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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.

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MCB orbit correctors

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  1. 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

  2. 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

  3. 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

  4. 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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