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C. Ohmori ( KEK)
2009/7/2 PRISM FFAG workshop@Imperial College
ContentsPRISM RF
IntroductionsPresent status, RF for beamRF for 6 cell ringUpgrade planEMMA RFRF system for PRSIM
2009/7/2 PRISM FFAG workshop@Imperial College
Requirements for RFHigh voltage
at 3.8 MHz Total 2-3 MV200 kV/m8 straights
for RF
2009/7/2 PRISM FFAG workshop@Imperial College
•Saw-Tooth RF–Linear RF bucket–Composed of 3 harmonics
Requirements for RF
2009/7/2 PRISM FFAG workshop@Imperial College
MA cavity for PRISMHigh field gradient at low frequencyWideband (low Q)Thin cavity (about 30 cm / cavity )Use the maximum size for MA cores
(1.7m X 1m)Very low duty RF system
To reduce the costSmall tetrodes for the end stageSmall APS (anode power supply)
2009/7/2 PRISM FFAG workshop@Imperial College
High Field Gradient : around 200 kV/m few MV RF for quick phase rotation (around 1.5 us)Dedicated system for pulse operation (low duty : 0.1%)
2009/7/2 PRISM FFAG workshop@Imperial College
Characteristics of Magnetic Cores
1.00E+09
1.00E+10
1.00E+11
1 10 100 1000 10000
up'Q
f
Brf[Gauss]
SY2
N5C
4M2-302
FT-small
FT-large200V/div, 5ms/div
High Loss Effect
Magnetic Alloys
Ferrites
2000 Gauss
シャントインピー
ダンス
に比例
電圧に比例
2009/7/2 PRISM FFAG workshop@Imperial College
1.7m
1m
1.0m
2009/7/2 PRISM FFAG workshop@Imperial College
Thin RF cavities surrounded by RF amplifiers2009/7/2 PRISM FFAG workshop@Imperial College
Dedicated system for low dutyAMP
Use small tubesWorks for short moment; 1-2 us X 1 kHz
For 1 kHz repetition, need to minimize RF-ON time99 % of time: zero anode current,
99.9%:zero RF output Cavity loss : few kW Tube loss : few ten kW
APSOld fashion to minimize cost: Crowbar, 3-
phase Full-wave rectification J-PARC :1MW system, no crowbar, switching with
IGBTSupplies power to 4 AMPs, several MW in
total.
2009/7/2 PRISM FFAG workshop@Imperial College
Tube ON by modulation of CG voltage
RFON
Cathode current
2009/7/2 PRISM FFAG workshop@Imperial College
100kW tube AMP, >1MW output1.4X0.7X0.8m
J-PARC600kW tube AMP500kW output1.4X1.0X2.4m
Multi-MW APS, 1X1.5X2.0m 1.2 MW APS for J-PARC, 4.5X2X2.7m
Dedicated RF system for low duty
2009/7/2 PRISM FFAG workshop@Imperial College
STATUS of PRISM RFRF frequency 5 -> 3.8 MHz (larger
circumference)->2 MHz for beamAMP has modified for low frequency
operation.Achieved 30 kV/gap, 100 kV/m.
Core impedance : 100 /core @2 MHz128 /core @3.8 MHz 244/core@ 18 MHz
Number of cores: 4 instead of 6 (design : 6 cores, total 1k)
2009/7/2 PRISM FFAG workshop@Imperial College
6 cell ring
2009/7/2 PRISM FFAG workshop@Imperial College
2009/7/2 PRISM FFAG workshop@Imperial College
Gap voltage
2009/7/2 PRISM FFAG workshop@Imperial College
6 cell PRISMTest using beam has been carried out.At 2 MHz, 100 kV/m was achievedSaw-tooth will be tried.
2009/7/2 PRISM FFAG workshop@Imperial College
Hybrid RF systemProposed by A. Schnase.Combination of MA cavity with a resonant
circuit composed by inductor and capacitor.
Developed for J-PARC RCS cavities.
f=1/2√LC
1/L=1/Lcore+1/Lind
J-PARC: add C and L to control Q and f PRISM : add L to control f
Q=Rp/LRp: shunt
2009/7/2 PRISM FFAG workshop@Imperial College
Parallel inductor for J-PARC
Inside of PRISM AMP2009/7/2 PRISM FFAG workshop@Imperial College
Hybrid (+ 8 uH inductor) Hybrid ( +18 uH), 3.8 MHz
Total C =180pF Hybrid (+40 uH inductor)
Expected impedance with parallel inductor
2009/7/2 PRISM FFAG workshop@Imperial College
Saw-Tooth : RF Cavity will be a wideband cavity.
But, bandwidth of AMP is still limited (1/RC).To obtain high RF voltage, a large drive
voltage is still required for CG-Cathode.Solutions
Low duty high power DAMP based on CERN/J-PARC DAMP.
Drive from both CG and Cathode is possible in case of short pulse operation. Narrow bandwidths are enough for both CG and
Cathode. -> save the cost for Driver AMPBoth need test.
2009/7/2 PRISM FFAG workshop@Imperial College
Over 30 kV anode voltage, soft X-ray was observed.Additional X-ray shields were add on vacuum tubes and AMP.Most sensitive X-ray detector was used.
2009/7/2 PRISM FFAG workshop@Imperial College
Upgrade PlanHigh Field GradientCost reduction
2009/7/2 PRISM FFAG workshop@Imperial College
Improvements of cavity impedance
Improvements of cavity cores X 2 by annealing
under magnetic field for thinner ribbon
Small cores : OK Large core ?
uQf (磁性体コアの特性)
0
2
4
6
8
10
12
14
0 1 2 3 4 5 6
frequency MH( z)
uQf (
GH
z)
uQf(FT3L,13um)uQf(FT3L,18um)uQf(FT3M,18um)
∝sh
unt i
mpe
danc
e
2009/7/2 PRISM FFAG workshop@Imperial College
How to improve MA consists of Fe, Si, B, Cu and Nb.Amorphous ribbon (<20 m) is annealed and
crystallized. Combination of magnetic field during annealing and
thinner ribbon (13 m)The small crystal has an axis magnetized easily. By the
special annealing, the axis is equal. But relation between core impedance and this effect is
not clear. Small cores : proved by Hitachi MetalLarge core : need big magnet and special oven. =>
Appling JSPS grant to produce these special core in KEK.
B-H curve of MA core produced by annealing with/without magnetic field.(by Hitachi Metal)
2009/7/2 PRISM FFAG workshop@Imperial College
Polarized μ
N_forwardN_backward
finemet‖cylinder
⊥cylinder
Decayed positron
Asymetry =(N_forward - N_backward)/(N_forward+N_backward)2009/7/2 PRISM FFAG workshop@Imperial College
2009/7/2 PRISM FFAG workshop@Imperial College
2009/7/2 PRISM FFAG workshop@Imperial College
It clearly showed the effects on magnetic properties by applying the magnetic field during the crystallization process in production.
It suggests that the magnetic axis of nano-scale crystalline in FT3L are aligned to the direction of the magnetic field during the annealing process. In the case that the initial spin direction of implanted muons is
perpendicular to the assumed easy-axis of nano-crystalline FT3L, the polarization of muons showed a quite fast damping.
In contrast, a slow relaxing time spectrum was obtained when the initial direction was aligned with the axis along which the magnetic field had been applied during the annealing, suggesting that the muon polarization is retained due to the local magnetic field.
On the other hand, such a drastic change was not seen in the case of FT3M. It turned out, however, that an anisotropic behaviour against the initial muon spin direction in FT3M was still observed, in spite of the absence of the magnetic field during the production. The muon implanted in parallel to the ribbon surface depolarizes slightly
faster than that implanted in perpendicular. This may suggest that the shape of MA, e.g. thickness, causes magnetic
anisotropy. It hints that the characteristics of FT3L depends more on the
thickness of ribbon than on an expected eddy current effect. 2009/7/2 PRISM FFAG workshop@Imperial College
High impedance coreFurther experiments using SR to confirm the effects of
ribbon thickness.We will Make larger cores to confirm the impedance
measurements. 27 cm size cores will be produced in this summer.
These R&D are also important for high intensity accelerators (J-PARC RCS, MR, ISIS-upgrade, CSNS etc.).
To confirm finally, it is important to build a cavity structure.
2009/7/2 PRISM FFAG workshop@Imperial College
Cost issuesSo far, 6 cores were necessary to generate 50
kV. However, 4 cores will be enough to generate 60 kV in case of high impedance cores. Achieving 1 k impedance will make a system
design similar to original one (6 cores, 5 MHz).The cavity cost seems to be larger than other
cost in case of PRISM. Higher voltage per core is preferable.
However, total cost to obtain 2MV is still expensive.
2009/7/2 PRISM FFAG workshop@Imperial College
conclusions
Beam test was performed by using PRISM rf cavity
Demonstrate > 100 kV/m.Also plan to test saw-tooth RFTo reduce the rf cost, developments of high
impedance cores are important.
2009/7/2 PRISM FFAG workshop@Imperial College
EMMA MA System* Many FFAG applications require slow acceleration* Non-scaling FFAGs cross many resonances
- Nonlinear resonances - Imperfection resonances
* Resonances damage beam more when you cross them slowly
* There is thus a minimum rate at which you can cross resonances - May depend on magnitude of errors
* Low-frequency RF to allow slow acceleration - EMMA as-is only allows very rapid acceleration - Primarily due to high-frequency RF system
* Accelerate rapidly then reduce rate - Start with 100 turns to insure success - Reduce acceleration rate and study effects
2009/7/2 PRISM FFAG workshop@Imperial College
Parameters frequency 18 MHz =1.3 GHz/72
frequency sweep 3 %
Total Voltage 100 kV per turn 100 turns/cycle
Number of cavities 3
Voltage 33 kV
Length of cavity 10 cm
Number of MA cores 2 per cavity
Size of MA core 27 cm O.D, 10 cm I.D x 2.5 cm
MA core Cut core
Q-value About 20
Cavity impedance 700(1.4 k)
Core material FT3M (FT3L)
2009/7/2 PRISM FFAG workshop@Imperial College
EMMA MA CAVITY
2009/7/2 PRISM FFAG workshop@Imperial College