1 / 22

Laser System Upgrade Overview

This overview provides information on the upgrade requirements for laser systems used in RF Guns, including laser energy, temporal pulse shaping, and continuous operation. It also highlights the challenges faced in existing laser systems and the need for collaboration with various organizations.

sharonl
Download Presentation

Laser System Upgrade Overview

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Laser System Upgrade Overview RF Gun workshop @ 6, June, 2016

  2. Requirement of laser system for RF-Gun • Laser energy • 500 mJ for Ir5Ce cathode • 50 mJ for Ce2Te cathode • 50 Hz, 2-bunch (96ns spacing) => Regenerative amplifier + 96ns delay => Large regenerative amplifier (unstable) => Multi-pass amplifier (Upgrade existing underground laser ) • Temporal pulse shaping to reduce energy spread => Broadband laser crystal (Yb or Ti:Sapphire) => postponded until Phase-III • Continuous operation (limited cost / human resource) • Support cost for commertial product is very high. (1,000-2,000$/day/person + a(margin) ) • No laser system company in Japan. • Recovering time.

  3. Required laser pulse energy Current laser energy(500μJ) QE=10-4 Ce2Te Charge( C ) QE=10-3 Offline measurement S-polarization Offline measurement P-polarization QE=10-5 5nC Inclined injection ATF Normal injection (old 3-2) Laser power ( J )

  4. How to generate 2-bunch with 96 ns spacing. • Amplification time of standard regenerative amplifier (usually adopted in commertial product) is around 1 ms. • Regenerative amplifier and 96 ns delay (ground laser) • Large regenerative amplifier (built & failed) • Unstable output energy due to low gain. • Difficult to compensate thermal lens. • High gain fast regenerative amplifier (built & failed) • Difficult to reduce the ghost pulse from first bunch due to limted extinction ratio of pockels cell. • Multi-pass amplifier (upgrade existing underground laser)

  5. Nd laser system for 3-2 RF-Gun Properties of laser medium Nd-doped τ～200μs, 40% ○ 4-state laser is easy to operate. ○ High power pump LD is available. ○ Large crystal is available × Pulse width is determined by SESAM. (Gaussian) SHG(532nm) 40% FHG(266nm) 20% 5HG(213nm) 3% LD Pump (808nm) Nd:YVO4 Nd:YAG 808nm 1064nm Yb-doped τ～900μs, 40% ○ Wide bandwidth => pulse shaping ○ Long fluorescent time => High power ○ Fiber laser => Stable ○ Small state difference × ASE × Absorption SHG(520nm)40% FHG(260nm) 20% 5HG(208nm) 3% Yb-glass Yb:YAG Yb:BOYS LD Pump (941/976nm) 941/976nm 1040nm τ～3μs, 40% τ=200μs, 40% Ti-doped Pump SHG(400nm)40% THG(266nm) 20% FHG(200nm) 10% 40% Pump (808nm) Ti:Sapphire Nd:YAG SHG 808nm 1064nm 800nm 532nm Ti:Sapphire laser system for beam monitor. ○ Very wide bandwidth ○ High breakdown threshold × Low cross section × Short fluorescent time => Q-switched laser is required for pumping TW laser is based on Ti-Sapphire

  6. Schedule Following the RF-Gunreviewer’s comments • Last RF-Gun review • Reconfigure thermal gun for positron generation • Step by step RF-Gun RF ageing. • Done • SuperKEKB injection using stabilized existing undergroud laser (25Hz) • New laser system in 3-2 and A-1 ground laser room • Increase stability & pulse energy from fiber laser • Simplify the laser system (Nd/Yb Regenerative amplifier) • On going • Third RF-Gun (nomal laser injection / cavity modification / cathode change) • Simple Nd amplifier for Phase-I & II stable injection (Postponed the pulse shaping until Phase-III ) 10 psgaussian is enough for Phase-I (1nC) & II (2nC), postponed the pulse shaping until Phase-III

  7. Short term upgrade for laser development • UndegroundYb-Fiber(Upgraded) + Yb:YAG(Existing) • Downgrade to 25Hz 2-loop amplifier => Fix configuration • Stability improvement : Improvements on Yb-Fiber laser. • Increase monitor points / quadrant detector etc.. • GroundYb-Fiber + Nd:YAG / Yb:YAG • Installation of MENLO Orange oscillator(commertial) However it doesn’t cover 1064nm. => New stable oscillator for 1064nm was installed. • Existing fiber amplifier is best fit to amplify 1064nm. (p.9) • Nd:YAG50 Hz regenerative amplifier is used for Phase-II • Yb:YAG 50Hz regenerative amplifier is under construction. • Better room environment / Virtual cathode. • (Cryogenic Yb:YAG) => Postpond until Phase-III.

  8. Collaboration • Collaboration • IMS / Taira Lab. Laser Crystal / Bonding • Hamamatsu Laser Diode / Disk Laser • HiLASEYb Fiber & Disk Laser • Waseda Univ. Yb-Oscillator • Tokyo Univ. Room temperature bonding

  9. Spectrum compare

  10. Underground laser under operation 0.2 nJ @ 1037 nm Yb-doped fiber pre amplifier Transmission grating pair stretcher Yb-doped fiber oscillatorwith Transmission grating Yb-doped fiber pre amplifier Pulse picker 51.9 MHz 10 MHz 2, 5, 25, 50 Hz Single or Double bunch >μJ @ 1037 nm Synchronization system Yb-doped fiber main amplifier Yb-doped fiber main amplifier Pulse picker 2856 MHz trigger From Accelerator Yb:YAG thin-disk multipass amplifier ×3 Yb:YAG thin-disk multi-pass cavity amplifier Fix the configuration to 25 Hz operation SHG RF GUN SHG

  11. Improvement of Yb fiber and Yb:YAGlaser • Simplify and increase the pulse energy • Semiconductor Optical Amplifier (SOA) for pulse picker (114 to 10 MHz) and amplification • Bunch length control • Strecheradjustment • Multi-pass Yb:YAGthin disk laser • Careful tuning not to exceed damage threshold

  12. Optimized pulse shape by streak camera(After adjustment 2015.12.17) ω：~10 mJ, 2ω： ~2 mJ, 4ω： 230 μJ Output power limitation is reached.

  13. Simplify the Yb:YAG solid laser New high gain multi-pass amplifier (10-15 pass x 2 loop) Laser Diode LD 1pass 10-15pass OUTPUT INPUT ←

  14. Laser stability 7 hours beam charge stability. (5/19)

  15. Yb fiber and Nd/Yb solid laser system on the A-1 ground Yb fiber part (already installed) Repetition frequency 114.24MHz Wavelength selection 1030nm & 1064nm Repetition frequency 10MHz 1064nm oscillator (ANDi type) Grating stretcher (Transmission) SOA pulse picker Yb single mode fiber amp Menlo 1030nm oscillator FBG FBG Yb-doped double clad fiber amp ASE rejection grating pair 1030nm oscillator (ANDi type) 1064nm 1030nm 1030nm oscillator (10.38 MHz) EO pulse picker Yb:YAG Thin disk regenerative amplifier 1064nm Nd:YAG regenerative amplifier Cryogenic Yb:YAG Thin disk main amplifier Nd:YAG main amplifier Nd:YAG for Phase-II Output(1064nm) Output(1030nm) Yb:YAG for Phase-III 96ns Delay => Combine => SHG => FHG

  16. Strecher for Yb:YAG & Nd:YAG Gain spectrum of Yb:YAG Distance of grating pair 2.0nm 10 ps Grating pair

  17. Nd solid laser • 4-state laser is easy to operate • Small band width / Thermal lens effect • Crystal type • Rod - Side pump: Thermal lens effect, High gain • Thin disk: Less thermal lens, Low gain • Pumping Laser Diode • 808nm : Commercial product • 885nm : Direct pump, Higher LD power, Lower cross section

  18. Nd:YAGDiode-pumped solid-state(DPSS) Laser ○ 4-state laser is easy to operate. ○ High power pump LD is available. ○ High gain efficiency. ○ Large crystal is available × Small gain bandwidth. (Gaussian) 1.1% Dia. 4×93mm AR/AR@1064nm

  19. Nd:YAG regenerative amplifier

  20. On-going development. • 10 MHz oscillator to simplify the laser system • Nd regenerative amplifier for the Phase-II stable injection. • Yb regenerative amplifier is for Rui’s R&D under collaboration with HiLASE. • Virtual cathode will be built on the optical board. • Vacuum optical duct is under development.

  21. Oscillator of 10 MHz repetition rate

  22. I. Yb:YAG thin disk regenerative amplifier • New dichroic mirror with high optical quality and high damage threshold (this March) • Additional Yb PCF amplifier A1 ground Yb:YAG laser system 4 of 13

More Related