International Conference on New Photo-Detectors (PD15)

Review talk on SiPM's

Silicon Photomultipliers (SiPMs) are a novel generation of photon detectors designed as an array of independently operated Geiger-mode APDs (pixels) with common output. SiPM provides proportional detection of low-level light pulses starting from single photons with remarkable photon number and time resolution at room temperature. Now they are worldwide recognized to be competitive with vacuum photomultiplier tubes (PMTs) and avalanche photodiodes (APDs) for scintillation and Cherenkov light detections in such areas as particle physics and nuclear medicine. Well-known specific drawbacks of SiPMs are excess noises caused by stochastic processes of crosstalk and afterpulsing as well as non-linearity and saturation of SiPM response to intense light pulses due to limited number of pixels and non-instant pixel recovery.
This study presents an analysis of SiPM performance based on probability distributions of the key stochastic processes affecting SiPM response: photo-conversion, dark generation, avalanche multiplication, crosstalk and afterpulsing, non-linearity and saturation losses. SiPM performance in photon number resolution (energy) is represented in terms of specific excess noise factors of these processes identified as comparable metrics of their contributions. SiPM time resolution is shown to be defined by photon number resolution and by temporal profiles of photon arrival and photon detection time distributions, and a single electron response.
Analytical results of this approach are applied to compare a performance of the modern SiPMs with each other and with conventional PMTs and APDs in typical scintillation and Cherenkov detection applications. The results also seem to be useful for SiPM characterization, selection, and application-specific optimization as well as for SiPM design improvements.

Silicon Photomultipliers (SiPMs) are attractive candidates for light detectors for next generation liquid xenon double-beta decay experiments, like nEXO. One of the main requirements that the SiPMs must satisfy in order to be suitable for nEXO is high photon detection efficiency (PDE) at 175 nm, either directly or using a wavelength shifter. In addition, the devices should demonstrate sufficiently low levels of dark noise and correlated avalanche rates at liquid xenon temperature. We currently collaborate with several manufacturers for the development of SiPMs with high photon detection efficiency at 175nm. In parallel, we are also investigating new wavelength shifting materials produced by Luminotech (Moscow, Russia) that are coated on top of SiPMs and promise high performance, ease of handling, and compatibility with operation in liquid xenon. Devices produced by FBK, Hamamatsu, and other vendors have been characterized in details, measuring key SiPM parameters at cryogenic temperatures (-100C) in vacuum including absolute PDE at 175 nm, rates of dark noise, after-pulses, and cross-talk. A new test setup has recently been commissioned for measuring SiPMs performance in liquid xenon. Additionally, the nEXO collaboration is performing sensitive assessment of radioactivity content of the SiPMs to ensure that their pass our stringent radio-purity requirements. In this talk, we will describe the test setups, the measurement approaches, and present recent results obtained with the latest generations of SiPMs produced by FBK, Hamamatsu, and other vendors, including Hamamatsu MPPCs coated with wavelength shifters.

The DIAPHANE project is pluri-disciplinary collaboration between particle and ge
o-physicists to perform the tomography of large geological structure mainly devoted to the study of active volcanoes. The detector used for this tomography, hereafter referred to as telescope, uses a standard, robust, cost-effective and
 well-known opto-electronics technology based on photomultipliers (either multichannel pixelized PM or silicon PM). The electronics system is built on the concept of autonomous, triggerless, smart sensor directly connected on a standard fast Ethernet network. 
In this talk the potential of the technique is detailed and discussed in the context of underground laboratories (long-term storage problems) and of active volcanoes. I will present recent results obtained on the Lesser Antilles volcanoes (Soufrière of Guadeloupe, Soufriere Hills of Montserrat), on the Etna in Sicily and on the Mayon in the Philippines.  
In particular I will show how the technique improved with time (embedding a sub-nanosecond resolution TDC within the existing programmable logic to reject background) and allows nowadays to monitor the activity of phreatic volcanoes and to constrain the geophysical models.

The First G-APD Cherenkov Telescope (FACT) has been operating since
October 2011. Its construction was a major step forward in establishing
solid state photon counters as detectors in focal plane
instrumentations. The camera is comprised of 1440 sensor arrays of
Geiger-mode avalanche photo diodes (G-APD), equipped with solid light
guides to increase the light collection area of each sensor.  Methods
were successfully developed to overcome the temperature dependence of
the gain of these sensors and to correct for the voltage drop induced
during moonlit nights increasing the duty cycle of such instruments
significantly. The availability of this number of sensors allowed for a
detailed study of the dependence of their properties on overvoltage and
temperature. High statistics featured the study of optical crosstalk up
to high multiplicities. With its outstanding gain stability and its
high duty cycle, the telescope is ideally suited for monitoring of
bright TeV blazars. A technical overview of this novel type camera and
a summary of the achieved sensor performance will be presented.

MAGIC is an imaging atmospheric telescope used for gamma ray astronomy. Both the original and the upgraded imaging telescope cameras in use rely on photomultipliers as the photon detectors. In preparation for their possible future use in MAGIC or subsequent telescopes, a camera module with silicon photomultiplier detectors has been developed for operation alongside the existing camera in the telescope. Front end imaging and electronics challenges and solutions are discussed, including the issues of fast analog pulse summation (~4 nsec) of several devices, and the tradeoffs specific to this application's operating environment.

In order to improve hadron energy measurement, we are investigating to utilize active absorber in the sampling hadron calorimeter. The active absorber consists of heavy transparent material such as Lead Glass and thin photo-sensors attached to form sampling calorimeter. The detection of Cherenkov lights needs to overcome the low light yield and to have enough sensitivity for short wave length region. We discuss our current study and further improvements at the conference.

The scintillation detectors characteristics of GAMMA-400 gamma-ray space telescope constructed with the implementation of silicon photomultipliers manufactured by different manufacturers are reported. The measurements were carried out at the technological model of the gamma-ray telescope. The efficiency, amplitude ant timing properties of fast plastic large area scintillators and also calorimeter detectors based on non-organic CsI(Tl) scintillators were investigated. The detectors characteristics matching to the requirements for the systems of gamma-ray telescope is shown.

Scintillating fibers coupled to photosensors provide flexible, fast and high granularity detectors
which are able to work in a high rate environment. We will report about the performances obtained
with several detector prototypes (single and multi-layers) based on 250 $\mu$m multi clad square
scintillating fibers coupled to Hamamatsu silicon photomultiplier (SiPMs).
Current measurements show results never reached up to now: very high detection efficiency for
minimum ionizing particles (m.i.p.) already for a single layer (95%, mean collected light/fiber 8 phe), and full efficiency for multilayer configurations. Spatial resolutions $< 100 \mu$m are foreseen
for single layer and much less for multilayer devices. Such spatial resolutions can be achieved by
keeping the optical cross-talk between fibers at a negligible level ($<$ 1%), a level which we have
proven to be obtainable when coating the fibers with aluminum. Finally, timing resolutions of
the order of 500 ps have been achieved for m.i.p. (single layer configuration), resolutions that
become better for multi hit events (multilayer configuration). A comparison between the detector
performances for m.i.p. and highly ionizing particle (stopped muons) will also be given, showing
the possibility of particle identification based on the large difference of the energy deposit on the
scintillator by the two particles.
Finally results as beam monitoring tool will be shown, with measurements performed along the
Paul Scherrer Institute beam lines, which provide the most intense continuous muon beam in the
world.
All measurements have been supported with a Monte Carlo simulation based on Geant4 and a
custom code, describing the response of the SiPMs.

The compact size, fast response time and insensitivity to magnetic fields, turn the silicon photomultipliers (SiPM) into a suitable solution for experiments like Mu3e, where time information, with less than a nanosecond precision, is required. In the present talk we report on the performance of $250{\mu m}$ scintillating fibers staggered into ribbons and readout by Hamamatsu MPPCs. The analogue signals were first amplified and then fed to constant fraction discriminators, after which they were digitized through standard VME TDC and QDC modules. We have tested two fiber-SiPM coupling configurations: one with individual fibers matched to single sensors, and another with whole ribbons attached to LHCb-type arrays. The time and position resolving capabilities of the systems were evaluated in conditions where either very low or extremely high number of photons were incident on the photodetectors.

We have been developing a positron timing counter for the MEG II experiment which aims to search for $\mu^{+} \rightarrow e^{+} \gamma$ decay with an unprecedented sensitivity. It is expected to have an ultimate time resolution of $\sim$30 ps in the high rate environment of the MEG II experiment. We employed a “pixelated” design with $\sim$500 small counters, each of which is based on a fast plastic scintillator plate readout by multiple SiPMs connected in series. 
This SiPM readout scheme provides a sharp signal waveform and a maximum light collection and thus, a good time resolution of each counter.
Furthermore the overall time resolution can be significantly improved by simultaneous multiple timing measurements with several counters.
We performed beam tests with a prototype detector and achieved an excellent overall time resolution of $\sim$35ps.
In this talk the design and performance of the pixelated timing counter will be presented

Highlights of Poster Session

In this talk, recent progress in the development of photomultiplier tubes (mainly ones with a large aperture) will be reviewed. The status of the large aperture hybrid photodetector (HPD) development will also be covered.

Hamamatsu Photonics has been providing several types of vacuum photon detectors for HEP experiments in many years. We have been making effort to develop new products accordingly. In this time, fast time response PMT series is shown as example. It includes 4 kinds of PMT sizes from 1-inch to 2-inch. T.T.S. of 170 ps was achieved in 1-1/8-inch PMT. This fast time response PMT series is suitable for TOF counter as well as PET in medical field. A new 20-inch PMT has been also developed for Neutrino physics experiments. It has high C.E. and fast time response. The details of these PMTs and other developmental products will be shown in this presentation.

Hyper-Kamiokande is a proposed future neutrino experiment with various physics goals such as the discovery of leptonic CP violation, nucleon decay, supernova neutrino, and so on, using a 1 Mton water Cherenkov detector.
Because of the large volume, About 99000 of 20 inch photosensors are planed to set in 
the detector. (About 9 times as many as 20 inch photosensor in Super-Kamiokande)
Considering a cost of photodetectors in Hyper-Kamiokande detector, more
cost-effective and higher performance large-area photodetectors are desired.

A 20-inch diameter Box and Line PMT is a candidate photodetector for Hyper-Kamiokande, which has different type dynodes from PMTs in Super-Kamiokande (Hamamatsu R3600). 
Owing to an improvement on dynodes shape, a collection efficiency of photoelectrons becomes better than the R3600 PMT. In addition, a good timing resolution is obtained by a little variation of electrons’ path during its multiplication.
The first type of Box and Line PMT was developed in 2014 and the basic performances evaluation is ongoing to decide the photosensor for Hyper-Kamiokande.

In this presentation, I will describe the current evaluation status of the basic performance like 1 photoelectron charge distribution, timing resolution, gain, dark rate, and status of more detailed performance like after pulse rate measurement.

Hyper-Kamiokande is a next generation huge water Cherenkov detector proposed for a discovery of proton decay and neutrino observations. It is planed to have 20 times larger volume than Super-Kamiokande, with 100,000 next generation photo sensors. One candidate of the sensor is a 50 cm Box-and-Line dynode photomultiplier tube (BL PMT), which have excellent time resolution and energy resolution. However, the performance of the BL PMT is to be confirmed under a condition expected in Hyper-Kamikoande. For example, a response of the BL PMT is affected by a geomagnetic field especially in a certain direction. Since Hyper-Kamiokande is a large detector, the geomagnetic field cannot be completely canceled and the effect cannot be ignored. And the temperature in Hyper-Kamiokande is presumably different with usual environment, therefore, the temperature dependency has to be also checked. Such kind of a precise investigation in BL PMT has never been performed, though the design concept and the basic performance are established.

In this presentation, several results of these specific characteristics will be reported, i.e., the effect of the magnetic field, the temperature, the incident point of photons, and the high-voltage value. The comparison of their effects to the original designed value will be also discussed.

A large-aperture photodetector is essential for a large-volume detector aiming at a neutrino physics and a nuclear decay search. Several new photodetectors with high resolution and efficiency have been developed for a one megaton water Čerenkov detector, Hyper-Kamiokande, planned in Japan. A proof test started in 2013 using a 200-ton water Čerenkov detector to evaluate feasibility of high quantum efficiency (HQE), a hybrid photodetector (HPD) and a photomultiplier tube (PMT) with a box-and-line (BL) dynode. 
Eight HPDs with a 20 cm diameter were installed to the 200-ton water tank in advance of a 50 cm HPD. A 50 cm Venetian-blind PMT used in Super-Kamiokande was improved with the HQE of 30% from 22%, and there were five PMTs attached as well in 2013. In addition, three 50 cm HQE BL PMTs joined in 2014, which showed high detection performance at a single photoelectron. In total in the 200-ton tank, 240 photodetectors including the 50 cm conventional Super-Kamiokande PMT have been tested over a year. Based on results in the proof test, the best candidate photodetector for Hyper-Kamiokande will be decided in 2016. A primary result on a calibration, long-term stability for a year and performance will be reported.

Photomultiplier Tubes (PMT) are the most wide spread light detectors for measuring fast and faint signals. About six years ago we started an improvement program for the PMT candidates for the Cherenkov Telescope Array (CTA) project with the companies Hamamatsu Photonics K.K. (Japan) and Electron Tubes Enterprises Ltd. (England). CTA is the next major Imaging Atmospheric Cherenkov Telescopes array for high energy gamma-ray astrophysics, about 100 telescopes of sizes of 23m, 12m and 4m will be built in Northern and Southern hemispheres.  For CTA we need PMTs with the highest quantum efficiency, maximized photo electron collection efficiency, short pulse width of a few ns, very low after-pulsing and transit time spread.  The manufacturers were able to produce 1.5 ‘ PMTs of enhanced peak quantum efficiency of ~ 40%. These can collect up to 95-98% of photo electrons onto the first dynode for the wavelengths ≥ 400nm. A pulse width of ≤ 3ns has been achieved at the selected operational gain of 40k. The after-pulsing for a threshold of ≥ 4 photo electrons is reduced down to the level of 0.02%.
We will report on the measurements of PMT R-12292-100 from Hamamatsu and the PMT D573KFLSB as the latest iteration from Electron Tubes Enterprises as candidate PMTs for the CTA project.

Detectors, based on liquefied noble gases, are becoming more and more important in the field of neutrino and rare events physics. The measurement of scintillation light produced at the passage of an ionizing particle in the liquid medium plays a crucial role in these detectors and Photo-Multiplier Tubes (PMTs), directly immersed in liquid argon or xenon at cryogenic temperature, represent the most adopted devices, when working in absence of magnetic field. In view of future application, the behavior of a number of large cathode area (8 inches diameter) PMT models has been studied both at room and at cryogenic temperature. A complete characterization at cryogenic temperature has been performed in terms of gain, timing, signal shape, linearity, photo-cathode uniformity, dark counts and after-pulses rates and spectra. Moreover, an evaluation of the Quantum Efficiency of these devices, coated with wave-length shifter materials,  has been carried out in the VUV region (from $\lambda$=120 nm to $\lambda$ = 220 nm incident light).

Photomultiplier tubes (PMT) used as photodetectors, are of current importance nowadays. Wide application of photon detectors in high-energy physics, cosmic ray physics, astrophysics, security systems and medical diagnostics requires huge variety of photomultiplier tubes’ types both by dimensions and parameters.
"MELZ FEU" Ltd. is a leading Russian designer and manufacturer of various types of PMTs with high sensitivity, low noise level, high-speed impulse counting and excellent energy resolution.

One of the state-of-the-art developments of MELZ is PMT designed for registration of nanosecond luminous impulses, generated neutrino within operating volume of detector of deep-water neutrino telescope for KM3Net project. This photomultiplier is constructed in glass shell having 3 inches (76 mm) of photocathode useful diameter and 43,2 mm curvature radius. Overall length without pins is 105 mm, external diameter of the neck – 52 mm.
In this PMT we use electro-optical system of linear type with 10 dynodes and underfocusing electrode on its input, which is mounted upon ceramics and has a mesh anode that works on reflection. Spectral response range of bialkali photocathode is 320-650 nm. Spectral sensitivity at 404 nm wavelength is not less than 130 mA/W. Gain is $5\times 10^6$ at the least. Impulse duration at its half-altitude could be not more than 3 ns.

FEU-86U with potted voltage divider is also of interest to the consumer. It has 16 mm photocathode diameter with maximum 22 mm of overall diameter, weighting not more than 50 g. Luminous noise equivalent of the dark current of the anode is not more than $5\times 10^{-13} lm/Hz^{1/2}$, and dark impulses counting rate at one-electron peak not is not greater than 300 1/s. All this parameters in the aggregate allow us to consider FEU-86U as the best threshold photomultiplier manufactured in Russia. It’s been widely used in portable monitoring equipment for air environment in enclosed spaces.

Photomultipliers with 30 mm bulb diameter (photocathode diameter 25 mm) – FEU-85B, and FEU-115M8 are also commonly spread and well known. Their general feature is bialkali photocathode which considerably improves energy characteristics of the products. For example FEU-85B has not more than 800V voltage at the luminous sensitivity of anode 10 A/lm, and not more than 1000V at 100 A/lm. Energy resolution with crystal NaI (Tl) $25\times 25$ mm, with $^{137}$Cs – not more than 8.5%, and energetic equivalent of intrinsic noise doesn’t exceed 1 keV. According to customer’s request, this PMT can be issued with potted voltage divider encapsulated into bulb 30 mm diameter.

FEU-115M8 is used in the large area portals to detect radioactive objects in the traffic flow. Having 30 mm bulb diameter and not more than 67 mm length, its weight does not transcend 50g and, moreover, this PMT has at least 25 mm useful diameter of photocathode. By using fiber-optics it provides You an opportunity to collect light from a large volume of the scintillator very effectively. With operating voltage in the range 1300-1400 V, it has energetic equivalent of intrinsic noise less than 6 keV and energy resolution with crystal NaI (Tl) $25\times 25$ mm, with $^{137}$Cs - not more than 10%. In addition, it is a preferable alternative to the previously made by another manufacturer FEU-35 and FEU-35-1, since in comparison to them it has 2 times more spectral sensitivity at 410 nm wavelength of $5\times 10^{-2}$ A/W and lower operating voltage.

We can not ignore FEU-184, being manufactured by MELZ for many years and on the basis of which many modifications were developed. FEU-184 has 52 mm bulb diameter, 46 mm useful photocathode diameter, 110 mm length and weights not more than 120 g. With luminous sensitivity of anode 10 A/lm its operating voltage does not exceed 1350 V, and typical value is 650-750 V; energy resolution with crystal NaI (Tl) $40\times 40$ mm, with $^{137}$Cs - not less than 7%; with $^{57}$Co - not less than 9.6% (typical value is 8.4 - 8.8%), energetic equivalent of intrinsic noise does not exceed 3 keV (typical value is 0.7 keV). The same parameters has a three-inch photomultiplier FEU-184TD. In addition to that, we have designed a heat-resistant modification FEU-184T, capable of working at ambient temperatures up to 150$^\circ$C, having at the mentioned temperature energetic equivalent of intrinsic noise less than 40 keV, and not more than 50% decay of anode sensitivity.
LLC "MELZ PMT" also serially produces heat-resistant PMT of 20 and 30 mm diameter with operating temperatures – 120, 150 and 200$^\circ$C.

KM3NeT is a multi-cubic-kilometer neutrino telescopes under construction in the Mediterranean Sea. KM3NeT will study of neutrinos of cosmic origin in the TeV-PeV energy range, and neutrino oscillation and mass hierarchy using atmospheric neutrinos in the GeV range. Both projects will use the same design of active elements to detect Cherenkov light of charged secondary particles – the optical modules.  In the current first phase of the project, 31 detection units – a few hundred meters high vertical structures holding 18 Digital Optical Modules (DOMs) each – will be produced and deployed in the Mediterranean deep sea. The KM3NeT DOM consists of pressure resistant glass sphere encapsulating 31 photomultiplier tubes of 80 mm diameter produced by Hamamatsu, readout electronics and additional instrumentation for calibration and monitoring. The use of ~3 inch diameter PMTs recently developed by ETL, HZC and MELZ is under investigation. This contribution describes the design and characteristics of the KM3NeT DOM and reviews suitable PMT types for this application.

Hyper-Kamiokande is a proposed next generation underground water Cherenkov detector capable of observing leptonic CP violation, nucleon decay, supernova neutrino and so on. Because of its large volume, 20(25) times larger than that of Super-Kamiokande for total (fiducial) mass, the total cost of photo-detectors will be expensive. Therefore cost-effective and high performance large-area photo-detectors are required to realize such a large detector.
As one of photo-detector candidates, a hybrid photo-detector (HPD), which is made of a phototube and an avalanche diode (AD), is under development. Because of its simple structure, the manufacture cost is expected to be low. And a fast drift time of electron and large bombardment gain bring a good timing resolution and high photoelectron detection efficiency.
The HPD with a diameter of 50 cm is expected to have a better performance than the existing photomultiplier tube with the same diameter. However, because of the large photoelectric surface, an AD with a diameter of 20mm is used in 50 cm HPD in order to ensure the collection efficiency. As a result, a new preamplifier for high parasitic capacitance is needed. Moreover, a new kind of HPD with a multi-channel AD is also under development to reduce the parasitic capacitance seen by preamplifier.
In this presentation, we will report the development status of 50 cm HPD and the performance of two prototypes: one is the HPD with a single-channel AD and an improved preamplifier, the other one is the HPD with a multi-channel AD.

The Vacuum Silicon PhotoMultiplier Tube (VSiPMT) is a new concept of photodetector based on the combination of the outstanding performances of SiPMs and the large sensitive surfaces of PMTs.  Such device is made of a PMT standard envelope, with a photocathode for photon-electron conversion and an electrostatic focusing system that accelerates and focuses the generated photoelectrons towards a small focal area covered by a SiPM.
The electron multiplication stage is the heart of the device and represents the real innovation with respect to the standard PMT technology. Therefore, a huge preliminary work aimed at the study of the performances of SiPMs as electron multipliers has been mandatory in order to investigate the feasibility of the VSiPMT.
The extremely positive results achieved in this phase encouraged Hamamatsu Photonics to realize some prototypes of VSiPMT, that have been extensively characterized in the laboratories of INFN – Section of Naples.
In this presentation some highlights about the main milestones of the project will be provided. In particular, taking as a starting point the results of the prototype characterization, the so-called “phase 2” aimed at the realization of a new optimized generation of VSiPMT prototypes will be discussed.

The VSiPMT (Vacuum Silicon PhotoMultiplier Tube) is an innovative design for a revolutionary hybrid photodetector.
The idea, born with the purpose to use a SiPM for large detection volumes, consists in replacing the classical dynode chain with a SiPM. In this configuration, we match the large sensitive area of a photocathode with the performances of the SiPM technology, which therefore acts like an electron detector and so like a current amplifier.
The excellent photon counting capability, fast response, low power consumption and great stability are among the most attractive features of the VSiPMT.
In order to realize such a device we first studied the feasibility of this detector both from theoretical and experimental point of view, by implementing a Geant4-based simulation and studying the response of a special non-windowed MPPC by Hamamatsu with an electron beam.
Thanks to this result Hamamatsu realized two VSiPMT industrial prototypes with a photocathode of 3mm diameter. We now present the results of a full characterization of the VSiPMT industrial prototypes and the preliminary tests we are performing to realize a 2-inches and 3-inches VSiPMT prototype.

The RED100 double-phase emission detector is currently being prepared for the experiment aimed on the registration of the phenomenon of coherent neutrino scattering off xenon nuclei, having several dozens of Hamamatsu R11410-20 PMTs in its structure. Since the detector must be capable to detect rare events with small amount of the released energy, it is mandatory to evaluate the sensitivity and noise characteristics of the PMTs involved. For this purpose, a characterization procedure has been carried out for each PMT unit, including the study of its single photon response and noise characteristics. 
Among the systematic characteristics of 34 PMT samples, results of a special study of a number of non-standard features are presented. For example, observation of single photon emission of the PMT’s internal structure is described, including the results of the photon emission intensity study as a function of the PMT bias voltage and temperature. 
Another important feature of the device concludes in an unusually big Cherenkov light yield of charged particles in the volume of the PMT quartz window. Properties of the window material together with high quantum efficiency for VUV light ($>$30%) lead to appearance of signals with amplitudes about 100 photoelectrons from atmospheric muons passing the horizontally placed PMT window. Such effect makes feasible the usage of a R11410-20 as a standalone particle detector. Special investigations were held concerning the value of 511 keV photons (among the atmospheric muons) Cherenkov light yield during their registration with the R11410-20 PMT window.

The original mathematical models and algorithms developed within the code “Monte Carlo Simulator 3D” (MCS-3D) are presented. These algorithms are devoted to model the photo-emission and cascades of secondary electron emission in micro-channel plate (MCP) amplifiers are widely used as photo detectors in accelerator physics, medical diagnostics, astrophysics etc. A theoretical method for calculation of secondary electron emission (SEE) yields has been developed. The method uses Monte Carlo simulation, empirical theories and close comparison to experimental data in order to parameterize the SEE yields of highly emissive materials for the MCPs. Numerical simulations were used to study the statistical properties for the prototype of large-area fast photo detectors which was developed at Argonne National Laboratory.

Photek are currently in a three year development program with CERN to produce a novel square PMT for the proposed TORCH detector which is aimed at the upgrade of the LHCb experiment. The PMT will be MCP based for the inherent timing accuracy that this brings, and has three main novel features that need to be developed:

1. Long lifetime, it should be able to produce 5 C / cm$^2$ of accumulated anode charge without noticeable degradation in sensitivity.
2. Multi-anode output with a spatial resolution in the “y” direction of 0.4 mm and 6 mm in the “x” direction.
3. Close packing on 2 opposing sides with an active area fill factor target of 88% in the “x” direction.
We will describe the work completed so far including the building and testing of lifetime prototypes, multi-anode prototypes and high fill factor (square) tube body shape developments.
Previous work published by Photek has demonstrated a significant lifetime improvement in an MCP-PMT when the MCP is coated by Atomic layer Deposition (ALD). We believe that the ALD layer forms a barrier that prevents the outgassing of material from the MCP under heavy electron bombardment that, from an uncoated MCP, gets ionised and reacts with the photocathode, thus reducing the sensitivity.
The front-end read-out of choice is currently the NINO ASIC and we will describe our developed method of efficiently coupling the PMT output pads to a PCB through an ACF film that minimises any parasitic input capacitance by allowing very close proximity between the NINO and the detector.
We will also report on preliminary results from a charge sharing technique that enables position resolution that exceeds the granularity of the multi-anode.

The time-of-propagation (TOP) counter is a novel ring imaging Cherenkov detector.
It is a key device of particle identification in Belle II to extend the physics reach
toward a new physics. The essence of the TOP counter is to detect the Cherenkov photons
with a high efficiency and a better time resolution than 50 ps.
Thus we developed the micro-channel-plate photomultiplier tube (MCP-PMT).


We succeeded in producing all the 512 MCP-PMTs used for the TOP counter.
The photon detection efficiency and the response to single photons were measured
systematically for every MCP-PMT: the average quantum efficiency is greater than 28%
at 380 nm wavelength and the time resolution is 30-40 ps as expected.
The detailed results will be presented including the high voltage dependence of the
performance. In addition we measured the degradation of the gain, time resolution and
collection efficiency in a 1.5 T magnetic field. These results will also be presented.
In summary we would like to discuss that the systematic mass measurement showed not only
the excellent performance of the MCP-PMTs for the TOP counter but also helped us to
reveal the basic properties of the MCP-PMT.


Our R&D is now focused on upgrade of the MCP-PMT performance in terms of the lifetime,
which we define as the total output charge where the quantum efficiency declines
down to 80% of the beginning. We improved the production process of the MCP-PMT and
succeeded in extending the lifetime longer than 10 C/cm$^2$ for all of four test samples.
The lifetime test results as well as the R&D status will be included in the presentation.

Review talk on electronics

Silicon Photomultipliers (SiPM) are a new class of photon sensors featuring single photon detection sensitivity, high photon detection efficiency, low excess noise factor, extended dynamic range and magnetic field immunity. Operated at voltages not exceeding 100 V with a power consumption lower than 100 mW, SiPM benefit from the tremendous development of the Silicon technology in terms of cost production, design flexibility and performances.

They have been proven to be suitable for an increasing number of applications in science and industry and they are bound to open new perspectives in low light detection systems. This is the main reason why, few years ago, an R&D program was started in collaboration with CAEN S.p.A. to design a modular set-up that allows to easily operate SiPMs from different producers. The system, together with a dedicated simulation of the sensor response, is meant to be the base for the device characterization and the proof of concepts for new SiPM-based applications. 

The main characteristics of the system will be presented together with a series of exemplary applications in medical dosimetry and homeland security, within projects funded by the European Commission with the Frameworks programs 6 and 7.

A readout scheme has been designed for the plastic scintillator bars of the Baby-MIND detector modules. This spectrometer will measure momentum and identify the charge of ~1 GeV/c muons with magnetized iron plates interleaved with detector modules. One challenge the detector aims to address is that of keeping high charge identification efficiencies for momenta as low as ~300 MeV/c where multiple scattering in the iron plates degrades momentum resolution. A front-end board has been developed, with 3 CITIROC readout chips per board and up to 96 channels. Functional prototypes of the front-end board are planned for April 2015. Hamamatsu MPPCs type S12571-025C were chosen following extensive comparisons, mapping of the light output from the wavelength shifting fiber and validation of the custom optical connector. Procurement of the MPPCs has been carried out to instrument 3000 channels in total. Design choices and first results of this readout scheme are presented, along with an outlook for potential applications.

Silicon Photomultipliers (SiPM) are well-known low level light detectors and are potentially devices to replace Photomultiplier Tubes (PMT).


Essential technical key features for the sensors are the timing performance and the optical crosstalk probability. In order to achieve considerable improvements, KETEK has realized process modifications of its established SiPM technology:


The first modification is an optimized signal read-out for the micro pixel network, bringing down the single photon time resolution (SPTR) by a factor of 2.5.


Secondly, there is an improved optical trench isolation which leads to a further suppression of the optical cross talk down to a level of 3% in Geiger saturation regime, which corresponds to 5 V overvoltage (20% relative overvoltage) for the new KETEK device.


The processed devices will be presented and compared to the earlier established technology and an outlook on coming features will be given. 


In addition KETEK has successfully transferred the SiPM production into a CMOS foundry. Beside cost advantages compared to a customized production process this also enables the integration of electronics on sensor level. In a close cooperation with MEPHI, KETEK  has started R&D on analogue CMOS SiPM with integrated fast electronics.

Amplitude, charge and recovery time for a single cell and real SiPMs for under- and oversaturation light intensities have been investigated.
It has been shown that a SiPM illuminated by high intensity light flash (many photons/SiPM cell) is able to generate a signal with an amplitude that is higher then A1$\times$N, where  A1 – one-cell signal amplitude for low light conditions, N - total number of  cells inside the SiPM.
This effect can be explained by creation of multiple avalanche starting points inside of a SiPM cell which leads to the development of multiple avalanches inside of the cell and thus to a higher discharge current with shorter pulse duration when compared with a case of a single avalanche per cell.
It will be shown that under strong oversaturation conditions even the charge from SiPM cell is not remaining a constant and increases with increasing intensity of light. The later effect leads to longer cell recovery times for higher light intensities.
Work has been supported by Megagrant 2013 program of Russia, agreement  N14.A12.31.0006 from 24.06.2013

The NEXT-100 experiment aims at searching the neutrinoless double decay ($\beta\beta 0\nu$) of the Xe-136 isotope, using a TPC filled with 100 kg of enriched and highly pressurized gaseous xenon. The key technological feature of NEXT TPC is the electroluminescence (EL), which requires the optical readout of the signals using Photomultiplier Tubes (PMT) and Silicon Photomultipliers (SiPMs) for energy and tracking measurements respectively. This technology has been implemented and extensively tested during the last years in the demonstrator prototype NEXT-DEMO, achieving high energy resolution ($<$ 1% FWHM) and tracking capabilities required for a robust $\beta\beta$ decay experiment.

The interaction of the $\beta$ particles in the xenon gas produces excitation and ionization signals that are both used in the TPC for the identification of the $\beta\beta 0\nu$ events. The excitation signal is a prompt VUV scintillation, that is read out by an array of PMTs at the TPC cathode, providing a start-of-event signal. The ionization signal, which is proportional to the deposited energy in the gas, is amplified through the electroluminescence process that converts proportionally the charge signal to an optical signal, with very low statistical fluctuations. This optical signal known as the secondary scintillation, is of much larger amplitude and duration (few $\mu$s) than the primary scintillation signal. It builds up in the EL region at the TPC anode, several hundreds of $\mu$s after the starting of the event and is read out by the PMTs for the energy measurement. It is also read out by the array of SiPMs located right behind the EL region for the events topology measurement. 

In the proposed talk, I will describe the NEXT concept and the signals induced by charged particles in the high-pressure xenon TPC read out by PMTs and SiPMs. I will especially address the SiPM readout technique implemented in the demonstrator prototype NEXT-DEMO, and its upgrade for the upcoming NEXT physics runs in the Canfranc Underground Laboratory (LSC) with the detectors NEXT-NEW and NEXT-100.

The first studies of VUV detection by the SiPM have shown that it is necessary to use a WLS. Some manufacturers produce native VUV sensitive SiPMs at present. Collaborations Gerda, MEG, NEXT, nEXO plan to use these SiPMs in their detectors. The PDE of these SiPMs is lower than green or blue sensitive SiPMs. In our previous studies, it was obtained in the WLS + SiPM system about 50% of the sensitivity of the SiPM. We started to develop a WLS + SiPM system for use it in the nEXO prototype. In this study, we used the SiPMs developed at the MEPhI (MEPhI-KETEK) and Sensel and nanostructured organosilicon luminophores (NOL) as the WLS from the ISPM RAS.

Detection of neutrinos and the search for proton decay require large
volume detectors. The electrical and optical properties of liquid argon
(LAr), its affordability and its availability make LAr a suitable medium
for detectors with masses up to several tens of kilotons.

After an introduction to the physics scope and a conceptual overview of
LAr time projection chambers I will address the relevance, challenges and
requirements of 128 nm LAr scintillation light detection in large volume
cryogenic detectors. I describe work on large area VUV photon detector
panels with a focus on the SiPM readout and associated cryogenic tests of
SiPM properties in our laboratory.

An avalanche photodiode capable of detecting the fast component of the scintillation light of barium fluoride is being developed by a Caltech/JPL/RMD collaboration. The device has high quantum efficiency at 220nm, the wavelength of the fast scintillation component (0.9ns) and excellent discrimination against the 300nm slow scintillation component (650ns) of barium fluoride, as well as good rise and decay times. This device is intended for the calorimeter of the Mu2e experiment at Fermilab.

The CMS Barrel (HB) and Endcap (HE) Hadron Calorimeters are scintillator sampling calorimeters with embedded wavelength shifting fibers (WLS) in scintillator tiles. The photo-sensors that are currently used are hybrid photodiodes (HPDs). In 2012 the HCAL Phase I upgrade was approved for the increased luminosity (5*1034) of SLHC. A key aspect of the HCAL upgrade is to add longitudinal segmentation to improve background rejection, energy resolution and scintillator radiation damage compensation. The increased segmentation can be achieved by replacing the HPDs with silicon photomultipliers (SiPMs)). The SiPMs for the CMS HCAL upgrade have to operate in a very hostile SLHC radiation environment (we expect a maximum total dose of 1012 n/cm2 for an integrated luminosity of 3000 fb-1). They should have good linearity for a wide range of scintillating signals and excellent reliability. During the last years we have successfully completed the R&D for instrumentation of SiPMs for the Phase 1 upgrade of HE/HB in 2017 and 2018.
Here we report on the final SiPM parameters of two manufactures considered for the 2015 preproduction run.  These candidates Hamamatsu (Japan) and KETEK (Germany) have developed state of the art custom large dynamic range SiPMs with large PDE and small ENC for the CMS HCAL Upgrade project. An overview of all results of our measurements of photon detection efficiency, spectral response, cell recovery time will be reported in this presentation. 
Results from a study on the radiation hardness of silicon photomultipliers (SiPMs) are also presented. The SiPMs were exposed to hadrons (protons and neutrons) at fluences up to 1*10^12 hadrons/cm2. The SiPM's main parameters were measured before and after irradiation. The effects of the hadron radiation on breakdown voltage, quenching resistance value, gain, photon detection efficiency, dark current and dark count rate for these devices are shown and discussed.

A muon spin spectroscopy has been utilized for both of particle physics and material science. At J-PARC (Japan Proton Accelerator Research Complex), the world's highest-intensity pulsed muon beam has been realized. With the increase of the beam intensity, requirement for the detector's high-rate capability becomes essential.

Spectroscopy of muon spin is performed by measurement of positron angular asymmetry from muon decays. A new muon spin spectrometer with the silicon photomultiplier (SiPM) readout is under development for precision measurement of muonium hyperfine splitting [1]. The positron detector consists of tiled plastic scintillators, SiPMs (MPPC manufactured by Hamamatsu), and fast readout-circuits with ASIC based ASD and FPGA multi-hit TDC [2]

A prototype of the detector was developed and its performance was evaluated with the high intensity pulsed muon beam at J-PARC [3]. Based on an understanding of SiPM's characteristics and analog circuit response, a realistic event generator was developed for evaluation of systematic uncertainties of the measurement. Several methods of pileup correction were studied to minimize the systematic uncertainty. Characteristics of new types of SiPM were evaluated for further upgrade of the detector.

In this presentation, overview of the project and detail of the detector R&D will be discussed. As a major application of the detector, precision measurement of muonium hyperfine splitting will be introduced.

[1] : S. Kanda et al., Proceedings of the 2nd International Symposium on Science at J-PARC (to be published).
[2] : K. M. Kojima et al., J. Phys. Conf. Ser. 551 012063 (2014).
[3] : S. Kanda et al., JPS Conf. Proc. 2, 010404 (2014).

We review some aspects of new and old developments in photon detection techniques. Particular emphasize is made on connections of “new” and “old” ideas in photon detection: quite often “new” ideas are well forgotten “old” ones. Comparisons are made for some “new” ideas claimed recently with “old” ideas discussed earlier, for some ideas – more than 40 years ago. Lessons learnt in studies of old developments will help to avoid not only “bicycle invention” but also give seeds for new genuine ideas as well. 

The review covers different approaches in vacuum photodetectors developments including classical photomultipliers and hybrid phototubes pushed forward for the last 50 years. Some other issues concerning WLS and light guide techniques for increasing photodetectors sensitivity are discussed too. Rather detailed discussion of large area vacuum photodetectors (classical PMTs and Hybrid Phototubes) developments are presented.  

Particular attention is paid to various applications by which photodetector developments have been driven by.

In the paper the light output and the time resolution of polystyrene scintillators-WLS samples have been measured with use wavelength shifting (WLS) fiber readout.  The samples of different thickness (7-30 mm) have been made in the shape of bricks and plates with the areas of  25×80 and 108×134 (268) of  mm$^2$  respectively. Besides samples of  “ordinary” scintillator with additions of  2% p-Terphenyl + 0,05%  POPOP,  the rapid ultraviolet   scintillator with one 2% additive PBD was used. For the light collection were used WLS-fibers BCF92, Y11 and scintillation fiber SCSF-78M as re-emitting. The fibers were glued into the grooves on the front surface of scintillators. As the photo detectors silicon photomultipliers (SiPM) were used, which were produced by CPTA (Russia) and SensL (Ireland). It is shown that the dependence of light output on the thickness of scintillator is nonlinear and close to the power function with ½ index, which is also confirmed by the calculations carried out by Monte Carlo. The measured value of a light output makes it possible to obtain time resolution of about 0.5 ns. The best result (0.22 ns) of the time resolution with the MIP detection is obtained for the pair of ultraviolet scintillator and SCSF-78M fiber.

A fully automated measurement setup for measuring SIPM detectors will be presented. Light source, positioning table, cooling system and data acquisition system will be described. Example results for MAPD-3N and MPPC S12572-010P will be shown.

Gamma locator is a handheld lightweight and compact gamma probe based on a scintillation crystal LaBr3:Ce and SensL MicroFB-30035-SMT silicone photomultiplier to be used for detection of gamma-radiation emitted by radionuclides such as Tc-99m, I-125, In-111, F-18.
There are two main applications of gamma locator: intraoperative detection of sentinel lymph nodes and non-invasive scanning the surface of the body. In the first case, a radiotracer is injected into the patient preoperatively and surgeon checks the presence of metastasis in the lymph nodes after the removal of the tumor. In the second case, the gamma locator can detect tumors located superficially, and accurately determine their boundaries.
When selecting the scintillator the following requirements should be considered: high relative light yield compared to NaI(Tl), the high value of the effective atomic number. The lanthanum cerium bromine has demonstrated the best features: the light yield higher than that of NaI(Tl) (130%), high density, high atomic number provide high efficiency of photoelectric absorption of gamma rays, and the decay time of the order of tens of nanoseconds provides high temporal resolution of the detector.
Silicon photomultiplier is a device for detection of low intensive and very fast (several hundred nanosecond duration) light flashes. SiPM is used due to its high detection efficiency, low bias voltage, compact dimensions and high gain of signals. 
The scintillation crystal of 5 mm diameter and 10 mm length is optically connected with the SensL MicroFB-30035-SMT SiPM of 3x3 mm2 sensitive area. Experimental studies have shown that a scintillator packaged separately from the photodetector provides only 10.7% energy resolution at 662 keV (Cs-137) while being packed in a single enclosure with the SiPM it provides 6.9% FWHM energy resolution.
Gamma probe can be constructed in corded or cordless configuration and equipped with a lithium-ion battery. Indication is performed by an acoustic signal and LED. Adjusting of the bias voltage of the photodetector and the thresholds of the discriminator is carried out by changing the resistance of the trimmers. 
The main technical characteristics of the prototype gamma locator were determined in the laboratory of NRNU MEPhI. Spatial resolution of gamma locator is the minimum distance between two point sources on which they can be resolved separately, or FWHM of the dependence of counting rate of the transverse distance between the detector and the source, and is measured to be 18 mm in the air and 20 mm in the scatter medium. Spatial selectivity is the polar angle, at which the count rate drops twice and it is measured to be 17 degrees in the air and 26 degrees in the scatter medium. Sensitivity is 191 cps/MBq in the air and 112 cps/MBq in the scatter medium. 
This work was supported in part by the Ministry of Education of the Russian Federation (State Contract with the NRNU MEPhI no. 11.G34.31.0049 of Oct. 19, 2011) and the Skolkovo Institute of Science and Technology (a part of the Skoltech/MIT Initiative project).

Russian domestic medicine is suffering from a crippling deficit of modern equipment for diagnostics. Almost all of this equipment was imported. Most of them are operated for more than 10 years and are now needed to be either modernized or completely replaced.

Proof-of-principle prototype of the gamma-camera module was assembled. The prototype consists of 64-channel matrix of $6\times 6 ~mm^2$ KETEK SiPMs ($\href{http://www.ketek.com}{www.ketek.com}$), assembled at Scientific-Production Enterprise “Pulsar”, Moscow. Front-end analogue readout and digitazing of the signals from the matrix is performed by 64-channel ASIC MAROC, which is commercial available and produced by French company WeeRoc ($\href{http://www.weeroc.com}{www.weeroc.com}$). Further processing of digitized signal is made on PC. The experimental measurements with NaI(Tl) $\oslash ~30 ~mm \times 20 ~mm$ scintillator were carried out. The aim of the researching was to check an obtaining of necessary energy resolution since the signal is a sum of the eight center signals from the individual channels that operating under common bias voltage and having dark count rate, also integration time of MAROC3 is 150 ns and this time is less than decay time of scintillator, and as a consequence it leads to integrating at least half of the light. As result, energy spectrum of sum signal from the detectors with Cs-137 source has been built and energy resolution of 23.8% (for the 31-35 keV lines) has been obtained. In fact, this result is equal to 25.2% resolution obtained with PMT XP2020 with the full integration of the signal (all light has been collected) on digital oscilloscope LeCroy WaveRunner 620Zi with the same scintillator. It is assumed to make a tests with scintillator from the real gamma camera. The Monte-Carlo simulating of the full-size gamma camera is performed using Geant4 libraries (transportation of the photons), MATLAB (simulating of SiPM characteristics) and ROOT (fitting and histogramming) to obtain required energy and spatial resolution.

In parallel, we are developing the detector for dose monitoring in neutron capture therapy (NCT). It was suggested to utilize a LaBr3(Ce) scintillation crystal, that have the best energy resolution, using SiPM matrix for readout. The usage of SiPM matrix allows to create a dose detector, that capable not only to estimate the dose in the region of interests but also to restore a dose distribution shape in the real time during radiation process. To decrease a contribution of a background events it is suggested to use an active protection surrounding LaBr3(Ce) and operate in anti-coincidence mode. To perform the measurements the test prototype was assembled. LaBr3(Ce) cylindrical crystal made in Chernogolovka is surrounded by LYSO crystals, 64-channel matrix of $6\times 6 mm^2$ KETEK SiPMs and the test board with MAROC3 electronics. The measurements with Cs-137 source were performed, resolution of 4.5% (662 keV) was obtained and result of using of the active protection was demonstrated. Currently, we have improved LaBr3(Ce) crystal with higher light output. The protection geometry is being optimized as well.

Also in collaboration with “POSITOM-PRO” company is related to the development of TOF-PET
(time-of-flight PET) module using SiPM with the following requires: 10-15% energy resolution on 511 keV line, spatial resolution of about 3-4 mm FWHM, maximum count rate no less than 100 kHz and time resolution of about 300-400 ps, which is state-of-art commercial TOF-PET. Simultaneously, a module with the time resolution on 100 ps level for the next generation TOF-PET is being developed. One reason for worsening the time resolution is a slope of the leading front of the detector signal. The slope is higher, the time jitter related to the obtaining of the cut-off time is less. Thus, it is necessary to amplify the signal and not to change the slope of the front (to transmit the high frequencies without distortion). To do this, the selection of different high frequency amplifiers is being studied.

The latest obtained results will be presented.

Project NICA/MPD is dedicated to study of hot and dense baryonic matter in collisions of heavy ions (up to Au$^{+79}$) in energy region $4\leq \sqrt{S_{NN}} \leq 11$ GeV. The ToF system of MPD is the main detector for particles identification. It has to have time resolution better than 100 ps for separate pion/kaon in the momentum range 0-2.5 GeV/c and proton/kaon in the range 0-4.5 GeV/c. The stop signal for ToF measurments is given by barrel of Multigap Resistive Plat Chambers (MRPC). The start signal for ToF measurements is given by stations of Cherenkov quartz counters (FFD - Fast Forward Detector). 

A modular Cherenkov detector with picosecond time resolution is developed and created at LHEP/JINR in Dubna. The aim of this detector is production of start signal for ToF detector and fast triggering. This goal is achieved by registration of high-energy photons and charged pions in the detector modules based on MCP-PMTs XP85012/A1- Q from Photonis. The high-energy photons are detected via conversion to electrons in 10-mm lead layer in front of the 15-mm quartz radiator. The detector concept, module characteristics, and the detector performance studied by MC simulation and by using deuteron beam of Nuclotron are discussed. The time resolution of the detector module obtained in ToF measurements on deuteron beam is 24 ps for DRS4 digitizer readout and 37 ps for TDC (HPTDC chip) readout.

In long baseline neutrino oscillation experiments, properties of neutrino are measured with neutrino interaction with the nucleus. Hence, understanding of the neutrino-nucleus interaction is critical for precise measurements of neutrino oscillation parameters. We have been developing a new neutrino detector named WAGASCI, to measure the cross section ratio of neutrino interaction with water and plastic targets with a large angular acceptance at J-PARC. In the T2K experiment, the far detector, Super-Kamiokande, uses water target while the near detectors use mainly plastic target. The uncertainty due to the difference of the target materials is one of major systematic uncertainties in T2K. The target of WAGASCI detector consists of 3-mm thick plastic scintillators assembled into a 3D grid-like structure. Multi-Pixel Photon Counters (MPPCs) are used to detect the light from scintillators. Because of the small light yield from thin scintillators, MPPCs are required to have low crosstalk rate and high photo detection efficiency (PDE).

We will use newly developed, crosstalk-suppression type MPPCs for WAGASCI detector. The new MPPC has an order of magnitude lower dark noise rate and crosstalk rate than old MPPC. We can operate the new MPPC with higher over voltage, which results in higher PDE. The total number of channels will be about 8,000. In order to realize a compact readout of large number of channels, we developed an array type MPPCs that have 32 MPPCs of 1.5 mm diameter active regions with 50 micron pixel size. A measurement system to test a large number of MPPCs is being developed. In this talk, the performance of new MPPC and the result of measurement with mass production will be presented.

In FBK we develop different custom SiPM technologies. The so called NUV-SiPM are based on a p-on-n junction type, on n-type epi/substrate. This configuration enhances the photon detection efficiency (PDE) in the blue-wavelength region (PDE typically peaked at 400 nm), thanks to the electron-triggered avalanche when incoming photons are absorbed near the surface. The electron impact-ionization coefficient is higher than for holes and the trigger probability rises sharp already with few volts of excess bias (i.e. the difference between bias and breakdown voltage). 

We recently developed a new high-density version of NUV-SiPM, called NUV-HD. Like RGB-HD technology, presented in [1], the devices feature a considerably high fill factor (FF) while reducing the correlated noise. This new NUV-HD technology combined all the benefits of the HD technology, i.e. high FF, increased photon detection efficiency, low correlated noise and high cell-density (thus high dynamic range), with the advantages of NUV approach (p-on-n junction) for light detection at short wavelength.

In the HD technology we use a small cell size (CS) and we implement trenches between cells. The reduction of cell size gives a lower gain of the cell, reducing both the afterpulsing and the amount of secondary-electrons, thus the optical crosstalk. Moreover, the trenches between cells provide optical isolation, further decreasing the crosstalk between cells. Thanks to this reduced correlated noise, it was possible to increase the FF to have a dead border region of about $1\div1.7~\mu m$.

We produced different SiPM prototypes with cell size of $15\times 15~\mu m^2, 20\times 20~\mu m^2, 25\times 25~\mu m^2, 30\times 30~\mu m^2$. The fill factor is 77% for the bigger cell and about 55% for the $15\times 15~\mu m^2$. Thanks to the technology development, the HD technology shows the same low dark count rate (DCR) of “standard” NUV-SiPM, i.e. in the order of 100 kcps (kilo counts per second), for 1 $mm^2$ device. The direct crosstalk probability is $\sim$30% for the bigger cell and only $\sim$7.5% for the SiPM with the smaller one, at $\sim$6 V of excess bias, while the afterpulsing and the delayed crosstalk is only $\sim$1%. The PDE of the 30-$\mu m$ cell SiPM is $\sim$40% already at low excess bias (as shown in the figure below), and it increases to $\sim$55% with 7 V. For the 15-$\mu m$ cell PDE is $\sim$33% with 7 V.


[1]	C. Piemonte, A. Ferri, A. Gola, T. Pro, N. Serra, A. Tarolli, N. Zorzi, “Characterization of the First FBK High-Density Cell Silicon Photomultiplier Technology,” IEEE Trans. Electron Devices., vol. 60, no. 8, pp. 2567-2573, Aug. 2013.

We characterized the first RGB SiPMs with Ultra-High-Density cells (RGB-UHD) manufactured at Fondazione Bruno Kessler (FBK), Trento. These devices employ narrow trenches to separate the SiPM microcells and feature extremely high cell density, very low gain and correlated noise and ultra-fast recovery time. Such characteristics are of great interest in applications that require high dynamic range and/or good resistance to radiation damage, such as the CMS ECAL/HCAL upgrade.

The devices have cell pitch of 7.5 $\mu m$, 10 $\mu m$ and 12.5 $\mu m$, are arranged in a honeycomb configuration and have a circular active area with a 1.5 mm diameter. The cells have an hexagonal shape, thus, for example, the area of the 10 $\mu m$ cell is 87 $\mu m^2$. The cell density is 20500, 11500 and 7400 cells/mm$^2$, for the three cell sizes, respectively. For each cell, there are four layout splits, differing in one very critical parameter, which is the distance of the active area from the cell border and from the isolating trenches. We call these split D1…D4, ordered from the most challenging layout, D1, to the most conservative one, D4. Depending on these splits, the fill factor (FF) of the cells varies between 57% and 33% and between 68% and 47%, for the 7.5 and 10 $\mu m$ cells, respectively.

The automatic IV measurements showed that all cell sizes and layout splits were working in Geiger mode. We focused on the characterization of the cells with a 7.5 $\mu m$ and a 10 $\mu m$ pitch. The measured Gain was very small, in the order of $3.5\times 10^4$ and $4.5\times 10^4$ per 1 V of over-voltage ($V_{OV}$), for the 7.5 $\mu m$ and the 10 $\mu m$ cells, respectively. These values correspond to a cell capacitance ($C_T$) of 4.5 fF and 5.7 fF for the two cell sizes. The low value of $C_T$ allowed obtaining a very fast cell recovery time-constant, which was in the order of 3.5 ns and 4.5 ns, for the 7.5 $\mu m$ and 10 $\mu m$ cells. The primary, Poisson-distributed DCR measured at 20 $^\circ$C with the D3 splits was 80 kHz/mm$^2$ and 200 kHz/mm$^2$, for the 7.5 $\mu m$ and 10 $\mu m$ cells, respectively.

Thanks to the low gain, we measured extremely low correlated noise probability ($P_{CN}$), which represents the sum of afterpulsing and optical crosstalk probabilities. For both cell sizes, $P_{CN}$ was below 10% at 6 V over-voltage, resulting in ENF of $\sim$1.1. We also carried out a first PDE measurement at 515 nm on the 7.5 $\mu m$ and 10 $\mu m$ D1 cells, obtaining a PDE of 13.5% and 30% at 7 $V_{OV}$, which are remarkable values, considering the cell sizes. Finally, using a pulsed light source, we demonstrated single photon resolution at 20 $^\circ$C for both cell sizes.

In conclusion, we demonstrated the functionality (with a pulsed light source) and characterized the properties (in the dark) of the RGB-UHD SiPM technology, featuring an ultra-high density of cells, extremely low gain, very fast recovery time constant and good PDE. We expect that the UHD characteristics will reduce the effects of radiation damage on SiPMs. The fast recovery time and the high cell density reduce the PDE loss due to cells busy because of the increased DCR, while the low gain reduces afterpulsing and power consumption. In the conference presentation, we will describe the RGB-UHD technology and we will report in detail on the experimental characterization of the different cell sizes and layout splits.

The main problems with existing hardware random number generators today are either low speed and/or prohibitively high cost. This presentation shows the physical concept and test results of sample data of the high-speed hardware true random number generator design based Hamamatsu MPPC photo sensor. Main features of this concept are the high speed of the true random numbers generation (tens of Mbt/s), miniature size and estimated lower production cost. This allows the use of such a device not only in large companies and government offices but for the end-user data cryptography, in classrooms, in scientific Monte-Carlo simulations, computer games and any other place where large number of true random numbers is required. The physics of the operations principle of using a Geiger-mode avalanche photo detector is briefly discussed and the high quality of the data collected is demonstrated.

For several years Silicon Photomultipliers (SiPM) have been attractive candidates in order to replace conventional Photomultiplier Tubes (PMT) in many experiments. Besides several advantages of SiPM over PMT, like the increased photo detection efficiency (PDE), the compact design and the insensitivity to magnetic fields, the dark count rate (DCR) of SiPM is still a large drawback. Especially concerning applications with the need of a large photosensitive area or applications for which cooling of the detector is not an option.  
Reducing the dark count rate of SiPM would lead to an enormous enhancement of the application range of this promising photo-detector. As a first step towards the reduction of the DCR, the main mechanisms leading to dark breakdowns of the micro-cells have to be understood. 
By monitoring the dark current and the dark count rate as a function of temperature, an extraction of activation energies of mechanisms responsible for dark events is possible, using Arrhenius plots. The goal of the presented work is to develop a reliable method for the investigation of dark events and their origins.

The electromagnetic calorimeter of the BELLE II detector for experiments at SuperKEKB $e^+e^-$ collider is described. A core part of the calorimeter, 8736 counters based on CsI(Tl) crystals read out by PIN photodiodes, is reused from the Belle detector which operated at the KEKB asymmetric energy collider from 1999 to 2010. Since the project luminosity of the SuperKEKB, $8\times 10^{35}$, is 40 times higher than that of the previous collider, much more severe background conditions are expected. Therefore all readout electronics will be replaced to a new one that will be able to cope with high event rate. 
	A second step of the upgrade when the crystals in the end caps  are replaced to the fast pure CsI crystals is under study. Since the photon emission of undoped CsI crystal is roughly 10 times smaller than that of doped one, the photosensors with amplification should be used. Current baseline option is vacuum photopenthods, their characteristics and performance study is presented. An option of a read out with the large area APD is also under study.

The Belle II detector at the SuperKEKB e+ e- collider is the only
Super Flavor Factory in the nearest future. Electromagnetic calorimeter
(ECL) is one of the most important subsystems of Belle II.
To cope with extremely high luminosity and severe background
conditions it was decided to upgrade the end cap ECL and utilize
pure CsI scintillation crystals.
We report about development and study of the counter based on
the pure CsI crystal and APD(s) (Hamamatsu S8664-55, S8664-1010).

A Multi Purpose Detector (MPD) is being constructed for the Heavy-Ion Collider at Dubna (NICA). One of the important components of MPD setup is an Electromagnetic Calorimeter, which will operate in the magnetic field of MPD solenoid and provide good energy and space resolution to detect photons in the energy range from ~100MeV to few GeV. For this purpose the, so-called, “shashlyk” sampling structure with the fiber readout to the silicon Multipixel Avalanche Photodetector is used. The genuine design is similar to the one developed by us for COMPASS experiment but a number of important modifications have been introduced to better meet MPD resolution, large volume thermo-stabilization and other requirements. These details are presented in the report along with the beam test results obtained with the MPD/NICA module prototypes.

Autors:
N.Anfimov, V.Chalyshev, I.Chirikov-Zorin, Z.Krumshtein,B.Marinova,  A.Olshevskiy, T.Rezinko, A.Rybnikov, A.Selyunin, I.Tyapkin

A giant (10-50 kt) liquid argon TPC has been proposed as the detector for an underground observatory for the study of neutrino oscillations, neutrino astrophysics and proton decay.
This detector has excellent tracking and calorimetric capabilities much superior to currently operating neutrino detectors. 

LBNO-DEMO (WA105) is a large demonstrator of the double phase liquid argon TPC based on the GLACIER design, with a 6$\times$6$\times$6~m$^3$ (appr. 300t) active volume. Its construction and operation test scalable solutions for the crucial aspects of this detector: ultra-high argon purity in non evacuable tanks, long drifts, very high drift voltages, large area MPGD, cold preamplifiers. 

The TPC will be built inside a tank based on industrial LNG technology. Electrons produced in the liquid argon are extracted in the gas phase. Here, a readout plane based on LEM detectors provides amplification before the charge collection onto an anode plane with strip readout. PMT located on the bottom of the tank containing the liquid argon provide the readout of the scintillation light.   

This demonstrator is an industrial prototype of the design proposed for a large underground detector. WA105 is under construction at CERN and will be exposed to a charged particle beam (0.5-20 GeV/c) in the North Area in 2018. 
The data will provide necessary calibration of the detector performances and benchmark sophisticated reconstruction algorithms.
This project is a crucial milestone providing feedback for the long baseline neutrino program, including projects like LBNO and DUNE.

Summary talk of the PD15

Announcements from LOC/IPC