1. BT1 SMV10 Stripline Failure 09.11.2017
The location of the Stripline, underneath the BT1 vacuum tank
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2. History Current stability problems since several weeks
EPC Power converter suspected and several interventions to try to correct the stability issue
Multiple trips during last week
Spare stripline prepared in building 867 (Identified as the most likely cause)
Fire alarms on Thursday 09/11 at 23h06
Firemen enter booster at 23h37
No fire or smoke detected
SMV restarted again but eventually failed soon after – open circuit discovered by EPC when trying to measure the inductance.
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3. Actions on Friday 10.November 2017
Beams stopped 08h25
Access to PSB at 09h15 for diagnostic which only took 30 seconds, exited PSB at 09h15 (2 mins duration)
DIMR created with RP (No )
Impact created with RP (No )
Intervention started at 11h30
Intervention finished at 13h45
Converter testing started at 14h15
Released to CCC soon after
Beams back at 15h01
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4. Photo taken during brief intervention at 09h15
Severe arcing, melted material and projection of copper and insulating materials in the immediate area.
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5. The intervention Space is very limited Conditions cramped,
hot, dirty , radioactive,
Working underneath the BT1 requires some degree of flexibility and no claustrophobia !
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6. The Stripline (or what was left of it), after dismantling
A normal connection
A not so normal connection
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7. Reason for the failure Magnet history:
Stripline has been operational since about 2012/3
Total number of pulses since installation on is 93x106 at approximately 26 kA
Fatigue of the copper flexible braid is the cause of the failure. Broken individual strands caused a gradual reduction in cross section of the current carrying connection and increased heat dissipation in the reduced area. This led to the severe electrical arcing at both sides of the braid with the inevitable mechanical failure of the central part which went to open circuit mode.
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8. Lessons learnt…
When there are fluctuations or drifts in the current stability..
Investigate the magnet connections asap
Smoke alarms or fire detection…
Indicate to the firemen on specific areas to check
Make closer inspections each shutdown (and during TS), especially in the least accessible areas.
Efficient planning and the help of RP to compile and approve DIMR’s and IMPACTs allowed for a rapid intervention.
The accumulated collective dose was kept well below the estimate by using experienced specialists. For info:Estimated collective dose was 400 μSv Real dose 266 μSv
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9. Actions…
Molten copper and other debris has been projected on to the bellows assembly.
This bellows assembly allows for remote positioning of the septum in both the vertical and angular directions.
It has not been ascertained yet if molten debris has been projected between the individual bellows membranes.
During YETS the assembly will be inspected more closely to evaluate the risks. For the moment, all adjustment of the position of the septum should be limited and only moved when absolutely necessary.
Manufacture of another spare stripline has already been launched.
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10. Thanks to, RP for their very fast and efficient response, Gerald Dumont and Jean-Francois Gruber. EPC for their efforts to keep the septum running.. and starting it up again, Firstline for the fast lock out and reconnection of the power converters.
Questions ?
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11. M. Hourican nABTEF

12. SMH42
SMH16
SMH26 Variant
SMH16
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13. Septa operating regime
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14. Problematics Low Inductance imperative (Tx on secondary > N2)
Low resistance is crucial (Converter)
Separation distance between conductors a maximum – lower forces!
Ensure flexibility allows positioning of the magnets
Adequate clamping (Forces can be up to several T per metre)
Power dissipation causes temperature rise (Resistance variations, reduction in mechanical strength)
Copper OFE is very susceptible to fatigue
Fatigue properties are normally available for up 1x107 cycles
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15. Shape configuration…? Moulded flexible connection
Not so flexible but good insulation properties
Reasonably resistant to radiation
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16. Material choices…?
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