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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

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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

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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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Thomas Jefferson National Accelerator Facility

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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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Thomas Jefferson National Accelerator Facility

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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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Thomas Jefferson National Accelerator Facility

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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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Thomas Jefferson National Accelerator Facility

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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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Thomas Jefferson National Accelerator Facility

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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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Thomas Jefferson National Accelerator Facility

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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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Thomas Jefferson National Accelerator Facility

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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

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

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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 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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Thomas Jefferson National Accelerator Facility

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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

Page 31

Y. Roblin, CLAS12 workshop march 7-11, 2011

Vertical clearance for separators

Courtesy: Mike Spata