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This study addresses various characteristics of computing and nuclear technology research through a scientometric analysis of the literature related to the IEEE Nuclear Science Symposium, spanning approximately three decades from the LEP and Tevatron era to the LHC era. It analyzes technological research pertaining to computing and instrumentation in nuclear and particle physics, astrophysics and medical physics, and compares the evolution of some diversity parameters within intechnological and fundamental physics research in these fields.

Laser shock peening (LSP) is applied to potassium iodide (KI) crystals. A selective etching technique is used to reveal the dislocation structure induced by the LSP process, confirming that LSP multiplies and moves dislocations in an alkali halide. Increasing the crystal temperature during LSP is shown to eliminate cracking along cleavage-planes caused by the LSP process and increases the range of dislocation motion in the crystal. LSP has long been used to increase surface toughness and fatigue life in metals. Having shown that LSP affects the mechanical properties in the ionic crystal KI, we propose studying the possible benefit of LSP in other halide crystals, including scintillators. One potential application might be reducing crack initiation and propagation at surfaces during Bridgman growth.

Lithium indium diselenide (6LiInSe2) has drawn interest in recent years as a thermal neutron detector due to its high volumetric thermal neutron detection efficiency. Enriched in 6Li, the single crystalline semiconductor can reach thermal neutron detection efficiencies approaching 80% at thickness of 0.5 cm. With a Q-value of 4.78 MeV, the material also offers neutrongamma discrimination capabilities. Identification and implementation of a contact scheme that is both robust and reproducible is important for its commercial potential. Thorough testing of a myriad of contact schemes yielded a viable Ohmic contact with sufficient adhesion to endure gold wire wedge bonding. Furthermore, characterization of the semiconducting properties, such as the charge carrier mobility-lifetime constant of this material as a radiation detector is important to identify the application space of this material. Using the single charge carrier approximation to the Hecht relation, the electron mobility-lifetime product was found to be on the order of 3.8–90 cm2/V with a mean ionization energy of 400 eV/e-h pair.

A collaborative study of relative hygroscopicity of anhydrous halide scintillators grown at various laboratories is presented. We have developed a technique to evaluate moisture sensitivity of both raw materials and grown crystals, in which the moisture absorption rate is measured using a gravimetric analysis. Degradation of the scintillation performance was investigated by recording gamma-ray spectra and monitoring the photopeak position, count rate and energy resolution. The accompanying physical degradation of the samples exposed to ambient atmosphere was photographically recorded as well. The results were compared with benchmark commercial scintillators such as NaI:Tl and LaBr 3 :Ce.

Cd 0.9 Zn 0.1 Te (CZT) gamma radiation detectors are presently among the best semiconductor materials for room temperature operation. CZT crystals in pixilated geometry can be efficiently used in the field of Homeland security and medical diagnosis for high resolution imaging purpose and position sensitive measurements using x-rays and high energy gamma rays. Large area CZT single crystals has been grown using a tellurium solvent method. A 10×10 guarded pixilated detector has been fabricated on a ∼19.5×19.5×5 mm3 crystal cut out from the grown ingot. A full area planar Au contact was used as the cathode. Each pixel of the pixilated detector was 1.3×1.3 mm2 in area and pitched at 1.8 mm. A 100 μm wide guard grid was used to reduce inter-pixel leakage. The crystal was characterized in planar configuration using electrical and optoelectronic methods prior to the fabrication of pixilated geometry. Current-voltage (I–V) measurements revealed a leakage current of 29 nA at an operating bias voltage of 1100 V. A resistivity of ∼3.1×1010 ∖.cm was calculated from the I–V measurements. Infrared transmission imaging revealed an average tellurium inclusion/precipitate size less than 8μm. Pockels measurement has revealed a near-uniform depth-wise distribution of the internal electric field. The mobility-lifetime product in this crystal was calculated to be 6.2 × 10−3 cm2/V using alpha ray spectroscopic method. Gamma spectroscopy using a 137Cs source on the pixelated structure showed fully resolved 662 keV gamma peaks for all the pixels, with percentage resolution (FWHM) as low as 1.8 %.

High energy resolution gamma-ray detectors that can be formed into relatively large sizes while operating at room temperature offer many advantages for national security applications. We are working toward that goal through the development of SrI 2 (Eu) scintillator detectors, which routinely provide 10 cm3. In this study, we have tested pure, undoped SrI 2 to gain a better understanding of the scintillation properties and spectroscopic performance achievable without activation. An undoped crystal grown from 99.999% pure SrI 2 pellets was tested for its spectroscopic performance, its light yield, and uniformity of scintillation light collection as a function of gamma-ray interaction position relative to the crystal growth direction. Undoped SrI 2 was found to provide energy resolution of 5.3% at 662 keV, and the light collection nonuniformity varied by only 0.72% over the length of the crystal. Measurements of both a 3% Eu-doped and the undoped SrI 2 crystal were carried out in the SLYNCI facility and indicate differences in their light yield non-proportionality. The surprisingly good scintillation properties of the pure SrI 2 crystal suggests that with high-purity feedstock, further reduction of the Eu concentration can be made to grow larger crystals while not adversely impacting the spectroscopic performance.

The current gamma ray/neutron instrumentation development effort at NASA Goddard Space Flight Center?s Astrochemistry Laboratory aims to extend the use of neutron interrogation techniques, using a 14 MeV Pulsed Neutron Generator (PNG) combined with neutron and gamma ray detectors, to probe the surface and subsurface of planetary bodies in situ without the need to drill. One aspect of the current work includes the development of taking timed tagged event-byevent data using our custom designed software with the Canberra Lynx Digital Signal Analyzer to provide a unique three-dimensional master data set with channel/energy, time, and intensity information. Since the master data set is not limited to predetermined coincidence timing gates set for a specific nuclear process, the user is allowed the flexibility to slice the data cube in a multitude of ways without loss of information or experimental time due to the need for additional acquisition windows. Time tagged event-by-event data allows the user to isolate a particular energy line from the spectrum over a specific window in time with respect to the PNG pulse, analyze a gamma ray spectrum resulting from either neutron capture, between the burst, or inelastic scattering events, during the neutron burst, and extract data for engineering purposes to optimize timing windows to look at specific elements in different environments. In this paper, we will present the results of our experimental data using the time tagged event-by-event data analysis technique compared with non-time-gated data taken at the test facility at NASA Goddard Space Flight Center. Comparison of these data will show the advantages and validity of this method to obtain more precise, sensitive, and accurate elemental composition measurements.

Europium-doped strontium iodide (SrI 2 :Eu) crystals are reported to be high light yield scintillator materials with good energy resolution, the best energy resolution of SrI 2 :Eu at 662 keV having reached 2.6%. To improve the crystals growth quality and to protect the crystals from hydration, it is practical to distinguish the pure crystals from impurity and structural defects by Raman spectroscopy. In this report, SrI 2 :Eu crystals grown from the vertical Bridgman method have been characterized with the polarized Raman spectroscopy. Orientations of the crystals were determined with the spectroscopy assisted with the polarized optical microscopy. The crystals are highly hygroscopic, the intensity of new peak at 87 cm−1 associated with SrI 3 − anions continues to increase with time even the samples are kept in mineral oil or encapsulated in parylene. Micro-Raman mapping on the distributions of SrI 3 − anions in SrI 2 crystals stored in mineral oil are reported.

There is an ever increasing demand for gamma-ray detectors which can achieve good energy resolution, high detection efficiency, and room-temperature operation. We are working to address each of these requirements through the development of large volume SrI 2 (Eu) scintillator detectors. In this work, we have evaluated a variety of SrI 2 crystals with volumes >10 cm3. The goal of this research was to examine the causes of energy resolution degradation for larger detectors and to determine what can be done to mitigate these effects. Testing both packaged and unpackaged detectors, we have consistently achieved better resolution with the packaged detectors. Using a collimated gamma-ray source, it was determined that better energy resolution for the packaged detectors is correlated with better light collection uniformity. A number of packaged detectors were fabricated and tested and the best spectroscopic performance was achieved for a 3% Eu doped crystal with an energy resolution of 2.93% FWHM at 662keV. Simulations of SrI 2 (Eu) crystals were also performed to better understand the light transport physics in scintillators and are reported. This study has important implications for the development of SrI 2 (Eu) detectors for national security purposes.

We are developing new scintillator materials that offer potential for high resolution gamma ray spectroscopy at low cost. Single crystal SrI 2 (Eu) offers ∼3% resolution at 662 keV, in sizes of ∼1 in3. We have developed ceramics processing technology allowing us to achieve cubic inch scale transparent ceramic scintillators offering gamma spectroscopy performance superior to NaI(Tl). Our bismuth-loaded plastic scintillator demonstrates energy resolution of ∼8% at 662 keV, for samples of ∼0.5 cm3.

We report on the development and test of a novel type of Cadmium Zinc Telluride (CZT) detector: Dual Anode Detectors. Our work focuses on large volume (10 × 20 × 20 mm3) CZT crystals contacted with dual anodes, and either a segmented cathode or four lateral contacts, and a monolithic cathode. The charge induced on all contacts can be used to determine the energy and the 3-D interaction location of detected X-ray and gamma-ray photons. We give an overview of the status of the detector development program, emphasize strengths and weaknesses of the dual anode designs in comparison to conventional coplanar grid and pixel detectors, and discuss possible applications of Dual Anode Detectors in Homeland Security applications.

In an effort to optimize the spectroscopic performance of large volume Cadmium Zinc Telluride (CZT) radiation detectors grown by the Traveling Heater Method (THM), especially for higher energy gamma detection applications, bulk material and pixellated detector performance of THM CZT crystals at 15mm-thick and 10mm-thick were compared to that at 5mm-thick. We demonstrate that the outstanding performance of monolithic pixellated THM CZT detectors was thickness-scalable. For the same monolithic 20×20 mm2 “Compton Camera” pixellated detector configuration, detector performance can certainly be significantly improved as the thickness of the detector increases from 5mm to 10mm and thicker as demonstrated via both 57Co 122 keV and 137Cs 662 keV spectral responses. Depth of interaction information obtained from 3D depth sensing measurement system, IR microscopy and x-ray topography were used to study the correlation between structural quality and detector performance. Additional material characterizations and detector performances of various sizes and configurations were also presented and discussed.

The optically-pumped semiconductor disk laser is shown to be a practical low-noise pump source for Cr2+:chalcogenide lasers. Results on cw-pumping of a Cr2+:ZnSe and quasi-cw-pumping of a Cr2+:CdZnTe laser are presented.

Gamma ray spectroscopy for remote sensing applications requires a high sensitivity that can be achieved by a combination of high efficiency and high energy resolution for high energy gamma rays (up to 1 MeV) . While cryogenic germanium detectors or LaBr3:Ce3+ scintillators could in principle satisfy the requirements of many such applications, the search for compact, portable systems that do not require cooling or the use of photomultiplier tubes are still underway. State-of-the-art CdZnTe spectrometers having an energy resolution exceeding 1% have been recently demonstrated, however they have a typical volume that is less than 1 cm3. Large volume (greater than 3 cm3) CdZnTe spectrometers with an energy resolution that is better than 3% are not yet commercially available, although the size of large single crystals that would satisfy the volume requirement can now be grown by various companies with reasonable yield. In this study we have investigated the feasibility of using commercially available large (1-6 cm3) detector grade CdZnTe single crystals to fabricate co-planar gamma spectrometers with a targeted performance that exceeds 3% energy resolution at 662 keV. The fabrication of optimal performance coplanar detectors requires a custom design that might vary for each crystal growth method. Besides the knowledge of the average values of charge carrier concentrations, mobilities and trapping times the physics-based model requires the knowledge of bulk nonuniformities and their effects on local variations in the electric field and electron mobility-trapping-time product. All crystals investigated had tellurium, as second phase. A new type of material inhomogeneity, and its influence on detector's performance, became apparent only in large volume crystals and will be reported.

The layered III-VI semiconductor Gallium Telluride has potential for room temperature gamma ray spectroscopy applications due to its band gap of 1.67 eV, and average atomic number of 45 : 31 (Ga) and 52 (Te). The physical properties of GaTe are highly anisotropic due to covalent bonding within the layer and van der Waals bonding between layers. This work reports the results of surface and bulk processing, surface characterization, and electrical characterization of diodes formed on both the laminar and non-laminar GaTe surfaces. Alpha detection measurements were also performed.

We present the design and parameters of an energy recovery linac (ERL) facility, which is under construction in the Collider-Accelerator Department at BNL. This R&D facility has the goal of demonstrating CW operation of an ERL with an average beam current in the range of 0.1 - 1 ampere and with very high efficiency of energy recovery. The possibility of a future upgrade to a two-pass ERL is also being considered. The heart of the facility is a 5-cell 703.75 MHz super-conducting RF linac with strong Higher Order Mode (HOM) damping. The flexible lattice of the ERL provides a test-bed for exploring issues of transverse and longitudinal instabilities and diagnostics of intense CW electron beams. This ERL is also perfectly suited for a far-IR FEL. We present the status and plans for construction and commissioning of this facility.

We developed four types of GaAs PCDs: bremsstrahlung (two types), soft X-ray, and gamma for pulsed reactors. GaAs PCDs are advantageous in applications that require fast response, high dose rate, and/or neutron insensitivity. Desired detector sensitivity and response were obtained through modification of carrier lifetime by neutron irradiation, size of the sensing element, and orientation of the sensing element. The GaAs PCDs were used to characterize pulsed radiation sources in over 10 different tests and the measured data from these tests are presented. GaAs PCDs (E7 - E11 rad(Si)/s) for use with pulsed bremsstrahlung sources were tested at DTRA Radiation sources, Linac (Idaho Accelerator Center), Linac (White Sands), hybrid radiation source (NRL), GAMBLE II (NRL), and HERMES III (Sandia). GaAs PCDs for gamma characterization in pulsed reactors (E6 - E7 rad(Si)/s) were calibrated with a Linac (White Sands), checked for high dose rate (E12 rad(Si)/s) response at HERMES III, checked for low dose rate response (5-500 rad(Si)/s) and stability at a Co-60 source (Sandia), and checked for stability, sensitivity, and residual radioactivity at the ACCR reactor (Sandia). Soft X-ray (1 to 15 keV) GaAs PCDs (E2-E6 Watts/cm2) were used to measure the argon plasma free-bound continuum temperature from a plasma radiation source (PRS) and compared with the plasma temperature obtained from line ratio measurements.

Using modified vertical Bridgman and a seeded technique, 3-inch-diameter CdZnTe (CZT) ingots were successfully grown with 40% of the ingots having single-crystal volumes of over 300 cm/sup 3/, and 80% of the ingots with single-crystal volumes of over 100 cm/sup 3/. High-yield growth of CZT crystals with these dimensions enables the production of novel monolithic, multi-element detectors. Defects such as Cd-vacancies, indium dopant and impurities were studied systematically. The studies show that by appropriately reducing the Cd-vacancy and the Group III dopant, one can increase the /spl mu//spl tau/(e) and /spl mu//spl tau/(h) products. Furthermore, the indium doping and the purity of the CZT were found to limit the value of the /spl mu//spl tau/(e) product. The "best" purity source material coupled with an optimized indium doping concentration will produce /spl mu//spl tau/(e) products as high as 1.8x10/sup -2/ cm/sup 2//V (collimated and the "best" area), and the best /spl mu//spl tau/(h) is 7x10/sup -4/ cm/sup 2//V.

Laser activity has been achieved in low-phonon energy, moisture-resistant neodymium-doped bromide host crystals, also resulting from the /sup 4/F/sub 5/2/+/sup 2/H/sub 9/2/ level for the first time in any solid-state material. Pump-probe spectra reveal mechanisms feasible for more efficient laser operation.

Results will be reported on a new technique to grow cadmium zinc telluride crystals for radiation detector applications without the use of an expensive, high-pressure chamber. This technique, based on the Modified Vertical Bridgman (MVB) method, has partly resolved problems resulting from the lack of control of the thermal environment during growth, leading to better melt stabilization, interface control, and crystallinity. For example, single crystal volumes exceeding 120 cm/sup 3/ have been produced, which is 5-10 times larger that the typical single-crystal volumes produced using the high-pressure Bridgman method. The crystals exhibit simultaneously high electrical resistivity, good uniformity, and excellent electron mobility-lifetime products. The yield of spectrometer-grade crystals is >50%. Electrical resistivities in the range of 2-9/spl times/10/sup 10/ Ohm-cm are obtained, and electron mobility-lifetime products up to 1/spl times/10/sup -2/ cm/sup 2//V are measured using collimated low-energy gamma rays. These material advances have enabled production of large-volume planar detectors, co-planar grid detectors, and large-area pixellated imaging arrays. The detectors exhibit good counting efficiency, excellent peak-to-valley ratios, and low leakage currents. Individual pixels of multi-element arrays have spectral resolutions of up to 3% for uncollimated 122-keV photons. Co-planar grid detectors with dimensions of (10 mm)/sup 3/ show resolutions of up to 2.2%, and energy resolutions of 1.2% are measured with 5.4 MeV alpha particles. Prototype large-volume planar detectors were fabricated, and the photopeak at 122 keV was approximately Gaussian in shape with practically all of the events in the peak, instead of counts at lower channels. New records for detector thickness (25 mm) and volume efficiency (3600 mm/sup 3/) have been achieved. Results on the material and detector properties will be presented.