cebaf in hall b after the 12gev upgrade
DESCRIPTION
CEBAF in Hall B after the 12GeV upgrade. Yves Roblin. CLAS12 European workshop Paris 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. From 6 GeV to 12 GeV. - PowerPoint PPT PresentationTRANSCRIPT
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Thomas Jefferson National Accelerator Facility
Page 1
Y. Roblin, CLAS12 workshop march 7-11, 2011
Yves Roblin
CLAS12 European workshopParis
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
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Y. Roblin, CLAS12 workshop march 7-11, 2011
From 6 GeV to 12 GeV
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Thomas Jefferson National Accelerator Facility
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Y. Roblin, CLAS12 workshop march 7-11, 2011
6 GeV 12 GeV
Energy to Halls A,B,C / D 6 GeV 11 GeV / 12 GeV
Number of passes for Halls A,B,C / D
5 5 / 5.5 (add a tenth arc)
Duty Factor CW CW
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 Power 1 MW 1 MW
Emittance at max. energy (unnormalized, rms): x, y
1 nm-rad, 1 nm-rad 10 nm-rad, 2 nm-rad
Energy spread at max. energy (rms)
2.5 x 10-5 5 x 10-4 /5 x 10-3
6 GeV vs 12 GeV CEBAF Top Level Parameters
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Y. Roblin, CLAS12 workshop march 7-11, 2011
Hall B Electron Beam Requirements
Geometric Emittance εx<10nm.rad, εy<10 nm.radEnergy Spread <0.1 %
Absolute Energy <0.1 %
Spot Size σx <400μm
σy <400μm
Beam Halo <0.01 %
Position stability Δx<200μm, Δy<200μm
Beam Current 0.3 nA < Ie <3μA
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Y. Roblin, CLAS12 workshop march 7-11, 2011
From 6 GeV to 12 GeV
AR
C1
AR
C2
AR
C3
AR
C4
AR
C5
AR
C6
AR
C7
AR
C8
AR
C9
AR
CA
HA
LL
D
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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.
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Y. Roblin, CLAS12 workshop march 7-11, 2011
12GeV DBA optics
Arc6 thru ArcA changed to DBA
Bet
a(m
)
δ (m
)δ
(m)
Bet
a(m
)
200
0
3
-3
200
0 -3
3
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Thomas Jefferson National Accelerator Facility
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Y. Roblin, CLAS12 workshop march 7-11, 2011
Transverse Emittance* and Energy Spread†
Area p/p
[x10-3]
x
[nm]
y
[nm]
Chicane 0.5 4.00 4.00
Arc 1 0.05 0.41 0.41
Arc 2 0.03 0.26 0.23
Arc 3 0.035 0.22 0.21
Arc 4 0.044 0.21 0.24
Arc 5 0.060 0.33 0.25
Arc 6 0.090 0.58 0.31
Arc 7 0.104 0.79 0.44
Arc 8 0.133 1.21 0.57
Arc 9 0.167 2.09 0.64
Arc 10 0.194 2.97 0.95
Hall D 0.18 2.70 1.03
* Emittances are geometric† Quantities are rms
DBA option
Sync. Rad.
Damping
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Y. Roblin, CLAS12 workshop march 7-11, 2011
Bunchlength and energy spread
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Y. Roblin, CLAS12 workshop march 7-11, 2011
Beam line occupancy
R=4(beam + orbit) = 4beam + 2.4mm
orbit <600 µm RMS
Consistent with current operating practices
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Y. Roblin, CLAS12 workshop march 7-11, 2011
Extraction Scheme
Current 12GeV scope is to deliver hall DAnd 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 beamsWith the option of having 2 at 5 pass.
Also possible to do A/B/C at 5 pass (no D)
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Y. Roblin, CLAS12 workshop march 7-11, 2011
Scope Description
12 GeV Upgrade Plan View
Recirculation ARCS
RelocatedNew12 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
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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 passOr deliver Hall D + two halls at 5 pass
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Y. Roblin, CLAS12 workshop march 7-11, 2011
Adding Vertical RF separation
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Y. Roblin, CLAS12 workshop march 7-11, 2011
Vertical clearance for separators
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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 cardQY:stronger version of QR, being developed.
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Y. Roblin, CLAS12 workshop march 7-11, 2011
Tuning of the beamline
Well Defined independent knobs
MQR2C21, MQK2C22MQY2C23,MQK2C24
MQA2C01,MQA2C02
MQK2C03,MQK2C04
Beam spot
δy , δy'
Match to fodo
MQR2C09, MQR2C17
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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 2Alphas by +/1
All optics can be corrected within existing quadrupole range
Before rematch After rematch
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Y. Roblin, CLAS12 workshop march 7-11, 2011
Beam sizes in Hall B at 11 GeV
x < 400 μm
y < 400 μm
Within Specs
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Thomas Jefferson National Accelerator Facility
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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
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Y. Roblin, CLAS12 workshop march 7-11, 2011
Beam at Hall B target
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Y. Roblin, CLAS12 workshop march 7-11, 2011
Beam spot tuning range
QR2C21
QK2C22
QY2C23*
QK2C24
-100 100
10 % 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
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Thomas Jefferson National Accelerator Facility
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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
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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 minutesUsing ELEGANT on the LQCD clusters
Invaluable for validating 12GeV optics
• Synchrotron radiation• Skew and normal multipoles
• Apertures• Orbit coverage• Misalignments• Mis-powering
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Y. Roblin, CLAS12 workshop march 7-11, 2011
Horizontal Beam Profile at HALLD Radiator
Halo is 8E-6 << 5E-5
Within Specs
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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/E2
4 times easier at 12 GeV
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Y. Roblin, CLAS12 workshop march 7-11, 2011
Halo From Vacuum in 6GeV machine
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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 bedetermined with hall B collaboration
Engage with collaboration and start refining
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Y. Roblin, CLAS12 workshop march 7-11, 2011
APPENDIX. NOT SHOWN DURING TALK UNLESS NEEDED.
CAN BE PRINTED.
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Thomas Jefferson National Accelerator Facility
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Y. Roblin, CLAS12 workshop march 7-11, 2011
Vertical clearance for separators
Courtesy: Mike Spata