Multi-anode Photomultiplier Tube Research Articles

The COMPASS RICH-1 detector upgrade

The COMPASS experiment at CERN provides hadron identification in a wide momentum range employing a large size gaseous Ring Imaging CHerenkov detector (RICH). The presence of large uncorrelated background in the COMPASS environment was limiting the efficiency of COMPASS RICH-1 in the very forward regime. A major upgrade of RICH-1 required a new technique for Cherenkov photon detection at count rates of several 106/s per channel in the central detector part, and a read-out system allowing for trigger rates of up to 100 kHz. To cope with these requirements, the photon detectors of the central region have been replaced with a fast photon detection system described here, while, in the peripheral regions, the existing multi-wire proportional chambers with CsI photo-cathodes have been equipped with a new read-out system based on APV preamplifiers and flash ADC chips. The new system consists of multi-anode photomultiplier tubes (MAPMTs) coupled to individual fused silica lens telescopes, and fast read-out electronics based on the MAD4 amplifier-discriminator and the dead-time free F1 TDC chip. The project was completely designed and implemented in less than two years: The upgraded detector is in operation since the 2006 CERN SPS run. We present the photon detection design, constructive aspects and test studies to characterise the single photon response of the MAPMTs coupled to the read-out system as well as the detector performance based on the 2006 data.

The COMPASS RICH-1 fast photon detection system

A fast photon detection system has been built as a part of the upgrade of the COMPASS RICH-1 detector: it is based on 576 multi-anode photomultiplier tubes (MAPMTs) coupled to individual fused silica lens telescopes and fast readout electronics. This system has replaced the MWPCs with CsI photo-cathodes in the central region ( 1.3 m 2 , 25% of the total area) of the COMPASS RICH-1 photon detectors and has successfully been operated during the data taking in 2006 and 2007. We report about the fast photon detection system design, construction and commissioning, in particular about the design optimization and the validation tests of the lens telescopes. Preliminary values for the increased performances of COMPASS RICH-1 after the upgrade are also presented.

The characterisation of the multianode photomultiplier tubes for the RICH-1 upgrade project at COMPASS

A major upgrade of the Cherenkov photon detection system of COMPASS RICH-1 has been performed and it has been in operation since the 2006 physics run. The inner part of the photon detector has been replaced by a different technology in order to measure Cherenkov photons at high photoelectron rates, up to several times 10 6 per second and per channel. Cherenkov photons from 200 to 750 nm are detected by 576 multianode photomultiplier tubes (MAPMTs) with 16 channels each, coupled to individual fused silica lens telescopes and fast, high sensitivity and high time resolution electronics read-out. To guarantee an optimal performance of the complete system, parameters like dark current, gain, uniformity, relative quantum efficiency have been measured for a totality of more than 600 MAPMTs (about 10 000 channels) in a fully automated test-stand, developed for this purpose. The ideal working point for each individual pixel could be ascertained by these measurements. In 2006 the newly equipped detector exhibited an excellent performance: about 56 detected photons per ring at saturation and a time resolution of better than 1 ns. We report about the MAPMT characterisation and the quality control set-up, protocol and results.

The fast readout system for the MAPMTs of COMPASS RICH-1

A fast readout system for the upgrade of the COMPASS RICH detector has been developed and successfully used for data taking in 2006 and 2007. The new readout system for the multi-anode PMTs in the central part of the photon detector of the RICH is based on the high-sensitivity MAD4 preamplifier-discriminator and the dead-time free F1-TDC chip characterized by high-resolution. The readout electronics has been designed taking into account the high photon flux in the central part of the detector and the requirement to run at high trigger rates of up to 100 kHz with negligible dead-time. The system is designed as a very compact setup and is mounted directly behind the multi-anode photomultipliers. The data are digitized on the front-end boards and transferred via optical links to the readout system. The readout electronics system is described in detail together with its measured performances.

Cherenkov detector of 90Sr based on aerogel as radiator

90Sr is a highly radiotoxic fission product, which may pollute the environment following an accident in a nuclear power plant. It is a pure β emitter and thus difficult to detect by standard methods. Recent progress in silica aerogel production, as well as the new multianode photomultiplier tubes (PMTs), offer possibilities for the detection of 90Sr, based on Cherenkov radiation of β particles emitted by its daughter 90Y. An appropriate choice of the aerogel refractive index (produced in the range between 1.005 and 1.06) determines the threshold for Cherenkov radiation and thus separates between higher and lower energy β particles. Multianode PMTs permit the determination of the Cherenkov photon yield, offering additional discrimination. An apparatus was constructed for the detection of the relatively higher energy β particles emitted by 90Y ( E max = 2.28 MeV ) and the detector performance was studied.

Status and perspectives of vacuum-based photon detectors for single photon detection

Recent developments in vacuum-based photon detectors for single photon detection, in particular, innovative techniques such as position-sensitive hybrid photon detectors and photo-multiplier tubes, have stimulated increased interest from a variety of fields. These devices are sensitive to single photons with an energy spectrum defined by the transmission of the optical entrance window and the photo-cathode type. Their spatial resolution ranges from a few millimetres, for pad hybrid photon detectors and multi-anode photo-multiplier tubes, down to a few tens of microns for pixel hybrid photon detectors. Basic technological and design aspects are assessed in this paper. The performance of such devices in terms of gain, intrinsic speed, single- and multiple photon counting capability, active-to-total area ratio, and magnetic field sensitivity are discussed. Specific problems related to the particular front-end and readout electronics requirements are outlined. Examples of applications are given, and some current research and development programmes are presented.

MAPMT H7546B Anode Current Response Study for an ILC SiD Muon System Prototype

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The proposed Silicon Detector concept for the International Linear Collider has a barrel and end cap muon systems. The scintillator based muon system prototype has 256 scintillating strips, wavelength-shifting fibers, and clear fibers connected to multianode photo multiplier tubes (MAPMT). Six Hamamatsu H7546B tubes were used. To understand strip output, each of 384 MAPMT outputs was independently measured at a given luminous flux and the same photocathode to anode voltage of 800 V. For the test, a custom made source of light was used. The anode currents have a wide spread; for all tubes the maximum value is 5.23 times larger than the minimum value. The MAPMT cross talk was measured for one of the central inputs. The maximum cross talk value is about 4.9%. The average cross talk for the nearest four neighboring channels is 3.9%, for the farther four 1%. To assure reproducibility and repeatability of the measurements a double reference method was used. </para>

Operation and performance of the FAST detector at the AD machine

The FAST (Fiber Antiproton Scintillating Tracker) detector has been installed at the Antiproton Decelerator at the CERN PS. Its goal is the measurement of the annihilation cross section of slow antiprotons (around 5 MeV) in gaseous targets in the ASACUSA experiment. FAST has to reconstruct the charged pions tracks to identify the annihilation vertices. The detector consists of 2 axial and 4 stereo layers of scintillating fibers. Each layer is built with 1 mm 50 cm long BCF-10 fibers readout by 64 channel multianode PMTs for a total of 2688 readout channels. The anode outputs, amplified and discriminated, are sampled with a 320 MHz clock inside a Cyclone II FPGA by Altera, in order to retrieve the time information of each hit. The readout system is designed to cope with a spilled beam which lasts 250 ns every minute. The expected number of events per spill was around 10. This paper will describe the operation and the performance of the FAST detector during the tests with cosmic rays (August 2006) and during the data taking on the beam (September 2006).

The neutrino oscillation OPERA experiment Target Tracker

The main task of the Target Tracker of the long baseline neutrino oscillation OPERA experiment, is to locate in which of the target elementary constituents, the lead/emulsion bricks, the neutrino interactions have occurred and also to give calorimetric information about each event. The technology used consists in walls of two planes of long plastic scintillator strips, one per transverse direction. Wavelength shifting fibres collect the light signal emitted by the scintillator strips and guide it to both ends where it is read by multi-anode photomultiplier tubes. The Target Tracker is composed of 62 scintillating walls of a total surface of about 6000 m 2 . Each wall is made by assembling 4 horizontal and 4 vertical modules of 64.7 m long, scintillating strips. This detector has observed the first neutrino interactions during August 2006. In this paper we will describe all elements used for the construction and operation of this detector and we will also give its main characteristics.

Development of a parallel detection and processing system using a multidetector array for wave field restoration in scanning transmission electron microscopy

A parallel image detection and image processing system for scanning transmission electron microscopy was developed using a multidetector array consisting of a multianode photomultiplier tube arranged in an 8 x 8 square array. The system enables the taking of 64 images simultaneously from different scattered directions with a scanning time of 2.6 s. Using the 64 images, phase and amplitude contrast images of gold particles on an amorphous carbon thin film could be separately reconstructed by applying respective 8 shaped bandpass Fourier filters for each image and multiplying the phase and amplitude reconstructing factors.

Fast photon detection for particle identification with COMPASS RICH-1

Particle identification (PID) at high rates is an important challenge for many current and future high-energy physics experiments. The upgrade of the COMPASS RICH-1 detector requires a new technique for Cherenkov photon detection at count rates of several 10 6 per channel in the central detector region, and a read-out system allowing for trigger rates of up to 100 kHz. To cope with these requirements, the photon detectors in the central region have been replaced with the detection system described in this paper. In the peripheral regions, the existing multi-wire proportional chambers with CsI photocathode are now read out via a new system employing APV pre-amplifiers and flash ADC chips. The new detection system consists of multi-anode photomultiplier tubes (MAPMT) and fast read-out electronics based on the MAD4 discriminator and the F1-TDC chip. The RICH-1 is in operation in its upgraded version for the 2006 CERN SPS run. We present the photon detection design, constructive aspects and the first Cherenkov light in the detector.

An operative gamma camera for sentinel lymph node procedure in case of breast cancer

Large field of view gamma cameras are widely used to perform lymphoscintigraphy in thesentinel lymph nodes (SLN) procedure in case of breast cancer. However, they are not specified for thisapplication and their sizes do not enable their use in the operative room to control the excision of the allSLN. We present the results obtained with a prototype of a new mini gamma camera developed especiallyfor the operative lymphoscintigraphy of the axillary area in case of breast cancer. This prototype iscomposed of 10 mm thick parallel lead collimator, a 2 mm thick GSO:Ce inorganic scintillating crystalfrom Hitachi and a Hamamatsu H8500 flat panel multianode (64 channels) photomultiplier tube(MAPMT) equipped with a dedicated electronics. Its actual field of view is 50 × 50mm2. The gammainteraction position in the GSO scintillating plate is obtained by calculating the center of gravity of thefired MAPMT channels. The measurements performed with this prototype demonstrate the usefulness ofthis mini gamma camera for the pre, per and post-operative identification of SLN's and how itscomplementary role with an intraoperative handheld gamma probe enables to improve the efficiency ofthis practice. A 100 × 100mm2 field of view camera designated to cover the entire axillary area is underinvestigation.

The OPERA experiment Target Tracker

The main task of the Target Tracker detector of the long baseline neutrino oscillation OPERA experiment is to locate in which of the target elementary constituents, the lead/emulsion bricks, the neutrino interactions have occurred and also to give calorimetric information about each event. The technology used consists in walls of two planes of plastic scintillator strips, one per transverse direction. Wavelength shifting fibres collect the light signal emitted by the scintillator strips and guide it to both ends where it is read by multi-anode photomultiplier tubes. All the elements used in the construction of this detector and its main characteristics are described.

Wide field aplanatic two-mirror telescopes for ground-based γ-ray astronomy

Aplanatic telescopes with two aspheric mirrors, configured to correct spherical and coma aberrations, are considered for application in γ-ray astronomy utilizing the ground-based atmospheric Cherenkov technique. We explore the phase space of optical system parameters to find telescope configurations which minmize astigmatism. It is shown that unlike the traditional prime-focus Davies-Cotton design, such telescopes provide a solution for wide field of view γ-ray observations. The designs are isochronous, can be optimized to have no vignetting across the field, and allow for significant reduction of the plate scale, making them compatible with finely-pixilated cameras, which can be constructed from modern, cost-effective image sensors such as multi-anode PMTs, SiPMs, or image intensifiers.

Progress in tagged neutron beams for cargo inspections

The use of neutron beams produced via the D+T reaction and tagged by the associated particle technique has been recently applied to cargo container inspections. In the EURITRACK project, a portable sealed-tube neutron generator has been designed and built to deliver 14MeV neutron beams tagged by a matrix of 64 YAP:Ce alpha-particle detectors read by a multi-anode HAMAMATSU H8500 Photomultiplier Tube. The performances of this alpha-particle detector have been determined as a function of the count rate at the Rudjer Boskovic Institute, Zagreb (Croatia). Moreover, tests of the final detector operated inside the sealed-tube neutron generator are fully satisfactory.

Multifocal multiphoton microscopy based on multianode photomultiplier tubes

Multifocal multiphoton microscopy (MMM) enhances imaging speed by parallelization. It is not well understood why the imaging depth of MMM is significantly shorter than conventional single-focus multiphoton microscopy (SMM). In this report, we show that the need for spatially resolved detectors in MMM results in a system that is more sensitive to the scattering of emission photons with reduced imaging depth. For imaging depths down to twice the scattering mean free path length of emission photons (2xl (s) (em)), the emission point spread function (PSF(em)) is found to consist of a narrow, diffraction limited distribution from ballistic emission photons and a broad, relatively low amplitude distribution from scattered photons. Since the scattered photon distribution is approximately 100 times wider than that of the unscattered photons at 2xl (s) (em), image contrast and depth are degraded without compromising resolution. To overcome the imaging depth limitation of MMM, we present a new design that replaces CCD cameras with multi-anode photomultiplier tubes (MAPMTs) allowing more efficient collection of scattered emission photons. We demonstrate that MAPMT-based MMM has imaging depth comparable to SMM with equivalent sensitivity by imaging tissue phantoms, ex vivo human skin specimens based on endogenous fluorophores, and green fluorescent protein (GFP) expressing neurons in mouse brain slices.

Performance of a four-output front-end electronics for multi-anode PMTS readout of scintillator arrays

We have developed a front-end electronics for the readout of Hamamatsu H8500 64 channels multi-anode Photomultiplier tube based on a dedicated active resistive charge divider network between anodes, and a fast acquisition board. The used resistive chain reduces the number of outputs from 64 down to 4 only. In this work, we present the performance study of the system in terms of spatial resolution, peak-to-valley ratio ( P/V) and energy resolution for various scintillators (YAP:Ce, LYSO, NaI), pixel pitches (2.0 mm down to 1.5 mm), and γ-ray energy.

Design and Testing of a Position-Sensitive Plastic Scintillator Detector for Fast Neutron Imaging

We describe the design and performance of a position sensitive scintillator detector developed for neutron measurements. Several of these detectors are to be used in the assembly of the Fast Neutron Imaging Telescope (FNIT), an instrument with imaging and energy measurement capabilities, sensitive to neutrons in the 2-20 MeV energy range. FNIT was initially conceived to study solar neutrons as a candidate instrument for the Inner Heliospheric Sentinels (IHS) program under formulation at NASA. It is now being adapted to locate Special Nuclear Material (SNM) for homeland security purposes by detecting fission neutrons and reconstructing the image of their source. The detection principle is based on multiple elastic neutron-proton scatterings in organic scintillator. The detector presented here utilizes wavelength-shifting (WLS) fibers, grooved into the plastic scintillator and read out by multianode photomultiplier tubes (MAPMTs) to determine scattering locations. By also measuring the recoil proton and scattered neutron's energies, the direction and energy spectrum of incident neutrons can be determined and discrete sources identified

FAST: A scintillating fiber tracker for antiprotons annihilation detection

A new fiber detector has been developed for the measurement of the annihilation cross-section of slow antiprotons (5 MeV for the 2006 run, < 1 keV in 2007) in gaseous targets in the framework of the ASACUSA experiment at the AD Antiproton Decelerator at CERN. The cylindrical gaseous target, 10 cm in radius, is surrounded by 2 axial and 4 stereo scintillating fiber layers built with 1 mm BCF-10 fibers from Bicron. The scintillation light released by charged pions originating in the annihilation vertex is readout by 64 channel multianode PMTs produced by HAMAMATSU. The anode outputs are amplified and discriminated with VLSI ASICs manufactured by IDEAS (VA64TAP2.1) and then sampled with a 320 MHz clock in order to extract the hit and time information by a set of ALTERA FPGAs. The paper describes the detector assembly, the custom electronics readout chain and the results of the tests during the commissioning phase.

Inter-crystal scatter identification for a depth-sensitive detector using support vector machine for small animal positron emission tomography

In a conventional positron emission tomography (PET) detector, detected events are projected onto a 2D position histogram by an Anger calculation for crystal identification. However, the measured histogram is affected by inter-crystal scatterings (ICS) which occur in the entire detector. Peaks which are projected for each crystal in the histogram are blurred, and this causes ICS mispositioning. A depth-of-interaction (DOI) detector has been developed for the small animal PET scanner jPET-RD. This DOI detector uses 32×32 crystals with four layers and a 256-channel multi-anode flat panel photomultiplier tube (FP-PMT) which was developed by Hamamatsu Photonics K.K. Each crystal element is 1.45×1.45×4.5 mm 3. The FP-PMT has a large detective area (49×49 mm 2) and a small anode pitch (3.04 mm). Therefore, the FP-PMT can extensively trace the behavior of incident γ rays in the crystals including ICS event. We, therefore, propose a novel method for ICS estimation using a statistical pattern recognition algorithm based on a support vector machine (SVM). In this study, we applied the SVM for discriminating photoelectric events from ICS events generated from multiple-anode outputs. The SVM was trained by uniform irradiation events generated from a detector simulator using a Monte Carlo calculation. The success rate for ICS event identification is about 78% for non-training data. The SVM can achieve a true subtraction of ICS events from measured events, and it is also useful for random correction in PET.