Accelerator Physics, JU, First Semester, 2010-2011 (Saed Dababneh).

1

Electron pick-up. ~1/E

What about fission fragments?????What about fission fragments?????

Bragg curve

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

Principles of Spectrometry

Target

Acc

eler

ated

be

am

Accelerator Physics, JU, First Semester, 2010-2011 (Saed Dababneh).

2

Hadrontherapy

Accelerator Physics, JU, First Semester, 2010-2011 (Saed Dababneh).

3

Principles of Spectrometry

Accelerated beam

Accelerator Physics, JU, First Semester, 2010-2011 (Saed Dababneh).

4

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

Principles of Spectrometry

Accelerator Physics, JU, First Semester, 2010-2011 (Saed Dababneh).

5

E-E detection.

Principles of Spectrometry

Accelerator Physics, JU, First Semester, 2010-2011 (Saed Dababneh).

6

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

Principles of Spectrometry

Accelerator Physics, JU, First Semester, 2010-2011 (Saed Dababneh).

7

Principles of Spectrometry

Accelerator Physics, JU, First Semester, 2010-2011 (Saed Dababneh).

8

Accelerator Physics, JU, First Semester, 2010-2011 (Saed Dababneh).

9

Stopping timeStopping time

Problem…!!

• Detector response time. • 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.Ranges?

Principles of Spectrometry

• Units?• Applicability?

HW 12

HW 13

Accelerator Physics, JU, First Semester, 2010-2011 (Saed Dababneh).

10

Fast Electron Interactions.Fast Electron Interactions.

• CollisionalCollisional

• Radiative (Bremsstrahlung)Radiative (Bremsstrahlung)

What is the main difference for positrons?

Principles of Spectrometry

Accelerator Physics, JU, First Semester, 2010-2011 (Saed Dababneh).

11

Range .. !

Ran

ge x

den

sity

Mon

oene

rget

ic

Elec

tron

Beam

What about electrons?

Principles of Spectrometry

12

nea

rly m

onoe

ner

getic

.

ICAuger

bexeEEE

Hig

h ke

V to

MeV

rang

e.

Few keV.

En

erg

y R

eso

luti

on

Easily self absorbed.

Principles of Spectrometry

Accelerator Physics, JU, First Semester, 2010-2011 (Saed Dababneh).

Accelerator Physics, JU, First Semester, 2010-2011 (Saed Dababneh).

13

BackscatteringBackscattering

Fra

ctio

n b

ack

sca

ttere

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

Principles of Spectrometry

Accelerator Physics, JU, First Semester, 2010-2011 (Saed Dababneh).

14

Principles of Spectrometry

Accelerator Physics, JU, First Semester, 2010-2011 (Saed Dababneh).

15

nteI

I 0

Principles of Spectrometry

From 185W.Endpoint = 0.43 MeV.

In Al

Accelerator Physics, JU, First Semester, 2010-2011 (Saed Dababneh).

16

Nuclear Reactions

X(a,b)Y• First in 1919 by Rutherford:

4He + 14N 17O + 1H14N(,p)17O

• Incident particle may: change direction, lose energy, completely be absorbed by the target……• Target may: transmute, recoil……• b = Radiative Capture.• If B.E. permits fission (comparable masses).• Different exit channels a + X Y1 + b1

Y2 + b2

Y3 + b3 …….

Accelerator Physics, JU, First Semester, 2010-2011 (Saed Dababneh).

17

Nuclear Reactions• Recoil nucleus Y could be unstable or emission.

• One should think about: Reaction dynamics and conservation laws i.e. conditions necessary for the reaction to be energetically possible. Reaction mechanism and theories which explain the reaction. Reaction cross section i.e. rate or probability.

Accelerator Physics, JU, First Semester, 2010-2011 (Saed Dababneh).

18

Nuclear Reaction Energetics (revisited)

• If the reaction reaches excited states of Y

58Ni(,p)61Cu

Highest proton energy

exbexYaXex EQcmEcmcmcmQ 02222 )(

less proton energy

even less ….

Accelerator Physics, JU, First Semester, 2010-2011 (Saed Dababneh).

19

Nuclear Reaction Energetics (revisited)

20

Nuclear Reactions

Categorization of Nuclear Reactions• According to: bombarding particle, bombarding energy, target, reaction product, reaction mechanism.• Bombarding particle:

Charged particle reactions. [ (p,n) (p,) (,) heavy ion reactions ]. Neutron reactions. [ (n,) (n,p) ….. ]. Photonuclear reactions. [ (,n) (,p) … ]. Electron induced reactions………….

• Bombarding energy: Thermal. Epithermal. Slow. Fast. Low energy charged particles. High energy charged particles.

Neutrons.?

Accelerator Physics, JU, First Semester, 2010-2011 (Saed Dababneh).

21

Nuclear Reactions• Targets:

Light nuclei (A < 40). Medium weight nuclei (40 < A < 150). Heavy nuclei (A > 150).

• Reaction products: Scattering. Elastic 14N(p,p)14N

Inelastic 14N(p,p/)14N* Radiative capture. Fission and fusion. Spallation. …..

• Reaction mechanism: Direct reactions. Compound nucleus reactions.

• More ….• What is a transfer reaction….?????

Stripping

Pickup

Reson

ant

Non-resonant

Accelerator Physics, JU, First Semester, 2010-2011 (Saed Dababneh).