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Junior Professorship for Accelerator Physics

Jun.-Prof. Dr. Wolfram Helml

Department of Physics
Center for Synchrotron Radiation
Maria-Goeppert-Mayer-Str. 2
44227 Dortmund

Room: 01
E-Mail: wolfram.helmltu-dortmundde
Tel.: +49 (0)231 755-5376
Fax: +49 (0)231 755-5383

Portrait of Wolfram Helml © Wolfram Helml​/​TU Dortmund


"In our research, we deal with ultrafast processes of electron dynamics at the fundamental level, from simple excitation processes in atoms to the complex biological processes in human cells. The relevant time scales are in the range of attoseconds, i.e. 10-18 seconds-illustratively, an attosecond is to a second what a second is to the entire age of the universe!
To measure these electron dynamics, an ultrafast stopwatch is needed: In our experiments, we use X-ray pulses superimposed with the oscillations of a circularly polarized laser field and an angle-resolved electron spectrometer. This allows us to build a so-called "streaking camera" with an extremely short exposure time. We first demonstrated this principle at the LCLS free-electron laser in Stanford, USA, in 20181. We are currently working with a "machine intelligence" group at the University of Kassel to develop a new experimental setup that will be tested at DELTA in Dortmund, Germany, and should allow time- and angle-resolved X-ray spectroscopy at the European XFEL in Hamburg with online analysis in the near future."

1 Hartmann, N. et al. Attosecond time-energy structure of X-ray free-electron laser pulses. Nat. Photonics 12, 215-220 (2018).

Further information

"The image shows a typical streaking camera: An ultrashort one X-ray flash (shown in blue, coming into the image from the left) is superimposed with a laser pulse (red wave train) in the center of the measurement setup. There, the X-ray flash knocks electrons out of gas atoms, which are accelerated or decelerated by the electric field of the laser pulse depending on the time of their emission. The energies of these electrons (shown in green) are measured by a detector (top right), and conclusions are drawn about the duration of the original X-ray flash and the sequence of fundamental excitation processes in the gas atoms."

Streaking-Camera / Accelerator Physics © Christian Hackenberger​/​MPQ


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Location & approach

The campus of the Technical University of Dortmund is located near the freeway junction Dortmund West, where the Sauerland line A45 crosses the Ruhr expressway B1/A40. The Dortmund-Eichlinghofen exit on the A45 leads to the South Campus, the Dortmund-Dorstfeld exit on the A40 leads to the North Campus. The university is signposted at both exits.

The "Dortmund Universität" S-Bahn station is located directly on the North Campus. From there, the S-Bahn line S1 runs every 20 or 30 minutes to Dortmund main station and in the opposite direction to Düsseldorf main station via Bochum, Essen and Duisburg. In addition, the university can be reached by bus lines 445, 447 and 462. Timetable information can be found on the homepage of the Rhine-Ruhr transport association, and DSW21 also offer an interactive route network map.



One of the landmarks of the TU Dortmund is the H-Bahn. Line 1 runs every 10 minutes between Dortmund Eichlinghofen and the Technology Center via Campus South and Dortmund University S, while Line 2 commutes every 5 minutes between Campus North and Campus South. It covers this distance in two minutes.



From Dortmund Airport, it takes just over 20 minutes to get to Dortmund Central Station by AirportExpress and from there to the university by S-Bahn. A wider range of international flight connections is offered by Düsseldorf Airport, about 60 kilometers away, which can be reached directly by S-Bahn from the university's train station.

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The facilities of TU Dortmund University are spread over two campuses, the larger Campus North and the smaller Campus South. Additionally, some areas of the university are located in the adjacent "Technologiepark".

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