lECHWQVE DE CRYOGEM CEA/SACLAY El DE MiAGHÉllME DSM
FR0107756
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DAPNIA/STCM-00-07 May 2000
SUPERCONDUCTING MAGNETS FOR FUTURE PARTICLE ACCELERATORS
A. Devred
Présenté aux « Sixièmes Journées d'Aussois (France) », 16-19 mai 2000
Dénnrtfimpnt H'Astrnnhvsinnp rJp Phvsinue des Particules, de Phvsiaue Nucléaire et de l'Instrumentation Associée PLEASE NOTE THAT ALL MISSING PAGES ARE SUPPOSED TO BE BLANK Superconducting Magnets for Future Particle Accelerators
Arnaud Devred CEA-DSM-DAPNIA-STCM
Sixièmes Journées d'Aussois 17 mai 2000 Contents
Magnet Types Brief History and State of the Art Review of R&D Programs - LHC Upgrade -VLHC -TESLA Muon Collider Conclusion Magnet Classification
• Four types of superconducting magnet systems are presently found in large particle accelerators - Bending and focusing magnets (arcs of circular accelerators) - Insertion and final focusing magnets (to control beam optics near targets or collision points) - Corrector magnets (e.g., to correct field distortions produced by persistent magnetization currents in arc magnets) - Detector magnets (embedded in detector arrays surrounding targets or collision points) Bending and Focusing Magnets
• Bending and focusing magnets are distributed in a regular lattice of cells around the arcs of large circular accelerators
106.90 m
^ j ~ 14.30 m 14.30 m 14.30 m
MBA I MBB .MB ._A. Ii p71 ^M^^;. t " MB. .__i B ^-• • MgAMBA, | MBMBB B ,
MQ: Lattice Quadrupole MBA: Dipole magnet Type A MO: Landau Octupole MBB: Dipole magnet Type B MQT: Tuning Quadrupole MCS: Local Sextupole corrector MQS: Skew Quadrupole MCDO: Local combined decapole and octupole corrector MSCB: Combined Lattice Sextupole (MS) or skew sextupole (MSS) and Orbit Corrector (MCB) BPM: Beam position monitor
Cell of the proposed magnet lattice for the LHC arcs (LHC counts 8 arcs made up of 23 such cells) Bending and Focusing Magnets (Cont.)
• These magnets are in large number (e.g., 1232 dipole magnets and 386 quadrupole magnets in LHC), • They must be mass-produced in industry, • They are the most expensive components of the machine. => any new circular machine beyond LHC will require significant value-engineering efforts to improve magnet performance and limit costs Insertion and Final Focusing Magnets
• Circular and linear accelerators usually require sets of special magnets to transport and strongly focus the beam(s) near the target or collision points
t,5K 45K i 00 Q1 Q2 D1 D2 Q4 Q5 DFBM MCBW MQXA MQXB MQXA)F3XMBX X2ZDC MBRC MOT MQM IP2
Proposed magnet lattice for the right-hand side of the #2 interaction point of LHC Insertion and Final Focusing Magnets (Cont.)
• These magnets are in limited number • They must be customized to their crowded environment • The requirements for the final focusing quadrupole magnets can be very stringent (high field gradient in large aperture, good field quality, and/or high heat load from beam losses) => can be used as a test bench for more innovative designs Contents
• Magnet Types • Brief History and State of the Art • Review of R&D Programs - LHC Upgrade -VLHC -TESLA • Muon Collider • Conclusion Magnet Design
• Most dipole and quadrupole magnets built up to now (Tevatron, HERA, SSC, LHC...) rely on similar design concepts • These concepts were pioneered in the late 70's for the Tevatron at Fermilab • Improvements in superconductor and magnet fabrication have led to more than double the field over the last 20 years Magnetic Design
• Field is produced by saddle-shape coils, which, in their long straight sections approximate cos#or cos20 conductor distributions
vacuum pipe
Saddle-shape coil assembly Cos<9 conductor distribution in a for a dipole magnet dipole coil assembly quadrant (Courtesy R. Gupta) Rutherford-Type Cable
• Coils are wound from flat, two-layer Rutherford type cable, made up of NbTi multifilamentary composite strands
Rutherford-type cable NbTi strand for accelerator (Courtesy T. Ogitsu) magnet application (Courtesy Alstom/MSA/Fil) Mechanical Design
• Coils are restrained mechanically by means of laminated collars, locked ON together by keys or tie rods
Collared-coil assembly section of LHC arc quadrupole magnet developed at CEA/Saclay Iron Yoke
• Collared-coil(s) is(are) surrounded by an iron yoke providing a return path for the magnetic flux • In some designs, the yoke contributes to the mechanical support
Twin-aperture, LHC arc quadrupoie magnet design developed at CEA/Saclay Tevatron
• The Tevatron dipole magnets rely on a warm iron yoke and are operated reliably since 1983 at a field of 4 T
IRON YOKE LAMINATION
00 SUSPENSION- PRELOAD CARTRIDGE SUSPENSION SUSPENSION BRACKET BUFFER SHIELD AND Q HEAT SUSPENSION RING INTERCEPT
BEAM VACUUM SINGLE PHASE TWO PHASE HEUUM HELIUM LIQUID NITROGEN O BRAID STRAP SUSPENSIONS SUSPENSION PRELOAD SCREW
S / / / / S 77•/'SS/ HERA
• Starting with HERA, the iron yoke is included in the cold mass • HERA was commissioned in 1990 and the dipole magnets are operated at 4.7 T SSC Preproduction Billets 34(X) • Fi'nikuwa (Fine Filaments) • The SSC magnet n IGC 3200 M inC (Fine Filaments) R&D program has O O5»T • allowed significant !T (Fine Filaments) 3000 • 02 j&. Supercon • improvements in the I A. Supercon (Fine Filaments) O 2800 • HA performances and SSC Conceptual Design Re| Oft April 191!6 production costs of • 2600 NbTi wires • 2400 \ SSCProv isional S|«cificalion May 198' D 2200 n Ne rFermiK ;
2000 «|TEV kTRON fflt c BA 1800 H 198•1 I9S•2 1983 198m4 1985 1986 1987 1988 1989 1990 1991 NbTi Superconducior for Dipole Magnets LHC
• LHC will rely on twin aperture magnets operated in superflu id helium
ALICNMENT TARGET
.„ MAIN QUADRIPOLE BUS-BARS
— HEAT EXCHANGER PIPE
_^ SUPERINSULATION
. SUPERCONDUCTING COILS
BEAM PIPE
,. VACUUM VESSEL
1 BEAM SCREEN
—- AUXILIARY BUS-BARS
SHRINKING CYLINDER / HE I-VESSEL
THERMAL SHIELD (55 to 75K)
NON-MAGNETIC COLLARS
IRON YOKE (COLD MASS, 1.9K)
DIPOLE BUS-BARS
SUPPORT POST LHC (Cont.)
• The LHC magnet R&D program shows that the limit of NbTi at 1.9 K could be between 9 and 10 T
MBSM Dipole Models - First 15 Training Quenches at 1.8K 10.5
JOO 200 300 400 500 Quench Number (Courtesy A. Siemko) State of the Art in NbTi Magnets
• The most successful NbTi dipole magnet model was built at CERN (in collaboration with Helsinki University) and reached a maximum field of 10.53 T at 1.77 K
11.00 •
10.50 • ;'S.S. Limit si 2 if:
p 10.00
1 9.50 Û. at 0 A/s due to - CT temperature increase TO 2 9.00 • i -f- o •3 Ï 8.50 c (0
.'S.S. Limit at 4.35 K; S 8.00
Run In 1995 I 7.50 7.00 0 2 6 8 10 12 14 16 18 20 22 24 26 Quench Number
(Courtesy D. Leroy) (Courtesy A. Siemko) State of the Art in Nb3Sn Magnets
• At the beginning of the 90's, Twente University (in the Netherlands) and LBNL (in the USA) have carried out R&D programs aimed at building Nb3Sn dipole magnet models 1 • Both magnets were single aperture (50 mm) and relied on design concepts similar to those previously described • Both models were assembled according to the 'wind, react & impregnate" technique and were quite successful Program at Twente University
• The Twente University dipole magnet model was tested at CERN in the Summer of 1995
I™ Me • It reached 11.03 T I (O 1 on its first quench at Y Aluminium collars 4.4 K • Copper wedges
Stainless steel inserts
steel
(Courtesy H.HJ. ten Kate) Program at LBNL
• The LBNL dipole magnet model was tested in 1997 and after ~40 quenches at 4.2 K and 1.8 K reached a record field of 13.5 T at 1.8 K
wire wrap D20: Training History
13-
12-
-1H4.4K
10- • -2nd UK -2ndUK -M4.4K M1JK
• 4II4.4K -•-0M Wortd Rtcofd 10 20 30 40 50 Training #
(Courtesy S. Caspi) (Courtesy A. Mclnturf) Contents
• Magnet Types • Brief History and State of the Art • Review of R&D Programs - LHC Upgrade -VLHC -TESLA • Muon Collider • Conclusion Program for LHC Upgrade at INFN Milan (LASA)
• In the mid-1990s, INFN Milan (LAS A) has investigated various designs of large- aperture, high-field-gradient quadrupole magnets for a possible upgrade of the LHC final focusing quadrupole magnets • and has collaborated with Europa Metalli to develop high-Jc Nb3Sn wires • The program was put on hold because of lack of funding Program for LHC Upgrade at INFN Milan (Cont.)
ST. STEEL COLLAR R260 BROI-1/L CC/JJR WEDGI R273 • Example of conceptual design for a 70-mm-aperture, 300 T/m quadrupole magnet • The operating current is 17.9 kA and the peakfield is 11.5 T • It requires a high- performance Nb3Sn wire, with a Jc(non-Cu) of 1800 A/mm2 at 4.2 K and 12 T (to be operated at 1.8 K)
(G. Ambrosio, 1996) Program for LHC Upgrade at Twente University
• Twente University has signed in 1998 a 3- year contract with CERN and NIKEF to build a large aperture (88 mm) dipole magnet model
I with an operating field of 10 T and an operating temperature of 4.4 K • Such a magnet could be used for an upgrade of the low-field (2.74 T and 3.8 T), beam- separation dipole magnets, localized near the crowded LHC interaction points Program for LHC Upgrade at Twente University (Cont.)
• The design is completed and practice coils are now being wound. The magnet model should be tested at CERN in June 2001.
outer shell
iron yoke
ss collar copper wedge ss pole piece
(Courtesy A. den Ouden) Program for LHC Upgrade at Twente University (End)
• The Twente magnet will use a Rutherford-type cable made up of Nb3Sn wires produced according
Co to the "Powder-in-Tube" (PIT) process by ShapeMetal Innovation (SMI) • SMI has recently achieved a 2 record 7c(non-Cu) of 2300 A/mm at 4.2 K et 12 T with an effective filament size of 50 juin (50 kg billet) (Courtesy A. den Ouden) Contents
• Magnet Types • Brief History and State of the Art
CXI • Review of R&D Programs - LHC Upgrade -VLHC - TESLA • Muon Collider • Conclusion Origins of VLHC
• 1994: Drell panel suggests that "it may be technically feasible to build a proton collider with beam energies up to 10 times those of the LHC with technology that could be developed during the next decade7'. • 1996: Snowmas workshop where various proposals of hadron colliders with 100 TeV center-of-mass energy are examined. • 1997: Gilmann panel recommends"... an expanded program of R&D on cost reduction strategies, enabling technologies, and accelerator physics issues for a VLHC". => In response, the Directors of BNL, Fermi lab, LBNL, Cornell University and, more recently, SLAC, have appointed a VLHC steering committee to coordinate the R&D efforts. VLHC Activities in the USA
• National materials R&D program in industry to improve the performance and decrease the cost of Nb3Sn wires • Vigorous magnet R&D programs at 00 BNL, Fermilab, LBNL and Texas A&M • Investigations of tunneling techniques and geological studies on Fermilab site VLHC Design Options
• Two design options are presently considered for VLHC — a low-field option (2 T), relying on low-cost, i superferric magnets (G.W. Foster, et al.) f (Fermilab)
— a high-field option (>11 T), relying on Nb3Sn or HTS magnets (BNL, Fermilab, LBNL and Texas A&M) Low-Field Option
Transmission Line Magnet
"Ooubk-C " VIRSJUC! I k:\ R.'tnni l'-Kîruded Aiuminuin lïeam Pipes wish puntpi ng i:h;miber
i LMIL- Al lernaii i\g-Gradisn! Pole tips (no Qiiadrupolc?) ->structure ts continuous in lony icnL^h^ KEY FEATURES: Simple Cryogenic System Struirtunil Support 1 sihe r Small Superconductor Usage C n ol .incVaciîiîm Jacket Small Cold Mass Low Heat Leak CiyupipiS i'or Rl!)g- Widc Distribution of Continuous in Long Lengths Siniile-l'hasa Helium No Quads or Spool Pieces Warm Bore Vacuum System Standard Construction Methods Cunen! Return Low-Field Option (Cont.)
BASELINE (Rutherford Cable-in-Conduit) DESIGIS
\ Perforated \ Spiral Wrap ~ Copper Invar Solid Invar Superconducting Tape Former Cryopipe Cables (SSC Outer) • Surplus SSC wires and cables can be used to produce a 30-km-long line Low-Field Option (End)
• A 17-m-long demonstration loop has been built at Fermilab and has been excited up to 100 kA • The plan is to build, within 2 years, a 60-m- long magnet section High-Field Option
• Four different high-field magnet designs are being investigated - Conventional 2-in-l, cos<9design, extending
SSC and LHC technology to Nb3Sn (Fermilab) - Innovative "common coil" design proposed by R. Gupta (BNL, Fermilab, LBNL) - Sophisticated "stress management" design proposed by P. Mclntyre (Texas A&M) Cos/ Design at FNAL
* Fermilab has started in 1998 an ambitious high field magnet program • The plan is to build four Nb3Sn dipole magnet models (11 T in a 43.5 mm aperture) • First single-aperture version to be tested in September 2000 • First twin-aperture version to be tested in ^^^^ September 2001 (Courtesy S. Zlobin) Common Coil" Design
• In 1996, R. Gupta has proposed an innovative twin-aperture dipole magnet design based on pairs of racetrack-type coils
250.0
200.0
150.0
50.0
-50.0
-100.0
0b, /40.0 80.0 120.0 180:0. 240 0 30O.0
(Courtesy R. Gupta) Common Coil" Design at LBNL
• LBNL has tested in 1998 a "proof of principal" model
made up of one pair of Nb3Sn coils separated by 40 mm, which reached 5.9 T on its first quench at 4.2 K
Alum Draw Bolts (Nuts not shown)
SST Clamp Bar
—AiCu Cover Plate Pressure Point
SST Pressure Pad Nb3Sn Double Pancake "Racetrack Coil
1 cm Square Bore
(Courtesy S.A. Gourlay) "Common Coil" Design at LBNL (Cont.)
• LBNL is now building at 14 T model made up of two pairs of Nb3Sn coils with a spacing of 40 mm -Wire Wrap • The outer pair was I tested in March 2000 (with a 10 mm spacing) and has reached 11.5 T Outer Layers • The plan is to test the Inner Layer full assembly in September 2000
(K.P. Chow, 1998) Common Coil" Design at Fermilab
• Fermilab is developing a lower field variant (11T) relying on two pairs of coils with -a Nb3Sn outer pair built
GO according to the "react & wind" technique - a NbTi inner pair • The plan is to build a short model magnet by the Summer of 2001
(Courtesy G. Ambrosio) Common Coil" Design at BNL
• BNL has built a 1-m-long magnet model relying on NbTi coils designed to produce a 6-to-7 T background field to test racetrack-shaped insert coils
• A first set of insert coils
wound from pre-reacted Nb3Sn tapes was tested in 1999 • The plan is to use this facility as a test bench for HTS tapes
(A.K. Ghosh, 1999) \\ Common Coil" Design at BNL
en ?
Nb3Sn Insert NbTi Outsert Stress Management" Design
• Texas A&M University has ;"j5*"Jny developed a 16 T dual-dipole magnet design, where the conductors are divided into blocks to limit the stresses to l cjn less than 100 M Pa • A single-aperture, NbTi tiSXTS model is under construction
cm
(Courtesy P. Mclntyre) Contents
Magnet Types Brief History and State of the Art Review of R&D Programs - LHC Upgrade -VLHC -TESLA Muon Collider Conclusion Final Focusing of TESLA
R(m) I dode agonai shape TESLA Detector Magnetic Configuration 6.45 YB01 YB11 CEA/Saclay 5.85 DAPNIA/STCM 16/03/2000 -( mem iron + 4c m space) * it) times- =YB10=
4.45
3.85 3.5 Cryostat + Vacuum tank YE2 YE3 YE4 3.16 3.0 2.65
YE1 (inner profile to be adjusted) 11 sectors
Br/Bz < few 10 83 mrad
1.15 1.18 2.5 3.0 3.5 4.25 4.7 5.4 6.0 6.7 7.2 z(m) limit for end cap yoke |«£—: ' (Courtesy F. Kircher) Final Focusing of TESLA (Cont.)
• The 4 final focusing quadrupole magnets are modeled after the LHC arc quadrupole magnets (with a single aperture of 56 mm and a field gradient of 250 T/m), • but two of the magnets are positioned within the detector solenoid and must sustain a 4 T axial field. • The presence of the background field precludes the use of NbTi and calls for the use of Nb3Sn. Nb3Sn Program at CEA/Saclay
• CEA/DSM/DAPNIA/STCM has started in 1996 a collaboration with Alstom to develop high performance Nb3Sn wire and cable and to build a short quadrupole magnet model • The program has been slow moving at CEA because of lack of manpower, but Alstom has completed its share of the R&D work and is ready to start the production of the final cable lengths (5 x 60 m) Results of Alstom Program
• The collaboration has enabled Alstom to produce r - a Nb3Sn wire with a 7c(non Cu) of 750 A/mm2 at 4.2 K o and 12 T and an effective 00 O n O _ filament size of 18 jam - a Rutherford-type cable , O L % J- ^ ^ A with a 25-jum-thick stainless steel (annealed 316L) core (Courtesy R. Otmani) Status of Saclay Program
/ , \ 7 ? • The detailed design of 0 quadrupole magnet model is presently underway • It relies extensively on the design of the LHC arc quadrupole magnets (with a single aperture and no iron yoke) • The plan is to test the model in March 2003 • The model is expected to achieve 223 T/m at 4.2 K (Courtesy J. Thinel) New Collaboration Program
• Discussions are underway with Alstom for a new collaboration to develop a wire with a Jc(non-Cu) of 2000 A/mm2 at 4.2 K and 12 T and no specifications on effective filament diameter (except that the wire should be stable against flux jump) • Such wire could be used to build a second quadrupole magnet model that would be suitable for TESLA Contents
• Magnet Types • Brief History and State of the Art
ON I • Review of R&D Programs - LHC Upgrade -VLHC -TESLA • Muon Collider • Conclusion Why Muons?
1 VLHC 100 TeV pp • Muons are spin- /2, {I I 17 point-1 ike, Dirac particles, with a mass
I ^207 that of an ON electron => They radiate far less, enabling higher energies to be reached and smaller collider 100 TeV pp 1? TeV) rings to be used (CM. Ankenbrandt, 1999) 2x2 TeV Muon Collider Schematic
PROTON SOURCE \('r- proions ) per v CLU ai 8 ('icV/c TA3lif-T fi^gh ? :iq);irl ;ftP*'.JH: SOLENOID > POLARIZATION & ? SELECTION Snake + Collimatur Muon Collider I0NI2ATI0N COOLING A'EDGL 20 S»8« • The muons must be ^ \ i '..' ltJTAl. J IJeV UIXI rr i muons.Vr ai produced, cooled, t - 100 MeV/c LINACS+ HEClRCULATtON accelerated and collided within 2.2 |as (cr» 659 m) i i SC L MACS • Each stage requires a 'PUlSEDai RDTATiKG . SC MAGMTS significant step in FAST ACCELERATION I ^ I- ? X &C> Cjp technology • 2x I01- iiunu'is/buncli x 4 hunches 4/# COILIOER \ 15 11/ ' [k (}' = 3 fflti RING >?t^«' Pion Production and Capture O on ;L^35=2^J 'matching solenoids superconducting solenoid I rf Linac liquid metal target protons decay solenoids o z (m) (CM. Ankenbrandt, 1999) Muon Collider Ring • Conceptual design for a low-cost, 5-T, NbTi dipole magnet with a large opening at the midplane to clear decay products Pole Warm Yoke Coil Beam Tub Decay Products Muon Beam (Courtesy R. Gupta) Contents • Magnet Types • Brief History and State of the Art ON • Review of R&D Programs - LHC Upgrade -VLHC -TESLA • Muon Collider • Conclusion Conclusion • LHC magnet R&D program shows that the limit for NbTi at 1.9 K could be ON O between 9 and 10 T • Encouraging results have been obtained on a few Nb3Sn magnet models, opening the 10 to 15 T range • Given that LHC will have taken nearly 25 years to build, it is already time to of the future