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At least 1,171 records · Page 65
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

A comparative study of cerium oxides formed by pulsed laser ablation and continuous wave laser heating

Abstract The formation of Ce 2 O 3 from cerium metal requires complex reducing conditions. Alternatively, we show that different stoichiometries and structures of cerium oxides can be generated in high‐temperature laser experiments by varying the availability of oxygen and the use of either pulsed laser ablation (PLA) or continuous wave (CW) laser heating of cerium metal. X‐ray diffraction and Raman spectroscopy suggest that a low structural order Ce 2 O 3 /CeO 2 mixed structure is formed in a 1% O 2 atmosphere with PLA. For CW heating in a 1% O 2 environment, Raman measurements show the formation of crystalline A‐type Ce 2 O 3 in proximity to the point of laser impingement. These experiments were repeated in 18 O 2 and allowed us to report for the first time the corresponding Raman spectrum of Ce 2 18 O 3 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Early prediction of tumor recurrence based on CT texture changes after stereotactic ablative radiotherapy (SABR) for lung cancer

Purpose: Benign computed tomography (CT) changes due to radiation induced lung injury (RILI) are common following stereotactic ablative radiotherapy (SABR) and can be difficult to differentiate from tumor recurrence. The authors measured the ability of CT image texture analysis, compared to more traditional measures of response, to predict eventual cancer recurrence based on CT images acquired within 5 months of treatment. Methods: A total of 24 lesions from 22 patients treated with SABR were selected for this study: 13 with moderate to severe benign RILI, and 11 with recurrence. Three-dimensional (3D) consolidative and ground-glass opacity (GGO) changes were manually delineated on all follow-up CT scans. Two size measures of the consolidation regions (longest axial diameter and 3D volume) and nine appearance features of the GGO were calculated: 2 first-order features [mean density and standard deviation of density (first-order texture)], and 7 second-order texture features [energy, entropy, correlation, inverse difference moment (IDM), inertia, cluster shade, and cluster prominence]. For comparison, the corresponding response evaluation criteria in solid tumors measures were also taken for the consolidation regions. Prediction accuracy was determined using the area under the receiver operating characteristic curve (AUC) and two-fold cross validation (CV). Results: For this analysis, 46 diagnostic CT scans scheduled for approximately 3 and 6 months post-treatment were binned based on their recorded scan dates into 2–5 month and 5–8 month follow-up time ranges. At 2–5 months post-treatment, first-order texture, energy, and entropy provided AUCs of 0.79–0.81 using a linear classifier. On two-fold CV, first-order texture yielded 73% accuracy versus 76%–77% with the second-order features. The size measures of the consolidative region, longest axial diameter and 3D volume, gave two-fold CV accuracies of 60% and 57%, and AUCs of 0.72 and 0.65, respectively. Conclusions: Texture measures of the GGO appearance following SABR demonstrated the ability to predict recurrence in individual patients within 5 months of SABR treatment. Appearance changes were also shown to be more accurately predictive of recurrence, as compared to size measures within the same time period. With further validation, these results could form the substrate for a clinically useful computer-aided diagnosis tool which could provide earlier salvage of patients with recurrence.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

TU-F-BRE-07: In Vivo Neutron Detection in Patients Undergoing Stereotactic Ablative Radiotherapy (SABR) for Primary Kidney Cancer Using 6Li and 7Li Enriched TLD Pairs

Purpose: Stereotactic ablative radiotherapy (SABR) for primary kidney cancer often involves the use of high-energy photons combined with a large number of monitor units. While important for risk assessment, the additional neutron dose to untargeted healthy tissue is not accounted for in treatment planning. This work aims to detect out-of-field neutrons in vivo for patients undergoing SABR with high-energy (>10 MV) photons and provides preliminary estimates of neutron effective dose. Methods: 3 variations of high-sensitivity LiF:Mg,Cu,P thermoluminescent dosimeter (TLD) material, each with varying {sup 6}Li / {sup 7}Li concentrations, were used in custom-made Perspex holders for in vivo measurements. The variation in cross section for thermal neutrons between Li isotopes was exploited to distinguish neutron from photon signal. Measurements were made out-of-field for 7 patients, each undergoing 3D-conformal SABR treatment for primary kidney cancer on a Varian 21iX linear accelerator. Results: In vivo measurements show increased signal for the {sup 6}Li enriched material for patients treated with 18 MV photons. Measurements on one SABR patient treated using only 6 MV showed no difference between the 3 TLD materials. The out-of-field photon signal decreased exponentially with distance from the treatment field. The neutron signal, taken as the difference between {sup 6}Li enriched and {sup 7}Li enriched TLD response, remains almost constant up to 50 cm from the beam central axis. Estimates of neutron effective dose from preliminary TLD calibration suggest between 10 and 30 mSv per 1000 MU delivered at 18 MV for the 7 patients. Conclusion: TLD was proven to be a useful tool for the purpose of in vivo neutron detection at out-of-field locations. Further work is required to understand the relationship between TL signal and neutron dose. Dose estimates based on preliminary TLD calibration in a neutron beam suggest the additional neutron dose was <30 mSv per 1000 MU at 18 MV.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Sci—Sat AM: Stereo — 08: Stereotactic Ablative Radiotherapy (SABR) for low, intermediate and high risk prostate cancer using Volumetric Modulated Arc Therapy (VMAT) with a 10x Flattening Filter Free (FFF) beam

Purpose: To determine the feasibility of using Volumetric Modulated Arc Therapy (VMAT) with a 10x Flattening Filter Free (FFF) beam for Stereotactic Ablative Radiotherapy (SABR) for low, intermediate and high risk prostate cancer. Methods and Materials: Ten anonymized patient CT data sets were used in this planning study. For each patient CT data set, three sets of contours were generated: 1) low risk, 2) intermediate risk, and 3) high risk scenarios. For each scenario, a single-arc and a double-arc VMAT treatment plans were created. Plans were generated with the Varian Eclipse™ treatment planning system for a Varian TrueBeam™ linac equipped with Millenium 120 MLC. Plans were created using a 10x-FFF beam with a maximum dose rate of 2400 MU/min. Dose prescription was 36.25Gy/5 fractions with the planning objective of covering 99% of the Planning Target Volume with the 95% of the prescription dose. Normal tissue constraints were based on provincial prostate SABR planning guidelines, derived from national and international prostate SABR protocols. Plans were evaluated and compared in terms of: 1) dosimetric plan quality, and 2) treatment delivery efficiency. Results: Both single-arc and double-arc VMAT plans were able to meet the planning goals for low, intermediate and high risk scenarios. No significant dosimetric differences were observed between the plans. However, the treatment time was significantly lower for a single-arc VMAT plans. Conclusions: Prostate SABR treatments are feasible with 10x-FFF VMAT technique. A single-arc VMAT offers equivalent dosimetric plan quality and a superior treatment delivery efficiency, compared to a double-arc VMAT.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

SU-E-T-91: Accuracy of Dose Calculation Algorithms for Patients Undergoing Stereotactic Ablative Radiotherapy

Purpose: The purpose of this study was to investigate and quantify the variation in dose distributions in small field lung cancer radiotherapy using seven different dose calculation algorithms. Methods: The study was performed in 21 lung cancer patients who underwent Stereotactic Ablative Body Radiotherapy (SABR). Two different methods (i) Same dose coverage to the target volume (named as same dose method) (ii) Same monitor units in all algorithms (named as same monitor units) were used for studying the performance of seven different dose calculation algorithms in XiO and Eclipse treatment planning systems. The seven dose calculation algorithms include Superposition, Fast superposition, Fast Fourier Transform ( FFT) Convolution, Clarkson, Anisotropic Analytic Algorithm (AAA), Acurous XB and pencil beam (PB) algorithms. Prior to this, a phantom study was performed to assess the accuracy of these algorithms. Superposition algorithm was used as a reference algorithm in this study. The treatment plans were compared using different dosimetric parameters including conformity, heterogeneity and dose fall off index. In addition to this, the dose to critical structures like lungs, heart, oesophagus and spinal cord were also studied. Statistical analysis was performed using Prism software. Results: The mean±stdev with conformity index for Superposition, Fast superposition, Clarkson and FFT convolution algorithms were 1.29±0.13, 1.31±0.16, 2.2±0.7 and 2.17±0.59 respectively whereas for AAA, pencil beam and Acurous XB were 1.4±0.27, 1.66±0.27 and 1.35±0.24 respectively. Conclusion: Our study showed significant variations among the seven different algorithms. Superposition and AcurosXB algorithms showed similar values for most of the dosimetric parameters. Clarkson, FFT convolution and pencil beam algorithms showed large differences as compared to superposition algorithms. Based on our study, we recommend Superposition and AcurosXB algorithms as the first choice of algorithms in lung cancer radiotherapy involving small fields. However, further investigation by Monte Carlo simulation is required to confirm our results.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

SU-E-T-290: Dosimetric Accuracy of Acuros XB and Analytical Anisotropic Algorithm in Stereotactic Ablative Radiotherapy of Small Lung Lesions

Purpose: The accuracy of dose calculation for lung stereotactic ablative radiotherapy (SABR) of small lesions critically depends on the proper modeling of the lateral scatter in heterogeneous media. In recent years, grid-based Boltzman solvers such as Acuros XB (AXB) have been introduced for enhanced modeling of radiation transport in heterogeneous media. The purpose of this study is to evaluate the dosimetric impact of dose calculation between AXB and convolution-superposition algorithms such as analytical anisotropic algorithm (AAA) for small lesion sizes and different beam energies. Methods: Five lung SABR VMAT cases with GTV ranged from 0.8cm to 2.5cm in diameter were studied. For each case, doses were calculated by AAA, AXB (V11031) and Monte Carlo simulation (MC) with the same plan parameters for 10MV and 6MV. The dose calculation accuracy were evaluated by comparing DVHs and dose distributions with MC as the benchmark. The accuracy of calculated dose was also validated by EBT3 film measurement with a field size of 3cmx3cm in a thorax phantom. Results: For 10MV and GTV less than 1cm, dose calculated by AXB agrees well with MC compared to AAA. Dose difference calculated with AXB and AAA could be up to 30%. For GTV greater than 2cm, calculation results of AXB and AAA agree within 5% in GTV. For 6MV, the difference between calculated doses by AXB and AAA is less 10% for GTV less than 1cm. Based on film measurements, lung dose was overestimated 10% and 20% by AAA for 6MV and 10MV. Conclusion: Lateral scatter and transport is modeled more accurately by AXB than AAA in heterogeneous media, especially for small field size and high energy beams. The accuracy depends on the assigned material in calculation. If grid-based Boltzman solvers or MC are not available for calculation, lower energy beams should be used for treatment.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Technical Note: Validation and implementation of a wireless transponder tracking system for gated stereotactic ablative radiotherapy of the liver

Purpose: Tracking soft-tissue targets has recently been cleared as a new application of Calypso, an electromagnetic wireless transponder tracking system, allowing for gated treatment of the liver based on the motion of the target volume itself. The purpose of this study is to describe the details of validating the Calypso system for wireless transponder tracking of the liver and to present the clinical workflow for using it to deliver gated stereotactic ablative radiotherapy (SABR). Methods: A commercial 3D diode array motion system was used to evaluate the dynamic tracking accuracy of Calypso when tracking continuous large amplitude motion. It was then used to perform end-to-end tests to evaluate the dosimetric accuracy of gated beam delivery for liver SABR. In addition, gating limits were investigated to determine how large the gating window can be while still maintaining dosimetric accuracy. The gating latency of the Calypso system was also measured using a customized motion phantom. Results: The average absolute difference between the measured and expected positional offset was 0.3 mm. The 2%/2 mm gamma pass rates for the gated treatment delivery were greater than 97%. When increasing the gating limits beyond the known extent of planned motion, the gamma pass rates decreased as expected. The 2%/2 mm gamma pass rate for a 1, 2, and 3 mm increase in gating limits was measured to be 97.8%, 82.9%, and 61.4%, respectively. The average gating latency was measured to be 63.8 ms for beam-hold and 195.8 ms for beam-on. Four liver patients with 17 total fractions have been successfully treated at our institution. Conclusions: Wireless transponder tracking was validated as a dosimetrically accurate way to provide gated SABR of the liver. The dynamic tracking accuracy of the Calypso system met manufacturer’s specification, even for continuous large amplitude motion that can be encountered when tracking liver tumors close to the diaphragm. The measured beam-hold gating latency was appropriate for targets that will traverse the gating limit each respiratory cycle causing the beam to be interrupted constantly throughout treatment delivery.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

SU-F-T-558: ArcCheck for Patient Specific QA in Stereotactic Ablative Radiotherapy

Purpose: Stereotactic Ablative Radiotherapy (SABR) is one of the most preferred treatment techniques for early stage lung cancer. This technique has been extended to other treatment sites like Spine, Liver, Scapula, Sternum etc., This has resulted in increased physics QA time on machine. In this study, we’ve tested the feasibility of using ArcCheck as an alternative method to replace film dosimetry. Methods: Twelve patients with varied diagnosis of Lung, Liver, scapula, sternum and Spine undergoing SABR were selected for this study. Pre-treatment QA was performed for all the patients which include ionization chamber and film dosimetry. The required gamma criteria for each SABR plan to pass QA and proceed to treatment is 95% (3%,1mm). In addition to this routine process, the treatment plans were exported on to an ArcCheck phantom. The planned and measured dose from the ArcCheck device were compared using four different gamma criteria: 2%,2 mm, 3%,2 mm, 3%,1 mm and 3%, 3 mm. In addition to this, we’ve also introduced errors to gantry, collimator and couch angle to assess sensitivity of the ArcCheck with potential delivery errors. Results: The ArcCheck mean passing rates for all twelve cases were 76.1%±9.7% for gamma criteria 3%,1 mm, 89.5%±5.3% for 2%,2 mm, 92.6%±4.2% for 3%,2 mm, and 97.6%±2.4% for 3%,3 mm gamma criteria. When SABR spine cases are excluded, we observe ArcCheck passing rates higher than 95% for all the studied cases with 3%, 3mm, and ArcCheck results in acceptable agreement with the film gamma results. Conclusion: Our ArcCheck results at 3%, 3 mm were found to correlate well with our non-SABR spine routine patient specific QA results (3%,1 mm). We observed significant reduction in QA time on using ArcCheck for SABR QA. This study shows that ArcCheck could replace film dosimetry for all sites except SABR spine.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

SU-F-T-617: Remotely Pre-Planned Stereotactic Ablative Radiation Therapy: Validation of Treatment Plan Quality

Purpose: We propose a workflow to improve access to stereotactic ablative radiation therapy (SABR) for rural patients. When implemented, a separate trip to the central facility for simulation can be eliminated. Two elements are required: (1) Fabrication of custom immobilization devices to match positioning on prior diagnostic CT (dxCT). (2) Remote radiation pre-planning on dxCT, with transfer of contours/plan to simulation CT (simCT) and initiation of treatment same-day or next day. In this retrospective study, we validated part 2 of the workflow using patients already treated with SABR for upper lobe lung tumors. Methods: Target/normal structures were contoured on dxCT; a plan was created and approved by the physician. Structures were transferred to simCT using deformable image registration and the plan was re-optimized on simCT. Plan quality was evaluated through comparison to gold-standard structures contoured on simCT and a gold-standard plan based on these structures. Workflow-generated plan quality in this study represents a worst-case scenario as these patients were not treated using custom immobilization to match dxCT position as would be done when the workflow is implemented clinically. Results: 5/6 plans created through the pre-planning workflow were clinically acceptable. For all six plans, the gold-standard GTV received full prescription dose, along with median PTV V95%=95.2% and median PTV D95%=95.4%. Median GTV DSC=0.80, indicating high degree of similarity between the deformed and gold-standard GTV contours despite small GTV sizes (mean=3.0cc). One outlier (DSC=0.49) resulted in inadequate PTV coverage (V95%=62.9%) in the workflow plan; in clinical practice, this mismatch between deformed/gold-standard GTV would be revised by the physician after deformable registration. For all patients, normal tissue doses were comparable to the gold-standard plan and well within constraints. Conclusion: Pre-planning SABR cases on diagnostic imaging generated clinically acceptable plans. Coupled with rapid-prototyped custom immobilization, this workflow may improve treatment access for rural patients.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

SU-F-T-644: Reproducibility of Target Position Using Moderate Voluntary Breath- Hold During Liver Stereotactic Ablative Radiotherapy

Purpose: To evaluate the reproducibility of target position using moderate voluntary breath-hold during liver stereotactic ablative radiotherapy (SABR). Methods: Two patients who underwent liver SABR on a Varian TrueBeam STx linac were used for this study. Fiducial markers were placed in and around the target in the liver as surrogates for the target position and motion. GTVs were contoured by assessing tumor extent on contrast enhanced CT. The PTV was created from the GTV by adding 2 mm margins to account for the residual motion during breath-holds. A portable biofeedback system was used to facilitate the breath-hold to a reproducible position. The Varian RPM system was used for gating the linac. Proceeding each treatment, orthogonal kV pairs were taken, and alignment to nearby bony anatomy was performed. Then the breath-hold CBCT was acquired to align the fiducial markers. On-line fluoroscopy was used to fine-tune the breath-hold gating thresholds to correlate with the positions of the fiducial markers. The inter-fraction reproducibility of the target was evaluated by the offsets of the daily breath-hold CBCTs from the paired kV matches as a direct measure of the target position relative to the bony anatomy. The intra-fraction reproducibility of the target position was assessed by the gated window of the RPM marker block for each fraction. Results: The absolute mean offsets between the CBCT and paired kV matches in the vertical, longitudinal, and lateral directions were 0.06 cm, 0.10 cm, and 0.06 cm for patient 1, and 0.37 cm, 0.62 cm, and 0.09 cm for patient 2. The gated window of the RPM marker block for the breath-hold for each fraction was within 0.63 ± 0.16 cm and 0.59 ± 0.12 cm for patients 1 and 2, respectively. Conclusion: Moderate voluntary breath-hold showed good inter- and intra-fraction reproducibility of target position during liver SABR.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Electron Temperature Distribution Measurements in Clouds of Polystyrene Pellets Ablating in LHD Heliotron Plasma

Two methods for measuring the spatial distribution of the temperature of electrons in a cloud near a polystyrene pellet that ablates in LHD heliotron plasma are described. The first method is based on measuring the ratio of the local emission-coefficient values at wavelengths of 486 ± 5 nm (the H{sub β} line) and 630 ± 5 nm (continuum). The second (new) method is based on the measurement of radiation distributions of the H{sub β} line in the direction along the magnetic field. Both the methods use an assumption about the partial local thermodynamic equilibrium in the cloud and show close results. It is shown for the first time that the temperature of cloud electrons increases from 0.8 eV in the immediate vicinity of the pellet surface to 6.0–7.0 eV at a distance of 6–8 mm from the pellet in the direction along the magnetic field, which agrees with the experimentally observed longitudinal distribution of the H{sub β} radiation in the cloud.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Modelling of Ablatant Deposition from Electromagnetically Driven Radiative Pellets for Disruption Mitigation Studies

The Electromagnetic Particle Injector (EPI) concept is advanced through the simulation of ablatant deposition into ITER H-mode discharges with calculations showing penetration past the H-mode pedestal for a range of injection velocities and granule sizes concurrent with the requirements of disruption mitigation. As discharge stored energy increases in future fusion devices such as ITER, control and handling of disruption events becomes a critical issue. An unmitigated disruption could lead to failure of the plasma facing components resulting in financially and politically costly repairs. Methods to facilitate the quench of an unstable high current discharge are required. With the onset warning time for some ITER disruption events estimated to be less than 10 ms, a disruption mitigation system needs to be considered which operates at injection speeds greater than gaseous sound speeds. Such an actuator could then serve as a means to augment presently planned pneumatic injection systems. The EPI uses a rail gun concept whereby a radiative payload is delivered into the discharge by means of the JxB forces generated by an external current pulse, allowing for injection velocities in excess of 1 km/s. The present status of the EPI project is outlined, including the addition of boost magnetic coils. These coils augment the self-generated rail gun magnetic field and thus provide a more efficient acceleration of the payload. The coils and the holder designed to constrain them have been modelled with the ANSYS code to ensure structural integrity through the range of operational coil cu

disruption↗
DOE OSTI2021

Laser Ablation Reducer Application

The LARA code imports laser ablation experiments data and reduces the data according to mass and IC gain standards selected by the user. It produces graphics illustrating the results, and writes output data to file. The LARA code was developed in R, and is run within a session of RStudio.

Samperton, KyleM.↗
DOE OSTI2016

Process Development and Micro-Machining of MARBLE Foam-Cored Rexolite Hemi-Shell Ablator Capsules

For this study, machined CH hemi-shell ablator capsules have been successfully produced by the MST-7 Target Fabrication Team at Los Alamos National Laboratory. Process development and micro-machining techniques have been developed to produce capsules for both the Omega and National Ignition Facility (NIF) campaigns. These capsules are gas filled up to 10 atm and consist of a machined plastic hemi-shell outer layer that accommodates various specially engineered low-density polystyrene foam cores. Machining and assembly of the two-part, step-jointed plastic hemi-shell outer layer required development of new techniques, processes, and tooling while still meeting very aggressive shot schedules for both campaigns. Finally, problems encountered and process improvements will be discussed that describe this very unique, complex capsule design approach through the first Omega proof-of-concept version to the larger NIF version.

42 ENGINEERING↗
DOE OSTI2017

Quantitative Defect Analysis of Ablator Capsule Surfaces Using a Leica Confocal Microscope and a High-Density Atomic Force Microscope

High-density carbon (HDC) is being evaluated as an alternative to the current National Ignition Facility (NIF) point-design ablator material (glow discharge plasma, or GDP, plastic) due to its high density and optimal opacity, which leads to a higher implosion velocity. Chemical-vapor-deposition-coated HDC capsules have a near perfect surface figure but a microscopically rough surface. After polishing, the surface becomes smooth at nanometer scales but has numerous micron-sized surface pits, whose volumes, morphology, and distribution must be quantified to guide NIF target selection. Traditional metrology tools for GDP surface defects, such as the atomic force microscope (AFM) based Spheremapper and a phase-shifting differential interferometer, lack the resolution to characterize these localized features. In this paper, we describe how this metrology challenge is met by developing automated surface metrology solutions based on a high-density (HD) AFM and a Leica confocal microscope. Furthermore, these tools are complementary in nature. HD-AFM has a 0.1-μm spatial resolution and determines the overall shape distortion and pit statistics by tracing great circles on a capsule with high throughput.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Dynamic stabilization of the ablative Rayleigh-Taylor instability for heavy ion fusion

Dynamic stabilization of the ablative Rayleigh-Taylor instability of a heavy ion fusion target induced by a beam wobbling system is studied. Using a sharp-boundary model and Courant-Synder theory, it is shown, with an appropriately chosen modulation waveform, that the instability can be sta- bilized in certain parameter regimes. It is found that the stabilization e ect has a strong dependence on the modulation frequency and the waveform. Modulation with frequency comparable to the instability growth rate is the most e ective in terms of stabilizing the instability. A modulation with two frequency components can result in a reduction of the growth rate larger than the sum of that due to the two components when applied separately.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Demonstration of femtosecond laser ablation inductively coupled plasma mass spectrometry for uranium isotopic measurements in U-10Mo nuclear fuel foils

The use of femtosecond laser ablation inductively coupled plasma mass spectrometry was used to demonstrate the feasibility of measuring the isotopic ratio of uranium directly in U-10Mo fuel foils. The measurements were done on both the flat surface and cross sections of bare and Zr clad U-10Mo fuel foil samples. The results for the depleted uranium content measurements were less than 10% of the accepted U235/238 ratio of 0.0020. Sampling was demonstrated for line scans and elemental mapping over large areas. In addition to the U isotopic ratio measurement, the Zr thickness could be measured as well as trace elemental composition if required. A number of interesting features were observed during the feasibility measurements which could provide the basis for further investigation using this methodology. The results demonstrate the feasibility of using fs-LA-ICP-MS for measuring the U isotopic ratio in U-10Mo fuel foils.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

Trace metal analysis by laser ablation-inductively coupled plasmamass spectrometry and x-ray K-edge densitometry of forensic samples

This dissertation describes a variety of studies on the determination of trace elements in samples with forensic importance. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used to determine the trace element composition of numerous lipstick samples. Lipstick samples were determined to be homogeneous. Most lipstick samples of similar colors were readily distinguishable at a 95% confidence interval based on trace element composition. Numerous strands of a multi-strand speaker cable were analyzed by LA-ICP-MS. The strands in this study are spatially heterogeneous in trace element composition. In actual forensic applications, the possibility of spatial heterogeneity must be considered, especially in cases where only small samples (e.g., copper wire fragments after an explosion) are available. The effects of many unpredictable variables, such as weather, temperature, and human activity, on the retention of gunshot residue (GSR) around projectile wounds were assessed with LAICP- MS. Skin samples around gunshot and stab wounds and larvae feeding in and around the wounds on decomposing pig carcasses were analyzed for elements consistent with GSR (Sb, Pb, Ba, and Cu). These elements were detected at higher levels in skin and larvae samples around the gunshot wounds compared to the stab wounds for an extended period of time throughout decomposition in both a winter and summer study. After decomposition, radiographic images of the pig bones containing possible damage from bullets revealed metallic particles embedded within a number of bones. Metallic particles within the bones were analyzed with x-ray, K-edge densitometry and determined to contain lead, indicating that bullet residue can be retained throughout decomposition and detected within bones containing projectile trauma.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗