First tests and commissioning of the emittance scanner for SPIDER

Poggi, C.; Berton, G.; Brombin, M.; Agostini, F. Degli; Fasolo, D.; Franchin, L.; Laterza, B.; Pasqualotto, R.; Ravarotto, D.; Sartori, E.; Taliercio, C.; Tollin, M.; Serianni, G.

doi:10.1016/j.fusengdes.2021.112659

Cited by 9 publications

(4 citation statements)

References 13 publications

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“…At present, the beam source is operated in pulsed mode and it is equipped with a number of beam diagnostics and source diagnostics (see [21] and references therein). The diagnostic calorimeter STRIKE [22], beam emission spectroscopy (BES) [23], optical cameras, Allison emittance scanner [24], single-beamlet current monitors (new diagnostics based on LEM sensors) provide independent measurements of the beam properties, while Langmuir probes [25], optical emission spectroscopy [26], cavity ring down spectroscopy [27], laser absorption spectroscopy [28], Langmuir-Tayor detectors [29] can provide insight on the plasma and surface processes inside the plasma source.…”

Section: Experimental Configuration Of Spider and Operation With Caesiummentioning

confidence: 99%

First operations with caesium of the negative ion source SPIDER

Sartori¹,

Agostini²,

Barbisan³

et al. 2022

Nucl. Fusion

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The negative-ion based neutral beam injector for heating and current drive of the ITER plasma (ITER HNB) is under development, at present focusing on the optimization of the full-scale plasma source in the SPIDER test stand. The production of H- or D- ions in the ion source is based on the low work function surfaces obtained by caesium evaporation. This paper describes the caesium conditioning procedure and the corresponding beam performances during the first operation of SPIDER with caesium. Technical solutions to overcome present limitations of the test stand are described. The influence of source parameters on the caesium effectiveness was investigated in short beam pulse operation; with total RF power of 400 kW and filling pressure below 0.4 Pa, and a limited number of extraction apertures, a negative ion current density of about 200 A/m2 was extracted in hydrogen, with beam energy lower than 60 keV. Beam optics and beam uniformity were assessed thanks to the acceleration of isolated ion beamlets. A possible procedure to accelerate a uniform beam was demonstrated at low RF power. The results obtained in this first investigation provided key indications on the operation of one of the largest existing sources of accelerated negative hydrogen-like ions.

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Section: Experimental Configuration Of Spider and Operation With Caesiummentioning

confidence: 99%

First operations with caesium of the negative ion source SPIDER

Sartori¹,

Agostini²,

Barbisan³

et al. 2022

Nucl. Fusion

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“…The angular velocity distribution of an isolated beamlet simultaneously measured by the Allison emittance scanner [35] (AES-left column) and the beam emission spectroscopy [36] (BES-right column) is shown in Fig. 10 for the previously mentioned plasma pulses.…”

Section: Beam Halo and Operation With Deuteriummentioning

confidence: 99%

SPIDER, the Negative Ion Source Prototype for ITER: Overview of Operations and Cesium Injection

Serianni¹,

Sartori²,

Agnello³

et al. 2023

IEEE Trans. Plasma Sci.

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“…This is essential to quantify, from the accelerated beamlets, the non-uniformity of the extracted current. For the complete characterization of the beam optics in the phase space, the design and prototyping of many "beamlet plugs" was carried out to allow the isolation of a few beamlets by closing surrounding apertures of the plasma grid: with this configuration, to be applied only to a limited number of beamlets, it will be possible to continue the single-beamlet optics study via IR calorimetry and the emittance scanner [14], for the optimization -2 -…”

Section: Jinst 18 C09001 2 Measurement Of the Beam Currentmentioning

confidence: 99%

Highlights of recent SPIDER results and improvements

Sartori,

Agnello,

Agostini

et al. 2023

J. Inst.

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Three years of experiments on SPIDER allowed characterization of the main features of the source plasma and of the negative ion beam, in the original design configuration. For the large dimensions of the source chamber, and of the extraction area, the investigation of the single-beamlet currents and of the source plasma uniformity had to be carried out to extend the knowledge gained in smaller prototype sources. The configuration of the multiple RF drivers and filter field topologies were found to cause a peculiar behavior in the plasma confinement in the drivers, creating left-right asymmetries which were also visible in the extracted negative ion currents, even after the early implementation of a new scheme of plasma-grid current send and return busbars that greatly improved performance at high filter fields. The plasma properties in the driver and expansion region as well as the positive ion energy at the extraction region were studied in different experimental conditions, and interpreted also with the support of numerical models, suggesting that an improved plasma confinement could contribute to the increase of the plasma density, and to a certain extent to a lowering of the plasma potential profile; both effects shall contribute to increase the presence of cold negative ions for the formation of low-divergence beamlets. Early results related to unwanted RF discharges on the back of the plasma source and the gas conductance of the beam source suggested the reduction of the vessel pressure as mitigation, leading to the definition of a new pumping system. The difficulties related to the simultaneous operation, stable control and high-power operation of multiple RF self-oscillating vacuum tube based RF generators were an unambiguous obstruction to the experimentation, calling for the implementation of RF solid-state amplifiers. The initial tests related to caesium management, the non-uniform plasma properties at different locations across the plasma grid, and the challenges in the measurement of the current and divergence of the accelerated beamlet, unambiguously resulted in the need of new diagnostic systems to investigate with better resolution the spatial uniformities. This contribution summarises how the main experimental findings in the previous experimental campaigns are driving modifications to the SPIDER experiment, during the present shut down, in view of future operations.

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First tests and commissioning of the emittance scanner for SPIDER

Cited by 9 publications

References 13 publications

First operations with caesium of the negative ion source SPIDER

First operations with caesium of the negative ion source SPIDER

SPIDER, the Negative Ion Source Prototype for ITER: Overview of Operations and Cesium Injection

Highlights of recent SPIDER results and improvements

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