Hannover 2020 – scientific programme

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A: Fachverband Atomphysik

A 14: Poster Session - Atomic Physics II

A 14.22: Poster

Tuesday, March 10, 2020, 16:00–18:00, Empore Lichthof

Active Control of a Femtosecond Enhancement Cavity for XUV Spectroscopy — •Patrick Knauer, Janko Nauta, Jan-Hendrik Oelmann, Alexander Ackermann, Ronja Pappenberger, Nick Lackmann, Steffen Kühn, Julian Stark, Thomas Pfeifer, and José R. Crespo López-Urrutia — Max Planck Institute for Nuclear Physics, Heidelberg, Germany

Driving narrow transitions of highly charged ions in the extreme ultraviolet (XUV) regime requires a coherent XUV source. A femtosecond enhancement cavity can provide this by transferring an infrared frequency comb with a peak intensity of up to ≈ 3·10¹⁴ W/cm² at a repetition rate of 100 MHz to the XUV through high-harmonic generation [1,2]. The enhancement cavity is mounted on a rigid titanium structure for stable long-term operation, and vibrations from the vacuum pumps are isolated from the optical setup by air-lifted feet [3]. To achieve a high enhancement of the driving infrared frequency comb, the cavity has to be precisely stabilised at high intra-cavity powers of several kW. Noise caused by thermal expansion, residual vibrations or other sources has to be cancelled. For this, we present an active stabilisation control consisting of a short and long term feedback loop, which is implemented using a field programmable gate array equipped micro controller.

[1] C. Gohle et al., Nature 436, 234-237 (2005).

[2] G. Porat et al., Nat. Photon, 12, 387 - 391 (2018).

[3] J. Nauta et al., Nucl. Instrum. Meth. B 408, 285 (2017).