Particle accelerator pulse power measurement

Particle accelerators investigate the structure of matter. These accelerators often run 24/7 for international experimenters, so it is vital to have equipment that can be relied on to work perfectly and for many years. Spectrum Instrumentation digitizer cards are proving the signal capture equipment of choice for a major European research facility.

    Aerial view of Hamburg's DESY's research site
Aerial view of Hamburg's DESY's research site. Here high energy physics with elementary particles is performed. Linac-2 is just a part of DESY's extensive facilities. Further information at www.desy.de

Who is the customer?

DESY, short for Deutsches Elektronen-Synchrotron, based in Hamburg, Germany is a national research centre in Germany that operates particle accelerators used to investigate the structure of matter at the smallest scale. DESY attracts more than 3000 guest researchers from over 40 countries every year and a partner for national and international cooperations. Chemists, physicists, materials scientists and biologists are just some of the specialists undertaking cutting edge research at this centre.

Application Detail

This application requires the power measurement of pulses produced in the Linac-2 particle accelerator. The Linac-2 has 12 RF stations, each producing 5 microsecond RF pulses of 20 MW at 50 Hz which the cards needed to sample at 25 MHz. A bonus would be a 'tag' of each RF pulse with information from the central timing system for use in detailed analysis.


DESY computer simulation of particle acceleration within rf cavities.

A radiofrequency (RF) cavity is a metallic chamber that contains an electromagnetic field, these cavities can be structured like beads on a string, where the beads are the cavities and the string is the beam pipe of a particle accelerator, through which particles travel in a vacuum (see computer simulation image to left). Charged particles passing through the cavity feel the overall force and direction of the resulting electromagnetic field, which transfers energy to push them forwards along the accelerator. As a part of this application it is necessary to monitor the strengths and timing stability of so-called 'Kickers' that are used to transfer particle beams from one accelerator to another. That is straightforward except that a false-trigger can result in a Kicker generating a pulse on their own, without an external trigger. Ideally, the monitoring system would catch these pulses as well as the intentional ones triggered by the timing system.


Requirements

  • Multiple synchronous A/D channels
  • Sampling rate of 25MHz
  • Additional digital inputs, synchronous to the analogue sampling
  • A versatile triggering setup. Fast re-arm time.
  • Support for programming in Visual Basic
  • Capable of operating over a period of many years

Solution

Initially the scientists at DESY thought that no digitiser card would be capable of being configured to trigger a capture on the intentional external timing signal, or false rogue pulse signals. However as Mark Lomperski, Staff Scientist at DESY put it, "Spectrum said that its cards could be configured to do this and they worked flawlessly - I have always been impressed by their technical support. This dual trigger feature is brilliant. The false-triggers happen very seldom but, when they do, we catch them! I just wished we had had it 25 years ago." The card they chose was the 8 channel, 25 mega sample per second Mi.3132, fitted with the digital synchronous option.

"Spectrum's products have certainly proven themselves to be reliable" said Mark Lomperski. "The first digitizer cards that we bought for our group more than 15 years ago are still in use today, happily sampling away".

Footnote

One of the Linac-2 diagnostics systems has recently received an upgrade as the latest requirements for the system were beyond the range of the older cards. The new PXI-Express M4x.44xx-x4 cards provide 14-bits rather than 12-bits and 500 MHz rather than 20 MHz. Changing hardware can often present a challenge in adapting the existing software. To get the new software running for the new M4x cards, the customer decided to 'bite the bullet' and upgrade the old VB-6 Code that has been running happily for years to VB-NET. As Mark Lomperski explained: "Upgrading the Spectrum parts of the code from Visual-Basic 6 to Visual-Basic 14 was trivial; it's my own code that is driving me bananas!"

Gisela Hassler, Spectrum's CEO, added, "Research institutions and universities run projects and experiments that can take years so they have to know that they can rely on every part to work perfectly for the lifetime of the experiment. Spectrum products are built to last for years as can be seen by these cards still in use after 15 years. For further peace of mind, we provide a unique five years warranty, as well as an out-of-warranty repair service."

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Based on an application story by Spectrum Instrumentation GmbH
Images are courtesy of Deutsches Elektronen-Synchrotron, a Research Centre of the Helmholtz Association.
DataQuest Solutions Ltd. 27.07.18 E&OE