CHG spectra analysis - Delta - TU Dortmund

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Location & approach

By car

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.

By bus and train

The "Dortmund Universität" S-Bahn station is located directly on the North Campus. From there, the S-Bahn line S1 runs every 15 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.

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By H-Bahn

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.

By plane

From Dortmund Airport, the AirportExpress takes just over 20 minutes to Dortmund Central Station and from there the S-Bahn (suburban train) takes you to the university. 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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Cafeteria menus

To overview

Location & approach

By car

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.

By bus and train

The "Dortmund Universität" S-Bahn station is located directly on the North Campus. From there, the S-Bahn line S1 runs every 15 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.

Translated with www.DeepL.com/Translator (free version)

By H-Bahn

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.

By plane

From Dortmund Airport, the AirportExpress takes just over 20 minutes to Dortmund Central Station and from there the S-Bahn (suburban train) takes you to the university. 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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CHG spectra analysis

Atomic transition processes usually occur on very short time scales. To temporally resolve these processes, very short light pulses are generated at the synchrotron radiation source DELTA using a technique so-called Coherent Harmonic Generation (CHG). For this purpose, a pulsed laser beam is overlapped with the stored electron beam in a specialized magnet (undulator) to modulate the electron energies (modulator). As the modulated electrons pass through a magnetic chicane, the energy modulation is converted into a density modulation, so that CHG radiation is emitted from a subsequent second undulator, which acts as a radiator (see picture top right). The CHG method provides ultrashort (sub-picosecond), coherent light pulses with wavelengths extending into the vacuum-ultraviolet range (VUV). The spectral characteristics of this radiation depend, among others, on the adjustment parameters of the "seeding" laser beam and the chicane strength. Further information can be found in the project descriptions and publications of the research groups (see: Khan, Helml).

The figure shows a schematic representation of the CHG principle. — Schematic illustration of the CHG principle.

The figure shows the topology of a convolutional multilayer neural network (CNN). — Convolutional multilayer neural network (CNN) for the analysis of CHG spectra.

The figure shows the comparison of measured (1st row) and with CNN predicted (2nd row) CHG spectra for different settings of the laser compressor (GDD, TOD) and strengths of the chicane (R56). — Comparison of measured (1st row) and CNN predicted (2nd row) CHG spectra for different settings of the laser compressor (GDD, TOD) and strengths of the chicane (R56).

For the NN-based analysis of CHG radiation spectra, they were first simulated for laser pulses with different spectral phases and different strengths of the magnetic chicane (R56). In particular, the influence of two laser pulse parameters, group delay dispersion (GDD) and third-order dispersion (TOD), on the spectra was primarily investigated. To predict the GDD and TOD values from the measured CHG spectra, a convolutional neural network (CNN) was developed (see second figure above) and then trained with a data set of over 40000 numerically simulated spectra for different combinations of GDD and TOD values. Subsequently, the trained surrogate models were capable of predicting the GDD and TOD values of the laser pulse for different pulse properties, from the measured spectra (see left image). Further details can be found in the conference contribution for the IPAC-2023.