DESIGN STUDIES IR Magnet Design P. Wanderer LARP Collaboration Meeting April 27, 2006

Thanks … Thanks to Paolo, Giorgio, and Vadim, who prepared summaries of their work and many of the following slides.

Topics #1: Analysis and comparison of IRQ based on shell-type and block-type coils (Ferracin, Maura Monville + N. Mokhov) #2: Analysis of a 110-mm shell-type IR quads with different supporting structures (Ambrosio)

Topics #3: Analysis of aperture and field quality limitations for double-bore IR Quads (Vadim Kashikhin) #4: Field quality analysis and error tables for Nb3Sn IRQ (Kashikhin, Zlobin)

#1: Compare block, shell quads Status: For a reasonable set of IR quad requirements, a block quad was developed. The mechanical and magnetic properties of this quad and a shell quad which met the same requirements have been compared. Next: Study response of these quads to IR radiation, iterate designs.

Shell-type vs. block-type Previous work: V.V. Kashikhin, et al., “2 nd generation LHC IR quadrupoles based on Nb 3 Sn racetrack coils”, EPAC 2004.

Upgrade scenario* Phase 1: increase of luminosity with hardware changes only in the interaction regions β * = 0.25 m σ = mm D trip = 78.5 mm – 77 mm (T. Sen, et al., 2001) Increase the triplet magnet diameter Same gradient –G nominal ~ 200 T/m –G short sample ~ 250 T/m L = x cm -2 s -1 *O. Bruning, et al., “LHC luminosity and energy upgrade: a feasibility study”, LHC Project Report 626 (2002)

Coil aperture and beam envelope D trip = 78.5 mm 80 mm 105 mm 80mm 105mm

Magnetic design: gradient and field quality TQ-v1 cable (27 strands) J c = 3000 A/mm K Harmonics < 0.05 at R ref InnerOuter I ss [kA]13.3 N turns2637 B ss [T] G ss [T/m]251 SC area [cm 2 ] 52

Mechanical design: support structure Aluminum shell Iron yokes Stainless steel pad Stainless steel poles Stainless steel mid- plane spacers Aluminum bore

Mechanical analysis: coil and bore stresses Coil stress < 170 MPa Bore stress < 150 MPa (293 K, 4.3 K and excitation)

#2: Study of different support structures in quads 110 mm aperture, shell-type, 228 T/m. Generic structures for high forces –Not specific to a particular coil Two types of coil arrangements: –Four layers, all glued together (complete) –Four layers, glued together in pairs (now starting)

Structure for 4 layers as 1 Needs & solutions: –Very rigid structure  ss collars + (ss skin or Al skin with bladders & keys) –Extra coil support at midplane  collar- yoke support only at midplane –Yoke open when warm –Stresses < 150 MPa under all conditions  dummy cable at midplane of outer coil

Best solution up to now Yoke GapYoke-Collars contact Yoke with gap at 45 deg. 300 K –Closed at 4.2 K –Closed at 228 T/m Gap control spacers 15 mm SS collar ring Collar-Yoke contact 0-6 deg. Outer shell: –15 mm SS skin or –30 mm Al (bladders & keys) Gap control spacer

#3: Study double-bore quads Quads for dipole-first optics Two cases: warm and cold iron 100 mm aperture, 205 T/m 194 mm beam separation Determine dynamic aperture (10 -4 FQ) –Achieving good FQ a challenge –Correctors = LHC baseline Results presented April 19.

Warm yoke design –Maximizing the aperture at the fixed nominal gradient and the beam separation distance brings the adjacent coils close to each other; –There is not enough space for a ferromagnetic screen of sufficient thickness to individually shield each coil and avoid mutual influence; –In the “warm” yoke design the ferromagnetic part was removed from the cold mass and the coils are of an unusual asymmetric type to achieve a good field quality.

Cold yoke design –It is possible to bring the iron closer to the coils in the “cold” yoke design that increases the gradient and eliminates the eccentricity forces between the coils and the yoke; –The yoke inner surface has to be optimized simultaneously with the coil geometry to achieve good geometrical field quality and correct the yoke saturation effect; –The coils are still asymmetric, but the degree of asymmetry is lower than in the “warm” yoke design; –The coil aperture limit is 100 mm for both designs.

Geometrical radius Field quality Harmoni c IRQ design Warm yoke Cold yoke b b b b b b b b b LHC has correctors for b3, b4, and b6.

2-in-1 quad good field region Green: 27 mm radius beam envelope Red: warm yoke, FQ Blue: cold yoke, FQ

Comparison MQXB beam envelope (2x9  ) = 40 mm MQXB FQ (measured) at 40 mm = in-1 quads region = 54 mm LARP beam envelope (1.1x18  ) = 70(60) mm LARP beam envelope (18  ) = 64(54) mm

#4: Error tables Error tables will combine calculated and measured errors from magnets of different radii. Status: underway. There are more magnets to measure this FY, so the database is still being expanded.