Database for Accelerator Optics
B . A utin,F. D i M aio,M . G ourber-Pace,M . Lindroos,J.

SchinzelC E R N ,PS D ivision
C H -1211G eneva23,Sw itzerland
Abstract
The A utom ated B eam Steering and Shaping (A B S)
projectaim s to provide an autom atic,generic and reliable
softw are system to ensure the provision of high quality
particle beam s to users of an accelerator com plex. A n
im portant com ponent of this project is the access tovalidatedreferencedatadescribingthedifferentcom ponents
instaled in the m achines,such as m onitorsas w ellas the
optical and m agnetic properties of all m agnets. These
properties are dependent on the type of particle,on theenergy and on the destination ofthe beam .The data m odel
m usttherefore be able to representseveralparticle beam s
along different trajectories through the sam e elem ent.
Furtherm ore, the database design m ust be sufficiently
general to allow the description of the elem ents from asim ple dipole to com plex
m ulti-coilm agnets.Fora given
operation, the sequence of optics elem ents w ith theparam eters appropriate to the type of beam m ust be
extracted,suitably form atted and passed asinputto a beam
optics program . This paper describes the problem s
encountered during the analysis,the resulting data schem aandthesoftw aredevelopedfordatam aintenance.E xam plesaregivenforthem achinesoftheC E R N PS com plex.
1 Introduction
D atabases foracceleratorshave been designed to fitthe
num erous requirem ents im posed by everm ore com plex
m achines[1].The purposeofthisdatabaseisto serve asa
general reference docum ent sim ilar to an electronicparam eterlistdescribing the inputvaluesneeded foroptics
calculations.M uch ofthe data describing the optics ofthem achinesin thePS C om plexcurrentlyresideson paperandon files.A firstfeasibility test[2],w hichtook placeduring
1996,revealed the im portance ofproviding a datam odelw hich is sufficiently general to describe all possible
m achine configurations.The aim ofusing a databaseisto
provideasingle,correctsourceofdata,essentialforon-line
beam correction. These corrections are considered as
perturbations ofthe reference m achine docum ented in the
database. The database is thus static and unaffected by
accidentalvariations.Thisw arrantsthereproducibilityofan
operation. A n operation defines the list ofcom ponents
w hich acton a particle beam ,the com ponentpositionsand
theiropticsparam eters.B yspecifyingtheoperation,particle
andm om entum ,the position andshapeoftheparticlebeam
can be calculated and corrections m ade. The result isobservedusingbeam m easurem entm onitors.

Thearchitecture ofthe databaseisdeveloped around theconcept of a m achine operation. It accom m odates thedescription of the com plex m agnets used to m ake up am achine.C are hasbeen taken to avoid any redundantdata.
Thecurrentsystem isrestrictedto thebending andfocusingparam eters of a com plex of m achines. The object
m anagem ent softw are, A C C IS ( A C C elerator Inform ation
System ),w hich is used to describe,editand brow se thedata,isdescribed.
2 Machine operation
A m achine operation as defined here is the action ofpassing abeam from onepartofam achineto anotherfora
given purpose such as injection and acceleration. A n
exam plesin theC E R N contextisthe5-turnextraction fromthe PS to the SPS.A n operation requires a sequence of
optics com ponents,e.g.m agnets and m onitors,w hich areused to acton orm easure the beam and the corresponding
setofreferenceopticsproperties.A noperationalsorequires
thepositionofeachcom ponentalongthebeam trajectory.
2.1 Beam path
The sequence ofcom ponents isderived from a databaseobjectknow n as a beam path.A beam path describes thephysicalstructureofapartofanacceleratorortransferline
and m ay be used to describe m ore than one operation.A nexam ple isshow n in Fig.1.The beam path
Linac/B oostertransferline is m ade up oftw o transfer-line sections,theLinac transferline LT and the
Linac to B oosterline LTB .
The L T section is m ade up, for exam ple,of the dipole
L T .B H Z 10, the focusing
quadrupole LT.Q FN 20 anddefocusing quadrupole LT.Q D N 22. The L T B section
includes tw oquadrupoles and a beam position m onitor
L T .U M A 10.
To createasequence ofopticscom ponents,abeam pathisexpandedintoitscom ponentpartsandthenstrippedofall
non-opticscom ponents.
So that beam path parts can be reused in different
operations,the parts of a beam path should not include
elem entssituatedondifferentbranchesoflinesections.The
branching ofthe L T A transfer line into the LT and L T E
lines is represented as three sections. L T A includes thebranchingcom ponentLT.B H Z 10.Thisisshow ninFig.2.
2.2 Topology
To positionopticscom ponentsalongabeam path,theThecorrectionscurrentlybeing exploredaresteering andm atching forthe injection ofparticles from thetheB oosterandforthetransferbetw eentheB oosterandPS,
asw ellasforthe closed orbitcorrection ofthe PS and thecorrectionofthecoherenttransverseoscilationsatinjection
intothePS ring.

Linac/Booster
rtransfer lineLT

2.4 Component usage in an operation

LTB

LT.BHZ10

LTB.QFN10

LT.QFN20

LTB.QDN20

LT.QDN22

LTB.UMA10
etc.

Fig.1:A

Linac intoetc.

L inac/B oosterbeam path

The inform ation describing how a com ponentis to be
used inanoperationiscalledtheusage''.Theterm indicatesw hether a com ponentis to be used for correction in theoperation,and,ifso,for w hattype of correction.W hilem onitorshave no otherreference param eters,m agnetsm ay
have optics param eters.These are referenced by thew hich belongs to the relationship betw een the com ponent
and operation. If this relationship is rem oved, so is theusage.The m agnetoptics,how ever,m ay be referenced byother com ponents and are therefore preserved. In the
databasenodistinctionism adebetw eenacorrectorandany
otherm agnet.A lm agnetsm ay have opticsparam etersand
m aybeusedascorrectors.A nexam pleofausageisshow n
in Fig3.
.

usage

L T E K H Z10
L T E .K V T10

LTE
LTA

L T .M T R 10 L T .Q D N 12 L T .B H Z10

B T .Q N O 10

LTV erticalsteering?Y es
H orizontalsteering?Y es
M atching?N o

L T .Q FN 20

B T .Q N O 10
Protoninjectionoptics

Fig.2:LT A linesplitinginto LT andL T E
lineardisplacem entbetw een theentrypointofeachelem ent
w ithrespecttothestartoftheparentobjectm ustbedefined.
T akingtheexam plein Fig.2,thedipoleL T .B H Z 10m ustbe
positioned relative to the parentm achine partL T ,and L T
relative to the beam path LT-L T B .Form agnets the entry
pointindicatesthestartofthem agneticfield.
2.3 Reference optics and correction
O n-line correction forsteering orm atching abeam isthedaily task ofthe operation crew .A correction requires thesolution ofalinearsystem characterised by am atrix w hoseelem ents represent the effect of a unit correction at am onitor.Forexam ple,the data required forcorrecting theclosed orbitin the PS ring
includesthe reference optics of
one hundred m agnetsproducing the m ain m agneticfield as
w ellas thatof
quadrupoles to setthe transverse tunes.It
also includesthehorizontalorverticaldipolecorrectorsand
the m onitorsw hich m easure the displacem entofthe beamin a transverse plane ata given position in the ring.This
data is then passed to a sym bolic optics program [3] fortreatm ent.A resulting correction toa field strength can beconverted to a current variation given the m easured
m agnetic rigidity inT esla m etres, that is the particle
m om entum /electriccharge.M onitorreadingscanbeusedto
com parem easuredandcalculatedbeam profiles.

ProtoninjectionforC PS

Fig.3:

A quadrupolew iththereferenceopticsusedfor
bothsteeringandm atchingduringCPS injection.

3 Magnets
M agnets,both those used in the PS today and thoseforeseen forLH C [4],can be com plex.A
m agnetm ay besupplied by a currentpassing through m ore than one coil.
Thesam epow ersourcem aysupplyseveralcoils.A m agnet
m aybeoperatinginanunsaturatedorinasaturation regim edepending on thecurrentbeingsupplied.C oilsm aybeused
tocorrectthereferencem agneticfield in ordertoadjustthetuneand chrom aticityasw ellastocom pensateirregularities
in the m agnetic field.C orrection m agnets m ay them selves
have a nom inal field. W hen a m agnet is m ade up of
superposedcoils,them agneticfieldsm ayoverlap.A coilofam agnetm ayprovideafield w ithasinglepolarity,suchas
a dipole orquadrupole,or a field w hich is m ade up of
severalfieldcom ponents.
C E R N PS m agnetsareusedasanexam ple.E achism ade
upoftw ohalves:am agneticfocusingsectorandam agnetic
defocusingsector.E ach sectoriscom posed ofseveralcoils:
them aincoilandcorrectioncoils.Them aincoildefinesthenom inalm agnetic field ofthe bare m achine (no correctors
included).Itisacom bined function coilasitprovidesboth
bending and focusing fields.The correction coilsinclude abackleg w inding coil,acting asaradialcorrection dipole.A
pole face w inding coil w ith
quadrupolar andsextupolarcom ponentsisused athigh energy in orderto com pensate
saturation effectsand to adjustthenatural
chrom aticitiesof
the m achine.A specialloop w ith aquadrupolarcom ponent
isused athigh energy to controlthetransversetunesofthem achine.
B eam spliting m agnets m ay actin a differentw ay on
differentparticlebeam s.ThePS boosterverticaldistributor
m agnetconsistsofsix dipoles located in the sam e verticalplanebutinsequenceontheinjectionline(Fig4)
..

0

1

2

3

D istrib u to rm a g n e ts

Fig.4:

4
C o m m o n v erticald e flecto rm a g n e t

TheD istributorconsistsoffivedipolespositionedin
the sam e plane butin sequence on the injectorline.
Thefifthm agnetisacom m ondeflectorm agnet.

E ach of the five first dipoles, so called distributor
m agnets, have one single nom inalbending angle.Thesixth
m agnetservesasacom m onverticaldeflector,alsow ith one
single bending angle.To getto the low estPSB ring,only
distributorm agnet0 isactiveandto gettothetop ring,fourof the distributor m agnets are active. In both cases thecom m on deflector m agnet is at its nom inal value.
C onsequently,the databasehas,in addition to dealing w ith
non-activem agnets,also to dealw ith m agnetsw ithasingle
nom inalbending angle butw ith differentedge-up and edge
dow nangles.
3.1 Magnet elements
In ordertocopew ith thedefinitionofcom positem agnets
in the database,the conceptofm agnetelem enthas been
introduced.A m agnet elem ent provides a m agnetic field
generatedbyacurrentpassingthroughasinglecoilorbyno
currentatallifitisaperm anentm agnet.Forexam ple,an
L H C m agnetis com posed ofthree m agnetelem ents:them ain dipole, the correction
sextupole and the correction
decapole.E ach coilisconnected to a single pow ersource,
supplied by one or m ore pow er supplies. A com posite
m agnetm aybem adeupofseveralsequentialorsuperposed
m agnetelem entsw ith totalyorpartialyoverlapping fields.
M agneticfieldsm ayhaveasinglecom ponent,suchasa

dipole or quadrupole com ponent,orm ay be described byseveralfield com ponents.E ightcom ponents are currently
included in the data m odel.The opticsfield strengthsused
form atrixcalculationsare given in particleand m om entum
independent unitsw hich reducesthe num berofoperations
to bedefinedtoam inim um .Thejustification forthechoice
offieldm odelparam etersisdescribedbelow .
3.2 Magnet field model
Thefield m odelisthe one ofa hard edge m agnetw ith atransverse field w hoseT aylorexpansion istruncated atthe
octupole term .The field is thus characterised by dipole,quadrupoleand sextupolecoefficients.E ach coefficienthas
an upright and a skew com ponent so that the field isdeterm ined by eight independent coefficients. The field
coefficients are those m easured in the laboratory w ith thereference system ofthe m easurem entbench.In the caseof
iron m agnets,the field is,to a very good precision,uprightandtheskew com ponentsarenegligible.Insuperconducting
m agnets, the skew com ponents have to be considered.
Insideam achineandespecialyin transferlines,them agnet
orientation m ay be different from its orientation in thelaboratory.Itslongitudinalaxis
Oz isalw ayscollineartothe
beam orbitand the only
angle w hich m attersin practice istheangleabout Oz calledthetilt ofthem agnet.Thetiltisa
specialattributeofam agnetelem ent.
The Lorentz force exerted by the m agnetic field on aparticleisproportionalto the field itselfintegrated overthem agnetic length
l of the elem ent,to the particle electriccharge and inversely proportional to the particle
m om entum . To each field com ponent corresponds an
optical coefficient, nam ely the particle deflection, the-2integrated focusing strength
Kl,m easured in m
and thefirstandsecond radialderivativesof
Kl.A sw asthecaseforthefield,thereareuprightandskew opticalcoefficients.
A correction isfirstexpressed in physicalunits such as-2
radiansfora deflection,mfora beam envelope ora tune
shift. The physical unit is converted into a currentor a
voltage viaacalibration
coefficientw hich isdefined asthe
derivative of som e field coefficient w ith respect to thecurrent(orthe voltage).W ith thisdefinition,thecalibration
coefficientm ay be a function ofthe currentas ithappens
w hen a m agnetoperatesinasaturatedregim e.D ividing thecalibration coefficientby the m agneticrigidity achievesthetransform ationofphysicalintoengineeringunits.
3.3 Calibration
In the data m odela m agnetic elem entisdescribed by am agnetic field w hich has a m agnetic length and fieldm easurem entpoints taken atdifferentcurrents orvoltages
for each of the eight upright and skew com ponents. A
m agnetic field description m ay be shared by m any m agnet
elem entssuch asthose in the m ain m agnetsofthe C E R N
PS.Fig.5 show s the definition of calibration data for am agnetelem ent.

Magnet element

Magnet element
tilt

Power
sourceVertical steering?
Hortizontal steering?
Matching?

Magnetic fieldmagnetic length

Operation

Measurement point
Current/voltage
Vertical dipole component [Tm]
Horizontal dipole component [Tm]
Quadrupole component [T]Skew quadrupole component [T]Sextupole component [Tm-1]
Skew sextupole component [Tm-1]
Octupole component [Tm-2]
Skew octupole component [Tm-2]

Fig.5:

Beam
path

Thedatabasedefinit
ionofam agneticfieldreferencedbyam agnetelem ent.

Fig.6:

3.4 Reference optics
A m agnetelem entm aybetilted,andtheangleoftiltm ay
be defined inm iliradians.The m agnetoptics param eters
includethe verticaland horizontalbending anglesgiven in
m iliradians,the uprightand skew
quadrupole strengthsin-3m-2 , sextupolestrengthsinm
and octupolestrengthsin m
They also include the optics type, currently dipole orquadrupole,and the angles ofthe norm alto the entry andexitm agnetfaces,edge up-stream and edge dow n-stream ,andthetrajectorylength.A setofm agnetopticsparam eters
m ay be used in m ore than one operation,butonly one set
m ay be referenced peroperation.Them odelissum m arisedin Fig6.
.

-4

4 Database functionality
Thedatam odelm aybeextended to referencedatastoredin O R A C L E tables m aintained outside the A B S system ,suchasinthePS controlsystem [5]andsurveydatabases.
A B S specific object m ethods have been developed topasstreated opticsdatatoasym bolic opticsprogram w here
itcan be used to generate the reference opticsand
correction m atricesforan operation.Thesem ethodsalso provide
listsofpositioned correctorsand m onitorsasw ellascalibration data and pow er supply
nam es to application program s[6].
Thesym bolic opticsprogram requiresaform atted listof
opticselem entsw iththeirpropertiesinordertocalculate
am atrix to describe the nom inalopticsasw ellasalist
ofcorrectorsandm onitorsw iththeirpositions.Inorderto.

Magnet optics
Optics type (dipole/quadrupole)
Trajectory length [m]Vertical deflection angle [mrad]
Horizontal deflection angle [mrad]
Quadrupole strength [m -2]
Skew quadrupole strength [m -2]
Sextupole strength [m -3]
Skew sextupole strength [m -3]
Octupole strength [m -4]
Skew octupole strength [m -4]
Edge up-stream [mrad]
Edge down-stream [mrad]

Thedescriptionoftheopticsofam agnetelem ent
foranoperation.

generate the data describing a beam optics channel, theoperation beam path w ould first be expanded into its
com ponentelem ents.The resulting data isthen stripped ofthose elem ents w hich are notused in the operation.The
channelisassum edtostartandendatthebeginningandendof the beam path. The position of each elem ent canbederived from the displacem ent of each elem ent given
relative to the parent m achine part in the beam pathstructure.The operation optics ofeach m agnetelem entis
treated: positions and drift spaces calculated, the data
form atted and then sentto the sym bolic optics program .
Lists of correctors and m onitors are included in the
expandedinform ationw iththeirpositionrelativetothestartof the beam path. In order to im port this data into thesym bolic optics program , the user has to type a sim ple
com m and follow ed by the operation and type of steeringcorrectionhew ishestotreat.
5 Data management software (ACCIS)
The softw are used to m anage the data is A C C IS
(A C C elerator Inform ation System ), a generic object
m anagem ent system developed at C E R N . The datarepository is the relational database m anagem ent system
O R A C L E . The softw are provides tools to define object
classesasw ellasabasicsetofobjectm anagem entm ethods
on top ofw hichm ethodsparticularto theA B S can bebuilt.
O nce the object classes have been defined the user can
im m ediately start to enter data w ithout further softw aredevelopm entusingagenericform attedscreen fordataentry(Fig.7).

Fig.7:TheO R A C LE Form sdataentryand
m aintenancescreen.

A C C IS includes a W E B brow ser for interrogating thedata.A nexam pleofaW E B pageisshow n in Figure8.The
brow serhastheW eblook-and-feel,i.e.w hentheuserclicks
on a reference field,a new page w il be displayed.The
A C C IS W ebpages,how ever,aredynam icallycreated fromdata in the database using procedures also stored in the
database using the O R A C L E
W ebServer facilities.
Thereforeassoon as the data ischanged,the m odification
canbeseenusingthe
brow ser.

elem ent concept has also been verified by using thedatabase to describe the m ore com plex C PS and LH C
m agnets. Since the testing of the system has begun,
anom alies have been detected arising from incorrectreferenceparam eters w hich have subsequently beencorrected,i.e.the A cceleratorO pticsD atabasecan be used
toverifythecorrectnessofthedata.
The A C C IS softw are allow s the definition of further
descriptive properties w ithoutthe necessity of m odifying
thesoftw are.Thereisno need to restrictthedataenteredto
thatrequired forthe A B S project.Indeed apartfrom thestructuraldecom position ofan acceleratorortransferline,
the database also includes specification data thatprovides
supplem entary on-line inform ation to operators.This data
can also be seen using the W eb
brow ser and is being
increasingly interrogated. This inform ation could beeventuallyextendedtoincludeacom pletedocum entationof
thePS com plex.
The data entered into the earlierversion ofthe databasehasbeen successfully m igrated into the new objectm odel.
Thenextstepistocom pleteandcheckthedescriptionofthe
rem ainderofthePS com plexoperations.
Acknowledgements
Theauthorsw ould liketothank
L.Giulicchi,
and M Mar. tinifortheirhelp in providing the data forthis
project.

A .Lom bardi

References
[1]

[2]

[3]
Fig.8:TheO ptics

databaseW eb brow ser.

6 Evolution and conclusion
The m ain aim ofthe A cceleratorO ptics D atabase is to
fully describe the m achine operations in an accelerator
com plex and to im port the data into a sym bolic optics
program for generating correction m atrices.The databasem ust also provide lists of correctors and m onitors andcalibration data to the application softw are.The objectives
have been achieved forthe
L inac to B oostertransferw ith
the correction inform ation forverticalsteering.Them agnet

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