SC Undulators protection and commissioning W. Venturini Delsolaro Acknowledgements: R. Denz, R. Maccaferri

Circuit diagram R extr= 0.8 Ω R i= 0.15 Ω; L(i) function of current, 1.5 H at 450 A RPMBBRPMBB.UA47.RU.R4EE Protection based on parallel resistors + coupling + EE. Quench Detection?

Non linear inductance Hall probes measurement

Energy extraction in Helium Energy extraction resistor & quench heater 150 m 4.2 K 35% extracted energy Mutually coupled single turn resistor 10m 4.2 K 15% extracted energy  Cu-Be 300K = 10.7  x cm ; RRR=1.3  300K = 75  x cm ; RRR=1.9 Stored energy in a single coil 18 kJ (450 A) R.M. 9 May 06 Question: how much do we extract in the dump resistor at room temperature? Certainly less than 50% about 100 kJ go into the helium in case of quench at 450 A Heat load during ramp of the order of a few W

Hot spot calculation (S. Bettoni) 450A R.M. 9 May 06

BI follow up of a point raised at the 28 th LHCCWG LHCCWG LHCCWG “The best operating scenario is to have the Undulator ramped up before injection (pre- pulses etc.) and then when the beam passes the 2 TeV level, start reducing the current. The Undulator has been designed and tested to be magnetically “neutral”, so the ramp down should not be affect the beam. The nominal current in the undulator is 450A, the maximum allowed dI/dt is 1A/s so the ramp down will take some time. “

The dilemma Limitations on current speed and acceleration come from QPS and cryogenics (to be assessed) On the other hand, the current must be ramped down (ideally) to zero as fast as possible to avoid background noise in the profile measurement once we switch to the dipole light

In summary: No midpoint to make a voltage bridge Block 4 experience: “close your eyes” until you are above 50 A Quench detection strategy as for the 600 A (Reiner) Inductance table is available (from measured B(i), not from direct measurement) Can be ramped up slowly (≈ 15’ to nominal) and in the shadow of the MB pre cycling (≈ 18’) But: ramp down after 2 TeV will be just as long! Need to install the QPS current sensor Therefore not powered in this run (?) Test procedure: very similar to the 600 A, we should iterate on speed and acceleration to see how much can be achieved