/******************************************************************************* * McStas instrument definition URL=http://www.mcstas.org * * Instrument: RTP_SANS * * %Identification * Written by: E. Farhi and Megat Harun Al-Rashid * Date: June 2014 * Origin: ILL/RTP * %INSTRUMENT_SITE: TRIGA * * The SANS instrument installed at Reactor TRIGA PUSPATI (Malaysia) * * %Description * This is a 4m long SANS installed on a radial beam port 4 at the Reactor TRIGA * PUSPATI (RTP). Te beam port 4 is a radial tube that originates from the core, * through the graphite reflector. A thick Be filter selects the cold tail of the * thermal spectrum, and removes higher order PG reflections. * A PG(002) monochromator selects the 5A neutrons that are sent into a 4m - 4m * SANS with a 60 cm PSD detector 128x128 pixels. * The monochromator is here used in fixed double focusing geometry. * The accessible Q range is then 0.01-0.1 Angs-1. * * This model contains a detailed description of the Be filter, monochromator * and SANS set-up. The Be filter is in the monochromator block. * * Example: mcrun RTP_SANS.instr lambda=5 * * %Parameters * lambda: [Angs] monochromator selected wavelength * dlambda: [Angs] monochromator wavelength spread * DM: [Angs] d-spacing for the monochromator reflection * Mono_tilt: [deg] angle tilt between the 3 monochromator layers * mono_rotation: [deg] additional monochromator offset rotation for e.g rocking curves * Be_Filter_depth: [m] Depth of Be filter * * %Link * Nuclear Malaysia * %Link * M. Sufi et al., J. AppL Cryst. (1997). 30, 884-888 [doi:10.1107/S0021889897001738] * * %End *******************************************************************************/ DEFINE INSTRUMENT RTP_SANS(lambda=5, DM=3.355, dlambda=.2, Be_Filter_depth=.15, Mono_tilt=-1, mono_rotation=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 A1,L; %} USERVARS %{ double mono_index; %} /* The INITIALIZE section is executed when the simulation starts */ /* (C code). You may use them as component parameter values. */ INITIALIZE %{ /* monochromator rotation angle for Bragg reflection [deg] */ A1 = asin(lambda/2/DM)*RAD2DEG; /* distance used for focusing [m] */ L = 4; printf("RTP_SANS: Monochromator take-off angle=%g [deg]\n", 2*A1); %} /* Here comes the TRACE section, where the actual */ /* instrument is defined as a sequence of components. */ TRACE /* The Arm() class component defines reference points and orientations */ /* in 3D space. Every component instance must have a unique name. Here, */ /* Origin is used. This Arm() component is set to define the origin of */ /* our global coordinate system (AT (0,0,0) ABSOLUTE). It may be used */ /* for further RELATIVE reference, Other useful keywords are : ROTATED */ /* EXTEND GROUP PREVIOUS. Also think about adding a neutron source ! */ /* Progress_bar is an Arm displaying simulation progress. */ COMPONENT Origin = Progress_bar() AT (0,0,0) ABSOLUTE /* the source is focused in wavelength to provide 5 Angs neutrons */ /* to study the Be filter, use white beam e.g. dlambda = 4.5 */ COMPONENT source = Source_gen( radius = .154/2, dist = 1.16+1.50, focus_xw = .082, focus_yh = .09, lambda0 = 5, dlambda = dlambda, I1 = 2.79e12/25, T1 = 300) AT (0, 0, 0) RELATIVE Origin COMPONENT source_monitor = Monitor_nD( xwidth=.154, yheight=.154, options="x y") AT (0, 0, 0.01) RELATIVE Origin COMPONENT CoarseCollimator1 = Guide(w1=.154, h1=.154, l=1.16125,m=0) AT (0, 0, 0.01) RELATIVE PREVIOUS COMPONENT CoarseCollimator2 = Guide(w1=.11, h1=.11, l=1.5,m=0) AT (0, 0, 1.16125+0.003) RELATIVE PREVIOUS /* a slit that also detects wavelength */ COMPONENT lmon = Monitor_nD( xwidth=.11, options="slit disk, auto wavelength", bins=50) AT (0, 0, 1.5+0.01) RELATIVE PREVIOUS /* Be filter ---------------------------------------------------------------- */ COMPONENT Be_Position = Arm() AT (0, 0, .147+.15/2) RELATIVE PREVIOUS COMPONENT Be_Cryostat = PowderN( yheight=.2, radius=.144, thickness=.002, reflections = "Al.lau", concentric=1, p_transmit=.95, p_inc=1e-4) AT (0,0,0) RELATIVE Be_Position COMPONENT Be_Filter = PowderN( xwidth=.15, yheight=.15, zdepth=Be_Filter_depth, reflections="Be.laz", p_inc=1e-4) AT (0,0,0) RELATIVE Be_Position COMPONENT Be_Cryostat_out = COPY(Be_Cryostat)(concentric=0) AT (0,0,0) RELATIVE Be_Position COMPONENT lmo_afterBe = Monitor_nD( xwidth=.082, yheight=0.09, options="slit, auto wavelength", bins=50) AT (0, 0, .145+.15/2+1e-3) RELATIVE Be_Position /* monochromator ------------------------------------------------------------ */ SPLIT COMPONENT mono_cradle = Arm() AT (0, 0, .145+.15/2+.176) RELATIVE Be_Position COMPONENT mono_rotation = Arm() AT (0, 0, 0) RELATIVE mono_cradle ROTATED (0, -A1+mono_rotation, 0) RELATIVE mono_cradle EXTEND %{ mono_index=0; %} COMPONENT mono1 = Monochromator_curved( width=.11, height=.09, NH=2,NV=3, RV=2*L*sin(DEG2RAD*A1), RV=2*L/sin(DEG2RAD*A1), DM=DM, mosaich=48, mosaicv=48, reflect="HOPG.rfl" ,transmit="HOPG.trm") AT (-.01, 0, 0) RELATIVE mono_rotation ROTATED (0, Mono_tilt, 0) RELATIVE mono_rotation EXTEND %{ if (SCATTERED) mono_index=1; %} COMPONENT mono2 = COPY(mono1) AT (0, 0, 0) RELATIVE mono_rotation ROTATED (0, 0, 0) RELATIVE mono_rotation EXTEND %{ if (SCATTERED) mono_index=2; %} COMPONENT mono3 = COPY(mono1) AT (0.01, 0, 0) RELATIVE mono_rotation ROTATED (0, -Mono_tilt, 0) RELATIVE mono_rotation EXTEND %{ if (SCATTERED) mono_index=3; %} COMPONENT mono_takeoff = Arm() AT (0, 0, 0) RELATIVE mono_cradle ROTATED (0, -2*A1, 0) RELATIVE mono_cradle COMPONENT psd_transmit = Monitor_nD(xwidth=.12, yheight=.12, options="x y", bins=50) AT (0, 0, 0.25) RELATIVE mono_cradle GROUP mono_rt /* primary collimator (flight path) 3.8 m ----------------------------------- */ COMPONENT psd_reflect = Monitor_nD(xwidth=.12, yheight=.12, options="x y", bins=50) AT (0, 0, 0.574) RELATIVE mono_takeoff GROUP mono_rt EXTEND %{ if (!mono_index) ABSORB; %} COMPONENT lmon_reflect2 = Monitor_nD( xwidth=.05, yheight=.05, options="disk, auto wavelength", bins=50) AT (0, 0, 0.575) RELATIVE mono_takeoff /*COMPONENT lmon_reflect = Monitor_nD( xwidth=.02, yheight=.02, user1=mono_index, options="disk slit, auto wavelength, user1 limits=[0 4]", bins=50) AT (0, 0, 0.575+1e-4) RELATIVE mono_takeoff*/ COMPONENT coll1=Guide(w1=.05,h1=.05,l=3.8) AT (0, 0, 0.575+1e-3) RELATIVE mono_takeoff COMPONENT sample_psd = Monitor_nD( xwidth=.02, yheight=.02, options="disk slit, x y", bins=50) AT (0, 0, 0.575+3.80+1e-2) RELATIVE mono_takeoff /* sample ------------------------------------------------------------------- */ /* from JAC 1997: flux at sample = 3900 n/s/cm2 */ SPLIT 100 COMPONENT sample = Sans_spheres( R = 100, Phi = 1e-3, Delta_rho = 0.6, sigma_abs = 0.5, xwidth=0.01, yheight=0.01, zdepth=0.005) AT (0, 0, .575+3.80+.10) RELATIVE mono_takeoff EXTEND %{ if (!SCATTERED) ABSORB; %} /* secondary flight path (detector tube) 4m --------------------------------- */ COMPONENT det = Monitor_nD(xwidth=.6, yheight=.6, bins=128, options="x y slit") AT (0, 0, 3.8) RELATIVE sample COMPONENT PSDrad = PSD_monitor_rad( filename = "psd2.dat", filename_av = "psd2_av.dat", rmax = 0.45) AT (0, 0, 1e-2) RELATIVE det COMPONENT det_tube = Shape(radius=1, yheight=4) AT (0, 0, .1+4/2) RELATIVE sample ROTATED (90,0,0) RELATIVE sample COMPONENT reactor = Shape(radius=.7/2, yheight=.4) AT (0,0,-.35) RELATIVE Origin /* 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