The µSR Spectrometers          


A μSR spectrometer is a magnet (or magnets) plus an array of counters to detect incoming muons and decay positrons.

The magnets are of various types - Helmholtz, solenoid, or solid pole electromagnet; superconducting or not. In fact, most spectrometers have more than one magnet. The main magnet of an apparatus is usually oriented so the field is along the beam axis (z direction) which allows surface muons to enter the sample without being turned away. Other coils provide weaker fields in perpendicular directions either for zeroing the field or for applying weak fields (<10 mT) transverse (x,y directions) to the beam direction.

Most of the counter systems are movable in various ways, and many follow a uniform standard design of multi-counter modules mounted on tracks on tables attached to the spectrometer. Some counter arrangements are partially built into the sample inserts. These are the low background apparatuses for small or thin samples which have veto counters to reject counts from anything but the sample itself.

All apparatuses rest, and roll, on standardized rails so they can be reproducibly positioned in any beamline. They can be rolled back from the beam snout (to access collimators etc) at any time and accurately rolled back into position by one person. The four beam lines, M15, M20, M9B and M13 which are used for µSR have such rail systems.


Helios

Magnet Type: Superconducting solenoid
        
Field Strength/Orientation: 6 T / z, and 2 mT / y
Field Calibration: 0.096233 T/A
Counter acceptance: 1-3 π
Experiment types: LF, TF, HTF, RF-microwave
 
  Thermometry
 

 


DR (Pandora)

A spectrometer combining a superconducting Helmholtz magnet and dilution refrigerator

Magnet Type: Superconducting Helmholtz
        
Field Strength/Orientation: 5 T / z, 2.5 mT / x
Field Calibration: 0.0617 T/A
Counter acceptance: 0.1-1.5 π
Experiment types: LF, TF, ZF, HTF
 
  Thermometry


NuTime

Magnet Type: Superconducting Solenoid
        
Field Strength/Orientation: 7.0 T / z
Field Calibration: 0.09950 T/A
Counter acceptance: 3 π
Experiment types: HTF, HLF
 
  Thermometry


Omni-Prime

Magnet Type: 2 x Helmholtz
        
Field Strength/Orientation: 0.3 T / z, 20 mT / y, and 20 mT / x
Field Calibration: 0.000425 T/A (4.25 G/A) z
0.0000341 T/A (0.341 G/A) x

Counter acceptance: 4 π
Experiment types: LF, TF, LTF, ZF, RF-microwave
 


LAMPF

Magnet Type: 4 x Helmholtz
        
Field Strength/Orientation:   0.3 T / z (0.39 T on M15), and 10 mT / x, y
Field Calibration: 4 G/A (0.0004 T/A) z
0.3077 G/A x

Counter acceptance: 4 π
Experiment types: LF, TF, LTF, ZF, RF-microwave


SFUmu

Magnet Type: LF/TF Helmholtz
        
Field Strength/Orientation:   0.45 T / z (surface muons), y (backward muons)
10 mT / x

Field Calibration: 0.0006 T/A (6 G/A) main magnet
0.3077 G/A x

Counter acceptance: 3 π
Experiment types: TF with high momentum muons, LF, TF, LTF, ZF, RF-microwave


Hodge-Podge

Magnet Type: Solid Pole Electromagnet
        
Field Strength/Orientation: 0.3 T / x
Counter acceptance: 1 π
Experiment types: TF


Gas Cart

Magnet Type: LF/TF Helmholtz
        
Field Strength/Orientation: 33 mT / z, y
Counter acceptance: 1-2 π, x-direction
Experiment types: TF, LTF, ZF


Defunct spectromenters


High-Time

Magnet Type: Superconducting Split Pair
        
Field Strength/Orientation: 7.0 T / z
Field Calibration: 0.09068 T/A
Counter acceptance: 3 π
Experiment types: HTF, HLF
 
  Thermometry


Belle

Obsolete - Replaced by HiTime.

Magnet Type: Superconducting Helmholtz
        
Field Strength/Orientation: 7.5 T / z
Field Calibration: 0.0747 T/A
Counter acceptance: 3 π
Experiment types: HTF


Varian

Magnet Type: Solid Pole Electromagnet
        
Field Strength/Orientation: 1 T / x
Counter acceptance: 1-2 π
Experiment types: TF with high momentum muons


Omni

Magnet Type: 3 x Helmholtz
        
Field Strength/Orientation: 0.3 T / z, and 20 mT / x, y
Field Calibration: 0.0004 T/A (4 G/A)
Counter acceptance: 4 π
Experiment types: LF, TF, LTF, ZF, RF-microwave


Notes

LF = Longitudinal Field.
ZF = Zero Field (with a flux gate magnetometer and ZF controller available).
TF = Transverse Field (usually requiring spin rotation).
LTF = Low Transverse Field (without spin rotation, <10 mT).
HTF = High Transverse Field (spin rotation and fast-timing counters and perhaps with feedback field control).
RF = Radio Frequency.
z = The beam direction
x = Up (perpendicular to beam - the spin direction of spin-rotated surface muons )
y = Right (perpendicular to beam - the spin direction of spin-rotated muons in M9b)


Maintained by Donald Arseneau, asnd@triumf.ca
For the TRIUMF ÁSR Facility