RF phase effect on ion transmission in TRIUMF's ion-guide laser ion source (IG-LIS)

A phase-locked radio frequency quadrupole (RFQ) ion-guide laser ion source (IG-LIS) has been developed and tested offline at TRIUMF's laser ion source test stand and commissioned online at the isotope separator and accelerator facility. In this device, a master clock is used to synchronize the laser pulse trigger for laser ionization and the RF driving the ion guide. The ions generated by laser pulses encounter a specific RF phase either at the moment of ionization or when entering the RFQ, which affects their transmission. The study shows that a 10%-50% improvement in ion transmission can be achieved by locking and optimizing the initial phase experienced by ions compared to the conventional IG-LIS without phase-locking. The method also provides an additional function of IG-LIS to modulate ion intensity at hundreds of kHz and to fast gate ions, which allows phase-sensitive detection and beam purification for experiments downstream.