update on jlab meic project vasiliy morozov for jlab’s meic study group eic generic detector...

Update on JLab MEIC Project

Vasiliy Morozov for JLab’s MEIC Study Group

EIC Generic Detector R&D Advisory Committee Meeting, BNL, January 13, 2014

V.S. Morozov January 13, 2014 -- 2 --

Outline

• Introduction

• MEIC project overview

• Accelerator design Luminosity

Polarization

• Detector Concept

Machine integration

Performance

Backgrounds

• Summary


EIC at JLab

• Stage I MEIC CEBAF as full-energy

e-/e+ injector 3-12 GeV e-/e+

25-100 GeV protons 12-40 GeV/u ions

• Stage II EIC up to 20 GeV e-/e+

up to 250 GeV protons up to 100 GeV/u ions

• Two independent but

complementary detectors

Pre-booster

Ion linacMEIC

High-Energy Arc (Stage II)

e injection

IP2

IP1

Hall D

Halls A-C

C E

B A

F


MEIC Layout

Cross sections of tunnels for MEIC

Warm large booster(up to 25 GeV/c)

Warm 3-12 GeV electron collider ring

Medium-energy IPs withhorizontal beam crossing

Injector

12 GeV CEBAF

Prebooster

SRF linac

Ionsource

Cold 25-100 GeV/cproton collider ring

Three Figure-8 rings stacked vertically

Electron cooling


MEIC Design Features

• CEBAF as a full-energy electron/positron injector

• Luminosity– Multi-stage DC and ERL-based conventional electron cooling: small-emittance ion bunches– Beam parameter choice: short low-charge bunches at a high repetition rate– Interaction region design: small beam size at IP, crab crossing

• Ion polarization stability and ease of manipulation – All ion species including deuterons– Figure-8 ion booster and collider ring design

• Novel detector concept– Full acceptance– Far-forward hadron detection

• Technical design limited to conventional technology as much as possible– Electron current <3 A, proton/ion current <0.5 A– Synchrotron radiation <20 kW/m– Warm magnets <1.7 T– Cold magnets <6 T


arXiv:1209.0757

Table of ContentsExecutive Summary

1. Introduction

2. Nuclear Physics with MEIC

3. Baseline Design and Luminosity Concept

4. Electron Complex

5. Ion Complex

6. Electron Cooling

7. Interaction Regions

8. Outlook

MEIC Design Report


Design Parameters for Full-Acceptance Detector

Design point 50 5 GeV2 100 5 GeV2

Proton Electron Proton Electron

Beam energy GeV 50 5 100 5

Collision frequency MHz 748.5 748.5 748.5 748.5

Particles per bunch 1010 0.21 2.2 0.42 2.5

Beam Current A 0.25 2.6 0.5 3

Polarization ~80% >70% ~80% >70%

Energy spread 10-4 ~3 7.1 ~3 7.1

RMS bunch length mm 10 7.5 10 7.5

Horizontal emittance, normalized µm rad 0.3 54 0.4 54

Vertical emittance, normalized µm rad 0.06 5.4 0.04 5.4

Horizontal and vertical β* cm 10 and 2 10 and 2 10 and 2 10 and 2

Vertical beam-beam tune shift 0.015 0.014 0.014 0.03

Laslett tune shift 0.053 <0.0005 0.03 <0.001

Distance from IP to 1st FF quad m7 (downstream)3.5 (upstream)

37 (downstream)3.5 (upstream)

3

Luminosity per IP, 1033 cm-2s-1 2.4* 8.3*

* Including space-charge effects and assuming conventional electron cooling


Electron Cooling in MEIC

• Use conventional electron cooling mechanism

• Multi-stage cooling scenario

– Prebooster: standard DC electron cooling for beam accumulation from positive source– Collider ring: bunched high-energy electron cooling after injection (initial), after acceleration

and re-bunching (final), and during collisions (continuous) Magnetized injector of high-charge short electron bunches

(a similar injector operates at BINP) Energy recovery linac to reduce power

consumption Ultra-fast (beam-beam or RF) kicker Compact circulator ring to reduce electron

source current

to high-energycollider ring

Ionsource

SRF linacPrebooster

(accumulator ring)

Large booster Medium-energy collider ring

Cooling Cooling

electron bunch

ion bunch

circulator ring

Cooling section

solenoid

Fast kickerFast kicker

SRF Linac dumpinjector

energy recovery


• Lattice design of geometrically-matched collider rings is completed

• Detector locations minimize synchrotron and hadronic backgrounds– Close to arc where ions exit– Far from arc where electrons exit

Collider Rings

IPs

e-

ions

e-

ions

IP


Nonlinear Beam Dynamics

• Tight beam focusing (small *) at IP causes momentum-dependence of particle oscillation frequencies, i.e. chromaticity d/(dp/p)

– Each interaction region contributes x,y of ~130 in the ion ring and ~50 in the electron ring

– Chromatic betatron tune spread may cause particle loss due to resonances– Chromatic beam smear at IP may increase beam size and reduce luminosity

• Chromaticity compensation scheme– Local chromaticity compensation: dedicated insertions cancel chromatic effects in each IR– Insertion design utilizes dynamical and magnetic field symmetries for optimal performance– Simultaneous compensation of chromatic betatron tune spread and beam smear at IP– The concept has been successfully demonstrated,

example of chromaticity compensation using only two sextupole families:

p/p = 0.310-3 at 60 GeV/c

5 p/p

Ions

p/p = 0.710-3 at 5 GeV/c

5 p/p

Electrons


Ion Polarization

• Design requirements– High polarization (>70%) of protons and light ions (d, 3He++, and possibly 6Li+++)– Both longitudinal and transverse polarization orientations available at all IPs– Spin flipping (can be done e.g. at the source)

• Figure-8 ring as a solution– No preferred periodic spin direction, energy-independent zero spin tune

Polarization can be controlled by small magnetic fields– Eliminates depolarization problem during acceleration– Works for all ion species including deuterons

• Acceleration and spin matching– Polarization is stabilized by weak (<3 Tm)

solenoids in all ion rings– Injection and extraction from straight with solenoid

• Polarization control in the collider ring– Beam is injected longitudinally polarized, accelerated

and then the desired spin orientation is adjusted – Weak solenoids for deuterons (<1.5 Tm each)– Weak radial-field dipoles for protons (<0.25 Tm each)– Small or no orbit excursions, easy magnet field ramp

Prebooster

LargeBooster

Collider


Electron Polarization with Continuous Injection

• Design requirements– High polarization (>70%) and sufficiently long life time– Longitudinal polarization at all interaction points– Spin flipping (can be done e.g. at the source)

• Electron polarization scheme– Fully-polarized electron beam is injected from CEBAF– Polarization is vertical in the arcs to avoid spin diffusion– Universal spin rotators turn polarization from vertical

to longitudinal and back in straights– Spin matching to extend polarization lifetime– Continuous injection to maintain high polarization

at high energies

arc

dipolearc dipole

Solenoid 1

Solenoid 2

α2≈4.4º α1≈8.8º

spin

φ1

e-

φ2spin

Lost or Extracted

P0 (>Pt)

Pt

10 )1(

injdk

ringrevequ I

ITPP


Full-Acceptance Detector Concept

• 50 mrad crossing angle– Improved detection, no parasitic collisions, fast beam separation

• Forward hadron detection in three stages– Endcap with 50 mrad crossing angle– Small dipole covering angles

up to a few degrees– Far forward,

up to one degree,

for particles passing

the accelerator quads

• Low-Q2 tagger– Small-angle electron detection


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 forwardfar forwardhadron detectionhadron detectionlow-Q2

electron detectionelectron detection large-apertureelectron quads

small-diameterelectron quads

central detectorcentral detector with endcaps

ion quads

50 mrad beam(crab) crossing angle

n,

ep

p

small anglesmall anglehadron detectionhadron detection

~60 mrad bend

(from GEANT4)

2 Tm 2 Tm dipoledipole

EndcapEndcap Ion quadrupolesIon quadrupoles

Electron quadrupolesElectron quadrupoles

1 m1 m11 m m

IP FP

Roman potsRoman potsThin exit Thin exit windowswindows

Fixed Fixed trackers in trackers in vacuum?vacuum?

Trackers and “donut” calorimeterTrackers and “donut” calorimeter

RICH+

TORCH?

dual-solenoid in common cryostat4 m coil

barrel DIRC + TOF

EM

ca

lori

met

er

EM calorimeter

Tracking

EM

ca

lori

met

er

e/π

th

res

ho

ldC

he

ren

ko

v


Central Detector

• Two independently designed but complementary central detectors– No need for beam sharing in a ring-ring collider

• Novel iron-free dual solenoid for one of the detectors– Improved endcap acceptance– Efficient fringe-field compensation– Easily accessible and light weight

dual-solenoid in common cryostat4 m coil

EM

cal

ori

met

er

e/π

th

resh

old

Ch

eren

kov RICH

+TORCH?

EM calorimeter

EM

cal

ori

met

er

barrel DIRC + TOF

(top view)

2 m deep1 m deep

3 m

Co

il w

all

5 m3 m

Si-pixel vertex + disks

central tracker

forward tracker

forward tracker

Co

il w

all

First TOSCA model of 3T dual solenoid (inspired by ILC 4th concept detector)


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 m89 T/m, 9.0 T, 1.2 m 51 T/m, 9.0 T, 2.4 m51 T/m, 9.0 T, 2.4 m36 T/m, 7.0 T, 1.2 m36 T/m, 7.0 T, 1.2 m

Permanent magnetsPermanent magnets

34 T/m34 T/m 46 T/m46 T/m 38 T/m38 T/m2 x 15 T/m2 x 15 T/m e

5 T, 4 m dipole5 T, 4 m dipole

Ion quadrupoles: Ion quadrupoles: gradient, peak field, lengthgradient, peak field, length

2 T 2 T dipoledipole

Endcap detectorsEndcap detectors

Electron quadrupolesElectron quadrupoles

TrackingTracking CalorimetryCalorimetry

1 m1 m1 m1 m

7 m from IP to first ion quad7 m from IP to first ion quad

Crossing angle


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 D 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 Roman pots at focal pointfocal point

Thin exit Thin exit windowswindows

Aperture-free drift spaceAperture-free drift spaceZDCZDC

S-shaped dipole configuration S-shaped dipole configuration optimizes acceptance for neutralsoptimizes 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)


Far-Forward Acceptance for Charged Fragments

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)


Far-Forward Acceptance

• Transmission of particles with initial angular and p/p spread vs peak field– Quad apertures = B max / (fixed field gradient @ 100 GeV/c)– Uniform particle distribution of 0.7 in p/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

elec

tron

bea

m


Far-Forward 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


Momentum & Angular Resolution

– Protons with p/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

elec

tron

bea

m

±10 @ 60 GeV/c

|p/p| > 0.005 @ x,y = 0


Far-Forward Detection Summary

e

p

n, γ20 Tm dipole

2 Tm dipole

solenoid

• Neutrals detected in a 25 mrad (total) cone down to zero degrees Space for large (> 1 m diameter) Hcal + Emcal

• Excellent acceptance for all ion fragments

• Recoil baryon acceptance: up to 99.5% of beam energy for all angles down to at least 2-3 mrad for all momenta full acceptance for x > 0.005

• Resolution limited only by beam longitudinal p/p ~ 310-4

angular ~ 0.2 mrad

• 15 MeV/c resolution for 50GeV/u tagged detueron beam


Detector Background

• Synchrotron radiation background– Suppressing SR in the detector

Detector solenoid is aligned with the electron beam Detector is placed far from electron arc exit Soft last bend

– Working on SR background calculations with a consultant, M. Sullivan, from SLAC SR from the last bend does not seem to be an issue Preliminary conclusion is that overall SR background is under control

• Hadronic background– Dominated by interaction of beam ions with residual gas upstream of IP– Suppressing hadronic background

Detector is placed close to ion arc exit– Simple estimate by scaling from HERA gives ~10 times lower hadronic background

s of 4,000 at MEIC and of 100,000 at HERA Same ion current and vacuum Upstream straight distance ratio: 50 m / 120 m = 0.4 Average hadron multiplicity: (4000/100000)1/4 = 0.4 p-p cross section (fixed target): σ(90 GeV)/σ(920 GeV) = 0.7


Summary

• First MEIC design completed and comprehensive design report released– Emphasis on luminosity

Multi-stage electron cooling Beam parameter choice Interaction region design

– Emphasis on polarization Figure-8 ring design Polarized light ions including deuterons Electron polarization maintained by continuous injection

• Fully-integrated detector and interaction region design completed– Detector features full acceptance and high resolution

Excellent detection of recoil baryons, spectators, and target fragments– Optimized for minimizing detector background– Consistent with non-linear dynamics requirements– Matched beam line footprints

• Many studies still in progress – Optimization and comprehensive simulation of the detector region and background– Optimization of the non-linear dynamics – Design of the second detector


Acknowledgements to JLab EIC Study Group


Announcement

EIC14 The International Workshop for Accelerator science and

Technology for Electron-ion ColliderIncluding a dedication session on Detector Design, Integration and Backgrounds

March 17 – 21, 2014

Newport News, Virginia, USA

Welcome to Virginia!


Back Up


MEIC Design Goals

• Energy– Natural continuation of 12 GeV CEBAF program bridging the gap to HERA/LHeC– Full coverage of s from a few 100 to a few 1000 GeV2

– Electrons 3-12 GeV, protons 25-100 GeV, ions 12-40 GeV/u

• Ion species– Polarized light ions: p, d, 3He, and possibly Li– Unpolarized light to heavy ions up to A above 200 (Au, Pb)

• Up to 2 individually designed detectors

• Luminosity– About 1034 cm-2s-1 per interaction point– Maximum luminosity should optimally be around √s=45 GeV

• Polarization– At IP: longitudinal for both beams, also transverse for ions only– All polarizations >70% desirable

• Upgradeable to higher energies and luminosity– 20 GeV electrons, 250 GeV protons, and 100 GeV/u ions


Electron Source for Electron Cooling

• MEIC high-energy electron cooling requires a source of ~2 nC few-cm long electron bunches with a repetition rate of ~15 MHz and an average current of ~30 mA.

• Slava suggested using a short-pulse high-bunch-charge high-repetition-rate magnetized DC gun with subsequent bunch compression.

• Such a scheme, with the exception of beam magnetization, seem to exist at BINP and has been used as an electron source for NovoFEL since 2003.

• A DC gun with a thermionic metal-oxide gridded cathode has the following parameters:

• All gun (and injector) parameters seem consistent with the electron cooler requirements.

• A thermionic RF gun is being developed at BINP to replace the DC gun. The reasons for upgrade are not clear but, perhaps, involve improved cathode lifetime and higher current.

• Beam tests of the RF gun started recently with encouraging results.

Electron energy 300 kVBunch charge ~1.5-2 nCMaximum peak current ~1.8 AMaximum average current ~30-45 mAMaximum bunch repetition rate 22.5 MHzBunch length ~1.3 nsNormalized emittance 10 mmmrad


Magnetized Injector and ERL for HEEC


Crab Crossing

• Effective head-on bunch collisions restored with 50 mrad crossing angle– Luminosity preserved

• Two feasible technologies– Dispersive crabbing using regular accelerating/bunching cavities in dispersive region– Deflective crabbing using transverse electric field of SRF cavities (developed at ODU)

Incoming At IPOutgoing


Continuous Injection Scheme

X0

• During the injection time: kickers on. Septum Magnet

X2

• Kickers on during the first few turns (~9-15 μs). The injected beam won’t be close to the Septum Magnets (physically) due to the betatron tune.

• Kickers off after a few turns (~9-5μs). The injected beam will dampen to the closed orbit after a few horizontal damping times.

X1

Magnet Field

Septum Magnet

Septum Magnet

Magnet Field

Magnet Field


Continuous Injection Bunch Pattern

• Bunch pattern: I II III• Comments

– The peak current in I can be reduced by more turns injection (Iave1 keeps constant). But this may disturb the injected beams due to the septum field with kickers on. Two to three turns injection is acceptable.

– The Iave2 can be increased by reducing the time interval between the macro bunches in II. While this leaves less time for injected beams to damp and may interference with the new injected beams.

– The Iave3 can be increased by increasing Iave1 and Iave2 or reducing the time interval in III. While this will reduce the experimental time.

duty factor 7.5e-4

Iave1

t=Trev

……

1.33ns (40cm) 748.5MHz

<ps (<1mm) 3.192pC

4.7μs (1 turn), Iave1=2.4mA

I

duty factor 5e-4

Iave2

t

……

9.4ms, 2000 turn

1s, Iave2=1.2μA

II

duty factor 0.0167

Iave3

t

……

60s

Iave3=20nA

III

• I : micro bunch trains from CEBAF in 4.7μs (one revolution time of MEIC electron ring), providing a 2.4mA averaged beam current.

• II : macro bunch trains in 1 second, providing 1.2μA averaged beam current.

• III: macro bunch trains every one minute, providing 20nA averaged beam current.


Beam Synchronization & Collision Pattern

• Path length difference in collider rings– Electrons travel at the speed of light, protons/ions are slower– Slower proton/ion bunches may not meet electron bunch again at IP after one revolution– Synchronization must be achieved at every IP in the collider rings simultaneously

• Conceptual solution– Varying number of bunches (harmonic number) in

the ion collider ring would synchronize beams at IPs

for a set of ion energies (harmonic energies)– To cover the energies between the harmonic values

varying electron orbit length up to half bunch spacing varying RF frequency (less than 0.01%)

CEBAF RF frequency fixed, dynamic adjustment

of electron bunch spacing at injection

• Collision pattern at IP– Each time an ion bunch returns to IP, it will collide with

a different electron bunch

(it may collide with all or a subset of electron bunches)

Bunches in ion ring

Energy (GeV/u)

Proton Lead

3370 100

3371 35.9 35.9

3372 26.3 26.3

3373 21.7 21.7

3374 18.9

3375 17.0

* Number of electron bunches is 3370** Assuming the same electron and

ion orbit lengths (1350 m) at 100 GeV proton energy


Small-Angle Electron Detection

• Low-Q2 tagger– Dipole chicane for high-resolution detection of low-Q2 electrons

low-Q2 tagger

final focusing elements

e-

ions

e-

ions

Electron beam aligned with solenoid axis

x e-

(top view)


Far-Forward Angular Acceptance

– Quad apertures = 9, 9, 7 T / (By /x @ 100 GeV/c), dipole aperture = -30/+50 40 cm– Uniform distribution of 1 in x and y angles around proton beam at IP for a set of p/p– The circle indicates neutrals’ cone

electron beam electron beam

p/p = -0.5

p/p = 0

p/p = 0.5

neutrons


Momentum & Angular Resolution

– Protons with different p/p launched with x spread around nominal trajectory

– Resulting deflection is observed 12 m downstream of the dipole– Particles with large deflections can be detected closer to the dipole

|x| > 3 mrad @ p/p = 0

elec

tron

bea

m

electron beam

±10 @ 60 GeV/c


Initial SR Background Calculations

FF1 FF2

e-

P+

1 2 3 4 5-1

40 mm30 mm

50 mm

240

3080

4.6x104

8.5x105

2.5W

38

2

Synchrotron radiation photons incident on various surfaces from the last 4 electron quads

Rate per bunch incident on the surface > 10 keV

Rate per bunch incident on the detector beam pipe, assuming 1% reflection coefficient and 4.4% solid angle acceptance

M. SullivanJuly 20, 2010F$JLAB_E_3_5M_1A

Beam current = 2.32 A 2.9x1010 particles/bunch

X

P+

e-

ZElectron energy = 11 GeVx/y = 1.0/0.2 nm-rad

M. Sullivan’s talk at the 2nd Detector/IR Mini-workshop


Lattice Elements in the Straights


Immediate Outlook & R&D

• Electron cooling– Electron cooling of medium energy ion beam (by simulations)– ERL circulator cooler design optimization, technology development– ERL-circulator cooler demo (using JLab FEL facility)

• Interaction region– Detector integration– Sufficient dynamic aperture with low beta insertions

• Polarization– Demonstrate superior ion polarization with figure-8 ring– Electron spin matching

• Collective beam effects– (Long time scale) beam-beam with crab crossing– Space charge effects in pre-booster– Electron cloud in the ion rings and mitigation

• Ion injector complex optimization and beam studies

Bold font indicates high priority

update on jlab meic project vasiliy morozov for jlab’s meic study group eic generic detector...

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energy ee injector3

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