Detector

The existing "backend" of the instrument consists of a thermo-electrically cooled detector usually operated at about -25 degrees C. The phototube is an EMI 6256, with a quartz window. This "blue" tube has good sensitivity from 3000 to 5200 A, then falls-off out to 6000-6500 A, and has no throughput redward of this. Dark current averages to 1-2 counts/s. Measured dead time correction is 60 ns.