Plasma density estimation of a fusion grade ICP source through electrical parameters of the RF generator circuit

Bandyopadhyay, M.; Sudhir, Dass; Chakraborty, Arun

doi:10.1088/0029-5515/55/3/033017

Cited by 12 publications

(9 citation statements)

References 39 publications

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“…The knowledge of driver impedance variation could provide beneficial information about the features of the generated plasma like the estimation of electron density [11]. It is also a key parameter for the estimation of power transfer efficiency to the plasma inside the driver of SPIDER [10,12] and, in perspective, for producing a more accurate design of matching networks, which can allow achieving improvements in the power transfer to the plasma.…”

Section: Introductionmentioning

confidence: 99%

Investigation of RF driver equivalent impedance in the inductively coupled SPIDER ion source

Jain¹,

Recchia²,

Maistrello³

et al. 2022

Plasma Phys. Control. Fusion

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SPIDER experiment includes an RF inductively coupled plasma source working at 0.3 Pa of gas pressure (H/D) where plasma is generated and heated by 8 RF drivers, fed by 4 RFcircuits. A single RF circuit is composed of 2 drivers connected in series, attached to a capacitive matching network, fed by 200 kW 1 MHz RF oscillator through a coaxial transmission line. The knowledge of driver impedance in different experimental conditions is a valuable window for knowing the characteristics of generated plasma. Direct measurement of driver impedance in SPIDER is not possible, it has been estimated via the development of a suitable electrical model of the RF circuit using as input, measurements at the oscillator’s output. The paper reports on the progress in the model of the SPIDER RF circuit and discusses a procedure to estimate the driver impedance exploiting also the recently available experimental measurements from the dual directional coupler. The impedance obtained with this approach, derived from measurements obtained in a recent SPIDER campaign, is reported for various operating conditions such as RF power, gas pressure, Plasma Grid current, Cesium injection rate, type of gas (Hydrogen and Deuterium), etc.

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Section: Introductionmentioning

confidence: 99%

Investigation of RF driver equivalent impedance in the inductively coupled SPIDER ion source

Jain¹,

Recchia²,

Maistrello³

et al. 2022

Plasma Phys. Control. Fusion

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“…Another interesting technique used to derive the plasma electron density was first discussed and developed by Bandyopadhyay et al in [15]. It is based on the transformer model in an inductively coupled plasma, where the RF coil is considered as a primary of the transformer and the plasma can be considered as the one-turn secondary of an air-core transformer.…”

Section: Alternative Model (Am)mentioning

confidence: 99%

“…In this approach, the plasma electron density is determined at the plasma sheath; then; using suitable conversions like edge to center density ratios, the uniform electron density is obtained in the plasma region. The second approach is given by Bandyopadhyay et al [15], where the plasma electron density is determined in the skin-depth region. This approach is based on the classical plasma conductivity [14,16] and skindepth models [17].…”

Section: Introductionmentioning

confidence: 99%

Use of electrical measurements for non-invasive estimation of plasma electron density in the inductively coupled SPIDER ion source

Jain¹,

Recchia²,

Sartori³

et al. 2023

Plasma Phys. Control. Fusion

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SPIDER is the full-scale prototype of the ITER Neutral Beam Injector ion source. The plasma heating takes place inside eight drivers via inductive coupling, through the radio frequency (RF) coil. To achieve the optimum conditions during source operation it is necessary to know the plasma behaviour under various operational conditions. One of the essential parameter, is the plasma electron density. It is possible to experimentally measure this parameter, and currently, different methods are being explored, like the estimations coming from the Langmuir probe and optical emission spectroscopy. However, these methods are either available for temporary measurements or require dedicated analyses with large uncertainties. In this perspective, an alternative, reliable, and fast diagnostic tools will be beneficial for the estimation of the order of magnitude of electron density inside the driver. Two models for the estimation of electron density are recalled, discussed, and further modified in this work: one is based on the classical power balance equation and the other is recently described in the literature and relies on classical plasma conductivity. Both models use equivalent electrical parameters of the driver derived from available electrical measurements at the output of the RF generator and through the knowledge of the matching network and the transmission line length. This work explicitly focuses on the application of these models to estimate the plasma electron density in a single driver of SPIDER. Furthermore, the estimations are compared with the first experimental results obtained from temporary electrostatic probe measurements and are found to be in good agreement in terms of magnitude and trends.

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“…For INTF beam source plasma characterization, two non-invasive diagnostics: optical emission spectroscopy (OES) and CRDS are envisaged. However, different standard electrical measurements in the RF and HV circuits [16] are also utilized to monitor the ion source performance. Plasma in the extraction zone which is near the plasma grid is crucial to optimize the extracted beam performance.…”

Section: Ion Source Diagnosticsmentioning

confidence: 99%

Performance evaluation of various diagnostics developed for a negative ion based neutral beam injector program in IPR

Bandyopadhyay¹,

Deka²,

Mukhopadhyay³

et al. 2019

Nucl. Fusion

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The characteristics of a negative hydrogen ion (H-) source and its neutralization efficiency determine the performance of a negative ion based neutral beam injector (NNBI). Therefore, for the safe operation of an NNBI system, it is necessary to monitor the performance of the ion source and its beam through a systematic characterization process. A judicious selection of different diagnostics based on electrical, optical and thermal types and including calorimetric techniques are required. In this regard, a number of diagnostics are being developed under the NNBI R&D program in the Indian Test Facility (INTF). These diagnostics are versatile in nature in terms of their working principles and independent prototype experimental efforts have been carried out to establish them and prepare them for operational use. Electrical probes (EP), optical emission spectroscopy and cavity ring down spectroscopy (CRDS) are mainly envisaged for ion source plasma characterization. Additionally, standard electrical measurements in RF and DC power supply circuits are already in regular use in the operational experimental setups, ROBIN and HELEN-I, for monitoring the power supplies. Doppler shift spectroscopy (DSS) and optical emission tomography (TOMO) are developed for beam characterization in terms of divergence, stripping and beam profile. Some of these are characterized on separate prototype experiments and are already integrated and have been tested in the available operational plasma experimental setups: ROBIN and HELEN-I. The DSS system, with multiple lines of sight (LOS) (blue-shifted and red-shifted), is integrated in the ROBIN setup and CRDS is arranged in HELEN-I. The TOMO technique is used to find the beam power density profile from the hydrogen beam emitted Balmer line intensity. The optical brightness profile of a neutral beam due to beam emission radiation is proportional to the beam power density. In this regard, a tomography code based on maximum entropy is developed to reconstruct the 2D optical emissivity profile of the INTF beam by inverting the LOS integral of the brightness of the beam. The code has been validated with the simulated INTF beam power density profile, in terms of the mathematical functions representing it. In the present manuscript, the performance evaluations of these diagnostics are presented.

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Plasma density estimation of a fusion grade ICP source through electrical parameters of the RF generator circuit

Cited by 12 publications

References 39 publications

Investigation of RF driver equivalent impedance in the inductively coupled SPIDER ion source

Investigation of RF driver equivalent impedance in the inductively coupled SPIDER ion source

Use of electrical measurements for non-invasive estimation of plasma electron density in the inductively coupled SPIDER ion source

Performance evaluation of various diagnostics developed for a negative ion based neutral beam injector program in IPR

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