RADIATION HARDENING

SOWMYA THYAGARAJANAISST

ROLLNO:25A4717210013

Radiation hardening  electronic components systems resistant ionizing radiation, high electromagnetic radiation.  outer space, high-altitude flight, around nuclear reactors , particle accelerators, during nuclear accidents or nuclear warfare.

Radiation hardening

A single charged particle can knock thousands of electrons  loose electronic noise, signal spikes Digital circuits inaccurate or unintelligible. serious problem artificial satellites, spacecraft, military aircraft, nuclear weapons.

PROBLEMS

Van Allen radiation belts satellites  residual radiation from isotopes

in chip packaging materials  cosmic radiation spacecraft, high-

altitude aircraft  nuclear explosions military and

civilian electronics

RADIATION DAMAGE SOURCES

Cosmic rays 85% protons, 14% alpha particles, and 1% heavy ions particles 108 and 2*1010eVatmosphere filters primarily a concern for spacecraft, high-altitude aircraft.

Solar particle events sun large flux of high-energy (several GeV) protons, heavy ion, x-ray radiation.

Van Allen radiation belts electrons(10 MeV) protons (100s MeV) in  geomagnetic field.

The particle flux in the regions farther from the Earth actual conditions of the sun and the magnetosphere.

Due to their position they pose a concern for satellites.

Hardened chips manufactured on insulating substrates  Silicon dioxide (SOI) and sapphire(SOS)

Normal commercial-grade chips withstand 50 and 100gray (5 and 10 krad)

space-grade SOI and SOS chips can survive doses many orders of magnitude greater4000 series chips were available in radiation-hardened versions

PHYSICAL TECHNIQUES

Bipolar integrated circuits higher radiation tolerance than CMOS circuits.

Low-power Schottky (LS) 5400withstand 1000 krad, ECL devices withstand 10 000 krad

Magneto-resistive RAM, MRAM radiation hardened, rewritable, non-volatile conductor memory.

Error correcting memory additional parity bits to check possibly correct corrupted data.

radiation effects damage memory

content even when system is not accessing the RAMa "scrubber" circuit must continuously sweep the RAM reading out the data, checking the parity for data errors then writing back any corrections to the RAM.

LOGICAL TECHNIQUES

Redundant elements can be used at the system level.

3separate microprocessor boards independent compute an answer to a calculation and compare their answers.

Any system with minority result will recalculate. Logic added if repeated errors occur from the same system, that board is shut down.

Hardened latches may be used.

watchdog timer hard reset of a system unless some sequence done indicates the system is alive write operation from an on board processor.

normal operation software schedules a write to the watchdog timer at regular intervals to prevent the timer from running out.

If radiation causes the processor to operate incorrectly the software will work correctly enough to clear the watchdog timer.

The watchdog times out, forces a hard reset to the system a last resort to other methods of radiation hardening.

1886VE10 microcontroller

MARS ROVER