[PPT] - Medium-energy Electron Ion Collider (MEIC) Project at Jefferson Lab PowerPoint Presentation

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Informal JLab seminar, December 9, 2015 Vasiliy Morozov for MEIC design team

Medium-energy Electron Ion Collider (MEIC) Project at Jefferson Lab

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Outline

Introduction

– EIC purpose – JLab’s approach to the design – MEIC design overview

Electron complex

– CEBAF as a full-energy injector – Electron collider ring – Electron polarization

Ion complex

– Ion injector complex – Ion collider ring – Electron cooling – Ion polarization

Detector region

– Detector design and integration – Forward detection – Crab crossing

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MEIC Study Group

A. Bogacz, P. Brindza, A. Camsonne, E. Daly, Ya.S. Derbenev, M. Diefenthaler, D. Douglas,
R. Ent, Y. Furletova, D. Gaskell, R. Geng, J. Grames, J. Guo, L. Harwood, T. Hiatt, Y. Huang,
A. Hutton, K. Jordan, G. Kalicy, A. Kimber, G. Krafft, R. Li, F. Lin, T. Michalski, V.S. Morozov,
P. Nadel-Turonski, H.K. Park, F. Pilat, M. Poelker, R. Rimmer, Y. Roblin, T. Satogata, M. Spata, R.

Suleiman, A. Sy, C. Tennant, H. Wang, S. Wang, C. Weiss, H. Zhang, Y. Zhang, Z. Zhao – JLab, Newport News, VA D.P. Barber – Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany

A. Kondratenko, M. Kondratenko – Sci. & Tech. Laboratory Zaryad, Novosibirsk, Russia
Yu. Filatov – MIPT, Dolgoprydny, Russia and JINR, Dubna, Russia
P. N. Ostroumov – Argonne National Laboratory, Argonne, IL
S. Abeyratne, B. Erdelyi – Northern Illinois University, DeKalb, IL
A. Castilla, J. Delayen, C. Hyde, K. Park, B. Terzic – Old Dominion University, Norfolk, VA
Y. Cai, Y.M. Nosochkov, M. Sullivan, M-H Wang, U. Wienands – SLAC, Menlo Park, CA
J. Gerity, T. Mann, P. McIntyre, N.J. Pogue, A. Sattarov – Texas A&M Univ., College Station, TX

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Electron Ion Collider

Recommendations in NSAC LRP 2015:

1. Continue existing projects: CEBAF, FRIB, RHIC. 2. “…a U.S.-led ton-scale neutrinoless double beta decay experiment” 3. “…a high-energy high-luminosity polarized EIC as the highest priority for new facility construction following the completion of FRIB” 4. “…small-scale and mid-scale projects and initiatives that enable forefront research at universities and laboratories”

EIC Community White Paper arXiv:1212.1701

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EIC Physics Highlights

An EIC aims to study the sea quark and gluon-dominated matter

– 3D structure of nucleons

§ How do gluons and quarks bind into 3D hadrons?

– Role of orbital motion and gluon dynamics in the proton spin

§ Why do quarks contribute only ~30%?

– Gluons in nuclei (splitting/recombining)

§ Does the gluon density saturate at small x?

Need luminosity, polarization and good acceptance to detect spectator & fragments

P. Nadel-Turonski

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(M)EIC Realization Imagined

Shown as most optimistic (wishful) schedule
Start EIC construction after FRIB completion
Fixed-target 12 GeV CEBAF operations can

continue throughout the construction period

Assumes endorsement for an EIC at the next

(this) NSAC Long Range Plan (came true)

Assumes relevant accelerator R&D for down-

select process done around 2016/17

CD3 is year when long-lead

procurements can start, we think this is FY20 at the earliest.

The EIC TPC and an assumed 15

year of operations ($117M/yr in FY15$) would be of similar cost as the CEBAF 4-6 GeV life cycle costs: $3.24B vs. $2.98B.

Nuclear Physics can afford this.
EIC Cost Review

suggested a TPC of $1,500M for a generic EIC including detector

Design studies continue

for reduction of the TPC below this

The relatively low

technical risk of the MEIC design requires

nly minor investments

in pre-R&D

Year 4 ~ CD3 FY20? Year 12 ~ CD4 FY28?

F. Pilat at Spring 2015 MEIC Collaboration Meeting

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MEIC Design Parameters

Energy

– Full coverage of √s from 15 to 65 GeV – Electrons 3 -10 GeV, protons 20 -100 GeV, ions 12 - 40 GeV/u

Ion species

– Polarized light ions: p, d, 3He, and possibly Li – Un-polarized light to heavy ions up to A above 200 (Au, Pb)

Space for at least 2 detectors

– Full acceptance is critical for the primary detector

Luminosity

– 1033 to 1034 cm-2s-1 per IP in a broad CM energy range

Polarization

– At IP: longitudinal for electrons, longitudinal or transverse for ions – All polarizations >70%

Upgrade to higher energies and luminosity possible

– 250 GeV proton, and 100 GeV/u ion

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Design Strategy for High Luminosity

The MEIC design concept for high luminosity is based on high bunch

repetition rate CW colliding beams

Beam Design

High repetition rate
Low bunch charge
Short bunch length
Small emittance

IR Design

Small β*
Crab crossing

Damping

Synchrotron

radiation

Electron cooling

“Traditional” hadrons colliders

Small number of bunches
Small collision frequency f
Large bunch charge n1 and n2
Long bunch length
Large beta-star

1 2 1 2 *

~ 4

x y y

n n n n L f f πσ σ εβ

∗ ∗

=

KEK-B already reached above 2x1034 /cm2/s Linac-Ring colliders

Large beam-beam parameter for the

electron beam

Need to maintain high polarized electron

current

High energy/current ERL

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MEIC Layout & Detector Location

Warm Electron Collider Ring (3 to 10 GeV) Cold Ion Collider Ring (8 to 100 GeV)

Two IP locations:

One has a new detector, fully instrumented Second is a straight-through, minor additional magnets needed to turn into IP

Considerations:

Minimize synchrotron radiation – IP far from arc where electrons exit – Electron beam bending minimized in the straight before the IP Minimize hadronic background – IP close to arc where protons/ions exit

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JLAB Campus Layout

~2.2 km circumference E-ring from PEP-II Ion-ring with 3 T super-ferric magnets Tunnel consistent with a 250+ GeV upgrade

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CEBAF - Full Energy Injector

new 5 cryomodules new 5 cryomodules

CEBAF fixed target program

– 5-pass recirculating SRF linac – Exciting science program beyond 2025 – Can be operated concurrently with the MEIC

CEBAF will provide for MEIC

– Up to 12 GeV electron beam – High repetition rate (up to 1497 MHz) – High polarization (>85%) – Good beam quality up to the mA level

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Electron Collider Ring Layout

Circumference of 2154.28 m = 2 x 754.84 m arcs + 2 x 322.3 straights Figure-8 crossing angle 81.7°

e-

Arc, 261.7°

81.7° Forward e- detection

IP

Future 2nd IP Electron collider ring w/ major machine components

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MEIC Electron Complex

IP Dx(m) βx(m), βy(m) Electron Collider Ring Optics

CEBAF provides up to 12 GeV, high repetition rate and high polarization (>85%) electron beams, no further upgrade needed beyond the 12 GeV CEBAF upgrade Electron collider ring design

– Meets design requirements – Circumference of 2154.28 m = 2 x 754.84 m arcs + 2 x 322.3 m straights – Provides longitudinal electron polarization at IP(s) – Incorporates forward electron detection – Accommodates up to two detectors – Incorporates correction of beam nonlinearity – Reuses PEP-II magnets, vacuum chambers and RF

Beam characteristics

– 3A beam current up to 6.95 GeV – Normalized emittance 1093 um @ 10 GeV – Synchrotron radiation power density 10kW/m – Total power 10 MW @ 10 GeV

CEBAF and electron collider provide the required electron beams for the MEIC

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e- Inj. from CEBAF to Electron Ring

Electron injection bunch pattern (@6 GeV) from CEBAF with

– fring/ fcebaf = 476.3MHz/1497MHz = 7/22 – Two polarization states injection – Existing CEBAF source gun

Transfer line 333.25m utilizes PEP-II LER dipoles (156) and quads (68) Injection scheme starts with PEP-II-like design

– Dispersion free injection insertion – Septum + DC + RF kickers – Vertical injection because of greater dynamic aperture, absence

f synchrotron oscillations and less

3416*10.5turns/476.3MHz=75.3ms

14.69 ns, 68.05 MHz (7 ring buckets)

220 bunches, 3.233µs (Iave= 0.9mA @6GeV CEBAF) Bunch train, up polarization

……

Bunch train, down polarization

Waiting for 72.07µs

Mid-cycle 1, inject the 1st of every 7 buckets in the ring

13 pC bunch ……

Waiting for damping 12-700ms

2ns, 476.3 MHz(ring freq.)

12-700ms, ~2× e-ring damping time at different energy

Injection Time and Beam Current vs. Energy

nominal Synchrotron power limit Impedance limit

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Electron Polarization

Comprehensive electron polarization strategies:

– Vertically-injected polarized electron beam from CEBAF – Vertical polarization in the arcs (to avoid spin diffusion) and longitudinal at collision points – Spin rotator for the polarization rotation – Spin flipping through changing the source polarization – Polarization configuration with figure-8 geometry removes electron spin tune energy dependence – Compton polarimeter has been integrated to the interaction region design and is considered to measure the electron polarization – Spin matching in some key regions is considered to further improve polarization lifetime

IP

e-

Magnetic field Polarization Half Sol. Half Sol.

Dec. Quad. Insert

Solenoid decoupling

νc Laser + Fabry Perot cavity e- beam Low-Q2 tagger for low-energy electrons Low-Q2 tagger for high- energy electrons Electron tracking detector Photon calorimeter

IP

Energy (GeV) 3 5 7 9 10 Estimated Pol. Lifetime (hours) 66 5.2 2.2 1.3 0.8

H. Sayed, A. Bogacz

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Ion Injector Complex Overview

Ion injector complex relies on demonstrated technologies for sources and injectors

– ABPIS for polarized or unpolarized light ions, EBIS and/or ECR for unpolarized heavy ions – Design for an SRF linac based on the ANL linac for FRIB – 8 GeV Booster design to avoid transition for all ion species and based on super-ferric magnet technology – Injection/extraction lines to/from Booster are designed

Ion Sources SRF Linac (285 MeV) Booster (8 GeV) (accumulation)

DC e-cooling

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Ion Linac – Parameters and Layout

Optimum lead stripping energy: 13 MeV/u 10 cryostats 4 cryostats 2 Ion Sources

QWR QWR HWR IH RFQ MEBT

10 cryos 4 cryos

2 cryos Ion species: p to Pb Ion species for the reference design

208Pb

Kinetic energy (p, Pb) 285 MeV 100 MeV/u Maximum pulse current: Light ions (A/Q<3) Heavy ions (A/Q>3) 2 mA 0.5 mA Pulse repetition rate up to 10 Hz Pulse length: Light ions (A/Q<3) Heavy ions (A/Q>3) 0.50 ms 0.25 ms Maximum beam pulsed power 680 kW Fundamental frequency 115 MHz Total length 121 m

Linac design based on the ANL linac for FRIB. Pulsed linac capably of accelerating multiple charge ion species (H- to Pb67+) – Warm Linac sections (115 MHz)

RFQ (3 m)
MEBT (3 m)
IH structure (9 m)

– Cold Linac sections

QWR + QWR (24 + 12 m) 115 MHz
Stripper, chicane (10 m) 115 MHz
HWR section (60 m) 230 MHz

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Booster

Straight

Inj. Arc

(2550) Straight (RF + extraction) Arc (2550)

=

56

273 M cm

272.306 70 6

6

BETA_X&Y[m] DISP_X&Y[m] BETA_X BETA_Y DISP_X DISP_Y

A. Bogacz

extraction

RF cavity

Crossing angle: 75 deg.

Ekin = 285 MeV – 8 GeV

injection

8 GeV Booster serves for

– Accumulation of ions injected from Linac – Cooling – Acceleration of ions – Extraction and transfer of ions to the collider ring

Injection: multi-turn 6D painting

– 0.22 – 0.25 ms long pulses ~180 turns – Proton single pulse charge stripping at 285 MeV – Ion 28-pulse drag-and-cool stacking at 100MeV/u – Ion energies scaled by mass-to-charge ratio to preserve magnetic rigidity

Design

– Circumference of 273 m – Super-ferric magnets – No transition energy crossing – Figure-8 shape for preserving ion polarization

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Figure-8 ring with a circumference of 2153.9 m Two 261.7° arcs connected by two straights crossing at 81.7°

Ion Collider Ring Layout

R = 155.5 m Arc, 261.7°

IP ions

81.7°

future 2nd IP

Polarimeter

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Ion Collider Ring

~2.2 km circumference to match the geometry of PEP-II-component-based electron ring Use Super-ferric magnets

– ~3 T maximum field for maximum proton momentum of 100 GeV/c, 4.2 K operating temperature – Cost effective construction and operation (factor of ~2 cheaper to operate, GSI)

Ion collider ring design

– Has an arc FODO cell § length of 22.8 m (1.5 x PEP-II FODO cell) § optimized for an 8m long SF dipole magnet – Provides high polarization adjustable to any

rientation at IP(s)

– Incorporates forward ion detection – Accommodates up to two detectors – Incorporates correction of beam nonlinearity

Ion collider ring design meets the design requirements

βx(m), βy(m) Ion Collider Ring Optics IP Dx(m)

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MEIC Super-Ferric Dipole

2 x 4 long dipole 3 T Correction sextupole Common cryostat Rutherford-based design CIC-based design

P. McIntyre and colleagues, Texas A&M Univ.

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Chromaticity Compensation Scheme

Compensation of momentum dependence of betatron tunes (primarily due to strong focusing at IP) using properly-phased sextupole families

– FFB focusing is momentum dependent – Sextupole focusing is transverse position dependent – Create momentum-correlated transverse position inside sextupoles, i.e. dispersion – Use additional sextupoles to compensate effect on the non-correlated position component

Distributed sextupole compensation strategy

– Build-up chromatic β wave in the arcs to cancel FFB’s chromatic kick

§ Two sextupole families, each with an even number of magnets § π phase advance between individual sextupoles of each family § nπ+π/2 phase advance from the last sextupole of each family to IP

– Compensation of 1/6 residual linear chromaticity

§ Two sextupole families, each with a multiple of 4 magnets

FFB IP FFB

nπ nπ π π π/2 π/2 … … … …

nπ+ π/2 nπ+ π/2

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Chromaticity Compensation

–I sextupoles pairs in the arcs Compensate momentum dependence of the beam size (~ to W function) at the IP (equivalent to compensating the momentum-dependent FFB focusing) Control the global dependence of the betatron tunes on momentum (chromaticities) with additional sextupoles

IP

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Momentum Acceptance & DA

Dependence of the betatron tunes on momentum Dynamic aperture: region of stable motion in the transverse plane

(- 8σΔp/p , + 13σΔp/p)

Δp/p = 0 Δp/p = 0.3% Δp/p = -0.3%

> (±70σ) in x & y

G. Wei

at IP

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Misalignment & Strength Errors

Dipole Quadrupole [FFQ] Sextupole BPM noise Corrector σx (mm) 0.3 0.3 [0.03] 0.3 0.02

σy (mm)

0.3 0.3 [0.03] 0.3 0.02

rms roll (mrad)

0.3 0.3 [0.05] 0.3

0.3

σs (mm) 0.3 0.3 [0.03] 0.3

Strength error (%)

0.1 0.2 [0.03] 0.2

0.01
G. Wei

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Orbit Correction

Thread the beam through, find closed orbit and minimize distortion using BPMs and correctors

G. Wei

5×10-6 5×10-6 < 4×10-4 < 1×10-4

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Dynamic Aperture Correction

Correct: orbit, beta-beat, tune, chromaticity, and coupling

G. Wei

Δp/p = 0 Δp/p = 0.3% Δp/p = -0.3%

> (±70σ) in x & y at IP Before ~(±50σ) in x & y at IP

Δp/p = 0 different seeds

After

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Magnet Multipole Effect

Nominal systematic multipoles of super-ferric arc dipoles Apply them to all dipoles in the ion ring

G. Wei

Multipole errors of super-ferric dipole at radius 20 mm (unit: 10^-4) multipole type systematic

0.151 -0.537 0.126 0.850 0.714 0.366 -0.464 -0.410 0.009 0.027

Random

Without multipoles With multipoles

Δp/p = 0 Δp/p = 0.3% Δp/p = -0.3%

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Magnet Multipole Effect

Different categories of magnets Different specifications for different categories

G. Wei

D Q S ALL 133 205 75 IR area, β > 1 km 2 6 β > 200 m 21 19 8

nly β < 1 km

> (±20σ) in x & y

nly β < 200 m

~ (±50σ) in x & y

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Time between collisions:

Synchronized Beams

i i e e i e i i i e

c c L L T T n c n c T λ λ β β = = = = = =

Ions Electrons

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Issue: energy-dependence of ion velocity desynchronizes ions with electrons Suppose ion energy set significantly lower:

Desynchronization

i i e e i e i i i e

c c c L c L T T n n λ λ β β = = ≠ = =

Ions Electrons

i i

β β <

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Ion path length change such that

One Synchronization Option

i i e e i i e i i i e

L L T T T n n c c c c λ λ β β = = = = = =

Ions Electrons

,

i i i i

L L β β < <

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Harmonic jump such that

Harmonic Jump at “Magic” Energies

i i e e i e i i i i e

L L T T T c c n c c n λ λ β β = = = = = =

Ions Electrons

,

i i i i

n n β β < >

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100 GeV/c protons: L = 2153.78 m, f = 476.3 MHz, h = 3422 (bunch spacing = 62.94 cm) Observations – A path-length chicane probably not practical without harmonic jump for the whole momentum range – When moving whole arcs without harmonic jump § Maximum transverse shift ΔR = ΔL / θ = 24.9 cm where θ = 523.4° § With ~256 gaps between arc dipoles and quadrupoles, max gap change = 8.9 mm – When moving whole arcs with harmonic jump § ΔR = (bunch spacing) / θ = 69 mm § Max gap change = 2.5 mm

Synchronization Parameters

p (GeV/c) β Without harmonic jump With harmonic jump h Δl (m) Δf (MHz) h Δl (m) Δf (MHz) 100 0.999956 3422 0.0000 0.0000 3422 0.0000 0.0000 90 0.999946 3422

0.0222
0.0049

3422

0.0222
0.0049

80 0.999931 3422

0.0533
0.0118

3422

0.0533
0.0118

70 0.99991 3422

0.0987
0.0218

3422

0.0987
0.0218

60 0.999878 3422

0.1685
0.0373

3422

0.1685
0.0373

50 0.999824 3422

0.2843
0.0629

3422

0.2843
0.0629

40 0.999725 3422

0.4975
0.1100

3423 0.1317 0.0291 30 0.999511 3422

0.9579
0.2118

3424 0.3004 0.0664 20 0.998901 3422

2.2715
0.5023

3426 0.2434 0.0538

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Synchronization – highly desirable – Smaller magnet movement: ±(bunch spacing)/2 – Smaller RF adjustment Detection and polarimetry – highly desirable – Cancellation of systematic effects associated with bunch charge and polarization variation – great reduction of systematic errors, sometimes more important than statistics – Simplified electron polarimetry – only need average polarization, much easier than bunch-by-bunch measurement Dynamics – question – Possibility of an instability – needs to be studied Luminosity reduction by about twice the beam gap size (instead of one)

Implications of Harmonic Jump

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Linear Simulation Results

Raising number of bunches in linear simulation quickly produced instabilities – as low as N=(10,11)! – A verification but of course many details left out

ξ1,2 = 0.003

T. Satogata

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Things Missing…

Linear model doesn’t look good BUT – MEIC is strong focusing (transverse and longitudinal, e and p) – Landau damping may damp instabilities faster than even the pessimistic growth rates § Typical damping times are o(1/σQ) (chromatic dominates nonlinear) § Hadron rebunching should be performed without e- beam § Nonlinear beam-beam tune spread may help Many dynamical effects were not included in H/L/P paper – Nonlinear beam transport – 6D effects (e.g. chromatic tune spread, tune modulation) – Higher order moment instabilities – Assumed only round beams

T. Satogata

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More realistic simulation needed by challenging

– In case of MEIC, 1 turn = ~3000 beam-beam interactions + non-linear dynamics – Non of the existing codes seem adequate

Developing a new code GHOST in collaboration with ODU

– Accuracy: high-order transfer map, symplecticity, bunch slicing – Speed: Bassetti-Erskine solution for each pair of slices, single-term map, GPU

Simulating Non-Pair-Wise Collisions

B. Terzic et al.

GHOST & BeamBeam3D, 10 cm bunch 40k particles

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Pivoting Electron Chicane

Magnets are connected rigidly in each half of the chicane, each half is rotated about the respective chicane end point, path length is adjusted by changing the spacing between the two central dipoles Maximum path-length change with five FODO cells is 29.0 cm Change in distance between the central dipoles 2×14.5 cm Maximum radial shift is 1.48 m

1.48 m +29 cm

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Multi-Step Electron Cooling Scheme

DC cooling for emittance reduction BBC cooling for emittance preservation

ion sources ion linac Booster (0.285 to 8 GeV) collider ring (8 to 100 GeV) BB cooler DC cooler

Ring Cooler Function Ion energy Electron energy

GeV/u MeV Booster ring DC Injection/accumulation of positive ions 0.11 ~ 0.19 (injection) 0.062 ~ 0.1 Emittance reduction 2 1.1 Collider ring Bunched Beam Cooling (BBC) Maintain emittance during stacking 7.9 (injection) 4.3 Maintain emittance Up to 100 Up to 55

d z cool 4 2

~ ε σ γ γ γ τ Δ

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Bunched Beam Electron Cooler

Baseline cooling requirements

– Emittance 0.5 to 1 mm-mrad -> reduce IBS effect – Magnetized beam, up to 55 MeV energy, 200 mA current – Linac for acceleration – Must utilize energy-recovery-linac (beam power is 11 MW)

Solution : cooling by a bunched electron beam

ion bunch electron bunch Cooling section solenoid SRF Linac dump injector energy recovery Electron energy MeV up to 55 Current and bunch charge A / nC 0.2 / 0.42 Bunch repetition MHz 476 Cooling section length m 60 RMS Bunch length cm 3 Electron energy spread 10-4 3 Cooling section solenoid field T 2 Beam radius in solenoid/cathode mm ~1 / 3 Solenoid field at cathode KG 2

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Spin tune (number of spin precession per turn) in a conventional ring A spin resonance occurs whenever the spin precession becomes synchronized with the frequency of spin perturbing fields – Imperfection resonances due to alignment and field errors – Intrinsic resonances due to betatron oscillations – Coupling and higher-order resonances

Ion Polarization: Spin Resonances

, 1.793, 0.143

s p d

G G G ν γ = ≈ ≈ − 0.523 GeV 13.12 G V , , e

s d p

n n n E E ν = = =

s y

n ν ν = ±

s x y s

n m l k ν ν ν ν + + = +

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Booster Ep = 1.22 – 8 GeV, Ed = 2.03 – 8.16 GeV

– Protons

§ ~13 imperfection resonances § ~26 intrinsic resonances

– Deuterons

§ 0 imperfection resonances § 1 or 2 intrinsic resonances

Collider ring Ep = 8 – 100 GeV, Ed = 8.16 – 100 GeV

– Protons

§ ~175 imperfection resonances § ~350 intrinsic resonances

– Deuterons

§ 7 imperfection resonances § ~12 intrinsic resonances

Spin Resonances in Racetrack

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Device rotating the spin by some angle about an axis in horizontal plane

– A “full” Siberian snake rotates the spin by 180° – Overcomes all imperfection and most intrinsic resonances

Spin tune with a snake Solenoidal snake at low energies Dipole snake at high energies

Siberian Snake

1

1 cos cos( )cos 2 1/ 2

s s

G φ ν γπ π φ π ν

− ⎡

⎤ = ⎢ = ⇒ ⎥ ⎣ ⎦ =

|| ||

(1 ) / , 9 GeV/c 34 T m for and 110 T m for Ze G B ds p p B ds p d φ φ π = + = = ⇒ ≈ ⋅ ⋅

∫ ∫

(1 ) , at 100 GeV/c, 5.5 T m for and 158 T m for Ze G B ds B ds p d p γ φ

⊥ ⊥

+ = = ⋅ ⋅

∫ ∫

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Figure-8 shape has been chosen for all MEIC rings to achieve high ion (and electron) polarization

– Spin precession in one arc is exactly cancelled in the other – Zero spin tune independent of energy – Spin control and stabilization with small solenoids or other compact spin rotators

Advantages of the figure-8 scheme for ions

– Efficient preservation of ion polarization during acceleration

§ Energy-independent spin tune § High polarization of all light ions

– Ease of spin manipulation

§ Any desired polarization orientation at the IP § Spin flip

– A simple way to accommodate polarized deuterons

§ Particles with small anomalous magnetic moment

– Spin control without affecting the beam dynamics

Figure-8 Concept

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Polarization in Booster stabilized and preserved by a single weak solenoid

– 0.7 Tm at 9 GeV/c – νd / νp = 0.003 / 0.01

Longitudinal polarization in the straight with the solenoid Conventional 9 GeV accelerators require B||L of ~30 Tm for protons and ~110 Tm for deuterons

Pre-Acceleration & Spin Matching

beam from Linac

Booster

to Collider Ring BIIL

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“3D spin rotator” rotates the spin about any chosen direction in 3D and sets the stable polarization orientation nx control module (constant radial orbit bump) ny control module (constant vertical orbit bump) nz control module

Polarization Control in Collider

y

ϕ

1 z

ϕ

IP ( )

z y x

n n n S , , =

Control of radial (nx)

spin component Control of vertical (ny) spin component Control of longitudinal (nz) spin component

y

ϕ 2 −

y

ϕ

1 z

ϕ −

2

1 z

ϕ − 2

1 z

ϕ

z x

x

ϕ −

2 z

ϕ

x

ϕ 2

x

ϕ −

2 z

ϕ −

2

2 z

ϕ − 2

2 z

ϕ

z y

3

2

z

ϕ

1

sin

x z y

n ϕ πν ϕ =

6 m, 12 mm L x Δ = ≈

2

sin

y z x

n ϕ πν ϕ =

3 z z

n ϕ πν =

6 m, 12 mm L y Δ = ≈ 2.4 m L ≈

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Placement of the 3D spin rotator in the collider ring Integration of the 3D spin rotator into the collider ring’s lattice

– Seamless integration into virtually any lattice

Another 3D spin rotator suppresses the zero-integer spin resonance strength

Polarization Control in Collider

IP

Spin-control solenoids Vertical-field dipoles Radial-field dipoles Lattice quadrupoles

, 4

0.6m 1.2m 3 T, / · 1 3.6 T 0.01/ .5 0 2

x y z x y z p d

L L L B B ν ν

−

= = = < < =

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MEIC lattice, no errors, 60 GeV/c proton, initial spin nz = 1, reference orbit Proton on one-sigma phase-space trajectories in both x and y

Spin-Tracking Perfect Figure-8 Ring

using Zgoubi in collaboration with F. Meot

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One arc dipole rolled by 0.2 mrad, no closed orbit correction After addition of a 1° spin rotator solenoid in the straight

Error Effect and Correction

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With 0.2 mrad dipole roll, no orbit correction, no spin rotator, 200⋅103 turns After addition of a 5° spin rotator in the straight , 300⋅103 turns

Acceleration

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50 mrad crossing angle

– Improved detection, no parasitic collisions, fast beam separation

Forward hadron detection in three stages

– Endcap – Small dipole covering angles up to a few degrees – Far forward, up to one degree, for particles passing through accelerator quads

Low-Q2 tagger

– Small-angle electron detection

Full-Acceptance Detector

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Detector Modeling & Machine Integration

Fully-integrated detector and interaction region satisfying

– Detector requirements: full acceptance and high resolution – Beam dynamics requirements: consistent with non-linear dynamics requirements – Geometric constraints: matched collider ring footprints

far forward hadron detection low-Q2 electron detection large-aperture electron quads small-diameter electron quads central detector with endcaps ion quads 50 mrad beam (crab) crossing angle

n, γ e p p

small angle hadron detection ~60 mrad bend

(from GEANT4)

2 Tm dipole Endcap Ion quadrupoles Electron quadrupoles 1 m

1 m IP FP Roman pots Thin exit windows Fixed trackers Trackers and “donut” calorimeter

RICH + TORCH? dual-solenoid in common cryostat 4 m coil barrel DIRC + TOF EM calorimeter EM calorimeter

Tracking

EM calorimeter e/π threshold Cherenkov

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Forward Hadron Detection

Large crossing angle (50 mrad)

– Moves spot of poor resolution along solenoid axis into the periphery – Minimizes shadow from electron FFQs

Dipole before quadrupoles

– Further improves resolution in the few-degree range

Low-gradient quadrupoles

– Allow large apertures for detection of all ion fragments

89 T/m, 9.0 T, 1.2 m 51 T/m, 9.0 T, 2.4 m 36 T/m, 7.0 T, 1.2 m

Permanent magnets

34 T/m 46 T/m 38 T/m 2 x 15 T/m e 5 T, 4 m dipole

Ion quadrupoles: gradient, peak field, length

2 T dipole Endcap detectors Electron quadrupoles

Tracking Calorimetry

1 m 1 m

7 m from IP to first ion quad

Crossing angle

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Far-Forward Hadron Detection

Good acceptance for ion fragments

– Large downstream magnet apertures/ small downstream magnet gradients

Good acceptance for low-pT recoil baryons

– Small beam size at second focus – Large dispersion

Good momentum and angular resolution

– Large dispersion – No contribution from Dʹ to angular spread at IP – Long instrumented magnet-free drift space

Sufficient separation between the beam lines

e p (n, γ)

20 Tm dipole (in) 2 Tm dipole (out)

solenoid

Roman pots at focal point Thin exit windows Aperture-free drift space ZDC S-shaped dipole configuration

ptimizes acceptance for neutrals

50 mrad crossing angle

Ions x IP FP βx* = 10-20 cm βy* = 2 cm D* = D'* = 0 βFP < 1 m DFP ~ 1 m

Asymmetric IR (minimizes chromaticity)

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Far-Forward Acceptance

Δp/p = -0.5 Δp/p = 0.0 Δp/p = 0.5

(protons rich fragments) (exclusive / diffractive recoil protons) (tritons from N=Z nuclei) (spectator protons from deuterium) (neutron rich fragments)

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Far-Forward Ion Acceptance

Transmission of particles with initial angular and Δp/p spread vs peak field

– Quad apertures = B max / (fixed field gradient @ 100 GeV/c) – Uniform particle distribution of ±0.7 in Δp/p and ±1° in horizontal angle originating at IP – Transmitted particles are indicated in blue (the box outlines acceptance of interest)

6 T max 9 T max 12 T max

← electron beam

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Ion Momentum & Angular Resolution

– Protons with Δp/p spread are launched at different angles to nominal trajectory – Resulting deflection is observed at the second focal point – Particles with large deflections can be detected closer to the dipole

← electron beam

±10σ @ 60 GeV/ c

|Δp/p| > 0.005 @ θx,y = 0

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Forward e- Detection & Polarimetry

Dipole chicane for high-resolution detection of low-Q2 electrons Compton polarimetry has been integrated to the interaction region design

– non-invasive, same polarization as at the IP due to zero net bend

e- ions

IP

forward ion detection forward e- detection Compton polarimetry

local crab cavities local crab cavities local crab cavities

νc

Laser + Fabry Perot cavity e- beam from IP Low-Q2 tagger for low-energy electrons Low-Q2 tagger for high- energy electrons Compton electron tracking detector Compton photon calorimeter Compton- and low-Q2 electrons are kinematically separated! Photons from IP e- beam to spin rotator Luminosity monitor

SLIDE 60

Ion beam quad QIF: 90 T/m, 17 cm half-aperture, 40 cm from e-beam

T

Reverse-current winding kills fringe field at the location of the electron beam.

electron beam

Nb3Sn windings, 6 K

P. McIntyre and colleagues, Texas A&M Univ.

SLIDE 61

Dipole DI: 2 T, 340 mm aperture, 39 cm from the electron beam

m

Window-frame C-geometry dipole configured as a Lambertson septum to suppress fringe field at electron beam.

electron beam T

MgB2 windings, 20 K

P. McIntyre and colleagues, Texas A&M Univ.

SLIDE 62

T

ion beam beam

Quadrupole QE1d: 25 T/m gradient, 60 mm bore, 9 cm from the ion beam

MgB2 windings, 20 K

T

P. McIntyre and colleagues, Texas A&M Univ.

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Coherent orbit excursion (ignored for now in this talk) Transverse betatron coupling

̶ Dynamic effect

§ Coupling resonances § Rotates beam planes at the IP

̶ Spin effect

§ Breaks figure 8 symmetry

̶ Crab crossing

§ Complicates the design if crab cavities are installed in a coupled region

Detector Solenoid Effect

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Detector Solenoid Compensation

The simplest way to compensate coupling of a solenoid is to put an anti-solenoid (a solenoid with a field integral equal in magnitude and opposite in sign) next to it:

The resulting matrix is uncoupled.

This does not work if the anti-solenoid is separated from the solenoid by some non- trivial optics that does not commute with a rotation Let us rotate the insert by The resulting matrix is decoupled.

.

( ) ( ) ( ) ( ) ( ( ) ( ) ( ) )

a sol sol uncpl uncpl uncpl uncpl

M KL R KL R KL KL M KL M KL M KL KL M M − − = − − =

.

( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( )

a sol ins sol uncpl ins uncpl ins ins ins

M KL R KL M R KL KL R KL M R KL M M KL M M KL R KL K M R L M − = − − − ≠ − = ) ( ) : (

ins ins

R KL M R KL M KL − = − %

.

( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ( ) ( ) ( ) )

a sol ins sol uncpl ins uncpl ins ins ins

M KL R KL M R KL KL R KL R KL R KL R KL M M R KL R KL M M KL M KL M M − − − = − − = − = % % %

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Upstream FF as Example

No solenoid

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Upstream FF with Solenoid

3 T solenoid at 8 GeV/c

IP

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Upstream FF with Compensation

Of course, do not want to physically rotate the quads each time; each FF quad is “rotated” by placement of 10 cm skew quads before and after Skew quad fields are almost independent of energy Maximum skew quad strength < 17 T/m

skew quads

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Crab Crossing

π/2 3π/2

Location of crab cavities

Effective head-on bunch collisions restored with 50 mrad crossing angle Local crab scheme Two cavities are placed at (n+1)π/2 phase advance relative to IP Optimal βx at locations of crab cavities for minimizing the required kicking voltage Deflective crabbing using transverse electric field of SRF cavities (as at KEK-B)

− Design and analysis completed − Prototype fabricated and characterized − Final testing with promising results

Multipole Tailoring Beam Dynamics Studies

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Crab Dynamics

First crab cavity generates a (z-x') correlation Phase advance transforms it into a (z-x) correlation at the IP Further phase advance transforms it back into a (z-x') correlation The second crab cavity compensates the (z-x') correlation

z-x phase space without and with crabbing z-x' phase space

incoming after 1st crab at IP before 2nd crab after 2nd crab

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e-p Collision Luminosity

The baseline performance requires a ERL bunched beam cooler but NO circulator cooler 2 4 6 8 10 12 20 30 40 50 60 70

A full acceptance Luminosity CM energy

1034

(baseline)

1034 1033

Design point (CM) p energy (GeV) e- energy (GeV) Main luminosity limitation low 30 4 space charge medium 100 5 beam beam high 100 10 synchrotron radiation

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Conclusions and Outlook

MEIC is a ring-ring collider project with mature design. It can deliver luminosities of up to 1034 in the √s range of 15-65 GeV. It can provide beam polarizations of over 70%. Technical risks are intentionally kept low. The design is upgradable in energy and luminosity. The MEIC baseline design fulfills the white paper requirements. The current design is being further optimized for cost and performance. R&D continues with increasing effort.

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Backup

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JLab MEIC Figure 8 Concept

Initial configuration:

– 3-10 GeV on 20-100 GeV ep/eA collider – Optimized for high ion beam polarization: § polarized deuterons – Luminosity: § up to few × 1034 e-nucleons cm-2 s-1

Low technical risk Upgradable to higher energies

– 20 GeV electrons & 250 GeV protons

Flexible timeframe for construction

– consistent with running 12 GeV CEBAF

Thorough cost estimate completed

– presented to NSAC EIC Review

Cost effective operation

" Fulfills the White Paper Requirements

Jefferson Lab Mission: MEIC

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Design Strategy for High Polarization

Figure-8 shape has been chosen for all rings with the goal of achieving high ion and electron polarization

– Spin precession in one arc is exactly cancelled in the other – Zero spin tune independent of energy – Spin control and stabilization with small solenoids or other compact spin rotators

Advantage 1: Efficient preservation of ion polarization during acceleration

– Energy-independent spin tune – High polarization of all light ions

Advantage 2: Ease of spin manipulation

– Any desired polarization orientation at the IP – Spin flip

Advantage 3: A simple way to accommodate polarized deuterons

– Particles with small anomalous magnetic moment

Advantage 4: Strong reduction of electron depolarization thanks to the energy independent spin tune

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Design Optimization

The MEIC goals, strategy and basic design choices (figure-8, B-factory beam structure for high luminosity for e- and ion rings) have NOT changed since 2006 The goal of cost, performance and upgrade optimization led us to the following implementation:

– A circumference of ~2.2 km will allow:

§ Re-use of the PEP-II machine component for the electron ring and transfer lines § Use of super-ferric magnets for the ion ring instead of cosθ super-conducting magnets

– Only one booster needed, accelerating from 285 MeV to 8 GeV

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Collider Luminosity

Probability of generating an event in a collision of two bunches (with Gaussian transverse densities) Event rate with equal transverse beam sizes Luminosity

– Number of events per second per unit cross section

2 2 2 2

2 ( )( )

x x y y

N N P σ π σ σ σ σ

+ − ∗ ∗ ∗ ∗ + − + −

= + + 4

c x y

N N f dN L dt σ σ πσ σ

+ − ∗ ∗

= = 4

c x y

N N f L πσ σ

+ − ∗ ∗

=

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Another Parameterization

Beam-beam tune shift parameter

– Focusing of one bunch by the other

Express luminosity in terms of vertical tune shift

– Necessary but not sufficient for a self-consistent design – Valid for linac-ring and ring-ring colliders

Given the beam-beam tune shift limit (~0.02 for p and ~0.1 for e-), the only variables left to maximize luminosity are

– stored current – aspect ratio – β* (beta function value at the interaction point)

§ Must still be greater than or equal to the bunch length to avoid the hour-glass effect

(1 ) (1 ) 2 2

c y y y y y x y x

f N I L r er ξ γ σ ξ γ σ β σ β σ

∗ ∗ ± ± ± ± ± ± ∗ ∗ ∗ ∗ ± ± ± ±

= + = + 2 ( )

y y y x y

r N β ξ πγ σ σ σ

∗ ± ± ± ∗ ∗ ∗ ±

= +

m m m m

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MEIC Baseline Design

Machine components

– Collider rings’ circumference ~2.2 km – CEBAF – Electron collider ring and transfer lines: PEP-II magnets, RF (476 MHz) system and vacuum chambers – ABPIS and EBIS and/or ECR sources – SRF ion linac – Booster ring: super-ferric magnets – Ion collider ring: super-ferric magnets + FFQs cosθ superconducting magnets

Energy range

– Electron: 3 to 10 GeV – Proton: 20 to 100 GeV – Lead ions: up to 40 GeV/u

Design point (CM) p energy (GeV) e- energy (GeV) Main luminosity limitation low 30 4 space charge medium 100 5 beam beam high 100 10 synchrotron radiation

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Electron Ring Optics Parameters

Electron beam momentum GeV/c 10 Circumference m 2154.28 Arc/straight length m 754.84/322.3 RF frequency MHz 476 Bunch length cm 1.2 Beta stars at IP β*

x,y

cm 10 / 2 Detector space m

3 / +3.2

Maximum horizontal / vertical β functions βx,y m 949/692 Maximum horizontal / vertical dispersion Dx,y m 1.9 / 0 Horizontal / vertical betatron tunes νx,y 45.(89) / 43.(61) Horizontal / vertical chromaticities ξx,y

149 / -123

Momentum compaction factor α 2.2 ×10-3 Transition energy γtr 21.6 Horizontal / vertical normalized emittance εx,y µm rad 1093 / 378 Maximum horizontal / vertical rms beam size σx,y mm 7.3 / 2.1

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RF Cavities

Electron collider ring --- reuse proven PEP-II RF stations

– 476 MHz HOM damped 1-cell cavities, 34 cavities available – 1.2 MW klystrons including power supplies etc., 13 available – Current limited by synch. radiation power at high energy, impedance at low energy

Synchrotron power limited Impedance limited nominal

952.6 MHz single cell 4-seater CM (~4.3m flange to flange) New HOM damped cavity concept

Ion collider ring --- design 952.6 MHz HOM damped 1- cell cavities

– Modular Jlab type cryomodule – High frequency/high voltage for short bunch (re-bucket at energy) – Lower power couples, no synch. radiation power – Tunable within one harmonic (harmonic jumps for path length changes with energy) – Current limited by space charge (limits charge per bunch) – Impedance is still a concern so HOM damping is needed

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Electron Polarization Design

Schematic drawing and lattice of USR

IP Arc

S

S
Half Sol.

Half Sol.

Dec. Quad. Insert

Solenoid decoupling

1st Sol. + Dec. Quads Dipole set 2nd Sol. + Dec. Quads Dipole Set

P. Chevtsov et al., Jlab-TN-10-026

Electron polarization configuration to achieve: two polarization states simultaneously in the ring with 70% (or above) longitudinal polarizations at IPs

Electron polarization direction Universal Spin Rotator Spin tuning solenoid

Energy (GeV) Estimated Pol. Lifetime (hours) 3 66 5 5.2 7 2.2 9 1.3 10 0.86

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Ion Sources Prototype & Parameters

Electron-Cyclotron Resonance Ion Source (ECR) Universal Atomic Beam Polarized Ion Sources (ABPIS) Electron-Cyclotron Resonance Ion Source (ECR) Polarized light Ions Non-Polarized Ions

V. Dudnikov

Ions Source Type Pulse Width (µs) Rep. Rate (Hz) Pulsed current (mA) Ions/pulse (1010) Polarization (Pz) Emittance (90%) (π·mm·mrad) Note H-/D- ABPIS 500 5 4 (10) 1000 >90% (95) 1.0 / 1.8 (1.2) H-/D- ABPIS 500 5 150 / 60 40000/15000 1.8

3He++

ABPIS-RX 500 5 1 200 70% 1

3He++

EBIS 10 to 40 5 1 5 (1) 70% 1 BNL

6Li+++

ABPIS 500 5 0.1 20 70% 1 Pb30+ EBIS 10 5 1.3 (1.6) 0.3 (0.5) 1 BNL Au32+ EBIS 10 to 40 5 1.4 (1.7) 0.27 (0.34) 1 BNL Pb30+ ECR 500 5 0.5 0.5 (1) 1 Au32+ ECR 500 5 10.5 0.4 (0.6) 1

Numbers in red are “realistic extrapolation for future”; numbers in blue are “performance requirements of BNL EBIS
MEIC ion sources rely on existing and matured technologies
Design parameters are within the state-of-art

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Ion Collider Ring Parameters

Circumference m 2153.89 Straights’ crossing angle deg 81.7 Horizontal / vertical beta functions at IP β*

x,y

cm 10 / 2 Maximum horizontal / vertical beta functions βx,y max m ~2500 Maximum horizontal dispersion Dx m 3.28 Horizontal / vertical betatron tunes νx,y 24(.38) / 24(.28) Horizontal / vertical natural chromaticities ξx,y

101 / -112

Momentum compaction factor α 6.45 × 10-3 Transition energy γtr 12.46 Normalized horizontal / vertical emittance εx,y µm rad 0.35 / 0.07 Horizontal / vertical rms beam size at IP σ*

x,y

µm ~20 / ~4 Maximum horizontal / vertical rms beam size σx,y mm 2.8 / 1.3

All design goals achieved Resulting collider ring parameters

Proton energy range GeV 20(8)-100 Polarization % > 70 Detector space m

4.6 / +7

Luminosity cm-2s-1 > 1033

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Provide dispersion suppression and geometric match to the electron ring Arc end upstream of IP

̶ Shaped to provide 50 mrad crossing angle at the IP

Arc end downstream of IP

̶ Shaped to provide 1.5 m separation from the electron beam

Ion Arc Ends

ions IP

20 m 5 m

ions

10 m 2 m

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MEIC Super-Ferric Quadrupole

Arc quads ~ 50 T/m SF Matching quads ~ 80 T/m SF FF quads cosθ

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Linear optics without solenoid Linear optics with solenoid Betatron tune shift

Optical Effect of Solenoid

( )

2 , || || , 2 ||

( ) 1 const 16

x y x y

B L L B β ν π ρ Δ = =

4 ,

10 2

−

× ≈ Δ

y x

ν

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Radial polarization at IP assuming νd = 2.5⋅10-4, p = 100 GeV/c Vertical polarization at IP Longitudinal polarization at IP

Deuteron Polarization Behavior

nx ny nz

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The universal 3D spin rotator can be used to flip the polarization Consider e.g. longitudinal polarization at the IP at 100 GeV/c Polarization is flipped by reversing the fields of the solenoids in the radial and longitudinal spin control modules Polarization is preserved if – The spin tune is kept constant § No resonant depolarization – The rate of change of the polarization direction is slow compared to the spin precession rate § >0.1 ms for protons and >3 ms for deuterons

Spin Flipping

, const

spin spin c

dn dt ν Ω Ω Ω = = r =

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Far-Forward Ion Acceptance for Neutrals

Transmission of neutrals with initial x and y angular spread vs peak field

– Quad apertures = B max / (fixed field gradient @ 100 GeV/c) – Uniform neutral particle distribution of ±1° in x and y angles around proton beam at IP – Transmitted particles are indicated in blue (the circle outlines ±0.5° cone)

6 T max 9 T max 12 T max ← electron beam

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Downstream Electron Acceptance

Transmission of particles with initial angular and Δp/p spread

– 5 GeV/c e-, uniform spreads: -0.5/0 in Δp/p and ±25 mrad in horizontal/vertical angle – Apertures: Quads = 6, 6, 3 T / (∂By /∂x @ 11 GeV/c), Dipoles = ±20 × ±20 cm

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