M. Ziolkowski

The ATLAS Silicon Pixel Sensors

Prototype sensors for the ATLAS silicon pixel detector have been developed. The design of the sensors is guided by the need to operate them in the severe LHC radiation environment at up to several hundred volts while maintaining a good signal-to-noise ratio, small cell size, and minimal multiple scattering. The ability to be operated under full bias for electrical characterization prior to attachment of the readout integrated circuit electronics is also desired.

A measurement of Lorentz angle and spatial resolution of radiation hard silicon pixel sensors

Silicon pixel sensors developed by the ATLAS collaboration to meet LHC requirements and to withstand hadronic irradiation to fluences of up to

Electrical characteristics of silicon pixel detectors

10^{15} n_eq/cm^{2}

Time-resolved x-ray diffraction study of the piezoelectric crystal response to a fast change of an applied electric field

have been evaluated using a test beam facility at CERN providing a magnetic field. The Lorentz angle was measured and found to alter from 9.0 deg. before irradiation, when the detectors operated at 150 V bias at B=1.48 T, to 3.1 deg after irradiation and operating at 600 V bias at 1.01 T. In addition to the effect due to magnetic field variation, this change is explained by the variation of the electric field inside the detectors arising from the different bias conditions. The depletion depths of irradiated sensors at various bias voltages were also measured. At 600 V bias 280 micron thick sensors depleted to ~200 micron after irradiation at the design fluence of 1 10^{15} 1 MeV n_eq/cm2 and were almost fully depleted at a fluence of 0.5 * 10^{15} 1 MeV n_eq/cm2. The spatial resolution was measured for angles of incidence between 0 deg and 30 deg. The optimal value was found to be better than 5.3 micron before irradiation and 7.4 micron after irradiation.

The drift chamber electronics and readout for the NA48 experiment at the CERN SPS

Prototype sensors for the ATLAS silicon pixel detector have been electrically characterized. The current and voltage characteristics, charge-collection efficiencies, and resolutions have been examined. Devices were fabricated on oxygenated and standard detector-grade silicon wafers. Results from prototypes which examine p-stop and standard and moderated p-spray isolation are presented for a variety of geometrical options. Some of the comparisons relate unirradiated sensors with those that have received fluences relevant to LHC operation.

Study of the reaction pp → ΛΛ below 6 MeV excess energy

Time-resolved measurements of the macroscopic and microscopic strains in piezoelectric crystals were performed with a novel data acquisition technique implemented on the basis of a field programmed gate array system. Both types of strains were induced in a crystal by an applied periodic high voltage with fast (within 100 ns) switches between opposite polarities and measured simultaneously by respective angular shifts and integrated intensities of synchrotron x-ray diffraction rocking curves. The time resolution achieved with the developed data acquisition system was 100 ns. The paper demonstrates the particular application of this technique for the investigations of time dynamics of lattice constants and atomic positions in a unit cell for piezoelectric BiB3O6 and Li2SO4⋅H2O crystals. It has been found that 100 ns fast rising time of an applied external electric field induces oscillations of the crystal lattice constants, visible as oscillations of Bragg peak angular positions. At the same time, these osc...

Measurement of the {ital {bar p}}{ital p}{r_arrow}{bar {Lambda}}{Lambda} and {ital {bar p}}{ital p}{r_arrow}{bar {Sigma}}{sup 0}{Lambda}+c.c. reactions at 1.726 and 1.771 GeV/{ital c}

Abstract A drift chamber readout system for a bout 8000 channels with continuous sensitivity, i.e. concurrent data recording and readout, is described. Drift times are measured in bins of 1.56 ns with respect to a continuously running 40 MHz clock. The clock interval of 25 ns is divided into 16 bins by means of a 16-element delay chain. The length of this chain is linked to the clock interval by a phase-locked loop. An ASIC chip was developed to perform time measurements and data storage for 16 channels. In an asynchronous readout of this chip, data are tranferred to intermediate buffers, for use in a first-level trigger and eventual final readout. The design of the electronics is described and results from data-taking runs are presented.

Design, production, and reliability of the new ATLAS pixel opto-boards

Abstract The reaction p p → Λ Λ → p π + pπ − is studied in the experiment PS185 at the CERN Low Energy Antiproton Ring (LEAR). A precise measurement of the excitation function in the immediate threshold region below 6 MeV excess energy was achieved. The total cross section shows an unexpected behaviour around 1 MeV excess energy.

Combining high time and angular resolutions: time‐resolved X‐ray powder diffraction using a multi‐channel analyser detector

Interest in the production of hyperon-antihyperon pairs following antiproton-proton annihilation stems largely from attempts to understand the nature of flavor production. To date the major focus of both the experimental and the theoretical effort has been on the p¯p??¯? reaction. In this paper, we present data on the complementary channels p¯p?S¯ 0? and p¯p??¯S0. Events from the kinematically similar p¯p??¯? reaction were obtained in parallel. The procedure to distinguish these three separate reactions is described and results for all channels are presented. These include the total and differential cross sections, hyperon polarizations, and spin correlation coefficients. Data were obtained at incident antiproton lab momenta of 1.726 and 1.771 GeV/c which correspond to excess kinetic energies in the p¯p??¯S0+c.c. reaction of 26 and 40 MeV, respectively, above threshold. Comparisons are made to earlier work at similar excess energies in the p¯p??¯? channel. The low-energy regime has been highlighted in this experiment to reduce the complexity in the theoretical analysis.

A scalable, fast, and multichannel arbitrary waveform generator

New fiber optical transceivers, opto-boards, were designed and produced to replace the first generation opto-boards installed in the ATLAS pixel detector and for the new pixel layer, the insertable barrel layer (IBL). Each opto-board contains one 12-channel PIN array and two 12-channel VCSEL arrays along with associated receiver and driver ASICs. The new opto-board design benefits from the production and operational experience of the first generation opto-boards and contains several improvements. The new opto-boards have been successfully installed. Additionally, a set of the new opto-boards have been subjected to an accelerated lifetime experiment at 85 C and 85% relative humidity for over 1,000 hours. No failures were observed. We are cautiously optimistic that the new opto-boards will survive until the shutdown for the detector upgrade for the high-luminosity Large Hadron Collider (HL-LHC).