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MKDV upgrade LIU-SPS ABT meeting

MKDV upgrade LIU-SPS ABT meeting. V. Senaj, L. Ducimetiere, P. Faure November 4 th 2014. MKDV up-grade. Motivation Proposed solution Present status Risks Cost estimation. Extraction and dilution of the beam. Present configuration.

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MKDV upgrade LIU-SPS ABT meeting

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  1. MKDV upgradeLIU-SPS ABT meeting V. Senaj, L. Ducimetiere, P. Faure November 4th 2014

  2. MKDV up-grade • Motivation • Proposed solution • Present status • Risks • Cost estimation

  3. Extraction and dilution of the beam

  4. Present configuration • Two 2 Ohm magnets driven by 3 composite switches from three 3 Ohm PFNs • PFN nominal voltage of 60 kV; magnet current 15 kA with ±15% ripples • In case of sparking energy of all 3 PFNs goes into spark and results in a total loss of kick

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

  6. Proposed solution • Complete separation of 2 magnets: PFN – Switch – Magnet – TMR: • Safer operation: keeping at least ½ of kick in case of sparking in one magnet • Less energy in spark and hence less damage to magnet • Possibility of individual PFN voltage adjustment in case of magnet weakness • Replacement of gas switches by semiconductors: • due to I.t product (+50 % compared to 3 switches) more robust thyratron would be necessary - risk of obsolescence; semiconductor switches preferred • Reduction of complexity of supporting electronics (PS for heaters, reservoirs) • Reduction of restart time (no heat-up time); Elimination of mercury hazard (ignitrons)

  7. Present status • Self healing capacitors for new PFN developed, produced and tested (AVX) • Prototype of 2 Ohm PFN with adjustable coils built and tested • Test of single ring gate GTO with PFN prototype and real magnet done • Design of GTO stack ongoing (2 stacks of 10 GTOs in series; 2 branches of 2 series stacks in parallel); 40 GTO per PFN • Design of fast triggering transformer with reduced stray inductance (topology similar to MKD one) ongoing • Preliminary measurements shows magnet field rise time (2% - 85%) of ~ 1.2 – 1.3 µs (~ 100-200 ns longer compared to composite switch) • Test of current compression with saturation ferrite under preparation with the goal to gain ~ 50 ns of field rise time

  8. New PFN with self-healing capacitors • Use of self-healing capacitors (higher energy density) allowed to store 50% more energy in 30% less space (still many of old capacitors) • Possibility to incorporate semiconductor switches into PFN

  9. 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

  10. Solid state switch development

  11. 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

  12. GTO triggering current influence to Trise • Strong influence of the GTO trigger current on T_rise observed • Very slow initial field build-up due to low GTO commutation speed Trise = 1.288 µs @ Itrig = 500 A & Vpfn = 2500 V Trise = 1.188 µs @ Itrig = 1000 A & Vpfn = 2500 V

  13. T_rise dependence on GTO voltage • GTO commutation starts very slowly compared to thyratron resulting in slower field rise around lower threshold of the T_rise measurement (2% level) • In order to keep the rise time below 1.2 µs, the PFN output cell was modified compared to optimised simulation (output cell more capacitive) resulting in a field distortion and a peak voltage at the magnet entry ~ 13% higher than simulated one

  14. In progress/ to be done • Triggering transformers + semiconductor switchesdesign in progress • Triggering system: depending on test of MKD type PTM - design of higher voltage/current triggering might be necessary • Surveillance – discussion ongoing • Control system: upgrade done during LS1; heavy modifications not expected • GTO ~ 150 pcs to be acquired (50 GTO already delivered) • Mechanical modification of existing 3 PFN tanks (1 done)

  15. Provisionnal Budget

  16. Conclusion • Preliminary test shows magnetic field Trise (2% - 85%) < 1.2 µs within the range 100 V – 3 kV per GTO • Full scale measurement to be done • Importance of GTO triggering (>1 kA needed) • Compromise between Trise and magnet entry voltage to be done • Abort gap duration will need to be increased by ~ 100 - 200 ns • Some T_rise reduction expected with saturation coil (~ 50 ns)

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