capitulo 3 danos feixe part%c3%adculas

8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas

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Defeitos associados a feixe de

artculas ener ticas

Mrio E G Valerio

Defeitos em SlidosNPGF!"FS!#$%%&%


2/48

ntrodu'(o Stopping power is defined as t)e a*erage energ+

loss of t)e particle per unit pat) lengt),

-)e stopping po.er depends on t)e t+pe and

energ+ of t)e particle and on t)e properties oft)e material it passes,

Since t)e production of an ion pair /usuall+ a

pos *e on an an e ec ron re1u res a xeamount of energ+ /for example2 34eV in air02 t)edensit+ of ionisation along t)e pat) isproportional to t)e stopping po.er of t)e

material, 5ot) electrons and positi*e ions lose energ+

.)ile passing t)roug) matter,

#$%%&% #Defeitos em Slidos ! Mrio E G Valerio


3/48

6Stopping po.er6 is treated as a propert+ of t)e

material2 .)ile 6energ+ loss per unit pat) lengt)6descri7es .)at )appens to t)e particle,

8o.e*er2 numerical *alue and units are identical

for 7ot) 1uantities9 t)e+ are usuall+ .ritten .it)a minus sign in front:

Stopping po.er of aluminum for protons

.)ere Emeans energ+2

andxis t)e pat)lengt),

-)e minus sign ma;es Spositi*e,

,

#$%%&% 3Defeitos em Slidos ! Mrio E G Valerio


4/48

S(E) < linear stopping po.er /MeV&mm0

< mass stopping po.er /MeV&/mg&cm#00( )S E



5/48

Electronic and nuclear stopping power

5+ electronic stopping power2 one means slo.ing do.n dueto t)e inelastic collisions 7et.een 7ound electrons in t)e

medium and t)e ion mo*ing t)roug) it,

-)e term inelastic is used to signif+ t)at t)e collisions ma+result 7ot) in excitations of 7ound electrons of t)e medium2

and in excitations of t)e electron cloud of t)e ion,

electrons is large2 and since t)e c)arge state of t)e ion .)ile

tra*ersing t)e medium ma+ c)ange fre1uentl+2 it is *er+

difficult to descri7e all possi7le interactions for all possi7le ion

c)arge states, nstead2 t)e electronic stopping po.er is often gi*en as a

simple function of energ+ Se/E0 .)ic) is an a*erage ta;en o*er

all energ+ loss processes for different c)arge states,#$%%&% =Defeitos em Slidos ! Mrio E G Valerio


6/48

5+ nuclear stopping power2 one means elastic

collisions 7et.een t)e ion and atoms in t)esample,

f one ;no.s t)e form of t)e repulsi*e

potential V/r0 7et.een t.o atoms2 it is possi7le

n ,

n t)e stopping po.er for protons in

aluminum2 nuclear stopping is negligi7le exceptat t)e lo.est energ+,

#$%%&% >Defeitos em Slidos ! Mrio E G Valerio


7/48

Nuclear stopping increases .)en t)e mass of

t)e ion increases, Nuclear stopping can 7elarger t)an electronic stopping at lo. energ+,

For *er+ lig)t ions slo.ing do.n in )ea*+

materials2 t)e nuclear stopping is .ea;er t)an

t)e electronic at all energies,

Electronic and nuclear stopping

po.er for ?l ions in ?l,

8 Paul

#$%%&% @Defeitos em Slidos ! Mrio E G Valerio


8/48

?t not too )ig) energies2 t)e stopping po.er

is t)erefore t)e sum of t.o terms:

Se*eral semi!empirical stopping po.er

S E S E S E e n

( ) ( ) ( )= +

, -)e model gi*en 7+ Aiegler2 5iersac; and

Bittmar; /t)e so called CA5BC stopping02

implemented in different *ersions of t)e-M&SM codes2 is used most often toda+,

#$%%&% Defeitos em Slidos ! Mrio E G Valerio


9/48

Aiegler2 5iersac;2 and Bittmar; A5B

t)eor+

, F, Aiegler2 , P, 5iersac;2 and ", Bittmar;, n

-)e Stopping and ange of ons in Matter2*olume %2 Ne. Hor;2 %I=, Pergamon, S5N

)ttp:&&...,srim,org&index,)tmJSM

PARTICLE INTERACTIONS WITH MATTER

SRIM - Te Stopping and Range o! Ions inMatter

#$%%&% IDefeitos em Slidos ! Mrio E G Valerio


10/48

?t e*en )ig)er energies2 one )as to consider2

in addition2 radiati*e stopping po.er .)ic) isdue to t)e emission of 7remsstra)lung in t)e

electric fields of t)e nuclei of t)e material

tra*ersed,

#$%%&% %$Defeitos em Slidos ! Mrio E G Valerio


11/48

Te slowing-down process in solids

n t)e 7eginning of t)e slo.ing!do.n process at )ig)energies2 t)e ion is slo.ed do.n mainl+ 7+ electronicstopping2 and it mo*es almost in a straig)t pat),

K)en t)e ion )as slo.ed do.n sufficientl+2 t)ecollisions .it) nuclei /t)e nuclear stopping0 7ecomemore and more pro7a7le2 finall+ dominating t)e

,

K)en atoms of t)e solid recei*e significant recoilenergies .)en struc; 7+ t)e ion2 t)e+ .ill 7e remo*edfrom t)eir lattice positions2 and produce a cascade of

furt)er collisions in t)e material, -)ese collision cascades are t)e main cause of damage

production during ion implantation in metals andsemiconductors,

#$%%&% %%Defeitos em Slidos ! Mrio E G Valerio


12/48

K)en t)e energies of all atoms in t)e s+stem )a*e

fallen 7elo. t)e tresold displace"ent energ#2t)e production of ne. damage ceases2 and t)econcept of nuclear stopping is no longer meaningful,

-)e total amount of energ+ deposited 7+ t)enuclear collisions to atoms in t)e materials is calledt)e nuclear deposited energ+,

Lai Nordlund#$%%&% %#Defeitos em Slidos ! Mrio E G Valerio


13/48

-)e mean range can 7e calculated 7+

integrating t)e reciprocal stopping po.er o*erenerg+,

-)e de osited ener can 7e o7tained 7

( )0

1

R dES E

=

integrating t)e stopping po.er o*er t)e entirepat) lengt) of t)e ion .)en it mo*es in t)e

solid,

( )0 0

max maxx x dEE S E dx dx

dx= =

#$%%&% %3Defeitos em Slidos ! Mrio E G Valerio


14/48

Interato"ic Screening Potential -)e interaction potential is calculated 7+ assuming t)at

t)e c)arge distri7utions of t)e atoms remain unc)angedduring t)e penetration of t)e electron sp)eres and t)att)e c)arge distri7utions are sp)ericall+ s+mmetric,

-)e follo.ing contri7utions to t)e potential energ+ areconsidered,-)e classical terms of oulom7 interaction 7et.een

t)e nuclei of t)e particles t)e electrons of t)e particles t)e nuclei and t)e electrons of t)e ot)er particle

-)e increase of t)e ;inetic electron energ+ due to t)e Pauli

exclusion principle and an increase of t)e exc)ange energ+in t)e areas .)ere t)e electron sp)eres o*erlap, -)e )ig)erelectron concentrations in t)ese regions re1uire a )ig)erelectronic ;inetic energ+ .)ic) is approximated 7+ t)e;inetic energ+ of a degenerated free electron gas,

#$%%&% %4Defeitos em Slidos ! Mrio E G Valerio


15/48

Aiegler2 5iersac; and Bittmar; )a*e performed

potential calculations for a .ide range ofparticle pairs /=## atoms pairs0,

n t)e 7asis of t)eir calculations t)e+ could

extract an approximate anal+tical expressionfor t)e dimensionless screening potential2 t)euniversal screenin otential (USP).

#$%%&% %=Defeitos em Slidos ! Mrio E G Valerio


16/48

-)e de*iation 7et.een t)e =## calculated potentials and t)e fitted uni*ersalscreening potential is approximatel+ % O as long as t)e potential energ+ is

a7o*e # eV, For lo.er potential energies t)e de*iation is significantl+ larger

.)ic) pro7a7l+ limits t)e use of t)e uni*ersal screening potential,

#$%%&% %>Defeitos em Slidos ! Mrio E G Valerio


17/48

A$erage Nuclear Stopping Power Lno.ing t)e interatomic potential it is possi7le to

deri*e t)e a*erage nuclear stopping po.er Sn/E$0.)ic) defines t)e a*erage energ+ t)at is

transfered 7+ eac) nuclear collisions if t)eparticle energ+ is E$,

Numerical solutions :

educed enreg+ for t)e colisions of ion % .it) t)e target ions #

#$%%&% %@Defeitos em Slidos ! Mrio E G Valerio


18/48

educed nuclearstopping po.er as

function of t)e reduced

energ+,

$23#@

Maxima of the averagenuclear stopping

power for various atom

pairs.

#$%%&% %Defeitos em Slidos ! Mrio E G Valerio

ncident particle -arget particle

po.er maximum/;eV0

5oron Silicon 3

P)osp)orus Silicon %>

?rsenic Silicon >?ntimon+ Silicon %>$

5oron x+gen #

P)osp)orus x+gen %#

?rsenic x+gen =?ntimon+ x+gen %43


19/48

Electronic Stopping Power

%st t)eor+ 5et)e %I3$

-)e relati*istic *ersion of t)e formula reads:

Q v& c

v *elocit of t)e article

Eenerg+ of t)e particle xdistance tra*elled 7+ t)e particle

c speed of lig)t

ze particle c)arge

e c)arge of t)e electron

me rest mass of t)e electron n electron densit+ of t)e target I

Imean excitation potential of t)e target

$ *acuum permitti*it+

Onl# $alid !or ig

$elocit# particles%

#$%%&% %IDefeitos em Slidos ! Mrio E G Valerio


20/48

Modeling t)e electronic stopping process is *er+ complicated2

7ecause se*eral p)+sical effects contri7ute to t)e inelastic

energ+ loss, E&citation o! conduction and 'and electrons (non-locali)ed wea*l#

'ound electrons+,

E&citation or ioni)ation o! target ato"s (pro"otion o! locali)edelectrons+,

Ioni)ation or electron capture o! te proectile,

electron interaction,

-)e most .idel+ used tec)ni1ue for modeling t)e electronic

stopping process is 7ased on t)e local densit+ approximation,

t assumes t)at in eac) /infinitesimal0 *olume element of t)etarget t)e interaction 7et.een t)e proRectile and t)e target

electrons depends onl+ on one propert+ of t)e target2 namel+

t)e local electron densit+ .it)in t)is *olume element,#$%%&% #$Defeitos em Slidos ! Mrio E G Valerio


21/48

.inar# collision appro&i"ation

Met)od used to ena7le efficient computersimulation of t)e penetration dept) and defectproduction 7+ energetic ions in solids,

n t)e met)od2 t)e ion is approximated to tra*elt)roug) a material 7+ experiencing a se1uence ofinde endent 7inar collisions .it) sam le atoms,

5et.een t)e collisions2 t)e ion is assumed totra*el in a straig)t pat)2 experiencing electronic

#$%%&% Defeitos em Slidos ! Mrio E G Valerio #%

stopping po.er2 7ut

losing no energ+ incollisions .it) nuclei,


22/48

n t)e 5? approac)2 a single collision

7et.een t)e incoming ion and a target atomis treated 7+ sol*ing t)e classical scattering

integral 7et.een t.o colliding particles for

t)e impact parameter of t)e incoming ion,

Solution of t)e integral gi*es t)e scatteringangle of t)e ion as .ell as its energ+ loss to

t)e sample atoms2 and )ence .)at t)e energ+

is after t)e collision compared to 7efore it,

#$%%&% Defeitos em Slidos ! Mrio E G Valerio ##


23/48

-)e selection met)od for t)e impact parameter di*ided5? codes into t.o main *arieties: CMonte arloC 5? and

cr+stal!5? codes,

n t)e Monte arlo 5? approac) t)e distance to andimpact parameter of t)e next colliding atom is c)osen

randoml+ for a pro7a7ilit+ distri7ution .)ic) depends onl+on t)e atomic densit+ of t)e material, -)is approac)essentiall+ simulates ion passage in a full+ amorp)ousmaterial,

t is also possi7le 5? met)ods for cr+stalline materials2suc) t)at t)e mo*ing ion )as a defined position in a cr+stal2and t)e distance and impact parameter to t)e next

colliding atom is determined to correspond to an atom int)e cr+stal, n t)is approac) 5? can 7e used to simulatealso atom motion during c)annelling,

#$%%&% Defeitos em Slidos ! Mrio E G Valerio #3


24/48

-)e 5? simulations can 7e furt)er su7di*ided 7+t+pe depending on .)et)er t)e+ onl+ follo. t)eincoming ion2 or also follo. t)e recoils produced7+ t)e ion /full cascade mode2 e,g,2 in t)e popular5? code SM0,

f t)e initial recoil&ion mass is lo.2 and t)ematerial .)ere t)e cascade occurs )as a lo.

densit+ /i,e, t)e recoil!material com7ination )as alo. stopping po.er02 t)e collisions 7et.een t)einitial recoil and sample atoms occur rarel+2 andcan 7e understood .ell as a se1uence of

independent 7inar+ collisions 7et.een atoms,-)is ;ind of a cascade can 7e t)eoreticall+ .elltreated using 5?,

#$%%&% Defeitos em Slidos ! Mrio E G Valerio #4


25/48

Sc)ematic illustration of a linear

collision cascade, -)e t)ic; line

#$%%&% Defeitos em Slidos ! Mrio E G Valerio #=

illustrates t)e position of t)e

surface2 and t)e t)inner lines

t)e 7allistic mo*ement pat)s of

t)e atoms from 7eginning until

t)e+ stop in t)e material, -)e

purple circle is t)e incoming ion,ed2 7lue2 green and +ello.

circles illustrate primar+2

secondar+2 tertiar+ and

1uaternar+ recoils2 respecti*el+,

Knordlun, 2!!


26/48

Damage production estimates:-)e 5? simulations gi*e naturall+ t)e ion penetration dept)2

lateral spread and nuclear and electronic deposition energ+distri7utions in space,-)e+ can also 7e used to estimate t)e damage produced in

materials2 7+ using t)e assumption t)at an+ recoil .)ic)

recei*es an energ+ )ig)er t)an t)e t)res)old displacementenerg+ of t)e material .ill produce a sta7le defect,8o.e*er2 t)is approac) s)ould 7e used .it) great caution for

se*eral reasons, it does not account for an+ t)ermall+ acti*ated recom7ination of

damage2 t does not consider t)e .ell ;no.n fact t)at in metals t)e damage

production is for )ig) energies onl+ somet)ing li;e #$O of t)eprediction2

t)is approac) onl+ predicts t)e damage production as if all defects.ere isolated Fren;el pairs2 .)ile in realit+ in man+ cases collisioncascades produce defect clusters or e*en dislocations as t)e initialdamage state2

t)e a*erage t)res)old displacement energ+ is not *er+ accuratel+

;no.n in most materials,#$%%&% Defeitos em Slidos ! Mrio E G Valerio #>


27/48

)annelling

)annelling is t)e process t)at constrains t)e pat) of ac)arged particle in a cr+stalline solid,

K)en t)e target material is )omogeneous and

isotropic2 t)e impact!parameter distri7ution isindependent of t)e orientation of t)e momentum oft)e particle and interaction processes are also

! ,

K)en t)e target material is monocr+stalline2 t)e +ieldsof p)+sical processes are *er+ strongl+ dependent ont)e orientation of t)e momentum of t)e particlerelati*e to t)e cr+stalline axes or planes,

r in ot)er .ords2 t)e stopping po.er of t)e particle ismuc) lo.er in certain directions t)an ot)ers, -)iseffect is commonl+ called t)e Cc)annellingC effect,

#$%%&% Defeitos em Slidos ! Mrio E G Valerio #@


28/48

Sputtering

Sputtering is a process .)ere7+ atoms areeRected from a solid target material due to7om7ardment of t)e target 7+ energeticparticles,

P)+sical sputtering is

#$%%&% Defeitos em Slidos ! Mrio E G Valerio #

dri*en 7+ momentumexc)ange 7et.een

t)e ions and atoms in

t)e materials2 due tocollisions,


29/48

-)e incident ions set off collision cascades in t)etarget,

K)en suc) cascades recoil and reac) t)e target surface.it) an energ+ a7o*e t)e surface 7inding energ+2 anatom can 7e eRected,

f t)e target is t)in on an atomic scale t)e collisioncascade can reac) t)e 7ac; side of t)e target andatoms can escape t)e surface 7inding energ+ intransmission6,

-)e a*erage num7er of atoms eRected from t)e targetper incident ion is called t)e sputter +ield and dependson t)e ion incident angle2 t)e energ+ of t)e ion2 t)emasses of t)e ion and target atoms2 and t)e surface

7inding energ+ of atoms in t)e target, For a cr+stalline target t)e orientation of t)e cr+stal

axes .it) respect to t)e target surface is rele*ant,

#$%%&% Defeitos em Slidos ! Mrio E G Valerio #I


30/48

Mtodos computacionais

Mtodo de Monte arlo

DinTmica molecular )ttp:&&...,srim,org&index,)tmJSM

-

#$%%&% 3$Defeitos em Slidos ! Mrio E G Valerio


31/48

Exemplos

#$%%&% 3%Defeitos em Slidos ! Mrio E G Valerio


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#$%%&% 3#Defeitos em Slidos ! Mrio E G Valerio


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#$%%&% 3=Defeitos em Slidos ! Mrio E G Valerio


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)ttp:&&cleanroom,7+u,edu&mplantonal,p)tml

#$%%&% 3>Defeitos em Slidos ! Mrio E G Valerio

Neutron adiation Damage


37/48


Neutrons are attenuated 7+ t)ree maRorinteractions: elastic scatter2 inelastic scatter2 and

a7sorption,

n elastic scatter, a neutron collides .it) a nucleus

and 7ounces off, -)is reaction transmits some of

t)e ;inetic energ+ of t)e neutron to t)e nucleus oft)e atom2 resulting in t)e neutron 7eing slo.ed2

and t)e atom recei*es some ;inetic energ+,

?s t)e mass of t)e nucleus approac)es t)e mass of t)eneutron2 t)is reaction 7ecomes more effecti*e in slo.ing

t)e neutron, 8+drogenous material attenuates neutrons

most effecti*el+,#$%%&% Defeitos em Slidos ! Mrio E G Valerio 3@



38/48


Neutrons are attenuated 7+ t)ree maRorinteractions: elastic scatter2 inelastic scatter2 and

a7sorption,

n t)e inelastic scatter reaction2 t)e same

neutron&nucleus collision occurs as in elastic

scatter, 8o.e*er2 in t)is reaction2 t)e nucleusrecei*es some internal energ+ as .ell as ;inetic

energ+,

-)is slo.s t)e neutron2 7ut lea*es t)e nucleus in an excitedstate, K)en t)e nucleus deca+s to its original energ+ le*el2

it normall+ emits a gamma ra+,

#$%%&% Defeitos em Slidos ! Mrio E G Valerio 3



39/48


Neutrons are attenuated 7+ t)ree maRor

interactions: elastic scatter2 inelastic scatter2

and a7sorption,

n t)e a"sorption reaction2 t)e neutron is

actuall+ a7sor7ed into t)e nucleus of an atom,-)e neutron is captured2 7ut t)e atom is left in an

excited state,

f t)e nucleus emits one or more gamma ra+s to reac)

a sta7le le*el2 t)e process is called radiati*e capture,

#$%%&% Defeitos em Slidos ! Mrio E G Valerio 3I


40/48

5ecause neutrons are unc)arged2 t)e+ can 7emore penetrating t)an alp)a radiation or 7eta

radiation,

n some cases t)e+ are more penetrating t)an

)ig) atomic num7er,

n materials of lo. atomic num7er suc) as

)+drogen2 a lo. energ+ gamma ra+ ma+ 7e morepenetrating t)an a )ig) energ+ neutron,

#$%%&% Defeitos em Slidos ! Mrio E G Valerio 4$

Neutrons can degrade "aterials:


41/48

Neutrons can degrade "aterials:

7om7ardment of materials .it) neutrons creates collision

cascades t)at can produce point defects and dislocations int)e materials,

?t )ig) neutron fluences t)is can lead to em7rittlement ofmetals and ot)er materials2 and to s.elling of some of

t)em, Em"rittlementis a loss of ductilit+ of a material2 ma;ing it 7rittle,

#eutron$induced s%elling is t)e increase of *olume and decrease,

Neutrons impacting t)e material6s lattice rearrange its atoms2causing 7uildup of dislocations and *oids,

-)is are potential pro7lem for nuclear reactor *essels2 andsignificantl+ limits t)eir lifetime /.)ic) can 7e some.)atprolonged 7+ controlled annealing of t)e *essel2 reducingt)e num7er of t)e 7uilt!up dislocations0, Grap)ite moderator 7loc;s are especiall+ suscepti7le to t)is

effect2 ;no.n as Kigner effect2 and )a*e to 7e annealedperiodicall+

#$%%&% Defeitos em Slidos ! Mrio E G Valerio 4%

Neutron acti$ation:


42/48

Neutron acti$ation:

process in .)ic) neutron radiation inducesradioacti*it+ in materials2 and occurs .)enatomic nuclei capture free neutrons2 7ecoming)ea*ier and entering excited states,

-)e excited nucleus often deca+s immediatel+ 7+emitting particles suc) as neutrons2 protons2 oralp)a particles,

-)e neutron capture2 e*en after an+ intermediatedeca+2 often results in t)e formation of anunsta7le acti*ation product,

Suc) radioacti*e nuclei can ex)i7it )alf!li*esranging from small fractions of a second to man++ears,

#$%%&% Defeitos em Slidos ! Mrio E G Valerio 4#

? l f )i ;i d f l i


43/48

?n example of t)is ;ind of a nuclear reaction

occurs in t)e production of co7alt!>$ .it)in anuclear reactor:

-)e >$o deca s 7 t)e emission of a 7eta

59 60

27 27Co n Co+

particle plus gamma ra+s into >$Ni, -)is reaction )as a )alf!life of a7out =,#@

+ears2 and >$o is a *alua7le source of nuclear

radiation for radiot)erap+,


t) d d di t) ;i ti


44/48

n ot)er cases2 and depending on t)e ;inetic

energ+ of t)e neutron2 t)e capture of aneutron can cause nuclear &ission,

f t)e fission re1uires an input of energ+2 t)at

comes from t)e ;inetic energ+ of t)e neutron,

?n example of t)is ;ind of fission in a lig)t

element can occur .)en t)e onl+ sta7leisotope of 7er+llium2 I5e2 is 7om7arded .it)

fast neutrons and undergoes t)e follo.ing

nuclear reaction:


( )9 44 22Be n He 2n energy+ + +


45/48

#$%%&% Defeitos em Slidos ! Mrio E G Valerio 4=

esearc) Betters in P)+sicsVolume #$$2 ?rticle D @4>I#

doi:%$,%%==$$&@4>I#

omputer Modeling of Displacement ascades in

5er+llium rradiated .it) ntensi*e Neutron Flux

'. 'roev, #. #anov, . Petrov, and E. Popov

neutron acti$ation anal#sis (NAA+:


46/48

neutron acti$ation anal#sis (NAA+:

is a nuclear process used for determining t)econcentrations of elements in a *ast amount ofmaterials,

N?? allo.s discrete sampling of elements as it

disregards t)e c)emical form of a sample2 and focusessolel+ on its nucleus,

-)e met)od is 7ased on neutron acti*ation and

t)erefore re1uires a source of neutrons,-)e sample is 7om7arded .it) neutrons2 causing t)eelements to form radioacti*e isotopes,

-)e radioacti*e emissions and radioacti*e deca+ pat)s for

eac) element are .ell ;no.n,"sing t)is information2 it is possi7le to stud+ spectra of t)e

emissions of t)e radioacti*e sample2 and determine t)econcentrations of t)e elements .it)in it,

#$%%&% Defeitos em Slidos ! Mrio E G Valerio 4>

N?? can detect up to @4 elements depending


47/48

p p gupon t)e experimental procedure,

Sensiti$it# /pg&g0 Ele"ents

% D+2 Eu

%%$ n2 Bu2 Mn

%$%$$ ?u2 8o2 r2 e2 Sm2 K

%$$%$$$?g2 ?r2 ?s2 5r2 l2 o2 s2 u2 Er2 Ga2 8f2 2 Ba2

#$%%&% Defeitos em Slidos ! Mrio E G Valerio 4@

2 2 2 2 2 2 2 2 2

%$$$%$4 ?l2 5a2 d2 e2 r2 8g2 Lr2 Gd2 Ge2 Mo2 Na2Nd2 Ni2 s2 Pd2 72 )2 u2 Sr2 -e2 An2 Ar

%$4%$= 5i2 a2 L2 Mg2 P2 Pt2 Si2 Sn2 -i2 -l2 Ue2 H

%$=%$> F2 Fe2 N72 Ne

%$@ P72 S

Esti"ated /etection li"its !or NAA using deca# ga""a ra#s, Assu"ing irradiation in

a reactor neutron !lu& o! 0&0102 n c"34 s30,


48/48


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