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How CERN uses digitizers & AWGs by Spectrum | Spectrum

Spectrum PC cards perform many different tasks at CERN
Over 140 digitizer and AWG cards from Spectrum Instrumentation are being used at CERN: They serve in the machine protection systems of the Large Hadron Collider, simulate kicker magnet waveforms or send timing & control signals to help to develop new protection systems.

In CERN’s Large Hadron Collider (LHC), two high-energy particle beams travel at close to the speed of light in opposite directions in the 27 km accelerator ring. They are then made to collide at four locations around the ring for runs of several hours. The particles are so tiny that the task of making them collide is akin to firing two needles 10 kilometers apart with such precision that they meet halfway. The energy stored in the two beams is so high that, in the case of loss of control of the beams, the LHC machine could suffer serious damage. To safely dispose of the beams in the case of an emergency, or at the end of a collision run, the LHC Beam Dumping System (LBDS) must extract the full beams from LHC in one revolution and transport them to an absorber block located about 700m away from the LHC rings. After every beam dump, post-operation check systems will make sure that all elements within LBDS performed correctly and that the beams were cleanly extracted.

A key part is checking that the fast-pulsed magnets, called kicker magnets, have accurately deflected the particle beams from the LHC rings to the extraction lines. Digitizer cards are used to capture the current pulse waveforms to check that they had the correct shape and were correctly synchronized with the beam. To give an idea, the LBDS extraction magnet current pulses themselves are about 20 kA with rise times of less than 3 µs and a synchronization error below 20 ns. At LBDS alone, for every beam dump event, nearly 500 analog signals are acquired using digitizer cards and more than 150 synchronization signals are captured using digital I/O cards.

A very high level of precision is naturally required for the measurements of these kicker pulse events. For example, the most demanding systems require a pulse-to-pulse reproducibility error for the delay of lower than 10 ns, and for the amplitude of lower than 0.5% within a dynamic range of 16. To achieve this, the precision of the acquisition has to be even greater by an order of magnitude, hence the choice, for instance, of a Spectrum Instrumentation M4i.4451-x8 digitizer with a time resolution of 2 ns and an Effective Number Of Bits (ENOB) larger than 10.

“We also make use of Spectrum Instrumentation Arbitrary Waveform Generator (AWG) cards to simulate kicker current waveforms and Spectrum Instrumentation Digital Pattern Generators cards to send timing and control signals to help to develop and validate surveillance and protection systems on our test benches. We sometimes also use LabVIEW on Windows for test benches, as Spectrum Instrumentation hardware is directly compatible with this environment.”
More than 140 Spectrum Instrumentation cards are presently used in operation for kicker systems on all CERN accelerators, on PCI/PCIe and more recently, PXIe platforms.

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