Component Manual for the Neutron Ray-Tracing Package McStas, version 3.8.6

14.5  The SNS_source_analytic McStas Component

A source that produces a time and energy distribution from parameterized SNS moderator files

Identification

Description

Produces a time-of-flight spectrum from SNS moderator files moderator files can be obtained from the author IMPORTANT: The output units of this component are N/pulse IMPORTANT: The component needs a FULL PATH to the source input file Notes: (1) the raw moderator files are per Sr. The parameters focus_xw focus_yh and dist provide the solid angle with which the beam line is served. The best practice is to set focus_xw and focus_yh to the width and height of the closest beam component, and dist as the distance from the moderator location to this component. (2) Be sure that Emin and Emax are within the limits of 1e-5 to 100 eV (3) the proton pulse length T determines short- and long-pulse mode

Beamport definitions: BL11: a1Gw2-11-f5_fit_fit.dat BL14: a1Gw2-14-f5_fit_fit.dat BL17: a1Gw2-17-f5_fit_fit.dat BL02: a1Gw2-2-f5_fit_fit.dat BL05: a1Gw2-5-f5_fit_fit.dat BL08: a1Gw2-8-f5_fit_fit.dat

Input parameters

Parameters in boldface are required; the others are optional.

Name

Unit

Description

Default

filename

Filename of source data

xwidth

m

width of moderator (default 0.1 m)

0.10

yheight

m

height of moderator (default 0.12 m)

0.12

dist

m

Distance from source to the focusing rectangle (no default)

focus_xw

m

Width of focusing rectangle (no default)

focus_yh

m

Height of focusing rectangle (no default)

Emin

meV

minimum energy of neutrons (default 0.01 meV)

0.01

Emax

meV

maximum energy of neutrons (default 1e5 meV)

1.0e5

tinmin

us

minimum time of neutrons (default 0 us)

0.0

tinmax

us

maximum time of neutrons (default 2000 us)

2000.0

sample_E

sample energy from: (default 0)

0

sample_t

sample t from: (default 0)

0

proton_T

us

proton pulse length (0 us)

0.0

p_power

MW

proton power (default 2 MW)

2.0

n_pulses

number of pulses (default 1)

1.0

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