A convenient energy analyzer calibration technique

Abstract

As part of a continuing program of fast ion beam spectroscopy studies and of investigation of the ion-foil interaction process, the need arose for a convenient technique for in situ calibration of an electrostatic energy analyzer. We describe here a calibration procedure based upon observation of the collisional dissociation of diatomic molecular ions in a gas cell which is biased by a precision power supply to a potential V in the range −16 to +16 kV. By measuring the apparent energy of the monatomic ions resulting from dissociation in the gas cell as a function of the applied voltage V, one can obtain the actual ion energy and the analyzer calibration factor; the undissociated ion peak then furnishes a second calibration point. This technique is particularly convenient for the energy range of the low energy heavy-ion accelerators, used here: energies less than a few hundred keV. Limitation of the precision obtained is due to the accuracy with which the center of the somewhat broad energy spectrum of the ion from molecular dissociation can be determined and, to a lesser extent, by the accuracy of the calibration of the output of the precision power supply employed.