Download - Charged Particle Interactions - Detection

Excitation Ionization ion-pair, suppress recombination in detectors.

Energy loss

Radiation Detection and Measurement, JU, 1st Semester, 2008-2009 (Saed Dababneh).

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Charged Particle Interactions - Detection

Interaction of heavy charged particles

• Electronic or nuclear (Rutherford, nuclear reactions, …).

• Depletion layer.• Delta rays and secondary electrons.• Electron suppression for charge integration.• Faraday Cup.• Tracks.

Detectors mainly designed to make use of electronic interactions.

SRIMhttp://www.srim.org

http://www.srim.org/


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2

220

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1ln2

ln4

c

v

c

v

I

vmNZ

vm

ze

dx

dE

Stopping power Stopping power Bethe-Bloch formula

Minimum ionizing particles

~1/E


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Electron pick-up. ~1/E

Charged Particle Interactions - DetectionWhat about fission fragments?????What about fission fragments?????

Bragg curve

• Energy loss is a stochasticstochastic process, thus energy straggling.energy straggling.


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eV / Å keV / m MeV / mm keV / (g/cm2) MeV / (mg/cm2) keV / (mg/cm2) eV / (1x1015 atoms/cm2)


UnitsUnits

(conversion)(conversion)You will encounter this when you run SRIM


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Range of charged particles Range of charged particles Compare to gamma … !!!Compare to gamma … !!!Range straggling?Range straggling?

Mean and extrapolated range.

• An “old” idea to measure energy..!• Surface barrier, PIPS.• For a detector to register the full energy of charged particles, its thickness should be more than the range at that energy.• Sometimes we look for partial energy.• E-E detection. • Energy and position position sensitive detectors.sensitive detectors.• Radioactive ion beams.Radioactive ion beams.

Counts number


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Use SRIMData to

reproduce the

graphs.

Energy deposited in an Energy deposited in an absorber (or detector).absorber (or detector).

Or, if “thin” absorber:Or, if “thin” absorber:

Both are not accurate. Both are not accurate. Why?Why?You can do it better with You can do it better with SRIM.SRIM.

tdx

dEE

ave


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E-E detection.

http://www.ph.ed.ac.uk/nuclear/louvain/louvain1.1.jpeg


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Stopping timeStopping time

Problem…!!

• Effect on Doppler shift and broadening in nuclear reactions.

Compare the application of scaling laws and Bragg-Kleeman rule with SRIM.Work out many examples.


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Fast Electron Interactions.Fast Electron Interactions.

• CollisionalCollisional

• Radiative (Bremsstrahlung)Radiative (Bremsstrahlung)

What is the main difference for positrons?


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Range .. !

Ra

nge

x d

ens

ity

Mon

oene

rget

ic

What about electrons?


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nteI

I 0


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BackscatteringBackscattering

Fra

ctio

n b

ack

sca

ttere

d• Detector entrance window or dead layer.• Source backing.

Download - Charged Particle Interactions - Detection

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