Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 1 Y. Roblin, CLAS12 workshop march 7-11, 2011 Yves Roblin CLAS12 European workshop Paris March 7-11, 2011 CEBAF in Hall B after the 12GeV upgrade

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 2 Y. Roblin, CLAS12 workshop march 7-11, 2011 OUTLINE From 6 GeV To 12 GeV Top level parameters Beam specifications Double bend achromat Beam Halo Extraction scheme Current status Conclusion

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 3 Y. Roblin, CLAS12 workshop march 7-11, 2011 From 6 GeV to 12 GeV

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 4 Y. Roblin, CLAS12 workshop march 7-11, GeV12 GeV Energy to Halls A,B,C / D6 GeV11 GeV / 12 GeV Number of passes for Halls A,B,C / D 55 / 5.5 (add a tenth arc) Duty FactorCW Max. Current to Halls A+ C / B 200  A / 5  A Max. Current to Halls A+C / B+D 85  A / 5  A (with appropriate dump) Max. Beam Power1 MW Emittance at max. energy (unnormalized, rms): x, y 1 nm-rad, 1 nm-rad10 nm-rad, 2 nm-rad Energy spread at max. energy (rms) 2.5 x x /5 x GeV vs 12 GeV CEBAF Top Level Parameters

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 5 Y. Roblin, CLAS12 workshop march 7-11, 2011 Hall B Electron Beam Requirements Geometric Emittanceε x <10nm.rad, ε y <10 nm.rad Energy Spread<0.1 % Absolute Energy<0.1 % Spot Sizeσ x <400μm σ y <400μm Beam Halo<0.01 % Position stabilityΔx<200μm, Δy<200μm Beam Current0.3 nA < I e <3μA

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 6 Y. Roblin, CLAS12 workshop march 7-11, 2011 From 6 GeV to 12 GeV ARC1ARC2ARC3ARC4ARC5ARC6ARC7ARC8ARC9 ARCA HALLD

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 7 Y. Roblin, CLAS12 workshop march 7-11, 2011 Optimal ARC choices for 12GeV Optimization for 6 GeV was aimed at preserving small dp/p (a few 10 -5) — Arcs were achromatic and isochronous. 12 GeV beam is dominated by Synchrotron radiation past Arc6 —Relax isochronous requirement and instead go for emittance minimization —Double Bend Achromat optics Synchrotron radiation loss in ARCS compensated by adjusting dipole via trim coils. S/R step ratio changed to accommodate ranges.

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 8 Y. Roblin, CLAS12 workshop march 7-11, GeV DBA optics Arc6 thru ArcA changed to DBA Beta(m) δ (m) Beta(m)

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 9 Y. Roblin, CLAS12 workshop march 7-11, 2011 Transverse Emittance* and Energy Spread † Area  p/p [x10 -3 ]  x [nm]  y [nm] Chicane Arc Arc Arc Arc Arc Arc Arc Arc Arc Arc Hall D * Emittances are geometric † Quantities are rms DBA option Sync. Rad. Damping

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 10 Y. Roblin, CLAS12 workshop march 7-11, 2011 Bunchlength and energy spread

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 11 Y. Roblin, CLAS12 workshop march 7-11, 2011 Beam line occupancy R=4(  beam +  orbit ) = 4  beam + 2.4mm  orbit <600 µm RMS Consistent with current operating practices

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 12 Y. Roblin, CLAS12 workshop march 7-11, 2011 Extraction Scheme Current 12GeV scope is to deliver hall D And two beam A/C or A/B or B/C at two different passes However, upgrade to D+2 is being done. Will allow to: Deliver D beam + 2 other beams With the option of having 2 at 5 pass. Also possible to do A/B/C at 5 pass (no D)

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 13 Y. Roblin, CLAS12 workshop march 7-11, 2011 Scope Description 12 GeV Upgrade Plan View Recirculation ARCS RelocatedNew 12 GeV Upgrade Elevation View Horizontally deflecting RF cavities (499MHz, copper) Horizontally deflecting septa Horizontally deflecting dipoles Pass 1 Pass 2 Pass 4 Pass 3 Pass 5 Modified Horizontally deflecting Lambertson Courtesy: Mike Spata

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 14 Y. Roblin, CLAS12 workshop march 7-11, 2011 Upgrade to D+2 Courtesy: Mike Spata Addition of RF separators on Pass 5 to restore the capability to deliver 3 halls at 5 pass Or deliver Hall D + two halls at 5 pass

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 15 Y. Roblin, CLAS12 workshop march 7-11, 2011 Adding Vertical RF separation

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 16 Y. Roblin, CLAS12 workshop march 7-11, 2011 Vertical clearance for separators

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 17 Y. Roblin, CLAS12 workshop march 7-11, 2011 Changes to Hall B beamline (not including detectors) Quadrupoles upgraded, corrector upgraded QA QY QA QR QA QK C03,C04,C24 C05 -> C20 C22,23 QK: 30cm QA with 20A card QR: 35.56cm steel, 20A card QY:stronger version of QR, being developed.

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 18 Y. Roblin, CLAS12 workshop march 7-11, 2011 Tuning of the beamline Well Defined independent knobs MQR2C21, MQK2C22 MQY2C23,MQK2C24 MQA2C01,MQA2C02 MQK2C03,MQK2C04 Beam spot δ y, δ y ' Match to fodo MQR2C09, MQR2C17

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 19 Y. Roblin, CLAS12 workshop march 7-11, 2011 Sensitivity to input parameters Many input variations, with re - matching of the transport and beam spot. Beta’s varied by factor of 2 Alphas by +/1 All optics can be corrected within existing quadrupole range Before rematchAfter rematch

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 20 Y. Roblin, CLAS12 workshop march 7-11, 2011 Beam sizes in Hall B at 11 GeV  x < 400 μm  y < 400 μm Within Specs

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 21 Y. Roblin, CLAS12 workshop march 7-11, 2011 Start to end simulations DBA optics Arc6 thru 9 Floor coordinates Beamline modeled with errors, multipoles, misalignments, apertures, … Full start to end simulation including extraction Use of LQCD clusters for massive halo studies (hallD) HallB Exit of injector

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 22 Y. Roblin, CLAS12 workshop march 7-11, 2011 Beam at Hall B target

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 23 Y. Roblin, CLAS12 workshop march 7-11, 2011 Beam spot tuning range QR2C21 QK2C22 QY2C23* QK2C % engineering margin Can cover beam spot size range from 200 to 800 µm sigma *QY2C23 quad range actually taken as a QR and it is sufficient

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 24 Y. Roblin, CLAS12 workshop march 7-11, 2011 Halo in hall B Estimated from studies done for Hall D Full scale simulation to be done with hall B collaboration Can use beam distributions has a seed for detector Monte-carlo simulations

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 25 Y. Roblin, CLAS12 workshop march 7-11, 2011 Massively parallel ELEGANT simulations Beam at RADIATOR in Hall D, DBA optics Simulation across the whole machine. 2Millions particles Jlab LQCD cluster 128 cpus, 50 minutes Using ELEGANT on the LQCD clusters Invaluable for validating 12GeV optics Synchrotron radiation Skew and normal multipoles Apertures Orbit coverage Misalignments Mis-powering

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 26 Y. Roblin, CLAS12 workshop march 7-11, 2011 Horizontal Beam Profile at HALLD Radiator Halo is 8E-6 << 5E-5 Within Specs

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 27 Y. Roblin, CLAS12 workshop march 7-11, 2011 Beam gas scattering Beam gas Bremsstrahlung Inelastic scattering off atomic electrons Thermal photons scattering Elastic Scattering off Nuclei Most of these proportional to 1/E 2 4 times easier at 12 GeV

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 28 Y. Roblin, CLAS12 workshop march 7-11, 2011 Halo From Vacuum in 6GeV machine

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 29 Y. Roblin, CLAS12 workshop march 7-11, 2011 Conclusions 12 GeV CEBAF design is robust and has been reviewed many times User specifications will be met Detailed beamline layout (diagnostics, etc..) to be determined with hall B collaboration Engage with collaboration and start refining

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 30 Y. Roblin, CLAS12 workshop march 7-11, 2011 APPENDIX. NOT SHOWN DURING TALK UNLESS NEEDED. CAN BE PRINTED.

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 31 Y. Roblin, CLAS12 workshop march 7-11, 2011 Vertical clearance for separators Courtesy: Mike Spata

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 32 Y. Roblin, CLAS12 workshop march 7-11, 2011 Power deposition issues Photon Desorption and Vacuum Load Line Load (watt/m) Critical Energy (KeV) Average Energy (KeV) N γ /m-sec Molecules/ m-sec Load Torr- l/sec Arc Arc Arc Arc Arc Designed pump capacity is 50 l/sec at torr <10 % pump capacity, not a problem

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 33 Y. Roblin, CLAS12 workshop march 7-11, 2011 Power Deposition Issues Where does energy goes Dipole Length (m) Beam Energy Beam Current Total Radiated Power (Watt) Line Load (Watt/m) Arc Arc Arc Arc ArcA Hall D Δ T<50 0 cThru the arcs

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy Thomas Jefferson National Accelerator Facility Page 34 Y. Roblin, CLAS12 workshop march 7-11, GeV Beam Requirements HallEmittance Energy spread (  ) Spot size (s)Halo A ε x < 10 nm-rad, ε y < 5 nm-rad 12 GeV: 0.05% 2-4 GeV: 0.003% 12 GeV:  x <400μm,  y < 200μm 2-4 GeV:  y < 100 μm <0.01%(1) B ε x < 10 nm-rad, ε y < 10 nm-rad 0.1%  x < 400 μm  y < 400 μm <0.01%(1) C ε x < 10 nm-rad, ε y < 5 nm-rad 0.05% 6 GeV:0.03%  x < 400 μm  y < 200 μm <0.01%(1) D ε x < 10 nm-rad, ε y < 5 nm-rad <0.5% At radiator:  x < 1550 μm,  y < 550 μm At collimator:  x < 540 μm,  y < 520 μm <1% (2) 1)Ratio of non-Gaussian tail to Gaussian core 2)Ratio of Halo background event rate to physics event rate.