The Photon Scintillator

A new sealed-off detector for accurate photon counting in the ultraviolet (1100-1800 A%o) is described. The resultant pulse height distributions exhibit a clear separation between signal and multiplier dark current. At operating voltages of 20-25 KV across the photon scintillator the peak of the signal distribution occurs at pulse heights greater than 30 times that of the average single electron. Because of the broad valley between signal and dark current the counting rate is relatively insensitive to substantial changes in bias level. The integral background above the bias level due to both the photon scintillator and the coupled photomultiplier dark current is of the order of 1 count/ sec or less. The pulse height resolution (FWHM) at 25 KV for low-light level ultraviolet radiation (single events) is approximately 45%.