Metodi di Produzione: In-Flight, ISOL

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Lezione 1

Fasci Radioattivi

Metodi di Produzione: In-Flight, ISOL

In Flight: David J. Morrissey and Brad M. Sherrill,

“In-Flight Separation of Projectile Fragments”

The Euroschool Lectures on Physics with Exotic Beams, Vol. 1 , Springer-Verlag (2004)

ISOL: P. Butler,

“ISOL techniques to reach radioactive nuclei – from birth to EURISOL”

Fermi School “From the Big-Bang to the nucleosynthesis” Varenna 19-24 July 2010

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• L (10

^-10

sec)

• X (10

^-10

sec)

• Li

¹¹

(neutron rich)

• Sn

¹⁰⁷

(proton-rich)

barioni nuclei

(3)

(4)

284 stable isotopes with T

_1/2

> 10

⁹

year Our beams till 1989 !

Un po’ di Storia…

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<1940 495

Un po’ di Storia…

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<1940 1940 495 822

Reactors: n on U

Un po’ di Storia…

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<1940 1940 1950 495 822 1244

First Isotope Separator experiment Niels Bohr Institute 1951

fast n on U: Kr and Rb isotopes

Un po’ di Storia…

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<1940 1940 1950 1960 495 822 1244 1515

Selective detection method: a decay

Un po’ di Storia…

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<1940 1940 1950 1960 1970 495 822 1244 1515 2010

Light-ion induced spallation Heavy-ion induced fusion

Un po’ di Storia…

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<1940 1940 1950 1960 1970 1980 495 822 1244 1515 2010 2270

Projectile and target fragmentation

Un po’ di Storia…

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Comment to Nature

,

by M. Thoenessen and B. Sherrill

5 M AY 2 0 1 1 | VO L 4 7 3 | N AT U R E | 2 5 In occasion of Rutherford centennial 2011

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TODAY :

Around 3000 of the expected > 6000 nuclei

have been observed

Different Decay Modes

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8 20

28

50

82

28

50

126

82

2 20

2 8

Neutron number N

Pr ot on num be r Z

248 Stable

~3000 discovered

Quest for a UNIFIED DESCRIPTION of ALL Nuclei

Challenges in MODERN NUCLEAR PHYSICS

> 6000 expected

50

126

82

BASIC SCIENCE

Many Body Finite Quantum System

Symmetry Principle

n p

(14)

8 20

28

50

82

28

50

126

82

2 20

2 8

Neutron number N

Pr ot on num be r Z

Quest for a UNIFIED DESCRIPTION of ALL Nuclei

Challenges in MODERN NUCLEAR PHYSICS

50

126

82

BASIC SCIENCE

n p

208Pb

132Sn

48Ca

78Ni

100Sn

16O

² SHELL STRUCTURE

(Magic Numbers)

(15)

8 20

28

50

82

28

50

126

82

2 20

2 8

Neutron number N

Pr ot on num be r Z

Quest for a UNIFIED DESCRIPTION of ALL Nuclei

Challenges in MODERN NUCLEAR PHYSICS

50

126

82

BASIC SCIENCE

n p

² SHELL STRUCTURE (Magic Numbers)

224 Ra

Stable octupole

Clusters 12 c

Halos 11 Li

² SHAPES

² EXCITATIONS

GIANT DIPOLE

N SKIN OSCILLATION pygmy DIPOLE

Collective Excitations:

RESONANCES

Shape Evolution

(16)

8 20

28

50

82

28

50

126

82

2 20

2 8

Neutron number N

Pr ot on num be r Z

Quest for a UNIFIED DESCRIPTION of ALL Nuclei

Challenges in MODERN NUCLEAR PHYSICS

50

126

82

² SHELL STRUCTURE (Magic Numbers)

² SHAPES

² EXCITATIONS

C

r-pr oc es s pa th

INTERDISCIPLINARITY Astrophysics

Nucleosynthesis

Impact on abundances

Element ABUNDANCES

BASIC SCIENCE

n p

Applications

Radioisotopes, Reactors, …

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1. Production of exotic nuclei

2. Study of their excitations and decay modes

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Intensity (particle/sec)

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Intensità Minime di RIB

basic properties

basic properties (via selective techniques) First

excited states

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di fasci primari

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Tipico calcolo di count rate

(usato per pianificare esperimenti)

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1 particle nA = 6.25 x 10

⁹

pps

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µm

(25)

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Angular momentum transferred

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In generale:

• Piccate ad angoli in avanti

• ^{s @} 10

^-1

– 10 mbarn

• few-nucleons away from projectile and target

Reazioni di Produzione

T ransfer

(Proj. Energy: Few MeV/A)

Efficient mechanism to move into neutron-rich regions

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Reazioni di Produzione

Fusion

292 MeV

⁵⁴

Fe +

⁹²

Mo ®

¹⁴⁶

Er(p4n)

¹⁴¹

Ho 402 MeV

⁷⁸

Kr +

⁵⁸

Ni ®

¹³⁶

Gd(p4n)

¹³¹

Eu

A.A. Sonzogni et al., Phys. Rev. Lett. 83 1116 (1999) D. Seweryniak et al., Phys. Rev. Lett. 86 1458 (2001)

(Proj. Energy: Few MeV/A)

Efficient mechanism to reach proton-rich nuclei

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Participant-spectator reactions at relativistic energies

( above 100 AMeV )

Reazioni di Produzione

Projectile Fragmentation

0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0

N (A-Z) 0.0

10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0

Z

r-process path

rp-process path

RI yield in ions/s

>1012 1010 108

102 1 .01 10-4 10-6 106 104

Region of Known Nuclei

(Proj. Energy: > 100 MeV/A)

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(Proj. Energy: ≥ 100 MeV/A)

(Proj. Energy: few MeV/A) (and Transfer)

(proj. excited in Coulomb field to unbound states;

equivalent to absorption of virtual photons)

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Reazioni di Produzione

Induced Fission

with neutrons

Carefull:

fission yields and not

absolute cross sections !!!

s _(n

_th

,fission) = 585 b (

²³⁵

U)

(32)

Reazioni di Produzione

Induced Fission

with protons

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Neutron Induced Fission – CROSS SECTIONS !!!

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Random removal of protons and neutrons from heavy target nuclei by energetic light projectiles

(pre-equilibrium and equilibrium emissions).

Spallation

Reazioni di Produzione

Target Fragmentation

High energy projectile (up to GeV)

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Competing mechanisms

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ISOLDE (CERN) Target

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ISOLDE (CERN) Target

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Spallation/Fragmentation in Inverse Kinematics

( ∽ 1 GeV/A)

(forward focus reaction products:

efficient detection)

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Reazioni di Produzione

Comparisons

stable isotopes

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Optimum Reazioni di Produzione

ISOLDE SPES (Legnaro)

Meccanismi di produzione alternativi e

complementari

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prodotto di reazione ad alta velocità

(relativistico)

prodotto di reazione fermo (E_kin∽ 10 keV)

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à High energy (relativistic) secondary beams

starting from high energy relativistic primary beams

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The relative energy loss in the degrader is given by:

K: constant typical of the degrader A: nucleus mass

e: thickness of the degrader Z: atomic number

L

ENERGY STRAGGLING

L

ANGULAR STRAGGLING

L

NUCLEAR REACTIONS

INTENSITY LOSS

Thickness and material are chosen as a compromise between

desired and undesired effects

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Forte complementarietà con fasci da frammentazione

(In-Flight radioactive beams: discovery of new systems, ...)

(ISOL-beams: precision physics)

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U fission

Ionization

Mass separation

(d,n) d

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Letter to the Editor

Phys. Rev. 82, 96 (1951)

Published 1 April 1951

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Similar ISOL production scheme in today’s facilities

(54)

Efficiency loss

can be up to a factor

of 100

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p (1.4 GeV) +

²³⁸

U, others 2 μA spallation,

fission, fragmentation

ISOLDE

ISOL Facilities in Europe-Production Schemes

126

2 2

8

8 20

20 28

28 50

50

82 82

(pps)

p (40 MeV) +

²³⁸

U 200 μA

fission

SPES

n, p, d, HI +

²³⁸

U,others fission, in-flight, …

SPIRAL1/SPIRAL2

Intensity ≥ 10-1000 than present

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Efficienza di diffusion-effusion da temperatura

Beam

Multi-slice target

Neutron dose

efficienza

temperatura

d = 15 µm d = 4 µm d = 1 µm

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Ottima qualità dei Fasci ISOL

N.B. all’uscita del target di produzione i fasci ISOL sono «fermi»

(hanno energie di ∽ 10 keV).

Possono essere usati per studi di beta-decay o post-accelerazione

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A

laser is tuned to a wavelength

which excites only one isotope of the material and ionizes those atoms preferentially.

The

resonant absorption

of light for an isotope is dependent upon its mass and certain

hyperfine interactions between electrons and the nucleus, allowing finely tuned lasers to

interact with only one isotope.

After

the atom is ionized

it can be removed from the sample by applying an electric

field.

Resonant Laser Ionization sources (RILIS)

for on‐line mass separators for radioactive ion beams

The RILIS is a chemically selective ion source

which relies on resonant excitation of atomic transitions

using tunable laser radiation

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RILIS @ ISOLDE-CERN

20-40 % efficiency of ionization

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RILIS @ ISOLDE-CERN

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-200 0 200 400 600 800 1000 1200

30534,6 30534,8 30535 30535,2 30535,4 30535,6 30535,8 30536

Frequency of first transition (cm^-1)

Intensity (arb. units)

1+

3- 6-

(1⁺)

(3^-) (6^-) 70

Cu

₄

1 2 9

6.6(2) s 33(2) s 44.5(2) s

0 100 200

(keV)

b

V. Fedoseev, U. Koster,

J. Van Roosbroeck et al., ISOLDE

• laser ionization in a hot cavity

• different hyperfine splitting for the different isomers

• enhancement of specific isomers

• increase selectivity of laser ion sources

• reduce power, pressure and Doppler broadening

Production of isomeric beams:

⁷⁰

Cu

^m1,m2,g

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Progetto Italiano per fasci Radioattivi (Laboratori Nazionali di Legnaro)

(69)

Radioactive Beam Project at Legnaro Laboratory

INFN - Italy

ISOL target

operated at 2000°C Ionization

and extraction

with 1+ Plasma source

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Radioactive Beams

ISOL (Isotope Separation on Line) In-Flight (Fragmentation)

Advantages

^:

no chemical processes involved, high-intensity beams

high intensity beam p,He

§ heavy elements

§ target nuclei break into fragments (desired isotopes)

§ fragments are extracted heating the target to high T (diffusion process)

§ diffused atoms are collected

§ ionized

§ separated

§ re-accelerated

• high intensity beam of heavy elements hits thin production target

• beam atoms fragment into smaller atoms

• fragments proceed with same speed and are separate by a magnet

Relativstic beams, forward focus

Advantages

^: excellent beam quality

Disadvantages

^:development of diffusion process for

each elements

GSI:

fast beams ³ 50 MeV/A

RIA:

primary beams: 400MeV/A up to 1pµA

RIKEN:

primary beams: 400MeV/A

up to 1pµA (first phase:May 2005)

Rex-Isolde:

3.1 MeV/A (Z=2-88), ≈10⁴-10¹¹ ions/s

Spiral:

1.7-25 MeV/A (Z=2-36), up to 10¹¹ ions/s

Spes:

20 MeV/A (Z=80-160), up to 10⁹ ions/s

t > 100 ms

t < 1 µs

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