O. Napoly - IEEE Xplore Author Profile

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With the local chromaticity correction scheme [1], the luminosity optimisation of the e+e- International Linear Collider (ILC) beam delivery system is challenging. It is a long and complex process and its automation becomes a necessity. It was recently shown that it is possible to employ a simplex minimization method of the beam sizes at the Interaction Point (IP) [2], without adding any other con...Show More
The beam delivery system for the linear collider focuses beams to nanometer sizes at its interaction point, collimates the beam halo to provide acceptable background in the detector and has a provision for state-of-the art beam instrumentation in order to reach the ILCs physics goals. This paper describes the design details and status of the baseline configuration considered for the reference desi...Show More
It is well known that an electron beam excites higher order modes (HOMs) as it passes through an accelerating cavity. The properties of the excited signal depend not only on the cavity geometry, but on the charge and trajectory of the beam. It is, therefore, possible to use these signals as a monitor of the beam's position. Electronics were installed on all forty cavities present in the FLASH lina...Show More
An interaction region with head-on collisions is considered as an alternative to the baseline ILC configuration. Progress in the final focus optics design includes engineered large bore superconducting final doublet magnets and their 3D magnetic integration in the detector solenoids. Progress on the beam separation optics is based on technical designs of electrostatic separator and special extract...Show More
An interaction region with head-on collisions is being developed for the ILC as an alternative to the base line 14 mrad crossing angle design, motivated by simpler beam manipulations upstream of the interaction point (IP) and a more favourable configuration for the detector and physics analysis. The design of the post-collision beam line in this scheme involves however a number of technological ch...Show More
Each nine cell superconducting (SC) accelerator cavity in the TESLA Test Facility (TTF) at DESY [1] has two higher order mode (HOM) couplers that efficiently remove the HOM power [2]. They can also provide useful diagnostic signals. The most interesting modes are in the first 2 cavity dipole passbands. They are easy to identify and their amplitude depends linearly on the beam offset from the cavit...Show More
To reach design luminosity, the International Linear Collider (ILC) must be able to create and reliably maintain nanometer size beams. The ATF damping ring is the unique facility where ILC emittances are possible. In this paper we present and evaluate the proposal to create a final focus facility at the ATF which, using compact final focus optics and an ILC-like bunch train, would be capable of ac...Show More
CARE, an ambitious and coordinated programme of accelerator research and developments oriented towards high energy physics projects, has been launched in January 2004 by the main European laboratories and the European Commission. This project aims at improving existing infrastructures dedicated to future projects such as linear colliders, upgrades of hadron colliders and high intensity proton driv...Show More
This report describes studies performed in the framework of the Collimation Task Force organized to support the work of the second International Linear Collider Technical Review Committee. The post-linac beam-collimation systems in the TESLA, JLC/NLC and CLIC linear-collider designs are compared using the same computer code under the same assumptions. Their performance is quantified in terms of be...Show More
We study the main implications of increasing the last drift length l* from 3 to 5 meters, in the TESLA interaction region: namely, the design of a new final focus system with a better chromatic correction, the extraction of the beam after the collision through the opposite doublet, and the new collimation requirements.Show More
This paper reports on recent beam measurements of higher order modes in the TESLA Test Facility (TTF) accelerating modules. Using bunch trains of about 0.5 ms with 54 MHz bunch repetition and up to 90% modulated intensity, transverse higher order modes are resonantly excited when the beam is offset and their frequency on resonance with the modulation frequency. With this method, the trapped modes ...Show More
The technical design report (TDR) of the TESLA superconducting linear collider with an integrated X-ray FEL facility, has been published in the spring of 2001 by an international collaboration. It includes a description of the high energy physics programme, a proposal for the detector, and the collider design relying on the technical results from the TESLA Test Facility (TTF). We review the result...Show More
The vertical beam profile distortions induced by wakefield effects in linear colliders (the so-called "banana effect") generate a beam-beam instability at the collision point when the vertical disruption parameter is large. We illustrate this effect in the case of the TESLA linear collider project. We specify the tolerance on the associated emittance growth, which translates into tolerances on inj...Show More
A beam experiment has been conducted on the first accelerating module of the TESLA Test Facility (TTF) to investigate transverse higher order modes (HOM) in the superconducting cavities. By injecting the beam with a transverse offset and by modulating the intensity of the 216 MHz bunch train with a tunable frequency in the 0-108 MHz range, transverse HOMs can be excited resonantly. On a resonance ...Show More
We describe a generalized method to compute wake potentials created in axisymmetric structures. It relies on expressing the wake potentials, of any multipole order, as integrals over the e.m. fields along an arbitrary one-dimensional contour spanning the structure longitudinally. For perfectly conducting structures, the integration along the axis can then be replaced by choosing a contour beginnin...Show More
An alternative set of beam parameters at the IP is presented for TESLA. Thanks to a larger aspect ratio, it allows a substantial reduction of the beamstrahlung effect. The optics of a final focus system based on the standard sextupole correction of the chromatic aberrations is described. The particularity of this system is, along with the 3 m long last drift space, the large aperture of the last q...Show More
The final focus system has been adapted to the revised parameter list for CLIC (CERN Linear Collider). It is expected that lower emittances are obtainable in the damping rings and the blowup in the main linac can be contained to 25%. In that case the luminosity would no longer be limited by synchrotron radiation in the final quadrupoles, and a luminosity above 10/sup 33/ cm/sup -2/ s/sup -1/ could...Show More