Home > Publications database > Paving the way of high repetition rate laser wakefield acceleration by solving heat induced grating deformation issues |
Master Thesis | PUBDB-2020-05063 |
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2020
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Please use a persistent id in citations: doi:10.3204/PUBDB-2020-05063
Abstract: The goal of this thesis was to enable high repetition rate Laser Wakefield Acceleration(LWFA) by solving heat induced grating deformation issues in a Chirped PulseAmplification (CPA) based 25 TW Ti:sapphire laser system centred at 800 nm. Thesepreviously limited the intensity and wavefront quality of the pulse. An increase of maximumrepetition rate, limited by heat induced grating deformation, from 1 to 10 Hz wasachieved. Through simulations it was shown that the grating deforms due to heatingup from absorbed laser energy which induces spatial-distortions in the wavefront. Byreplacing the NZK-7 based grating with one made from ZERODURR , a glass ceramicproduced by the Schott AG with a vanishing thermal expansion coefficient a, it wasexpected, and later verified through measurements, that the introduction of such distortionsinto the beam wavefront could be inhibited. During operating at 10 Hz, thefocal spot size of the far field was measured to increase from 51 mm to 204 mm inthe vertical-, and 61 mm to 202 mm in the horizontal axis within 5 minutes usingthe NZK-7 grating and kept growing to 244 mm in the vertical-, and 434 mm inthe horizontal axis over 8 hours. With the Zerodur grating installed it stayed constantin both axis at 51 mm during the whole measurement. It was also possible to reducethe change in position of the focus by one order of magnitude. Lastly, a RadioFrequency (RF) plasma cleaning setup was successfully tested and implemented intothe compressor chamber to remove the Carbon layer that was coated onto the gratingsurface by the high intensity of the laser. Heat induced grating deformation is one ofthe things that inhibit high repetition rate LWFA experiments. In summary, this thesispresents a possibility to resolve these challenges.
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