L. Ficcadenti

The SPARC linear accelerator based terahertz source

Ultra-short electron beams, produced through the velocity bunching compression technique, are used to drive the SPARC linear accelerator based source, which relies on the emission of coherent transition radiation in the terahertz range. This paper reports on the main features of this radiation, as terahertz source, with spectral coverage up to 5 THz and pulse duration down to 200 fs, with an energy per pulse of the order of several micro-joule, and as electron beam longitudinal diagnostics.

The Project Plasmonx for Plasma Acceleration Experiments and A Thomson X-Ray Source at SPARC

We present the status of the project PLASMONX, recently approved by INFN. This project, based on a collaboration between INFN and CNR-IPCF, aims at a long term upgrade of the SPARC system with the goal to develop at LNF an integrated facility for advanced beam-laser-plasma research in the field of advanced acceleration techniques and ultra-bright X-ray radiation sources and related applications. The project, in its first phase, foresees the development at LNF of a High Intensity Laser Laboratory (HILL) whose main component is a 100 TW-class Ti: Sa laser system synchronized to the SPARC photo-injector. Experiments of self-injection and acceleration of electrons into laser driven plasma waves will be conducted at HILL-LNF, early in this first project phase. Eventually an additional beam line will be built in the SPARC bunker in order to transport the SPARC electron beam at an interaction point, where a final focus system will allow to conduct experiments either of laser-beam co-propagation in plasma waves for high gradient acceleration, or experiments of laser-beam head-on collisions to develop a Thomson source of bright ultra-short X-ray radiation pulses, with X-ray energies tunable in the range 20 to 1000 keV and pulse duration from 30 fs to 20 ps. Preliminary simulations of plasma acceleration with self-injection are illustrated, as well as external injection of the SPARC electron beam.

Tuning procedure for traveling wave structures and its application to the C-Band cavities for SPARC photo injector energy upgrade

In this paper we illustrate the tuning procedure we implemented to tune the traveling wave structures designed and constructed for the SPARC photo-injector energy upgrade. The procedure has been derived from that proposed and adopted for the CLIC structures at CERN (J. Shi et al., Tuning of clic accelerating structure prototypes at Cern, Proc. of LINAC 2010, Tsukuba, Japan, 2010). In the first part of the paper we go through the analytical formulas also illustrating and discussing an algorithm to tune the input and output couplers. A detailed description of the measurements we have done before and after the tuning of the SPARC C-band structure prototype is then illustrated.

RF measurements results of the final brazed SPARC RF deflector

The longitudinal phase space and the horizontal beam slice emittance measurements of the SPARC 150 MeV - 1 nC electron beam, foresee the use of a RF deflector. The device is a five cells standing wave structure operating on the TM110-like dipole mode at 1.856 Ghz and allows reaching a longitudinal resolution of ~12 um with 2 MW of peak input power. In the paper we illustrate the RF measurements results on the final brazed copper device.

Charge and wavelength scaling of the ucla/urls/infn hybrid photoinjector

The SW/TW hybrid photoinjector is being developed at UCLA, INFN/LNF, and University of Rome. The hybrid gun has SW cells and TW cells in one structure. It can produce the low emittance and high peak current beam. PARMELA simulation showed the emittance and the bunch length were 2.8 mm.mrad and 0.16 mm, respectively. With the charge and frequency scaling law of the photoinjector, low charge and higher frequency case were also calculated.

RF design of the UCLA/INFN hybrid SW/TW photoinjector

With increasing demand for high brightness, low emittance beams for use with free‐electron lasers, Compton scattering systems and wake‐field accelerator experiments, stringent requirements have been placed on the design and operation of the 1.6 cell photoinjector. The proposed hybrid photoinjector combines the BNL/UCLA/SLAC style 1.5/1.6 cell standing wave gun with a traveling wave accelerator. Our goal is an injector that meets today’s requirements and is scalable in design to meet tomorrow’s demands: emittances in the region of 1 mm‐mrad for higher brightness as well as higher currents. The hybrid photoinjector also offers higher energy operation, enhanced cost effectiveness and better scalability than current designs such as integrated PWT photoinjectors and split gun/accelerating sections. The use of both SW and TW systems allows for higher gradients (Eo = 70 MV/m) in the SW gun for effective capture at lower emittances, while the lower energy acceleration in the TW sections (Eo = 13.5 MV/m) allows ge...

Beam Dynamics in a Hybrid Standing Wave‐Traveling Wave Photoinjector

We discuss the dynamics of a photoinjector beam in a hybrid traveling wave‐standing wave photoinjector. With the field profile deduced from electromagnetic simulations, it is seen that the acceleration program induces strong velocity bunching. The beam dynamics in this scenario are explored using UCLA PARMELA. With a solenoid field overlaid on the TW section one may control emittance oscillations during bunching and acceleration. It is seen that the S‐band device currently under development at UCLA may produce a 1 nC, 21 MeV, 100 micron rms pulse length beam, with emittance of 3 mm‐mrad. Applications of this beam for creating coherent radiation are discussed.

Wake fields effects in dielectric capillary

Abstract Plasma wake-field acceleration experiments are performed at the SPARC_LAB test facility by using a gas-filled capillary plasma source composed of a dielectric capillary. The electron can reach GeV energy in a few centimeters, with an accelerating gradient orders of magnitude larger than provided by conventional techniques. In this acceleration scheme, wake fields produced by passing electron beams through dielectric structures can determine a strong beam instability that represents an important hurdle towards the capability to focus high-current electron beams in the transverse plane. For these reasons, the estimation of the transverse wake-field amplitudes assumes a fundamental role in the implementation of the plasma wake-field acceleration. In this work, it presented a study to investigate which parameters affect the wake-field formation inside a cylindrical dielectric structure, both the capillary dimensions and the beam parameters, and it is introduced a quantitative evaluation of the longitudinal and transverse electric fields.

Production of high power terahertz radiation through the SPARC Free-Electron Laser

We present the TERASPARC project at the SPARC Free-Electron Laser in Italy. Sub-picosecond, high power terahertz pulses extended until 5 THz are produced using a coherent transition radiation source. Here we discuss the properties of the radiation, the possibility to produce exotic pulse shape and some of the planned pump-probe experiments.

Measurement of the UCLA/URLS/INFN hybrid gun

The hybrid photoinjector is a high current, low emittance photoinjector/accelerator that is under design with collaboration from Roma University La Sapienza, INFN - Laboratori Nazionali di Frascati and the UCLA Particle Beam Physics Lab. The hybrid standing wave-traveling wave photoinjector uses a coupling cell to divide power between a high gradient 1.6 cell standing wave photoinjector, for electron emission and collection, and a lower gradient traveling wave accelerator, for acceleration to desired energies at low emittances. Simulation results show promising beam properties of less than 4 mm-mrad emittance, energy spreads of 1.5 percent, and currents as high as 1.2 kA at energies of 21 MeV. We report on the progress of RF design and results of cold test RF measurements at the UCLA Pegasus Laboratory, including methods for measurements and difficulties arising in the transition from simulation to physical measurements.