In late 1975 a special UHV XPS instrument incorporating many novel features was supplied to the UK Central Energy Generation Board (CEGB).  This instrument was further developed into the latest electron spectrometer, the ES300, which was produced with excitation sources and vacuum pumping according to a customer's individual requirements.  A comprehensive data system DS-300 was also launched with the ES300.

From these specifications we can see that unlimate performance of the ES300 was defined as 20,000 cps at 0.92 eV FWHM for the Ag 3d_5/2 peak.