Special powering test proposals for LS1

1. TE-MPE Technical Meeting 06-12-2012 Special powering test proposals for LS1 Change of the EE resistor value in an RQTD/F circuit & Fast power aborts in 600A circuits By Daniel Egede Rasmussen, Scott Rowan & Emmanuele Ravaioli Thanks to Arjan Verweij, Knud Dahlerup-Petersen, Gert-Jan Coelingh Daniel Egede Rasmussen TE-MPE-PE

2. 1st proposal Change of the EE resistor value in an RQTD/F circuit Daniel Egede Rasmussen TE-MPE-PE

3. Motivation Why change something that works? • When a fast power abort is triggered at nominal current (550 A) a voltage drop of 300 V is reached across the EE resistor. • The dI/dtin the magnets when the EE resistor is switched in introduces high enough AC losses to cause a quench-back. • Both ‘high’ voltages and quench-backs stresses the magnets and seems unnecessary. (Hotspot temperature reached in current configuration: 101 K). • A lower EE resistor value would lower the voltage drop and avoid quench-backs. Principal drawing of RQTD circuit. Daniel Egede Rasmussen TE-MPE-PE

4. Motivation Voltage drop and hotspot temperature • The RQTD circuit has been simulated in PSpice and the hotspot temperature has been found by running QP3 with the MIITs from the PSpice simulation. • No quench-back has been added to the simulation, making it a worst-case hotspot temperature. • Voltage drop can be reduced without a significant increase in hotspot temperature in the quenching magnet. Daniel Egede Rasmussen TE-MPE-PE

5. Motivation Quench-back and EE resistance Events: FGC 51_self 110219-010757.080_RPMBB.UA67.RQTD.A67B1 FGC 51_self 080827-145831.100_RPMBB.UA23.RQTD.A12B1 FGC 51_self 080422-115213.960_RPMBB.UA63.RQTD.A56B2 FGC 51_self 110214-192759.320_RPMBB.UA27.RQTF.A23B2 Current decay in magnets simulated in PSpice Daniel Egede Rasmussen TE-MPE-PE

6. Test description • Ad extra EE resistors in parallel • 2 spare resistors - 3 combinations • FPA’s at a couple of current levels to determine quench-back limit. • Use DCCT for current measurements • Use external measurement devise for voltage measurements Daniel Egede Rasmussen TE-MPE-PE

7. Test description • Ad extra EE resistors in parallel • 2 spare resistors - 3 combinations • FPA’s at a couple of current levels to determine quench-back limit. • Use DCCT for current measurements • Use external measurement devise for voltage measurements Daniel Egede Rasmussen TE-MPE-PE

8. Test description • 2 spare 600 A EE resistors (0.7 Ω) • Cabling and connectors (bolting or clamps) • Measurement equipment (Scope or measurement board) • Test time: Connection and setup of measurement equipment in tunnel 3 times and ̴10 FPA’s with a recovery time of ̴15 min (est. test time of 1 day) Resources Daniel Egede Rasmussen TE-MPE-PE

9. Test description • Machine safety worst-case: • Worst-case is a quench at nominal current (550 A) with 0.233 Ω EE resistor and no quench-back. • According to simulation in QP3 with current decay from Pspice simulation the worst-case hotspot temperature for the test is 130 K compared to 101 K at normal operation (without quench-back: 115 K ). • Personnel safety: • Due to limited space additional “high voltage” EE resistors have to be placed outside PC cabinet. Safety Daniel Egede Rasmussen TE-MPE-PE

10. Test description • Can be done in any RQTD/F circuit. • Circuit has to be cold. • Access to the tunnel has to be allowed. • The estimated test time of 1 day, makes it hard to squeeze in during operation. • This leaves the very beginning of LS1. When? Daniel Egede Rasmussen TE-MPE-PE

11. 2nd proposal Fast power aborts in 600A circuits Daniel Egede Rasmussen TE-MPE-PE

12. Motivation The purpose of these FPA’s are to verify PSpicemodels More events at different current levels are needed for verification By E. Ravaioli Daniel Egede Rasmussen TE-MPE-PE

13. Motivation Why have PSpice models? • PSpice is not a tool to be used for modelling circuits where the circuit behaviour can easily be calculated. For quench modelling other software like ROXIE is much better. • The advantages of PSpice is when investigating: • Current change in magnets during quench in non-trivial circuits. • Effect of quench-back in circuits with multiple magnets. • Effect of failures in other circuit components (Switch, Crowbar, PC etc.). • Analysis of circuit behaviour during an unusual event. Daniel Egede Rasmussen TE-MPE-PE

14. Motivation Why have PSpice models? Principal drawing of RQTD circuit. Daniel Egede Rasmussen TE-MPE-PE

15. Test description • FPA at two current levels above quench-back limit to give a well-distributed set of events is proposed. • No quench-back in: RCD, RCS, ROD, ROF, RQ6, RQS (with 4 magnets) and RQS (Without EE). • Only one circuit of each type is going to be tested. Daniel Egede Rasmussen TE-MPE-PE

16. Test description List of proposed tests Note: all of based on the assumption that the circuits are going to be tested all nominal current during the powering tests in the beginning of LS1. Current levels will have to be revised in the case that restrictions on the maximum current levels are introduced. Daniel Egede Rasmussen TE-MPE-PE

17. Test description • The test involves 17 circuits with 2 fast power aborts per circuit. • Can be executed in parallel with a recovery and ramp-up time of ̴̴ 15 min. • Total test time of 2 hours. • No special equipment needed. Resources Daniel Egede Rasmussen TE-MPE-PE

18. Test description • No remarks since all tests fall within what can be characterised as ‘normal’ operation. Safety Daniel Egede Rasmussen TE-MPE-PE

19. Test description • The tests can be performed in any circuit of the defined type and do not have to be performed in the same sector. • Circuits have to be cold, which means in the very beginning of LS1. • Could be done during operation before LS1. When? Daniel Egede Rasmussen TE-MPE-PE

20. Thank you for your attention Daniel Egede Rasmussen TE-MPE-PE