Mechanical construction and installation of the ATLAS tile calorimeter

This paper summarises the mechanical construction and installation of the Tile Calorimeter for the ATLAS experiment at the Large Hadron Collider in CERN, Switzerland. The Tile Calorimeter is a sampling calorimeter using scintillator as the sensitive detector and steel as the absorber and covers the central region of the ATLAS experiment up to pseudorapidities +/- 1.7. The mechanical construction of the Tile Calorimeter occurred over a period of about 10 years beginning in 1995 with the completion of the Technical Design Report and ending in 2006 with the installation of the final module in the ATLAS cavern. During this period approximately 2600 metric tons of steel were transformed into a laminated structure to form the absorber of the sampling calorimeter. Following instrumentation and testing, which is described elsewhere, the modules were installed in the ATLAS cavern with a remarkable accuracy for a structure of this size and weight

Alignment of the low-β\beta magnets and the experiments in the LHC

For the LHC project the demands on alignment and positioning have been increased with respect to previous projects; this concerns the experiments as well as the accelerator. Alignment and continuous monitoring of the low-beta magnets in combination with new methods have become necessary. The layout of the measurement system provides a permanent follow up of the magnets, the possibility of remote alignment and has interfaces to the alignment reference network in the experimental area. The low-beta magnets define the Nominal Beam Line which is the reference for the experiments. The installation of the experiments started up to five years before the low-beta magnets arrived in the tunnel. The influence of deformation on the cavern had to be taken into account. This problem had to be considered for assembly and positioning work of the numerous detector parts

Evaluation of Streched Wire Measurement Based on Photogrammetry in the Context of CERN

Offset Measurements with respect to stretched wires are traditionally used for accelerator alignments at CERN i.e. for the SPS and the LHC, the position of the wire being measured either by an optical sensor or by a capacitive sensor. In recent years the resolution of digital cameras increased so that wires of few tenth of millimetres get visible in images at limited distances of 1-2 m. A method based on photogrammetry is able to measure the reference (wire) and the magnet fiducials simultaneously using the same measurement system. As an optical non-contact method it offers easier possibilities of automation in comparison to the manual procedure employed in the SPS and LHC so far. At the same time other uses of wire measurements like the calibration of wire chambers and detectors seem interesting. The presented photogrammetric measurements are based on the feature measurement of the commercial software from AICON 3D Systems. An evaluation has been done of the wire axis measurement without special signalisation and the magnets fiducials at distances of 1-2 m as for the LHC. For this different hardware components and parameters have been tested like lenses, light conditions or different wires. An estimation of the reachable precision is verified on a dedicated test bench and a scale 1:1 mock-up with respect to the classical offset measurements. The aim is to understand the capacities and constraints of the system that reaches precisions of few hundreds of millimetres in the tested setups

Geodetic deformation measurement and analysis of the ATLAS experimental cavern at CERN

Caverns for large physics detectors, such as the one for the Large Hadron Collider experiments, sit nearly 100 m underground and measure several tens of meters in length, width and height. The deformation of the cavern base slab over decades has a direct influence on the relative alignment of detectors with respect to the accelerator. The expected long-term movements are larger than the fine adjustment of detectors and accelerators. In this paper, the measured deformations of the ATLAS experiment's main cavern floor and lateral walls over nearly 20 years have been analysed. The measurement series have been performed in various time intervals getting down to half a year. The used measurement techniques, such as the polar method (total station and laser tracker) and precise levelling, allow to obtain sub-millimetre precision. Even if the deformations are significantly (four times) lower compared to the predictions of the civil engineering consultants at the moment of the cavern construction, the measured ones reach values up to 5.0 mm for the base slab and up to 14.7 mm for the lateral walls

Tsunami, a Unified In-Field Measurement and Alignment Software for Experiments and Accelerators at CERN Large Scale Metrology Section

TSUNAMI, The Survey Unified Notepad for Alignment and Measurement Interventions is a new software designed to replace two existing software, mainly dedicated to data acquisition and beam componentalignment using geodetic instruments. The use of different programs has been justified historically by the different needs, equipment and types of user. The two main ones have been written in obsolete VB 6.0 and VBA. Maintained for 20 years by different persons the code is now a mix of procedural and Object Oriented programming.The motivation is to create a single, modular and easy to maintain software written in a popular language for Windows applications (C#), that can be used in a “Standard mode” guided through well-defined steps or in a free “Advanced mode”.The approach is to build the application as a collection of wizards guiding the user through alignment and measurement modules, composed of more basic ones such as management and compute sub-modules.This paper presents the functionalities and the development strategy of TSUNAMI

The sensitivity limitation by the recording ADC to Laser Fiducial Line and Precision Laser Inclinometer

For metrology set-ups using a laser beam (The Laser Fiducial Line, the Precision Laser Inclinometer) the recording noise has been determined. This noise is limiting the measurement precision of the beam displacement Δx and consequently the precision Δψ of measurement of the beam inclination angle. For a 10 mm laser beam diameter the Δx = ±2.9 × 10$^{–9}$ m has been obtained. For a one-mode laser beam with a primary diameter of 10 mm and with subsequent focusing a value of Δψ = ±1.7 × 10$^{–11}$ rad has been found

The calibration of the Precision Laser Inclinometer

The calibration methods of the two-coordinate Precision Laser Inclinometer are presented. For the inclinometer studied sample of the, the calibration coefficients 630 ± 70 and 531 ± 66 μrad/V have been determined by two independent methods

The laser reference line method and its comparison to a total station in an ATLAS like configuration

A new type of measuring system, the Laser Reference Line, is proposed as a metrological tool and can be used within limited space to ensure a precise installation along an axis on the ATLAS interaction point. A simplified ATLAS like beam pipe mock-up is used for this test. The coordinates of the beam pipe are measured three times using the new method and a Total Station. The measurements agree within the measurement error of the Total Station, which indicates that the precision of the laser reference line is suitable for this specific task in the ATLAS experiment

The temperature stability of 0.005°C for the concrete floor in the CERN Transfer Tunnel #1 hosting the Precision Laser Inclinometer

To reach a sensitivity level of ~10$^{–9}$ rad for the Precision Laser Inclinometer (PLI) for the registration of the Earth surface angular oscillation in the low frequency band of [10$^{–6}$ Hz, 1 Hz] the temperature stability of the CERN Transfer Tunnel #1 has been investigated. The daily temperature variation was 0.082°C for the air and 0.005°C for the concrete floor. The last result opened the possibility to observe the Earth surface inclination caused by Moon and Sun if the PLI is thermally stabilized by the massive monolithic concrete floor of the tunnel