X-ray pulses on demand from electron storage rings

Some contemporary Synchroton Radiation methods need light pulsed x-rays with a specific time structure. HZB-users at BESSY II can use them now on demand. Graphics: Highway at night. Credit: Image: K. Holldack/HZB

Here, relativistic electrons in a storage ring are employed to generate very brilliant and partly coherent light pulses from the THz to the X-ray regime in undulators and other devices. However, most of the techniques used at synchrotrons are very “photon hungry” and demand brighter and brighter light pulses to conduct innovative experiments.

The general greed for stronger light pulses does, however, not really meet the requirements of one of the most important techniques in material science: photoelectron spectroscopy. Physicists and chemists have been using it for decades to study molecules, gases and surfaces of solids.

However, if too many photons hit a surface at the same time, space charge effects deteriorate the results. Owing to these limits, certain material parameters stay hidden in such cases. Thus, a tailored temporal pattern of x-ray pulses is mandatory to move things forward in surface physics at Synchrotrons.

Scientists from HZB's Institute for Methods and Instrumentation in Synchrotron Radiation Research and the Accelerator Department have now jointly solved the gordic knot as they published in the renowned journal Nature Communications.

Their novel method is capable of picking single pulses out of a conventional pulse train as usually emitted from Synchrotron facilities. They managed to apply this for the first time to time-of-flight electron spectroscopy based on modern instruments as developed within a joint Lab with Uppsala University, Sweden.

Picking single pulses out of a pulse train

The pulse picking technique is based on a quasi resonant magnetic excitation of transverse oscillations in one specific relativistic electron bunch that – like all others – generates a radiation cone within an undulator. The selective excitation leads to an enlargement of the radiation cone. Employing a detour (“bump”) in the electron beam path, the regular radiation and the radiation from the excited electrons can be easily separated and only pulses from the latter arrive – once per revolution – at the experiment. Thus, the arrival time of the pulses is now perfectly accommodated for modern high resolution time-of-flight spectrometers.

Users will be able to examine band structures with higher precision

“The development of the Pulse Picking by Resonant Excitation (PPRE) was science driven by our user community working with single bunch techniques. They demand more beamtime to improve studies on e.g. graphene, topological insulators and other “hot topics” in material science like the current debates about high Tc-Superconductors, magnetic ordering phenomena and catalytic surface effects for energy storage. Moreover, with pulse picking techniques at hand, we are now well prepared for our future light source with variable pulse lengths: BESSY-VSR, where users will appreciate pulse selection on demand to readily switch from high brightness to ultrashort pulses according to their individual needs” says Karsten Holldack, corresponding author of the paper.

First tests successful

The researchers have proven the workability of their method with ARTOF-time-of-flight spectrometers at different undulators and beamlines as well as in BESSY II's regular user mode. “Here we could certainly benefit from long year experiences with emittance manipulation”, says Dr. P. Kuske acting as head of the accelerator part of the team. Thanks to accelerator developments in the past, we are capable of even picking ultrashort pulses out of the bunch trains in low-alpha operation, a special operation mode of BESSY II. At last, the users can, already right now, individually switch – within minutes – between high static flux and the single pulse without touching any settings at their instruments and the sample.

###

The work has now been published on May 30th 2014 in Nature Communications: Single Bunch X-ray Pulses on Demand from a Multibunch Synchrotron Radiation Source, K. Holldack et al. DOI 10.1038/ncomms5010

Media Contact

Dr. Karsten Holldack Eurek Alert!

More Information:

http://www.helmholtz-berlin.de

All latest news from the category: Physics and Astronomy

This area deals with the fundamental laws and building blocks of nature and how they interact, the properties and the behavior of matter, and research into space and time and their structures.

innovations-report provides in-depth reports and articles on subjects such as astrophysics, laser technologies, nuclear, quantum, particle and solid-state physics, nanotechnologies, planetary research and findings (Mars, Venus) and developments related to the Hubble Telescope.

Back to home

Comments (0)

Write a comment

Newest articles

Lighting up the future

New multidisciplinary research from the University of St Andrews could lead to more efficient televisions, computer screens and lighting. Researchers at the Organic Semiconductor Centre in the School of Physics and…

Researchers crack sugarcane’s complex genetic code

Sweet success: Scientists created a highly accurate reference genome for one of the most important modern crops and found a rare example of how genes confer disease resistance in plants….

Evolution of the most powerful ocean current on Earth

The Antarctic Circumpolar Current plays an important part in global overturning circulation, the exchange of heat and CO2 between the ocean and atmosphere, and the stability of Antarctica’s ice sheets….

Partners & Sponsors