[ Identification | Description | Input parameters | Links ]

The ILL_IN6 Instrument

The IN6 Time-of-Flight simulation at the ILL (instrument only).

Identification

• Site: ILL
• Author: Emmanuel Farhi
• Origin: ILL (France)
• Date: 17th Jan 2005.

Description

IN6 is a time focussing time-of-flight spectrometer designed for quasielastic and
inelastic scattering for incident wavelengths in the range of 4 to 6 Angs.

An intense beam is extracted from the H15 guide by a vertically focussing
monochromator array. It consists of three composite pyrolytic graphite
monochromators using the full height (20 cm) of the guide and focussing the beam
at the sample position. In order to minimise the interference with the
subsequent instruments, the monochromator can deliver only four wavelengths:
4.1; 4.6; 5.1; and 5.9 Angs. The second order reflection from the graphite
monochromator is removed by a beryllium-filter cooled at liquid nitrogen
temperature.
To achieve the time-focussing condition, the beam is pulsed by a Fermi chopper.
It has a small slot length to ensure a good transmission. The normal distance
between the Fermi chopper and the sample is 38 cm. To prevent frame-overlap when
the chopper is rotating faster than 7500 rpm, a suppressor chopper is placed
before the Fermi chopper and rotates in phase with the latter.

The secondary spectrometer consists first of an evacuated sample area. The
detector bank is entirely covered with detector boxes, thus avoiding the
inconvenience of moving the counters.

This instrument model contains a cold source a triple monochromator
(using the GROUP), two Fermi Choppers (including one background chopper), a
liquid sample handling coherent and incoherent processes (elastic and inelastic)
with multiple scattering, customized monitors, and the SPLIT mechanism to
improve the statistics. The H15 guide is not described in this model.

Input parameters

Parameters in boldface are required; the others are optional.

Name	Unit	Description	Default
lambda	Angs	wavelength within 4.14|4.6|5.12|5.92	4.14
dlambda	Angs	wavelength HALF spread. default is 0.075	0.075
SPEED	rpm	Fermi chopper speed. -1=auto, 0=stopped in open pos.	-1
M1	coder values	monochromator motor 1 position. -1=auto	-1
M2	coder values	monochromator motor 2 positinn. -1=auto	-1
M3	coder values	monochromator motor 3 position. -1=auto	-1
MONITOR	something like time in s	monitor preset	1
CHA_WIDTH	us	channel width. -1=auto	-1
TOF_DELAY	us	TOF delay. -1=auto	-1
TOF_CHA_RESOL	1	number of channels.	128
ELPEAK	1	elastic peak channel. -1=auto	-1
RATIO	1	Suppressor speed ratio. -1=no suppressor.	1
mFC	1	super mirror FermiChopper coating m-value	0
PHASE	deg	Fermi phase w/r/ to Suppressor. -360=auto	-360
Sqw_coh	str	sample coherent S(q,w) file name	"Rb_liq_coh.sqw"
Sqw_inc	str	sample incoherent S(q,w) file name	"Rb_liq_inc.sqw"
radius	m	outer radius of sample hollow cylinder	0.01
thickness	m	thickness of sample hollow cylinder	0.005

Links

• Source code for ILL_IN6.instr.
• The IN6@ILL Yellow Pages
• R.Scherm et al, "Another Time of Flight Spectrometer", ILL Report 76S235, 1976
• R.Scherm, "A high-resolution spectrometer ...", report Jul-295-NP, Kernforschungsanlage Julich, 1965
• Y.Blanc, "Le spectrometre a temps de vol IN6", ILL Report 83BL21G, 1983
• K.H.Beckurts et al, Neutron physics, Kernforschungsanlage Karlsruhe, 1964 (p317)
• R.Scherm and T.Springer, "Proposal of a multiple Chopper...", Kernforschungsanlage Julich, 19xx

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[ Identification | Description | Input parameters | Links ]

Generated on 2022-12-12 13:20:16

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Last Modified: Wednesday, 09-Aug-2023 17:01:02 CEST