High Brightness Electron Source for Coherent Radiation Production

Adalberto Sciubba, Bruno Crosignani, Giuseppe Schettin

Simultaneous electronic and the magnetic excitation of a ferromagnet by intense THz pulses

The speed of magnetization reversal is a key feature in magnetic data storage. Magnetic fields from intense THz pulses have been recently shown to induce small magnetization dynamics in Cobalt thin film on the sub-picosecond time scale. Here, we show that at higher field intensities, the THz electric field starts playing a role, strongly changing the dielectric properties of the cobalt thin film. Both the electronic and magnetic responses are found to occur simultaneously, with the electric field response persistent on a time scale orders of magnitude longer than the THz stimulu

Laser and rf synchronization measurements at SPARC

The SPARC project consists in a 150 MeV S-band, high-brilliance linac followed by 6 undulators for FEL radiation production at 530 nm. The linac assembly has been recently completed. During year 2006 a first experimental phase aimed at characterizing the beam emittance in the first 2 m drift downstream the RF gun has been carried out. The low level RF control electronics to monitor and synchronize the RF phase in the gun and the laser shot on the photocathode has been commissioned and extensively tested during the emittance measurement campaign. The laser synchronization has been monitored by measuring the phase of the free oscillation of an RF cavity impulsively excited by the signal of a fast photodiode illuminated by the laser shot. Phase stability measurements are reported, both with and without feedback correction of the slow drifts. A fast intra-pulse phase feedback system to reduce the phase noise produced by the RF power station has been also positively tested

Nonlinear quantum magnetophononics in SrCu2_2(BO3_3)2_2

Harnessing the most advanced capabilities of quantum technologies will require the ability to control macroscopic quantum states of matter. Quantum magnetic materials provide a valuable platform for realizing highly entangled many-body quantum systems, and have been used to investigate phenomena ranging from quantum phase transitions (QPTs) to fractionalization, topological order and the entanglement structure of the quantum wavefunction. Although multiple studies have controlled their properties by static applied pressures or magnetic fields, dynamical control at the fundamental timescales of their magnetic interactions remains completely unexplored. However, major progress in the technology of ultrafast laser pulses has enabled the dynamical modification of electronic properties, and now we demonstrate the ultrafast control of quantum magnetism. This we achieve by a magnetophononic mechanism, the driving of coherent lattice displacements to produce a resonant excitation of the quantum spin dynamics. Specifically, we apply intense terahertz laser pulses to excite a collective spin state of the quantum antiferromagnet SrCu$_2$(BO$_3$)$_2$ by resonance with the nonlinear mixing frequency of the driven phonons that modulate the magnetic interactions. Our observations indicate a universal mechanism for controlling nonequilibrium quantum many-body physics on timescales many orders of magnitude faster than those achieved to date.Comment: 24 pages, 9 figure