AUTOMATIC CLEANING MACHINE FOR RF POWER COUPLERS

http://accelconf.web.cern.ch/AccelConf/SRF2011/papers/tupo011.pdfInternational audienceCouplers are technological devices that permit RF power matching between RF source and cavities. An high cleaning quality requirement especially for the coupler cold part directly linked to the cavity is needed. Even if the actual coupler preparation procedure at LAL works well, contamination risks remain due to the handling, no repeatability and a too long time duration (5 days) which is not acceptable for machines like ILC where around 16000 couplers would be prepared. Our challenge is to suppress these weak points, in designing an automatic coupler cleaning machine which give us a lower contamination risk, a fulthe cleaning and only 3 hours of process

RF Coaxial Resonator for Investigating Multipactor Discharges on Metal and Dielectric Surfaces

http://accelconf.web.cern.ch/AccelConf/LINAC2014/html/auth0693.htmTHPP096International audienceMultipactor discharge is a phenomenon in which electrons impact one or more material surfaces in resonance with an alternating electric field. The discharge can occur for a wide range of frequencies, from the MHz range to tens of GHz, and in wide array of geometries if the impacted surface has a secondary electron emission (SEE) yield larger than one. The discharge can take place on a single surface or between two surfaces. A novel coaxial resonator to investigate two-surface multipactor discharges on metal and dielectric surfaces in the gap region under vacuum conditions has been designed and tested. The resonator is ~ 100 mm in length with an outer diameter of ~ 60 mm (internal dimensions). A pulsed RF source delivers up to 30 W average power over a wide frequency range 650-900 MHz to the RF resonator. The incident and reflected RF signals are monitored by calibrated RF diodes. An electron probe provides temporal measurements of the multipacting electron current with respect to the RF power. These experiments were successful in identifying multipacting and allowed us the evaluation of a home made sputtered titanium nitride (TiN) thin layers as a Multipactor suppressor

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 $4\times10^6 \gamma$/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

Technology developments of ELI-NP gamma beam system

The ELI-NP gamma beam system (GBS) is a linac based gamma-source in construction in Magurele (RO) by the European consortium EuroGammaS led by INFN. Photons with tunable energy, from 0.2 to 19.5 MeV, and with intensity and brilliance beyond the state of the art, will be produced by Compton back-scattering between a high quality electron beam (up to 740 MeV) and an intense laser pulse at 100 Hz repetition rate. Production of very intense photon flux with narrow bandwidth requires multi-bunch operation and laser recirculation at the interaction point. In this paper, the main technological developments carried out by the EuroGammaS consortium for the generation of the ELI-NP gamma beam will be described with a special emphasis on the electron linac technology, such as: RF-gun and C-band accelerating structures design fabrication and tests; low level RF (LLRF) and synchronization systems specifications and development. Finally, the laser recirculation apparatus design is briefly described and first results reported

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 $e^+-e^-$ 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 $\pm$ 0.2 gamma rays per bunch crossing ($\sim3\times10^6$ gammas per second) during the commissioning

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

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

PERLE. Powerful energy recovery linac for experiments. Conceptual design report

A conceptual design is presented of a novel energy-recovering linac (ERL) facility for the development and application of the energy recovery technique to linear electron accelerators in the multi-turn, large current and large energy regime. The main characteristics of the powerful energy recovery linac experiment facility (PERLE) are derived from the design of the Large Hadron electron Collider, an electron beam upgrade under study for the LHC, for which it would be the key demonstrator. PERLE is thus projected as a facility to investigate efficient, high current (HC) (>10 mA) ERL operation with three re-circulation passages through newly designed SCRF cavities, at 801.58 MHz frequency, and following deceleration over another three re-circulations. In its fully equipped configuration, PERLE provides an electron beam of approximately 1 GeV energy. A physics programme possibly associated with PERLE is sketched, consisting of high precision elastic electron–proton scattering experiments, as well as photo-nuclear reactions of unprecedented intensities with up to 30 MeV photon beam energy as may be obtained using Fabry–Perot cavities. The facility has further applications as a general technology test bed that can investigate and validate novel superconducting magnets (beam induced quench tests) and superconducting RF structures (structure tests with HC beams, beam loading and transients). Besides a chapter on operation aspects, the report contains detailed considerations on the choices for the SCRF structure, optics and lattice design, solutions for arc magnets, source and injector and on further essential components. A suitable configuration derived from the here presented design concept may next be moved forward to a technical design and possibly be built by an international collaboration which is being established