The first Cherenkov ring segment obtained with PC49. The HPD is equipped only with a half silicon sensor and only 2 sectors are connected to the VA2 chips. C4F10 gas at a pressure of 1000 mbar served as Cherenkov radiator.

This data has been obtained with PC59 in a second beam period (10-14 Sept. 1999). It shows a Cherenkov ring originating from an air/C4F10 mixture (960 mbar). Left: Many events overlaid. Center: A single track. Right: Radius plot.

This data has been obtained with PC59 in a second beam period (10-14 Sept. 1999). It shows a Cherenkov ring originating from an C4F10 gas radiator (100 mbar). Left: Many events overlaid. Center: A single track. Right: Radius plot.