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Paul Scherrer Institut PSI LMU : Laboratory for Muon Spin Spectroscopy

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Updated:
14.01.2010
E-Mail: elvezio.morenzoni@psi.ch

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PSI µSR Facilities: Instrument Specifications

This page is intended to help choosing the appropriate instrument for a given problem you'd like to address with µSR. More details may be found on the individual instruments pages.

GPS and LTF | GPS | LTF | GPD | ALC | DOLLY

A) Instruments at the Dedicated Surface-Muon Beam Line piM3
(GPS and LTF)

  • Beam properties:

    • Positive muons, standard momentum 28MeV/c (energy 4MeV).
    • Muon range ~150mg/cm2, range width ~30mg/cm2 FWHM in CH2.
    • Beam sharing between GPS and LTF:
      • Passive splitting by means of a septum magnet.
      • Exclusively at PSI: Active sharing ("Muons On REquest", MORE).
        This mode has successfully been tested in November 1997 and can now be used as a routine option.
        Please contact the instrument scientist if you want to use it during your beam time.
    • Polarization: Longitudinal or transverse (angle between µ+ spin and momentum ~6-60°).
      Note: In beam-sharing mode, the spin orientation is the same for GPS and LTF.

    GPS and LTF | GPS | LTF | GPD | ALC | DOLLY

  • GPS (General Purpose Surface-Muon Instrument, area piM3.2)

    • Collimation:
      • External (in front of the septum): variable, 1x1-10x10mm2,
      • Internal (in front of the muon start detector): 7x7mm window in the Bveto detector ("active collimation", see below).
    • Detectors (fast plastic scintillators):
      • Incoming muons: 0.2mm thick.
      • Decay positrons: "forward", "backward", "up", "down", "right", 5mm thick each.
      • Veto for muons missing the sample ("Fveto").
        (Also rejects the decay positrons of these muons).
      • Veto for muons missing the internal collimator window ("Bveto").
        (Also rejects the decay positrons of these muons).
      • System time resolution: ~1ns.
    • Modes of operation:
      • "GPS only": The entire muon beam is optimised for the GPS branch. No beam at the LTF.
      • "Shared": The beam is widened horizontally at the Septum Magnet ASS31. Similar muon rates at GPS and LTF.
      • "MORE" (active sharing): The beam is switched to LTF when a muon is detected by GPS. Extremely low background at GPS, virtually full beam intensity at LTF.
    • Magnetic fields:
      • Main field 0-0.6T or 0-50mT (two power supplies), parallel to the beam.
      • Auxiliary field 0-10mT perpendicular to the µ+ polarization.
    • Sample Environment:

    GPS and LTF | GPS | LTF | GPD | ALC | DOLLY

  • LTF (Low Temperature Facility, area piM3.3)

    • Collimation:
      • External (in front of the septum): variable, 1x1-10x10mm2,
      • Internal (passive collimator in front of the muon start detector): 8x14mm (widthxheight) oval.
    • Detectors (fast plastic scintillators):
      • Incoming muons: 0.2mm thick.
      • Decay positrons: "forward", "backward", "left", "right", 5mm thick each.
      • System time resolution: ~1ns.
    • Modes of operation:
      • "LTF only": The entire muon beam is optimised for the LTF branch. No beam at the GPS.
      • "Shared": The beam is widened horizontally at the Septum Magnet ASS31. Similar muon rates at LTF and GPS.
      • "MORE" (active sharing): The beam is switched to GPS when a muon is detected by LTF. Very low background at LTF, virtually full beam intensity at GPS.
    • Magnetic fields:
      • Main field 0-3T (superconducting coils), parallel to the beam.
      • Auxiliary field 0-10mT perpendicular to the beam (vertical).
    • Cryostat:
      • Oxford Instruments 3He/4He dilution refrigerator.
      • Temperature range 10mK-4.2K. Sample in vacuum.
      • Maximum sample dimensions 23x12x5mm3.
      • Top loading.
      • Optional: Electrical top loading.

GPS and LTF | GPS | LTF | GPD | ALC | DOLLY

B) Relocatable Facility Instruments (GPD, ALC and DOLLY)

  • GPD (General Purpose Decay-Channel Instrument)

    • Beam properties
      • Area µE1
      • Positive or negative muons;
        momentum ranges ~60-125MeV/c (µE1).
      • Muon range ~1.5-10g/cm2, range width ~30mg/cm2-~4g/cm2 FWHM in CH2.
      • Polarization: Longitudinal (direction of the muon momentum; no spin rotation).

    • Collimation: Maximum dia. 12mm; inserts with dia. 10, 8, or 6mm available.
    • Degrader: Remote controlled; 0-24mm polyethylene.
    • Detectors (fast plastic scintillators):
      • Incoming muons: 'M' (single, between degrader and sample; 2mm thick plastic scintillator).
      • Decay positrons (electrons): 'forward' (single, fork), 'backward' (single, fork), 'up' (pair), 'down' (pair), 4mm thick each.
      • System time resolution: ~1ns.
    • Magnetic fields:
      • Main field 0-0.66T, parallel or perpendicular to the muon spin.
    • Cryostats:
      • "CCR" (Leybold Heraeus closed cycle refrigerator):
        • Sample chamber dia. 39mm (radiation shield); max. 50mm (without shield).
        • Temperature range 11-320K; sample in vacuum.
      • "Chemistry cryostat" (liq. nitrogen flow):
        • Sample chamber dia. 40mm.
        • Temperature range 77-400K; sample in nitrogen gas.
      • "Janis" (Janis Research continuous-flow 4He evaporation cryostat):
        • Sample chamber dia. 24mm.
        • Temperature range 2-320K; sample in 4He gas flow.
        • 360° sample rotation (optional; rotation axis perpendicular to muon spin).
      • "Heliox/Variox" (Oxford Instruments) sorption-pumped 3He cryostat:
        • Sample chamber dia. 40mm.
        • Temperature range 0.3-300K; Sample in vacuum1).
        • 360° sample rotation (optional; rotation axis perpendicular to muon spin).
          1) Sample in 4He contact gas is possible above 4K.

GPS and LTF | GPS | LTF | GPD | ALC | DOLLY
  • ALC (Avoided Level Crossing Instrument)

    • Beam properties:
      • Area piE3
      • Positive muons; standard momentum 28MeV/c (energy 4MeV).
      • Muon range ~150mg/cm2; range width ~30mg/cm2 FWHM in CH2.
      • Polarization: longitudinal (opposite to muon momentum).
        Spin rotator in preparation.
    • Collimation: External collimator, 50mm dia.
    • Detectors (plastic scintillators):
      • Positrons: "forward" (upstream): a ring of eight rectangular detectors, "backward": seven 45° sectors; for integral forward-backward decay asymmetry measurements.
      • Muons: Optional for low-resolution time-differential measurements.
    • Magnet:
      • Superconducting solenoid; 1m long, warm bore 200mm dia.
        Field ranges 0-5T with original power supply or 0-±0.13T with optional bipolar power supply.
    • Cryostat:
      • Two different cold-finger inserts (liq.N2 or liq.He).
      • Sample chamber 120mm dia., 20mm long.
        Preferred sample diameter ›50mm; sample in vacuum.
      • Temperature ranges: 77-320K (liq.N2) or 4.2-320K (liq.He).
    • Furnace:
      • Sample chamber dimensions as for the cryostat; sample in vacuum.
      • Temperature range: 290-600K.
    • Gas Can:
      • Contact H. Dilger, Stuttgart

GPS and LTF | GPS | LTF | GPD | ALC | DOLLY
  • DOLLY (Relocatable Surface-Muon Instrument)

    • Beam properties:
      • Area piE3 or piE1
      • Positive muons; standard momentum 28MeV/c (energy 4MeV).
      • Muon range ~150mg/cm2; range width ~30mg/cm2 FWHM in CH2.
      • Polarization: longitudinal only (opposite to muon momentum).
        Spin rotator in preparation (not available in 1999).
    • Collimation:
      • External (between two quadrupole pairs): various elliptical and circular openings,
      • Internal (in front of the muon start detector): 7x7mm window in the Bveto detector ("active collimation", see below).
    • Detectors (fast plastic scintillators):
      • Incoming muons: 0.2mm thick.
      • Decay positrons: "forward", "backward", "up", "down", "right" (foreseen for use with spin rotator; not mounted in 1999), 5mm thick each.
      • Veto for muons missing the sample ("Fveto").
        (Also rejects the decay positrons of these muons).
      • Veto for muons missing the internal collimator window ("Bveto").
        (Also rejects the decay positrons of these muons).
      • System time resolution: ~1ns.
    • Magnetic fields:
      • Main field 0-0.59T, parallel to the beam (coil design allows fields up to 0.8T).
      • Auxiliary field 0-15mT perpendicular to the beam.
    • Cryostat:
      • PSI-made continuous-flow 4He evaporation cryostat.
      • Temperature range 3-300K. Expected base temperature ~1K with appropriate pumping equipment (not yet available).
      • Sample in 4He flow. Size: max. 22mm dia. at a thickness of 3mm.
      • Manual sample rotation (360°, rotation axis perpendicular to muon spin) is possible.

    For specific questions regarding one of the Facility Instruments described above, please refer to the corresponding Instrument Page (GPS, LTF, DOLLY, GPD, or ALC) or contact the responsible Instrument Scientist.

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