IMPROVED ION-BEAM ANALYSIS FACILITIES AT THE UNIVERSITY-OF-SURREY

A number of hardware and software improvements to the Surrey 2 MV Van de Graaff accelerator have enabled the production of a more stable bea m, making the microbeam in particular easier to use, as well as a more accurate routine energy calibration, increasing the surface mass reso lution. A feedback loop to electrostatic beam steerers before the anal ysing magnet uses the generating voltmeter (GVM) to fix the entry poin t of the beam into the analysing magnet. This arrangement fixes the po sition of the beam in the beam line as well as accurately stabilising the beam energy with a precision of about 100 eV and an accuracy of ab out 500 eV. Four point energy calibration is determined automatically from specially prepared samples. The electronic gain and offset are de termined directly, leading to a precision in the determination of rela tive signal energies of about 500 eV for 1.5 MeV beam energy. (C) 1998 Elsevier Science B.V.