No abstract

We discuss the possibility of creating novel research tools by producing and storing highly relativistic beams of highly ionised atoms in the CERN accelerator complex, and by exciting their atomic degrees of freedom with lasers to produce high-energy photon beams. Intensity of such photon beams would be by several orders of magnitude higher than offered by the presently operating light sources, in the particularly interesting γ-ray energy domain of 0.1-400 MeV. In this energy range, the high-intensity photon beams can be used to produce secondary beams of polarised electrons, polarised positrons, polarised muons, neutrinos, neutrons and radioactive ions. New research opportunities in a wide domain of fundamental and applied physics can be opened by the Gamma Factory scientific programme based on the above primary and secondary beams.

We studied the second order optical nonlinearity of aluminum nitride films grown by sputtering onto silicon substrates. The crystalline properties of the films were investigated by x-ray diffraction measurements. Preliminary linear optical characterization of the films was carried out by spectrophotometric optical reflectance measurements at different incidence angles; thus the dispersion laws for both ordinary and extraordinary refractive indices were retrieved. Finally, second harmonic generation measurements in reflection mode were performed at a fixed angle from a fundamental beam provided by a picosecond Ti:sapphire laser system at λ = 800 nm. In the experiments a high blue light conversion efficiency was found for samples 1.5 and 2 μm thick, and the second order nonlinear coefficient d33 = 11±1 pm/V was found

(2+1)-dimensional spatial solitons in Bi12SiO20 (BSO) photorefractive crystals with large optical activity are experimentally demonstrated. The soliton formation when a Gaussian beam is injected at the input has been previously analyzed numerically and then experimentally investigated. We demonstrate analytically, numerically, and experimentally that by applying static electric biases of high values, the polarization rotation accelerates: this acceleration prevents the beam from broadening if the polarization rotation period becomes shorter than the diffraction length. Contemporary to this nonlinear optical activity, an induced birefringence affects the beam polarization state. Analysis of the polarization dynamics shows that the polarization changes nonuniformly across the beam (with a field dependent speed) until about 30-35 kV/cm; above this limit, the whole beam has just one polarization state. Representation on the Poincaré sphere of the polarization dynamics reveals the existence of a stable polarization trajectory closed around a polarization attractor that depends on the linear optical activity and on the photorefractive nonlinearity. The experimental soliton is well described by the analytical solutions already obtained [Fazio et al., Phys. Rev. E 66, 016605 (2002)].

Gravity can be studied in detail in near Earth orbits NEO's using laser-ranged test masses tracked with few-mm accuracy by ILRS. The two LAGEOS satellites have been used to measure frame dragging (a truly rotational effect predicted by GR) with a 10% error. A new mission and an optimized, second generation satellite, LARES (I. Ciufolini PI), is in preparation to reach an accuracy of 1% or less on frame dragging, to measure some PPN parameters, to test the 1/r 2 law in a very weak field and, possibly, to test select models of unified theories (using the perigee). This requires a full thermal analysis of the test mass and an accurate knowledge of the asymmetric thermal thursts due to the radiation emitted by the Sun and Earth. A Space Climatic Facility (SCF) has been built at INFN-LNF (Frascati, Italy) to perform this experimental program on LAGEOS and LARES prototypes. It consists of a 2 m × 1 m cryostat, simulators of the Sun and Earth radiations and a versatile thermometry system made of discrete probes and an infrared digital camera.The SCF commissioning is well underway. A test of all its subsystems has been successfully completed on August 4, 2006, using a LAGEOS 3 × 3 retroreflector array built at LNF. This prototype has been thermally modeled in detail with a commercial simulation software. We expect to demonstrate the full functionality of the SCF with the thermal characterization of this LAGEOS array by the beginning of September 2006.