W. Kroeger

A time-over-threshold machine: the readout integrated circuit for the BABAR Silicon Vertex Tracker

A low-noise, mixed-signal, 128-channel CMOS integrated circuit containing the complete readout electronics for the BABAR Silicon Vertex Tracker has been developed. The outstanding feature of the present implementation is the ability to perform simultaneously low-level signal acquisition, derandomizing data storage, sparsification and data transmission on a single monolithic chip. The signals from the detector strips are amplified, shaped by a CR-RC/sup 2/ filter with digitally selectable peaking time of 100 ns, 200 ns, 300 ns, or 400 ns, and then presented to a time-over-threshold processor to implement a compression type analog-to-digital conversion. The digital information is stored, sparsified and read out through a serial link upon receipt of a command. The digital section operates from a 60 MHz incoming clock. Noise measurements at 200 ns peaking time and 3.5 mW total power dissipation per channel yield an equivalent noise charge of 600 el. rms at 12 pF added source capacitance. The chip measures 5.7 mm/spl times/8.3 mm and contains 330 k transistors. The first full-scale prototype was fabricated in a radiation soft 0.8 /spl mu/m, 3-metal CMOS process. The same circuit is now being fabricated in an analogous radiation hard technology.

A silicon telescope for applications in nanodosimetry

The position- and energy-sensitive primary particle detectors of a nanodosimetry system are described. They consist of a telescope of silicon strip detectors, which allow the determination of the particles position from the hit strip address and its energy from the specific energy loss. In our implementation, the energy loss is measured through the time over threshold (TOT). When testing the performance of a single silicon strip detector, it was found that between the energies of 20 and 100 MeV, primary particle energy could be determined to an accuracy of 15%, decreasing to 25% at 250 MeV Below 20 MeV, we observed TOT saturation. It is concluded that the performance of the tested silicon strip detector is suitable for application in nanodosimetry.

Results from the Beam Test of the Engineering Model of the GLAST Large Area Telescope

This paper describes the results of a beam test using the Engineering Model of the GLAST Large Area Telescope, which was installed in a beam of positrons, hadrons and tagged photons at SLAC. The performance of the four subsystems, Anti Coincidence Detector, Silicon Tracker, Calorimeter and Data Acquisition will be described.

Development of radiation-hard materials for microstrip detectors

We present the search for new detector materials, which would replace silicon as the bulk material in strip detectors for application in high radiation fields. The investigation focuses on SiC, a material with higher bandgap and thus less degradation after irradiation when compared with silicon. Both static properties like the capacitance and leakage currents and dynamic measurements of the charge collection with low-noise amplifiers are presented.

The silicon tracker readout electronics of the Gamma-ray Large Area Space Telescope

A unique electronics system has been built and tested for reading signals from the silicon-strip detectors of the Gamma-ray Large Area Space Telescope mission. The system amplifies and processes signals from 884 736 36-cm strips using only 160 W of power, and it achieves close to 100% detection efficiency with noise occupancy sufficiently low to allow it to self trigger. The design of the readout system is described, and results are presented from ground-based testing of the completed detector system.

Evaluation of p-stop structures in the n-side of n-on-n silicon strip detectors

A large area (63.6 mm/spl times/64 mm) n-on-n silicon strip detector was fabricated, implementing various p-stop structures in the n-side. The detectors were characterized in laboratory and in beam tests. The inter-strip capacitance showed features in which the individual p-stop structure had the longest tail toward saturation. The beam tests showed other p-stop structures collected more charge in the mid-strip region than the individual p-stop structure. In addition, there was a source which lost or spread charge and induced noise where the over-depletion was insufficient.

Characterization of an irradiated double-sided silicon strip detector with fast binary readout electronics in a pion beam

We report on the characterization of an AC-coupled, double-sided silicon strip detector, with fast binary readout electronics, in a pion beam before and after proton irradiation. The proton irradiation was non-uniform and to increase the damage the detector was heated to accelerate the anti-annealing. The effective radiation level was about 1/spl times/10/sup 14/ p/cm/sup 2/. Both the bias voltage of the detector and the threshold of the discriminator of the binary readout electronics were varied, and the efficiencies were determined. The irradiated detector clearly shows the effect of bulk inversion. The binary system proved to be efficient well below the full depletion voltage on the p-n junction side. Due to the highly non-uniform irradiation, the depletion voltage changes from close to zero to about 120 V along a single strip, but the detector appears to work without any noticeable failures.

The silicon tracker of the beam test engineering model of the GLAST large-area telescope

The silicon tracker for the engineering model of the GLAST Large Area Telescope(LAT) has at least two unique features: it employs self triggering readout electronics, dissipating less than 200 mu-W per channel and to date represents the largest surface of silicon microstrip detectors assembled in a tracker (2.7 m{sup 2}). It demonstrates the feasibility of employing this technology for satellite based experiments, in which low power consumption, large effective areas and high reliability are required. This note describes the construction of this silicon tracker, which was installed in a beam test of positrons, hadrons and tagged photons at SLAC in December of 1999 and January of 2000.

Noise determination in silicon micro strips

We report the study of amplifier noise on silicon micro strip detectors. We have used a fast, low noise amplifier-comparator VLSI chip with 22 ns shaping time developed for the LHC to determine the noise at the pre-amp as a function of strip length and strip geometry, i.e., interstrip capacitance and ohmic strip resistance. In addition, we have tested the noise in irradiated detectors. We have compared the results with simulations using SPICE.

Functional characteristics and radiation tolerance of AToM, the front-end chip of BaBar silicon vertex tracker

The readout chip designed to process the microstrip signals in the BaBar silicon vertex tracker (SVT), after being realized twice in a radsoft technology has been transferred into the final radhard process. So far the circuit has gone through four different radhard submissions, one aiming at providing a preliminary insight into the characteristics of the radhard chip, the other ones constituting pre-production and production runs. Chips from these submissions have undergone a thorough set of tests addressing functional aspects, noise parameters and effects of radiation on signal and noise behavior. The present paper discusses the results of these tests and describes the final version of the circuit which has been proven to successfully meet the experiment requirements.