35 research outputs found
High flux polarized gamma rays production: first measurements with a four-mirror cavity at the ATF
The next generation of e+/e- colliders will require a very intense flux of
gamma rays to allow high current polarized positrons to be produced. This can
be achieved by converting polarized high energy photons in polarized pairs into
a target. In that context, an optical system consisting of a laser and a
four-mirror passive Fabry-Perot cavity has recently been installed at the
Accelerator Test Facility (ATF) at KEK to produce a high flux of polarized
gamma rays by inverse Compton scattering. In this contribution, we describe the
experimental system and present preliminary results. An ultra-stable
four-mirror non planar geometry has been implemented to ensure the polarization
of the gamma rays produced. A fiber amplifier is used to inject about 10W in
the high finesse cavity with a gain of 1000. A digital feedback system is used
to keep the cavity at the length required for the optimal power enhancement.
Preliminary measurements show that a flux of about /s with
an average energy of about 24 MeV was generated. Several upgrades currently in
progress are also described
Non-planar four-mirror optical cavity for high intensity gamma ray flux production by pulsed laser beam Compton scattering off GeV-electrons
As part of the R&D toward the production of high flux of polarised Gamma-rays
we have designed and built a non-planar four-mirror optical cavity with a high
finesse and operated it at a particle accelerator. We report on the main
challenges of such cavity, such as the design of a suitable laser based on
fiber technology, the mechanical difficulties of having a high tunability and a
high mechanical stability in an accelerator environment and the active
stabilization of such cavity by implementing a double feedback loop in a FPGA
THE FOUR-MIRROR LASER STACKING CAVITY FOR POLARIZED GAMMA-RAY/POSITRON GENERATION
Abstract A non planar four mirror cavity has been designed and constructed to demonstrate the production of high gamma ray fluxes from Compton scattering of laser and electron beams at ATF. A pulsed laser is amplified using the recent technology of Yb-doped photonic cristal fibres. Seeding the high finesse four-mirror cavity with this amplified laser beam will allow reaching average powers between 0.1MW and 1MW
Coupled structural and magnetic properties of ferric fluoride nanostructures part I: a Metropolis atomistic study
A modified Metropolis atomistic simulation is proposed to model the structure
of grain boundaries (GBs) and interfaces in ionic nanostructured systems and is
applied to the magnetically interesting case of iron trifluoride (FeF3). We
chose long-range interatomic potentials adjusted on experimental results, and
adapted a previously established Monte Carlo scheme consisting of various
modifications of the simulated annealing/ Metropolis algorithm. Atomic
structures of twisted and tilted GBs as a function of the relative
disorientation of the grains have been achieved yielding close to
experimentally measured properties. This approach takes into account the
structure of the grains far from the interface in order to constrain the
relative orientation of the grains, without any periodic boundary conditions.
One concludes that a long-range coulombic falloff of the interatomic potentials
is necessary to obtain GB structures presenting a correct local topology but
with a smooth transition from crystalline to amorphous states. The structural
features are finally discussed in terms of topological aspects and local
magnetic structure.Comment: submitted to JMM
Production of gamma rays by pulsed laser beam Compton scattering off GeV-electrons using a non-planar four-mirror optical cavity
As part of the positron source R&D for future colliders and Compton
based compact light sources, a high finesse non-planar four-mirror Fabry-Perot
cavity has recently been installed at the ATF (KEK, Tsukuba, Japan). The first
measurements of the gamma ray flux produced with a such cavity using a pulsed
laser is presented here. We demonstrate the production of a flux of 2.7
0.2 gamma rays per bunch crossing ( gammas per second) during
the commissioning
Technical Design Report EuroGammaS proposal for the ELI-NP Gamma beam System
The machine described in this document is an advanced Source of up to 20 MeV
Gamma Rays based on Compton back-scattering, i.e. collision of an intense high
power laser beam and a high brightness electron beam with maximum kinetic
energy of about 720 MeV. Fully equipped with collimation and characterization
systems, in order to generate, form and fully measure the physical
characteristics of the produced Gamma Ray beam. The quality, i.e. phase space
density, of the two colliding beams will be such that the emitted Gamma ray
beam is characterized by energy tunability, spectral density, bandwidth,
polarization, divergence and brilliance compatible with the requested
performances of the ELI-NP user facility, to be built in Romania as the Nuclear
Physics oriented Pillar of the European Extreme Light Infrastructure. This
document illustrates the Technical Design finally produced by the EuroGammaS
Collaboration, after a thorough investigation of the machine expected
performances within the constraints imposed by the ELI-NP tender for the Gamma
Beam System (ELI-NP-GBS), in terms of available budget, deadlines for machine
completion and performance achievement, compatibility with lay-out and
characteristics of the planned civil engineering
The ThomX project status
Work supported by the French Agence Nationale de la recherche as part of the program EQUIPEX under reference ANR-10-EQPX-51, the Ile de France region, CNRS-IN2P3 and Université Paris Sud XI - http://accelconf.web.cern.ch/AccelConf/IPAC2014/papers/wepro052.pdfA collaboration of seven research institutes and an industry has been set up for the ThomX project, a compact Compton Backscattering Source (CBS) based in Orsay - France. After a period of study and definition of the machine performance, a full description of all the systems has been provided. The infrastructure work has been started and the main systems are in the call for tender phase. In this paper we will illustrate the definitive machine parameters and components characteristics. We will also update the results of the different technical and experimental activities on optical resonators, RF power supplies and on the electron gun