1. Development of Transverse Modes Damped DLA Structure* C. Jing, P. Schoessow, A. Kanareykin, Euclid Techlabs, LLC R. Konecny, W. Gai, J. Power, W. Liu, HEP, ANL AAC08, July. 27 th ---Aug.2 nd, 2008 * work is supported by DoE SBIR Phase I funding.

2. 2 Outline Introduction Structure Design Planned Experiment Summary

3. 3 Introduction

4. 4 Transverse mode in DLA structure 10.18GHz 11.424GHz TM01 mode Ez HEM11 mode Ez Conventional Quartz DLA

5. 5 Surface current distributions for different modes Surface current TM01 mode (axial current only) HEM11 mode (azimuthal current included)

6. 6 Previous work by AWA fellows* * E. Chojnacki, W. Gai, C. Ho, R. Konecny, S. Mtingwa, J. Norem, M. Rosing, P. Schoessow, and J. Simpson, J. Appl. Phys. 69 (9), 1 May 1991. Insulated conductor wires Dielectric tube Longitudinal Wake Transverse Wake

7. 7 New Design to Heavily Damp Hybrid Modes in DLA Structure

8. 8 Design of transverse mode damping structure Hybrid mode damping DLA SiC(ε r ~13; tanδ ~0.22 @ 11GHz) Copper Dielectrics Vacuum

9. 9 Simulations E_TM 01 (0,1mm,z) E_HEM 11 (0,1mm,z) E field (TM01 mode) E-field (HEM11 mode)

10. 10 Simulated parameters *In the desired frequency band, SiC (εr = 13; tanδ = 0.22) and quartz (εr =3.78; tanδ= 0.5×104) are used in the calculations. ; Slots / circumference = 22%. Comparison of the 7.8GHz Conventional and the Transverse mode Damped DLA structure. Freq.Q in conventional DLA structure Q in transverse modes damped DLA structure Accelerating mode (TM 01 ) 7.8GHz6964*6738* Transverse modes (HEM 11 ) 6.34GHz6866*23*

11. 11 The longitudinal (red curve) and transverse (blue curve) wakefields and their spectrums in the 7.8GHz conventional DLA structure. Beam (black curve) parameters used in the calculation are: 40 nC charge, 4 mm bunch length, 30 MeV single bunch at 1 mm offset from the structure axis. The structure is currently under development, and planned to be tested at AWA facility in near future. Planned Experiment

12. 12 Summary We are developing a hybrid mode damped DLA structure. Structure will be tested at AWA facility along with a conventional DLA structure as a comparison.