12 Aug 2009




Technical Information for HET


Technical Summary

Moderator300K water moderator poisoned at 1.5 cm
Incident energy15-2000 meV
Energy resolutionDepends on the choice of Fermi chopper

D hw /Ei =1-2% (4m detectors) 1-3% (2.5m detectors)
Primary flight path12m
Secondary flight path2.5m and 4m
Fermi Chopper10m from moderator

50-600 Hz phased to ISIS pulse ± 0.1m s

Several chopper packages are available optimised for different incident energy and resolution requirements
Background chopper8.5m at 50 Hz or 100 Hz
Sample position11.82m from moderator
Beam size at sample45mm x 45mm, motorised jaws can define smaller beam sizes
DetectorsLow Angle Bank
2.5m from sample 256 10atm 3He tubes in 8 fold array covering 9-29º scattering angle

4.0m 52 position sensitive 3He detector array (10 bar partial pressure) 2.5 cm diameter, resolution 15mm along their lengths covering 3-7º scattering angle

110º - 125º 4m bank: 44 10 bar 3He tubes.
130º - 140º 2.5m bank: 44 10 bar 3He tubes.
MonitorsMonitor 1: incident beam monitor
Monitor 2: -1.615m from sample.
Monitor 3: 5.694m from sample.
Intensity at Sample.3x103n cm-2 s-1 at Ei=1eV (for 150Amps proton current)
Sample environmentAccepts all standard sample environment equipment
Data acquisitionAlphastation personal workstation