Laser cooling hydrogen on nanosecond time scales

We describe prospects of laser cooling an atomic hydrogen beam using pulsed nanosecond Lyman-α laser sources. Laser cooling a hydrogen beam will enable aggressive reduction of the limiting systematics of important measurements of hydrogen's structure, most notably the 1S-2S transition. The Lyman-α transition allows extremely rapid 10⁹ m/s² deceleration when the transition is saturated, due to hydrogen's very large 3.26 m/s recoil velocity and the 2P state's short 1.6 ns lifetime. Furthermore, laser sources with saturating intensities (at useful 1 mm beam sizes) have been demonstrated using non-resonant third-harmonic generation in krypton, namely a 190 nJ/pulse Ti:sapph based laser we have recently developed [1]. A single 16 ns pulse will noticeably affect a 6.5K hydrogen beam. We have simulated this basic scenario and discuss prospects of laser upgrades that could enable a robust laser cooling of hydrogen towards the Doppler limit. [1] G. Gabrielse et al., Opt. Lett. 43, 2905-2908 (2018).