Ferroelectric Based Technologies for Accelerators

1. AAC’08, Santa Cruz CA, 2008 Ferroelectric Based Technologies for Accelerators A.Kanareykin Euclid TechLabs LLC, Rockville, MD This work is supported by the DOE, High Energy Physics

2. TEAM A.Kanareykin, Euclid TechLabs LLC, Rockville, MD S.Kazakov, KEK, Tsukuba, Japan/Omega-P Inc., CT E. Nenasheva, Ceramics Ltd., St. Petersburg, Russia, A.Tagantsev, EPFL, Lausanne, Switzerland V.Yakovlev, Fermi National Lab PROJECT IN COLLABORATION WITH YALE/OMEGA-P, INC., FNAL, ORNL/SNS, ELTECH UNI. and ANL/AWA

3. Outline • BST(M) ferroelectric: ultra fast switching material • Properties required for the accelerator applications • Material development: what have been done • Large diameter bars/rings fabrication • Testing by Omega-P, Inc.; L, X and Ka band designs • Parallel and transverse biasing field • Summary

4. A concept of phase shifter design (Omega-P, Inc.) Ferroelectric Rings

5. Applications of tunability - Telecommunications - power - mW - W - Radars - power - W - kW - Accelerator technique - power - (0.5 -200) MW Materials development for theUS Department of Energy

6. Applications of Ferroelectrics in Accelerator Technique Tuning speed - RF tuning at X-band/Ka band - RF tuning at L-band - Fine tuning of dielectric structures 10-20 ns 10-20 μs

7. Requirements - Permittivity - Relative tunability - Tuning dc field - Loss tangent (10 GHz) - Commutation time - Size of elements < 3× 10-3 f/tanδ ~ const ! 20 ns - 20 μs

8. FERROELECTRIC PROPERTIES FOR ACCELERATOR APPLICATIONS - The dielectric constant should not exceed 300-500 to avoid problems caused by interference from high-order modes and extra wall losses. - The dielectric constant should be variable by 15-20% to provide the required switching and tuning properties. - Bias electric fields required to adjust the permittivity within this range should be reasonable, ~few 10’s of kV/cm - The loss tangent should be in the range of few10-3 or lower at 11-34 GHz to allow switching at 120-180 Hz rep rate.

9. FERROELECTRIC PROPERTIES • very short intrinsic response time of ~10–10 - 10-11 sec ( 1 ns for circuits) • - high dielectric breakdown strength of 150-200 kV/cm • high vacuum compatibility • easy mechanical treatment (similar to conventional ceramic) • Ferroelectrics should have the following properties to operate in high-power rf switching and tuning devices: • -  - 300-500 [500-600 current, recently reduced to 200-250] •  variation - 10% - 20% at 50 kV/cm, [15% - E┴, >30% E║] • DC field - 10’s of kV/cm loss [20-60 kV/cm tested] • tanδ~10-2-10-3 at 11-35 GHz [5×10-3 at X-band, 5 – 10 ×10-4 700 MHz ]

10. Tuning of permittivity in ferroelectrics For small tuning (nr<<1) Ferroelectrics !!!

11. Choice of material and approach Composite: (Ba,Sr)TiO3 + dielectric (bulk ceramics) Spherical inclusion composite (i) Use of BST with high e (ii) Dilution with dielectric

12. MgO and Mg2TiO4 additives Dependence permittivity ε′ (a), temperature Tm (b) and tunability kt for the samples BST (55/45) wt.% MgO (1) and Mg2TiO4 (2)

13. Ferroelectric properties vs. frequency and % wt of inclusions 55 %BaTiO3 - 45%.SrTiO3 with 20% МgO

14. Developed materials (Ba,Sr)TiO3 based composite Sengupta et al (patents)

15. BST(M) Ferroelectric: Size Effects Dimension studies for the BSM-3 (left) and BSM-4 (right) ferroelectric samples with thickness of 0.1 – 0.5 mm.

16. BST(M) Ferroelectric: Bulk Sample Measurements (Omega-P, Inc.)

17. Experimental Setup, ns Scale Switching Time Pictures of the experimental setup for the time response testing of the ferroelectric samples to high pulse voltages.

18. DC and Pulse Tunability Measurements Kdc =C(0)/C(Udc )=C(0)/Cdc corresponds to capacitance value Cdc measured in 1 min after the moment of Udc switching on). Kdyn =C(0)/Cpulse (Um) =C(0)/Cpulse Cpulse corresponds to the end of the leading front of the 20 ns pulse. Various Samples of BST(M) Various Samples of BST(M) ×10 kV/cm ×10 kV/cm

19. FAST ACTIVE X-BAND HIGH POWER PHASE SHIFTER S. Kazakov et al “First Measurements of RF Properties of Large Ferroelectric Rings " Ferroelectric ring elements for the X-band high power phase shifter. The same technology will be used for the L-band tuner fabrication. * Developed by Omega-P, Inc.

20. Loading with parallel bias Ferroelectric L-band Reflecting Phase Shifter RF field, TEM mode ferroelectric ring Copper electrodes dc field * Developed by Omega-P, Inc.

21. L-band Planar Design (Omega-P, Inc.) S. Kazakov et al. EPAC’08 * Developed by Omega-P, Inc.

22. Problem of transverse bias

23. BST(M) ferroelectric group of compositions E.Nenasheva. “Development of A Low Loss Microwave Ferroelectric Material for the High Power Tunable Devices”

24. Effect of dc bias orientations transverse longitudinal

25. n (E) 1 2 3 n (E) Edc, kV/cm 1 2 3 Edc, kV/cm Examples:nvs n (Ba0.65Sr0.35)TiO3 at 3150K ; data by Daimond (1961) (Ba0.8Sr0.2)TiO3 at 333 0K data by Pertov et al (1971) Acceptable loss of tunability when passing from n‖ to n┴

26. BST(M): what have been done ? • The group of materials have been developed: from BSM-1 to BSM-4 • Pulse measurements have been carried out : < 10 ns switching time ! • Theory of the BST(M) composite ferroelectric have been developed • Transverse dc bias feasibility has been demonstrated • Dielectric response and tunability have been measured/mechanical • Dimension effects have been studied • Metallization technology has been developed • First direct BST bulk sample measurements • First cold test of the L-band fast shifter: 1200 phase shift • Tunable DLA structure cold test : temperature and dc bias tuning

27. BST(M): what will be done ? • - Material improvement with lower loss tangent (Euclid) • - Vacuum testing (Euclid/ANL) • High power testing at X-band (Omega-P/NRL) • Beam testing of the tunable DLA (Euclid/ANL) • Fast switching of the L-band phase shifter (Omega-P) to be done: XI-Electroceramics, Manchester, UK August 31, 2008