First LHC beam data help finding magnet powering problems
Despite the extremely fast and successful start-up of the CERN LHC,
the incident occurred on September 19th 2008 stopped the LHC beam
commissioning
at an early stage, when beam optics was not fully probed.
Nevertheless, a single beam trajectory that was recorded over 90 turns
around the machine circumference has been used to spot a critical magnet
powering problem.
In this paper we present state of the art signal analyzes applied to beam
trajectories aimed at probing the beam optics, see attached figure.
This, combined with the
development of new algorithms for precise uncovering of magnetic errors,
led to the finding of a cable swap between magnets of the two LHC rings.
This cable swap was also confirmed by hardware tests. The LHC
commissioning,
to resume by mid-November 2009, will certainly benefit from this
improvement
of the machine. The newly developed algorithms for the optics error
localization will be further challenged during this exciting phase of
the LHC.
Caption of attached Figure: Relative deviation between LHC measured
and design optics together with
tolerances. The powering problem was found at about 10km.
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LD12594
A Black Hole on a Chip
Thirty five years ago, Stephen Hawking famously showed that black holes radiate energy according to a thermal spectrum. However, his calculations relied on assumptions as to the unknown physics of ultra-high energies and quantum gravity. Adding to this is the inability to measure and verify the exceedingly low radiation temperatures predicted for astronomical black holes. In this paper the authors show that a magnetic field-pulsed microwave transmission line comprising an array of superconducting quantum interference devices, or SQUID's, not only reproduces physics analogous to that of a radiating black hole, but does so in a system where the high-energy and quantum mechanical properties are well understood and can be directly manipulated in the laboratory. Furthermore, by tuning the strength of the applied magnetic field, the pulsed microwave SQUID array can be used to probe black hole radiation beyond the regime considered by Hawking, in particular where the quantum fluctuations in the analogue spacetime geometry are large. This may lead to experiments that help to shed light on the as yet unknown physics of quantum gravity.
