Effect of the two-close-frequency heating to the extracted ion beam and to the X-ray flux emitted by the ECR plasma

Rácz, R.; Biri, S.; Perduk, Z.; Pálinkás, J.; Mazzaglia, M.; Naselli, E.; Torrisi, G.; Castro, G.; Cellona, L.; Gammino, S.; Galatà, A.

doi:10.1088/1748-0221/13/12/c12012

Cited by 20 publications

(14 citation statements)

References 16 publications

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“…The definition of I S was consistent with the direct observation of the SA-recorded spectrum, increasing steadily with power, as expected. Details of correlations with other parameters (CSD, soft and hard volumetric x-ray measurements) and time-resolved x-ray data are provided in [15]. The twodimensional space-resolved measurements regarding an x-ray pin-hole camera to study the plasma structure and intensities of electron losses have already been analyzed and will be subsequently reported in a dedicated paper in the near future.…”

Section: Resultsmentioning

confidence: 99%

Impact of two-close-frequency heating on ECR ion source plasma radio emission and stability

Naselli

Mazzaglia

Biri

et al. 2019

Plasma Sources Sci. Technol.

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Experiments have recently demonstrated that kinetic instabilities occurring in magnetoplasma are huge limiting factors to the flux of highly charged ion beams extracted from ECR ion sources. Recently, it has been shown that the two-frequency-heating (TFH) mode has the proven potential to mitigate these instabilities. Since the fundamental physical mechanism of TFH is still unclear, a deeper experimental investigation is necessary. At ATOMKI-Debrecen, the effect on the kinetic instabilities of an argon plasma in a 'two-close-frequency heating' scheme has been explored for the first time by using a frequency gap smaller than 1 GHz (i.e. operating in the so-called twoclosed-frequency heating mode). A special multi-diagnostics setup has been designed and implemented. In this paper, we will show the data collected by a two-pin, plasma-chamber immersed antenna connected to an RF detector diode and/or to a spectrum analyzer for the detection of plasma radio-self-emission when varying the pumping frequency in single versus double frequency heating mode. Data have been collected simultaneously to the beam extraction and for different frequency gaps and relative power balances. The turbulent regime of the plasma has been tentatively described in a quantitative way, according to the properties of the plasma self-emitted RF spectrum. The measurements show that plasma self-emitted radiation emerges from the internal ECR region everytime (i.e. below the lower pumping frequency) but the almost total instability damping can be effective for some specific combinations of frequency-gap and power balance, thus eventually improving the plasma confinement. Keywords: electron cyclotron resonance ion source, plasma diagnostics, kinetic plasma instability 'scaling laws' [1]. More recently, this approach has become more difficult because of the technological limits. A deeper knowledge of plasma parameters (electron density, temperature and charge state distribution (CSD)) is thus fundamental: the characteristics of the extracted beam (in terms of current intensity and production of high charge states) are directly connected to plasma parameters and structure. Several experiments have, in fact, demonstrated that plasma instabilities limit the flux of highly charged ions extracted from ECR ion sources, causing beam ripple [2][3][4]. The

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Section: Resultsmentioning

confidence: 99%

Impact of two-close-frequency heating on ECR ion source plasma radio emission and stability

Naselli

Mazzaglia

Biri

et al. 2019

Plasma Sources Sci. Technol.

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“…In this system, the pin-hole camera was operated up to 200 W of total incident power in the plasma-namely, one order of magnitude higher than previous measurements (where the pumping power was limited to 30 W [17,18]). In this way, both stable and turbulent plasma regimes (typically triggered above certain power thresholds [29,30]) were investigated [31], as well as new plasma heating methods [32][33][34]. To allow for SPhC-based, quantitative, space-resolved spectral analysis, the ATOMKI plasma chamber walls were covered by thin layers of materials with different X-ray fluorescence energies, whilst the plasma was made by Ar, with a fluorescence emission at around 2.96 keV.…”

Section: The Experimental Setupmentioning

confidence: 99%

Innovative Analytical Method for X-ray Imaging and Space-Resolved Spectroscopy of ECR Plasmas

et al. 2021

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At the Italian National Institute for Nuclear Physics-Southern National Laboratory (INFN-LNS), and in collaboration with the ATOMKI laboratories, an innovative multi-diagnostic system with advanced analytical methods has been designed and implemented. This is based on several detectors and techniques (Optical Emission Spectroscopy, RF systems, interfero-polarimetry, X-ray detectors), and here we focus on high-resolution, spatially resolved X-ray spectroscopy, performed by means of a X-ray pin-hole camera setup operating in the 0.5–20 keV energy domain. The diagnostic system was installed at a 14 GHz Electron Cyclotron Resonance (ECR) ion source (ATOMKI, Debrecen), enabling high-precision, X-ray, spectrally resolved imaging of ECR plasmas heated by hundreds of Watts. The achieved spatial and energy resolutions were 0.5 mm and 300 eV at 8 keV, respectively. Here, we present the innovative analysis algorithm that we properly developed to obtain Single Photon-Counted (SPhC) images providing the local plasma-emitted spectrum in a High-Dynamic-Range (HDR) mode, by distinguishing fluorescence lines of the materials of the plasma chamber (Ti, Ta) from plasma (Ar). This method allows for a quantitative characterization of warm electrons population in the plasma (and its 2D distribution), which are the most important for ionization, and to estimate local plasma density and spectral temperatures. The developed post-processing analysis is also able to remove the readout noise that is often observable at very low exposure times (msec). The setup is now being updated, including fast shutters and trigger systems to allow simultaneous space and time-resolved plasma spectroscopy during transients, stable and turbulent regimes.

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“…By this system the pin-hole camera was operated up to 200 W total incident power in the plasma, namely one order of magnitude higher compared to the previous measurements (where the pumping power was limited to 30 W [20,21]). This way, both stable and turbulent plasma regimes (typically triggered above certain power thresholds [28,29]) have been investigated [30,31], also studying new plasma heating methods [32,33]. In order to allow SPhC-based quantitative space resolved spectral analysis, the The sketch of the ATOMKI plasma chamber is illustrated in the Figure 1a (on the right).…”

Section: The Experimental Setupmentioning

confidence: 99%

Innovative Analytical Method for X-Ray Imaging and Space-Resolved Spectroscopy of ECR Plasmas

Naselli¹,

Rácz²,

Biri³

et al. 2021

Preprint

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At INFN-LNS, and in collaboration with the ATOMKI laboratories, an innovative multi-diagnostic system with advanced analytical methods has been designed and implemented. This is based on several detectors and techniques (Optical Emission Spectroscopy, RF systems, Interfero-polarimetry, X-ray detectors) and here we focus on high resolution spatially-resolved X-ray spectroscopy, performed by means of a X-ray pin-hole camera setup operating in the 0.5−20 keV energy domain. The diagnostic system was installed at a 14 GHz Electron Cyclotron Resonance (ECR) ion source (ATOMKI, Debrecen), enabling high precision X-ray spectrally-resolved imaging of ECR plasmas heated by hundreds of Watts. The achieved spatial and energy resolution were 0.5 mm and 300 eV at 8 keV, respectively. We here present the innovative analysis algorithm that we properly developed for obtaining Single Photon-Counted (SPhC) images providing the local plasma emitted spectrum in a High-Dynamic-Range (HDR) mode, by distinguishing fluorescence lines of the materials of the plasma chamber (Ti, Ta) from plasma (Ar). This method allows a quantitative characterization of warm electrons population in the plasma (and its 2D distribution) which are the most important for ionization, and also to estimate local plasma density and spectral temperatures. The developed post-processing analysis is also able to remove the readout noise, that is often observable at very low exposure times (msec). The setup is now under update including fast shutters and trigger systems in order to allow simultaneously space and time-resolved plasma spectroscopy during transients, stable and turbulent regimes.

show abstract

Effect of the two-close-frequency heating to the extracted ion beam and to the X-ray flux emitted by the ECR plasma

Cited by 20 publications

References 16 publications

Impact of two-close-frequency heating on ECR ion source plasma radio emission and stability

Impact of two-close-frequency heating on ECR ion source plasma radio emission and stability

Innovative Analytical Method for X-ray Imaging and Space-Resolved Spectroscopy of ECR Plasmas

Innovative Analytical Method for X-Ray Imaging and Space-Resolved Spectroscopy of ECR Plasmas

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