1. Development of a Compact Dielectric-Loaded Test Accelerator at 11.4 GHz* S.H. Gold, a) A.K. Kinkead, b) W. Gai, c) J.G. Power, c) R. Konecny, c) C. Jing, c,d) and A.W. Fliflet a) a) Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 b) Icarus Research, Bethesda, MD 20814 c) Argonne National Laboratory, Argonne, IL 60439 d) Euclid TechLabs, Solon, OH 44139 Presented at 13 th Advanced Accelerator Concepts Workshop Santa Cruz, CA 27 July – 2 August 2008 *DoE Interagency Agreement #DE–AI02–01ER41170

2. NRL Magnicon Facility Magnicon Facility offers a flexible venue for hands-on experiments requiring high power 11.4 GHz radiation, with reasonable work and safety rules and minimal red tape Magnicon properties: high power (10–20 MW), adjustable pulse length (200-ns FWHM– 1-µs), repetition rate up to 10 Hz, stable gain, a modest (~0.1%) tuning range, phase stability, and stable operation into resonant loads Magnicon facility has been used for two series of collaborative experiments over the past 5 years: –Sixteen tests of DLA Structures –Eight tests of Active Pulse Compressors It is now being used to power a 5-MeV injector, the first stage of a compact test accelerator to study acceleration in DLA structures

3. Magnicon Facility Schematic

5. Magnicon Power Combiner/ Splitter Load 5 MeV Injector DLA Structure Spectrometer X-Band Test Accelerator

6. Magnicon Power Combiner/ Splitter Load 5 MeV Injector 20 MeV Dielectric-Loaded Accelerator Spectrometer Accelerator Section Focusing Quads Cathode Assembly Device under test X-Band Test Accelerator ICT YAG

7. Design Parameters Energy5.2 MeV Charge/Bunch>5 pC RF Frequency 11.430 GHz RF Power in ~2 MW Q~1000 Norm.Emittance 3.1  mm mrad Energy Spread~6% Matching Quads Injector NRL X-Band Injector LaB 6 Cathode Accelerator Lab of Tsinghua University 胡源 (Y. Hu, Student), 杜晓福 (X. Du), 唐传祥 (Prof. C. Tang), and 林郁正 (Prof. Y. Lin)

8. Measured Axial Field Profile and PARMELA Results

10. Temperature Tuning the Injector Linear Fit Experimental Data

11. Injector Cavity Filling Calculation Q 0 = 9700 Q e = 1115  = 8.7

12. Conditioning the Injector y = 0.65x

13. P forward (6 MW) P reflected ICT 4 mm (0.5 mA) Initial Accelerator Operation

14. Beam Deflection Measurement   ~ 7.5

15. Injector installed with rf window, gate valve, ICT, YAG, focusing quads, steering magnet RF conditioning completed Dark current electrons observed; energy of ~3–5 MeV, based on electron range in Al and bending in 1.2 kG magnetic field Initial operation with hot cathode at rated rf drive (~2 MW injected) produced ~1 mA, ~3.2 MeV, 4-mm-diam beam Low cathode temperature, apparent cathode poisoning limited beam current from LaB 6 cathode Temperature gradient along 24-cell structure may have limited beam energy These problems will be addressed in the near future Compact Accelerator Summary