ADC Channels Research Articles

High speed graphic program on a personal computer and its utilization in JIPP T-IIU online data-processing system.

A high speed graphic program was developed on a personal computer PC 9801. Using this program, one can draw a waveform of successive 16 bit-integer data, such as obtained by analog-to-digital convertor. The program is written by the machine language and has a form of a subroutine program which can be called from main programs under N88 BASIC. The time for drawing one waveform is 4 ms, which is two orders faster than the time with standard graphic routines of BASIC interpreter. This program is very convenient for the real-time display of plasma-monitoring raw data, such as plasma current, loop voltage, rf power etc. in tokamak experiments. This program has been utilized in JIPP T-IIU experiments and enables to display data of 8 channel ADC within a few seconds before the system transmits the data from CAMAC to the computer center of the institute. The program and its utilization are presented.

An automated micrograph image size analyser

An automated electro-optic image size analyser capable of rapid data collection is described. The device is especially suited to the determination of colloidal particle size distributions and grain or magnetic domain size analysis from electron or optical micrographs. The interfacing of the analyser, which is described, requires two input/output lines and a logic zero to an 8-bit parallel port of a microcomputer as well as two ADC channels. The apparatus is thus not fundamentally specific to any single type of microcomputer.

Soudan 2 Data Acquisition and Trigger Electronics

The 1.1 kton Soudan 2 detector is read out by 16K anode wires and 32K cathode strips. Preamps from each wire or strip are bussed together in groups of 8 to reduce the number of ADC channels. The resulting 6144 channels of ionization signal are flash-digitized every 150 ns and stored in RAM. The raw data hit patterns are continually compared with programmable trigger multiplicity and adjacency conditions. The data acquisition process is managed in a system of 24 parallel crates each containing an Intel 8086 microprocessors, which supervises a pipe-lined data compactors, and allows transfer of the compacted data via CAMAC to the host computer. The 8086's also manage the local trigger conditions and can perform some parallel processing of the data. Due to the scale of the system and multiplicity of identical channels, semi-custom gate array chips are used for much of the logic, utilizing 2.5 micron CMOS technology.

Microchannel Plate Position Sensitive Detector System for Charge Analysis of Low Energy Heavy Ions

A position sensitive detector (PSD) using a microchannel plate (MCP) of rectangular shape (46 mm × 13 mm) is developed and applied to measure the charge spectrum of low energy heavy ions. An analog position processor with a swift log-antilog operation is devised, which has a wide dynamic range of 50 mV–10 V suitable for the MCP pulse properties. A digital processor employing two 8 K channel ADC's and a minicomputer is also presented for comparison. The well resolved spectra are obtained when multiply charged heavy ions are separately and locally incident on the PSD.

An on-line data acquisition system for radiation therapy: External photon and electron beams

An on-line data acquisition system for external beam treatment planning has been developed. The hardware consists of a Tektronix 4054 Computer, an SHM Nuclear 3-D scanning water phantom, interfaces for 16 channels of ADC and 32 channels of digital I/O, and two detector probes for measuring dose distribution and monitoring fluctuations in machine output. The program to control the movement of the scanning probe and to collect data is written in BASIC. Results of the measurements are plotted in real time on the Tektronix screen. The beam data format consists of a set of percentage depth doses along the central axis and five sets of off-axis ratios at five different depths. In the electron mode, when ionization chambers are used, data points are averages of two measurements, one with positive bias and the other with negative bias. The beam data are stored on disk which can be accessed by the Capintec treatment planning system.

A square root metric in the analysis of the measurements of high energy physics instrumentation

A vast category of detectors are characterized by a charge output with a distribution which has a variance proportional to the mean value. In all these cases a square root scale achieved in the hardware seems more suitable from the point of view of the resolution of the measurements, of the number of ADC channels needed, and of a preliminary analysis in the stage of tuning and checking of the detector.

Micro-Computer Control for a HB501 STEM

Micro-computers conveniently provide the basis of a powerful data collection, display and storage system for an electron microscope. In the example described here a Vacuum Generators HB501 STEM has been interfaced with an APPLE II micro-computer. The APPLE, with 48k of available core memory and a single mini-diskette system of 256k. byte capacity, was fitted with 16 input channels of analog-to-digital conversion (Interactive Structures AI-Ø2) and 8 output channels of digital-to-analog conversion (Interactive Structures AO-Ø3).Figure (1) shows a block diagram of the system and its interconnections to the microscope. ADC channels Ø to 5 monitor the excitations of the six lenses (two condenser, one objective and three post specimen) of the HB501. These inputs are taken directly from the feedback shunt resistors in the lens power supply and fall directly in the range 0 to +5 volts required for the ADC. Channels 6 to 9 measure the X,Y coordinates and X,Y tilt-coordinates of the specimen stage, by monitoring the voltages derived from the position-sensing potentiometers on the stepping drive motors. These signals in the range ±0.5V are converted to the required 0 to + 5V level by operational amplifiers.

Mathematical study of successive approximation ADC's channel width

The influence of input and weight voltage variations, on channel width is examined. To obtain a mathematical expression for the differential linearity, the channel width is treated as a function of L tn - the channel width defined by the weights only. In a second step, L tn is supposed to be variable. To avoid errors due to the nonideal stretcher and transients during weights setting, the method of supplementary tests is examined. This method leads to improvements of very fast successive approximation ADC's.

Evolution of a Computer System for Acquisition of Angular Correlation Data

A system using an SEL 810A computer programmed as a flexible multi-parameter analyzer is described. Features include a time-shared ADC channel with software gain correction for each input, unrestricted selection of spectra on any 2 of 4 input parameters, and live display of coincidence spectra with chance coincidences subtracted.