Download Beam Diagnostic Requirements for Bunched Beam Cooling Demo

Beam Diagnostic System Analysis in
HIRFL-CSRm at IMP, China for the
Bunched Electron Cooling Demo
Experiment
Haipeng Wang
Lijun Mao (Experiment) at IMP and Yuhong Zhang, (LDRD 2014 PI) and
He Zhang (Cooling Simulation) at JLab
Thanks also for contribution from
Jie Li, Xiaoming Ma, and He Zhao, IMP, China and
ChinaVasily Parkhomchuk and Vladimir Reva1, BINP, Russia
MEIC Collaboration Meeting
(October 5-7, 2015)
HIREL-CSR Layout and Performance Specification
CSRm
CSRe
Circumference (m)
161.0014
128.8011
Geometry
Race-track
Race-track
Max. energy (MeV/u)
900 (C6+) 1100 (C6+)
400 (U72+) 2800 (p)
600(C6+) 700(C6+)
400(U90+) 450(U90+)
B (Tm)
0.91/10.64
0.81/12.04
1.20/8.40 0.50/9.00
B(T)
0.12/1.40
0.10/1.59
0.20/1.40 0.08/1.50
Ramping rate (T/s)
0.05 ~ 0.4
Repeating circle (s)
～ 17 (～10s for Accumulation )
0.1 ~ 0.2
Normal mode
Acceptance
EC-35 cooler
A h ( mm-mrad)
200 (p/p = 0.15 %)
150 (p/p =0.5%)
A v ( mm-mrad)
30
75
p/p (%)
1.25
2.6
Ion energy (MeV/u)
8---50
25---400
length (m)
4.0
4.0
(h= 50  mm-mrad)
(h= 10  mm-mrad)
E-cooler
RF system
Harmonic number
Accel. Accum.
1
16, 32,64
Capture
1
fmin/fmax (MHz)
0.24/1.81 6.0 / 14.0
0.5 / 2.0
Voltages (n  kV)
1  7.0
2  10.0
Vacuum (mbar)
1  20.0
10---450
6.0  10-11 (3.0  10-11)
MEIC Collaboration Meeting
(October 5-7, 2015)
Proposed Bunched Electron Cooling Experiment Parameters
MEIC Collaboration Meeting
(October 5-7, 2015)
EC-35 DC Cooler and Commissioned Performance
1—electron gun, 2—electrostatic bending
plates, 3—toroid, 4—solenoid of cooling
section, 5—magnet platform, 6—collector
for electron beam, 7—dipole corrector, 8—
vacuum flange for CSRm. Two BPMs placed
in the cooling station, one is at upstream of
electron beam at gun side in position 9,
another one is at downstream collector side
in the mirror symmetric position relative to
9.
Commissioned in March 2003
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•
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vacuum 21011 mbar,
high voltage 20 kV,
electron beam current 1.6 A,
collector efficiency >99.99%,
angle of magnetic field line in
cooling section <210-5
MEIC Collaboration Meeting
(October 5-7, 2015)
Terminal Circuit Diagram and Average Current Measurement
ions
electrons
Collector efficiency
MEIC Collaboration Meeting
(October 5-7, 2015)
EC-35 RF Modulation + DC Bias Scheme for Bunched Electron Beam Formation
bunch length
fm3 MHz
MEIC Collaboration Meeting
(October 5-7, 2015)
Beam Diagnostic Devices for Bunched Electron Cooling Demo Experiment
• existing
• modification
• new installation
Parameters
EC35-electron
CSRm-ions
Data-acquisition
average beam
current
dc readings on PSs,
sampling resistors
DCC(current)T(transfor
mer)s
existing calibra. and
DAS
peak beam current
mod. freq. fm
rf or harmonic freqs n*f0
fiber optical link
readout
Beam position
capacitive BPMs
capacitive BPMs
existing calibra. and
DAS
Beam trans.profile
capacitive BPMs
(off-line screen)
residual gas BPMs
DAS
Beam long.profile
resonant BCMs
on BPMs
resonant BCMs
on BPMs or DCCTs
fast scope and online DAS
Cooling rates
n.a.
Schorttky resonator and
pickups
fast scope and online DAS
Off-line side-band
signal analysis
MEIC Collaboration Meeting
(October 5-7, 2015)
RF Amplifier Resonant Circuit Design, Prototype and test Result
Courtesy of Dr. L.J. Mao, IMP
Bench prototype circuit
simulations
Input（mV p-p）
100
200
300
400
500
600
700
800
900
1000
Output voltage and impedance measurements
Output（V p-p）
4.63
25.4
73.8
145
222
305
398
476
547
606
MEIC Collaboration Meeting
(October 5-7, 2015)
Electron Gun Simulation by CST EM-Static and PS Tracking Solvers
E-potential
Solid beam
E-field-am
Hollow beam
MEIC Collaboration Meeting
(October 5-7, 2015)
Solid to Hollow Beam Formation in Simulation and Experiments
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•
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Reduction of transversal instability of cooled ion beam. It may be achieved by using the
electron beam with the density increasing radially but low at the center.
Problems arisen due to space charge effect may be partially solved by using the hollow
electron beam with low transversal electric field near its center.
Reduction of the effect of recombination between the accumulated ions and the electron beam.
Suppress the electron heating effect in the center
MEIC Collaboration Meeting
(October 5-7, 2015)
Existing BPM Devices at EC-35 Cooler and CSRm Ring
MEIC Collaboration Meeting
(October 5-7, 2015)
Capacitive Beam Pickup Principles and Sensitivity to Beam Current
Our bunched beam electron cooling
experiment is at the  range of
0.121~0.247. So either type of the pickup
is OK for the BCM
For RCs <<1, fm<<fc, R is preferred in low resistance for high roll-off frequency fc.
Too weak!
We need to modify the
external circuit of BPM
to be a resonant circuit in
order to improve the
bunch edge sensitivity
and S/N ratio.
MEIC Collaboration Meeting
(October 5-7, 2015)
Modification Suggestion to Existing BPM External Circuits to BCM
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Can tune harmonic of the ion accelerating
frequency f0 and electron modulation frequency
fm separately on different BPMs if not
synchronized
Detune due to the resistive loss is small and the
inductance can be compensated by a tunable
inductor element.
Bunch beam charging time t >> the resonance
RLC circuit (or cavity) filling time Q/r. Say 2
times at least. So the induced voltage V(t) will
not drop between the bunches 1/f0-t.
Data sampling rate fs has to be fast enough to
resolve the bunch rise time scale of ~10ns.
MEIC Collaboration Meeting
(October 5-7, 2015)
1D Signal Calculation for Square Bunch and Ring-shape Pickup
Electron (red solid line) and
ion (green solid line) bunch
signals picked up by modified
capacitive type BCM plates
and their bunch shapes
(dashed red line for electron,
dashed green line for ion)
calculated by MathCAD
program for =0.121, average
beam currents of 70mA for
electron and 3mA for 12C+6.
The voltage signal is picked
up on the total shunt resistor of
R=150. The voltage signal
gain on the ion current is 40dB
(80dB in power) for this
display. In this calculation
example, there are 7 electron
bunches with in one ion
bunch.
MEIC Collaboration Meeting
(October 5-7, 2015)
1D Signal Calculation for Gaussian Bunch and Ring-shape Pickup
Gaussian bunch shape distribution
(black) in 7ns (rms) bunch length
current picked up by 50  shunt
impedance’s voltage (red,
calculation) and comparison to the
experimental data (blue) for one of
12C+6 bunches accelerated in the
CSRm ring at the 0.5 velocity. The
blue data is measured by a fast
oscilloscope on a Ls=15cm pickup
cylinder. The voltage gain of such
signal is ~350. The ion current is
~3mA. Signal ringing on the back is
due to the pickup circuit.
MEIC Collaboration Meeting
(October 5-7, 2015)
Resonant Signal Processing and Sampling Rate to Improve S/N
Res.
BCMs
voltage
gain
E-cooler Ion-ring
0 dB
40 dB
sensitivit 7.8V/70 6.2mV/3
MEIC Collaboration Meeting
(October
y
mA 5-7, 2015) .2uA
BCM Resonant Circuit Design Parameters
MEIC Collaboration Meeting
(October 5-7, 2015)
Using Longitudinal Schottky Diodes to Measure the Cooling Rates
Courtesy of Dr. L.J. Mao, IMP
MEIC Collaboration Meeting
(October 5-7, 2015)
Summary
• Bunched electron Beam Cooling Demo Experiment at IMP has been proposed
in 2014 at JLab and carried out by the collaboration team at 2015 with JLab
LDRD fund and IMP internal fund.
• HV power supplies and RF amplifier hardware are under commissioning for
the electron beam modulation scheme
• Demo experiment is scheduled in 2016
• Modification of IMP CSRm BPM system into a BCM measurement device to
measure the beam bunch length and peak current is possible for our demo
bunched electron cooling experiment
• Using existing EC-35 BPM system, a minor circuit modification (or using
sum/diff. combined signals) using a resonant circuit is possible for the
electron bunch length and shape measurement
• Modification to resonant Schottky, using Palmer pickup devices (in CSRs
ring only), extraction kicker in CSRe ring (under the study) for the ion beam
bunch length and current measurement will greatly increase the S/N ratio. The
new BCM circuit design parameters have been specified.
• EC-35 Cooler and CSRm ring can do all of these schemes for the demo
experiment: DC to coasting, bunch to coasting and bunch to bunch,
synchronization and non-sychronization
MEIC Collaboration Meeting
(October 5-7, 2015)
References
[1] Yuhong Zhang, He Zhang, et al JLab LDRD 2014 proposal, funded in FY2015.
[2] CSR Design Group, “CSR Storage Ring Parameters List”, HIRFL-CSR/General/02-1, January 25, 2002,
Submitted by J.W. Xia.
[3] Li Guo-Hong, etc. “A Beam Position Monitor System for Electron Cooler in HIRFL 2 CSR (in Chinese)”,
Nuclear Physics Review, Issue 1, Vol. 27, March, 2010, Article No. 1007 - 4627 (2010) 04 - 0043 – 05.
[4] V. Bocharov et al. “HIRFL-CSR electron cooler commissioning”, Nuclear Instruments and Methods in Physics
Research A 532 (2004) 144–149.
[5] E. Bekhtene, L.J. Mao, H. Wang and Y. Zhang, the discussion of bunched beam formation by the RF modulation
scheme in the MEIC collaboration meeting in March, 2014.
[6] L.J.Mao et al, “Longitudinal electron cooling experiments at HIRFL-CSRe”, to be published in 2015.
[7] A.V. Bubley et al. “Measuring a hollow electron beam profile”, Nuclear Instruments and Methods in Physics
Research A 532 (2004) 413–417.
[8] A.V. Bubley et al, “The Electron Gun with Variable Beam Profile for Optimization of Electron Cooling”,
Proceedings of EPAC 2002, Paris, France, WEPRI049.
[9] G. R. Lambertson, Dynamic Devices – Pickups and Kickers, LBL-22085, BECON-63, LBL, UC Berkeley,
August, 1986.
[10] D. A. Goldberg and G. R. Lambertson, Dynamic Devices, A Primer on Pickups and Kickers LBL-31664,
November, 1991.
[11] Strehl P. Beam Instrumentation and Diagnostics. Berlin Heidelberg : Springer , 2006 , 155-211.
[12] Phone meeting conversation between Haipeng Wang, He Zhang and Yuhong Zhang at JLab with Lijun Mao at
IMP on August 5, 2015.
[13] Strehl, P., Klabunde, J., Schaa, V., Vilhjalmsson, H., Wilms, D., Das Phasen-sondensystem am Unilac :
Sondendimensionierung und Signalauswertung, GSI-Report 79–13, (1979), translated for the Los Alamos Scientific
Laboratory by Leo Kanner Associates, Redwood City, (1980), LA-TR-80–43.
[14] JLab technote publication JLab-TN-15-039.
MEIC Collaboration Meeting
(October 5-7, 2015)