Transcript Magnet and Power Supply Systems of Rapid Cycle Synchrotron

Rapid Cycling Synchrotron (I)
CAT-KEK-Sokendai School on Spallation Neutron Sources
K. Endo (KEK)
Feb. 2-7, 2004
CAT-KEK-Sokendai School on
Spallation Neutron Sources
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Contents
1) Rapid Cycling Synchrotron
2) Accelerator-Based Pulsed Neutron
Sources – Existing Facilities
3) Next Generation Spallation Neutron
Sources
4) Advantage/Disadvantage of RCS
5) Combined or Separated function RCS
6) Proton Driver for Neutrino Factory
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Spallation Neutron Sources
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Rapid Cycling Synchrotron (RCS) (1)
Increasing the repetition rate to 10~60Hz, it is possible to obtain much
higher proton intensity. This type is called as a “rapid cycling
synchrotron,” but it requires special design consideration including its
power supply.
Magnet: AC magnet made of laminated steel plates and requires
design study using 2D or 3D field simulation code.
Power supply: Resonant circuit to provide with sinusoidal current under
the operation of the basing DC power supply.
Operation: Combined function is easy.
Separated function requires a precise tracking between
Bending and Focusing fields.
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Rapid Cycling Synchrotron (2)
• Resonance Condition: Loads including magnets,
capacitor and choke transformer are in resonance
condition.
• Energy exchanged between magnets and capacitors,
while the pulse power supply provides the losses.
• Utilize Full AC Field Swing: superpose DC field to
AC field to have Injection at bottom AC field.
Choke Transformer is introduced to decouple
the pulse power supply.
• Reduce magnet voltage: adopt multi-mesh circuit.
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Rapid Cycling Synchrotron (3) – White circuit
Princeton 3GeV proton synchrotron in 1956.
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Rapid Cycling Synchrotron (4)
Example of magnet, coil and pole end
profile for rapid cycling synchrotron.
Effect of
magnet end
pole profile
(a) Rogowsky
profile, and
(b)
Distribution of
flux lines.
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Rapid Cycling Synchrotron (5)
1:n
I
Ip
Vs/n
Rm
Rch
Lm
C
2
Lch/n
Lch
I1
Choke trans.
Primary winding voltage
I2
Capacitor Magnet
Vs/n
(a)
Ti
t=0
T
(b)
Experimental setup for the control of pulse and dc power supplies
F-coil
DC bias PS
backleg winding
S-coil
VFC
settings of
flip number
& interval
FC
16 bits
SCR Firing
circuit
DAC
strobe
Bac
Motor
counter
16
DIO BOARD-1
Bdc
INT
Motor
controller
RS-232C
PC
DIO BOARD-2
Bac reference
16 bits
Numerical results of the single mesh magnet current for the
interval of t=0.0 ~ 0.2 sec and t=0.3 ~ 3.0 sec assuming
Lm=0.044 H, Rm=0.152W and T=0.020 sec. Amplitude is arbitrary.
VFC
counter
16
Vs/ n
NEC-9801
t=[0.0, 0.2] sec
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Spallation Neutron Sources
t=[3.0, 3.2] sec
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Rapid Cycling Synchrotron (6)
Multi-mesh circuit
NINA electron synchrotron
combined function magnet
Max. energy = 4GeV
Mean orbit rad. = 35.1m
Bending rad. = 20.8m
Injection energy = 40MeV
Field @4GeV = 0.64T
Repetition = 50Hz
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Accelerator-Based Pulsed Neutron Sources
Existing Facilities
Acc. type
Beam Energy
(MeV)
Rep. Rate (Hz)
Av. Beam Current
(mA)
Pulse Width (ms)
Beam Power (kW)
IPNS (ANL)
Linac/RCS (CF,
13.6m dia.)
50450
30
15
0.1
7
KENS (KEK)
Linac/RCS (CF,
12m dia.)
40500
20
6
0.1
3
ISIS (RAL)
Linac/RCS (SF,
52m dia.)
70800
50
200
0.1
160
LANSCE_PSR (LANL)
Linac/AR (SF,
30m dia.)
800
20
125
7500.25
100
SINQ (PSI)
Cyclotron
72590
continuous
1500
900
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Layout of Proton Sources
Layout of Spallation Neutron Source
LANL
Target
Linac
AR
Linac-driven
RAL, ANL, KEK
RCS
Synchrotron-driven
PSI
Cyclotron-driven
Cyclotron
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CAT-KEK-Sokendai School on
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Next Generation Spallation Neutron Sources
Scheme
Max. beam
power
(MW)
Bunch
compression
(msec)
Magnet
system
1GeV Linac
+60Hz-AR
1
2 (upgrade)
1000 to 0.5
SF
(FODO)
ESS
(EU)
1.334GeV
Linac + 50HzAR x 2
5
600 to 0.4
SF
(Triplet)
J-PARC
(Japan)
0.4GeV Linac
+25Hz-3GeV
RCS
1
500 to 0.1
SF
(FODO)
NSNS
(USA)
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NSNS (1) – ORNL1,2,3,4)
H- ion source+2.5MeV RFQ: LBNL 50mA-HLinac
NC-DTL+CCL: LANL (2.5200MeV).
SC-Linac: JLab. (2001000MeV).
Accumulation Ring: BNL
Charge exchange injection (H-p)
1200 turn injection, Short (1msec) and intense
proton pulses are extracted at 60Hz.
Mercury target: ORNL
Exp. Facilities: ANL+ORNL
Extraction is a single turn with full aperture at
a pulse repetition rate of 60Hz. Extraction
system consists of a full-aperture kicker
and a Lambertson magnet septum.
Vertically kicked and horizontally
extracted.
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NSNS (2)
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NSNS (3)
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ESS (European Spallation Source) (1)
Main parameters of ESS
Linac
Beam energy = 1.334 GeV
Beam power = 5.1 MW(av.)
Average / peak current = 3.8 / 107 mA
Repetition rate = 50 Hz
Beam pulse duration = 2 x 0.6 msec
Beam duty cycle = 6.0 %
Two Accumulator rings
Frequency = 50 Hz (parallel operation)
Proton beam / ring = 2.34 x 1014 ppp
Bunch length = 0.4 m sec at ejection
Mean radius = 26.0 m
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ESS (2) 5) - Options for 5MW proton beam @50Hz
in pulse of time duration 1ms or less
1.
2.
3.
4.
5.
0.8GeV H- linac + 3 ARs
1.334GeV H- linac + 2 ARs
0.8GeV H- linac + 2 RCSs of 3GeV and 25Hz
2.4GeV H- linac + 1 AR
0.8GeV H- linac + 1.6 or 3GeV superconducting FFAG,
30GeV KAON Factory type accelerator, or
1GeV proton induction linac
Expensive
2nd option: highest operational reliability
3rd option: secondary consideration for a long pulse (2ms) facility
Low energy injection: severe space charge limit
but less severe heat problem for H- stripping foil
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ESS (3) – AR option
Two 50Hz, 1.334GeV AR (Accumulation Ring).
AR’s act to compress the time duration of the Linac
Pulse by a multi-turn (1000 turns/ring) charge exchange
injection.
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ESS (4) – RCS option
Two 25Hz RCS operate out of
phase at 3GeV, 50Hz.
Very high power RF system
occupies more straight
sections than 1.334GeV AR,
leading to 4 superperiods.
Mean radius: 45.9m
Injection: 0.8GeV
Space charge tune shift: 0.2,
twice of AR.
Injection flat bottom: 2.5ms
Dual harmonics: 20Hz sinusoidal
rise and 40Hz fall.
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J-PARC (1)6)
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J-PARC (2)
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J-PARC (3) - Future upgrade
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Advantage/Disadvantage of RCS7)
1)
2)
3)
4)
5)
Neutron yield is proportional to beam power (Eb x Ib). Trade
off between repetition rate, beam current and beam energy.
RCS achieves high power at low repetition rate at reasonable
cost compared to linac/compressor scenario.
RCS requires high power RF cavity
Care for Eddy current due to rapid change of Magnetic field
Space charge limit at low energy injection, so the peak
current in RCS is several times smaller
Longer beam-in-ring time (10 to 20ms) compared to
linac/compressor ring (1 to 2ms) will have a greater risk of
instabilities associated with large number of cavities.
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Comparison of Linac- and RCS-based concepts
Linac-based
RCS-based
Beam energy
low
high
Beam current
high
low
severe
mitigated
high current
high duty
expensive
moderate
less costly
low
high
Beam loss control
H- ion source
Construction cost
Required RF power
for AR or RCS
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Reducing RCS-RF power by Dual-frequency mode
Excitation
For the case of IPNS upgrade study to 1 MW at ANL,
Single mode;
2 GeV, 0.5 mA, 30 Hz RCS requires 180 kV RF voltage.
Dual mode;
2 GeV, 0.5 mA, 20 / 60 Hz dual mode: 120 kV RF voltage.
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Combined or Separated function RCS
Tracking between dipole and quadrupole fields
• Combined
• Separated
• Tracking maintained but limited tunability.
NINA, Fermilab, KEK-PS
• Dipoles and quads are serially connected,
but requires trim quad windings or
dependent correction quad. SSC, SSRL
• Serial resonance circuit for quad. J-PARC
• Independent excitation of B, QF and QD,
each phase adjusted within ±1msec. No
magnet saturation. BESSY II Booster (10Hz)
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Tuning of QF and QD for Separated-function RCS
Bucking choke is used to cancel the induced voltage
in the trim coil caused by the main coil circuit.
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Proton Driver for Neutrino Factory (1)8) - RCS based
•
Proton driver for
neutrino factory,
fitting into CERN-ISR
beam power: 4MW
final bunch duration: 1ns
RAL: Synchrotron-based two RCS options
1) 1.2GeV @50Hz + 5GeV @25Hz
2) 3GeV @25Hz + 15GeV @12.5Hz
CERN: Linac-based proton driver
2.2GeV @75Hz linac + Accumulator
and Compressor rings
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Proton Driver for Neutrino Factory (2) - Linac-based
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References
1)
2)
3)
4)
5)
6)
7)
8)
W.T. Weng et al, “Accumulator Ring Design for the NSNS Project,” PAC97, pp.970.
D. Raparia et al, “The NSNS Ring to Target Beam Transport Line,” BNL/NSNS Technical
Note No.006.
J. Wei et al, “Low-Loss Design for the High-Intensity Accumulator Ring of the Spallation
Neutron Source,” PRST-AB, 3, 080101 (2000)
“Final Design Review: SNS Super Conducting Linac RF Control System,” 2000.
G. Bauer et al (ed.), “The ESS Feasibility Study Vol. III Technical Study,” ESS-96-53-M,
1996.
Draft of “Accelerator Technical Report for High-Intensity Proton Accelerator Facility
Project,” JEARI/KEK Joint Team, http://hadron.kek.jp/member/onishi/tdr/index.html
Y. Cho, “Synchrotron-Based Spallation N eutron Source Concept,” APAC98, Tsukuba, 1998.
C,.R. Prior et al, “Synchrotron-Based Proton Drivers for a Neutrino Factory,” EPAC2000,
Vienna, 2000, pp.963-965.
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