Low energy x-ray emission from magnetic fusion plasmas

Hill, K. W.; Bitter, M.; Eames, D.; Goeler, S. von; Sauthoff, N.

doi:10.1063/1.33150

Cited by 7 publications

(5 citation statements)

References 84 publications

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“…In addition to Ref. [ 11 ], a number of other useful summaries are available [105][106][107]. The K a lines of different ionization stages of intermediate-Z elements are shifted slightly from one another, for example by about 40 eV for Fe XVIII-Fe XXV [108].…”

Section: Impurity Identificationmentioning

confidence: 99%

“…Transitions from capture into n .= 4 and higher levels are even closer to the centre of w and their intensities are deduced from theoretical calculations in order to subtract their contributions. L-spectra of iron (n = 3 -*• n = 2 transitions) in the region from 5 to 25 A have been studied with a rotating-crystal spectrometer [105,107]. An example is shown in Fig.…”

Section: Fig17 K Spectrum Of CL Xvi From Alcatormentioning

confidence: 99%

“…These K a features are actually blends of unresolved lines from all the ionization stages. Total concentrations of metallic ions are often measured from PHA systems that have been absolutely calibrated, but accurate analysis requires some knowledge of the charge state distribution since the Is -*• 2p excitation coefficients are not the same for every stage [105]. The signal-to-background ratio for PHA data is not as favourable as it is for high-resolution spectroscopic methods, and,as is obvious from Fig.…”

Section: Fig17 K Spectrum Of CL Xvi From Alcatormentioning

confidence: 99%

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Impurities in tokamaks

Isler

1984

Nucl. Fusion

181

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Impurities continue to be a concern for future fusion devices, and ongoing efforts are made to study their generation, confinement, and control. Techniques for analysis of concentrations, power losses, and confinement of impurities are surveyed, and experimental examples illustrating typical observations in tokamak plasmas are presented. The use of impurities for diagnosing plasma properties is outlined briefly.

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Section: Impurity Identificationmentioning

confidence: 99%

Section: Fig17 K Spectrum Of CL Xvi From Alcatormentioning

confidence: 99%

Section: Fig17 K Spectrum Of CL Xvi From Alcatormentioning

confidence: 99%

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Impurities in tokamaks

Isler

1984

Nucl. Fusion

181

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“…which can be detrimental to the plasma [15]. Transmission electron microscopy suggests that the nanoscale tendrils of the fuzz contain gas bubbles and/or cavities [16], which implies that bubble evolution is an important process in fuzz formation in tungsten.…”

Section: Introductionmentioning

confidence: 99%

Tungsten surface evolution by helium bubble nucleation, growth and rupture

et al. 2013

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Molecular dynamics simulations reveal sub-surface mechanisms likely involved in the initial formation of nanometre-sized ‘fuzz’ in tungsten exposed to low-energy helium plasmas. Helium clusters grow to over-pressurized bubbles as a result of repeated cycles of helium absorption and Frenkel pair formation. The self-interstitials either reach the surface as isolated adatoms or trap at the bubble periphery before organizing into prismatic 〈1 1 1〉 dislocation loops. Surface roughening occurs as single adatoms migrate to the surface, prismatic loops glide to the surface to form adatom islands, and ultimately as over-pressurized gas bubbles burst.

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“…Impurity radiation can be a major source of power loss in tokamaks and can induce or exacerbate instabilities (e.g. by altering current profiles) or otherwise detract from achieving favourable fusion plasma parameters [1,2] (e.g. by depletion of the fuel ion density).…”

Section: Introductionmentioning

confidence: 99%

Studies of impurity behaviour in TFTR

et al. 1986

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Central medium and low Z impurity concentrations and Zeff have been measured by X-ray spectrometry in Tokamak Fusion Test Reactor discharges during three periods of operation. These were (1) startup period, (2) Ohmic heating, and (3) Ohmic heating portion of the two neutral beam periods, distinguished mainly by different vacuum vessel internal hardware and increasing plasma current and toroidal field capability. Plasma parameters spanned minor radius a = 0.41−0.83 m, major radius R = 2.1−3.1 m, current Ip = 0.25−2.0 MA, line averaged electron density n̄e = (0.9–4.0) × 1019 m−3, and toroidal magnetic field BT = 1.8−4.0 T. The metal impurities came mostly from the limiter. At low densities titanium or nickel approached 1% of ne during operation on a TiC-coated graphite or Inconel limiter, respectively. Lower levels of Cr, Fe, and Ni (⪅0.1%) were observed with a graphite limiter at similarly low densities; these elements were removed mainly from stainless steel or Inconel hardware within the vacuum vessel during pulse discharge cleaning or plasma operation on an Inconel limiter and then deposited on the graphite limiter. Hardware closest to the plasma contributed most to the deposits. Subsequent discharges slowly eroded the deposits from the limiter and reduced the metal impurity levels in the plasma. Both total low Z and metal impurity concentrations, relative to ne, decreased approximately exponentially with ne and increased with Ip. The metals showed much larger variations than did low Z elements, dropping to ≳10−5 ne at high density. Low Z impurities, mainly carbon and oxygen, ranged from 10% of ne at low ne to 3% at high ne and usually dominated Zeff and power loss. In low density plasmas with a TiC-coated graphite or Inconel limiter, the respective metals contributed 30–50% of Zeff and ⪅10–20% of the central input power. The metal contributions to Zeff and radiated power were much lower with the graphite limiter.

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Low energy x-ray emission from magnetic fusion plasmas

Cited by 7 publications

References 84 publications

Impurities in tokamaks

Impurities in tokamaks

Tungsten surface evolution by helium bubble nucleation, growth and rupture

Studies of impurity behaviour in TFTR

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