In this paper we review the design and development of a 100 J, 10 Hz nanosecond pulsed laser, codenamed DiPOLE100X, being built at the Central Laser Facility (CLF). This 1 kW average power diode-pumped solid-state laser (DPSSL) is based on a master oscillator power amplifier (MOPA) design, which includes two cryogenic gas cooled amplifier stages based on DiPOLE multi-slab ceramic Yb:YAG amplifier technology developed at the CLF. The laser will produce pulses between 2 and 15 ns in duration with precise, arbitrarily selectable shapes, at pulse repetition rates up to 10 Hz, allowing real-time shape optimization for compression experiments. Once completed, the laser will be delivered to the European X-ray Free Electron Laser (XFEL) facility in Germany as a UK-funded contribution in kind, where it will be used to study extreme states of matter at the High Energy Density (HED) instrument.

Using cryogenic laser technology, it is now possible to design and demonstrate lasers that have concomitant high average and peak powers, with near-diffraction-limited beam quality. We refer to these new laser systems as HAPP lasers. In this paper, we review important laser crystal materials properties at cryogenic temperature, with an emphasis on Yb lasers, and discuss the important design considerations, including the laser-induced damage threshold, nonlinear effects and thermal effects. A comprehensive model is presented to describe diode pulsed pumping with arbitrary duration and repetition rate, and is used with the Frantz–Nodvik equation to describe, to first order, the performance of HAPP laser systems. A computer code with representative results is also described.