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ESS End-to-End Optics and Layout Integration

ESS End-to-End Optics and Layout Integration. H åkan Danared European Spallation Source. Catania, 6 July 2011. E22. Odarslövsvägen. Present Geometry and Top-Level Parameters. Energy 2.5 GeV Current 50 mA Average power 5 MW

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ESS End-to-End Optics and Layout Integration

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  1. ESS End-to-End Optics andLayout Integration Håkan Danared European Spallation Source Catania, 6 July 2011

  2. E22 Odarslövsvägen

  3. Present Geometry and Top-Level Parameters Energy 2.5 GeV Current 50 mA Average power 5 MW Pulse length 2.86 ms (new value since April 2011, equal to 2×20/14) Rep rate 14 Hz (new value since April 2011) Length 392 m, plus HEBT Max cavity field 40 MV/m Longer than previously because of ”hybrid design”, smoother longitudinal phase advance, lower field gradients, ...

  4. Optimization of Linac Length HS_2011_06_22 All calculations for superconducting linac made by Mamad Eshraqi. Length of superconducting linac is 363 m in the HS_2011_06_22 layout, which is the currently favoured “smooth hybrid”. Total length from ion source to vertical bend, i.e. including HEBT/upgrade, is 492 m. Hybrid between fully segmented and cryo-string gives high serviceability, low cryo load, is good for instrumentation...

  5. Beam Envelope and Emittance Growth in Superconducting Linac (HS_2011_06_22) Envelope horizontal Envelope vertical Envelope long. (Δφ at 352 MHz) Emittance growth longitudinal Emittance growth horizontal Emittance growth vertical

  6. Accelerating Gradients (HS_2011_06_22) Ratio of peak surface field to accelerating field taken from fit to experimental data [P. Pierini], peak surface field chosen to be 40 MV/m. Is this the optimal value? Accelerating gradient (MV/m) in superconducting linac, for smooth and stepwise longitudinal phase advance. Cavity power (kW) in superconducting linac, for smooth and stepwise longitudinal phase advance (specification for power couplers now 900 kW).

  7. Tolerance against Cavity Failure (HS_2011_06_22) Failure of one cavity, or klystron, in the spokes section (most sensitive section) can be handled with maximum about 25% transverse and 12% longitudinal emittance growth. Failure of two adjacent cavities cannot be compensated without large emittance growth and beam loss. Transverse emittance increase due to a failed cavity where energy gain is largest (green bar above) is approximately 12%. It is expected that the elliptical sections are less sensitive to cavity failure than the spokes section.

  8. Effects of RF amplitude and phase errors (HS_2011_06_22) First study of tolerance to RF amplitude and phase errors. Results of 100 sets of ”random” coupled amplitude and phase offsets up to 3% and 3°. Effects start to be seen on emittances and energy and phase deviations at errors between 0.5 and 1.0 %,°. More statistics is needed and more kinds of errors must be included, like alignment errors, magnetic-field variations, multipole fields, current and emittance variations. Essential figures of merit include beam trans-mission (absence of particle losses) and beam stability on target.

  9. Current/Optimal Linac Parameters No. of spoke modules 14 No. of low-beta modules 16 No. of high-beta modules 15 Geometric beta spokes 0.57 Geometric beta low-beta 0.70 Geometric beta high-beta 0.90 Accelerating field spokes 8 MV/m Max surface field ellipticals 40 MV/m Max power per coupler 900 kW Optimization criterion linac length “Phase laws” ... Mechanical dimensions ... Chopper(s)/time structure ... Collimators ... Upgradability ... Energy 2.5 GeV Current 50 mA Average power 5 MW Pulse length 2.86 ms Rep rate 14 Hz Length 392 m, plus HEBT Max surface field ellipticals 40 MV/m Frequencies 352.21, 704.42 MHz Ion source output 75 keV RFQ output 3 MeV DTL output 50 MeV Spokes output 188 MeV Low-beta output 606 MeV High-beta output 2500 MeV Gaps per spoke cavity 3 Cells per low-beta cavity 5 Cells per high-beta cavity 5 Cavities per spoke module 2 Cavities per low-beta module 4 Cavities per high-beta module 8

  10. www.esss.se/linac Parameter Tables

  11. Lattice and Accelerator Science

  12. Integration ESS RFQ, A. Ponton HEBT, A. Holm / H. Thomsen FODO DTL, M. Comunian Source emittance,R. Miracoli Target footprint, H.D. SC Linac, M. Eshraqi • MEBT meeting, 4 May, Bilbao • Warm-linac meeting, 6 July, Catania • End-to-end beam-dynamics workshop, 31 Oct – 1 Nov, Lund • Integration of entire linac lattice end of 2011, gives emittance table, aperture requirements, ...

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