SBDS – MKDV/H: The new MKDV Generator and additional Magnet for BA5 installation V. Senaj, L. Ducimetière November 20 th 2015

Outline Reminder : beam extraction and sweep The MKDV PFN/Switch project Impact of moving to LSS5 SEB failure rate estimation for LSS5 Prototyping status and road map

Extraction and sweep of the beam Two 2  magnets driven by 3 composite switches from three 3  PFNs PFN nominal voltage of 47 kV; magnet current ~12 kA with ±15% ripples In case of sparking - energy of all 3 PFNs goes into spark and results in a total loss of kick and serious damage to magnet Three lumped inductance magnets

Magnet damage due to sparking Serious damage to magnet in case of sparking due to high energy stored in PFNs (5 50 kV) Machine down time to re-condition or repair magnet Irradiation of downstream equipment

The MKDV PFN/Switch project Replace composite Thyratron-Ignitron switches by ring gate GTO’s Elimination of mercury hazard (ignitrons) Reduction of restart time (no heat-up time) Dynamic range allows suppression of TIDH The Quad-stack switch : 2 series – 2 parallel ring gate GTO stacks of 10 ~ 50 kV op. Separate the Two 2  magnets by converting 2 PFN’s to 2  Safer operation: keeping redundancy in case of sparking in one magnet Less energy in spark

Budget and Manpower < MATERIAL (kCHF) FSU (FTE) Staff FTE (REALISTIC) Staff FTE (MISSING) New MKDH kicker magnet ; post LS2 MagnetMaterial (kCHF) FSU (kCHF) Staff (FTE) MKDH-L Original 2x PFNs / Switches & control project for LSS1 Material reduced by ~50% if we can refurbish existing old MKDH magnet

Impact of moving to LSS5 Adding a 3 rd MKDV magnet : reducing voltage, thus magnet sparking risk and preserve at least 2/3rd of kick in case of sparking in one magnet SPS dump moving to BA5 – reduction of radiation load to MKP ~ 50 kV op. ~ 34 kV op. Modify design of Quad-stack Switch to 2 parallel stacks of 12 (?) GTO’s Need to build :  two additional MKDV magnets (incl. 1 spare) + entrance box + capa boxes  one additional MKDV PFN (or substitute for Lab. tests)  RG220 cables + special MKDH cables + connectors One existing old MKDH magnet to be refurbished as spare – separate CONS

SEB failure rate estimation for LSS5 450 GeV Maximum MKDV PFN voltage34.8 kV (/12 = 2.9 kV/GTO) GTO (5STH20H4502) 2.9 kV/GTO [cm 2 ]8e-9 Number of GTO72 IGBT (IXGN100N170) [cm2]8e-9 No of IGBTs72 HEH fluence estimation [HEH.cm- 2.y- 1 ]2e5 Estimated SEB failure rate [y- 1 ]0.3 (0.15 GTO IGBT) HEH limit for 1 SEB/Y [HEH.cm- 2.y- 1 ]6e5 The choice of the number of GTO’s per stack is a compromise between safe operation and dynamique range. The power semiconductor of the power triggering system should be considered as well

Prototyping status and road map 1- New 2  PFN with self-healing capacitors Self-healing capacitors : 50% more energy in 30% less space (still many of old capacitors) Possibility to incorporate semiconductor switches into PFN Adjustable coil with reduced stray field Original design with possibility to adjust coil inductance within +-5% Reduced stay field and hence coils mutual coupling and PFN cover influence Simplifies PFN adjustment

2- Test of single ring gate GTO UPFN [V] T_rise [µs] Umag [V] Done with PFN prototype and real magnet; Dynamic range of ~ 30 GTO commutation starts very slowly compared to thyratron Magnet field rise time (2% - 85%) of ~ 1.2 – 1.3 µs (ref. 1.1 µs ) Saturable ferrite could gain ~ 50 ns of field rise time - under preparation

3- Assembly of a 10 GTO stack Assembly of 10 GTO stack (derived from the Quad-stack) just starting Fast trigger transformer included by design Fast power trigger  presentation from Janusz Rodziewicz Will allow representative tests : Dynamic range Rise time anode delay Linearity with voltage

4- Next steps HV tests with a 10 GTO stack and dedicated power trigger up to 30 kV Global design to be frozen, so that the number of GTO can be defined Modification of the switch design from 2x 20 GTOs to 2x 12(?) GTOs Validation Reevaluation of budget and merge CONS with LIU WU’s ?  Production phase

Conclusion Moving from LSS1 to LSS5 with additional MKDV magnet will improve reliability Key prototyping work on-going (both for FPS and EC) Realistic rise time still to be determined with HV measurement Abort gap duration might need to be increased by ~ ns Global budget to be reevaluated

Measurement setup Magnetic field measurement with a pickup coil inside magnet and integration of the induced voltage by scope T_rise measured between 2% and 85% of the kick

GTO triggering current influence to Trise Trise = Itrig = 500 A & Vpfn = 2500 VTrise = Itrig = 1000 A & Vpfn = 2500 V Strong influence of the GTO trigger current on T_rise observed Very slow initial field build-up due to low GTO commutation speed