Full PIC simulation of a first ACHIP experiment @ SINBAD

In laser illuminated dielectric accelerators (DLA) high acceleration gradients can be achieved due to high damage thresholds of the materials at optical frequencies. This is a necessity for developing more compact particle accelerator technologies. The Accelerator on a CHip International Program (ACHIP) funded by the Gordon and Betty Moore Foundation is researching such devices. DESY Hamburg is part of the collaboration. The dedicated accelerator research facility SINBAD is particularly well suited for DLA experiments at relativistic electron energies. High quality beams and short bunch lengths are anticipated from the ARES linac which is currently under construction at SINBAD. The aim of the experiment is the injection of a short electron bunch from the ARES linac into a DLA. In this study the results of one of the first possible experiments at the facility are estimated via a combination of particle-in-cell (PIC) and tracking simulations. ASTRA is used to simulate an electron bunch from the ARES linac at a suitable working point. The dielectric part of the setup will be simulated using the PIC code from CST Particle Studio incorporating the retrieved bunch from the ASTRA simulation. The energy spectra of the electron bunches are calculated as would be measured from a spectrometer dipole with and without the laser fields

Simulations and plans for possible DLA experiments at SINBAD

In this work we present the outlines of possible experiments for dielectric laser acceleration (DLA) of ultra-short relativistic electron bunches produced by the ARES linac, currently under construction at the SINBAD facility (DESY Hamburg). The experiments are to be performed as part of the Accelerator on a Chip International Program (ACHIP), funded by the Gordon and Betty Moore Foundation. At SINBAD we plan to test the acceleration of already pre-accelerated relativistic electron bunches in laser-illuminated dielectric grating structures. We present outlines of both the acceleration of ultra-short single bunches, as well as the option to accelerate phase-synchronous sub-fs microbunch trains. Here the electron bunch is conditioned prior to the injection by interaction with an external laser field in an undulator. This generates a sinusoidal energy modulation that is transformed into periodic microbunches in a subsequent chicane. The phase synchronization is achieved by driving both the modulation process and the DLA with the same laser pulse. In addition to the conceptual layouts and plans of the experiments we present start-to-end simulation results for different ARES working points.Comment: EAAC'17 conference proceeding

First Steps Toward an Autonomous Accelerator, a Common Project Between DESY and KIT

Reinforcement Learning algorithms have risen in popularity in recent years in the accelerator physics community, showing potential in beam control and in the optimization and automation of tasks in accelerator operation. The Helmholtz AI project "Machine Learning toward Autonomous Accelerators" is a collaboration between DESY and KIT that works on investigating and developing RL applications for the automatic start-up of electron linear accelerators. The work is carried out in parallel at two similar research accelerators: ARES at DESY and FLUTE at KIT, giving the unique opportunity of transfer learning between facilities. One of the first steps of this project is the establishment of a common interface between the simulations and the machine, in order to test and apply various optimization approaches interchangeably between the two accelerators. In this paper we present the first results on the common interface and its application to beam focusing in ARES, and the idea of laser shaping with spatial light modulators at FLUTE

Learning to Do or Learning While Doing: Reinforcement Learning and Bayesian Optimisation for Online Continuous Tuning

Online tuning of real-world plants is a complex optimisation problem that continues to require manual intervention by experienced human operators. Autonomous tuning is a rapidly expanding field of research, where learning-based methods, such as Reinforcement Learning-trained Optimisation (RLO) and Bayesian optimisation (BO), hold great promise for achieving outstanding plant performance and reducing tuning times. Which algorithm to choose in different scenarios, however, remains an open question. Here we present a comparative study using a routine task in a real particle accelerator as an example, showing that RLO generally outperforms BO, but is not always the best choice. Based on the study's results, we provide a clear set of criteria to guide the choice of algorithm for a given tuning task. These can ease the adoption of learning-based autonomous tuning solutions to the operation of complex real-world plants, ultimately improving the availability and pushing the limits of operability of these facilities, thereby enabling scientific and engineering advancements.Comment: 17 pages, 8 figures, 2 table

Studies towards Acceleration of Relativistic Electron Beamsin Laser-driven Dielectric Microstructures

In this work an approach to relativistic electron acceleration employing laser-driven dielectric microstructures (DLA) is considered. New DLA designs were developed, a simulation code for efficient DLA simulation was devised, the capabilities of dielectric microstructures as particle beam diagnostic devices were investigated and a laser induced damage threshold measurement setup was implemented and tested.To leverage well developed near-infrared laser sources new DLAs were designed that are robust against realistic manufacturing tolerances and exhibit a predicted increased electron transmission of up to \SI{44}{\percent} of the charge and longitudinal acceptance of around \SI{2}{\femto\second}, but are still able to produce \SI{}{\giga\volt/\meter} acceleration gradients. A great challenge is the numerical simulation of long interaction lengths of electrons with the short drive laser wavelengths present in DLAs due to the high demand in computation resources needed by the large simulation domain compared to the wavelength. A novel method was developed, which is able to efficiently model meter long DLAs without any resonant particle approximations by use of transfer maps generated from a single-period electromagnetic field simulation and a limited set of particle tracking simulations. In PIC simulations hundreds of DLA periods can be modeled using a high performance computing cluster. With the code presented in this work a meter long DLA (hundred thousands of periods) can be simulated on a workstation. This PhD work includes the numerical investigation of particle beam diagnostics capabilities of DLAs, namely as transverse deflecting structures and as new passive and active bunch length measurement devices for ultra-short particle bunches in the sub-femto second regime. All the presented methods are very compact in the particle beam line compared to existing methods.An experiment was devised to test the designed DLAs by injection of an electron bunch from a conventional state-of-the-art radio frequency accelerator with the potential to show first increase of the average energy of a relativistic electron beam in a DLA device. In contrast all experiments up to today are only modulating the particle beam energy. Finally an experimental setup was designed and implemented to measure the short pulse laser induced damage threshold of DLAs with characterization measurements taken on a bulk material

Simulation of a Many Period Dielectric Grating-based Electron Accelerator

Dielectric laser driven particle accelerators have become a research area of major interest due to the high acceleration gradients achievable. Those are mainly attributed to the high damage thresholds of dielectrics at optical frequencies. Simulations of these structures are usually computed with Particle-In-Cell (PIC) codes. Their accuracy and self consistency comes with a major drawback of high computation costs. Computation of structures consistent of hundreds to thousands of periods are only viable with High Performance Computing clusters. In this proceeding a compromise of CST* PIC simulations combined with a transfer function model is presented to simulate relativistic electron accelerators for particle energies up to the GeV regime or higher. In addition a simplified example accelerator design is investigated and the required electron bunch parameters from a sub-relativistic source are computed

A Fast Particle Tracking Tool for the Simulation of Dielectric Laser Accelerators

In order to simulate the beam dynamics in grating based Dielectric Laser Accelerators (DLA) fully self-consistent PIC codes are usually employed. These codes model the evolution of both the electromagnetic fields inside a laser-driven DLA and the beam phase space very accurately. The main drawback of these codes is that they are computationally very expensive. While the simulation of a single DLA period is feasible with these codes, long multi-period structures cannot be studied without access to HPC clusters. We present a fast particle tracking tool for the simulation of long DLA structures. DLATracker is a parallelized code based on the analytical reconstruction of the in-channel electromagnetic fields and a Boris/Vay-type particle pusher. It computational kernel is written in OpenCL and can run on both CPUs and GPUs. The main code is following a modular approach and is written in Python 2.7. This way the code can be easiliy extended for different use cases. In order to benchmark the code, simulation results are compared to results obtained with the PIC code VSim 7.2

Simulation of Phase-Dependent Transverse Focusing in Dielectric Laser Accelerator Based Lattices

The Accelerator on a CHip International Program (ACHIP) funded by the Gordon and Betty Moore Foundation aims to demonstrate a prototype of a fully integrated accelerator on a microchip based on laser-driven dielectric structures until 2021. Such an accelerator on a chip needs all components known from classical accelerators. This includes an electron source, accelerating structures and transverse focusing arrangements. Since the period of the accelerating field is connected to the drive laser wavelength of typically a few microns, not only longitudinal but also transverse effects are strongly phase-dependent even for few femtosecond long bunches. If both the accelerating and focusing elements are DLA-based, this needs to be taken into account. In this work we study in detail the implications of a phase-dependent focusing lattice on the evolution of the transverse phase space of a transported bunch

First Order Sensitivity Analysis of Electron Acceleration in Dual Grating Type Dielectric Laser Accelerator Structures

Symmetrically driven dual-grating type DLA (Dielectric Laser Accelerator) linac structures allow for in-channel electric field gradients on the order of GV/m at optical wavelengths. In this work we study the sensitivity of important final beam parameters like mean energy, energy spread and transverse emittance on DLA drive laser as well as input beam parameters. To this end a fast specialized particle tracking code (DLATracker) is used to compute the so called first order sensitivity indices based on a large number of Monte Carlo simulation runs of an exemplary external injection based DLA experiment. The results of this work point out important stability constraints on the drive laser setup and the externally injected electron beam

Introduction reminiscence therapy in the Home for the Elderly Tachov, U Penzionu 1711

Diplomová práce Zavedení reminiscenční terapie v Domově pro seniory Tachov, U Penzionu 1711, se zabývá zjištěním, zda je tento domov vhodným zařízením pro výkon reminiscenční terapie. Na základě realizace pilotního projektu reminiscenční terapie a rozhovorů s účastníky terapie a klíčovými pracovníky domova byla vytvořena metodika, která má být průvodcem při zavedení této terapeutické aktivity mezi plnohodnotné aktivizační činnosti v domově.Katedra pedagogikyObhájenoIntroduction reminiscence therapy in the Home for the Elderly Tachov, U Penzionu 1711,- to find out this Home is a suitable facility for a performance of the reminiscence therapy. Based on realization of a pilot project of reminiscence therapy and interviews with the therapy participants and key workers of the Home, a methodology, which should be used as a guide while establishing this therapeutic activity among valid activation activities in the Home, was set