Two wavelength laser interferometer for plasma diagnostics.
Plasma electron density measurement method using beat frequencies between two dual frequency lasers
ELECTRON DENSITY↗
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Plasma Assisted Combustion and Chemical Processing: Chapter 9 - Plasma Diagnostics
Plasma dynamics and chemistry have a broad range of timescales from picoseconds to milliseconds. In addition, it involves nonequilibrium energy transfer between electrons, ions, electronically and vibrationally excited states, radicals, intermediate species, and reactants and products as well as surface charges and chemistry. To understand plasma physics and chemistry, it is essential to conduct time and space resolved, quantitative detection of nonequilibrium temperature distributions, electron energy and number density, electric field, and species concentrations. There are enormous publications and review articles on this subject. The focus of this chapter is to be placed on the most recent progress in gas phase plasma properties and chemistry, especially on optical emission spectroscopy, laser absorption spectroscopy, Faraday rotational spectroscopy, Raman and Thompson scattering, femtosecond and picosecond (fs/ps) coherent anti-Stokes Raman scattering (CARS) spectroscopy, and electric field-induced second harmonic generation methods.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Basis set expansion for inverse problems in plasma diagnostic analysis
A basis set expansion method [V. Dribinski, A. Ossadtchi, V. A. Mandelshtam, and H. Reisler, Rev. Sci. Instrum. 73, 2634 (2002)] is applied to recover physical information about plasma radiation sources from instrument data, which has been forward transformed due to the nature of the measurement technique. This method provides a general approach for inverse problems, and we discuss two specific examples relevant to diagnosing fast z pinches on the 20–25 MA Z machine [M. E. Savage, L. F. Bennett, D. E. Bliss, W. T. Clark, R. S. Coats, J. M. Elizondo, K. R. LeChien, H. C. Harjes, J. M. Lehr, J. E. Maenchen, D. H. McDaniel, M. F. Pasik, T. D. Pointon, A. C. Owen, D. B. Seidel, D. L. Smith, B. S. Stoltzfus, K. W. Struve, W. A. Stygar, L. K. Warne, J. R. Woodworth, C. W. Mendel, K. R. Prestwich, R. W. Shoup, D. L. Johnson, J. P. Corley, K. C. Hodge, T. C. Wagoner, and P. E. Wakeland, in Proceedings of the Pulsed Power Plasma Sciences Conference (IEEE, 2007), p. 979]. First, Abel inversion of time-gated, self-emission x-ray images from a wire array implosion is studied. Second, we present an approach for unfolding neutron time-of-flight measurements from a deuterium gas puff z pinch to recover information about emission time history and energy distribution. Through these examples, we discuss how noise in the measured data limits the practical resolution of the inversion, and how the method handles discontinuities in the source function and artifacts in the projected image. We add to the method a propagation of errors calculation for estimating uncertainties in the inverted solution.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Fluorescence and absorption spectroscopy for warm dense matter studies and ICF plasma diagnostics
The burning core of an inertial confinement fusion (ICF) plasma produces bright x-rays at stagnation that can directly diagnose core conditions essential for comparison to simulations and understanding fusion yields. These x-rays also backlight the surrounding shell of warm, dense matter, whose properties are critical to understanding the efficacy of the inertial confinement and global morphology. In this work, we show that the absorption and fluorescence spectra of mid-Z impurities or dopants in the warm dense shell can reveal the optical depth, temperature, and density of the shell and help constrain models of warm, dense matter. This is illustrated by the example of a high-resolution spectrum collected from an ICF plasma with a beryllium shell containing native iron impurities. Lastly, analysis of the iron K-edge provides model-independent diagnostics of the shell density (2.3 × 10 24 e/cm 3 ) and temperature (10 eV), while a 12-eV red shift in Kβ and 5-eV blue shift in the K-edge discriminate among models of warm dense matter: Both shifts are well described by a self-consistent field model based on density functional theory but are not fully consistent with isolated-atom models using ad-hoc density effects.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Plasma diagnostics of a uranium plasma
Uranium plasma diagnostics, measuring emission and absorption coefficients as function of pressure and temperature
Campbell, H. D.↗
Talbot-Lau based Moiré deflectometry with non-coherent sources as potential High Energy Density plasma diagnostic
X-ray phase-contrast radiography could better characterize highly localized density gradients expected in High Energy Density (HED) plasma experiments than conventional attenuation radiography. In particular, the Talbot-Lau (TL) grating interferometer, which works with extended and polychromatic x-ray sources, is a potentially attractive HED diagnostic due to its high sensitivity. For HED characterization the TL setup and imaging techniques must be changed from the recently studied medical system. The object magnification must be increased greatly in order to resolve μm scale gradients while the Talbot magnification must be increased in order to keep the gratings away from the plasma. Additionally, techniques for retrieving the density profile from a single plasma image must be developed. We thus study the performance of high magnification TL interferometers, in conjunction with Moiré fringe deflectometry for single image phase retrieval. The results show a very good interferometer contrast (≤30%) at high magnification. The Moiré technique enables measuring both sharp and mild density gradients with good accuracy and spatial resolution. Both the laboratory and simulation studies indicate that the TL based Moiré deflectometry is more sensitive than the propagation phase-contrast method when utilizing an extended x-ray source (∼80 μm). In HED experiments this would allow for less demanding X-ray backlighters than those used at present.
36 MATERIALS SCIENCE↗
Spacelab 2 Plasma Diagnostics Package
The Plasma Diagnostics Package is a small, deployable satellite designed to study the interaction of the Space Shuttle Orbiter with the ionospheric environment as well as to be used in joint experiments with the plasma depletion and the vehicle charging and potential investigations during the Spacelab 2 mission. This paper provides a brief description of the small spacecraft, its instrumentation and operation, and the scientific objectives of the investigations. A brief summary of the scientific results obtained thus far is also presented.
Kurth, W. S.↗
Proposed framework for applying squeezed light to multi-photon absorption plasma diagnostics
We propose a quantum-enhanced plasma diagnostic based on squeezed states of light. Squeezed light can exhibit super-Poissonian photon statistics, leading to enhanced multiphoton absorption cross-sections compared to classical light. This effect enables improved sensitivity for two-photon excitation of high-energy atomic transitions such as ground-state excitation, and results in increased absorbed power and fluorescence in a plasma. We consider two methods of generating squeezed states and evaluate their advantages and limitations in the context of plasma absorption diagnostics. By comparing with and extending previous theoretical work, we predict an enhancement of the absorption signal by up to seven orders of magnitude at low intensities (10 1 W/m 2 ), with diminishing enhancement persisting up to high intensities (10 10 W/m 2 ). These results suggest that squeezed-light sources offer a viable pathway toward quantum-enhanced plasma diagnostics.
imaging↗
Structured light approaches in laser-based plasma diagnostics
There is a growing demand for plasma diagnostics suitable for industrial plasma reactors employed in semiconductor nanofabrication, especially relevant to microelectronics and quantum information systems. Such reactors typically have limited optical access and pose considerable diagnostic challenges, including intense background emission, significant thermal loads, and contamination of optical viewports. In this study, we outline research into structured light techniques (laser beams with tailored spatial, temporal, or phase characteristics) that effectively overcome these issues using laser-induced fluorescence (LIF) as an example. The focus of presented diagnostics is on ion kinetics analysis within an industrial plasma source, although this approach is broadly applicable to other plasma systems and diagnostic contexts. We present a confocal LIF implementation using an axicon-generated Bessel annular beam, achieving spatial resolutions of approximately 5 mm at a focal distance of 300 mm, with potential improvements to about 1 mm. This approach matches conventional orthogonal LIF performance but requires only one optical port. Wavelength-modulation LIF employs nonlinear laser wavelength tuning to measure spectral line derivatives, suppressing background emission and enhancing details of spectral line shape. Additionally, we present new results on applying vortex beams (laser beams carrying orbital angular momentum, OAM) for LIF measurements in an industrial plasma device. These measurements enable simultaneous axial and tangential velocity determination using a single laser beam and have been tested with xenon ion transition. Initial quantification of results was performed. Together, these structured-light approaches provide robust, background-resilient, multi-dimensional diagnostics for complex plasma environments.
Romadanov, Ivan [Princeton Plasma Physics Laborato↗
Influence of electron injection into 27 cm audio plasma cell on the plasma diagnostics
In this article, the plasma is created in a Pyrex tube (L = 27 cm, φ= 4 cm) as a single cell, by a capacitive audio frequency (AF) discharge (f = 10–100 kHz), at a definite pressure of ∼0.2 Torr. A couple of tube linear and deviating arrangements show plasma characteristic conformity. The applied AF plasma and the injection of electrons into two gas mediums Ar and N{sub 2} revealed the increase of electron density at distinct tube regions by one order to attain 10{sup 13}/cm{sup 3}. The electrons temperature and density strengths are in contrast to each other. While their distributions differ along the plasma tube length, they show a decaying sinusoidal shape where their peaks position varies by the gas type. The electrons injection moderates electron temperature and expands their density. The later highest peak holds for the N{sub 2} gas, at electrons injection it changes to hold for the Ar. The sinusoidal decaying density behavior generates electric fields depending on the gas used and independent of tube geometry. The effect of the injected electrons performs a responsive impact on electrons density not attributed to the gas discharge. Analytical tools investigate the interaction of the plasma, the discharge current, and the gas used on the electrodes. It points to the emigration of atoms from each one but for greater majority they behave to a preferred direction. Meanwhile, only in the linear regime, small percentage of atoms still moves in reverse direction. Traces of gas atoms revealed on both electrodes due to sheath regions denote lack of their participation in the discharge current. In addition, atoms travel from one electrode to the other by overcoming the sheaths regions occurring transportation of particles agglomeration from one electrode to the other. The electrons injection has contributed to increase the plasma electron density peaks. These electrons populations have raised the generated electrostatic fields assisting the elemental ions emigration to a preferred electrode direction. Regardless of plasma electrodes positions and plasma shape, ions can be departed from one electrode to deposit on the other one. In consequence, as an application the AF plasma type can enhance the metal deposition from one electrode to the other.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Recoverable Plasma Diagnostics Package (RPDP)
The recoverable plasma diagnostics package (RPDP) is an ejectable and recoverable satellite with flight and ground support systems so that it can be utilized in three modes: attached to an remote manipulator system; tethered; or as a subsatellite. The satellite is well instrumented with particle and field diagnostic as well as optical sensors to: investigate the dynamics of the natural environment or ejected perturbations from particle beams; measure the characteristics and propagation of electrostatic and electromagnetic waves; study wave particle interactions; and study natural properties of the magnetosphere, ionosphere, and upper atmosphere.
Roberts, W. T.↗
Recoverable Plasma Diagnostics Package (RPDP)
The recoverable plasma diagnostics package (RPDP) is an ejectable and recoverable satellite with flight and ground support systems so that it can be utilized in three modes: attached to an remote manipulator system; tethered; or as a subsatellite. The satellite is well instrumented with particle and field diagnostic as well as optical sensors to: investigate the dynamics of the natural environment or ejected perturbations from particle beams; measure the characteristics and propagation of electrostatic and electromagnetic waves; study wave particle interactions; and study natural properties of the magnetosphere, ionosphere, and upper atmosphere.
Roberts, B.↗
Interpretation of plasma diagnostics package results in terms of large space structure plasma interactions
The Plasma Diagnostics Package (PDP) is a spacecraft which was designed and built at The University of Iowa and which contained several scientific instruments. These instruments were used for measuring Space Shuttle Orbiter environmental parameters and plasma parameters. The PDP flew on two Space Shuttle flights. The first flight of the PDP was on Space Shuttle Mission STS-3 and was a part of the NASA/Office of Space Science payload (OSS-1). The second flight of the PDP was on Space Shuttle Mission STS/51F and was a part of Spacelab 2. The interpretation of both the OSS-1 and Spacelab 2 PDP results in terms of large space structure plasma interactions is emphasized.
Kurth, William S.↗
Additive Manufacture of Plasma Diagnostic Components Final Report Phase II
There is now a well-established set of plasma diagnostics (see e.g. [3]), but these remain some of the most expensive assemblies in fusion systems since for every system they have to be custom built, and time for diagnostic development can pace the project. Additive manufacturing (AM) has the potential to decrease production cost and significantly lower design time of fusion diagnostic subsystems, which would realize significant cost reduction for standard diagnostics. In some cases, these basic components can be additively manufactured for less than 1/100th costs of conventional manufacturing.In our DOE Phase II SBIR, we examined the impact that AM can have on plasma diagnostic cost by taking 15 separate diagnostics through an engineering design using Conventional Manufacturing (CM) techniques, then optimizing the design to exploit the benefits of AM. The impact of AM techniques on cost is found to be in several areas. First, the cost of materials falls because AM parts can be manufactured with little to no waste, and engineered to use less material than CM. Next, the cost of fabrication falls for AM parts relative to CM since the fabrication time can be computed exactly, and often no post-processing is required for the part to be functional. We find that AM techniques are well suited for plasma diagnostics since typical diagnostic complexity comes at no additional cost. Cooling channels, for example, can be builtin to plasma-facing components at no extra cost. Fabrication costs associated with assembly are lower for AM parts because many components can be combined and printed as monoliths, thereby mitigating the need for alignment or calibration. Finally, the cost of engineering is impacted by exploiting AM design tools that allow standard components to be customized through web-interfaces. Furthermore, we find that concept design costs can be impacted by scripting interfaces for online engineering design tools.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
STS-3/OSS-1 Plasma Diagnostics Package (PDP) measurements of the temperature pressure and plasma
Designed to withstand the thermal extremes of the STS-3 mission through the use of heaters and thermal blankets, the plasma diagnostics package sat on the release/engagement mechanism on the OSS-1 payload pallet without a coldplate and was attached to the RMS for two extended periods. Plots show temperature versus mission elapsed time for two temperature sensors. Pressure in the range of 10 to the -3 power torr and 10 to the -7 power torr, measured 3 inches from the skin of the package is plotted against GMT during the mission. The most distinctive feature of the pressure profile is the modulation at the obit period. It was found that pressure peaks when the atmospheric gas is rammed into the cargo bay. Electric and magnetic noise spectra and time variability due to orbiter systems, UHF and S-band transmitter field strengths, and measurements of the ion spectra obtained both in the cargo bay and during experiments are plotted.
Shawhan, S. D.↗
Investigation of plasma diagnostics using a dual frequency harmonic technique
Plasma diagnostic methods using harmonic currents analysis of electrostatic probes were experimentally investigated to understand the differences in their measurement of the plasma parameters. When dual frequency voltage (ω{sub 1},ω{sub 2}) was applied to a probe, various harmonic currents (ω{sub 1}, 2ω{sub 1},ω{sub 2}, 2ω{sub 2},ω{sub 2}±ω{sub 1},ω{sub 2}±2ω{sub 1}) were generated due to the non-linearity of the probe sheath. The electron temperature can be obtained from the ratio of the two harmonics of the probe currents. According to the combinations of the two harmonics, the sensitivities in the measurement of the electron temperature differed, and this results in a difference of the electron temperature. From experiments and simulation, it is shown that this difference is caused by the systematic and random noise.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
High-power terahertz optically pumped NH{sub 3} laser for plasma diagnostics
The parameter of a terahertz (THz) laser intended for plasma diagnostics in electrodynamic accelerators and tokamaks with a strong magnetic field are discussed. Generation of THz radiation in an ammonia laser under the action of high-power pulsed optical pumping by the radiation of a 10P(32) CO{sub 2} laser is simulated numerically. The main characteristics of the output radiation, such as its spectrum, peak intensity, time dependence, and total energy, are calculated.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Description of the plasma diagnostics package (PDP) for the OSS-1 Shuttle mission and JSC plasma chamber test in conjunction with the fast pulse electron gun (FPEG)
The objectives, equipment, and techniques for the plasma diagnostics package (PDP) carried by the OSS-1 instrument payload of the STS-4 and scheduled for the Spacelab-2 mission are described. The goals of the first flight were to examine the Orbiter-magnetoplasma interactions by measuring the electric and magnetic field strengths, the ionized particle wakes, and the generated waves. The RMS was employed to lift the unit out of the bay in order to allow characterization of the fields, EM interference, and plasma contamination within 15 m of the Orbiter. The PDP will also be used to examine plasma depletion, chemical reaction rates, waves, and energized plasma produced by firing of the Orbiter thrusters. Operation of the PDP was carried out in the NASA Space Environment Simulation Laboratory test chamber, where the PDP was used to assay the fields, fluxes, wave amplitudes, and particle energy spectra. The PDP instrumentation is also capable of detecting thermal ions, thermal electrons suprathermal particles, VHF/UHF EMI levels, and the S-band field strength.
Shawhan, S. D.↗