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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB Optical requirements for the magnetic lattice of the high energy injectors (SSPS in the SPS tunnel) G. Arduini – CERN-AB/ABP

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB Outline Constraints from SPS tunnel Expected functionalities Arc aperture SPS to SSPS transfer Slow extraction in the SSPS Fast extraction Other issues

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB Assumptions SSPS: –Injection momentum=100 GeV/c –Extraction momentum=1 TeV/c –Beam characteristics: LHC beam ( *=7 m, p/p=± 2×10 -3 ) FT beam ( *=12(H)/7(V) m, p/p=± 2×10 -3 )

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB Constraints for SSPS in the SPS tunnel The SPS tunnel geometry: –Circumference: 2 x 1100 m = 6911.5 m –6-fold symmetry 6 Long Straight Sections (LSS) ~ 130 m long Additional constraints if SSPS cohabitation with SPS: –Need installation at ~ 2 m from the tunnel floor –Need different radial position: ~ 1 m inside of the straight sections to be compatible with present SPS HW (e.g. RF waveguides and loads in LSS3) –SPS extraction, SSPS injection and SPS to SSPS transfer in the same LSS.

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB Constraints for SSPS in the SPS tunnel RF BI – TAIL CLEANING INJ. – BEAM DUMP

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB Constraints for SSPS in the SPS tunnel

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB Required functionalities 1. Injection 2. Acceleration 3. Fast extraction 1 to LHC (LSS4 if we want to use the TI8 tunnel) 4. Fast extraction 2 to LHC (LSS6 if we want to use the TI2 tunnel) 5. Slow resonant extraction (LSS2 if we want to use the TT20 tunnel to North area) 6. Beam dump 7. Betatron collimation 8. Momentum collimation Need to combine 2 functions in at least 2 LSSs

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB Present SPS lattice FODO structure – 6-fold symmetry ~90 0 phase advance per cell – 18 cell/sextant 4 dipoles/half-cell (each 6.26 m long – 8.45 mrad – 6.6 mm sagitta ~ 1.1mm×dipole length) Approximate dispersion suppression in the long straight sections by missing magnet scheme gives dispersion beating in the arcs Very simple lattice – 1 QF power supply, 1 QD power supply tr ~ 23

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB Present SPS lattice

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB Arc aperture Required half-aperture in the arcs for a lattice a la SPS 51 / 86 (H) × 27 (V) mm (value for slow extraction)

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB Arc aperture The estimated maximum amplitude of the separatrix in the arcs A sepmax is based on the assumption that the spiral step size at the electrostatic septum (ES) is approximately 16 mm to keep losses at % level. gain in increasing locally H at ZS need special insertion for the slow extraction e.g. H at ES = 400 m required half-aperture ~ 57 mm (instead of 86 mm) – now comparable with aperture at injection

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB Arc aperture A reduction of the required horizontal aperture can be achieved by a proper matching of the dispersion with independently powered quads in the insertion need to probably extend in 1 arc cell to get symmetric solution

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB Arc aperture Peak dispersion 4.5 to 3 m Required half-aperture in the arcs: 46 / 82 (H) × 27 (V) mm (10 % gain in the aperture at injection) Useful if together with increased H at ES proper insertions with independent powering of the quadrupoles in the dispersion suppressor, in the straight section and possibly in 1 arc cell might be required.

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB Arc aperture further reduce and D in the arcs by reducing the cell length, keeping the same phase advance per cell, and the same radius of curvature in the dipoles and therefore increasing the tune

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB Arc aperture Reduction of the length by a factor 2 Tune~51 tr ~ 45 Required aperture: 31 / 56 (H) × 21 (V) mm (value for slow extraction) Useful if together with increased H at ES

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB Arc aperture Pros: –Smaller aperture –Smaller sagitta (if we keep constant the number of magnets) Cons: –Larger number of magnets (if we do not increase the dipole length) –Stronger quads –Poorer “filling factor” –Reduction of the cell length and of the available space for auxiliary elements (instrumentation, correctors, kickers)

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB SPS to SSPS transfer Cohabitation with the SPS in the SPS tunnel will imply hosting the SPS fast extraction to the SSPS and the injection in the SSPS in the same straight section In order to gain space might need to install the SPS fast extraction kickers in the missing dipole section providing an H kick towards a Lambertson magnet in the following dispersion free section bending the beam vertically The Injection in the SSPS could be “symmetric” to the SPS extraction. This solution might be incompatible with a reduction of the cell length.

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB SPS to SSPS transfer Probably feasible taking into account the aperture of the existing SPS kickers for the fast extraction to LHC and CNGS and the favorable energy scaling laws assuming similar functions. The expected length of the transfer line from SPS to SSPS would be 50-60 m need to fit matching section to allow transfer without blow-up between the 2 machines ( , , D, D’) in both planes.

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB SPS to SSPS transfer Additional issues: –Protection elements (like injection stoppers) need to find place in a crowded area more difficult given the higher energy

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB Slow extraction Reliable operation of the electrostatic septa used to cut the separatrix limits the electric field they can provide (in the SPS 110 kV/cm) The increased extraction energy reduces the separation of the extracted and circulating beam at the downstream magnetic septa because of the limited length of the straight section increased losses

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB Slow extraction Brute force method = increase the number of septa in the FODO structure of the LSS (not very efficient use of the HW) Clearance: ~13 (17) mm at MST and ~39 (41) mm at MSE – present operational clearances Requirements for extraction bumpers and protection devices not considered ES septaThin MS-4 mm Thick MS-17 mm

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB Slow extraction Need dedicated insertion providing: –Dispersion free region for the septa –Larger horizontal beta at the ES –Increased strength for the defocussing quad after the ES to enhance the kick provided by the ES –Optimization of the length of the drift spaces to maximize the lever-arm between the ES and the MS maximizing the kick enhancement provided by the defocussing quad after the ZS. Additional issues: –Trajectory of the beam leaving the magnetic septa at large radial offset through the magnets of the dispersion suppressor –Cohabitation of the Slow Extraction with the SC environment and collimation

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB Fast extraction Brute force solution = increase the number of kickers and septa (MST) Clearance: ~19 mm at MST Interference of the extracted beam with the downstream magnetic elements? Pulsed magnetic septa could provide larger deflection angles for comparable gaps (development work for the SPS FE) Protection elements for higher energy

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB To be addressed Beam dump insertion –Can we afford an internal dump as for the SPS? –If not can it be based on the design of the LHC beam dump insertion (IR6)? –Tracking issues because of the faster ramp? Collimation insertion(s) How to integrate 8 distinct functionalities in 6 straight sections cohabitation issues

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1 st September 2005LHC-LUMI 05 - G.Arduini – CERN/AB Tentative summary Only a few issues have been sketched Constraint on the length of the straight sections and increased energy impose to design dedicated insertions (no simple FODO lattice) Slow-extraction and dispersion drive and/or contribute significantly to the aperture in the arcs proper matching and insertion design Cohabitation of different functionalities in the same straight section is necessary and implications need to be studied

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