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DOE OSTI2023

FY23 Status Report on MOOSE-Based Approaches to Modeling Core Bowing in Fast Reactors

Under the U.S. Department of Energy Office of Nuclear Energy’s Advanced Modeling and Simulation (NEAMS) Program, an integrated multiphysics approach is being developed to model the core bowing phenomena important to liquid metal-cooled fast reactors. Core bowing is an important passive safety mechanism whereby increased power (which leads to temperature and flux gradients) influences the core to bow into less reactive configurations when the restraint system is properly designed. The phenomenon includes a complex interplay of radiation transport, duct temperature calculations involving fluid flow and heat transfer, and thermo-mechanical responses to the induced temperature and flux gradients. Structural material properties are also important to determining inelastic response to longer term flux gradients which cause irradiation creep and swelling. While core bowing provides a strong negative reactivity feedback when the restraint system is designed properly, it also results in additional forces between assemblies which increase the loads required to extricate them during refueling or control rod movement. Therefore, the restraint system must be designed with these tradeoffs in mind. The first stage of the work, which commenced in FY21 and continues through FY23, assesses thermo-mechanical modeling tools for producing core bowing predictions consistent with conventional tools. The Multiphysics Object Oriented Simulation Environment (MOOSE) Tensor Mechanics and Contact Modules are employed. This status report describes work on additional thermo-mechanical benchmark verification problems with increased complexity from the examples demonstrated in FY21 and FY22. Several benchmark verification examples were selected from the IAEA verification and validation report with increased number of ducts and more complex contact interaction behavior. These examples involve a full symmetric sector with restraint rings at multiple load pad locations to simulate a limited free-bow restraint system concept, as well as irradiation induced swelling and creep effects in a sector. In addition, improvements to the contact module sideset assignment were assessed and compared with previous MOOSE results to verify the contact behavior. The MOOSE-based results were compared to IAEA benchmark participants’ results. In every case, the MOOSE results agreed with other simulations results for estimating bowing behavior, providing additional verification basis of the tools for this particular physics application. Estimation of contact forces were mostly in agreement, with a few outlier results. A plan was suggested for dealing with the discrepancies with estimating contact force values. In addition, a 1-way coupling demonstration was performed using subchannel analysis code Pronghorn-SC and MOOSE on an ABR-1000-design sodium-cooled fast reactor assembly to evaluate coolant and duct wall temperatures.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2024

Multiphysics Demonstration of Temperature-Driven Assembly Bowing in SFRs using MOOSE-Based Codes

Core bowing is an important passive safety mechanism in liquid metal cooled fast reactors. When the core restraint system is properly designed, temperature and flux gradients influence assemblies in the core to bow into less reactive configurations during accident scenarios, resulting in negative reactivity feedback. Prediction of core bowing involves complex interplay of radiation transport, impacts of fluid flow and heat transfer on duct temperature, and mechanical responses to the induced temperature and flux gradients. Under the U.S. Department of Energy Office of Nuclear Energy’s Advanced Modeling and Simulation (NEAMS) Program [1], an integrated multiphysics approach is being developed to model the core bowing phenomena in liquid metal-cooled fast reactors with the Multiphysics Object Oriented Simulation Environment (MOOSE) [2]. In this methodology, the MOOSE-based reactor physics code Griffin [3] will solve the neutron transport equation and determine the power distribution. With the detailed power distribution from Griffin, the subchannel analysis codes MOOSE-Subchannel [4] and Pronghorn [5] are utilized to calculate the assembly temperature distribution. MOOSE’s Solid Mechanics [6] and Contact [7] Modules are leveraged to calculate the thermal expansion and duct bowing displacement with the duct wall temperature from thermal hydraulics calculation. In this work, an initial one-way coupling demonstration of the integrated multiphysics approach has been performed on a seven-assembly problem based on the sodium-cooled fast reactor ABR-1000 design [8]. The neutronics calculation with Griffin is not yet involved in the current simulation. MOOSE-Subchannel and Pronghorn evaluate fluid and solid temperature based on a fixed power distribution. In addition, one-way coupling is utilized in this coupled calculation, via Pronghorn passing the duct temperature data to the MOOSE Solid Mechanics calculation. An assessment of the Solid Mechanics module was performed in parallel to verify duct bowing behavior with duct-to-duct contact phenomenon [9]. The displacement from MOOSE Solid Mechanics is not yet transferred back and utilized in the Pronghorn and MOOSE-Subchannel calculation. This model will be available on the National Reactor Innovation Center (NRIC) Virtual Test Bed (VTB) repository [10]. Future stages of this work will involve solving problems of increasing complexity as well as adding more physics (e.g. reactor physics) to the integrated workflow to reach the end goal of modeling the core bowing phenomenon with an integrated multiphysics workflow.

22 - GENERAL STUDIES OF NUCLEAR REACTORS↗

NASA NTRS2023

Modeling and Simulation for Exercise Vibration Isolation and Stabilization System Design

The microgravity environment that crew members experience on orbit presents a well-known health challenge, particularly when it comes to loss of muscle and bone mass. To counteract these negative effects, exercise countermeasures play a critical role in the daily routine of the crew on the International Space Station (ISS). To help inform requirements for upcoming exploration missions such as the Gateway Program, a new device, called the European Enhanced Exploration Exercise Device (E4D), is being built by the European Space Agency through their contractor, the Danish Aerospace Company. The E4D is being demonstrated on the ISS and is unique from other current exercise devices in that it provides four separate modalities in a single device: resistive, cycle ergometry, seated aerobic rowing, and rope pulling. To support the integration of E4D on ISS, a passive Vibration Isolation and Stabilization (VIS) system was required by NASA, and this responsibility was given to the Johnson Space Center. This paper describes the end-to-end process of modeling, simulation, and analysis used to inform the mechanical design of the VIS system. The process begins with the collection of representative exerciser motion capture (MoCap) through ground-based testing with the developmental E4D in both the Prototype Immersive Technology (PIT) Laboratory and the Active Response Gravity Offload System (ARGOS) facility at the Johnson Space Center. These collected MoCap data are processed through human biomechanics modeling to create forcing functions as input to a multibody dynamics simulation of the combined E4D/VIS system, with numerous resulting outputs. These outputs include microgravity accelerations, overall system displacements, internal and transmitted loads, as well as collisions. Microgravity accelerations are compared for compliance against ISS requirements while displacements are used for sway space determinations on the design and volumetric constraints within the targeted module. Internal loads are supplied to the supporting stress analysis teams and external loads for structural loads and dynamics teams, both at NASA and ESA. Finally, contact and clearance analysis is performed using the simulation to eliminate potential design issues. To ensure that the elements of the multibody simulation were verified and validated, correlation against multiple VIS related ground hardware testbeds was performed and characterized. In addition to the isolation part of the VIS problem, stabilization is also key to the integrated performance and evaluation. Due to the difficulty in defining ISS requirements in this area, the stability of the exerciser was inspected via analysis. Loss of balance was defined analytically as occurring when the resultant force vector acting on the exerciser lies outside the base of support of the feet. Both the VIS and E4D teams have recently gone through their Critical Design Reviews (CDRs) and the iterative model-based approach has been integral to inform mechanical design, particularly in the case of the VIS. This same end-to-end approach is now being applied for the Gateway Program, where an Exploration Exercise Device (EED) derived from the E4D and notional VIS for the device are under concept development.

Countermeasures↗

DOE OSTI2022

Structure and Fc-Effector Function of Rhesusized Variants of Human Anti-HIV-1 IgG1s

Passive transfer of monoclonal antibodies (mAbs) of human origin into Non-Human Primates (NHPs), especially those which function predominantly by a Fc-effector mechanism, requires an a priori preparation step, in which the human mAb is reengineered to an equivalent NHP IgG subclass. This can be achieved by changing both the Fc and Fab sequence while simultaneously maintaining the epitope specificity of the parent antibody. This Ab reengineering process, referred to as rhesusization, can be challenging because the simple grafting of the complementarity determining regions (CDRs) into an NHP IgG subclass may impact the functionality of the mAb. Here we describe the successful rhesusization of a set of human mAbs targeting HIV-1 envelope (Env) epitopes involved in potent Fc-effector function against the virus. This set includes a mAb targeting a linear gp120 V1V2 epitope isolated from a RV144 vaccinee, a gp120 conformational epitope within the Cluster A region isolated from a RV305 vaccinated individual, and a linear gp41 epitope within the immunodominant Cys-loop region commonly targeted by most HIV-1 infected individuals. Structural analyses confirm that the rhesusized variants bind their respective Env antigens with almost identical specificity preserving epitope footprints and most antigen-Fab atomic contacts with constant regions folded as in control RM IgG1s. In addition, functional analyses confirm preservation of the Fc effector function of the rhesusized mAbs including the ability to mediate Antibody Dependent Cell-mediated Cytotoxicity (ADCC) and antibody dependent cellular phagocytosis by monocytes (ADCP) and neutrophils (ADNP) with potencies comparable to native macaque antibodies of similar specificity. While the antibodies chosen here are relevant for the examination of the correlates of protection in HIV-1 vaccine trials, the methods used are generally applicable to antibodies for other purposes.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2025

Design of an Out-Of-Pile Experimental Facility to Demonstrate the Feasibility of In Situ Thermal Conductivity Measurements of Nuclear Fuels Under Irradiation

There is substantial merit in quantifying nuclear fuel performance under irradiation. At Oak Ridge National Laboratory (ORNL), the MiniFuel irradiation platform has become the primary test vehicle for conducting separate-effects fuel performance irradiation experiments. The MiniFuel experiment is a passively controlled capsule design deployed in the High Flux Isotope Reactor (HFIR) through which fuel performance data is collected post-irradiation. Separate effects fuels irradiation capabilities are being expanded at ORNL by developing instrumented capsule designs that aim to capture fuel performance phenomena in-situ. One such capsule will specifically target fuel specimen thermal conductivity changes as a function of fuel burnup. Due to the complexity of making this measurement on nuclear fuel in-pile, this paper describes the necessary out-of-pile testing conducted on the thermal conductivity capsule (TCC) design. The measurement is ascertained via a thermopile system with heat transferred unidirectionally through a surrogate fuel specimen sandwiched between two conductive materials. The capsules investigated in this study are representative of the in-pile design, with the primary departure from irradiation conditions being the distribution of heat generation within the capsule. In the out-of-pile experiment, an external heater was used to drive heat through the conductive slug materials and into the specimen. This paper expounds the design of the out-of-pile experimental system and the thermal conductivity measurement technique. Predictive models used to determine the sensitivity of the measurement to variables governing thermal contact conductance between the specimen and slug materials and to predict experimental results are also described. Data from the out-of-pile experiment will be used to validate the readiness of the design for insertion into HFIR for irradiation.

Parker, Trevor [ORNL]↗

NASA NTRS2001

Coriolis-force-induced trajectory and endpoint deviations in the reaching movements of labyrinthine-defective subjects

When reaching movements are made during passive constant velocity body rotation, inertial Coriolis accelerations are generated that displace both movement paths and endpoints in their direction. These findings directly contradict equilibrium point theories of movement control. However, it has been argued that these movement errors relate to subjects sensing their body rotation through continuing vestibular activity and making corrective movements. In the present study, we evaluated the reaching movements of five labyrinthine-defective subjects (lacking both semicircular canal and otolith function) who cannot sense passive body rotation in the dark and five age-matched, normal control subjects. Each pointed 40 times in complete darkness to the location of a just extinguished visual target before, during, and after constant velocity rotation at 10 rpm in the center of a fully enclosed slow rotation room. All subjects, including the normal controls, always felt completely stationary when making their movements. During rotation, both groups initially showed large deviations of their movement paths and endpoints in the direction of the transient Coriolis forces generated by their movements. With additional per-rotation movements, both groups showed complete adaptation of movement curvature (restoration of straight-line reaches) during rotation. The labyrinthine-defective subjects, however, failed to regain fully accurate movement endpoints after 40 reaches, unlike the control subjects who did so within 11 reaches. Postrotation, both groups' movements initially had mirror image curvatures to their initial per-rotation reaches; the endpoint aftereffects were significantly different from prerotation baseline for the control subjects but not for the labyrinthine-defective subjects reflecting the smaller amount of endpoint adaptation they achieved during rotation. The labyrinthine-defective subjects' movements had significantly lower peak velocity, higher peak elevation, lower terminal velocity, and a more vertical touchdown than those of the control subjects. Thus the way their reaches terminated denied them the somatosensory contact cues necessary for full endpoint adaptation. These findings fully contradict equilibrium point theories of movement control. They emphasize the importance of contact cues in adaptive movement control and indicate that movement errors generated by Coriolis perturbations of limb movements reveal characteristics of motor planning and adaptation in both healthy and clinical populations.

NASA Discipline Neuroscience↗

DOE OSTI2022

Bifacial CdTe Solar Cells with Copper Chromium Oxide Back-Buffer Layer

Bifacial solar cells have the potential to maintain energy output higher than monofacial devices under unfavorable weather conditions. A transparent back-buffer layer which can passivate the interface and improve the minority carrier lifetime is critical in CdTe-based bifacial devices. Herein, solution-processed Cu x Cr y O z as a promising back-buffer for CdTe/CdS solar cells is demonstrated. The carrier lifetimes measured at the front and back of the device are 31.2 and 3.1 ns, respectively, which correspond to an increase of ≈38% and 138%, respectively, compared to the reference device. This dramatic improvement in lifetime results in a 100% increase in short-circuit current measured with backside illumination. The best bifacial device has efficiencies 7.6% and 12.5%, respectively, from back and front illumination, yielding a bifaciality factor of 0.60.

14 SOLAR ENERGY↗

NASA NTRS2019

The Unrealized Potential of Superhydrophobic Substrates in Advanced Life Support Systems

Nearly all water processing equipment aboard spacecraft is to a large extent controlled by capillary forces arising from substrate wetting conditions. Superhydrophobic wetting conditions provide an essentially passive means to keep water away from certain substrates providing a level of no-moving-parts phase separation and control. This work presents a host of non-wetting aqueous microgravity capillary fluidics phenomena arising from interactions with easily fabricated superhydrophobic substrates. The value of such phenomena for potential life support applications aboard spacecraft is clear, especially for substrate properties that are thermally robust, corrosion resistant, and self-cleaning for both long- and short term applications. Large length scale low-g demonstrations of the phenomena are provided in HD video format for the extensive drop tower tests conducted. The broader crosscutting impacts to numerous fluids processing operations for life support are discussed. Current practical applications addressed in light of superhydrophobicity include urine-processing, water recovery, fire safety, and others.

Superhydrophoic↗

NASA NTRS1996

Functional and Multifunctional Polymers: Materials for Smart Structures

The ultimate goal of the research in smart structures and smart materials is the development of a new generation of products/devices which will perform better than products/devices built from passive materials. There are a few examples of multilayer polymer systems which function as smart structures, e.g. a synthetic muscle which is a multilayer assembly of a poly(ethylene) layer, a gold layer, and a poly(pyrrole) layer immersed in a liquid electrolyte. Oxidation and reductions of the active pyrrole layer causes the assembly to reversibly deflect and mimic biological muscles. The drawback of such a setup is slow response times and the use of a liquid electrolyte. We have developed multifunctional polymers which will eliminate the use of a liquid electrolyte, and also because the functionalities of the polymers are within a few hundred angstroms, an improved response time to changes in the external field should be possible. Such multifunctional polymers may be classified as the futuristic 'smart materials.' These materials are composed of a number of different functionalities which work in a synergistic fashion to function as a device. The device performs on the application of an external field and such multifunctional polymers may be scientifically labeled as 'field responsive polymers.' Our group has undertaken a systematic approach to develop functional and multifunctional polymers capable of functioning as field responsive polymers. Our approach utilizes multicomponent polymer systems (block copolymers and graft copolymers), the strategy involves the preparation of block or graft copolymers where the functionalities are limited to different phases in a microphase separated system. Depending on the weight (or volume) fractions of each of the components, different microstructures are possible. And, because of the intimate contact between the functional components, an increase in the synergism between the functionalities may be observed. In this presentation, three examples of multifunctional polymers developed in our labs will be reported. The first class of multifunctional polymers are the microphase separated mixed (ionic and electronic) conducting or MIEC block copolymers. The second class being developed in our labs are the biocompatible conductive materials and the conductive fluids. The final class may be considered microwave active smart polymers.

Arnold, S.↗

DOE OSTI2021

Investigations of the stability of etched or platinized p-InP(100) photocathodes for solar-driven hydrogen evolution in acidic or alkaline aqueous electrolytes

Here, the stability of p-InP photocathodes performing the hydrogen-evolution reaction (HER) has been evaluated in contact with either 1.0 M H 2 SO 4 (aq) or 1.0 M KOH(aq), with a focus on identifying corrosion mechanisms. Stability for the solar-driven HER was evaluated using p-InP electrodes that were either etched or coated with an electrodeposited Pt catalyst (p-InP/Pt). Variables such as trace O 2 were systematically controlled during the measurements. Changes in surface characteristics after exposure to electrochemical conditions as well as electrode dissolution processes were monitored using X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma mass spectrometry (ICP-MS). In either H 2 SO 4 or KOH, etched p-InP photoelectrodes corroded cathodically under illumination, forming metallic In 0 at the electrode surface. In contrast, electrodeposition of Pt kinetically stabilized illuminated p-InP photocathodes in both H 2 SO 4 and KOH by inhibiting the cathodic corrosion pathway. Notably, when held at 0 V vs. the reversible hydrogen electrode (RHE) in 1.0 M H 2 SO 4 (aq), p-InP/Pt exhibited a stable current density (J) of ~–18 mA cm –2 for >285 h under simulated 1 Sun illumination. The long-term current density vs. potential (J–E) behavior at pH 0 and pH 14 of p-InP/Pt photocathodes correlated with changes in the surface chemistry as well as the dissolution of p-InP. In acidic media, the J–E behavior of p-InP/Pt photocathodes remained nearly constant with time, but the surface of a p-InP/Pt electrodes gradually turned P-rich via a slow and continuous leaching of In ions. In alkaline electrolyte, the surface of p-InP/Pt electrodes was passivated by formation of an InO x layer that exhibited negligible dissolution but led to a substantial degradation in the J–E characteristics. Consequently, changes in the catalytic kinetics and surface stoichiometry are both important considerations for determining the corrosion chemistry and the long-term operational stability of InP photoelectrodes.

14 SOLAR ENERGY↗

NASA NTRS2020

Lunar Dust Simulant Particle Adhesion on Copolyimide Alkyl Ethers

Mitigation of lunar dust contamination is one of the greatest challenges to be overcome to realize a sustained lunar presence. Likely solutions will integrate active mitigation strategies, requiring the input of external energy, and passive materials, exhibiting an intrinsic resistance to lunar dust adhesion. In this work, a series of copolyimide alkyl ethers containing per fluorinated side-chains were generated to evaluate the influence surface modification agents have on surface chemical, topographical, and mechanical properties. An expanded testing protocol to characterize the adhesion interaction between lunar dust simulant and the copolyimide substrate was carried out. The interfacial adhesion strength was in-situ measured by a custom-built particulate adhesion instrument, utilizing a sonic wand. Surface mechanical properties were characterized by nanoindentation, utilizing the continuous stiffness measurement approach. A nominal presence of surface modifying agents, 1 wt%, resulted in a six-fold reduction in adhesion strength of the interface. A strong inverse correlation between the adhesion strength and Young’s modulus of the substrate was identified. The reduction was attributed to a synergistic interaction between the surface energy, surface roughness, and modulus of the copolyimide alkyl ethers film.

Lunar Dust, Particulate Adhesion, Surface Migratio↗

NASA NTRS2011

Helium-Cooled Black Shroud for Subscale Cryogenic Testing

This shroud provides a deep-space simulating environment for testing scaled-down models of passively cooling systems for spaceflight optics and instruments. It is used inside a liquid-nitrogen- cooled vacuum chamber, and it is cooled by liquid helium to 5 K. It has an inside geometry of approximately 1.6 m diameter by 0.45 m tall. The inside surfaces of its top and sidewalls have a thermal absorptivity greater than 0.96. The bottom wall has a large central opening that is easily customized to allow a specific test item to extend through it. This enables testing of scale models of realistic passive cooling configurations that feature a very large temperature drop between the deepspace-facing cooled side and the Sun/Earth-facing warm side. This shroud has an innovative thermal closeout of the bottom wall, so that a test sample can have a hot (room temperature) side outside of the shroud, and a cold side inside the shroud. The combination of this closeout and the very black walls keeps radiated heat from the sample s warm end from entering the shroud, reflecting off the walls and heating the sample s cold end. The shroud includes 12 vertical rectangular sheet-copper side panels that are oriented in a circular pattern. Using tabs bent off from their edges, these side panels are bolted to each other and to a steel support ring on which they rest. The removable shroud top is a large copper sheet that rests on, and is bolted to, the support ring when the shroud is closed. The support ring stands on four fiberglass tube legs, which isolate it thermally from the vacuum chamber bottom. The insides of the cooper top and side panels are completely covered with 25- mm-thick aluminum honeycomb panels. This honeycomb is painted black before it is epoxied to the copper surfaces. A spiral-shaped copper tube, clamped at many different locations to the outside of the top copper plate, serves as part of the liquid helium cooling loop. Another copper tube, plumbed in a series to the top plate s tube, is clamped to the sidewall tabs where they are bolted to the support ring. Flowing liquid helium through these tubes cools the entire shroud to 5 K. The entire shroud is wrapped loosely in a layer of double-aluminized Kapton. The support ring s inner diameter is the largest possible hole through which the test item can extend into the shroud. Twelve custom-sized trapezoidal copper sheets extend inward from the support ring to within a few millimeters of the test item. Attached to the inner edge of each of these sheets is a custom-shaped strip of Kapton, which is aluminum- coated on the warm-facing (outer) side, and has thin Dacron netting attached to its cold-facing side. This Kapton rests against the test item, but the Dacron keeps it from making significant thermal contact. The result is a non-contact, radiatively reflective thermal closeout with essentially no gap through which radiation can pass. In this way, the part of the test item outside the shroud can be heated to relatively high temperatures without any radiative heat leaking to the inside.

Tuttle, James↗

DOE OSTI2023

Ice Cryo-Encapsulation Balloon (Project ICEBall) Field Campaign Report

The Ice Cryo-Encapsulation Balloon (ICEBall) field campaign was designed to sample the ice crystals that compose high-altitude cirrus with a passive device. The campaign made use of a new instrument, ICEBall, which is a balloon-borne ice crystal sampling system. The ice crystal sounding system is capable of measuring ice crystal concentration, temperature, atmospheric pressure, ice crystal habit, aerosol particle morphology, and residual composition. The 3-kg instrument is carried upwards at 5 m s-1 by a high-altitude balloon. The instrument can be cut down from the balloon at any altitude up to 20 km, and the apparatus returns to the surface by parachute. Basic measurements such as temperature and pressure are recorded onboard, and high-frequency Global Positioning System (GPS) records altitude and latitude/longitude. Ice crystal concentrations are measured through the use of a high-resolution video camera mounted on the device. Ice crystals are collected through an open aperture leading to insulated collection chambers cooled with dry ice. Upon exiting the top of the cloud system, the chamber aperture is closed, and the ~1 mm3 sample cell is magnetically sealed and isolated at -78 °C, ensuring that ice particles do not sublimate or grow after collection. Once the crystals are returned to the surface, they are double-sealed and immersed at liquid nitrogen temperature in “dry-cryo shippers” before being transported back to the laboratory. Dr. Magee’s laboratory at The College of New Jersey contains a cryo-stage scanning electron microscope (SEM), which was used to interrogate the crystals and aerosol particles. The main purpose of this pilot field campaign was to provide an unprecedented level of detail on the crystal habits and ice surface complexity in mid-latitude cirrus, which may help resolve issues associated with habit identification and classification in cirrus. The ICEBall campaign was originally scheduled to run from March 28 to April 18 of 2021 at the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) Southern Great Plains observatory. The COVID-19 pandemic intervened and caused us to shift the dates of the experiment to October 16-November 6 of 2021. This period is also climatologically favorable for cirrus. The approximately six-month gap between our original field campaign dates and the actual dates afforded us the opportunity to build two new ICEBall payload instruments. These instruments were tested during an August 2021 trip to The College of New Jersey. During this field testing phase, we decided to launch the ICEBall payload upstream from the ARM SGP site with the goal of landing in the vicinity of the site. Our goal was to sample the ice crystals before the cirrus were advected over the remote-sensing instruments at the SGP site. The team assembled for the field campaign consisted of the Principle Investigator (PI) and Co-Principle Investigator (Co-PI) (Drs. Harrington and Magee), The Pennsylvania State University research scientist Dr. Alfred Moyle, and two graduate students (Ms. Marley Majetic and Gwenore Pokrifka). The team operated out of a house rented in Enid, Oklahoma. We successfully sampled seven cirrus cloud systems during the three-week field campaign (October 21, 23-26, 31, and November 1). This was a much higher success rate than either of the PIs anticipated (our goal was closer to sampling three or four cases). The balloon was typically launched from oil pads or farm fields northwest of Enid and the payload was typically retrieved somewhat north of the SGP site. We never landed directly at the SGP site, and so did not need regular access to the SGP facilities. Our greatest concern going into the field campaign was the longer-term storage of crystals in the -196°C cryo dry-shipper dewars and the subsequent transport across the country. We had tested storage and transport prior to the field campaign, but we had never stored crystals for a few weeks nor had we transported the dewars over long distances. To our great relief, the storage and transport worked flawlessly and we were able to image a large number of crystals from six of the seven cases. Working with the staff at the ARM SGP office was excellent. They not only helped us find the sources we needed for helium, liquid nitrogen, and other materials, but also helped with contacts within the Federal Aviation Administration (FAA) and Vance Air Force Base. One goal of our field project was to tie the in situ measurements of ice crystal habits to the radar signatures derived from the Ka-band ARM Zenith-pointing Radar (KAZR). Unfortunately KAZR was down for the duration of our experiment. However, the Ka-band Scanning ARM Cloud Radar (KASACR) was put into vertically pointing mode during the ICEBall campaign and those data, along with Doppler lidar measurements, have proved very useful.

54 ENVIRONMENTAL SCIENCES↗