Transcript EURISOL, Trento Jv 06

Unbound states in dripline nuclei
Physics & Instrumentation
Trento, 16-20 January 2006
Drip-lines : limit of nuclear binding, large isospin
Exploration : new structures
EXOTIC NUCLEI
Tests : nuclear modelling & interactions VNN(Tz)
Extension of the systematics of neutron excitation along isotopic chains
Probe the structure & spectroscopy at large isospin
Measure unbound states
n , p
Tools & detection devices
V. Lapoux DAPNIA/SPhN
EURISOL 16-20 Jan. 06
Nuclear structure towards the drip-lines : phenomena to explore & to understand
Evolution of structure
at large isospin ?
Neutron skins
Change in shell structure
New magic numbers
Local properties (N,Z)
halo,clusters
Neutron
skin
halo
6He
4He
V. Lapoux DAPNIA/SPhN
8He
2006 : what is known ?
2016 : area to explore ?
4He
EURISOL 16-20 Jan. 06
Search for low-lying resonances and study of neutron excitations
(p,p’) probe
Particle spectroscopy
AZ
MUST (8 in a wall)
AZ*

A-1Z
+n …
p’
+ CATS
AZ
p
Beam profile :
CATS 1 & 2
Detection of the light charged recoil
particle in a dedicated array
 the strip-wall device MUST
beam
MUST : Y.Blumenfeld et al., NIM A421, 421 (‘99)
CATS : S. Ottini et al., NIM A431, 476 (‘99).
V. Lapoux DAPNIA/SPhN
(p,p’)
bound excited states close to thr :
E. Khan et al., 20O(p,p’) PLB 490 (‘00) 45
C. Jouanne, V. L., et al., 10,11C(p,p’)
PRC 72, 014308 (’05)
Modification of the
usual shell structure
new magic numbers
Neutronrich 20,22O
EURISOL 16-20 Jan. 06
>>> Specific tools
direct reactions in inverse kinematics
and missing mass method
Unbound excited states, low-lying resonances of weakly-bound nuclei :
A.Lagoyannis et al., 6He(p,p’) @ Ganil, PLB 518, 27 (‘01) .
Exotic
structures
3.6MeV
?S
2+
structure
of 8He :
 + 4n?
0+
4n =3.1
Sn =2.5
S2n = 2.1
8He
V. Lapoux DAPNIA/SPhN
6He
: 2n-halo
8He
: neutron-skin
Resonances of 7,8He
Prototype of (p,p’) & direct reactions
at low energy :
8He(p,p’)
SPIRAL beam
MUST+CATS
EURISOL 16-20 Jan. 06
Unbound states studies : what we have learnt from SPIRAL beam
Structure of the 8He nucleus via direct reactions on proton target
2n Transfer 8He(p,t)6He
g.s 0+
E405S experiment, MUST collab.
8He
8He excitation energy spectrum
+p @ 15.6 MeV/n
2+
2+ 3.62 ± 0.14 MeV
?
5.4 ± 0.5 MeV
Γ = 0.3 ± 0.2 MeV
Γ = 0.3 ± 0.5 MeV
1n transfer : 8He(p,d)7He
* Large (p,d), (p,t)
cross sections
• DWBA not valid
F. Skaza,
PhD thesis SPhN
V. Lapoux DAPNIA/SPhN
• GENERAL framework :
Coupled Reactions calc.
needed, PLB619, 82 (‘05)
EURISOL 16-20 Jan. 06
2006
Nuclear landscape towards the drip-lines
31
F
24
8
Z
23
6
12
22
19
4
11Li
2
p d
n
6He
t
8He
N
C
B
Be
14Be
4He
H
O
Li
He
borromean
N
2
4
6
8
10
12
14
16
6He
Which drip-line nuclei have their identity card complete ?
Masses, size, densities, neutron excitation,
Drip-line : 8He
low-lying spectroscopy,
neutron-skin
Shell structure ?
V. Lapoux DAPNIA/SPhN
EURISOL 16-20 Jan. 06
2006
Nuclear landscape towards the drip-lines
Next drip-line nuclei ?
18
Z
16
43Si
14
33Na
10
38Mg 39
34Mg
12
4He
30,31,32Ne
36
37Na
33
31F
8
24O
structure of 24O ?
Tarasov97
Sakurai97
Notani02,
Lukyanov02
Low-lying
resonances ?
Neutron skin ?
Density Profiles ?
New shell effects ?
23N
22C
16
N
18
20
22
V. Lapoux DAPNIA/SPhN
24
26
28
30
EURISOL 16-20 Jan. 06
Shell effects far away from stability with new generations of RIB s
systematics of neutron excitations vs N
Search for new magic numbers
neutrons
stability
p3/2
f7/2
fp
sd-fp
20
sd
sd-fp
d3/2
s1/2
d5/2
N = 20
sd
16
N = 16
Z=14
30Si
p1/2
p3/2
s1/2
neutrons
p3/2
f7/2
d3/2
fp
8
82
drip-line N = 16, Z=8, 24O
s1/2
d5/2
N=8
N = 16
N = 14
22O
N=8
N=16  Learnt from 1st generation of RIBs
(f7/2)
(1h11/2-
Local properties (Z,N)
N=34,40,70 instead of N=50,82 ?
 EURISOL
)12
V. Lapoux DAPNIA/SPhN
EURISOL 16-20 Jan. 06
Explorations of nuclear landscape using SPIRAL2, GSI, EURISOL beams
drip-lines & properties in the vicinity of new doubly magic nuclei ?
 doubly magic stable nuclei
 doubly magic unstable nuclei ?
82
50
50
40
132-140...Sn
20
28
82
70
78Ni
20
8
2
2
8
?
110Zr
FAIR
neutron drip-line known
up to Z=8 (24O)…
28
V. Lapoux DAPNIA/SPhN
EURISOL 16-20 Jan. 06
2016 : 10 years of exploitation of SPIRAL2
Regions of the chart of nuclei
accessible with SPIRAL2 beams
Primary beams:
 deuterons
 heavy ions
Z
N
V. Lapoux DAPNIA/SPhN
EURISOL 16-20 Jan. 06
2016 : starting EURISOL beams
Z
Will all our beams be as intense as we believe ???
the 109/s beams of EURISOL
are the 104 /s of SPIRAL2 and co.
If the beams are new (36Ne ? 60-68Ca ?)
or rare at present (24O few/s at GANIL, RIKEN)
with EURISOL : counting rates less or around 103-105 /s
N
V. Lapoux DAPNIA/SPhN
EURISOL 16-20 Jan. 06
Going closer to driplines with higher intensities : opened physics fields
Skin and halos
Soft collective modes
Exotic shapes and resonances
Alpha-clusters
states
One-particle state
Spectroscopic factors
Z
Evolution of neutron excitation
Mn vs N along isotopic chains
2009+
N
2016+
Far ..far away
Beams Variety A,Z
Limit of nuclear binding, I 
Which beams ? We want to gain in exoticity
Complete the (p,p’) chains O (24O), Ne + Mg, Si, S, Ar
+spectroscopy of neutron-rich around N=28, N=40 (new), N=50, N=70 (new)
Examples : 38Ne (if not unbound),
V. Lapoux DAPNIA/SPhN
60-70Ca, 104Se
(Z=34, N=70)
EURISOL 16-20 Jan. 06
S2n =8.5
?
Sn = 5.2
1.52
4+
2+
0+
0.67 MeV
94Kr
S2n =7.91
2+ ?
6? MeV
Sn = 4.95
0+
96Kr
Similar trend for all
neutron-rich EURISOL beams :
few bound states
Calc : M.V. Stoitsov, et al., Phys. Rev. C68, 054312 (‘03)
Data AME2003
V. Lapoux DAPNIA/SPhN
EURISOL 16-20 Jan. 06
NEW GENERATION of MUST array
NIM A421, 421 (‘99)
MUST
6x6
cm2
CsI
1.5 cm
Si(Li) 3mm
Si Strips 300 m
MUST2 developed by:
 DAPNIA/SEDI : µ-electronics R&D ASIC
 GANIL
IPN Orsay
MUST : ~30cm behind !
2004-6
MUr à STrips 2
Si(Li)
4.5 mm
Si strips
300 m
DE
2
100 x 100 mm
X, Y , T, E
128X
128Y
CsI 3 cm
4x4
segments
collaboration : CEA-DAPNIA, GANIL, IPN Orsay
MUST 1  MUST 2:
 factor 3 larger active area
 factor 6 smaller volume of PA
 better time resolution
V. Lapoux DAPNIA/SPhN
MUST2
compactness due to
ASIC technology allows
particle -  coincidences
EURISOL 16-20 Jan. 06
Probes, reactions and beam energies
Experimental method
Direct reactions
collaboration
MUST2 : DAPNIA,
GANIL, IPN-Orsay
Assets : beam tracking
+ LCP arrays
E-TOF,E-DE, ID
Measure a complete set of direct reactions :
investigation of nuclear structure
form factors (densities) + Neutron excitations
spectroscopic factors
Spin & parity
Analysis :
Microscopic
potentials
Coupled channels
+CDCC
2+
?
0+
via (p,p ’)
via (d,p) (p,d) transfers
via transfer on polarized targets
At which energies do we need to accelerate ?
Optimize between :
Energies required by physics case & experimental difficulties
1. Access to high energy excited states : higher Einc compared to SPIRAL2
2.
energy resolution for excitation energies  lower Einc
V. Lapoux DAPNIA/SPhN
EURISOL 16-20 Jan. 06
Structure studies from direct reactions with EURISOL beams (100MeV/n)
small uncertainty
in Theta(LAB)
 huge variation in
excitation energies
V. Lapoux DAPNIA/SPhN
EURISOL 16-20 Jan. 06
Structure studies from direct reactions with EURISOL beams (25MeV/n)
V. Lapoux DAPNIA/SPhN
EURISOL 16-20 Jan. 06
Charged-Particle
 needed
toparticle
explore unbound
states
Requirementsspectroscopy
for improved
charged
spectroscopy
(p,p’), (p,d) (p,t) (d,p) Thin light targets p, d DE ~ 400keV to 1 MeV
Means…
particle spectroscopy, requirements
* Angular coverage (FWD and BWD)  4
& Granularity (Dx ~ Dy ~ 1mm)
* Large Dynamics and Particle Id
[p,d,t, 3,4,6,8He 6Li
Energies up to ~ 300 MeV tot
E-De and E-TOF correlations
for identification
low E threshold needed ~ < 300 KeV
to measure small c.m. angles
* Kinematics
Reconstruction of the Scattering angle
for variable (!) beam optical quality
angle & impact on target required
 array of Si strip telescopes
 stage-telescopes Si + SiLi +CSI
 For each channel,TAC for TOF,
DT (part. det) ~ 500 ps to ~ 1ns
start : particle in the Si stage
stop : time before target : beam detector
 2 beam tracking detectors
for x,y, T event by event 1mm x-y, 300 ps DT
D ~ 0.5deg MUST@ 15 cm
Intrinsic DE (Si) ~ 50 keV
DE resolution (with thin target ~ 1mg/cm2)
~ 400-700 keV
* Coupling with Gamma-spectroscopy,
 Compacity
V. Lapoux DAPNIA/SPhN
Precision on centroid, bound states ~ 30 keV
resonant states ~ 100-200 keV
 ASICs
EURISOL 16-20 Jan. 06
Detection for EURISOL experiments
Low Sn, S2n, S4n,…
Phase space background due to neutrons produced by decaying unbound states
+ AZ ID of
78Ni(p,p’)78Ni*
78Ni
+p  p’ + 78Ni*
p’ +
78Ni*
p+
76Ni
+ 2n
 p + 74Ni + 4n
78Ni(p,d)77Ni
78Ni
+p  d +
d+
77Ni
unbound? d + 76Ni + n
77Ni*
 d + 74Ni + 3n
78Ni(p,t)76Ni
78Ni
+p 
 t + 76Ni*
 t + 76Ni
 t + 75Ni* + n
t+
74Ni
forward focused
heavy fragments :
Spectrometer or
SiLi, CSI arrays
close to targets ?
+ neutron detection
Check alpha-neutrons
correlations ::
needs
LCP and neutron devices
granularity & efficiency
+ 2n
ID, E vs Theta of LCP
V. Lapoux DAPNIA/SPhN
EURISOL 16-20 Jan. 06
Improved detection for EURISOL experiments
2016 Wishes for Coupled Detection devices
Charged-Particle spectroscopy
needed to explore unbound states
Thin light targets p, d
DE ~ 400keV to 1 MeV
(p,p’), (p,d) (p,t)
+
Inverse kinematics :
good Energy resolution in Eexc
requires : beam profile on target
 beam tracking detectors
+
Gamma-ray spectroscopy
 needed to separate
close excited states
Thick target DE ~ 20keV
(d,p) @ 9 MeV/n
+ A,Z ID of heavy fragment
in a spectrometer
or SiLi CsI array
+ NEUTRON DETECTION
V. Lapoux DAPNIA/SPhN
Steps beyond in the detection :
- ASIC technology
(Application Specific Integrated Circuit)
(compacity of all devices)
- Mixed detection
(gamma+ charged particles
+… neutrons) :
Ex : Ge + Si + scintillator
in a crystal-Ge-Si ball array
-Higher multiplicities in LCP arrays (3,4,..)
challenges in acquisition systems :
synchronize separated arrays & triggers
needs to reduce dead time
EURISOL 16-20 Jan. 06
EURISOL : specific experiments and beams
Exotic structure at the neutron drip-line :
24O
Ex :
34-38Ne
Complete the systematic studies of neutron excitation vs N
from Z=8 to Z=28 chains
 EURISOL
Cluster structures : alpha-n correlations & molecular bands
Ex : 30Ne : 5 Alpha + 10 n
Probes : (p,p’)
+ transfer reactions
+ (p,2p)
V. Lapoux DAPNIA/SPhN
EURISOL 16-20 Jan. 06
EURISOL : specific experiments and beams
Present (1st generation) intensities : few part/s
Needed : (at least) 103-105 /s
20-50 MeV/n : enough
Looking back in the past !
See multi-nucleon transfer
Ex : 9Be(13C,14O)8He H. Bohlen et al., ZPhysA 330 (’88)
10Be(12C,14O)8He
Th. Stolla et al., ZPhysA 356 (’96)
SPIRAL2 production of light exotic nuclei
R&D for a 9Be target allowing 40 kW beam
SIMILAR TECHNIQUES FOR EURISOL ?
V. Lapoux DAPNIA/SPhN
EURISOL 16-20 Jan. 06
conclusions
Means
BEAMS OF RARE ISOTOPES
Today 1/s, EURISOL 103-105
/s
Einc ~ 20-50 MeV/n
Nearly (~90%) pure beam
Means
DIRECT PROBES
i.E p &d targets,
+ Polarized p,d
DIRECT REACTIONS
target: cryogenic
D2 or CD2
exotic beam
EURISOL
AZ
Beam Tracking
Devices BTD
p
Light charged
particle (LCP) detection
V. Lapoux DAPNIA/SPhN
A+1Z
-ray detection:
future AGATA
EURISOL 16-20 Jan. 06
Diffusion (p,p’) en cinématique inverse
CsI
1.5 cm
MUST
Si(Li) 3mm
Si Strips 300
m
Pre-Amps
Si
Strip
6x6
cm2
CATS
S. Ottini
et al.,
NIM A431
(‘99) 476
MUST
Y. Blumenfeld
et al.,
NIM A421
(‘99) 471
détection du
faisceau (x,y,t)
V. Lapoux DAPNIA/SPhN
détection d’ions légers
x,y,E,t) Z & A (1,2,3H, 3,4He)
• gamme étendue E DE+DE+E
• bas seuil (~ 500 keV)
• Résolution en position
Dx, Dy ~ 1 mm
EURISOL 16-20 Jan. 06
11C
(p,p ’) @ 40,6 MeV/nucléon : l ’effet des CATS sur MUST
+
Information cruciale apportée
par les détecteurs de faisceau
DE* = 750 keV
Analyse : Cédric JOUANNE,
Thèse 98-01, CEA-Saclay,
DSM/DAPNIA/SPhN
C. Jouanne, V. L et al., PRC 72, 014308 (’05)
V. Lapoux DAPNIA/SPhN
précision centroïde ~ 30keV
réactions de référence
EURISOL 16-20 Jan. 06
For beams Ispiral2 > ~ 104 /s
TOOL : direct reactions (p,p) (p,d) (p,alpha) & (d,d) (d,p) (d,3He)
AZ(d,p)A+1Z
3.6MeV
?S
2+
Q = Sn(A+1,Z)-Sn(d) = Sn(A+1,Z) - 2.24 MeV
4n =3.1
Sn =2.5
S2n = 2.1
AZ(p,d)A-1Z
Q(p,d)= Sn(d)-Sn(A,Z) = 2.224 -Sn
AZ(p,t)A-2Z
Q(p,t)=S2n(t)-S2n(A,Z) = 8.482 –S2n
Q [96Kr(p,d) ]~ - 2.8MeV
0+
8He
Ex : Q 8He(p,d) = -0.35
Q 8He(p,t) = 6.34
Q [96Kr(p,t) ]~ - 0.45 MeV
Q 8He(p,) = 3.57MeV
Using the A+3Z+1 nucleus with higher I to produce and excite AZ
81Cu
(~80-82Zn) I ~ 105 /s
Q [ 81Cu(p,)
78Ni]
~ 7MeV
Sn, S2n weak : High cross sections for the 1n, 2n transfer
compared to elastic
angular momentum window, selectivity
134Sn(d,p) 135Sn
@ 4.9 MeV/n DL ~ 2.5 @ 10 MeV/n DL ~ 3.2
+ to extend the transfer structure studies
 more suitable range of beam E for (d,p) : E ~ 10-20 MeV/n
V. Lapoux DAPNIA/SPhN
Typical conditions
for transfer reactions
 ~ 1mb / sr
Beams  10 4-5 pps
S ~ 10 - 15 % error
d/d ~ 10 - 15 %
Beam time ~ 2 weeks
EURISOL 16-20 Jan. 06