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High-current and low-voltage step-down converter for feeding cold superconducting magnets. P. Varela.
Design, prototype and manufacture of a large series of 10V/50A DC/DC power converters for driving superconducting magnets into the 4km X-Ray free-electron laser tunnel, located in the research facilities of DESY, Hamburg
XFEL Project: the Application
Project sponsored by
Smaller, faster, more intense: The European XFEL will open up areas of research that were previously inaccessible. Using the X-ray flashes of the European XFEL, scientists will be able to map the atomic details of viruses, decipher the molecular composition of cells, take 3D images of the nano-world, film chemical reactions and study processes such as those occurring deep inside planets.
How it works?
To generate the X-ray flashes, bunches of electrons will first be accelerated to high energies and then directed through special arrangements of magnets. In the process, the particles will emit radiation that is increasingly amplified until an extremely short and intense X-ray flash is finally created.
The Power Supply
±10V / 50A
η, size, T, …
(2 power modules per power PCB)
THE LOAD: ELECTROMAGNET
Normal operation: L(2H) + verylow R
Enhances repeatability & reduces assembling cost (500 units)
Low Cu loss (50A)
For low ringing
Bipolar Synchronous Rectification (4 MOSFETs)
2 LF switches
2 HF switches
(rectify Vsec waveform)
Usual operation: free-wheeling
Saves transformer losses when running at almost 0V
3. Adaptation to control interface
Outer loop: iout control, which creates the field
Inner loop: Vout control, which defines the magnet di/dt
Variable fsw control for optimal losses balance (switching vs on)
1st prototype with FPGA open-loop control
50A/10V, detail of the current share among both inductors in a module
2. Initial prototype
Failure in the magnet, detected by a voltage rise in the magnet terminals
Quench transient evolution
η up to 92,5%
(planar transformer, no driving nor control losses)
50A/1.4V, detail of a secondary MOSFET turn-on
2nd version of the power PCB
Cold magnet: Electromagnet whose superconductivity comes from its low temperature (<10K). The low temperature is achieved by using liquid He cryostats.
Hot magnet:Superconductingelectromagnet at “muchhighertemperature” (>77K)
Quench: A quench is an abnormal termination of magnet operation that occurs when part of the superconducting coil enters the resistive state, mainly due to magnetic field excess. That part sinks power which increases T in the surroundings, making them enter the resistive state as well.