99 research outputs found
Apparent superluminal advancement of a single photon far beyond its coherence length
We present experimental results relative to superluminal propagation based on
a single photon traversing an optical system, called 4f-system, which acts
singularly on the photon's spectral component phases. A single photon is
created by a CW laser light down{conversion process. The introduction of a
linear spectral phase function will lead to the shift of the photon peak far
beyond the coherence length of the photon itself (an apparent superluminal
propagation of the photon). Superluminal group velocity detection is done by
interferometric measurement of the temporal shifted photon with its correlated
untouched reference. The observed superluminal photon propagation complies with
causality. The operation of the optical system allows to enlighten the origin
of the apparent superluminal photon velocity. The experiment foresees a
superluminal effect with single photon wavepackets.Comment: 11 pages, 2 figure
Generation of primary photons through inverse Compton scattering using a Monte Carlo simulation code
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Improving performance of inverse Compton sources through laser chirping
We present a new paradigm for computation of radiation spectra in the
non-linear regime of operation of inverse Compton sources characterized by high
laser intensities. The resulting simulations show an unprecedented level of
agreement with the experiments. Increasing the laser intensity changes the
longitudinal velocity of the electrons during their collision, leading to
considerable non-linear broadening in the scattered radiation spectra. The
effects of such ponderomotive broadening are so deleterious that most inverse
Compton sources either remain at low laser intensities or pay a steep price to
operate at a small fraction of the physically possible peak spectral output.
This ponderomotive broadening can be reduced by a suitable frequency modulation
(also referred to as "chirping", which is not necessarily linear) of the
incident laser pulse, thereby drastically increasing the peak spectral density.
This frequency modulation, included in the new code as an optional
functionality, is used in simulations to motivate the experimental
implementation of this transformative technique.Comment: 7 pages, 5 figure
A Laser Frequency Transverse Modulation Might Compensate for the Spectral Broadening Due to Large Electron Energy Spread in Thomson Sources
Compact laser plasma accelerators generate high-energy electron beams with increasing quality. When used in inverse Compton backscattering, however, the relatively large electron energy spread jeopardizes potential applications requiring small bandwidths. We present here a novel interaction scheme that allows us to compensate for the negative effects of the electron energy spread on the spectrum, by introducing a transverse spatial frequency modulation in the laser pulse. Such a laser chirp, together with a properly dispersed electron beam, can substantially reduce the broadening of the Compton bandwidth due to the electron energy spread. We show theoretical analysis and numerical simulations for hard X-ray Thomson sources based on laser plasma accelerators
Study of the beam dynamics in a linac with the code retar
The three-dimensional fully relativistic and self- consistent code RETAR has been developed to model the dynamics of high-brightness electron beams and, in particular, to assess the importance of the retarded radiative part of the emitted electromagnetic fields in all conditions where the electrons experience strong accelerations. In this analysis we evaluate the radiative energy losses in the electron emission process from the photocathode of an injector, during the successive acceleration of the electron beam in the RF cavity and the focalization due to the magnetic field of the solenoid. The analysis is specifically carried out with parameters of importance in the framework of the SPARC and PLASMONX projects
GeV-Class two-fold CW linac driven by an arc-compressor
We present a study of an innovative scheme to generate high repetition rate (MHz-class)
GeV electron beams by adopting a two-pass two-way acceleration in a super-conducting Linac
operated in Continuous Wave (CW) mode. The beam is accelerated twice in the Linac by being
re-injected, after the first pass, in opposite direction of propagation. The task of recirculating the
electron beam is performed by an arc compressor composed by 14 Double Bend Achromat (DBA).
In this paper, we study the main issues of the two-fold acceleration scheme, the electron beam
quality parameters preservation (emittance, energy spread), together with the bunch compression
performance of the arc compressor, aiming to operate an X-ray Free Electron Laser. The requested
power to supply the cryogenic plant and the RF sources is also significantly reduced w.r.t a
conventional one-pass SC Linac for the same final energy
OPTIMIZING RF LINACS AS DRIVERS FOR INVERSE COMPTON SOURCES: THE ELI-NP CASE
The design guide-lines of RF Linacs to fulfil the requirements of high spectral density Inverse Compton Sources for the photo-nuclear science are mostly taken from the expertise coming from high brightness electron Linacs driving X-ray FEL's. The main difference is the quest for maximum phase space density (instead of peak brightness), but many common issues and techniques are exploited, in order to achieve an optimum design and layout
for the machine. A relevant example in this field is the design of the hybrid C-band multi-bunch RF Linacs for the ELI-NP Gamma Beam System, aiming at improving by two orders of magnitude the present state of the art in spectral density available for the gamma-ray beam produced
BriXs ultra high fluxinverse compton source based on modified push-pull energy recovery linacs
We present a conceptual design for a compact X-ray Source BriXS (Bright and compact
X-ray Source). BriXS, the first stage of the Marix project, is an Inverse Compton Source (ICS) of
X-ray based on superconducting cavities technology for the electron beam with energy recirculation
and on a laser system in Fabry-Pérot cavity at a repetition rate of 100 MHz, producing 20–180 keV
monochromatic X-Rays devoted mainly to medical applications. An energy recovery scheme based on
a modified folded push-pull CW-SC twin Energy Recovery Linac (ERL) ensemble allows us to sustain
an MW-class beam power with almost one hundred kW active power dissipation/consumption
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