Monoenergetic Proton Beams from Laser Driven Shocks Dan - PowerPoint PPT Presentation

Monoenergetic Proton Beams from Laser Driven Shocks Dan Haberberger Neptune Laboratory, Department of Electrical Engineering, UCLA In collaboration with: Sergei Tochitsky, Chao Gong, Warren Mori, Chan Joshi Neptune Laboratory, Department of Electrical Engineering, UCLA Frederico Fiuza, Luis Silva, Ricardo Fonseca Instituto Superior Technico, Lisbon, Portugal

Outline • Applications of Laser Driven Ion Acceleration (LDIA) : Hadron cancer therapy • Localized energy deposition : Bragg Peak • Therapy centers : conventional accelerators vs. lasers • Ion source requirements • Collisionless Shock Wave Acceleration (SWA) of protons • 1D OSIRIS Simulations • Laser driven case • UCLA proton acceleration experiment : CO 2 laser and a H 2 gas jet target • Results : Spectra, emittance • Interferometry : Plasma density profile • 2D OSIRIS simulations • Modeling the experiment • Scaling to higher power lasers • Using 1µm laser systems • Conclusion Neptune Laboratory AAC (Jun 2012)

Laser Driven Ion Beam Applications Probing of strong electric fields in dense plasma on the picosecond timescale – Borghesi, Phys. Plasmas (2002) – ~ 1 μ m resolution, 5-20MeV • 50 μ m Ta wire • Imaging with 6-7MeV protons VULCAN Laser, 20J, 10 19 W/cm 2 -15ps -5ps 5ps Picosecond injectors for conventional accelerators – 1-10MeV, <.004 mm . mrad, <10 -4 eV . s [ Cowan, Phys. Rev. Lett. (2004) ] Fast Ignition Hadron Cancer Therapy – 15-23MeV – 250MeV, 10 9 -10 10 protons/s – <20ps – ΔE/E ≤ 5% – Eff = 10% Neptune Laboratory AAC (Jun 2012)

Energy Deposition : Ions vs. Photons Bragg Peak for ions results in localized energy deposition Neptune Laboratory AAC (Jun 2012)

Multi-beam Localization Simulations of Irradiating the Human Skull Radiation dose relative to peak (100%) GSI Helmholtz Centre for Heavy Ion Research in Darmstadt http://www.weltderphysik.de/gebiet/leben/tumortherapie/warum-schwerionen/ Neptune Laboratory AAC (Jun 2012)

Problem : Cost and Size Cost : ~ 200 Million USD 20 meters • Accelerator ring (20m) • Transport magnets • Complicated Gantry • Radiation shielding Only a few in operation along with ~ 30 small facilites • 10 ’s of thousands of people treated • Need more than an order of magnitude more therapy centers Heidelberg Ion-Beam Therapy Center, Commissioned in 2009 http://www.klinikum.uni-heidelberg.de/Welcome.113005.0.html?&L=1 Neptune Laboratory AAC (Jun 2012)

Solution : Laser Based Accelerators Goal Cost : 10-20 million USD Table top laser system (developing) Transportation : Mirrors Only has focusing magnet Gantry : small, protons generated in direction of patient M. Murakami, et al., AIP Conf. Proc. 1024 (2008) 275, doi:10.1063/1.2958203 Neptune Laboratory AAC (Jun 2012)

Proton Beam Requirements Laser Driven Ion Radiation Beam Requirements Acceleration (LDIA) Lasers can accelerate up to 10 12 2 Gray in 1 liter tumor in a few minutes Dose protons in a single shot -Translates to 10 10 protons per second Worlds most powerful lasers Energy Proton energies in range of 250 MeV have produced 75 MeV protons Energy Vast majority of beams have Energy Spread of ~ 5% Spread continuous energy spread Future Work Focusability, Energy Accuracy, Energy Variability, Dose Accuracy, etc. Neptune Laboratory AAC (Jun 2012)

What is a Shock Wave? A disturbance that travels at supersonic speeds through a medium Subsonic Sonic Supersonic • At supersonic speeds, pressure will • Characterized by a rapid change in build at the front of a disturbance pressure (density and/or temperature) forming a shock of the medium In a plasma, a shock wave is characterized by a propagating electric field at speeds useful for ion acceleration (V sh > 0.01c) Neptune Laboratory AAC (Jun 2012)

1D OSIRIS Simulations In Plasmas, the driver is a potential or electric field Driven Shocks Expansion Shocks Initial drift causes overlap; Ambipolar electric field of overlap causes local density Plasma 1 is driven into increase and again ambipolar Plasma 2 electric field is driven into the plasma V d /2 → ← V d /2 Plasma 1 n e1 Plasma 2 Plasma 1 Plasma 2 T e n e2 n e1 = n e2 n e1 = n e2 Cold Ions T e T e1 T e1 Cold Ions Cold Ions Cold Ions Neptune Laboratory AAC (Jun 2012)

1D Sims : Driven Shocks (T e = 511 keV C s = 0.0233c). Wave train response Proton trapping begins Proton reflection begins Strong damping of wave Reflection Condition eɸ > 1/2mv 2 No interaction Neptune Laboratory AAC (Jun 2012)

Shock formation in laser driven plasmas Shock acceleration High-intensity E laser pulse Sheath Field (TNSA) • Linearly polarized laser incident upon an overcritical Beam quality destroyed target creates and heats the by TNSA fields plasma • Ponderomotive force creates density spike and imparts a velocity drift on surface plasma Denavit PRL 1992, Silva PRL 2004 Neptune Laboratory AAC (Jun 2012) F. Fiuza | Prague, April 20 | SPIE 2011

CO 2 Laser Interacting with a Gas Jet Target Gas jet target advantages for Gas plume Shock Wave Acceleration (SWA) • Gas jets can be operated at or above 10 19 cm -3 (n cr for 10µm) • Long scale length plasma on the back side of the gas jet inhibits strong TNSA fields preserving proton spectrum • High repetition rate source • Clean source of ions (H 2 , He, N 2 , O 2 , Ar , etc…) Steepened hybrid PIC Extended Plasma • Low plasma densities allows for Plasma E TNSA ~ 1/L probing of plasma dynamics using visible wavelengths Neptune Laboratory AAC (Jun 2012)

CO 2 Laser Pulse Temporal Structure Experimentally Measured Calculated CO 2 Gain Spectrum Temporal Profile E = 50 J Pressure = 8atm P peak = 4TW Line Separation = 55GHz Pulse Separation = 1/55GHz = 18.5ps Line Center : 10.6µm 1 7-10 pulses long CO 2 Gain Spectrum at 8atm 4 3ps Input Pulse Spectrum 55GHz Overlapped Spectrums 0.8 Normalized Amplitude Peak Power (TW) 18.5ps 3 0.6 1.2THz ~70ps ~ 70ps 2 0.4 3ps 1 0.2 0 400 450 500 550 600 0 27 27.5 28 28.5 Time (ps) Frequency (THz) D. Haberberger et al., Opt. Exp. 18, 17865 (2010) Neptune Laboratory AAC (Jun 2012)

CR-39 Proton Detection 100x100mm Imaging Proton 150mm Spectrometer 10 μ m Laser Pulse Protons 1mm CR-39 1 MeV 27 MeV Energy Deposition of Protons in CR-39 vs. Distance 1 dE/dx (Normalized Units) 0.8 CR-39 CR-39 CR-39 CR-39 CR-39 0.6 1mm 1mm 1mm 1mm 1mm Detection: Detection: Detection: Detection: Detection: 0.4 <1-10 MeV 11-15 MeV 16-19 MeV 20-22 MeV 23-25 MeV 0.2 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 Distance (mm) Neptune Laboratory AAC (Jun 2012)

CO 2 Laser Produced Proton Spectra Energy spreads measured to 1mm CR-39 be FWHM ΔE/E ̴ 1% Noise Floor Jan 25 th Jan 25 th Feb 22 th CR-39 #99 CR-39 #92 CR-39 #179 Haberberger, Tochitsky, Fiuza, Gong, Fonseca, Silva, Mori, Joshi, Nature Phys., 8, 95-99 (2012) Neptune Laboratory AAC (Jun 2012)

Emittance Estimation 150mm CR-39 Protons H 2 Gas Jet Laser σ x 11/30/10 22MeV Source Size : d = 120µm Beam Size (RMS) : σ x ̴ 5.7mm 50mm σ y ̴ 2.2mm σ y Divergence : θ x ̴ 37mrad θ y ̴ 14mrad Emittance : ε x = d . θ x = 4.6mm . mrad ε y = d . θ y = 1.7mm . mrad 50mm Neptune Laboratory AAC (Jun 2012)

Plasma Density Profile -600 Observations Laser Y-Distance (  m) -300 1. Strong profile modification on the 0 front side of the plasma : hole boring 300 600 2. Sharp rise (10 λ ) to 4 overcritical plasma where laser pulse is Plasma Density stopped 3 (10 19 cm -3 ) Laser 2 3. Long (1/e 30 λ ) exponential plasma tail 1 0 -600 -400 -200 0 200 400 X-Distance (  m) Neptune Laboratory AAC (Jun 2012)

2D OSIRIS Simulations : Input Deck Initial Plasma Profile linear ramp Laser Laser exponential ramp a o = 2.5 a o = 2.5 (plasma expansion) Δτ = 3ps Δτ = 3ps 18 ps Neptune Laboratory AAC (Jun 2012)

2D OSIRIS Simulations : Results Time = 122ps Time = 17ps Time = 52ps

2D Simulations : Energy Scaling -F. Fiuza, Phys. Rev. Lett., Submitted UCLA 3 2 𝐹 𝑞 ∝ 𝑏 𝑝 -K. Zeil et. al., New J. Phy 12, 045015 (2010) AAC (Jun 2012)

Proposed Shock Wave Acceleration at 1µm 10µm Laser – Gas Jet Target 1µm Laser – Exploded Foil Target High Power Drive Pulse Gas plume Low Power Pre-heater Foil target of thickness Δ x Ion beam Δ x and Δ t • Peak density for Drive Pulse is 5- hybrid PIC Extended Plasma 15n cr = 5-15 x 10 21 cm -3 E TNSA ~ 1/L • Extended plasma profile (1/e - 30 λ ) Neptune Laboratory AAC (Jun 2012)

Conclusions Laser-driven, electrostatic, collisionless shocks in overdense plasmas produce monoenergetic protons at high energies Protons accelerated to 15-22 MeV (at I L ~ 4x10 16 W/cm 2 ) • • Energy spreads as low as 1% (FWHM) • Emittances as low as 2x4 mm·mrad • Interferometry uncovers unique plasma profile • Plasma simulations elucidate shock wave acceleration of protons through the backside of the plasma Step towards achieving 200-300 MeV protons needed for cancer therapy • Simulations show scaling to ~ 300 MeV with a laser a o = 15 • Proposed method of exploding foil target for 1µm laser systems Neptune Laboratory AAC (Jun 2012)