GPS - General Purpose Surface-Muon Instrument

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The GPS Instrument is the "workhorse" of the Facilities. It is permanently installed in area piM3, using a so-called "surface-muon beam" (i.e., positive muons originating from the decay of positive pions stopped near the surface of the production target). The typical range of these muons is about 1.5mm in polyethylene. The piM3 beamline is equipped with an electromagnetic separator / spin rotator allowing to choose spin directions ranging from almost parallel to perpendicular to the muon momentum.

The instrument is designed for zero- (ZF), longitudinal- (LF), and transverse-field (TF) µSR experiments in wide ranges of temperature and external magnetic field. A special detector arrangement allows to investigate very small samples. Sample rotation is provided for the study of orientation-dependent effects in single crystals.

Since August 1995, the GPS Instrument can be used simultaneously with the Low Temperature Facility (LTF) Instrument either by switching the beam at fixed time-intervals from one area to the other by means of an electrostatic deflector ("kicker") and septum magnet or by splitting the beam continuously by widening the spot in front of the collimators located at the entrance to the septum magnet.

Since 1998, it is also possible to share the beam by triggering the deflector on request of one of the Instruments (Muons On REquest, MORE).

Instrument Scientist:
Alex Amato, E-mail: alex.amato@psi.ch
Co-responsible Person:
Hubertus Luetkens, E-mail: hubertus.luetkens@psi.ch

LTF - Low Temperature Facility

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The LTF Instrument is based on a Oxford Instruments He-3/He-4 dilution refrigerator reaching a base temperature of 10mK. It shares the piM3 surface-muon beam with the GPS Instrument (see above).
Similar to GPS, LTF is designed for zero-, longitudinal-, and transverse-field experiments, but the field range is a factor of 5 larger than in GPS due to a built-in superconducting magnet.

Instrument Scientist:
Christopher Baines, E-mail: chris.baines@psi.ch

DOLLY - Relocatable Surface-Muon Instrument

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DOLLY is a copy (with few modifications) of the GPS Instrument. In contrast to GPS or LTF, it is not permanently installed in a dedicated area but may be set up in either piE1 or piE3, using - like GPS and LTF - so-called "surface-muons" (i.e., 4.2MeV positive muons originating from the decay of positive pions stopped near the surface of the production target). The typical range of these muons is about 1.5mm in polyethylene. For the use of DOLLY in piE1 or piE3, some additional beam-line elements have to be installed in these areas: an electromagnetic separator or spin rotator (the latter not being available yet) and additional quadrupole lenses. With the existing separator, only longitudinal polarisation of the muons is available.

The design of the instrument is almost identical with that of the GPS, allowing for zero- (ZF), longitudinal- (LF), and transverse-field (TF) µSR experiments in wide ranges of temperature (2-300K) and external magnetic field (LF 0-0.5T, TF 0-15mT). The detector arrangement with veto-detectors in both forward and backward directions allows to investigate very small samples. Sample rotation is foreseen for the study of orientation-dependent effects in single crystals.

Instrument Scientists:
Robert Scheuermann, E-mail: robert.scheuermann@psi.ch
Co-responsible Person:
Alexey Stoykov, E-mail: alexey.stoykov@psi.ch

GPD - General Purpose Decay-Channel Instrument

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The GPD Instrument is designed for the use of higher energy (positive or negative) muons from the decay of pions in flight (area µE1) having ranges up to 130mm in polyethylene.

Zero-, longitudinal-, and transverse-field experiments are possible in similar field ranges as with GPS. The available temperature range extends to somewhat lower temperatures than in GPS when a He-3 evaporation cryostat is used. Some of the cryostats allow sample rotation.

The use of GPD is recommended when big samples are available and is mandatory for samples which have to be sealed in containers.

Instrument Scientist:
Ulrich Zimmermann , E-mail: ulrich.zimmermann@psi.ch
Co-responsible Person:
Rustem Khasanov, E-mail: rustem.khasanov@psi.ch

ALC - Avoided Level Crossing Spectrometer

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The ALC Instrument is designed for integral forward-backward decay asymmetry measurements in longitudinal magnetic fields up to 5T, making use of the full available muon intensities. As a rule, the instrument will be set up in area piE3 for the use of surface muons coming from Target E.

Instrument Scientist:
Alexey Stoykov, E-mail: alexey.stoykov@psi.ch
Co-responsible Person:
Robert Scheuermann, E-mail: robert.scheuermann@psi.ch