Speaker
Mathias Hamberg
(Uppsala University)
Description
Manipulating electron bunches with an external laser has many attractive applications, both for beam shaping purposes and for diagnostics. In this talk two projects in which Uppsala University was involved are discussed: the XFEL laser heater and the optical replica synthesizer (ORS) experiment.
An inherent problem with the current design of the XFEL is micro-bunching instabilities in the bunch compressors and the acceleration sections. To overcome this problem it was suggested to heat up those bunches by overlapping them with an IR-laser (1030 nm) when passing through a few period undulator. The laser is travelling ~50 m within an evacuated pipe to an adjusting focusing telescope before entering the accelerator vacuum chambers. Longitudinal laser beam waist position is determined by splitting the beam and scanning a virtual waist with a camera. XY-positioning will be monitored via OTR screens located before and after the undulator and beam overlap will be obtained by adjusting translation stages in the periscope before the UHV inlet. Temporal overlap will be controlled by reading out signals from a BPM (e-beam) and photo-diode (laser beam) whereas the adjustment is made with an optical delay line.
A setup similar to the laser heater was already used in FLASH, where the energy modulation induced in the undulator was transformed into bunching that caused the emission of a coherent light pulse in a second undulator. This light pulse carries information about the bunch characteristics and is analyzed by an ultrashort laser pulse method (FROG).
We report on the progress of designing and building up the laser heater of the XFEL and briefly go through the ORS, its results and prospects.
Author
Mathias Hamberg
(Uppsala University)
Co-authors
Dr
Gergana Angelova
(Uppsala University)
Dr
Vitaliy Goryashko
(Uppsala University)
Volker Ziemann
(Uppsala University)
