EMU Technical
29 May 2009







EMU is a 32-detector µSR spectrometer which is optimised for zero field and longitudinal field measurements. Fields of up to 4000 G can be applied, and sample temperatures in the range of 350mK to 1000K can be produced using a variety of sample environment equipment.


Technical Summary

Production target5, 7, or 10 mm graphite at 45o 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++ < 0.15 with separator voltage > 70kV
Beam size at focusVertical: 10 mm fwhm, horizontal: adjustable, 10-27 mm fwhm
Intensity4x105 µ+ /s shared by the three south-side muon areas
Data rateevent rates of typically 10-20 million events per hour (5 mm muon production target, ISIS current of 180 µA
Muon polarisation100%
Muon energy; range3.2 MeV; range approx. 100 mg.cm-2 for surface momentum
Backgroundhistograms contain a constant background of approx. 10-5 times the number of counts in the first bins
Instrument geometrylongitudinal (LF) or zero (ZF) applied magnetic fields, low transverse fields (TF)
Detectors32 scintillator segments in two circular arrays. Grouped 2x16 for ZF, LF
Sample environment
  • Helmholtz coils (0-400 mT), LF or TF,
  • calibration coils (0-10 mT) TF
  • zero field compensation to <3 µT
  • sorption crysotat (350 mK - 50 K)
  • Oxford instruments cryostat (2 K - 300 K)
  • closed cycle refrigerator (CCR) (12 K - 340 K)
  • furnace (300 K - 1000 K)
Data acquisitionInstrument controlled by a VAXstation 3200
Timing resolution32 TDCs with time resolution settings of 8, 16, 24, or 32 ns
Measurable frequencies0.1-10 MHz (upper limit due to finite muon pulse width)

Emu Sample Environment 

So that you can check the sample environment equipment that you have been assigned, the following ‘codes’ are used to denote the various cryostats, etc, on the schedules you have received.

Schedule Code




Sorption cryostat

350 mK – 50 K


Closed cycle refrigerator

12 K – 600 K



300 K – 1000 K


Gas Handling



Liquid Handling



Reflector furnace

300 K – 1500 K


Radio Frequency