Hifi technical information

Technical information for the HiFi instrument

Production target7 or 10 mm graphite at 45° to proton beam
BeamPositive muons, at or near surface momentum
Incident momentum26.5 MeV/c, 10% momentum bite
Pulse structureSingle pulse, 80 ns fwhm
Contaminatione+ / µ+ <0.15 with separator voltage > 70 kV
Beam size at focusZero field: vertical 13mm fwhm, horizontal: adjustable 10-27mm fwhm. Reduces in high field.
Intensity1×105 µ+/s
Data rateevent rates of typically 40-45 million events per hour (40Hz beam to Target Station 1)
Muon polarisation100%
Muon energy; range3.2 MeV; range approximately 100 mg cm-2
Backgroundhistograms contain a constant background of approx 10-5 times the number of counts in the first bins
Instrument geometryMain field parallel to the incoming muon beam and muon spin
Magnetic fields

Superconducting magnet with 4 coils. Operating modes are:

  • Longitudinal, up to 5 Tesla (50000G). Reversible, persistent or non-persistent operation
  • Longitudinal with additional modulation or sweep up to ±400G
  • Low fields (LF or TF) up to ±400G LF and ±100G TF (x and y)
  • Zero field compensating remanent field to <0.1G
Detectors64 scintillator segments in two circular disc arrays. Grouped 2*32 for LF or ZF
Sample environment
  • Helium cryostat 1.5-300K
  • Dilution refrigerator insert 30mK-6K in dilution mode
  • Flow cryostat 4-400K
  • CCR 10-600K
  • Furnace 300-1500K
Data acquisitionInstrument controlled by SECI.
Timing resolution64 channel TDC (ISIS DAE-2) with standard time bins of 16 ns, optionally down to 0.5 ns for RF. Time range 0-32 µs
Measurable frequencies0.1-10 MHz (when limited by muon pulse width); RF precession up to ~200 MHz
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