Laser-Wakefield Acceleration Application to Endoscopic Oncology - PowerPoint PPT Presentation

Laser-Wakefield Acceleration Application to Endoscopic Oncology Scott Nicks, Toshi Tajima, Dante Roa, Ales Necas Workshop on Beam Acceleration in Crystals and Nanostructures June 25, 2019

Laser Wakefield Acceleration (LWFA) 𝒘 𝒒𝒊 ≫ 𝒘 𝒄𝒗𝒎𝒍 • Collective force ~𝑂 2 • Coherent, robust • Coherent, smooth, robust (not stochastic) • No turbulence • Driven by laser or beams • Deep-ocean tsunami • High acceleration gradient: ~ GeV/cm • Wake phase velocity 𝑤 𝑞ℎ ≫ bulk velocity 𝑤 𝑐𝑣𝑚𝑙 𝒘 𝒒𝒊 ~𝒘 𝒄𝒗𝒎𝒍 𝑤 𝑞ℎ ≫ 𝑤 𝑐𝑣𝑚𝑙 • Wavebreak No bulk coupling • Turbulence • Near-shore tsunami 𝑤 𝑐𝑣𝑚𝑙 𝑤 𝑞ℎ T. Tajima and J. M. Dawson, Phys. Rev. Lett. 43 , 267 (1979) E. Esarey, C. B. Schroeder, and W. P. Leemans, Rev. Mod. Phys. 81 , 1229 (2009) 2

Laser Wakefield Theory 𝒘 𝒒𝒊 ≫ 𝒘 𝒄𝒗𝒎𝒍 Laser critical density • Τ ∆ℰ ≫ 𝑛 𝑓 𝑑 2 Laser group velocity: 𝑤 𝑕 = 𝑑 1 − 𝑜 𝑓 𝑜 𝑑 Plasma density • Wake phase velocity 𝑤 𝑞ℎ = 𝑤 𝑕 • Low-density regime  𝑤 𝑞ℎ ≫ 𝑤 𝑐𝑣𝑚𝑙 • High-density regime  𝑤 𝑞ℎ ~𝑤 𝑐𝑣𝑚𝑙 • Electron energy gain: ∆ℰ = 2𝑛 𝑓 𝑑 2 𝒘 𝒒𝒊 ~𝒘 𝒄𝒗𝒎𝒍 Τ 𝑜 𝑑 𝑜 𝑓 ∆ℰ ≲ 𝑛 𝑓 𝑑 2 • Robust wave saturation  Tajima-Dawson field: 𝐹 𝑈𝐸 = 𝑛𝜕𝑤 𝑞ℎ 𝑓 3

Wakefields as Tsunamis 1 Pristine wakefield Bulk solid-target interaction (TNSA) 1 Plasma wavelength 𝑤 𝑕 ≈ 0 𝑤 𝑕 ≫ 𝑤 𝑐𝑣𝑚𝑙 Black wave Blue wave Clean, no dredging Extensive sediment dredging, mass transport ProtoThema.gr SurferToday.com 4 1 B. M. Hegelich et al., Nature 439 , 441-444 (2006)

Linear accelerator Endoscopic Oncology Cone • Bring radiation directly to tissue • Endoscopic or intra-operative • No collateral tissue damage Cone • Low-energy particles • LWFA  LINAC alternative Professor Dante Roa, Radiation Oncology, UCI A. Giulietti, ed., Laser-Driven Particle Acceleration Towards Radiobiology and Medicine , 2016 5 A. S. Beddar et al. Med. Phys. 33 , 1476 (2006)

Fiber lasers for LWFA • Coherent Amplification Network (CAN) • Optical lasers • Many lasers together • Technology reached critical stage • Fiber laser for endoscopic LWFA G. Mourou, W. Brocklesby, T. Tajima, and J. Limpert, Nat. Photonics 7 , 258 (2013) 6

Nanomaterials for LWFA Nanotube Porous alumina on SI substrate Nanomaterials: Uniform  Wakefield guide Solid  Optical laser 𝑜 𝑑 N. V. Myung, J. Lim, J-P Fleurial, M. Yun, W. West, and D. Choi, Nanotech. 15 , 833 (2004) X. Zhang et al., Phys. Rev. Accel. Beams 19 , 101004 (2016) 7 T. Tajima, Eur. Phys. J. Spec. Top. 223 , 1037 (2014)

LWFA for Endoscopic Oncology Paper and Collaborators • Putting the pieces together  low-energy electrons  near-critical density LWFA  Nanomaterial provides density/guide  CAN laser (optical) for endoscopy Submitted, Phys. Rev. Accel. Beams (2019) • Next steps  Wakefield physics at Τ 𝑜 𝑓 𝑜 𝑑 ≈ 1  Scaling: density, intensity  Self-modulation 8

Modeling Critical-Density Wakefields • • Critical density  𝑤 𝑕 = 0 1D 3V Particle-in-cell (PIC) code • • Laser enters plasma  sheath formation Ti:Sapphire laser, 𝜇 = 1 μm • • Laser 𝐹 𝑧 = 𝐹 0 sin 𝑙𝑦 − 𝜕𝑢 − 𝜚 ℎ 𝑦, 𝑢 Sheath accelerates electrons • Simulation  laser injected from vacuum • ℎ 𝑦, 𝑢  flat-top, resonant profile Early Impedance-matching boundary Later Uniform Plasma Slab Sheath Laser (dispersed) Laser Electrons 𝑦 = 0 𝑦~𝜇 𝑞 𝑦 = 0 9

Density Scaling of Electron Energy • Electron energy gain: ∆ℰ = 2𝑛 𝑓 𝑑 2 Τ 𝑜 𝑑 𝑜 𝑓 • Τ Linear dependence on 𝑜 𝑑 𝑜 𝑓 • 𝑜 𝑑 𝑜 𝑓  linear ∆ℰ trend agrees Τ Scan over • Low density  wakefield not constant  deviation from linearity 10

Low-Density Regime • Τ Typical wakefield regime, 𝑜 𝑑 𝑜 𝑓 = 10 • Clear, robust wakefield Wakefield 𝐹 𝑦 • Wakefield  train of trapped electrons • “Blue” wave  no bulk coupling/turbulence Electron phase Laser space 𝐹 𝑧 Plasma wavelength 𝜇 𝑞 = 2𝜌𝑑 𝜕 𝑞 11

High-Density Regime • • Streams build up  sheath exhausted Τ Critical density regime, 𝑜 𝑑 𝑜 𝑓 = 1 • • 𝑤 𝑕 = 0  sheath oscillation Novel regime • “Black” wave  bulk coupling • Sheath  low-energy electron streams Later Early Sheath 𝐹 𝑦 Sheath 𝐹 𝑦 12

Transition Regime • Τ Intermediate regime, 𝑜 𝑑 𝑜 𝑓 = 5 • Modest electron trapping Proto-sheath 𝐹 𝑦 𝐹 𝑦 • Transition  sheath physics beginning • “Grey” wave 13

Intensity Scaling of Electron Energy 1 2 − 1 • Τ 2 Electron energy gain in high-density regime • Ponderomotive potential 𝑕 𝑏 0 = 1 + 𝑏 0 • 𝑏 0  Normalized laser intensity • Density fixed, ∆ℰ scanned over 𝑏 0 • Energy gain 𝑏 0 dependence: ∆ℰ ∝ 𝑕 𝑏 0 • ∆ℰ compared  𝑕 𝑏 0 Τ Τ 𝑜 𝑑 𝑜 𝑓 = 10 𝑜 𝑑 𝑜 𝑓 = 3 14

Self-Modulation • Fiber lasers  long pulse better • Τ Τ Pulse length 𝜇 𝑚 𝜇 𝑞 scanned, 𝑜 𝑑 𝑜 𝑓 = 10 , 𝑏 0 = 1 • Self-modulation: long pulse breaks  small pulses • Long pulses  Laser/wakefield modulated Τ Τ Τ 𝜇 𝑚 𝜇 𝑞 = 0.5 𝜇 𝑚 𝜇 𝑞 = 3 𝜇 𝑚 𝜇 𝑞 = 5 J. Krall, A. Ting, E. Esarey, and P. Sprangle, in Proceedings of the 1993 Particle Accelerator Conference , Vol. 4 E. Esarey, C. B. Schroeder, and W. P. Leemans, Rev. Mod. Phys. 81 , 1229 (2009) 15

Self-Modulation at the Critical Density Long pulse • Critical plasma + long laser pulse 𝜇 𝑚 = 8𝜇 𝑞 • 𝑤 𝑕 = 0  huge sheath oscillation Sheath Later streams • Violent sheath  huge electron acceleration from sheath • Laser  initial burst • Sheath  later streams Resonant pulse Initial burst from laser 16

Electron Tissue Penetration • Critical plasma + long laser pulse 𝜇 𝑚 = 8𝜇 𝑞 • Electron energy spectrum  tissue penetration • Continuous slowing-down approximation (CSDA) • Penetration  tuned by Τ 𝑜 𝑑 𝑜 𝑓 , 𝑏 0 17

Linear accelerator Summary Cone • Laser evolution  CPA to fiber • Endoscopic therapy  keV electrons • Fiber  tiny keV accelerator Cone • Technology exists  quick deployment • Low-hanging fruit for large medical benefit • Critical-density wakefield  Novel physics regime 18