The probe beam linac in CTF3

JACoW web site http://accelconf.web.cern.ch/AccelConf/e06/The test facility CTF3, presently under construction at CERN within an international collaboration, is aimed at demonstrating the key feasibility issues of the multi-TeV linear collider CLIC. The objective of the probe beam linac is to "mimic" the main beam of CLIC in order to measure precisely the performances of the 30 GHz CLIC accelerating structures. In order to meet the required parameters of this 200 MeV probe beam, in terms of emittance, energy spread and bunch-length, the most advanced techniques have been considered: laser triggered photo-injector, velocity bunching, beam-loading compensation, RF pulse compression ... The final layout is described, and the selection criteria and the beam dynamics results are reviewed

Background Light in Potential Sites for the ANTARES Undersea Neutrino Telescope

The ANTARES collaboration has performed a series of {\em in situ} measurements to study the background light for a planned undersea neutrino telescope. Such background can be caused by $^{40}$K decays or by biological activity. We report on measurements at two sites in the Mediterranean Sea at depths of 2400~m and 2700~m, respectively. Three photomultiplier tubes were used to measure single counting rates and coincidence rates for pairs of tubes at various distances. The background rate is seen to consist of three components: a constant rate due to $^{40}$K decays, a continuum rate that varies on a time scale of several hours simultaneously over distances up to at least 40~m, and random bursts a few seconds long that are only correlated in time over distances of the order of a meter. A trigger requiring coincidences between nearby photomultiplier tubes should reduce the trigger rate for a neutrino telescope to a manageable level with only a small loss in efficiency.Comment: 18 pages, 8 figures, accepted for publication in Astroparticle Physic

Sedimentation and Fouling of Optical Surfaces at the ANTARES Site

ANTARES is a project leading towards the construction and deployment of a neutrino telescope in the deep Mediterranean Sea. The telescope will use an array of photomultiplier tubes to detect the Cherenkov light emitted by muons resulting from the interaction with matter of high energy neutrinos. In the vicinity of the deployment site the ANTARES collaboration has performed a series of in-situ measurements to study the change in light transmission through glass surfaces during immersions of several months. The average loss of light transmission is estimated to be only ~2% at the equator of a glass sphere one year after deployment. It decreases with increasing zenith angle, and tends to saturate with time. The transmission loss, therefore, is expected to remain small for the several year lifetime of the ANTARES detector whose optical modules are oriented downwards. The measurements were complemented by the analysis of the ^{210}Pb activity profile in sediment cores and the study of biofouling on glass plates. Despite a significant sedimentation rate at the site, in the 0.02 - 0.05 cm.yr^{-1} range, the sediments adhere loosely to the glass surfaces and can be washed off by water currents. Further, fouling by deposits of light-absorbing particulates is only significant for surfaces facing upwards.Comment: 18 pages, 14 figures (pdf), submitted to Astroparticle Physic

The ANTARES Optical Module

The ANTARES collaboration is building a deep sea neutrino telescope in the Mediterranean Sea. This detector will cover a sensitive area of typically 0.1 km-squared and will be equipped with about 1000 optical modules. Each of these optical modules consists of a large area photomultiplier and its associated electronics housed in a pressure resistant glass sphere. The design of the ANTARES optical module, which is a key element of the detector, has been finalized following extensive R & D studies and is reviewed here in detail.Comment: 26 pages, 15 figures, to be published in NI

Overview of a new test facility for the W7-X coils acceptance tests

In the frame of the W7X stellerator project, a cooperation agreement between the Max-Planck-Institut fur Plasma-physik and CEA has been set-up in order to perform the acceptance tests of all the 70 superconducting coils that compose the W7X magnet system. The main purpose of these tests is to demonstrate that each coil can work at nominal operating conditions, with enough margin to ensure the coil safety during the stellerator operations. For that purpose, CEA has built a new test facility at Saclay. This paper presents a general overview of the test facility. It is mainly composed of two large cryostats (useful space of 5 m diameter and 4.2 m height), a cryogenic source to produce super-critical helium at 4.5 K and 6 bar with a power rating of 200 W, and an electrical power supply of 25 kA. Each cryostat can contain two coils. It is then possible to cool down two coils at the same time, and to warm up two others. But only one coil can be energized at the same time. As the assembly of the facility is now nearly completed, the first cryogenic tests with the prototype coil (DEMO) have started. The first conclusions of these tests and the facility performances will also be discussed in this paper

Overview of a new test facility for the W7-X coils acceptance tests

In the frame of the W7X stellerator project, a cooperation agreement between the Max-Planck-Institut fur Plasma-physik and CEA has been set-up in order to perform the acceptance tests of all the 70 superconducting coils that compose the W7X magnet system. The main purpose of these tests is to demonstrate that each coil can work at nominal operating conditions, with enough margin to ensure the coil safety during the stellerator operations. For that purpose, CEA has built a new test facility at Saclay. This paper presents a general overview of the test facility. It is mainly composed of two large cryostats (useful space of 5 m diameter and 4.2 m height), a cryogenic source to produce super-critical helium at 4.5 K and 6 bar with a power rating of 200 W, and an electrical power supply of 25 kA. Each cryostat can contain two coils. It is then possible to cool down two coils at the same time, and to warm up two others. But only one coil can be energized at the same time. As the assembly of the facility is now nearly completed, the first cryogenic tests with the prototype coil (DEMO) have started. The first conclusions of these tests and the facility performances will also be discussed in this paper