Position-sensitive detectors detection of muons and positrons

The useable rate of incoming muons can be increased by implementing a so-called vertex reconstruction technique. The continuous muon beams of SµS require a limitation of the incoming-muon rate to ~40 kcps to keep pileup events at a tolerable level. In a traditional µSR setup, an incoming muon is registered in a ‘muon counter’, which opens a data gate of typically 10-µs length. A valid µSR event is given by the detection of the decay positron in one of the scintillators of the positron spectrometer. In case of a pileup event, where a second muon or a second positron is observed, it is not possible to determine which muon belongs to which positron, and the event is discarded. At a beam rate of 40 kcps, the accepted rate of 18 kcps is the maximum for a data gate of 10 µs. However, when the position of the incoming muon can be detected and the emitted positron tracked, each decay positron can be assigned unambiguously to its parent muon by vertex reconstruction. In this way, at least ten times higher incoming-muon rates would become feasible, thus enabling new kinds of µSR applications by measuring very weak effects on µSR precession frequencies or depolarization rates, or to measure several samples simultaneously. With modern silicon-based pixel detectors of 50-µm thicknesses, the vertex inside the µSR instrument can be determined within about 1 mm. In the course of the High Intensity Muon Beam (HIMB) study, initiated by LTP to deliver a muon beam with 1010/s intensity for new particle physics and µSR applications, members of LTP in collaboration with LMU have started a feasibility study of such a vertex reconstruction. The detection system is based on the planned silicon pixel detectors for the upcoming Mu3e experiment at PSI, which is being developed by the University of Heidelberg in collaboration with LTP.


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  • AMS - Austria Micro Systems - Front-end electronics for radiation detectors.
  • Bicron - Scintillators, sci-fi, detector assemblies (Saint Gobain).
  • CAEN - Nuclear physics and microelectronics.
  • Canberra - Nuclear physics and many other aspects of detectors.
  • CiS - Institut für Mikrosensorik - Silicon detectors.
  • CSEM - Centre Suisse d'Electronique et de Microtechnique - Silicon detectors.
  • Hamamatsu - Photonics: PMTs, APDs, and much more.
  • IDEAS - Electronic front-ends for radiation detection.
  • Kuraray - Mainly scintillating fibers.
  • Micron - Micron Semiconductor - Silicon detectors.
  • Silena - Nuclear physics.
  • SINTEF - Senter for Industriforskning (Oslo) - Microelectronics, front-ends, detectors.
  • VTT - Detectors and microelectronics.