Emission of radio waves in particle showers : validation of microscopic simulations with the SLAC T-510 experiment and their potential in the future square kilometre array

142 Pages·2017·24.58 MB·English

by  Zilles

Springer Theses
Recognizing Outstanding Ph.D. Research
Anne Zilles

Emission of Radio
Waves in Particle
Showers
Validation of Microscopic Simulations
with the SLAC T-510 Experiment and
their Potential in the Future Square
Kilometre Array
Springer Theses
Recognizing Outstanding Ph.D. Research
Aims and Scope
The series “Springer Theses” brings together a selection of the very best Ph.D.
theses from around the world and across the physical sciences. Nominated and
endorsed by two recognized specialists, each published volume has been selected
foritsscientificexcellenceandthehighimpactofitscontentsforthepertinentfield
of research. For greater accessibility to non-specialists, the published versions
includeanextendedintroduction,aswellasaforewordbythestudent’ssupervisor
explainingthespecialrelevanceoftheworkforthefield.Asawhole,theserieswill
provide a valuable resource both for newcomers to the research fields described,
and for other scientists seeking detailed background information on special
questions. Finally, it provides an accredited documentation of the valuable
contributions made by today’s younger generation of scientists.
Theses are accepted into the series by invited nomination only
and must fulfill all of the following criteria
(cid:129) They must be written in good English.
(cid:129) ThetopicshouldfallwithintheconfinesofChemistry,Physics,EarthSciences,
Engineeringandrelatedinterdisciplinary fields such asMaterials,Nanoscience,
Chemical Engineering, Complex Systems and Biophysics.
(cid:129) The work reported in the thesis must represent a significant scientific advance.
(cid:129) Ifthethesisincludespreviouslypublishedmaterial,permissiontoreproducethis
must be gained from the respective copyright holder.
(cid:129) They must have been examined and passed during the 12 months prior to
nomination.
(cid:129) Each thesis should include a foreword by the supervisor outlining the signifi-
cance of its content.
(cid:129) The theses should have a clearly defined structure including an introduction
accessible to scientists not expert in that particular field.
More information about this series at http://www.springer.com/series/8790
Anne Zilles
Emission of Radio Waves
in Particle Showers
Validation of Microscopic Simulations
with the SLAC T-510 Experiment
and their Potential in the Future Square
Kilometre Array
Doctoral Thesis accepted by the
Karlsruher Institute of Technology, Karlsruhe, Germany
123
Author Supervisor
Dr. Anne Zilles Prof. JohannesBlümer
Institute of Experimental NuclearPhysics Karlsruhe Institute of Technology (KIT)
Karlsruhe Institute of Technology (KIT) Karlsruhe
Karlsruhe Germany
Germany
ISSN 2190-5053 ISSN 2190-5061 (electronic)
SpringerTheses
ISBN978-3-319-63410-4 ISBN978-3-319-63411-1 (eBook)
DOI 10.1007/978-3-319-63411-1
LibraryofCongressControlNumber:2017946669
©SpringerInternationalPublishingAG2017
Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpart
of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations,
recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission
orinformationstorageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilar
methodologynowknownorhereafterdeveloped.
The use of general descriptive names, registered names, trademarks, service marks, etc. in this
publicationdoesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfrom
therelevantprotectivelawsandregulationsandthereforefreeforgeneraluse.
The publisher, the authors and the editors are safe to assume that the advice and information in this
book are believed to be true and accurate at the date of publication. Neither the publisher nor the
authorsortheeditorsgiveawarranty,expressorimplied,withrespecttothematerialcontainedhereinor
for any errors or omissions that may have been made. The publisher remains neutral with regard to
jurisdictionalclaimsinpublishedmapsandinstitutionalaffiliations.
Printedonacid-freepaper
ThisSpringerimprintispublishedbySpringerNature
TheregisteredcompanyisSpringerInternationalPublishingAG
Theregisteredcompanyaddressis:Gewerbestrasse11,6330Cham,Switzerland
’
Supervisor s Foreword
Cosmic rays were first detected more than one hundred years before this disserta-
tionprojectwasconducted.In1912,theAustrianphysicistVictorHessdiscovered
onhigh-altitudeballoonflightsthationizingradiationfromspacewasimpingingon
hisinstrument,aspecialformofelectrometer.In1936,hereceivedtheNobelPrize
forhiswork.Sincethen,muchprogresshasbeenmadeinunderstandingtheorigin,
propagationandnatureofcosmicparticles,butuptonow,wehavenotarrivedata
complete and consistent picture. The energies of cosmic particles can be much
higher than the energies of particles accelerated in our terrestrial accelerators; they
exceedeventheenergyoftheLargeHadronCollider(LHC)atCERNbyahundred
million times. When a cosmic particle of very high energy hits the atmosphere, its
energyistransformedintobillionsofsecondaryparticles,whichcascadedownasa
so-called extensive air shower until they finally hit one or many particle detectors.
Unfortunately, the most energetic particles are extremely rare, and hence, huge
observatories are required to collect them in sufficient quantities. To give an
impression,the Pierre Auger ObservatoryinArgentina isthelargestinstallationof
its kind; it covers 3000 km2 with a wireless network of 1600 particle detectors.
This is where the doctoral thesis of Anne Zilles is rooted. Those charged par-
ticlesalsoemitradiosignalsontheirwaydown,whichweredetectedalreadyinthe
1960’s. At the time, a few traces of such radio signals in the 10–100 M Hz fre-
quency range were recorded with analog oscilloscopes. This way of getting data
about cosmic rays was soon laid to rest. Only recently has digital technology
allowed the deployment of large antenna arrays, which are read out by fast elec-
tronics and digital circuitry. The detailed analysis can then be done off-line on a
computer. In parallel, the emission mechanism has been investigated more thor-
oughlyandisnowunderstoodtobedominantlycausedbythemagneticfieldofthe
Earth: negative particles like electrons are deflected in one direction, and positive
particles like positrons are deflected in the opposite direction. This charge separa-
tioncreatesadynamicallychangingdipoleflyingalmostatthespeedoflightandis
calledthegeo-magneticeffect.Pioneeringinthedevelopmentofthistechniquewas
the LOPES experiment, which was conducted at the Karlsruhe Institute of
v
vi Supervisor’sForeword
Technology in a co-location of antenna with the KASCADE-(Grande) cosmic ray
detectorarray.LOPESalsopavedthewayformicroscopicsimulationsoftheradio
emission mechanisms, which were developed under the direction of Tim Huege.
AnneZilleswasgivenaconsiderablechallenge:sheshoulddevelopthedetailed
simulationofanaccelerator-basedradioemissionexperiment,inwhichtheshower
was to develop in a dense material like polyethylene. The experiment T-510 was
conductedatSLAC,anddatawererecordedandanalyzedandcomparedtoAnne’s
simulation. The agreement between data and simulation was striking—Anne had
done a marvellous job, including, for example, all fine details of the experimental
set-up.Theresultsalsoimplythatthemodellingcodeoftheemissionmechanismis
sufficiently universal to cope with such different materials as air and polyethylene.
Anne did not stop at this remarkable achievement. She applied the code to
another radically different setting, the planned Square Kilometre Array project
(SKA),whichaimstoperformradioastronomyofunprecedentedquality.Thegoal
wastofindoutwhetherSKAwouldalsobeabletomakeausefulmeasurementon
airshowersbydetectingtheirradioemission.Thesetransientsignalswouldbequite
different from the astronomical signals and probably some SKA design change
would be required to do so. Anne Zilles indeed found that SKA should be able to
measure the atmospheric depth of the maximum of the longitudinal shower
development with a very good precision. SKA might be comparable to or better
than the best alternative method using UV telescopes like in the Pierre Auger
Observatory.
Theaforementionedresultshavebeenpresentedatinternationalconferencesand
in peer-reviewed papers. My feeling, however, is that this excellent piece of
research should be made readily available to a large readership, in particular to
Ph.D. students and young postdocs; even the expert will find here a wealth of
insights and interesting discussions. I wish to thank Anne Zilles for her excellent
work and the Springer publishing company for giving it a place in this series.
June 2017 Prof. Johannes Blümer
Head of KIT Division V—Physics and Mathematics
Karlsruhe Institute of Technology (KIT)
Karlsruhe, Germany
Abstract
If a high-energetic cosmic ray particle enters the Earth’s atmosphere, it induces
an extensive air shower of secondary particles which emits a radio signal. The
interpretation of air-shower data measured by an antenna array is based on the
comparison of the detected radio signals to the results of detailed simulations
of the radio emission. This is a common way to interpret air-shower data, but it
relies on a complete understanding of the radio emission by a particle shower as
well as the ability to model the underlying physics in simulations.
To validate the ability of established microscopic simulations to predict radio
emissionfromaparticleshower,theSLACT-510experimentwasperformed.Here,
anelectronbeamofknownprimaryenergywasshotintoadensetarget,whichwas
positioned in a strong magnetic field, inducing a pure electromagnetic cascade. As
an integral part of the experiment and in the context of this thesis, microscopic
Geant4 simulations were prepared and performed. The simulations include the
details of the experimental set-up, such as the beam energy, target geometry and
material, and the magnetic field configuration as well as both well-established
formalisms for the calculation of radio emission, the endpoint and the ZHS for-
malisms,runninginparallel.Detailsoftheimplementationarediscussedwithinthis
work. As will be shown, a comparison of the measured data of the SLAC T-510
experiment with the results of the detailed simulation study led to the conclusion
thatbothformalismscanpredicttheabsolutescaleoftheradiosignalproducedbya
particleshoweraccuratelywithintheuncertaintiesoftheSLACT-510experiment.
These uncertainties turned out to be dominated by internal reflections of the radio
signal at the bottom surface of the target. Furthermore, in this thesis it will be
presented that the detailed simulation can describe features of the radio emission
fromparticleshowers.Featuressuchasthescalingoftheemittedradiosignalwith
themagneticfieldstrengthandtheformationofaCherenkovconeforthemagnetic
aswellaschargeexcessemissioncomponentsoftheradiosignalcanbereproduced
as measured experimentally within the systematic uncertainties.
The verification of the formalisms for the calculation of radio emission from
particleshowersiscrucialinparticularforfuturehigh-precisionexperimentsforthe
radio detection of cosmic rays such as the future SKA1-low antenna array.
vii
viii Abstract
Also within this thesis, an initial simulation study is performed, demonstrating
that a LOFAR-like approach for the reconstruction of the depth of the shower
maximumisapplicabletoSKA1-lowdata.Theusedreconstructionmethodisbased
on the comparison of simulated two-dimensional lateral distribution functions to
measured data. It is expected that SKA1-low can measure the depth of the shower
maximum for individual air-shower events in the energy region, where the transi-
tion from Galactic origin to Extragalactic origin of cosmic rays is assumed to take
place, with such a high precision that a decomposition of the cosmic ray spectrum
into individual element spectra might become feasible. Here, SKA1-low should
especiallyprofitfromthelargerbandwidthathigherfrequenciesaswellasfromthe
extreme density of the antenna array compared to LOFAR.
Acknowledgements
First of all, I would like to thank Prof. Johannes Blümer for the opportunity to
prepare this thesis and for being the referee of my work. I would like to thank
Prof. Michael Feindt for the being the co-referee.
IgivethankstoTimHuegewhoguidedmeasmysupervisorthroughthewhole
process of graduation.
In addition, I would like to say thank you to Andreas Haungs, Frank Schröder
and Qader Dorosti who helped me with words and deeds all the time.
Furthermore,IamverygratefulforthegreattimeIcouldspendinmyoffice135!
Persons who contributed to that are Katrin, Aswathi and Agnieska, as well as in
former times, Daniel, Andi and Martin.
My special thanks for a cordial affiliation to the IKP to all the other Ph.D.
students and students, as well as to all the staff of the IKP, especially to Sabine,
Jürgen and Doris who supported my work, e.g., by the preparation of simulations,
by providing more disc space and by printing my thesis.
Additionally,IwouldliketothankmanypeopleIhadthechance toworkwith:
(cid:129) To the SLAC T-510 collaboration: thank you that you gave me the chance to
contribute to the experiment in such an important way! Special thanks to
Konstantin,Steph,Katie,Andres,Dave,DaveandBrianforthefaith,inputand
the help I got from you!
(cid:129) To theSKAFocusGroupon High-Energy Particles:especially,Iwould liketo
thank Clancy,Justinand Stijn who gave meinput and supportedme, e.g., with
setting up the simulations study.
Outside of the institute, I got the chance to meet so many people so that this
acknowledgement would never end. I would like to thank for all the discussion,
Icouldlearnfromorjusthadfun,andforallthemomentswesharedin-andoutside
science.
Many thanks to Flo for proofreading this work!
DergrößteDankgehtanmeineEltern,meineSchwester,meinenSchwagerundan
meine Nichte.
ix