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DOE OSTI2022

Toward Emittance Measurements at 11.7 GHz Short-Pulse High-Gradient RF Gun

A short pulse high gradient RF gun has been recently tested at Argonne Wakefield Accelerator (AWA) facility. The carried-out test showed that the 1,5-cell gun was able to inject 3 MeV, up to 100 pC bunches at room tem-perature being fed by 9 ns up to 300 MW 11.7 GHz puls-es. The cathode field was as high as about 400 MV/m. So high field is aimed to mitigate repealing Coulomb forces substantially. In accordance with simulations the emit-tance could be as low as less than 0.2 mcm. To obtain so low emittance in the experiment, the gun is assumed to be equipped with a downstream linac to be fed from the same power extractor as the gun itself. Here we report design of the RF power distribution system splitting RF power among the gun and the linac, results of low-power tests, and emittance measurement plans for upcoming new experiment at AWA.

43 PARTICLE ACCELERATORS↗

NASA NTRS2001

Dynamic Finite Element Predictions for Mars Sample Return Cellular Impact Test #4

The nonlinear finite element program MSC.Dytran was used to predict the impact pulse for (he drop test of an energy absorbing cellular structure. This pre-test simulation was performed to aid in the design of an energy absorbing concept for a highly reliable passive Earth Entry Vehicle (EEV) that will directly impact the Earth without a parachute. In addition, a goal of the simulation was to bound the acceleration pulse produced and delivered to the simulated space cargo container. EEV's are designed to return materials from asteroids, comets, or planets for laboratory analysis on Earth. The EEV concept uses an energy absorbing cellular structure designed to contain and limit the acceleration of space exploration samples during Earth impact. The spherical shaped cellular structure is composed of solid hexagonal and pentagonal foam-filled cells with hybrid graphite-epoxy/Kevlar cell walls. Space samples fit inside a smaller sphere at the enter of the EEV's cellular structure. The material models and failure criteria were varied to determine their effect on the resulting acceleration pulse. Pre-test analytical predictions using MSC.Dytran were compared with the test results obtained from impact test #4 using bungee accelerator located at the NASA Langley Research Center Impact Dynamics Research Facility. The material model used to represent the foam and the proper failure criteria for the cell walls were critical in predicting the impact loads of the cellular structure. It was determined that a FOAMI model for the foam and a 20% failure strain criteria for the cell walls gave an accurate prediction of the acceleration pulse for drop test #4.

Fasanella, Edwin L.↗

NASA NTRS1997

The GSFC Combined Approach of ODC Stockpiling and Tribological Testing to Mitigate the Risks of ODC Elimination

In response to the elimination of production of several Ozone Depleting Chemicals (ODC's) which have been widely used in successful space flight mechanism cleaning and lubricating procedures, GSFC developed and implemented an overall philosophy of mitigating the risks to flight hardware during the transition phase to ODC-free cleaning procedures. The short term leg of the philosophy was the stockpiling of an appropriate amount of ODC solvents such that all short term GSFC missions will be able to stay with or revert to heritage cleaning and lubricating procedures in the face of life issues. The long-term leg of that philosophy was the initiation of a several tier testing program that will deliver increasing amounts of information over the next few years, starting with accelerated lubricant life tests that compare lubricant life on surfaces cleaned with ODC solvents with lubricant life on surfaces cleaned with ODC-free solvents. While tribological testing, mechanism life testing and space-flight experience will ultimately bring us into the 21st century with environmentally friendly means of cleaning long-life precision mechanism components, many satellites will be launched over the next few years before a number of important tribological questions can be answered. In order to prepare for this challenge, the Materials Engineering Branch in cooperation with the Electromechanical Branch launched an intensive review of all ongoing missions. The failure risk was determined for each long-life lubricated mechanism based on a number of parameters, including 4 comparison of flight solvents used to clean the heritage/life test hardware. Also studied was the ability of the mechanism manufacturers to stockpile ODC's based on state laws and company policies. A stockpiling strategy was constructed based on this information and subsequently implemented. This paper provides an overview of the GSFC ODC elimination risk mitigation philosophy as well as a detailed examination of the development of the ODC stockpiling plan.

Predmore, Roamer↗

NASA NTRS1977

Motion sickness and otolith sensitivity - A pilot study of habituation to linear acceleration

Astronauts, particularly in Skylab flights, experienced varying degrees of motion sickness lasting 3-5 days. One possible mechanism for this motion sickness adaptation is believed to be a reduction in otolith sensitivity with an attendant reduction in sensory conflict. In an attempt to determine if this hypothesis is valid, a ground-based pilot study was conducted on a vertical linear accelerator. The extent of habituation to accelerations which initially produced motion sickness was evaluated, along with the possible value of habituation training to minimize the space motion sickness problem. Results showed that habituation occurred for 6 of the 8 subjects tested. However, in tests designed to measure dynamic and static otolith function, no significant differences between pre- and post-habituation tests were observed. Cross habituation effects to a standard Coriolis acceleration test were not significant. It is unlikely that ground-based pre-habituation to linear accelerations of the type examined would alter susceptibility to space motion sickness.

Potvin, A. R.↗

DOE OSTI2021

Vibration of a cryomodule’s coupler during road transportation: Multibody analysis and experimental validation

The road transportation of critical components for cryogenic cryomodules is a challenging task. Indeed, the shipping and the handling of fundamental sub-assemblies can expose these components to harmful dynamic loads that can jeopardize their structural integrity. This article has the purpose of developing a finite element multibody model capable of assessing the acceleration on a test coupler for a cavity of the Single Spoke Resonator 1 subjected to a typical road transportation trip. A multibody model consisting of rigid bodies and finite element–imported flexible bodies has been created allowing a comparison of the simulated and experimental acceleration. Afterwards, an experimental on-road test, whose set-up is described in this article, has been carried out at Fermilab with instrumented components. Being able to effectively simulate and validate the dynamic effects on such sub-assemblies makes it possible, for the future, to simulate more complex structures subject to dynamic loadings, such as the entire cryomodules during shipping. Furthermore, the results from the simulations can be used to guide the design of new suspension systems suitable for the reduction mitigation of structural vibration during the road transportation of cryomodules.

42 ENGINEERING↗

DOE OSTI2020

Full-Scale Assembly 30 cm Drop Test

Can Spent Nuclear Fuel withstand the shocks and vibrations experienced during normal conditions of transport? This question was the motivation for the multi-modal transportation test (MMTT) (Summer 2017), 1/3-scale cask 30 cm drop test (December 2018), and full-scale assembly 30 cm drop tests (June 2019). The full-scale ENSA ENUN 32P cask with 3 surrogate 17x17 PWR assemblies was used in the MMTT. The 1/3-scale cask was a mockup of this cask. The 30 cm drop tests provided the accelerations on the 1/3-scale dummy assemblies. These data were used to design full-scale assembly drop tests with the goal to quantify the strain fuel rods experience inside a cask when dropped from a height of 30 cm. The drop tests were first done with the dummy and then with the surrogate assembly. This paper presents the preliminary results of the tests.

Transportation↗

NASA NTRS1974

Evaluation report for toggle switches: Micro Switch and Cutler-Hammer models per MIL-S-3950

Several models of hermetically sealed toggle switches meeting the requirements of MIL-S-3950, were evaluated to determine the probability that they would withstand the environmental requirements of, and therefore be suitable for use on, the space shuttle vehicle. The evaluation was started with a comparison of the environmental requirements for space shuttle hardware. This was followed with in-house testing for those environments where a reasonably firm conclusion could not be drawn in the comparison. Space simulation, acceleration, and vibration testing were performed in-house.

Labberton, D.↗

NASA NTRS1980

Stress corrosion cracking evaluation of martensitic precipitation hardening stainless steels

The resistance of the martensitic precipitation hardening stainless steels PH13-8Mo, 15-5PH, and 17-4PH to stress corrosion cracking was investigated. Round tensile and c-ring type specimens taken from several heats of the three alloys were stressed up to 100 percent of their yield strengths and exposed to alternate immersion in salt water, to salt spray, and to a seacoast environment. The results indicate that 15-5PH is highly resistant to stress corrosion cracking in conditions H1000 and H1050 and is moderately resistant in condition H900. The stress corrosion cracking resistance of PH13-8Mo and 17-4PH stainless steels in conditions H1000 and H1050 was sensitive to mill heats and ranged from low to high among the several heats included in the tests. Based on a comparison with data from seacoast environmental tests, it is apparent that alternate immersion in 3.5 percent salt water is not a suitable medium for accelerated stress corrosion testing of these pH stainless steels.

Humphries, T. S.↗

NASA NTRS2018

Pre-Flight Training of Autonomic Responses for Mitigating the Effects of Spatial Disorientation During Spaceflight

The National Aeronautics and Space Administration (NASA) has identified a potential risk of spatial disorientation, motion sickness, and degraded performance to astronauts during re-entry and landing of the proposed Orion crew vehicle. The purpose of this study was to determine if a physiological training procedure, Autogenic-Feedback Training Exercise (AFTE), can mitigate these adverse effects. Fourteen men and six women were assigned to two groups (AFTE, no-treatment Control) matched for motion sickness susceptibility and gender. All subjects received a standard rotating chair test to determine motion sickness susceptibility; three training sessions on a manual performance task; and four exposures in the rotating chair (Orion tests) simulating angular accelerations of the crew vehicle during re-entry. AFTE subjects received 2 hours of training before Orion tests 2, 3, and 4. Motion sickness symptoms, task performance, and physiological measures were recorded on all subjects. Results showed that the AFTE group had significantly lower symptom scores when compared to Controls on test 2 (p=.05), test 3 (p=.03), and test 4 (p=.02). Although there were no significant group differences on task performance, trends showed that AFTE subjects were less impaired than Controls. Heart rate change scores (20 revolutions per minute minus baseline) of AFTE subjects indicated significantly less reactivity on Test 4 compared to Test 1 (10.09 versus 16.59, p=.02), while Controls did not change significantly across tests. Results of this study indicate that AFTE may be an effective countermeasure for mitigating spatial dis-orientation and motion sickness in astronauts.

Orion↗

DOE OSTI2021

Dip leg plug formation evaluation and abatement testing in support of the H-Canyon accelerated basin de-inventory

As requested in the Technical Task Request (TTR), the Savannah River National Laboratory (SRNL) performed testing on the current typical bubbler dip leg design used in the H-Area Canyon (HCA). The TTR has a functional classification of General Services. Testing was initiated to ascertain if the plugging described in the TTR could be reproduced and, if so, to obtain general metrics on the resulting plugging dynamics, and evaluate possible mitigating methods, including design changes and cleaning/purging protocols. The bubblers were to be suspended in a simulant typical of H-Canyon solutions containing aluminum nitrate and silica at a temperature of 25°C using a nominal bubbler air flowrate of 7.5 SCFH. Emphasis was placed on minimizing equipment changes necessary to accomplish the mitigations, as equipment changes in the existing facility would be costly. Testing evolved into four (4) phases, concluding that plugging could indeed be reproduced (believed to be attributed to localized evaporation and bridging of crystals in the dip legs). During testing, plug formation information was obtained, including time, pressure, and temperature traces leading to plugging were defined; solution compositions leading to plugging were determined, and various physical characteristics (visual and mechanical) of the crystallized plug were obtained.

42 ENGINEERING↗

NASA NTRS1999

Correlation of Fin Buffet Pressures on an F/A-18 with Scaled Wind-Tunnel Measurements

Buffeting is an aeroelastic phenomenon occurring at high angles of attack that plagues high performance aircraft, especially those with twin vertical tails. Previous wind-tunnel and flight tests were conducted to characterize the buffet loads on the vertical tails by measuring surface pressures, bending moments, and accelerations. Following these tests, buffeting responses were computed using the measured buffet pressures and compared to the measured buffeting responses. The calculated results did not match the measured data because the assumed spatial correlation of the buffet pressures was not correct. A better understanding of the partial (spatial) correlation of the differential buffet pressures on the tail was necessary to improve the buffeting predictions. Several wind-tunnel investigations were conducted for this purpose. When compared, the results of these tests show that the partial correlation scales with flight conditions. One of the remaining questions is whether the wind-tunnel data is consistent with flight data. Presented herein, cross-spectra and coherence functions calculated from pressures that were measured on the High Alpha Research Vehicle indicate that the partial correlation of the buffet pressures in flight agrees with the partial correlation observed in the wind tunnel.

Moses, Robert W.↗

NASA NTRS1998

Spatial Characteristics of F/A-18 Vertical Tail Buffet Pressures Measured in Flight

Buffeting is an aeroelastic phenomenon which plagues high performance aircraft, especially those with twin vertical tails, at high angles of attack. Previous wind-tunnel and flight tests were conducted to characterize the buffet loads on the vertical tails by measuring surface pressures, bending moments, and accelerations. Following these tests, buffeting estimates were computed using the measured buffet pressures and compared to the measured responses. The estimates did not match the measured data because the assumed spatial correlation of the buffet pressures was not correct. A better understanding of the partial (spatial) correlation of the differential buffet pressures on the tail was necessary to improve the buffeting estimates. Several wind-tunnel investigations were conducted for this purpose. When combined and compared, the results of these tests show that the partial correlation depends on and scales with flight conditions. One of the remaining questions is whether the windtunnel data is consistent with flight data. Presented herein, cross-spectra and coherence functions calculated from pressures that were measured on the high alpha research vehicle (HARV) indicate that the partial correlation of the buffet pressures in flight agrees with the partial correlation observed in the wind tunnel.

Moses, Robert W.↗

DOE OSTI2020

Monolithic ATF MiniFuel Sample Capsules Ready for HFIR Insertion

Several advanced nuclear fuel concepts are being considered throughout the nuclear industry. Implementation of these concepts could increase accident tolerance or enhance performance beyond the capabilities of the UO₂-based nuclear fuel currently in use. Qualification and deployment of any new fuel requires rigorous irradiation testing to demonstrate performance under representative normal and off-normal operating conditions. The traditional approach for qualifying new fuels requires exhaustive execution of many integral fuel tests. However, due to the long timeframe for executing these integral tests and the limited number of available materials test reactors, this approach is becoming impractical. To accelerate fuel qualification, Oak Ridge National Laboratory developed the MiniFuel irradiation vehicle for use in conducting accelerated separate effects irradiation testing of a wide range of nuclear fuel materials in the High Flux Isotope Reactor (HFIR). The first MiniFuel irradiations performed in the facility tested sol gel–derived uranium nitride kernels and tristructural isotropic (TRISO)-coated particle fuels. This report describes the preparation and assembly of the first set of monolithic MiniFuel irradiations conducted to support accident-tolerant fuel (ATF) development and accelerated fuel qualification. Two irradiation targets containing a variety of UO₂ and U₃Si₂ disk fuel specimens were fabricated and assembled for irradiation to burnups of 8-10 and 28-40 MWd/kg U. The target irradiation temperature is 450-550°C. Irradiation of U₃Si₂ will provide new data regarding the irradiation performance of a candidate ATF to complement current ATF-1 integral experiments being performed in the Advanced Test Reactor. UO₂ samples were included as a reference so that the results from the MiniFuel experiments can be compared with the extensive UO₂ fuel performance database. The monolithic MiniFuel capsules were successfully assembled, welded, and tested per HFIR requirements and are ready for insertion into the reactor. Pictures of the assembly process are included in this report. The experiment is planned for insertion into the HFIR during cycle 487 in April 2020.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2022

Beamline for E-beam processing at UITF

Electron beam irradiation is a method that has shown a good potential to reduce several pollutants in wastewater. One of the main challenges towards wider adoption of this method is the need for compact, reliable, cost-effective, high-power accelerators. Jefferson Lab is working on the design and prototyping of accelerator components, based on superconducting radio-frequency (SRF) technology, aiming at accelerators for industrial applications. The LDRD project aimed at designing, procuring, installing, and commissioning a beamline at the Upgraded Injector Test Facility (UITF) accelerator to allow electron-beam irradiation studies of different materials, beginning with wastewater. The availability of such beamline allows exploring the ability of electron-beam radiation to reduce or eliminate so-called “forever chemicals” that can be found in wastewater or industrial sites. After successful commissioning, the beamline was used to irradiate wastewater samples with different concentrations of 1,4-dioxane, in collaboration with Hampton Roads Sanitation District (HRSD).

42 ENGINEERING↗

NASA NTRS2001

Measurement of Charged Particle Interactions in Spacecraft and Planetary Habitat Shielding Materials

The Microgravity Materials Program, through its 98-HEDS-04 Research Announcement, has called for research to support 'enhanced human radiation protection through the development of light weight soft goods with high radiation protection characteristics.' Given the nature of the particle flux from the Galactic Cosmic Radiation (GCR), and the many constraints on the depth and type of shielding in spacecraft and planetary habitats, it is clear that the health risks these particles present to astronauts in deep space cannot be entirely eliminated. It is the objective of this project to develop a highly accurate model of GCR transport so that NASA can develop and validate the properties of protective shielding materials with the best available information. The validity of the GCR transport model depends in large part on having accurate and precise input data in the form of the charge-changing and fragment production cross sections for the heavy ions of greatest biological significance. The accuracy of the transport model can be evaluated and enhanced by employing the following a three-step strategy: (1) New cross section data will be made available to the NASA-Langley scientists responsible for the transport codes, and will be used as inputs to the codes; (2) The codes will be used to predict additional cross sections and/or details of the radiation field behind realistic shielding arrangements, where the materials and configurations may be quite complex. Mock-ups of the shielding configurations suitable for use in accelerator experiments will obtained by the NASA-Langley co-investigators; and (3) The transport model predictions will be tested in accelerator-based experiments. The time scale for one pass through these steps is well-suited to a four-year schedule. Over a longer term, these steps may be repeated, leading to still further refinements of the transport code, new predictions, and an additional round of measurements, until the desired predictive accuracy is achieved. The focus of this work is primarily on the first of these steps, the determination of fragmentation cross sections, which will be the main task in years one and two. The detailed strategy for carrying out the remainder of the program is more difficult to specify, as it depends on unpredictable factors such as the extent to which the transport model must be modified, schedules for accelerator time, target fabrication, etc.

Zeitlin, C.↗

DOE OSTI2017

TM 4: Beam through the Main Linac Cryomodule

On May 15th 2017, the CBETA project reached the major funding milestone, “Beam through the MLC.” For this test, the team had to successfully accelerate the electron beam to 6 MeV in the Injector Cryomodule (ICM), and then to a final energy of 12 MeV in the Main Linac Cryomodule (MLC). The MLC contains six superconducting accelerating cavities; for this initial test only a single cavity was powered.

43 PARTICLE ACCELERATORS↗

NASA NTRS1972

Performance of a neutralizer for electron bombardment thruster.

Results of the SERT II flight indicate that the hollow cathode neutralizer not only represents a power and propellant weight penalty but can be a contributing cause to accelerator grid erosion. Tests with a 30-cm diameter thruster have shown that a neutralizer position of approximately 9 cm axially downstream of the accelerator grid and approximately 9 cm radially away from the outer edge of the accelerator grid and pointing parallel to the thruster axis provides the best overall performance. The estimated grid wear rate was less than 0.08 mm in 10,000 hr. The coupling voltage (neutralizer to beam voltage) was approximately 17 volts at a neutralizer flow rate of 22 equivalent milliamperes of mercury and a beam current of 1.5 amperes. Neutralizer power (excluding heaters) was 31 watts and the effect of neutralizer flow on overall propellant utilization efficiency is a 1.2 percentage point reduction at a thruster utilization efficiency of 90 percent.

Bechtel, R. T.↗

NASA NTRS1973

Studies of dished accelerator grids for 30-cm ion thrusters

Geometrically different sets of dished accelerator grids were tested on five 30-cm thrusters. The geometric variation of the grids included the grid-to-grid spacing, the screen and accelerator hole diameters and thicknesses, the screen and accelerator open area fractions, ratio of dish depth to the dish diameter, compensation, and aperture shape. In general, the data taken over a range of beam currents for each grid set included the minimum total accelerating voltage required to extract a given beam current and the minimum accelerator grid voltage required to prevent electron backstreaming.

Rawlin, V. K.↗