what is the relationship with ? what is alto ? what is (currently) and what is expected to be (in a...
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What is the relationship with ?
What is ALTO ?
What is (currently) and what is expected to be (in a near future) the physics output of the facility ?
?
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Ate
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A few elements on “how to produce exotic nuclei” (a pedestrian approach)
?
1
2
3 Physics at ALTO
ALTO in the context of the construction of SPIRAL2
Atelier ESNT 4-6/02/08 l’Orme des Merisiers
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Recent history (80’s – 00’s) of the experimental research on exotic nuclei in France (especially structure)
Terra incognita of the medium mass n-rich nuclei
Fragmentation of intense stable ion beams
1- General context1
- G
en
era
l co
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SPIRAL 1
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Fission was understood as being probably the best nuclear reaction to be used for the production of medium mass n-rich nuclei
1-
Ge
ne
ral c
on
text
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from P.W.Lisowski et al, OECD/NEA Report NEANDC-305 'U' 1991 p.177
Thesis Nicolas PauwelsIPN Orsay
Production of fission fragmentsby photo-fission
Production of fission fragmentsusing fast neutrons
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2. Fusion reaction with n-rich beams
1. Fission products (with converter)
4. N=Z Isol+In-flight5. Transfermiums In-flight
3. Fission products (without converter)
Primary beams: deuterons heavy ions
7. High Intensity Light RIB
6. SHE
8. Deep Inelastic Reactions with RNB
Regions of the chart of the nuclei accessible with SPIRAL2 beams
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2- How to produce exotic nuclei
1 Choose the good reaction mechanism
At ALTO : fission (and nothing else)
2 Choose the production method
1983
Neutron rich
Neutron deficient
Thanks to th
e S3
project
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2 cyclotrons CSS1 and CSS2
Heavy ions 50-100 AMeV (so called “intermediate energy”)
Electrons 10 µA 50 MeV
LINAG : light ion beam high intensity (few mA !) see Stéphane
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Isotopic Separation On Line
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thermalization
Reaction products are fully stopped inside the target and neutreulized
No thermalization
Ex : SISSI target, “production” target at LISE etc
Ex : Christmas tree shaped like target at SPIRAL1-GANIL
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The fission target : 72g of uranium carbide heated at 2200°C for the releaseof the elements. Total length 19 cm
Typical design of a target
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Production of fission fragmentsby photo-fission at alto
Incident electron beam 50 MeV 10 µA
Photon flux
target
fission
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At ALTO : Carburation room, dimensioned for SPIRAL2 targets
Tests of target ion sources for ISOLDE, SPIRAL2 and EURISOL at ALTOCollaboration with Argonne for dense uranium carbide
R&D studies for
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Prototype in steel to test mechanical rigidity and temperature distribution
validation of simulations
Ta prototype under tests of long term heating
Transfert tube(Ta)
UCx target
Graphite container
Tantalium oven
Cooled chamber
R&D studies for
Design of the oven
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The target-ion source ensemble : le nerf de la guerre
Carburization at 1600°C
UC+UC2+C
2200°C UC2 + C
2000°C UC2 + C
UO2 grain (~20m)+ C grain(~44m)
Before carburization (C/U = 6)
Heating time ~ 10h
The microscopic structure of the target plays a fondamental role for the release of the elements
Electronic microscopeX-ray spectroscopy
Ni Z=28
Sr Z=38
Pd Z=46
Prohibiting release times
Target : limiting factor = release time of the elements
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Taken from PIAFE projectReport based on Studsvikmeasurements
NiCu
ZnGeAs
SeBrKrRb
Sr
YZr
NbMoTcRu
RhPd
Ag
CdInSnSbTe
I XeCsBa
LaCePrNdPmSmEu
NiCu
Zn
Ga
Ge
AsSe
BrKr
Rb
Sr
ZrNbMo
TcRuRh
Pd
Ag
Cd
InSn
SbTe
IXe
CsBa
LaCePrNdPm
SmEu
Ga
Y
-500
500
1500
2500
3500
4500
5500
25 35 45 55 65Z
oCpoint de fusion
point d'ebullition
1,0E-011,0E+00
1,0E+011,0E+021,0E+031,0E+04
1,0E+051,0E+061,0E+07
1,0E+081,0E+09
25 30 35 40 45 50 55 60 65
Z
Rel
ease
tim
e (s
) Calculations from M.-G. Saint-Laurent
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separation
Reaction products are fully stopped inside the target and neutralized
identification
Ex : LISE, SPEG, VAMOS
The PARRNe mass separator
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detection
Reaction products are fully stopped inside the target and neutralized
Ex : EXOGAM
Detection system
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Detection system
Ex : Ge detector array :OSCAR (the Orsay Segmented lover Array)
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The target-ion source ensemble : le nerf de la guerre
Ion source : limiting factor = Z dependence
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Laser ion source (quasi exclusive in Z)
Surface ion source (limited to alkali and alkali like)
Hot plasma (Z « universal »)
High temperature (1900 °C)
Compact: the target is part of the source high efficiency
well adapted for a large number of elements
No selectivity
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Does it work ?
Measured effective yieldsJune 2006 Ie=100 nA (instead of 10 µA nominal)
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Where do the R&D efforts should apply ?
2 main R&D axes
Release of the elements Selectivity of the elements
High density U carbide (SPIRAL 2)
Release using molecules
Microscopic studies( ISOLDE collaboration)
Chemical selectivity
Selectivity using lasers
combinaison trap+laser
bunch of the beam
Magnetic selectivity
detarg......
separsourceettNI
optimization of the production
-Selectivity-Release
Accelerator(driver)
Reaction(fission)
Nbr ofAtoms in target
Intensity of the signal
Detection system
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Used as such (good optical quality)
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Summary : ISOL technique, key features Incidentally : why do we (experimentalists) us it ?ISOL
The key aspect :The radioactive nuclei are available as an ion source
This is THE method which allows to produce the largest amount of radioactive nuclei per unit of time
The radioactive nuclei are created in an experimental environment similar to the traditional stable ion sources
30-50 keV1
2
Injection into an accelerator
Secondary reactions
Coulomb excitation(ex REX ISOLDE)
Direct reaction(ex SPIRAL1 GANIL)
appr
ox 1
0
AMEV
Few
AM
EV
50-1
00
AMEV
FragmentationFuture ?
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1011-1012 photofission
1013-1014 fast neutrons
>1015 protonsFissions/sec
Fissions/sec
Fissions/sec
How does ALTO compare to the major fission based ISOL projects ?
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A=132
Cs Xe I Te Sb Sn In
Comparison with ISOLDE/CERN
ALTO = ISOLDE with less isobaric contaminants !(for fission products only)
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Where is it ?
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1/3 ISOL1/3 Stable beams
1/3 Agregats
General layout
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Radioactivité :
dérouleur de bande; géométrie rapprochée
SPLIT POLEBACCHUS
ligne 420
ligne « basse énergie »lignes ions stables équipées d’un spectromètre
lignes ions stables non équipées d’un spectromètre
ligne 410(ré-ouverture en 2008)
OSCAR
(Orsay Segmented Clover Array)
ORGAM phase1
(ORsay GAMma array)
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5 . 1011 fissions /s
The ISOL facility
Electron driver
Target ion source ensemble
PARRNe mass separator
Lines towards experiments
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The electron driver
the LEP injector arriving from CERN-Geneva
The LEP injector installed
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The output of LEP injector and deviation
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From the deviation to the target-ion source ensemble
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The electron driver
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detarg......
separsourceettNI
4Plastic Scintillator
OSCAR: Orsay Segmented Clover Array -Ring : 4 segmented clovers @ 6cm ~ 10% efficiency
Conversion electron detector
Neutron detector 3He
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3-
Ph
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3- Physics at ALTO
What we currently do
Structure of medium mass neutron rich nuclei Our “spécialité” : evolution of the N=50 shell effect towards 78Ni
Measurement of the evolution of mean square charge radius
strength functions
n 2n decay measurements (Pn, P2n, T1/2)
g factor measurements
Fast timing measurements
Structure of medium mass neutron rich nuclei : evolution of the N=82 shell effect, search for “exotic” shell effects eg HO magic shell effects
ray spectroscopy
Laser spectroscopy
Immediate thematic extension with the existing instruments
T1/2 (ps range)feasable within 2 to 3 years
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3-
Ph
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Which nuclei ?
ObservableExperimental
techniquePhysics case
Synopsis
Energy level pattern
spectroscopy following -decay
<r2>
Static moments :Q, Laser spectroscopy
Exploration of the valence space extending N-E to 78Ni
Evolution of the N=50 and N=82 shell effects far from stabilityOnset of the collectivity and nature of the correlationsT1/2 of the excitation
levels->dynamic moments :B(M1) (E2)
Fast timing
Polarization effects
Pn P2n and T1/2 Neutron detection
Nature of the em transitions
Electron conversion
g-factor and spin Nuclear orientation
Many purpose (including systematics)
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LE LION ET LE RAT Il faut, autant qu’on peut, obliger tout le mondeOn a souvent besoin d’un plus petit que soi.De cette vérité deux fables feront foi, Tant la chose en preuves abonde. Entre les pattes d’un lionUn rat sortit de terre assez à l’étourdie.Le roi des animaux, en cette occasion,Montra ce qu’il était et lui donna la vie.Ce bienfait ne fut pas perdu.Quelqu’un aurait-il jamais cruQu’un lion d’un rat eût affaire ?Cependant il avint qu’au sortir des forêtsCe lion fut pris dans des rets,Dont ses rugissements ne le purent défaire.Sire rat accourut, et fit tant par ses dentsQu’une maille rongée emporta tout l’ouvragePatience et longueur de tempsFont plus que force ni que rage.
Jean de La Fontaine, Fables, Livre II, 11
Based on a tale from Esope (VII-VI BC)
Technical issues and administrative traps
Ate
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