Table of contents

A Kalman Filter alignment algorithm has been applied to cosmic-ray data. We discuss the alignment algorithm and an experiment-independent implementation including outlier rejection and treatment of weakly determined parameters. Using this implementation, the algorithm has been applied to data recorded with one CMS silicon tracker endcap. Results are compared to both photogrammetry measurements and data obtained from a dedicated hardware alignment system, and good agreement is observed.

A precise and fast Fabry-Perot cavity polarimeter, installed in the HERA tunnel in the summer of 2003, was used to measure the longitudinal polarisation of the lepton beam. A complete theoretical model has been developed in order to control at the per mill level the degree of circular polarisation of the laser beam. The transport of this quantity within the whole optical setup has also been performed and controlled at the same level of precision. This is the first time that such a precision is achieved in the difficult, hostile and noisy environment of a particle collider.

A Fabry-Perot cavity polarimeter, installed in 2003 at HERA for the second phase of its operation, is described. The cavity polarimeter was designed to measure the longitudinal polarisation of the HERA electron beam with high precision for each electron bunch spaced with a time interval of 96 ns. Within the cavity the laser intensity was routinely enhanced up to a few kW from its original value of 0.7 W in a stable and controllable way. By interacting such a high intensity laser beam with the HERA electron beam it is possible to measure its polarisation with a relative statistical precision of 2% per bunch per minute. Detailed systematic studies have also been performed resulting in a systematic uncertainty of 1%.

Langmuir probes are used to study the expansion of a laser plasma into a large (17m long × 0.6m diameter) ambient magnetized cylindrical plasma. The expansion is either perpendicular or at 45° to the 300-600 G axial background field. One probe geometry allows data collection close to the ablation surface, inside a diamagnetic bubble formed during the laser plasma expansion. We measure expansion velocities of this diamagnetic cavity and the bulk laser plasma. Additionally, we detect fast ions along the axis of the ambient plasma column when the laser plasma expansion is directed at 45° to the background field. We obtain the fast ion velocity distribution by comparing the measured ion gyroradii to those predicted by Monte Carlo simulations of the ion trajectories in an external magnetic field. Experimental measurement of fast ion velocity distributions can help tune the experimental parameters that are required to drive collisionless shock waves through a laboratory plasma.

A dedicated test of the effects of Nitrogen contamination in liquid Argon has been performed at the INFN-Gran Sasso Laboratory (LNGS, Italy) within the WArP R&D program. A detector has been designed and assembled for this specific task and connected to a system for the injection of controlled amounts of gaseous Nitrogen into the liquid Argon. The purpose of the test is to detect the reduction of the Ar scintillation light emission as a function of the amount of the Nitrogen contaminant injected in the Argon volume. A wide concentration range, spanning from ∼ 10⁻¹ ppm up to ∼ 10³ ppm, has been explored. Measurements have been done with electrons in the energy range of minimum ionizing particles (γ-conversion from radioactive sources). Source spectra at different Nitrogen contaminations are analyzed, showing sensitive reduction of the scintillation yield at increasing concentrations. Direct PMT signal acquisition exploiting high time resolution by fast waveform recording allowed high precision extraction of the main characteristics of the scintillation light emission in contaminated LAr. In particular, the decreasing behavior in lifetime and relative amplitude of the slow component is found to be appreciable starting from (1 ppm) of Nitrogen concentrations. The rate constant of the quenching process induced by Nitrogen in liquid Ar has been found to be k_Q(N₂) = 0.11 ± 0.01 μs⁻¹ppm⁻¹, consistent with a previous measurement of this quantity but with significant improvement in precision. On the other hand, no evidence for absorption by N₂ impurities has been found up to the higher concentrations here explored.

The PMTs of the CMS Hadron Forward calorimeter were found to generate a large size signal when their windows were traversed by energetic charged particles. This signal, which is due to Čerenkov light production at the PMT window, could interfere with the calorimeter signal and mislead the measurements. In order to find a viable solution to this problem, the response of four different types of PMTs to muons traversing their windows at different orientations is measured at the H2 beam-line at CERN. Certain kinds of PMTs with thinner windows show significantly lower response to direct muon incidence. For the four anode PMT, a simple and powerful algorithm to identify such events and recover the PMT signal using the signals of the quadrants without window hits is also presented. For the measurement of PMT responses to Čerenkov light, the Hadron Forward calorimeter signal was mimicked by two different setups in electron beams and the PMT performances were compared with each other. Superior performance of particular PMTs was observed.

This paper presents the test results of a single element of a Cesium Iodide CsI(TI) crystal calorimeter matrix using proton beam energies of 35 MeV, 100 MeV and 200 MeV. The detector element was designed to comply with the demands of high energy resolution of a few percent and with a dynamic range of two orders of magnitude under a counting rate of 10 kHz per channel. The energy range investigated in the current work was an order of magnitude less than the design capability. The readout was provided by a 28 × 28 mm² Hamamatsu S3584-08 photodiode coupled with the crystal through a silicone optical interface. A charge-sensitive preamplifier with low noise at high photodiode capacitance was chosen. We also report on the data acquired during crystal calibration with cosmic rays, and give a description of our data acquisition (DAQ) system.

Measurements are shown of GeV pions and muons in two 300μm thick, Si Medipix pixel detector assemblies that are stacked on top of each other, with a 25μm thick brass foil in between. In such a radiation imaging semiconductor matrix with a large number of pixels along the particle trail, one can determine local space vectors for the particle trajectory instead of points. This improves pattern recognition and track reconstruction, especially in a crowded environment. Stacking of sensor planes is essential for resolving directional ambiguities. Signal charge sharing can be employed for measuring positions with submicron precision. In the measurements one notices accompanying 'delta' electrons that emerge outside the particle trail, far beyond the boundaries of the 55μm pixel cells. The frequency of such corrupted position measurements is ∼ one per 2.5mm of traversed Si.

Designs of stable, low-mass support and cooling structures for intelligent trackers should take into account the additional power dissipation associated with local trigger generation, high speed communications, and power delivery, as well as the spatial distributions of heat sources. For many applications, a modular design can alleviate cooling and support issues and allow parallel fabrication at multiple locations. A proposed design for CMS phase 2 upgrade track trigger formation will be used to illustrate the extent to which design requirements are specific to intelligent tracking, ways in which those design requirements might be met, and implications for local tracker geometry, material selection, structural stability, and the material budget.

The development of deep N-Well (DNW) CMOS active pixel sensors was driven by the ambitious goal of designing a monolithic device with similar functionalities as in hybrid pixel readout chips, such as pixel-level sparsification and time stamping. The implementation of the DNW MAPS concept in a 3D vertical integration process naturally leads the designer towards putting more intelligence in the chip and in the pixels themselves, achieving novel device structures based on the interconnection of two or more layers fabricated in the same technology. These devices are read out with a data-push scheme that makes it possible to use pixel data for the generation of a flexible level 1 track trigger, based on associative memories, with short latency and high efficiency. This paper gives an update of the present status of DNW MAPS design in both 2D and 3D versions, and presents a discussion of the architectures that are being devised for the Layer 0 of the SuperB Silicon Vertex Tracker.

The FF-LYNX protocol provides an innovative solution for the integrated distribution of Timing, Trigger and Control signals and the data readout in future High Energy Physics experiments. Transmitter and receiver interfaces implementing the FF-LYNX protocol have been simulated with a high-level simulator and in an FPGA based emulator. The design of the interfaces in a commercial CMOS technology as radiation tolerant and low power modules is ongoing and the submission of a test circuit is foreseen in fall 2010. The key features of the protocol are described in this paper as well as its possible application for the transmission from Silicon Trackers to trigger processors with short and constant latency of data to be used for the L1 trigger generation.