TITAN's Digital RFQ Ion Beam Cooler and Buncher, Operation and Performance

TL;DR

This paper describes TITAN's digitally driven RFQ ion trap for cooling and bunching radioactive ion beams, highlighting its novel operation mode and performance results from systematic tests with stable and radioactive ions.

Contribution

It introduces the first digitally driven RFQ ion trap with a wide bandwidth square-wave drive and demonstrates its unique reverse extraction mode.

Findings

Achieved efficient cooling and bunching of radioactive ions.

Demonstrated reverse extraction mode of ion bunches.

Provided systematic performance data with stable and radioactive ions.

Abstract

We present a description of the Radio Frequency Quadrupole (RFQ) ion trap built as part of the TITAN facility. It consists of a gas-filled, segmented, linear Paul trap and is the first stage of the TITAN setup with the purpose of cooling and bunching radioactive ion beams delivered from ISAC-TRIUMF. This is the first such device to be driven digitally, i.e., using a high voltage ($V_{pp} = \rm{400 \, V}$), wide bandwidth ($0.2 < f < 1.2 \, \rm{MHz}$) square-wave as compared to the typical sinusoidal wave form. Results from the commissioning of the device as well as systematic studies with stable and radioactive ions are presented including efficiency measurements with stable $^{133}$Cs and radioactive $^{124, 126}$Cs. A novel and unique mode of operation of this device is also demonstrated where the cooled ion bunches are extracted in reverse mode, i.e., in the same direction as previously injected.