1. IMAT: imaging + diffraction
Monitors: - 6; 5 of which: vanadium-foil
- 1D; TOF
- in-house development M5
1 portable 1x1x1 mm3
GS1 cube
Used around sample position for commissioning
1 Normalisation: M5
V-foil + GS20
Movable
High efficiency
4 Diagnostic M1-M4
V-foil + GS20
Low efficiency
Disk Chopper
Disk +T0 Choppers
Pinhole Selector M3
(diagnostic) M2
(diagnostic) M1
(diagnostic)
GS1 portable
M5 / diffraction
normalisation
M4 (diagnostic)
Temporary/ Spare

2. Experience with tof beam monitors: @IMAT M2
(diagnostic) M1
(diagnostic) M3
(diagnostic)
GS1 portable
M5 / diffraction
normalisation
M4 (diagnostic)
Temporary/ Spare

3. Experience / plans with TOF beam monitors: @IMAT
How are monitors used?
1) Diagnostic: Monitor changes of neutron flux and spectrum: moderator response; shutter misalignment; gate valves closed for some reason; wavelength spectra at different points of the beamline;
2) Set-up instrument for experiment: wavelength selection;
3) Image collection control: neutron counts - threshold for imaging cameras; (flux fluctuates a lot at spallation sources);
4) Image analysis: scaling/normalisation of images
5) Diffraction analysis: Normalization to incoming beam spectrum
6) Commissioning / calibration: use portable monitor to survey spectrum on sample

4. Experience with TOF beam monitors: @ENGIN-X
Monitors: - 2 Li glass bead array
- 1D; TOF
ISIS in-house development:
Diagnostics: to monitor changes of neutron flux and spectrum
Not used for data processing

5. Experience with TOF beam monitors:
Questions:
How many are needed at minimum to operate a tof beamline with many choppers?
Number of beam monitors (necessary for operation/commissioning, nice to have)
IMAT has 6 monitors for commissioning; it will need 4 for operating the beamline;
ENGIN-X has 2 monitors
3) Position of beam monitors
Diagnostic: Upstream / downstream choppers etc that change the sprectum;
Normalisation: Close / not too close to the detectors
Which kind of beam monitors (PSD, 1D, …) 1D suffient for imaging beamline as we have 2D cameras;
Monitor technology: advantages/disadvanages (neutron and gamma sensitivity, absorption, size, radiation hardness …) low attenuation; continous sheets – point – strips – crosses; cover the whole beam or not;
Mounting of beam monitor (on chopper, in vacuum housing, in neutron guide, … )
In neutron guide; accessible; sufficient redundancy
Fixed or movable?
(i) Fixed; (ii) re-movable after commissioning ; (iii) movable (e.g. IMAT M5);