[en] We have presented the conceptual principle of the CMS Link Alignment System and the details of the experimental set-up, installed at the 14 ISR hall, at CERN to validate the design. The experimental set-up reproduces one half of a Φ CMS alignment plane with the final dimensions and covers a surface of 20x17 m². We have described the different instrumentation present in the system (including calibration procedures and results), the DAS and the reconstruction software. The set-up includes a network of reference points that are accurately measured by levelling and photogrammetry survey techniques. Link System measurements are compared with the survey data. Results from this first global test performed with all the link elements running validates the conceptual optomechanical design. Spatial and angular reconstruction precisions reached in the present experimental set-up are already close to the CMS requirements. (author)

[en] 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

[en] Semitransparent amorphous silicon sensors have been proposed as the 2D positioning sensors for the link system of the CMS alignment. An in-depth study of the actual performance of these sensors is here reported

[en] 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

[en] Semitransparent amorphous silicon sensors are the key elements for laser light 2D position reconstruction in the CMS alignment system. Some of them have to work in very extreme radiation environment. We have irradiated with gammas, up to 10 MRad, two different sensors and measured their change in performance

[en] A new, accurate and un expensive device for measuring short distances, intended for monitoring in LHC experiments is presented. Data taken with a very simple prototype are shown and performance is extracted. (Author) 4 refs

[en] 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

[en] In this note we present first tests done with the tiltmeters proposed as the key elements of the Laser Level systems to be used in the CMS alignment system. The response of the sensors under moderated longitudinal and transverse tilts is studied and intrinsic performance is extracted. (author)

[en] The general specifications of the new, high-performance large-size, amorphous silicon position detector (ASPD), sensors and their measured properties in a sample of more than 100 units, are presented. Results from the monitoring of five in-line sensors in a 5-m-long laser beam path are given.

[en] A preliminary full size test of a simplified version containing some relevant elements of the CMS (compact muon solenoid) Link Alignment System has been installed in an experimental area of the ISR (interaction storage ring) tunnel at CERN. Previously a calibration bench was prepared with standard precise survey methods. The environmental conditions, temperature, atmospheric pressure and relative humidity in the hall were controlled revealing quite stable conditions all along the tests period. The stability measurements done under these conditions show that the light spot on sensors located at about 6 m from the light source are smaller than 5 μm, which satisfies the requirements. Induced changes in the environmental conditions have different effects. Air flows degrades significantly the spatial resolution (∼5μm) but the background due to the environmental light does not degrades the resolution in position reconstruction. A geodesic network defines a reference system common to all opto-mechanical components and can be used to do absolute measurements of the angle between the two light beams coming out from the splitter. The accuracy in the reconstruction of angles with the help of the geodesic network depends on the errors in the network definition. These errors propagate with a smaller or larger strength depending on the distances between the network points. In our tests, the accuracy in the angle reconstruction is 14 μrad when using 4 in and 5.9 m long arms and 17 μrad for 4 m and 2.9 m arms. We found a precision 4 μrad in the angular reconstruction. (authors)