在

RIBLL

上开展的质子晕与双质子发射实验研究

中国原子能科学研究院

C

hina

I

nstitute of

A

tomic

E

nergy

林承键、徐新星、贾会明、杨峰、刘祖华、张焕乔等 中国原子能科学研究院，北京

275

信箱

10

分箱，

102413

王建松、徐瑚珊、雷相国、胡正国、孙志宇、杨彦云等 中国科学院近代物理研究所，甘肃兰州，

730000

内 容 一、研究背景与历史回顾 二、用透射法开展的质子晕结构研究 三、运动学完全测量进行的双质子发射研究 四、总结与展望 五、

RIBLL

合作的一些想法

一、研究背景与历史回顾

1.

国内奇特核结构（晕核）研究的兴起



1998

年之前：

HI-13

串列加速器，低能重离子熔合

-

裂变研究

垒下熔合

-

裂变碎片角分布各向异性异常的实验研究与预平衡裂变模型 的理论解释 － 低能核物理实验研究跻身世界先进水平的标志。 然而，课题申请困难。。。 

1998 – 2004

：

HI-13

串列加速器，激发态晕结构研究

12 B, 13 C

激发态中子晕结构研究 －

(d,p)

反应，

Q3D

磁谱仪

ANC

方法、核天体

(n,



)

反应、晕核标度定律

… …



2000

年至今：

HIRFL-RIBLL

装置，放射性核束，质子晕与双质子 发射研究

2000 – 2004

：

29 S, 27,28 P

，透射法、反应截面、

Glauber

理论、质子晕

2004

年至今：

17,18 Ne, 28,29 S

，运动学完全测量、双质子关联、奇特衰变

Z.H. Liu, C.J. Lin et al., Chin. Sci. Bull. 46, 43 (2001); Phys. Rev. C64, 034312 (2001); C.J. Lin, Z.H. Liu et al., Chin. Phys. Lett. 18, 1183 (2001); Chin. Phys. Lett. 18, 1446 (2001).

Tanihata, H. Hamagaki et al., Phys. Lett. B160, 380 (1985); Phys. Rev. Lett. 55, 2676 (1985).

图：目前实验发现的晕核及其种类（截至

2002

年）

二、用透射法开展的质子晕结构研究

1.

实验过程：

主束： 36 Ar, 69 MeV/u 初级靶： Be, 98.8 mg/cm 2

T2

方靶室：  Position & TOF: PPAC + Sci. + PPAC   E: Si (150  m,  20 mm)  Targets & detectors: 6-Si (300  m, 45  45 mm 2 ) 次级束：  29 S: ~ 5 pps   27 28 P: ~ 15 pps P: ~ 30 pps 图：典型的束流粒子鉴别谱

Reaction cross section:

A:

mass number 

:

density of target 

:

Avogadro’s number 

x i

:

thickness of 

Ei



i

:

reaction probability, the ratio of the reaction events to the total events (gated on TOF 

E i

) [cf: R. E. Warner et al., Phys. Rev. C 52, R1166 (1995).] 图：拟合提取反应几率的示意图

2.

29

S

双质子晕的现象：

图：实验截面与理论计算的比较 图：实验截面与理论计算的差别

图：

29 S

及其核芯

27 Si

反应截面的比较

Z. H. Liu et al., Chin. Phys. Lett. 21, 1711 (2004).

3.

27,28

P

质子晕与核芯增大的现象：

1/2 1/2 = 3.470 fm = 4.875 fm 1/2 = 3.190 fm

图：

28 P

及其核芯

27 Si

的比较 图：

27 P

及其核芯

26 Si

的比较

Z. H. Liu et al., Phys. Rev. C 69, 034326 (2004).

三、运动学完全测量进行的双质子发射研究

1. Introduction – 1p & 2p radioactivity

   Radioactivity (H. Becquerel, 1896)  ,  decay (P. Curie, M. Curie, and E. Rutherford, 1899)  radiation (P. Villard, 1900)  Fission (O. Hahn and F. Strassmann, 1938)  ♣ 1p & 2p radioactivity: First proposed by V.I. Goldanskii & Y.B. Zeldovich in 1960 cf: V.I. Goldanskii, Nucl. Phys. 19, 482 (1960); Y.B. Zeldovich, Sov. Phys.-JETP 11, 812 (1960).

♣ 1p (Up to now, about 25 emitters were found) Isomer state – 53 Co m was observed in 1970 cf: K.P. Jackson et al., Phys. Lett. B 33 , 281 (1970); J. Cerny et al., Phys. Lett. B 33, 284 (1970).

Ground state – 151 Lu & 147 Tm were observed in 1982 cf: S. Hofmann et al., Z. Phys. A 305, 111 (1982); O. Klepper et al., Z. Phys. A 305, 125 (1982).

♣ 2p (3 emitters were certified – 45 Fe, 54 Zn, 48 Ni) cf: J. Giovinazzo et al., Phys. Rev. Lett. 89, 102501 (2002); B. Blank et al., ibid 94, 232501 (2005).

Ground state – 6 Be, 12 O, 16 Ne, 19 Mg, 45 Fe, 48 Ni, 54 Zn …… Excited state – 14 O, 17,18 Ne, 94 Ag …… (directly 2p emitters)

Basic concept of 1p & 2p emission

1 S

1p emission 2p emission cf: B. Blank and M. Ploszajczak, Rep. Prog. Phys. 71, 046301 (2008).

Meanings:

1) A good probe to extract the information of nuclear structure for the proton-rich nuclei close to or beyond the proton drip-line.

2) A good tool to study the nucleon-nucleon (like

p

-

p

) pair correlation inside a nucleus and the relative topics (such as superfluidity, BCS, BEC …) 3) A good way to investigate the astronuclear processes like (2

p

,  ) and (  ,2

p

).

4) And more ……

2p halo structure



2p correlated emission

Basic idea: 2p halo/skin 2p correlated emission 2p valence pair  above 2p emission threshold weak link with core (decoupled) Beyond 1p drip-line Ground state 6 Be, 12 O, 16 Ne, 19 Mg, 45 Fe, 48 Ni, 54 Zn …… Initial state configuration 2p resonance state Excited state: 14 O, 17,18 Ne, 28,29 S, ……

BCS crossover?

BEC

Our interesting points

Heavy emitters:

( A > 40 ) 39 Ti, 42 Cr, 45 Fe , 48 ,49 Ni , 54 Zn …     High Coulomb barrier Ground state Long lifetime ( > ps) Offline decay measurement

Intermediate emitters:

( 20 < A < 40 ) 22-24 Si, 26-29 S, 31,32 Ar, 34 Ca…     Medium Coulomb barrier Ground state, lowly or highly excited state Short lifetime (~ fs/keV/MeV order) Online complete-kinematics measurement

Light emitters:

( A < 20 ) 6 Be, 12,14 O, 16, 17,18 Ne , 19 Mg …     Low Coulomb barrier Ground state or lowly excited state Short lifetime (~ keV order) Online complete-kinematics measurement Z 8 20 N 8 28 20 28

Two-proton halo/skins in

27-32

S

Figure: Density distributions of valence particles For the proton-rich sulfur isotopes, Z=16, 2p in the 2s 1/2 orbit.

Calculated by single-particle potential model.

c.f. C.J. Lin et al., Phys. Rev. C 66, 067302 (2002).

2p S 2p = 0.9 MeV 3.4

5.4

7.1

11.7

16.2

Figure: Contributions of valence particles

2. RIBLL Experiment 2005 – –

29

S+

28

Si

p 29 S 27 Si p

PPAC1

Collimators

PPAC 2



E 12 C X1 Y1 X2 Y2 Stop CsI+PIN

Target Chamber 121 124

.

8 176

.

5 240.7

Z(mm) -906

.

3 -37.3

-3.1

0 2.9

4.7

Collimators:



E:

150  m Si   30mm &  20mm.

E detector, combined with TOF (upstream) for particle identification.

12 C:

target, 300  m.

X1, Y1, X2, Y2 :

300  m Si strip  E detectors, 18 strips each, 1.2mm/strip with 0.1 mm interval.

Stop:

300  m Si  E detector, for stopping all the heavy fragments.

CSI:

CSI(Tl)+PIN array, 24 segments, for light particle (p, d, etc.) identification.

CIAE-RIBLL-2005 detector array

 自制的硅条探测器、

CsI

闪烁体阵列和电荷灵敏前置放大器；  首次实现参数达

200

余路的运动学完全测量。

Secondary beam identification

Primary beam: 36 Ar 80.4 MeV/u Secondary beam: 29 S 46.8 MeV/u intensity: ~ 10 pps Purity: 1% 1  10 7 29 S was accumulated

30 S 29 P 27 P 29 S 28 Si 28 P 27 Al 26 Si 25 27 Si Al 26 Al 25 Mg 24 Mg 23 Na 22 Ne

Yields of light particles in 28 P, 29 S+ 12 C( 28 Si) reactions IMP data:

without any coincidence, M. Wang et al., High Energy Physics and Nuclear Physics 26, 803 (2002).

CIAE data:

coincide with heavy fragments this work.

Proton removal cross sections 29 S:  1p 28 P:  1p = 3.15

 0.32 b = 2.13

 0.22 b  2p = 1.85

 0.20 b

2p angular correlation 2p relative momentum 2p singlet s state 2p sequentially emitted q = |p 1 -p 2 |/2

C.J. Lin et al., INPC2007

口头报告

, Nucl. Phys. A805, 403 (2008)

3. RIBLL Experiment 2007 – –

17,18

Ne+

197

Au

Complete-kinematics measurement

Identifications of the secondary beams

Primary beam: 20 Ne, 78.2 MeV/u; Primary target: 9 Be, 1590  m Degrader: 27 Al, 1024  m; Secondary target: 197 Au, 200  m Secondary beam:

17 Ne

, 50.0 MeV/u, Secondary beam:

18 Ne

, 51.8 MeV/u, intensity  200 pps, purity  10% intensity  800 pps, purity  40%

Identification of heavy fragments

17 Ne 18 Ne

Identification of light particles

17 Ne 18 Ne

17,18 Ne results

Excitation-energy spectra F. Jia, C. J. Lin, H. Q. Zhang et al., Chin. Phys. Lett. 26, 032301 (2009).

X10 17 Ne Main results from relative momenta & opening angles 1) No obvious 2 He emission from 17 Ne, at present. 2) 2 He emission from 6.15 MeV state of 18 Ne was confirmed.

momentum correlation functions and HBT analyses

17 Ne 18 Ne Exc: 5.17

+0.09

-0.08

fm Inc: 7.50

+0.09

-0.09

fm Exc: 5.44

+0.19

-0.17

fm Inc: 6.06

+0.08

-0.09

fm

Preliminary

17 Ne: NPA733, 85(2004) BCS or BEC ?

2p opening angel 74.5

 3.4

BCS/BEC crossover 17 Ne

4. RIBLL Experiment 2007 – –

28,29

S+

197

Au

Detector array for 28,29 S experiment

Complete-kinematics measurements

Secondary target:

197

Au, 100 µm SD: Silicon detectors, 325, 1000 µm SSSD: Single sided Silicon Strip Detectors, 300 µm, 24 strips with 2 mm in the width and 0.1 mm in the interval for the construction of the particle trajectories CsI(Tl) array: 6

×

6 lattices, each 15

×

15

×

20 mm, read out through PIN photodiodes

Face Back

Identifications of the secondary beams 28

S: 48.0 MeV/u Intensity:  Purity:  1% 30 pps Dose: ~ 3  10 6

29

S: 49.2 MeV/u Intensity:  Purity:  3% 200 pps Dose: ~ 2.5  10 7

29 S time window Events induced only by 29 S Eliminate the contamination of 26,27 Si directly from the secondary beam and the accidental coincidences.

Selection of heavy fragments

Si-isotope band

Selection of light particles

blue dots: single-hit events red dots: double-hit events In this way, the unmixed 29 S  27 Si+

p

+

p

events are selected.

Trajectory tracking – selection of reactions in the target

Cross point of trajectories before and after reaction 29 S  28 P+

p

events 29 S  27 Si+

p+p

events

Results: Monte-Carlo simulations Three extreme decay modes

40 30 20 20 50 20 20 50 40 30 2 He cluster decay 3-body democratic decay 2-body sequential decay 140 120 100 80.0

60.0

40.0

20.0

0 50 40 1000 875 750 625 500 375 250 125 0 50 40 900 800 700 600 500 400 300 200 100 0 30 30 30 40 E p2 (MeV) 50 4 2 10 8 6 20 20 50 20 20 30 40 E p2 (MeV) 50 30 40 E p2 (MeV) MC simulations, sampling in phase space, no FSI.

Experimental results, likely 2 He cluster decay.

30 40 E p2 (MeV) 50

Relativistic-kinematics reconstruction for 29 S  27 Si+p+p events Relative momentum,

q pp

= |

p

1 -

p

2 |/2 Feature 1: small

q pp

(~ 20 MeV/c) Opening angle, 

pp

cm Feature 2: small 

pp

cm (< 90  ) Invariance mass

E

*  ( 

E i

) 2  ( 

P i c

) 2 

M

Strong

p-p

correlations 2 He cluster decay ?

3-body simultaneous decay ?

2-body sequential decay ?

or more complicated mode ?

7.4

10.0

3-body system of the final state

Excitation-energy spectrum of 29 S reconstructed by 27 Si+

p

+

p

Experimental evidences of 2 He emission from the 10 MeV excited states of 29 S 29   10 11 %

More evidences… Relative energy of two protons,

E pp

Resonance of 2 He quasi-bound states ?

Precise theoretical description is required ! C. J. Lin et al., Phys. Rev. C 80, 014310 (2009).

2p emission from

28

P

2p correlated emission Large deformation? 2p intrinsic configuration?

X. X. Xu, C. J. Lin, H. M. Jia et al., Phys. Rev. C 81, 054317 (2010).

2



emission from

28

P

2



uncorrelated emission or correlated ( 8 Be) emission?

X. X. Xu, C. J. Lin, H. M. Jia et al., Phys. Rev. C 82, 064316 (2010).

四、总结、展望与感想

1. 2p halo and 2p emission

2

p

BCS/BEC 2

p

halo cf: K. Hagino

et al

., Phys. Rev. Lett.

99

, 022506 (2007).

Decay with large Spectroscopic factor Link between 2p halo and 2p emission cf: C.J. Lin

et al

., Phys. Rev. C

66

, 067302 (2002).

2. Outlook

Pay attention to:



The link between 2p halo and 2p emission & pygmy resonance.



Explore the ground-state emitter: 26 S, 30 Ar, 34 Ca , 38 Ti, 48 Ni, 59 Ge, 63 Se, 67 Kr …



Precise theoretical descriptions embedded in the MC simulations.

RIBLL Experiment 2012 – –

34, 35 ,36,37

Ca Directly 2p emission &



-delayed 2p emission

T 1 T 2 SD0 Scint1.

PPAC1 Scint2.

SD1 PPAC2 Clover SD2 DSSD SD3,4 SD0,1,2 (

Silicon detectors, 300 µm

) SD3,4 (

Silicon detectors, 1500 µm

) DSSD (

Double sided Silicon Strip

Detectors,500 µm, 16 strips

)

34, 35 Ca

ToF: Start: T1, RF Stop: T2, SD Clover

37

Ca

的初步结果

GANIL results: T1/2 = 181.7(36) ms, E

decay

~ 3.1 MeV

探测技术的发展

N early 4-



covered charged-particle detector array

Under construction at CIAE

Layer 1

-- DSSD, T: 64 / 300  m , A: 64  64 mm 2 , W: 0.96 mm, I: 0.04

D: 90 mm, H:  m.

 10 mm, W: 0.96mm, I: 0.04mm, 12 sectors

Layer 2

– DSSD, T: 300  m / 1 mm , same type of layer 1.

Layer 3

– CsI+PIN array, 4  4 (6  6)  50 mm 3 units.

hodoscopes heavy particle & Light particle

五、

RIBLL

合作的一些想法：



国际合作

VS

国内合作



RIBLL

设置的最佳化 － 沟通与协调



数据分析 － 成果共享



电子学（前放）与获取系统（

VME

获取）



大型实验设备的共建与共享



谢 谢 ！

