STFC/RAL/ASTeC, Chilton, Didcot, Oxon
STFC/RAL/ISIS, Chilton, Didcot, Oxon
STFC/RAL, Chilton, Didcot, Oxon
Funding: Work supported by EU/FP6/CARE (HIPPI) RII3-CT-2003-506395
Among present challenges for beam diagnostics and instrumentation are issues presented by high beam intensity, brightness, resolution and the need to avoid inserting mechanical parts into the beam. This very often means applying non-destructive methods, which avoid interaction between ions and mechanical parts and, furthermore, allow on-line measurements during normal beam operation. The preferred technique for H- beams is the photo-detachment process where (laser) light within the range of 400-1000 nm has a sufficient continuous cross section to neutralize negative ions. The actual diagnostics are then applied to either the neutrals produced or the electrons. The latter are typically used for beam profiles whereas neutrals are more suitable for emittances, and form the subject of the present paper. This provides an overview of the basic features of the diagnostic technique, followed by a more intensive discussion of some experimental and theoretical aspects with emphasis on computing the 4 dimensional emittance using a method called Maximum Entropy (MaxEnt).
