Feasibility and R&D Needed For A TeV Class HEP e+e- Collider Based on AWA Technology Chunguang Jing for Accelerator R&D Group, HEP Division, ANL Aug. 2014

Essential features of a future linear collider Low Cost High Efficiency High Luminosity Two approaches will help: 1.Higher gradient (e.g. >200MV/m)  shorter total main linac length  lower the infrastructure cost 2.Less complicated accelerating structures  lower the fabrication cost Beam Power Wall Plug AC Power > 5% Beam Power >10MW 2

Low Cost Shorten the rf pulse length down to ~20ns level —experimental observations from SLAC and CLIC show strong dependence of the gradient over the rf pulse length. Gradient needs 200~300MV/m  ~1GW level rf power  TBA Dielectric based technology  simple fabrication, easy BBU control. AWA strategies to achieve a high gradient and lower the cost: Power Extractor Short pulse accelerator 3

AWA strategies to achieve a high efficiency High Efficiency TBA scheme in the main linac  fast rf rise time. Broad band dielectric accelerator(>150MHz)  fast rf rise time (<3ns). Large (~10%c) Vg  less filling time. high frequency and optimal beam loading  higher rf- to-beam efficiency. 3ns T rf =28ns T f =9ns T beam =16ns e.g. rf-to-beam efficiency of a 26GHz Short Pulse Accelerator: Competitive rf-beam efficiency for the short pulse TBA 6.5A 267MV/m 0.3m 1.264GW 16ns 25ns 4

Power and efficiency flow chart (Example) Main beam injection, magnets, services, infrastructure, and detector Power supplies to klystrons gallery Drive beam acceleration DPETS Drive beam Dumps Main linac Main beam Wall Plug 31.2MW 120.1MW 126.4MW  rf-main =26%  rf-tran =95% 137.6MW  rf-drive =86% 160MW 302MW 129MW * 431MW  total =7.2% * Borrowed from the CLIC design  AC-rf =55% 5

AWA strategies to achieve a high beam power: Increase in pulse beam current (a few Amps) Introduce the locally repetitive drive and main beam pulses to increase average current High energy beam (TeV scale) High Luminosity 16ns 5us 100us 200ms 1s #1 #2 #20 #21 #40 #22 #81 #82 #100 e.g. main beam of a 26GHz 3TeV Short Pulse Accelerator: In pulse beam current =6.5A Average current=10.4uA Average beam power=15.6MW 0.5nC/bunch 6

Layout of ANL 26GHz 3TeV Flexible Linear Collider 7

AWA Facility---Test Bed for short pulse TBA LC technologies 8

9 Train of 32 X 20nC 16 X 40nC 8 X 60nC 4 X 100nC FCT signal of a bunch train

High Power RF 10

11 Development of Dielectric-Based Wakefield Power Extractors 30ns,1MW & 10ns, 40MW 7.8GHz rf pulse produced C-Band Wakefield Power extractor Dielectric-Loaded deceleration waveguide TM 01 -TE 10 coupler rf output port 16ns,1MW & 10ns, 20MW 26GHz rf pulse produced K-Band Wakefield Power extractor = GHz Downconverted signal

RF output coupler Impedance matching section Dielectric loaded waveguide Transverse mode damping Quartz tube metalization SiC tube Brazed copper ring 3 section of damper Quartz tube 12 Full Featured Dielectric Power Extractor

X-Band Metallic Power Extractor LO=8GHz Calculated Trf=3.5ns P~10MWTrf=8.9ns 13

Short rf Pulse Dielectric 14

15 Fabricated 26GHz short pulse DLA Structure parametersvalue ID / OD of dielectric tube3 mm /5.025 mm Dielectric constant9.7 Length of dielectric tubes105 mm Vg11.13%c R/Q k  /m Q (loss tan=10^-4)2295 Shunt impedance M  /m E acc for 316MW input 158 MV/m S21=-2.1dB

16 X-band High Gradient Metallic Accelerator is Under Fabrication 200MW  230MV/m

Two Beam Acceleration and 17

Two Beam Acceleration at AWA 8X40nC 18

19 AWA Two Beam Acceleration Beamline (Ready for Experiments Soon) 15MeV Witness Beamline 75MeV Drive Beamline Interaction Area

20 photons 1.3GHz SW Linac rf delay mrf delay 1rf delay mrf delay 1 rf delay1=0; rf delay2=2L s /c; rf delay m=2*(m-1)*L s /c, m is the # of structures in each stage, L s is the length of a single structure. Module 2 Module 1 L L 2L /c Main beam Drive beam New Scheme to avoid 180 degree drive beam bend (using rf delay to obtain a sync timing)

21 15MeV 1nC 100MeV 4X40nC Simplified Staging at AWA 4X40nC

22 Full Version Staging at AWA 15m 1.5m 1m 0.225m  =2  75MeV 15MeV Drive bunch spacing=50ns (15m) The exit of LINAC6 The exit of Wit LINAC Rf delay=4ns=0.9m WR34 waveguide at 26GHz w/14% rf power loss

Summary A 3TeV Linear Collider based on the short pulse TBA scheme is proposed. Preliminary parameter scan has been done, which shows the feasibility of building an efficient, high gradient, short pulse linear collider. More details need to be further studied. AWA 75MeV GW drive beamline and 15MeV high brightness witness beamline is serving as a main platform to demonstrate the short pulse TBA concept. 23