Some of the major developments over the past year on ISIS
instruments are described here.
The 13 m long, 3.25 m diameter vacuum tank for Sans2d was the first major TS-2 beamline component to be delivered (in March 2007). Later in the year it will disappear under a very large wax shielding blockhouse. A contract has been placed for the design and installation of the rails and trolleys for the moving detectors, the beam stops and shielding baffles inside the tank. Two 1 m square multiwire detectors have been delivered from the USA and tested. The five 2 m sections of straight neutron guides and 3.5 m long, 9 channel, supermirror bender from Switzerland are awaiting installation.
Polref, Inter and Offspec
Polref, Inter and Offspec are the three day-1 TS-2 reflectometers. Work has started on their respective blockhouses and should be complete by early June. Final design reviews have been held for the guide systems and work on choppers, sample positions, detector mounts and incident optics continues. We have also obtained our first spin echo data from the Offspec equipment running at Delft, Holland.
Progress on Nimrod for TS-2 has been substantial over the past year. The beam stop has now been installed. The incident beamline and collimation are now designed and much of it is under manufacture. The vacuum tank is now fully detailed and will be built by CNR in Italy, releasing money for the purchase of an extra 5 detector modules. The detector moulding is now in progress, following satisfactory tests of a prototype detector on Sandals. Work is in progress to finalise the detector support frame and the low angle detector bank. Much of the electronics for the instrument is under construction and a full set of detector cables will be installed ready for the complete set of detectors when they become available.
Let is low energy chopper instrument that is being built on the ISIS second target station. It is a versatile multichopper instrument with a wide dynamic range (incident energies in the range between 0.5 and 80 meV) and the ability to collect several incident energies simultaneously. By trading incident energy for resolution it will be able to achieve either 5μeV resolution (with an incident energy of 1 meV), or fluxes an order of magnitude greater than the group’s other chopper instruments at low energies. With 5 choppers, a 25 m guide and a sample tank 4 m in radius and 5 m tall Let is a huge piece of engineering. It is on target to be ready for commissioning towards the end of 2008.
Wish (Wide angle In a Single Histogram) is a long-wavelength TS-2 diffractometer primarily designed for powder diffraction in magnetic and large unit cell systems. Over the last year, progresses have been made in many areas. The elliptic guide is currently being manufactured and the optic bench and supporting frame are being installed. Testing of the 8 mm 3He 1m-long detector tubes was completed in December and 750 tubes have been ordered from Reuter-Stokes. Successful testing of the curved tank windows has released the sample tank for manufacture. The contract for the oscillating radial collimator has been awarded to JJXray. Delivery of disk-choppers is expected before the end of the summer, and work is also progressing on the design of ADC cards.
Fires is a proposal for a new high resolution back scattering spectrometer to replace Iris. It aims to achieve an order of magnitude higher energy resolution through having a long supermirror flight path, with a concomitant unchanged range of momentum transfers. The extension to μeV resolution will provide new opportunities in diverse fields such as viscous liquids, biopolymers or quantum magnets and liquids. Short neutron pulses will be generated with a fast chopper, with variable pulse width to enable resolution to be traded against intensity. The secondary spectrometer will consist of huge plates covered with silicon wafers to reflect neutrons in near back scattering geometry on to position sensitive detectors. Detailed Monte Carlo simulation study is now underway.