Assessment of the SPIDER beam features by diagnostic calorimetry and thermography

Pimazzoni, A.; Brombin, M.; Canocchi, Gloria; Delogu, R.; Fasolo, D.; Franchin, L.; Laterza, B.; Pasqualotto, R.; Serianni, G.; Tollin, M.

doi:10.1063/1.5128562

Cited by 22 publications

(23 citation statements)

References 8 publications

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“…4, right). Similar values of the beamlet divergence, down to 20-30mrad 27 , were estimated by the various beam diagnostics and the same dependency on the extraction voltage was found.…”

Section: Iib Source and Beam Characterisationsupporting

confidence: 78%

“…The SPIDER beam features can be studied by means of several diagnostic systems: apart from the electrical measurements provided by the power supplies, dedicated diagnostics include visible cameras (constituting the first set of cameras of the beam tomographic system 26 ), beam emission spectroscopy and the Short-Time Retractable Instrumented KalorimEter (STRIKE) 27 ; an emittance scanner is also under preparation 28,29 . The electrical measurement of the beam current at the accelerator power supply and the electrical current collected by STRIKE (located at 0.7m from the grounded grid) were found to be comparable and to increase with the extraction voltage (Fig.…”

Section: Iib Source and Beam Characterisationmentioning

confidence: 99%

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First operation in SPIDER and the path to complete MITICA

Serianni

Toigo

Bigi

et al. 2020

Review of Scientific Instruments

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The requirements of ITER neutral beam injectors (1 MeV, 40 A negative deuterium ion current for 1 h) have never been simultaneously attained; therefore, a dedicated Neutral Beam Test Facility (NBTF) was set up at Consorzio RFX (Padova, Italy). The NBTF includes two experiments: SPIDER (Source for the Production of Ions of Deuterium Extracted from Rf plasma), the full-scale prototype of the source of ITER injectors, with a 100 keV accelerator, to investigate and optimize the properties of the ion source; and MITICA, the full-scale prototype of the entire injector, devoted to the issues related to the accelerator, including voltage holding at low gas pressure. The present paper gives an account of the status of the procurements, of the timeline, and of the voltage holding tests and experiments for MITICA. As for SPIDER, the first year of operation is described, regarding the solution of some issues connected with the radiofrequency power, the source operation, and the characterization of the first negative ion beam.

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“…4, right). Similar values of the beamlet divergence, down to 20-30mrad 27 , were estimated by the various beam diagnostics and the same dependency on the extraction voltage was found.…”

Section: Iib Source and Beam Characterisationsupporting

confidence: 78%

Section: Iib Source and Beam Characterisationmentioning

confidence: 99%

First operation in SPIDER and the path to complete MITICA

Serianni

Toigo

Bigi

et al. 2020

Review of Scientific Instruments

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“…In the present conditions the electron current density je can be approximated as the ratio between the EGPS current and the total area of the active PG apertures. To estimate the H -/Dcurrent density jH -jD, the beam current was estimated as the APGS current, multiplied by a factor 0.4; this correction coefficient was estimated by a comparison of beam electric and calorimetric measurements, to measure the effective amount of negative ions in the beam [29]. In absolute terms, the measurements of H -/Ddensity in Figure 6 are more than a factor 2 higher than the similar measurements shown in Figure 5 for psource=0.3 Pa (and higher RF power).…”

Section: Resultsmentioning

confidence: 99%

Negative ion density in the ion source SPIDER in Cs free conditions

Barbisan¹,

Agnello²,

Casati³

et al. 2022

Plasma Phys. Control. Fusion

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The SPIDER experiment, operated at the Neutral Beam Test Facility of Consorzio RFX, Padua, hosts the prototype of the H-/D- ion source for the ITER neutral beam injectors. The maximization of the ion current extracted from the source and the minimization of the amount of co-extracted electrons are among the most relevant targets to accomplish. The Cavity Ring-Down Spectroscopy diagnostic measures the negative ion density in the source close to the plasma grid (the plasma-facing grid of the ion acceleration system), so to identify the source operational parameters that maximize the amount of negative ions which can be extracted. In this study SPIDER was operated in hydrogen and deuterium in Cs-free conditions, therefore negative ions were mostly produced by reactions in the plasma volume. This work shows how the magnetic filter field and the bias currents, present in SPIDER to limit the amount of co-extracted electrons, affect the density of negative ions available for extraction. The results indicate that the magnetic filter field in front of the acceleration system should be set between about 1.6 mT, condition that maximizes the density of available negative ions, and about 3.2 mT, condition that minimizes the ratio of electron current to ion current. The negative ion density also resulted to be maximized when the plasma grid and its surrounding bias plate was positively biased against the source body with a total current in the range 0 A÷100 A. The paper shows also how much, in Cs-free conditions, the electric fields in the acceleration system can affect the density of negative ions in the source, close to the plasma grid apertures.

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“…The power supplies for extraction and acceleration gaps, ISEG and AGPS respectively, measure two currents, which are interpreted as the sum of extracted negative ions and co-extracted electrons for the ISEG power supply, and as extracted negative ions and a part of electrons for the AGPS power supply. The extracted negative ion current is estimated starting from the calorimetric evaluation on STRIKE calorimeter [13,14], and corresponds to about 75% of the AGPS current. The co-extracted electron current is obtained by subtracting the extracted negative ion current from the ISEG current.…”

Section: Methodsmentioning

confidence: 99%

Plasma emission monitored via optical emission spectroscopy during the Cs conditioning at SPIDER

Mario,

Zaniol,

Serianni

et al. 2023

J. Inst.

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The SPIDER test facility is the full-size ITER neutral beam injector (NBI) ion source, required to provide 355 A/m2 extracted negative ion current density in hydrogen (285 A/m2 in deuterium) with an electron-to-ion ratio lower than 0.5 (one in deuterium). The negative ion source is attached to a three-grids extraction and acceleration system. The operational conditions for the cases presented in this work involve short pulses (up to about 30 s length) repeated every five to six minutes. The duty cycle can be adjusted. In order to fulfil the requirement on the extracted negative ion current with reduced amount of co-extracted electrons, the evaporation of caesium into the ion source through Cs ovens (three in SPIDER) and the optimisation of Cs conditioning techniques are mandatory. At SPIDER, the plasma is monitored via optical emission spectroscopy techniques measuring the plasma emission in a line-of-sight (LOS) integrated manner in several positions inside the ion source. In particular, close to the extraction region, two sets (centred at 5 mm and at 35 mm distance from the plasma grid) of four horizontal LOSs are used to retrieve the vertical profile of the plasma emission. During the Cs conditioning campaign performed at SPIDER, although the extraction capabilities were reduced due to technical problems, the RF power coupled to the plasma reached 400 kW with all four RF generators working simultaneously. The negative ions produced by surface emission affects the plasma radiation, and the ion source performances in terms of extracted negative ions and co-extracted electrons. The aim of this work is to study the evolution of the plasma emission over the initial phase of the Cs conditioning campaign. The effect of Cs conditioning on the extracted negative ions and electrons is also presented and discussed.

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Assessment of the SPIDER beam features by diagnostic calorimetry and thermography

Cited by 22 publications

References 8 publications

First operation in SPIDER and the path to complete MITICA

First operation in SPIDER and the path to complete MITICA

Negative ion density in the ion source SPIDER in Cs free conditions

Plasma emission monitored via optical emission spectroscopy during the Cs conditioning at SPIDER

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