Plasma Physics and Controlled Nuclear Fusion Research (Summaries of the 10th IAEA International Conference, London, 12–19 September 1984)

Yoshikawa, M.; Pease, R. S.; Callen, J. D.; Witkowski, S.; Velikhov, E. P.

doi:10.1088/0029-5515/25/2/009

Cited by 43 publications

(68 citation statements)

References 6 publications

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“…The extreme ultraviolet (EUV) spectra of highly charged ions of high-Z elements are characteristic of hot plasmas and are of interest for their application to water-window sources [1], soft-x-ray laser development [2], fusion research [3], atomic spectroscopy [4] and plasma diagnostics [5]. Since early studies in the 1970s, many spectra at wavelengths longer than 7 nm have already been observed for most medium-Z and high-Z elements in laboratory and astrophysical plasmas [6][7][8][9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Analysis of extreme ultraviolet spectra from laser produced rhenium plasmas

Higashiguchi

et al. 2015

J. Phys. B: At. Mol. Opt. Phys.

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Extreme ultraviolet spectra of highly-charged rhenium ions were observed in the 1–7 nm region using two Nd:YAG lasers with pulse lengths of 150 ps and 10 ns, respectively, operating at a number of laser power densities. The maximum focused peak power density was 2.6 × 1014 W cm−2 for the former and 5.5 × 1012 W cm−2 for the latter. The Cowan suite of atomic structure codes and unresolved transition array (UTA) approach were used to calculate and interpret the emission properties of the different spectra obtained. The results show that n = 4-n = 4 and n = 4-n = 5 UTAs lead to two intense quasi-continuous emission bands in the 4.3–6.3 nm and 1.5–4.3 nm spectral regions. As a result of the different ion stage distributions in the plasmas induced by ps and ns laser irradiation the 1.5–4.3 nm UTA peak moves to shorter wavelength in the ps laser produced plasma spectra. For the ns spectrum, the most populated ion stage during the lifetime of this plasma that could be identified from the n = 4-n = 5 transitions was Re23+ while for the ps plasma the presence of significantly higher stages was demonstrated. For the n = 4-n = 4 4p64dN-4p54dN+1 + 4p64dN−14f transitions, the 4d-4f transitions contribute mainly in the most intense 4.7–5.5 nm region while the 4p-4d subgroup gives rise to a weaker feature in the 4.3–4.7 nm region. A number of previously unidentified spectral features produced by n = 4-n = 5 transitions in the spectra of Re XVI to Re XXXIX are identified.

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Section: Introductionmentioning

confidence: 99%

Analysis of extreme ultraviolet spectra from laser produced rhenium plasmas

Higashiguchi

et al. 2015

J. Phys. B: At. Mol. Opt. Phys.

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“…Research related to electron cyclotron heating (ECH) has recently been intensified for several types of plasma confinement devices because of the development of a high power microwave source (gyrotron) [1][2][3][4][5][6][7][8]. Plasmas produced by injecting microwaves near the electron cyclotron resonance (ECR, a?…”

Section: Introductionmentioning

confidence: 99%

Observation of hot electrons produced by second harmonic electron cyclotron heating in the axisymmetric tandem mirror GAMMA 10

et al. 1987

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Microwave power, P ECH < 140 kW, has been injected at 28 GHz into the axisymmetric plug/barrier cell in the axisymmetrized tandem mirror GAMMA 10. As observed by soft X-ray measurements, the microwaves generate a hot (50-60 keV) electron population, radially peaked on the magnetic axis, which results in the formation of a thermal barrier. The production mechanism of these hot electrons is found to be second harmonic electron cyclotron heating (ECH), corrected for the effects of the relativistic mass variation and the Doppler shift. This mechanism also explains the first experimental observation of a saturation of the single-component hot electron temperature T eh as being caused by the finite width of the incident microwave lobe. The dependence of the plasma parameters on the filling gas pressure, the plasma density and the ECH power is studied. It is found that the heating process can be interpreted as a competition between electron acceleration by the incident wave, electron deceleration by collisions, and the mirror trapping efficiency of the source electrons for hot electrons. The axial profile of the soft X-rays is investigated in relation to the mechanism of the second harmonic ECH. The heating process is discussed in terms of the electron pitch angle and the magnetic field intensity.

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“…In this case, the electron transit time r r rotating from the upper half plane to the lower one in the poloidal section should be smaller than the collision time T U , i.e. T T <T V (14) r r can be expressed in terms of the safety factor q as (15) where T e is in eV, while T J ,= 5.9Xl(T 9 T e 3/2 (16) Substituting Eqs ( 15) and ( 16) into Eq. ( 14), we obtain the condition for instability suppression as q < T | / 3 5 0…”

Section: Suppression Of the Macroinstability By Lh-driven Currentmentioning

confidence: 99%

“…Discharges, produced by injecting microwaves near the electron cyclotron resonance (ECR, co = I2 e ) are used effectively in many plasma confinement devices. In stellarators [13] and in heliotrons [14], a currentless plasma is produced by an ECR discharge. In tokamaks, pre-ionization by ECH is effective for reduction of the breakdown voltage in the initial stage of the discharge, where the volt-seconds of the transformer are saved and the production of runaway electrons is suppressed in WT-1 [15] and ISX-B [16].…”

Section: Introductionmentioning

confidence: 99%

Toroidal plasma production by electron cyclotron heating in the WT-2 device

Cho¹,

Ogura²,

Andõ³

et al. 1986

Nucl. Fusion

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By injecting microwave power (120 kW, 35.6 GHz) into the WT-2 device, a toroidal plasma is produced by electron cyclotron heating near the upper-hybrid resonance. (1) The production mechanism is interpreted as the result of damping of electron Bernstein waves and described by a ray-tracing code. (2) The production mechanism of high-energy electrons in such a plasma is studied and interpreted as a competition between electron acceleration by the incident wave and deceleration by collisions. These electrons interact resonantly with the lower hybrid wave during the startup of an RF tokamak discharge. (3) The first experimental observation, in an ECR plasma, of the resulting macroinstability, consistent with a theory suggested by Peng et al., is reported. (4) This instability is suppressed by the lower-hybrid driven current, the required rotational transform being produced by this current.

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Plasma Physics and Controlled Nuclear Fusion Research (Summaries of the 10th IAEA International Conference, London, 12–19 September 1984)

Cited by 43 publications

References 6 publications

Analysis of extreme ultraviolet spectra from laser produced rhenium plasmas

Analysis of extreme ultraviolet spectra from laser produced rhenium plasmas

Observation of hot electrons produced by second harmonic electron cyclotron heating in the axisymmetric tandem mirror GAMMA 10

Toroidal plasma production by electron cyclotron heating in the WT-2 device

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