A Multi-Moded Delay Line RF Distribution System for the Next

Linear Collider

Sami G. TantawiSLAC

Motivation• The Current Next Linear Collider design have accelerator structure sections

that requires a 200 MW, 375 nS pulses at 11.424 GHz. The available power supplies are 75 MW klystrons which produces more than 1.5 S pulses. Hence, pulse compression is needed.

Topics Discussed at ISG2

• Different Pulse Compression Techniques and Topologies• Component Development• Joint Experimental Work• High Power Experiments

TE21

TE01 Mode Extractor

TE01 Mode Extractor(Power is Extracted Evenly Between Four Waveguides)

TE01

TE12 (Vertically Polarized)

TE01

TE12 (Vertically Polarized)TE12 (Horizontally Polarized)

Accelerator Structure (~1.8 m)

~7.4 cm Circular Waveguide

TE01

Mode Launcher (Fed by Four Rectangular Waveguides)

Klystrons

~ 6 m

TE12 to TE01 Mode Converter ~53 m

~12.7 cm Circular Waveguide

TE01 Tap-Off TE01 Mode Converter (Fed by Four Rectangular Waveguides)

TE21-TE01 Mode Converter

Eight 75-megawatt klystrons

RF

e+ or e- A Cluster of 9 Multi-Moded DLDS Sections

RF Power Sources

A Single Multi-Moded Delay Line RF Distribution System

Accelerator Structures

Delay Lines

Modular Launcher

TE11 Launcher TE01 LauncherTE01 Launcher

Both Polarizations of TE 11

TE 01

TE 01

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TE12-TE11 Mode Converter TE12-TE11 Mode ConverterTE11-TE01 Mode Converter

TE01 Mode Extractor5”

Extraction of The TE01 is done with the help of a “wrap-around mode converter”. The circular guide is tapered down to cutoff the TE01 mode while allowing the TE11 Mode to go through

Instead of using a cutoff section to allow the extraction of the TE01 mode, one can use two mode converters cascaded together

A short circuit

Y0=1 Y0=1

Y0=1 Y0=1

Y0=1

Y0=1

Y0=1Y0=1

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jj

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S

4/

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Port 1

Port 2

Port 3

Port 4

If a signal is injected in port 1, it will all appear in port 3.

TE12-TE01 Mode Converter

TE01 Mode Extractor

Compact Mode Extractor

~7.4 cm Circular Waveguide

TE01 Mode Extractor(Power is Extracted Evenly Between Four Waveguides)

TE01

TE12 (Vertically Polarized)TE12 (Horizontally Polarized)

TE01

TE12 (Vertically Polarized)

TE01

TE01 Mode Extractor

Mode Launcher (Fed by Four Rectangular Waveguides)

TE21

TE21-TE01 Mode Converter

Klystrons

~ 6 mTE01 Mode Converter (Fed by Four Rectangular Waveguides)

TE12 to TE01 Mode Converter

~12.7 cm Circular Waveguide

TE01 Tap-Off

SLAC

KEK

55 m

Circular Taper

TE11-TE12 Mode Converter

TE11-TE10

4.75” Waveguide Pump-Out/Flange

Purpose of Experiment

* Determine the attenuation of TE12 mode in Circular Waveguides.* Determine the stability of the TE12 mode.

Mode Analyzer

High Power RF Sources and Systems

Yong Ho Chin, Sami G. Tantawi, and Arnold E. Vlieks

• Two DLDS are under development. – 2x2 DLDS at KEK– 3x1 DLDS at SLAC– Both systems uses the same set of components.

While the 3x1 requires a slightly more complicated extractor, it uses less waveguide. The 2x2 is slightly more efficient and can handle the mode rotation problem better

Components needed for both systems

• Launchers– A common design for the launcher was adapted by

both KEK and SLAC, We both produced a cold test model.

• SLAC model had one degree of freedom and produced a 98% effivient device

• KEK model had two degrees of freedum and produced a system that khas an efficiency of better than 99%

– A launcer based on circular to rectangular tapers is being devolped at SLAC

• Extractors– An extraction system based on wrap around-

mode converter is due to be delivered at KEK shortly

• The serpentine mode converter part has been delivered and test

– An extractor based on the circular to rectangular taper is being devloped at SLAC

• Tapers– Compact tapers for circular waveguides has been

desined and tested at SLAC– Circular Linear tapers has been developed at KEK– Mode-structure preserving Circular to Rectangular

tapers have been developed at SLAC – A type of Mode-Structure preserving Circular to

square tapers has been devloped at KEK

• Circular TE01 bends– A bend based on circular to square tapers has

been developed at SLAC– A bend based on the same concept has been

developed at KEK

• Tap-offs – A system of tap-offs have been developed at SLAC. The

system is based on rectangular components and circular to rectangular tapers.

• Hybrids– Two types of H-Plane over moded hybrids have been

developed at SLAC. Both have a chance to withstand very high fields.

• High power loads – A super High power load tree is developed at SLAC.

Alternative Pulse compression system

• Binary Pulse compression and active systems starts to be attractive at a higher Compression ratio.

• All the component development will fit into these systems

• There are some work on Circulators and Active switches, but it is still a premature art.

Mode Stability experiment

• Eerily April, After the PAC conference, a meeting at SLAC is going to take place to discuss the final preparation steps.

• All the basic components needed for the experiment are designed and most of it is ordered.

• A method for measuring a phase stable signal has been developed during the meeting by Y. Chin. The required instrumentation for this method is going to be discussed between now and April.

• The experiment most likely will take place in during the second half of July. However we may make it earlier because ATF is available all summer