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Register a new userInvestigation of avalanche photodiodes radiation hardness for baryonic matter studies
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Added by
Vasily Mikhaylov S.
Publication date
2015
fields
Physics
and research's language is
English
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Modern avalanche photodiodes (APDs) with high gain are good device candidates for light readout from detectors applied in relativistic heavy ion collisions experiments. The results of the investigations of the APDs properties from Zecotek, Ketek and Hamamatsu manufacturers after irradiation using secondary neutrons from cyclotron facility U120M at NPI of ASCR in v{R}ev{z} are presented. The results of the investigations can be used for the design of the detectors for the experiments at NICA and FAIR.
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Low Gain Avalanche Detectors (LGAD) are based on a n++-p+-p-p++ structure where an appropriate doping of the multiplication layer (p+) leads to high enough electric fields for impact ionization. Gain factors of few tens in charge significantly improve the resolution of timing measurements, particularly for thin detectors, where the timing performance was shown to be limited by Landau fluctuations. The main obstacle for their operation is the decrease of gain with irradiation, attributed to effective acceptor removal in the gain layer. Sets of thin sensors were produced by two different producers on different substrates, with different gain layer doping profiles and thicknesses (45, 50 and 80 um). Their performance in terms of gain/collected charge and leakage current was compared before and after irradiation with neutrons and pions up to the equivalent fluences of 5e15 cm-2. Transient Current Technique and charge collection measurements with LHC speed electronics were employed to characterize the detectors. The thin LGAD sensors were shown to perform much better than sensors of standard thickness (~300 um) and offer larger charge collection with respect to detectors without gain layer for fluences <2e15 cm-2. Larger initial gain prolongs the beneficial performance of LGADs. Pions were found to be more damaging than neutrons at the same equivalent fluence, while no significant difference was found between different producers. At very high fluences and bias voltages the gain appears due to deep acceptors in the bulk, hence also in thin standard detectors.
The upgrades of ATLAS and CMS for the High Luminosity LHC (HL-LHC) highlighted physics objects timing as a tool to resolve primary interactions within a bunch crossing. Since the expected pile-up is around 200, with an r.m.s. time spread of 180 ps, a time resolution of about 30 ps is needed. The timing detectors will experience a 1-MeV neutron equivalent fluence of about $Phi_{eq}=10^{14}$ and $10^{15}$ cm$^{-2}$ for the barrel and end-cap regions, respectively. In this contribution, deep diffused Avalanche Photo Diodes (APDs) produced by Radiation Monitoring Devices are examined as candidate timing detectors for HL-LHC applications. To improve the detectors timing performance, the APDs are used to directly detect the traversing particles, without a radiator medium where light is produced. Devices with an active area of $8times8$ mm$^2$ were characterized in beam tests. The timing performance and signal properties were measured as a function of position on the detector using a beam telescope and a microchannel plate photomultiplier (MCP-PMT). Devices with an active area of $2times2$ mm$^2$ were used to determine the effects of radiation damage and characterized using a ps pulsed laser. These detectors were irradiated with neutrons up to $Phi_{eq}=10^{15}$ cm$^{-2}$.
The development of instrumentation to be operated in high-radiation environments is one of the main challenges in fundamental research. Besides space and nuclear applications, particle physics experiments also need radiation-hard devices. The focus of this paper is a new irradiation facility based on the medical cyclotron located at the Bern University Hospital (Insespital), which is used as a controlled 18 MeV proton source. The adjustable beam current allows for dose rate dependent characterisation over a large dynamic range, from 0.1 to 1000 Grad per hour. The beam can be tuned so that the user can obtain the desired irradiation conditions. A complete study of the device under irradiation is possible thanks to dedicated beam monitoring systems as well as a power control system for the device under irradiation, which can be operated on-line. Further characterisations of the irradiated devices are possible thanks to a laboratory equipped with gamma spectroscopy detectors, ammeters and transient current technique setups.
The prototype of the hadron calorimeter module consisting of 66 scintillator/lead layers with the 15x15 cm^2 cross section and 5 nuclear interaction lengths has been designed and produced for the zero degree calorimeter of the BM@N experiment. The prototype has been tested with high energy muon beam of the U-70 accelerator at IHEP. The results of the beam test for different types of photo multipliers and light guides are presented. The results of the Monte-Carlo simulation of the calorimeter response and energy resolution are presented for the 2-16 GeV protons.
Detectors based on polystyrene scintillator strips with WLS fiber readout are widely used to register charged particles in many high-energy physics experiments. The fibers are placed into grooves or holes along the strip. The detection efficiency of these devices can be significantly increased by improving the optical contact between the scintillator and the fiber by adding an optical filler into the groove/hole. This work is devoted to the study of the light yield of a 5-m-long scintillator strip with a 1.2-mm-diameter Kuraray Y11(200)~MC WLS fiber inserted into the strips co-extruded hole filled with synthetic silicon resin SKTN-MED(E). The light yield was studied using cosmic muons and a $^{60}$Co radioactive source. Radiation hardness study of viscous fillers and short strip samples were performed on the IBR-2 pulsed research reactor of fast neutrons at JINR.
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