General research interest
Understanding the lower limit on the energy resolution of a SiPM based scintillation detectorThe limited number of active pixels in a SiPM results not only in a non-linearity but also in an additional ﬂuctuation of its response. Both these effects are taken into account to calculate the amplitude resolution of an ideal SiPM, which is shown to be ﬁnite. As one of the consequences, the energy resolution of a scintillation detector based on a SiPM is shown to be limited to some minimum value deﬁned by the number of pixels in the SiPM.
A. Stoykov et al., “On the limited amplitude resolution of multipixel Geiger-mode APDs”, Journal of Instrumentation 2 (2007) P06005
Understanding the time resolution with a plastic scintillator readout by a SiPMWe establish the current lower limit on the time resolution of such detector as about 20 ps per 1 MeV detected energy scaling inversely proportional to the square root of the energy. The result allows accurate predictions on the performance of eventual practical detectors as shown by the MEG collaboration.
A. Stoykov et al., “A time resolution study with a plastic scintillator read out by a Geiger-mode Avalanche Photodiode”, Nucl. Instr. and Meth. A 695 (2012) 202
K. Sedlak et al., “A GEANT4 study on the time resolution of a fast plastic scintillator read out by a G-APD”, Nucl. Instr. and Meth. A 696 (2012) 40
A SiPM based ZnS(Ag):6LiF scintillation neutron detector for neutron scattering instrumentation
The application of SiPMs in such detectors has been hindered by their orders of magnitude higher dark count rate at room temperature. We solve this problem by substantially improving the light collection from the scintillator and by using an efficient algorithm for separating the signals from the dark counts. The developed prototype detector shows performance parameters comparable or exceeding those of the current PMT based detectors.
The use of SiPMs in ZnS:6LiF scintillation detectors for application in the neutron scattering experimental technique opens new possibilities in designing this kind of detection systems and thus will serve for further progress in this field.
J.-B. Mosset et al., “Trigger Efficiency of a ZnS:6LiF Scintillation Neutron Detector Readout with a SiPM”, IEEE Transactions on Nuclear Science, Vol. 63, No. 4, 2016
J.-B. Mosset et al., “A 16-ch module for thermal neutron detection using ZnS:6LiF scintillator with embedded WLS fibers coupled to SiPMs and its dedicated readout electronics”, Nucl. Instr. and Meth. A, article in press
J.-B. Mosset et al., “Digital signal processing for a thermal neutron detector using ZnS(Ag):6LiF scintillating layers read out with WLS fibers and SiPMs”, Nucl. Instr. and Meth. A 824 (2016) 319
M. Hildebrandt et al., “Detection of thermal neutrons using ZnS(Ag):6LiF neutron scintillator read out with WLS fibers and SiPMs”, Nucl. Instr. and Meth. A 824 (2016) 204
A. Stoykov et al., “A SiPM-based ZnS:6LiF scintillation neutron detector”, Nucl. Instr. and Meth. A 787 (2015) 361
J.-B. Mosset et al., “Evaluation of two thermal neutron detection units consisting of ZnS/6LiF scintillating layers with embedded WLS fibers read out with a SiPM”, Nucl. Instr. and Meth. A 764 (2014) 299
A. Stoykov et al., “Use of Silicon Photomultipliers in ZnS:6LiF scintillation neutron detectors: signal extraction in presence of high dark count rates”, Journal of Instrumentation 9 (2014) P06015
J.-B. Mosset et al., “Upgrade of the POLDI diffractometer with a ZnS(Ag)/6LiF scintillation detector read out with WLS fibers coupled to SiPMs”, Journal of Physics: Conference Series 528 (2014) 012041
Upgrade of the μSR instrument GPS at PSILaboratory for Muon Spin Spectroscopy.
Bulky detector system of the GPS instrument representing a set of scintillation detectors consisting of plastic scintillators, long and bended light guides, and PMTs was replaced by a more compact and lightweight version in which the light guides are excluded and PMTs are replaced by SiPM arrays. The geometry of the detector and accordingly its acceptance are preserved, while the time resolution is substantially improved due to the exclusion of the light guides and reading out the scintillators from their two opposite sides. The GPS instrument is already the third (out of six) μSR instruments in operation at the Laboratory for Muon Spin Spectroscopy equipped with SiPMs.
High-time resolution detector for the 9.5 Tesla μSR instrument at PSIHAL-9500 instrument was developed. The detector satisfies strict requirements on the time resolution and compactness. Muon-spin precession signals with frequencies up to 1.3 GHz in magnetic ﬁelds up to 9.5 T are easily detected, the reduction of the signal amplitude does not exceed 20 %. The accuracy in measuring the muon-positron time correlations is about 80 ps (sigma) – the time resolution unprecedented for such high ﬁelds. The small radial dimension of the detector ring allows detecting the decay positrons with the spiral radius down to 1 cm. To preserve the 10 ppm uniformity of the magnetic ﬁeld at the sample position all detector components located in the vicinity of the sample are non-magnetic.
A. Stoykov et al., “High field muSR instrument at PSI: detector solutions”, Physics Procedia 30 (2012) 7
A lens-coupled scintillation counter in cryogenic environment
This approach is used to incorporate a set of scintillation counters serving as a Veto detector into a dilution refrigerator used by the HAL-9500 instrument. The scintillation part of the detector is operated at the temperature of 1 K. Any other solution would require modifications to the cryostat design with enormously increased cost of the system.
A. Stoykov et al., “A lens-coupled scintillation counter in cryogenic environment”, Journal of Instrumentation 6 (2011) P02003
ALC μSR instrument at PSI
A. Stoykov et al., “A new detector system for the ALC spectrometer – first experience with G-APDs in muSR instrumentation”, Physica B 404 (2009) 986
A scintillating fiber detector for muon-beam profile measurements
A. Stoykov et al., “A scintillating fiber detector for muon beam profile measurements in high magnetic fields”, Nucl. Instr. and Meth. A 550 (2005) 212
T. Lancaster et al., “Magnetic field effects on particle trajectories in the muon-spin relaxation experiment: Towards a high-field spectrometer”, Nucl. Instr. and Meth. A 580 (2007) 1578