E. Todesco CERN, Geneva Switzerland QXF protection meeting 28th October 2013 PROTECTION FOR QXF E. Todesco CERN, Geneva Switzerland

MARGIN VS COPPER Estimate of the gain in time margin and temperature vs copper fraction Estimate of the gain in time margin and temperature vs operational gradient

HQ RESULTS 14-17 ms available to So we are just there See the quench (5 ms) Validate (10 ms) So we are just there I took the MIITs at 350 K PRELIMINARY Quench integral measured in HQ [G. Chlachidze]

HQ RESULTS 27-32 ms available to So we are just there See the quench (5 ms) Validate (10 ms) Heater delay (15 ms) So we are just there I took the MIITs at 350 K Quench back could have helped but it will not PRELIMINARY Quench integral measured in HQ [G. Chlachidze]

EXTRAPOLATION TO QXF Hypothesis Tmax set at 350 K: this gives 33.2 MIITs Scaling of the MIITs consumed with HQ results So we gain 8 ms (previous estimates: in general QXF has 10 ms more margin w.r.t. HQ) Pretty compatible with previous estimate (see first slide giving 33 ms) So we have to gain 10-15 additional ms

CONCLUSIONS HQ test show that quench back induced by dump resistor in the machine will be nigligible To have some gain for protection one would need 8 circuits, not feasible Going from 2 to 4 power converter seems to add negligible margin Extrapolation to QXF shows that we have a margin of 35 ms, still 10-15 ms too small Limited impact of increasing copper Lowering gradient by 7% would solve the problem Quench back will not play a role in protection That’s why we put the core … It is the most difficult quantity to scale to QXF so we would need to wait until first test I feel more confident to have a QPS relying on other phenomena rather than quench back

CONCLUSIONS Until now we did not address the issues related to 90% operation But magnets must reach 90% We did not address issues related to failure of one or more circuits So even though we manage to have 50 ms time margin by lowering the operational gradient we would need additional margin This is to be provided with the other studies outlined in the working group