A fast RF kicker for the MEIC electron cooler

Andrew KimberAmy Sy31st March 2015

Thomas Jefferson National Accelerator Facility is managed by Jefferson Science Associates, LLC, for the U.S. Department of Energy's Office of Science

Outline

MEIC Collaboration Meeting, JLab, March 31st 2015 Slide 2/11

• Kicker requirements for the MEIC• The problem• The kicker concept• The proposed experiment• Initial results• Next steps

Andrew Kimber, Fast Kicker LDRD

Kicker requirements for the MEIC• Current MEIC proposal includes an

electron cooler to attain design luminosity

• Cooler requires ~3 nC bunches at 54 MeV and 476 MHz repetition rate

• Source current = 1.5 A (!)• Dump power = 81 MW (!)• Use energy recovery and a reused

cooling bunch to address these issues

• For instance, 100 passes with energy recovery reduces source current to 15 mA and dump power to 75 KW

• Requires a very fast kicker operating with ~1 ns rise and fall times at MHz repetition rates

• Beyond current driver technology

400 200 200 400

200

100

100

200

MEIC Collaboration Meeting, JLab, March 31st 2015 Slide 3/11Andrew Kimber, Fast Kicker LDRD

The problem

~ns ~ tens of ns

476 MHz pulse train

Few kV

Pulsed power supplies, especially with these characteristics are beyond state of the art.An alternative driving method is needed…

MEIC Collaboration Meeting, JLab, March 31st 2015 Slide 4/11Andrew Kimber, Fast Kicker LDRD

The kicker concept• Mathematically, the concept works by summing simple sine waves at sub-

frequencies of the final beam repetition frequency* to generate a continuous waveform.

• Many ‘theoretical’ solutions exist, I will present one example† that is of particular interest for the ‘real world’ application.

• If every nth bunch is kicked then (n-1) harmonics are required.• Gradient of the slope is zero at bunch interaction points.

*Concept originally proposed by Dr. Hutton, † Based on work by Balsa Terzic

1 DC offset

750 Mhz bunches, 1 in 1 bunches kicked

0.5 DC offset

375 Mhz, 1 pk-pk

750 Mhz bunches, 1 in 2 bunches kicked

0.33 DC offset

250 Mhz, 0.89 pk-pk

500 Mhz, 0.44 pk-pk

750 Mhz bunches, 1 in 3 bunches kicked

0.25 DC offset

187.5 Mhz, 0.75 pk-pk

375 Mhz, 0.5 pk-pk

562.5 Mhz, 0.25 pk-pk

750 Mhz bunches, 1 in 4 bunches kicked

0.2 DC offset

150 Mhz, 0.64 pk-pk

300 Mhz, 0.48 pk-pk

450 Mhz, 0.32 pk-pk

600 Mhz, 0.16 pk-pk

750 Mhz bunches, 1 in 5 bunches kicked

0.17 DC offset

125 Mhz, 0.56 pk-pk

250 Mhz, 0.44 pk-pk

375 Mhz, 0.33 pk-pk

500 Mhz, 0.22 pk-pk

625 Mhz, 0.11 pk-pk

750 Mhz bunches, 1 in 6 bunches kicked

0.14 DC offset

107.1 Mhz, 0.49 pk-pk

214.3 Mhz, 0.41 pk-pk

321.4 Mhz, 0.33 pk-pk

428.6 Mhz, 0.24 pk-pk

535.7 Mhz, 0.16 pk-pk

642.9 Mhz, 0.08 pk-pk

750 Mhz bunches, 1 in 7 bunches kicked

0.13 DC offset

93.8 Mhz, 0.44 pk-pk

187.5 Mhz, 0.38 pk-pk

281.3 Mhz, 0.31 pk-pk

375 Mhz, 0.25 pk-pk

468.8 Mhz, 0.19 pk-pk

562.5 Mhz, 0.13 pk-pk

656.3 Mhz, 0.06 pk-pk

750 Mhz bunches, 1 in 8 bunches kicked

0.11 DC offset

83.3 Mhz, 0.4 pk-pk

166.7 Mhz, 0.35 pk-pk

250 Mhz, 0.3 pk-pk

333.3 Mhz, 0.25 pk-pk

416.7 Mhz, 0.2 pk-pk

500 Mhz, 0.15 pk-pk

583.3 Mhz, 0.1 pk-pk

666.7 Mhz, 0.05 pk-pk

750 Mhz bunches, 1 in 9 bunches kicked

0.1 DC offset

75 Mhz, 0.36 pk-pk

150 Mhz, 0.32 pk-pk

225 Mhz, 0.28 pk-pk

300 Mhz, 0.24 pk-pk

375 Mhz, 0.2 pk-pk

450 Mhz, 0.16 pk-pk

525 Mhz, 0.12 pk-pk

600 Mhz, 0.08 pk-pk

675 Mhz, 0.04 pk-pk

750 Mhz bunches, 1 in 10 bunches kicked

0.09 DC offset

68.2 Mhz, 0.33 pk-pk

136.4 Mhz, 0.3 pk-pk

204.5 Mhz, 0.26 pk-pk

272.7 Mhz, 0.23 pk-pk

340.9 Mhz, 0.2 pk-pk

409.1 Mhz, 0.17 pk-pk

477.3 Mhz, 0.13 pk-pk

545.5 Mhz, 0.1 pk-pk

613.6 Mhz, 0.07 pk-pk

681.8 Mhz, 0.03 pk-pk

750 Mhz bunches, 1 in 11 bunches kicked

MEIC Collaboration Meeting, JLab, March 31st 2015 Slide 5/11Andrew Kimber, Fast Kicker LDRD

The kicker concept (2)

Two parts to this LDRD project:

RF DriverVerification of waveform requiredGeneration of waveformLow level signal processingPhase and amplitude stabilityActive feedback required?Amplification…

Cavity(s)Cavity design that can support waveform

Cavity technologyStrip line? (We have one to test)Cavity layout and configuration

Multiple cavities?Simulations of real world performance

…

MEIC Collaboration Meeting, JLab, March 31st 2015 Slide 6/11Andrew Kimber, Fast Kicker LDRD

The proposed experiment

~/2

/4

/8

/x

combiner

broadbandamplifier

phase shifters

variableattenuators

stripline kicker cavity

load matching

source

• A simple experiment at low power can be setup with parts on hand

• The ‘proof of concept’ would include a LLRF board and broadband amplifier that can cover the required range of frequencies

• There are many ways this can be demonstrated, one example shown above

frequency dividere.g. AD9510

MEIC Collaboration Meeting, JLab, March 31st 2015 Slide 7/11Andrew Kimber, Fast Kicker LDRD

Initial results

Signal generator

Signal generator

Signal generator

Signal generator

Signal generator

Amplifier

RFCombiner

O’Scope

Using signal generators allows fine phase and amplitude control

Signal was passed through the amplifier and then attenuated to see the affect (if any) on the response – looks good, with caveats. Very sensitive to phase.

Particle tracking simulations have been initiated and show promising results. More work to do here to show both ideal and real world effects on bunches as they are kicked in and out of the cooler ring.

MEIC Collaboration Meeting, JLab, March 31st 2015 Slide 8/11Andrew Kimber, Fast Kicker LDRD

MEIC Collaboration Meeting, JLab, March 31st 2015 Slide 9/11Andrew Kimber, Fast Kicker LDRD

Next steps

0. Repair shipping damage to cavity1. Setup a Goubau line experiment to explore driving the cavity with the

generated waveform2. Simulate both this cavity and an ‘ideal’ cavity for supporting said waveform3. Complete simulations on the effects of this kicker on electron bunches in the

cooler ring4. Establish recommendations for what a fast kicker driver and cavity concept

would look like for MEIC

Strip line cavity currently on loan from SLAC

MEIC Collaboration Meeting, JLab, March 31st 2015 Slide 10/11Andrew Kimber, Fast Kicker LDRD

Questions?

MEIC Collaboration Meeting, JLab, March 31st 2015 Slide 11/11Andrew Kimber, Fast Kicker LDRD

Backup slides

Thomas Jefferson National Accelerator Facility is managed by Jefferson Science Associates, LLC, for the U.S. Department of Energy's Office of Science

Backup slides (I)

Backup I (slide 13)

Diagram of a cascade arrangement of stripline kickers for beam extraction.

Image from T. Naito et. al. “Development of a 3 ns rise and fall time strip-line kicker for the International Linear Collider,” [source]

MEIC Collaboration Meeting, March 31st 2015, Fast Kicker LDRD, Andrew Kimber

Backup slides (II)

Backup I (slide 14)

Possible arrangements of multiple stripline kickers.

A. Mikhailichenko “Fast Kicker,” Cornell University, LEPP, Ithaca, New York, U.S.A. CBN 09-03, August 12, 2009

MEIC Collaboration Meeting, March 31st 2015, Fast Kicker LDRD, Andrew Kimber