Self-consistent modelling of overdense plasmas in ECR discharges

Hemmers, D.; Kempkens, H; Uhlenbusch, J.

doi:10.1088/0022-3727/31/17/013

Cited by 10 publications

(11 citation statements)

References 19 publications

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“…There are two possible reasons to be considered. First, the assumption of a Maxwellian EEDF might not apply because at least at very low pressures (0.02 Pa, 0.05 Pa) and high power (4800 W) results from Thomson scattering show the existence of overthermal electrons at energy states above 10 eV [12]. However, at the pressure of 0.5 Pa the characteristic time of thermalization (τ ee ∼ T 3/2 e /n e ) is considerably smaller than at low pressure due to larger electron density and lower temperature so that we expect possible deviations of the EEDF from a Maxwellian to be rather small.…”

Section: Resultsmentioning

confidence: 99%

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Comparative measurement of electron density and temperature profiles in low-temperature ECR discharges by a lithium atom beam and Thomson scattering

Beck¹,

Hemmers²,

Kempkens³

et al. 2000

J. Phys. D: Appl. Phys.

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In this paper a method to determine spatially-resolved profiles of the electron temperature T e and density n e in an electron-cyclotron-resonance (ECR) discharge is presented. This technique is based on the observation of line emission from a neutral Li atom beam, which is injected into the plasma and excited by electron collisions. A collisional-radiative model valid for the injected Li atoms is used to predict the emission intensities as function of n e and T e for several lines theoretically. In contrast to the electron temperature regime representative for the edge of tokamak discharges (T e > 5 eV), the ECR discharge offers a T e range where selected line intensity ratios strongly depend on the electron temperature. Therefore, a comparison of the measured ratios with the calculated ones yields T e profiles for the first time. The n e measurement is performed as in tokamaks by observing the attenuation of the beam due to ionization in the plasma. We present radial profiles of T e and n e for discharges in argon and xenon under different operating conditions. These results are compared with results obtained by Thomson scattering. Our measurements give evidence for a satisfying agreement between the two methods.

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Section: Resultsmentioning

confidence: 99%

“…A detailed description of the experimental set-up of the investigated ECR plasma source can be found in [10]. The cylindrical discharge vessel (length 1.6 m, diameter 180 mm) is immersed in a static magnetic mirror field.…”

Section: Experimental Set-upmentioning

confidence: 99%

Comparative measurement of electron density and temperature profiles in low-temperature ECR discharges by a lithium atom beam and Thomson scattering

Beck¹,

Hemmers²,

Kempkens³

et al. 2000

J. Phys. D: Appl. Phys.

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“…Two 0.2 µm aluminum foils located at the entrance aperture of the spectrometer block the intense visible radiation. The transmitted XUV emission [26] is imaged by a nickel-coated toroidal mirror onto the CCD camera. A transmission grating consisting of freestanding gold bars with 1000 lines mm −1 is used to disperse the XUV radiation.…”

Section: Methodsmentioning

confidence: 99%

Generation of 10μW relativistic surface high-harmonic radiation at a repetition rate of 10 Hz

et al. 2012

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Experimental results on relativistic surface HHG at a repetition rate of 10 Hz are presented. Average powers in the 10 µW range are generated in the spectral range of 51 to 26 nm (24-48 eV). The surface harmonic radiation is produced by focusing the second-harmonic of a high-power laser onto a rotating glass surface to moderately relativistic intensities of 3 × 10 19 W cm −2 . The harmonic emission exhibits a divergence of 26 mrad. Together with absolute photon numbers recorded by a calibrated spectrometer, this allows for the determination of the extreme ultraviolet (XUV) yield. The pulse energies of individual harmonics are reaching up to the µJ level, equivalent to an efficiency of 10 −5 . The capability of producing stable and intense high-harmonic radiation from relativistic surface plasmas may facilitate experiments on nonlinear ionization or the seeding of free-electron lasers.

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“…At the opposite end to the VINETA device the ECR heating setup is installed. Microwaves were previously used on linear magnetized devices as plasma sources [11,12,13,14]. The goal is a direct coupling of the microwave electric field to the electron gyro motion which allows resonant energy transfer to the plasma electrons.…”

Section: Experimental Setup and Diagnosticmentioning

confidence: 99%

ECR Heating in a Helicon Device

Zalach

Grulke

Klinger

2006

AIP Conference Proceedings

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Abstract. This paper presents a microwave electron cyclotron resonance heating system for the linear magnetized VINETA helicon device. Thereby, a relatively cold helicon wave generated plasma is heated by resonant electron cyclotron waves. The magnetic field configuration is adjusted such that resonant energy transfer occurs locally to heat the plasma electrons. Electron temperatures of 12 eV are obtained for an Argon plasma at a pressure of 0.02 Pa. The absorption of the microwave across the resonance layer is measured with capacitive probes. Plasma parameters are characterized using compensated Langmuir probes. Additionally, a 160 GHz microwave interferometer is used to measure the line integrated plasma density. The evolution of these quantities for different microwave powers is compared to power balance computations, which indicate that the applied microwave power is dissipated by the ionization collisions; after saturation of ionization processes the power is transferred into electron kinetic energy.

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Self-consistent modelling of overdense plasmas in ECR discharges

Cited by 10 publications

References 19 publications

Comparative measurement of electron density and temperature profiles in low-temperature ECR discharges by a lithium atom beam and Thomson scattering

Comparative measurement of electron density and temperature profiles in low-temperature ECR discharges by a lithium atom beam and Thomson scattering

Generation of 10μW relativistic surface high-harmonic radiation at a repetition rate of 10 Hz

ECR Heating in a Helicon Device

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