Open AccessPlasma commissioning in a high power external RF-coil volume-type H- ion source
Author(s) -
Scott Lawrie,
Robert Abel,
Dan Faircloth,
Tiago Sarmento,
J. Speed,
O. Tarvainen
Publication year - 2022
Publication title -
journal of physics. conference series
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.21
H-Index - 85
eISSN - 1742-6596
pISSN - 1742-6588
DOI - 10.1088/1742-6596/2244/1/012033
Subject(s) - duty cycle , electromagnetic coil , amplifier , rf power amplifier , materials science , plasma , electrical engineering , ion source , optoelectronics , physics , voltage , engineering , nuclear physics , cmos
A high power, high duty cycle, negative hydrogen ion source is in development at ISIS. It will operate in pure volume-production mode and is driven by a 52-turn RF-coil mounted external to the plasma chamber. A solid-state amplifier with a maximum output of 100 kW in 50 Hz, 1 ms pulses delivers RF power to the coil via an impedance-matching network. The amplifier has a relatively wide bandwidth, able to deliver full power from 1.8-4.0 MHz. This flexibility allowed straightforward commissioning of the matching network into an inductively-coupled plasma. Striking of the pulsed plasma is facilitated by a compact microwave ignition gun, requiring only 10 W of power at 2.45 GHz to deliver 1 mA seed pulses of electrons. Experiments have shown that it is vital to encapsulate the RF-coil properly to mitigate high voltage sparking. In addition, the location of the coil relative to the ion source’s permanent magnets has a critical effect on the ease of plasma ignition. The result of commissioning work is that a full duty-factor (50 Hz, 800 ^s) plasma has been achieved at nominal operating power (30 kW) and detailed optical studies have begun.