We present the development and first use of a set of movable electrostatic probes on the full-scale ITER heating neutral beam prototype negative-ion source SPIDER. The probes access the ion source plasma from the multi-aperture accelerator aiming at the study of the plasma formation and expansion from the RF drivers through the transverse magnetic filter. The magnetic filter separates the relatively high electron-temperature region for plasma formation and hydrogen dissociation form the negative-ion extraction region in which low electron-temperature is required to avoid negative-ion destruction, but also causes non-uniformities and drifts in the large plasma discharge which will be studied by this setup. The set of electrostatic probes encompasses eight RF-compensated Langmuir probes, one double probe, one Mach probe for the assessment of plasma drift velocities, and two gridded retarding field energy analyzers to measure the positive-ion energy distribution function. Electric aspects as well as mechanical constraints given by the large in-vacuum movable structure, and thermal requirements of these relatively heat-flux components made the design challenging. Prototyping and commissioning of the measurement system is discussed offering examples of measured characteristics with the various probes.

Development of a set of movable electrostatic probes to characterize the plasma in the ITER neutral beam negative-ion source prototype

Sartori E.
;
Zuin M.;Fadone M.;Jain P.;Kisaki M.;Maistrello A.;Moro G.;Pimazzoni A.;Poggi C.;Segalini B.;Tollin M.;Ugoletti M.;Veltri P.;Serianni G.
2021

Abstract

We present the development and first use of a set of movable electrostatic probes on the full-scale ITER heating neutral beam prototype negative-ion source SPIDER. The probes access the ion source plasma from the multi-aperture accelerator aiming at the study of the plasma formation and expansion from the RF drivers through the transverse magnetic filter. The magnetic filter separates the relatively high electron-temperature region for plasma formation and hydrogen dissociation form the negative-ion extraction region in which low electron-temperature is required to avoid negative-ion destruction, but also causes non-uniformities and drifts in the large plasma discharge which will be studied by this setup. The set of electrostatic probes encompasses eight RF-compensated Langmuir probes, one double probe, one Mach probe for the assessment of plasma drift velocities, and two gridded retarding field energy analyzers to measure the positive-ion energy distribution function. Electric aspects as well as mechanical constraints given by the large in-vacuum movable structure, and thermal requirements of these relatively heat-flux components made the design challenging. Prototyping and commissioning of the measurement system is discussed offering examples of measured characteristics with the various probes.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/3388686
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