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Institute for Research in Institute for Research in Electronics & Applied PhysicsElectronics & Applied Physics

University of Maryland, College Park, MD

UMER : The University of Maryland UMER : The University of Maryland Electron Storage RingElectron Storage Ring

Research sponsored by US Department of Energy

Rami A. Kishekon behalf of UMERUMER collaboration

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We Thank:

Charles Tobin

Ingo HoffmanTom Wangler

Others

University of Maryland Electron Ring (UMER)University of Maryland Electron Ring (UMER) Team:

PPPLRon DavidsonHong QinEric Gilson

Terry F. GodloveDon FeldmanRenee Feldman

Ioannis SiderisCourt BohnNIU

Peter SeidelChristine CelataSteve LundSimon Yu

Alex FriedmanDave GroteJean-Luc VayJohn Barnard

Virtual National Lab for Heavy Ion Fusion (also provided WARP)

Former:Yun ZouYupeng CuiHui LiYijie Huo

Graduate:John HarrisGang Bai Kai TianMike HollowayC PapadopoulosDiktys Stratakis

Junior Scientists:Santiago BernalMark WalterBryan Quinn

Patrick O’Shea Martin ReiserIrving HaberRami Kishek

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Outline

1. The University of Maryland Electron Ring:

Why and What?

2. UMER Design

3. Transverse Physics and Control

4. Longitudinal Physics

5. Summary

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Why electrons? Scaling Laws1000 1000000 1000000000 1E+121 keV 1 MeV 1 GeV 1 TeV

e-

p

HI

electrons

protons

heavy ions

UMER

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Common Beam Dynamics Challenges

Transverse:– Errors & Control

– Halo Formation & Beam Losses

– Emittance Growth

– Instabilities

– Resonances

Longitudinal:– Energy Spread

– Transverse-Longitudinal Coupling

– Compression

– Instabilities

IREAPIREAP 3.7 m

Extraction/diagnostic

section

10 kV Gun

Injection/matchingsection

UMER Schematic

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Electron GunInjection Line

Ring Chambers

Diagnostic Chamber

UMER is a Complex Machine

> 150 Magnets

Assembly, Alignment

Power Supplies, Wiring

Diagnostics

Beam Control

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UMER as of Aug. 2004

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Review of UMER Design

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UMER Beams

Non-Relativistic:– Negligible radiation, below transition, etc.– Earth field important!

Low Energy SpreadCurrent and Emittance Adjustable:

– using apertures in the gun (large jumps)– by varying the gun grid voltage (fine-tuning)

0.2-3 µmrms Emittance n Range

0.6-100 mACurrent Range

20 eVEnergy Spread

10 keVEnergy

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Beam2a

k02a

external focusing

2

3

Ka a

ε+

%

Space charge + emittance

Dimensionless Space Charge Intensity

2 2

space charge forceexternal focusing force

≡ =o

Kk a

χ

0 ≤ χ ≤ 1

Intensity Parameter:

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85 mA

Beams Circulated

Present UMER Operating PointsEmittanceDominated

Space-chargeDominated

Existing rings

Intensity Parameter (χ)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0.0 0.2 0.4 0.6 0.8 1.0

BetatronOscillations

Curve

1ω

χω

= −0

0

2Pωχ

ω=

PlasmaOscillations

Curve

0.6 mA

24 mA

7.2 mA

UMER Range

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UMER Lattice Parameters

Tune adjustable, currently 3 operating pointsInterested also in anisotropic focusing (different tunes in

x and y)

7.6Zero-Current Tune

32 cmLattice Period

11.52 mRing Circumference

1.83 mRing Radius

1.4-10 mmAverage Beam Radius7.2-8.5Zero-Current Tune Range

36/turnNumber Lattice Periods

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UMER Magnets & Lattice

PC Dipoles (34 X)

Dipole field 15.4 GCurrent 3 APhysical length 4.4 cmEffective length 3.8 cmRadius 2.8 cmField integral 20 G-cm/AResistance 3 Ω

PC Quadrupoles (68x)Field gradient ~ 8 G/cmCurrent 2 APhysical length 4.4 cmEffective length 3.6 cmRadius 2.8 cmField integral 15 G/AResistance 3 Ω

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UMER Goals

1. Maintain emittance growth ∆ε/ε < 4, while:– At full current, without acceleration, 10 turns

– At lower current or with acceleration, 100 turns

2. Conduct a wide range of beam dynamics

experiments on UMER!

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Diagnostics Presently Installed

Invasive (can only be used over first turn):– Phosphor screen imagers:

• Beam-intensity image, size, position, and skew angle• Beam emittance and transverse phase space

(in combination with a quad scan and Tomographic techniques)• Beam emittance (in combination with quincunx mask at gun)

Non-Invasive (multi-turn diagnostics):– Beam Position Monitors:

• Beam position• Beam current

– Bergoz Coils (Beam Current)– Perturbation Techniques (Line Charge)

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Diagnostics to be Added

1. Energy Analyzers (invasive, can be placed in any chamber)

2. End Diagnostic Chamber (non-invasive):• Time resolved high-resolution Energy Analyzer • Slit-slit time-resolved transverse phase space mapper• Pepper-pot transverse-phase-space mapper• Current measurement devices• Phosphor Screen Imager

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Quadrupole Linearity & Field Profile

Constant k adjusted for best uniformity (dipole) or linearity (quad); e.g., k = 0.976 for ring dipole; deviations <0.1%

3-D field calculations: Z-integrals used for

field quality.

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Rotating coil and pulsed wire systems

Normal Multipole Harmonics

Expected (w/ errors)

Quadrupole 104 Sextupole 20 Octupole 68 Decapole 13 Duodecapole 130

Allowed Max 104 150 90 45 22

Measured

104 32 53 4.8 3.2

Magnet Harmonic Measurements

Zhang, et al., PRST-AB, 3, 122401 (2000).

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New Injection Y in place

Injector

Ring

PD

IQF

RQ1

SD

SD BigDCQ

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Beam Control

IREAPIREAP1.0 cm

24 mA, 10 keV

1.0 m

S. Bernal (PAC ’03)

First Experiments (during construction)

Rotated Beam

RMS Mismatched

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Beam Control System Software

Quadrupoles ControlCentral Control Platform

Dipoles Control

BPMs Control

Steering Module

Skew Correction Module

Matching Module

Tomography Module

network

network

network

Hui Li

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Beam Steering

Steps:• Scan Q1, find all rays

through Q1’s center• Scan Q2, find the optimal

ray

D1 D2 Q1 Q2

Screen/BPM

I1(A)

I2(A)

optimal point

candidate

candidate

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-20.00

-18.00

-16.00

-14.00

-12.00

-10.00

-8.00

-6.00

-4.00

-2.00

0.000 20 40 60 80 100 120 140 160 180 200 220

Angle (degrees)

B-f

ield

(G

auss

) Dipole Field (G)Scaled BEz (G)NET Field (G)

Beam Steering Results

Dipole fields calculated w/ the steering algorithm

Two pilot beams (7mA, 0.6mA) have given similar results.

Measured Bz of Earth Field

Rough Scaled Sum of Earth and Dipole Fields

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Beam Rotation Correction

Electronic Skew Corrector

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Beam Rotation Correction24mA Beam (RC1-12) Before Skew Correction

24mA Beam (RC1-12) After Skew Correction

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Beam Rotation Correction

24mA Beam (RC1-12) Rotation Angle Before Correction v.s After Correction

-25

-20

-15

-10

-5

0

5

10

15

20

25

0 1 2 3 4 5 6 7 8 9 10 11 12

Chamber Index (RC1 to RC12)

Bea

m R

ota

tio

n A

ng

le

(deg

ree)

Skew = 0A

Skew = 0.13A

Skew corrector at here

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Beam Matching

24mA beam pictures (RC 1-12) after beam-based matching

24mA Beam (RC1-12) after Skew Correction

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Before empirical matching:σx=0.20mm σy =0.18mm

Beam Matching

0 2 4 6 8 10 120

1

2

3

4

5

6

7

8

9

2*rm

s be

am s

ize

(mm

)

Chamber #

Before Empirical matching, Var(x)=0.2002mm, Var(y)=0.1813mm

X-2*rms sizeY-2*rms size

0 2 4 6 8 10 120

1

2

3

4

5

6

7

8

9

2*rm

s be

am s

ize

(mm

)

Chamber #

After Empirical matching, Var(x)=0.0784mm, Var(y)=0.0438mm

X-2*rms sizeY-2*rms size

After empirical matching:σx=0.08mm σy=0.04mm

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Longitudinal Dynamics:Inducing Perturbations

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Photo & Thermionic Emission Electron Beams

Beam Current

Photoemission only (Cool cathode)

Thermionic only, 100ns pulse

Photoemission + Thermionic 5ns pulse

Drive Laser

Heated Photocathode

Electron Beam

Yijie Huo

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Drive Laser Setup

Nd:YAGLaser

KTP

BBO

Mirrors/filters

Telescope

Laser Mask

UV (355nm) LaserPhoton energy: 3.5 eVWork function: 2.7 eV

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Experiment Data PositionsIC1

IC2RC1

RC2

RC3

4

5

67

891011

RC12

Laser

8.95 mBPM : RC128.31 mBPM : RC117.67 mBPM : RC107.03 mBPM : RC96.39 mBPM : RC85.75 mBPM : RC75.11 mBPM : RC64.47 mBPM : RC53.83 mBPM : RC43.19 mBPM : RC32.55 mBPM : RC21.91 mBPM : RC10.80 mBPM : IC20.62 mBergoz Coil

0.36 mWindow : IC1

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Conclusion

• UMER Mechanically Closed

• Beam Control algorithms and systems developed.

• Poised for Multi-Turn Operation

• Can use laser to produce localized density perturbations – good agreement with WARP simulations.

• Rich physics content promises exciting results

Website: http://www.ireap.umd.edu/umer

Publications: http://www.umer.umd.edu/

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Extras

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Design of Printed Circuit Magnets

• 10 keV ⇒ use ironless printed-circuit magnets

• Quadrupole, Dipoles, and additional Short Dipoles for small

steering corrections

• Can handle up to 3 Amps DC/conductor.

• Double-sided: minimizes effect of external leads & doubles the field.

• Algorithm:sin(mΦn) = 1 - (2zn/kL)2 , n = 20 loops for ring

dipoles (m=1) and quad’s (m=2)

Courtesy of T.F. Godlove

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FFT of Rotating Coil Signal

-80

-70

-60

-50

-40

-30

-20

-10

0

0 10 20 30 40 50 60FF

T o

f R

ota

tin

g C

oil

Sig

nal

(dB

m)

Frequency (Hz)

PC QUADRUPOLE

-80

-70

-60

-50

-40

-30

-20

-10

0

0 10 20 30 40 50 60FF

T o

f R

ota

tin

g C

oil

Sig

nal

(dB

m)

Frequency (Hz)

PC DIPOLE

-80

-70

-60

-50

-40

-30

-20

-10

0

0 10 20 30 40 50 60FF

T o

f R

ota

tin

g C

oil

Sig

nal

(dB

m)

Frequency (Hz)

NO MAGNET

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Sources of Quad Multipole Spectrum

H V R