Development of compact RF pulse compressors and pulse

Development of compact RF pulse compressors and pulse modulation experiments Yuliang Jiang, Ping Wang, Jiaru Shi, Huaibi Chen Tsinghua University 2018/6/6 International workshop on high-gradient acceleration, HG 2018, Shanghai, China

Outline • I. Introduction • II. Pulse modulation experiments • III. Compact RF pulse compressors • IV. Summary HG 2018 -Yuliang Jiang-Development of compact RF pulse compressors and pulse modulation experiments

Outline • I. Introduction 1. Pulse compression 2. High power test facilities at Tsinghua University • II. Pulse modulation experiments • III. Compact RF pulse compressors • IV. Summary HG 2018 -Yuliang Jiang-Development of compact RF pulse compressors and pulse modulation experiments

I. Pulse compression • Concept Pulse from RF sources Pulse compressor Pulse need by linacs • Types Cavities SLED-II Delay lines Input pulse RF source 3 d. B hybrid Resonance Delay Lines HG 2018 -Yuliang Jiang-Development of compact RF pulse compressors and pulse modulation experiments

I. High power test facilities at THU • S-band • X-band HG 2018 -Yuliang Jiang-Development of compact RF pulse compressors and pulse modulation experiments

I. S-band test stand at THU • Low Level RF system • Double klystrons • SLED-I type pulse compressor • Stainless steel RF load HG 2018 -Yuliang Jiang-Development of compact RF pulse compressors and pulse modulation experiments

Outline • I. Introduction • II. Pulse modulation experiments 1. Phase-to-amplitude modulation 2. High efficiency pulse compression • III. Compact RF pulse compressors • IV. Summary HG 2018 -Yuliang Jiang-Development of compact RF pulse compressors and pulse modulation experiments

II. Phase-to-amplitude modulation • Theory Phase-to-amplitude SLED I HG 2018 -Yuliang Jiang-Development of compact RF pulse compressors and pulse modulation experiments

II. Phase-to-amplitude modulation • Demonstration Before modulation Sharply decaying output pulse After modulation Flat top output pulse HG 2018 -Yuliang Jiang-Development of compact RF pulse compressors and pulse modulation experiments

II. High efficiency pulse compression Typical: Use flat input pulse at a stable modulator voltage. l Longer the modulator pulse width l Lower pulse compression efficiency(61%) This power ti p is inefficient Ensure a same peak power Improved: Make use of the rising edge. l Shorten the modulator pulse width l Higher pulse compression efficiency(70%) The power tip is eliminated HG 2018 -Yuliang Jiang-Development of compact RF pulse compressors and pulse modulation experiments

Outline • I. Introduction • II. Pulse modulation experiments • III. Compact RF pulse compressors(PC) 1. S-band PC with a spherical cavity 2. X-band PC with a corrugated cylindrical cavity • IV. Summary HG 2018 -Yuliang Jiang-Development of compact RF pulse compressors and pulse modulation experiments

III. S-band pulse compressor • Design Parameter New type Old SLED type Frequency 2. 856 GHz TE 112 TE 015 100, 000 8 5 Input pulse length [μs] 3. 6 Output pulse length [ns] 300 7 5. 6 5. 2 4. 6 25. 58 20. 51 Resonant mode Unloaded quality factor (Q 0) Coupling factor (β) Peak power gain Average power gain Diameter of the cavity [cm] l Higher power gain and capability l Single resonant cavity HG 2018 -Yuliang Jiang-Development of compact RF pulse compressors and pulse modulation experiments

III. S-band pulse compressor • Design Q 0=100, 000 β=8 HG 2018 -Yuliang Jiang-Development of compact RF pulse compressors and pulse modulation experiments

III. S-band pulse compressor Magnetic probe plugged in to detect the frequencies in different directions • Test Shorten the middle cylinder length for frequency tuning RF polarizer Main Components Before brazing HG 2018 -Yuliang Jiang-Development of compact RF pulse compressors and pulse modulation experiments After brazing

III. S-band pulse compressor • Test S-parameters after brazing and tuning S 12=-2. 2 d. B Q 0~98, 000 β~7. 86 Peak power ~560 MW ! HG 2018 -Yuliang Jiang-Development of compact RF pulse compressors and pulse modulation experiments

III. X-band pulse compressor • Design Compress the RF pulse from 1. 5 us to 100 ns Peak power gain more than 5 β~3. 5 Spherical Smooth cylindrical Corrugated cylindrical TE 01 mode TE 11 mode HE 11 mode Q 0=100, 000 β=3. 5 HG 2018 -Yuliang Jiang-Development of compact RF pulse compressors and pulse modulation experiments

III. X-band pulse compressor • Design Compress the RF pulse from 1. 5 us to 100 ns Peak power gain more than 5 β~3. 5 Port 2 Port 3(1) Port 3(2) Port 1 HG 2018 -Yuliang Jiang-Development of compact RF pulse compressors and pulse modulation experiments

III. X-band pulse compressor • Cold test before brazing l Power transmission efficiency > 0. 9 l 10 MHz below the designed frequency (11. 424 GHz) l Calculated Qe= 34971 (designed Qe~35000) HG 2018 -Yuliang Jiang-Development of compact RF pulse compressors and pulse modulation experiments

Outline • I. Introduction 1. Pulse compression 2. High power test facilities at Tsinghua University • II. Pulse modulation experiments 1. Phase-to-amplitude modulation 2. High efficiency pulse compression • III. Compact RF pulse compressors(PC) 1. S-band PC with a spherical cavity 2. X-band PC with a corrugated cylindrical cavity • IV. Summary HG 2018 -Yuliang Jiang-Development of compact RF pulse compressors and pulse modulation experiments

Summary • A S-band high power test facility is in operation and an X-band one is initially completed at Tsinghua. • The phase-to-amplitude modulation has been demonstrated. -- by a low level RF system and two klystrons -- SLED-I type pulse compressor outputs a flat top pulse rather than a sharply decaying pulse • Pulse compression using the rising edge of the modulator voltage is proposed. -- increase the pulse compression efficiency -- shorten the required modulator pulse width • A compact S-band pulse compressor with a spherical cavity is tested, generating about 560 MW peak power with a peak power gain of 7. • A novel X-band pulse compressor with a corrugated cylindrical cavity has been designed. HG 2018 -Yuliang Jiang-Development of compact RF pulse compressors and pulse modulation experiments

Thank you for your attention! HG 2018 -Yuliang Jiang-Development of compact RF pulse compressors and pulse modulation experiments