Richard Pausch

Richard Pausch
Helmholtz-Zentrum Dresden-Rossendorf | HZDR · Institute of Radiation Physics

Dr. rer. nat. (physics)

About

52
Publications
6,784
Reads
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504
Citations
Introduction
I am working on radiation processes and their implementation in the GPU based particle-in-cell code PIConGPU and developing in-situ data analysis plugins and post processing software for PIConGPU simulations.
Additional affiliations
January 2015 - March 2020
Helmholtz-Zentrum Dresden-Rossendorf
Position
  • PostDoc Position
May 2013 - December 2014
Technische Universität Dresden
Position
  • PhD Student
Education
April 2013 - March 2019
Technische Universität Dresden
Field of study
  • Physics
October 2007 - December 2012
Technische Universität Dresden
Field of study
  • Physics

Publications

Publications (52)
Article
We report on experimental investigations of plasma wave structures in a plasma wakefield acceleration (PWFA) stage which is driven by electron beams from a preceding laser plasma accelerator. Femtosecond optical probing is utilized to allow for direct visualization of the plasma dynamics inside the target. We compare two regimes in which the driver...
Preprint
We present experimental results on a plasma wakefield accelerator (PWFA) driven by high-current electron beams from a laser wakefield accelerator (LWFA). In this staged setup stable and high quality (low divergence and low energy spread) electron beams are generated at an optically-generated hydrodynamic shock in the PWFA. The energy stability of t...
Preprint
Free-electron lasers generate high-brilliance coherent radiation at wavelengths spanning from the infrared to the X-ray domains. The recent development of short-wavelength seeded free-electron lasers now allows for unprecedented levels of control on longitudinal coherence[1], opening new scientific avenues as ultra-fast dynamics on complex systems...
Article
Full-text available
We present the experimental demonstration of density downramp injection at a gas-dynamic shock in a beam-driven plasma accelerator. The ultrashort driver electron beam with a peak-current exceeding 10 kA allows operation in the blowout regime and enables injection of electron witness bunches at gentle density ramps, i.e., longer than the plasma wav...
Article
Full-text available
Matched beam loading in laser wakefield acceleration, characterizing the state of flattening the accelerating electric field along the bunch, leads to the minimization of energy spread at high-bunch charges. Here, we experimentally demonstrate by independently controlling injected charge and accelerating gradients, using the self-truncated ionizati...
Preprint
Invertible neural networks are a recent technique in machine learning promising neural network architectures that can be run in forward and reverse mode. In this paper, we will be introducing invertible surrogate models that approximate complex forward simulation of the physics involved in laser plasma accelerators: iLWFA. The bijective design of t...
Preprint
In this work we propose a deep neural network based surrogate model for a plasma shadowgraph - a technique for visualization of perturbations in a transparent medium. We are substituting the numerical code by a computationally cheaper projection based surrogate model that is able to approximate the electric fields at a given time without computing...
Article
Full-text available
Plasma wakefield accelerators are capable of sustaining gigavolt-per-centimeter accelerating fields, surpassing the electric breakdown threshold in state-of-the-art accelerator modules by 3-4 orders of magnitude. Beam-driven wakefields offer particularly attractive conditions for the generation and acceleration of high-quality beams. However, this...
Chapter
Solving partial differential equations (PDE) is an indispensable part of many branches of science as many processes can be modelled in terms of PDEs. However, recent numerical solvers require manual discretization of the underlying equation as well as sophisticated, tailored code for distributed computing. Scanning the parameters of the underlying...
Article
Full-text available
Laser-plasma proton acceleration was investigated in the target normal sheath acceleration regime with a target composed of a gas layer and a thin foil. The laser’s shape, duration, energy and frequency are modified as it propagates in the gas, altering the laser-solid interaction leading to proton acceleration. The modified properties of the laser...
Article
Full-text available
We report on a new approach to measure the accumulated B-integral in the regenerative and multipass amplifier stages of ultrashort-pulse high-power laser systems by B-integral-induced coupling between delayed test post-pulses and the main pulse. A numerical model for such non-linear pulse coupling is presented and compared to data taken at the high...
Preprint
Solving partial differential equations (PDE) is an indispensable part of many branches of science as many processes can be modelled in terms of PDEs. However, recent numerical solvers require manual discretization of the underlying equation as well as sophisticated, tailored code for distributed computing. Scanning the parameters of the underlying...
Preprint
Laser-plasma proton acceleration was investigated in the Target Normal Sheath Acceleration (TNSA) regime using a novel gas-foil target. The target is designed for reaching higher laser intensity at the foil plane owing to relativistic self-focusing and self compression of the pulse in the gas layer. Numerical 3D particle-in-cell (PIC) simulations w...
Preprint
Full-text available
We present experimental measurements of the femtosecond time-scale generation of strong magnetic-field fluctuations during the interaction of ultrashort, moderately relativistic laser pulses with solid targets. These fields were probed using low-emittance, highly relativistic electron bunches from a laser wakefield accelerator, and a line-integrate...
Article
Full-text available
Thomson scattering sources with their hard x-ray pencil beams represent a promising candidate to drive high-resolution X-ray Fluorescence Imaging (XFI). As XFI is a scanning imaging modality, it specifically requires pencil-beam geometries along with a high beam mobility. In combination with laser-wakefield acceleration (LWFA) such sources could pr...
Preprint
Full-text available
Plasma wakefield accelerators are capable of sustaining gigavolt-per-centimeter accelerating fields, surpassing the electric breakdown threshold in state-of-the-art accelerator modules by 3-4 orders of magnitude. Beam-driven wakefields offer particularly attractive conditions for the generation and acceleration of high-quality beams. However, this...
Article
Full-text available
Compact electron accelerators are paramount to next-generation synchrotron light sources and free-electron lasers, as well as for advanced accelerators at the TeV energy frontier. Recent progress in laser-plasma driven accelerators (LPA) has extended their electron energies to the multi-GeV range and improved beam stability for insertion devices. H...
Preprint
Full-text available
Matched beam loading in laser wakefield acceleration (LWFA), characterizing the state of flattening of the acceleration electric field along the bunch, leads to the minimization of energy spread at high bunch charges. Here, we demonstrate by independently controlling injected charge and acceleration gradients, using the self-truncated ionization in...
Preprint
We present a conceptual design for a hybrid laser-driven plasma wakefield accelerator (LWFA) to beam-driven plasma wakefield accelerator (PWFA). In this set-up, the output beams from an LWFA stage are used as input beams of a new PWFA stage. In the PWFA stage, a new witness beam of largely increased quality can be produced and accelerated to higher...
Article
Full-text available
We show how optical free-electron lasers and enhanced incoherent Thomson scattering radiation sources can be realized with Traveling-Wave Thomson-Scattering (TWTS) today. Emphasis is put on the realization of optical free-electron lasers (OFELs) with existing state-of-the-art technology for laser systems and electron accelerators. The conceptual de...
Article
Full-text available
Extreme field gradients intrinsic to relativistic laser-interactions with thin solid targets enable compact MeV proton accelerators with unique bunch characteristics. Yet, direct control of the proton beam profile is usually not possible. Here we present a readily applicable all-optical approach to imprint detailed spatial information from the driv...
Article
We report on tailoring ionization-induced injection in laser wakefield acceleration so that the electron injection process is self-truncating following the evolution of the plasma bubble. Robust generation of high-quality electron beams with shot-to-shot fluctuations of the beam parameters better than 10% is presented in detail. As a novelty, the s...
Article
Full-text available
Quantitative predictions from synthetic radiation diagnostics often have to consider all accelerated particles. For particle-in-cell (PIC) codes, this not only means including all macro-particles but also taking into account the discrete electron distribution associated with them. This paper presents a general form factor formalism that allows to d...
Article
Full-text available
Interaction of relativistic electron beams with high power lasers can both serve as a secondary light source and as a novel diagnostic tool for various beam parameters. For both applications, it is important to understand the dynamics of the inverse Compton scattering mechanism and the dependence of the scattered light's spectral properties on the...
Article
Full-text available
Laser-plasma wakefield accelerators have seen tremendous progress, now capable of producing quasi-monoenergetic electron beams in the GeV energy range with few-femtoseconds bunch duration. Scaling these accelerators to the nanocoulomb range would yield hundreds of kiloamperes peak current and stimulate the next generation of radiation sources cover...
Article
Full-text available
We report on first commissioning results of the DRACO Petawatt ultra-short pulse laser system implemented at the ELBE center for high power radiation sources of Helmholtz-Zentrum Dresden-Rossendorf. Key parameters of the laser system essential for efficient and reproducible performance of plasma accelerators are presented and discussed with the dem...
Article
For the relativistic Kelvin-Helmholtz instability (KHI), which occurs at shear interfaces between two plasma streams, we report results on the polarized radiation over all observation directions and frequencies emitted by the plasma electrons from ab initio kinetic simulations. We find the polarization of the radiation to provide a clear signature...
Conference Paper
The injection process of electrons into the plasma cavity in laser-wakefield accelerators is a nonlinear process that strongly influences the property of the accelerated electrons. During the acceleration electrons perform transverse (betatron) oscillations around the axis. This results in the emission of hard x-ray radiation (betatron radiation) w...
Code
PIConGPU is a fully relativistic, many GPGPU, 3D3V particle-in-cell (PIC) code. The Particle-in-Cell algorithm is a central tool in plasma physics. It describes the dynamics of a plasma by computing the motion of electrons and ions in the plasma based on Maxwell’s equations. This release of PIConGPU, providing ”beta” status for users, implements fu...
Conference Paper
We demonstrate that optical free-electron lasers (OFELs) realized with Traveling-Wave Thomson-Scattering (TWTS) are by orders of magnitude more efficient and brilliant than corresponding OFELs utilizing head-on Thomson scattering geometries. In addition, we emphasize that TWTS OFELs as opposed to standard head-on Thomson scattering geometries scale...
Data
This releases fixes a potential deadlock encountered during checkpoints and initialization. Furthermore, we forgot to highlight that the 0.2.0 release also included a QED synchrotron emission scheme (based on the review in A. Gonoskov et al., PRE 92, 2015). Please refer to our CHANGELOG.md for a full list of features, fixes and user interface chang...
Article
Full-text available
We present a fully analytic model of an all-optical free electron laser (OFEL) undulator based on the Traveling-Wave Thomson-Scattering (TWTS) scheme. The TWTS undulator provides for sub-mm undulator wavelengths, does not require any material or plasma to generate or contain the undulator field and allows for sub-meter saturation lengths. Starting...
Conference Paper
A measurement of laser Thomson-backscattering X-ray spectra recorded as a function of the observation angle and quantitatively reproduced in simulations is presented. A traveling wave scheme is proposed that increases the yield and may allow for all-optical free-electron laser operation.
Article
Full-text available
Emerging new technologies in plasma simulations allow tracking billions of particles while computing their radiative spectra. We present a visualization of the relativistic Kelvin-Helmholtz Instability from a simulation performed with the fully relativistic particle-in-cell code PIConGPU powered by 18,000 GPUs on the USA's fastest supercomputer Tit...
Conference Paper
Full-text available
We present a self-consistent method to compute angularly resolved far-field spectra for both coherent and incoherent radiation which enables unprecedented quantitative predictions by taking into account emissions from all ∼10^10 electrons simulated in PIC codes for hundreds to thousands of directions and frequencies. This is applied to predicting t...
Conference Paper
Full-text available
We present a particle-in-cell simulation of the relativistic Kelvin-Helmholtz Instability (KHI) that for the first time delivers angularly resolved radiation spectra of the particle dynamics during the formation of the KHI. This enables studying the formation of the KHI with unprecedented spatial, angular and spectral resolution. Our results are of...
Code
That's our our open alpha release. The alpha release is developer and power user release only! Users should wait for our beta release!
Article
The particle-in-cell code PIConGPU provides the feature of calculating angular resolved radiation spectra in the far field based on Liénard─Wiechert potentials for all macroparticles of a plasma simulation. In order to verify the physics of our code we present a series of physics test scenarios, which compare numerical results to analytic solutions...
Article
We show that X-ray optical free-electron lasers (OFELs) can be realized using Traveling-Wave Thomson-Scattering (TWTS). In TWTS pulse front tilted laser pulses are scattered off relativistic electron bunches in a side-scattering geometry. The pulse-front tilt guarantees overlap between laser and electrons over distances in the meter range while bot...
Article
Full-text available
This report summarizes the study of the magnetic flux densities for two different optical matching devices (OMD) proposed for the positron source of the International Linear Collider (ILC). The goal of this study was to simulate the magnetic fields of the various OMDs and to find a way to include the results in a beamline simulation of the positron...

Projects

Projects (2)
Project
Test, verify and improve the spectrally resolved far field radiation in PIConGPU