Thermographic Measurement of the Emittance Plot of a Single Positive Ion Beamlet Thermographic Measurement of the Emittance Plot of a Single Positive Ion Beamlet

Preprint of Paper to be submitted for publication in Review of Scientific Instruments " This document is intended for publication in the open literature. It is made available on the understanding that it may not be further circulated and extracts or references may not be published prior to publication of the original when applicable, or without the consent of the Publications Officer, ABSTRACT Measurements have made of the emittance plot of a partly neutralised positive ion beamlet, using a slit, a polymer target and an infrared camera. This thermographic approach is intrinsically linear and absolute (since the properties of the target are known and approximately independent of temperature). It is sufficiently sensitive that only one short pulse is required to capture the entire range of the angular coordinate y′. Ions and neutral atoms are both detected with equal sensitivity. The measurement is unaffected by secondary electrons emitted by the target, and by electrons travelling with the positive ion beam, as both types of electron carry very little energy. No specialised electronics or beam deflection devices are required. Providing the region downstream of the mask is free of fields, the target can be several metres away from the mask, allowing good resolution in the y′ axis. The target can be as large as required.