Cosmic ray effect on microchips benefits from accelerated neutron testing (2/21/2008)

UK neutron scientists are tackling the challenge of cosmic radiation and its damaging effect on sensitive microchips in the aviation industry in the drive to develop more robust electronic equipment. Accelerated testing of microelectronic components at the Science and Technology Facilities Council's (STFC) world leading ISIS neutron research centre replicates the effect of thousands of hours of flying time in just a few minutes.

When cosmic rays consisting of energetic particles originating from outer space, or the flow of fast-moving charged particles in the solar wind from the sun, collide with the Earth's atmosphere they produce a cascade of lighter particles, a so-called 'air shower'. High energy neutrons from air showers collide with microchips and upset or damage microelectronic devices. These occurrences known as 'Single Event Effects' (SEEs), can affect circuitry on the ground, but the problem is 300 times greater at high altitude. This makes it of particular concern to both the civil and military aerospace industry.

A microchip in an aircraft can be struck by a cosmic neutron every few seconds. When a neutron hits silicon, a nuclear reaction occurs causing an electrical charge shower that can interfere with the normal operation of electronic equipment.

Dr. Chris Frost, Project Leader of chip irradiation research at the ISIS neutron source explains the phenomenon.

'A SEE occurs when a high energy particle in the atmosphere strikes sensitive regions of an electronic device, disrupting its correct operation. This can lead to temporary loss of RAM memory or even permanent burnout of equipment.'

Although SEEs have been recognised as an issue since 2001, the problem is being compounded by the drive for greater RAM density in computers. Smaller electronic circuitry is more vulnerable to this buffeting from neutrons.

One of the ways of tackling the issue is to test the quality and susceptibility of components under accelerated conditions. The ISIS neutron source, a world leading facility for research in the physical and life sciences, can replicate the experience of thousands of hours of flying time in a very condensed period. Dr Chris Frost says that by exposing components to neutron beams produced at ISIS, the industry can learn lessons about the best way forward.

'At ISIS we have the ability to produce intense beams of neutrons with similar energy ranges to those occurring naturally. This enables accelerated reliability testing of microelectric elements used in the aerospace industry. Once manufacturers understand where the biggest susceptibility problems lie, they can begin to redesign circuitry on a more robust basis.'

Initial tests occurred at the end of 2006 at the ISIS neutron source in Oxfordshire. A £140 million new 'target station' or neutron source is currently in the final stages of completion alongside the original ISIS neutron source. The plan, subject to funding, is for the ISIS Second Target Station to include a dedicated and full-time instrument to test the effects of SEEs and chip irradiation.

Results from this testing will allow manufacturers to mitigate against the problem and build triple redundancy into their electronic components. This increased confidence in the quality of electronic systems will help to make both civil and military aircraft safer.

Note: This story has been adapted from a news release issued by the Science and Technology Facilities Council

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