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MCB orbit correctors. There are 752 MCBH(V) SSS orbit corrector circuits. Individually powered by a ± 60 A, ± 8 V converter. PCs installed in the tunnel (radiation). PCs are in production today. The design MTBF is 100’000 hours  1 failure in operation every 100 hours.

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Mcb orbit correctors
MCB orbit correctors

  • There are 752 MCBH(V) SSS orbit corrector circuits.

  • Individually powered by a ± 60 A, ± 8 V converter.

  • PCs installed in the tunnel (radiation).

  • PCs are in production today.

  • The design MTBF is 100’000 hours

    •  1 failure in operation every 100 hours.

    • Assuming ½ MCBs have significant kicks, we may get 1 MCB-induced beam loss per week due to our orbit tight tolerances !

AB-CO TC / J. Wenninger


Crowbar
Crowbar

In case of PC failure the magnet is shorted and discharged through a crowbar.

  • Time constants :

  • without crowbar 85-130 seconds

  • with crowbar 30-35 seconds - mostly due to 100 mresistors

AB-CO TC / J. Wenninger


Remedies
Remedies

  • The orbit FB could save the beam :

    • The FB must switch in a compensating scheme based on nearby correctors (or equivalent)  reduce effect to a local bump.

    • The FB must be informed rapidly – time scale of 1 second or less.

    • The circuit time constants should be as long as possible.

    • With the 2 crowbar resistors the situation is very tight…

  • From MP point of view, the MCBs are slow enough even with crowbar resistors not to present a major problem.

    But the slow is beautiful for MP  slower is better !

AB-CO TC / J. Wenninger


Can we remove 1 or both crowbar resistors
Can we remove 1 or both crowbar resistors ?

  • Meeting with all concerned parties (AB & AT) :

    • The crowbar resistors have no role in protecting the magnets. The magnets are self-protected.

    • Motivation behind resistors seems to be a shorter circuit discharge time.

  • PC tests performed without crowbar resistors by AB/PO indicate that the resistors can be removed.

    • Implications for electrical safety, since it takes then ~ 10 minutes for the current to go from 60 to below 1 A for the slowest elements.

  • need a rapid decision since the PCs are in production.

  • ECR will be prepared this week.

AB-CO TC / J. Wenninger


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