E. Delagnes

AFTER, an ASIC for the Readout of the Large T2K Time Projection Chambers

The T2K (Tokai-to-Kamioka) experiment is a long baseline neutrino oscillation experiment in Japan, for which a near detector complex (ND280), used to characterize the beam, will be built 280 m from the target in the off-axis direction of the neutrino beam produced using the 50 GeV proton synchrotron of J-PARC (Japan Proton Accelerator Research Complex). The central part of the ND280 is a detector including 3 large Time Projection Chambers based on Micromegas gas amplification technology with anodes pixelated into about 125,000 pads and requiring therefore compact and low power readout electronics. A 72-channel front-end Application Specific Integrated Circuit has been developed to read these TPCs. Each channel includes a low noise charge preamplifier, a pole zero compensation stage, a second order Sallen-Key low pass filter and a 511-cell Switched Capacitor Array. This electronics offers a large flexibility in sampling frequency (50 MHz max.), shaping time (16 values from 100 ns to 2 ), gain (4 ranges from 120 fC to 600 fC), while taking advantage of the low physics events rate of 0.3 Hz. Fabricated in 0.35 CMOS technology, the prototype has been validated and meets all the requirements for the experiment so that mass production has been launched at the end of 2007.

The Micromegas detector of the CAST experiment

A low-background Micromegas detector has been operating in the CAST experiment at CERN for the search for solar axions during the first phase of the experiment (2002?2004). The detector, made out of low radioactivity materials, operated efficiently and achieved a very high level of background rejection (5 ? 10?5 counts keV?1?cm?2?s?1) without shielding.

Micromegas as a large microstrip detector for the COMPASS experiment

Abstract Recent results on the gaseous microstrip detector Micromegas which will be used to track particles in the COMPASS experiment at CERN are presented. Developments concerning its mechanical and electrical design, associated readout electronics and gas mixture were carried out. Particular attention was paid to the discharge phenomenon which affects this type of microstrip detector. The adequacy of the options finally retained, especially the SFE16 readout and the use of a Ne–C 2 H 6 –CF 4 gas mixture, was demonstrated in a set of beam tests performed on a 26×36 cm 2 prototype. Operating at a gain of ∼6400, full efficiency is reached along with a spatial resolution of ∼50 μm and a timing accuracy of 8.5 ns . Discharges are kept at a low rate, less than one per SPS spill in a COMPASS-like environment. Via a decoupling of the strips through individual capacitors their impact is greatly reduced. They generate a dead time on the full detector of ∼ 3 ms , affecting marginally the detection efficiency given their rate. The probability of discharge, at a given value of efficiency, is found to decrease with the mean value of the gas mixture atomic number. In view of these results, the commissioning of Micromegas for COMPASS is foreseen in the near future.

Architecture and implementation of the front-end electronics of the time projection chambers in the T2K experiment

The tracker of the near detector in the T2K neutrino oscillation experiment comprises three time projection chambers based on micro-pattern gaseous detectors. A new readout system is being developed to amplify, condition and acquire in real time the data produced by the 124.000 detector channels. The cornerstone of the system is a 72-channel application specific integrated circuit which is based on a switched capacitor array. Using analog memories combined with deferred digitization enables reducing the initial burstiness of traffic from 50 Tbps to 400 Gbps in a practical manner and with a very low power budget. Modern field programmable gate arrays coupled to commercial digital memories are the next elements in the chain. Multi-gigabit optical links provide 140 Gbps of aggregate bandwidth to carry data outside of the magnet surrounding the detector to concentrator cards that pack data and provide the interface to commercial PCs via a standard Gigabit Ethernet network. We describe the requirements and constraints for this application and justify our technical choices. We detail the design and the performance of several key elements and show the deployment of the front-end electronics on the first time projection chamber where the final tests before installation on-site are being conducted.

The gaseous microstrip detector micromegas for the COMPASS experiment at CERN

Abstract The measurements foreseen in the COMPASS experiment at CERN, require high resolution tracking detectors, with low radiation length and high rate capability. For this purpose we have developed and optimized a gaseous microstrip detector ‘Micromegas’. Twelve planes with 1024 strips each, assembled in 3 stations of 4 views XYUV, have been operated with success in the summer of 2002 in the COMPASS environment. We describe here the performances and results obtained.

Industrial transfer and stabilization of a CMOS-JFET-bipolar radiation-hard analog-digital SOI technology

DMILL technology integrates mixed analog-digital very rad-hard (>10 Mrad and >10/sup 14/ neutron/cm/sup 2/) vertical bipolar, 0.8 /spl mu/m CMOS and 1.2 /spl mu/m PJFET transistors on SOI substrate. In this paper, after a presentation of the DMILL program goal, we discuss more into details the main technological choices, the main milestones from the R&D to the industrial implementation, and the main results obtained after stabilization of the final process-flow in the MHS foundry.

Large bulk-micromegas detectors for TPC applications in HEP

Bulk-MicroMegas detectors are based on a novel technology which is of particular interest for large area Micro Pattern Gas Detectors (MPGD). Their manufacturing process combines detector construction simplicity and robustness, allowing large sensitive areas to be produced at low cost. Such devices provide very good gas gain uniformity and detection coverage with small dead spaces. They are ideally suited in HEP applications where large volume tracking detectors with low material budget are required. This is the case, for instance, of the T2K neutrino experiment in Japan, in which large Time Proportional Chamber (TPC) devices will be used. Bulk- MicroMegas detectors are also being considered for the future Linear Collider Detector. We present in this paper the recent developments and performance of bulk-MicroMegas detectors for the T2K TPC.

Thick film SOI technology: characteristics of devices and performance of circuits for high-energy physics at cryogenic temperatures; effects of ionizing radiation

Abstract We report here the characteristics of elementary devices and circuits when they are exposed at low temperature (≈ 90 K) to ionizing radiation. These devices and circuits are implemented in a radiation-hardened SOI monolithic technology. We have made irradiations both at high dose rates (≈ 100 krads/h) and low dose rate (≈ 0.02 krad/h), the low dose rate is of the order of magnitude of the value which should be encountered in high-energy physics calorimeters during future experiments. A reduction of the dose rate, at identical total dose received, has a favourable effect on the threshold voltage shift of MOSFETs and, consequently, on the behaviour of circuits designed with these devices. For example, a preamplifer remained functional with no significant change in its characteristics (noise and rise time) after ≈ 100 krads irradiation during a longer than 6 months exposure at 90 K (liquid-argon temperature). This is of key importance for the future development of silicon microelectronics for Liquid-Argon Calorimetry.

AFTER, the front end ASIC of the T2K Time Projection Chambers

The T2K (Tokai-to-Kamioka) experiment is a long baseline neutrino oscillation experiment in Japan. A near detector, located at 280m of the production target, is used to characterize the beam. One of its key elements is a tracker, made of three Time Projection Chambers (TPC) read by Micromegas endplates. A new readout system has been developed to collect, amplify, condition and acquire the data produced by the 124,000 detector channels of these detectors. The front-end element of this system is a a new 72-channel application specific integrated circuit. Each channel includes a low noise charge preamplifier, a pole zero compensation stage, a second order Sallen-Key low pass filter and a 511-cell Switched Capacitor Array. This electronics offers a large flexibility in sampling frequency, shaping time, gain, while taking advantage of the low physics events rate of 0.3 Hz. We detail the design and the performance of this ASIC and report on the deployment of the frond-end electronics on-site.