1. AT-MEI-PE, RD, LIUWG 31-JUL-2008 1 R. Denz AT-MEI-PE LHC Luminosity Upgrade Protection of the Inner Triplet, D1, Correctors and Superconducting Links/Leads

2. AT-MEI-PE, RD, LIUWG 31-JUL-2008 2 Outline  Protection of IT corrector circuits  D1 protection  Inner triplet protection  Conclusions

3. AT-MEI-PE, RD, LIUWG 31-JUL-2008 3 Protection IT corrector circuits today  Standard protection system for LHC corrector magnet circuits with dedicated QPS –Midpoint voltage tap not available –Requires additional current sensor and sophisticated digital detection electronics –Dedicated protection system for HTS leads

4. AT-MEI-PE, RD, LIUWG 31-JUL-2008 4 Protection IT corrector circuits after upgrade  Bridge based protection system using asymmetric midpoint tap –Radiation tolerant version feasible using analog circuitry –Enhanced noise immunity  Energy extraction system can be based on mechanical circuit breakers or on semiconductor devices  Dedicated protection system for HTS leads and/or links –Voltage taps, thresholds etc. still to be defined  Space requirements for complete system: –0.5 x 19’’ rack per circuit

5. AT-MEI-PE, RD, LIUWG 31-JUL-2008 5 Protection IT corrector circuits after upgrade  Bridge based protection system –Already in use for D1 in point 2 and 8  Dedicated protection system for HTS leads and/or links  Space requirements for complete system: –0.5 x 19’’ rack per circuit

6. AT-MEI-PE, RD, LIUWG 31-JUL-2008 6 IT protection today  Advantages –It works ! –Limited space requirements (2 standard 19’’ racks only)  Drawbacks –Relies on functionality of cold quench heater circuits –Dumps stored energy into He bath

7. AT-MEI-PE, RD, LIUWG 31-JUL-2008 7 IT protection after luminosity upgrade I  Different options for protection of the magnets and superconducting bus-bars –Quench detection always based on bridge configuration  Dedicated protection system for HTS leads and/or links  Protection schemes can be easily adapted to other triplet layouts  Choice depends strongly on boundary conditions –Radiation levels –Available space courtesy D. Nisbet, R. Ostojic

8. AT-MEI-PE, RD, LIUWG 31-JUL-2008 8 IT protection after luminosity upgrade – options I  Quench heaters only –Equivalent to insertion region magnet protection in LHC Works as well with one detector for both magnets –Heaters of both magnets always fired  energy dumped in He bath –Robust, radiation tolerant, small (1 x 19’’ rack for two magnets) –System can be build with existing designs – some components may be re-used –As an option the development of a new quench power supply allowing long distance feeding and different heater pulse shaping is feasible

9. AT-MEI-PE, RD, LIUWG 31-JUL-2008 9 IT protection after luminosity upgrade – options II  Quench heaters, warm by-pass and energy extraction –Only heaters of quenching magnets are fired, warm by-pass (thyristor) and energy extraction system activated Other magnets will only quench due to propagation –Cold by-pass (like for MB, MQ) is excluded due to high radiation load –Semiconductor based energy extraction systems IGCT (Integrated Gate Commutated Thyristor) in parallel with a DC contactor DC contactor carries the current in closed state; IGCT ruptures the current in case of trigger Possible in radiation free area only – about 4 x 19’’ racks for two magnets (complete system) –Mechanical circuit breakers Can be used in present areas as those systems are radiation tolerant Main constraints are space, procurement and maintenance

10. AT-MEI-PE, RD, LIUWG 31-JUL-2008 10 IT protection after luminosity upgrade – options III  Quench heaters and energy extraction –dI/dt created by energy extraction system will exceed quench-back limit –Both magnets will be quenched but most of the energy will be transferred to dump resistor Less stress for magnet and cryogenics Faster cooling after quench possible –Quench heaters will be fired as well but serve basically as a back-up –Warm by-pass is not required –Space requirements: about 4 x 19’’ racks for two magnets Valid for semiconductor based energy extraction system

11. AT-MEI-PE, RD, LIUWG 31-JUL-2008 11 Conclusions  Protection of inner triplet correctors and D1 based on established designs and technologies –In case correctors are powered with I > 600 A protection can be adapted  Protection of inner triplet –Compatible with all powering layouts currently in discussion but the split powering solution is the preferred option –Several options for protection possible – final choice will depend on boundary conditions –Location of protection systems to be defined prior to any further development –There won’t be sufficient manpower for extensive new developments Re-use of existing designs with necessary modifications applied Use of components available in industry (e.g. for energy extraction systems)