H.K. Soltveit

The ALICE TPC, a large 3-dimensional tracking device with fast readout for ultra-high multiplicity events

The design, construction, and commissioning of the ALICE Time-Projection Chamber (TPC) is described. It is the main device for pattern recognition, tracking, and identification of charged particles in the ALICE experiment at the CERN LHC. The TPC is cylindrical in shape with a volume close to 90 m(3) and is operated in a 0.5T solenoidal magnetic field parallel to its axis. In this paper we describe in detail the design considerations for this detector for operation in the extreme multiplicity environment of central Pb-Pb collisions at LHC energy. The implementation of the resulting requirements into hardware (field cage, read-out chambers, electronics), infrastructure (gas and cooling system, laser-calibration system), and software led to many technical innovations which are described along with a presentation of all the major components of the detector, as currently realized. We also report on the performance achieved after completion of the first round of stand-alone calibration runs and demonstrate results close to those specified in the TPC Technical Design Report

Energy loss of pions and electrons of 1– in drift chambers operated with Xe,CO2(15%)

Abstract We present measurements of the energy loss of pions and electrons in drift chambers (DC) operated with a Xe,CO 2 (15%) mixture. The measurements are carried out for particle momenta from 1 to 6 GeV /c using prototype DC for the ALICE transition radiation detectors. Microscopic calculations are performed using input parameters calculated with GEANT3. These calculations reproduce well the measured average and most probable values for pions, but a higher Fermi plateau is required in order to reproduce our electron data. The widths of the measured distributions are smaller for data compared to the calculations. The electron/pion identification performance using the energy loss is also presented.

Associative memory design for the fast track processor (FTK) at ATLAS

We propose a new generation of VLSI processors for pattern recognition, based on associative memory architecture, optimized for online track finding in high-energy physics experiments. We describe the architecture, the technology studies and the prototype design of a new associative memory project: it maximizes the pattern density on the ASIC, minimizes the power consumption and improves the functionality for the fast tracker processor proposed to upgrade the ATLAS trigger at LHC.

The PreAmplifier ShAper for the ALICE TPC detector

In this paper the PreAmplifier ShAper (PASA) for the Time Projection Chamber (TPC) of the ALICE experiment at LHC is presented. The ALICE TPC PASA is an ASIC that integrates 16 identical channels, each consisting of Charge Sensitive Amplifiers (CSA) followed by a Pole-Zero network, self-adaptive bias network, two second-order bridged-T filters, two non-inverting level shifters and a start-up circuit. The circuit is optimized for a detector capacitance of 18-25 pF. For an input capacitance of 25 pF, the PASA features a conversion gain of 12.74 mV/fC, a peaking time of 160 ns, a FWHM of 190 ns, a power consumption of 11.65 mW/ch and an equivalent noise charge of 244e + 17e/pF. The circuit recovers smoothly to the baseline in about 600 ns. An integral non-linearity of 0.19% with an output swing of about 2.1 V is also achieved. The total area of the chip is 18 mm(2) and is implemented in AMSs C35B3C1 0.35 mu m CMOS technology. Detailed characterization tests were performed on about 48 000 PASA circuits before mounting them on the ALICE TPC front-end cards. After more than two years of operation of the ALICE TPC with p-p and Pb-Pb collisions, the PASA has demonstrated to fulfill all requirements

Pulse height measurements and electron attachment in drift chambers operated with Xe, CO2 mixtures

We present pulse height measurements in drift chambers operated with Xe,CO2 gas mixtures. We investigate the attachment of primary electrons on oxygen and SF6 contaminants in the detection gas. The measurements are compared with simulations of properties of drifting electrons. We present two methods to check the gas quality: gas chromatography and 55 Fe pulse height measurements using monitor detectors.

MSGCROC - an ASIC for high count rate readout of position sensitive Microstrip Gas Chambers for thermal neutrons

In this paper we report on the development of an ASIC for readout of position sensitive neutron detectors based on low-pressure Micro-Strip Gas Chambers with solid composite 157Gd/CsI converter. Global counting rates of 108 cps for a detector area of 25×25 cm2 covered with 400×400 strips requiring 2 ns time resolution for coincidences of signals from X- and Y-strips set very demanding requirements for the ASIC performance.

Position reconstruction in drift chambers operated with Xe, CO2 (15%)

Abstract We present measurements of position and angular resolution of drift chambers operated with a Xe, CO 2 (15%) mixture. The results are compared to Monte Carlo simulations and important systematic effects—in particular the dispersive nature of the absorption of transition radiation and non-linearities—are discussed. The measurements were carried out with prototype drift chambers of the ALICE Transition Radiation Detector, but our findings can be generalized to other drift chambers with similar geometry, where the electron drift is perpendicular to the wire planes.

Space charge in drift chambers operated with the Xe,CO2(15%) mixture

Using prototype modules of the ALICE Transition Radiation Detector (TRD) we investigate space-charge effects and the dependence of the pion rejection performance on the incident angle of the ionizing particle. The average pulse height distributions in the drift chambers operated with the Xe; CO2ð15%Þ mixture provide quantitative information on the gas gain reduction due to space charge accumulating during the drift of the primary ionization. Our results demonstrate that the pion rejection performance of a TRD is better for tracks which are not at normal incidence to the anode wires. We present detailed simulations of detector signals, which reproduce the measurements and lend strong support to our interpretation of the measurements in terms of space-charge effects. r 2004 Elsevier B.V. All rights reserved. PACS: 29.40.Cs

Multi-gigabit wireless data transfer at 60 GHz

In this paper we describe the status of the first prototype of the 60 GHz wireless Multi-gigabit data transfer topology currently under development at University of Heidelberg using IBM 130 nm SiGe HBT BiCMOS technology. The 60 GHz band is very suitable for high data rate and short distance applications. One application can be a wireless multi Gbps radial data transmission inside the ATLAS silicon strip detector, making a first level track trigger feasible. The wireless transceiver consists of a transmitter and a receiver. The transmitter includes an On-Off Keying (OOK) modulator, a Local Oscillator (LO), a Power Amplifier (PA) and a Band-pass Filter (BPF). The receiver part is composed of a Band-pass Filter (BPF), a Low Noise Amplifier (LNA), a double balanced down-convert Gilbert mixer, a Local Oscillator (LO), then a BPF to remove the mixer introduced noise, an Intermediate Amplifier (IF), an On-Off Keying demodulator and a limiting amplifier. The first prototype would be able to handle a data-rate of about 3.5 Gbps over a link distance of 1 m. The first simulations of the LNA show that a Noise figure (NF) of 5 dB, a power gain of 21 dB at 60 GHz with a 3 dB bandwidth of more than 20 GHz with a power consumption 11 mW are achieved. Simulations of the PA show an output referred compression point P1dB of 19.7 dB at 60 GHz.

Towards Multi-Gigabit readout at 60 GHz for the ATLAS silicon microstrip detector

In this paper we present the status of s feasibility study for a wireless readout of the Silicon inner-tracker for the ATLAS silicon strip detector with use of the 60 GHz band, also known as the Millimeter wave band due to its wavelength of 5 mm. The 60 GHz band is very suitable for high data rate and short distance applications, which can provide wireless Multi Gigabit per second radial data transmission inside the ATLAS silicon strip detector, making a first level track trigger processing all hit data feasible. A first prototype of the 60 GHz wireless multigigabit data transfer topology is currently under development at the University of Heidelberg using the 130 nm SiGe HBT BiCMOS 8HP technology. The wireless transceiver consists of a transmitter and a receiver. The transmitter includes an On-Off-Keying scheme (OOK) modulator, a Local Oscillator (LO), a Power Amplifier (PA) and a BandPass Filter (BPF). The receiver part is composed of a BPF, a Low Noise Amplifier (LNA), a double balanced down convert Gilbert mixer, a LO, BPF to remove the mixer introduced noise, a Intermediate Frequency (IF) amplifier and a OOK Demodulator that converts the signal back to its original form. The first prototype will be designed to handle a data rate of 3.5 Gbps over a link distance of 1 m. The required distance for the ATLAS silicon strip detector is about 10 cm. First simulations of the LNA show that a Noise Figure (NF) of 5 dB, a power gain of 21 dB at 60 GHz with a 3dB bandwidth of more than 20 GHz with a power consumption of 11 mW are achieved. A mixer with a NF of 9.3 dB, a conversion gain of 8.5 dB with a input power PLO of -2 dBm and RF power of -30 dBm@60 GHz with a power consumption of 7 mW is here achieved. Simulations of the PA show an output referred compression point P1dB of 19.7 dB at 60 GHz.