Helicon wave-generated plasmas for negative ion beams for fusion

Furno, I.; Agnello, R.; Fantz, U.; Howling, A.A.; Jacquier, R.; Marini, C.; Plyushchev, G.; Guittienne, Ph.; Simonin, A.

doi:10.1051/epjconf/201715703014

Cited by 30 publications

(34 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…RAID is a linear plasma device developed at the Swiss Plasma Center of Ecole Polytechnique Fédérale de Lausanne for negative ion studies for fusion (Marini et al 2017;Agnello et al 2018) and for basic plasma physics investigations (Furno et al 2017). A schematic of the RAID main components is shown in figure 1.…”

Section: Implementation Of Thomson Scattering Diagnostic On Raidmentioning

confidence: 99%

Application of Thomson scattering to helicon plasma sources

et al. 2020

View full text Add to dashboard Cite

The possibility of performing electron density and temperature measurements in a high power helicon plasma is a crucial issue in the framework of the AWAKE (Advanced WAKefield Experiment) project, which demonstrates acceleration of particles using $\text{GeV}~\text{m}^{-1}$ electric fields in plasmas. For AWAKE, a helicon is currently envisaged as a candidate plasma source due to its capability for low electron and ion temperature, high electron density and production of an elongated plasma column. A plasma diagnostic to accurately determine the electron density in AWAKE regimes would be a valuable supporting tool. A demonstration Thomson scattering (TS) diagnostic was installed and successfully tested on the resonant antenna ion device (RAID) at the Swiss Plasma Center of Ecole Polytechnique Fédérale de Lausanne. RAID produces a helicon plasma column with characteristics similar to those of the AWAKE helicon source, and is therefore an optimal testbed for application to the AWAKE device. The spectrometer employed in RAID is based on polychromators which collect the light scattered by plasma electrons in spectrally filtered wavelength regions. Results from TS on RAID demonstrate conditions of electron density and temperature respectively of $n_{e}=1.10\,(\pm 0.19)\times 10^{19}~\text{m}^{-3}$ and $T_{e}=2.3\,(\pm 0.6)~\text{eV}$ in a steady-state discharge in an Ar plasma with 5 kW of RF power. If the same polychromator system is used for AWAKE, where the electron density attained is $2\times 10^{20}~\text{m}^{-3}$ , the contribution to measurement error due to coherent scattering is ${\sim}2.5\,\%$ . Presented here are details of the TS diagnostic and the first tests in RAID, and the expectations for the system when employed on the AWAKE device.

show abstract

Section: Implementation Of Thomson Scattering Diagnostic On Raidmentioning

confidence: 99%

Application of Thomson scattering to helicon plasma sources

et al. 2020

View full text Add to dashboard Cite

show abstract

“…Balmer lines. OES is a widely used plasma diagnostic technique for the measurement of plasma parameters such as electron density, electron temperature [6,7] etc. This is then allowed to fall on the detector through a dispersive medium and wavelength resolved intensity profile is recorded.…”

Section: Optical Emission Spectroscopy (Oes)mentioning

confidence: 99%

Characterization of hydrogen plasma in a permanent ring magnet based helicon plasma source for negative ion source research

Pandey¹,

Mukherjee²,

Bandyopadhyay³

et al. 2019

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

HELicon Experiment for Negative ion source (HELEN-I) with single driver is developed with a focus on the production of negative hydrogen ions. In the Helicon wave heated plasmas, very high plasma densities (~10 !" !! ) can be attained with electron temperatures as low as ~ 1 eV in the downstream region. These conditions favor the production of negative hydrogen ions. In HELEN-I device at IPR, helicon plasma is produced using Hydrogen gas in a diverging magnetic field, created by a permanent ring magnet. RF Power (P RF ) of 800-1000W at 13.56 MHz frequency is applied to a Nagoya-III antenna to excite m = 1 helicon mode in the plasma. The plasma is confined by a multi-cusp field configuration in the expansion chamber. The transition from inductively coupled mode to Helicon mode is observed near P RF ~ 700W with plasma density ~ 10 18 m -3 and electron temperature ~ 5 eV in the driver and ~ 1eV in the expansion volume. Line integrated negative hydrogen ion density is measured in the expansion chamber by employing an Optical Emission Spectroscopy (OES) diagnostic technique using ! / ! ratio and Laser photo-detachment based Cavity Ring Down spectroscopic (CRDS) diagnostic technique. The measured value of negative hydrogen ion density is in the order of 10 16 m -3 at 6 mTorr pressure and does not vary significantly with power in the helicon mode, pressure and downstream axial magnetic field variation. The negative ion density measurements are compared with theoretically estimated values calculated using particle balance method considering different reaction rates responsible for negative hydrogen ion creation and destruction. It is to be noted that at present Caesium (Cs) is not injected in the plasma discharge to enhance ! ion density.In surface process, H-ion are produced on a low work-function surface due to surface conversion of energetic H atoms (H 0 * ) or hydrogen ions (H n + ) in the plasma [9];

show abstract

“…Research performed in the Resonant Antenna Ion Device (RAID) [8] at the Swiss Plasma Center aims at broadening the current knowledge of the physics of volume production of negative hydrogen and deuterium ions in helicon plasmas, which has been explored, apart from RAID, to the best of our knowledge, only in a few helicon plasma devices [9,10]. The possible integration of such a source, if able to reach the RAMI and efficiency requirements compatible for future NBIs, requires considerable experimental, numerical and technical development.…”

Section: Introductionmentioning

confidence: 99%

Negative ion characterization in a helicon plasma source for fusion neutral beams by cavity ring-down spectroscopy and Langmuir probe laser photodetachment

et al. 2019

View full text Add to dashboard Cite

Negative ions are characterized in the helicon plasma source RAID (Resonant Antenna Ion Device) at the Swiss Plasma Center by means of Cavity Ring-Down Spectroscopy (CRDS) and Langmuir Probe (LP)-assisted laser photodetachment. A high density and axially homogeneous plasma column is produced via a RF antenna able to sustain the propagation of helicon waves in a steady state regime. An electron density n e ∼ = 2.0 × 10 18 m −3 in H 2 plasma at 0.3 Pa and 3 kW of input power is measured in the center of the plasma column by LP and microwave interferometry. The electron temperature profile is peaked on axis reaching T e ≈ 5 eV and decreasing to 1.5 eV at r = 0.05 m. Thus, a hot core region forms where H 2 molecules are rovibrationally excited (H 2 (ν)), and a cold edge, where low energy electrons can attach to H 2 (ν) and produce H − ions by dissociative attachment. In this work we use LP-assisted laser photodetachment and CRDS diagnostics to measure H − and D − radial density profiles and how they depend on source parameters. We show that negative ions are distributed on a shell of 0.06 m radius with a peak value of ∼ 2.0 × 10 16 m −3 in H 2 plasma. These results suggest that, although substantial technical development is needed, helicon plasmas could be considered as a possible candidate as sources of negative ions for future NBIs.

show abstract

Helicon wave-generated plasmas for negative ion beams for fusion

Cited by 30 publications

References 10 publications

Application of Thomson scattering to helicon plasma sources

Application of Thomson scattering to helicon plasma sources

Characterization of hydrogen plasma in a permanent ring magnet based helicon plasma source for negative ion source research

Negative ion characterization in a helicon plasma source for fusion neutral beams by cavity ring-down spectroscopy and Langmuir probe laser photodetachment

Contact Info

Product

Resources

About