On the Resonant Properties of THz Laminated Accelerating Structures

1. On the Resonant Properties of THz Laminated Accelerating Structures V. Tsakanov CANDLE SRI 25-29 March 2018, Oxford, UK 4th EAAC Workshop, 15-21 Sep 2019, Isola d'Elba, Italy

2. Contents • Introduction • Laminated metallic structures • Narrow band Longitudinal Impedance • Dispersion Relation & Wake potential • Cu-Ge flat chamber S12 measurements • Accelerating structures at 0.5 THz • Metal dielectric structures • Summary

3. 2015-2019 – 4 Experimental Stations Nanotechnology AREAL-5 MeV Exp-1 MicroFab DELTA Biomedicine Exp-2 Microscopy

4. Precise machining and micro fabrication Mechanical Workshop Laser Microfabrication Station Diffraction elements and integrated devices Deflecting cavity Two-photon polymerization micro-needles, photonic band-gap, waveguides Surface patterning of semiconductors, metals, dielectrics… Direct writing of Si-based dielectric waveguides and sub-micron 3D structures

5. AREAL –2020-2022 2015 Laser IR UV DELTA Gun MS MF Mid IR Free Electron LASER 20-50 MeV H1 ALPHA Linac H2 Acc1 Acc2 BETA BETA - Booster forEmergingTechnologyAccelerators AREAL Energy 20-50 MeV Charge 20 - 400 pC Bunch length (rms) 0.4 – 8 ps Energy spread < 0.5% Norm emittance (rms) ~1.2 um Repetition rate - 1-20 Hz • New High Freq. Structures • Advanced Accel. concepts • Advanced radiation sources • New diagnostic tools

6. Schematic layout of THz station (0.3-0.4 THz) • THz Radiation • Beam manipulation • THz acceleration Rad Accel

7. q Laminated Metallic structures Cu Narrow band Resonant Impedance NEG a- radius, d- thickness k0 High Frequency region Thin inner layer  >>d Skin depth TM01 TM monopole modes Dispersion relation Exact solution. Field matching technique

8. Laminated Metallic structures a=2cm, d=1um 1=103,104,105 -1m-1 2,2 1,1 d a Q Exact -solid, analytic – dashed. Skin depth  >>d Imp. of parallel resonance circuit

9. Wake potentials Cu-NEG Radiation from open end f=4.7 THz

10. Copper –Germanium flat chamber Measurements of reflection S11 and transmission coefficients S12 are made with and without Ge plates over a frequency range of 4 GHz to 14 GHz. ~ b=2, 3, 4 cm

11. Accelerating Structures at 0.35 THz σ=104 Ω-1m-1 Cu-NEG Cu-NEG  (CdS)= 600 -1m-1  (Ge)= 2 -1m-1 Cu-Ge

12. Metal –Dielectric structures a=2mm Metal finite conductivity Copper Dielectric layer with losses Layer thickness: thick d=200m thin d=2m Silicon, Si 11.7 Ceramics 10 - 200 Glass 3.8-14.5

13. f_1 f_2 f_3 0 0.08765 0.29007 0.5234 0.1 0.08765 0.29005 0.52336 0.5 0.08764 0.28974 0.52257 3 0.0871 0.279 0.4953 Longitudinal Impedance, a=2mm, d=200μm Resonance frequencies (THz)

14. Dispersion curves and longitudinal wake functions a=2mm, d=200μm Gaussian Bunch, rms length σ=0.5ps (150μm)

15. Impedance, Wake function and dispersion curves for thin dielectric layer d=2μm

16. Transverse Impedance, Wake function and dispersion curves for thick dielectric layer d=200μm Dispersion curves

17. Transverse Impedance, Wake function and dispersion curves for thin dielectric layer d=2μm Mode only Dispersion curve

18. Summary • BETA Experimental line design • Construction and test • THz radiation and acceleration • New THz structures and sources Acknowledgments K.Floettmann, F. Lemery, M. Dohlus, (DESY) M. Ivanyan, L. Aslyan, A. Vardanyan, B. Grigoryan (CANDLE)