IREAPIREAP
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