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

2 Parameters for Spreader ParameterValueUnit Energy4GeV Kick1mRad Rate1MHz Length6 ?m Aperture1cm Pulse to pulse stability100ppm Jitter When Off (compared to main pulse) 50ppm “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 Figure from [2] 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,

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

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

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 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 pp. Published in CERN , pp Presented at Conference: C Proceedings. [2] M. Placidi, G.C. Pappas, J. Galvion, M. Orocz. “Update on Kicker Development for the NGLS”, TUPPR095, Proceedings of IPAC2012.