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May 2018

Optimizing the 8Li yield for the IsoDAR Neutrino Experiment


August 2017

MIST-1 Ion Source Test

The first step in the IsoDAR project is the production of the H2+ ions. In order to do this, the experiment requires an ion source. The ion source will ionize hydrogen gas, and produce the necessary H2+ ions. These ions are at the core of the experiment, as the same ions that are produced here will be extracted and accelerated using a cyclotron. Due to the use of H2+ produced by our ion source rather than protons or H-, our beam is affected less by space charge, and our cyclotron is able to reach generate higher currents. To keep up with the needs of the experiment, the ion source must be designed so that it can produce sufficient current.

A short summary of our ion source is that a plasma is confined by permanent magnets (Sm2Co17), electrons are produced by a filament and are accelerated by an externally applied electric field of order 100V. Due to the short source and the plasma being produced close to the extraction region, there is not enough time for dissociation to occur, favoring H2+ over proton production.

In the first commissioning phase, a thinner (0.4mm diameter) pure tungsten filament was used instead of the nominal filament described the previously. Currents were measured in a Faraday cup right after the extraction system, thus not allowing species separation. During the accumulated run time of approximately 30 hours, the source showed good stability for about 4 hours at a time, reaching a maximum current density of 16 mA/cm2 (4.6 mA total) . While at this point the commissioning results are preliminary, we are confident that our source will have similar species ratios. A paper on the final commissioning results using a short analysis low energy beam line with dipole magnet for mass separation is forthcoming.


The Ion source: A vacuum pumped six way cross connected to a hydrogen line. The stainless steel covers and glass windows are bolted and sealed shut, to prevent any outside forces from air to interfere with the beam, as well as to prevent contamination of the ion source.


The Faraday Cup: When pressure is slightly elevated, the beam interacts with the air and is able to glow. This makes the Ion beam visible as it leaves the source and goes to the Faraday cup.


The Extraction System: The Faraday cup is visible on the right, on the left is the extraction system. The extraction system is a series of electrodes that shape, steer, and slightly accelerate the ions in the beam before going into the rest of the beam line.