Theory of foil-absorption techniques for plasma X-ray continuum measurements

Donaldson, T. P.

doi:10.1088/0032-1028/20/12/005

Cited by 35 publications

(20 citation statements)

References 10 publications

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“…7 The measured SXR emissivity and brightness f, along the lineof-sight L, due to bremsstrahlung radiation in the plasma are given by…”

Section: Methodsmentioning

confidence: 99%

“…8 between the ratio and the temperature is a polynomial function whose coefficients can be found by modeling the bremsstrahlung radiation for many plasma temperatures. 3,7 Simulations explore the temperature measuring capabilities of the diagnostic upgrade using both the direct brightness and tomographic emissivity techniques. Simulated emissivity due to bremsstrahlung radiation from a model plasma with a characteristic profile T e ͑r͒ is combined with the diagnostic geometry to create a model brightness profile.…”

Section: Methodsmentioning

confidence: 99%

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A new double-foil soft x-ray array to measure Te on the MST reversed field pinch

McGarry

Franz

Hartog

et al. 2010

Review of Scientific Instruments

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A soft x-ray (SXR) diagnostic to measure electron temperature on the Madison Symmetric Torus using two complementary methods is presented. Both methods are based on the double-foil technique, which calculates electron temperature via the ratio of SXR bremsstrahlung emission from the plasma in two different energy ranges. The tomographic emissivity method applies the double-foil technique to a tomographic reconstruction of SXR emissivity, creating a two-dimensional map of temperature throughout the plasma. In contrast, the direct brightness method applies the double-foil technique directly to the measured brightness and generates vertical and horizontal radial profiles. Extensive modeling demonstrates advantages and limitations in both techniques. For example, although the emissivity technique provides a two-dimensional mapping of temperature, its reliance on multiple tomographic inversions introduces some artifacts into the results. On the other hand, the more direct brightness technique avoids these artifacts but is only able to provide a radial profile of electron temperature.

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“…7 The measured SXR emissivity and brightness f, along the lineof-sight L, due to bremsstrahlung radiation in the plasma are given by…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

A new double-foil soft x-ray array to measure Te on the MST reversed field pinch

McGarry

Franz

Hartog

et al. 2010

Review of Scientific Instruments

View full text Add to dashboard Cite

show abstract

“…Two sets of polynomial coefficient for the ranges 0.1-1.0 and 1.0-10 of variable x are of interest for the present case of analysis. 35 For the former range the polynomial coefficients are a 1 = 1.319 and a 2 = 0.140, whereas for the latter range they are a 1 = 0.995 and a 2 = 0.018. In order to have an estimate of the electron temperature, we try a set of arbitrary signal ratios along with cutoff energies for these foils.…”

Section: Evaluation Of Plasma Electron Temperaturementioning

confidence: 98%

“…Donaldson 35 made a theoretical analysis of foil absorption technique. His analysis determines the method of selecting appropriate foil parameters in order to minimize the measurement errors.…”

Section: Evaluation Of Plasma Electron Temperaturementioning

confidence: 99%

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Effect of insulator sleeve material on the x-ray emission from a plasma focus device

et al. 2010

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The effect of insulator sleeve material on x-ray emission from a 2.3 kJ Mather type plasma focus device operated in argon-hydrogen mixture is investigated. The time and space resolved x-ray emission characteristics are studied by using a three channel p-i-n diode x-ray spectrometer and a multipinhole camera. The x-ray emission depends on the volumetric ratio of argon-hydrogen mixture as well as the filling pressure and the highest x-ray emission is observed for a volumetric ratio 40% Ar to 60% H 2 at 2.5 mbar filling pressure. The fused silica insulator sleeve produces the highest x-ray emission whereas nonceramic insulator sleeves such as nylon, Perspex, or Teflon does not produce focus or x-rays. The pinhole images of the x-ray emitting zones reveal that the contribution of the Cu K␣ line is weak and plasma x-rays are intense. The highest plasma electron temperature is estimated to be 3.3 and 3.6 keV for Pyrex glass and fused silica insulator sleeves, respectively. It is speculated that the higher surface resistivity of fused silica is responsible for enhanced x-ray emission and plasma electron temperature.

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Plasmas at High Temperature and Density

Hora¹

1991

Lecture Notes in Physics Monographs

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Preface"New physics" is an appealing new keyword, not yet devalued by the ravages of inflation. But what has this to do with such an ugly field as plasma physics, steeped in classical physics, mostly outworn, with all its unsolved and ambiguous technological problems and its messy and open ended numerical studies?"New physics" is concerned with quarks, Higgs particles, grand unified theory, superstrings, gravitational waves, and the profound basics of cosmology and black holes. It is the field of astonishing quantum effects, demonstrated by the von Klitzing effect and hightemperature superconductors. But what can plasma physicists offer, after so many years of expensive and frustrating research to solve the problem of fusion energy?One may suggest that the fascinating research of chaos with applications to plasma, or the achievements of statistical mechanics applied to plasmas, has something to offer and should be the subject of attention. However, this is not the aim of this book.Complementing the traditional aim of physics, which is to interpret the phenomena of nature by generalizing laws such that exact predictions about new properties and effects can be drawn, this book demonstrates how new physics has been derived over the last 30 years from the state of matter which exists at high temperatures (plasma). The advent of the laser, with its very high energy densities and its concentration to extremely small volumes and to very short time periods, opened up a whole new regime for the interaction of materials and high-density plasmas, which enforced the appearance of the "rather new physics".Here are a few examples:• Who would have expected that optical waves in vacuum have a longitudinal component? Thomas Young discovered in 1801 the pure transversality of optical radiation. This was not understandable at that time, when it was known that mechanical waves never exist without longitudinal components. Maxwell's equation then only revealed solutions of the purely transverse plane waves in electromagnetism. Against all this traditional knowledge, the recent findings about the dynamics of electrons driven by laser beams by nonlinear forces led to thẽ xact derivation of longitudinal optical wave components.• The same nonlinear force interaction, in view of momentum transfer in experiments, led to the clarification of the angular momentum ofoptical beams and brought about the first substantiation of the photon spin by a macroscopic property.• The conditions of very high laser intensities led to nonlinear and relativistic generalization of the optical response (dielectrics and absorption) with a prediction of relativistic self-focusing to understand how GeV ions are produced by laser irradiation of solid targets.• The quantum generalization of Coulomb collisions in plasmas at high temperatures explains the anomalous resistivity, in agreement with observations where links are given between the simply derived Coulomb collision frequency and quantum electrodynamics, including stimulated emission. IX that after the first l...

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Theory of foil-absorption techniques for plasma X-ray continuum measurements

Cited by 35 publications

References 10 publications

A new double-foil soft x-ray array to measure Te on the MST reversed field pinch

A new double-foil soft x-ray array to measure Te on the MST reversed field pinch

Effect of insulator sleeve material on the x-ray emission from a plasma focus device

Plasmas at High Temperature and Density

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