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Silicon (Si) single-photon avalanche diode (SPAD) arrays sensitive to the 400- to 900-nm wavelength range have been studied for a number of uses due to their high detection efficiency; zero readout noise; low timing jitter; mechanical robustness; low-voltage ( $256\times256$ array of 10- $\mu \text{m}$ active diameter SPADs, each with live recording of their dark count rate (DCR), up to a cumulative displacement damage dose equivalent to that delivered by a 1-MeV neutron fluence of $5.69\cdot 10^{9}$ cm $^{-2}$ in Si (11.59 TeV/g). A small fraction (~2.57%) of the SPADs in the array experienced a significant step increase in their DCR, which we ascribe to displacement damage. The remainder experienced a far more gradual and subdued increase. For this reason, an operational concept for SPAD arrays, whereby SPADs that begin to exhibit a step increase in DCR are disabled, should significantly extend the useful performance of such arrays in radiation environments. We report the surviving proportion of an array implementing such an operational concept per unit dose and its DCR.

We propose to use the High Momentum Spectrometer of Hall C combined with the Neutral Particle Spectrometer (NPS) to perform high precision measurements of the Deeply Virtual Compton Scattering (DVCS) cross section using a beam of positrons. The combination of measurements with oppositely charged incident beams is the only unambiguous way to disentangle the contribution of the DVCS $$^2$$ term in the photon electroproduction cross section from its interference with the Bethe-Heitler amplitude. This provides a stronger way to constrain the Generalized Parton Distributions of the nucleon. A wide range of kinematics accessible with an 11 GeV beam off an unpolarized proton target will be covered. The $$Q^2-$$ dependence of each contribution will be measured independently.

An Electron-Ion Collider (EIC) has been proposed to further explore the strong force and QCD, focusing on the structure and the interaction of gluon-dominated matter. A generic detector RD a dual-radiator RICH, consisting of an aerogel radiator and C2F6 gas in a mirror-focused configuration. We present the simulations of the two detectors and their estimated performance.

A powerful new electron–ioncollider (EIC) has been recommended in the 2015 Long Range Plan for Nuclear Science for probing the partonic structure inside nucleons and nuclei with unprecedented precision and versatility [1] . EIC detectors are currently under development [2] , all of which require hadron identification over a broad kinematic range. A prototype ring imaging Cherenkov detector has been developed for hadron identification in the momentum range from 3 GeV/c to 10 GeV/c. The key feature of this new detector is a compact and modular design, achieved by using aerogel as radiator and a Fresnel lens for ring focusing. In this paper, the results from a beam test of a prototype device at Fermilab are reported.

Advanced detector R&D requires performing computationally intensive and detailed simulations as part of the detector-design optimization process. We propose a general approach to this process based on Bayesian optimization and machine learning that encodes detector requirements. As a case study, we focus on the design of the dual-radiator Ring Imaging Cherenkov (dRICH) detector under development as part of the particle-identification system at the future Electron-Ion Collider (EIC). The EIC is a US-led frontier accelerator project for nuclear physics, which has been proposed to further explore the structure and interactions of nuclear matter at the scale of sea quarks and gluons. We show that the detector design obtained with our automated and highly parallelized framework outperforms the baseline dRICH design within the assumptions of the current model. Our approach can be applied to any detector R&D, provided that realistic simulations are available., 22 pages, 11 figures

The motivation of this paper is to explore the parameters that affect the performance of Microchannel Plate Photomultiplier Tubes (MCP-PMTs) in magnetic fields with the goal to guide their design to achieve a high magnetic field tolerance. MCP-PMTs based on two different designs were tested. The magnetic field tolerance of MCP-PMT based on a design providing independently biased voltages showed a significant improvement (up to 0.7 T) compared to the one utilizing an internal resistor chain design (up to 0.1 T), indicating the importance of individually adjustable voltages. The effects of the rotation angle of the MCP-PMT relative to the magnetic field direction and of the bias voltage between the photocathode and the top MCP were extensively investigated using the MCP-PMT based on the independently biased voltage design. It was found that the signal amplitude of the MCP-PMT exhibits an enhanced performance at a tilt angle of ± 8°, due to the 8°bias angle of the MCP pores. The maximum signal amplitude was observed at different bias voltages depending on the magnetic field strength.

Investigating human brain function in response to environmental stimuli requires freely moving humans without attached instrumentation. The RoomPET concept provides a feasible solution for human brain imaging. A RoomPET system is a room that contains an optical head tracking system and PET detectors that move to keep the head in the PET detector field-of-view. As a proof of principle, a small box-size prototype was built to demonstrate feasibility of RoomPET with gantry mechanics, tracking capabilities, and control systems.

A new laser-based externally-modulated electro-optically coupled detector (EOCD) architecture is being developed to enable high-density readout for radiation detectors with accurate analog radiation pulse shape and timing preservation. Unlike digital conversion before electro-optical modulation, the EOCD implements complete analog optical signal modulation and multiplexing in its detector front-end. The result is a compact, high performance detector readout that can be both radiation tolerant and immune to magnetic fields. In this work, the feasibility of EOCD was explored by constructing a two-wavelength laser-based externally-modulated EOCD, and testing analog pulse shape preservation and wavelength-division multiplexing (WDM) crosstalk. Comparisons were first made between the corresponding initial pulses and the electro-optically coupled analog pulses. This confirmed an excellent analog pulse preservation over $ \sim {\hbox {29}}\% $ of the modulator’s switching voltage range. Optical spectrum analysis revealed less than $-{\hbox {14}}~\hbox{dB}$ crosstalk with 1.2 nm WDM wavelength bandgap, and provided insight on experimental conditions that could lead to increased inter-wavelength crosstalk. Further discussions and previous research on the radiation tolerance and magnetic field immunity of the candidate materials were also given, and quantitative device testing is proposed in the future.

We report on the measurement of the neutron radiation hardness of silicon photomultipliers (SiPMs) manufactured by Hamamatsu Corporation in Japan and SensL in Ireland. Samples from both companies were irradiated by neutrons created by a 1 GeV electron beam hitting a thin lead target at Jefferson Lab Hall A. More tests regarding the temperature dependence of the neutron radiation damage and self-annealing were performed on Hamamatsu SiPMs using a calibrated Am-Be neutron source from the Jefferson Lab Radiation Control group. As the result of irradiation both dark current and dark rate increase linearly as a function of the 1 MeV equivalent neutron fluence and a temperature dependent self-annealing effect is observed., arXiv admin note: substantial text overlap with arXiv:physics/0211118

GlueX is a new detector being constructed at Jefferson Laboratory to study gluonic excitations and confinement via the detection of exotic meson states. The hermetic detector includes a barrel calorimeter where the photodetectors must operate in a high magnetic field exceeding 0.5 T. After extensive tests with a variety of sensors, the chosen photodetector will be a custom silicon photomultiplier (SiPM) array manufactured by Hamamatsu Corporation. This paper will focus on the characterization of the first 80 production samples of these SiPMs, including dark rate, photodetection efficiency (PDE), crosstalk, response uniformity and radiation tolerance.

Several positron emitting radioisotopes such as (11)C and (13)N can be used in plant biology research. The (11)CO(2) tracer is used to facilitate plant biology research toward optimization of plant productivity, biofuel development and carbon sequestration in biomass. Positron emission tomography (PET) imaging has been used to study carbon transport in live plants using (11)CO(2). Because plants typically have very thin leaves, little medium is present for the emitted positrons to undergo an annihilation event. The emitted positrons from (11)C (maximum energy 960 keV) could require up to approximately 4 mm of water equivalent material for positron annihilation. Thus many of the positrons do not annihilate inside the leaf, resulting in limited sensitivity for PET imaging. To address this problem we have developed a compact beta-positive, beta-minus particle imager (PhytoBeta imager) for (11)CO(2) leaf imaging. The detector is based on a Hamamatsu H8500 position sensitive photomultiplier tube optically coupled via optical grease to a 0.5 mm thick Eljen EJ-212 plastic scintillator. The detector is equipped with a flexible arm to allow its placement and orientation over or under the leaf to be studied while maintaining the leaf's original orientation. To test the utility of the system the detector was used to measure carbon translocation in a leaf of the spicebush (Lindera benzoin) under two transient light conditions.

In its latest Long Range Plan for Nuclear Science Research in the U.S., the Nuclear Science Advisory Committee to the Department of Energy recommended that in regards to new nuclear-physics facilities, the construction of an Electron Ion Collider (EIC) be of the highest priority after the completion of the Facility for Rare Isotope Beams. In order to carry out key aspects of the scientific program of the EIC, the EIC central detector must be capable of hadron particle identification (PID) over a broad momentum range of up to 50 GeV/c. The goal of the EIC-PID consortium is to develop an integrated program for PID at EIC, which employs several different technologies for imaging Cherenkov detectors. Here we discuss the conceptual designs and the expected PID performance of two of these detectors, as well as the newest results of gain evaluation studies of photon sensors that are good candidates to read out these detectors. Development of a gas-aerogel dual-radiator Ring Imaging Cherenkov (dRICH) detector with outward focusing mirrors is being pursued for the hadron endcap. Simulations demonstrate that the dRICH can provide a continuous ≥ 3σ π /K/p separation from 2.5 GeV/c to 50 GeV/c. A modular aerogel Ring Imaging Cherenkov (mRICH) detector with a Fresnel lens as a focusing element is being pursued for the electron endcap. The design provides for hadron identification over a momentum range of 3 GeV/c–10 GeV/c. The working principle of the mRICH design has been proven in a beam test with a first prototype. The location of the sensor readout planes of the Cherenkov detectors in the magnetic field of the central-detector solenoid, which is expected to be within 1.5 T–3 T, makes is necessary to evaluate the limit of the acceptable performance of commercially available photosensors, such as microchannel-plate photomultipliers (MCP PMTs). Here we present the results of gain evaluation of multi-anode MCP PMTs with a pore size of 10 μm. Overall, our preliminary results suggest that the 10-μm pore-size sensors can be operated in a magnetic field with magnitude up to Bmax of 2 T. The value of Bmax depends on the relative orientation between the sensor and the field.

We propose a photon detector for recording low-level and ultra-fast optical signals, based on radio frequency (RF) analysis of low-energy photoelectrons (PEs). By using currently developed 500 MHz RF deflector, it is possible to scan circularly and detect single PEs, amplified in multi-channel plates (MCPs). The operation of the tube is investigated by means of thermionic electron source. It is demonstrated that the signals generated in the MCP can be processed event by event; by using available nanosecond electronics and that time resolution better than 20 ps can be achieved. Timing characteristics of the Cherenkov detector with RF phototube in a ‘head-on’ geometry is investigated by means of Monte Carlo simulation.

Improvements in the time resolution of the CEBAF Large Acceptance Spectrometer (CLAS) below ≈50ps will be required for experiments using the planned upgraded accelerator facility at Jefferson Lab. The improved time resolution will allow particle identification using time-of-flight techniques to be used effectively up to the proposed operating energy of 12GeV. The challenge of achieving this time resolution over a relatively large area is compounded because the photomultipliers (PM) in the CLAS “time-zero” scintillating counters must operate in very high magnetic fields. Therefore, we have studied the resolution of “time-zero” prototypes with microchannel plate PMs 85001-501 from Burle. For reference and comparison, measurements were also made using the standard PMs R2083 from Hamamatsu using two timing methods. The cosmic ray method, which utilizes three identical scintillating counters (Bicron BC-408, 2×3×50cm3) with PMs at the ends, yields σR2083=59.1±0.7ps. The location method of particles from a radiative source with known coordinates has been used to compare timing resolutions of R2083 and 85001-501. This method yields σR2083=59.5±0.7ps and it also provides an estimate of the number of primary photoelectrons. For the microchannel plate PM from Burle the method yields σ85001=130±4ps due to lower number of primary photoelectrons.

Our group is developing a scanner that combines x-ray, single gamma, and optical imaging on the same rotating gantry. Two functional modalities (SPECT and optical) are included because they have different strengths and weaknesses in terms of spatial and temporal decay lengths in the context of in vivo imaging, and because of the recent advent of multiple reporter gene constructs. The effect of attenuation by biological tissue on the detected intensity of the emitted signal was measured for both gamma and optical imaging. Attenuation by biological tissue was quantified for both the bioluminescent emission of luciferace and for the emission light of the near infrared fluorophore cyanine 5.5, using a fixed excitation light intensity. Experiments were performed to test the feasibility of using either single gamma or x-ray imaging to make depth-dependent corrections to the measured optical signal. Our results suggest that significant improvements in quantitation of optical emission are possible using straightforward correction techniques based on information from other modalities. Development of an integrated scanner in which data from each modality are obtained with the animal in a common configuration will greatly simplify this process.

A proximity focusing RICH detector has been constructed for the hadron High Resolution Spectrometer (HRS) of Jefferson Lab Experimental Hall-A. This detector is intended to provide excellent hadron identification up to a momentum of 2.5 GeV / c . The RICH uses a 15 mm thick liquid perfluorohexane radiator in proximity focusing geometry to produce Cherenkov photons traversing a 100 mm thick proximity gap filled with pure methane and converted into electrons by a thin film of CsI deposited on the cathode plane of a MWPC. The detector has been successfully employed in the fixed target, high luminosity and high resolution hypernuclear spectroscopy experiment. With its use as a kaon identifier in the 2 GeV / c region, the very large contribution from pions and protons to the hypernuclear spectrum was reduced to a negligible level. The basic parameters and the resulting performance obtained during the experiment are reported in this paper.

The ability to detect the emissions of radioactive isotopes through radioactive decay (e.g. beta particles, x-rays and gamma-rays) has been used for over 80 years as a tracer method for studying natural phenomena. More recently a positron emitting radioisotope of carbon: 11 C has been utilized as a 11 CO 2 tracer for plant ecophysiology research. Because of its ease of incorporation into the plant via photosynthesis, the 11 CO 2 radiotracer is a powerful tool for use in plant biology research. Positron emission tomography (PET) imaging has been used to study carbon transport in live plants using 11 CO 2 . Presently there are several groups developing and using new PET instrumentation for plant based studies. Thomas Jefferson National Accelerator Facility (Jefferson Lab) in collaboration with the Duke University Phytotron and the Triangle Universities Nuclear Laboratory (TUNL) is involved in PET detector development for plant imaging utilizing technologies developed for nuclear physics research. The latest developments of the use of a LYSO scintillator based PET detector system for 11 CO 2 tracer studies in plants will be briefly outlined.

Important information on the LN interaction can be obtained from High Resolution Hypenuclear Spectroscopy experiments with electromagnetic probes. A challenging experiment on electroproduction of hypernuclei is scheduled for 2003 in Hall A at Jefferson Lab. One of the challenges is the high performance particle identification system needed. The signal is expected to be rare compared to the very high pion and proton backgrounds due to the small electron and kaon detection angles. The ‘‘standard’’ Hall A PID apparatus (TOF and two aerogel threshold Cherenkov detectors) does not provide sufficient suppression of the background. Simulations and calculations have shown that a RICH detector would solve the problem. A proximity focusing fluorocarbon/CsI detector similar to the ALICE RICH detector has been designed, built, tested and commissioned. The results show that the detector performs as expected. r 2003 Published by Elsevier Science B.V. PACS: 29.40.Ka; 85.60.Gz

The design, construction, and performance of the CLAS Cherenkov threshold gas detector at Jefferson Lab is described. The detector consists of 216 optical modules. Each module consists of three adjustable mirrors of lightweight composite construction, a Winston light collecting cone, a 5-in. photomultiplier tube, and specially designed magnetic shielding. Efficiencies and response functions have been measured.

The CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab utilizes six iron-free superconducting coils to provide an approximately toroidal magnetic field. The six sectors are instrumented individually to form six independent spectrometers. The forward region (8deg < (theta) < 45deg) of each sector is equipped with a lead-scintillator electromagnetic sampling calorimeter (EC), 16 radiation lengths thick, using a novel triangular geometry with stereo readout. With its good energy and position resolution, the EC is used to provide the primary electron trigger for CLAS. It is also used to reject pions, reconstruct pi-0 and eta decays and detect neutrons, This paper treats the design, construction and performance of the calorimeter.

Results are presented on several new highly efficient, fast, safe, and “environmentally friendly” liquid scintillator. Liquid scintillators can be contained in tubes or FEP Teflon-lined containers serving, at the same time, as light guides. The immediate application areas are in scintillation hodoscopes and TOF counters whenever complicated counter shapes (bends, corners, etc.) are required.

PhytoPET is a modular positron emission tomography (PET) system designed specifically for plant imaging. The PhytoPET design allows flexible arrangements of PET detectors based on individual standalone detector modules built from single Hamamatsu H8500 position sensitive photomultiplier tubes and pixelated LYSO arrays. We have used the PhytoPET system to perform preliminary corn plant imaging studies at the Duke University Biology Department Phytotron. Initial evaluation of the PhytoPET system to image the biodistribution of the positron emitting tracer 11C in corn plants is presented. 11CO 2 is loaded into corn seedlings by a leaf-labeling cuvette and translocation of 11C-sugars is imaged by a flexible arrangement of PhytoPET modules on each side. The PhytoPET system successfully images 11C within corn plants and allows for the dynamic measurement of 11C-sugar translocation from the leaf to the roots.

Hall D at Jefferson Laboratory is building its new GlueX spectrometer to study QCD gluonic excitations. The hermetic detector includes a scintillating fiber-lead barrel calorimeter where the photodetectors must operate in a high magnetic field. The silicon photomultiplier (SiPM) array manufactured by Hamamatsu Corporation was chosen for the photodetector of the BCAL. We report on the measurement of neutron radiation hardness of SiPMs at Jefferson Lab.

Several applications of two Hamamatsu position sensitive photomultiplier tubes to the detection of high energy particles with scintillating fibers are discussed. The PMTs are of the multiwire anode grid design, type R2486 and R4135. These tubes were tested with both single samples and arrays of 2 and 3 mm diameter scintillating fibers. Measurements of position resolution of the PMTs using either the charge digitization or the delay line readout techniques were made. The results indicate an intrinsic inability of the technique to reconstruct the actual position of a fiber on the photocathode when its location falls halfway between two grid wires. A way to overcome this limit is suggested.

A radially-compact subsystem providing particle identification (e/π, π/K, K/p) over a wide momentum range is an essential requirement for the central detector of an Electron-Ion Collider (EIC). With a radial size of only a few cm, a detector based on Detection of Internally Reflected Cherenkov light (DIRC) principle is a very attractive solution. The R&D undertaken by the EIC PID consortium achieved the goal of showing feasibility of a high-performance DIRC that would extend the momentum coverage well beyond state-of-the-art allowing 3σ separation of π/K up to 6 GeV/c, e/K up to 1.8 GeV/c and p/K up to 10 GeV/c. A key component to reach such a performance is a special 3-layer spherical compound lens. This article describes the status of the design and R&D for the DIRC at EIC detector, with a focus on the detailed Monte Carlo simulation results for the high-performance DIRC.

Here we present preliminary results for the gain performance of commercially available 3-mu m and 6-mu m pore-size single-anode microchannel-plate photomultipliers (MCP PMTs) in magnetic fields up to 5 T and for various orientations of the sensor relative to the field direction. The measurements were performed at Thomas Jefferson National Accelerator Facility in Newport News, VA. Our results show that smaller-pore-size PMTs have better gain performance in magnetic fields. At various angles, the shape of the gain dependence on the strength of the magnetic field strongly depends on the type of the sensor. Also, for each sensor, the azimuthal dependence is strongly correlated with the polar angle. Overall, the sensors exhibit a reasonable performance up to 2 T, although that upper limit depends on the sensor, the applied high voltage, and the orientation of the sensor relative to the field. To optimize the operational and design parameters of MCP PMTs for performance in high magnetic fields, further measurements and simulation studies will be pursued. Our studies are part of an R&D for development of a Detector of Internally Reflected Cherenkov Light for the central detector of a future U.S. Electron Ion Collider.

We developed a novel calibration methodology for a PET detector with dual-ended readout of an LYSO array by two silicon photomultipliers (SiPMs). By introducing a detector gain balancing step in the calibration process, improved depth-of-interaction calibration uniformity and accuracy can be achieved. The entire calibration process has four steps: scintillation crystal array mappings for two SiPM readouts, detector gain balancing, energy calibration, and depth-of-interaction calibration. This document provides a detailed description on the detector calibration system setup.

A key feature of silicon photomultipliers (SiPMs) that can hinder their wider use in medium and high energy physics applications is their relatively high sensitivity to high energy background radiation, with particular regard to high energy neutrons. Dosages of 1010 neq/cm2 can damage them severely. In this study, some standard versions along with some new formulations are irradiated with a high intensity 241AmBe source up to a total dose of 5 × 109 neq/cm2. Key parameters monitored include dark noise, photon detection efficiency (PDE), gain, and voltage breakdown. Only dark noise was found to change significantly for this range of dosage. Analysis of the data indicates that within each vendor's product line, the change in dark noise is very similar as a function of increasing dose. At present, the best strategy for alleviating the effects of radiation damage is to cool the devices to minimize the effects of increased dark noise with accumulated dose.

Electromagnetic calorimeter modules are being constructed for the CEBAF Large Acceptance Spectrometer that will utilize plastic plate scintillators that can be over 4 meters in length. At shower maximum, it is expected that up to 100 Gray may be deposited over a ten year lifetime in the detector elements. Although it is believed that PVT-based scintillators are radiation-hard at that level, the large size of the plates motivated an ageing test of a 2 meter long sample so as to gain a realistic estimate of the loss in intrinsic light output and especially in attenuation performance of the chosen scintillator (Bicron BC412). A test setup was designed so that the sample was irradiated (by a /sup 60/Co line source) at a rate sufficiently low (0.5 Gray/hr) to allow complete diffusion of oxygen into the material during the irradiation. Additionally, in order to ensure complete diffusion and to gain a pessimistic estimate of damage, a pure oxygen atmosphere was circulated through the sample container during the irradiation, and the total dose was increased to a total of 160 Gray. Within the same setup, tests were also made of two additional materials: (1) a 1 meter long sample of an uniquely bright, fast green scintillator with superior attenuation properties, and (2) a customized acrylic scintillator (with a high doping level of fluors) read out by embedded (into smooth grooves cut into the surface of the scintillator) wavelength shifting fibers doped with the same green fluor as the aforementioned scintillator. The data indicates that the BC412 shows no loss in intrinsic light output, but does have an attenuation loss amounting to 10% at 1 meter and 16% at 2 meters. The fast green scintillator (and fibers) showed no damage. When read out by WLS fibers, the acrylic scintillator displayed a loss in intrinsic light output, but no change in attenuation. >

The 931B is a small inexpensive side-window photomultiplier tube (PMT) which has recently been found to be useful for the readout of scintillators. We present the results of a study to obtain improved performance from the PMT by facilitating the transport of light to the reflection type photocathode. Particular attention is given for the use of these PMTs for the readout of light guides, waveshifting and scintillating fibers. A CCD camera was positioned behind a glass envelope to simulate the photocathode to aid in quantifying the optimum combination of optical coupling and aiming of the fiber. We will also report on tests comparing a similar side-window PMT, the Thorn EMI model 9781B to the 931B. Tests on the operation of the side-window PMT at several orientations in a uniform magnetic field will also be reported. Comparisons between the side-window PMT and a RCA 31000M head-on tube will also be reported. >

We have tested a method of reading out light from long scintillators by embedding waveshifting fibers in longitudinal grooves created in the scintillators which are then connected to a photomultiplier (PMT). With PMTs on both ends of the fibers we have obtained attenuation lengths of over 5 m and light outputs of over 5 photoelectrons per MeV from both ends of a 4 m long BC408 scintillator with five embedded 2 mm diameter BCF92 fast green waveshifting fibers using a Hamamatsu green extended R580-17 PMT. With a reflector at one end of the fibers, we have easily obtained over 10 m attenuation lengths. Also presented are results using inexpensive acrylic scintillators with this method and measurements of a new experimental scintillator from Bicron with over a 5 m attenuation length.

Results of a search for an inexpensive and efficient liquid light guide are presented. 1 4 in. diameter FEP Teflon tubing filled with mineral oil have transmission properties almost matching those of an expensive commercial light guide and of standard polystyrene fibers with acrylic cladding. The main advantage of the technique is mechanical flexibility of the light guides obtained. Results of the optimization procedure, attenuation measurements in light guide tubes up to 2 m long and of angular and bending studies are shown and possible improvements are discussed. A possible application is the construction of inexpensive, flexible multitube light guides to collect light in sampling electromagnetic calorimeters.

The development and initial evaluation of a high-resolution positron emission tomography (PET) system to image the biodistribution of positron emitting tracers in live plants is underway. The positron emitting 11CO 2 tracer is used in plant biology research investigating carbon sequestration in biomass, optimization of plant productivity and biofuel development. This PhytoPET design allows flexible arrangements of PET detectors based on individual standalone detector modules built from single 5 cm × 5 cm Hamamatsu H8500 position sensitive photomultiplier tubes. Each H8500 is coupled to a LYSO:Ce scintillator array composed of 48×48 elements that are 10 mm thick arranged with a 1.0 mm pitch. An Ethernet based 12-bit flash analog to digital data acquisition system with onboard coincident matrix definition is under development to digitize the signals. The detector modules of the PhytoPET system can be arranged and stacked to accommodate various sized plants and plant structures.

We developed a prototype high resolution, high efficiency depth-encoding detector for PET applications based on dual-ended readout of LYSO array with two silicon photomultipliers (SiPMs). Flood images, energy resolution, and depth-of-interaction (DOI) resolution were measured for a LYSO array - 0.7 mm in crystal pitch and 10 mm in thickness - with four unpolished parallel sides. Flood images were obtained such that individual crystal element in the array is resolved. The energy resolution of the entire array was measured to be 33%, while individual crystal pixel elements utilizing the signal from both sides ranged from 23.3% to 27%. By applying a mutual-gain equalization method, a DOI resolution of 2 mm for the crystal array was obtained in the experiments while simulations indicate ∼1 mm DOI resolution could possibly be achieved. The experimental DOI resolution can be further improved by obtaining revised detector supporting electronics with better energy resolutions. This study provides a detailed detector calibration and DOI response characterization of the dual-ended readout SiPM-based PET detectors, which will be important in the design and calibration of a PET scanner in the future.

A series of high dose rate (20 kGy/hr) and low dose rate (

The results of evaluation studies of the new Hamamatsu R4760 multichannel photomultiplier tube (PMT) are presented. Operation parameters such as quantum efficiency, uniformity of response, amplification factors, position resolution and, most importantly, cross-talk effects were studied by injecting short light pulses producing on average from one to ten photoelectrons. A light pulse injecting 1 mm diameter fiber was mounted on a two-dimensional computer-controlled precision scanner and the photomultiplier response was measured for each fiber position.

The 11 CO 2 tracer is used to facilitate plant biology research towards optimization of plant productivity, biofuel development and carbon sequestration in biomass. Positron emission tomography (PET) imaging has been used to study carbon transport in live plants using 11 CO 2 . Plants typically have very thin leaves resulting in little medium for the emitted positrons to undergo an annihilation event. For the emitted positron from 11C decay approximately 1mm of water equivalent material is needed for positron annihilation. Thus most of the positrons do not annihilate inside the leaf, resulting in limited sensitivity for PET imaging. To address this problem we have developed a compact beta-positive beta-minus particle (BPBM) imager for 11 CO 2 leaf imaging. The detector is based on a Hamamatsu H8500 position sensitive photomultiplier tube optically coupled via optical grease and a 3mm thick glass plate to a 0.5mm thick Eljin EJ-212 plastic scintillator. The detector is equipped with a flexible arm to allow its placement and orientation on the leaf of the plant of interest while maintaining the leaf's original orientation. We are planning to utilize the imaging device at the Duke University Phytotron to investigate dynamic carbon transport differences between invasive and native species.

Results of evaluation studies of three types of commercially available multianode (or multidynode) photomultipliers with separate pad readout elements are presented. Operation parameters such as quantum efficiency, uniformity of response, position resolution and, most importantly, cross talk effects were studied for a Philips XP4722, Hamamatsu H4139/H4140 and a new R4670. Limitations and the need for improvements are discussed.

There are opportunities for the development of new tools to advance plant biology research through the use of radionuclides. Thomas Jefferson National Accelerator Facility, Duke University, West Virginia University and the University of Maryland are collaborating on the development of radionuclide imaging technologies to facilitate plant biology research. Biological research into optimizing plant productivity under various environmental constraints, biofuel and carbon sequestration research are areas that could potentially benefit from new imaging technologies. Using 11CO 2 tracers, the investigators at Triangle University Nuclear Laboratory / Duke University Phytotron are currently researching the dynamical responses of plants to environmental changes forecasted from increasing greenhouse trace gases involved in global change. The biological research primary focus is to investigate the impact of elevated atmospheric CO 2 and nutrients limitation on carbon and nitrogen dynamics in plants. We report here on preliminary results of 11CO 2 plant imaging experiments involving barley plants using Jefferson Lab dual planar positron emission tomography detectors to image 11CO 2 in live barley plants. New detector designs will be developed based on the preliminary studies reported here and further planned.

The authors present an update on research started three years ago with the goal of developing plastic scintillators able to endure annual doses of 10/sup 4/ to 10/sup 5/ Gy or more. Attention is given to radiation damage to plastic scintillators, techniques to improve radiation resistance (wavelength shifting and radiation-tolerant plastic bases), and other issues. It is concluded that, although the studies of scintillators must continue in order to define the limits of current capabilities, there is a need to move beyond the study of 'naked' scintillators (whether as plates or optical fibres) and to study them 'dressed' within a detector system. >

An initial examination of radiation-damage phenomenology in selected liquid scintillators was made. Standard liquid scintillators exhibited substantial radiation damage after dosage levels of several megarads. Unlike the case with plastic scintillators, no significant changes in transmission were detected, implying that no strong absorption of the secondary fluor should occur in long samples. The observed substantial drop in scintillation pulse height after exposures of several megarad from a /sup 60/Co gamma source is attributed to radiation-induced absorption of the primary fluor's emission by the damaged solvent. Some new formulations have shown significantly greater radiation resistance. >

With the planned construction of high-luminosity hadron colliders, the SSC (Superconducting Supercollider) and LHC (Large Hadron Collider), the issue of radiation resistance of detector components has arisen as a priority item. The radiation resistance of organic scintillators is discussed, with the dual goals of presenting a review of the problem and pointing the way to possible solutions. It is concluded that progress in producing sufficiently radiation-hard organic scintillators has been significant, but there remain many important details to be investigated. It is feasible that an organic scintillator may be produced within the next few years with a performance specification of 100 Mrad. >

The authors discuss two ways of insuring plastic scintillators against radiation damage: shifting to longer secondary fluor emission wavelengths and increasing secondary fluor concentration. They describe a scintillating-fiber-based calorimeter which can be made compensating. The calorimeter recovers its original resolution less than one month after receiving a dose of 10 Mrad via 100-MeV electrons. >

The GlueX collaboration is designing a detector system to study exotic hybrid meson states at the upgrade beam line of Jefferson Laboratory. The hermetic detector includes a cylindrical electromagnetic calorimeter based on the scifi design used in KLOE, SPACAL, and JETSET. Since the calorimeter will be placed within a 2.24 tesla axial magnetic field, the optimal readout solution will include a solid state photodetector known as the silicon photomultiplier. This is an array of avalanche photodiode microcells operated in geiger mode with the output summed from all the microcells. The result is a photodetector with many of the same characteristics of vacuum photomultipliers such as high gain (106) and fast response, but with the additional advantage of immunity to high magnetic fields and superior quantum efficiency. This study is a report on the characteristics of a variety of prototype devices being developed by SensL of Cork, Ireland. The chief parameters being studied are photon detection efficiency (PDE), gain, dark noise, linearity, dynamic range, optimum operating voltage, and stability. This is a status report for an ongoing study.

The preliminary results of the Λ 9 Li and Λ 16 N spectra obtained by electron scattering experiment in Hall A at Jefferson Lab in the framework of the experiment E94-107 are reported. These hypernuclei are produced bombarding respectively a 9Be and a waterfall target. After a short description of the experimental equipment and of the data analysis procedures, the main characteristics of the measured spectra, as excited levels, energy resolution, and signal to noise ratio are evidenced.

Multi-modality imaging is rapidly becoming a valuable tool in the diagnosis of disease and in the development of new drugs. Functional images produced with PET fused with anatomical structure images created by MRI will allow the correlation of form with function. Our group is developing a system to acquire MRI and PET images contemporaneously. The prototype device consists of two opposed detector heads, operating in coincidence mode. Each MRI-PET detector module consists of an array of LSO detector elements coupled through a long fibre optic light guide to a single Hamamatsu flat panel position-sensitive photomultiplier tube (PSPMT). The use of light guides allows the PSPMTs to be positioned outside the bore of a 3T MRI scanner where the magnetic field is relatively small. To test the device, simultaneous MRI and PET images of the brain of a male Sprague Dawley rat injected with FDG were successfully obtained. The images revealed no noticeable artefacts in either image set. Future work includes the construction of a full ring PET scanner, improved light guides and construction of a specialized MRI coil to permit higher quality MRI imaging.

Recently small animal research utilizing nuclear medicine based imaging has been combined with structural anatomical imaging from x-ray radiography providing a powerful tool for animal researchers. The addition of a third modality is the goal of our instrumentation development. Thomas Jefferson National Accelerator Facility and Case Western Reserve University have been collaborating on the development of a planar imaging system which in addition to radiopharmaceutical based functional imaging and x-ray radiography structural imaging also allows for the in vivo bioluminescence imaging thus providing another functional imaging modality. For the gamma camera we use is a Hamamatsu position sensitive photomultiplier tube coupled to a pixellated NaI(TI) scintillator array with individual crystal elements 1 mm /spl times/ 1 mm /spl times/ 5 mm in size and a 0.25 mm septum between each element. The gamma camera has a 10 cm diameter active area and can be used for /sup 125/I, /sup 99m/T and /sup 111/In radionuclide imaging. To acquire anatomical information we are using a Rad-Icon Shad-o-Box X-ray detector that provides a field of view of 5 cm /spl times/ 10 cm. The x-ray source is a Source-Ray compact x-ray generator. We are using a Princeton Instruments cooled CCD based detector for the imaging of the bio-distribution of bioluminescence. All three imaging instruments will be integrated into a single light tight / x-ray tight enclosure.