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

2CNS summer school 2002

RIBF is a multi-disciplinary facility

◆ Nuclear Physics◆ Nuclear Astrophysics◆ Atomic Physics◆ Material Science◆ Nuclear Chemistry◆ Biology◆ Medicine◆ Nuclear Power

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

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.

5CNS summer school 2002

Bird Eye View of RIBF

2005

6CNS summer school 2002

åªé{ê›

é¿å±é{ê›

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

7CNS summer school 2002

Accelerator SchemeAccelerators

ECR18 RILAC

CMSRRC fRC IRC

SRC

RFQ linac

8CNS summer school 2002

Primary Beam Energy @RIBF

1 pµA for all elements

With fRC

9CNS summer school 2002

IRC Sector magnet

10CNS summer school 2002

SRC design

11CNS summer school 2002

ECRIS-18

ECRIS-18

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

13CNS summer school 2002

RI Beam Separators (Big-RIPS)

first stage separationsecond stage separation and tagging

14CNS summer school 2002

Production Target

Cooling Water(293K)

BeamTargetRotating

Beam Spot(Al)CoolingPlate TargetFixingPlate(Al)

inVacuumsize unit[mm]

210260

1015

23510

220

Rotating

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

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

17CNS summer school 2002

Experimental Room.

γ-ball .Large acceptance spec

neutron wall

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

19CNS summer school 2002

Doubly Magic Nuclei IntensityParticles/ second100Sn56Ni132Sn78NiMass, lifetime,

Interaction cross section

Fragmentation

Coulomb excitation

Magnetic moment

Elastic scattering

20CNS summer school 2002

Search for Superheavy Elements

Confirmation in different laboratories is essential!

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

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

23CNS summer school 2002

GARIS

24CNS summer school 2002

GARIS target with Beam

Target and Beam in He gas

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>

26CNS summer school 2002

GARIS Detector

Strip PSD

SSD

27CNS summer school 2002

271[110] by 208Pb(64Ni,n)271[110]

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

29CNS summer school 2002

Collaborators:

K. Morita RIKENK. Morimoto RIKEND. Kaji RIKEN, Niigata U. And many others

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.

31CNS summer school 2002

234Bk chains

32CNS summer school 2002

234Bk

230Am

Unknown

One candidate possible

Decay chain of 234Bk

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

34CNS summer school 2002

SHE search is running at full speed