Development of Dielectric-Based Wakefield Power Extractors

1. Development of Dielectric-Based Wakefield Power Extractors Chunguang Jing1,2, W. Gai1, A. Kanareykin2, Igor Syratchev, CERN 1.High Energy Physics Division, ANL 2. Euclid Techlabs LLC April. 2010 * Now with National Light Source, BNL

2. Contents • Introduction • 7.8GHz Dielectric-Based Power Extractor--- design, fabrication, and test. • 26GHz Dielectric-Based Power Extractor--- design, fabrication, and test. • Proposed 12GHz Dielectric-Based Power Extractor (for CLIC) • Summary

3. Dielectric-lined Waveguide to Slow the Wave Dielectric loaded waveguide can slow the RF wave for acceleration like the conventional disk-loaded waveguide. Low-loss dielectric materials bring promise to this kind of structure. • Pros: simplicity of fabrication • potentially higher breakdown threshold • low surface field enhancement • Easy deflecting mode damping • Cons: Multipactor Er/Ez=a/ Electric Field Vectors (TM01)

4. 7.8GHz Dielectric-Based Wakefield Power Extractor* Two related journal publications: 1) F. Gao, et al, PR ST-AB, 11, 041301 (2008); 2) F. Gao, et al. IEEE Trans. NS, 56, 3, JUNE (2009) 1492-1497. *Prototype structure without transverse mode damping. It is to demonstrate the concept.

5. 7.8GHz Dielectric-Based Wakefield Power Extractor----design

6. mode launcher inside DL deceleration waveguide TM01-TE10 coupler rf output port 7.8GHz Dielectric-Based Wakefield Power Extractor----fabrication & bench test Reflection Insertion loss

7. 7.8GHz Dielectric-Based Wakefield Power Extractor----beam test (I): setup

8. 7.8GHz Dielectric-Based Wakefield Power Extractor----beam test (II): e-bunch train generation A UV laser pulse is split into two trains, each consisting eight micropulses spaced by 2T. e- bunch train generated: i). 16 bunches, Tb = 769ps, qmax = 4.8nC ii). 16 bunches, Tb = 1.54ns, qmax = 4.9nC iii). 4 bunches, Tb = 769ps, qmax = 26.5nC

9. 7.8GHz Dielectric-Based Wakefield Power Extractor----beam test (III): 1-16 bunches, Tb=769ps 15ns rf pulse generated, Pmax= 2.4MW @ qmax = 4.8nC.

10. 7.8GHz Dielectric-Based Wakefield Power Extractor----beam test (IV): 16 bunches, Tb=1.54ns 30ns rf pulse generated, Pmax= 1MW @ qmax = 4.9nC.

11. 44MW generated 40MW extracted 7.8GHz Dielectric-Based Wakefield Power Extractor----beam test (V): 4 bunches, Tb=769ps 7.5ns rf pulse generated, Pmax= 44MW @ qmax = 26.5nC. t - ns f - GHz

12. 26GHz Dielectric-Based Wakefield Power Extractor ----by Euclid Techlabs, supported by DoE SBIR program

13. 26GHz Dielectric-Based Wakefield Power Extractor----design

14. 26GHz Dielectric-Based Wakefield Power Extractor----power estimation *16, 20nC bunch train, steady output power of 148 MW and 56 MV/m peak gradient. The energy loss is 5.7 MeV for the last bunch in the bunch train . *20nC, single bunch, bunch length 1.5mm.

15. 26GHz Dielectric-Based Wakefield Power Extractor----fabrication 26GHz UHV rf power detector SiC based 26GHz UHV rf load

16. 26GHz Dielectric-Based Wakefield Power Extractor----beam test (I): setup Load Rf probe 16GHz scope 11.424GHz BPF (228MHz BW) LO=14.576GHz

17. 26GHz Dielectric-Based Wakefield Power Extractor----beam test (II): 16 bunches, Tb=769ps Down-converted rf Trace SiC based Rf load behaves well. 11.44+14.576=26.016 GHz

18. 26GHz Dielectric-Based Wakefield Power Extractor----beam test (III): 4 bunches, Tb=769ps Down-converted rf Trace SiC based Rf load behaves well. Background noise to the scope 11.44+14.576=26.016 GHz

19. 26GHz Dielectric-Based Wakefield Power Extractor----beam test (IV): charge sweeping, 4 bunches, Tb=769ps Theoretically, 9nC29.6MW, 24.8MV/m; 17MW was measured (bunch length effect, coupler loss, etc) Number is the percentage of charge transmission out of the structure, which indicates the BBU appears when charge goes high.

20. Transverse Damping---- to improve the high current beam transportation HEM11 mode Ez TM01 mode Ez TM01 mode (axial current only) HEM11 mode (azimuthal current included) SiC Copper Dielectrics Vacuum by Euclid Techlabs, supported by DoE SBIR program

21. Proposed 12GHz Dielectric-Based Wakefield Power Extractor ----submitted to DoE 2010 SBIR program by Euclid Techlabs In collaboration with CERN (Igor Syratchev)

22. 12GHz Quartz-Based Power Extractor Using CLIC Parameters: σz=1mm, Q=8.4nC, Tb=83ps

23. Preliminary Design of a 12GHz Quartz-Based Power Extractor (by Igor Syratchev) -The ceramic part is installed into the separate copper tube. The other compact piece integrates the choke and the matching grove and could be the part of the flange to be connected to the coupler. - Between the two, one can foresee the EB welding or another flange. With this approach the system cab be easily dismantled and the pieces recycled. - For later the slot can be equipped with damping material (for the HOM) and to be used for the vacuum pumping of the entire volume. - By design, the system is rather insensitive to the fabrication/installation errors (slot width, position of ceramic and etc.) - For the fabrication, it looks inexpensive.

24. Current Status • The 1st step is to build a 11.424GHz version DWPE so that we can high power rf test it at SLAC and explore the possible issues. • This work has been applied for 2010 DoE SBIR funding (just funded).

25. SUMMARY • Dielectric-based wakefield power extractors have been successfully demonstrated. • Two structures, 7.8GHz and 26GHz, were fabricated and tested. 40MW for 7.8GHz and 20MW for 26GHz were measured. • X-band DWPE is planned to develop soon.