[ Identification | Description | Input parameters | Links ]

The FermiChopper_ILL Component

Identification

• Site:
• Author: M. Poehlmann, C. Carbogno, H. Schober, E. Farhi
• Origin: ILL Grenoble / TU Muenchen
• Date: May 2002

Description

Models a Fermi chopper with optional supermirror coated blades
supermirror facilities may be disabled by setting m = 0, R0=0
Slit packages are straight. Chopper slits are separated by an infinitely
thin absorbing material. The effective transmission (resulting from fraction
of the transparent material and its transmission) may be specified.
The chopper slit package width may be specified through the total width 'xwidth'
of the full package or the width 'w' of each single slit. The other parameter
is calculated by: xwidth = nslit*w.

Example:
FermiChopper_ILL(phase=-50.0, radius=0.04, nu=100,
yheight=0.08, w=0.00022475, nslit=200.0, R0=0.0,
Qc=0.02176, alpha=2.33, m=0.0, length=0.012, eff=0.95,
zero_time=0)

Markus Poehlmann     
Christian Carbogno   
and Helmut Schober   

%VALIDATION
Apr 2005: extensive external test, most problems solved (cf. 'Bugs')
Validated by: K. Lieutenant

limitations:
no blade width used

%BUGS
- overestimates peak width for long wavelengths
- does not give the right pulse position, shape and width for slit widths below 0.1 mm
- fails sometimes when using MPI

Input parameters

Links

• Source code for FermiChopper_ILL.comp.

[ Identification | Description | Input parameters | Links ]