Emittance Measurements at Laser-Wakefield Accelerators

Winkler, Paul Viktor

Dissertation / PhD Thesis

PUBDB-2020-01735

Emittance Measurements at Laser-Wakefield Accelerators

Winkler, P. V. (Corresponding author)DESY*

2020

145 pp. (2020) = Dissertation, University of Hamburg, 2019

Abstract: Laser-wakefield accelerators enable the generation of electron beams with initially nm-small emittances and GeV-level beam energies within cm-scale distances and are thereforepromissing candidates for drivers of future experiments. However, the percent-level energy-spreads and shot-to-shot fluctuations in beam quality can pose a limit to the transportability of plasma-generated beams, and further impete the measurement of the beam emittance using conventional methods.In the framework of this thesis, two energy-resolved phase-space diagnostics, a single-shot and a multi-shot method, have been implemented at the LUX laser-plasma accelerator.Electron beams from ionization injection are imaged by a compact quadrupole doublet from a virtual source into a dispersive electron spectrometer, which allows to measurethe beam emittance, beam size, divergence and phase-space correlation on the singleenergy-slice level. The results from both methods agree within 3%, which verifies theapplicability of the single-shot method at our setup and prooves the reproducability ofthe generated electron beams. A complex variation of the phase-space within the broadenergy spectrum is observed.The implemented diagnostics further allow to measure the chromatic effects of the transportoptics on the beam phase-space and a first measurement of the chromatic emittanceis presented. For a 2%-energy-spread sub-interval of the spectrum the normalized beamemittance grows by 10% from (0.83 $\pm$ 0.07) mm mrad to finally (0.93 $\pm$ 0.07) mm mradinside the capturing optic and is conserved afterwards. With the achieved measurement precision, based on a detailed accuracy study andcalibrated with high statistic scans, a reliable phase-space diagnostic has been developedfor emittance optimization for future experiments at LUX.

Note: Dissertation, University of Hamburg, 2019

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