1. High-performance proton acceleration from a renewable cryogenic hydrogen target
L. Obst, S. Göde, M. Rehwald, F.-E. Brack, J. Branco, S. Bock, M. Bussmann, T. E. Cowan C. B. Curry, F. Fiuza, M. Gauthier, R. Gebhardt, U. Helbig, A. Huebl, U. Hübner, A. Irman, L. Kazak, J. B. Kim, T. Kluge, S. Kraft, M. Loeser, J. , R. Mishra, C. Rödel, H.-P. Schlenvoigt, M. Siebold, J. Tiggesbäumker, S. Wolter, T. Ziegler, U. Schramm, S. H. Glenzer and K. Zeil
3rd European Advanced Accelerator Concepts Workshop
La Biodola, Isola d’Elba
ard logo
M. Rehwald, J. Metzkes, K. Zeil, S. D. Kraft, T. Kluge and U. Schramm

2. Laser-Proton Acceleration at HZDR
Motivation: applicability of laser-driven proton beams
foil thickness ~µm
electron sheath
intense laser pulse ~ 1020 W/cm² ~ 10 – 100 fs pulse length
fs – ps ion pulse
1010 – 1013 ions/pulse
~ Hz repetition rate
compact proton acceleration in laser-driven plasmas: TV/m field strength  MeV ion energies within distance ~10 µm
broad proton spectra
big solid angle
potential applications:
radio oncology
inertial fusion energy
probing of ultra-fast field dynamics
Fernández, Nuclear Fusion, 2009
Inertial fusion with proton beams: (Roth, Fernandez)  E_ig of entire particle beam ~ 10 kJ, E_particle ~ 13 MeV (for protons), meaning that particle number in beam needs to be ~ 10^16
Borghesi, Physics of Plasmas, 2002
high particle yields ✓
Requirement: high proton beam quality
high proton energies ?

3. Laser-Proton Acceleration at HZDR
high particle yields ✓
Requirement: high proton beam quality
high proton energies ?
Laser development *
[*] T. Kluge et al., Physical Review Letters 107 (2011)
19 J on target
Draco Ti:Sapphire laser dual-beam:
150TW (3.5J in 30fs on target)
PW (30J / 30fs)
Diode pumped 150J / 150fs laser Penelope
in progress
U.Schramm et al, IPAC‘17 Proceedings
 Talk H.-P. Schlenvoigt

4. Laser-Proton Acceleration at HZDR
high particle yields ✓
Requirement: high proton beam quality
high proton energies ?
Laser development
Target development *
[*] T. Kluge et al., Physical Review Letters 107 (2011)
19 J on target
Draco Ti:Sapphire laser dual-beam:
150TW (3.5J in 30fs on target)
PW (30J / 30fs)
Diode pumped 150J / 150fs laser Penelope
in progress
U.Schramm et al, IPAC‘17 Proceedings
 Talk H.-P. Schlenvoigt

5. Hydrogen micro-jet source Draco high power ultrashort pulse laser
Cryogenic
Hydrogen micro-jet source
L. Obst, S. Göde, M. Rehwald, F.-E. Brack, J. Branco, S. Bock, M. Bussmann, T. E. Cowan C. B. Curry, F. Fiuza, M. Gauthier, R. Gebhardt, U. Helbig, A. Huebl, U. Hübner, A. Irman, L. Kazak, J. B. Kim, T. Kluge, S. Kraft, M. Loeser, J. , R. Mishra, C. Rödel, H.-P. Schlenvoigt, M. Siebold, J. Tiggesbäumker, S. Wolter, T. Ziegler, U. Schramm, S. H. Glenzer and K. Zeil
Draco high power ultrashort pulse laser
(3J beam)
S. Göde et al., Phys. Rev. Lett. 118 (2017)
L. Obst et al., Sci. Rep. 7 (2017)
M. Gauthier et al., APL 111 (2017)

6. Why using a cryogenic Hydrogen jet?
1. Target development for applications (e.g. ion therapy)
3 cm
jet
source
debris-free target (spares expensive optics)
pure proton target
flow speed ~ 100 m/s → repetition rate > 1 Hz
different geometries: cylindrical (2, 5, 10 µm diameter) and planar (2 x 20 µm2)
target network
Off-Axis Parabola
Off-Axis Parabola
~ 50cm
~ 50cm
Solenoid 1
Target
Target

7. Why using a cryogenic Hydrogen jet?
1. Target development for applications (e.g. ion therapy)
3 cm
jet
source
debris-free target (spares expensive optics)
pure proton target
flow speed ~ 100 m/s → repetition rate > 1 Hz
different geometries: cylindrical (2, 5, 10 µm diameter) and planar (2 x 20 µm2)
target network
Off-Axis Parabola
Off-Axis Parabola
study plasma dynamics with optical probing
~ 4cm
~ 4 cm
~ 50cm
~ 50cm
Solenoid 1
Target
Target
30 µm
S. Göde et al, Phys. Rev. Letters (2017)

8. Experimental Setup cryogenic H2 jet two target geometries:
LHe
LH2
Vacuum
Cryostat
3 cm
two target geometries:
cylindrical
Ø 5µm
planar
20µm x 2µm
Ti:Sapph Draco
3.1 J in 30 fs @ 1 Hz
max. intensity: 6· W/cm²

9. Experimental Setup cryogenic H2 jet proton beam diagnostics:
LHe
LH2
Thomson Parabola Spectrometers
radiochromic film stacks
Vacuum
Cryostat
3 cm
two target geometries:
cylindrical
Ø 5µm
planar
20µm x 2µm
Ti:Sapph Draco
3.1 J in 30 fs @ 1 Hz
max. intensity: 6· W/cm²

10. Experiment: proton beam generation
target normal acceleration of a wire-shaped target:
Line-out
Roth et al, Physical Review Special Topics - Accelerators and Beams, 2002
angle /°
angle /°
angle /°
L. Obst et al., Sci. Rep. 7, (2017)

11. Comparison to PIC simulations
target geometry study with PIConGPU
proton emission characteristics:
Schema zur erklärung der simulation z.B. erstmal oben links, dann unten links (winkel einmalen), dann geometrien einblenden

12. Comparison to PIC simulations
target geometry study with PIConGPU
proton emission characteristics:
higher proton beam quality (energies, flux) from planar jet than from cylindrical due to:
rear surface shape (more „foil“-like)
reduced mass target character

13. Experiment: proton beam generation
tailoring of temporal laser contrast:
controlled pre-pulse
6.7 MeV
8.7 MeV
10.3 MeV
plasma mirror contrast:
isotropic emission
plasma mirror contrast with tailored prepulse (50 ps delay):
more dose, smooth beam profile and potentially more directed beam

14. Summary debris-free pure proton target renewable controlled pre-pulse
angle /°
angle /°
angle /°

15. Thank you for your attention!
multiple filamentation of freely
propagating 100 TW beam in air