Perfomance [sic] tests of a three-element thin film detector with an analysis of large scattering angle charge state characteristics of germanium and selenium ions

204 Pages·1991·5.9 MB·English

by  Milosevich, Zoran

PERFOMANCETESTSOFATHREE-ELEMENTTHINFILMDETECTOR
WITH ANANALYSISOFLARGESCATTERINGANGLECHARGESTATE
CHARACTERISTICSOFGERMANIUM ANDSELENIUM IONS
By
ZORANMILOSEVICH
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL
OFTHEUNIVERSITYOFFLORIDA INPARTIALFULFILLMENT
OFTHEREQUIREMENTSFORTHEDEGREEOF
DOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
1991
ACKNOWLEDGMENTS
The authorgratefullyacknowledgesthehelp and supporthe
hasreceivedfrom anumberofpeoplethathehashadthe pleasure
ofknowing. ManythanksgotoDr. M.L.Mugaforhis patience, help
and advicethathehasgiveninhisroleaschairmanofthe
supervisorycommitteeandresearchadvisor. Also manythanksgo
outtotheotherpersonnelinthenuclearchemistrygroupatthe
UniversityofFlorida. D.J.BurnsedandS.D.Thompson.
The muchappreciatedhelpofDr.R.L.Coldwellthathehas
giveninsetting upcomputeraccounts, writingcodesfordata
analysis andhishelpand adviseisverygratefullyacknowledged.
Manythanks alsogoouttothepeoplewhowere associated
withtheSpace AstronomyLaboratoryfortheirhelp and supportin
theexperimentalworkand dataanalysis. ThisgroupincludesDr.F.
E.Dunnam, Dr.P.S.Haskins, Dr.R.B.Piercey, Dr.M.A.Herath-
Banda, Dr. A.C.ResterandA.D.Weisenberger. AlsothanksgotoDr.
G.J.BamfordforhishelpinadviceconcerningROBFIT.
ThanksgotoDr.R.J.Hanrahanforhis advise andforthe useof
hiscomputers and6ocosource. AlsothanksgoouttoDr.A.K.Gupta
forhisadviceand supportthroughouttheyears. Thanksalsogoout
totheothercommittee membersfortheir adviceand support. Dr.W.
B.PersonandDr.Z.R.PopStojanovic.
ManythanksgoouttothestaffattheHolifieldHeavy Ion
ResearchFacilityfortheirhelpincarryingouttheexperiments
describedinthistext. ThisgroupincludesR.L.Robinson, W.Milner.
11
R.Miles andR. Auble. Also manythanksgotoOak Ridge Associated
Universitiesfortheirsupport. Alsoproviding supportthroughout
theyearshavebeentheUFDepartmentofSponsoredResearch and
theDepartmentofChemistry. Alsothanksgoto IBMforcomputing
fundsthroughtheResearchComputing Initiative.
Mostofalltheauthorwishestoexpresshisappreciationforthe
patience andhelphehasreceivedfromhis mother and sisterand
latefatherwhilehewasingraduateschool.
iii
1
TABLEOFCONTENTS
ACKNOWLEDGMENTS ii
ABSTRACT vi
CHAPTERS
1 REVIEWOFCHARGEDPARTICLEDETECTORS 1
Introduction 1
Theory
1
ThinFilmDetectors 15
2 DETECTORRESPONSETOSELECTED
ACCELERATEDHEAVY IONS 23
Introduction 23
ExperimentalApparatus 26
ResultsandDiscussion 30
3 THINFILM DETECTORRESPONSETO
252CfFISSIONFRAGMENTS 113
Introduction 113
Experimental 119
Results andDiscussion 123
4 CHARGESTATECHARACTERISTICSOFGe ANDSe
IONS INVOLVED INSMALL IMPACTPARAMETER
COLLISIONSWITH AGOLDTARGET 137
Introduction 137
Theory 142
Experimental 144
ResultsandDiscussion 145
5 SUMMARY 157
APPENDIXA GUIDETOTHEUSEROFATFD 163
iv
APPENDIXB PERTINENTCODES 169
REFERENCES 187
BIOGRAPHICALSKETCH 195
V
AbstractofDissertationPresentedtotheGraduateSchool
oftheUniversityofFloridainPartialFulfillmentofthe
RequirementsfortheDegreeofDoctorofPhilosophy
PERFORMANCETESTSOFATHREE-ELEMENTTHINFILM DETECTOR
WITH AN ANALYSISOFLARGESCATTERINGANGLECHARGESTATE
CHARACTERISTICSOFGERMANIUM ANDSELENIUM IONS
By
ZoranMilosevich
May 1991
Chairman; M.LuisMuga
MajorDepartment: Chemistry
Twoexperimentshavebeencarriedoutwiththepurposeof
testingthethree-elementthinfilm detectorwithasurfacebarrier
detector(3TFD-SBD)for useasanuclearcharged particleidentifier.
Thedetectorconsistsofastackofthree sequentialthinfilm
detectors (TFD's)for measuringthespecificluminescence (AL/Ax)of
atransitingion, andaterminalsurfacebarrierdetectorfor
measuringtheionresidualenergy(Er)afterenergylossesin
traversingtheTFD's. Thepurposeofthetwoexperimentswasto
developabetter understandingoftheadvantagesofhavingathree
elementdesignandtotrytoquantitativelyrelatethe performanceof
aTFDincomparisontootherparticledetectors.
Thefirstexperimenttestedthedetectorassemblyresponseto
acceleratedGeandSeions, inthe 53 to 169 MeVrange, thatwere
VI
scattered 30°offagoldfoiltarget. Various detectorcharacteristics
are presentedincludingtheAL/Axresponseofasingle detector asa
functionoftheionvelocityandthetimeresolutionofthe detector
assembly. Itisalsopossibletoimprovethe detectorresponseby
taking advantageofthethree successiveAL/Ax measurementsofa
transitingion.
Thesecondexperiment measuredtheTFDresponseto252Q
fissionfragmentsincoincidencewiththe promptgammarays. The
nuclearchargeresolving power(Z/AZ)wasdeterminedforasingle
TFDandtheresultcomparedtoothernuclearcharged particle
detectors.
Inthe dataanalysisofthefirstexperiment, information
concerningcertaincharacteristicsofthechargestatesofthe
scatteredionswasrevealed. Theresultswerecomparedto
calculatedvaluesobtainedfrom twodifferent modelsthathavebeen
usedtopredictthe averagechargestateofionsafterelectronic
strippingfrom smallimpactparametercollisionswithneutral
targets. Theresultsfrom thisexperiment mightadd some
informationtothescarcedatadealingwithcharge statedistributions
ofheavy massionsinvolvedinsmallimpactparametercollisions.
vii
CHAPTER
1
REVIEWOFCHARGEDPARTICLEDETECTORS
Introduction
Charged particle detectorscanbe dividedintofive major
groups: (1)track detectors, (2)gasionizationdetectors, (3)solid
statedetectors, (4) secondaryelectronemissiondetectorsand(5)
scintillationdetectors. Allthesedetectorsworkonthe principleof
coulomb interactionbetweentheelectronsinthe detector material
andthehighlychargednuclear particle. Here, charged particleswill
berestricted topositivelychargedheavynucleiandthereforewill
notincludebetas, mesonsor anyotherhighenergyparticles.
Thefirstgroupofdetectors, nucleartrack detectors, have
beenused sincetheveryfirststudiesofradioactivity. In 1896,
HenriBecquerelreported theblackeningofphotographicplateswhen
inthe presenceofadouble sulfateofuranium and potassium [1].
Sincethis phenomenondid notdependonwhetherthe uranium salt
wasorwasnotinthe presenceoflight, Becquerelrealizedthatthe
radiationswerebeingemittedbythe saltitself. Thuswasbornthe
first methodofdetectingnuclearradiation.
Nuclearemulsionsconsistofgrainsofsilver bromide
suspendedinagelatin matrix, withthegrainsbeingtypicallyabout
0.25 pm indiameter. Asacharged particle passesthroughthe
1
2
emulsion, certaingrains are struck byit. Thesegrainsare
sensitized"and are abletocatalyzethereductionofsilverions to
metallicsilver. Whenthe silverbromidegrains areimmersed ina
suitable developing solution, allthe silverions areeventually
converted to metallicsilver. Butthe sensitizedgrainswhichwere
struck byapassingcharged particle developfaster. Thus avisual
track isleftwhichoccupiesthe siteofthe pathofthecharged
particle.
Theearlyphotographicemulsions usedwereoflargegrainsize
which made itdifficulttorecognizetheindividualtracksofthe
particles. Itwasnotuntilthe 1930sthatthe useoffinegrain, low
densitynuclearemulsions allowedfortheobservationofcleartracks.
These tracksareusuallyexamined undera microscopewherebythe
lengthofthetrackoneisabletodeterminetheparticlerangeor
energyandbythedensityofthetrackonecandistinguishbetween
differentparticleshaving differentvaluesofdE/dx.
The mid-1950ssawthe developmentoflargehigh precision
massspectrometers. Thisinspired afurtherdevelopmentofnuclear
emulsionssincetheywere used atthefocalplaneoftheearly
spectrometers. By measuringthe positionthattheionswould strike
theemulsions atthefocalplane, averyaccurate determinationof
particleenergywas made.
Anadvantagetousing nuclearemulsionsisthatonehasa
permanentrecordofthetracks madebytheions. Other advantages
arethattrackdetectors are relativelyinexpensivetouseandonecan
chooseanemulsiontosuitone'sexperimentalneeds. Certain
emulsions allowonetodevelopthetracksof moreionizing particles
3
leaving tracksofweaklyionizing particles undeveloped, thus
allowing anexperimentalisttoselectaccordingtohis/her needs. A
big disadvantage isthatitis along and tedioustask toscanthe
tracks athigh magnification and analyzethem. Thisisespecially
trueforemulsions used atthefocalplaneofa mass spectrometer,
sinceitisnotunusualtohavefocalplanesthatareseveral metersin
length.
Alongwiththesesolidnucleartrack detectors, therearealso
gas andliquidversionsintheformofcloudchambersand bubble
chambers. Cloudchamberswerefirst used byWilsonin 1911 to
detecttracks madebyalpha particlesinanexpansiontypecloud
chamber [2]. Anexpansioncloudchamberisachamberfilledwith
gas, whichcanbealmostanygas. Asacharged particle passes
throughthechamber, thevolumeisadiabaticallyexpanded. The
vaporsbecome supersaturated andcondenseontheionsformedby
the passingcharged particle. Thesedroplets arevisible under
illuminationand are usuallyrecorded photographically. Thebubble
chamberoperatessimilarlytothecloudchamber. Boththecloud
chamberandbubblechamberare used morefrequentlyinhigh
energyphysics applications.
WhileBecquerelwas using photographicplatestolook at
radiationemittedbyradioactive substances, MarieCurienotedthat
the airbetweentwometalplatesbecameelectricallyconducting
wheninthe presenceofradioactive substances13]. Thiswasan
earlyversionofagasionizationchamber, whichisthesecond, and
mostcommon, groupofcharged particle detectors. Allgasion
chambersoperate byusing anelectricfield tocollectallthecharges