Plan for Beam Extraction using strip-line kicker with pulse bump orbit Present extraction kicker...
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Transcript of Plan for Beam Extraction using strip-line kicker with pulse bump orbit Present extraction kicker...
Plan for Beam Extraction using strip-line kicker with pulse bump orbit
•Present extraction kicker system
•Strip-line kicker system for ILC
•Beam extraction using strip-line kicker at ATF
• Preliminary test
•Magnets and power supplies for pulse bump
•Experiment plan
T.Naito
Septum MagnetExtraction Line
Damping Ring
Injected Beam
Extracted Beam
Extraction kicker(2nd kicker)
Damping Ring
Extraction kicker (1st kicker)
Injection kicker
L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 Lec2 L13 L14 L15 L16Lec1
Damping Ring
S-band injector Linac
L0
KEK/ATF(Accelerator Test Facility) Beam Transport
Line
Extraction Line
Present beam extraction (Pulse magnet kicker system)
1st kicker2nd kicker
Beam
design orbit
extra kickΔθ1
Δθ2
Phase advance π
Kick angle Stability1x10-3 -> 2.8x10-4
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1↓
1↓
2 >
2 >
1) Ch1: 10 mV 50 ns
2) Ch1: 100 mV 50 ns Thy. Current 1 Amplitude Droop at 300ns
3 bunches, 154ns spacing
308ns pulse width
The number of bunches are limited.
Strip-line kicker system for ILC
Delay Delay
TriggerSeptum
Delay
Circular beam orbit
Extracted beam orbit
DummyLoad
LBeam
stlip-line
d V
PPS-5kV
PPS+5kVDelay
Trigger
V
Delay
PPS : Pulse Power Supply
DummyLoad
~20 units for 0.6mrad kick angle
€
Δθ = 2g eVE
Ld
L = strip − line lengthd = distance between the electrodesV = pulse voltageE = Beam energy
€
g = tanh πω2d ⎛ ⎝ ⎜
⎞ ⎠ ⎟
ω = strip − line widthd = distance between the electrodes
Design of Strip-line electrode for ILC
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The shape of the electrode is designed to keep good uniformity of the deflecting field. The calculated flatness is 0.07% in the area of +/-1.8mm from the center.
Max field2.0MV/m
1.27MV/m
Geometric factor(analytical) =0.955
FID FPG5-3000M(1)
-1000
0
1000
2000
3000
4000
5000
-200 0 200 400 600 800 1000 1200Time(us)
FID FPG-3000M (3MHz, 3000 pulses)
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Burst pulses(3MHz, 3000pulses) droop : ~3%
Single pulse waveform
FID FPG5-3000M(2)Pulse width(FWHM) = 2nsPulse height = 5.8kVRise time = 1.5ns(5%~95%)Time jitter = 29psAmplitude jitter = 0.72%(limited by the scope resolution)
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Timing jitter measurement29ps(1s)
Amplitude jitter measurement0.72%(1s)
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Beam kick experiment at ATF-DR
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Single unit of strip-line kicker
DummyLoad
LBeam
stlip-line
d V
PPS+5kV
DummyLoad
DelayTrigger
The kick effect of the single strip-line kicker was measured by measuring the amplitude of the betatron oscillation in the ring. A turn-by-turn BPM system was used for the measurement of the betatron oscillation.
Timing scan of the kick pulse
Rise time = 3.2ns(1%~100%)Fall time = 4.0ns(100%~1%)
Beam kick profile measurementThe timing of the kick pulse is scanned for the timing of the beam with 200ps steps.
The kick angle is estimated from the amplitude of the betatron frequency of the FFT signal.
Septum MagnetExtraction Line
Damping Ring
Injected Beam
Extracted Beam
Extraction kicker(2nd kicker)
Damping Ring
Extraction kicker (1st kicker)
Injection kicker
L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 Lec2 L13 L14 L15 L16Lec1
Damping Ring
S-band injector Linac
L0
KEK/ATF(Accelerator Test Facility) Beam Transport
Line
Extraction Line
Location of strip-line kicker
Strip-line kicker
The bunch spacing in extraction line does not completely the same interval. A 2.8ns( or 5.6 ns) is added at every three bunches, for example, 154ns, 154ns, 154ns, 156.8ns, 154ns . . . .
The extraction pulse magnet is replaced by two units of strip-line kickers. Three cycles of the injected beam, which include up to 60 bunches, are extracted bunch-by-bunch with 154ns (or 308ns) spacing.
Strip-line electrode and pulser for ATF beam extraction
Electrode distance:12mmChamber diameter : 24mmImpedance :50ohmMax field at 10kV : 4.7MV/m
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FID developed 6MHz burst,7kV peak pulser.
A 60cm long kicker magnet makes a 4.6mrad kick angle. Two strip-line kickers can make only1.3mrad kick angle. It is not enough for the kick angle to extract the beam.
Replacement plan from kicker magnet to strip-line kicker
Beam extraction design with two strip-line kicker
The kick angle of the strip-line kicker is not enough to make the beam extraction orbit. A design uses pulse bump magnets and an auxiliary septum magnet, which has thin separator, to help in making the extraction orbit. This design makes a bump orbit after the beam damping, then the selected beam is extracted bunch-by-bunch by the strip-line kicker.
Timing chart of 60(30) bunches beam extractionThe bump orbit is gradually increased after all of the bunches have been damped. The strip-line kicker kicks out the beams at the timing of the flat-top of the bump orbit. The beams are extracted as one long bunch train, which is a 10micro-sec long with 154ns (or 308 ns) spacing.
Local bump test by using present magnets and DC power supplies(1)
The aperture survey was carried out by using present magnets and DC power supplies. The required bump height is 5mm to separate the extraction beam and the circular beam. However, the local bump could make only +4mm and -2mm height.
Local bump test by using present magnets and DC power supplies(2)
Bump height
The measurement has agreed with the optics settings. The aperture limit at +4mm and -2mm are assumed that the limits show the miss-alignment of the septum or a large orbit distortion at the location.
Beam extraction design with two strip-line
The bump orbit is optimized to eliminate the aperture limit at the septum area. This design has no orbit change at the septum area, however the bending angle of the bump magnets is increased.
Bump orbit
Required magnet parameters
1. Magnets(not yet designed)• Steering magnets
• Bending angle: 9mrad(max)• Effective length 100mm• 0.4T(max)
• Septum magnet • Bending angle: 14mrad• 1000AT, 0.6m, 1 turn coil
2. Power supplies• Steering magnets - 50A(MAX), 10V(pulse)• Septum magnet - 1000A, 1V(DC)
Proposed Schedule
•10kV fast pulser order and test Summer 2007
•Fabrication strip-line electrodes Fall 2007
•Fabrication bump magnets and pulse PS Summer 2007
•Pulse bump magnet test Fall 2007
•Fabrication Septum magnet Fall 2007 -
•Installation strip-line electrodes and septum Spring 2008
•Beam test Spring 2008