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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A few elements on “how to produce exotic nuclei” (a pedestrian approach)

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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

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

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SPIRAL 1

Fission was understood as being probably the best nuclear reaction to be used for the production of medium mass n-rich nuclei

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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

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

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

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

Production of fission fragmentsby photo-fission at alto

Incident electron beam 50 MeV 10 µA

Photon flux

target

fission

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

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

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)

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

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......

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optimization of the production

-Selectivity-Release

Accelerator(driver)

Reaction(fission)

Nbr ofAtoms in target

Intensity of the signal

Detection system

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 ?

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 ?

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

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

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......

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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- 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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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)

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

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