Chromaticity adjustment - 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.

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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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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Setting the chromaticity values

Energy deviations of electrons stored in a storage ring result in misfocusing effects in the quadrupole magnets. The chromaticity values of a storage ring quantify the sum of these misfocusing effects. Sextupole magnets can be used to variably adjust these chromaticity values within certain technical limits. The DELTA storage ring is equipped with a total of 13 individually controllable sextupole circuits, which are software-grouped into 7 families. Until now, the adjustment of the magnet circuit currents has been done manually based on empirical knowledge.

The histogram plot shows the number of measured chromaticity changes caused by variations of sextupole strengths. — Number of measured chromaticity changes caused by statistical variations of the sextupole strengths.

The picture shows the adjustment of the chromaticity values using 7 independent sextupole magnetic circuits. — Adjustment of chromaticity values (red lines) as a function of iterative current changes of 7 sextupole magnetic circuits (blue lines).

Similar to the procedure for adjusting operating points, an ML-based approach was utilized for automating the control in this context as well. In this case, the strengths of the sextupole magnets were systematically and randomly varied (actuator data), and the resulting influences on the chromaticity values were measured (sensor data). Using this data, Gaussian Process Regressors (GPR) as well as neural networks were trained. These models can then be used as predictive models for optimizing sextupole settings during operation. Investigations revealed that classical machine learning methods, such as conventional feed-forward neural networks, are suitable for regulating chromaticity in both simulation and real storage ring operations.
Furthermore, it was demonstrated that the separation of sextupole circuits increases the flexibility in achieving desired chromaticity values during actual storage ring operations. Further details are described in the IPAC-22 conference paper, the DELTA Annual Report 2022, and the master thesis [12].