Wakefield in Structures: GHz to THz Chunguang Jing Euclid Techlabs LLC, / AWA, Argonne National Laboratory AAC14, July, 2014
Wakefield (beam structure)
Measured Wakefield: GHz to THz Wz S. Antipov et. al. Appl. Phys. Lett. 100, 132910 (2012) Energy spread by Wz Beam Breakup by W W M. Rosing and W. Gai, Phys. Rev. D 42 (1990) 1829. Nature phys. 2005
Structures: GHz to THz Quartz DPETS, ID=23mm (12GHz) Ceramic DWA, ID=7 mm (26GHz) Quartz DWA, ID=300 um (0.9THz) Metallic PETS, ID=23mm (12GHz) Metallic PETS, 2a=0.8mm (120GHz) Metallic THz radiator,(0.4thz) a=1mm, =50um, Igor Syratchev, CLIC Valary Dolgashev, SLAC p=160um Karl Bane, SLAC
beam image after the mask, triangle length is 247 micron Example of Applications of Wakefields Collinear wakefield acceleration 70 80 90 100 110 Energy chirp correction 200 250 300 350 spectrometer image of unperturbed beam THz Radiation 57 57.05 57.1 57.15 57.2 57.25 57.3 Energy, MeV spectrometer image of a beam that passed through the structure 1.2 THz 400 GHz 57 57.05 57.1 57.15 57.2 57.25 57.3 Energy, MeV Courtesy to G. Andonian Two Beam Acceleration High power RF source Wakefield undulator
Recent Wakefield Structures Experiments 7.8GHz power extractor (40MW) 100MV/m 11.4GHz PETS: 40MW@100ns ASTA, SLAC Enhanced Transformer Ratio: 3.4 Witness Acceleration Tunable DWA structure Wake mapping Bragg structure 26GHz power extractor Metallic corrugated pipe. Woodpile THz generation UCLA, Neptune GV/m FFTB GV/m FACET Metallic corrugated pipe. Chirp corrector Tunable THz Second harmonic Resonant excitation 1GHz 10GHz 30GHz 100GHz 300GHz 1THz AWA ATF BNL FACET SLAC 6
Mission of Wakefield Accelerator Technologies High Energy e - e + Collider: High efficiency: ~10% (wall plug) High gradient: >200MV/m (effective) High luminosity (high beam power ) Technologies extended beyond HEP --- High Rep. Rate FEL Ultrahigh repetition rate: >100KHz High efficiency collinear wakefield acceleration: >10% Low construction and operational cost
Argonne 26GHz 3TeV Flexible Linear Collider Average drive beam power (1.5TeV, e - ) Average main beam power (1.5TeV, e - ) 68.8 MW 15.6 MW
Application for high efficiency dielectric collinear wakefield acceleration: soft X-Ray FEL example A Schematic of a FEL facility based on a 2.4 GeV DWA Rep = 10~100KHz C. Jing, J. Power, and A. Zholents ANL/APS/LS-326 (2011)
Collinear Wakefield Acceleration
Wakefield Acceleration (I) : High Gradient q (gain energy) Q (lose energy) Accel. Voltage: V ( t) Examples: 100MV/m for MW structure @ AWA v.s. GV/m for THz structure @ FACET t I( ) W z Drive bunch current: bunch length related; favors shorter bunch; t d Wake function: structure related; favors high frequency;
Wakefield Acceleration (II) : High Efficiency q (gain energy) Q (lose less energy) Transformer Ratio: TR E E max gain max loss (Trailing bunch) (driving bunch) Directly related to efficiency; >>2 is preferred; temporal shape of the bunch determined; favors ramped charge profile and its variations;
Rule of Thumb: W z ~ Q/a^2, W ~ Q/a^3 Case I a=0.5mm Q=1nC Freq.=300GHz z/ =0.2 Case II a=2mm Q=16nC Freq.=75GHz z/ =0.2
Boundary of Sustainable Wakefield Gradient Upper boundary of beam charge vs beam aperture (radius) Ez~Q*a -2 Q max [nc] ~ a[mm] 5/2 BBU control area Chen Li, et al, submitted to PRSTAB (2014) THz MW
Sustained Collinear Wakefield Accelerator Y. Iwashita, et al, PAC2003 By Scott Doran, ANL Conceptual design in collaboration among APS (A. Zholents); AWA (J. Power); Euclid (C. Jing); LANL (E. Simakov), etc.
Demands by Collinear Wakefield Acceleration High Frequency (0.1THz ~ 1THz) wakefield structures: Dielectric wakefield Accelerator (DWA) is a very good candidate. Robust Bunch shaping techniques: (EEX-based; Dual frequency Linacs; and other nonlinear beam optics based techniques, etc.) Bunch transportation: BBU control, thermal management High stability of trailing bunch in time.
Two Beam Wakefield Acceleration
Wakefield Power Generation E t P k l 2 L I 2 F 2 tr t f Structure Beam t d T b... s RF pulse packet from first bunch From N-th bunch From n-th bunch t
AWA 75MeV Beamline --- a drive for RF Power FCT signal of a bunch train Train of 32 X 20nC 16 X 40nC 8 X 60nC 4 X 100nC
1 st beam test of 11.7GHz Metallic PETS@AWA Calculated Trf=3.5ns P~10MW Trf=8.9ns LO=8GHz
Previous Wakefield Power Extractors C-Band 30ns,1MW & 10ns, 40MW 7.8GHz rf pulse produced Dielectric-Loaded deceleration waveguide TM 01 -TE 10 coupler rf output port F. Gao et al. PRSTAB 11, 041301 (2008) K-Band 16ns,1MW & 10ns, 20MW 26GHz rf pulse produced Downconverted signal 11.44+14.576=26.016 GHz
W-Band Wakefield Power Generator
High Power rf Generation by AWA Drive Beam Freq. (GHz) Aperture (mm) L (cm) Q (nc) z (mm) Form factor Grad. (MV/m) Power (MW) C-Band (7.8) 12 30 100 2.5 0.92 62 1107 X-Band (11.7) 10 30 80 2.5 0.83 79 1012 Ku-Band (15.6) 8 30 60 2.3 0.75 88 766 K-Band (26) 6 30 30 1.7 0.65 75 276 W-Band (91) 2 30 10 1 0.16 50 14
AWA Two Beam Acceleration Beamline 5m to meet
Two Beam Acceleration at AWA 16X40nC 100MeV 15MeV 1nC
Other Activities: LANL 11.7GHz PBG Wakefield Yale two channel wakefield Yale two channel wakefield
Intensity [arb. untis] Normalized Signal [arb. units] intensity [arb. units] DWA with Bragg-like boundaries Modal confinement Constructive interference Alternating dielectric layers Eliminate metal cladding DWA: SiO2, 240µm beam gap Bragg layers SiO2, ZTA Assembled at UCLA BNL ATF experiment 50MeV, 100pC, t~1ps (a) Results =1.4mm (210GHz) e-beam Energy chirp mitigation Confirmed with simulation Submitted to PRL Beam Energy 1.0 0.8 0.6 no structure after structure 1.0 0.5 d 2 d 1 d m 2a (a) e-beam (b) Interferogram FACET, E-201 collaboration, 2012 d 2 d 1 d m 2a 2.0 1.5 (b) FFT OOPIC Sims f =210GHz 0.4 0.0 1.0 0.2 0.5 0.0 57.0 57.2 57.4 57.6 57.8 58.0 Energy [MeV] -0.5-0.003-0.002-0.001 0.000 0.001 0.002 0.003 Step Size [m] 0.0 0.0 0.5 1.0 1.5 frequency [THz] Courtesy G. Andonian, UCLA 27
Summary Structure based wakefield accelerator technologies is nearly mature to be used in the large scale future facilities. New ideas and new applications of structure based wakefield technologies are greatly explored lately, and more to come.