I suggest that this blog may be a load of codswallop. The official
report does not mention any solder joint as being causal and I think I
would prefer to believe it rather than a journalist's blog. Extract:
"On 19 September 2008 morning, the current was being ramped up to 9.3 kA
in the
main dipole circuit at the nominal rate of 10 A/s, when at a value of
8.7 kA, a
resistive zone developed in the electrical bus in the region between
dipole C24 and
quadrupole Q24. The first evidence was the appearance of a voltage of 300 mV
detected in the circuit above the noise level: the time was 11:18:36
CEST. No
resistive voltage appeared on the dipoles of the circuit, individually
equipped with
quench detectors with a detection sensitivity of 100 mV each, so that
the quench of
any magnet can be excluded as initial event. After 0.39 s, the resistive
voltage had
grown to 1 V and the power converter, unable to maintain the current
ramp, tripped
off at 0.46 s (slow discharge mode). The current started to decrease in
the circuit and
at 0.86 s, the energy discharge switch opened, inserting dump resistors
in the circuit
to produce a fast power abort. In this sequence of events, the quench
detection,
power converter and energy discharge systems behaved as expected."
I find it very hard to believe that the passage of a 9.3 kA current
relies on a solder joint, least of all one made by a soldering iron on a
PCB as the illustration in the blog suggests. The reason for the
potential difference, rising from 0 to 300 mV to 1 V is not explicit,
but at currents approaching 10,000 A, it suggests that the
superconducting magnet became slightly resistive. As this was, by
definition, highly inductive, it was impossible just to throw a switch
as the voltage generated would be excessive. As it is, they discharged
the inductive energy into dump resistors foreseen for such an emergency.
However, it transpired that this dump was too rapid and a flashover
caused an arc to develop and this punctured the helium enclosure and
this was the start of a whole chain of events.
The official report is downloadable at
https://edms.cern.ch/file/973073/1/Report_on_080919_incident_at_LHC__2_.pdf
I'm always sceptical when popular journalism "explains" science. The
technical level of the comments following the article gives an insight
into the readership of the blog, reflecting on the magazine.
Brian
Smith, Rick wrote:
> http://www.dailytech.com/Single+Bad+Solder+Costs+CERNs+LHC+a+Year+21M+USD/article13460.htm
>
>
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