PAC2013 - List of Authors (Najmudin, Z.)

Paper	Title	Page
MOPAC34	Spectral Broadening of Ions Accelerated by a Radiation Pressure Driven Shock	144
	N.M. Cook, P. Shkolnikov Stony Brook University, Stony Brook, New York, USA N. Dover, Z. Najmudin Imperial College of Science and Technology, Department of Physics, London, United Kingdom C. Maharjan SBU, Stony Brook, New York, USA I. Pogorelsky, M.N. Polyanskiy, O. Tresca BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Laser driven ion acceleration has been the focus of considerable research efforts since multi-MeV energies were first demonstrated. Most experiments use solid state laser pulses focused onto thin foil targets. However, recent progress in CO2 laser technology allows for the creation of intense pulses at λ ~10μm. The longer wavelength permits the use of low density targets. In these conditions ion acceleration is primarily driven by a shock wave due to the radiation pressure of the laser. This acceleration mode has the advantage of producing narrow energy spectra while scaling well with pulse intensity. New improvements to the CO2 laser at the Accelerator Test Facility allow for the unique production of single picoseconds-scale pulses with 1TW peak power. We report on the interaction of an intense CO2 laser pulse with overdense hydrogen and helium gas jets. Using a two pulse optical probe, we are able to obtain real-time density profiles at different times during the interaction, allowing for the characterization of shock wave velocities and peak density conditions. Ion energy spectra are measured using a Thomson spectrometer and scintillating screen. This work has been supported by the United States Department of Energy, Grant DE-FG02-07ER41488.

THPSM12	A Ready-to-use Application of Laser-Plasma Accelerators using Gabor Lenses	1409
	J.K. Pozimski, M. Aslaninejad, N. Dover, Z. Najmudin, R.M. Nichols, P.A. Posocco Imperial College of Science and Technology, Department of Physics, London, United Kingdom
	Funding: R.M. Nichols was supported by EPSRC. A realistic particle distribution for a proton beam generated by laser-plasma interaction is required in order to simulate its transport through a Gabor lens system intended for use in radiobiology experiments. A stack of radiochromic films were exposed to a laser-driven proton beam of 25 MeV at the Vulcan Petawatt Experiment at Rutherford Lab and subsequently analysed to find the energy deposited per film and therefore the energy spectrum of the beam. Combined with the information on the radial profile of the dose in the films, it was possible to generate an idealised particle distribution. This distribution was sampled and used as a realistic proton source in a simulation through the Gabor lens system published at IPAC’13, scaled down to 4 MeV to fit the radiobiology experiment requirements.

THPSM13	Characterisation of Nitrogen Clusters and Gas Jet Targets Under Varied Nozzle Geometries	1412
	C. Hughes, N. Dover, Z. Najmudin, P.A. Posocco Imperial College of Science and Technology, Department of Physics, London, United Kingdom
	Funding: C. Hughes was supported by the Ogden Trust. Gas jets are widely used for targets in laser-plasma driven article acceleration experiments. Optimising the mechanism requires tailored gas jet density profiles. Therefore, high density gas profiles have been investigated and characterised using different types of nozzles: sonic, supersonic, slit and supersonic slit. Gas jet profile optimisation was examined using nozzles of different diameters while varying gas pressure between 0 and 100 bar and valve opening duration. Gas jets produced by the nozzles were characterised using an optical probe laser. The gas jet density profile was measured through interferometry which was captured using a CCD camera. A second camera was used to record the Rayleigh scattering from the laser to confirm the presence clustering in nitrogen at high pressures.

Paper

Title

Page

Spectral Broadening of Ions Accelerated by a Radiation Pressure Driven Shock

144

N.M. Cook, P. Shkolnikov
Stony Brook University, Stony Brook, New York, USA
N. Dover, Z. Najmudin
Imperial College of Science and Technology, Department of Physics, London, United Kingdom
C. Maharjan
SBU, Stony Brook, New York, USA
I. Pogorelsky, M.N. Polyanskiy, O. Tresca
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Laser driven ion acceleration has been the focus of considerable research efforts since multi-MeV energies were first demonstrated. Most experiments use solid state laser pulses focused onto thin foil targets. However, recent progress in CO2 laser technology allows for the creation of intense pulses at λ ~10μm. The longer wavelength permits the use of low density targets. In these conditions ion acceleration is primarily driven by a shock wave due to the radiation pressure of the laser. This acceleration mode has the advantage of producing narrow energy spectra while scaling well with pulse intensity. New improvements to the CO2 laser at the Accelerator Test Facility allow for the unique production of single picoseconds-scale pulses with 1TW peak power. We report on the interaction of an intense CO2 laser pulse with overdense hydrogen and helium gas jets. Using a two pulse optical probe, we are able to obtain real-time density profiles at different times during the interaction, allowing for the characterization of shock wave velocities and peak density conditions. Ion energy spectra are measured using a Thomson spectrometer and scintillating screen.
This work has been supported by the United States Department of Energy, Grant DE-FG02-07ER41488.

THPSM12

A Ready-to-use Application of Laser-Plasma Accelerators using Gabor Lenses

1409

J.K. Pozimski, M. Aslaninejad, N. Dover, Z. Najmudin, R.M. Nichols, P.A. Posocco
Imperial College of Science and Technology, Department of Physics, London, United Kingdom

Funding: R.M. Nichols was supported by EPSRC.
A realistic particle distribution for a proton beam generated by laser-plasma interaction is required in order to simulate its transport through a Gabor lens system intended for use in radiobiology experiments. A stack of radiochromic films were exposed to a laser-driven proton beam of 25 MeV at the Vulcan Petawatt Experiment at Rutherford Lab and subsequently analysed to find the energy deposited per film and therefore the energy spectrum of the beam. Combined with the information on the radial profile of the dose in the films, it was possible to generate an idealised particle distribution. This distribution was sampled and used as a realistic proton source in a simulation through the Gabor lens system published at IPAC’13, scaled down to 4 MeV to fit the radiobiology experiment requirements.

THPSM13

Characterisation of Nitrogen Clusters and Gas Jet Targets Under Varied Nozzle Geometries

1412

C. Hughes, N. Dover, Z. Najmudin, P.A. Posocco
Imperial College of Science and Technology, Department of Physics, London, United Kingdom

Funding: C. Hughes was supported by the Ogden Trust.
Gas jets are widely used for targets in laser-plasma driven article acceleration experiments. Optimising the mechanism requires tailored gas jet density profiles. Therefore, high density gas profiles have been investigated and characterised using different types of nozzles: sonic, supersonic, slit and supersonic slit. Gas jet profile optimisation was examined using nozzles of different diameters while varying gas pressure between 0 and 100 bar and valve opening duration. Gas jets produced by the nozzles were characterised using an optical probe laser. The gas jet density profile was measured through interferometry which was captured using a CCD camera. A second camera was used to record the Rayleigh scattering from the laser to confirm the presence clustering in nitrogen at high pressures.