Development of multiple laser frequency control system for Ca⁺ isotope ion cooling

We here developed and evaluated a laser frequency control system which synchronizes the laser frequency to the resonance of target Ca ⁺ isotope ion whose having more than 8 GHz of isotope shift based on the Fringe Offset Lock method for simple operation of ICPMS-ILECS (Inductively Coupled Plasma Mass Spectrometry - Ion trap Laser Cooling Spectroscopy) The system fulfilled the minimum requirements of four slave lasers stability for Doppler cooling of Ca ⁺ ions. A performance of the system was evaluated by cooling ⁴⁰Ca ⁺ ions with the stabilized slave lasers. All the stable even Ca ⁺ isotope ions were trapped and their fluorescence was observed by switching laser frequencies using the system. An odd calcium isotope ⁴³Ca ⁺cooling was also succeeded by the control system