14.3  The ViewModISIS McStas Component

ISIS Moderators

Identification

• Author: G. Skoro, based on ViewModerator4 from S. Ansell

• Origin: ISIS

• Date: February 2016

Description

Produces a neutron distribution at the ISIS TS1 or TS2 beamline shutter front face (or corresponding moderator) position. The Face argument determines which TS1 or TS2 beamline is to be sampled by using corresponding Etable file. Neutrons are created having a range of energies determined by the E0 and E1 arguments. Trajectories are produced such that they pass through the shutter front face (RECOMENDED) or moderator face (defined by xw and yh) and a focusing rectangle (defined by focus_xw, focus_yh and dist).

Example 1:   ViewModISISver1(Face="TS1_S04_Merlin.mcstas", E0 = E_min, E1 = E_max,

dist = 1.7, focus_xw = 0.094, focus_yh = 0.094, modPosition=0,

xw=0.12,yh=0.12)

MERLIN simulation. modPosition=0 so initial surface is at (near to) the moderator face. In this example, focus_xw and focus_yh are chosen to be identical to the shutter opening dimension. dist = 1.7 is the ’real’ distance to the shutter front face => This is TimeOffset value (=170 [cm]) from TS1_S04_Merlin.mcstas file.

Example 2:   ViewModISISver1(Face="Let_timeTest_155.mcstas", E0 = E_min, E1 = E_max,

modPosition=1, xw=0.196, yh = 0.12, focus_xw = 0.04, focus_yh = 0.094, dist = 0.5)

LET simulation. modPosition=1 so initial surface is at front face of shutter insert.

(IMPORTANT) If modPosition=1, the xw and yh values are obsolete. The dimensions of initial surface are automatically calculated using "RDUM" values in Let_timeTest_155.mcstas file.

In this example, focus_xw and focus_yh are arbitrary chosen to be identical to the shutter opening dimension.

N.B. Absolute normalization: The result of the Mc-Stas simulation will show neutron intensity for beam current of 1 uA.

Input parameters

Parameters in boldface are required; the others are optional.

Links

• Component source code found in file ViewModISIS.comp.