Bergsma, F

Borisov, O N

Budagov, Yu A

Karamysheva, G A

Lomakina, O V

Nessi, Marzio

Vorozhtsov, S B

CERN Document Server

QD! OCR Output*CERN, Geneva, SwitzerlandProtvino, 1994Submitted to <<XIV Meeting on Charged Particle Accelerat0rs»,LARGE TileCal MAGNETIC FIELD SIMULATIONO.V.L0makina, G.A.Karamysheva, J .A.Budag0vM.Nessi*, F.Bergsma*, S.B.V0r0zhts0v, O.N.B0ris0v,SN (5 5 2,SCAN-9506097l lllllllllllllllllllllllllllllllllllllllllllllliCERN LIBRARIES, GENEVAcoordinates was used for the simplihed model No stray field from coil toroids is included OCR OutputCalculation with the 2D code POISCR for the system configuration in the polar R—Z3.1 Simpliiied model representation results3 Magnetic Held in the scintillators08 was taken from [5,6].the slots for tiles {hut it still has not been done up to now). Magnetic characteristic for steelby iron with a suitable packing factor = 0.76 and anisotropic properties taking into accountsymmetry condition has been taken into consideration. The active section should be replacedwere assigned at the enclosure of the region of calculation. Periodical along gc »co0rdinatetaken into consideration. Proper boundary conditions reflecting the symmetry of the systemiron along the Z—axis (Fig. 2.2) and only 4 sectors along the tp-coordinate (Fig. 2.3) werepart of iron needed for calculations is shown in Fig. 2.2 and Fig. 2.3. Only half of the TileCaland on both sides of the system V very simplified images of the end·cap toroids. MinimalFig. 2.l. One can see the solenoid in the very centre, 8—coil Barrel toroid around the solenoidATLAS coil system constructed with the help of the preprocessor OPERA-3D [4] is shown inare identified the only elements ofthe detector which are Held sources or magnetized media.Schematically various aspects of system are shown in Figs 2.1+2,3. ln these Figures thereThe adopted ATLAS simulation modelMechanical toleran<‘es/forces arising from asymmetries [ll?yokeThe attractive forces l>etwe·t·n cnd—cap toroids and Barrel toroids through theThe force between Barrel and lixtended BarrelEstimation of pondcrrnol ive force distribution, acting on individual units ofthe system:Calculation of the e1°l`e<rt of Held disturbances due to studies in the tile zone.Calculation of tlic effect of field flux distortion in the feet region of 'l`ileCal.Study ot uniformity distortions arising from the geometric effects:PMT shielding and the B—lield eilbct on scintillator [2]:Calculation of the magnetic field of scintillating tile calorimeter in order to quantify theprograms.fields outside the rnagiivt Submitting calculated lield map into various simulationCalculation of thc A'I`L.¤\S space map for thc llcld inside the magnet and for fringeFormulation of the problemZmu values. ln l*ig.3.l held values along the lst from the Barrel edge ( Z: 2.9275 nt) and OCR OutputFirstly the real tile structure area was introduced at the Barrel corner with the Ifmm andwhat the maximum iield value would be inside the tiie regions ot. the 'l`ileCal.have been loin=d out in the previous model. The purpose of the model is to get a feelingthe most eritiral points with the maximum induction value in the 'l`ileCal iron. These pointsIt is constructed as the previous model but with inserting the real tile structure regions into3.2 Results with a more realistic tile structurewhich is equal to ().—l il'.the cross—section of solenoicl. This can he rornpared with the Barrel field value for Hmm, Z,,l,,,connected with the much larger rrossrsertion area tor the tlux in the "l`ileCal in relation toThis rather low value as compared with solenoid field 2 T reflects a geometrical factorcylindrical surlace at the Ifmm. rlhen we shall get IBWEMQ, m 0.13 Fl` at this TileCal surface.total flux coming out of solenoid is unitormly distributed over Barrel and Extended Barrel\Ve can make an estimation for the lower limit of the Held in the 'l`ileCal assuming that thethe border, namely, at the corners ot` Barrel and Extended Barrel contour.region concerned. l·`rom these calculations one can see that such points are situated alongThis would give us the most critical points as lar as the held lines penetration into tileto Find out where there are places within 'l`ileCal absorber with the maximum Held values.into calculation. We need this model to get an impression of the Hux line distribution andldigure 2.15: Barrel and Extended Barrel 4 sectors cross—section in XOY planelW¤·=·;u;=e/ \\./,¤’ _v¤o0.B’\»·""*\\ l s. V ¥.$D0.0 X 100.4} X IDU D .> Flbl.0 FD0,0 POB] i 7 B ' ` `~ ~ B ` B_VlW¤\ 7_VSDG.D20/JunI|1712i¤ Pnqa lOCR Output.., , °,,..ii ' W MB` iw"`pYiY?##Bw /`\K/ ;'$\$i/tile regions for various number of rows with the real tile structure OCR OutputFigure 3.1: Field insideddd dddd ddiwZE 24 25 T5 .*0 32 14 36 3.5» *•\_ \ \X Q_ Y¤`,·i_POT > 1efB \ R1 5) ZWr·;·~$; @(9) x 5 nodesTOLPOY =1e»76 rows, 6 x 3 nodes·\ 1 2U \» `»\TOLPOY I 7 &—75 row; $1 x 5 ncdes~>Z 1 2 92 75 rn{$..»7Wm)10 12 $4 56 $82P Z4 I6 28.` ; 1" J \\'CFLPOT = 1e-BL z_\`11r0ws;6(9)¤ 5 ncdesW x\\ 1\ ` J]TOLPOT z 7e#75} •- °`¤\\ \ 6 rows, 6 x 3 nodes./·\\5 2)TOLDOT =1c-75 mv.;11 X 3 nodes4} ` · 1)Zi29275mi`•.'$'Vregion between the Barrel toroid and the TileCal, R : 4.2 m + 5.0 m. ln this Figure the OCR OutputIn Fig. 4.1 one can observe that the toroid stray field shows 16 — poles behavior in theThe rest of the ATLAS coil system was without current at all.This set of calculations was done with the only Barrel toroid coils with the nonzero current.4.1 Central (Z E 0) Ti1eCal barrel planefield distribution [9] with the help of the VF software TOSCAHere we mainly shall consider the three—dimensional model (3D) of the TileCal magnetic4 Magnetic field at the PMT locationtile field is also no more than G mT.2D calculations near Z E U show that the flux lines are z parallel to the Z·axis and theand safely screening tile slots from the magnetic fiux penetration.as there is thick solid return flux iron connecting Extended Barrel and Barrel along Z·axiswith (Hmm, Zmu But in this region situation differs from the corner with (R,,,.;,,, Zmu, )One could also expect the tile field increase with radius in the vicinity of the Barrel cornerwhich is safely below desired limit l0 mT.maximum iron field l.6 T the maximum induction value in tiles does not exceed 6 mTi2mTthe 2-nd ( Z=2.9l75 m) R~coluinns are given. One can notice that for the region with theFigure 4.l: Barrel toroid stray field pattern near the TileCa1 support partA _v:oo.n ` 5 ’» ` WonaruyV , 4 ` K ` I `I \ WV , %v•zp Y Iv 4 5 { I \ $* r J 1 quo[? x \ w *Qui Qu Mp i mn i f v En _ ai uu "`~J(V//' / ` _`7lz `~~»_,*3 i { { Lévu,vs2¤.¤20/.Inn/Il ILGI ll Pig: 1 \i{» /I/i\\\;/parameters and probably sonic methodological improvements in conducting the calculations. OCR Output2-02-94) The reason for this dramatic change in the field level is modilgications of theestimated 2 one year ago and reported at the TilcCal — collaboration meeting (31—0l»94 andNow we have the held level of more than two orders of magnitude less than it has beenPMT region field of 2 0.15 inrl(2: 3000). This calculation also confirms the result of the 2l) POISCR calculations with thebecause at the given iron held level the relative permeability of iron is very high for steel»08region from the outer support part. So low PMT held level could not be of any surprisewhich could he explained by the normal induction component penetration into the PMTPMT location field is at the middle azimuthal position of the iron taken for calculationupper (408 cm) radii within the radial range of the PMT location windows. The maximumFig. 4.2). ln this lfigure three curves correspond to the low (394 cm). middle (400 cm) andField at the PMT location is not more than 04l mT for the Z E 0 plane (4 gauss intoroid coils.M 0.8 T. The maximum Held occurs at the azimuth of the toroid coil and in between the twoOn the outer surface of iron exposed to the toroid stray field the maximum field value isvaries from 80 mT at R:380 cm to 200 mT at R:420 cm.toroid in the system ( no iron. no other coils). In the support part the toroid stray fieldlength of vectors represents in relative units an induction value at the point. There is onlyFigure 4.2: PMT location field distribution in Z E 0 planeA., , ,.,, Y`:c¤mp¤¤•m; n·on,m»•,,.i.zin¤i.¤ i7r_:_ W-OPEQAAQCflmpcnarl. IIOD,I\IIgul¤II7||J.0Z cnnrd GJ! 0.0 D 0 FLD 0 ¤¤,¤ Campmnnl: IIOD, Inkgnt ¤ |D5Z40.DVcnmd III.0Il 3¥I.I42 593 7I SBLYI SOI Ill .\l!¤IIXword GIAIYI 4|.II42 ll.75U4 ILTSB4 ·l1|IA2 VM H7!mf».o)~•¤~l mtr ' l (IU;i 7Uun/Il 1\‘020I Pay: Isolenoid return flux (separated—functions device). OCR Output(in Fig. 2.3) shields the PMT from the toroid stray field and the lower part conducts theThe situation also is a bit simplified due to the fact that the upper part of thc supporttolerable as the relative permeability of steel—08 at this induction is still high ( as 1000).value of the maximum field value could be z 1.5 T in iron. This field level seems to be stillnot algebraic addition of the induction vectors in this region. ln this case an approximateworst case one could expect ac. 50% of the total field level increase due to geometrical butAs toroid and solenoid induction vectors have always a 90° angle between them, in therise in the PMT held in this area because of nonlinear effects in ferromagnetic material.combined magnetization of the support part from the toroid and solenoid could give a rapidAlthough this field is Q an order of magnitude of one obtained with Barrel toroid the0.3 mT due to the support magnetization from the solenoid return Hux.Near the crack region (Z : 294.7 cm + 344.7 cm) the PMT location field is not more thanthe help of the POISCR codeto the return flux of the solenoid and was already observed in the previous calculations withsurface of the support the field is 1 T and on the outer surface z 0.6 T. This happens dueregion [10] between the Barrel and Extended Barrel part of the TileCal. On the innerThe iron surface maximum field value is in the support part inside the so——called crackwithout the current at all.Now we switch on the current only for the solenoid with the rest of the ATLAS coil system5 The return fiux field mapPMT window near the Extended Barrel edge became no more than 0.6 mT (6 gauss) now.Of course, the plate would be substantially magnetized ( z 2 T) but the field inside thestray field.one can notice the proposed shielding ring separating the PMT windows from the toroidit was successfully used for the outer radius of the support part. On the left side of Fig. 2.2Naturally, one can use the same 10 cm thick iron plate to close the open PMT window asto the PMT location.PMT shielding at the Extended Barrel edge where there occurs the highest fiux penetrationHaving in mind the result of section 4.2 one should probably foresee some extra set—up for the4.3 Shielding at the edge of the end-capinside the TileCal PMT windows.toroid field of ¤ 120 mT gradually decreases from the edge (2::614.6 cm) down along Z-axisDue to the open PMT window at the edge of the Extended Barrel the rather large outsidebe explained by the Barrel toroid stray field flux lines attracting to the TileCal iron.z 1.5 T. This is M twice higher field level than in the middle of the Barrel part which couldOn the outer surface of iron exposed to the toroid stray field the maximum field value is4.2 Edge of the end-cap (ZM,-plane )on December 13, 1994. OCR OutputReceived by Publishing DepartmentMinutes ofthe ATLAS Plenary Meeting held on 21 and 22 April 1994.[10} M.Nessi. Summary of the recent activities of the Tile calorimeter detector unit. ln:018, 24 June 1994.[9} M.Nessi et al. TileCal Magnetic Field Simulation. ATLAS Internal Note Ti}eCal—NOlnterna} Note TileCal-NO—U12, 9 May 1994.{8} M.Nessi ct al. Computer Models for the '1`i}eCal Magnetic Field Distributions. ATLASCERN Program Library Writeup T602.[7}CERN/EP/N/\—4 Note. August 21. 1984.[6} \/.\/.l{Ll1(l1tlI1. Measurements of a Magnetization Curve for the Iron Samples.by Calculation of Stand Magnets. April 3. 1993. SDC-93-486.l5l S.B.Voroz}itsov et al. Permeability Measurements with the Systematic Error CorrectionTosca User Guide. Version 6.3. 1993.lil27, Jan. 1994). ln; Minutes of the Muon Working Group Meeting 2 February 1994.CERN on 27 January 1994. (sec also minutes of the Toroid meeting held at Saclay onVV. Kozanecki (MUO-TR—180). Report on the highlights of the Toroid meeting held atl3lTiletlal — collaboration meeting (31·01-94 and 2—02—94).M. Nessi. Status of B»field calculations and return flux design. Presentation to the{2}F. Dydak and P. Jenni. Questions to 1.11CC Magnet Expert Panel. 10 Nov 1992.lllReferencesthe expensive high magnetic permeability material ( pmetal) for the PMT shielding.terial cost and manpower for R&D will take place. The decision could be taken to abandonsimplified and the drawers mechanics getting much simpler. Substantial saving of the maDue to results obtained here the problem of the individual PMT shielding is considerablycan increase somewhat and some intermediate solution should be adopted then.of iron near PMT location (5 times less than in the previous case). But in this case tile fieldcase of filling the whole crack region with iron our calculation shows only 0.2 T magnetizationOne could also insert more iron for the support part in the crack region. ln the limitingproblem with the PMT location field would be completely solved.helpful to reduce neutron backgrounds to the muon chambers and the above-mentionedand electronics for the detectors inside the tile calorimeter. Filling the gap would also beshould be ”plugged" with calorimetry, leaving of course sufficient space for services, cablesat the outer radius. The tile calorimeter community brought up the question if this gapgap of 50 cm is foreseen, bridged only partially by the structure connecting the flux returnsregion between the Barrel and The Extended Bairro] of {hc vnd-cap region [IO]. Prcscntly aAt the April {994 ATLAS week Merc was discusskm concerning thc problem 0f the crackPrepririt of the Joint Institute for Xurlcar Research Dubzia, 1994 J OCR OutputProblems, JINR.The investigation has been performed at the Laboratory of Nuclearfor the field simulation of the sx stem.electromagnetic software OPERA—TOSCA and CERN POISCR code were useddistribution, acting on individual units of the system was performed. VFbarrel edge does not exceed 0.6 mT. Estimation of pondermotive forceto close the open drawer window the field inside the PMT near to the extendedvalue in the scintillating tiles does not exceed 6 mT. When an iron plate is usedsolenoid and 8 superconducting air-core toroid coils. The maximum inductionand its implications on the calibration. The field source is based on a centralthe needs for individual PMT shielding, the effect on the scintillator light yieldof the hadron tile calorimeter. This is an important issue in order to quantifyThe ATLAS magnetic field map has been estimated in the presenceLarge TileCal Magnetic Field SimulationNessi M. etal.TTDCUDMHT ()6‘¤CQll/lHCHH()I‘t7 vtitt`i14‘ryTa sijieptthtx Mccqteuouaumi. Lly6Ha, 1994Pa6o·ra BBIHOJIHCHEI B .Ha6opa1‘op1414 smepuisix r1po6;1eM OI/ISH/I.OPERA—TOSCA I/I CERN POISCR.MoTop11B1x ycym14171 B c14c*reMe. llrisi pac¤1eroB np14Me11s1J114cB 11porpaMMB1 VF14a¤J1e>1<a111e171 91<pa1114poBx14, 0.6 MT. Ebma BbII`IOJIH€H3 'l"3K>K€ OLIBHKH no1~1,tiepo—H3 CHI/XHTI/IJIJISITO].)£1X ne npemsituaer 6 MT, a B aoue t1>oroyM1~1o>1<14*rer1e171, HOCJICHbIX O6MO'I`OK. B peaymsrare pacqeros oxasarrocb, qro MZYHPITHOC noneCOBZIHCTCH aa cuer LI€HTp3JIbHOI`0 COJICHOYIIIB 14 8 cBepxr1poBo¤1111114x T0pOPI]I8JIb·CLIPIHTHJUISITOQOB. 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Large TileCal magnetic field simulation

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