Multivariate negative aging in an exchangeable model of heterogeneity

We introduce an exchangeable model, which accounts for heterogeneity and dependence at a time. Based on this model, we show how situations of multivariate negative ageing arise in a natural way from conditions of heterogeneity

Study of charge state enhancement by means of the coupling of a Laser Ion Source to the ECR ion source SERSE

The possibility to produce intense ion beams from solid elements, by using a pulsed Laser ion source as the first stage of the superconducting ECR ion source SERSE is discussed in the following. The Laser ion source may be used to produce negative or positive ions and electrons that are injected into the plasma of SERSE. The design of the experimental setup and the study of the extraction of ions from a target by means of Nd:Yag laser irradiation are briefly described. This Laser ion source will be located in the plasma chamber of the source SERSE, in presence of its magnetic field. A simple evaluation of the charge state enhancement inside the ECR plasma is also presented in the following

Protons accelerated in the target normal sheath acceleration regime by a femtosecond laser

Advanced targets based on thin films of graphene oxide covered by metallic layers have been irradiated at high laser intensity (∼1019 W/cm2) with 40 fs laser pulses to investigate the forward ion acceleration in the target normal sheath acceleration regime. A time-of-flight technique was employed with silicon-carbide detectors and ion collectors as fast on-line plasma diagnostics. At the optimized conditions of the laser focus position with respect to the target surface was measured the maximum proton energy using Au metallic films. A maximum proton energy of 2.85 MeV was measured using the Au metallization of 200 nm. The presence of graphene oxide facilitates the electron crossing of the foil minimizing the electron scattering and increasing the electric field driving the ion acceleration. The effect of plasma electron density control using the graphene oxide is presented and discussed

Low power RF test of a quadrupole-free X-Band mode launcher for high brightness applications

In this work we present the low power RF characterization of a novel TM01 X-band mode launcher for the new generation of high brightness RF photo-injectors. The proposed mode launcher exploits a fourfold symmetry which minimizes both the dipole and the quadrupole fields in order to mitigate the emittance growth in the early stages of the acceleration process. Two identical aluminum mode launchers have been assembled and measured in back-to-back configurations for three different central waveguide lengths. From the back-to-back results we infer the performance of each mode launcher. The low power RF test, performed at the Istituto Nazionale di Fisica Nucleare Laboratori Nazionali del Sud (INFN-LNS), validate both the numerical simulations and the quality of fabrication. An oxygen-free high-conductivity copper version of the device is being manufactured for high power and ultra high vacuum tests that are planned to be conducted at SLAC