PHYS40422: Applied Nuclear Physics

Paul CampbellRoom 4.11

Paul.Campbell-3@manchester.ac.uk

1. Interaction of Radiation with Matter

2. Radiation Detection

3. Biological Effects of Radiation

4. Applications of Nuclear Techniques

5. Nuclear Fission

6. Nuclear Fusion

http://personalpages.manchester.ac.uk/staff/Paul.Campbell-3/phys40422.htm

Applications of Nuclear Physics

1) Medical diagnosis:X-ray imagingRadioactive tracers to examine organ function and locate tumoursRadioactive isotopes in pharmaceuticals to follow their actionPositron emission tomographyNuclear magnetic resonance imaging 2) TherapyElectron and photon radiotherapyTherapy using protons and other heavy charged particles Local use of radioactive sources to treat tumoursHeart pacemakers powered by α-particle sources

3) Industrial and other usesSterilisation by strong sourcesThickness monitoring in manufacture of thin materialsLooking for leaks in underground pipesTesting welds in installed pipework

4) The use of long-lived isotopes produced by cosmic raysDating of artefacts (14C)Study of ancient groundwaters (36Cl)Study of aluminium toxicity (26Al)

Single beam irradiation with photons or electrons

Comparison with four beam irradiation

The benefits of fractionation of dose (several hours between dose fractions)

Effect of putting patient into an oxygen chamber

no change in sensitivity

increase in sensitivity

Effect of local oxygen starvation

decrease in sensitivity

no change

The Waikato Laboratory in New Zealand determines 14C activity through the measurement of beta particles.

Samples are converted to benzene.

Residual radiocarbon activity is measured using ten Liquid Scintillation (LS) low-background spectrometers.

The spectrometers have extensive shielding designed to reduce the effects of background radiation, enabling both older and smaller samples to be dated more accurately.

The instrument also contains twin analysers which provide information on both sample and background spectra, necessary for quality control.

A rat gnawed seed A feather Linen wrapping froma mummy

Linen cloth with image in negative

Burial shroud of Christ?

No apparent signs of forgery

Kept in Royal Chapel in the Cathedral of St. John, Turin.

Small piece sent for Carbon dating.

Nature, Vol. 337, No. 6208, pp. 611-615, 16th February, 1989

Dating of the Turin Shroud

A piece of the shroud was divided amongst and measured independently by laboratories in Arizona, Oxford and Zurich.

The final weighted mean result was that the tested samples dated from 690 (16) BP, where “present” is conventionally defined as 1950.

Note the precision of the dating.

This apparent age has to be converted to calendar date by calibrating with tree ring data.

Calibration curve using dendrochronological dating which can reveal the effects of natural variations in atmospheric 14C

Published calendar date:

1273-1288 AD at 68% confidence level

1262-1312; 1353-1384 at 95% confidence level – double valued from calibration curve

Therefore date is 1260-1390

Note “accuracy” compared to “precision” of measurement.

This date caused quite a furore.

Following chemical and other tests, it is now being suggested that a mediaeval “patch” was dated!

i.e. the published date is correct, but the test sample was not from theoriginal linen of the shroud.

The layout of an accelerator-based mass spectrometry system

t is time elapsed

t1/2 is the half-life of 40K

Kf is the amount of 40K remaining in the sample

Arf is the amount of 40Ar found in the sample.

Geological dating (example):

Rock originally containing potassium but no argon (molten lava formation). Over time 40K will decay to 40Ar, 10.9% of the time…