Robust energy enhancement of ultra-short pulse laser accelerated protons from reduced mass targets

Transcription

1 Robust energy enhancement of ultra-short pulse laser accelerated protons from reduced mass targets K. Zeil, J. Metzkes, T. Kluge, M. Bussmann, T. E. Cowan, S. D. Kraft, R. Sauerbrey, B. Schmidt, M. Zier, U. Schramm Seite 1 Prof. Karl Zeil Peter Laser Mustermann Particle Acceleration Institut xxxxx

2 Our motivation Laser driven ion therapy Proton number Conventional ion therapy Localized dose deposition for precise tumor treatment Beneficial for 10-20% of patients Laser driven ion therapy high acceleration gradients TV/m compact source and laser beam transport ~1 ns 1 s GSI Darmstadt Large scale setup: accelerator, beam guidance & radiation shielding Time to ions per pulse Short ion pulses: fs to ps at source Broad energy spectrum Investigation of radiobiological effects Facility Image courtesy by Stern, Gruner+Jahr AG & Co KG, Germany Dose Image courtesy by O. Jäkel, DKFZ Heidelberg, Germany Page 2

3 Our motivation Laser driven ion therapy in vitro irradiations have been performed [Yogo APL 2011, Zeil APB 2012, Bin APL 2012, Doria AIP 2012] Ti:Sapph Draco so far 4 J in 30 fs upgrade to 30 J in 30 1 Hz Page 3

4 TNSA from Reduced Mass Targets TNSA at large foil electrons laterally spread along the target surface RMT electron reflection at target edges T e and n e increased electron reflux further heating Psikal Phys. Plasm. 15 (2008), Kluge Phys. Plasm. 17 (2010) increased proton energies Page 4

5 First experimental demonstration max. proton energy [MeV] LULI experiment 100 TW LULI laser L = I W/cm 2 on target 2 µm thick foil sections of gold 65 x 65 µm 2 > x2 Laser surface [µm 2 ] But small repetition rate : LULI ca. 3 h -1 Draco 10 Hz Exploration of maximum energy increase for the given laser parameter and target thickness Buffechoux et al., PRL 105 (2010) Page 5

6 Target design Gold disks Si wafer Deposition of Si 3 N 4 (800 nm) Structuring of Si 3 N 4 -layer Deposition of Au Page 6 Etching of wafer Diameters: µm Thicknesses: 100 nm 1 µm

7 Experimental Setup 30 fs, 3 J W/cm 2 Mounting of single targets Novel target holder design with separated target support Page 7

8 Results gold disks with ultra-short pulses maximum proton energy proton yield Au thickness 100 nm reference 2µm Ti + 87%! absolute gain in proton energy and yield for given laser parameters!! time averaged hotter, denser and more homogenous sheath Page 8

9 Results of thickness dependency Page 9

10 Results of thickness dependency Less pronounced thickness dependence for RMT Robust against laser contrast fluctuation Page 10

11 Energy drop for smallest targets? smallest target size would allow for reacceleration of electrons during main pulse interaction Page 11

12 Effect of preplasma? Surrounding preplasma corona worsens rear side field gradient no surounding preplasma for given contrast Sokollik NJP 12 (2010), Toncian Phys. Plasm. 18 (2011) Page 12

13 Influence of edge fields reduced proton acceleration performance and destruction of smooth proton beam profile Page 13

14 Influence of target mounting Stalk width 2µm large Ti foil 1.3MeV 4.8MeV 7.0MeV 8.6MeV 10.1MeV 11.4MeV 12.6MeV 50µm 20µm 10µm 5µm Page 14 2µm thick Si RMT size 100µm x 100µm similar field strength at edges as in focal region edge fields prevent efficient plasma expansion target area stalk

15 500 µm Target design Silicon RMTs 2 µm thickness SOI-Wafer SiO 2 layer from thermal oxydation and deposition of a 500 nm Si 3 N 4 layer as etching mask photo lithography to structure front and rear side front and rear side etching, burried layer as boundary Silicon membrane: free-standing, robust structuring and deposition of layers possible optical surface quality Page 15

16 Summary Profit from robust acceleration performance and enhanced proton number Robustness against laser contrast fluctuations Novel target designs by avoiding destructive edge effects Page 16

17 Thank you for your attention multiple filamentation of freely propagating 100 TW beam in air Page 17

18 Center for high power radiation sources DESY Hamburg Düsseldorf Jena Berlin HZDR Dresden HSQ laser labs and target areas GSI Darmstadt MPQ München New lab space (800 m 2 ): clean rooms workshop cell lab Page 18

19 High power lasers Yb:CaF 2 active medium 150 J in 150 fs on 1 Hz PW diode pumped system M. Siebold, F. Röser, D. Albach, M. Löser laser labs and target areas Draco flash lamp pumped Page 19 Ti:sapphire active medium TW ultra-short beam DRACO experiments 15 max. J in J fs in on 30 target fs on 1 10 Hz

20 Our motivation Laser driven ion therapy in vitro irradiations have been performed [Yogo APL 2011, Zeil APB 2012, Bin APL 2012, Doria AIP 2012] Proton energy scaling [4] T. Kluge et al., PRL 107, (2011) Page 20 Ti:Sapph Draco so far 4 J in 30 fs upgrade to 30 J in 30 1 Hz

21 In vivo irradiations with laser protons Gantry for laser-driven proton therapy *U. Masood, et al. F. Kroll, et al. U. Masood, et al. Page 21