Bagnoud, V.

Blazevic, A.

Brabetz, C.

Busold, S.

Deppert, O.

Hofmann, I.

Kroll, F.

Roth, M.

Schumacher, D.

GSI Repository

A laser-driven proton beamline at GSI∗S. Busold1, D. Schumacher4, O. Deppert1, C. Brabetz2, F. Kroll3, A. Blazevic4,5, V. Bagnoud4,5,I. Hofmann4, and M. Roth11TU Darmstadt, IKP, Germany; 2JWG Universita¨t Frankfurt, IAP, Germany; 3Helmholtz - ZentrumDresden-Rossendorf, Germany; 4GSI, Darmstadt, Germany; 5Helmholtz Institut Jena, GermanyThe LIGHT beamline. Laser-based ion accelerationbecame an extensively investigated field of research dur-ing the last 15 years. Within several micrometers parti-cles are accelerated to MeV energies. The main draw-back for many applications is their continuous exponentialenergy spectrum and large divergence angle from source.The exploration of proper beam shaping and transport isthe major goal of the LIGHT collaboration [1], for whichan experimental test beamline has been built at GSI. ThisLIGHT beamline at GSI is located at the Z6 area withinthe experimental hall. The PHELIX 100 TW laser beam-line is currently capable of delivering up to 15 J of laserenergy in a 650 fs short pulse on target, focused to inten-sities exceeding 1019 W/cm2 within the Z6 target chamber.Protons could be accelerated via the TNSA mechanism tomaximum energies of 28.4 MeV and propagated through apulsed high-field solenoid with a field strength up to 9 T,which is used to select a specific energy interval from thecontinuous initial spectrum via chromatic focusing. A largecapture efficiency of 34% of the initial protons within a se-lected energy interval (ΔE=(10±0.5)MeV) was measured[2].The protons are weakly focused to a 15×15 mm2 spot at3 m distance to the source, containing particle numbers>109 in a single 8 ns short bunch. The energy spread ofthe bunch is (18±3)% and the central part of the bunch canbe described by a Gaussian-like distribution:dNdE=N0Eexp(− (E − E0)22σ2)(1)Figure 1 (upper graph) shows the experimental results(E0=9.6 MeV, σ=(0.7±0.06)MeV) compared to simula-tions.First experiments on phase rotation. The cavity is a threegap spiral resonator, inserted to the beamline between 2and 2.55 m distance to the laser target and connected to theUNILAC rf system. Injection at -90 deg synchronous phaseand 100 kW input power leads to energy compression of thebunch. The energy spread at FWHM (ΔE/E0=2.35σ/E0)could be reduced to (2.7±1.7)% at a central proton energyof E0=9.7 MeV (see lower graph in figure 1) and particlenumbers of 1.2×109 (±15%) within the FWHM were mea-sured. A detailed description has been published in [3].Furthermore, the experimental setup allows for phase fo-cusing. Simulations predict shortest possible bunch dura-tions down to the sub nanosecond regime. Highest single∗This work is supported by the Helmholtz Institute Jena and HIC forFAIR.bunch intensities of 1010 protons/ns are accessible. An ex-perimental campaign is planned for 2014.Thanks to the compact laser-driven source the whole beam-line is only 3 m long in total and represents a currentlyunique combination of novel laser and conventional accel-erator technology to generate highest single bunch intensi-ties in the multi-MeV region.8.5 9 9.5 10 10.5 1100.20.40.60.81proton energy [MeV]norm. dN/dE [(10 keV)−1]  simulationerrorlimitsno rf8.5 9 9.5 10 10.5 1100.20.40.60.81proton energy [MeV]norm. dN/dE [(10 keV)−1]  −78 degerrorlimitssimulationFigure 1: Simulated and measured proton spectra at a dis-tance of 3 m to the source for solenoid focusing only (up-per) and additional energy compression (lower figure) for acentral bunch energy of E0=(9.6±0.1)MeV.References[1] S. Busold et al., Shaping laser accelerated ion for futureapplications - the LIGHT collaboration, NIMA 740, 94-98(2014)[2] S. Busold et al., Focusing and transport of high-intensitymulti-MeV proton bunches from a compact laser-drivensource, PRSTAB 16, 101302 (2013)[3] S. Busold et al., Commissioning of a compact laser-basedproton beamline for high intensity bunches around 10 MeV,PRSTAB 17, 031302 (2014)PNI-PP-09 GSI SCIENTIFIC REPORT 2013190 doi:10.15120/GR-2014-1-PNI-PP-09

A laser-driven proton beamline at GSI

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A laser-driven proton beamline at GSI

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