Control systems and data management for high-power laser facilities

The next generation of high-power lasers enables repetition of experiments at orders of magnitude higher frequency than what was possible using the prior generation.Facilities requiring human intervention between laser repetitions need to adapt in order to keep pace with the new laser technology.A distributed networked control system can enable laboratory-wide automation and feedback control loops.These higher-repetition-rate experiments will create enormous quantities of data.A consistent approach to managing data can increase data accessibility,reduce repetitive data-software development and mitigate poorly organized metadata.An opportunity arises to share knowledge of improvements to control and data infrastructure currently being undertaken.We compare platforms and approaches to state-of-the-art control systems and data management at high-power laser facilities,and we illustrate these topics with case studies from our community.

X-ray polarimetry and its application to strong-field quantum electrodynamics

Polarimetry is a highly sensitive method to quantify changes of the polarization state of light when passing through matter and is therefore widely applied in material science.The progress of synchrotron and X-ray free electron laser(XFEL)sources has led to significant developments of X-ray polarizers,opening perspectives for new applications of polarimetry to study source and beamline parameters as well as sample characteristics.X-ray polarimetry has shown to date a polarization purity of less than 1.4×10^(-11),enabling the detection of very small signals from ultrafast phenomena.A prominent application is the detection of vacuum birefringence.Vacuum birefringence is predicted in quantum electrodynamics and is expected to be probed by combining an XFEL with a petawatt-class optical laser.We review how source and optical elements affect X-ray polarimeters in general and which qualities are required for the detection of vacuum birefringence.

Enhanced ion acceleration from transparency-driven foils demonstrated at two ultraintense laser facilities

Laser-driven ion sources are a rapidly developing technology producing high energy,high peak current beams.Their suitability for applications,such as compact medical accelerators,motivates development of robust acceleration schemes using widely available repetitive ultraintense femtosecond lasers.These applications not only require high beam energy,but also place demanding requirements on the source stability and controllability.This can be seriously affected by the laser temporal contrast,precluding the replication of ion acceleration performance on independent laser systems with otherwise similar parameters.Here,we present the experimental generation of>60 MeV protons and>30 MeV u-1 carbon ions from sub-micrometre thickness Formvar foils irradiated with laser intensities>1021 Wcm2.Ions are accelerated by an extreme localised space charge field≥30TVm-1,over a million times higher than used in conventional accelerators.The field is formed by a rapid expulsion of electrons from the target bulk due to relativistically induced transparency,in which relativistic corrections to the refractive index enables laser transmission through normally opaque plasma.We replicate the mechanism on two different laser facilities and show that the optimum target thickness decreases with improved laser contrast due to reduced pre-expansion.Our demonstration that energetic ions can be accelerated by this mechanism at different contrast levels relaxes laser requirements and indicates interaction parameters for realising application-specific beam delivery.

Characterization of the plasma mirror system at the J-KAREN-P facility

We report on the design and characterization of the plasma mirror system installed on the J-KAREN-P laser at the Kansai Photon Science Institute,National Institutes for Quantum Science and Technology.The reflectivity of the single plasma mirror system exceeded 80%.In addition,the temporal contrast was improved by two orders of magnitude at 1 ps before the main pulse.Furthermore,the laser near-field spatial distribution after the plasma mirror was kept constant at plasma mirror fluence of less than 100 kJ/cm^(2).We also present the results of investigating the difference and the fluctuation in energy,pulse width and pointing stability with and without the plasma mirror system.