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Thomas, C. E.

Publications and source records attributed to Thomas, C. E..

10 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Recent Developments in Dual-Laser Digital Holography for Plasma-Facing Surface Characterization

A digital holography device is currently undergoing development at the Oak Ridge National Laboratory for the purpose of measuring surface topography, with the goal of deployment as a real-time plasma-facing component diagnostic for the study of materials that could be utilized in a nuclear fusion device. The holography system utilizes one or two lasers depending on the scale of surface features under measurement. Measurements of surface roughness were performed in a single-laser mode and compared with the data from profilometry, with a linear correlation of increased holographic measurement fidelity as surfaces became smoother. Characterization of the dual-laser operating mode has been performed via surface measurement of stainless steel targets with ``stair-step'' features in various sizes. Results demonstrated that surface features with known sizes as small as 25.4 μm could be resolved. Measurements were within ~55 μm or less deviation from the actual sizes, and measurement accuracy was improved as feature size was increased, corresponding to the effect of noise becoming less pronounced. In conclusion, a target exposed to plasma generated by an electrothermal (ET) arc source was analyzed with flat-field correction and averaging of sequential image frames to demonstrate the improved measurement quality in preparation for future use of holography on ET arc-exposed targets.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Dual laser holography for in situ measurement of plasma facing component erosion (invited)

A digital holography (DH) surface erosion/deposition diagnostic is being developed for 3D imaging of plasma facing component surfaces in situ and in real time. Digital holography is a technique that utilizes lasers reflected from a material surface to form an interferogram, which carries information about the topology of the surface when reconstructed. As described, dual CO 2 lasers at 9.271 and 9.250 μm wavelengths illuminate the interrogated surface (at a distance of ~1 m) in a region of ~1 cm × 1 cm. The surface feature resolution is ~0.1 mm in the plane of the surface, and the depth resolution ranges from ~0.0001 to ~2 mm perpendicular to the surface. The depth resolution lower limit is set by single-laser and detector optical limitations, while the upper limit is determined by 2π phase ambiguity of the dual-laser synthetic wavelength. Measurements have been made “on the bench” to characterize the single-laser and dual-laser DH configurations utilizing standard resolution targets and material targets that were previously exposed to high flux plasmas in either the Prototype Material Plasma Exposure eXperiment (Proto-MPEX) or the electro-thermal (ET) arc source. Typical DH measurements were made with 0.03 ms integration with an IR camera that can be framed at rates approaching 1.5 kHz. Finally, the DH diagnostic system is progressing toward in situ measurements of plasma erosion/deposition either on Proto-MPEX or the ET arc source.

47 OTHER INSTRUMENTATION↗
DOE OSTI2014

Digital Holography for in Situ Real-Time Measurement of Plasma-Facing-Component Erosion

In situ, real time measurement of net plasma-facing-component (PFC) erosion/deposition in a real plasma device is challenging due to the need for good spatial and temporal resolution, sufficient sensitivity, and immunity to fringe-jump errors. Design of a high-sensitivity, potentially high-speed, dual-wavelength CO2 laser digital holography system (nominally immune to fringe jumps) for PFC erosion measurement is discussed.

Thomas, C. E.↗
NASA NTRS1978

Ozone damage detection in cantaloupe plants

Ozone causes up to 90 percent of air pollution injury to vegetation in the United States; excess ozone affects plant growth and development and can cause undetected decrease in yields. Laboratory and field reflectance measurements showed that ozone-damaged cantaloupe (Cucumis melo L.) leaves had lower water contents and higher reflectance than did nondamaged leaves. Cantaloupe plants which were lightly, severely, and very severely ozone-damaged were distinguishable from nondamaged plants by reflectance measurements in the 1.35- to 2.5 micron near-infrared water absorption waveband. Ozone-damaged leaf areas were detected photographically 16 h before the damage was visible. Sensors are available for use with aircraft and spacecraft that possibly could be used routinely to detect ozone-damaged crops.

Gausman, H. W.↗
NASA NTRS1978

Using reflectance and photography to detect ozone damage to cantaloupe plants

Laboratory and field reflectance measurements showed that ozone-damaged cantaloupe (Cucumis melo L.) leaves had lower water contents and higher reflectance than nondamaged leaves. Cantaloupe plants with lightly, severely, and very severely ozone-damaged leaves were distinguishable from nondamaged plants by reflectance measurements in the 1.35-2.5-micron near-IR water absorption band. Ozone-damaged leaf areas were detected photographically 16 hours before the damage was visible.

Gausman, H. W.↗
NASA NTRS1974

Rechargeable, silver-zinc battery conditioner/monitor unit and state-of-charge indicator

Unit automatically charges batteries to desired state-of-charge levels, monitors functional battery parameter data both on meters and printer, and automatically activates alarm in event of battery malfunctions. Unit consists of state-of-charge indicator panel, control panel, monitor panel, power panel, charging-current power supply, and load panel.

Thomas, C. E.↗