Studies of Exotic Nuclei using (p,2p) Proton Knockout Reactionsand

Construction of a Broad-Range Magnetic Spectrometer

T. Kobayashi (Tohoku Univ.)

9-Feb-2007

T.Kobayashi , K.Ozeki, K.Maeda, T.Tamae, N.Chiga, Y.Matsuda　(Tohoku Univ.)E.Takada (NIRS)H.Sakaguchi (Miyazaki Univ.)T.Noro (Kyushu Univ.)H.Otsu, H.Takeda, S.Terashima (RIKEN)Y.Sato (Tokyo Inst. Tech.)R.C.Lemmon, M.Labiche (Daresbury Lab.)M.Chartier, B.Fernandez-Dominquez (Liverpool Univ.)W.Catford (Surry Univ.)T.Aumann, O.Kiselev, P.Egelhof (GSI)W.Mittig, L.Gaudefroy (GANIL)N.Orr (LPC-Caen)A.S.Fomichev, G.M.Ter-Akopian, M.S.Golovkov, S.A.Krupko, A.M.Rodin, S.I.Sidorchuk,S.V.Stepantsov, R.Wolski (JINR)

participants

(p,2p) proton knockout reaction in Inverse Kinematics

A A-1

β0 β0

rp1

rp2

rq

−rq

(A-1) system(hole state)

Decay mode of hole state

rq⊥ =

rp1 +

rp2( )⊥

rq // =

rp1 +

rp2( )

//−γβ MA −MA−1( )γ

Es = T0 −γ T1 + T2( ) − 2 γ −1( )mp + βγrp1 +

rp2( )

//−

q2

2MA−1

Measured Quantities : information on single-particle orbit

Separation Energy　(Es, Sp)

Momentum Distribution (q)

Decay mode of hole states

Angular Momentum (LLLL)

Nucleon knockout via quasi-free N-N scattering

Beam energy : need to be "high" ➡ suitable for RIBF

S factor

rE

proton neutron

valenceorbit

inner-shell(core) orbitCoincidence measurements

offorward particles

0

5

10

15

20

25

30

5 10 15 20 25

Sp

Sn

Sp

Sn

carbon

oxygen

Mass [amu]

Knockout Reactions

(p,2p), (p,pn)on proton target

Knockout reactionby tagging γ-rayson nuclear target @MSU/GSI

Es resolution ～1 MeV (➡～0.5MeV) few keV

Final state unbound/bound bound

Sensitivity nuclear interiorinner shell

surface(?)

(1) Charge radii of inner shell (π1s1/2)

3,4,6,8He6,7,8,9,11Li14,15,16,17,18C19,21,23,24,25F

(2) Oxygen isotopes around N=16

18,20,22,23,24O from 19,21,23,24,25F

(3) Proton-rich nucleus 17Ne16F

momentum distribution

#Valence protons

any 1

(1) Charge radii of inner shell (π1s1/2)

1.5

2

2.5

3

4 8 12 16 20

Mass Number

6 Li

9 Li

11Li

4 He

3He

6 He

8 He9 C 16 C

12 C

He Rch(tot)Laser

He Rch(tot)( p,p)

He Rch(tot)SignaI

Li Rch(tot)Laser

Li Rch(tot)SigmaI

C Rch(1s)( p,2p)

C Rch(tot)( e,e)

C Rch(tot)SigmaI

9-16C(p,2p)(π1s1/2)-1 momentum distribution➡charge rms radius of π1s1/2

shirinking, with possible zig-zag pattern, towards neutron-rich side.binding energy (?) Sp=20-50MeVexcitation effect (?) π1s1/2➡π1p1/2 　Ikeda, Toki

3,4,6,8He(p,2p) comparison with Laser spectroscopy

6,7,8,9,11Li(p,2p) comparison with Laser spectroscopy, additional information on Rch(π1s1/2)

14,15,16,17,18C(p,2p) cross check of HIMAC exp. by optimizing to s-orbit, towards more neutron-rich side

19,21,23,24,25F(p,2p) π1p1/2 orbit filled probably O(p,2p)N reaction will be better/simpler

π1s1/2

π1s1/2

π1s1/2

π1s1/2+π1p3/2

π1s1/2+π1p3/2

π1s1/2

π1s1/2+π1p3/2

π1s1/2+π1p3/2

(2) Oxygen Isotopes around N=16

23,24O no particle-stable excited states, 24O=double magic

25O particle unbound ground state (beam intensity < 7kHz)

24,25,26F(p,2p)

0

10

20

30

40

50

60

5 10 15 20 25

Mass Number

Sp(1s)

HHHHeeee

LLLLiiii

CCCC

FFFF

Sp(1s)

Sp(1p)

Sp(1p)

Sp(1s)

Sp(1d)

＊limited to proton holes : behavior of π1s1/2, π1p3/2, π1p1/2 by adding neutronsinteresting part : ν2s1/2, ν1d3/2,

Rch(π1s1/2) when π1p1/2 orbit is fully occupied (?)

(3) Proton-rich nucleus 17Ne

17Ne(p,2p)16F

Two valence protons in π2s1/2/π1d5/2

mixing information from momentum distribution16F : particle unbound

Experimental Setup

BV

BDC1/2SF12A/B

HOD

A/Z=1 1.5

2

3

4

0 5m

FDC2

SHT

CVC

PDCΔE NaI(Tl)

C-typemagnet

FDC3

FDC4

F5: Momentum tag

F8-F12: TOF(17m)

F12 area

beam

FDC2

NaI(Tl)

PDC

CVC

SHT

BV

BDC2BDC1

SF12A/B

0 1m

ΔE

Experimental Setup : (p,2p)

Forward (Broad Range) Magnetic Spectrometer

Secondhand C-type Magnet (Kappa) + existing tracking detectors

0

2000

4000

6000

8000

110 4

1.210 4

-200 -150 -100 -50 0 50 100 150 200

By@1100A

By@1400A

By@1700A

By@2000A

By@2300A

X[cm]

Power Supply : 2300A/300VTARN-II PS (2500A/600V)

One on the missing Facility @RIBF

Secondary Beam Parameters / Measuring time

Intensity > 105Hzmeasuring time / isotope ～ 10 hours / I I I I b=3x105Hztime for beam switching (?)

P

3-8He

6-11Li

14-18C

19-25F

17Ne

1240

53

50

65

10

Position Detectors

Electronics: ASD board --->(LVDS) ---> VME 64ch TDC (VME) -->(fiber)--> DAQ PC

Gas: He+50%C2H6 or He+60%CH4

Readiness

(1) Most detectors/targets are from HIMAC exp.(2) to be constructed

DetectorsBeam MWPC @F5 momentum tagging in vacuumVertex chamber around SHT improve angular resolution

Detector StandsSpacer stand for (p,2p) standDownstream tracking detetors (FDC3/FDC4)

(3) Magnetic SpectrometerKappa magnet: transfer from KEK, re-assemblyPower Supply: transformer (6.6kV → 3.3kV)

power line between PS & magnet need utilitiesCooling System

(4) Ligth Ion Beam ?

Future Option1: (p,pn) Neutron Knockout Reaction

0 5 m

L(TOF)=6m ±9.5o(H), ±4.8o(V)2m x １m x 4 layers

25cmt

σ=3mrad

Neutron hodoscope

F12 Area

Future Option2 : larger solid angle

Drift Chamber + NaI(Tl)：　Ω～0.1sr/arm

(100+300um) DSSM + CsI(Tl)/PD

larger angular coverage～weaker beam

70mm x 40mm100um pitch

Daresbury / GSI

JINR

50mm x 100mm x 100mm

Resolution @250MeV/A (Simulation)

(1) Beam momentum

(2) Scattering angle

(3) Proton energy

σσ

( )Epsp≈ 5 MeV

σ σθ( ) .Es ≈ 0 21 MeV/mrad σ σθ( ) .q⊥ ≈ 0 45 MeV/c/mrad

σσ

( ) .ETsT≈ 0 36 MeV/% σ

σ( ) .//q T

T≈ 2 6

σ σθ( ) .//q ≈ 0 21

σσ

( ) .qTT

⊥ ≈1 4 MeV/c/%

Separation energy MomentumEs

q// q⊥

＊SHT target (5mmt)

L LR/ .(SHT) ≈ × −0 46 10 3 σMCS ( ) .T MeV mradp = ≈125 0 8

0

0.01

0.02

0.03

0.04

0.05

0 0.5 1 1.5 2 2.5 3 3.5 4

r [fm]

10C12C14C16C

RMF calculation by Lwin

Density Distribution of πs1/2

0

5

10

15

20

25

30

5 10 15 20 25

Sn(C)Sp(C)Sn(O)Sp(O)

Mass [amu]

Separation Energy, Sn, Sp, in C / O Isotopes

CCCCaaaarrrrbbbboooonnnn

OOOOxxxxyyyyggggeeeennnn

(((( ))))

Summary of 9-16C(p,2p) @250MeV/A

ΔE(1p-1s) Momentum Width Total Yield

●Inner-shell (s1/2) orbit

　＊s-hole states

systematically observed

　＊ΔE(1p-1s)

wider at proton/neutron-rich side

　＊Momentum distribution

　＊Charge rms radii (1s)

shrinking toward neutron-rich side

●Valenceshell (p3/2) orbit

　＊momentum distribution

　＊Total yield

Y(12C)/Y(9C)～60%

S-factor(?)

1.3MeV

4.0MeV

8.7MeV16MeV

22.6MeV

Experimental Setup @HIMAC

0 4m

F2/Mass SlitFe Shield75cm

Pb Collimator20cm

BeamScintillator

Drift Chamber

Proton Detectors

H-type Dipole Magnet

Forward Magnetic Spectrometer

Drift ChamberHodoscope

DriftChamber

ΔENaI(Tl)

Beam Detectors

A/Z

32

1

p

p

Residue

Solid Hydrogen Target

Setup from downstream side

BL= 0.8 Tm

g=25cm

Solid Hydrogen Target (SHT)

Hydrogen Target

-30 -20 -10 0 10

Carbon CH2

17mm

Vertex Position [mm]

0

1000Reaction vertex

Cou

nts

[/MeV

]

p(15C,2p)X

CH2

C

0

80

Proton Separation Energy [MeV]

p(15C,2p)BX

400

0

0 40 80

● CH2(100mg/cm2)-C(50mg/cm2) ●Solid Hydrogen Target：

Target：　 44 mg/cm2

thickness

Vac window：　50μm kapton

~CH2 3mmt

SolidHydrogen

CuBlock

Horizontal Position [mm]Vertex [mm]

Entrancewindow

SHT +Cu block

Exitwindow

0 40 80

p(15C,2p)X

p(15C,2p)BX

Proton Separation Energy [MeV]

Cou

nts

0

600

0

80

SHT in

SHT out

30mmφ, 5mm t (W：9μm Mylar)

p gy [ ]

Sp Distribution

Inclusive

Sp [MeV]

9C(p,2p)X

10C(p,2p)X

11C(p,2p)X

12C(p,2p)X

13C(p,2p)X

14C(p,2p)X

15C(p,2p)X

16C(p,2p)X

2α

9C(p,2p)8B

11C(p,2p)10B

10C(p,2p)2α

12C(p,2p)11B

13C(p,2p)12B

14C(p,2p)13B

15C(p,2p)14B

16C(p,2p)15B

11C(p,2p)B_

12C(p,2p)B_

13C(p,2p)B_

14C(p,2p)B_

15C(p,2p)B_

16C(p,2p)B_

σ(Es)~1.2 MeV

tagging A-1B ～A-1Bgr

no B (B)～charged particle decay

9-16C(p,2p)

pppp----hhhhoooolllleeee

ssss----hhhhoooolllleeee

in FWD

Momentum distribution

1p1/2 1p1/21s1/2 1s1/2

Sp [MeV]

9-16C(p,2p) s-hole states

ΔE

(1s-

1p)

( )

( )

3He

4He

3He

4He

Es(1s)

Es(1p)

Peak

FWHMpeak & width

gap

0

50

100

150

200

8 10 12 14 16

1p_qz1p_q1s_qz1s_qIAS_qzIAS_q

σ [M

eV/c

]

Mass

9-16C(p,2p) Momentum Distribution

d

dq

σ

d

dqz

σ

Assume : Harmonic Oscillator

p-hole s-hole

s-hole

d

dq

d

q dqq

ql l l

l

3

3 22

2

2σ σ

σr ∝ ∝ −

⎛

⎝⎜

⎞

⎠⎟exp

1111ssss

1111ppppIIIIAAAASSSS

Momentum Width

Momentum Distribution

Acceptance Correction by 2 methods

(1) Radial (q) distribution

(2) qz distribution

d

dqq

ql l

l

σ

σ∝ −

⎛

⎝⎜

⎞

⎠⎟

+2 22

2exp

d

dq

qs

z s

σ

σ∝ −

⎛

⎝⎜

⎞

⎠⎟exp

2

2

d

dqq a

qp

zz p

p

σσ

σ∝ +( ) −

⎛

⎝⎜⎜

⎞

⎠⎟⎟

2 22

2exp

cccchhhhaaaannnnggggeeee ffffiiiittttttttiiiinnnngggg rrrreeeeggggiiiioooonnnn

d

dq

d

dqdq dq q

qp

z

px y z p

z

p

σ σσ

σ= ∝ +( ) −

⎛

⎝⎜⎜

⎞

⎠⎟⎟∫

3

32 2

2

2r expcf

2

2.4

2.8

3.2

Rm(C)

0

5

10

15

20

25

30

8 10 12 14 16 18 20 22

Sn(C)Sp(C)

A [amu]

Carbon Isotopes

Acceptance

● (p,pp) in 60's-70's Beam energy : 150-1000 MeV @synchro-cyclotrons Resolution : ~4 MeV FWHM each orbits roughly separated

R. of Mod. Phys. 1973

Proton-induced (p,pN) Reaction

Separation Energy Momentum Distribution Binding Energy

● High-Resolution Mesasurement (p,pp) & (p,pn)@RCNP(400MeV), IUCF(150MeV),

Beam energy-1

(1) Knockout cross section : Energy dependence

d, 3,4He(p,2p) Sp= 2.2, 5.5, 20.0 MeV

Neff ≒ 0.5xNreal @Ein ≒ 20xSp

(2) N-N cross section @Θcm 90o

pp pn50

450

350

250

150

0 20 40 60 80

50

150

250 350 450

Angular distribution of N-N (lab)

(5) Proton detection

<Ep>≒ Ebeam/2, Ep_max ≒ Ebeam ~30% reaction loss @Ep~200MeV

(4) Opening Angle of N-N

250 MeV/A

170 MeV/A

90 MeV/A

Θopen

Beam energy-2

30

35

40

45

0 10 20 30 40 50

Sp [MeV]

Ebeam

=250MeV/A

p(6He,pn)5He, p(11Li,pn)10Li

BDC

TOF/Z

0 4m

n,p

p

C Magnet

ResidueMWPC

FDC2

FDC3

Hod

Plastic

NeutronHodoscope

Veto

2 weakly-bound valence neutrons

Sn(11Li)～0.7MeV , Sn(6He)～1.9MeV

RIKEN / RIPSbeam: EB= 85MeV/A, I B～104/sec

target: 0.1-0.2g/cm2 CH2

Experimental Setup

Sn Distribution

Momentum Distribution

Momentum Width

p(6He,pn)5He, p(11Li,pn)10Li Summary

＊ Momentum distributionof single valence neutronw/o exclusive mes.

＊ Widthνp1/2(11Li)～νp3/2(11Li)～νp3/2(6He)

　>> ν2s1/2(11Li)

σ(Sn) ～ 1.1MeV

σ(q)～8 MeV/c

Vertex Chamber

Hexagonal structureor

Jet-type