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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS2020

Infrared Properties of High-Purity Silicon

High-purity silicon is a readily available material of utility in realizing a variety of long-wavelength optical and guided wave components. The transmittance of uncompensated for silicon is measured in the far- and mid-infrared regimes at room and cryogenic temperatures. The experimental and analysis techniques used to extract the refractive index from 100-1000 per cm (100–10µm) are presented, and the results are compared to the literature. An average refractive index below 300 per cm, n̂(300 K)=3.417 + i 8.9 x10(exp -5), which transitions in cooling to n̂(10 K)=3.389 + i 4.9 x 10(exp -6), is observed.

Edward J. Wollack↗
NASA NTRS2001

Electroactive polymers as artificial muscles - reality and challenges

For many years, electroactive polymers (EAP) received reIatively little attention due to the small number of available materials and their limited actuation capability. The recent emergence of EAP materials with large displacement response changed the potential capability and paradigms of these materials. The main attractive characteristic of EAP is their operational similarity to biological muscles, particularly their resilience and ability to induce large actuation strains. Even though the actuation force of existing EAP materials and their robustness require further improvement, there has already been a series of reported successes. The successful applications that were demonstrated include catheter steering element, miniature manipulator, dust-wiper, miniature robotic arm, and grippers. Some of the currently considered applications may be difficult to accomplish and it is important to scope the requirements to the level that current materials can address. Using EAP to replace existing actuators may be a difficult challenge and therefore it is highly desirable to identify a niche application where it would not need to compete with existing capabilities. The application of these materials as actuators to drive various manipulation, mobility and robotic devices involves multidiscipline including materials, chemistry, electro-mechanics, computers, electronics, etc. This paper reviews the current efforts and the expectations for the future.

Bar-Cohen, Yoseph↗
NASA NTRSDate not supplied

VIPER: Introduction to the Resource Prospecting Mission

With the Artemis Program, NASA plans to return humans to the Moon to stay, which means if there are local materials available, they could be deployed to help support extended lunar stays. Since the moon’s polar regions have confirmed the presence of volatiles, as revealed by LCROSS, LRO and other lunar missions, the next step is to understand the nature and distribution of those candidate resources and how they might be extracted. Recent studies have even indicated local volatiles could be processed into propellants and human life-supporting resources, significantly aiding in sustaining humans on the Moon, and eventually and later to support missions to Mars. The Volatiles Investigating Polar Exploration Resource (VIPER) is an in-situ resource utilization (ISRU) mission within NASA’s Science Mission Directorate (SMD), based on the pathfinding development of the Resource Prospector (RP) mission concept. This clever mission is targeting late 2023 and may spend over 100 days mapping and surveying four different Ice Stability Regions to understand the nature and distribution of water and volatiles already confirmed to be there, including measuring mineralogical content such as silicon and light metals from lunar regolith. The knowledge attained by a mission like VIPER could have many-fold benefits for space exploration, but also commercial applications. VIPER is an essential, early mission supporting the “moon rush” which has developed over the past few years, with both governments and commercial entities making their cases for lunar exploration. VIPER aims to understand just how the water-ice and other volatiles are distributed, both horizontally and vertically, enabling creation of volatiles resource maps, which will guide what might be required to harvest those resources at scale. With sufficient infrastructural investment, led by governments and then optimized by the commercial marketplace, VIPER will be a pathfinder mission addressing key decadal lunar science and early strategic knowledge gaps.

Daniel Andrews↗
NASA NTRSDate not supplied

Implementation of Charged Particle Behavior in Discrete Element Method (DEM) Simulations

Lunar landers will agitate the surface of the Moon with an exhaust plume during descent which will, due to the particulate nature of the lunar regolith, loosen and eject grains from the surface. This ejection is not only coupled with the charged plume gas, but also results in significant particle-particle interactions. Settling of these grains after plume effects have subsided takes much longer than expected in a ballistic trajectory. The prevailing hypothesis attributes this behavior to the accumulated charge on the particles. We are thus developing a discrete element method (DEM) approach to explore these charged particle interactions on the lunar surface. The Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) Improved for General Granular and Granular Heat Transfer Simulations (LIGGGHTS) software package provides a DEM modeling framework for granular interactions. It includes many complexities such as non-spherical particle shapes, cohesion and frictional forces, and heat transfer, but has no provision for inter-particle electrostatic forces and charge transfer that are important to examine in the lunar environment. In this work, a standard Coulomb potential and a Yukawa potential are integrated into the LIGGGHTS framework to provide a basis for particle-particle electrostatic interactions, as well as a gravitational potential to enable inter-grain gravitational interactions. A preliminary approach to charge transfer between grains incorporating properties such as work function and electrical conductivity to the library of available material characteristics will be presented. Several scenarios have been simulated that include charged particle interactions within a diffuse granular gas, settling of charged grains into a regolith bed, sliding of granular material along an incline, and vibration of settled grains to produce a behavior similar to fluidization. There are numerous challenges to incorporate realistic interactions between complex lunar particles. Currently, grains are modeled to behave as if the entirety of the charge acts at the center of mass, such as conductors with spherical symmetry and insulators with homogeneously distributed charge. We are developing improvements that will include the use of non-spherical particle geometries, as well as reasonable approximations of insulating/dielectric materials that have non-uniform charge distributions. The cases simulated thus far will be examined in a relevant environment within a vacuum chamber to validate the simulations. These simulations will be bounded by experiments utilizing high-speed camera observations of the motion for validation. The grains in the experiment will exchange charge during their motion and this can be quantified by collection within a charge measurement device such as a Faraday cup. Such a device may be modeled within the software by defining an integration region and computing the contained charge as a function of simulation time, allowing for side-by-side comparison of simulated and measured bulk charging results. Any differences will be reconciled by updating the mathematical mechanisms described within the simulation suite. Successfully combining results from experiments within a relevant environment into the LIGGGHTS framework will improve modeling of the charged grain dynamics experienced on the Moon to provide insights into dust behavior for future lunar exploration missions.

Electrostatics↗
NASA NTRSDate not supplied

Fabrication of monocrystalline silicon x-ray mirrors

Progress within the fi eld of x-ray astronomy depends on astronomical x-ray observations of ever-increasing quality and speed. Fast and high-resolution x-ray observations over a broad spectral range promise amazing new discoveries. These observations, however, require a spaceborne x-ray telescope of unprecedented imaging power. Of the numerous technological concerns associated with the design and construction of such a telescope, the x-ray focusing optics present a particularly complex and arduous set of challenges. An x-ray optical assembly comprises many thousands of x-ray mirrors, a most critical element. Our group at NASA Goddard Space Flight Center (GSFC) pursues the development of an x-ray mirror manufacturing process capable of meeting the stringent quality, production time, and cost requirements of the next-generation of x-ray telescopes. The manufacturing process employs monocrystalline silicon: a lightweight, stiff, thermally conductive, and readily available material which is free of internal stress; it is a nearly ideal material for a thin mirror substrate. The process involves various traditional optical fabrication techniques adapted to x-ray mirror geometry. Presently, our process is capable of fabricating sub-arcsecond half-power diameter (HPD) resolution mirror pairs (primary and secondary) at a mirror thickness of 0.5 mm and of virtually any x-ray optical design (e.g. Wolter-I, Wolter-Schwarzschild, etc.). The mirror substrate surface quality is comparable to, and sometimes exceeding, that of the mirrors on the Chandra X-ray Observatory. This paper describes the various manufacturing steps involved in the production of x-ray mirror substrates and a present status report.

Raul E. Riveros↗
NASA NTRSDate not supplied

Development of a Ground Multi-Mission Low-Cost Optical Terminal (LCOT) for Free-Space Optical Communications

Once confined to the realm of laboratory experiments and theoretical papers, space-based laser communications (lasercomm) are on the verge of achieving mainstream status. Organizations from Facebook to NASA, and missions from cubesats to Orion are employing lasercomm to achieve gigabit communication speeds at mass and power requirements lower than that of traditional radio frequency (RF) methods. Since first demonstrating free-space optical communications services with Lunar Laser Communications Demonstration (LLCD) in 2013, NASA has invested in developing optical communications technologies and capabilities to enhancing its space communications networks. Along with evolving optical space terminals, NASA is also developing lasercomm grounds stations capable of meeting the rapidly increasing data volume demands of upcoming missions, from low-earth to lunar orbits and beyond and integrating these advanced capabilities into its Near-Space and Deep Space Networks. To meet this emerging need, the Low-Cost Optical Terminal (LCOT) project at NASA’s Goddard Space Flight Center (GSFC) is designing, building and validating a prototype for a flexible, multi-mission, and economical optical ground terminal that could be used as a blueprint for a global network of optical ground stations, capable of supporting a wide variety of missions. To date a major impediment to widespread adoption of laser communication has been the lack of an existing ground network infrastructure. A mission that wishes to take advantage of laser communication not only needs to invest in an optical space terminal, but it must also finance the creation of ground terminals to receive the downlink signal. This adds significant additional cost. Missions that do decide to incur the cost of financing a network of ground terminals end up building highly specialized optical receivers that are operable as receivers for that specific mission only. Significant Non-Recurring Engineering (NRE) cost is invested to build highly specialized one-of-a-kind ground terminals that go into storage after that particular mission is over. This is not an economical approach and does nothing to grow the number of optical ground stations available to future missions. In essence each mission that wants to take advantage of the benefits of lasercom has to start from scratch to provide a ground terminal network to support it. As long as this is the case, the cost for using laser communications will be too high for most missions to consider. LCOT intends to close this gap in technology by designing and developing a standard optical ground terminal design that is flexible enough to serve as a receiver for a wide range of future missions – a ground terminal that can be quickly reconfigured to receive downlinks at different wavelengths using different signal formats. Not only does LCOT have the industry-building objectives of utilizing commercial-off-the-shelf (COTS) components to the maximum extent possible, but also spurs the commercial development of other necessary lasercomm components not currently offered by industry. Finally, LCOT will give NASA scientists and engineers a facility where they can gain real-world experience with optical communications. It will give engineers a cost-effective way to try out new concepts and processes by providing the infrastructure for such testing. In this way it is hoped LCOT will serve as a stimulus for innovation in optical communications and speed its widespread adoption by future missions. The LCOT is comprised of five subsystems: Free-Space Optical, Transceiver, Amplifier, Monitor and Control, and Observatory Infrastructure. In August 2021, the LCOT team installed a 70 cm telescope, developed by Planewave Instruments that was optimized for optical communications. Free-Space Optical subsystem comprises of the telescope and its associated hardware, including a transmitter optical assembly, wide field cameras, two optical benches, and an adaptive optics subsystem. The transmit optical assembly, a unique concept design, is a cluster of four functionally independent transmit subassemblies located on the receive telescope. In addition to receiving optical signals and directing the expanded beam with high precision to the space terminal, it also performs tracking functions. The transmit optical assembly will support operations from Low Earth Orbit (LEO) through lunar and will be used as a template for industry manufacturing. The Optical Infrastructure subsystem is responsible for providing environmentally controlled shelters for LCOT equipment and various other systems. To maintain the safety and proper functionality of the telescope, a 16 ft Astrohaven clamshell dome procured which provides all-sky coverage without the need to rotate the dome. Additionally, Atmospheric Monitoring Assembly (AMA) will be part of optical infrastructure subsystem to ensure accurate performance of the LCOT. Like existing optical ground stations, LCOT will measure standard weather station parameters, infrared all sky image of cloud cover, and cloud height. LCOT, however, adds requirements for measuring night time seeing and, in the future, daytime seeing. Unlike other optical ground terminals, the LCOT is transceiver agnostic; user transceivers may be duplex transceivers, standalone receivers, or standalone transmitters with or without acquisition beacon functionality. As such, the LCOT project accommodates testing with external customer transceivers in a flexible manor, further complimenting its intended multi-mission goals. Another unique component of LCOT is the use of a new amplifier technology – the Very Large Mode Area (VLMA) amplifiers. This new technology allows LCOT to avoid the issues faced by previous laser communications ground terminals, gives users more flexibility and modular capability, and is capable of reaching an order of magnitude higher peak power than traditional High Power Optical Amplifiers (HPOA). One drawback of the VLMA HPOA approach is that the amplified light is output into free-space. The solution developed by LCOT is an optics train that couples the output of the VLMA amplifier into a short fiber for transport to the transmit telescopes with high efficiency. Like many of the LCOT components, a set of detailed manufacturing drawings have been created for the optics train to allow any machine shop with a multi-axis Computer Numerical Control (CNC) machine to fabricate the piece parts from commonly available materials. In line with the goals of LCOT, the monitor and control functions are developed as a modular and flexible system with the ability to support future hardware or algorithm changes, minimizing disruptions. A main priority of development in the Monitor and Control Subsystem (MCS) is the safety monitor system.

laser communication↗
NASA NTRSDate not supplied

Development of a Ground Multi-mission Low Cost Optical Terminal(LCOT) for Free-Space Optical Communication

Once confined to the realm of laboratory experiments and theoretical papers, space-based laser communications (lasercomm) are on the verge of achieving mainstream status. Organizations from Facebook to NASA, and missions from cubesats to Orion are employing lasercomm to achieve gigabit communication speeds at mass and power requirements lower than that of traditional radio frequency (RF) methods. Since first demonstrating free-space optical communications services with Lunar Laser Communications Demonstration (LLCD) in 2013, NASA has invested in developing optical communications technologies and capabilities to enhancing its space communications networks. Along with evolving optical space terminals, NASA is also developing lasercomm grounds stations capable of meeting the rapidly increasing data volume demands of upcoming missions, from low-earth to lunar orbits and beyond and integrating these advanced capabilities into its Near-Space and Deep Space Networks. To meet this emerging need, the Low-Cost Optical Terminal (LCOT) project at NASA’s Goddard Space Flight Center (GSFC) is designing, building and validating a prototype for a flexible, multi-mission, and economical optical ground terminal that could be used as a blueprint for a global network of optical ground stations, capable of supporting a wide variety of missions. To date a major impediment to widespread adoption of laser communication has been the lack of an existing ground network infrastructure. A mission that wishes to take advantage of laser communication not only needs to invest in an optical space terminal, but it must also finance the creation of ground terminals to receive the downlink signal. This adds significant additional cost. Missions that do decide to incur the cost of financing a network of ground terminals end up building highly specialized optical receivers that are operable as receivers for that specific mission only. Significant Non-Recurring Engineering (NRE) cost is invested to build highly specialized one-of-a-kind ground terminals that go into storage after that particular mission is over. This is not an economical approach and does nothing to grow the number of optical ground stations available to future missions. In essence each mission that wants to take advantage of the benefits of lasercom has to start from scratch to provide a ground terminal network to support it. As long as this is the case, the cost for using laser communications will be too high for most missions to consider. LCOT intends to close this gap in technology by designing and developing a standard optical ground terminal design that is flexible enough to serve as a receiver for a wide range of future missions – a ground terminal that can be quickly reconfigured to receive downlinks at different wavelengths using different signal formats. Not only does LCOT have the industry-building objectives of utilizing commercial-off-the-shelf (COTS) components to the maximum extent possible, but also spurs the commercial development of other necessary lasercomm components not currently offered by industry. Finally, LCOT will give NASA scientists and engineers a facility where they can gain real-world experience with optical communications. It will give engineers a cost-effective way to try out new concepts and processes by providing the infrastructure for such testing. In this way it is hoped LCOT will serve as a stimulus for innovation in optical communications and speed its widespread adoption by future missions. The LCOT is comprised of five subsystems: Free-Space Optical, Transceiver, Amplifier, Monitor and Control, and Observatory Infrastructure. In August 2021, the LCOT team installed a 70 cm telescope, developed by Planewave Instruments that was optimized for optical communications. Free-Space Optical subsystem comprises of the telescope and its associated hardware, including a transmitter optical assembly, wide field cameras, two optical benches, and an adaptive optics subsystem. The transmit optical assembly, a unique concept design, is a cluster of four functionally independent transmit subassemblies located on the receive telescope. In addition to receiving optical signals and directing the expanded beam with high precision to the space terminal, it also performs tracking functions. The transmit optical assembly will support operations from Low Earth Orbit (LEO) through lunar and will be used as a template for industry manufacturing. The Optical Infrastructure subsystem is responsible for providing environmentally controlled shelters for LCOT equipment and various other systems. To maintain the safety and proper functionality of the telescope, a 16 ft Astrohaven clamshell dome procured which provides all-sky coverage without the need to rotate the dome. Additionally, Atmospheric Monitoring Assembly (AMA) will be part of optical infrastructure subsystem to ensure accurate performance of the LCOT. Like existing optical ground stations, LCOT will measure standard weather station parameters, infrared all sky image of cloud cover, and cloud height. LCOT, however, adds requirements for measuring night time seeing and, in the future, daytime seeing. Unlike other optical ground terminals, the LCOT is transceiver agnostic; user transceivers may be duplex transceivers, standalone receivers, or standalone transmitters with or without acquisition beacon functionality. As such, the LCOT project accommodates testing with external customer transceivers in a flexible manor, further complimenting its intended multi-mission goals. Another unique component of LCOT is the use of a new amplifier technology – the Very Large Mode Area (VLMA) amplifiers. This new technology allows LCOT to avoid the issues faced by previous laser communications ground terminals, gives users more flexibility and modular capability, and is capable of reaching an order of magnitude higher peak power than traditional High Power Optical Amplifiers (HPOA). One drawback of the VLMA HPOA approach is that the amplified light is output into free-space. The solution developed by LCOT is an optics train that couples the output of the VLMA amplifier into a short fiber for transport to the transmit telescopes with high efficiency. Like many of the LCOT components, a set of detailed manufacturing drawings have been created for the optics train to allow any machine shop with a multi-axis Computer Numerical Control (CNC) machine to fabricate the piece parts from commonly available materials. In line with the goals of LCOT, the monitor and control functions are developed as a modular and flexible system with the ability to support future hardware or algorithm changes, minimizing disruptions. A main priority of development in the Monitor and Control Subsystem (MCS) is the safety monitor system.

Haleh Safavi↗
NASA NTRS2024

Development of a Single Level Assessment Module for Simulating the Human Factors Concept Trade Space

This paper is a synopsis of the design and development of the Single Level Assessment Module (SLAM), a habitation mockup aimed at simulating volumetric conditions for astronauts in transit to Mars. Utilizing repurposed materials to enable low cost and constrained by various other design requirements from its parent vehicle, the SLAM embodies a critical step towards understanding human/habitat dynamics and interactions within the framework of the Mars Transit Habitat (TH) concept trade space. The synopsis begins by outlining the design constraints and goals, focusing on material availability and functional area volume requirements. Through various 3D design solutions, the SLAM emerges as a versatile habitat prototype, capable of accommodating various functional areas within its reconfigurable framework. The construction phase is then explored, highlighting the practical challenges and solutions encountered in assembling the SLAM's components. From panel assembly to outfitting functional areas, the construction process demonstrates a methodical approach to realizing the habitat's design intent. Looking ahead, the paper outlines future work, emphasizing the SLAM's adaptability for analysis and its potential to inform the design trade space future habitation concepts across the Moon to Mars architecture. By incorporating hinges for reconfigurability and facilitating volume assessments, the SLAM emerges as a crucial tool in advancing NASA’s ability to assess focused habitation configurations in conjunction with the development of the Moon to Mars architecture. In conclusion, this paper showcases the iterative process of habitat design, from conceptualization to construction.

Keith Lindsey↗
NASA NTRSDate not supplied

Contracting Quality Early in the Lifecycle Using AS9145 Data Deliverables

Development schedules and a highly dynamic supply chain are a challenge to developers of complex systems produced at low volume. Flaws in designs, parts and materials availability problems, poor manufacturability, and a lack of knowledge about critical items and key process attributes can be realized well before traditional second-party quality assurance activities begin. Supplier audits and product inspections may have little mitigating effect once these foundational problems have been realized. Their impacts can be significant lifecycle disruption, cost overruns, inability to deliver to plan, and even project cancellation. AS9145, Requirements for Advanced Product Quality Planning and Production Part Approval Process, can be used to drive quality engineering practices into early development lifecycles to significantly reduce this late-cycle risk and to reduce the cost of quality overall. Since its initial publication in 2016, it has had very limited adoption by the DoD, no adoption by NASA, and sparse adoption in the aerospace and defense supply chain. A task group within the Aerospace Industries Association's (AIA) Joint Strategic Quality Council (JSQC) identified that both acquirers and suppliers see as AS9145 as a cost-adder and are hesitant to use it as an alternative to late-stage-heavy quality assurance approaches. A lack of prior use creates large capability gaps in request-for-proposal (RFP) teams, proposal teams, suppliers’ quality management systems (QMS), and in experienced personnel executing the early lifecycle approach. To create a more realizable on-ramp for using AS9145 in the space and defense sectors, the AIA JSQC task team created five deliverable requirements descriptions (DRDs) that can be used in a contract to begin to engage both parties in early lifecycle quality engineering and quality assurance activities, that reduce exposure to late-stage cost and schedule collapse due to unidentified risks in design, supply chain, and manufacturability. These DRDs drive the parties to engage in planning and analysis discussions early on to understand what production risks can be known and how they will focus resources based on safety criticality and the key elements of design and construction. The suppliers and acquirers who will produce the data and information required by the DRD will be able to incrementally evolve their QMS and the acquirer will incrementally be able to track and understand the benefits of cost shifting from late to early development phases. A white paper describing this approach and the five recommended DRDs will be published by the AIA in late 2024 or early 2025.

Jeannette Plante↗
DOE OSTI2017

Fissile Material Stockpile Declarations and Cooperative Nuclear Archaeology

With the beginning of the Cold War, the United States and the Soviet Union quickly began to produce fissile material (plutonium and highly enriched uranium, HEU) for military purposes on an industrial scale. By the mid-1950s, both countries were already making ton-quantities of fissile material per year to supply their growing nuclear arsenals. They were soon joined by the United Kingdom (1951), France (1955), China (1964), and Israel (1965)—and later by India, Pakistan, and finally North Korea. By the time most of these production efforts ended in the early 1990s, the global stockpile of military fissile material had reached fantastic levels. While the combined global nuclear weapon inventory had peaked at about 64,000 in 1986,1 the military fissile-material stockpile ultimately reached almost 2200 tons (240 tons of plutonium and 1960 tons of highly enriched uranium), which is sufficient to make about 200,000 simple nuclear weapons.2 Since the end of the Cold War, almost 700 tons of highly enriched uranium have been down-blended and other material is now reserved for naval fuel. Overall, the military material available for weapon purposes today is sufficient for more than 150,000 weapons (Figure 1).

Glaser, Alexander↗
DOE OSTI2019

Development of self-healing films to improve durability of VIPs by in-situ remediation of film defects

The integrity of the VIP barrier film or envelope is a critical for maintaining the ultra-low thermal conductivity of VIPs. Here, the concept of a self-healing barrier film is described and demonstrated. The self-healing concept is based on an addition reaction between two chemicals, without the need for any external stimuli. The chemicals are incorporated as coatings in a multi-layered film and are initially kept separate with a partition layer. In case of damage, the chemicals would mix, react and heal the damage. Tests of small-scale film samples in a custom vacuum pump apparatus by puncturing the samples demonstrated the proof-of-concept. The tests indicated that the chemicals reacted and healed the puncture immediately to maintain the system vacuum. The intact and punctured self-healing films showed near-identical behaviour, while a control sample allowed the pressure to rise to atmospheric levels on puncturing. Development of films with coated chemicals using tape casting and slot die coating methods is also described. These are low-cost and mature technologies, which are commonly used by various industries. The proposed chemicals are low-cost, commercially available materials. Thus, the self-healing technology is expected to be inexpensive and scalable.

Biswas, Kaushik↗
DOE OSTI2019

Rural K-12 School Workforce Development and Training

This fact sheet summarizes some of the available materials, trainings, and certification courses for building operators of rural K-12 school facilities who wish to expand their energy efficiency knowledge and apply it to their schools.

Energy Efficiency, K-12, K-12 Schools, Education, ↗
DOE OSTI2022

White Paper on High Temperature Superconducting Bi-2212 Magnets for Energy Frontier Circular Colliders

As the only high-temperature superconducting (HTS) material available as an isotropic, twisted, multifilamentary round wire, Bi-2212 is very promising for expanding the high-field superconducting accelerator magnet toolbox beyond the round-wire, isotropic Nb-Ti and Nb3Sn conductors used by HEP so far. In this paper, we describe the important roles that Bi-2212 might play for future high energy circular colliders including both high energy proton and muon colliders. We describe its present technology status (conductor development, magnet design concepts, prototype magnet status) and then provide a ten-year plan for >15 T accelerator magnets and >25 T solenoid magnets within an integrated strategy to engage industry and the entire US and international scientific enterprise interested in HTS magnet applications.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

{sup 6}LiF:ZnS(Ag) Neutrons Scintillator Detector Configuration for Optimal Readout

A Chromatic Analysis Neutron Diffractometer Or Reflectometer (CANDOR) is under development at the NIST Center for Neutron Research (NCNR). The CANDOR neutron sensor will rely on scintillator material for detecting the neutrons scattered by the sample under test. It consists of {sup 6}LiF:ZnS(Ag) scintillator material into which wavelength shifting (WLS) fibers have been embedded. Solid state photo-sensors (silicon photomultipliers) coupled to the WLS fibers are used to detect the light produced by the neutron capture event ({sup 6}Li (n,α) {sup 3}H reaction) and ionization of the ZnS(Ag). This detector configuration has the potential to accomplish the CANDOR performance requirements for efficiency of 90% for 5 A (3.35 meV) neutrons with high gamma rejection (10{sup 7}) along with compact design, affordable cost and materials availability. However this novel design includes challenges for precise neutron detection. The recognizing of the neutron signature versus the noise event produce by gamma event cannot be easy overcome by pulse height discrimination obstacle as can be achieved with {sup 3}He gas tube. Furthermore the selection of silicon photomultipliers (SiPM) as the light sensor maintains the obstacle of dark noise that does not exist when a photomultiplier tube is coupled to the scintillator. A proper selection of SiPM should focus on increasing the output signal and reducing the dark noise in order to optimize the detection sensitivity and to provide a clean signal pulse shape discrimination. The main parameters for evaluation are: - Quantum Efficiency (QE) - matching the SiPM peak QE with the peak transmission wavelength emission of the WLS. - Recovery time - a short recovery time is preferred to minimize the pulse width beyond the intrinsic decay time of the scintillator crystal (improves the gamma rejection based output pulse shape (time)). - Diode dimensions -The dark noise is proportional to the diode active area while the signal is provided by the WLS fibers; therefore the diode area should ideally be only minimally larger than fiber bundle area. - Low dark noise - it is desirable to minimize the dark noise during the pulse integration period so as to minimize the background for pulse shape discrimination. - Photon Detection Efficiency - it is desirable to increase the SiPM PDE in order to enhance light collection. This will increase the likelihood of detecting neutron events with lower light production and will present a cleaner raw signal for pulse shape discrimination. We will present the SiPM optimization process and studies of dark noise and gamma and neutron sensitivity as a function of bias voltage and operating temperature that have enabled us to optimize the detector sensitivity and gamma rejection. The gamma rejection performance goal requires to overcome the challenge of discriminating between the light signature accepted by neutron event to the one received by the noise. In addition there is a huge variation between the number of light photons that reaching the WLS fibers for different neutron events caused by the heavy ions energy losses prior to ionizing the ZnS(Ag) and the high light attenuation of the scintillation mixture. This variation in the light signal along with the long decay time of the ZnS(Ag) (tens of microseconds) can cause double counting of the same neutron event in the case of high light output signature or preventing the detection of low sequential light output signature neutron event. We will presents the algorithm developed for {sup 6}LiF:ZnS(Ag) sensor readout and the results achieved by an off-line analysis by Matlab software code that successfully achieved both the high gamma rejection with a sensitive and accurate neutron event detection. (authors)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Idaho-Developed Technologies, Processes Offer Unique Solutions to Waste Management Challenges - 19281

INL Site cleanup contractor Fluor Idaho, LLC (Fluor Idaho) and its predecessors have developed a host of state-of-the-art technologies and specialized processes for nuclear waste handling, treatment, storage, and shipping. The cleanup program has also repurposed and upgraded previously idled Cold War-era buildings to treat and repackage both on- and off-site generated radioactive and hazardous wastes. And lastly, Fluor Idaho is using one-of-a-kind equipment to protect waste management personnel as they undertake their work to meet cleanup commitments that the Department of Energy (DOE) made to the state of Idaho. Such applications, although developed for Idaho's wastes, have the potential to benefit other facilities within the DOE Complex. Engineers and fabricators have teamed up to develop truly unique devices made of specialized metals, like stainless steel alloys, and more readily available materials such as Lexan. All waste types that Fluor Idaho manages daily - spent nuclear fuel, both high- and low-level wastes, and both remote-handled (RH) and CH-TRU - benefit from these innovations. Without question, the greatest number of specialized equipment, processes, and worker-protection technologies developed are for the retrieving, characterizing, repackaging, and shipping of TRU wastes, which makes sense considering the INL Site stores the most TRU waste in the DOE Complex. On the CH-TRU retrieval front, crews are using specially modified Gradall excavators to protect workers while they exhume Rocky Flats Plant wastes that were sent to Idaho in the 1950's and 1960's and buried in a shallow landfill. The excavators are supplied with extra Lexan windows to protect operators from the potential for flying debris during exhumation. On-board supplied air, pumped into the cab, and individual air supplies protect workers from inhalation hazards. Also on-board infrared cameras allow operators to detect heat generating from reactive metals at the dig face. At the Advanced Mixed Waste Treatment Facility (AMWTP), Brokk robotic arm operators use a 'super clam' claw, designed and built at the INL Site, on the remotely operated heavy equipment to size-reduce waste boxes, drums, concrete, and metal containing TRU constituents. The super clam is so powerful and dexterous that operators can crush a 55-gallon drum into the size of a basketball, but also delicately turn the pages of a magazine. Boxes too large to be sized at the AMWTP's box-lines are sent to the Accelerated Retrieval Project VII facility to be sized by Waste Management personnel. Such waste boxes, which sometimes contain 'flighty' plutonium-238 material, have forced the project to employ a heavily ventilated and filtered interior tent. Not all technologies developed for the Waste Management program are high-technology; in fact, one piece of equipment is so simple it's literally ingenious. Operators who inspect and repackage RH-TRU inside a hot cell at the Idaho Nuclear Technology and Engineering Center (INTEC) needed a backup plan in case the hot cell port couldn't be closed in the event of a power outage. Engineers and fabricators collaborated to develop a port cover actuator mechanism, which allows operators to open and close the cell's hatch cover with nothing more than a cordless drill. Also at INTEC, Maintenance Shop fabricators developed a Lexan container or 'pig' suitable for shielding neutron-emitting TRU waste sources. Lexan was chosen as the preferred shielded container material for this special type of waste because neutrons are best shielded with materials containing lots of hydrogen, such as plastics, which are composed of carbon and hydrogen molecules. Once approved for shipment, the high-activity waste will be loaded into specialty casks and shipped to WIPP for permanent disposal. Although all these technologies and processes were initially developed for resolving challenges at the INL Site, their applications could be far-reaching. Like the INL Site, many other facilities in the DOE Complex manage, treat, store, and ship TRU, low-and high-level wastes, and spent nuclear fuel. The technologies and processes developed in Idaho protect Waste Management personnel as they undertake their work, but these benefits could be utilized by other facilities and personnel doing similar work. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Thin Film Solid State Active Dosimetry

With the many advances in semiconductor manufacturing, the pool of available materials for use in their production also continues to broaden. One such example is aluminum antimonide (AlSb). Its promising properties for radiation detection have attracted multiple researchers, and allow for the possibility that it may be a high resolution, room temperature x-ray/gamma detector. Antimony has an atomic number of 51 (Z=51) and is responsible for the majority of photon interactions. Furthermore, the mass attenuation coefficient is comparable with other well-known solid state gamma detectors such as CZT. With a band gap of 1.6 eV (CZT=1.5 eV), low leakage current at room temperature is expected, and high charge carrier statistics from radiation interactions can be expected. Charge carrier statistics are driven by high charge mobility (μ) and lifetime (τ). μτ for CZT is on the order of 5x10{sup -3} cm{sup 2}/V for electrons, but two orders of magnitude smaller for holes. This results in large variations in detector pulse height depending on the location of interaction (close to the anode vs. close to the cathode). Theoretically, AlSb should exhibit much more symmetric electron and hole properties near 5x10{sup -3} cm{sup 2}/V. According to the Hecht relation, this should produce a more uniform detector response and increase the number of generated charge carriers, improving resolution. An added benefit is that AlSb can be grown directly onto Si substrates, enabling fully integrated circuit board-level sensors. However, several characteristic properties remain unknown and inconsistent published results due to difficulties in producing the material. Difficulties in bulk growth methods (material interactions with growth hardware such as crystals and air) resulted in high levels of defects. The use of AlSb in optoelectronics from thin film growth methods has been documented, including growth directly onto Si, and provides the potential for much more controlled material. In our work we use thin film growth of AlSb geared towards high quality material for understanding the properties for radiation detection. (authors)

36 MATERIALS SCIENCE↗