Recent results of PTB's primary clock CS1

This paper describes the current performance of the PTB primary clock CS1. After major reconstruction during 1995 and 1996, routine clock operation was started in May 1997, and since July 1998 the CS1 again determines with other primary clocks the duration of the scale unit of TAI. An evaluation of the CS1 Type B uncertainty yielded 7.10/sup -15/ (1/spl sigma/). The performance of the CS1 is illustrated by comparison results with TAI and free atomic time scales.