Improvements of the versatile multiaperture negative ion source NIO1

M. Cavenago, G. Serianni, M. De Muri, P. Veltri, V. Antoni, C. Baltador, M. Barbisan, M. Brombin, A. Galatá, N. Ippolito, T. Kulevoy, R. Pasqualotto, S. Petrenko, A. Pimazzoni, M. Recchia, E. Sartori, F. Taccogna, V. Variale, B. Zaniol, P. BarbatoL. Baseggio, V. Cervaro, D. Fasolo, L. Franchin, R. Ghiraldelli, B. Laterza, M. Maniero, D. Martini, L. Migliorato, A. Minarello, F. Molon, G. Moro, T. Patton, D. Ravarotto, R. Rizzieri, A. Rizzolo, M. Sattin, F. Stivanello, S. Zucchetti

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Abstract

The ion source NIO1 (Negative Ion Optimization 1) was developed and installed as a reduced-size model of multiaperture sources used in neutral beam injectors. NIO1 beam optics is optimized for a 135 mA H- current (subdivided in 9 beamlets) at a Vs = 60 kV extraction voltage, with an electron-to-ion current ratio Rj up to 2. Depending on gas pressure used, NIO1 was up to now operated with Vs < 25 kV for beam extraction and Vs= 60 kV for insulation tests. The distinction between capacitively coupled plasma (E-mode, consistent with a low electron density plasma ne) and inductively coupled plasma (H-mode, requiring larger ne) was clearly related to several experimental signatures, and was confirmed for several gases, when applied radiofrequency power exceeds a given threshold Pt (with hysteresis). For hydrogen Pt was reduced below 1 kW, with a clean rf window and molybdenum liners on other walls; for oxygen Pt ≤ 400 W. Beams of H-and O-were separately extracted; since no caesium is yet introduced into the source, the expected ion currents are lower than 5 mA; this requires a lower acceleration voltage Vs(to keep the same perveance). NIO1 caesium oven was separately tested and Cs dispensers are in development. Increasing the current in the magnetic filter circuit, modifying its shape, and increasing the bias voltage were helpful to reduce Rj(still very large up to now, about 150 for oxygen, and 40 for hydrogen), in qualitative agreement with theoretical and numerical models. A second bias voltage was tested for hydrogen. Beam footprints and a spectral emission sample are shown.
Original languageEnglish
DOIs
Publication statusPublished - 9 Aug 2017
Externally publishedYes
Event5th International Symposium on Negative Ions, Beams and Sources, NIBS 2016 - Oxford, United Kingdom
Duration: 9 Aug 2017 → …

Conference

Conference5th International Symposium on Negative Ions, Beams and Sources, NIBS 2016
CountryUnited Kingdom
CityOxford
Period9/8/17 → …

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All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

Cite this

Cavenago, M., Serianni, G., De Muri, M., Veltri, P., Antoni, V., Baltador, C., Barbisan, M., Brombin, M., Galatá, A., Ippolito, N., Kulevoy, T., Pasqualotto, R., Petrenko, S., Pimazzoni, A., Recchia, M., Sartori, E., Taccogna, F., Variale, V., Zaniol, B., ... Zucchetti, S. (2017). Improvements of the versatile multiaperture negative ion source NIO1. Paper presented at 5th International Symposium on Negative Ions, Beams and Sources, NIBS 2016, Oxford, United Kingdom. https://doi.org/10.1063/1.4995727