Study of exotic nuclei with radioactive beams

Congresso del Dipartimento di Fisica
Highlights in Physics 2005
11–14 October 2005, Dipartimento di Fisica, Università di Milano
Study of exotic nuclei with radioactive beams
O. Wieland
Dipartimento di Fisica, Università di Milano; INFN – Sezione di Milano
Nuclear physics under extreme conditions
How exotic nuclei are produced and measured
Milano University and INFN Milano
A.Bracco, G.Benzoni, N.Blasi, F.Camera,
S.Leoni, B.Million, M.Pignanelli,O.Wieland
Shell structure in nuclei
• Structure of doubly magic nuclei
Test of (new)symmetries Nuclei at the drip lines
• Very large proton-neutron asymmetries
Nuclear shapes
• New Resonant excitation modes
• Exotic shapes and isomers
• Neutron, Proton Decay
• Hyperdeformation
Proton number
• Coexistence and transitions
+.
..
Heavy Nuclei
Shell stabilization
Shell evolution
and SUPER Heavy
Fe
Neutron number
Developement of radioactive beams to access exotic nuclei
The ISOL production Method
Isotope Separation On Line
Life-time
> 100 ms
projectile
1 GeV/u
p,.. C…
Heavy Ions
•
•
•
•
(very) Thick targets
Stopped reaction products
“Chemistry” dependence (extraction)
High quality post-accelerated RIB beam
In-flight or Fragmentation Method
complementare insieme con ISOL
• Heavy ion production beam
BEAM
TARGET
Fragments
• “Thin” target
•
•
•
•
RIB utilizes production beam
momentum
No species dependence
“Fast” measurements “in flight”
Projectile Fragmentation and Fission
GeV/u
Ion Source
For short
lifetimes
<1ms
Types of reactions used for „in flight g-spectroscopy“
• Relativistic Coulomb excitation (large cross section of ca. 100 mb & thick targets)
- first excited 2+states => B(E2)
- excitation of Giant Resonances
• Secondary fragmentation
- excited states at higher spins
and higher excitation energy
Relativistic Coulomb Scattering of neutron rich isotopes
Primary Beam
86Kr (109 pps)
400…700 MeV/u
HECTOR
INCOMING
Ca
Ar K
Cl
S
P
Si
Al
Mg
Na
DE
(~ 103 pps)
100 MeV/u
OUTGOING
POSITION
Z=20
37Ca (85 %)
2*103 p/sec
Selection, identification
and tracking
E
of the
Isotop cocktail
38Ca
(<1 %)
Z=19
36K (14 %)
+ timegate
RISING detectors
v/c fino a 0.8
Target
Milano
: Au or Be
Milano
RISING detectors
v/c fino a 0.8
After doppler correction
Phys.Lett.B622(2005)29
• collettivita’ (B(E2) dello stato 2+ nel 56Cr e’ minore di quella dei nuclei vicini
• Evidenza della chiusura di una nuova sottoshell a N=32 ?
Future RIB facilities in Italy, Europe, WORLDWIDE
Next step:
Next generation spectrometers
based on years of worldwide R&D
•Higher efficiency
•Higher selectivity,sensitivity
•Higher position resolution
For measuring gamma rays
Is needed !!!
Segmentation of the
HPGe detector cristals
and gamma-ray tracking
AGATA
the ultimate gamma-ray spectrometer
Basic ingredients of AGATA
1
Highly segmented
HPGe detectors
Identified
interaction
points
Milano AGATA group
(x,y,z,E,t)i
4
Reconstruction of tracks
evaluating permutations
of interaction points
·
Pulse Shape Analysis
to decompose
recorded waves
·
3
2
Digital electronics
to record and
process segment
signals
Milano AGATA group
Reconstructed
gamma-rays
See poster
AGATA
Advanced GAmma Tracking Array
4p- Array of segmented HPGe
180 hexagonal crystals 3 shapes
each crystal is segmented in 36 sectors
each crystal is encapsulated
60 triple-clusters
all equal
Inner radius (Ge)
23.5 cm
Solid angle coverage
82 %
More than 6000 segments
Amount of germanium 362 kg
v/c=45%
v/c=45%
Lots of technological development has to be done
SPIN off ?
benefits other than intellectual, cultural, scientifical, philosophical, …
Medicine
(tracking new imaging techniques , low irradiation methods)
 National

Safety (tracking source location)
 Environment science
non destructive analysis
 space science
Germanium
Encapsulation technique
Water/Ice
on Mars ?
INTEGRAL SATELLITE INTERNATIONAL GAMMA RAY
ASTROPHYSICS LABORATORY
Mars Odyssey
Gamma-Ray
Spectrometer
Milano Nuclear Structure Group