Speaker
Description
The resonance ionization laser ion source (RILIS) is the principal ion source at ISOLDE, providing efficient and element-selective ion creation by laser radiation tuned to unique electronic transitions of the atoms of interest. The laser system’s 10 kHz pulsed operation imprints a respective bunch structure on the extracted ion beam. This characteristic can be used for partial suppression of contamination by applying a synchronized beam gating, only letting the bunches of laser-ionized species pass while blocking the contaminant, non-laser related DC-component in between. Clearly, the efficacity of this method is enhanced if the ion bunch width is reduced.
The bunch width is predominantly determined by the applied voltage gradient along the ion source. For standard operation, an electric current of ~300 A is needed to resistively heat the source to approximately 2000 °C, leading to a fixed gradient of ~2V. Voltage gradient manipulation transparent to temperature requirements can be achieved by introducing a modulated heating scheme. While the average dissipated power is kept constant to reach the defined temperature, the voltage is applied with a duty cycle: During on-time, the required electrical power (and ergo voltage) is accordingly higher. Ions of choice would then be created by the laser in the time frame of active heating and high voltage gradient, and therefore formed to a narrower ion bunch compared to standard continuous heating.
Following previous exploration work [1, 2], simulation, development, and testing of respective equipment for µs-switching of high currents for the existing ISOLDE target/ion source system is conducted in cooperation with the SY/ABT group, providing expertise in high current fast switching systems at CERN.
References:
[1] S. Mishin et al, AIP Conference Proceedings 1104, 207 (2009)
[2] S. Rothe et al, Nucl Instrum Methods Phys Res B 376 (2016), 86–90
