Cone-guided hemispherical target geometries: Annular shaped laser accelerated proton beams

Transport of laser accelerated ions

O. Deppert, K. Harres, F. Nürnberg, G. Schaumann, D. Schumacher, S. Busold, M. Schollmeier, M. Geissel, V. Bagnoud, and M. Roth

31. Januar 2011 | Oliver Deppert | Physics of High Energy Density in Matter | Hirschegg 2011 | Plasma physics workgroup TUD | 1

Motivation:Annular shaped proton beams

• Fast-ignition (FI) -> Driver: p+ or e-

-> Increase in energy gain

• M. Roth et al. [1]

-> Intense proton beam (TNSA) driver

-> TNSA spectrum meets FI demands

• M. Temporal et al. [2]

-> Two time-delayed laser-accelerated proton beams

-> Required beam parameters: Annular shaped

-> Reduction igniting energy: (6-8 kJ = 1 kJ + 5-7 kJ)

• Heat and compress matter isochoric (“WDM”)

-> Annular beam: Shock-wave radial symmetric

[5] M. Temporal et al., Fast ignition induced by shocks generated by laser-accelerated proton beams

31. Januar 2011 | Oliver Deppert | Physics of High Energy Density in Matter | Hirschegg 2011 | Plasma physics workgroup TUD | 2

Experimental results

• More homogeneous

• Very concentric

• Focus around 9 MeV

• Annular feature above 12 MeV

31. Januar 2011 | Oliver Deppert | Physics of High Energy Density in Matter | Hirschegg 2011 | Plasma physics workgroup TUD | 3

Experimental results

Low energetic protons:

• Collimation

-> Transport through “bottle-neck”

• Transverse Gaussian vs. Flat-Top profile

-> Higher density along symmetry axis

-> 9 MeV focal spot

Protons above 12 MeV:

• Formation of a stable “ring-structure”

• Higher proton density on the “ring”

• “star-shaped” sub-structure [3]

-> interaction: strong electric field

31. Januar 2011 | Oliver Deppert | Physics of High Energy Density in Matter | Hirschegg 2011 | Plasma physics workgroup TUD | 4

Preliminary resultsSmaller geometries

Sandia National Laboratory

Z-PetaWatt

• “shrinked” target geometry, factor of two

• Cup of full hemisphere inside cone

• Annular feature shifted to higher energies

-> around 20 MeV

• No obvious focal spot

• Focussing effect over a long energy range

31. Januar 2011 | Oliver Deppert | Physics of High Energy Density in Matter | Hirschegg 2011 | Plasma physics workgroup TUD | 5

Size of cone-guided target geometry

-> Significant impact on the propagation of the proton beam

Particle-In-Cell simulation (PIC)

Ion-density and divergence:

• Tapering of the outlet-port -> expanding plasma

• Ion-beam in center of cone -> lower transverse width

-> Waist of proton-beam with diameter of outlet-port

-> Guided transport of protons through “bottle-neck“

31. Januar 2011 | Oliver Deppert | Physics of High Energy Density in Matter | Hirschegg 2011 | Plasma physics workgroup TUD | 6

• Higher density on axis for high energetic protons

-> Discrepancy with experiment?

but: simulation geometry factor of eight shrinked

Particle-In-Cell simulation (PIC)

Transverse electrical field – Cone:

• High electric field at inner wall of the outlet-port

-> Cylindrical symmetric

• Temporal evolution: Plunges slower compared to typical TNSA “sheath” field

-> Up to 0.48 TV/m -> protons collimated to middle-axis

-> Comparable to “electro-static microlens” by Toncian et al. [4]

31. Januar 2011 | Oliver Deppert | Physics of High Energy Density in Matter | Hirschegg 2011 | Plasma physics workgroup TUD | 7

Summary & Outlook

• Target is able to generate an annular shaped proton beam profile (reproducible)

• Size of target has a significant influence on the proton beam profile

• High electric field interacting with the proton beam -> collimation and annular structure

• Publication in preparation…

• Further investigations from simulation side -> underlying physics of beam manipulation

• Relevance for the proton fast-ignition approach (FI) and WDM generation

31. Januar 2011 | Oliver Deppert | Physics of High Energy Density in Matter | Hirschegg 2011 | Plasma physics workgroup TUD | 8

• Accepted proposal PPAC 2011:

-> Detailed beam parameters study, different types and geometries, comparison to PIC simulations

• Interaction with matter: Cu probe-foil

-> Isochoric heating

-> K-alpha shift -> temperature-map

• ps-streak camera

-> Time-resolved heating

-> Thermal Planckian [5] -> average temperature

31. Januar 2011 | Oliver Deppert | Physics of High Energy Density in Matter | Hirschegg 2011 | Plasma physics workgroup TUD | 9

[6] K. Harres et al.

Phys. Plasmas, 17, 023107, 2010

[7] K. Harres, Strahltransportlaserbeschleunigter Ionen, Dissertation, Technische Universität Darmstadt, 2010

Transport of laser accelerated ionsK. Harres, F. Nürnberg et al.

Simulations - WarpRZF. Nürnberg et al.

Electrons Protons phase-space

Space-charge effectsof the electrons

-> Aggregation ofprotons on axis

-> Influence on protoncollimation/focussing

31. Januar 2011 | Oliver Deppert | Physics of High Energy Density in Matter | Hirschegg 2011 | Plasma physics workgroup TUD | 10

[8] F. Nürnberg, Laser-Accelerated Proton Beams as a New Particle Source, Dissertation, Technische Universität Darmstadt, 2010

3.7 MeV 6.5 MeV 8.7 MeV 11.7 MeV 14.2 MeV 16.4 MeV

experiment

withoutspace-charge

withspace-charge

31. Januar 2011 | Oliver Deppert | Physics of High Energy Density in Matter | Hirschegg 2011 | Plasma physics workgroup TUD | 11

Simulations - WarpRZF. Nürnberg et al.

Initial Protons:  

Protons lost:  

Collimination - Transmission:   

 

 

Focus - Transmission:  

 

 

 

Ø  

31. Januar 2011 | Oliver Deppert | Physics of High Energy Density in Matter | Hirschegg 2011 | Plasma physics workgroup TUD | 12

Simulations - WarpRZF. Nürnberg et al.

References

[1] M. Roth et al., Fast Ignition by Intense Laser-Accelerated Proton Beams,

Phys. Rev. Lett., 86, 436, 2001

[2] M. Temporal et al., Fast ignition induced by shocks generated by laser-accelerated proton beams,

Plasma Phys. Control. Fusion, 51, 035010, 2009

[3] M. Borghesi et al., Proton imaging: a diagnostic for inertial confinement fusion/fast ignitor studies,

Plasma Phys. Control- Fusion, 43, A267, 2001

[4] T. Toncian et al., Ultrafast Laser-Driven Microlens to Focus and Energy-Select Mega-Electron Volt Protons, Science 312 (5772), 410-413, 2006

[5] P.K. Patel et al., Isochoric Heating of Solid-Density Matter with an Ultrafast Proton Beam,

Phys. Rev. Lett., 91, 12, 2003

[6] K. Harres et al., Collimation and transport of laser-accelerated protons with pulsed high field solenoids,

Phys. Plasmas, 17, 023107, 2010

[7] K. Harres, Strahltransport laserbeschleunigter Ionen,

Dissertation, Technische Universität Darmstadt, 2010

[8] F. Nürnberg, Laser-Accelerated Proton Beams as a New Particle Source,

Dissertation, Technische Universität Darmstadt, 2010

31. Januar 2011 | Oliver Deppert | Physics of High Energy Density in Matter | Hirschegg 2011 | Plasma physics workgroup TUD | 13