High Rate Kicker Preliminary Study (Quick Update)

1. High Rate Kicker Preliminary Study (Quick Update) Tony Beukers/Tao Tang 4/8/14

2. Parameters for Spreader • “Jitter When Off” from “Post Laser Heater Diagnostic Beam-Line PRD” • Works out to integrated field of 13.4mT-m required • For all topologies considered, 5mT most reasonable  3ea. 1-meter sections • Bi-polar pulse possible with two separate kickers, so not an area of extreme focus.

3. Magnet Cross Section • 2-types of magnets shown to the right. C-core and Window frame. Best choice depends a bit on driver topology. • Ferrite loaded magnet. Losses from drive field highly dependent on the core type. For 5mT, 100ns sine wave excitation at 1MHz  11W/m for 4M2, 450W/m CMD5005 (common kicker material). • On the order of 2% change in effective µ over duration of pulse. • Coated beam-pipe used to shield beam current from magnetic coupling to ferrite.

4. Beam Coating Losses • Losses in conductive coating increase with beam current, high frequency components of pulse, and pulse rate. • Eddy currents from the driver pulse go down with increased coating resistivity. . .but loss from the beam image current goes up. • Beam image current losses (length =8.3µm, q=0.5nC): • Eddy current losses found through simulation. • Total loss is 600W/m with 90Ω/m coating. • Reduce loss (if necessary) with conductive strips, Figure from [2]

5. In-Tunnel Driver • Mount MOSFET drivers directly on Ferrite loaded magnets in tunnel. • Multiple drivers reduces the inductance of each section so each driver can rise in tens of ns. • Easily redundant for longer system lifetime. • 5mT/m achievable goal. Figures from LBNL NGLS paper. [2]

6. Driver Types 3 Segments/meter MOSFET Losses 456W/m 4 Segments/meter MOSFET Losses 128W/m Resistive Losses 944W/m 9 Segments/meter MOSFET Losses 1000W/m Resistive Losses 3285W/m 5 Segments/meter MOSFET Losses 520W/m *Losses assume NON rad-hard MOSFET

7. Driver Types 3 Segments/meter MOSFET Losses 456W/m 4 Segments/meter MOSFET Losses 128W/m Resistive Losses 944W/m 9 Segments/meter MOSFET Losses 1000W/m Resistive Losses 3285W/m Too much power! 5 Segments/meter MOSFET Losses 520W/m *Losses assume NON rad-hard MOSFET

8. Tunnel Radiation • Total ionizing dose causing non-recoverable failure in MOSFET is main problem. Back-of-envelope yields ~15kRad/year. • 1 rad-hard device rated at 100kRad (6 years). Expensive, not electrically great, hard to get. • Collimator reduces radiation by a factor of 10-100. • Like to put NON rad-hard device in total dose test. Could it survive behind a collimator? • More input and/or modeling from RP may be useful.

9. Transmission Line Kicker • Loaded sections of ferrite and discrete capacitors simulate a transmission line. • Used at SLAC in damping ring and at CERN. • Typically used in high voltage. But for our low voltage, possible to tune magnet impedance with small chip capacitors.

10. Transmission Line Ringing • Ringing damps to below 50ppm of the main pulse within 1µs. Ringing reduced with more sections. Sum of all magnet currents. Traveling Waves

11. Conclusions • “In Tunnel” and “Transmission Line” Kicker both still options. • “In Tunnel” Kicker does not have a perfect driver solution, but three topologies are possible. Need testing and more RP input to fully evaluate radiation effects. • “Transmission Line Kicker” looks promising according to simulations. Some testing on the spare NDR magnet would be useful. • Bottom line: Both methods look feasible. Additional testing to determine which is best.

12. References • [1] M.J. Barnes, L. Ducimetiere, T. Fowler, V. Senaj, L. Sermeus. “Injection and extraction magnets: Kicker magnets” Mar 2011. 26 pp. Published in CERN-2010-004, pp. 141-166. Presented at Conference: C09-06-16 Proceedings. • [2] M. Placidi, G.C. Pappas, J. Galvion, M. Orocz. “Update on Kicker Development for the NGLS”, TUPPR095, Proceedings of IPAC2012.