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P. A. Posocco – CERN (BE-ABP-HSL)

sLHC. Sensitivity study on the SPL : definition of alignment tolerances, diagnostics and correction systems. P. A. Posocco – CERN (BE-ABP-HSL). Overview of SPL. Source. LEBT. RFQ. MEBT. DTL. CCDTL. PIMS. HEBT. Source: 70 mA of H - ions at 45 keV RFQ: 60 mA , 352.2 MHz

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P. A. Posocco – CERN (BE-ABP-HSL)

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  1. sLHC Sensitivity study on the SPL : definition of alignment tolerances, diagnostics and correction systems P. A. Posocco – CERN (BE-ABP-HSL)

  2. Overview of SPL Source LEBT RFQ MEBT DTL CCDTL PIMS HEBT Source: 70 mA of H- ions at 45 keV RFQ: 60 mA, 352.2MHz DTL: Three tanks (FFDD+FD) CCDTL: 7 Tanks (FD) PIMS: 12+1 Tanks (FD) Elliptical: 2 generations of elliptical cavities, β0=0.65 and 1.0 (FD or F0D0) 704.4 MHz Low β High β 100 160 3 MeV 50 165 5 GeV See next slide Linac4 SPL sLHC P. A. Posocco - "Sensitivity studies on the SPL”

  3. SPL layout Doublet (FD), baseline, design: 10 low beta cryomodules (780 MeV) 5 high beta cryomodules (1516 MeV) Extraction to ISOLDE 6 high beta cryo. (2586 MeV) Extraction to EURISOL 12 high beta cryomodules(Final Energy 4989 MeV) 5 × High β 6 × High β 10 × Low β 12 × High β Extraction Extraction sLHC P. A. Posocco - "Sensitivity studies on the SPL”

  4. SPL design lattices: FD vs. F0D0 Low beta elliptical FD Not on scale!!! F0D0 14.8 m 12.3 m High beta elliptical FD F0D0 15.1 m P. A. Posocco - "Sensitivity studies on the SPL”

  5. SPL Beam dynamics (1/2) RMS beam envelopes for a beam generated at PIMS input for the FD option RMS beam envelopes for a beam generated at PIMS input for the F0D0 option X Y Z sLHC P. A. Posocco - "Sensitivity studies on the SPL”

  6. SPL Beam dynamics (2/2) X Y Z unit: π mm mrad (RMS) sLHC P. A. Posocco - "Sensitivity studies on the SPL”

  7. Error study philosophy (1/3) • Test the line from PIMS to 5 GeV with errors on magnets (misalignment and gradient): • Check how the lattices (PIMS, HEBT, SPL) “amplify” the errors • Look for beam losses, emittance increase, output beam misalignment • Find the tolerance range and foresee different alignment tolerances for PIMS and SPL sLHC P. A. Posocco - "Sensitivity studies on the SPL”

  8. Error study philosophy (2/3) • Test the PIMS and HEBT line with errors on magnets (misalignment and gradient) and with a residual beam misalignment: • Define the alignment tolerances for PIMS • Switch on the steerers and see how good the beam out of HEBT can be centered • Define a residual beam misalignment as input for the SPL alone sLHC P. A. Posocco - "Sensitivity studies on the SPL”

  9. Error study philosophy (3/3) • Test the SPL alone with the residual steering from HEBT: • Check the tolerances without correction • Find the limit for magnet misalignment • Switch on the steerers and correct it • Check the differences between the doublet (FD) layout and the F0D0 layout for SPL • Different tolerances? • Different correction strategy? sLHC P. A. Posocco - "Sensitivity studies on the SPL”

  10. Criterion of tolerances • 100% transmission • Correction system not be used to correct structure misalignment but input beam misalignment • Emittance growth less than 20% (3 sigma) sLHC P. A. Posocco - "Sensitivity studies on the SPL”

  11. Error study resume sLHC P. A. Posocco - "Sensitivity studies on the SPL”

  12. STEP I: From PIMS to 5GeV (1/3) Comparison between the doublet (FD) and the F0D0 solutions. All the line magnets are “Gaussian” randomly displaced and an error of 0.5% on the gradient is added. 100% transmission limit P. A. Posocco - "Sensitivity studies on the SPL”

  13. STEP I: From PIMS to 5GeV (2/3) Horizontalemittance Vertical emittance 20% emit. increase limit sLHC P. A. Posocco - "Sensitivity studies on the SPL”

  14. STEP I: From PIMS to 5GeV (3/3) FD configuration (0.2 mm magnet displacement) F0D0 configuration (0.2 mm magnet displacement) sLHC P. A. Posocco - "Sensitivity studies on the SPL”

  15. STEP II: From PIMS to SPL Since no significant emittance increase, used the nominal HEBT out distribution displaced (±0.2 mm ±0.2 mrad) for SPL alone simulations sLHC P. A. Posocco - "Sensitivity studies on the SPL”

  16. SPL design and diagnostics Low beta elliptical Y steerer (D quad) X steerer (F quad) BPM (±0.1 mm) FD F0D0 Not on scale!!! 14.8 m 12.3 m High beta elliptical FD F0D0 15.1 m sLHC P. A. Posocco - "Sensitivity studies on the SPL”

  17. STEP III: SPL alone (1/4) Comparison between the doublet (FD) and the F0D0 solutions. All the line magnets are “Gaussian” randomly displaced and an error of 0.5% on the gradient is added. For all cases: ±0.2 mm ±0.2 mrad input beam misalignment. 100% transmission limit sLHC P. A. Posocco - "Sensitivity studies on the SPL”

  18. STEP III: SPL alone (2/4) Horizontal emittance (±0.2 mm ±0.2 mrad input beam mis.) Vertical emittance (±0.2 mm ±0.2 mrad input beam mis.) 20% emit. increase limit sLHC P. A. Posocco - "Sensitivity studies on the SPL”

  19. STEP III: SPL alone (3/4) ±0.2 mm ±0.2 mrad input beam mis. ±0.2 mm quad misal. not corrected (FD) ±0.2 mm ±0.2 mrad input beam mis. ±0.2 mm quad misal. corrected (FD) sLHC P. A. Posocco - "Sensitivity studies on the SPL”

  20. STEP III: SPL alone (4/4) ±0.2 mm ±0.2 mrad input beam mis. ±0.2 mm quad misal. not corrected (F0D0) ±0.2 mm ±0.2 mrad input beam mis. ±0.2 mm quad misal. corrected (F0D0) sLHC P. A. Posocco - "Sensitivity studies on the SPL”

  21. Conclusions on alignment • PIMS and HEBT must be aligned within ±0.1mm (LINAC4 tolerance) • SPL, due to the larger bore and the different lattice, requires a slightly more relaxed limit (±0.2mm) • The correction system foresees at the moment: • 1 steerer for each quad (strength less than 0.02 Tm) • 1 BPM after 2 quads (just before the following quad) • Further diagnostics still in progress sLHC P. A. Posocco - "Sensitivity studies on the SPL”

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