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THz driven accelerator components

English title THz driven accelerator components
Applicant Feurer Thomas
Number 178812
Funding scheme Project funding (Div. I-III)
Research institution Institut für angewandte Physik Universität Bern
Institution of higher education University of Berne - BE
Main discipline Other disciplines of Physics
Start/End 01.04.2018 - 31.03.2022
Approved amount 700'000.00
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Keywords (4)

Electron acceleration and diagnostics; Nearfield enhancement; Electron optics; THz near-field imaging

Lay Summary (German)

Lead
Mittels detaillierter Simulationen konnten wir zeigen, dass sich die unterschiedlichsten THz Metamaterialien zu interessanten Beschleunigerkomponenten umfunktionieren lassen, zum einen als relevante Diagnostik zum anderen zur Erzeugung ultrakurzer Strahlungsblitze. Um deren zeitliche Struktur genau zu vermessen entwickeln wir Rekustruktionsverharen, welche auf den Prinzipien der Ptychography beruhen.
Lay summary
Mittels detaillierter Simulationen konnten wir zeigen, dass sich verschiedene THz Metamaterialien in modernen Beschleunigern als Komponenten unterschiedlicher Funktionalität einsetzen lassen. Zum Beispiel können sogenannte Split Ring Resonatoren benutzt werden, um die ultrakurzen Elektronenpakete solcher Beschleuniger zeitlich zu vermessen. Um den experimentellen Nachweis dazu zu erbringen, sind in diesem Projekt Experimente an verschiedenen Beschleunigern weltweit geplant.

Desweitern untersuchen wir in diesem Projekt weitere komplexere THz Strukturen, zum Beispiel solche die sich als Mikroundulatoren zur Erzeugung von Strahlung einsetzen lassen. Hierzu sind theoretische Modelle zu erarbeiten und unterschiedliche Simulationen zu machen bevor die Strukturen dann letztendlich hergestellt und in geeigneten Beschleunigern getestet werden sollen.

Ein letztes Teilprojekt beschäftigt sich mir der Diagnostik der in solchen Maschinen erzeugten Strahlung, vor allem den in sogenannten freien Elektronenlasern erzeugten Röntgenblitze. Diese sind oft nur wenige Femtosekunden lang und erfordern eine entsprechend schnelle Diagnostik. In den vergangenen Jahren haben wir dazu eine Methodik entwickelt, die auf dem in der Bildgebung bekannten Verfahren der Ptychography beruht. Wir konnten theoretisch zeigen, dass man die entsprechenden Prinzipien auf den Zeitbereich übertragen und zur Rekonstruktion solch ultrakurzer Röntgenblitze einsetzen kann. Nun sind sowohl der experimentelle Nachweis als auch diverse Weiterentwicklungen geplant.
Direct link to Lay Summary Last update: 17.03.2020

Responsible applicant and co-applicants

Employees

Associated projects

Number Title Start Funding scheme
165686 Nearfield enhanced THz electron acceleration and spectroscopy 01.04.2016 Project funding (Div. I-III)

Abstract

Over the past funding period we started to transfer our expertise on THz meta-materials to a new field, namely advanced accelerator science. It turns out that THz radiation is useful, especially in diagnostics: the wavelength is comparable to typical transverse and longitudinal bunch sizes; it can be generated with high electric fields and it can be synchronized to other lasers in the system. Moreover, strong near-field enhancement, which is found in many meta-materials, alleviates limitations imposed on the interaction of charged particles with electromagnetic fields in vacuum; e.g., the Woodward-Lawson or the Panovsky theorem. Both can be circumvented if either electric or magnetic field is enhanced compared to the other and in the past we demonstrated electric field enhancements in excess of 10’000. Meta-materials offer flexibility because resonance frequency, Q factor or whether electric or magnetic field is enhanced can be controlled via a judicious choice of resonator geometry. Recently, we showed theoretically that such structures can serve as useful tools to characterize the longitudinal electron bunch length with a design that is reminiscent of a streak camera. Currently, we are preparing experiments at different laboratories where, in most cases, we provide the high-field THz source and design, simulate, fabricate and evaluate the structures with the tools and equipment developed in previous funding periods.Our next goal is to extend the scheme towards more sophisticated and complex devices, for example a THz driven undulator. During the current funding period we have analyzed different such devices from a theoretical viewpoint, now we would like to deepen the theoretical understanding and test their performance in practice. We want to verify the design of a THz-driven compact radiation source with two examples: (1) a soft X-ray source with wavelengths around 10s of nanometers, and (2) a directional hard X-ray source from relativistic electrons (100s of MeV). Contacts to suitable laboratories are established. Also, we will extend our studies to structures and devices that rely on magnetic rather than electric field enhancement.Another, but related area in which we became active about 4 years ago (within an international collaboration) is arrival time monitors and temporal X-ray pulse diagnostics for XFEL machines. We demonstrated, for soft X-ray energies, an arrival time monitor with femtosecond time resolution. In a next step, we extended the concept to a high fidelity single-shot X-ray pulse monitor with 0.5 fs time resolution. With his device we characterized, for the first time, the structure of un-seeded XFEL pulses and compared the result to theoretical predictions. Our main contribution in this project was to develop and test methodologies for the reconstruction of temporal waveforms. In the future we want to intensify our efforts by including our recently developed expertise on time-domain ptychography. We were the first to demonstrate time-domain ptychography and its application to a variety of scenarios in ultrafast optics and spectroscopy. Preliminary simulations indicate that this technique can also be used to retrieve the temporal structure of XFEL pulses from energy resolved photoelectron measurements. Moreover, we would like to develop space-time ptychography theoretically as well as experimentally for future laser-matter interaction investigations.
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