New self-consistent parameter sets are presented and discussed for muon
collider rings at center-of-mass energies of 10, 30 and 100 TeV. All three
parameter sets attain luminosities of 3 x 10^35 /cm^2/s. The parameter sets
benefit from new insights gained at the HEMC'99 workshop that considered the
feasibility of many-TeV muon colliders.Comment: 3 pages, no figures. Submitted to Proc. EPAC 200

King, B. J.

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arXiv

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‘. BNL – 67742CAP–289–NuFact-OOC4.Further Studies on the Prospects for Many-TeVMuon CollidersB.J.KingBrookhaven NationaILaborato~, Upton, New YorkSeptember 2000Pres. at “7* European Particle Accelerator Conference (EPAC-2000)”, Austria Center,Vienna, June 26-30, 2000..FURTHER STUDIES ON THE PROSPECTS FOR MANY-TEV MUONCOLLIDERS *B.J. King, BNL, Upton, NY 11973, USAAbstractNew self-consistent parameter sets are presented and dis-cussed for muon collider rings at center-of-mass energiesof 10, 30 and 100 TeV. All three parameter sets attain lumi-nosities of Z = 3 x 1035 cm–2 .s–l. The parameter setsbenefit from new insights gained at the HEMC’99 work-shop [3] that considered the feasibility of many-TeV muoncolliders.1 INTRODUCTIONTable 1 of this paper presents self-consistent parameter setsfor muon collider storage rings at center-of-mass energiesof EcOkl = 10, 30 and 100 TeV. The parameter sets havebenefited and evolved from previous attempts at definingplausible parameter sets for many-TeV muorl colliders. Itis helpful to begin by reviewing these previous studies andtheir motivation in order to provide a context for the dis-cussion of the current parameters.Parameter sets for muon collider rings at energies up toEcO~ = 100 TeV were presented in 1998 [1] and 1999 [2].Following this, a much improved level of understandingwas then obtained from the first substantial dedicated studyof such many-TeV muon colliders, which took place at theweek-long HEMC’99 workshop [3]. The majority of thestudies at HEMC’99 either assumed or critiqued straw-manparameter sets [4], one at EcOhf = 10 and two at 100 TeV,that were provided expressly for this purpose.Besides presenting an overview of the HEMC’99 param-eter sets, reference [4] also reviewed the feed-back on theparameters that was provided by the workshop. This pa-per should be referred to for many discussions that remainrelevant for the current parameter sets of table 1.The 48 participants at HEMC’99 considered side-by-side the accelerator challenges and the high energy physics(HEP) potential of many-TeV muon colliders. The HEPmotivation for the workshop was very strong because ex-perimental discoveries in HEP normally come from ad-vances in energy reach, as has been emphasized and dis-cussed in, for example, references [5] and [6]. HEP discus-sions specific to many-TeV muon colliders can be foundin [7] and, mainly, in the HEMC’99 Proceedings [3].Of the three many-TeV parameter sets in table 1, those at10 TeV and 100 TeV evolved directly from the correspond-ing 10 TeV and (the first of the) 100 TeV parameter sets forHEMC’99, taking into account the constructive criticismsthat emerged from the workshop. A mid-po mt energy wasconsidered valuable for examining parameter trends with“Submitted to Proc. EPAC2000. This work was performed under tireauspices of the U.S. Department of Energy under contract no. DE-AC02-98CHI0886.increasing energy, and the 30 TeV parameter set providessuch an interpolation between the lower and higher energysets.Invaluable benchmarks for all of these many-TeV studieswere provided by lower energy parameters that have beenstudied and evaluated [8, 9] by the Muon Collider Collabo-ration (MCC). The first column of table 1 shows, for com-parison, the range of parameters for the muon colliders inthe range ECOM = 0.1, 3 TeV from the MCC’S status re-port [9].2 DISCUSSION ON PARAMETER SETSThe energy scale and some other parameter choices in ta-ble 1 were strongly influenced by considerations of syn-chrotrons radiation. This imposes a natural cut-off scale forcircular muon storage rings in the range EcOkl N 100 TeVsince the synchrotrons radiation loss at such energies hasrisen rapidly to become comparable to the beam power.At HEMC’99, Telnov made the additional observation [10]that the quantum nature of the sychrotron radiation couldlead to beam heating, rather than cooling, for sufficientlyhigh beam energies and small emittances. This observa-tion effectively invalidated the more aggressive of the twoHEMC’99 parameter sets at 100 TeV – which thereforewon’t be discussed further in this paper – and also castsome doubt on the 100 TeV parameter set with the largeremittance.The synchrotrons radiation concerns were addressed inthe 100 TeV parameter set in table 1 by:1.2.3.Theraising the emittance in each of the transverse coordi-nates by the large factor of 90. This should comfort-ably address Telnov’s concern and result in net syn-chrotrons cooling by raising the horizontal emittanceto well above the quantum break-even valueincreasing the collider ring circumference by a fac-tor of two and, correspondingly, reducing the averagebending magnetic field by a factor of two, to 5.3 Teslareducing the average beam current by nearly a factorof 2, to 4 mA.combined effect of the second and third changes wasto reduce the synchrotrons radiation to 50 MW, down fromthe previous, somewhat problematic level of 195 MW inthe HEMC’99 parameter set. Although still a factor of 2.5larger than the synchrotrons power at LEP II, this reducedlevei was considered very appropriate for a far future col-lider at the energy frontier.These changes should also help to address reservationsexpressed by Harrison [1 I ] at HEMC’99 about the femi-‘..bility of 10 Tesla cosine theta dipoles in the presence oflarge amounts of synchrotrons radiation. Besicles loweringthe average required magnetic field by a factor of two, itis noted that the synchrotrons radiation power deposited perunit length around the collider ring has fallen by almost afactor of 8 from the HEMC’99 parameter set at 100 TeV.In addition to the adjustments just mentioned that werespecific to the 100 TeV parameter set, all three many-TeVparameter sets in table 1 were made more conservative thanthe HEMC’99 parameter sets in several areas:●●●●in recognition of the difficulty and novelty of ioniza-tion cooling, the phase space densities in table 1 wereall scaled back to coincide with the upper end of theparameter choices from reference [9] for lower energymuon colliders, i.e. 2.4 x 1022 m-3.the final focus parameters are perhaps the most dif-ficult of all for a non-specialist to evaluate. As hasbeen discussed in references [1, 2, 4], the final focusdifficulty can be usefully benchmarked to other muoncollider and e+e– collider parameter sets accordingto the value of 3 parameters in particular: the /?” inthe x and y coordinates and of two other defined pa-rameters, the so-called “dernagnification factor” and“chromaticity quality factor”. All three benchmarkparameters have been somewhat relaxed in responseto feed-back [4] from the studies by final focus latticeexperts at HEMC’99. Further explicit magnet latticedesigns, now for each of the three parameter sets intable 1, would be invaluable for assessing whether thenew, more relaxed parameters have reached an accept-able level of plausibilitythe average beam currents and resulting beam powerswere reduced so that the worst case, at 100 TeV, hada summed beam plus synchrotrons power of 180 MW,i.e. comparable to the 170 MW beam power that hasbeen under consideration for the Accelerator Produc-tion of Tritium project [12]the beam-beam tune disruption parameter was low-ered slightly for all three sets to a value, in the worstcase, of AU = 0.091. This is not far ;above the im-pressive new LEP II record of Av = 0.083that wasreported in this conference [13].The unavoidable cost of these relaxed machine param-eters was to lower the luminosity to Z = 3 x 1035cm–2 .S–l for each of the 10, 30 and 100 TeV param-eters. This is a reduction to 30% of the luminosities,Z = 1 x 1036 cm–2.s-1, of the corresponding HEMC’99parameter sets for 10 TeV and 100 TeV. To put this in per-spective, the new luminosities are still orders of magnitudehigher than at any existing colliders and are also higherthan any speculated parameters the author is aware of forplausible future machines other than muon colliders.3 SUMMARYThe extremely high constituent particle energies and lu-minosities of the parameter sets presented in table 1 con-tinue to emphasize the impressive potential of muon col-liders for exploring the energy frontier of elementary par-ticle physics. Therefore, further paper studies and simu-lations for many-TeV muon colliders should continue toplay a valuable role in our field. More specifically, the pa-rameter sets presented in this paper would certainly benefitfrom feed-back and constructive criticism by experts in ar-eas such as the design of final focus lattices.[1[2][3][4][5][6][7][8][9]4 REFERENCESB J. King, Discussion on Muon Collider Parameters at Cen-ter of Mass Energies from 0.1 TeV to 100 TeV, Proc. EPAC’98,BNL-657 16. available from LANL preprint archive asphysics#908016.B.J. King, Muon Colliders from 10 TeV 10100 TeV, Proc.PAC’99, New York, 1999, pp. 3038-40, available from LANLpreprint archive as physicsf1908018.HEMC’99 workshop, “Studies on Colliders and ColliderPhysics at the Highest Energies: Muon Colliders at 10 TeVto 100 TeV”, Montauk, NY. U.S.A., 27 Sept- 1 Ott, 1999,Proceedings published by American Institute of Physics, webpage: http://pubweb.bnl.gov/peoplekkin@eshop/ .13.J. King, Parameter Sets jor 10 TeV and 100 TeV MuonColliders, and their Study at the HEMC’99 Workshop, Proc.HEMC’99 [3], also available from the LANL preprint archiveas physics/0005008.Bill WNis, Muon Collider Workshop Summa~, Proc.HEMC’99 [3].B J. King, Prospects for Colliders and Collider Physics to the1 PeV Energy Scale, Proc. HEMC’99 [3], also available fromthe LANL preprint archive as hep-etiOO05008.B.J. King, Muon Colliders: New Prospects for PrecisionPhysics and the High Energy Frontier, Proc. Second LatinAmerican Symposium on High Energy Physics, San Juan,Puerto Rico, 8-11 April, 1998, Also available from the LANLpreprint archive as hep-e,@908041.The Muon Collider Collaboration, P+p- Collider: A Fea-sibility Study, BNL-52503, Ferrnilab-Conf-961092, LBNL-38946, hdy 1996.The Muon Collider Collaboration, Sratus of Muon ColliderResearch and Development and Future Plans, Phys. Rev. STAccel. Beams, 3 August, 1999.[10] Valery Telnov, Limit on Horizontal Emitrance in High En-ergy Muon Colliders due to Synchrotrons Radiation, Proc.HEMC’99 [3].[11] Mike Harrison, Magnet Challenges: Technology and Afford-ability, oral presentation at HEMC’99 [3].[12] The Accelerator Production of Tritium ~oject,http: //apt. lanl. gov.[13] R. Assmann et al., LEP (>pera/ion and Pe~ormance with100 GeV Colliding Beams, these proceedings.‘.Table 1: Self-consistent collider ring parameter sets for many-TeV muon colliders. For comparison, the first columndisp YSthe range of parameters for the lower ~parameter setcenter of mass energy, EcO.Mcollider physics parameters:luminosity, Z [1035cm-2. s-1 IJ Ldt [fb-’/yearlNo. of pp + ee eventsldetiyearNo. of 100 GeV SM Higgs/yearCOM energy spread, aE/E [10-3 ]collider ring parameters:circumference, C [km]ave. bending B field [T]beam parameters:(p- or) p+/bunch, NO[1012](p- or) p+ bunch rep. rate, fb [Hz]6-dim. norm. emit., @/[10-12m3]66N[lo–4m3.Mev/c3]P.S. density, NO/@~[1022m-3]x,y emit. (unnorm.) [n.pm.mrad]x,y normalized emit. [r.mm.mrad]long. emittance [10-3 eV.s]fract. mom. spread, J [10-3]relativistic T factor, EP /ml~time to beam dump, tD [yTfl ]effective turnslbunchave. current [mA.]beam power [MW]synch. rad. critical E [MeV]synch. rad. E Iosslturn [GeV]synch. rad. power [MW’]beam + synch. power [MW’]power density into magnet liner [kW/m]interaction point parameters: –spot size, Oz,v [pm]bunch length, m. [mm]@;,v [mm]ang. divergence, ue [mra(i]beam-beam tune disruption, Avpinch enhancement factor, HBbeamstrahlung frac. E losslcollisicmfinal focus lattice parameters: –max. poletip field of quads., B50 [T]max. fuli aper. of quad., A+sm[cnl]quad. gradient, 2B5C /A&S~ [T/m]&~~[kn~]ff demag., M E ~m~chrom. aualitv factor, 0- M .6neutrino radiation parameters:collider reference depth, D[rn]ave. rad. dose in plane [mSvlyr]str. sec. len. for 10x ave. rad. [m]v beam distance to surface [km]v beam radius at surface [m]mgy muon colliders discussed in reference [9]. -A B c0.1to 3 TeV 10 TeV 30 TeV 100 TeV8 X 10-5+ 0.5 3.0 .3.0 3.00.08+540 3000 3000 3000650+10000 2600 ~90 264000+600 000 4 x 106 5><106 6 X 1060.02+ 1.1 0.42 0.080 0.0710.35+ 6.0 15 39 2003.O-i5.2 7.0 8.1 5.22.0+4.015+30170+1702.0+2.01.2+2.43.5+62050+2900.81 + 240.030+ 1.6473+14200no dump450+78017+301.0+295 X 10-7 + 8 x 10-47 x 10-9 + 3 ~ ~(3-41 x 10-7 +0.0101.0+291.0+ 1.72.9151251.52.30.8440280.5047300no dump104029700.0120.0170.48702.02.07.5851.02.40.1927400.20142000no dump120012720.120.526.0780.84—1.65700.832.30.04019680.075473000no dump7804.01281.7525501800.483,3+290 1.7 0.88 0.473.0+140 3.4 4.0 5.43.0+140 3.4 4.0 5.41.1+2.1 0.50 0.22 0.0860.015+0.051 0.079 0.079 0.0911,00+1.01 1.06 1.06 1.09negligible 2.3 X 10–s 1.0 X 10–7 5.5 X 10-76+12 12 12 1214+24 21 25 3150+90 120 97 771.5+150 520 3200 24000220+7100 12000 28000” 670000.007+ 11 6.2 5.7 5.010+300 100 100 1002 x 10-5+0.02 1.2 4.8 201.3+2.2 0.95 1.6 8.411+62 36 36 364.4+24 0.75 0.25 0.075

Further Studies on the Prospects for Many-TEV Muon Colliders

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Further Studies on the Prospects for Many-TeV Muon Colliders

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