| abstract |
A single photon counting apparatus comprising a SPAD and a controller. The controller is operable to vary the operating parameters of the SPAD during use in response to a count rate detected by the SPAD. The operating parameters comprising at least one of the voltage across the SPAD during an active period, the voltage across the SPAD during a quench period, the duration of the quench period and the temperature of the SPAD. Particle characterisation instruments comprising the apparatus are also disclosed. |