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

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Outline

• Introduction

• Structure Design

• Planned Experiment

• Summary

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Introduction

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Transverse mode in DLA structure

10.18GHz11.424GHz

TM01 mode Ez HEM11 mode Ez

Conventional Quartz DLA

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Surface current distributions for different modes

Surface current

TM01 mode (axial current only)

HEM11 mode (azimuthal current included)

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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

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New Design to Heavily Damp Hybrid Modes in DLA Structure

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Design of transverse mode damping structure

Hybrid mode damping DLA

SiC(εr ~13; tanδ ~0.22 @ 11GHz)CopperDielectricsVacuum

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Simulations

E_TM01(0,1mm,z)

E_HEM11(0,1mm,z)

E field (TM01 mode)

E-field (HEM11 mode)

0

1000

2000

3000

4000

5000

6000

7000

8000

0 50 100 150 200

Length (mm)

E_a

mpl

itude

(V/m

)

Conventional DLA

Transverse Moded Damped DLA

0

100

200

300

400

500

600

700

0 50 100 150 200

Length (mm)

E_a

mpl

itude

(V/m

)

Conventional DLA

Transverse mode damped DLA

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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 (TM01)

7.8GHz 6964* 6738*

Transverse modes (HEM11)

6.34GHz 6866* 23*

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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

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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.