Single Photon Counting Capability Research Articles

A readout system based on SiPM for the dRICH detector at the EIC

The ePIC experiment at the future Electron-Ion Collider (EIC) aims to use silicon photomultipliers (SiPMs) as the photodetector technology for the dual-radiator ring-imaging Cherenkov detector (dRICH). Despite their advantages for this low light application and insensitivity to high magnetic fields, SiPMs are sensitive to radiation and require rigorous testing to ensure that their single-photon counting capabilities and dark count rate are kept under control over the years of operation. The presented results show the successful use of a complete prototype readout chain based on the ALCOR chip for SiPM characterization measurements and assembled in an optical plane for test-beam measurements using the dRICH prototype.

A SiPM-based optical readout system for the EIC dual-radiator RICH

Silicon photomultipliers (SiPM) are candidates selected as the potential photodetector technology for the dual-radiator Ring-Imaging Cherenkov (dRICH) detector at the future Electron-Ion Collider (EIC). SiPM are cheap devices, highly efficient and insensitive to the high magnetic field at the expected location of the sensors in the experiment. On the other hand, SiPM are not radiation tolerant. Despite the integrated radiation level is expected to be moderate it should be tested whether single photon-counting capabilities and the increase in dark count rate can be kept under control to maintain the optimal dRICH detector performance across the years. The current status of the research for the EIC dRICH application and the first results on studies performed on a sample of commercial and prototype SiPM sensors are presented.

Front-End Design for SiPM-Based Monolithic Neutron Double Scatter Imagers.

Neutron double scatter imaging exploits the kinematics of neutron elastic scattering to enable emission imaging of neutron sources. Due to the relatively low coincidence detection efficiency of fast neutrons in organic scintillator arrays, imaging efficiency for double scatter cameras can also be low. One method to realize significant gains in neutron coincidence detection efficiency is to develop neutron double scatter detectors which employ monolithic blocks of organic scintillator, instrumented with photosensor arrays on multiple faces to enable 3D position and multi-interaction time pickoff. Silicon photomultipliers (SiPMs) have several advantageous characteristics for this approach, including high photon detection efficiency (PDE), good single photon time resolution (SPTR), high gain that translates to single photon counting capabilities, and ability to be tiled into large arrays with high packing fraction and photosensitive area fill factor. However, they also have a tradeoff in high uncorrelated and correlated noise rates (dark counts from thermionic emissions and optical photon crosstalk generated during avalanche) which may complicate event positioning algorithms. We have evaluated the noise characteristics and SPTR of Hamamatsu S13360-6075 SiPMs with low noise, fast electronic readout for integration into a monolithic neutron scatter camera prototype. The sensors and electronic readout were implemented in a small-scale prototype detector in order to estimate expected noise performance for a monolithic neutron scatter camera and perform proof-of-concept measurements for scintillation photon counting and three-dimensional event positioning.

Rising Speed Limits for Fluxons via Edge-Quality Improvement in Wide MoSi Thin Films

Ultra-fast vortex motion has recently become a subject of extensive investigations, triggered by the fundamental question regarding the ultimate speed limits for magnetic flux quanta and enhancements of single-photon detectors. In this regard, the current-biased quench of a dynamic flux-flow regime - flux-flow instability (FFI) - has turned into a widely used method for the extraction of information about the relaxation of quasiparticles (unpaired electrons) in the superconductor. However, the large relaxation times $\tau_\epsilon$ deduced from FFI for many superconductors are often inconsistent with the fast relaxation processes implied by their single-photon counting capability. Here, we investigate FFI in $15$ nm-thick $182$ $\mu$m-wide MoSi strips with rough and smooth edges produced by laser etching and milling by a focused ion beam. For the strip with smooth edges we deduce, from the current-voltage ($I$-$V$) curve measurements, a factor of 3 larger critical currents $I_\mathrm{c}$, a factor of 20 higher maximal vortex velocities of 20 km/s, and a factor of 40 shorter $\tau_\epsilon$. We argue that for the deduction of the intrinsic $\tau_\epsilon$ of the material from the $I$-$V$ curves, utmost care should be taken regarding the edge and sample quality and such a deduction is justified only if the field dependence of $I_\mathrm{c}$ points to the dominating edge pinning of vortices.

Pre-flight qualification tests of the Mini-EUSO telescope engineering model

Mini-EUSO is part of the JEM-EUSO program and operates on board the International Space Station (ISS). It is a UV-telescope with single-photon counting capability looking at nighttime downwards to the Earth through a nadir-facing UV-transparent window. As part of the pre-flight tests, the Mini-EUSO engineering model, a telescope with 1/9 of the original focal surface and a lens of 2.5 cm diameter, has been built and tested. Tests of the Mini-EUSO engineering model have been made in laboratory and in open-sky conditions. Laboratory tests have been performed at the TurLab facility, located at the Physics Department of the University of Turin, equipped with a rotating tank containing different types of materials and light sources. In this way, the configuration for the observation of the Earth from space was emulated, including the Mini-EUSO trigger schemes. In addition to the qualification and calibration tests, the Mini-EUSO engineering model has also been used to evaluate the possibility of using a JEM-EUSO-type detector for applications such as observation of space debris. Furthermore, observations in open-sky conditions allowed the studies of natural light sources such as stars, meteors, planets, and artificial light sources such as airplanes, satellites reflecting the sunlight, and city lights. Most of these targets could be detected also with Mini-EUSO. In this paper, the tests in laboratory and in open-sky conditions are reported, as well as the obtained results. In addition, the contribution that such tests provided to foresee and improve the performance of Mini-EUSO on board the ISS is discussed.

The 2-inches VSiPMT industrial prototypes

Photon detection is a key factor to study many physical processes in several areas of fundamental physics research. Focusing the attention on photodetectors for particle astrophysics, we understand that we are very close to new discoveries and new results. In order to push the progress in the study of very high-energy or extremely rare phenomena (e.g. dark matter, proton decay, neutrinos from astrophysical sources) the current and future experiments require additional improvements in linearity, gain, quantum efficiency and single photon counting capability. To meet the requirements of these classes of experiments, we propose a new design for a modern hybrid photodetector: the VSiPMT (Vacuum Silicon PhotoMultiplier Tube).The idea is to replace the classical dynode chain of a PMT with a SiPM, which therefore acts as a single stage Geiger electron detector and amplifier, without statistical fluctuations. The aim is to match the large sensitive area of a photocathode with the performances of the SiPM technology. The previous VSiPMT prototypes already showed many attractive features such as low power consumption, very large dynamic range, excellent photon counting capability and low voltage driven gain.We now present the results of the full characterization of the latest and largest version achieved up to now, a 2-inches VSiPMT manufactured by Hamamatsu.

On the Charge Collection Efficiency of the PERCIVAL Detector

The PERCIVAL soft X-ray imager is being developed by DESY, RAL, Elettra, DLS, and PAL to address the challenges at high brilliance Light Sources such as new-generation Synchrotrons and Free Electron Lasers. Typical requirements for detector systems at these sources are high frame rates, large dynamic range, single-photon counting capability with low probability of false positives, high quantum efficiency, and (multi)-mega-pixel arrangements. PERCIVAL is a monolithic active pixel sensor, based on CMOS technology. It is designed for the soft X-ray regime and, therefore, it is post-processed in order to achieve high quantum efficiency in its primary energy range (250 eV to 1 keV) . This work will report on the latest experimental results on charge collection efficiency obtained for multiple back-side-illuminated test sensors during two campaigns, at the P04 beam-line at PETRA III, and the CiPo beam-line at Elettra, spanning most of the primary energy range as well as testing the performance for photon-energies below 250 eV . In addition, XPS surface analysis was used to cross-check the obtained results.

Quantum Random Number Generation Using a Quanta Image Sensor.

A new quantum random number generation method is proposed. The method is based on the randomness of the photon emission process and the single photon counting capability of the Quanta Image Sensor (QIS). It has the potential to generate high-quality random numbers with remarkable data output rate. In this paper, the principle of photon statistics and theory of entropy are discussed. Sample data were collected with QIS jot device, and its randomness quality was analyzed. The randomness assessment method and results are discussed.

Characterisation of a PERCIVAL monolithic active pixel prototype using synchrotron radiation

PERCIVAL (“Pixelated Energy Resolving CMOS Imager, Versatile And Large”) is a monolithic active pixel sensor (MAPS) based on CMOS technology. Is being developed by DESY, RAL/STFC, Elettra, DLS, and PAL to address the various requirements of detectors at synchrotron radiation sources and Free Electron Lasers (FELs) in the soft X-ray regime. These requirements include high frame rates and FELs base-rate compatibility, large dynamic range, single-photon counting capability with low probability of false positives, high quantum efficiency (QE), and (multi-)megapixel arrangements with good spatial resolution. Small-scale back-side-illuminated (BSI) prototype systems are undergoing detailed testing with X-rays and optical photons, in preparation of submission of a larger sensor. A first BSI processed prototype was tested in 2014 and a preliminary result—first detection of 350eV photons with some pixel types of PERCIVAL—reported at this meeting a year ago. Subsequent more detailed analysis revealed a very low QE and pointed to contamination as a possible cause. In the past year, BSI-processed chips on two more wafers were tested and their response to soft X-ray evaluated. We report here the improved charge collection efficiency (CCE) of different PERCIVAL pixel types for 400eV soft X-rays together with Airy patterns, response to a flat field, and noise performance for such a newly BSI-processed prototype sensor.

VSiPMT a new photon detector

Photon detection is a key factor to study many physical processes in several areas of fundamental physics research. Focusing the attention on photodetectors for particle astrophysics, the future experiments aimed at the study of very high-energy or extremely rare phenomena (e.g. dark matter, proton decay, neutrinos from astrophysical sources) will require additional improvements in linearity, gain, quantum efficiency and single photon counting capability. To meet the requirements of these class of experiments, we propose a new design for a modern hybrid photodetector: the VSiPMT (Vacuum Silicon PhotoMultiplier Tube). The idea is to replace the classical dynode chain of a PMT with a SiPM, which therefore acts as an electron detector and amplifier. The aim is to match the large sensitive area of a photocathode with the performances of the SiPM technology.

The PERCIVAL soft X-ray imager

With the increased brilliance of state-of-the-art Synchrotron radiation sources and the advent of Free Electron Lasers enabling revolutionary science on atomic length and time scales with EUV to X-ray photons comes an urgent need for suitable photon imaging detectors. Requirements include high frame rates, very large dynamic range, single-photon counting capability with low probability of false positives, and (multi)-megapixels. PERCIVAL (``Pixelated Energy Resolving CMOS Imager, Versatile And Large'') is currently being developed by a collaboration of DESY, RAL, Elettra, DLS and Pohang to address this need for the soft X-ray regime. PERCIVAL is a monolithic active pixel sensor (MAPS), i.e. based on CMOS technology. It will be back-thinned to access its primary energy range of 250 eV to 1 keV with target efficiencies above 90%. According to its preliminary specifications, the roughly 10 × 10 cm2, 3.5k × 3.7k monolithic ``PERCIVAL13M'' sensor will operate at frame rates up to 120 Hz (commensurate with most FELs) and use multiple gains within its 27 μm pixels to measure 1 to ∼ 105 (500 eV) simultaneously-arriving photons. A smaller ``PERCIVAL2M'' with ∼ 1.4k × 1.5k pixels is also planned. Currently, small-scale back-illuminated prototype systems (160 × 210 pixels of 25 μm pitch) are undergoing detailed testing with X-rays and optical photons. In March 2014, a prototype sensor was tested at 350 eV–2 keV at Elettra's TwinMic beamline. The data recorded include diffraction patterns at 350 eV and 400 eV, knife edge and sub-pixel pinhole illuminations, and comparisons of different pixel types. Another prototype chip will be submitted in fall 2014, first larger sensors could be in hand in late 2015.

Radiation hardness of silicon photomultipliers under 60Co γ-ray irradiation

Radiation damage in silicon photomultipliers (SiPM) caused by exposure to 60Co γ-rays is experimentally evaluated and discussed. SiPM devices were irradiated to doses up to 9.4kGy. Dark current, dark count rate, gain, single photon counting capability, and cross-talk probability among SiPM pixels are evaluated as a function of irradiation dose.

High-Temperature Single Photon Detection Performance of 4H-SiC Avalanche Photodiodes

In this letter, the high-temperature performance of 4H-SiC avalanche photodiodes (APDs) working in Geiger mode is studied for the first time. At unity gain bias, the maximum quantum efficiency of the APD increases from 53.4% at 290 nm to 63.3% at 295 nm as temperature rises from room temperature to 150 °C. Meanwhile, the dark current of the APD before breakdown increases by more than two to three orders of magnitude. At a fixed gain of 1.3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> , the single photon counting efficiency at 280 nm only slightly drops from 6.17% to 6% in the same temperature range, whereas the dark count rate increases from 22 to 80 KHz. This letter indicates that SiC APDs have the potential to work in a high-temperature harsh environment with single photon counting capability.

The PERCIVAL soft X-ray imager

With the increased brilliance of state-of-the-art Synchrotron radiation sources and the advent of Free Electron Lasers enabling revolutionary science with EUV to X-ray photons comes an urgent need for suitable photon imaging detectors. Requirements include high frame rates, very large dynamic range, single-photon counting capability with low probability of false positives, and (multi)-megapixels.PERCIVAL (``Pixelated Energy Resolving CMOS Imager, Versatile and Large'') is currently being developed by a collaboration of DESY, RAL, Elettra and DLS to address this need for the soft X-ray regime. PERCIVAL is a monolithic active pixel sensor (MAPS), i.e. based on CMOS technology. It will be back-thinned to access its primary energy range of 250 eV to 1 keV with target efficiencies above 90%. According to its preliminary specifications, the roughly 10 × 10 cm2, 3520 × 3710 pixel monolithic sensor will operate at frame rates up to 120 Hz (commensurate with most FELs) and use multiple gains within its 27 μm pixels to measure (e.g. at 500 eV)1 to ∼ 105 simultaneously-arriving photons.Currently, small-scale front-illuminated prototype systems (160 × 210 pixels) are undergoing detailed testing with visible-light as well as X-ray photons.

Simulating the Counting Mechanism of PILATUS2 and PILATUS3 Detectors for Improved Count Rate Corrections

PILATUS systems are well established as X-ray detectors at most synchrotrons. Their single photon counting capability ensures precise measurements, but introduces a short dead time after each hit, which becomes significant for photon rates above a million per second and pixel. The resulting loss in the number of counted photons can be corrected for by applying corresponding rate correction factors. This article presents a Monte-Carlo simulation, which computes the correction factors taking into account the detector settings as well as the time structure of the X-ray beam at the synchrotron. For the PILATUS2 detector series the simulation shows good agreement with experimentally determined correction factors for various detector settings at different synchrotrons. The application of more accurate rate correction factors will improve the X-ray data quality at high photon fluxes. Furthermore we report on the simulation of the rate correction factors for the new PILATUS3 systems. The successor of the PILATUS2 detector avoids the paralysation of the counter, and allows for measurements up to a rate of ten million photons per second and pixel. For fast detector settings the simulation is capable of reproducing the data within one to two percent at an incoming photon rate of one million per second and pixel.

K-shell spectroscopy of silicon ions as diagnostic for high electric fields

We developed a detection scheme, capable of measuring X-ray line shape of tracer ions in μm thick layers at the rear side of a target foil irradiated by ultra intense laser pulses. We performed simulations of the effect of strong electric fields on the K-shell emission of silicon and developed a spectrometer dedicated to record this emission. The combination of a cylindrically bent crystal in von Hámos geometry and a CCD camera with its single photon counting capability allows for a high dynamic range of the instrument and background free spectra. This approach will be used in future experiments to study electric fields of the order of TV/m at high density plasmas close to solid density.

47 GOALS AND CHALLENGES OF THE ENDOTOFPET-US FP7 PROJECT

EndoTOFPET-US is an approved European FP7 multidisciplinary project involving an international collaboration of 6 academic institutions (CERN, DESY, Delft Technical University, Lisbon LIP laboratory, University of Heidelberg, University Milano Biccoca), 3 university hospitals (Marseilles Timone, Lausanne CHUV, Minich Technical University hospital) and 3 companies (Fibercryst, KLOE, Surgiceye). The main clinical objective is the development of new biomarkers for the pancreatic cancer and more generally image-guided diagnosis and minimally invasive surgery. In the frame of this project it is proposed to design and build one prototype of a bimodal PET-US (Positron Emission Tomography and Ultrasound) endoscopic probe combining in a miniaturized system a fully digital, 200ps time resolution Time of Flight PET detector head (TOF-PET) coupled to a commercial ultrasound (US) assisted biopsy endoscope and to launch a pilot clinical study focusing on pancreatic cancer, after a first step of preclinical feasibility tests on pigs. As an example of novel development of biomarkers, promising antibodies already developed for pancreatic cancer will be pushed towards clinical application. In order to achieve this very ambitious goal this project will implement a number of novel technologies, among which a new generation of fully digital SiPM photodetectors with single optical photon counting capability, a very compact diffractive optics coupling system between the crystal and the photodetector to compensate for the reduced fill-factor of the later, a low noise time over threshold front end electronics based on the NINO chip developed at CERN for the LHC ALICE experiment and an elaborate tracking system to reconstruct in real time the six coordinates of the internal endoscopic probe and the external plate of the PET detection system. First performance results of these different components will be presented, including an impressive coincidence time resolution of 155 to 210ps FWHM obtained with crystals of realistic dimensions for the PET (for a length ranging between 5mm and 20mm respectively) using the NINO electronics and a commercial, not yet digital SIPM photodetector. The possible implementation of such techniques in an on-line dose monitoring PET system in hadrontherapy machines will be discussed. * corresponding author e-mail: paul.lecoq@cern.ch

APDs as single-photon detectors for visible and near-infrared wavelengths down to Hz rates

For the SPECTRAP experiment at GSI, Germany, detectors with single-photon counting capability in the visible and near-infrared regime are required. For the wavelength region up to 1100 nm we investigate the performance of 2 × 2 mm2 avalanche photo diodes (APDs) of type S0223 manufactured by Radiation Monitoring Devices. To minimize thermal noise, the APDs are cooled to approximately -170°C using liquid nitrogen. By operating the diodes close to the breakdown voltage it is possible to achieve relative gains in excess of 2⋅104. Custom-made low noise preamplifiers are used to read out the devices. The measurements presented in this paper have been obtained at a relative gain of 2.2⋅104. At a discriminator threshold of 6 mV the resulting dark count rate is in the region of 230 s−1. With these settings the studied APDs are able to detect single-photons at 628 nm wavelength with a photo detection efficiency of (67±7)%. Measurements at 1020 nm wavelength have been performed using the attenuated output of a grating spectrograph with a light bulb as photon source. With this setup the photo detection efficiency at 1020 nm has been determined to be (13±3)%, again at a threshold of 6 mV.

SiPM interdisciplinary application in the fields of astroparticle physics and bio-molecular science

In the last few years we have developed a sub-μs 256 channel camera using Silicon Photomultipliers (SiPMs) for interdisciplinary application in various fields such as astroparticle physics and bio-molecular science.The camera consists of 256 pixels of SiPMs (16×16-ch Hamamatsu MPPCs) read by 16 of 16-ch ASICs, and two data processing system boards which are capable of a sampling data rate of 166MHz.The technology of this camera is based on a space-borne fluorescence telescope, JEM-EUSO [1]. Also, the SiPMs that we use for the camera are the ones developed for astroparticle physics applications in imaging atmospheric Cherenkov telescopes (IACTs) such as MAGIC/MAGIC-II (Albert et al., 2008 [2]) and CTA [3].The fast, high spatial and temporal resolution camera with single photon counting capability enables us to open a new window not only in astroparticle physics but also in bio-molecular science.Here we report on the camera development. Also, status of the applications in imaging air Cherenkov events and protein dynamics observations, molecular motor dynamics observations will be reported.

Medipix2 based CdTe microprobe for dental imaging

Medical imaging devices and techniques are demanded to provide high resolution and low dose images of samples or patients. Hybrid semiconductor single photon counting devices together with suitable sensor materials and advanced techniques of image reconstruction fulfil these requirements. In particular cases such as the direct observation of dental implants also the size of the imaging device itself plays a critical role. This work presents the comparison of 2D radiographs of tooth provided by a standard commercial dental imaging system (Gendex 765DC X-ray tube with VisualiX scintillation detector) and two Medipix2 USB Lite detectors one equipped with a Si sensor (300 μm thick) and one with a CdTe sensor (1 mm thick). Single photon counting capability of the Medipix2 device allows virtually unlimited dynamic range of the images and thus increases the contrast significantly. The dimensions of the whole USB Lite device are only 15 mm × 60 mm of which 25% consists of the sensitive area. Detector of this compact size can be used directly inside the patients' mouth.