Keywords: accelerator physics (174) BESSY II (269)

Science Highlight    15.03.2018

Twin Orbit operation successfully tested at BESSY II

A synchrotron source point image of a bending magnet of the Twin Orbit modus. The second orbit closes after three revolution and is winding around the standard orbit at the center.
Copyright: HZB

The first “Twin Orbit User Test week” at BESSY II in February 2018 was a big success and can be considered as an important step towards real user operation. Physicists at Helmholtz-Zentrum Berlin have been able to store two separate electron beams in one storage ring. The twin orbit operation mode can serve users with different needs of the time structure of the photon pulses simultaneously and offers elegant options regarding the future project BESSY VSR.

The Twin Orbit operation mode makes use of non-linear beam dynamics and provides two stable well separated orbits for storing two electron beams in one storage ring. The bunch fill patterns of both orbits can be chosen, to some extent, independently, which allows for fulfilling normally incompatible user needs, simultaneously. For example, one orbit can be used to store a homogenous multi bunch fill to deliver high average brilliance for photon hungry experiments, whereas only one single bunch is stored on the other orbit for timing experiments, providing a much lower pulse repetition rate.

First experiments in 2015

It is a long process from an idea to a real operational week, especially at a running multi user facility. First studies of this mode started already 2015 at the smaller ring, the Metrology Light Source (MLS), resulting in a successful user experiment with the Physikalisch Technische Bundesanstalt (PTB) [1]. In parallel a group of HZB experts implemented and optimized this mode at BESSY II in single machine commissioning shifts. Important milestones have been the operation of a large number of insertion devices as well as the topping up injection scheme to keep the stored current constant. In 2017 a successful overnight run with topping up injection and some participating beamlines gave confidence for a first longer test week [2].

Excellent availabilty of synchrotron light

The days of this “Twin Orbit User Test week” have been used for common experiments of machine group and beamline scientists in order to characterize this operational mode and generate feedback for further optimization. During the nights and the complete weekend ‘normal’ user time was scheduled with two different fill patterns (multibunch and single bunch) on both orbits. The availability and stability of the synchrotron source were comparable to the current standard user mode and exceeds/reaches 99 per cent.

Elegant option for BESSY VSR

“There is still a lot of work to do, but nevertheless this proof-of-principle week showed that a development towards a realistic user mode should be possible. And even more, for the future BESSY VSR project, it could be a very elegant way to separate short and long bunches”, Prof. Andreas Jankowiak concludes.




Dr. Paul Goslawski


You might also be interested in
  • <p>Experiments at the femtoslicing facility of BESSY II revealed the ultrafast angular momentum flow from Gd and Fe spins to the lattice via orbital moment during demagnetization of GdFe alloy.</p>SCIENCE HIGHLIGHT      10.05.2019

    Laser-driven Spin Dynamics in Ferrimagnets: How does the Angular Momentum flow?

    When exposed to intense laser pulses, the magnetization of a material can be manipulated very fast. Fundamentally, magnetization is connected to the angular momentum of the electrons in the material. A team of researchers led by scientists from the Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy (MBI) has now been able to follow the flow of angular momentum during ultrafast optical demagnetization in a ferrimagnetic iron-gadolinium alloy at the femtoslicing facility of BESSY II. Their results are helpful to understand the fundamental processes and their speed limits. The study is published in Physical Review Letters. [...]

  • <p>Tomography of a lithium electrode in its initial condition.</p>SCIENCE HIGHLIGHT      06.05.2019

    3D tomographic imagery reveals how lithium batteries age

    Lithium batteries lose amp-hour capacity over time. Microstructures can form on the electrodes with each new charge cycle, which further reduces battery capacity. Now an HZB team together with battery researchers from Forschungszentrum Jülich, the University of Munster, and partners in China have documented the degradation process of lithium electrodes in detail for the first time. They achieved this with the aid of a 3D tomography process using synchrotron radiation at BESSY II (HZB) as well at the Helmholtz-Zentrum Geesthacht (HZG). Their results have been published open access in the scientific journal "Materials Today". [...]

  • <p>SnSe is a highly layered orthorhombic structure. SnSe undergoes a phase transition of second order at 500&deg;C with an increase of the crystal symmetry from space group Pnma (left) to Cmcm (right).</p>SCIENCE HIGHLIGHT      24.04.2019

    High-efficiency thermoelectric materials: new insights into tin selenide

    Tin selenide might considerably exceed the efficiency of current record holding thermoelectric materials made of bismuth telluride. However, it was thought its efficiency became enormous only at temperatures above 500 degrees Celsius. Now measurements at the BESSY II and PETRA III synchrotron sources show that tin selenide can also be utilised as a thermoelectric material at room temperature – so long as high pressure is applied. [...]