Observation of 2-component bunched beam signal with laser cooling

Soda, Hikaru*; Nakao, Masao*; Noda, Akira*; Tongu, Hiromu*; Ito, Kiyokazu*; Okamoto, Hiromi*; Yuri, Yosuke; Jimbo, Koichi*; Grieser, M.*; He, Z.*

The longitudinal temperature of 40 keV Mg beams was measured through bunch length measurement during laser cooling at S-LSR. The bunch length was measured as time-domain signals from a pair of parallel-plate electrostatic pickups. Injected non-cooled beams gave a bunch length of 2.5 m and cooled beams had two components of broad and sharp distributions. The broad distribution had a longitudinal length of 2.2 m, which is close to that of the initial beam. The length of the sharp distribution shrunk to 0.25 m and is expected as a cooled part. The capture efficiency of cooling, which represents the ratio of particle numbers of the cooled part and the total particle number, varied with laser detuning. With a scanning range of 2 GHz, it was improved from 66% to 92%, while the bunch became longer by 10% with scanning. A new scheme for improving the capture efficiency will be applied to attain a strong signal from a low-current low-temperature beam.