2) RELATIVE mono_out
EXTEND
%{
if(!SCATTERED) ABSORB; /*perfect beamstop*/
%}
/************************sample_out************************/
COMPONENT sample_out = Arm(
)
AT (0, 0, 0) RELATIVE Sample
ROTATED (0, -2*A2, 0) RELATIVE Sample
/************************detector before slit_after********************/
COMPONENT PSDbeforeSlit_after = PSD_monitor(
filename = "PSDbeforeSlit_after", xwidth = 0.008,
yheight = 0.050)
AT (0, 0, 0.01) RELATIVE sample_out
/************************aperture after sample***************************/
COMPONENT slit_after = Slit(
width = 0.008, height = 0.050)
AT (0, 0, 0.02) RELATIVE sample_out
/************************detector*********************************/
COMPONENT PSDafterSample = PSDlin_monitor(
nx = 200, filename = "PSDafterSample", xwidth = 0.2,
yheight = 0.2)
AT (0, 0, L3) RELATIVE sample_out
/* This section is executed when the simulation ends (C code). Other */
/* optional sections are : SAVE */
FINALLY
%{
%}
/* The END token marks the instrument definition end */
END
Regards,
Tom
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