Claude Hauviller

The L3 silicon microvertex detector

Abstract The design and construction of the silicon strip microvertex detector (SMD) of the L3 experiment at LEP are described. We present the sensors, readout electronics, data acquisition system, mechanical assembly and support, displacement monitoring systems and radiation monitoring system of the recently installed double-sided, double-layered SMD. This detector utilizes novel and sophisticated techniques for its readout.

Study of straw proportional tubes for a transition radiation detector/tracker at LHC

Abstract The most relevant properties for operation of straw proportional tubes at LHC are described. Particular attention is paid to the possibility of straw operation in a strong magnetic field and a high radiation environment.

The L3 Silicon Microvertex Detector: installation and results on 1993 performance

Abstract The status of the Silicon Microvertex Detector (SMD) and its installation into the LEP-L3 experiment are presented, highlighting novel features and sophisticated techniques. Preliminary results based on 1993 data are given and compared with Monte Carlo predictions, to understand the detector performances and its tracking capabilities.

Review: Inertial sensors for low-frequency seismic vibration measurement

The objective of this paper is to review recent advances in the sensors used to measure seismic linear vibrations at low frequencies. The main types of inertial sensors are reviewed: absolute displacement sensors, geophones, accelerometers, and seismometers. The working principle of each of them is explained, along with the general strategies to extend their bandwidth. Finally, the principle fundamental limitations of all inertial sensors are reviewed: tilt‐to‐horizontal coupling, zero‐length springs, and sources of noise.

Fully hydroformed RF cavities

Niobium-coated copper cavities are an attractive solution for RF superconducting structures. The copper parts are usually obtained by spinning and subsequent weldings. However, the defects of welded surfaces may create local coating problems. One way to minimize them is to hydroform monolithic cavities starting from OFHC (oxygen-free high-conductivity) copper tubes. Manufacturing procedures are presented. The very encouraging results obtained on multicell pieces for frequencies of 2.1 GHz and 1.5 GHz are correlated with theoretical computations. Extrapolation to the hundreds of megahertz frequency range is discussed from the technical and financial points of view. On the technical side, the main advantages of hydroforming over the present manufacturing technique are the suppression of the critical welds, a better geometrical accuracy, and better thickness repartition. On the financial side, the proposed fabrication is easier and shorter per cavity and the large initial investment is quickly amortized even in the case of a small series production.<<ETX>>

Active vibration isolation of high precision machines

This paper provides a review of active control strategies used to isolate high-precisionmachines (e.g. telescopes, particle colliders, interferometers, lithography machines or atomic force microscopes) from external disturbances. The objective of this review is to provide tools to develop the best strategy for a given application. Firstly, the main strategies are presented and compared, using single degree of freedom models. Secondly, the case of huge structures constituted of a large number of elements, like particle colliders or segmented telescopes, is considered.

Study of the electronics architecture for the mechanical stabilisation of the quadrupoles of the CLIC linear accelerator

To reach a sufficient luminosity, the transverse beam sizes and emittances in future linear particle accelerators should be reduced to the nanometer level. Mechanical stabilisation of the quadrupole magnets is of the utmost importance for this. The piezo actuators used for this purpose can also be used to make fast incremental orientation adjustments with a nanometer resolution. The main requirements for the CLIC stabilisation electronics is a robust, low noise, low delay, high accuracy and resolution, low band and radiation resistant feedback control loop. Due to the high number of controllers (about 4000) a cost optimization should also be made. Different architectures are evaluated for a magnet stabilisation prototype, including the sensors type and configuration, partition between software and hardware for control algorithms, and optimization of the ADC/DAC converters. The controllers will be distributed along the 50 km long accelerator and a communication bus should allow external control. Furthermore, one might allow for an adaptive method to increase the S/N ratio of vibration measurements by combining seismometer measurements of adjacent magnets. Finally a list of open topics, the current limitations and the plans to overcome them will be presented.

Mechanical dynamic analysis of the LHC arc cryo-magnets

The arcs of the Large Hadron Collider (LHC) will contain around 1700 main superconducting dipoles and quadrupoles. The long and heavy magnets are placed on fragile composite support posts inside a cryostat to reduce the heat in-leak to the magnets super fluid helium bath. The presence of such fragile components like the support posts, the beam position monitors and the corrector magnets make the cryo-magnets very difficult to handle and transport. Furthermore, keeping the geometry of the cryo-magnets unchanged (in the range of 0.1 mm) throughout the various transports and handling is essential for the good functioning of the future LHC. A detailed dynamic analysis was performed to determine the behavior of the cryo-magnets under all the handling and transport conditions and to choose the related optimum parameters. The results of finite element modal calculations as well as experimental modal analyses are presented and compared. The maximum accelerations admissible during transport with several types of vehicle were computed. The accelerations experienced by both types of cryo-magnets were measured during real transport with different vehicles. The dynamic deformation of the support posts in the cryo-dipole was also measured. The methodologies of these analyses and their results are reported as well as the resulting specification for the transport during the LHC installation.

An alignment method for the ATLAS end-cap TRT detector using a narrow monochromatic X-ray beam

Abstract The end-cap Transition Radiation Tracker (TRT), consisting of 36 modules (wheels), is being constructed as a part of the ATLAS Inner Detector at the CERN LHC. This paper describes a method for determining the wire positions inside the straw proportional tubes (SPT), which are the basic building blocks of the ATLAS TRT, with an accuracy of better than 10 μm . The procedure involves moving a narrow monochromatic X-ray beam across the straw and measuring the counting rate as a function of the position of the X-ray beam in the straw. To achieve this goal, a Beam Directing Device (BDD), providing the possibility to direct the X-ray beam in a chosen direction within some solid angle and supplying an accurate angular measurement system, has been constructed. The results of the wire position measurements performed using this BDD on a full-scale mechanical prototype end-cap wheel of the TRT are presented in this paper.

Design and construction of double-sided silicon ladders for the L3 microvertex detector

Abstract The techniques used in the construction of the double-sided ladders for the L3 Silicon Microvertex Detector (SMD) are presented. The detector consists of two cylindrical layers, each of 12 ladders, with double-sided silicon detectors which provide r-phi and z coordinates measurements. This description includes ladder mechanical design and the assembly. A novel solution to readout the z-coordinates is presented. It optimizes very effectively the removal of heat generated by the readout electronics and minimizes the radiation length in the central region. Some results from the survey of the individual ladders are also discussed.