Beam Delivery System: status and plans of R&D until CDR R. Tom´ as, D. Angal-Kalinin, B. Dalena, L. Fernandez, F . Jackson, J. Resta, G. Rumolo, A. Seryi, P . Schuler and D. Schulte CLIC ACE 2009 Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.1/23
Contents • New instrumentation: The polarimeter • Preservation of emittances: - Transport aberrations � . - Failure to tune the FFS - ATF2 Resistive wall - Collective effects Fast ion instability Collimator w akefields • Machine protection: - Collimation systemm • Plans towards CDR Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.2/23
Contents • New instrumentation: The polarimeter • Preservation of emittances: - Transport aberrations � ′′ - Failure to tune the FFS - ATF2 Resistive wall - Collective effects Fast ion instability Collimator w akefields • Machine protection: - Collimation systemm • Plans towards CDR Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.2/23
Contents • New instrumentation: The polarimeter • Preservation of emittances: - Transport aberrations � ′′ - Failure to tune the FFS - ATF2 Resistive wall - Collective effects Fast ion instability Collimator w akefields • Machine protection: - Collimation systemm • Plans towards CDR Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.2/23
The BDS Diagnostics Energy Transverse Final collimation collimation Focus system 600 0.45 1/2 β x 0.4 1/2 β y 500 0.35 D x 0.3 400 β 1/2 [m 1/2 ] 0.25 D [m] 300 0.2 0.15 200 0.1 0.05 100 0 0 -0.05 0 0.5 1 1.5 2 2.5 3 Longitudinal location [km] Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.3/23
Polarimeter location & performance 0.5 BDS layout IP directions (0.6mrad) 0 -0.5 x[m] -1 -1.5 -2 0 500 1000 1500 2000 2500 3000 Longitudinal location [m] Laser IP at 742 m and detector at 907 m. Relative polarization measurement error is 0.61% (for 1s). Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.4/23
BDS emittance “spoilers” by design • CLIC BDS transport aberrations have been extensively minimized (MAPCLASS, extra non-linear elements, etc) • Aberrations increase vertical IP beam size by 15% • Synchrotron radiation reduces luminosity by 20% • (in ILC these effects are below the 1%) Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.5/23
Vertical IP beam sizes and chromaticities Project Status σ ∗ y [nm] ξ y FFTB Measured 70 17000 ATF2 Commissioning 37 19000 ILC Design 6 15000 ILC low power Proposed 4 30000 CLIC Design 1 63000 CLIC, the most challenging. Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.6/23
Imperfections as emittance “spoilers” • 10 µ m transverse misalignments can decrease lumi by 10 − 6 • 10 − 5 relative gradient error in QD0 decreases lumi by 0.94 • Tuning algorithms are fundamental! • Can we tune the FFS using the Simplex to maximize lumi? Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.7/23
Current status of FFS tuning Pre-alignment is 10 µ m 14 12 10 Counts 8 6 4 2 0 0.6 0.8 1 1.2 Relative final luminosity [L 0 ] 80% of the cases reach 80% of the lumi in 18000 iterations. Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.8/23
How to improve tuning performance? • Use of more clever algorithms than the Simplex (presently on-going) • Tune in a beta-squeeze sequence (like colliders) • Relax the optics • Andrei Seryi proposed a new optics with double L* to ease QD0 stabilization, let’s see what happens Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.9/23
Comparing Andrei’s FFS to CLIC nominal 900 Andrei’s proposal 800 CLIC nominal 700 600 β y [km] 500 400 300 200 100 0 0 100 200 300 400 500 600 700 800 Longitudinal location [m] Andrei’s prop: L*=8.0m, β ∗ y =0.10mm CLIC nominal: L*=3.5m, β ∗ y =0.07mm Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.10/23
Sensitivity to misalignments 10 0 L*=3.5m L*=8.0m 10 -2 Relative luminosity (L/L 0 ) 10 -4 10 -6 10 -8 10 -10 10 -12 0 2 4 6 8 10 Transverse misalignments ( σ x,y ) [ µ m] Doubling L* increases sensitivity to misalign- ments by a factor of 4 Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.11/23
Sensitivity to QD0 gradient error 1.02 L*=8.0m L*=3.5m 1 fits Luminosity (L/L 0 ) 0.03 0.05 0.98 0.96 0.94 0.92 0.9 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 QD0 relative gradient error [10 -4 ] Doubling L* increases sensitivity to gradient error by a factor of 2 Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.12/23
QD0 specifications L*=3.5m L*=8.0m Gradient 575T/m 211T/m Aperture (radius) 3.5mm 8.5mm Outer radius 35mm 70mm QD0 jitter 0.15nm 0.18nm QD0 support detector ground QD0 technology PM PM 5 × 10 − 6 3 × 10 − 6 QD0 grad tol. A superconducting QD0 adds the extra challenge of stabilizing coils. Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.13/23
Tuning longer L* with better pre-alignment Pre-alignment is 2 µ m 18 16 14 12 Counts 10 8 6 4 2 0 0.5 0.6 0.7 0.8 0.9 1 Relative final luminosity L/L 0 Same tuning performance as for nominal by re- ducing pre-alignment a factor 5 Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.14/23
ATF2 ultra-low β proposal • CARE/ELAN-2008-002 proposed a squeeze of the ATF2 IP β -functions by a factor of 4 • σ y ≈ 20 nm, ξ y ≈ 76000 • ATF2 ultra-low β will experimentally prove CLIC-like aberrations and tuning algorithms. • Beneficial for the ILC project, more in particular for the ILC low power option. • This proposal was accepted • Presently a CERN PhD working on this Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.15/23
Collective effects: Resistive wall Resistive wall effect (Cu beam pipe) 25 Last bunch vertical excursion [ µ m] radius=2mm 20 radius=3mm radius=4mm 15 radius=6mm 10 5 0 -5 -10 -15 Initial batch offset=0.2 µ m -20 -25 0 0.5 1 1.5 2 2.5 3 Longitudinal location [km] 8mm Cu beam-pipe is enough to neglect resistive wall. Only QD0 has a smaller aperture. Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.16/23
Collective effects: Fast ion Two sources: • Scattering ionization • Field ionization 10 nTorr seem enough to avoid fast ion instabili- ties. Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.17/23
Collective effects: Collimator wakefields 25 coll wakefield no coll wakefield 20 15 10 10 σ x ,44 σ y 5 0 0 0.05 0.1 0.15 0.2 0.25 ∆ L/L 0 Assuming an initial jitter of 0.2 σ wakefields peak lumi reduction is 20%. Open the collimator gaps? Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.18/23
Energy collimator (Be) survivability Temperature increment in a Be spoiler with tapers and a 0.5 rad. lengths body hit by a full CLIC train 550 500 450 Temperature increment [K] 400 350 300 250 200 150 100 50 0 50 100 150 200 250 300 350 Distance [mm] Temperature raise after impact of a full train below melting level. ( different philosophy than ILC ) Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.19/23
Collimator gap scan Good particles for QF1 and QD0 Bad particles for QF1 or QD0 100 100 100 a c y y y b σ σ σ N N N 80 80 80 60 60 60 40 40 40 20 20 20 0 0 0 0 10 20 30 40 50 60 0 10 20 30 40 50 60 0 10 20 30 40 50 60 N σ N σ N σ x x x 100 100 100 e y y y d f σ σ σ N N N 80 80 80 60 60 60 40 40 40 20 20 20 0 0 0 0 10 20 30 40 50 60 0 10 20 30 40 50 60 0 10 20 30 40 50 60 N N N σ σ σ x x x Acceptable collimation depths are between 10- 15 σ x and 44-55 σ y . Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.20/23
Plans towards CDR • CLIC 500 GeV lattice optimization (new CERN student on August) • New tuning algorithms and knobs (help from SLAC, LAL, ATF2...) • ATF2 ultra-low β progress (new CERN PhD since March and ILC) • Review and optimization of collimation: • wakefields with new parameters (UK) • simulations including secondaries (UK) • QD0 review (Detlef) • Global feedback studies (new CERN fellow since May) Rogelio Tom´ as Garc´ ıa Beam Delivery System: status and plans of R&D until CDR – p.21/23
Recommend
More recommend
