S. U. Pandey

ANALYSIS OF DIVACANCY RELATED TRAPS INDUCED BY PROTON, NEUTRON AND GAMMA RADIATION IN HIGH RESISTIVITY SILICON DETECTORS

Abstract Defects with deep levels induced in high-resistivity silicon detectors by low and high radiation fluence of protons and neutrons are studied using capacitance and current DLTS. Numerical simulation of I-DLTS and C-DLTS spectra based on the model of charge carrier emission and redistribution of electric field in the detector enabled one to perform the detailed investigation of DLTS spectra. It has been shown that the main DLTS peak in the range of 200 to 260 K may be considered as a result of the interference of deep levels near the midgap – negatively charged divacancy VV− and the Ci–Oi complex. The model describing the broadening of the VV− component of the spectrum, which arises from the divacancy localization inside a cluster, is discussed. The results are compared with those obtained for gamma irradiation, for which the dominant contribution in DLTS spectra arises just from the Ci–Oi complex.

Silicon drift detectors for the STAR/SVT experiment at RHIC

Large area linear Silicon Drift Detectors (SDD) were developed to be used in the Silicon Vertex Tracker (SVT) of the STAR experiment at the BNL relativistic heavy ion collider (RHIC). The SDD is in its final design and has been submitted for large scale production. Test results show that the detector exhibits excellent position resolution and low noise. A special characterization procedure was developed to test detector wafers in order to select good detectors for the SVT. Recently, 15 STAR/SVT SDDs were assembled as a tracking device in a BNL-AGS heavy ion experiment (E896). It is the first tracking application of these detectors and their corresponding front-end electronics in an experimental environment. Preliminary results indicating good detector performance are shown and discussed in this paper.

An update on the strangeness production measurements and H0 di-baryon search as performed by the AGS experiment 896

E896 was designed to search for the predicted short-lived six-quark H0 di-baryon. The goal is to enhance the existing knowledge by extending the search into regions of shorter lifetimes (approximately half that of the lambda) and via exploring a new creation channel, that of the coalescence of two lambdas. Two main tracking chambers are used, a distributed drift chamber positioned to measure low-pt and high-rapidity neutral particle decay products and a silicon drift detector array which measures particle production at mid-rapidity. Both detectors are also investigating lambda polarization, over their respective coverages, for Au-Au collisions at 11.3 GeV/nucleon. The current status of the H0 di-baryon search and preliminary results of the strange particle production and polarization measurements will be presented.

Studies of dynamics of electron clouds in STAR silicon drift detectors

Abstract The dynamics of electrons generated in silicon drift detectors was studied using an IR LED. Electrons were generated at different drift distances. In this way, the evolution of the cloud as a function of drift time was measured. Two methods were used to measure the cloud size. The method of cumulative functions was used to extract the electron cloud profiles. Another method obtains the cloud width from measurements of the charge collected on a single anode as a function of coordinate of the light spot. The evolution of the electron cloud width with drift time is compared with theoretical calculations. Experimental results agreed with theoretical expectations.

New experimental and analysis methods in I-DLTS

Abstract A simple modification to traditional experimental apparatus to perform I-DLTS measurements is presented. This setup is shown to be faster and more sensitive than traditional double boxcar I-DLTS systems. A novel analysis technique utilising multiple exponential fits to the I-DLTS signal from a highly neutron irradiated silicon sample is presented along with a discussion of the results. It is shown that the new method has better resolution and can deconvolute overlapping peaks more accurately than previous methods.

Electron injection in semiconductor drift detectors

Abstract We report on the injection of electrons from surface structures of Silicon Drift Detectors into the bulk of the detector for calibration purposes. Also, with these injector structures, detection of magnetic field components perpendicular to the detector’s surface is possible. Implanted line and dot injectors along with MOS injectors are discussed. Studies of lateral uniformity of injection, biasing of injectors to facilitate injection and dot injection are discussed.

The silicon drift vertex detector for the STAR experiment at RHIC

Abstract The current status of the STAR Silicon Vertex Tracker (SVT) is presented. The performance of the Silicon Drift Detectors (SDD) is discussed. Results for a recent 15 layer SDD tracker which prototypes all components of the SVT are presented. The enhanced physics capabilities of the STAR detector due to the addition of the SVT are addressed.

The STAR Silicon Drift Vertex Detector

Abstract The current status of the STAR Silicon Vertex Tracker (SVT) is presented. The performance of the Silicon Drift Detectors (SDD) is discussed. The enhanced physics capabilities of the STAR detector due to the addition of the SVT are addressed.

Silicon drift detectors as tracking devices

Abstract Silicon drift detectors provide unambiguous two-dimensional position information for charged particle detection in a single detector layer. Like most other semi-conductor technologies, Silicon drift detectors are presently used in vertexing detectors. By taking into account, the drastic reduction in channel count compared to other silicon-based devices this specific technology is also well suited for large coverage tracking detectors. The first larger area Silicon Drift Tracker (6.3 cm ×6.3 cm ) was developed as the inner tracking detector (SVT) of the STAR experiment at the RHIC collider. Advantages and limitations of this detector will be discussed. Recent results of detector performance based on an application in a heavy ion fixed target experiment at the BNL-AGS (E896) are presented.

First results from the H0 di-baryon search and hyperon production measurements by the AGS Experiment 896.

Abstract The AGS Experiment 896 was designed to study strangeness production in Au—Au collisions at 11.6A GeV/c, in particular the formation of a six-quark di-baryon the H 0 . Heavy ion collisions provide favorable conditions for the H 0 formation either via coalescence of two Λ particles (owing to the large Λ production cross section) or direct production from the possible formation of a quark-gluon plasma. E896 also measured strange meson and baryon distributions from mid-rapidity. Preliminary results from this experiment are presented as well as details of the expected sensitivity for the H 0 search.