Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Plasma materials processing”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

A three-point velocity estimation method for two-dimensional coarse-grained imaging data

Time delay and velocity estimation methods have been widely studied subjects in the context of signal processing, with applications in many different fields of physics. The velocity of waves or coherent fluctuation structures is commonly estimated as the distance between two measurement points divided by the time lag that maximizes the cross correlation function between the measured signals, but this is demonstrated to result in erroneous estimates for two spatial dimensions. We present an improved method to accurately estimate both components of the velocity vector, relying on three non-aligned measurement points. We introduce a stochastic process describing the fluctuations as a superposition of uncorrelated pulses moving in two dimensions. Using this model, we show that the three-point velocity estimation method, using time delays calculated through cross correlations, yields the exact velocity components when all pulses have the same velocity. The two- and three-point methods are tested on synthetic data generated from realizations of such processes for which the underlying velocity components are known. The results reveal the superiority of the three-point technique. Finally, we demonstrate the applicability of the velocity estimation on gas puff imaging data of strongly intermittent plasma fluctuations due to the radial motion of coherent, blob-like structures at the boundary of the Alcator C-Mod tokamak.

Materials Science↗
DOE OSTI2022

Particle transport in Markov stochastic mixtures with spatial gradients

Markov geometries are a prototype class of stochastic media that are widely used to model complex disordered systems. In a series of recent works, we have shown that spatially homogeneous (but possibly non-isotropic) Poisson tessellations can be conveniently used in order to generate three-dimensional realizations of Markov media and thus characterize the features of particle transport e.g. in fragmented fuel elements following severe nuclear accidents or Rayleigh-Taylor turbulent mixing for inertial confinement fusion. In this paper we show that Poisson tessellations can be extended to take into account the presence of spatial gradients, which commonly occur in real-world applications due to material stratification. For this purpose, we will provide an explicit construction of spatially-non-homogeneous Poisson tessellations, fully characterize their statistical properties, and finally illustrate the behaviour of particle transport in such random media. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2022

Chemical looping based ammonia production - A promising pathway for production of the noncarbon fuel

Ammonia, primarily made with Haber–Bosch process developed in 1909 and winning two Nobel prizes, is a promising noncarbon fuel for preventing global warming of 1.5 °C above pre-industrial levels. However, the undesired characteristics of the process, including high carbon footprint, necessitate alternative ammonia synthesis methods, and among them is chemical looping ammonia production (CLAP) that uses nitrogen carrier materials and operates at atmospheric pressure with high product selectivity and energy efficiency. To date, neither a systematic review nor a perspective in nitrogen carriers and CLAP has been reported in the critical area. So, this work not only assesses the previous results of CLAP but also provides perspectives towards the future of CLAP. It classifies, characterizes, and holistically analyzes the fundamentally different CLAP pathways and discusses the ways of further improving the CLAP performance with the assistance of plasma technology and artificial intelligence (AI).

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2020

Experimental Investigation of Uranium Volatility during Vapor Condensation

The predictive models that describe the fate and transport of radioactive materials in the atmosphere following a nuclear incident (explosion or reactor accident) assume that uranium-bearing particulates would attain chemical equilibrium during vapor condensation. Here, we show that kinetically driven processes in a system of rapidly decreasing temperature can result in substantial deviations from chemical equilibrium. This can cause uranium to condense out in oxidation states (e.g., UO 3 vs UO 2 ) that have different vapor pressures, significantly affecting uranium transport. To demonstrate this, we synthesized uranium oxide nanoparticles using a flow reactor under controlled conditions of temperature, pressure, and oxygen concentration. The atomized chemical reactants passing through an inductively coupled plasma cool from ~5000 to 1000 K within milliseconds and form nanoparticles inside a flow reactor. The ex situ analysis of particulates by transmission electron microscopy revealed 2–10 nm crystallites of fcc-UO 2 or α-UO 3 depending on the amount of oxygen in the system. α-UO 3 is the least thermodynamically preferred polymorph of UO 3 . The absence of stable uranium oxides with intermediate stoichiometries (e.g., U 3 O 8 ) and sensitivity of the uranium oxidation states to local redox conditions highlight the importance of in situ measurements at high temperatures. Therefore, we developed a laser-based diagnostic to detect uranium oxide particles as they are formed inside the flow reactor. Our in situ measurements allowed us to quantify the changes in the number densities of the uranium oxide nanoparticles (e.g., UO 3 ) as a function of oxygen gas concentration. Our results indicate that uranium can prefer to be in metastable crystal forms (i.e., α-UO 3 ) that have higher vapor pressures than the refractory form (i.e., UO 2 ) depending on the oxygen abundance in the surrounding environment. This demonstrates that the equilibrium processes may not dominate during rapid condensation processes, and thus kinetic models are required to fully describe uranium transport subsequent to nuclear incidents.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Enhanced minority carrier lifetime in bulk hydrogen-passivated InAsSbBi

We investigate the bulk passivation of the dilute bismide alloy InAsSbBi by plasma-assisted hydrogenation. InAsSbBi is of significant interest for mid- to long-wave infrared photodetection due to its bandgap flexibility and potential integration with heterostructured photodetector architectures. Epitaxially grown InAsSbBi samples are characterized by photoluminescence and time-resolved photoluminescence measurements for a range of hydrogenation conditions. Increases in the minority carrier lifetime of over 3× are reported, with no degradation over a period of months following the treatment. Photoluminescence measurements confirm that the hydrogenation process improves the InAsSbBi optical properties. These results offer a path toward the improved performance of InAsSbBi-based photodetectors and potentially other narrow bandgap semiconductor materials and material systems.

Physics↗
DOE OSTI2022

Beam-driven dynamics of aluminium dopants in graphene

Abstract Substituting heteroatoms into graphene can tune its properties for applications ranging from catalysis to spintronics. The further recent discovery that covalent impurities in graphene can be manipulated at atomic precision using a focused electron beam may open avenues towards sub-nanometer device architectures. However, the preparation of clean samples with a high density of dopants is still very challenging. Here, we report vacancy-mediated substitution of aluminium into laser-cleaned graphene, and without removal from our ultra-high vacuum apparatus, study their dynamics under 60 keV electron irradiation using aberration-corrected scanning transmission electron microscopy and spectroscopy. Three- and four-coordinated Al sites are identified, showing excellent agreement with ab initio predictions including binding energies and electron energy loss spectrum simulations. We show that the direct exchange of carbon and aluminium atoms predicted earlier occurs under electron irradiation, although unexpectedly it is less probable than the same process for silicon. We also observe a previously unknown nitrogen–aluminium exchange that occurs at Al–N double-dopant sites at graphene divacancies created by our plasma treatment.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Functionalized carbon nanotubes for thermionic emission and cooling applications

Barium strontium oxide-coated carbon nanotubes (CNTs) were implemented as a work function lowering and field enhancing functional coating on a coiled tungsten filament to create a new thermionic cathode. This cathode resembles conventional oxide cathodes in structure. It has the same coiled tungsten filament as a conventional oxide cathode but uses barium strontium oxide-coated CNTs instead of the traditional barium strontium calcium oxide powder mixture as an emissive coating. The cathode produces a strong thermionic emission. At 1395 K and 2.5 V/μm, the thermionic emission current of 0.87 A or current density of 2.9 A/cm 2 was obtained from this oxide-coated CNT cathode. This level of emission is about three times as large as a conventional oxide cathode operating at similar temperature and field strength. Strong thermionic emissions from the cathode also lead to a large thermionic cooling effect. Temperature reduction as large as 90° was observed from the cathode surface when it was emitting electrons. Strong thermionic emission and a large cooling effect obtained are the result of the combination of the low work function of barium strontium oxide (1.6 eV) and the large field effect induced by the CNTs. Plasma enhanced chemical vapor deposition was used to grow CNTs, and magnetron sputtering deposition was used to deposit the barium strontium oxide functional coating; details of the cathode fabrication are presented to illustrate both the versatility of the processing techniques and the adaptability of barium strontium oxide-coated CNTs as a functional coating. Finally, measurements on thermionic emission and thermionic cooling of the cathode are also presented.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Investigation of the significance of excited species in wave-heated dense non-ideal microplasmas using particle-in-cell Monte Carlo-collision modeling

A computational model for the interaction of a high-pressure microplasma with an electromagnetic wave is presented. A one-dimensional particle-in-cell Monte Carlo collision model is used to investigate the plasma non-ideality effects in a second-stage laser-heated xenon plasma with a comprehensive chemistry mechanism, including excited species. A xenon microplasma at a temperature of 300 K and pressure of 10 bar becomes non-ideal after the laser heating stage with lower ionization and electronic excitation barriers, which makes the presence of excited species important to the plasma generation process. For these conditions, two-step ionization via excited species becomes a major contributor to plasma ionization. We find that full ionization of the plasma is obtained in ~2 ps when excited species are included in the chemistry model, as opposed to ~2.5 ps for a chemistry mechanism that does not consider their effect. With excited species, the ionization mode transitions from direct ionization via electron-neutral collisions to direct and stepwise ionization as the plasma generation progresses.

36 MATERIALS SCIENCE↗
NASA NTRS1978

Can X-ray bursts be caused by substorms at a neutron star

A model for X-ray bursts from accreting neutron stars is developed by analogy with geomagnetic substorms. The essential steps in the substorm process are the nearly steady merging or reconnection of the magnetic field in the magnetosphere with the field in the stellar wind, the transport of some of the merged plasma into a magnetically controlled tail, and the explosive release of plasma from the tail into the magnetosphere. The strength of the magnetic field in the stellar wind required to drive a substorm is approximately 0.1 gauss. If the stellar wind is organized into large-scale magnetic sectors, as is the solar wind, topological dissipation will not occur, and the large-scale field will be available for merging at the magnetopause. Once the material is in the tail, the time scales for the Kruskal-Schwarzschild instability and the unidentified instability which drives terrestrial substorms may be comparable. Alternating periods of burst activity and quiescence could be caused by passage from one sector to another with opposite polarity, or be seasonal variations.

Neugebauer, M.↗
NASA NTRS1985

DE 1 RIMS operational characteristics

The Retarding Ion Mass Spectrometer (RIMS) on the Dynamics Explorer 1 spacecraft observes both the thermal and superthermal (50 eV) ions of the ionosphere and inner magnetosphere. It is capable of measuring the detailed species distribution function of these ions in many cases. It was equipped with an integral electrometer to permit in-flight calibration of the detector sensitivities and variations thereof. A guide to understanding the RIMS data set is given. The reduction process from count rates to physical quantities is discussed in some detail. The procedure used to establish in-flight calibration is described, and results of a comparison with densities from plasma wave measurements are provided. Finally, a discussion is provided of various anomalies in the data set, including changes of channeltron efficiency with time, spin modulation of the axial sensor heads, apparent potential differences between the sensor heads, and failures of the radial head retarding potential sweep and of the -Z axial head aperture plane bias. Studies of the RIMS data set should be conducted only with a thorough awareness of the material presented here, or in collaboration with one of the scientists actively involved with RIMS data analysis.

Olsen, R. C.↗
NASA NTRS2000

The Generation of Smooth High Speed Solar Wind From Plume-Interplume Mixing

Ulysses has shown that fast solar wind is extremely smooth, with a variance of less than 5%, in contrast to slow wind with a variance of approximately 30%. Now UVCS has produced the surprising result that the flow speed within coronal holes, the source of fast wind, is not at all smooth. Specifically, Giordano et al. (ApJ, v531, L79-L82, 2000) report that at 1.7 R(sub SUN) the interplume flow speed is typically more than twice the plume flow speed. Other less direct evidence supports this same result, with speeds from less than 300 to over 1000 km/s reported at approximately 5 R(sub SUN). This presents the paradox of how strongly differing plume and interplume flow speeds can exist near the Sun and be absent far from the Sun. The only answer is that plume and interplume material or momentum must be strongly mixed and that the mixing must occur mainly inside 0.3 AU to be consistent with Helios observations of smooth fast wind. Pressure balance structures (PBSs) and He abundance anomalies (Reisenfeld, et al., GRL, v26(13), 1805-1808, 1999) have been identified as interplanetary remnants of plumes, implying momentum mixing is the dominant coronal process. One possible source for plume/interplume momentum mixing is MHD Kelvin-Helmholtz (KH) shear instabilities occurring on the velocity shear interfaces. The velocity shear is a source of free energy and KH fluctuations could, through nonlinear cascade, provide the forcing required for the plasma oscillations (Cranmer, ApJ, v532, 1197-1208, 2000) reported to exist in coronal holes. The physical properties in coronal holes are now sufficiently well known that we can show plume/interplume shear interfaces become unstable to the KH instability at 5 - 10 R(sub SUN). The KH dispersion relation can be used to analyze marginal stability, the most unstable wavelengths, and linear growth rates. Numerical simulations can be used to verify results from the linear analysis and study the nonlinear development of KH modes. Here we will describe the marginal stability criterion for the KH instability, how and where this condition is met in the corona, and the possible character of the resultant fluctuations.

Suess, Steve↗
NASA NTRS2012

NASA Tech Briefs, September 2012

Topics covered include: Beat-to-Beat Blood Pressure Monitor; Measurement Techniques for Clock Jitter; Lightweight, Miniature Inertial Measurement System; Optical Density Analysis of X-Rays Utilizing Calibration Tooling to Estimate Thickness of Parts; Fuel Cell/Electrochemical Cell Voltage Monitor; Anomaly Detection Techniques with Real Test Data from a Spinning Turbine Engine-Like Rotor; Measuring Air Leaks into the Vacuum Space of Large Liquid Hydrogen Tanks; Antenna Calibration and Measurement Equipment; Glass Solder Approach for Robust, Low-Loss, Fiber-to-Waveguide Coupling; Lightweight Metal Matrix Composite Segmented for Manufacturing High-Precision Mirrors; Plasma Treatment to Remove Carbon from Indium UV Filters; Telerobotics Workstation (TRWS) for Deep Space Habitats; Single-Pole Double-Throw MMIC Switches for a Microwave Radiometer; On Shaft Data Acquisition System (OSDAS); ASIC Readout Circuit Architecture for Large Geiger Photodiode Arrays; Flexible Architecture for FPGAs in Embedded Systems; Polyurea-Based Aerogel Monoliths and Composites; Resin-Impregnated Carbon Ablator: A New Ablative Material for Hyperbolic Entry Speeds; Self-Cleaning Particulate Prefilter Media; Modular, Rapid Propellant Loading System/Cryogenic Testbed; Compact, Low-Force, Low-Noise Linear Actuator; Loop Heat Pipe with Thermal Control Valve as a Variable Thermal Link; Process for Measuring Over-Center Distances; Hands-Free Transcranial Color Doppler Probe; Improving Balance Function Using Low Levels of Electrical Stimulation of the Balance Organs; Developing Physiologic Models for Emergency Medical Procedures Under Microgravity; PMA-Linked Fluorescence for Rapid Detection of Viable Bacterial Endospores; Portable Intravenous Fluid Production Device for Ground Use; Adaptation of a Filter Assembly to Assess Microbial Bioburden of Pressurant Within a Propulsion System; Multiplexed Force and Deflection Sensing Shell Membranes for Robotic Manipulators; Whispering Gallery Mode Optomechanical Resonator; Vision-Aided Autonomous Landing and Ingress of Micro Aerial Vehicles; Self-Sealing Wet Chemistry Cell for Field Analysis; General MACOS Interface for Modeling and Analysis for Controlled Optical Systems; Mars Technology Rover with Arm-Mounted Percussive Coring Tool, Microimager, and Sample-Handling Encapsulation Containerization Subsystem; Fault-Tolerant, Real-Time, Multi-Core Computer System; Water Detection Based on Object Reflections; SATPLOT for Analysis of SECCHI Heliospheric Imager Data; Plug-in Plan Tool v3.0.3.1; Frequency Correction for MIRO Chirp Transformation Spectroscopy Spectrum; Nonlinear Estimation Approach to Real-Time Georegistration from Aerial Images; Optimal Force Control of Vibro-Impact Systems for Autonomous Drilling Applications; Low-Cost Telemetry System for Small/Micro Satellites; Operator Interface and Control Software for the Reconfigurable Surface System Tri-ATHLETE; and Algorithms for Determining Physical Responses of Structures Under Load.

Source record↗
NASA NTRSDate not supplied

Low Energy Ionizing Radiation and Plasma Contributions to Radiation Dose in Materials at Sun-Earth Lagrange Points

- High energy radiation environments responsible for radiation damage to thick materials are well characterized and modeled: - Galactic cosmic rays — Badhwar-O’Neil 2020, CREME96, Nymmik - Solar particle events — Emission of Solar Protons, SAPPHIRE, JPL, King 1972 - Trapped radiation belts — AE8/AP8, AE9/AP9/IRENE - Low energy radiation environments responsible for radiation damage to thin materials relevant to Lagrange points and interplanetary missions have not been treated as comprehensively to date: - Solar wind - Magnetosheath - Magnetotail - Concern to spacecraft design and operations is radiation damage to surfaces and thin materials with mission critical applications on exterior of spacecraft - Applications: thermal control coatings, sunshields, multilayer insulation, optical thin film coatings, solar sails, thermo-optical properties of space exposed materials - Damage processes: radiation degradation (total dose), light ion sputtering, proton blistering of soft metals, modification of optical properties (α/ε), modification of charging properties (SEY, surface conductivity)

Joseph I. Minow↗
DOE OSTI2023

MRT 7365: Power flow physics and key physics phenomena

The Z accelerator at Sandia National Laboratories conducts z-pinch experiments at 26 MA in support of DOE missions in stockpile stewardship, dynamic materials, fusion, and other basic sciences. Increasing the current delivered to the z-pinch would extend our reach in each of these disciplines. To achieve increases in current and accelerator efficiency, a fraction of Z’s shots are set aside for research into transmission-line power flow. These shots, with supporting simulations and theory, are incorporated into this Advanced Diagnostics milestone report. The efficiency of Z is reduced as some portion of the total current is shunted across the transmission-line gaps prior to the load. This is referred to as “current loss”. Electrode plasmas have long been implicated in this process, so the bulk of dedicated power-flow experiments are designed to measure the plasma environment. The experimental analyses are enhanced by simulations conducted using realistic hardware and Z voltage pulses. In the same way that diagnostics are continually being improved for sensitivity and resolution, the modeling capability is continually being improved to provide faster and more realistic simulations. The specifics of the experimental hardware, diagnostics, simulations, and algorithm developments are provided in this report. The combined analysis of simulation and data confirms that electrode plasmas have the most detrimental impact on current delivery. Experiments over the last three years have tested the theoretical current-loss mechanisms of enhanced ion current, plasma gap closure, and Hall-related current. These mechanisms are not mutually exclusive and may be coincident in the final feed as well as in upstream transmission lines. The final-feed geometries tested here, however, observe lower-density plasmas without dominant ion currents which is consistent with a Hall-related current. The picture of plasma formation and transport formed from experiment and simulation is informing hardware designs being fielded on Z now and being proposed for the Next-Generation Pulsed Power (NGPP) facility. In this picture, the strong magnetic fields that heat the electrodes above particle emission thresholds also confine the charged particles near the surface. Some portion of the plasmas thus formed is transported into the transmission-line gap under the force of the electric field, with aid from plasma instabilities. The gap plasmas are then transported towards the load by a cross-field drift, where they accumulate and contribute to a likely Hall-related cross-gap current. The achievements in experimental execution, model validation, and physical analysis presented in this report set the stage for continued progress in power flow and load diagnostics on Z. The planned shot schedule for Z and Mykonos will provide data for extrapolation to higher current to ensure the predicted performance and efficiency of a NGPP facility.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

Synthesis‐Related Nanoscale Defects in Mo‐Based Janus Monolayers Revealed by Cross‐Correlated AFM and TERS Imaging

2D Janus transition metal dichalcogenides (TMDs) are promising candidates for various applications including non-linear optics, energy harvesting, and catalysis. These materials are usually synthesized via chemical conversion of pristine TMDs. Nanometer-scale characterization of the obtained Janus materials’ morphology and local composition is crucial for both the synthesis optimization and the future device applications. In this work, we present the results of cross-correlated atomic force microscopy (AFM) and tip-enhanced Raman spectroscopy (TERS) study of Janus monolayers synthesized by the hydrogen plasma-assisted chemical conversion of MoSe 2 and MoS 2 . We demonstrate that the choice of both the growth substrate and the starting TMD influences the residual strain, thereby shaping the nanoscale morphology of the resulting Janus material. Furthermore, by employing TERS imaging, we show the presence of nanoscale islands (≈20 nm across) of MoSe 2 - ${\mathrm{Mo}}_{{\mathrm{Se}}}^{\mathrm{S}}$ (MoS 2 -${\mathrm{Mo}}_{\mathrm{S}}^{{\mathrm{Se}}}$) vertical heterostructures originating from the bilayer nanoislands in the precursor monolayer crystals. The understanding of the origins of nanoscale defects in Janus TMDs revealed in this study can help with further optimization of the Janus conversion process towards uniform and wrinkle-/crack-free Janus materials. Moreover, this work shows that cross-correlated AFM and TERS imaging is a powerful and accessible method for studying nanoscale composition and defects in Janus TMD monolayers.

2D materials↗
NASA NTRS1977

Gaseous-fuel nuclear reactor research for multimegawatt power in space

In the gaseous-fuel reactor concept, the fissile material is contained in a moderator-reflector cavity and exists in the form of a flowing gas or plasma separated from the cavity walls by means of fluid mechanical forces. Temperatures in excess of structural limitations are possible for low-specific-mass power and high-specific-impulse propulsion in space. Experiments have been conducted with a canister filled with enriched UF6 inserted into a beryllium-reflected cavity. A theoretically predicted critical mass of 6 kg was measured. The UF6 was also circulated through this cavity, demonstrating stable reactor operation with the fuel in motion. Because the flowing gaseous fuel can be continuously processed, the radioactive waste in this type of reactor can be kept small. Another potential of fissioning gases is the possibility of converting the kinetic energy of fission fragments directly into coherent electromagnetic radiation, the nuclear pumping of lasers. Numerous nuclear laser experiments indicate the possibility of transmitting power in space directly from fission energy. The estimated specific mass of a multimegawatt gaseous-fuel reactor power system is from 1 to 5 kg/kW while the companion laser-power receiver station would be much lower in specific mass.

Thom, K.↗
NASA NTRS2007

Space Plasma Ion Processing of the Lunar Soil: Modeling of Radiation-Damaged Rim Widths on Lunar Grains

Chemically and microstructurally complex altered rims around grains in the finest size fraction (<20 micron) of the lunar regolith are the result of multi-stage processes involving both solar ion radiation damage and nanoscale deposition of impact or sputter-derived vapors. The formation of the rims is an important part of the space weathering process, and is closely linked to key changes in optical reflectance and other bulk properties of the lunar surface. Recent application of field-emission scanning transmission electron microscope techniques, including energy dispersive X-ray spectral imaging, is making it easier to unravel the "nano-stratigraphy" of grain rims, and to delineate the portions of rims that represent Radiation-Amorphized (RA) host grain from overlying amorphous material that represents vapor/sputter deposits. For the portion of rims formed by host grain amorphization (henceforth called RA rims), we have been investigating the feasibility of using Monte Carlo-type ion-atom collision models, combined with experimental ion irradiation data, to derive predictive numerical models linking the width of RA rims to the grain s integrated solar ion radiation exposure time.

Chamberlin, S.↗
DOE OSTI2022

Exploration of methods to remove implanted 210 Pb and 210 Po contamination from silicon surfaces

Radioactive contaminants on the surfaces of detector components can be a problematic source of background events for physics experiments searching for rare processes. Exposure to radon is a specific concern because it can result in the relatively long-lived 210 Pb (and progeny) being implanted to significant subsurface depths such that removal is challenging. Here, in this article, we present results from a broad exploration of cleaning treatments to remove implanted 210 Pb and 210 Po contamination from silicon, which is a material frequently used in rare-events searches. We demonstrate for the first time that heat treatments (“baking”) can effectively mitigate such surface contamination, with a 1200 °C bake resulting in a 97$^{+2}_{-3}$% reduction. We also report results using wet-chemistry and plasma-based methods, which show that etching can be highly effective provided the etch depth is sufficiently aggressive. Our survey of cleaning methods suggests consideration of multiple approaches during the different phases of detector construction to enable greater flexibility for efficient removal of 210 Pb and 210 Po surface contamination.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗