Beam and installation improvements of the NIO1 ion source

Cavenago, M.; Barbisan, M.; Delogu, R.; Pimazzoni, A.; Poggi, C.; Ugoletti, M.; Agostini, M.; Antoni, V.; Baltador, C.; Cervaro, V.; Muri, M. De; Giora, D.; Jain, Palak; Laterza, B.; Maero, G.; Maniero, M.; Martini, D.; Minarello, A.; Ravarotto, D.; Recchia, Dino; Rizzolo, A.; Romé, M.; Sartori, E.; Sattin, M.; Serianni, G.; Taccogna, F.; Valentino, V.; Variale, V.; Veltri, P.

doi:10.1063/1.5128658

Cited by 7 publications

(13 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…NIO1 (Negative Ion Optimization phase 1) is a radiofrequency Hion source, built and operated by Consorzio RFX and INFN-LNL, with the aim of studying the production and acceleration of negative ions, to address present and future issues and needs of negative ions sources for neutral beam injectors in fusion reactor (DEMO in particular) [ [1]- [4]]. The NIO1 source is designed to be compact and flexible for the test of new concepts, components and instrumentation.…”

Section: Introductionmentioning

confidence: 99%

“…Keeping the fraction of co-extracted electrons as low as possible is a fundamental target for the sources of future neutral beam injectors, and resulted to be challenging for long plasma operation in other experiments [11]. The diffusion of electrons towards the PG is limited by a vertical magnetic field [12] (from 9 mT to 12.5 mT in proximity of the PG, as configuration F3 in reference [4]). The magnetic field is generated by permanent magnets and by a current flowing in the PG.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Cs Evaporation in a Negative Ion Source and Cs Cleaning Tests by Plasma Sputtering

Barbisan

Delogu

Pimazzoni

et al. 2022

IEEE Trans. Plasma Sci.

Self Cite

View full text Add to dashboard Cite

The compact radio frequency negative ion source NIO1 (Negative Ion Optimization phase 1) has been designed, built and operated by Consorzio RFX and INFN-LNL in order to study and optimize the production and acceleration of Hions in continuous operation. In 2020 Cs was evaporated in the source to increase the total extracted ion current. After an initial reduction of extracted electron to ion ratio and subsequently an increase of extracted negative ion current, the source performances progressively worsened, because of the excessive amount of Cs evaporated in the source; the extracted electron to ion ratio increased from below 1 to more than 10, while ion current density reduced from max. 67 A/m 2 ion current to not more than 30 A/m 2 ). The paper presents the experimental observations collected during Cs evaporation (reduction of plasma light, Cs emission and Hβ/Hγ ratio, etc.) that can help stopping the process before an excessive amount of Cs is introduced in the source. The paper also reports the cleaning techniques tested to remove the Cs excess by the action of hydrogen or argon plasmas; while argon was predictably more effective in surface sputtering, a 3 h Ar plasma treatment was not sufficient to recover from overcesiation.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Cs Evaporation in a Negative Ion Source and Cs Cleaning Tests by Plasma Sputtering

Barbisan

Delogu

Pimazzoni

et al. 2022

IEEE Trans. Plasma Sci.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Our example follows NIO1 [9,17] set-up with plasma chamber 𝑅 𝑤 = 48.5 mm, 𝑧 1 = −78.7 mm, 𝑧 2 = 𝑧 1 + 𝐿 𝑝 = 133.3 mm and a 7 turn coil, centered on the 𝑧 = 0 plane; frequency 𝑓 2 MHz. Simulated plasma extends up to 𝑟 < 𝑅 𝑝 with a small gap from 𝑅 𝑤 (to remember of sheath layer); for visualization 𝑅 𝑝 = 48 mm.…”

Section: Magnetic Field and Other Input Datamentioning

confidence: 99%

“…In turn, 𝑛 𝑒 depends on ionization due to energetic electrons and on plasma transport to walls. A cylindrical geometry (with lateral wall covered by multipoles [9]) is effective in confining electrons; for rapid calculation a stationary 2D axisymmetric model is here developed. Effect of filter field 𝐵 𝑓 and of end wall multipoles is also included.…”

Section: Introductionmentioning

confidence: 99%

A model of radiofrequency and plasma coupling for compact ion sources and design

Cavenago

2024

J. Inst.

Self Cite

View full text Add to dashboard Cite

Inductive coupling of radiofrequency power to plasma is a complicate process, since it depends from the density of plasma itself, because ionization is a chain reaction process, and, at low density a capacitive coupling may mix with inductive coupling (with no Faraday screen). Plasma temperature Te , density ne and vector potential are closely coupled, giving nonlinear and singular systems of Partial Differential equations, which require slow iterative solutions, motivating the consideration of a 2D model, also as rapid design and first approximation tool. Plasma conductivity and heating depend on collision rate, which includes also the so-called stochastic collisions (mainly electron collisions with walls), proportionally more important at low gas density ng . Conductivity is also affected by static and radiofrequency magnetic fields; results for skin depth and stochastic collision estimates are reported. The transport of Te and ne inside source can be controlled by a magnetic filter B f . Considering a 5 cm radius H- ion source as example, solution of ne and Te are reported as a function of filter strength B fa, applied rf power and wall status; solver convergence methods and key plasma observables are briefly discussed. Due to small dimension, a filter strength B fa in the order of 8 mT is needed to achieve electron temperature lower than 2 eV (for negative ion production) at extraction.

show abstract

“…NIO1 aims at studying the source plasma and the beam production, to support the development of neutral beam injectors (NBI) for future fusion reactors (DEMO in particular). [1][2][3][4] Differently from other larger facilities in this field, NIO1 was designed to withstand plasma generation and beam extraction for several hours. [5][6][7] The structure of NIO1 is shown in the 3D section of figure 1.…”

Section: Introductionmentioning

confidence: 99%

Continuous pulse advances in the negative ion source NIO1

Barbisan,

Agnello,

Cavenago

et al. 2023

J. Inst.

Self Cite

View full text Add to dashboard Cite

Consorzio RFX and INFN-LNL have designed, built and operated the compact radiofrequency negative ion source NIO1 (Negative Ion Optimization phase 1) with the aim of studying the production and acceleration of H- ions. In particular, NIO1 was designed to keep plasma generation and beam extraction continuously active for several hours. Since 2020 the production of negative ions at the plasma grid (the first grid of the acceleration system) has been enhanced by a Cs layer, deposited though active Cs evaporation in the source volume. For the negative ion sources applied to fusion neutral beam injectors, it is essential to keep the beam current and the fraction of co-extracted electrons stable for at least 1 h, against the consequences of Cs sputtering and redistribution operated by the plasma. The paper presents the latest results of the NIO1 source, in terms of caesiation process and beam performances during continuous (6 ÷ 7 h) plasma pulses. Due to the small dimensions of the NIO1 source (20 cm×∅10 cm), the Cs density in the volume is high (1015 ÷ 1016 m-3) and dominated by plasma-wall interaction. The maximum beam current density and minimum fraction of co-extracted electrons were respectively about 30 A/m2 and 2. Similarly to what done in other negative ion sources, the plasma grid temperature in NIO1 was raised for the first time, up to 80 °C, although this led to a minimal improvement of the beam current and to an increase of the co-extracted electron current.

show abstract

Beam and installation improvements of the NIO1 ion source

Cited by 7 publications

References 14 publications

Cs Evaporation in a Negative Ion Source and Cs Cleaning Tests by Plasma Sputtering

Cs Evaporation in a Negative Ion Source and Cs Cleaning Tests by Plasma Sputtering

A model of radiofrequency and plasma coupling for compact ion sources and design

Continuous pulse advances in the negative ion source NIO1

Contact Info

Product

Resources

About