Development of 26GHz Dielectric-Based Wakefield Power Extractor*

C. Jing, P. Schoessow, A. Kanareykin, Euclid Techlabs, LLC

M. Conde, R. Konecny, J. Power, W. Gai, HEP, ANLS. Kazakov, KEK

A. Kustov4 , Dynamics Software, Helsinki, Finland

AAC08, July. 27th---Aug.2nd , 2008 * work is supported by DoE SBIR Phase I funding.

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Outline

• Motivation

• Structure Design

• Structure Construction

• Planned Experiment

• Summary

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Motivation

Stable high power RF sources, because of numerous potential applications in a number of areas, have been pursued for decades using different technologies over different frequency bands. C-band dielectric-based wakefield power extractor has been successfully demonstrated recently. Here, using a similar idea, we present a higher frequency rf power extractor to demonstrate a good frequency scalability of this scheme.

Argonne Wakefield Accelerator facility has a unique capability of providing high quality, high charge, and short bunch length beams using their 1.3 GHz photoinjector RF gun. According to their upgrade schedule, within the next three years the facility will be able to generate a 20 MeV bunch train (16 bunches) with up to 50 nC charge per bunch by using a new high QE CsTe cathode and an additional 30 MW klystron. This represents an opportunity for testing high charge related applications like our proposed 26 GHz wakefield RF power extractor.

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Parameters of 26GHz Dielectric Based RF Power Extractor

Geometric and accelerating parameters value

ID / OD of dielectric tube 7 mm /9.068 mm

Dielectric constant 6.64

Loss tangent 1×10-4

Length of dielectric tubes 300 mm

Synchronous frequency of TM01/HEM11 mode 26 GHz/23.5 GHz

Group velocity 0.25c/0.42c

R/Q of TM01/HEM11 mode 9788(W/m )/ 556(W/m/mm)

Q of TM01/HEM11 mode 2950/3372

Structure Design

Parameters

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*20nC, single bunch, bunch length 1.5mm.

Est. output*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 .

Structure Design

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Output coupler design

Structure Design

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26GHz Power Extractor: coupler

Structure Construction

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Structure Construction

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Structure Construction

Bench test results

26GHz TM01 mode launcher

WR34-coaxial adaptor

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Planned Experiment

Experiment is planned to perform at AWA facility.

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Snapshots of the electron distributions in the x-z plane traversing the 26GHz decelerator (five bunch train computed using DWA-BD-07). The frames top to bottom show bunches 1-5 at 40ps intervals. The bunches are injected with an initial offset of 0.4mm in the positive x direction. Initial energy of each bunch is 20MeV. Distances in cm; the vertical extent of each plot corresponds to the width of the vacuum channel (±0.35 cm).

Simulation using the DWA-BD-07 particle code of the longitudinal and transverse wake of a 20nC single drive bunch passing through the power extractor.

Planned Experiment

beam simulation by Euclid self-developed code

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Planned Experiment

Components developed for beam experiment.

26GHz power detector

WR-34 rf flange

Heterodyne rf detection circuit

26GHz SiC based rf load is under development.

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Summary

•We have developed a 26GHz dielectric-based wakefield power extractor.

•148MW, 10ns rf power is expected using AWA to-be-upgraded facility.

•1st experiment is planned early next year.