INTERACTIONS OF IONS WITH MATTER

This website contains software on TWO Topics:

SRIM - The Stopping and Range of Ions in Matter

SER - Soft Error Rates from Cosmic Rays (see bottom of this page)

SRIM Web Statistics

Above links in Green are links to other websites.

The topping and R ange of I ons in M atter

Software -

SRIM is a collection of software packages which calculate many features of the transport of ions in matter. Typical applications include:

· Ion Stopping and Range in Targets: Most aspects of the energy loss of ions in matter are calculated in SRIM, the Stopping and Range of Ions in Matter. SRIM includes quick calculations which produce tables of stopping powers, range and straggling distributions for any ion at any energy in any elemental target. More elaborate calculations include targets with complex multi-layer configurations.

· Ion Implantation: Ion beams are used to modify samples by injecting atoms to change the target chemical and electronic properties. The ion beam also causes damage to solid targets by atom displacement. Most of the kinetic effect s associated with the physics of this kind of interactions are found in the SRIM package.

· Sputtering: The ion beam may knock out target atoms, a process called ion sputtering. The calculation of sputtering, by any ion at any energy, is included in the SRIM package.

· Ion Transmission: Ion beams can be followed through mixed gas/solid target layers, such as occurs in ionization chambers or in energy degrader blocks used to reduce ion beam energies.

· Ion Beam Therapy: Ion beams are widely used in medical therapy, especially in radiation oncology. Typical applications are included.

Science -

The science of ion beams goes back almost a century to the earliest explanations of radioactive particles transiting thin films (1904). The field is so rich that it is difficult for a non-expert to understand any of the current papers in the field. But basically, the stopping of ions in matter can not be calculated from first principles. Hidden in stopping theories are parameters which normalize calculated stopping powers to existing data. The "Science" section of SRIM will review the basic theories of the stopping of ions in matter. Then some of the major parameters are reviewed and it will be shown how they are derived from experimental data. Examples are shell corrections, mean ionization potentials, the effective charge of ions and the Fermi velocity of solids.

Over 2000 papers have been published in the experimental stopping of ions in solids. Experimental measurements of stopping powers is a difficult task, and there is wide variation in the results.. Plots will show how existing stopping calculations compare to experimental data from these papers. Since the stopping calculations are based in great part on theory, the interpolation of stopping powers between various ions and targets is often more accurate than individual measurements, especially for difficult targets.

E lectronic R eliability -

E ffects of T errestrial C osmic R ays

Technology Soft Error Rates Science of Terrestrial Cosmic Rays Introduction History Current Status (1MB) Neutron Sea Level Flux History of Accelerated Testing Neutron Spectrometers Current Status Accelerated Testing

Above links in Green are not yet active.

Although this subject is more about the effects of energetic hadrons on terrestrial electronics than about ion beams, it is scientifically in a similar field (hadrons = protons, neutrons and pions, i.e. particles which respond to the nuclear force / strong interaction). The science and technology about cosmic ray induced soft fails was considered proprietary by IBM for more than 15 years. In 1996, a complete issue of the IBM Journal of Research and Development was devoted to reviewing this work. A summary of the issue, and the complete first article (the 15 year history of the development of the IBM scientific understanding of soft fails from radiation) is given at IBM J. R.& D.

The scientific history of this field is reviewed in detail. The field is not static because the technology of integrated circuits is still rapidly changing and the effects of cosmic rays on integrated circuits (ICs) show trends which are not well understood. The trends in the sensitivity of ICs to cosmic rays are reviewed for SRAMs, DRAMs and logic over the last 15 years.

Fundamental to any estimates of the fail rate of ICs is an understanding of the ambient flux of cosmic rays in the environment. As this flux has been investigated over the last 15 years, it has become fuzzier rather than more precise. Previous measurements of the ambient flux which were considered reliable have been shown to be suspect. New measurements rarely agree with past measurements. Recent reports of the flux of sea level cosmic ray hadrons vary by more than 10x, even though they were performed by highly competent scientists. The problem will probably be resolved by understanding that the immediate materials nearby an experiment can have significant effect on the measured flux. The field of the terrestrial flux of cosmic rays will be reviewed.

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