A New Emittance Measuring Device of the Unilac

For continuous monitoring of emittances and online calculation of beam envelopes during routine operation of the Unilac a fast measurement device was installed in the low energy beam transport line. Two orthogonal slit-collector systems are positioned parallel to the beam line. A microprocessor controlled electric deflecting system sweeps the beam by stepwise variation of the high voltage. The ratio between deflected and undeflected part of the pulsed beam can be varied within broad ranges. The minimum refresh rate for a complete emittance display in both transverse planes is 0.5 s. Although using fixed voltage steps the device can be adjusted to various charge to mass ratios. For comparison the slit-detector system can also be moved mechanically through the beam. Therefore the device combines a very fast nearly non-destructive emittance scan with a slow destructive system.