B. Lofstedt

Performance of the ALEPH Time Projection Chamber

Abstract The performance of the ALEPH Time Projection Chamber (TPC) has been studied using data taken during the LEP running periods in 1989 and 1990. After correction of residual distortions and optimisation of coordinate reconstruction algorithms, single coordinate resolutions of 173 μm in the azimuthal and 740 μm in the longitudinal direction are achieved. This results in a momentum resolution for the TPC of Δp / p 2 = 1.2 × 10 −3 (GeV/ c ) −1 . In combination with the ALEPH Inner Tracking Chamber (ITC), a total momentum resolution of Δp / p 2 = 0.8 × 10 −3 (GeV/ c ) −1 is obtained. With respect to particle identification, the detector achieves a resolution of 4.4% for the measurement of the ionisation energy loss.

SICAL — a high precision silicon-tungsten luminosity calorimeter for ALEPH

Abstract The design, construction and performance of a silicon-tungsten electromagnetic calorimeter built to achieve an experimental luminosity measurement precision at LEP≤0.1% is described. The detector uses homogeneous construction to give full azimuthal acceptance for Bhabha scattering over polar angles from 24 to 58 mrad. Detailed information concerning shower development is obtained from zero-suppressed readout of the 12288 pads of the detector. Trigger decisions are generated from a rapid flash-ADC system using programmable gate arrays.

FERMI: a digital Front End and Readout MIcrosystem for high resolution calorimetry

We present a digital solution for the front-end electronics of high resolution calorimeters at future colliders. It is based on analogue signal compression, high speed A/D converters, a fully programmable pipeline and a digital signal processing (DSP) chain with local intelligence and system supervision. This digital solution is aimed at providing maximal front-end processing power by performing waveform analysis using DSP methods. For the system integration of the multichannel device a multi-chip, silicon-on-silicon multi-chip module (MCM) has been adopted. This solution allows a high level of integration of complex analogue and digital functions, with excellent flexibility in mixing technologies for the different functional blocks. This type of multichip integration provides a high degree of reliability and programmability at both the function and the system level, with the additional possibility of customising the microsystem to detector-specific requirements. For enhanced reliability in high radiation environments, fault tolerance strategies, i.e. redundancy, reconfigurability, majority voting and coding for error detection and correction, are integrated into the design. (Less)

A digital front-end and readout microsystem for calorimetry at LHC

Abstract A digital solution to the front-end electronics for calorimetric detectors at future supercolliders is presented. The solution is based on high speed A D converters, a fully programmable pipeline/digital filter chain and local intelligence. Questions of error correction, fault-tolerance and system redundancy are also being considered. A system integration of a multichannel device in a multichip, Silicon-on-Silicon Microsystem hybrid, is used. This solution allows a new level of integration of complex analogue and digital functions, with an excellent flexibility in mixing technologies for the different functional blocks. It also allows a high degree of programmability at both the function and the system level, and offers the possibility of customising the microsystem with detector-specific functions.

Optimized digital feature extraction in the FERMI microsystem

Abstract We describe the digital filter section of the FERMI readout microsystem. The filter section, consisting of two separate filter blocks, extracts the pulse amplitude and time information for the first-level trigger process and performs a highly accurate energy measurement for higher-level triggering and data readout purposes. An FIR-order statistic hybrid filter structure is used to improve the amplitude extraction performance. Using a training procedure the filters are optimized to produce a precise and accurate output in the presence of electronics and pile-up noise, sample timing jitter and the superposition of high-energy pulses. As the FERMI system resides inside the detector where accessibility is limited, the filter implementations are presented together with fault tolerance considerations. The filter section is modelled with the VHDL hardware descriptive language and the subsystems are further optimized to minimize the system latency and circuit area.

Delta: a charge sensitive front-end amplifier with switched gain for low-noise, large dynamic range silicon detector readout

The design and results of a radiation hard switched gain charge amplifier optimised for a large dynamic range and large input capacitance are described. The peaking time is 25 ns, dynamic ranges are 0.1–50 minimum ionising particles (MIPs) (high gain) and 1–400 MIPs (low gain), signal to noise (S/N)>10 for Cin<56 pF and radiation tolerance to 10 Mrads(Si) and 4×1013 n cm−2.

The readout system of the CPLEAR electromagnetic calorimeter

Abstract A digital readout system for the CPLEAR electromagnetic calorimeter is described. The calorimeter is composed of 2.5 m long ministreamer tubes and pick-up strip boards interleaved with lead converter sheets. The Fastbus standard is used throughout for the electronics. A novelty is the utilisation of daisy-chain lines for the fast block transfer mode. A total of 64 000 channels requires 42 Fastbus (front-end) crates to house the 1000 front-end modules, each containing 64 channels. Modern design techniques have been used to achieve the required performance, including the development of two application specific integrated circuits (ASICs) using CMOS gate arrays.

Investigations of the dynamic compression principle for fast detector pulses

Abstract For detectors at LHC, fast and accurate data acquisition systems are required. The method of analog dynamic range compression in order to overcome the technological limits of quantization circuits is presented and shown for an application at the electromagnetic calorimeter (ECAL) for CMS. A model of the detector pulses and an analysis of the compressed pulses in time and frequency domain is given. As a consequence the demands on the electronics are derived. A method to specify the bandwidth and the slew rate requirements for the very front end electronics is presented. For nonlinear circuits approximated by piecewise-linear circuits a detailed analysis is worked out and applied to the dynamic range compressor. This work is meant to be a guideline to determine bandwidth requirements also for other topologies and should help to optimize overall system performance.

The CPLEAR Electromagnetic Calorimeter

A large-acceptance lead/gas sampling electromagnetic calorimeter (ECAL) was constructed for the CPLEAR experiment to detect photons from decays of π0s with momentum pπ0 ≤ 800 MeV/c. The main purpose of the ECAL is to determine the decay vertex of neutral-kaon decays K0 → π0π0 → 4γ and K0 → π0π0π0 → 6γ. This requires a position-sensitive photon detector with high spatial granularity in r−, ϕ−, and z−coordinates. The ECAL - a barrel without end-caps located inside a magnetic field of 0.44 T - consists of 18 identical concentric layers. Each layer of 13 radiation length (X0) contains a converter plate followed by small cross-section high-gain tubes of 2640 mm active length which are sandwiched by passive pick-up strip plates. The ECAL, with a total of 6X0 has an energy resolution of α(E)E ≈ 13%(E(GeV)and a position resolution of 4.5 mm for the shower foot. The shower topology allows separation of electrons from pions. The design, construction, read-out electronics, and performance of the detector are described.

System level policies for fault tolerance issues in the FERMI project

The FERMI system, performing acquisition and DSP of calorimeter data in high energy collision experiments, planned at the LHC collider (CERN, Geneva, CH) is briefly overviewed. The system relies mainly upon the FERMI module, a dedicated VLSI multichip device performing most of the above functions, which is to be installed in large quantities (around 10/sup 5/) in the immediate neighborhood of the collider itself, requiring rad-hard features. The issues for a system which absolutely requires fault diagnosis and possibly fault tolerance are described, with regard to the FERMI module itself.