H. Röcher

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/)). >

High energy heavy ion interactions studied with SSNTDs

We have continued our studies of heavy ion projectile fragmentation using nuclear track detectors. Based on automatic track measurement it was possible to perform experiments with high statistical significance. Beams of different ions from the Berkeley BEVALAC, the Dubna Synchrophasotron, the Brookhaven AGS and the GSI Darmstadt SIS have been used. With CR-39 and BP-1 glass detectors we have studied the process of electromagnetic dissociation, we investigated multifragmentation and continued the search for quark nuclear complexes. This paper gives an overview of these experiments. Details of the experimental technique are discussed.

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. >

Fragmentation cross section measurements of iron projectiles using CR-39 plastic nuclear track detectors

Abstract For long term space missions in which larger radiation doses are accumulated it is necessary to improve the precision of models predicting the space radiation environment. Different models are available to determine the flux of cosmic ray heavy ions behind shielding material. The accuracy of these predictions depends on the knowledge of the fragmentation cross sections, especially at energies of several hundred MeV/nucleon, where the particle flux is at a maximum and especially for those particles with high LET, i.e. iron nuclei. We have measured fragmentation cross sections of 56 Fe projectiles at beam energies of 700 and 1700 A MeV using experimental set-ups with plastic nuclear track detectors. In this paper we describe the experimental technique to study the fragmentation reactions of 56 Fe projectiles using CR-39 plastic nuclear track detectors. Results for different targets are presented.

The high-LET radiation component measured during the EUROMIR-94 mission

Stacks of CR-39 plastic nuclear track detectors were mounted inside the MIR-station during the EUROMIR-94-mission. We present LET-spectra determined separately for long range cosmic ray heavy ions and for short range target fragments produced in nuclear interactions of cosmic rays and measured charge distributions for relativistic and stopping particles.

Energy spectrum of iron nuclei measured inside the MIR space craft using CR-39 track detectors

We have exposed stacks of CR-39 plastic nuclear track detectors inside the MIR space craft during the EUROMIR95 space mission for almost 6 months. Over this long period a large number of tracks of high LET events was accumulated in the detector foils. The etching and measuring conditions for this experiment were optimized to detect tracks of stopping iron nuclei. We found 185 stopping iron nuclei inside the stack and identified their trajectories through the material of the experiment. Based on the energy-range relation the energy at the surface of the stack was determined. These particles allow the determination of the low energy part of the spectrum of iron nuclei behind shielding material inside the MIR station.

Investigation of single event effects of high energetic heavy ions

The authors started a research program using heavy ion beams to investigate radiation effects on microelectronic devices. In order to expose static random access memory (SRAM) devices to heavy ions a test system was installed. This setup was first operated using different ions at the GSI UNILAC with energies below 20 MeV/nucleon. After these first tests further measurements were performed with ions of different charge and energy up to 1 GeV/nucleon at the GSI-SIS. As ions with energies of some hundred MeV/nucleon are a good representation of space conditions such beams are interesting for reliability tests of microelectronic space equipment. The experimental setup and the exposure conditions at GSI are described and first results are presented.<<ETX>>

Study of fragmentation interactions at beam energies from 1 to 158 A GeV

Abstract We have investigated fragmentation interactions of relativistic heavy ion projectiles using the plastic nuclear track detector CR-39 (C 12 H 18 O 7 ). Stacks with detector foils and different targets have been exposed to Au- and Pb-ions at the Berkeley BEVALAC, the GSI Darmstadt SIS, the Brookhaven AGS and the CERN SPS. These experiments have been performed with high statistical significance. Charge yields and charge correlations determined for beam energies of 1, 10.6 and 158 A GeV were investigated. Our first experiments with 1 A GeV Au-nuclei have shown that the transverse momenta of the fragments are enlarged in comparison to a simple statistical model (Goldhaber model). For the new data at higher energies, we observed a dependence of the momentum transfer on the beam energy.

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.

Cross sections of 197Au at 10 A GeV and of 207Pb at 158 A GeV

Abstract We have measured total and elemental charge changing cross sections fro the fragmentation of 10 AGeV 197 Au- and 158 AgeV 207 Pb-beams interacting with different targets (C, CH 2 , Al, Cu, Ag, and Pb) using stacks of CR-39 and of BP-1 nuclear track detectors. Electromagnetic dissociation (ED) significantly contributes to these interactions besides nuclear fragmentation. Based on the factorization of elemental cross sections it is possible to separate electromagnetic dissociation cross sections from the measured data. The analysis of the Au 10 AGeV experiment is completed. For the Pb-beam the analysis is in progress. First results will be reported.