Muon Beams at the Paul Scherrer Institute
Intense beams of spin-polarised muons are available
at the PSI Accelerator
in the experimental areas µE1, µE4, piM3, piE1 and piE3. Areas with "M" in their name are connected to
a thin target M
("Mince" in french, 5 mm of graphite), those with "E" to the
thick E target ("Epaisse" in french,
60 mm or 40 mm of graphite). The muons originate
from the decay of pions produced by the interaction of the 2 mA,
590 MeV proton beam with the nuclei of the target material.
The µE1 beam line is dedicated to the
µSR User Facilities and is equipped with a
superconducting decay channel, providing beams of positive
or negative muons
with useful momentum ranges 40-125 MeV/c.
The new µE4 beam is a large
acceptance beam line for muons with low momentum (< 40 MeV/c). It was specially
designed to serve the needs of the low-energy muon (LEM)
beam facility at PSI, i.e. maximum positive muons intensity at 28 MeV/c and a
beam spot fitting to the size of the muon moderator target of the
The piM3 beam line is entirely dedicated to the
µSR User Facilities. It is equipped with a spin
rotator and a fast-switching electrostatic "kicker".
The surface-muon beam can be shared or switched ("muons on request",
MORE) between the
Depending on the beamline, one can obtain:
- Positive muons emerging from the production targets:
"surface" (1) and "sub-surface muons" (2)
(momentum range 5-30 MeV/c)
- Positive or negative "cloud muons" (3) (momentum 10-280 MeV/c).
- Low energy positive muons are created in µE4 by converting with a
cryogenic moderator surface muons to epithermal muons. A system of electrostatic
elements for reacceleration and low-energy muon transport can provide muons
energies up to 30 keV.
|(1) ||Surface muons originate from pions stopped close to
the surface of the target. They have kinetic energies around 4.1 MeV
(momentum 28 MeV/c).|
|(2) ||Sub-surface muons originate from pions stopped
in the bulk of the target, thus losing some energy on their way to the
|(3) ||Cloud muons originate from pions decaying
outside the target.|