Dr. Ulrich Hilmar Wagner

Physicist

Paul Scherrer Institute
Forschungsstrasse 111
5232 Villigen PSI
Switzerland






Ulrich Wagner studied Physics at the University of Goettingen, developing a laser-plasma based droplet source for x-ray microscopy. He then continued his studies at the University of Jena to obtain a PHD in the field of plasma-physics and x-ray optics.

During his PHD he became a Marie-Curie  fellow to study at the Rutherford-Appleton Laboratory in the United Kingdom. There he collaborated with the Imperial College in London to employ soft-x ray polarimetry to study Megagauss magnetic fields in laser produced fs-plasmas.

After graduating from the University of Jena he joined the Diamond Light Source in the United Kingdom as an x-ray optics scientist, contributing to the beamline design and the metrology programme. He then became a beamline and senior beamline scientist, making significant contributions to Diamond’s Imaging and coherence beamline I13.

In 2017 he joined the Paul Scherrer Institut to work on x-ray optics and metrology with an emphasise on the SwissFEL project. Since 2019 he is a tenured staff scientist. 

Development, installation and commissioning of the SwissFEL beamlines, in particular the soft x-ray ATHOS beamlines.

Ulrich Wagner is  interested in advanced experiments with photon sources of unprecedented properties, which open up new scientific opportunities, but also create challenges for the beamline instrumentation and photon optics. Therefore, he is particularly interested in advancing an integrated approach for instrumentation design, where an optical system is considered as a single entity, which requires combined mechanical, controls and optical simulations and metrology to meet its specified performance.   

Consequently, he is working on advancing the capabilities of PSI’s optical metrology laboratory and progressing at-wavelength metrology methods from proof of principle experiments into a standardised quantitative diagnostic tools to study the performance of x-ray optical components and facilitate the in-situ beamline alignment.

In addition to this, he enjoys advancing coherence based high resolution 5d x-ray imaging techniques, namely time-resolved x-ray microscopy in three dimensions with spectral resolution.

For an extensive overview we kindly refer you to our publication repository  DORA

A photon beam diffusor for the ATHOS beamlines at SwissFEL, Ulrich Wagner, Rolf Follath, Uwe Flechsig and Luc Patthey, Proceedings of the 13th international conference on synchrotron radiation instrumentation - SRI2018. Vol. 2054. AIP conference proceedings. AIP Publishing (2019)
SwissFEL is a free electron laser at the Paul Scherrer Institut in Switzerland, which became operational by the end of 2017. Initially, it will host two undulators ARAMIS and ATHOS. The former is operational and generating tender to hard x-rays (2 to 12 keV), whilst the latter is in the process of being installed and will provide soft x-rays ranging from 0.2 to 2 keV. Each undulator will eventually serve three different endstations. Recent Genesis simulations have shown that the ATHOS branch can operate in a high-power mode, which will increase the photon pulse energy by one order of magnitude to 8.1 mJ at 250 eV. This will lead to peak beam intensities inside the frontend, which will damage any normal incidence absorber. To overcome this issue a photon beam diffusor is proposed in this paper. At the core of this instrument is a bent rod, which is positioned at a grazing angle relative to the incident beam, so that it acts like a defocussing mirror, reflecting most of the incident power and increasing the divergence of the reflected beam. Due to the increased divergence, the beam diameter is increased by a factor of 10 after propagating over a few meters, thus reducing the peak intensity by a factor of 100 to a level, which can be safely absorbed by a normal incidence absorber.
 
Optical design of the Athos beamlines at SwissFEL, Rolf Follath, Uwe Flechsig, Ulrich H. Wagner and Luc Patthey, Proceedings of the 13th international conference on synchrotron radiation instrumentation - SRI2018. Vol. 2054. AIP conference proceedings. AIP Publishing (2019)
The Paul Scherrer Institut is currently constructing Athos, its second Free Electron Laser with a photon energy range from 250 eV to 1900 eV and pulse energies up to 8 mJ. A single soft X-ray beamline is attached to the undulator section and distributes the radiation into three branches. The beamline design is based on a variable line space spherical grating monochromator with a grating chamber and two retractable distribution mirrors. An achromatic focusing with individual KB-mirror systems downstream of the exit slits focus the beam to the endstations. The stations can operate alternatively without interfering with each other.
 
Inspecting adaptive optics with at-wavelength wavefront metrology, Jurai Krempaský, F. Koch, Patric Vagovič, L. Mikeš, Andreas Jaggi, Cris Svetina and Ulrich H. Wagner, Proceedings of SPIE: Vol. 10761. Adaptive X-ray optics V (2018)
Preserving the coherence and wavefront of a diffraction limited x-ray beam from the source to the experiment poses stringent quality requirements on the production processes for X-ray optics. In the near future this will require on-line and in-situ at-wavelength metrology for both, free electron lasers and diffraction limited storage rings. A compact and easy to move X-ray grating interferometry (XGI) setup has been implemented by the Beamline Optics Group at PSI in order to characterize x-ray optical components by determining the aberrations from reconstructing the x-ray wavefront. The XGI setup was configured for measurements in the moiré mode and tested with focusing optic at Swiss Light Source, Diamond Light Source and LCLS. In this paper measurements on a bendable toroidal mirror, a zone plate, a single and a stack of beryllium compound refractive lenses (CRL) are presented. From these measurements the focal position and quality of the beam spot in terms of wavefront distortions are determined by analysing the phase-signal obtained from the XGI measurement. In addition, using a bendable toroidal mirror, we directly compare radius of curvature measurements obtained from XGI data with data from a long-trace profilometer, and compare the CRL wavefront distortions with data obtained by ptychography.
 
Mirror systems for SwissFEL, from concept to commissioning with x-rays, Sibylle Spielmann, Uwe Flechsig, Vincent Thominet, Rolf Follath, Jurai Krempasky, Ulrich Wagner and Luc Patthey, Proceedings of the 13th international conference on synchrotron radiation instrumentation - SRI2018. Vol. 2054. AIP conference proceedings. AIP Publishing (2019)
The two Aramis beamlines at SwissFEL are currently under commissioning, first pilot experiments have already been carried out. In total we have 10 mirror systems, 6 offset mirrors and 4 mirrors in KB [1] configuration. We use bilayer mirror coatings to handle the single shot damage challenge at FELs. The optics has to keep the coherence of the FEL pulses. We use flat mirrors with figure errors on the single nm level in two-actuator mechanical bender systems. The vertically deflecting KB mirrors have a polished-in gravity sag compensation. The performance of the mirror systems has been verified with X-rays.
 
  • German Physical Society
  • Visiting Scientist at the University of Southampton: Coherent Imaging & Scattering