Muon Spectroscopy - JRA8
Technology Development for Muon Spectroscopy

Muon spectroscopy is a powerful way of studying atomic level properties of matter, often producing complementary results to neutron scattering. Europe is fortunate in having two muon sources, ISIS in the UK and PSI in Switzerland, which each provide different facilities for muon experiments. The aim of this JRA was to develop technologies and techniques which extend the range of capabilities of the muon method available to European users at these two facilities.

The JRA was split into three primary work packages, and key results from each are listed.

WP1: Detector development
o New muon detector technology: avalanche photo-diodes (APDs) were tested and found to provide an excellent way of making a compact detector array for high-field muon spectrometers. They are field-resistant, and have very good (fast) timing characteristics.
o Application: A muon beam profile monitor suitable for use in high magnetic fields was built using APDs and used to characterise muon beam behaviour in applied fields.
o A demonstration detector for a muon spectrometer was successfully built and tested based on avalanche micro-channel photo-diodes.
o Application: This new detector technology will be used to refurbish the ALC spectrometer at PSI. This will be the first muon spectrometer in the world to use APDs as opposed to conventional photomultiplier tubes.

WP2: Instrument Simulation
o A package has been developed, based on the CERN GEANT4 libraries, to simulate muon spectrometers.
o The package includes modelling of the incoming muon beam, outgoing positrons, the effects of applied fields and variable detector geometry
o The package has been tested by comparison with existing instruments
o Application: For new high-field muon spectrometers being built at ISIS and PSI, the package has proved to be invaluable for designing the instrument geometries and detector arrays.

WP3: Advanced Techniques
o Apparatus for AC-susceptibility measurements simultaneous with muon measurements has been produced and used for user experiments.
o A variety of radio-frequency (RF) μSR techniques have been developed. These include generation of circularly polarised RF (Application: measurement of shallow donor muonium states in semiconductors) and multi-pulse stimulation (Application: studies of ionic conductors)
o A high-temperature (1500 K) furnace has been equipped for RF studies using small samples. RF measurements have been extended to liquid and gaseous samples.
o Microwave μSR has been demonstrated, extending the frequency range of stimulation into the GHz region.

Partners, meetings and publications
The JRA has involved four partners: ISIS and PSI muon sources, the University of Oxford and the University of Parma. In addition to formal collaboration meetings which have occurred throughout the project, partners have had a large number of informal contacts and have worked together regularly on JRA topics. The JRA has resulted in nine publications in peer-reviewed journals, as well as a variety of technical reports.

For more details on ÁSR Spectroscopy click here.

Co-ordinator: Cesare Bucci (INFM)

Updated 8 February 2008

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