Large-area Photomultiplier Tubes Research Articles

Characterization of the Hamamatsu 8-inch R14688-100 PMT

Large-scale optical neutrino and dark-matter detectors rely on large-area photomultiplier tubes (PMTs) for cost-effective light detection. The new R14688-100 8-inch PMT developed by Hamamatsu provides state-of-the-art timing resolution of around 1 ns (FWHM), which can help improve vertex reconstruction and enable Cherenkov and scintillation light separation in scintillation-based detectors. This PMT also provides excellent charge resolution, allowing for precision photoelectron counting and improved energy reconstruction. The Eos experiment is the first large-scale optical detector to utilize these PMTs. In this manuscript we present a characterization of the R14688-100 single photoelectron response, such as the transit-time spreads, the dark-rates, and the afterpulsing. The single photoelectron response measurements are performed for the 206 PMTs that will be used in Eos.

Time calibration and synchronization of the scintillation light detection system in ICARUS-T600

The ICARUS-T600 Liquid Argon (LAr) Time Projection Chamber (TPC) is presently taking data in the Short Baseline Neutrino (SBN) program at Fermilab (U.S.A.) to search for a possible LSND-like sterile neutrino signal at Δm 2 ≈ 1 eV2 with the Booster Neutrino Beam (BNB). A light detection system, based on 360 large area Photo-Multiplier Tubes (PMTs), has been realized for ICARUS-T600 to detect VUV photons produced by the passage of ionizing particles in LAr. This system is fundamental for the TPC operation, providing an efficient trigger and contributing to the 3D reconstruction of events. Moreover, since the detector is exposed to a huge flux of cosmic rays due to its shallow depths installation, the light detection system allows for the time reconstruction of events, contributing to the identification and to the selection of genuine neutrino interactions. The correct time reconstruction of events requires the precise knowledge of the delay of each PMT channel and a good synchronization of recording electronics, this last based on fast sampling digitizers. To achieve a time resolution better than 1 ns, we perform three consecutive timing corrections deployed at different stages of the optical data flow. Results demonstrate the capability of the ICARUS-T600 light detection system to allow a precise reconstruction of the temporal evolution of each event occurring in the detector and the association of neutrino events with the bunched structure of BNB.

A new large area MCP-PMT for high energy detection

20-inch Large area photomultiplier tube based on microchannel plate (MCP-PMT) is newly developed in China. It is widely used in high energy detection experiments such as Jiangmen Underground Neutrino Observatory (JUNO), China JinPing underground Laboratory (CJPL) and Large High Altitude Air Shower Observatory (LHAASO). To overcome the poor time performance of the existing MCP-PMT, a new design of large area MCP-PMT is proposed in this paper. Three-dimensional models are developed in CST Studio Suite to validate its feasibility. Effects of the size and bias voltage of the focusing electrodes and MCP configuration on the collection efficiency (CE) and time performance are studied in detail using the finite integral technique and Monte Carlo method. Based on the simulation results, the optimized operating and geometry parameters are chosen. Results show that the mean ratio of photoelectrons landing on the MCP active area is 97.5%. The acceptance fraction of the impinging photoelectrons is close to 100% due to the emission of multiple secondary electrons when hitting the MCP top surface. The mean transit time spread (TTS) of the photoelectrons from the photocathode is 1.48 ns.

Geomagnetic field effects on the performance of 8-inch dynode photomultiplier tubes

Two different systems have been built to study the geomagnetic field effect on the performance of large area photomultiplier tubes. The main characteristics of photomultiplier tubes such as gain, collection efficiency, transition time spread and energy resolution were measured to investigate the effect. This study shows that both the dynode structure and the orientation of photomultiplier tubes have a large influence on the performance due to the geomagnetic field effect. Different methods were proposed and tested to reduce these effects. The results were obtained with and without high-permeability permalloy foil shielding. It is found that the effect of the geomagnetic field can be significantly reduced by the permalloy foil. The influence of the geomagnetic field under different installation geometries is also studied and discussed in this paper.

Large area MCP-PMT design with good time performance.

A new large area photomultiplier tube based on the microchannel plates (MCP-PMT) with high collection efficiency (CE) and good time performance is proposed in this paper. A novel focusing system with two cylindrical and a conical barrels is designed to generate the accelerating and focusing electric field. A three-dimensional model is developed by CST Studio Suite to validate its feasibility. Finite Integral Technique and Monte Carlo method are combined to simulate the process. Results predict that CE of the novel MCP-PMT is expected to be 100%. TTS of the photoelectrons from the whole photocathode achieves 1.2 ns. Differ from other large area PMTs, it performs well in the geomagnetic field.

Measurement of liquid argon scintillation light properties by means of an alpha source placed inside the CERN 10-PMT LAr detection system

A particle detection system that exploits the scintillation light produced by ionizing particles in liquid argon (LAr) has been assembled at CERN. The system is based on 10 large-area photomultiplier tubes (PMT) immersed in a 1500-liter dewar filled with liquid argon and equipped with an extendible feed-through and mechanical support for an alpha source (241Am). The position of the source can be changed with respect to the PMT plane in vertical and horizontal directions. Arrays of silicon photomultiplier (SiPM) photodetectors, integrated in the source support, are used for the data acquisition trigger and to define the t0 of the light generation. PMT and SiPM signals can be recorded at different distances and different positions allowing the measurement of some of the LAr scintillation light properties. The system was studied and characterized in detail, and physics results on LAr scintillation properties are expected soon.

Charge reconstruction in large-area photomultipliers

Large-area PhotoMultiplier Tubes (PMT) allow to efficiently instrument Liquid Scintillator (LS) neutrino detectors, where large target masses are pivotal to compensate for neutrinos' extremely elusive nature. Depending on the detector light yield, several scintillation photons stemming from the same neutrino interaction are likely to hit a single PMT in a few tens/hundreds of nanoseconds, resulting in several photoelectrons (PEs) to pile-up at the PMT anode. In such scenario, the signal generated by each PE is entangled to the others, and an accurate PMT charge reconstruction becomes challenging. This manuscript describes an experimental method able to address the PMT charge reconstruction in the case of large PE pile-up, providing an unbiased charge estimator at the permille level up to 15 detected PEs. The method is based on a signal filtering technique (Wiener filter) which suppresses the noise due to both PMT and readout electronics, and on a Fourier-based deconvolution able to minimize the influence of signal distortions—such as an overshoot. The analysis of simulated PMT waveforms shows that the slope of a linear regression modeling the relation between reconstructed and true charge values improves from 0.769 ± 0.001 (without deconvolution) to 0.989 ± 0.001 (with deconvolution), where unitary slope implies perfect reconstruction. A C++ implementation of the charge reconstruction algorithm is available online at [1].

Characterization of SiPM arrays in different series and parallel configurations

A number of innovative experiments dedicated to neutrino and rare-event physics use liquefied noble-gases both as a target and as a detector. These media have the remarkable property to efficiently produce scintillation photons after the passage of ionizing particles. Scintillation light, which is used for triggering and timing purposes, is traditionally detected by large area Photo-Multiplier Tubes (PMTs) working at cryogenic temperature. Silicon Photo-Multiplier (SiPM) arrays are gradually substituting PMTs in many applications, especially where low voltages are required and magnetic field is present. One of the problems of this devices is the small active area. For this reason we built several prototype arrays made by different SiPM models with a common readout: the basic unit is a device with an active area of (1.2×1.2)cm2. A fast signal leading edge is crucial to realize devices to be used for triggering and timing. To this purpose we studied different series/parallel electrical configurations to obtain the best timing performance, by operating our custom arrays both at room and cryogenic temperatures.

Comparison between large area PMTs and SiPM arrays deployed in a Liquid Argon Time Projection Chamber at CERN

Liquid argon Time Projection Chambers (LAr-TPCs) are among the most promising detectors for the study of neutrino oscillations. They are composed by a multi-wire drift chamber to collect the charge and a photodetection system to detect the scintillation light, both produced by ionizing charged particles that cross the argon volume. Scintillation light plays a fundamental role for the event reconstruction because it permits to calculate the absolute time t0 of the event and it is also used for triggering purposes. We present a comparison between the performances of large area Photo-Multiplier Tubes (PMTs) and Silicon Photo-Multiplier (SiPM) arrays deployed in a small LAr-TPC exposed to cosmic rays at CERN, both in terms of light collected and timing performances.

Total Emission Detection for Efficient and Affordable Two-Photon Fluctuation Correlation Spectroscopy (2P-Fcs)

Two-photon excitation is a convenient means to generate a tiny “privileged” excitation volume in solution or within a cell; within that sub-fL volume, one may glean photophysical properties: triplet quantum yield, diffusion rate, blinking probability, brightness, conformational mobility, etc. We recently developed the Total Emission Detection (TED) method and devices to recover the entirety of emission from cells and tissues being probed with multiphoton excitation (Combs et al., J Microsc. 2007, v.228,pp.330-7). TED is being exploited now for single (few) molecule spectroscopy studies such as FCS, PCHA, FLIM-FCS, etc. These approaches demand not only high light collection and detection efficiency but also negligible contribution from artifacts arising from detector dark noise and after-pulsing. The latter usually necessitate the use of expensive TE-cooled avalanche photodiodes (APDs) or hybrid PMTs.In this study we show that conventional large-area photomultiplier tubes (PMTs), tightly coupled with TED devices, help overcome challenges arising from highly scattering samples, low signal-to-noise ratios and afterpulses coming after true fluorescence photon detection. In some TED versions, a conventional non-descanned detection (NDD) pathway for fluorescence is still available, so a second PMT can be employed for one- or two-color cross-correlation (FCCS).In short, TED increases “effective” quantum efficiency enough for one to use less expensive PMTs as FCS/FCCS detectors, and this also permits one to select among PMTs with better picosecond, nanosecond or microsecond behaviors compared to APDs.

Comparison between large area photo-multiplier tubes at cryogenic temperature for neutrino and rare event physics experiments

An evaluation of the behavior of three large cathode area photo-multiplier tubes, Hamamatsu R5912 Mod and R5912-02 Mod, and ETL 9357 KFLB, was carried out both at room and cryogenic temperature, using a 405nm light source. The main electrical and optical features of the devices were studied; the obtained results were compared with the characteristics of the ETL 9357 FLA tubes, used in the ICARUS experiment. Tubes were also studied as a function of the Earth׳s magnetic field and an evaluation of the quantum efficiency was made in the vacuum ultraviolet light region.

Characterization of large area photomultiplier ETL 9357FLB for liquid argon detector

The China Dark Matter Experiment (CDEX) Collaboration will carry out a direct search for weakly interacting massive particles with germanium detectors. Liquid argon will be utilized as an anti-Compton and cooling material for the germanium detectors. A low-background and large-area photomultiplier tube (PMT) immersed in liquid argon will be used to read out the light signal from the argon. In this paper we have carried out a careful evaluation on the performance of the PMT operating at both room and cryogenic temperatures. Based on the single photoelectron response model, the absolute gain and resolution of the PMT were measured. This has laid a foundation for PMT selection, calibration and signal analysis in the forthcoming CDEX experiments.

Design and assembly of the optical modules for phase-2 of the NEMO project

The NEMO collaboration team has undertaken a Phase-2 project, which aims at the realization and installation of a new infrastructure at the Capo Passero (Italy) deep-sea site at a depth of 3500m. With this objective in mind, a fully equipped tower with 8-storey hosting two optical modules at each end is under construction. Following a well established procedure, 32 optical modules have been assembled. The optical module consists of a large area photomultiplier tube enclosed in a pressure resistant glass sphere with a diameter of 13in. The photomultiplier is a R7081 type, produced by Hamamatsu, with a photocathode area with a diameter of 10in. and 10 dynodes. Mechanical and optical contacts between the front of the photomultiplier tube and the glass surface are ensured by an optical bi-component silicone gel. A mu-metal cage is used to shield the photomultiplier against the influence of the Earth's magnetic field.

Design and production of the IceCube digital optical module

The first string of 70 in the IceCube neutrino observatory was deployed at the South Pole site in January 2005 and is now taking data. An IceCube string is composed of 60 digital optical modules (DOMs) each of which is an integrated package of a large area photomultiplier tube, high voltage unit, LED flasher calibration board, and embedded digital data acquisition system encased inside a glass pressure housing. The DOM posed a challenging design problem that had to simultaneously meet the extremes of high reliability in a remotely-deployed high pressure and low temperature environment, low power, wide dynamic range from single photon hits emitted by passing cosmic ray muons to tens of thousands of photons from immense electromagnetic showers, and fast time tagging of events to nanosecond precision. In addition the DOM had to be cost effective and reliably producible in quantities of several thousand units. The first year of real DOM production and testing was 2004: 400 DOMs were produced worldwide and tested in special dark freezer laboratories at temperatures ranging from + 25 to - 55 ∘ C . Two hundred and eighty DOMs were sent to the South Pole for deployment and tested there again prior to deployment. Now frozen in the ice, the DOMs are showing exceptionally promising functionality.

Study of large hemispherical photomultiplier tubes for the ANTARES neutrino telescope

The ANTARES neutrino telescope, to be immersed depth in the Mediterranean Sea, will consist of a three-dimensional matrix of 900 large area photomultiplier tubes housed in pressure-resistant glass spheres. The selection of the optimal photomultiplier was a critical step for the project and required an intensive phase of tests and developments carried out in close collaboration with the main manufacturers worldwide. This paper provides an overview of the tests performed by the collaboration and describes in detail the features of the photomultiplier tube chosen for ANTARES.