Thomas Jefferson National Accelerator Facility Page 1 Design Status of ELIC G. A. Krafft for ELIC Design Team EIC Collaboration meeting Hampton, May 19-23,

Thomas Jefferson National Accelerator Facility

Page 1

Design Status of ELIC

G. A. Krafft for ELIC Design Team

EIC Collaboration meeting

Hampton, May 19-23, 2008


Page 2

ELIC Study Group & CollaboratorsELIC Study Group & Collaborators

A. Afanasev, A. Bogacz, P. Brindza, A. Bruell, L. Cardman, Y. Chao, S. Chattopadhyay, E. Chudakov, P. Degtiarenko, J. Delayen, Ya. Derbenev, R. Ent, P. Evtushenko, A. Freyberger, D. Gaskell, J. Grames, A. Hutton, R. Kazimi, G. A. Krafft, R. Li, L. Merminga, J. Musson, M. Poelker, R. Rimmer, Chaivat Tengsirivattana, A. Thomas, H. Wang, C. Weiss, B. Wojtsekhowski, B. Yunn, Y. Zhang - Jefferson Laboratory

W. Fischer, C. Montag - Brookhaven National Laboratory

V. Danilov - Oak Ridge National Laboratory

V. Dudnikov - Brookhaven Technology Group

P. Ostroumov - Argonne National Laboratory

V. Derenchuk - Indiana University Cyclotron Facility

A. Belov - Institute of Nuclear Research, Moscow, Russia

V. Shemelin - Cornell University


Page 3

OutlineOutline

ELIC: An Electron-Ion Collider at CEBAF

Basic parameters

List of recent developments/specs

Some R&D Issues

Forming Ion Beams

Electron Cooling

Crab Crossing

Summary


Page 4

Energy• Center-of-mass energy between 20 GeV and 90 GeV• energy asymmetry of ~ 10,

3 GeV electron on 30 GeV proton/15 GeV/n ion up to 9 GeV electron on 225 GeV proton/100 GeV/n ion

Luminosity • 1033 up to 1035 cm-2 s-1 per interaction point

Ion Species• Polarized H, D, 3He, possibly Li• Up to heavy ion A = 208, fully stripped

Polarization• Longitudinal polarization at the IP for both beams • Transverse polarization of ions• Spin-flip of both beams• All polarizations >70% desirable

Positron Beam desirable

ELIC Design Goals


Page 5

Energy Recovery Linac-Storage-Ring (ERL-R) ERL with Circulator Ring – Storage Ring (CR-R) Back to Ring-Ring (R-R) – by taking CEBAF advantage

as full energy polarized injector Challenge: high current polarized electron source

• ERL-Ring: 2.5 A• Circulator ring: 20 mA• State-of-art: 0.1 mA

12 GeV CEBAF Upgrade polarized source/injector already meets beam requirement of ring-ring design

CEBAF-based R-R design still preserves high luminosity, high polarization (+polarized positrons…)

Evolution of the Principal Scheme


Page 6

ELIC Conceptual Design

3-9 GeV electrons

3-9 GeV positrons

30-225 GeV protons

15-100 GeV/n ions

Green-field design of ion complex directly aimed at full exploitation of science program.

prebooster

12 GeV CEBAF

Upgrade


Page 7

ELIC Ring-Ring Design Features

Unprecedented high luminosity

Enabled by short ion bunches, low β*, high rep. rate

Large synchrotron tune

Require crab crossing

Electron cooling is an essential part of ELIC

Four IPs (detectors) for high science productivity

“Figure-8” ion and lepton storage rings

Ensure spin preservation and ease of spin

manipulation

No spin sensitivity to energy for all species.


Page 8

Achieving High Luminosity of ELIC

ELIC design luminosityL~ 7.8 x 1034 cm-2 sec-1 (150 GeV protons x 7 GeV electrons)

ELIC luminosity Concepts• High bunch collision frequency (f=1.5 GHz)

• Short ion bunches (σz ~ 5 mm)

• Super strong final focusing (β* ~ 5 mm)• Large beam-beam parameters (0.01/0.086 per IP,

0.025/0.1 largest achieved)

• Need High energy electron cooling of ion beams• Need crab crossing

• Large synchrotron tunes to suppress synchro-betatron resonances

• Equidistant phase advance between four IPs


Page 9

ELIC (e/p) Design Parameters

Parameter Unit Ring-Ring

Beam energy GeV 225/9 150/7 100/5 30/3

e/A ring circumference km 1.5

Bunch collision frequency GHz 1.5

Number of particles/bunch 1010 0.42/.77 0.4/1 0.4/1.1 0.12/1.7

Beam current A 1/1.85 1/2.4 1/2.7 0.3/4.1

Energy spread, rms 10-4 3/3

Bunch length, rms mm 5/5

Beta* mm 5/5

Horizontal emittance, norm m 1.25/90 1/90 .7/70 .2/43

Vertical emittance, norm m .05/3.6 .04/3.6 .06/6 .2/43

Beam-beam tune shift (vertical) per IP

.006/.086 .01/.086 .01/.078 .009/.008

Peak luminosity per IP, 1034

(including hourglass effect) cm-2 s-1 5.7 6.0 5.0 .7

Number of IPs 4

Core & lumi. IBS lifetime hrs 24


Page 10

ELIC (e/A) Design Parameters

Ion Max Energy

(Ei,max)

Luminosity / n

(7 GeV x Ei,max)

Luminosity / n

(3 GeV x Ei,max/5)

(GeV/nucleon) 1034 cm-2 s-1 1033 cm-2 s-1

Proton 150 7.8 6.7

Deuteron 75 7.8 6.73H+1 50 7.8 6.7

3He+2 100 3.9 3.34He+2 75 3.9 3.312C+6 75 1.3 1.1

40Ca+20 75 0.4 0.4208Pb+82 59 0.1 0.1

* Luminosity is given per nuclean per IP


Page 11

Electron Polarization in ELIC• Produced at electron source

Polarized electron source of CEBAF Preserved in acceleration at recirculated CEBAF Linac Injected into Figure-8 ring with vertical polarization

• Maintained in the ring (to be reported by Pavel Chevtsov) High polarization in the ring by electron self-polarization SC solenoids at IPs removes spin resonances and energy

sensitivity. spin rotator

spin rotator

spin rotatorspin rotator

collision point

spin rotator with 90º solenoid snake

collision point

collision point

collision point

spin rotator with 90º solenoid snake


Page 12

Electron Polarization in ELIC (cont.)

* Time can be shortened using high field wigglers.

** Ideal max equilibrium polarization is 92.4%. Degradation is due

to radiation in spin rotators.

Parameter Unit Energy GeV 3 5 7 Beam cross bend at IP mrad 70 Radiation damping time ms 50 12 4 Accumulation time s 15 3.6 1 Self-polarization time* h 20 10 2 Equilibrium polarization, max** % 92 91.5 90 Beam run time h Lifetime

Electron/positron polarization parameters


Page 13

Positrons in ELIC

• Non-polarized positron bunches generated from modified electron injector through a converter

• Polarization realized through self-polarization at ring arcs

115 MeV

converter

e-

e-15 MeV

5 MeVe+

e-

e-

e-

e+

10 MeV

15 MeV

e-

e+e+

unpolarizedsource

polarized source

dipole

Transverse emittance

filter

Longitudinal emittance filter

dipole dipole115 MeV

converter

e-

e-15 MeV

5 MeVe+

e-

e-

e-

e+

10 MeV

15 MeV

e-

e+e+

unpolarizedsource

polarized source

During positron production: - Polarized source is off - Dipoles are turned on

dipole

Transverse emittance

filter

Longitudinal emittance filter

dipole dipole


Page 14

Recent Developments/specs

• Rings Lattice design update for higher energies• Interaction Region update (reduced crab…)

(to be reported by Alex Bogacz, Paul Brindza)

• Chromaticity Correction

(to be reported by Hisham Sayed)

• Beam-beam study/simulation(to be reported by Yuhong Zhang)

• IBS Study

(to be reported by Chaivat Tengsirivattana)

• Stochastic Cooling/Stacking all species ion beams• Electron Cooling specs/advances (cool protons…)


Page 15

2700

Fri Nov 30 08:10:43 2007 OptiM - MAIN: - D:\ELIC\Ion Ring\FODO\low_emitt_225\spr_rec.opt

300

50

BE

TA_X

&Y

[m]

DIS

P_X

&Y

[m]

BETA_X BETA_Y DISP_X DISP_Y

Figure-8 Ion Ring (half) Lattice at 225 GeV

42 full cells

11 empty cells

11 empty cells

3 transition cells

3 transition cells

phase adv./cell (x= 600, y=600)

Arc dipoles::

$Lb=170 cm$B=73.4 kG$rho =102 m

Arc quadrupoles:

$Lb=100 cm$G= 10.4 kG/cm

Minimum dispersion (periodic) lattice

Dispersion suppression via ‘missing’ dipoles (geometrical)

Uniform periodicity of Twiss functions (chromatic cancellations)

Dispersion pattern optimized for chromaticity compensation with sextupole families (3 × 600 = 1800)


Page 16

Figure-8 Electron Ring (half) Lattice at 9 GeV

54 superperiods (3 cells/superperiod)

83 empty cells

Arc dipoles::

$Lb=100 cm$B=3.2 kG$rho =76 m

Arc quadrupoles:

$Lb=60 cm$G= 4.1 kG/cm

83 empty cells

880

Fri Nov 30 07:58:46 2007 OptiM - MAIN: - D:\ELIC\InteractionRegion\Electron\FODO_120_90_arc.opt

20

0

0.3

-0.3

BE

TA

_X

&Y

[m]

DIS

P_

X&

Y[m

]


phase adv./cell (x= 1200, y=1200)

‘Minimized emittance dilution due to quantum excitations

Limited synchrotron radiated power (14.3MW (total) @ 1.85A)

Quasi isochronous arc to alleviate bunch lengthening (~10-5)

Dispersion pattern optimized for chromaticity compensation with sextupole families


Page 17

Figure-8 Rings – Vertical ‘Stacking’


Page 18

IP Magnet Layout and Beam Envelopes

IP 10cm 1.8m 20.8kG/c

m

3m 12KG/cm

0.5m 3.2kG/cm

0.6m 2.55kG/c

m

8.4cm

22.2 mrad

1.27 deg

0.2m

Vertical intercept4.5m

3.8m

14.4cm 16.2cm

Vertical intercept

22.9cm

Vertical intercept

10.30

Thu Nov 29 23:19:38 2007 OptiM - MAIN: - D:\ELIC\InteractionRegion\IR\IR_ions_y.opt

0.5

0

10

Siz

e_

X[c

m]

Siz

e_

Y[c

m]

Ax_bet Ay_bet Ax_disp Ay_disp

ion5mm

10.30

Thu Nov 29 23:16:54 2007 OptiM - MAIN: - D:\ELIC\InteractionRegion\IR\IR_elect_y.opt

0.5

0

0.5

0

Siz

e_

X[c

m]

Siz

e_

Y[c

m]

Ax_bet Ay_bet Ax_disp Ay_disp

4mmelectron

N

β* OK


Page 19

Optimization • IP configuration optimization• “Lambertson”-type final focusing quad angle reduction: 100 mrad 22 mrad

IR Final Quad

10 cm

14cm3cm

1.8m

20.8kG/cm

4.6cm 8.6cm

Electron (9GeV)

Proton (225GeV)

2.4cm

10cm

2.4cm

3cm

4.8cm

1st SC focusing quad for ion

Paul Brindza


Page 20

Lambertson Magnet Design

magnetic Field in cold yoke around electron pass.

Cross section of quad with beam passing through


Page 21

β Chromaticity correction with sextupoles

β- functions around the interaction region, the green arrows represent the sextupoles pairs.

The phase advance, showing the –I transformation between the sextupoles pairs

1800

Thu May 15 15:29:20 2008 OptiM - MAIN: - D:\Hisham Work\Accelerator Physics\Alex\IR\ELIC\IR_Arc\IR_elect_mirror

90

00

5-5

BE

TA

_X

&Y

[m]

DIS

P_

X&

Y[m

]


1800

Thu May 15 15:30:10 2008 OptiM - MAIN: - D:\Hisham Work\Accelerator Physics\Alex\IR\ELIC\IR_Arc\IR_elect_mirror

0.5

10

PH

AS

E_

X&

Y

Q_X Q_Y


Page 22

Local Correction of Transfer Map

Initial phase spacephase space after one pass through 2 IR’s No correction

phase space after one pass through 2 IR’s after correction

Vertical plane Δp/p~0.0006

0.003-0.003 Y [cm] View at the lattice beginning

1.2

-1.2

Y`[

mra

d]

0.003-0.003 Y [cm] View at the lattice end

1.2

-1.2

Y`[

mra

d]

0.003-0.003 Y [cm] View at the lattice end

1.2

-1.2

Y`[

mra

d]

Y

Y`

Phase space in both transverse planes before and after applying the sextupoles


Page 23

Beam-Beam Effect in ELICTransverse beam-beam force

– Highly nonlinear forces– Produce transverse kicks between colliding

bunches

Beam-beam effect– Can cause size/emittance growth or blowup– Can induce coherent beam-beam instabilities– Can decrease luminosity and its lifetime

Impact of ELIC IP design– Highly asymmetric colliding beams

(9 GeV/2.5 A on 225 GeV/1 A)– Four IPs and Figure-8 rings– Strong final focusing (beta* 5 mm)– Short bunch length (5 mm)– Employs crab cavity– vertical b-b tune shifts are 0.087/0.01– Very large electron synchrotron tune (0.25) due

to strong RF focusing– Equal betatron phase advance (fractional part)

between IPs

Electron bunch

Proton bunch

IP

Electron bunchproton bunch

x

y

One slice from each of opposite beams

Beam-beam force


Page 24

• Simulation Model– Single/multiple IPs, head-on collisions– Strong-strong self consistent Particle-in-Cell codes,

developed by J. Qiang of LBNL– Ideal rings for electrons & protons, including

radiation damping & quantum excitations for electrons

• Scope and Limitations– 10k ~ 30k turns for a typical simulation run – 0.05 ~ 0.15 s of storing time (12 damping times)

reveals short-time dynamics with accuracy can’t predict long term (>min) dynamics

• Simulation results– Saturated at 70% of peak luminosity, 5.8·1034 cm-2s-1,

the loss is mostly due to the hour-glass effect– Luminosity increase as electron current linearly (up

to 6.5 A), coherent instability observed at 7.5 A– Luminosity increase as proton current first linearly

then slow down due to nonlinear b-b effect, electron beam vertical size/emittance blowup rapidly

– Simulations with 4 IPs and 12-bunch/beam showed stable luminosity and bunch sizes after one damping time, situated luminosity is 5.5·1034 cm-2s-1 per IP, very small loss from single IP and Single bunch operation

Supported by SciDAC

Beam-Beam Simulations(cont.)

0.5

1

1.5

2

2.5

2 3 4 5 6 7 8

electron current (A)

lum

i (n

orm

)

Old Working Point

New Working Point

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

1 1.5 2 2.5 3 3.5 4

proton current (A)

lum

i (n

orm

)

old Working Point

New Working Point

0.6

0.625

0.65

0.675

0.7

0.725

0.75

0.775

0.8

0 1000 2000 3000 4000 5000 6000turns

lum

i (no

rm)

4IPs, 12 bunches/beam


Page 25

ELIC Additional Key Issues

• To achieve luminosity at 1033 cm-2 sec-1 and up High energy electron cooling

• To achieve luminosity at ~ 1035 cm-2 sec-1

Circulator Cooling

Crab cavity

Stability of intense ion beams

Detector R&D for high repetition rate (1.5 GHz)


Page 26

ELIC R&D: Forming Intense Ion Beam

Use stochastic cooling for stacking and pre-cooling Stacking/accumulation process

Multi-turn (10 – 20) injection from SRF linac to pre-booster Damping of injected beam Accumulation of 1 A coasted beam at space charge limited emittence RF bunching/acceleration Accelerating beam to 3 GeV, then inject into large booster

Ion space charge effect dominates at low energy region Transverse pre-cooling of coasted beam in collider ring (30 GeV)

Parameter Unit Value

Beam Energy MeV 200

Momentum Spread % 1

Pulse current from linac mA 2

Cooling time s 4

Accumulated current A 0.7

Stacking cycle duration Min 2

Beam emittance, norm. μm 12

Laslett tune shift 0.03

Transverse stochastic cooling of coasted proton beam after injection in collider ring

Parameter Unit Value

Beam Energy GeV 30

Momentum Spread % 0.5

Current A 1

Freq. bandwidth of amplifiers GHz 5

Minimal cooling time Min 8

Initial transverse emittance μm 16

IBS equilibrium transverse emitt. μm 0.1

Laslett tune shift at equilibrium 0.04

Stacking proton beam in pre-booster with stochastic cooling


Page 27

Injector and ERL for Electron Cooling

• ELIC CCR driving injector 30 mA@15 MHz, up to 125 MeV energy, 1 nC bunch charge, magnetized

• Challenges Source life time: 2.6 kC/day (state-of-art is 0.2 kC/day)

source R&D, & exploiting possibility of increasing evolutions in CCR High beam power: 3.75 MW Energy Recovery

• Conceptual design High current/brightness source/injector is a key issue of ERL based light source

applications, much R&D has been done We adopt light source injector as initial baseline design of ELIC CCR driving

injector

• Beam qualities should satisfy electron cooling requirements (based on previous computer simulations/optimization)

500keV DC gun

solenoids

buncher

SRF modules

quads


Page 28

Electron Cooling with a Circulator Ring.Effective for heavy ions (higher cooling rate), difficult for protons.

State-of-Art• Fermilab electron cooling demonstration (4.34 MeV, 0.5 A DC)

• Feasibility of EC with bunched beams

remains to be demonstrated

ELIC Circulator Cooler• 3 A CW electron beam, up to 125 MeV

• SRF ERL provides 30 mA CW beam

• Circulator cooler for reducing average current from source/ERL

• Electron bunches circulate 100 times in

a ring while cooling ion beam

• Fast (300 ps) kicker operating at 15 MHz

rep. rate to inject/eject bunches into/out circulator-cooler ring


Page 29

Fast Kicker for Circulator Cooling Ring• Sub-ns pulses of 20 kW and 15 MHz are

needed to insert/extract individual bunches.

• RF chirp techniques hold the best promise of generating ultra-short pulses. State-of-Art pulse systems are able to produce ~2 ns, 11 kW RF pulses at a 12 MHz repetition rate. This is very close to our requirement, and appears to be technically achievable.

• Helically-corrugated waveguide (HCW) exhibits dispersive qualities, and serves to further compress the output pulse without excessive loss. Powers ranging from up10 kW have been created with such a device.

Estimated parameters for the kicker

Beam energy MeV 125

Kick angle 10-4 3

Integrated BdL GM 1.25

Frequency BW GHz 2

Kicker Aperture Cm 2

Peak kicker field G 3

Kicker Repetition Rate

MHz 15

Peak power/cell KW 10

Average power/cell W 15

Number of cells 20 20

kicker

kicker

• Collaborative development plans include studies of HCW, optimization of chirp techniques, and generation of 1-2 kW peak output powers as proof of concept.

• Kicker cavity design will be considered


Page 30

Cooling Time and Ion Equilibrium

* max.amplitude** norm.,rms

Cooling rates and equilibrium of proton beam

yx /

Parameter Unit Value Value

Energy GeV/MeV

30/15 225/123

Particles/bunch 1010 0.2/1

Initial energy spread* 10-4 30/3 1/2

Bunch length* cm 20/3 1

Proton emittance, norm* m 1 1

Cooling time min 1 1

Equilibrium emittance , ** m 1/1 1/0.04

Equilibrium bunch length** cm 2 0.5

Cooling time at equilibrium min 0.1 0.3

Laslett’s tune shift (equil.) 0.04 0.02

Multi-stage cooling scenario:

• 1st stage: longitudinal cooling at injection energy (after transverses stochastic cooling)

• 2nd stage: initial cooling after acceleration to high energy

• 3rd stage: continuous cooling in collider mode


Page 31

ELIC R&D: Crab Crossing High repetition rate requires crab crossing to avoid parasitic beam-

beam interaction Crab cavities needed to restore head-on collision & avoid luminosity

reduction Minimizing crossing angle reduces crab cavity challenges & required

R&D

State-of-art:

KEKB Squashed cell@TM110 Mode

Crossing angle = 2 x 11 mrad

Vkick=1.4 MV, Esp= 21 MV/m


Page 32

Crab cavity development Electron: 1.2 MV – within state of art (KEK, single Cell, 1.8 MV)Ion: 24 MV (Integrated B field on axis 180G/4m)

Crab Crossing R&D program – Understand gradient limit and packing factor – Multi-cell SRF crab cavity design capable for high

current operation.– Phase and amplitude stability requirements – Beam dynamics study with crab crossing

ELIC R&D: Crab Crossing (cont.)


Page 33

ELIC at JLab Site

920 m360 m

WMSymantec

SURA

City of NN

VA State

City of NN

JLab/DOE


Page 34

Summary

The ELIC Design Team has continued to make progress on the ELIC design More complete beam optics Chromaticity correction Crab crossing and crab cavity reduction Beam-beam effects

The ELIC design has evolved CW electron cooling with circulator ring Ions up to lead now in design

We continue design advances/optimization Resolve (design) high rep.rate issue (high lumi vs detector) Minimize quantum depolarization of electrons (spin matching) Study ion stability


Page 35

Zeroth–Order

Design Report

for the

Electron-Ion Collider

at CEBAF A. Afanasev, A. Bogacz, P. Brindza, A. Bruell, L. Cardman, Y. Chao, S. Chattopadhyay, E. Chudakov, P. Degtiarenko, J. Delayen, Ya. Derbenev, R. Ent, P. Evtushenko, A. Freyberger, D. Gaskell, J. Grames, A. Hutton, R. Kazimi, G. Krafft, R. Li, L. Merminga, J. Musson, M. Poelker, A. Thomas, C. Weiss, B. Wojtsekhowski, B. Yunn, Y. Zhang Thomas Jefferson National Accelerator Facility Newport News, Virginia, USA W. Fischer, C. Montag Brookhaven National Laboratory Upton, New York, USA V. Danilov Oak Ridge National Laboratory Oak Ridge, Tennessee, USA V. Dudnikov Brookhaven Technology Group New York, New York, USA P. Ostroumov Argonne National Laboratory Argonne, Illinois, USA

V. Derenchuk

Indiana University Cyclotron Facility Bloomington, Indiana, USA

A. Belov

Institute of Nuclear Research http://c

asa.jlab.org/re

search/elic/elic_zdr.doc

Documents

Thomas Jefferson National Accelerator Facility Page 1 Design Status of ELIC G. A. Krafft for ELIC Design Team EIC Collaboration meeting Hampton, May 19-23,