arXiv subjects

Bernd Steffen

Publications and source records attributed to Bernd Steffen.

3 recordsLinked to original sources

arXiv2022

Phase Diversity Electro-optic Sampling: A new approach to single-shot terahertz waveform recording

THz spectroscopy is an emerging tool for detection of microorganisms and harmful compounds in the food industry, the study of proteins in biomedicine and the development of electron-beam X-ray sources for molecular imaging and lithography. Recording of THz electric field evolution in single-shot is crucially needed in terahertz spectroscopy of irreversible processes in such applications as well as for data communication in the THz portion of the spectrum where there is an abundance of untapped bandwidth. However, achieving sub-picosecond resolution over a long time window has been an open problem for electro-optic sampling -- the standard technique for recording terahertz waveforms. We introduce a new conceptual framework for this open problem that is inspired by time-stretch theory. The novel framework unveils a solution to this 20 year-old problem leading to a dramatic enhancement of the achievable temporal resolution. We validate this new technology in two applications. First, we present single shot recordings of long free-propagating terahertz transients with record time resolution. Second, we present recordings of ultra-short relativistic electron bunches at the European X-ray Free Electron Laser. These results show that electric signals may be now recorded with terahertz bandwidth over arbitrarily long windows, thus enabling the realization of "single-shot terahertz oscilloscopes" and single-shot time-domain spectroscopy systems with an arbitrary time-bandwidth product.

physics.optics↗

arXiv2019

Revealing the dynamics of ultrarelativistic non-equilibrium many-electron systems with phase space tomography

The description of physical processes with many-particle systems is a key approach to the modeling of countless physical systems. In storage rings, where ultrarelativistic particles are agglomerated in dense bunches, the measurement of their phase-space distribution (PSD) is of paramount importance: at any time the PSD not only determines the complete space-time evolution but also provides fundamental performance characteristics for storage ring operation. Here, we demonstrate a non-destructive tomographic imaging technique for the 2D longitudinal PSD of ultrarelativistic electron bunches. For this purpose, we utilize a unique setup, which streams turn-by-turn near-field measurements of bunch profiles at MHz repetition rates. To demonstrate the feasibility of our method, we induce a non-equilibrium state and show, that the PSD microstructuring as well as the PSD dynamics can be observed in great detail with an unprecedented resolution. Our approach offers a pathway to control ultrashort bunches and supports, as one example, the development of compact accelerators with low energy footprints.

physics.acc-ph↗

arXiv2018

Real-time Data Acquisition and Processing System for MHz Repetition Rate Image Sensors

One of the optimization goals of a particle accelerator is to reach the highest possible beam peak current. For that to happen the electron bunch propagating through the accelerator should be kept relatively short along the direction of its travel. In order to obtain a better understanding of the beam composition it is crucial to evaluate the electric charge distribution along the micrometer-scale packets. The task of the Electro-Optic Detector (EOD) is to imprint the beam charge profile on the spectrum of light of a laser pulse. The actual measurement of charge distribution is then extracted with a spectrometer based on a diffraction grating. The article focuses on developed data acquisition and processing system called the High-speed Optical Line Detector (HOLD). It is a 1D image acquisition system which solves several challenges related to capturing, buffering, processing and transmitting large data streams with use of the FPGA device. It implements a latency-optimized custom architecture based on the AXI interfaces. The HOLD device is realized as an FPGA Mezzanine Card (FMC) carrier with single High Pin-Count connector hosting the KIT KALYPSO detector. The solution presented in the paper is probably one of the world fastest line cameras. Thanks to its custom architecture it is capable of capturing at least 10 times more frames per second than fastest comparable commercially available devices.

physics.ins-det↗