Beam Manipulation by Self-Wakefields John Power Argonne Wakefield Accelerator Facility Sergey Antipov, Alexei Kanareykin Euclid Techlabs LLC

Beam manipulation by self-wakefield Various structures – dielectric loaded, corrugated, single mode, multimode Study of wakefield (/THz) Applications of self-wakefield – Dechirper, energy modulation, transformer ratio

DRIVE – WITNESS BEAM MAPPING 1 of 7 3

Wakefield Mapping at ATF Image after (adjustable) mask Bunch Train wakefield structure spectrometer

Wakefield Mapping at ATF 0.25 THz S. Antipov, C. Jing, A. Kanareykin, J. E. Butler, V. Yakimenko, M. Fedurin, K. Kusche, and W. Gai, Appl. Phys. Lett. 100, (2012) Planar Dielectric Structure adjustable mask spectrometer image

TRANSFORMER RATIO 2 of 7 6

Collinear Acceleration, Transformer Ratio Transformer Ratio: C. Jing et. al. PRL, 98, , April (2007) TR = 3.4 experiment at AWA, ANL S. Antipov et. al., AAC 2014 TR = 3.5 experiment at ATF, BNL Collaboration with LANL (E. Simakov, D. Schegolkov) attempted at ATF... Small effect to measure

Collinear Acceleration, Transformer Ratio 8 Kapton capillary ID = 600um Single mode f ≈ 800 GHz Tunable mask: Drive + witness Spectrometer measurement: Witness beam (ac/de)celeration Experimental setup

Transformer ratio measurement 9 Witness beam acceleration measurement 130 keV energy gain (2.6 MV/m grad) Drive beam deceleration measurement (front portion only) 21 keV energy loss Transformer ratio: 130/(21*1.75 current correction ) ≈ 3.5

DECHIRPER 3 of 7 10

First Energy Chirp Correction Experiment at ATF Spectrometer image of the original beam Chirp corrector – passive wakefield tube: dielectric loaded waveguide Spectrometer image after chirp corrector Self-deceleration! Triangular-shaped (current) beam with energy chirp S. Antipov, C. Jing, M. Fedurin, W. Gai, A. Kanareykin, K. Kusche, P. Schoessow, V. Yakimenko, and A. Zholents, Phys. Rev. Lett. 108, (2012) HEAD TAIL

Tunable Energy Chirp Correction Experiment at ATF Triangular-shaped (current) beam with energy chirp Correlated energy spread was removed by closing the dechirper gap S. Antipov, S. Baturin, C. Jing, M. Fedurin, A. Kanareykin, C. Swinson, P. Schoessow, W. Gai, and A. Zholents, Phys. Rev. Lett. 112, (2014) Dechirper  multimode rectangular dielectric loaded waveguide with tunable beam gap

Semiconductor dechirper Dechirpers tested ATF Ceramic PAL Copper ATF Silicon Q, pC Structure, L, m0.11 Gap size, mm152.4 ΔE, keV Strength, MeV/mm/m/nC Semiconductor – resistivity for charge drain Balance between σ and ε Silicon – doping, radiation hard In the experiment: 5kOhm × cm resistivity but skin depth is 35 mm Propose: Dechirper – Collimator! - collimator! With A. Zholents (APS)

ENERGY MODULATION BY SELF- WAKEFIELD 4 of 7 14

Observation of energy modulation at ATF S. Antipov, C. Jing, M. Fedurin, W. Gai, A. Kanareykin, K. Kusche, P. Schoessow, V. Yakimenko, A. Zholents, Phys. Rev. Lett. 108, (2012) Periodic self-deceleration! simulation Measurement: spectrometer 0.95 THz structure 0.76 THz structure Original chirped beam

ENERGY  DENSITY MODULATION 5 of 7 16

Chicane: energy  density modulation

Chicane: energy  tunable density modulation Chirp = Energy – z correlation Chirp is convenient for experiment Chirp allows to increase the bunch train frequency for a given wakefield modulation structure

THZ GENERATION SCHEME: ENERGY MODULATION  DENSITY MODULATION  THZ GENERATION 6 of 7 19

High power beam-based THz source Energy modulation via self-wakefield Chicane energy modulation conversion to bunch train THz radiation wakefield structure THz Flexible: each step has a tuning range S. Antipov, C. Jing et. al. Phys. Rev. Lett. 108, (2012) G. Andonian et. al. Appl. Phys. Lett. 98, (2011) S. Antipov, et. Al. AAC 2014 D. Xiang et. al PRL. 108, (2012) S. Antipov, et. al., PRL. 111, (2013) Measured beam spectrum Energy chirped rectangular beam Measured beam spectrum Energy modulated rectangular beam Bunch train frequency content Tunable 100% source: Range: THz Pulse bandwidth: 1% Energy in pulse: ~ mJ ATF (100A, 2.4mm) 6 MW peak, 0.7THz, 160ps pulse, 1%BW, 1.4mJ pulse Stage IStage II Stage III

Tunable picosecond bunch train production at ATF S. Antipov, M. Babzien, C. Jing, M. Fedurin, W. Gai, A. Kanareykin, K. Kusche, V. Yakimenko, A. Zholents, prepared for Phys. Rev. Lett. PM chicane is used to convert energy modulation into density modulation CTR interferometry shows that THz periodicity can be tuned by energy chirp We proposed a high power terahertz radiation source based on this scheme (electron beam wakefields). A third stage, yet another dielectric tube will be installed after chicane to coherently extract THz power from the bunch train

Multimode structure + tunable bunch train Bunch train is produced by a mask Changing the beam chirp controls the bunch train spacing = frequency content Tunable bunch train excites a TM 0N mode selectively in the same multimode structure S. Antipov, et. al., IPAC (2015) Extending original experiment by G. Andonian at ATF Appl. Phys. Lett. 98, (2011)

EFFICIENT THZ POWER EXTRACTION 7 of 7 23

Efficient THz extraction: improved s/n Classical configuration Recent configuration

Recent measurements: ~ 100, 500 GHz With improved signal / noise we can sample longer signals – narrowband S. Antipov et. al. prepared for publication

Summary / Discussion Efficient THz power extraction is the most straightforward fit for FACET. E-201 collaboration plans to use this technology soon Transformer ratio can be studied when the photoinjector for the witness beam is installed 26

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