Bologna 1st-5th September 1 Neutron dosimetry and spectrometry: problems, solutions, perspectives and the role of track detectors Carles Domingo Grup de

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Bologna Bologna 1st-5th September1st-5th September

Neutron dosimetry and spectrometry:Neutron dosimetry and spectrometry: problems, solutions, perspectives and the role of problems, solutions, perspectives and the role of

track detectorstrack detectors

Carles DomingoCarles Domingo

Grup de Física de les RadiacionsGrup de Física de les RadiacionsDepartament de FísicaDepartament de Física

Universitat Autònoma de Barcelona, Bellaterra (Spain)Universitat Autònoma de Barcelona, Bellaterra (Spain)

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OverviewOverview

IntroductionIntroduction Dosimetry (general)Dosimetry (general) Dosimetry (neutron specific)Dosimetry (neutron specific) Spectrometry and unfoldingSpectrometry and unfolding CalibrationCalibration Track detectorsTrack detectors ConclusionConclusion

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Introduction

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Ancient references…Ancient references…

...And God said, ...And God said, "Let there be light“"Let there be light“; and ; and there was light... [Genesis,1,3 (-XXXX)]there was light... [Genesis,1,3 (-XXXX)]

So… the So… the photonsphotons were there. were there.

What about the neutrons?...What about the neutrons?...

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Ancient references…Ancient references… 11 First God made heaven & earth First God made heaven & earth 22 The earth was without form and void, and darkness was upon the face of the deep; and the The earth was without form and void, and darkness was upon the face of the deep; and the

Spirit of God was moving over the face of the waters. Spirit of God was moving over the face of the waters. 33 And God said, "Let there be light"; and there was light. And God said, "Let there be light"; and there was light. 44 And God saw And God saw that the light was good; and God separated the light from the darkness. that the light was good; and God separated the light from the darkness. 55 God called the light Day, and the darkness he called God called the light Day, and the darkness he called Night. And there was evening and there was morning, one day. Night. And there was evening and there was morning, one day. 66 And God said, "Let there be a firmament in the midst of the And God said, "Let there be a firmament in the midst of the waters, and let it separate the waters from the waters." waters, and let it separate the waters from the waters." 77 And God made the firmament and separated the waters which were And God made the firmament and separated the waters which were under the firmament from the waters which were above the firmament. And it was so. under the firmament from the waters which were above the firmament. And it was so. 88 And God called the firmament Heaven. And God called the firmament Heaven. And there was evening and there was morning, a second day. And there was evening and there was morning, a second day. 99 And God said, "Let the waters under the heavens be gathered And God said, "Let the waters under the heavens be gathered together into one place, and let the dry land appear." And it was so. together into one place, and let the dry land appear." And it was so. 1010 God called the dry land Earth, and the waters that were God called the dry land Earth, and the waters that were gathered together he called Seas. And God saw that it was good. gathered together he called Seas. And God saw that it was good. 1111 And God said, "Let the earth put forth vegetation, plants And God said, "Let the earth put forth vegetation, plants yielding seed, and fruit trees bearing fruit in which is their seed, each according to its kind, upon the earth." And it was so. yielding seed, and fruit trees bearing fruit in which is their seed, each according to its kind, upon the earth." And it was so. 1212 The The earth brought forth vegetation, plants yielding seed according to their own kinds, and trees bearing fruit in which is their seed, earth brought forth vegetation, plants yielding seed according to their own kinds, and trees bearing fruit in which is their seed, each according to its kind. And God saw that it was good. each according to its kind. And God saw that it was good. 1313 And there was evening and there was morning, a third day. And there was evening and there was morning, a third day. 1414 And And God said, "Let there be lights in the firmament of the heavens to separate the day from the night; and let them be for signs and God said, "Let there be lights in the firmament of the heavens to separate the day from the night; and let them be for signs and for seasons and for days and years, for seasons and for days and years, 1515 and let them be lights in the firmament of the heavens to give light upon the earth." And it and let them be lights in the firmament of the heavens to give light upon the earth." And it was so. was so. 1616 And God made the two great lights, the greater light to rule the day, and the lesser light to rule the night; he made the And God made the two great lights, the greater light to rule the day, and the lesser light to rule the night; he made the stars also. stars also. 1717 And God set them in the firmament of the heavens to give light upon the earth, And God set them in the firmament of the heavens to give light upon the earth, 1818 to rule over the day and over the to rule over the day and over the night, and to separate the light from the darkness. And God saw that it was good. night, and to separate the light from the darkness. And God saw that it was good. 1919 And there was evening and there was And there was evening and there was morning, a fourth day. morning, a fourth day. 2020 And God said, "Let the waters bring forth swarms of living creatures, and let birds fly above the earth And God said, "Let the waters bring forth swarms of living creatures, and let birds fly above the earth across the firmament of the heavens." across the firmament of the heavens." 2121 So God created the great sea monsters and every living creature that moves, with So God created the great sea monsters and every living creature that moves, with which the waters swarm, according to their kinds, and every winged bird according to its kind. And God saw that it was good. which the waters swarm, according to their kinds, and every winged bird according to its kind. And God saw that it was good. 2222 And God blessed them, saying, "Be fruitful and multiply and fill the waters in the seas, and let birds multiply on the earth." And God blessed them, saying, "Be fruitful and multiply and fill the waters in the seas, and let birds multiply on the earth." 2323 And And there was evening and there was morning, a fifth day. there was evening and there was morning, a fifth day. 2424 And God said, "Let the earth bring forth living creatures according to And God said, "Let the earth bring forth living creatures according to their kinds: cattle and creeping things and beasts of the earth according to their kinds." And it was so. their kinds: cattle and creeping things and beasts of the earth according to their kinds." And it was so. 2525 And God made the And God made the beasts of the earth according to their kinds and the cattle according to their kinds, and everything that creeps upon the ground beasts of the earth according to their kinds and the cattle according to their kinds, and everything that creeps upon the ground according to its kind. And God saw that it was good. according to its kind. And God saw that it was good. 2626 Then God said, "Let us make man in our image, after our likeness; and let Then God said, "Let us make man in our image, after our likeness; and let them have dominion over the fish of the sea, and over the birds of the air, and over the cattle, and over all the earth, and over them have dominion over the fish of the sea, and over the birds of the air, and over the cattle, and over all the earth, and over every creeping thing that creeps upon the earth." every creeping thing that creeps upon the earth." 2727 So God created man in his own image, in the image of God he created him; So God created man in his own image, in the image of God he created him; male and female he created them. male and female he created them. 2828 And God blessed them, and God said to them, "Be fruitful and multiply, and fill the earth And God blessed them, and God said to them, "Be fruitful and multiply, and fill the earth and subdue it; and have dominion over the fish of the sea and over the birds of the air and over every living thing that moves and subdue it; and have dominion over the fish of the sea and over the birds of the air and over every living thing that moves upon the earth." upon the earth." 2929 And God said, "Behold, I have given you every plant yielding seed which is upon the face of all the earth, and And God said, "Behold, I have given you every plant yielding seed which is upon the face of all the earth, and every tree with seed in its fruit; you shall have them for food. every tree with seed in its fruit; you shall have them for food. 3030 And to every beast of the earth, and to every bird of the air, and And to every beast of the earth, and to every bird of the air, and to everything that creeps on the earth, everything that has the breath of life, I have given every green plant for food." And it was to everything that creeps on the earth, everything that has the breath of life, I have given every green plant for food." And it was so. so. 3131 And God saw everything that he had made, and behold, it was very good. And there was evening and there was morning, And God saw everything that he had made, and behold, it was very good. And there was evening and there was morning, a sixth day.a sixth day. [Genesis 1,1:31(-XXXX)] [Genesis 1,1:31(-XXXX)]

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IntroductionIntroduction

Origin:Origin: Natural: cosmic raysNatural: cosmic rays Artificial: industry, Artificial: industry,

research, medical research, medical application, …application, …

Concern: need to Concern: need to estimate radiological estimate radiological riskrisk

Energy range: 10-3 – 109 eV

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IntroductionIntroduction

NeutralNeutral Indirectly ionising radiationIndirectly ionising radiation Complex interaction mechanisms with matterComplex interaction mechanisms with matter

secondary charge particles Detection

Ionization of the medium Measurable signals

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Dosimetry (general)

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Dosimetric quantitiesDosimetric quantities

Primary standard quantities or Primary standard quantities or physical quantitiesphysical quantities Characterise the radiation field and its interaction with Characterise the radiation field and its interaction with

matter matter

FluenceFluence

KermaKerma

Absorbed doseAbsorbed dose

Mean absorbed dose averaged over an organ or tissue T Mean absorbed dose averaged over an organ or tissue T

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Limiting quantitiesLimiting quantities Take into account the biological effects of Take into account the biological effects of

radiationradiation DDT,RT,R is not able to estimate the biological effects, is not able to estimate the biological effects,

which depend on the type of radiation and tissuewhich depend on the type of radiation and tissue

Equivalent dose in an organ or tissueEquivalent dose in an organ or tissue

Effective doseEffective dose

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Operational quantitiesOperational quantities Limiting quantities cannot be directly measuredLimiting quantities cannot be directly measured Operational quantities are quantities defined for use in

radiation protection measurements to estimate limiting quantities in practice, in either area or individual monitoring.

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Adapted from ICRP74, 1995

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But… be careful!But… be careful!

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Dosimetry (neutron specific)

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Operational quantitiesOperational quantities

In air H*In air H*

Presence of phantom HPresence of phantom Hpp

Dependent from irradiation geometry (AP, iso, rot, …)Dependent from irradiation geometry (AP, iso, rot, …)

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Primary to operationalPrimary to operational

Conversion coefficients: Conversion coefficients: fluence to ambient dose fluence to ambient dose equivalent equivalent

Highly energy dependentHighly energy dependent Double number of neutron Double number of neutron

does not mean double does not mean double dose…dose…

ICRP publication 75, 1997; ICRU report 57, 1998.

dEEhH E )( )10()10( **

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Neutron measurementsNeutron measurements

EEhkER )()(

System reading

dEEERM )()( E dEEEhH )()( E

M H

Dose equivalent

not possible

Ideal case

B

BB

B B B B B B B B B B B B B B B

B

B

B

B

B

B

B

B

B

BBBBB B BBBBBBBB

BBBBBB

J

J

J

JJ

JJ

JJ

J JJ J J J J J

JJ

J JJ

JJ

JJ

J

JJJJJ

J J J JJJJJJJ JJJJJ

1

10

100

1000

1.0

E-1

0

1.0

E-9

1.0

E-8

1.0

E-7

1.0

E-6

1.0

E-5

1.0

E-4

1.0

E-3

1.0

E-2

1.0

E-1

1.0

E+

0

1.0

E+

1

1.0

E+

2

pS

v *

cm

^2

Energia (MeV)

B h*(E) ICRP 74

J R(E) Berthold

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Neutron measurementsNeutron measurements

Determination of neutron fluence energy distribution: E(E)

dEEEhH )()( E

Neutron spectroscopy

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Spectrometry and unfolding

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SpectrometrySpectrometry

NN detectors with different responses detectors with different responses RRii(E) to (E) to

neutronsneutrons

dEEERM

dEEERM

)()(

)()(

Enn

E11

3He BSS

197Au BSS

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UnfoldingUnfolding

j jjjjjjj

j jjjjjjj

EEEREEERM

EEEREEERM

)()()()(

)()()()(

nnn

111

jE j )(

j

jjjE EEEhdEEEhdEEEhH )()()()()()(

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Unfolding methodsUnfolding methods

Need some informationNeed some information Prior knowledge of a similar spectrumPrior knowledge of a similar spectrum

Mathematical approachMathematical approach BayesianBayesian

Knowledge of physical conditionsKnowledge of physical conditions Parametric approach Parametric approach

Take into account routine operation

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Adapted from ICRP74, 1995

Spectrometry

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Range of applicationRange of application

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Calibration

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ReadingsReadings

Given an instrument, we obtain a readingGiven an instrument, we obtain a reading counts·scounts·s-1-1

TLD unitsTLD units tracks·cmtracks·cm-2-2

Saturation activity (Bq·gSaturation activity (Bq·g-1-1)) ……

Readings are not the result of the measurement!!

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CalibrationCalibration

Need to calibrate in a reference installationNeed to calibrate in a reference installation Equal instruments to a similar neutron fieldEqual instruments to a similar neutron field

GeometryGeometry EnergyEnergy AngleAngle

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CalibrationCalibration

SpectrometersSpectrometers Should be calibrated both toShould be calibrated both to

Monoenergetic beamsMonoenergetic beams ISO sources ISO sources

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Track detectors

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Etching conditionsEtching conditions

ChemicalChemical Simple etching procedureSimple etching procedure Optical microscope (automated for routine work)Optical microscope (automated for routine work) LET information (of secondaries!!) keptLET information (of secondaries!!) kept

ElectrochemicalElectrochemical Simple reading devicesSimple reading devices Need of power source (HV, HF)Need of power source (HV, HF) LET information lostLET information lost

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SensitivitySensitivity

Fast neutronsFast neutrons With hydrogenated With hydrogenated

convertersconverters

Thermal neutronsThermal neutrons With Li, B or N With Li, B or N

convertersconverters

Intermediate Intermediate (epithermal neutrons)(epithermal neutrons) NoNo

Polyethylene(3mm)

Makrofol(300m)

Nylon(100m)

CR - 39(500m)

Methacrylate(5mm)

Phantom (15cm)

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Typical spectraTypical spectra

1E-9 1E-8 1E-7 1E-6 1E-5 1E-4 1E-3 0.01 0.1 1 100

200

400

600

800

1000

1200

1400

AscóI.1 AscóI.2 AscóI.3 AscóI.4 AscóII.1 AscóII.2 AscóII.3 AscóII.4

MITOM solution for Ascó I and Ascó II measured points

E·

/E

(c

m-2

·s-1

)

Energy (MeV)

Nuclear power plants

Medical electron LINACs

PET cyclotrons

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Extension to high energiesExtension to high energies

NeedNeed Accelerators for research and for medical Accelerators for research and for medical

treatmentstreatments Crew dosimetry in aircraftsCrew dosimetry in aircrafts

Adequate boxing in heavy metals (Pb, W, Adequate boxing in heavy metals (Pb, W, Cu, …)Cu, …)

Calibration facilities?Calibration facilities?

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ConclusionConclusion

Intrinsic complexity of neutron dosimetry Intrinsic complexity of neutron dosimetry and spectrometryand spectrometry

Before giving numbers, be sure!Before giving numbers, be sure!

NTDs adequate for neutron dosimetryNTDs adequate for neutron dosimetry

Need for calibration facilities for HE Need for calibration facilities for HE (CERF, PTB, …)(CERF, PTB, …)

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The End

Thank you!

Documents

Bologna 1st-5th September 1 Neutron dosimetry and spectrometry: problems, solutions, perspectives and the role of track detectors Carles Domingo Grup de