Low Background Inserts

Dealing with Small Samples

Although a muon beam can be focused and/or collimated down to a narrow diameter, it becomes impractical to go below about 1 cm because
  1. the muons fill a large phase space, so they can't be focused indefinitely;
  2. the rate is too low if they are collimated ruthlessly; and
  3. even for a small collimator, the beam will diverge between the collimator and the sample as there must be some appreciable distance between them (for cryostat vacuum etc).
The alternative of having most muons miss the sample is also undesirable because their `background' signal would overwhelm the sample signal.

For these reasons, very small or very thin samples require a veto of muons which do not stop in the sample. While vetos may be used with any counters, there are some specific counter systems provided as cryostat inserts.



Maintained by Donald Arseneau,