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May 2-6, 2010
La Fonda on the Plaza
Santa Fe, New Mexico USA

Los Alamos National Laboratory

Faraday Cup Award Recipients

The BIW10 recipients of the Faraday Cup Award are Florian Loehl (Cornell University) and Kristen Hacker (DESY).

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Femtosecond Resolution Beam Arrival Time Monitor
ID: 1231
Authors: Florian Loehl (CLASSE, Ithaca, New York), Kirsten Elaine Hacker (DESY, Hamburg)

A need for femtosecond resolution beam arrival time measurements has arisen with the transition from many-picosecond-long bunches in ring-based accelerators to a few femtosecond-long bunches in high- gain free-electron lasers. Here we present an electro-optical detection scheme that uses the signal of a beam pick-up to modulate the intensity of a femtosecond laser pulse train. By detecting the energies of the laser pulses, the bunch arrival time can be deduced.
We tested this scheme by distributing a laser pulse train to two locations in the FLASH linac, separated by 60 m, using length-stabilized optical fibers. By measuring the arrival times of the same electron bunches at these two locations, we determined an rms bunch arrival time resolution of 6 fs. This unprecedented monitor resolution allowed us to reduce the beam arrival time jitter from almost 200 fs down to 25 fs with an intra-bunch train feedback. Alternatively, the same detection scheme can be used for large dynamic range micrometer-resolution beam position measurements by using a stripline-type pickup mounted perpendicularly to the beam path, and then detecting the arrival time difference of both pick-up signals.


Congratulations, Florian and Kirsten!
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