![[Diagram of counter telescope]](telescope.png)
Rather than (or in addition to) vetoing muons that do not stop in the sample, one can sometimes arrange the positron detectors so they cannot "see" the location where the errant muons go. this typically involves multiple scintillation counters with wide spacing between them that form a "telescope".
Start clock = M and not V
Stop(U) = U1 and U2
Stop(D) = D1 and D2
Start pileup gate = M and not V
The configuration shown here uses "up" and "down" telescopes in conjunction with a simple muon veto. The counter geometry ensures that decay positrons coming from the veto counter cannot be detected by a coincidence of U1 and U2 or D1 and D2. Therefore those muons can be completely ignored: they will not start the clock, and the pileup gate need not wait for them to decay.
Telescopic counter arrangements generally need quite an open geometry, and they typically give low detection efficiencies due to low solid-angle coverage.