1. First draft of the CLIQ test plan for the HQ2b magnet Emmanuele Ravaioli Thanks to Hugo Bajas & GianLuca Sabbi 02/05/2014

2. First draft of the CLIQ test plan for the HQ2b magnet Emmanuele Ravaioli First draft of the CLIQ test plan for the HQ2b magnet 02-05-2014 2 CLIQ HQ2b Discussion FNAL Data EE Delay High-MIIt Training Goals of the tests Main parameters (HQ2 cpr MQXC2) Working principle Highlights from the MQXC2 test campaign

3. Concept of CLIQ – Coupling-Loss Induced Quench Emmanuele Ravaioli First draft of the CLIQ test plan for the HQ2b magnet 02-05-2014 3 Current Change Magnetic Field Change Coupling- Losses (Heat) QUENCH Temperature Rise E. Ravaioli et al., MT23, 2013. E. Ravaioli et al., EUCAS11, 2013. EU Patent EP13174323.9, June 2013. E. Ravaioli et al., CHATS-AS, 2013. E. Ravaioli et al., SuST, 2014.

4. CLIQ – Coupling-Loss Induced Quench – MQXC2 Tests at CERN Emmanuele Ravaioli Protecting a Magnet with a CLIQ - Hybrid System 26-09-2013 4 CLIQ EE + -- - +- + -

5. CLIQ Tests on the HQ2b – Main Goals Emmanuele Ravaioli First draft of the CLIQ test plan for the HQ2b magnet 02-05-2014 5 Test the CLIQ on a Nb 3 Sn magnet for the first time (higher energy density to introduce to provoke and propagate a quench in the coil, more fragile coil) Information about the protection of larger coils (larger inductance, lower dI/dt, different frequency) Comparison with quench-heater performance: quench load (MIIt’s), hot-spot temperature, development of quench resistance Test of the hybrid protection system composed of CLIQ + Quench Heaters Test of both CLIQ units (500 V, 28.2 mF vs 1 kV, 8.8 mF) (different frequency, different power) Preliminary! CLIQ Unit1 500 V, 28.2 mF CLIQ Unit2 1000 V, 8.8 mF

6. CLIQ in the HQ2b cpr CLIQ in the MQXC2 Emmanuele Ravaioli First draft of the CLIQ test plan for the HQ2b magnet 02-05-2014 6 HQ2bMQXC2 6.4 mH (5.8 mH) ~30% higher 8.4 mH (7.8 mH) ~30% lower Inductance ~10% higher~10% lowerAverage magnetic field 19 mm ~50% higher 15 mm / 18 mm ~50% lower Filament twist pitch ??? Effective Cu resistivity higher5-50 mJ/cm 3 Enthalpy margin The effective copper resistivity (unknown for the HQ2) plays a major role in the CLIQ performance: higher resistivity means less inter-filament losses are deposited, but more quickly (for a closer look to the involved equations see slide 3) May mechanical stress damage Nb 3 Sn filaments? Which is the max allowed stress?

7. Discussion: How to best profit from the FNAL data? Emmanuele Ravaioli First draft of the CLIQ test plan for the HQ2b magnet 02-05-2014 7 Interesting sets of data: PHs performance EE discharges, no PHs (to evaluate quench-back) Ramps at different dI/dt until quench is induced (to evaluate quench-back) Side note: If quench-back is induced after >100 ms (probably the case for EE discharges and ramps) the main contribution to quench-back comes from inter-strand coupling losses. The main contribution to CLIQ deposited losses comes from inter-filament coupling losses (time constant ~10 times smaller). During HQ2a the magnet was extensively tested, so it makes sense to use the FNAL data whenever possible to maximize the time available for other tests. However, it is also necessary to check that the different setup in the CERN test facility (helium temperature, PH discharge circuits, resistance in the current leads, etc) does not introduce significant differences in the magnet behaviour. If the first PH tests at CERN show that no significant differences (heater delays, current discharge,…) are present between CERN and FNAL data, we can skip further PH tests at CERN and free up some time for other tests. Very minimum: Testing the performance of CLIQ at the same current levels used during the tests at FNAL. (input from Guram?)

8. Proposed delays (with R_EE=60 mΩ) (OK?) With these delays, the magnet protection is assured by the EE alone even if a natural quench occurs and no other protection system works. (thanks to Hugo for his help!) Discussion: Which is the optimum delay for the EE system? Emmanuele Ravaioli First draft of the CLIQ test plan for the HQ2b magnet 02-05-2014 8 Why do we need to delay the triggering of the extraction-system? Avoid interference between CLIQ and EE system Avoid superposition of voltage across CLIQ and across EE (max voltage 1 kV!) Avoid reducing CLIQ performance Delay the quench-back effects induced by the fast discharge provoked by the EE system (we only want to see the quench resistance generated by the protection system) Record a clean signal of the oscillation introduced in the magnet current (frequency, damping factor) Limitations (OK?) Always, maximum voltage to ground < 1 kV At 1.9 K, maximum quench load < 18 MIIt’s (to keep the hot-spot temperature < 300 K) At 4.2 K, maximum quench load < 13 MIIt’s (to avoid excessive pressure in the cryostat) Delays [s] Current Level [kA] 36912.814.616.5 T=1.9 K10.450.150.080.050.035 T=4.2 K10.30.130.050.030.02

9. Discussion: How to use CLIQ during training? Emmanuele Ravaioli First draft of the CLIQ test plan for the HQ2b magnet 02-05-2014 9 It would be sensible to profit from the training quenches at high current in order to assess the performance of various quench protection systems (CLIQ, CLIQ+PHs, PHs). On the other hand, it is interesting to assess the training performance of the magnet with as little interference as possible from the protection systems. Before the training campaign, it is necessary to test the correct behaviour of the quench detection system, PHs, CLIQ, and PHs+CLIQ. These tests (manually triggered) can be performed at 3 and 6 kA. Hopefully CLIQ will be powerful enough to start a quench at least at 6 kA; if not, we can consider the possibility to test CLIQ at 9 kA before the training campaign. (OK?) After some (?) training quenches, the quench current will reach a plateau. At this moment, we can stop the first phase of training tests and focus on testing the performance of various quench protection systems (CLIQ, CLIQ+PHs, PHs, the latter only if FNAL data are not usable). After the performance tests, we can start the second phase of training. It is expected that after several quenches with medium quench load (10-15 MIIt’s) the magnet may not reach the same training current at the very first training test (1-2 quenches to reach the same training current?). (OK?) During the second phase of the training tests, we can profit from the tests at high current (>16 kA) to test different protection systems (CLIQ+PHs, CLIQ, PHs). (OK?) The first test of this kind should not trigger only CLIQ but also PHs (to avoid surprises). If we observe that after triggering CLIQ the following training quench does not reach higher current, we can consider stopping using CLIQ during training. (OK?)

10. Discussion: Should we use CLIQ during high-MIIt tests? Emmanuele Ravaioli First draft of the CLIQ test plan for the HQ2b magnet 02-05-2014 10 The high-MIIt tests are another occasion to profit from natural quenches at high current and test various quench protection systems (CLIQ, CLIQ+PHs, PHs). On the other hand, one of the main goals of the tests is assessing the degradation of hot spots in the coil subjected to increasing quench loads. For this reason, protecting the magnet with CLIQ during these tests is not preferable because CLIQ introduces a different current change in the two sides of the magnet, so the current is not uniform in the magnet. CLIQ (hopefully!) quickly provokes a quench in large portions of the coil, but during these tests it would be better to deposit more energy in the hot-spot, thus not spreading the normal zone much (somewhat the opposite of the usual scope of quench protection…). No CLIQ tests during high-MIIt tests? (OK?) OR do we profit at least from the first high-MIIt tests to try CLIQ at very high current? (especially if for any reason CLIQ was not used during training) (OK?)

11. Emmanuele.Ravaioli@cern.ch QUESTIONS? Ask me the CLIQ Recipe! Thanks to Vladimir Datskov, Glyn Kirby, Herman ten Kate, Arjan Verweij, Alexey Dudarev, Tim Mulder, Kevin Sperin, Michal Maciejewski, Bernhard Auchmann, Christian Giloux, Jerome Feuvrier, Francois-Olivier Picot, Hugo Bajas, GianLuca Sabbi, …