Optimal Beam Loading in a Laser-Plasma Accelerator.

Applications of laser-plasma accelerators demand low energy spread beams and high-efficiency operation. Achieving both requires flattening the accelerating fields by controlled beam loading of the plasma wave. Here, we optimize the generation of an electron bunch via localized ionization injection, such that the combination of injected current profile and averaged acceleration dynamics results in optimal beam loading conditions.

Bayesian Optimization of a Laser-Plasma Accelerator.

Generating high-quality laser-plasma accelerated electron beams requires carefully balancing a plethora of physical effects and is therefore challenging-both conceptually and in experiments. Here, we use Bayesian optimization of key laser and plasma parameters to flatten the longitudinal phase space of an ionization-injected electron bunch via optimal beam loading. We first study the concept with particle-in-cell simulations and then demonstrate it in experiments.

Wavefront degradation of a 200 TW laser from heat-induced deformation of in-vacuum compressor gratings.

High-repetition-rate high-power laser systems induce a high average power heat deposition into the gold-coated diffraction gratings. To study the effects of the thermal expansion of in-vacuum Pyrex gratings on the laser properties, we scan the pulse energy and repetition rate of a 200 TW laser system while monitoring the laser wavefront. Through the measured changes in laser divergence and focusability, we define an average power limit below which the in-vacuum compressor can be used with no degradation of the laser focus quality.

Waiting times for elective treatments according to insurance status: A randomized empirical study in Germany.

Background: Health insurance coverage for all citizens is often considered a requisite for reducing disparities in health care accessibility. In Germany, health insurees are covered either by statutory health insurance (SHI) or private health insurance (PHI). Due to a 20%-35% higher reimbursement of physicians for patients with PHI, it is often claimed that patients with SHI are faced with longer waiting times when it comes to obtaining outpatient appointments.