Annealing effect for supersolid fraction in 4He

We report on experimental confirmation of the non-classical rotational inertia (NCRI) in solid helium samples originally reported by Kim and Chan. The onset of NCRI was observed at temperatures below approximate to 400 mK. The ac velocity for initiation of the NCRI suppression is estimated to be approximate to 10 mu m/sec. After an additional annealing of the sample at T=1.8 K for 12 hours, similar to 10% relative increase of NCRI fraction was observed. Then after repeated annealing with the same conditions, the NCRI fraction was saturated. It differs from Reppy's observation on a low pressure solid sample.