R. Beuttenmuller

The Maia Spectroscopy Detector System: Engineering for Integrated Pulse Capture, Low-Latency Scanning and Real-Time Processing

The Maia detector system is engineered for energy dispersive x‐ray fluorescence spectroscopy and elemental imaging at photon rates exceeding 107/s, integrated scanning of samples for pixel transit times as small as 50μs and high definition images of 108 pixels and real‐time processing of detected events for spectral deconvolution and online display of pure elemental images. The system developed by CSIRO and BNL combines a planar silicon 384 detector array, application‐specific integrated circuits for pulse shaping and peak detection and sampling and optical data transmission to an FPGA‐based pipelined, parallel processor. This paper describes the system and the underpinning engineering solutions.

Development of a high-rate high-resolution detector for EXAFS experiments

A new detector for EXAFS experiments is being developed. It is based on a multi-element Si sensor and dedicated readout application specific integrated circuit (ASIC). The sensor is composed of 384 pixels, each having 1 mm/sup 2/ area, arranged in four quadrants of 12/spl times/8 elements and it is wire-bonded to 32-channel ASICs. Each channel implements low-noise preamplification with self-adaptive continuous reset, high-order shaper, bandgap referenced baseline stabilizer, one threshold comparator, and two digital-analog converter (DAC) adjustable window comparators, each followed by a 24-bit counter. Fabricated in 0.35 /spl mu/m CMOS, the ASIC dissipates about 8 mW per channel. First measurements show at room temperature a resolution of 14e/sup -/ rms without the detector and 40 e/sup -/ rms (340 eV) with the detector connected and biased. Cooling to -35 C a full width at half maximum (FWHM) of 205 eV (167 eV from electronics) was measured at the Mn-K/spl alpha/ line. A resolution of about 300eV was measured for rates approaching 100 kc/s per channel, corresponding to an overall rate in excess of 10 Mc/s/cm/sup 2/. Channel-to channel threshold dispersion after DAC adjustment 2.5 was e/sup -/ root mean square.

Maia X-ray Microprobe Detector Array System

Maia is an advanced system designed specifically for scanning x-ray fluorescence microprobe applications. It consists of a large array of photodiode detectors and associated signal processing, closely coupled to an FPGA-based control and analysis system. In this paper we will describe the architecture and construction of the system.

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.

Novel prototype Si detector development and processing at BNL

Abstract A variety of Si detectors have been developed and processed at BNL with its unique detector fabrication facility. These detectors include Si drift detectors (SDD); Si micro- and mm-strip detectors; Si pad detectors; and Si pixel detectors with a variety of configurations. In this paper, the details of the design and processing technology of large area SDD for the STAR SVT at RHIC, micro- and mm-strip detectors for CERN RD39/NA60 experiments; and radiation tolerant n/n, n/p pixel detectors for LHC experiments will be given. In addition, simulation results of new types of Si strip/pixel detectors with improved radiation tolerance will be presented for the first time.

Performance of a novel silicon detector

The performance of a silicon detector with two-dimensional pad readout, intended to be used in the trigger of experiment HELIOS (NA34), has been investigated in a proton/pion beam of 200 GeV/c momentum at the CERN SPS. The data can be described by the convolution of the Landau distribution with a Gaussian, taking into account long distance collisions and electronics noise. Uniformity in peak loss was found to be better than 7%. The response for single tracks through the detector is characterized by the total number of pads with a threshold value (multiplicity), and the number of adjacent pads, responding to a single particle (cluster size). Data on multiplicity and cluster size as a function of threshold will be discussed. Detection efficiency for particles has been measured over the pad area and across the pad boundaries.

The NSLS 100 element solid state array detector

X-ray absorption studies of dilute samples require fluorescence detection techniques. Since signal-to-noise ratios are governed by the ratio of fluorescent to scattered photons counted by a detector, solid state detectors which can discriminate between fluorescence and scattered photons have become the instruments of choice for trace element measurements. Commercially available 13 element Ge array detectors permitting total count rates < 500000 counts per second are now in routine use. Since X-ray absorption beamlines at high brightness synchrotron sources can already illuminate most dilute samples with enough flux to saturate the current generation of solid state detectors, the development of next-generation instruments with significantly higher total count rates is essential. We present the design and current status of the 100 element Si array detector being developed in a collaboration between the NSLS and the Instrumentation Division at Brookhaven National Laboratory. The detecting array consists of a 10×10 matrix of 4 mm×4 mm elements laid out on a single piece of ultrahigh purity silicon mounted at the front end of a liquid nitrogen dewar assembly. A matrix of charge sensitive integrating preamplifiers feed signals to an array of shaping amplifiers, single channel analyzers, and scalers. An electronic switch, delay amplifier, linear gate, digital scope, peak sensing A/D converter, and histogramining memory module provide for complete diagnostics and channel calibration. The entire instrument is controlled by a LabView 2 application on a MacII ci; the software also provides full control over beamline hardware and performs the data collection.

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.

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.

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.