The new McPherson 671MX amplifier is a high vacuum compatible, current-to-voltage converting amplifier developed for use with vacuum ultraviolet silicon photodiodes. With an integral socketed photodiode mount, the combination detector/amplifier hybrid can be used to measure small photo generated currents with resolutions of 10fA and dynamic ranges of four orders of magnitude. The 671MX consists of a low noise operation amplifier with a selectable feedback resistor. The feedback resistor is also socketed and may be changed to match the gain and dynamic range requirements of your experiment.
The company’s VUV series photodiodes are used for the detection of UV, EUV and X-ray photons. Unlike common p-n junction diodes, the photodiodes do not have a doped dead-region and have zero surface recombination. These devices can be used to cover the complete photon spectral rage (0.0124nm to 1,100nm) because of their extremely thin 6nm oxide window and 100 per cent internal quantum efficiency.
During the CW XUV radiation measurements, general purpose electrometers are used to measure current generated by the photodiodes. The relatively large size of many commercial electrometers – and vacuum chambers for VUV applications – may make it difficult to locate them very close to the detector. Long interconnecting cables can pick up significant amounts of noise from electromagnetic interference and mechanical vibration.
All amplifier components are low tolerance, resulting in consistent current-to-voltage transfer characteristics with minimal offset voltage. The amplifier is produced on a vacuum compatible ceramic board and uses all vacuum compatible components. It is sold without the photodiode and requisite ±15V power supply required for operation.