8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
1/48
Defeitos associados a feixe de
artculas ener ticas
Mrio E G Valerio
Defeitos em SlidosNPGF!"FS!#$%%&%
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
2/48
ntrodu'(o Stopping power is defined as t)e a*erage energ+
loss of t)e particle per unit pat) lengt),
-)e stopping po.er depends on t)e t+pe and
energ+ of t)e particle and on t)e properties oft)e material it passes,
Since t)e production of an ion pair /usuall+ a
pos *e on an an e ec ron re1u res a xeamount of energ+ /for example2 34eV in air02 t)edensit+ of ionisation along t)e pat) isproportional to t)e stopping po.er of t)e
material, 5ot) electrons and positi*e ions lose energ+
.)ile passing t)roug) matter,
#$%%&% #Defeitos em Slidos ! Mrio E G Valerio
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
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,
,
#$%%&% 3Defeitos em Slidos ! Mrio E G Valerio
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
4/48
S(E) < linear stopping po.er /MeV&mm0
< mass stopping po.er /MeV&/mg&cm#00( )S E
#$%%&% 4Defeitos em Slidos ! Mrio E G Valerio
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
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,#$%%&% =Defeitos em Slidos ! Mrio E G Valerio
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
6/48
5+ nuclear stopping power2 one means elastic
collisions 7et.een t)e ion and atoms in t)esample,
f one ;no.s t)e form of t)e repulsi*e
potential V/r0 7et.een t.o atoms2 it is possi7le
n ,
n t)e stopping po.er for protons in
aluminum2 nuclear stopping is negligi7le exceptat t)e lo.est energ+,
#$%%&% >Defeitos em Slidos ! Mrio E G Valerio
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
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
#$%%&% @Defeitos em Slidos ! Mrio E G Valerio
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
8/48
?t not too )ig) energies2 t)e stopping po.er
is t)erefore t)e sum of t.o terms:
Se*eral semi!empirical stopping po.er
S E S E S E e n
( ) ( ) ( )= +
, -)e model gi*en 7+ Aiegler2 5iersac; and
Bittmar; /t)e so called CA5BC stopping02
implemented in different *ersions of t)e-M&SM codes2 is used most often toda+,
#$%%&% Defeitos em Slidos ! Mrio E G Valerio
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
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
#$%%&% IDefeitos em Slidos ! Mrio E G Valerio
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
10/48
?t e*en )ig)er energies2 one )as to consider2
in addition2 radiati*e stopping po.er .)ic) isdue to t)e emission of 7remsstra)lung in t)e
electric fields of t)e nuclei of t)e material
tra*ersed,
#$%%&% %$Defeitos em Slidos ! Mrio E G Valerio
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
11/48
Te slowing-down process in solids
n t)e 7eginning of t)e slo.ing!do.n process at )ig)energies2 t)e ion is slo.ed do.n mainl+ 7+ electronicstopping2 and it mo*es almost in a straig)t pat),
K)en t)e ion )as slo.ed do.n sufficientl+2 t)ecollisions .it) nuclei /t)e nuclear stopping0 7ecomemore and more pro7a7le2 finall+ dominating t)e
,
K)en atoms of t)e solid recei*e significant recoilenergies .)en struc; 7+ t)e ion2 t)e+ .ill 7e remo*edfrom t)eir lattice positions2 and produce a cascade of
furt)er collisions in t)e material, -)ese collision cascades are t)e main cause of damage
production during ion implantation in metals andsemiconductors,
#$%%&% %%Defeitos em Slidos ! Mrio E G Valerio
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
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#$%%&% %#Defeitos em Slidos ! Mrio E G Valerio
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
13/48
-)e mean range can 7e calculated 7+
integrating t)e reciprocal stopping po.er o*erenerg+,
-)e de osited ener can 7e o7tained 7
( )0
1
R dES E
=
integrating t)e stopping po.er o*er t)e entirepat) lengt) of t)e ion .)en it mo*es in t)e
solid,
( )0 0
max maxx x dEE S E dx dx
dx= =
#$%%&% %3Defeitos em Slidos ! Mrio E G Valerio
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
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,
#$%%&% %4Defeitos em Slidos ! Mrio E G Valerio
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
15/48
Aiegler2 5iersac; and Bittmar; )a*e performed
potential calculations for a .ide range ofparticle pairs /=## atoms pairs0,
n t)e 7asis of t)eir calculations t)e+ could
extract an approximate anal+tical expressionfor t)e dimensionless screening potential2 t)euniversal screenin otential (USP).
#$%%&% %=Defeitos em Slidos ! Mrio E G Valerio
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
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,
#$%%&% %>Defeitos em Slidos ! Mrio E G Valerio
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
17/48
A$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
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
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
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
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
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
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
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
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
#$%%&% Defeitos em Slidos ! Mrio E G Valerio #%
stopping po.er2 7ut
losing no energ+ incollisions .it) nuclei,
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
22/48
n t)e 5? approac)2 a single collision
7et.een t)e incoming ion and a target atomis treated 7+ sol*ing t)e classical scattering
integral 7et.een t.o colliding particles for
t)e impact parameter of t)e incoming ion,
Solution of t)e integral gi*es t)e scatteringangle of t)e ion as .ell as its energ+ loss to
t)e sample atoms2 and )ence .)at t)e energ+
is after t)e collision compared to 7efore it,
#$%%&% Defeitos em Slidos ! Mrio E G Valerio ##
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
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,
#$%%&% Defeitos em Slidos ! Mrio E G Valerio #3
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
24/48
-)e 5? simulations can 7e furt)er su7di*ided 7+t+pe depending on .)et)er t)e+ onl+ follo. t)eincoming ion2 or also follo. t)e recoils produced7+ t)e ion /full cascade mode2 e,g,2 in t)e popular5? code SM0,
f t)e initial recoil&ion mass is lo.2 and t)ematerial .)ere t)e cascade occurs )as a lo.
densit+ /i,e, t)e recoil!material com7ination )as alo. stopping po.er02 t)e collisions 7et.een t)einitial recoil and sample atoms occur rarel+2 andcan 7e understood .ell as a se1uence of
independent 7inar+ collisions 7et.een atoms,-)is ;ind of a cascade can 7e t)eoreticall+ .elltreated using 5?,
#$%%&% Defeitos em Slidos ! Mrio E G Valerio #4
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
25/48
Sc)ematic illustration of a linear
collision cascade, -)e t)ic; line
#$%%&% Defeitos em Slidos ! Mrio E G Valerio #=
illustrates t)e position of t)e
surface2 and t)e t)inner lines
t)e 7allistic mo*ement pat)s of
t)e atoms from 7eginning until
t)e+ stop in t)e material, -)e
purple circle is t)e incoming ion,ed2 7lue2 green and +ello.
circles illustrate primar+2
secondar+2 tertiar+ and
1uaternar+ recoils2 respecti*el+,
Knordlun, 2!!
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
26/48
Damage production estimates:-)e 5? simulations gi*e naturall+ t)e ion penetration dept)2
lateral spread and nuclear and electronic deposition energ+distri7utions in space,-)e+ can also 7e used to estimate t)e damage produced in
materials2 7+ using t)e assumption t)at an+ recoil .)ic)
recei*es an energ+ )ig)er t)an t)e t)res)old displacementenerg+ of t)e material .ill produce a sta7le defect,8o.e*er2 t)is approac) s)ould 7e used .it) great caution for
se*eral reasons, it does not account for an+ t)ermall+ acti*ated recom7ination of
damage2 t does not consider t)e .ell ;no.n fact t)at in metals t)e damage
production is for )ig) energies onl+ somet)ing li;e #$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,#$%%&% Defeitos em Slidos ! Mrio E G Valerio #>
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
27/48
)annelling
)annelling is t)e process t)at constrains t)e pat) of ac)arged particle in a cr+stalline solid,
K)en t)e target material is )omogeneous and
isotropic2 t)e impact!parameter distri7ution isindependent of t)e orientation of t)e momentum oft)e particle and interaction processes are also
! ,
K)en t)e target material is monocr+stalline2 t)e +ieldsof p)+sical processes are *er+ strongl+ dependent ont)e orientation of t)e momentum of t)e particlerelati*e to t)e cr+stalline axes or planes,
r in ot)er .ords2 t)e stopping po.er of t)e particle ismuc) lo.er in certain directions t)an ot)ers, -)iseffect is commonl+ called t)e Cc)annellingC effect,
#$%%&% Defeitos em Slidos ! Mrio E G Valerio #@
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
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
#$%%&% Defeitos em Slidos ! Mrio E G Valerio #
dri*en 7+ momentumexc)ange 7et.een
t)e ions and atoms in
t)e materials2 due tocollisions,
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
29/48
-)e incident ions set off collision cascades in t)etarget,
K)en suc) cascades recoil and reac) t)e target surface.it) an energ+ a7o*e t)e surface 7inding energ+2 anatom can 7e eRected,
f t)e target is t)in on an atomic scale t)e collisioncascade can reac) t)e 7ac; side of t)e target andatoms can escape t)e surface 7inding energ+ intransmission6,
-)e a*erage num7er of atoms eRected from t)e targetper incident ion is called t)e sputter +ield and dependson t)e ion incident angle2 t)e energ+ of t)e ion2 t)emasses of t)e ion and target atoms2 and t)e surface
7inding energ+ of atoms in t)e target, For a cr+stalline target t)e orientation of t)e cr+stal
axes .it) respect to t)e target surface is rele*ant,
#$%%&% Defeitos em Slidos ! Mrio E G Valerio #I
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
30/48
Mtodos computacionais
Mtodo de Monte arlo
DinTmica molecular )ttp:&&...,srim,org&index,)tmJSM
-
#$%%&% 3$Defeitos em Slidos ! Mrio E G Valerio
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
31/48
Exemplos
#$%%&% 3%Defeitos em Slidos ! Mrio E G Valerio
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
32/48
#$%%&% 3#Defeitos em Slidos ! Mrio E G Valerio
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
33/48
#$%%&% 33Defeitos em Slidos ! Mrio E G Valerio
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
34/48
#$%%&% 34Defeitos em Slidos ! Mrio E G Valerio
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
35/48
#$%%&% 3=Defeitos em Slidos ! Mrio E G Valerio
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
36/48
)ttp:&&cleanroom,7+u,edu&mplantonal,p)tml
#$%%&% 3>Defeitos em Slidos ! Mrio E G Valerio
Neutron adiation Damage
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
37/48
Neutron adiation Damage
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+,#$%%&% Defeitos em Slidos ! Mrio E G Valerio 3@
Neutron adiation Damage
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
38/48
Neutron adiation Damage
Neutrons are attenuated 7+ t)ree maRorinteractions: elastic scatter2 inelastic scatter2 and
a7sorption,
n t)e inelastic scatter reaction2 t)e same
neutron&nucleus collision occurs as in elastic
scatter, 8o.e*er2 in t)is reaction2 t)e nucleusrecei*es some internal energ+ as .ell as ;inetic
energ+,
-)is slo.s t)e neutron2 7ut lea*es t)e nucleus in an excitedstate, K)en t)e nucleus deca+s to its original energ+ le*el2
it normall+ emits a gamma ra+,
#$%%&% Defeitos em Slidos ! Mrio E G Valerio 3
Neutron adiation Damage
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
39/48
Neutron adiation Damage
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,
#$%%&% Defeitos em Slidos ! Mrio E G Valerio 3I
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
40/48
5ecause neutrons are unc)arged2 t)e+ can 7emore penetrating t)an alp)a radiation or 7eta
radiation,
n some cases t)e+ are more penetrating t)an
)ig) atomic num7er,
n materials of lo. atomic num7er suc) as
)+drogen2 a lo. energ+ gamma ra+ ma+ 7e morepenetrating t)an a )ig) energ+ neutron,
#$%%&% Defeitos em Slidos ! Mrio E G Valerio 4$
Neutrons can degrade "aterials:
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
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$ation:
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
42/48
Neutron acti$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,
#$%%&% Defeitos em Slidos ! Mrio E G Valerio 4#
? l f )i ;i d f l i
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
43/48
?n example of t)is ;ind of a nuclear reaction
occurs in t)e production of co7alt!>$ .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 >$o is a *alua7le source of nuclear
radiation for radiot)erap+,
#$%%&% Defeitos em Slidos ! Mrio E G Valerio 43
t) d d di t) ;i ti
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
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:
#$%%&% Defeitos em Slidos ! Mrio E G Valerio 44
( )9 44 22Be n He 2n energy+ + +
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
45/48
#$%%&% 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$ation anal#sis (NAA+:
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
46/48
neutron acti$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,
#$%%&% Defeitos em Slidos ! Mrio E G Valerio 4>
N?? can detect up to @4 elements depending
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
47/48
p p gupon t)e experimental procedure,
Sensiti$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
%$@ P72 S
Esti"ated /etection li"its !or NAA using deca# ga""a ra#s, Assu"ing irradiation in
a reactor neutron !lu& o! 0&0102 n c"34 s30,
8/12/2019 Capitulo 3 Danos Feixe Part%c3%Adculas
48/48
#$%%&% Defeitos em Slidos ! Mrio E G Valerio 4
Top Related