15-20 October 2017
CERN
Europe/Zurich timezone

Extraction of Many H$^-$ Beamlets from Uncesiated Ion Source NIO1

16 Oct 2017, 16:30
2h 30m
CERN

CERN

Centre international de Conférence Genève (CICG). http://www.cicg.ch/
Poster presentation Negative ion sources Poster Session 1

Speakers

Marco Cavenago (INFN-LNL) Marco Cavenago (INFN-LNL)

Description

The installation of molybdenum liners in the ion source NIO1 (Negative Ion Optimization phase 1) has proven to be successful in order to largely decrease the contamination of rf window by wall sputtering; intense hydrogen plasma are thus achievable even at moderate rf power (1200 W) in a continuous regime operation (much longer than one hour), which enabled prolongated campaign at several plasma conditions; operation down to 0.5 Pa is possible, while best beam conditions were observed among 1 and 2 Pa, which is satisfying considering that NIO1 was never cesiated up to now. This has motivated a delay in the installation of the existing Cs oven, to investigate the following items: best combination of plasma grid (PG) and bias plate (BP) voltages (usually separately controllable in NIO1) in order to reduce the coextracted electrode current $I_e$; effect of magnetic filter; improved extraction grid EG with ion deflection compensation; correlation of EG magnetic field and discharges in the extraction gap: achieved acceleration voltage for H$^-$ is indeed 12 kV up to now, at the relatively high pressure there (>0.2 Pa) due to the limited pumping installed.
Database of results with H is compared to previous results with Oxygen (and Oxygen/Argon mixtures), where a much larger coextracted electron current $I_e$ was measured as expected, and ion beam current was thus limited below 3 mA. On the contrary for H, the limited rf power used resulted in a low extracted current (6 mA), consistently with the stated limitation in voltage.
Maintenance experience, concerning gasket erosion and ceramic surface alteration is discussed; the thin insulators among BP and PG and other walls show plasma related embrittlement, and are being rebuilt in a more compact BN grade.
Performance of some installed beam diagnostic (side view luminosity, Doppler-shifted emission, and carbon plate calorimetry) is critically reviewed, especially for effectiveness of beam imaging, as also compared to other beam diagnostics. As to the former method, in vertical side view projection, three columns of beamlets clearly show, while the horizontal projection is somewhat blurred by ion deflection up to now. Finally steady progress of acquisition software is noted. Related advancement of simulation tools is summarized.

Primary authors

Co-authors

Dr Matteo Agostini (Technische Universität München & Gran Sasso Science Institute) Vanni Antoni (Consorzio RFX) Carlo Baltador (Consorzio RFX) Paolo Barbato (Consorzio RFX) Marco Barbisan (Consorzio RFX) Andrea Barzon (Consorzio RFX) Lucio Baseggio (Consorzio RFX) Marco Bigi (Consorzio RFX) Matteo Brombin (Consorzio RFX) Laura Buonincontri (UNIPD) Vannino Cervaro (Consorzio RFX) Fabio Degli Agostini (Consorzio RFX) Enrico Fagotti (INFN-LNL) Luca Franchin (Consorzio RFX) NIcola Ippolito (INFN-BA) Kulevoy Timur (ITEP) Bruno Laterza (Consorzio RFX) Luca Lotto (Consorzio RFX) Andrea Ludovici (UNIPD) Giancarlo Maero (UNIMI/INFN-MI) Moreno Maniero (Consorzio RFX) Luisa Migliorato (Consorzio RFX) Alessandro Minarello (INFN-LNL) Pierpaolo Minelli (CNR-Nanotec) Federico Molon (Consorzio RFX) Gianluca Moro (Consorzio RFX) Roberto Pasqualotto (Consorzio RFX) Tommaso Patton (Consorzio RFX) Sergey Petrenko (ITEP) Antonio Pimazzoni (Consorzio RFX) Diego Ravarotto (Consorzio RFX) Mauro Recchia (Consorzio RFX) Livio Romanato (Consorzio RFX) Massimiliano Romé (UNIMI/INFN-MI) Federico Rossetto (Consorzio RFX) Emanuele Sartori (Consorzio RFX/UNIPD) Manuele Sattin (INFN-LNL) Fabio Spinazzè (UNIPD) Fabrizio Stivanello (INFN-LNL) Francesco Taccogna (CNR-Nanotec) Marco Tollin (Consorzio RFX) Lauro Trevisan (Consorzio RFX) Vincenzo Variale (INFN-BA) Marco Zanini (UNIPD) Barbara Zaniol (Consorzio RFX) Simone Zucchetti (Consorzio RFX) Piergiorgio Sonato (Consorzio RFX)

Presentation materials