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Nuclear fusion reactions of D-D are examined in an environment comprised of high density cold fuel embedded in metal lattices in which a small fuel portion is activated by hot neutrons. Such an environment provides for enhanced screening of the Coulomb barrier due to conduction and shell electrons of the metal lattice, or by plasma induced by ionizing radiation (\ensuremath{\gamma} quanta). We show that neutrons are far more efficient than energetic charged particles, such as light particles (${e}^{\ensuremath{-}},{e}^{+}$) or heavy particles ($p,d,\ensuremath{\alpha}$) in transferring kinetic energy to fuel nuclei (D) to initiate fusion processes. It is well known that screening increases the probability of tunneling through the Coulomb barrier. Electron screening also significantly increases the probability of large vs small angle Coulomb scattering of the reacting nuclei to enable subsequent nuclear reactions via tunneling. This probability is incorporated into the astrophysical factor $S(E)$. Aspects of screening effects to enable calculation of nuclear reaction rates are also evaluated, including Coulomb scattering and localized heating of the cold fuel, primary D-D reactions, and subsequent reactions with both the fuel and the lattice nuclei. The effect of screening for enhancement of the total nuclear reaction rate is a function of multiple parameters including fuel temperature and the relative scattering probability between the fuel and lattice metal nuclei. Screening also significantly increases the probability of interaction between hot fuel and lattice nuclei increasing the likelilhood of Oppenheimer-Phillips processes opening a potential route to reaction multiplication. We demonstrate that the screened Coulomb potential of the target ion is determined by the nonlinear Vlasov potential and not by the Debye potential. In general, the effect of screening becomes important at low kinetic energy of the projectile. We examine the range of applicability of both the analytical and asymptotic expressions for the well-known electron screening lattice potential energy ${U}_{e}$, which is valid only for $E\ensuremath{\gg}{U}_{e}$ ($E$ is the energy in the center of mass reference frame). We demonstrate that for $E\ensuremath{\le}{U}_{e}$, a direct calculation of Gamow factor for screened Coulomb potential is required to avoid unreasonably high values of the enhancement factor $f(E)$ by the analytical---and more so by the asymptotic---formulas.

The propagation of electrons through several linear pore densities of reticulated vitreous carbon (RVC) foam was studied using a Frisch-grid parallel-plate ionization chamber pressurized to 1 psig of P-10 proportional gas. The operating voltages of the electrodes contained within the Frisch-grid parallel-plate ionization chamber were defined by measuring counting curves using a collimated 241Am alpha-particle source with and without a Frisch grid. RVC foam samples with linear pore densities of 5, 10, 20, 30, 45, 80, and 100 pores per linear inch were separately positioned between the cathode and anode. Pulse-height spectra and count rates from a collimated 241Am alpha-particle source positioned between the cathode and each RVC foam sample were measured and compared to a measurement without an RVC foam sample. The Frisch grid was positioned in between the RVC foam sample and the anode. The measured pulse-height spectra were indiscernible from background and resulted in negligible net count rates for all RVC foam samples. The Frisch grid parallel-plate ionization chamber measurement results indicate that electrons do not traverse the bulk of RVC foam and consequently do not produce a pulse.

LiZnAs is being explored as a candidate for solid-state neutron detectors. The compact form, solid-state device would have greater efficiency than present day gas-filled 3He and 10BF3 detectors. Devices fabricated from LiZnAs having either natural Li (nominally 7.5% 6Li) or enriched 6Li (usually 95% 6Li) as constituent atoms may provide a material for compact high efficiency neutron detectors. The 6Li(n,t)4He reaction yields a total Q-value of 4.78 MeV, an energy larger than that of the 10B reaction, which can easily be identified above background radiations. LiZnAs material was synthesized by preparing equimolar portions of Li, Zn, and As sealed under vacuum (10−6 Torr) in quartz ampoules lined with boron nitride and subsequently reacted in a compounding furnace (Montag et al. in J Cryst Growth 412:103, 2015). The raw synthesized LiZnAs was purified by a static vacuum sublimation in quartz (Montag et al. in J Cryst Growth 438:99, 2016). Bulk crystalline LiZnAs ingots were grown from the purified material with a high-temperature Bridgman-style growth process described here. One of the largest LiZnAs ingots harvested was 9.6 mm in diameter and 4.2 mm in length. Samples were harvested from the ingot and were characterized for crystallinity using a Bruker AXS Inc. D8 AXS Inc. D2 CRYSO, energy dispersive x-ray diffractometer, and a Bruker AXS Inc. D8 DISCOVER, high-resolution x-ray diffractometer equipped with molybdenum radiation, Gobel mirror, four bounce germanium monochromator and a scintillation detector. The primary beam divergence was determined to be 0.004°, using a single crystal Si standard. The x-ray based characterization revealed that the samples nucleated in the (110) direction and a high-resolution open detector rocking curve recorded on the (220) LiZnAs yielded a full width at half maximum (FWHM) of 0.235°. Sectional pole figures using off-axis reflections of the (211) LiZnAs confirmed in-plane ordering, and also indicated the presence of multiple domains. The LiZnAs bulk crystals exhibited a Primitive Cubic Bravais lattice instead of the commonly reported Face-centered Cubic Bravais lattice. The lattice constant was determined to be 5.5146 ± 0.0003 A.

Nowotny-Juza compounds continue to be explored as candidates for solid-state neutron detectors . Such a device would have greater efficiency, in a compact form, than present day gas-filled 3He and 10BF3 detectors. The 6Li(n,t)4He reaction yields a total Q-value of 4.78 MeV, larger than 10B, an energy easily identified above background radiations. Hence, devices fabricated from semiconductor compounds having either natural Li (nominally 7.5% 6Li) or enriched 6Li (usually 95% 6Li) as constituent atoms may provide a material for compact high efficiency neutron detectors. Starting material was synthesized by preparing equimolar portions of Li, Zn, and As sealed under vacuum (10−6 Torr) in quartz ampoules lined with boron nitride and subsequently reacted in a compounding furnace [1] . The raw synthesized material indicated the presence high impurity levels (material and electrical property characterizations). A static vacuum sublimation in quartz was performed to help purify the synthesized material [2] , [3] . Bulk crystalline samples were grown from the purified material [4] , [5] . Samples were cut using a diamond wire saw, and processed into devices. Bulk resistivity was determined from I–V curve measurements, ranging from 106–1011 Ω cm. Devices were characterized for sensitivity to 5.48 MeV alpha particles , 337 nm laser light, and neutron sensitivity in a thermal neutron diffracted beam at the Kansas State University TRIGA Mark II nuclear reactor. Thermal neutron reaction product charge induction was measured with a LiZnP device, and the reaction product spectral response was observed.

Preparation of thin U- and Th-coated 0.3 mm diameter Pt working electrodes by the cyclic potential sweep method is described. Uranyl- and thorium hydroxide layers were electrodeposited from ethanol solutions containing 0.02 M natural uranyl and 0.02 M natural thorium nitrate, each with 3.6 M ammonium nitrate. The cell for electrodeposition was specially developed in order to accommodate the small working electrodes for this research by including a working electrode probe, 3-D translation stage, and microscope. The source material deposition was analyzed using digital microscopy and scanning electron microscopy, and confirmed using x-ray fluorescence measurements. The appropriate potential range for electrodeposition was determined to be −0.62 V to −0.64 V for a 0.3 mm diameter Pt working electrode placed 1 cm from the counter electrode. Smooth, uniform deposition was observed near the central region of the working electrode, while surface cracking and crystalline formations were found near the edge of the working electrode. The final procedure for sample substrate preparation, electrolytic solution preparation and electrodeposition are described.

Neutron sensors capable of real-time measurement of neutrons in high-flux environments are necessary for tests aimed at demonstrating the performance of experimental nuclear reactor fuels and materials in material test reactors (MTRs). In-core Micro-Pocket Fission Detectors (MPFDs) have been studied at Kansas State University for many years. Previous MPFD prototypes were successfully built and tested with promising results. Efforts are now underway to develop advanced MPFDs with radiation-resistant, high-temperature materials capable of withstanding irradiation test conditions in high performance material and test reactors. Stackable MPFDs have been designed, built, and successfully demonstrated as in-core neutron sensors. Advances in the electrodeposition and measurement of neutron reactive material, along with refinements to composition optimization simulations, have enhanced the capabilities of contemporary MPFDs.

Refinement of the class A I B II C V materials continue as a candidate for solid-state neutron detectors. Such a device would have greater efficiency, in a compact form, than present day gas-filled 3 He and 10 BF 3 detectors. The 6 Li( n , t ) 4 He reaction yields a total Q value of 4.78 MeV, larger than 10 B, and easily identified above background radiations. Hence, devices composed of either natural Li (nominally 7.5% 6 Li) or enriched 6 Li (usually 95% 6 Li) may provide a semiconductor material for compact high efficiency neutron detectors. A sub-branch of the III–V semiconductors, the filled tetrahedral compounds, A I B II C V , known as Nowotny–Juza compounds, are known for their desirable cubic crystal structure. Starting material was synthesized by equimolar portions of Li, Zn, and As sealed under vacuum (10 −6 Torr) in quartz ampoules with a boron nitride lining, and reacted in a compounding furnace [1] . The synthesized material showed signs of high impurity levels from material and electrical property characterization. In the present work, a static vacuum sublimation of synthesized LiZnAs loaded in a quartz vessel was performed to help purify the synthesized material. The chemical composition of the sublimed material and remains material was confirmed by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Lithium was not detected in the sublimed material , however, near stoichiometric amounts of each constituent element were found in the remains material for LiZnAs. X-ray diffraction phase identification scans of the remains material and sublimed material were compared, and further indicated the impurity materials were removed from the synthesized materials. The remaining powder post the sublimation process showed characteristics of a higher purity ternary compound.

Nowotny–Juza compounds continue to be explored as a candidate for solid-state neutron detectors. Such a device would have greater efficiency, in a compact form, than present day gas-filled 3 He and 10 BF 3 detectors. The 6 Li( n , t ) 4 He reaction yields a total Q -value of 4.78 MeV, larger than 10 B, an energy easily identified above background radiations. Hence, devices fabricated from semiconducting compounds containing either natural Li (nominally 7.5% 6 Li) or enriched 6 Li (usually 95% 6 Li) may provide a semiconductor material for compact high efficiency neutron detectors. Starting material was synthesized by preparing equimolar portions of Li, Zn, and P sealed under vacuum (10 −6 Torr) in quartz ampoules lined with boron nitride and subsequently reacted in a compounding furnace [1] . The synthesized material showed signs of high impurity levels from material and electrical property characterizations. A static vacuum sublimation in quartz was performed to help purify the synthesized material [2] . Bulk crystalline samples were grown from the purified material. An ingot 9.6 mm in diameter and 4.0 mm in length was harvested. Individual samples were characterized for crystallinity on a Bruker AXS Inc. D2 CRYSO, energy dispersive x-ray diffractometer, and a Bruker AXS D8 DISCOVER, high-resolution x-ray diffractometer with a 0.004° beam divergence. The (220) orientation was characterized as the main orientation with the D2 CRYSO, and confirmed with the D8 DISCOVER. An out-of-plane high-resolution rocking curve yielded a 0.417° full width at half maximum (FWHM) for the (220) LiZnP. In-plane ordering was confirmed by observation of the (311) orientation, where a rocking curve was collected with a FWHM of 0.294°.

Research for a reliable solid-state semiconductor neutron detector continues because such a device has not been developed, and would have greater efficiency, than present-day gas-filled 3 He and 10 BF3 neutron detectors. Further, a semiconductor neutron detector would be more compact and rugged than most gas-filled or scintillator neutron detectors. The 6 Li(n,t) 4 He reaction yields a total Q value of 4.78 MeV, a larger yield than the 10 B(n,α) 7 Li, and is easily identified above background radiation interactions. Hence, devices composed of either natural Li (naturally 7.5% 6 Li) or enriched 6 Li (approximately 95% 6 Li) may provide a semiconductor material for compact high-efficiency neutron detectors. A sub-branch of the III-V semiconductors, the filled tetrahedral compounds, known as Nowotny-Juza compounds (A I B II C V ), are desirable for their cubic crystal structure and semiconducting electrical properties. These compounds were originally studied for photonic applications. In the present work, Equimolar portions of Li, Zn, and P or As were sealed under vacuum (10 � 6 Torr) in quartz

A 550 cm 2 thermal neutron detector was constructed with five parallel sheets of 75 µm thick 6 Li foil (95% enrichment) spaced 1.63 cm apart. Anode wire banks containing a plurality of anode wires were strung on both sides of each foil, six banks in total. The chamber was backfilled with P-10 proportional gas and over-pressured to 1.1, 1.5, 2.0, and 2.8 atm (111, 151, 202, and 284 kPa). The design was tailored to allow the products from the 6 Li(n,t) 4 He reaction to escape both sides of the Li foil simultaneously, thereby, allowing for concurrent measurement in the proportional gas. The measured intrinsic thermal neutron detection efficiency of the detector with normal incident thermal neutrons to the foil sheets was 53.8±0.20%. When the detector was angled (55° from normal) such that a 0.5 cm diameter thermal neutron beam intersected all of the foil layers, the intrinsic thermal neutron detection efficiency increased to 58.6±0.21%. A 252 Cf neutron source positioned at a distance of 2.0 m yielded an absolute neutron detection efficiency of 0.73 cps ng −1 . The gamma-ray rejection ratio (GRR) was 7.67×10 –9 as measured from a 60 Co source for an exposure rate of 40 mR hr −1 . Theoretical pulse-height spectra obtained with MCNP6 agreed well with experimental data and allowed pulse-height spectra and discriminator settings to be energy-calibrated. These results demonstrate the potential for the Li foil multi-wire proportional counter (MWPC) as a viable 3 He neutron detector replacement.

Accurately resolving the ambient neutron dose equivalent spanning the thermal to 15 MeV energy range with a single configuration and lightweight instrument is desirable. This paper presents the design of a portable, high intrinsic efficiency, and accurate neutron rem meter whose energy-dependent response is electronically adjusted to a chosen neutron dose equivalent standard. The instrument may be classified as a moderating type neutron spectrometer, based on an adaptation to the classical Bonner sphere and position sensitive long counter, which, simultaneously counts thermalized neutrons by high thermal efficiency solid state neutron detectors. The use of multiple detectors and moderator arranged along an axis of symmetry (e.g., long axis of a cylinder) with known neutron-slowing properties allows for the construction of a linear combination of responses that approximate the ambient neutron dose equivalent. Variations on the detector configuration are investigated via Monte Carlo N-Particle simulations to minimize the total instrument mass while maintaining acceptable response accuracy—a dose error less than 15% for bare 252 Cf, bare AmBe, an epi-thermal and mixed monoenergetic sources is found at less than 4.5 kg moderator mass in all studied cases. A comparison of the energy dependent dose equivalent response and resultant energy dependent dose equivalent error of the present dosimeter to commerciallyavailable portable rem meters and the prior art are presented. Finally, the present design is assessed by comparison of the simulated output resulting from applications of several known neutron sources and dose rates.

Micro-Pocket Fission Detectors (MPFDs) continue to be an important development in advancing nuclear research capabilities. Commonly, nuclear reactor cores are located far from the location which is desired for read-out electronics. For example, the core of the TRIGA Mk II research nuclear reactor at Kansas State University is submerged under approximately 16 feet of water. Research nuclear reactor facilities often possess unanticipated sources of noise due to the aging facilities, electronic pump and compressor motors, and electromechanical control systems. A robust method to transmitMPFD pulse signals from the MPFD sensors to the readout electronics is under development. Numerous pre-amplifiers were tested to determine the preferred signal processing method for MPFDs. An MPFD emulator was developed which enabled benchtop electronics testing and optimization of the pre-amplifier circuit for future MPFD sensor testing. Finally, an MPFD was constructed and tested at the Kansas State University TRIGA Mk. II nuclear research reactor with the preferred electronics and compared to the MPFD emulator. Emulated pulses were produced with an amplitude of 144 mV and a rise- time of 115 ns using a shaping time of 0.25μs and gain of -1.3. Similarly, neutron-induced pulses were observed with an amplitude of 116 mV and a rise-time of 316 ns using a shaping time of 1.0μs and a gain of -1.3.The improved electronics increased the signal-to-noise ratio for the neutron-induced signal from approximately 2 to approximately 5.

This study focuses on the use of restaurant waste for production of ethanol. Food wastes (corn, potatoes, and pasta) were converted to ethanol in a two-step process: a two-part enzymatic digestion of starch using α-amylase and glucoamylase and then fermentation of the resulting sugars to ethanol using yeast. Because of the low initial composition of starch in the food waste, low ethanol concentrations were achieved: at best 8 mg/mL ethanol (0.8% by mass). Ethanol concentration increased with increasing enzyme dosage levels. Calculations were conducted to evaluate whether waste heat from restaurant waste could be used to drive flash vaporization to purify ethanol. If the solution produced by fermenting food waste is flashed at a temperature of 99.7°C, 77% of the ethanol is recovered in a vapor stream with 1.14 mol % ethanol (2.87 mass %). Waste heat could provide over a third of the energy for this vaporization process. If 4 mol % ethanol could be produced in the fermentation step by increasing the initial starch content in the waste solution and improving the fermentation process, then a single flash at 98.9°C will recover nearly 99% of the ethanol, giving a mass concentration of ethanol of 10.3%, which is similar to that achieved in industrial grain fermentation. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 1280–1283, 2013

CdZnTe has previously been shown to operate as an electro-optic radiation detector by utilizing the Pockels effect to measure steady-state nuclear reactor power levels. In the present work, the detector response to reactor power excursion experiments was investigated. Peak power levels during an excursion were predicted to be between 965 MW and 1009 MW using the Fuchs–Nordheim and Fuchs–Hansen models and confirmed with experimental data from the Kansas State University TRIGA Mark II nuclear reactor. The experimental arrangement of the Pockels cell detector includes collimated laser light passing through a transparent birefringent crystal, located between crossed polarizers, and focused upon a photodiode. The birefringent crystal, CdZnTe in this case, is placed in a neutron beam emanating from a nuclear reactor beam port. After obtaining the voltage-dependent Pockels characteristic response curve with a photodiode, neutron measurements were conducted from reactor pulses with the Pockels cell set at the 1/4 and 3/4 wave bias voltages. The detector responses to nuclear reactor pulses were recorded in real-time using data logging electronics, each showing a sharp increase in photodiode current for the 1/4 wave bias, and a sharp decrease in photodiode current for the 3/4 wave bias. The polarizers were readjusted to equal angles in which the maximum light transmission occurred at 0 V bias, thereby, inverting the detector response to reactor pulses. A high sample rate oscilloscope was also used to more accurately measure the FWHM of the pulse from the electro-optic detector, 64 ms, and is compared to the experimentally obtained FWHM of 16.0 ms obtained with the 10B-lined counter.

238U projectile fragments have been created at the entrance of the fragment separator FRS, spatially separated in flight within 0.45 μs and injected into the storage-cooler ring ESR at 7.9 Tm corresponding to about 70% light velocity. Accurate new mass values and lifetime information of the stored exotic nuclei in the element range from platinum to uranium have been obtained with single-particle Schottky spectrometry. In this experiment the new isotopes of 236Ac, 224At, 221Po, 222Po, and 213Tl were discovered. The isotopes were unambiguously identified and their masses measured. In addition, the time-correlated data have provided information on the lifetime of the new nuclides. The discovery of isotopes along with accurate mass measurement has been achieved for the first time at the FRS-ESR facility. The results will contribute to the knowledge of the decay products from the r-process nuclei and enable a crucial test of the predictive power of modern nuclear mass and half-life models.

A Compton-coincidence scintillator light yield non-proportionality measurement system was constructed and tested. Improved testing procedures and timing resolution have allowed the use of significantly less active excitation sources without lengthening test times or degrading data integrity. Previous methods typically required 100 mCi Cs-137 sources, but an increase in solid angle between source and sample as well as improved timing resolution have allowed the use of sources with activities less than 10 μCi. Representative samples of BGO and NaI(Tl) were tested to validate the system against literature single-source data.

Electromagnetic transitions within nuclei reflect specific aspects of nuclear structure. This is particularly true for metastable excited states, or isomers, like 178 Hf m 2 ( T 1 / 2 = 31 years, excitation energy 2446 keV). The interaction of external radiation with isomers can be used to study atomic and nuclear properties and, perhaps, to induce a release of the stored energy. Some experiments indicated that low-energy photons near the L 3 edge (9.561 keV) of hafnium could cause this to occur for 178 Hf m 2 , but the lack of a viable physical model and null experiments by other groups have left these claims in doubt. The present work describes a new experiment to examine this process by closely duplicating the irradiation conditions in positive studies, but using a more advanced multi-detector γ array. No support for an induced depletion of 178 Hf m 2 by low-energy photons was obtained, with an upper limit for the integral cross section that is eight orders-of-magnitude below the reported value.

Several potential neutron conversion materials have been studied over the past several years due to the 3He shortage. One candidate neutron conversion material is reticulated vitreous carbon (RVC) foam which can function as a coated substrate and is also suitable for high temperate environments. However, one concern with the material is the charge carrier propagation characteristics through the bulk of RVC foam. Electron propagation through the bulk of RVC foam samples was studied by comparing the resulting count rates and peak channel locations, with and without a sample present, for samples with linear pore densities ranging from 5–100 pores per linear inch (PPI). Count rates and pulse-height spectra from charge carriers generated by collimated 5.48 MeV 241Am alpha particles were studied and are reported here. The observed count rate and pulse height peak locations indicate that some electrons are able to drift through the 5 PPI sample. The peak channel locations with and without the 5 PPI sample were 230 and 360, respectively. However, all other linear pore density samples tested yielded much lower pulse heights, indicating loss of induced charge. Additionally, the intrinsic thermal neutron detection efficiency of a 10B 4 C-coated 45 PPI RVC foam sample was 3.23 ± 0.05%, indicating that the 10B 4 C-coated sample essentially functioned similar to a thin-film-coated device. Finally, the coating thickness of the 10B 4 C coating layer was measured using a SEM to be 1.29 ± 0.47 μm.

Reports that incident photons near 10 keV can induce the emission of gamma rays with concomitant energy release from the 31-year isomer of 178 Hf challenge established models of nuclear and atomic physics. In order to provide a direct and independent assessment of these claims, a multi-detector system was designed as a specialized research tool. The YSU miniball is unique in its combination of performance characteristics, compact size and portability, enabling it to be easily transported to and placed within the confines of beamline hutches at synchrotron radiation sources. Monochromatic synchrotron radiation was used in the most recent studies from which evidence of prompt triggering was claimed, suggesting similar sites for independent tests of these results. The miniball array consists of six high-efficiency BGO scintillators coupled with a single 65% Ge detector and provides time-resolved gamma-ray calorimetry rather than purely spectroscopic data. The need to record high detected folds from the array (up to seven-fold gamma coincidences) makes this system different in practice from standard spectroscopic arrays for which data is typically restricted to triples or lower folds. Here the system requirements and design are discussed, as well as system performance as characterized using the well-known natural decay cascades of 178m2 Hf. This serves as the foundation for subsequent high-sensitivity searches for low-energy triggering of gamma emission from this isomer.

Presently, fission chamber technology utilizes neutron-sensitive coatings often composed of radioisotopes that are becoming increasingly difficult to obtain. Using only natural uranium and thorium, a maximized stable device lifetime in a constant neutron flux can be obtained by optimizing the regenerative fission chamber coating. A system of coupled differential equations was developed by considering neutron-induced fission, neutron absorption, and radioactive decay of 17 radioisotopes spanning the product family tree from 232Th to 241Pu. By solving the system of coupled differential equations, the interaction rate of the regenerative fission chamber coating can be found as a function of time (or total fluence) in a constant neutron flux. The Kansas State University (KSU) TRIGA Mark II nuclear reactor was used as a basis to study the effectiveness of mixed fission chamber coatings over time. By varying the initial composition of the fission chamber coating, an optimal composition of 232Th and natural uranium is capable of maintaining stable device operation (

Nowotny-Juza compounds continue to be explored as candidates for solid-state neutron detectors. Such devices would have greater efficiency, in a compact form, than present day gas-filled 3He and 10BF3 detectors. The 6Li(n,t)4He reaction yields a total Q value of 4.78 MeV, larger than 10B, an energy easily identified above background radiations. Hence, devices fabricated from semiconducting compounds containing either natural Li (nominally 7.5% 6Li) or enriched 6Li (usually 95% 6Li) may provide a semiconductor material for compact high efficiency neutron detectors. Starting material was synthesized by preparing equimolar portions of Li, Zn, and P sealed under vacuum (10−6 Torr) in quartz ampoules lined with boron nitride and subsequently reacted in a compounding furnace. A static vacuum sublimation in quartz was then performed to remove the volatile impurities from the synthesized material. Samples from the sublimation process were analyzed by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), which showed that binaries and unreacted materials were sublimed out of the ternary material. Bulk crystalline samples were grown from the purified material. Individual samples were characterized for crystallinity on a Bruker AXS D8 DISCOVER, high-resolution x-ray diffractometer with a 0.004° beam divergence. The (220) oriented LiZnAs and LiZnP samples yielded rocking curves with a 0.235° full width at half maximum (FWHM) and 0.417° FWHM respectively.

A collaboration between the Idaho National Laboratory (INL), the Kansas State University (KSU), and the French Alternative Energies and Atomic Energy Commission, Commissariat a l'Energie Atomique et aux Energies Alternatives, (CEA), is funded by the Nuclear Energy Enabling Technologies (NEET) program to develop and test Micro-Pocket Fission Detectors (MPFDs), which are compact fission chambers capable of simultaneously measuring thermal neutron flux, fast neutron flux and temperature within a single package. When deployed, these sensors will significantly advance flux detection capabilities for irradiation tests in US Material Test Reactors (MTRs). Ultimately, evaluations may lead to a more compact, more accurate, and longer lifetime flux sensor for critical mock-ups, and high performance reactors, allowing several Department of Energy Office of Nuclear Energy (DOE-NE) programs to obtain higher accuracy/higher resolution data from irradiation tests of candidate new fuels and materials. Specifically, deployment of MPFDs will address several challenges faced in irradiations performed at MTRs: Current fission chamber technologies do not offer the ability to measure fast flux, thermal flux and temperature within a single compact probe; MPFDs offer this option. MPFD construction is very different than current fission chamber construction; the use of high temperature materials allow MPFDs to be specifically tailored tomore » survive harsh conditions encountered in-core of high performance MTRs. The higher accuracy, high fidelity data available from the compact MPFD will significantly enhance efforts to validate new high-fidelity reactor physics codes and new multi-scale, multi-physics codes. MPFDs can be built with variable sensitivities to survive the lifetime of an experiment or fuel assembly in some MTRs, allowing for more efficient and cost effective power monitoring. The small size of the MPFDs allows multiple sensors to be deployed, offering the potential to accurately measure the flux and temperature profiles in the reactor. This report summarizes the status at the end of year two of this three year project. As documented in this report, all planned accomplishments for developing this unique new, compact, multipurpose sensor have been completed.« less

Performance of a 4 cm long 64-pixel perforated diode neutron detector array is compared with an identical array of thin-film coated diodes. The perforated neutron detector design has been adapted to a 1-D pixel array capable of 120mm spatial resolution and counting efficiency greater than 12%. Deep vertical trenches filled with 6 LiF provide outstanding improvement in efficiency over thin-film coated diode designs limited to only 4.5%. This work marks the final step towards the construction of a much larger array consisting of 1024 pixels spanning 10 cm. The larger detector array will be constructed with a sub-array of 64-pixel sensors, and will be used for small-angle neutron scattering experiments at the Spallation Neutron Source of Oak Ridge National Laboratory. Published by Elsevier B.V.

Research for a reliable solid-form semiconductor neutron detector continues because such a device would have greater efficiency, in a compact form, than present day gas-filled 3He and 10BF3 detectors. The 6Li(n,t)4He reaction yields a total Q value of 4.78 MeV, larger than 10B, and easily identified above background radiations. Hence, devices composed of either natural Li (nominally 7.5% 6Li) or enriched 6Li (usually 95% 6Li) may provide a semiconductor material for compact high efficiency neutron detectors. A sub-branch of the III-V semiconductors, the filled tetrahedral compounds, AIBIICV, known as Nowotny-Juza compounds, are known for their desirable cubic crystal structure, and were originally studied for photonic applications. Equimolar portions of Li, Zn, and P or As were sealed under vacuum (10-6 Torr) in quartz ampoules with a graphite lining, loaded into a compounding furnace, and heated to 560 °C to form the ternary compound, LiZnP or LiZnAs, and further annealed to promote crystallization. The chemical composition of the synthesized starting material was confirmed at Galbraith Laboratories, Inc. by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), which showed the compounds were reacted in equal ratios, 1-1-1, to form ternary compounds. Bulk single crystal samples were grown by a high temperature technique described elsewhere. Samples were cut, polished, and prepared for electrical characterization by depositing a Ti/Au contact onto one side of the one of the samples and using silver epoxy to form the other contact. Current-voltage curves were collected for a sample with silver epoxy for both anode and cathode contact, and for a sample with a Ti-Au anode contact and silver epoxy cathode contact. A much higher resistivity was calculated, 6.6 x 1010 Ω·cm, for the sample with a Ti-Au contact compared the high conductivity seen with the sample using silver epoxy contacts.

A research program has been initiated by the NEET program for developing and testing compact miniature fission chambers capable of simultaneously measuring thermal neutron flux, fast neutron flux and temperature within a single package. When implemented, these sensors will significantly advance flux detection capabilities for irradiation tests in US Materials Test Reactors (MTRs).Ultimately, evaluations may lead to a more compact, more accurate, and longer lifetime flux sensor for critical mock-ups, high performance reactors and commercial nuclear power plants. Deployment of Micro-Pocket Fission Detectors (MPFDs) in US DOE-NE program irradiation tests will address several challenges: Current fission chamber technologies do not offer the ability to measure fast flux, thermal flux and temperature within a single compact probe, MPFDs offer this option. MPFD construction is very different then current fission chamber construction; the use of high temperature materials allow MPFDs to be specifically tailored to survive harsh conditions in typical high performance MTR irradiation tests. New high-fidelity reactor physics codes will need a small, accurate, multipurpose in-core sensor to validate the codes without perturbing the validation experiment; MPFDs fill this requirement. MPFDs can be built with variable sensitivities to survive the lifetime of an experiment or fuel assembly in some MTRs; allowingmore » for more efficient and cost effective power monitoring. The small size of the MPFDs allows multiple sensors to be simultaneously deployed; obtaining data required to visualize the reactor flux and temperature profiles. This report summarizes the research progress for year 1 of this 3 year project. An updated design of the MPFD has been developed, materials and tools to support the new design have been procured, construction methods to support the new design have been initiated at INL’s HTTL and KSU’s SMART Laboratory, plating methods are being updated at KSU, new detector electronics have been designed, built and tested at KSU. In addition, a project meeting was held at KSU and a detector evaluation plan has been initiated between INL and KSU. Once NEET program evaluations are completed, the final MPFD will be deployed in MTR irradiations, enabling DOE-NE programs evaluating the performance of candidate new fuels and materials to better characterize irradiation test conditions.« less

Cadmium zinc telluride (CdZnTe or CZT) is a well-known problematic material once dimensions exceed ∼1cm∧3, due to material imperfections that cause severe charge carrier (hole) trapping, compromising the energy resolution for basic planar detector designs. Advances in CZT detector design at Kansas State University (KSU) have demonstrated that room-temperature energy resolution less than 0.9% for 662 keV gamma rays can be consistently achieved. The Frisch-collar detector, developed at KSU, is a design based on the Frisch grid effect, which changes a basic planar detector from a low-resolution device into a high-resolution device by suppressing deleterious effects from charge carrier (hole) losses. We studied the application of Frisch-collar CZT detectors to hand-held or remotely-deployable rapid spectroscopic devices, designed to operate in signal-summation and Compton-suppression modes, employed for greater counting efficiency and improved energy resolution, respectively. The array is made from small volumes of Frisch-collar CZT, lowering cost and easing purity requirements for ingot growth. Timing resolution for signals arising from Compton-scattered gamma rays as a function of detector bias voltage will be discussed.

A new method to detect neutron radiation based on an electro-optic Pockels cell is reported. Collimated laser light passes through a radiation-sensitive electro-optic Pockels cell crystal sandwiched between crossed polarizers and onto a light sensitive photodiode. As radiation interacts in the crystal, free charge carriers are generated and perturb the electric field in the crystal, thereby altering the light polarization and causing a change in light intensity passing through the Pockels cell/polarizer system. The device can detect a neutron flux as low as a few neutrons cm−2 s−1 with an upper saturation limit exceeding 1010 neutrons cm−2 s−1. The unique electro-optic system separates the processing electronics from the detecting sensor, thereby allowing for operation in high neutron flux environments‥

Many homeland security applications involving gamma-ray detectors require energy resolution of better than 1%–2% for isotope identification. Existing High-Purity germanium (HPGe) detectors have the needed energy resolution but suffer from large size and the need for liquid-nitrogen or electromechanical cooling. Compact, inexpensive, room-temperature-operated devices are needed for handheld monitors, portal monitors, and monitors for nuclear materials in storage or transit. At Kansas State University, CdZnTe (CZT) gamma-ray detectors with better than 1% energy resolution have been developed. Mercuric Iodide detectors with better than 2% energy resolution have also been developed. Both devices make use of the Frisch-collar technology developed at KSU, and the quoted results were achieved without electronic corrections. The goal of the research at KSU is to maximize the energy resolution of the signals coming from the detectors, before any electronic corrections are made. The characteristics of these small, inexpensive devices will be discussed.

Despite the outstanding scintillation performance characteristics of CeBr 3 and LaBr 3 :Ce, commercial availability and application is limited due to the difficulties with crystal growth of large, crack-free single crystals of these fragile materials. Aliovalent doping was employed to strengthen CeBr3 in an effort to ease crystal growth constraints and improve ingot yields. Six divalent (Ca 2+ , Sr 2+ , Ba 2+ , Zn 2+ , Cd 2+ and Pb 2+ ) and two tetravalent cations (Zr 4+ and Hf 4+ ) were investigated as dopants to strengthen CeBr3 without negatively impacting scintillation performance. Ingots containing nominal concentrations of 500ppm and 1000ppm of each dopant were grown. Fluorimetry, preliminary scintillation, and preliminary fracture toughness measurements are presented for these aliovalently-doped scintillators. While Ca 2+ , Zn 2+ , Cd 2+ , and Hf 4+ all exhibited little or no change in the peak fluorescence emission for 300nm excitation, Sr 2+ , Ba 2+ , Pb 2+ , and Zr 4+ exhibited varying degrees of red-shifting. As expected, Pb 2+ had a drastic detrimental effect on scintillation. Initial microindentation data indeed indicates a noticeable increase in the fracture toughness of the doped crystals as compared to undoped CeBr 3 .

A 1024-channel pixel array has been constructed utilizing the perforated diode neutron detector design currently produced at Kansas State University. In this design a single pixel consists of a pn-junction diode fabricated around a single trench 4 cm long, 30 microns wide and 100 microns deep. The trench is filled with LiF powder to provide conversion of neutrons to energetic charged particles which can be captured in the diode depletion region. A pitch of 100 microns between pixels has been achieved and less than 120 micron spatial resolution has been demonstrated experimentally with a 32-channel prototype in previous work. Also, the first array demonstrated 12% thermal neutron counting efficiency. The 1024-channel array was produced by tiling 16 chips side-by-side, each containing 64 pixels. Signal processing is handled by 16 PATARA chips for amplification and thresholds, developed at University of Tennessee. The entire board assembly and digital communications to PC were handled by the KSU Electronics Design Laboratory utilizing a PCI card developed at ORNL.

CdZnTe crystals equipped with Frisch collars are studied at the Semiconductor Materials and Radiological Technologies Laboratory (S.M.A.R.T. Lab) at Kansas State University for use as room-temperature, high-resolution, semiconductor gamma-ray detectors. Obtaining plots of Relative Pulse Height vs. Input Photon Energy by testing with monoenergetic radioactive sources yields widely-spaced data points, but a Compton-scattering two-detector system can generate electrons with a range of energies within the crystal being tested, yielding a continuous curve. The linearity of the resulting curve is a limiting factor for the energy resolution of the semiconductor material.

Time-resolved Schottky mass spectrometry has been applied to uranium projectile fragments which yielded the mass value for the Hg-208 (Z=80, N=128) isotope. The mass excess value of ME=-13 265(31) keV has been obtained, which has been used to determine the proton-neutron interaction strength in Pb-210, as a double difference of atomic masses. The results show a dramatic variation of the strength for lead isotopes when crossing the N=126 neutron shell closure, thus confirming the empirical predictions that this interaction strength is sensitive to the overlap of the wave functions of the last valence neutrons and protons.

Two new pixellated neutron detectors developed at the Semiconductor Materials and Radiological Technologies Laboratory (SMART Lab) at Kansas State University, for eventual use at Oak Ridge National Laboratory Spallation Neutron Source, were tested for resolution, count rate and efficiency.

A Compton-coincidence scintillator light yield proportionality measurement system was constructed and tested. Improved testing procedures and timing resolution have allowed the use of significantly less active excitation sources without lengthening test times or degrading data integrity. Previous methods typically required 100μCi 137Cs sources, but an increase in solid angle between source and sample as well as improved timing resolution have allowed the use of sources with activities less than 10μCi. Representative samples of BGO and NaI(Tl) were tested to validate the system against single source data in the literature. Light yield from an in-house grown, doped CeBr 3 sample was also measured.

The time dependence of the polarization of a stored proton beam was measured near an induced depolarizing resonance. The resonance was created by a magnetic field which oscillated along the beam axis. The distance to the resonance was varied by changing the frequency of the oscillating field. The resonance was approached from either side and the time dependence of the polarization was found to be symmetric with respect to the resonance, and in agreement with an earlier measurement that involved an intrinsic depolarizing resonance.

Erratum to ‘‘Nuclear reactor pulse tracing using a CdZnTe electro-optic radiation detector’’ [Nucl. Instr. and Meth. A 680 (2012) 97–102] Kyle A. Nelson , Jeffrey A. Geuther , James L. Neihart , Todd A. Riedel , Ronald A. Rojeski , Philip B. Ugorowski , Douglas S. McGregor a a S.M.A.R.T. Laboratory, Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506, USA b TRIGA Mark II Nuclear Reactor, Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506, USA c Nanometrics, Inc., 1550 Buckeye Drive, Milpitas, CA 95035, USA

We report measurements for in-plane and out-of-plane correlations for p,d,t,/sup 3/He, and /sup 4/He from 40 MeV/nucleon C+C. Silicon-NaI light particle telescopes were placed at (theta,phi) = (45/sup 0/,90/sup 0/) and (45/sup 0/,180/sup 0/) and another telescope was moved from theta = 25/sup 0/ to 120/sup 0/ at phi = 0/sup 0/. No peak was observed in the ratio of in- to out-of-plane proton-proton correlations at energies corresponding to quasi-elastic scattering. The angular distributions of the ratio of in- to out-of-plane for p-p, d-d, t-t, /sup 3/He-/sup 3/He, and /sup 4/He-/sup 4/He peak around 35/sup 0/ and the maximum value increases monotonically with mass of the particles reaching a value near 4 for /sup 4/He-/sup 4/He. A calculation incorporating simple kinematic effects cannot reproduce the observed correlations for any of the paritcle pairs.

This paper will describe the polarized internal gas target installed in the Indiana Cooler and focus to a large extend on operational properties from the experimenters point of view. Measurements of pp elastic spin correlation parameters Axx, Ayy, Axz and Azz have been finished and some of the recent results will be presented as well. Studies of systematic effects from background reactions and target beam interactions will be presented also.