SC-ECR ion source for RIKEN RIBF
1. IntroductionRequirements for RIKEN RIBF
2. Physics of ECR ion sourceEffects of the key components on the beamintensity and ECR plasma
3. RIKEN SC-ECRISSc-coils, plasma chamber, RF power supply
4. ResultsBeam intensity with 28GHz microwaveX-ray heat load
5. Future plan
T. NAKAGAWA (RIKEN)
RIKEN RIBF
Heavier than Xe ion
Lighter than Xe ion
~345MeV/u
18GHz ECR ion source
28GHZ SC-ECRIS
RILAC II
RILAC
RRC
FRCIRC
SRCBig RIPS(fragment separator)
18GHz ECRIS U ion beam ~60pnA(U35+ 2emA)
on target ~0.4pnA(345MeV/u)
>40 new isotopes were producedby in-flight fission reaction(4 days experiments)
New isotopes
T. Ohnishi et al, JPSL 79(2010)073201
Recent result at RIKEN RIBF I (new isotopes)
U35+(1010cm-3sec)
U20+(109 cm-3sec)
nq : ion densityV : plasma volumeti : ion confinement time
ne LargerV Largertc Shorterneti Constant (1010(cm-3ms)
(I)Plasma condition
(II)Beam intensity
QuestionHow to make these conditions ?
ne : electron densityti : ion confinement timeTopt: electron temperature
nq(cm-3) 1011 1012
ti(ms) 100 10I 1012 1014
U35+(1010cm-3sec)
Factor 100!
Production mechanism of intense beam of Highly Charged Heavy Ions
1)Magnetic field configurationplasma confinement & power absorption
2)Gas pressure3)Microwave frequency4)Plasma chamber size
ne : electron densityti : ion confinement timeTopt: electron temperature
Mechanism?
ne LargerV Largertc Shorterneti Constant (1010(cm-3ms)
Effect of the key components on the beam
Beam intensity
O5+ (14GHz)
Magnetic field configuration I (Bmin effect )
18GHz
14GHz~0.4T(0.8Becr)
~0.5T(0.8Becr)
N. I. M. A 491(2002)9 H. Arai et al,
3 solenoid coils magnetic mirror
Coil #1 Coil #2Coil #3
Sextupole CoilIronAluminum
Ex., “Flat Bmin “ structureG. D. Alton and D. N. Smithe,Rev. Sci. Instrum. 65 (1994) 775
3 solenoid coils Several solenoid coils (>3 coils)
SC-ECRISSuSI MSURIKEN28 RIKEN
Field gradient and surface size effect I
Field gradient
Energy transfer at ECR zone
Gentler field gradient
large energy transfer
Higher beam intensity
Larger zone size
Lager absorption
Higher beam intensity
Bext ~2Becr
Binj~3.5Becr
Magnetic field configuration II (Mirror ratio)
G. Ciavola et al, RSI 63(1992)2881
Gas pressure effect
Total beam current increases with increasing gas pressure
2x10-7Torr 7x10-7Torr~30pmA ~70pmA
Mean charge state decreases with increasing gas pressure
2x10-7Torr 7x10-7Torr<q>~3.5 ~2.2
Gas pressure effect
Electron density
Ion confinement time
(II)SECRAL(2009)
(I)SERSE (~2000)
Frequency effect I
SERSERF power1.8kW
Binj~3.5Becr,Bmin~0.8Becr,Bext~2BecrBr~2Becr
SECRAL
Binj~3.5Becr,Bmin~0.8Becr,Bext~2BecrBr~2Becr
H.W. Zhao et al, RSI 2010(81)02A202
S. Gammino et al, RSI 1999(70)3577
Y. Higurashi et al, accepted for publication to RSI
(III)RIKEN SC-ECRIS(2011)
Collision term HF term Source term
Strength of electric field(RF power)
Magnetic field gradient(Bmin effect)
m
BFokker-planck equation electron
Microwave Frequency effect II
A. Girard et al, J. Computational Phys.191(2003)228
Microwave Frequency effect III
Fokker planck equation
A. Girard et al, J. Computational Phys.191(2003)228
Absorption power
Total beam intensity
Optimization of magnetic field configuration
Gas pressure
Scenario to increase the beam intensity
Increase microwavefrequency
RF power
Bmin
BinjGas pressure
frequency
Chamber size effect (ion confinement time) I
Chamber size (quadrumafios)10times larger than caprice
q: charge stateL: chamber length
Ion confinement time
D. Hitz et al, Physica Scripta 1999
Physics background for designing of Sc-ECRIS
Magnetic field Binj ~4T Bext ~2T Br~2T (High B mode)(plasma confinement)Bmin <1T (~0.8Becr) (choose the optimum field gradient)ECR zone size as large as possible
Chamber size Diameter >15cm (comparison between RIKEN 18 GHzand VENUS, SCRAL)
Length >50cm (Long confinement time)
Microwave 28GHzPower >10kW ( 1kW/L)(High power density)
Binj ~3.8T Bmin <1.0T Bext ~2.3T
Br ~2.1T
For 28GHz operations
SC Solenoid coilsHexapole magnet
Microwave guide
Plasma chamber
Beam extraction system
Solenoid coil
Plasma chamber
Iron yoke
SC ECR ion source (RIKEN 28)
High energy Physics and Nuclear Physics 31(2007)37J. Ohnishi et al,
“Flat Bmin “ structureG. D. Alton and D. N. Smithe, Rev. Sci. Instrum. 65 (1994) 775
Main parameters of SC-Coils
High energy Physics and Nuclear Physics 31(2007)37J. Ohnishi et al,
Superconducting coils
Solenoid coils
Hexapole magnet
-400-200
0200400600800
10001200
-60 -40 -20 0 20 40 60Z (cm)
F (kN
/m)
Ft coil1Ft coil2Fr
-25cm 0 25cm
Strong force to hexapole magnet(~1100kNm max.)
Cryostat
(W)
Item Heliumvessel
Low temp.radiation
shield
High temp.radiation
shieldDesign temp. 4.2 K 20 K 70KRadiation 0.005 5.5 40Conduction
Support 0.005 0.3 4Port 0.06 1.5 20Current lead 0.07 10 64
Total heat load 0.14 17.3 128
GM refrig. 35W(45K), 6.3W(10K)
GM. Refrig. 50W(43K), 1.0W(4.2K)
CG310SC(SUMITOMO)(GM-JT refrig.)
Cooling capacity4.2W/[email protected](50/60Hz)
Electric power consump. 5.1/6.1kW(50/60Hz)Electric power AC200V 3 phaseWeight ~220kgrDimension 700Wx520Dx1095H
SC Solenoid coilsHexapole magnet
Microwave guide
Movable biased disc
Beam extraction system
Solenoid coil Plasma chamber
Iron yoke
Plasma chamber
Plasma electrodeExtraction electrode (accel)
Extraction electrode (decel) Plasma chamber
SC Hexapole coil
Beam extraction system
RF injection side Beam extraction side
GM refrigerators
GM-JT refrigerator
Solenoid coilIron yoke
Picture (SC-ECRIS)
Analyzing magnet
Vacuum chamberECR ion source
beam
New injector system
U35+ beam productionSputtering method20~30emAlong term operation(> 1month)~100pmm mrad (~90%)
Gyrotron
Arc sensorMode converterTE02 TE01
Mode filter
High voltage break
Vacuum window
Plasma chamber
Conversion efficiency >95%TE02 TE01
RF 10kWmax
SC-ECRIS + Gyrotron
28GHz Gyrotron
Gyrotron
Xe ion production
Binj~3.2T, Bmin~0.63T, Bext~1.8TBr~1.85T
Binj~3.2T, Bext~1.8T,Br~1.85T
Plasma chamberExtraction electrode
Plasma electrode
Sc-solenoide coils
Biased disc
U rod
ECR zone
U-rod
Support rod(water cooled)
U ion beam production
Sputtering method
Injected power (plasma chamber) vs. U35+ beam
Output power (Gyrotron)vs. U35+ beam
Binj~3.2T, Bmin~0.63T, Bext~1.8TBr~1.85T
Bo : axial magnetic fieldq: charge stateM: mass
Bo 18GHz ~1.2T28GHz ~1.8T
Cal: same q/M same emittance
: higher Bo larger emittance
Emittance measurements
VENUS 28GHz
RIKEN SC-ECRIS 28GHz
X-ray heat load
High energy x-ray (>several 100keV)
plasmacryostat
D. Leitner et al, RSI 79(79)033302
Y. Higurashi et al, accepted for publication to RSI
X-ray heat load (field gradient effect) I
Gentler field gradient
Higher beam intensity
Cooling power is limited by cryo-cooler(several W)
Increase the cooling power
Minimizing the heat load while keeping or increasing the beam intensity
X-ray heat load (field gradient effect) III
D. Leitner et al, RSI 79(2008)02C710
RF power >6kW U35+~200emA
using High temp. Ovenmore U vapour
Next step – increase of U beam-
Next step-RIKEN SC-ECRIS
1. Optimizing the magnetic field distribution for 28GHz
2. Use of Al chamber ( cold electron doner)
3. Increase the RF power (>6kW)
4. Stabilizing the beam intensity
5. Optimizing the extraction
Top Related