BESTIA – the next generation ultra-fast CO 2 laser for advanced accelerator research Igor Pogorelsky Misha Polyanskiy, Marcus Babzien, John Skaritka, Ilan Ben-Zvi

2 BESTIA – the next generation ultra-fast CO 2 laser for advanced accelerator research Brookhaven Experimental Source of Terawatt Infrared at ATF Berkeley Lab Laser Accelerator Why BESTIA? =0.8  m =10  m

3 String of innovative technical solutions never applied before to CO 2 or molecular gas lasersString of innovative technical solutions never applied before to CO 2 or molecular gas lasers Solid-state front endSolid-state front end Chirped-pulse amplificationChirped-pulse amplification Isotopic amplifiersIsotopic amplifiers Nonlinear pulse compressionNonlinear pulse compression Unprecedented high peak power for mid-IRUnprecedented high peak power for mid-IR BESTIA – the next generation ultra-fast CO 2 laser for advanced accelerator research Why next generation?

4 From state of the art picosecond CO 2 lasers providing 100-cycle pulses to 3-cycle femtosecond pulses focused to a 0 =10-20 Why ultra-fast? BESTIA – the next generation ultra-fast CO 2 laser for advanced accelerator research

5 I will show in my talk how to take advantage from =10-  mI will show in my talk how to take advantage from =10-  m for ion acceleration and LWFA for ion acceleration and LWFA However, mid-IR can be productive for a wider variety of strong-field physics studies and applications such asHowever, mid-IR can be productive for a wider variety of strong-field physics studies and applications such as IFELs or Compton x - and  - ray sources Why for advanced accelerators? BESTIA – the next generation ultra-fast CO 2 laser for advanced accelerator research

6 Solid-state lasers for plasma accelerators Electron accelerationIon acceleration Under-critical gas Strongly over-critical solids

7 Ponderomotive potential note the   2 dependence Energy of the electron quiver motion in laser field E (classic physics) Relativistic motion in diffraction-limited focus

CO 2 ( =10  m) scaling factors as compared to solid-state ( 1  m) lasers: #1 100 times stronger ponderomotive effects at the same laser intensity #2 100 times lower critical plasma density #3 10 times more photons per Joule #4 favorable scaling of accelerating structures, better electron phasing into the field 8 8 More arguments to choose mid-IR (≈10 m)

9 Shock Wave Ion Acceleration Laser energy absorbed within critical plasma layer creates electrostatic shock wave at velocity Lower n cr ~  2 higher v sh. The shock field reflects ions at double velocity 2v sh. Lower n cr gas jets pure proton source, no pollution High hot-electron currents ~200 kA produce single-cycle THz radiation with 10 GW peak power and 50 mJ of total energy. Benefits from 10  m: simulationexperiment Evidence of high-currents through filamentation

10 Shock Wave Ion Acceleration 10 Hydrogen jet N o z z l e 1.7 MeV protons (light or neutrals) Laser-induced electrostatic shock reflects protons upon its propagation through the ionized H 2 jet. Energy spread 10% Spectral brightness proton/MeV/str Proton energy up to 3.2 MeV

11 Extra benefit special for ATF: Combination of a high-power laser with femtosecond e-bunches for wake field probing and external injection Combination of a high-power laser with femtosecond e-bunches for wake field probing and external injection. 10x lower GeV/m 10x lower GeV/m 1000x bigger bubble volume 1000x bigger bubble volume better control over e-beam parameters and phasing between accelerator stages better control over e-beam parameters and phasing between accelerator stages 10x higher trapped charge 10x higher trapped charge High-current bubble LWFA 100 TW 10-  m compared to 1 PW 1-  m laser: Courtesy of Wei Lu, Tsinghua Univ.

ε n =50 nm 10 μm a o = μm a o =

13 Developing 100 TW CO 2 laser

Energy level diagram Vibrational modes OOC NN Symmetric stretch  1388 cm -1 Bending  667 cm -1 Asymmetric stretch  2349 cm -1 CO 2 N2N2N2N cm E, cm -1 CO2 N2 V=1 V=0 ΔE =18 cm -1 (001) (010) (100) (000) 10 µ m 9 µ m Gain spectrum 14 CO 2 laser basics (020)

High-pressure CO 2 laser 15

16 Optics Express 19:7717 (2011) Natural CO 2 Isotopic CO 2 SimulationsExperiment Isotopic active medium

MAIN AMPLIFIER 3 ps 6 J REGENERATIVE ISOTOPIC AMPLIFIER 400 fs 40 µ J SOLID-STATE OPA INJECTOR 17 2 ps 10 mJ 2 TW BNL CO 2 laser system

18 OPA: fs seed Stretcher + compressor = Chirped pulse amplification High-pressure, isotopic amplifiers Nonlinear compressor Compressor Non-linear compressor 70 J 50 J 2 ps 25 TW OPA Ti:Al2O3 Amplifier 1 Stretcher 35 µJ 350 fs 10 µJ 100 ps 100 mJ Amplifier 2aAmplifier 2bAmplifier 2c 10 J 100 fs 100 TW Collection of innovations: 100TW CO 2 concept laser

6-meter long CO 2 laser final amplifier Final amplifier CPA compressor Regen. Pre- amplifier

20 First implementation of CPA in CO 2 laser

21 CPA simulation 2 ps 25 TW parasitic peak (1.7 % of max) This is what we expect after the 6-meter BESTIA amplifier: In spite of notable spectrum modulation and stretched pulse temporal distortion during amplification, the compressed pulse is well- defined

22 Nonlinear post-compression Amplifier Output SPM Focused Spatial Filtered Recompressed Amplifier Output SPM Focused Spatial Filtered Recompressed 1.7 ps 100 fs Kerr effect n = n 0 + n 2 I * US Patent pending S.N. 62/021,725

23 100TW CO 2 laser BESTIA 6-meter long final amplifier OPA Regen CPA Compr. Femto-sec Compressor CPA Stretch. Laser / e-beam interaction Ion acceleration 9-11  m 100 TW 100 fs a 0 = Hz available in 2018

24 Active and prospective user experiments will be reviewed at the upcoming meeting …Thank you for your attention