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

2. 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

3. 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]

4. 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]

5. 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 additional ms

6. 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 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

7. 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