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The central feature of the CMS Link alignment system is a network of Amorphous Silicon Position Detectors distributed throughout the muon spectrometer that are connected by multiple laser lines. The data collected during the years from 2008 to 2015 is presented confirming an outstanding performance of the photo sensors during more than seven years of operation. Details of the photo sensor readout of the laser signals are presented. The mechanical motions of the CMS detector are monitored using these photosensors and good agreement with distance sensors is obtained. [ABSTRACT FROM AUTHOR]

Magnet Cycles and Stability Periods of the CMS Experiment are studied with the Alignment Link System data recorded along the 2008–2013 years of operation. The motions of the mechanical structures due to the magnetic field forces are studied and the mechanical stability of the detector during the physics data taking periods is verified. [ABSTRACT FROM AUTHOR]

Abstract: Gamos is a software system for Geant4-based simulation. It comprises a framework, a set of components providing functionality to simulation applications on top of the Geant4 toolkit, and a collection of ready-made applications. It allows to perform Geant4-based simulations using a scripting language, without requiring the writing of C++ code. Moreover, Gamos design allows the extension of the existing functionality through user-supplied C++ classes. The main characteristics of Gamos and its embedded functionality are described. [Copyright &y& Elsevier]

Abstract: A study of the photo-response behaviour of carbon-doped hydrogenated amorphous silicon photo-detectors over 2800h of continuous illumination with white light is presented. Both direct and inverse Staebler–Wronski effects are observed in the data. [Copyright &y& Elsevier]

Abstract: A study of the time required for the CMS detector to reach structural equilibrium once the magnetic field is ramped to its operational value of 3.8T is presented. In addition, the results from a stability monitoring at 3.8T over an eight-month period are given. [Copyright &y& Elsevier]

Abstract: Compton camera systems can be used to image sources of gamma radiation in a variety of applications such as nuclear medicine, homeland security and nuclear decommissioning. To locate gamma-ray sources, a Compton camera employs electronic collimation, utilising Compton kinematics to reconstruct the paths of gamma rays which interact within the detectors. The main benefit of this technique is the ability to accurately identify and locate sources of gamma radiation within a wide field of view, vastly improving the efficiency and specificity over existing devices. Potential advantages of this imaging technique, along with advances in detector technology, have brought about a rapidly expanding area of research into the optimisation of Compton camera systems, which relies on significant input from Monte-Carlo simulations. In this paper, the functionality of a Compton camera application that has been integrated into GAMOS, the GEANT4-based Architecture for Medicine-Oriented Simulations, is described. The application simplifies the use of GEANT4 for Monte-Carlo investigations by employing a script based language and plug-in technology. To demonstrate the use of the Compton camera application, simulated data have been generated using the GAMOS application and acquired through experiment for a preliminary validation, using a Compton camera configured with double sided high purity germanium strip detectors. Energy spectra and reconstructed images for the data sets are presented. [Copyright &y& Elsevier]

Abstract: This document presents an application of the new generation of amorphous silicon position detecting (ASPD) sensors to multipoint alignment. Twelve units are monitored along a 20m long laser beam, where the light path is deflected by 90° using a pentaprism. [Copyright &y& Elsevier]

Abstract: We present the measured performance of a new generation of large sensitive area (28×28mm2) semitransparent amorphous silicon position detector sensors. More than 100 units have been characterized. They show a very high performance. To illustrate a multipoint application, we present results from the monitoring of five sensors placed in a 5.5-m-long light path. [Copyright &y& Elsevier]

The 40MHz bunched muon beam set up at CERN was used in May 2003 to make a full test of the drift tubes local muon trigger. The main goal of the test was to prove that the integration of the various devices located on a muon chamber was adequately done both on the hardware and software side of the system. Furthermore the test provided complete information about the general performance of the trigger algorithms in terms of efficiency and noise. Data were collected with the default configuration of the trigger devices and with several alternative configurations at various angles of incidence of the beam. Tests on noise suppression and di-muon trigger capability were performed. [Copyright &y& Elsevier]

A first global test of the CMS Alignment System was performed at the I4 hall of the CERN ISR tunnel. Positions of the network, reproducing a set of points in the CMS detector monitored by the Link System, were reconstructed and compared to survey measurements. Spatial and angular reconstruction precisions reached in the present experimental set-up are already close to the CMS requirements. [Copyright &y& Elsevier]

Abstract: The photo-response behaviour of Amorphous Silicon Position Detectors (ASPDs) under prolonged illumination with a 681nm diode–laser and a 633nm He–Ne laser is presented. Both direct and inverse Staebler–Wronski effects are observed. [Copyright &y& Elsevier]

Abstract: We present observations of the electrolytic clinometers behaviour inside magnetic field environments introducing phenomenological expressions to account for the measured output voltage variations as functions of field gradients and field strengths. [Copyright &y& Elsevier]

We have studied each of the physics options that Geant4 offers to simulate an X-ray radiotherapy treatment with the aim of obtaining those that provide the best possible match to the experimental data of dose profiles and at the same time reduce the CPU time. The procedure has been repeated for two linac setups: an ELEKTA Versa HD with an Agility Multileaf Collimator using two nominal energies, 6 MV and 10 MV, both without flattening filter. After combining the results with those of a previous similar study of a 6 MV VARIAN Clinac 2100 C/D linac with flattening filter, we can propose a set of optimized Geant4 physics options of general use for radiotherapy simulation. Together with this, we have optimized the CPU time using several of the optimization techniques that GAMOS offers, reaching a reduction of several hundred times for each setup. • Precise adjustment with GAMOS/Geant4 of three gamma radiotherapy setups. • Optimization of Geant4 electromagnetic physics for three gamma radiotherapy setups. • O(100) increase in CPU time with several optimization techniques. • Proposal of physics and CPU time optimized options for Geant4 radiotherapy simulation. [ABSTRACT FROM AUTHOR]

A novel, accurate and inexpensive device for measuring short distances is presented. Data taken with a very simple prototype are presented and its performance is extracted. [Copyright &y& Elsevier]

Modern high-energy physics experiments require tracking detectors to provide high precision under difficult working conditions (high magnetic field, gravity loads and temperature gradients). This is the reason why several of them are deciding to implement optical alignment systems to monitor the displacement of tracking elements in operation. To simulate and reconstruct optical alignment systems a general purpose software, named COCOA, has been developed, using the object oriented paradigm and software engineering techniques. Thanks to the big flexibility in its design, COCOA is able to reconstruct any optical system made of a combination of the following objects: laser, x-hair laser, incoherent source—pinhole, lens, mirror, plate splitter, cube splitter, optical square, rhomboid prism, 2D sensor, 1D sensor, distance-meter, tilt-meter, user-defined. COCOA was designed to satisfy the requirements of the CMS alignment system, which has several thousands of components. Sparse matrix techniques had been investigated for solving non-linear least squares fits with such a big number of parameters. The soundness of COCOA has already been stressed in the reconstruction of the data of a full simulation of a quarter plane of the CMS muon alignment system, which implied solving a system of 900 equations with 850 unknown parameters. Full simulation of the whole CMS alignment system, with over 30,000 parameters, is quite advanced. The integration of COCOA in the CMS software framework is also under progress. [Copyright &y& Elsevier]

Currently CMS event simulation is based on GEANT3 while the detector description is built from different sources for simulation and reconstruction. A new simulation framework based on GEANT4 is under development. A full description of the detector is available, and the tuning of the GEANT4 performance and the checking of the ability of the physics processes to describe the detector response is ongoing. Its integration on the CMS mass production system and GRID is also currently under development. The Detector Description Database project aims at providing a common source of information for Simulation, Reconstruction, Analysis, and Visualisation, while allowing for different representations as well as specific information for each application. A functional prototype, based on XML, is already released. Also examples of the integration of DDD in the GEANT4 simulation and in the reconstruction applications are provided. [Copyright &y& Elsevier]

In October 2001 the first produced CMS Barrel Drift Tube (DT) Muon Chamber was tested at the CERN Gamma Irradiation Facility (GIF) using a muon beam. A Resistive Plate Chamber (RPC) was attached to the top of the DT chamber, and, for the first time, both detectors were operated coupled together. The performance of the DT chamber was studied for several operating conditions, and for gamma rates similar to the ones expected at LHC. In this paper we present the data analysis; the results are considered fully satisfactory. [Copyright &y& Elsevier]

G eant 4 is a software toolkit for the simulation of the passage of particles through matter. It is used by a large number of experiments and projects in a variety of application domains, including high energy physics, astrophysics and space science, medical physics and radiation protection. Over the past several years, major changes have been made to the toolkit in order to accommodate the needs of these user communities, and to efficiently exploit the growth of computing power made available by advances in technology. The adaptation of G eant 4 to multithreading, advances in physics, detector modeling and visualization, extensions to the toolkit, including biasing and reverse Monte Carlo, and tools for physics and release validation are discussed here. [ABSTRACT FROM AUTHOR]

Abstract: We describe the construction process of large-area high-performance transparent amorphous silicon position detecting sensors. Details about the characteristics of the associated local electronic board (LEB), specially designed for these sensors, are given. In addition we report on the performance of a multipoint alignment monitoring application of 12 sensors in a 13m long light path. [Copyright &y& Elsevier]

Abstract: This document describes results obtained from the Link alignment system data recorded during the Compact Muon Solenoid (CMS) Magnet Test. A brief description of the system is followed by a discussion of the detected relative displacements (from micrometres to centimetres) between detector elements and rotations of detector structures (from microradians to milliradians). Observed displacements are studied as functions of the magnetic field intensity. In addition, the reconstructed positions of active element sensors are compared to their positions as measured by photogrammetry and the reconstructed motions due to the magnetic field strength are described. [Copyright &y& Elsevier]

Abstract: We present the measured performance of a new generation of semitransparent amorphous silicon position detectors. They have a large sensitive area (30×30mm2) and show good properties such as a high response (about 20mA/W), an intrinsic position resolution better than 3μm, a spatial-point reconstruction precision better than 10μm, deflection angles smaller than 10μrad and a transmission power in the visible and NIR higher than 70%. [Copyright &y& Elsevier]

Abstract: A measurement of the optical absorption, induced by photon irradiation up to a dose of 0.9MGy, in Nufern silica core single-mode optical fibres is presented. In addition, the fibres were irradiated with neutrons, up to a total fluence of 2×1014 cm−2 and the induced optical absorption was evaluated for four different wavelengths: 630, 670, 681 and 785nm. [Copyright &y& Elsevier]

Abstract: Optical absorption induced by photon radiation was evaluated for several commercial pure silica core, single mode, optical fibres. The study was performed for three different wavelengths: 630, 670 and 785nm. We have identified a fibre whose induced transmission loss stays below 1dB/m after 300kGy gamma-ray irradiation. [Copyright &y& Elsevier]

We report on irradiation studies done to a sample of high-precision electrolytic tiltmeters with gamma-rays, up to a maximum dose of 150kGy, and neutrons, up to a maximum fluence of 1.5×1014cm-2. The effect of the irradiation on their performance is discussed. [Copyright &y& Elsevier]

Geant4 is a toolkit for simulating the passage of particles through matter. It includes a complete range of functionality including tracking, geometry, physics models and hits. The physics processes offered cover a comprehensive range, including electromagnetic, hadronic and optical processes, a large set of long-lived particles, materials and elements, over a wide energy range starting, in some cases, from 250 eV and extending in others to the TeV energy range. It has been designed and constructed to expose the physics models utilised, to handle complex geometries, and to enable its easy adaptation for optimal use in different sets of applications. The toolkit is the result of a worldwide collaboration of physicists and software engineers. It has been created exploiting software engineering and object-oriented technology and implemented in the C++ programming language. It has been used in applications in particle physics, nuclear physics, accelerator design, space engineering and medical physics. [Copyright &y& Elsevier]

We report on the study made on commercial CMOS image sensors in order to determine their feasibility for light beam position reconstruction. Measurements of the intrinsic position resolution, sensor photoresponse and uniformity were done. The effect of eventual background illumination was evaluated. The precision on the spatial point reconstruction was determined from linearity measurements. First results on gamma-ray radiation tolerance are presented. [Copyright &y& Elsevier]

LHC, working at the expected nominal luminosity, will induce an extremely high irradiation in the CMS experiment. The CMS alignment system uses optical elements to build the laser beams paths. Optical properties of basic components such as glasses and glues may result affected and their transmission power may degrade significantly. We have proceeded to a first test of various glasses and glues and identified some of them that can stand up to 150 kGy of gamma-rays plus 5×1014 neutrons/cm2. [Copyright &y& Elsevier]