Energy-loss calculation of gain in a plane sinusoidal free-electron laser

The gain of a free-electron laser (FEL) made with a plane sinusoidal undulator is calculated by the electron beam energy loss

Spatial Coherence of Synchrotron Radiation

Theory and measurement of spatial coherence of synchrotron radiation beams are briefly reviewed. Emphasis is given to simple relationships between electron beam characteristics and far field properties of the light beam.Comment: 8 pages, 3 figure

Large angle Beamstrahlung as a beam-beam monitoring tool

A novel method to measure the beam-beam interaction in e+e- colliders is presented.Comment: 17 pages, four figures, to be published in Nuclear Instruments and Method

Magnetic Schumann Resonances in Swarm ASM Burst Mode, VFM HF and e-POP Data?

The Schumann Resonances (SR) consist of a series of peaks in spectral power in the magnetic and electric field at frequencies of around 8, 14, 22 and 27 Hz. They arise from the continuous occurrence of equatorial lightning strikes [1]. The broadband electromagnetic emission from each lightning strike is contained within a waveguide, bounded by the Earth’s surface and the ionosphere at around 80 km in altitude. The SR are detectable on the ground using sensitive search-coil magnetometers. They have a large Q-factor (i.e. broad peaks) and an obvious diurnal and seasonal variation due to the location of landmasses. Although, the electric field SR have been detected in space using the C/NOFS satellite in 2010/11 at altitudes of 600 km [2], there have been no confirmed measurements using magnetic field instruments. There are theoretical arguments that the ionosphere acts to fully shield the magnetic signal from penetrating out of the atmosphere to Swarm altitudes, though other models suggest some secondary signals occur [3].We examine data from the Swarm Absolute Scalar Magnetometer Burst Mode (250 Hz), the Swarm Vector Field Magnetometer High Resolution (50Hz) and enhanced Polar Outflow Probe (e-POP) Magnetic Field (160 Hz) instruments collected on the 19-Jan-2014 during the commissioning phase of the mission to look for SR signals

Thermally evaporated Cu-Co top spin valve with random exchange bias

A cobalt-copper top spin valve was prepared by thermal evaporation of a stack of ferromagnetic thin films separated by thin layers of the diamagnetic metal, with a cap layer containing an antiferromagnetic AFM exchange-biasing material. A nonconventional top AFM layer was used, in order to optimize the multilayer roughness and to avoid electrical interference with metallic layers; it consists of a composite material easily processed by means of optical lithography, basically a polymeric matrix composite with a dispersion of nickel oxide microparticles. Magnetization and magnetoresistance measurements were performed from 4 to 300 K. The measurements of both quantities indicate random pinning action of the top AFM layer, resulting in a small exchange-bias field and in asymmetric magnetization and magnetoresistance curves. A simple model explains the observed physical effect