Abraham Seiden

Type inversion in silicon detectors

Abstract Silicon strip detectors and photodiodes were irradiated in an 800 MeV proton beam. The change of the effective doping concentration was monitored by measuring diode C - V curves. Type inversion is observed at a fluence Φ = 1.5 × 10 13 cm −2 . Further evidence for type inversion is obtained from a study of pulses generated by an infrared LED in silicon strip detectors. A two-level parametrization is used to describe donor removal and acceptor state creation during proton irradiation: N eff = N 0 exp(− cφ )− βφ . We measure values of c = (5.5 ± 1.1) × 10 14 cm 2 and β = (0.031 ± 0.006) cm −1 . After type inversion the depletion voltage increases with proton fluence. This may set the limit for the lifetime of silicon detectors at future colliders. However, the occurence of type inversion does not degrade the performance of silicon strip detectors. The effective doping concentration showed a complex post irradiation behaviour. After a short term annealing period the doping concentration increased beyond the value that had been reached immediately after the exposure.

Temperature dependence of the radiation induced change of depletion voltage in silicon PIN detectors

Abstract We present a study of how temperature affects the change in the depletion voltage of silicon PIN detectors damaged by radiation. We study the initial radiation damage and the short-term and long-term annealing of that damage as a function of temperature in the range from −10°C to +50°C, and as a function of 800 MeV proton fluence up to 1.5×10 14 p/cm 2 . We express the pronounced temperature dependences in a simple model in terms of two annealing time constants which depend exponentially on the temperature.

Issues in Proton Computed Tomography

We report progress on a feasibility study of Proton Computed Tomography and Proton Transmission Radiography for applications in treatment planning and patient positioning for proton radiation therapy. We analyzed data from proton transmission studies through a hollow aluminum cylinder taken with a telescope of silicon detectors with very high spatial and good energy resolution. In addition, we explored the usefulness of applying a cut on the angular divergence of the transmitted beam in a GEANT4 simulation study.

Temperature dependence of radiation damage and its annealing in silicon detectors

Silicon detectors at future collider facilities such as the Superconducting Super Collider (SSC) will be exposed to large fluences of both neutral and charged particles, resulting in considerable bulk radiation damage. In order to reduce the increase in leakage current associated with that damage, the proposed operating temperature of the silicon detectors in the SSC Solenoidal Detector Collaboration (SDC) experiment is 0 degrees C. In order to explore any potential complications of operating detectors at 0 degrees C, two sets of detectors were irradiated. One set was kept close to 0 degrees C during the exposure and annealing period, while the other was maintained at room temperature throughout ( approximately 27 degrees C during the exposure, and approximately 23 degrees C during the annealing period). The full depletion voltage and leakage current of the detectors during the irradiation period and over the subsequent annealing period were monitored. It is concluded that detectors will have to be operated at 0 degrees C, and, once damaged, be maintained at 0 degrees C in order to keep their operating voltage at a reasonable value ( >

Measurement of the inclusive decay properties of charmed mesons

Abstract We report a high statistics study of the inclusive decay properties of the charmed D0 and D+ mesons, and the first inclusive study of the charmed Ds+. The data are collected at s =3.77 GeV and s =4.14 GeV with the Mark III detector at the e+e− storage ring SPEAR. For each charmed meson species, the charged-particle multiplicity, the strangeness content of the final state, and the average π0 multiplicity are determined.

Performance of ultra-fast silicon detectors

The development of Low-Gain Avalanche Detectors has opened up the possibility of manufacturing silicon detectors with signal larger than that of traditional sensors. In this paper we explore the timing performance of Low-Gain Avalanche Detectors, and in particular we demonstrate the possibility of obtaining ultra-fast silicon detector with time resolution of less than 20 picosecond.

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.

Tests of the radiation hardness of VLSI integrated circuits and silicon strip detectors for the SSC under neutron, proton, and gamma irradiation

As part of a program to develop a silicon strip central tracking detector system for the Superconducting Super Collider (SSC), the effects of radiation damage in silicon detectors and their associated front-end readout electronics are being studied. The authors report on the results of neutron and proton irradiations at the Los Alamos National Laboratory and gamma -ray irradiations at UC Santa Cruz. Individual components on single-sided AC-coupled silicon strip detectors and on test structures were tested. Circuits fabricated in a radiation-hard CMOS process and individual transistors fabricated using dielectric isolation bipolar technology were also studied. Bulk damage to the silicon itself is seen as the limiting factor in the lifetime of a detector system. In particular, it is the acceptor site creation in the active volume of the silicon detector that will limit the lifetime to approximately 10 yr for the innermost detectors. >

Charge collection studies in irradiated HV-CMOS particle detectors

Charge collection properties of particle detectors made in HV-CMOS technology were investigated before and after irradiation with reactor neutrons. Two different sensor types were designed and processed in 180 and 350 nm technology by AMS. Edge-TCT and charge collection measurements with electrons from 90Sr source were employed. Diffusion of generated carriers from undepleted substrate contributes significantly to the charge collection before irradiation, while after irradiation the drift contribution prevails as shown by charge measurements at different shaping times. The depleted region at a given bias voltage was found to grow with irradiation in the fluence range of interest for strip detectors at the HL-LHC. This leads to large gains in the measured charge with respect to the one before irradiation. The increase of the depleted region was attributed to removal of effective acceptors. The evolution of depleted region with fluence was investigated and modeled. Initial studies show a small effect of short term annealing on charge collection.

Design, testing and performance of the frontend electronics for the LPS silicon microstrip detectors

Abstract We present our experience in design, construction, testing and operation of the frontend electronics (FEE) for the LPS silicon strip detectors for HERA. A total of about 22 000 channels has been operated as close as the 10σ envelope of the 820 GeV proton beam. This FEE system is binary, controlled by one threshold set at about 0.8 fC, and has been optimized by combining a fast low-noise bipolar amplifier/comparator VLSI with a low-power digital pipeline manufactured in radiation-hard CMOS.