The RI-Beam Factory and Recent Development in Superheavy Elements Search at RIKEN
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Transcript of The RI-Beam Factory and Recent Development in Superheavy Elements Search at RIKEN
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1CNS summer school 2002
The RI-Beam Factory and
Recent Development in Superheavy Elements Search at
RIKEN
◆ Brief introduction to the RI Beam Factory◆ Confirmation of 271[110] and discovery of a
new transuranium isotope 234Bk
Isao Tanihata RIKEN
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2CNS summer school 2002
RIBF is a multi-disciplinary facility
◆ Nuclear Physics◆ Nuclear Astrophysics◆ Atomic Physics◆ Material Science◆ Nuclear Chemistry◆ Biology◆ Medicine◆ Nuclear Power
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3CNS summer school 2002
Nuclear Physics◆ Probe the limit of nuclear existence and to
understand the basic physics of the nuclear landscape
■ Exploration of the limit of existence Drip-line nuclei Nuclei outside the drip lines Superheavy nuclei
■ Magic numbers far from the stability■ Study of unbalanced nuclear matter and the role of isospin
◆ Explore the new forms and dynamics of nuclei■ Neutron skins & halos
Also excitations and correlation
■ Exotic shapes
◆ Testing of the Standard model and fundamental symmetries and conservation laws
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4CNS summer school 2002
Nuclear Astrophysics
◆ Provide the basic data of nuclear astrophysics■ Big bang nucleosynthesis■ The CNO cycle to the rp-process■ Alpha-rich freeze out■ The r-process■ Equation of state of asymmetric matter and neutron stars■ Highly ionized atoms of unstable nuclei■ Remarks
The measurement and the analysis of the nuclei far from stability will provide new test benches for theoretical nuclear models. This should allow one to reformulate these models in a more general form. Hence, the predictive power of these models, when applied to unknown nuclei for nuclear astrophysics applications, will be greatly increased.
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5CNS summer school 2002
Bird Eye View of RIBF
2005
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6CNS summer school 2002
åªé{ê›
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RIBF
MUSES
AVF
RRC
IRC
SRC
RILAC/RFQECR
The Beam Delivering Method
◆ AVF cyclotron --> will become free■ CNS/RIKEN
◆ Present facility --> primary and secondary beam from ISR
◆ BigRIPS --> two experimental beam lines
◆ MUSES --> ACR, DSR
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7CNS summer school 2002
Accelerator SchemeAccelerators
ECR18 RILAC
CMSRRC fRC IRC
SRC
RFQ linac
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8CNS summer school 2002
Primary Beam Energy @RIBF
1 pµA for all elements
With fRC
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9CNS summer school 2002
IRC Sector magnet
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10CNS summer school 2002
SRC design
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11CNS summer school 2002
ECRIS-18
ECRIS-18
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12CNS summer school 2002
ECRIS-18 Beam Intensity
. .
ECRIS18-chr. st. dist.
10
100
Charge State
q=6
7
911
1320
15 12
15
1115
1518
15 20
24
ArO Kr Fe Ni Ru Ta
MIVOC Solid rodGas
Z= 8 18 36 26 28 44 73
Gaseous element Ar 160 e A (Argon gas)MIVOC method Fe 80 e A (Fe(C H ) )Solid rod Ta 32 e A
11+
13+
20+
μμμ (Ta rod 2mm)
5 5 2
φ
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13CNS summer school 2002
RI Beam Separators (Big-RIPS)
first stage separationsecond stage separation and tagging
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14CNS summer school 2002
Production Target
Cooling Water(293K)
BeamTargetRotating
Beam Spot(Al)CoolingPlate TargetFixingPlate(Al)
inVacuumsize unit[mm]
210260
1015
23510
220
Rotating
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15CNS summer school 2002
R.T. Test Result Rot.Speed vs Temp.
050100150200250300350400450500
01020304050607080Target Rotation [rpm]
Spot Temp. [deg]
Tcent 1L/mTcent 3L/mTcent 5L/mTcent 8L/mTcent 10L/mThead 1L/mThead 3L/mThead 5L/mThead 8L/mThead 10L/mTal 1L/mTal 3L/mTal 5L/mTal 8L/mTal 10L/m
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16CNS summer school 2002
Rotating Target Extension
◆ Changing target thickness in one rotation■ 6000 rpm -> 1 rotation = 10 ms -> 10˚=0.27 ms■ Control of 0.3 ms is possible!■ 3mm/30cm diameter= 0.57
x at F1
time
ABCD
ABCD
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17CNS summer school 2002
Experimental Room.
γ-ball .Large acceptance spec
neutron wall
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18CNS summer school 2002
Secondary Beam Intensities
0.0 10.0
100
50
10050
RI Beam Intensity at the RI Beams FactoryPrimary beam of 1 pµA is assumed.Calculated by Intensity IIBy Nakamura
0 1010 10No. of particles per second
Production rate~ 10-5 /s
Z
N
Stable
limit of Tachibana
Nuclear Chart 1993by Chiharu Tanihata
Unstable
820 28
50
82
126
8
2028
50
82
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19CNS summer school 2002
Doubly Magic Nuclei IntensityParticles/ second100Sn56Ni132Sn78NiMass, lifetime,
Interaction cross section
Fragmentation
Coulomb excitation
Magnetic moment
Elastic scattering
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20CNS summer school 2002
Search for Superheavy Elements
Confirmation in different laboratories is essential!
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21CNS summer school 2002
Advantage of RIKEN
Yield = x T x I x = 10-36cm2 (1pb)T = 5x1017/cm2
I = 6x1012 /s (1 particle A) = 0.3
Y = 9x10-7 events/s 2.3 /month
◆ Heavy Element Search■ High-intensity beam from high-performance accelerator■ High-performance recoil separator
◆ Accelerator complex in RIKEN■ ECR ion source + RFQ Linac + RILAC + CSM■ Highest Energy 5.8AMeV■ Highest Intensity 10 particle A
◆ Gas-filled Recoil Separator GARIS■ Velocity & Charge -state focusing■ A large acceptance
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22CNS summer school 2002
Ring Cyclotron
GARIS
ECR+RFQ+RILAC + CSM
CSM(Charge State Multiplier)ECR ion source
RILAC(RIken Linear ACcelerator)
284. WE-Heraeus-Seminar 2002/08/08
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23CNS summer school 2002
GARIS
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24CNS summer school 2002
GARIS target with Beam
Target and Beam in He gas
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25CNS summer school 2002
.
<q>=0.62(v/v0)Z1/3
209Bi245Fm
255Lr254No
208Pb
271[110]
192Po
209Bi
169Tm
234Bk
203Fr
212Ac
265Hs
198Rn
208Pb
209Bi
208Pb
204Fr
(v/v0)Z1/3
<q>=0.62(v/v0)Z1/3
5 10 15 20 25 30
20
16
12
8
4
Principle of GARIS
◆ Magnetic rigidity
◆ is independent from ◆ the velocity of a nucleus.
€
R=mv/<q>
<q>∝v
R=mv0
0.62Z1/3
Vacuum
qc -1 q
c qc +1
gas
<q>
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26CNS summer school 2002
GARIS Detector
Strip PSD
SSD
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27CNS summer school 2002
271[110] by 208Pb(64Ni,n)271[110]
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28CNS summer school 2002
271[110] Summary
Reaction 208Pb(64Ni,1n)271[110]Target 208Pb 230 g/cm2
Efficiency 0.76Counting rate of PSD 2/s (@ 0.4 p A)
Beam energy 311.2 MeVTotal beam dose 8.8x1017
Event number 1Cross section 2.3 pb
Beam energy 314.2 MeVTotal beam dose 6.3x1017
Event number 2Cross section 6.3 pb
T(1/2) = 12.9 ms
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29CNS summer school 2002
Collaborators:
K. Morita RIKENK. Morimoto RIKEND. Kaji RIKEN, Niigata U. And many others
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30CNS summer school 2002
New Isotope of Bk
◆ 197Au(40Ar,3n)234Bk■ Beam energy at 196.9 and 188.4 MeV■ 1.5~2.5 particle µA
◆ 9 -chain events have been observed.
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31CNS summer school 2002
234Bk chains
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32CNS summer school 2002
234Bk
230Am
Unknown
One candidate possible
Decay chain of 234Bk
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33CNS summer school 2002
Comparison of -decay Q-value
◆ KUTY is the mass formula with shell energies on a spherical-basis,
◆ TUYY is the mass formula with an empirical shell term,
◆ FRDM is the finite-range-droplet model and folded-Yukawa single-particle potential, and
◆ HFBCS is to be based on the Hartree-Fock+BCS method with the MSk7 Skyrmeforce.
Alpha decay Q-value Comparison
-1.5
-1
-0.5
0
0.5
1
1.5
2
Bk Cm Pu U Th Ra Rn
elements
Q-value difference from experimental
value
DKUTY DTUYY DFRDM DHFBCS
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34CNS summer school 2002
SHE search is running at full speed