RNB project on the astrophysical element synthesis
20180921 TGSW2018 session8-9
H. Miyatake , WNSC, IPNS, KEK• Physics motivation of the KISS project• Recent activities at KISS stage I-> Lifetime and mass measurements• SummaryWhat is KISS ?

- How are the gold and platinum synthesized ? -3rd

Atomic number

So2nd p larr-peakroce

ssabunAdpeak anc(Ae~195)

H. Grawe et al., Rep. Prog. Phys. 70 (2007), 1525-1582.

esco) prdnipra
Neutron numbere

Waiting point forthe 3rd peaks Blank spotr(eturpacn
The third peak of the abundance patternoutr

Unclear estimations with various nuclear models
à Most important region to pin down theastrophysical origin of the r-process

Physics goalー Lifetime and Mass measurements ー),,-,Indirectly• neutron fraction (1-Ye)• production rates of fissile isotopes• nuclear properties in waiting region•-.

.

( ,from K. –L. Kratz, et al., Ap. J. 403(‘93)216.

Second peak(A~130)

Temperature (109 K

Directly• (n, γ)-(γ, n) equilibrium:r-process path• lifetimes of waiting nuclei
duration time to form the third peak• steady flow approx.:
correlation between T and Nn

First peak(A~80)

Third peak(A~195)???

(Neutron number density (n/cm3)
GW170817: from optical (UV, IR) observation• r-process heavy element synthesis is occurred in the NSM event(< Lanthanoid)• Further questions: heavier element synthesis, fission recycling, terminationof the r-process

KISS: KEK Isotope Separation System- New research method for waiting nuclei of A=195 peak -(1) Multi-nucleon transfer
reactionsn-rich beams (~10 MeV/u)i.e. (136-144)Xe+198Pt(2) In-gas laser ionization

232

Neutralization of RI by argon gas+ Laser resonance ionization (Z)+ mass separation (A)+ Det. system at low-background

33-33

33

Radioactive Isotope Beam Factory (RIBF)

2011~2012installation2013-2014: R&D’s
Y. Hirayama, EPJ 66(’14)11017.
Y.X. Watanabe, P.R.L. 115(’15)172503.

-32-

Uncertainty of lifetime & mass predictions
in N=126 isotones

β-decay half-life (sec)Stage I (~2020, 136Xe, 250 pnA) to Stage II (2021~, 238U, up to 10 pμA)
Waitingregionδ~100 keV

Waiting
regionΔT1/2/T1/2 < 10%Stage II

Stage IYb Lu Hf Ta W Re Os Ir Pt Au Hg) )(Stage II) )(Stage IKISS (KEK Isotope Separation System)
Y. Hirayama et al., NIMB 412 (2017) 11-18.

~50kPaDecay measurement
10-4kPa

30Pa

0.1Pa

M. Mukai et al., NIM A884(2018)1.

10-4PaTapehelium gas cell ion cooler
Multi-trap ion buncher
MRTOF-MSSUSKISS beam

IBS-KEK collaboration
Decay meas. St.

KISSbeamKb e ISSam

He gas cell ion cooler(coming soon)

200 mmMini-MRTOF-MS(under tuning)

SteererDeflector(already tested)

βMesh&Myler foil

EQQ
(already tested)
Multi-trap ion buncher (coming soon)

BG

2 layers
16 segmented
proportional
gas countersΔΩ = 79% (4π)
Ethr. ~ 140 eV
Emin. ~ 100 keV

Lifetime confirmation and decay spectroscopy
in FY2016 to 2017

New identification

198Os• Y. Hirayama et al., Phys. Rev. C96(2017)014307.
Phys. Rev. C98(2018)014321
KUTY : H. Koura, et al.,
http://wwwndc.jaea.go.jp/CN14/index.html Expected T1/2

measured region

Aut1/2=2.0(5) min

Pt 198Pt
203

Os202Os

Xe :20pnA Re
250pnA W

Stage ITaU:
500pnA Hf

Stage II@ present RIBF

238

Lu
10pμA Yb

Stage II @RIBF upgrade

201

Ir

1hTime (s)

Re

200
199

New198W

Ta

Waitingregion

136

Ir

1s

εext=0.1% 120 121 122 123 124 125 126 127
Neutron number• 12 n-rich isotopes (Pt, Ir, and Os) have been measured.
• 198Os has been newly identified with half-life of 2 min..
• Some discrepancies between the reported and present data• Some isomeric states would be newly assigned

Revised197

Os isotopes

Direct mass measurementwith Multi-Reflection Time-Of-Flight Mass Spectrograph (MRTOF-MS)→ Comprehensive mass determination ofradioactive isotopes available at RIBF
ion mirror

P. Schury et al,
PRC95(2017)011305R

ion mirror
after drinking
1 cc waterTermination properties of the r-process

Proton Number Z

proved by nuclear mass measurements

Direct Meas. (KEK)
Indirect Meas. (KEK)
Direct Meas. (GSI)
Indirect Meas. (GSI)
Identified isotopes(Mass Number)

Hot fusion
reactions
Cold fusionreactions

α decays

Nuclear fissions
β- decays

Neutron Number N
P. Schury et al, Phys. Rev. C95(2017)011305R
NIM B407(2017)160
Y. Ito et al., Phys. Rev. Lett. 120(2018)152501.

β- decays from the r-pathSummary• KISS project has been launched since FY2015 to determine astrophysicalconditions of the third abundance peak synthesized in the r-process.
• Decay measurements in the vicinity of N=126 waiting region has alreadybeen started using KISS at Riken.
• Decay properties of n-rich 12 isotopes has been investigated to contributenuclear model improvements.
• Newly developed MRTOF-MS has revealed its high performance in heavy
element region.
• Mass measurements at KISS will be ready within this year not only for theN=126 waiting region but also for the r-process termination region.

fin