Invariant-mass spectroscopy ofextremely neutron-rich nuclei
with SAMURAI at RIBF
Yosuke Kondo(Tokyo Institute of Technology)

ARIS2014, ITO International Research Center (University of Tokyo), June 1-6, 2014

1

Contents

1. Introduction of SAMURAI at RIBF

2. First experimental campaign using SAMURAI
for physics programs (Day-One campaign)Superconducting Analyzer for MUltiple-particles from RAdioIsotope Beam

Kinematically complete
measurements by detecting
superconducting
multiple particles in coincidence
coilpole(2m dia.)

RI beamfrom BigRIPS

vacuum chamber

Neutrontarget

Superconducting Magnet

3T with 2m dia. pole(designed resolution 1/700)

rotateProton

80cm gap (vertical)
 Heavy Ion Detectors
 Proton Detectors
 Neutron Detectors (NEBULA) Large Vacuum Chamber
 Rotational Stage
Heavy Ion
T. Kobayashi et al., NIMB317, 294, (2013)3

Commissioning in March 2012
Primary Beam: 18O: 290 MeV/nucleon: 500 pnA••••

Kickoff all the detectors, DAQs for the xn+HI setup
Beam transport to SAMURAI
Heavy ion detectors optimization
NEBULA calibration– Time-zero with high-energy gamma– Efficiency measurement (inc. 2n cross talk)with 7Li(p,n) reaction• Br scan for rigidity calibration• Physics measurements– 17C  16C+n 17C 15B+n– 15C  14C+n– 14Be12Be+2n

Everything worked perfectly !!

7Li(p,n)7Be(g.s.+0.43MeV)

En:194MeV

T. Sugimoto et al.,Phys. Lett. B 654, 160 (2007).

14Be (2+)87(5) keV (1σ)

E=68 MeV/nucleon

CountsCountsEth=6 MeVee

σTOF=335(5) ps

14Be+C

E=213 MeV/nucleon

14Be (2+)

100 keV (1σ)

6Li(p,n)6Be(4.4%)

preliminary

TOF(measured) - TOF(calculate) (ns)
Unfolding the resolutions from other detectors

 Intrinsic Resolution: σTOF=263(6) psErel (MeV)

Obtained only in 51min!
14Be: ~2x104 ppscf.) ~300 ps (designed value)

Good Resolution as designed !

First experimental campaign using
SAMURAI for physics programs(Day-One campaign)
Collaborators
Tokyo Institute of Technology: Y.Kondo, T.Nakamura, N.Kobayashi, R.Tanaka, R.Minakata, S.Ogoshi,S.Nishi, D.Kanno, T.Nakashima
LPC CAEN: N.A.Orr, J.Gibelin, F.Delaunay, F.M.Marques, N.L.Achouri, S.LeblondTohoku University : T.Koabayshi, K.Takahashi, K.MutoRIKEN: K.Yoneda, T.Motobayashi ,H.Otsu, T.Isobe, H.Baba,H.Sato, Y.Shimizu, J.Lee, P.Doornenbal,
S.Takeuchi, N.Inabe, N.Fukuda, D.Kameda, H.Suzuki, H.Takeda, T.Kubo
Seoul National University: Y.Satou, S.Kim, J.W.Hwang
Kyoto University : T.Murakami, N.Nakatsuka
GSI : Y.Togano
Univ. of York: A.G.Tuff
GANIL: A.Navin
Technische Universit¨at Darmstadt: T.Aumann
Rikkyo Univeristy: D.Murai
Universit´e Paris-Sud, IN2P3-CNRS: M.Vandebrouck

6

SAMURAI Day-One experiment(May 2012)20

Mg 21Mg 22Mg 23Mg 24Mg 25Mg 26Mg 27Mg 28Mg 29Mg 30Mg 31Mg 32Mg 33Mg 34Mg 35Mg 36Mg 37Mg 38Mg
2017Ne 18Ne 19Ne 20Ne 21Ne 22Ne 23Ne 24Ne 25Ne 26Ne 27Ne 28Ne 29Ne 30Ne 31Ne 32Ne
17Z=813O129C8B10Be97631HHe 4He2H

3HLi

10N

76CLiHe

1114O

13NC12B

11Na 21Na 22Na 23Na 24Na 25Na 26Na 27Na 28Na 29Na 30Na 31Na 32Na 33Na 34Na 35Na

15O

14NC

13B

1216F18O

1715NC

14B13F19O

1816NC15B

14Li98Li1120O

1917NC

16B

15Be 10Be 11Be 12Be

8F

14C

B

F21O

2018N

17C

F

22O

2119N

1817F23O

2220NC

19B

18F

24O

2321NC

20B

19CF

25O

2422N

21C

F26

O

2523

F

27O

26

F

29F

31343740Mg

Na

NeFO

N

22C

B

Be

Li

He

N=8

N=16

N=20First experimental campaign with SAMURAI for physics programs
1. Study of unbound nuclei 25O and 26O (SAMURAI02, Y. Kondo)
2. Coulomb breakup of 22C and 19B (SAMURAI03, T. Nakamura)
3. Study of unbound states of 22C, 21C, 19B, 18B (SAMURAI04, N. A. Orr/J. Gibelin)7Study of unbound nuclei 25O and 26O20Island of Inversion

Mg 21Mg 22Mg 23Mg 24Mg 25Mg 26Mg 27Mg 28Mg 29Mg 30Mg 31Mg 32Mg 33Mg 34Mg 35Mg 36Mg 37Mg 38Mg
2017Ne 18Ne 19Ne 20Ne 21Ne 22Ne 23Ne 24Ne 25Ne 26Ne 27Ne 28Ne 29Ne 30Ne 31Ne 32Ne
17Z=813O

129C8B10Be97631HHe 4He2H3HLi10N76CLiHe1114O13NC12B11Na 21Na 22Na 23Na 24Na 25Na 26Na 27Na 28Na 29Na 30Na 31Na 32Na 33Na 34Na 35Na

15O

14NC

13B

1216F18O

1715NC

14B

13F

19O

1816NC15B

14Li

98Li

1120O

1917NC

16B

15Be 10Be 11Be 12Be

8F

14C

B

F

21O

2018N

17C

F

22O

2119

N

1817C

B

F

23O

2220N

19C

F

24O

2321N

2019C

F

25O

24

22N

F

26O

25

23

N

22C

F

27O

26

F

29F

31343740Mg

Na

NeFO

Neutron drip line anomaly

B

BeLi

He

N=8

N=20Study of oxygen isotopes beyond the drip line––––Drip-line anomaly
Three nucleon force
South extreme of the Island of Inversion
2n radioactivity of 26O?

8Neutron drip line anomaly
20Mg 21Mg 22Mg 23Mg 24Mg 25Mg 26Mg 27Mg 28Mg 29Mg 30Mg 31Mg 32Mg 33Mg 34Mg 35Mg 36Mg 37Mg 38Mg
2017Ne 18Ne 19Ne 20Ne 21Ne 22Ne 23Ne 24Ne 25Ne 26Ne 27Ne 28Ne 29Ne 30Ne 31Ne 32Ne
17Z=813O

129C8B

10Be97631HHe 4He2H3HLi10N76CLiHe

1114O

13NC12B11Na 21Na 22Na 23Na 24Na 25Na 26Na 27Na 28Na 29Na 30Na 31Na 32Na 33Na 34Na 35Na

15O

14NC

13B

1216F18O

1715NC

14B13F

19O

1816NC

15B

14Li

98Li1120O

1917NC

16B

15Be 10Be 11Be 12Be

8F

14CB

Be

F

21O

20

18

N

17C

F

22O

2119N

1817C

B

F

23O

2220N

19C

F

24O

23

21

N

2019C

B

F

25O

2422N

F

26

F

27

F

29F

31343740Mg

NaNeF

O

23

N

22C

Anomalous behavior ofthe neutron drip line

Li

He

N=8

N=16

N=20What is the origin of this phenomenon?
9Neutron drip line anomaly
20Mg 21Mg 22Mg 23Mg 24Mg 25Mg 26Mg 27Mg 28Mg 29Mg 30Mg 31Mg 32Mg 33Mg 34Mg 35Mg 36Mg 37Mg 38Mg

T. Otsuka et al., PRL105, 032501 (2010)2017Ne 18Ne 19Ne 20Ne 21Ne 22Ne 23Ne 24Ne 25Ne 26Ne 27Ne 28Ne 29Ne 30Ne 31Ne 32Ne
17Z=813O

129C8B

10Be97631HHe 4He2H

3H

Li

10N

76CLiHe

1114O

13NC

12B

1115O

14NC

13B

1216F18F19F22O

17OO lineO ODrip181920211718192015NC14B

13Li98Li1116NC15B14Be 10Be 11Be 12Be8Na 21Na 22Na 23Na 24Na 25Na 26Na 27Na 28Na 29Na 30Na 31Na 32Na 33Na 34Na 35Na

NC16B

1514FCB

Be20F

N17C

21N

1817C

B

F

23O

22

N

19C

F

24O

2321

N

2019C

B

F

25O

2422NF

O

2326F

27F

29F

31343740Mg

NaNeF

Drip line

N

22C

Anomalous behavior of
the neutron drip line

LiHe

N=8
N=16
N=20G. Hagen et al. PRL 108, 242501 (2012)
CC method with int. from chiral EFT(includes continuum and 3NF effects)

What is the origin of this phenomenon?
10Where is south boundary of
Island of Inversion?
Island of Inversion

Mg 24Mg 25Mg 26Mg 27Mg 28Mg 29Mg 30Mg 31Mg 32Mg 33Mg 34Mg 35Mg 36Mg 37Mg 38Mg

Na 23Na 24Na 25Na 26Na 27Na 28Na 29Na 30Na 31Na 32Na 33Na 34Na 35Na

Ne 22Ne 23Ne 24Ne 25Ne 26Ne 27Ne 28Ne 29Ne 30Ne 31Ne 32Ne0F

21O

208N

197189C

F

22O

21

N

17C

BF

23O

2220N

19CF

24O

2321N

2019CF

25O

2422NF

26O

2523F27O26FCF

3128FMg

NaNeFON

2229343740

Z=8G. Christian et al.,
PRC85, 034327, (2012)

B

N=20
N=19 isotones
28F Ground state @ 220(50)keV

Z=9 is low-Z boundary of Island of Inversion at N=19
 What about the other isotones?

11

2n radioactivity of 26O?
L.V. Grigorenko et al. PRC 84, 021303 (2011)

Usual 1n decay
G~MeV or keV

12

2n radioactivity of 26O?
E. Lunderberg et al.PRL108, 142503 (2012)

C. Caesar et al.PRC88, 034313 (2013)

L.V. Grigorenko et al. PRC 84, 021303 (2011)

Er < 200keV

Z. Kohley et al,PRL110,152501 (2013)
T1/2=4.5+1.1-1.5ps(3ps systematic error)

Er < 120keV (95% CL)
t < 5.7ns

2n radioactivity?

Excite state at 4.2MeV?
Usual 1n decay
G~MeV or keV

Large uncertainty of experimental study• Only upper limit is given for the ground state energy• Large systematic error in the lifetime measurement 13

Invariant mass methodpc

one proton removal reaction
24O
24O

27F

nnnn

26O

~210MeV/uCpn1
pn 2(unbound)

Edecayneutrondecay

Decay energy (Relative energy)

Edecay E   p  M
2i

Invariant mass

26O

2ii
24O+2nNecessary to detect all the decay particles

n-decay
threshold

0MeV

14

Experimental setup
Ionization
Chamber
2Plastics

C target(1.8g/cm2)

2 MWDCs

MWDC
Superconducting
Dipole Magnet(B=3.0T)

NEBULAnn
27F ~210MeV/u

DALI2(from BigRIPS)
MWDC

Hodoscope

24O

15

Experimental Results

16

Counts /50keV

Decay energy spectrum(26F+C25O24O+n)
26F+C25O24O+n(preliminary)

C.R.Hoffman et al.,PRL100, 152502 (2008)

EdecayEdecay=770keV
24O+n

25O
gsn-decaythreshold

Edecay=770keV

Decay energy (MeV)

50 times higher statistics!
Another decay channel (25O23O+2n) can be studied
17

Counts /100keV

Ground state

Decay energy spectrum(27F+C26O24O+2n)

27F+C26O24O+2n

E. Lunderberg et al.PRL108, 142503 (2012)(preliminary)
Excited state（new）

Er<200keV

C. Caesar et al.PRC88, 034313 (2013)

Decay energy (MeV)
Ground state
5 times higher statistics
better determination of energy

Er<120keV(95% CL)

Excited state at ~1.3MeV
First observation
Most probably 2+No peak at ~4.2MeV

18

Comparison with USDB calculation
B.A. Brown, W.A. Richter
PRC74, 034315 (2006)

Preliminary

N=18
USDB

N=18
new26O

EXP
28Ne

32Si

34S

36Ar

30Mg

(assuming Edecay=0 for 26Ogs)

Ground state
Difference between groundstate energies of EXP andUSDB calculation– USDB predicts S2n= - 0.35MeV for 26O ground state(Almost consistent with experiment)

2+ state– Calculation overestimates at low Z
effect of pf-shell? or continuum effect?
– E.g. Continuum shell model predicts 1.8MeV
A. Volya, V. Zelevinsky, PRC74, 064314 (2006)

19SAMURAI Day-One experiment
20Mg 21Mg 22Mg 23Mg 24Mg 25Mg 26Mg 27Mg 28Mg 29Mg 30Mg 31Mg 32Mg 33Mg 34Mg 35Mg 36Mg 37Mg 38Mg
2017Ne 18Ne 19Ne 20Ne 21Ne 22Ne 23Ne 24Ne 25Ne 26Ne 27Ne 28Ne 29Ne 30Ne 31Ne 32Ne
17Z=813O

129C8B

10Be97631H

He 4He2H3HLi10N76CLiHe

1114O

13NC12B

11Na 21Na 22Na 23Na 24Na 25Na 26Na 27Na 28Na 29Na 30Na 31Na 32Na 33Na 34Na 35Na

15O

14NC13B

1216F18O

1715NC

14B

13F

19O

1816NC

15B

14Li

98Li

1120O

1917NC

16B

15Be 10Be 11Be 12Be

8F

14CB

F

21O

2018N

17C

F

22O

2119N

1817F

23O

2220NC

19B

18F

24O

2321NC

20B

19C

F

25O

2422N

21C

F

26O

2523F

27O

26F

29F

31343740Mg

NaNeFO

N

22CB

BeLi

He

N=8N=16N=20First experimental campaign with SAMURAI (May 2012)
1. Study of unbound nuclei 25O and 26O (SAMURAI02, Y. Kondo)
2. Coulomb breakup of 22C and 19B (SAMURAI03, T. Nakamura)
3. Study of unbound states of 22C, 21C, 19B, 18B (SAMURAI04, N. A. Orr/J. Gibelin)20

Coulomb breakup of 22C and 19B~Probe of di-neutron correlation~
nr2 rc-2ndB( E1)
B( E1)  dE x
dE x9Li

e.g. 11Li
nT.Nakamura et al.
PRL96,252502(2006)

r12 3  Ze  22r
r
2(r  121  r2 )4  A Low energy E1 excitation of 2n-halo dineutron-like correlation

B( E1)  1.42  0.18 e 2 fm 2 ( Erel  3MeV)
14
 1.78(22) e 2 fm 2  12  4818deg .

What about heavier Borromean nuclei 22C and 19B?

21

Study of the unbound nucleus 21C(Spokesperson: N.A. Orr/J. Gibelin)
23F 24F 25F 26F 27F 28F 29F 30F

31F

20
22O 23O 24O 25O 26O 27O 28O

16

21N 22N 23N

2S1/2
1d5/2

20C 21C 22C

New! N=16d?

s?
22N21C20C+n22C21C20C+nPreliminaryS.Leblond/M.Marques/R.Minakata

Erel(MeV)Counts/40keV

Counts/100keVs?

1d3/2

Preliminary
S.LeblondErel(MeV)

22

Summary• SAMURAI is now available– SAMURAI collaboration page
http://ribf.riken.jp/SAMURAI/Collaboration/• SAMRUAI Day-One Experimental campaign on 2012
1. Study of unbound nuclei 25O and 26O• Higher statistics for 26O(0+)• New observation of 26O(2+)

2. Coulomb breakup of 22C and 19B
3. Study of unbound states of 22C, 21C, 19B, 18B• Preliminary decay energy spectra have been obtained23