# Online Program Overview Session: N-08

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## Photodetectors I

Session chair: Fabrice Retiere TRIUMF; Gabriella A. Carini SLAC

Shortcut: N-08
Date: Tuesday, October 24, 2017, 08:00
Room: Centennial I
Session type: NSS Session

SiPM centric session

### Contents

8:00 am N-08-1

#### Characterization and Comparison of recent novel SiPMs for Cherenkov Telescope Applications(#3097)

N. Otte1

1 Georgia Institute of Technology, Atlanta, United States of America

Content

We present the characteristics of the latest generation of blue sensitive Silicon photomultipliers (SiPMs) from FBK, Hamamatu, Ketek, and SensL. Measured parameters include the breakdown probability and the photon detection efficiency from 200 nm to 1000 nm as well as temperature dependent measurements between -40°C and +40°C of dark rates, afterpulsing, direct and delayed optical crosstalk, quench resistor values, recovery times, and cell capacitances over a wide range of overvoltages. The results will be discussed in the context of their expected performance in Cherenkov Telescopes.

We also show how the temperature and overvoltage dependencies of the majority of the SiPM characteristics can be understood with a small set of physical parameters and thus provides a deeper insight into the device physics of SiPMs.

Keywords: SiPMs, GAPD
8:18 am N-08-2

#### Performance evaluation of MPPC used for MEG II gamma ray detector(#1801)

N. Matsuzawa1

1 The University of Tokyo, ICEPP, Bunkyo, Tokyo, Japan

On behalf of MEG II collaboration

Content

MEG II is the upgraded experiment from MEG experiment, which aims to find charged lepton flavor violation $\mu^+ \to e^+\gamma$ with the world highest sensitivity. The expected sensitivity of MEG II is 4 ¥times 10^{-14}, which is ten times better than that of MEG. The gamma-ray detector for MEG II consists of 900 L liquid xenon surrounded by photon sensors. For the upgrade of the detector, 216 photo-multipliers on the gamma-ray incident wall are replaced with 4092 UV-sensitive Multi Pixel Photon Counters (MPPCs) which are developed uniquely for this experiment in cooperation with Hamamatsu Photonics K. K. The performance of the detector is expected to improve greatly with high granularity and uniformity for scintillation photons readout. The characteristics of these newly developed MPPCs must be well understood for precise operation of the detector. The performance evaluation of MPPCs was done and photon detection efficiency (PDE) was measured to be more than 15%, which is a sufficiently good performance. In addition, we carried out following measurements to understand the characteristics of the MPPC in detail. First, PDE is measured as the function against incident angle of photons. This characteristic is important for the reconstruction of gamma-ray position in high precision. Second, the absolute value of PDE is measured with the improved setup whose wall is coated with a special anti-reflective material. Commissioning of the detector is just started this year. The performance of the all MPPCs installed to the MEG II detector will also be evaluated by using the calibration sources. The result of the detailed performance study for MPPCs as well as the result of the first performance test on the detector will be reported.

Keywords: Particle Physics
8:36 am N-08-3

#### Silicon Photomultipliers for nEXO(#3570)

A. K. Soma1, I. Ostrovskiy1, F. Retiere2

1 The University of Alabama, Department of Physics and Astronomy, Tuscaloosa, Alabama, United States of America

Photodetector group of the nEXO collaboration

Content

Silicon Photomultipliers is an attractive candidate for light detectors for the next generation liquid xenon double-beta decay experiments, like nEXO. The nEXO collaboration has embarked on a broad campaign to characterize the relevant SiPM properties, including  photodetection efficiency at 175 nm in vacuum and in liquid xenon, the angular dependence of detection efficiency and reflectivity of silicon photomultipliers and relevant materials in vacuum and liquid xenon, performance in the vicinity of high voltage, rates of dark noise and correlated avalanches (cross-talk and after-pulsing), radio-purity of the sensors and related components. The collaboration is also gearing up toward the large area integration and electronic readout tests. The characterization campaign concentrates on the FBK devices as ones of the more attractive candidates, but also covers devices produced by Hamamatsu and other vendors. Here we will present the latest results of the measurements and discuss the future directions.

Keywords: double beta decay, silicon photomultipliers, liquid xenon, photodetection efficiency, reflectivity
8:54 am N-08-4

#### Low-energy X-ray Spectroscopy With RGB-HD SiPMs Coupled to CsI:Tl Scintillator(#3448)

A. Gola1, 2, F. Acerbi1, 2, A. Mazzi1, S. Merzi1, 3, G. Paternoster1, 2, G. Pepponi1, 2, N. Zorzi1, 2, C. Piemonte1, 2

1 Fondazione Bruno Kessler (FBK), Trento, Italy
2 Trento Institute for Fundamental Physics and Applications, Trento, Italy
3 University of Trento, Trento, Italy

Content

The continuous development of Silicon Photomultiplier (SiPM) technology allows use of these devices in different, new applications, such as the scintillation light readout for the detection of middle to low-energy X-ray photons. This application can be more challenging for the photodetector than the traditional PET application because of the much lower number of secondary photons generated in the scintillator. Many SiPM characteristics are important in determining the energy resolution, including the Photon Detection Efficiency (PDE), the primary noise and the Excess Noise Factor (ENF). The most recent development of the RGB-HD SiPM technology at Fondazione Bruno Kessler (FBK, Italy) provides a PDE in excess of 45% at 550 nm while keeping the Dark Count Rate (DCR) as low as 200 KHz/mm2. The low value of the DCR is fundamental in improving the energy resolution at low energy. We coupled a 4x4 mm2 RGB-HD SiPM to a 2.8x2.8x10 mm3 CsI:Tl crystal for the readout of a 57Co source. The 6.4 keV peak was well separated from the baseline. The best energy resolutions that we measured were: 36% at 6.4 keV, 26% at 14.4 keV and 11% at 122 keV. The energy resolution of these peaks showed different trends with respect to the SiPM bias and to the signal integration time. This is because the different components of the energy resolution feature a different dependence on the photon energy. In the presentation, we will discuss the effects on the energy resolution of SiPM parameters, such as PDE, DCR and ENF, and of readout electronics parameters, such as integration time and shaping type. Furthermore, the results of tests with MoKa (~17.5 keV) and lower energy photons obtained by fluorescence performed on an adapted diffraction-fluorescence instrument will be presented and discussed.

Keywords: Silicon Photomultipliers, Scintillators, X-rays, X-ray Spectroscopy
9:12 am N-08-5

#### Towards a fully digital state-of-the-art analog SiPM(#4220)

A. Muntean1, E. Venialgo1, S. Gnecchi2, C. Jackson2, E. Charbon1, 3

1 Delft University of Technology, Faculty of Electrical Engineering, Delft, Netherlands
2 SensL, Cork, Ireland
3 EPFL, Lausanne, Switzerland

Content

We present a design that implements digitization of an analog SiPM’s fast output on chip, so as to minimize complexity and to pave the way to an increase of granularity in the digital conversion of the photon detection. The design comprises a comparator bank, time-to-digital converters (TDCs), and electronics for interfacing with the external world. The TDC is a multipath, gated ring oscillator with a counter and phase detector, implemented in 0.35μm CMOS technology. Initial simulation results indicate a highly linear behavior with a DNL below 0.1LSB and a large, adjustable range, with a maximum resolution of 30ps.

Keywords: Silicon photomultiplier, time-to-digital converter, DNL, INL
9:30 am N-08-6

#### Towards 10ps SPTR and Ultra-Low DCR in SiPMs Through the Combination of Microlenses and Photonic Crystals(#3600)

F. Gramuglia1, M. - J. Lee1, E. Venialgo2, C. Bruschini1, E. Charbon1, 2

1 EPFL, EDMI, Neuchâtel, Neuchâtel, Switzerland
2 TUDELFT, Delft, Netherlands

Content

Silicon Photomultipliers (SiPMs), which emerged as all solid state, MRI compatible alternative to PMTs, can provide high miniaturization and increased timing performance. Large effort has been spent in improving the figures of merit of such devices (e.g. jitter, timing resolution, sensitivity, noise, etc.). In this paper we propose a novel approach relying on the combination of photonic crystals with microlens arrays, integrated on top of each SPAD cell in the SiPM, to collimate and focus the light generated by a scintillator, in order to improve the overall timing performance of the system so as to approach the 10ps target, while at the same time reducing the noise floor (Dark Count Rate).

Keywords: Collimator, Low Jitter, Low noise, MD-SiPM, Microlens, Photonic crystal, Scintillator, SPAD