CERN Accelerator School Beam Diagnostics

606 Pages·2009·33.32 MB·English

CERN–2009–005
17August2009
ORGANISATION EUROP(cid:131)ENNE POUR LA RECHERCHE NUCL(cid:131)AIRE
CERN
EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH
CERN Accelerator School
Beam Diagnostics
Dourdan, France
28 May–6 June 2008
Proceedings
Editor: D. Brandt
GENEVA
2009
CERN–335copiesprinted–August2009
Abstract
These proceedings present the lectures given at the twenty-second specialized course organized by the CERN
Accelerator School (CAS), the topic being Beam Diagnostics. The course was held in Dourdan, France, from
28Mayto6June2008. AlthoughthisisthefirsttimethetopichasbeenselectedforaCASspecializedcourse,
it has already been covered on two occasions (Capri, Italy, 1988 and Montreux, Switzerland, 1998) by the
topicBeamDiagnosticsandMeasurementsintheframeworkoftheJointAcceleratorSchools(JAS).Afteran
intervaloftenyears,theaimofthiscoursewasthereforetopresentareviewoftheactualstateoftheartandto
highlightthelatestdevelopmentsinthefield.
The lectures start with a general overview of the boundary conditions of the field such as the different
typesofdiagnosticsrequiredfordifferentmachines,thekindofeffectsonewouldliketoobserve(longitudinal,
transverse,andcollectiveeffects),aswellasanintroductiontothemostbasicinstrumentssuchasbeamcurrent
monitors, beam position monitors, loss monitors, and the beam synchronous timing system. Included in this
introductory part are also lectures dedicated to special tools to deal with statistics and errors as well as the
transformationfromanalogtodigitalsignals.
Thesecondpartoftheschooldealswiththedifferenttypesofmeasurementsrathercommonintheframe-
work of accelerators such as measurements of tune, chromaticity, coupling, energy, lattice, closed orbit, emit-
tance,luminosity,feedbacksystems,aswellaslongitudinalandtransverseprofilesandSchottkymeasurements.
Thelastpartoftheprogrammefocusesonmethodswhicharerelativelynewinthefieldandrepresentthelatest
state-of-the-art applications, such as femto-second and photon beam line diagnostics, halo and bunch purity.
As far as the lectures are concerned, the programme also includes lectures of general interest such as electro-
magneticinterference,dynamicalalignment,andmachineprotectionsystems.
In addition to the academic part, the programme was completed by two visits to the synchrotron SOLEIL
includingavisitofthemachineandparticipationinvariousdemonstrationsofsomeofthehardwareintroduced
duringthelectures. Finally,apostersessionallowedtheparticipantstopresenttheirworktotheircolleagues.
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iv
Foreword
The aim of the CERN Accelerator School (CAS) to collect, preserve, and disseminate the knowledge ac-
cumulated in the world’s accelerator laboratories applies not only to general accelerator physics, but also to
relatedsub-systems,equipment,andtechnologies. Thiswideraimisachievedbymeansofspecializedcourses.
For 2008, the topic of the course was Beam Diagnostics and it was held at the Hotel ‘Le Normont’, France,
from28Mayto6June2008.
The topic of Beam Diagnostics had never been treated in the framework of specialized CAS courses, but
was retained on two occasions for the Joint Accelerator Schools (JAS), namely in 1988 in Capri, Italy, and in
1998inMontreux,Switzerland. However,aftertenyearsandconsideringtheenormousdevelopmentsachieved
inthefield,itwasunanimouslyfeltthattherewasanurgentneedtopresentanupdatedversionoftheprevious
course.
The present course was made possible by the active collaboration provided by the Synchrotron Light ma-
chineSOLEILandmanyindividuals. Inparticular,thecontributionsofthemanagementandstaffofSOLEIL,
andespeciallytheenthusiasticcontributionoftheLocalOrganizingCommitteecomposedofS.Podgornyand
J.-C.Denardweremostvaluable. Similarly,thehelpofA.Mosnier(CEA)inidentifyingthevenuewashighly
appreciated.
ThegenerousfinancialsupportprovidedbyJ.-M.Filhol(DirecteurdelaDivisionSourcesetAcce´le´rateurs
of the Synchrotron SOLEIL) as well as the successful efforts of the Local Organizing Committee to identify
sponsors allowed CAS and the Local Organizers to cover some costs inherent to the school and, even more
important, to offer scholarships to highly deserving young students, who otherwise would not have been able
toattendtheschool.
As always, the backing of the CERN management, the guidance of the CAS Advisory and Programme
Committees, the attention to detail of the Local Organizing Committee and the management and staff of the
Hotel‘LeNormont’ensuredthattheschoolwasheldunderoptimumconditions.
Veryspecialthanksmustgotothelecturersfortheenormoustaskofpreparing,presenting,andwritingup
theirtopics.
Finally, the enthusiasm of the participants who came from more than 24 different countries around the
worldwasconvincingproofoftheusefulnessandsuccessofthecourse.
Itismypleasureandprivilegetothankmostsincerelyallthosepersonswhohelpedmetomakethecourse
a success, including Barbara Strasser and the team of the CERN Scientific Text Processing Service for their
dedicationandcommitmenttotheproductionofthisdocument.
DanielBrandt
CERNAcceleratorSchool
v
Friday 6 June Buses to Airport
Thursday 5 June Transport to SOLEIL Photon Beam Line Diagnostics S. Hustache Dynamical Alignment S. Redaelli Halo and Bunch Purity K. Wittenburg Machine Protection Systems R. Schmidt VISIT/DEMOS SOLEIL VISIT/DEMOS SOLEIL Transport to Hotel) Dinner Summary Session
(
France Tuesday Wednesday 3 June 4 June Transport to Femto Second SOLEIL Diagnostics I V. Schlott Schottky Luminosity Diagnostics F. Caspers J. Wenninger C O F F E E Emittance Femto Second Diagnostics Diagnostics II II H. Braun V. Schlott Measurement of Bunch to Beam Energy Bunch Feedback I A. Muller M. Lonza L U N C H VISIT/DEMOS Bunch to Bunch SOLEIL Feedback II M. Lonza VISIT/DEMOS Electro Magnetic SOLEIL Interference A. Charroy T E A Poster Session Presentation of DITANET Transport to Hotel) C. Welsch Special Dinner Dinner
an, n n (
OGRAMME m Diagnostics e 2008, Dourd Monday 2 June Longitudinal Diagnostics I M. Ferianis Transverse Profiles I E. Bravin Longitudinal Diagnostics II M. Ferianis Transverse Profiles II E. Bravin Emittance Diagnostics I H. Braun eractive SessioI eractive SessioII Dinner
PRBea6 Jun Int Int
8 May – Sunday 1 June E X C U R S I O N Dinner
2
Saturday 31 May BST M. Ferianis ne, Chromaticity and Coupling I R. Steinhagen ne, Chromaticity and Coupling II R. Steinhagen Closed Orbit M. Boege Closed Orbit Feedback M. Boege Lattice Measurement J. Wenninger nalog to Digital II J. Belleman Dinner
u u A
T T

Friday 30 May Collective Effects A. Hofmann Beam Position Monitor I P. Forck C O F F E E Between Model and Reality II L. Nadolski Beam Position Monitor II P. Forck L U N C H Loss Monitors K. Wittenburg Analog to Digital I J. Belleman T E A Discussion Session Dinner

Thursday 29 May Specific Diagnostics Needs for Different Machines I G. Kube Between Model and Reality I H. Braun Specific Diagnostics Needs for Different Machines II G. Kube Longitudinal & Transverse Effects I A. Hofmann Beam Current Monitor J.-C. Denard Longitudinal &Transverse Effects II A. Hofmann Measurements, Statistics and Errors M. Hoffmann Welcome Drink Dinner
Time 08:30 09:30 09 :30 10 :30 11:00 12:00 12:00 13:00 14 :30 15:30 15:30 16:30 17:00 18:00 20:00

vi
Contents
Foreword
D.Brandt ...................................................................................... v
Specificdiagnosticsneedsfordifferentmachines
G.Kube ........................................................................................ 1
Dynamicsofbeamdiagnostics
A.Hofmann ................................................................................... 65
Beamcurrentmonitors
J.-C.Denard ................................................................................. 141
Measurements,statistics,anderrors
M.Hoffmann ................................................................................. 157
Beampositionmonitors
P.Forck,P.Kowina,andD.Liakin .............................................................. 187
Betweenmodelandreality,PartII
L.S.Nadolski ................................................................................ 229
Beamlossmonitors
K.Wittenburg ................................................................................ 249
Fromanalogtodigital
J.Belleman .................................................................................. 281
Tuneandchromaticitydiagnostics
R.J.Steinhagen .............................................................................. 317
Latticemeasurements
J.Wenninger ................................................................................. 361
Transversebeamprofiles
E.Bravin .................................................................................... 377
Schottkysignalsforlongitudinalandtransversebunched-beamdiagnostics
F.Caspers ................................................................................... 407
Measurementsofbeamenergy
A.-S.Mu¨ller .................................................................................. 427
Luminositydiagnostics
J.Wenninger ................................................................................. 453
Multi-bunchfeedbacksystems
M.Lonza .................................................................................... 467
Photonbeamlinediagnostics
S.Hustache-Ottini ............................................................................ 513
Dynamicalignmentinparticleaccelerators
S.Redaelli ................................................................................... 535
Beamhaloandbunchpuritymonitoring
K.Wittenburg ................................................................................ 557
Machineprotection
R.Schmidt ................................................................................... 581
ListofParticipants .............................................................................. 597
vii

Speci(cid:2)c diagnostics needs for different machines
G.Kube
DeutschesElektronen Synchrotron (DESY),Hamburg,Germany
Abstract
Beam diagnostics and instrumentation are an essential part of any accelera-
tor. There is a large variety of parameters to be measured for observation of
particle beams with the precision required to tune, operate, and improve the
performance of the machine. However, depending on the type of accelerator,
forthesameparametertheworkingprincipleofamonitormaystronglydiffer,
and thus the requirements for accuracy. This report will give an overview of
selected types of accelerators in order to illustrate speci(cid:2)c diagnostics needs
whichmustbetakenintoaccount beforedesigning anewinstrument.
1 Introduction
Nowadays particle accelerators play an important role in a wide number of (cid:2)elds where a primary or
secondary beam from an accelerator can be used for industrial or medical applications or for basic and
applied research. Theinteraction ofsuch beams withmatter isexploited i)in order to analyse physical,
chemical,orbiologicalsamples(example: particle-inducedX-rayemission,PIXE),ii)foramodi(cid:2)cation
of physical, chemical, or biological sample properties (example: sterilization), or iii) for fundamental
researchinbasicsubatomicphysics. Table1showsacompilationofdifferentacceleratorapplications[1]
basedontheyear2000. Ascanbeseen,morethanhalfoftheseaccelerators aredevotedtomodi(cid:2)cation
processes: ion implantation, surface modi(cid:2)cations, industrial applications in the main for sterilization
andpolymerization.
Table1:Worldwideinventoryofparticleacceleratorsintheyear2000[1]
Category Number
Ionimplantersandsurface modi(cid:2)cations 7000
Accelerators inindustry 1500
Accelerators innon-nuclear research 1000
Radiotherapy 5000
Medicalisotopeproduction 200
Hadrontherapy 20
Synchrotron radiation sources 70
Nuclearandparticle physicsresearch 110
Total 15000
Inordertocoversuchawiderangeofapplications, differentacceleratortypesarerequired. Asan
example,inarttheLouvremuseumutilizesthe2MVtandemPelletronacceleratorAGLAEforionbeam
analysis (IBA)studies [2]. Cyclotrons are often used toproduce medical isotopes for positron emission
tomography (PET)andsingle-photon-emission computed tomography (SPECT).Forelectron radiother-
apy,mainlylinearaccelerators(linacs)areinoperation,whilecyclotronsorsynchrotronsareadditionally
usedforprotontherapy [3]. Third-generation synchrotron lightsourcesareelectron synchrotrons, while
thenewfourth-generation lightsources(freeelectron lasers)operating atshortwavelengths areelectron
linac-based accelerators. Examples of these type of machines are SLAC/LCLS or DESY/FLASHand
XFEL. Neutrino beams for elementary particle physics are produced with large proton synchrotrons,
and in linear or circular colliders different species of particles are brought into collision. To give a few
1
G. KUBE
examples, this isrealized withe+e beams (SLAC/PEPII,KEK/KEKB,LNF/DAΦNE,BINP/VEPP4,
−
CERN/LEP, and the future international linear collider ILC), with ep beams (DESY/HERA), with pp¯
beams (FNAL/Tevatron), withppbeams (CERN/LHC),and with different ion(cid:150)ion beams (BNL/RHIC:
Au(cid:150)Au, CERN/LHC: Pb(cid:150)Pb). Reference [4] gives an overview of the large accelerator-based facili-
ties together with proposals for the next generation of machines with emphasis on elementary particle
physics.
As seen from this short list there exists a large number of accelerator types with different prop-
erties, and as a consequence the demands on beam diagnostics and instrumentation vary depending on
machinetypeandapplication. Tocoverallthesecasesisoutofthefocusofthisreport. Linearandcircu-
laraccelerators forhigh energy physics and synchrotron radiation applications are the primary concern,
butnevertheless connections toothertypesofaccelerators willbeprovided. However,beforegoinginto
details, the(cid:2)rstquestion toposeisaboutthebeamparameters ofinterest andabout theinformation that
canbegainedfromtheirmeasurement.
1.1 Beamparametersanddiagnostics
Thissectiongivesanoverviewofprimarybeamparameterstogetherwithexamplesforvalueswhichcan
be deduced. This list is far from complete, more details can be found in speci(cid:2)c textbooks or lecture
notesasinRefs.[5(cid:150)7].
Oneofthe(cid:2)rstquestions inthecommissioning ofanew accelerator is howmanyparticles are in
the machine, i.e., the beam intensity is one of the most important accelerator parameters. This can be a
measurementofthebunchcurrent(charge),ofthedccurrent,orofboth. Withknowledgeoftheintensity
it is possible to determine lifetime and coasting beam in circular machines, or transfer ef(cid:2)ciencies in
linacsandtransferlines.
Oneofthenextquestions whicharises maybewherethese particles arelocated, i.e.,the position
of the beam centroid. Position measurements give access to a wide number of very important acceler-
ator parameters. The most fundamental one is the determination of the beam orbit from which lattice
parameters can be deduced. Position measurements are also required for tune measurements and the
determination ofthechromaticity; theyareafundamental partoffeedback systemsandmore.
The next question might be how distribution of particles in space looks, i.e., the beam pro(cid:2)le in
both transversal and longitudinal dimensions are of interest. Beam size measurements are fundamental
for the determination of the beam emittance; time resolved beam size studies give information about
injection mismatch (betatron and dispersion matching) via the observation of turn-by-turn shape oscil-
lations, orabout dynamical processes as,forexample,the study ofbeamblow upofindividual bunches
under collision in a particle collider. Furthermore beam halo diagnostics rely mainly on measurements
ofthetransverse beamsize.
Another parameter of interest is the beam energy, but mainly for users. In a lepton collider, for
example, it de(cid:2)nes the reaction energy which is available in order to produce new particles, while in
synchrotronlightsources(third-generation aswellasfree-electron-lasers (cid:151)FELs)itde(cid:2)nesthespectral
characteristics oftheemittedradiation.
In a collider the luminosity is the key parameter because it de(cid:2)nes the count rate of the reaction
channelunderinvestigation. Whileanabsoluteonline-luminosity determinationissometimesdif(cid:2)cultto
provide, thedetermination ofarelative luminosity orsimply acount ratewhich isproportional to itis a
very important tool for the collision optimization (angle and position) of both beams via beam steering
withlocalbumps.
Inorder toidentify theposition ofbeamlosses, toprevent damagetotheaccelerator aswell asto
facilitycomponents,andtooptimizethedailyacceleratoroperation,beamlossmonitorsrepresentavery
importantdiagnostics system.
In the nextsections examples ofthese systems fordifferent accelerator types willbe given. Nev-
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