1 / 30

Dipole First Layout: Motivation, Advantages & Challenges

Explore the motivation, advantages, and challenges of the possible dipole first layout as an alternative solution to the nominal layout. Discuss beam separation, radiation issues, and design considerations.

raustin
Download Presentation

Dipole First Layout: Motivation, Advantages & Challenges

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. motivation and advantages: Possible Dipole First Options and Challenges - alternative solution to nominal layout pro & cons - early beam separation less long range interactions - no crossing-angle bump inside triplet magnets • requires less aperture inside triplet magnets (assuming equal b-function values) • no feed-down errors & simpler correction options • local field error correction per triplet assembly - reduced radiation inside the triplet magnets • relaxed magnet design and more aperture LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 1

  2. dis-advantages & challenges: Possible Dipole First Options and Challenges - increased quadrupole distance from IP  larger bmax • requires larger aperture inside triplet magnets • implies larger chromatic aberrations • large radiation levels for dipole magnets •  magnetic TAS (spectrometer dipole & absorber) • transfers design challenges for triplet quadrupole to D1 dipole design • is it a valid assumption that large aperture, high field dipole magnets are easier to design compared to large aperture, high gradient quadrupoles? LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 2

  3. long range beam-beam interactions options for a dipole first layout optics issues for the different layout options aperture requirements design issues related to radiation aspects related to the crossing angle generation aspects related to field error corrections Possible Dipole First Options and Challenges LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 3

  4. beam separation: Long Range Beam-Beam Interactions • the nominal IR layout features 32 long range beam-beam • interactions for a bunch spacing of 25ns: D1 Q3 Q2 Q1 Q1 Q2 Q3 D1 IP 2 x 23 m 35 m 35 m 24 m 24 m ca. 10 long range interactions 13 long range interactions ca. 10 long range interactions  all layout options benefit from reduced L*!  changing the sequence of D1 and triplet magnets cuts the number of long range interaction in half! LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 4

  5. Design Issues Related to Radiation Issues interactions at the IP generate debris that limits the magnet performance  operation of SC magnets requires additional absorbers (TAS and TAN) TAN D1 Q3 Q2 Q1 TAS TAS Q1 Q2 Q3 D1 TAN 2 x 23 m 35 m 35 m 24 m 24 m ca. 10 long range interactions 13 long range interactions ca. 10 long range interactions - plus additional cooling and absorbers inside triplet magnets LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 5

  6. Design Issues Related to Radiation Issues due to the deflection of charged particles inside the magnetic field of the triplet magnets some debris is still absorbed inside the SC magnets • nominal triplet magnets reach lifetime after 700 fb-1  ca. 0.5 years for L = 1035cm-2 sec-1! • a luminosity upgrade therefore implies an absorber upgrade, • a radiation hard magnet design and additional cooling options • magnetic TAS design • magnet design with special absorber + cooling sections • high temperature magnets • radiation hard materials LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 6

  7. Options For a Dipole First Layout 1) Simple swap of D1 and triplet magnets IP Q3 Q2 Q1 D1 D1 Q1 Q2 Q3 2 x 23 m 13 long range interactions separated beams separated beams  changing the sequence of D1 and triplet magnets cuts the number of long range interaction in half!  Increased L* increases beam size in triplet magnets LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 7

  8. 1) Simple swap of D1 and triplet magnets: Options for a Dipole First Layout D1 Q1 Q2 Q3 Q3 Q2 Q1 D1 IP 24 m 2 x 23 m 24 m Twice the distance of Q1 from the IP as compared to the nominal layout!  layout provides option of TAS absorber inside D1  requires non-parallel coils or large aperture triplet magnets  dispersion matching with quadrupole between the D1 and D2 dipole magnets still needs to be studied LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 8

  9. 2) swap of D1 and triplet magnets with large crossing angle: Q3 Q2 Q1 D1 D1 Q1 Q2 Q3 IP 24 m 2 x 23 m 24 m Twice the distance of Q1 from the IP as compared to the nominal layout! Options for a Dipole First Layout • layout provides option of TAS integration inside D1 magnet • early beam separation allows 2-in-1 triplet design  requires Crab cavities for luminosity optimization (ca.3 mrad)  dispersion matching with quadrupole magnets between the D1 and D2 dipole magnets still needs to be studied LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 9

  10. 3) swap of D1 AND D2 dipole magnets with triplet magnets: Options for a Dipole First Layout IP Q3 Q2 Q1 D2 D1 D1 D2 Q1 Q2 Q3 ?? m 2 x 23 m ?? m larger distance of Q1 from the IP as compared to the nominal layout!  layout provides option of TAS absorber inside D1 magnet  further increase in L* implies even larger beam size in triplet • early beam separation allows 2-in-1 triplet magnet design • 2-in-1 magnet requires special design for TAN absorber LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 10

  11. 3) Swap of D1/D2 magnets with triplet: Options for a Dipole First Layout D1  11.4 m * 15 T Q1  231 T/m Q2  257 T/m Q3  280 T/m • peak coil field and aperture! (more details in the talk by Riccardo de Maria)  dispersion matched at the IP LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 11

  12. 4) Combined function magnets for triplet and D1/D2 magnets: Options for a Dipole First Layout T. Nakamoto et al D2b D2a D1b D1a Q3b Q3 Q2 Q1 D1a D1b D2a D2b Q1 Q2 Q3 Q3b IP ?? m ?? m 2 x 23 m  layout provides option of TAS absorber inside D1 magnet  combined function magnets reduce L* compared to 3) • combined function magnet design allows anti symmetric optics with central hole in 2-in-1 magnets for neutron flux  dispersion matching still needs to be studied! LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 12

  13. 4) Combined function magnets for triplet and D1/D2 magnets: Options for a Dipole First Layout D1/D1  2.3 T Q1  47 T/m Q2  70 T/m Q3  47 T/m Q3b  6 T/m • peak coil field of 5.5 T provides diameter of 91 mm  dispersion matched to 10m in ‘triplet’ for Q’ correction! LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 13

  14. 4) Combined function magnets for triplet and D1/D2 magnets: Options for a Dipole First Layout D1/D1  2.3 T Q1  47 T/m Q2  70 T/m Q3  47 T/m Q3b  6 T/m • peak coil field of 5.5 T provides diameter of 91 mm  dispersion matched to 10m in ‘triplet’ for Q’ correction! LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 14

  15. single bore design requires aperture for beam separation: Aperture Requirements -10 s beam envelope -10 s beam separation -20% beta beat -closed orbit error (4 mm) -alignment errors + beam screen (3mm) 10 s 10 s 10 s d(triplet) > 33 s + 7 mm with s = b e + D2 d2 LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 15

  16. 2-in-1 magnet design requires no aperture for beam separation: 10 s 10 s Aperture Requirements -10 s beam envelope -20% beta beat -closed orbit error (4 mm) -alignment errors + beam screen 3mm? (economic use of space  flat beam screen) d(triplet) > 22 s + 7 mm with s = b e + D2 d2 LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 16

  17. diameter / mm 2-in-1 L* / m Aperture Requirements b(s) = b0 – 2a0 s + g0 s2; a = -1/2 db/ds; g = (1+a2)/b single aperture assume: at triplet entrance:Da = -2 a(L*) Ds (Q1 - Q2 ) = 12.5 m • all layout options require smaller magnet diameter for smaller L* • aperture of a single bore triplet magnet with L* = 23 m is approx. equal to the aperture of a 2-in-1 triplet magnet with L* = 50 m LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 17

  18. Optics Issues for Different Layout Options nominal layout: b* = 0.25 + x-ing + L* of 23 m  80 mm diameter: • only 4 m for TAS assembly! • bmax of approximately 9 km (see the presentation by Jean-Pierre Koutchouk for more details) LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 18

  19. Optics Issues for Different Layout Options D1-D2 first layout: b* = 0.25 and L* of 50 m  80 mm diameter: • ca. 27 m for D1-TAS-D2 assembly • bmax of approximately 18 km (see the presentation by Riccardo de Maria for more details) LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 19

  20. Optics Issues for different Layout Options chromaticity correction: • the natural chromaticity due to the triplet quadrupole magnets is proportional to the b-function • large b-functions inside the triplet magnets generate large Q’ and large off momentum b-beat • existing lattice sextupole correction system: • dipole first layout option 3) only compatible with b* = 0.25 m and linear Q’ correction (see Riccardo de Maria’s presentation for more details) additional correction circuits: • additional sextupole magnets in regions with dispersion could provide additional margins for Q’ correction LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 20

  21. Optics Issues for different Layout Options additional sextupole circuits in regions with dispersion: an efficient correction requires large D and b functions  ideal location near triplet magnets • D is small by design inside the triplet magnets • non-efficient correction • large sextupole fields will reduce dynamic aperture special optics with large dispersion inside triplet magnets: • efficient Q’ correction with additional sextupoles • Dispersion with long range beam-beam generates additional Q’ and chromatic coupling LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 21

  22. Optics Issues for different Layout Options orbit correction: • the orbit deflection due to the triplet quadrupole alignment errors is proportional to the b-function • large b-functions inside the triplet magnets imply • strong orbit corrector magnets (for correction via external corrector magnets) and • tight alignment tolerances emittance blow-up due to noise and ground motion: • emittance blow-up is proportional to b-functions • insertion upgrades might be sensitive to emittance blow-up due to noise and ground motion LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 22

  23. Aspects Related to the Crossing Angle Generation long range beam-beam interactions: • no issue for layout option 2) • reduced number of interactions for dipole first layout • horizontal x-in angle can be generated via D1/D2 and beam separation can be integrated into triplet magnet cross section for dipole first layout • vertical x-in requires either very strong corrector magnets or a tilt of the D1 / D2 dipole magnets • D1/D2 tilt is easily implemented for layout 3) • not obvious for other layout options LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 23

  24. vertical crossing angle in 2-in-1 magnet design: 10 s 10 s Aspects related to the Crossing Angle Generation • implies vertical offset of the two apertures!  is this feasible? • do we still need vertical crossing angles if we can generate large horizontal crossing angles in all IP’s? LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 24

  25. triplet field error corrector layout: Aspects Related to Field Error Corrections Q3 Q2 Q1 Q1 Q2 Q3 IP b1 / a1 b3, a3, b4, a4 b1 / a1 b3, a3, b4, a4 a2 b1/ a1 b1/ a1 b1/ a1 b1/ a1 a2 • the optic functions vary significantly along the triplet magnets implying a non-local kick minimization • if the two beams share the same magnet aperture the optic functions are different for both beams requiring a integrated kick minimization over the whole insertion LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 25

  26. Aspects Related to Field Error Corrections feed-down errors due to crossing angle offsets: QF QD IP lead end  feed down error have opposite sign rules compared to main body field errors • correction of feed down errors requires independent correction circuits • a triplet design with separate bores for the two beams therefore requires a smaller number of correction circuits and allows a ‘local’ field error correction on each side of the IP LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 26

  27. Summary beam-beam interaction: • dipole first layout reduces number of long range beam-beam interactions radiation: • any luminosity upgrade requires a TAS upgrade • a dipole first layout provides efficient magnetic TAS • a dipole first layout requires 2-in-1 magnets with central whole for neutron flux! dipole first layout options: • four options have been identified so far but only one is being studied in detail LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 27

  28. Summary aperture: • all IR upgrade options benefit from smaller L* • dipole first layout does not require larger magnet aperture and allows an efficient implementation of beam screens optics: • chromaticity increases with b-funtion inside triplet magnets • dipole first layout implies larger chromatic aberrations aspects related to crossing angle generation: • 2-in-1 magnet design allows large crossing angles (v-xing?) aspects related to field error corrections: • 2-in-1 magnet design provides efficient field error correction LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 28

  29. Layout and optics derived from Combined function solution: Options for a Quadrupole First Layout D1/D1  3.7 T Q1  47T/m  d = 212mm Q2  70T/m  d = 143mm Q3  47T/m  d = 212mm Q3b  6T/m • aperture estimate assumes a peak coil field of 5 T!  dispersion matched to 1.5m in ‘triplet’ for Q’ correction! LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 29

  30. Layout and optics derived from Combined function solution: Options for a Quadrupole First Layout D1/D1  3.7 T Q1  47T/m  d = 212mm Q2  70T/m  d = 143mm Q3  47T/m  d = 212mm Q3b  6T/m • aperture estimate assumes a peak coil field of 5 T!  dispersion matched to 1.5m in ‘triplet’ for Q’ correction! LHC LUMI 2005; 1.9.2005; Arcidosso Oliver Brüning 30

More Related