J. Dreute

An automatic measuring system for particle tracks in plastic detectors

Abstract In the last few years picture analysis methods have evolved into a powerful technique for measurements of nuclear tracks in plastic detectors. We have developed a microprocessor-based picture analysis system for automatic track measurements. The video pictures of particle tracks seen through a microscope are digitized in real time and the picture analysis is done by software. The microscope is equipped with a stage driven by stepping motors, which are controlled by a separate microprocessor. A PDP 11/23 supervises the operation of all microprocessors and stores the measured data on its mass storage devices. This paper describes the hard- and software of the system and the methods of picture analysis which are used for the track identification and measurement.

Heavy ion microscopy of single event upsets in CMOS SRAMs

The single event upset (SEU) imaging has been applied at the GSI heavy ion microprobe to determine the sensitivity of integrated circuits (IC) to heavy ion irradiation. This method offers the possibility to directly image those parts of an IC which are sensitive to ion-induced malfunctions. By a 3-dimensional simulation of charge collection across p-n-micro-junctions, we can predict SEU cross-sections. For a MHS65162 2k x 8bit CMOS SRAM we found two regions per bit with different sensitivity and measured a total cross-section of (71/spl plusmn/18) /spl mu/m/sup 2/ for a bitflip per cell and simulated 60 /spl mu/m/sup 2/ with an argon beam of 1.4 MeV/nucl. (LET of 19.7 MeV/(mg/cm/sup 2/)). >

Applications of plastic nuclear track detectors in heavy ion physics

Abstract The experimental technique of computerized track measurements for plastic nuclear track detectors was used in different experiments investigating interactions of relativistic heavy ions. In this paper the method is described, results are presented and discussed. To measure cross sections stacks were exposed at the BEVALAC, at Brookhaven and at CERN to different beam nuclei having energies from 0.6 GeV/nucleon up to 200 GeV/nucleon. The cross sections for one nucleon removal are considerably enhanced at high energies due to electromagnetic dissociation. We investigated the effect of electromagnetic dissociation for different targets and projectiles. For heavy projectiles an exclusive analysis of nuclear fragmentation on an event by event basis was performed. Based on this the effect of multifragmentation can be studied. We exposed a stack of 100 CR39 foils to a 1 GeV/nucleon 197 Au beam at the BEVALAC. Events with up to 10 projectile fragments having a charge Z≥5 and coming out of the same interaction vertex were observed. To search for projectile fragments with fractional charge in relativistic heavy ion collisions, we exposed stacks of 50 CR39 foils behind a lead block of 15 cm depth to the ultrarelativistic heavy ion beams at Brookhaven and CERN. The charge resolution achieved in these experiments is o=0.027e.

Study of SEUs generated by high energy ions

Using 1 GeV/nucleon ions SEUs have been studied in two types of CMOS-SRAMs with respect to tilt angle and tilt direction. Tracks of upset bits, which have been observed under large tilt angles, were used to determine the charge collection depth in these devices. >

The Siegen automatic measuring system for nuclear track detectors status and new developments

Abstract We developed a completely automatic scanning and measuring system for nuclear track detectors. The video pictures of particle tracks seen through a microscope are digitized and analyzed in real time by MC 68000 microprocessors. In this paper we present some new developments: The picture analysis software is extended to separate overlapping tracks and to measure elliptical tracks even if these are flawed by surface structures. A software autofocus, a faster hardware version based on the contrast and a modified commercial laser autofocus are now available. A new picture analysis system based on the faster 32-bit microprocessor MC 68020 will operate on two pictures of 1024 × 1024 pixels resident in memory together. This will allow three dimensional track measurements.

Interaction mean free path measurements for relativistic heavy ion fragments using CR39 plastic track detectors

Abstract This paper describes an experiment measuring the interaction mean free paths for charge changing nuclear collisions of relativistic heavy ion fragments. We use a stack of CR39 plastic nuclear track detectors that was irradiated with 1.8 GeV/nucleon 40 Ar ions at the Berkeley Bevalac. About 1.5 × 10 7 etch cones were measured in this experiment using an automatic measuring system. By tracing the etch cones over successive plastic foils the particle trajectories in the stack were reconstructed. For 14185 trajectories with 6444 nuclear collisions of fragments with charge 9–15 the interaction mean free path in the plastic was determined.

Anomalons: Current status and first evidence from plastic track detectors

Abstract A number of experiments have shown that enhanced cross sections exist for projectile fragments which are emitted in relativistic heavy ion collisions. The present status of these investigations is reviewed. An experiment is described in which this effect is measured with significantly better statistics. First results for fragments of charge 14 emerging from 1.8 MeV/nucleon 40 Ar projectiles are presented.

Fragmentation of heavy projectile nuclei with energies between 200 and 1000 MeV/nucleon

Abstract We exposed stacks containing plastic nuclear track detectors and different target materials to heavy ions at the Berkeley BEVALAC. Interactions of the beam particles with Ag and C target nuclei and with the constituents of our detector material CR-39 (C 12 H 18 O 7 ) were studied in detail. For each interaction vertex all projectile fragments with charge Z-6 were measured and their emission angles were determined. Charge yields, transverse momenta, correlations in charge and angle are studied separately for different multiplicities M of observed fragments. We present results of experiments with 980 MeV/nucleon Au projectiles on a Ag/CR-39 target, 1050 MeV/nucleon Au projectiles on a C target and with 920 MeV/nucleon U projectiles on a Ag/CR-39 target.

Study of radiation effects of heavy ions in microelectronic devices

Abstract We started a research program using heavy ion beams at the GSI Darmstadt accelerator to investigate radiation effects of heavy ions in microelectronic devices. The understanding of these radiation effects is of particular importance to estimate the radiation rise for microelectronic parts exposed to the cosmic radiation during space missions. In order to expose static RAM devices to heavy ion beams a test system was installed. Additionally we use CCD image sensors to measure the amount of charge deposited inside the sensitive volume of single picture elements. Measurements will be performed with ions of different charge and energy up to 1 GeV/N to investigate the LET dependence of the effects and possible influence of the track structure. The experimental setup is described in this paper and first results are presented.

Search for anomalons using plastic nuclear track detectors

Abstract Enlarged cross sections for projectile fragments of relativistic nuclei have been observed in Bevalac and cosmic ray experiments with nuclear emulsions. We performed an experiment using plastic track detectors to investigate the anomalon effect. A new automatic measuring technique for heavy ion tracks in plastic detectors enables us to analyze large numbers of fragmentation reactions in reasonable time. Thus we get better statistical significance. Results of the experiment are presented.