Search results for "Accelerator Physics"
showing 10 items of 1294 documents
Radiation pressure-assisted acceleration of ions using multi-component foils in high-intensity laser–matter interactions
2013
Experimental results on the acceleration of protons and carbon ions from ultra-thin polymer foils at intensities of up to 6x10(19)Wcm(-2) are presented revealing quasi-monoenergetic spectral characteristics for different ion species at the same time. For carbon ions and protons, a linear correlation between the cutoff energy and the peak energy is observed when the laser intensity is increased. Particle-in-cell simulations supporting the experimental results imply an ion acceleration mechanism driven by the radiation pressure as predicted for multi-component foils at these intensities.
Laser instabilities in a Gaussian cavity mode with Gaussian pump profile
1998
We analytically demonstrate that both single-mode and multimode instabilities may occur in a Gaussian-cavity-mode laser model with Gaussian pump profile. As a necessary condition, the ratio of the beam waist to the pump waist must exceed a given limiting value, which depends on the population decay rate. For an infinitely concentrated pump the plane-wave model instability thresholds are recovered, and there exists an optimum value of the waists ratio for which the second laser threshold is minimum.
First Observation of the Unbound NucleusNe15
2014
We report on the first observation of the unbound proton-rich nucleus Ne-15. Its ground state and first excited state were populated in two-neutron knockout reactions from a beam of 500 MeV/u Ne-17. The Ne-15 ground state is found to be unbound by 2.522(66) MeV. The decay proceeds directly to O-13 with simultaneous two-proton emission. No evidence for sequential decay via the energetically allowed 2(-) and 1(-) states in F-14 is observed. The Ne-15 ground state is shown to have a strong configuration with two protons in the (sd) shell around O-13 with a 63(5)% (1s(1/2))(2) component.
Spatial Beam Evolution in Nonlinear Multimode Fibers
2021
We discuss some recent results illustrating the role of input wave-front shaping, propagation dynamics and output beam diagnostics in order to observe spatial beam cleaning in nonlinear multimode fibers and amplifiers.
Screening of positrons in semiconductors and insulators
1989
Theoretical models are presented for the enhancement of the electron density at a positron in a semiconductor or insulator host. The model better suited for typical semiconductors is based on the many-body theory for the screening of a positron in electron gas. The starting point of the model for insulators is the atomic polarizability. The common parameter in both models is the high-frequency dielectric constant. Moreover, the enhancement depends on the ambient electron density in the semiconductor model and on the unit-cell volume in the insulator model. With use of the models developed, positron lifetimes in perfect semiconductor and insulator crystals have been calculated. In the calcul…
Spectroscopy of Low-lying States in $^{140}$Sm
2014
International audience; Electromagnetic transition strengths and spectroscopic quadrupole moments for Sm-140 were measured by means of multi-step Coulomb excitation with radioactive beam at the ISOLDE facility at CERN. A complementary experiment was performed at the Heavy Ion Laboratory in Warsaw to assign spins for non-yrast states using the angular correlation technique. Based on the new experimental data previous spin assignments need to be revised.
Neutron halos in the excited states of B12
2018
The differential cross sections of the $^{11}\mathrm{B}(d,p)\phantom{\rule{0.16em}{0ex}}^{12}\mathrm{B}$ reaction leading to formation of the ${1}^{+}$ ground state and the 0.95-MeV ${2}^{+}$, 1.67-MeV ${2}^{\ensuremath{-}}$, 2.62-MeV ${1}^{\ensuremath{-}}$, 2.72-MeV ${0}^{+}$, and 3.39-MeV ${3}^{\ensuremath{-}}$ excited states of $^{12}\mathrm{B}$ are measured at ${E}_{d}$ = 21.5 MeV. The analysis of the data is carried out within the coupled-reaction-channels method for the direct neutron transfer and the Hauser-Feshbach formalism of the statistical compound-nucleus model. The spectroscopic factors, asymptotic normalization coefficients, and rms radii of the last neutron in all states stu…
Direct Measurement of Focusing Fields in Active Plasma Lenses
2018
Active plasma lenses have the potential to enable broad-ranging applications of plasma-based accelerators owing to their compact design and radially symmetric kT/m-level focusing fields, facilitating beam-quality preservation and compact beam transport. We report on the direct measurement of magnetic field gradients in active plasma lenses and demonstrate their impact on the emittance of a charged particle beam. This is made possible by the use of a well-characterized electron beam with 1.4 mm mrad normalized emittance from a conventional accelerator. Field gradients of up to 823 T/m are investigated. The observed emittance evolution is supported by numerical simulations, which suggest the …
Developments on the 1.4 MeV/u Pulsed Gas Stripper Cell
2017
The GSI UNILAC in combination with SIS18 will serve as a high-current, heavy-ion injector for the FAIR facility. It must meet high demands in terms of beam brilliance at a low duty factor. As part of an UNILAC upgrade program dedicated to FAIR, a new pulsed gas stripper cell was developed, aiming for increased beam intensities inside the post-stripper. The pulsed gas injection is synchronized with the beam pulse timing, enabling a highly-demanded, increased gas density. First tests using uranium beams on a hydrogen target showed a 60%-increased stripping efficiency into the desired 28+ charge state. In 2015, the setup was improved to be able to deliver increased target thicknesses and enhan…
Determination of the eta'-proton scattering length in free space
2014
Taking advantage of both the high mass resolution of the COSY-11 detector and the high energy resolution of the low-emittance proton-beam of the Cooler Synchrotron COSY we determine the excitation function for the pp --> pp eta' reaction close-to-threshold. Combining these data with previous results we extract the scattering length for the eta'-proton potential in free space to be Re(a_{p eta'}) = 0+-0.43 fm and Im(a_{p eta'}) = 0.37(+0.40)(-0.16) fm.