BESSY II changes over to solid state RF amplifiers

One of the new solid state transmitters: the power supplies are located in the left rack (black), the RF section is located behind the grey doors in the middle and in the right rack the control units can be seen.

One of the new solid state transmitters: the power supplies are located in the left rack (black), the RF section is located behind the grey doors in the middle and in the right rack the control units can be seen. © HZB

BESSY II storage ring has four cavity resonators that are excited with high-power oscillating electromagnetic fields to compensate for the energy lost by the electron beam. Four Klystrons, as they are called (large high-power linear RF vacuum tubes), have provided extremely pure 500-MHz RF power for exciting these cavity resonators up to now. But there are no replacement klystrons available on the market. Wolfgang Anders and his team at the HZB’s Institute SRF – Science and Technology have therefore used the shutdown to replace two of the klystrons with modern solid-state RF amplifiers. The other klystrons are to be replaced until the end of the year.

“This technology was first developed and employed at the SOLEIL synchrotron in France. However, SOLEIL operates with an excitation frequency of 350 MHz. By comparison, we work with a frequency of 500 MHz like most synchrotron light sources. We had to develop a new design for that reason. The development and manufacture of the RF amplifiers was carried out by a German company named Cryoelectra. We're the first photon source with this technology to have reached an excitation power of 75 kilowatts per amplifier for 500 MHz”, explains Anders.

While the vacuum-tube klystrons required a supply voltage of 26 kilovolts, the solid-state semiconductor RF amplifiers operate at just 50 Volts, but require much higher current. The energy saved is a big advantage. This is because klystron vacuum-tube RF amplifiers constantly draw full power from the mains, whereas the semiconductor RF amplifiers’ current draw is demand-follow and they only pull as much power from their mains connection as needed to compensate for the electron beam energy losses. In addition, the new RF units produce much less RF-noise, because the cavity resonators are excited more purely, which in turn improves the beam quality.

“My team has been working on implementing the new technology at BESSY II for three years. Just the extensive programming for connecting up to the control system interface and performing the signal processing for the solid-state amplifiers took a year for the engineer we hired specially for this. Now we have a very robust solution that is probably of interest to other synchrotron light sources as well”, says Anders.

arö

You might also be interested in

  • Humboldt Fellow Alexander Gray comes to HZB
    News
    12.08.2022
    Humboldt Fellow Alexander Gray comes to HZB
    Alexander Gray from Temple University in Philadelphia, USA, is working with HZB physicist Florian Kronast to investigate novel 2D quantum materials at BESSY II. With the fellowship from the Alexander von Humboldt Foundation, he can now deepen this cooperation. At BESSY II, he wants to further develop depth-resolved X-ray microscopic and spectroscopic methods in order to investigate 2D quantum materials and devices for new information technologies even more thoroughly.
  • Green hydrogen: Nanostructured nickel silicide shines as a catalyst
    Science Highlight
    11.08.2022
    Green hydrogen: Nanostructured nickel silicide shines as a catalyst
    Electrical energy from wind or sun can be stored as chemical energy in hydrogen, an excellent fuel and energy carrier. The prerequisite for this, however, is efficient electrolysis of water with inexpensive catalysts. For the oxygen evolution reaction at the anode, nanostructured nickel silicide now promises a significant increase in efficiency. This was demonstrated by a group from the HZB, Technical University of Berlin and the Freie Universität Berlin as part of the CatLab research platform with measurements among others at BESSY II.
  • RBB Abendschau on visit at CatLab
    News
    01.08.2022
    RBB Abendschau on visit at CatLab
    CatLab got a visit from the rbb Abendschau.
    Under the title "Der Weg weg vom Erdgas" (The way away from natural gas), the programme was broadcast on Sunday, 31st July in the rbb Abendschau and will be available in the rbb media library for 7 days.