Multianode Photomultiplier Research Articles

High resolution scintillating-fibre hodoscope and its readout using peak-sensing algorithm

A pair of new hodoscopes made of 0.28 mm Ø scintillating fibre have been built and tested at T11 beam line of CERN PS. They consist of seven layers of fibres, and are read out using multi-anode photomultipliers. The average number of photoelectrons produced by a minimum ionizing particle is found to be about 11, which resulted in a very high detection efficiency (98.6%) at an appropriate threshold setting. The hit multiplicity for single-hit events was suppressed to 1.12 at this threshold setting, thanks to the Peak-Sensing Circuit used for the readout. A spatial resolution of ∼ 75 μ m and a time resolution of ∼ 0.56 ns (both in RMS) have been obtained with these hodoscopes. Further detailed study of the detector response such as double hit efficiency at very close distances, dependence on the incident angles has been performed.

A novel readout concept for multianode photomultiplier tubes with pad matrix anode layout

We have developed a new analog readout concept for multianode photomultiplier tubes with a pad matrix anode layout. This new readout technique is the result of a modification of a technique previously developed at the Detector Group of Jefferson Lab, (V. Popov, US patent No: 6,747,263 B1) [V. Popov, S. Majewski, A.G. Weisenberger, Readout Electronics for Multianode Photomultiplier Tubes with Pad Matrix Anode Layout, Thomas Jefferson National Accelerator Facility, IEEE 2003 Medical Imaging Conference Record, November 2003]. The new analog readout circuit provides the same analog conversion of matrix 2-D output into X and Y projective output with a significant reduction of analog outputs. The old readout network consists of resistors’ matrix and current collecting amplifiers, and it provides decoupling of each anode output into two directions (one to X and one to Y coordinates), but a decoupling function that is carried out independent of photomultiplier tube gains nonuniformity. A newly developed readout network (US patent pending) also consists of resistors’ matrix and current collecting amplifiers, but the new matrix includes an additional dumping resistor that provides an excess current from anode pad grounding. As a result, we subtract an extra current of high-gain pads in order to move the pads gain to an absolute minimum value for a given photomultiplier tube. This gain equalization procedure reduces image distortion related to gain nonuniformity. The new readout technique was used in several new radiation imaging detectors designed in the Detector Group of Jefferson Lab. It shows a visible readout uniformity and linearity improvement. The test results of an initial evaluation of this readout that is applied for data readout of four H8500 Hamamtsu PSPMT are presented.

Performance of 8- and 12-dynode stage multianode photo-multipliers

We report on studies of 64-channel Multianode Photo-Multiplier Tubes (MaPMTs) as photo-detectors for Ring Imaging CHerenkov (RICH) counters. The newly available 8-dynode stage MaPMT was tested in particle beams at CERN. The MaPMT signals were read out directly with the Beetle1.2 chip which was designed for the LHCb environment and operates at 40 MHz. The photon yield and signal losses were determined for a cluster of 3 × 3 close-packed MaPMTs. The performance of the 8-dynode stage MaPMT was compared to that of the 12-dynode stage MaPMT which has a larger intrinsic gain.

Optical adapters to improve the collection efficiency of the Multi-Anode Photo-Multipliers detectors

Aim of this work is to describe the optical system developed, with ray-tracing simulations, to improve the collection efficiency of Multi-Anode Photo-Multipliers (MAPMTs) detectors from Hamamatsu corp., used in nuclear, cosmic-rays and neutrino physics experiments. These optical collectors have imaging and filtering capability. Such characteristics allow to improve the collection efficiency of detectors, focusing all photons inside the sensitive area, and also to improve the signal-to-noise ratio by limiting the wave lengths band to the region of interest. These filtering properties allow to avoid background photons from nearby spectral regions and they are studied to minimize the wavelength shifting in comparison with the increasing of the incident angle. The spectrum of transmissivity have been realized with high transparency in wavelength range of interest and with a sharp cutoff outside. In this work, the application on different typologies of PMT have been studied. Particularly, the collection efficiency of the 64-channel PMT was improved from 45% to 75% using our optical adapters. On an electrostatic-focusing PMT, with an efficiency of 74%, the application of our innovative solutions have enhanced this efficiency exceeding 90%, including the band pass filter and keeping the mass below 25 g. First prototypes have been fabricated.

Design and prototype results of the FAST detector

A new fiber tracker is being developed for the ASACUSA experiment at the Antiproton Decelerator at CERN. The detector is based on 1 mm diameter scintillating fibers readout by HAMAMATSU 64 channel multianode photomultipliers (MA-PMTs) connected to a dedicated electronic chain. The paper gives a description of the testing procedures for time resolution, spatial resolution and efficiency measurements performed with standard NIM electronics and a commercial TDC and reports the results for different prototype detectors.

Design and status of COMPASS FAST-RICH

In the context of the upgrade of COMPASS RICH-1, we are developing a fast photodetection system for RICH counters, based on UV extended Multi-Anode PhotoMultiplier Tubes (MAPMT) and a custom, low dead-time electronic readout system. Photons are concentrated on the MAPMT photocathode by an optical system that preserves the position information. The ratio between the collection and the photosensitive surfaces is ∼ 7.5 in our design, larger than in previous applications. A new front-end electronics, based on a modified version of the MAD4 discriminator chip, is being realized to digitize the MAPMT signals. We report about the design of the photodetection system and of the associated electronic readout system, and on the preliminary test beam results.

Corrected position estimation in PET detector modules with multi-anode PMTs using neural networks

This paper studies the use of Neural Networks (NNs) for estimating the position of impinging photons in gamma ray detector modules for PET cameras based on continuous scintillators and Multi-Anode Photomultiplier Tubes (MA-PMTs). The detector under study is composed of a 49/spl times/49/spl times/10 mm/sup 3/ continuous slab of LSO coupled to a flat panel H8500 MA-PMT. Four digitized signals from a charge division circuit, which collects currents from the 8/spl times/8 anode matrix of the photomultiplier, are used as inputs to the NN, thus reducing drastically the number of electronic channels required. We have simulated the computation of the position for 511 keV gamma photons impacting perpendicularly to the detector surface. Thus, we have performed a thorough analysis of the NN architecture and training procedures in order to achieve the best results in terms of spatial resolution and bias correction. Results obtained using GEANT4 simulation toolkit show a resolution of 1.3 mm/1.9 mm FWHM at the center/edge of the detector and less than 1 mm of systematic error in the position near the edges of the scintillator. The results confirm that NNs can partially model and correct the non-uniform detector response using only the position-weighted signals from a simple 2D DPC circuit. Linearity degradation for oblique incidence is also investigated. Finally, the NN can be implemented in hardware for parallel real time corrected Line-of-Response (LOR) estimation. Results on resources occupancy and throughput in FPGA are presented.

Fast high resolution echelle spectroscopy of a laboratory plasma

An echelle diffraction grating and a multianode photomultiplier tube are paired to construct a high resolution (R=λ∕δλ≈2.5×104) spectrograph with fast time response for use from the UV through the visible. This instrument has analyzed the line shape of CIII impurity ion emission at 229.687nm over the lifetime (≈100μs) of the hydrogen plasmas produced at SSX. The ion temperature and line of sight average velocity are inferred from the observed thermal broadening and Doppler shift of the line. The time resolution of these measurements is about 1μs, sufficient to observe the fastest magnetohydrodynamic activity.

Performance of a multi-anode photomultiplier employing a weak electrostatic focusing system (Hamamatsu R8900 series)

We have developed and tested a new type of multi-anode photomultiplier: Hamamatsu R8900-03 series. The main feature of the R8900-03 series is a highly sensitive surface: ∼ 83 % of the physical area. In this paper we report on the results of measurements we performed to check several parameters of this new type of photomultiplier. R8900-03 photomultipliers are devices suitable for experiments where large collection area and uniform detection efficiency are essential characteristics.

Multichannel Time-Resolved Tissue Oximeter for Functional Imaging of the Brain

This paper reports the development and characterization of a novel multichannel time-resolved (TR) instrument for functional brain imaging studies. The instrument is based on picosecond diode lasers, fiber optics for light injection and delivery, a compact multianode photomultiplier, and a personal computer (PC) board for time-correlated single photon counting (TCSPC). The instrument has been characterized in terms of reproducibility among the nine sources and the 12 collection channels, linearity in the determination of optical properties (absorption and reduced scattering), and stability. Preliminary in vivo measurements were performed on volunteers to monitor the optical response to stimuli following a motor task (finger opposition, 5 Hz).

THE FOCAL SURFACE OF THE EUSO TELESCOPE

The Extreme Universe Space Observatory (EUSO) is a space mission to study extremely high-energy cosmic rays. The EUSO instrument is a wide-angle refractive telescope in near-ultraviolet wavelength region to observe time-resolved atmospheric fluorescence images of the extensive air showers from the International Space Station. The Focal surface is an aspherical curved surface, and its area amounts to about 4.5 m2. The focal surface detector is designed as a mosaic of multianode photomultipliers (MAPMT) for the single photoelectron counting capability. The strongest requirement for the focal surface detector is the maximization of the photon detection efficiency together with the uniformity over the focal surface. We have developed a new type of MAPMT. It is modified from the ordinary one and has a grid between the photocathode and the first dynode to electrostatically demagnify the photoelectron image on the dynode. We are also developing the HV supply system for a great number of MAPMTs. EUSO experiments the day-time and night-time every 90 minutes. The heat flow must be considered to stabilize the PMT characteristics, in parallel with the heat dissipation of the electronics attached on the focal surface supporting structure.

PHOTOMULTIPLIER DEVELOPMENT AND WAVELENGTH SHIFTER MANUFACTURING TO INCREASE THE DETECTION OF FAINT FLUORESCENCE SIGNALS

RIKEN has developed in collaboration with Hamamatsu a new type of Multi Anode Photomultiplier (MAPMT), R8900 series, with a large sensitive area of ~ 83% of the physical surface. The performance of R8900 is reviewed in the following. RIKEN has also manufactured a new type of wavelength shifter (w.s.) film to shift near-UV light (330 ÷ 400 nm ) to visible one. This film uses POPOP as a shifter and EPO-TEX as a substrate. The quantum efficiency of the film reaches ~ 80%.

Performance of 8-stage Multianode Photomultipliers

64-channel Multianode Photomultiplier (MaPMT) have been evaluated as a candidate photo detector for the LHCb Ring Imaging Cherenkov (RICH) counters. The newly available 8-dynode stage MaPMT were tested with particle beams at CERN. The MaPMT signals were read out directly by the Beetle 1.2 chip which is designed for silicon sensors operating at 40 MHz. The photon yield and signal loss in a cluster of 3x3 close-packed MaPMTs were determined and preliminary results matched expectations from simulations. The performance of the 8-stage MaPMT was compared to that of the 12-stage MaPMT which has a larger intrinsic gain. For the read out the Beetle 1.2MA0 chip has been designed to match the dynamic range of the 12-stage MaPMT. In addition by using a LED light source the performance of the MaPMTs was tested in magnetic fields up to 35 mT. In measurements without and with mu-metal shielding we determined the magnetic field in which the tubes still can be operated with 90% signal efficiency.

A Scintillator Tile Hadron Calorimeter for the Linear Collider Detector

Concept and design of a LC hadron calorimeter with so far unrivalled fine cell granularity are reviewed. Shown are first results from e+ beam-studies with a shower containing Fe/Scintillator sandwich mini-prototype with 107 small scintillator tiles of size of 5 × 5 × 0.5 cm 3 . The tiles were readout individually via inserted wavelength-shifting fibres. Multi-anode Photomultipliers (MAPM) and Silicon Photomultipliers (SiPM) were used alternatively for readout of the fibre signals. Detector resolution, linearity, calibration and stability are discussed. Within the estimated systematic errors no significant difference can be observed between both photodetector options. The results agree also with simulation results. Based on such studies, a 1 m3 prototype calorimeter with improved cell granularity ( 3 × 3 × 0.5 cm 3 ) will be built for extensive tests in hadron and electron beams at various particle energies and angles in order to improve the actual knowledge on hadronic shower patterns as needed for tuning of simulation programs and to optimize the reconstruction of all individual particles inside the narrow jets expected.

Development of front-end electronics with large dynamic range for space applications

A new low-noise, low-power, front-end chip with a dynamic range larger than 10 4 was designed for operation on space-based or balloon-borne experiments. Its performance were optimized with negative polarity signals for the readout of Multi-Anode Photomultipliers (MAPMT). A suitable set of operation parameters were also determined for the readout of Hybrid Photo Diodes (positive polarity). The chip performances were tested for both polarities with two different test boards implementing 16-bit digitization. Test results are reported.

Studies of MaPMTs with beetle-chip read-out

We have evaluated the 64-channel Multianode Photo-Multiplier (MaPMT) with 8-stage dynodes for the LHCb RICH detectors. With a Beetle 1.2 chip to read-out the MaPMT, we have demonstrated that the MaPMT performance is as expected using particle beams and LED light sources. We have also measured the pulse shape from 12-stage dynode MaPMTs, read out with the Beetle 1.2-MA0 chip.

Studies for a fast RICH

We are developing the design of a photon detection system for a fast RICH, to match the requirements arising from the foreseen enlarged luminosity of the COMPASS experiment. The system is based on UV extended multianode photomultipliers and a system of fused silica lenses that collect the light from a larger surface and guide it to the PMT photocathode, preserving the position information. In our design the ratio of the collection and the photosensitive surfaces is larger than in previous applications (it is of the order of 9), to keep the costs of the photon detection system affordable, while the emphasis is on the fast response of the detectors and the associated electronics. We report about the design parameters and the preliminary test beam results.

A new scintillator tile/fiber preshower detector for the CDF central calorimeter

A detector designed to measure early particle showers has been installed in front of the central CDF calorimeter at the Tevatron. This new preshower detector is based on scintillator tiles coupled to wavelength-shifting fibers read out by multi-anode photomultipliers and has a total of 3,072 readout channels. The replacement of the old gas detector was required due to an expected increase in instantaneous luminosity of the Tevatron collider in the next few years. Calorimeter coverage, jet energy resolution, and electron and photon identification are among the expected improvements. The final detector design, together with the R$&$D studies that led to the choice of scintillator and fiber, mechanical assembly, and quality control are presented. The detector was installed in the fall 2004 Tevatron shutdown and started collecting colliding beam data by the end of the same year. First measurements indicate a light yield of 12 photoelectrons/MIP, a more than two-fold increase over the design goals.

Design of a Base-Board for arrays of closely packed Multi-Anode Photo-Multipliers

We describe the design of a Base-Board to house Multi-Anode Photo-Multipliers for use in large-area arrays of light sensors. The goals, the design, the results of tests on the prototypes and future developments are presented.

Performance of Multi-anode Photomultiplier Tubes for the LHCb RICH detectors

An array of Multi-anode Photomultiplier Tubes (MaPMT) was evaluated for use in the LHCb Ring Imaging Cherenkov (RICH) detectors using a prototype RICH detector in a charged particle beam. The MaPMT performance was measured with different radiator gases with and without lenses. The performance of the MaPMTs in terms of photon yield and pixel cross-talk is presented.