Development of an X-band Dielectric PETS

C. Jing, Euclid Techlabs / ANL

HG Workshop, May. 2011

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• Motivation

• Previous Experiences on the dielectric based wakefield power extractors

• Development of an X-band Dielectric PETS

OUTLINE

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Motivation

• CLIC PETS is one of the key components in the CLIC TBA scheme. According to the 2008 CLIC design parameters, 71568 PETS units total are needed for this 3 TeV machine, contributing a large portion of the overall cost. A low cost wakefield power extractor with the same parameters as PETS will be attractive.

• Dielectric based wakefield power extractors, which can be inexpensively built, have been experimentally demonstrated in high power, short pulse conditions. We like to find out their performances in the CLIC required 240ns, 140MW rf pulse.

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Dielectric-lined Waveguide to Slow the Wave

Electric Field Vectors (TM01)

•Advantages: simplicity of fabrication

potentially higher breakdown threshold

low surface field enhancement

Easy deflecting mode damping•Challenges: Multipactor

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.

Ez

Er

Hphi

vacuum dielectric

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•30ns,1MW & 6ns, 40MW 7.8GHz rf pulse have been demonstrated in the current AWA beamline.

•20ns 500MW are expected with the upgraded AWA beamline.

C-Band Power extractor (2008)

•15ns,1MW & 6ns, 20MW 26GHz rf pulse have been demonstrated in the current AWA beamline.

• 148MW are expected with an improved beam control in the present AWA beamline.

Ka-Band Power extractor (2009)

11.44+14.576=26.016 GHz

Downconverted signal

44MW generated40MW extracted

Previous works

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Development of the 12GHz Dielectric PETS

1. Design 12GHz dielectric PETS; and build an 11.424GHz version of dielectric PETS.

2. High power rf test 11.4GHz version structure at SLAC ASTA (we like to thank Sami’s group in advance ).

3. Build 12GHz dielectric PETS with information obtained in Step 2.

4. Beam test at CLIC.

funded by DoE 2010 SBIR program Phase I.

Submitted to DoE 2011 SBIR Phase II.

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12GHz Quartz-Based Power Extractor Using CLIC Parameters:

σz=1mm, Q=8.4nC, Tb=83ps

Freq 11.994GHz

Effective Length 23cm

Beam channel 23mm

Thickness of the dielectric tube 2.582mm

Dielectric const. 3.75(Quartz)

Loss tangent (@10GHz) 6*10^-5

Q 7318

R/Q 2.171k/m

Vg 0.4846c

Peak surface Gradient Ell=12.65MV/m; E=18.28MV/m

Steady Power 142MW

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Design of a 12GHz Quartz-Based Power Ext

ractor (thanks to Igor Syratchev)

beam

Connected to rf coupler

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Design of a 12GHz Quartz-Based Power Ext

ractor (by Igor Syratchev)

Note: The peak magnetic field is 78.7 kA per 135 MW rf input 1.3C pulse heating.

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11.424GHz version dielectric PETS for

high power rf test

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11.424GHz version dielectric PETS for

high power rf test

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-40

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-20

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0

11.2 11.3 11.4 11.5 11.6

Freq.(GHz)

S-p

aram

eter

s (d

B)

S11 S21

-40

-30

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11.2 11.3 11.4 11.5 11.6

Freq.(GHz)

S-p

aram

eter

s (d

B)

S11 S21

11.424GHz version dielectric PETS for

high power rf test

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11.424GHz version dielectric PETS for

high power rf test

0

0.2

0.4

0.6

0.8

1

0 10 20 30 40 50 60 70

Distance (cm)

Nor

mal

ized

Ez

@11

.424

GH

z

Beadpull Result

Low field in the 23cm DLA section

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The 1st step, building a 11.424GHz version D-PETS, has been done.

We plan to high power rf test it at SLAC and explore the possible issues.

The rest of work has been applied for 2011 DoE SBIR Phase II funding.

Summary

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<0.5dB Insertion loss~200W average power dissipation per 240ns 135MW rf input, 60Hz <1 C temperature gradient with good contact cooling.

Simple cooling