Obergurgl -02/10/2007 Lecture 2

The Story so far--------

We looked at a) our present theoretical understanding of Nuclear Structure

b) Some simple physics from the undergraduate curriculum – which turned out not to be so straightforward.

c) Ways to study nuclear structure.

We saw that we needed beams of Radioactive nuclei!!

Now we want to look at how we can produce beams of radioactive ions.

We will find that this leads us inexorably to FAIR

Manipulating the system

Beam energyBeam energy spreadBeam speciesTarget speciesForm of target

We control

We can examine how properties vary with

Energy (temperature)Angular momentum (spin)Isospin or (N-Z)/A

Radioactive ion beams, production techniques

Isotopic separation on-line (ISOL)

thick target (100% of range) => high beam current (upto1016 s-1) long extraction and ionization time (ms) chemistry dependent

light projectilethick target

difussion

ion source

post-acceleration

mas separatorlow- or high-energy nucleus

short separation+identification time (100 ns) thinner targets (10% of range) =>lower beam currents (upto 1012 s-1) chemistry independent

high-energy nucleus

In-flight fragmentation

heavy projectilethin target spectrometer

J. Benlliure

Production techniques

J. Benlliure

Isotopic separation on-line (ISOL)

light projectile into a heavy target nucleus (target spallation) charged and neutral projectiles (n) thick target (100% of range) and high beam current (1016 p/s) high quality beams

long extraction and ionization time (ms) chemistry dependent target heat load activation

light projectile

thick target

diffusion

ion source

post-acceleration

mass separatorhigh-energy nucleus

Radioactive species are created in nuclear reactionsin a target-ion source maintained at high T.They diffuse/effuse from the target into an ion source where are ionised and then extracted by an electric field of ~ 60 keV.Following mass separation they can be used at 60 keVor injected into a post-accelerator to take them to the Coulomb Barrier or beyond.

EURISOL – The future ISOL facility for Europe

Eurisol is a very ambitious project. It is a classical ISOL facility with a driver accelerator delivering 5 mA of 1 GeV protons or intense deuteron beams etc. [cf present ISOLDE has 1.4 μA of 1.4 GeV protons]

This is beyond our current capabilities.

Accordingly several machines are being built as stepping stones to reach this future goal and there is intense development activity underway.

SPIRAL 2 at GANIL in France and HIE-ISOLDE at CERN are two such stepping stones.

So EURISOL represents a big challenge but it is a major goal for European

Nuclear Physicists.

Ionsources

1 GeV/qH-, H+, 3He++>200 MeV/q

D+, A/q=2

Chargebreeder

Low-resolutionmass-selector

UCx

target

1+ ionsource

n-generator

20-150 MeV/u (for 132Sn)

To low-energy areas

Secondaryfragmentation

target

One of severaltarget stations

High-resolution mass-selector

To medium-energy experimental areas

H-

H+, D+,3He++

9- 60 MeV/u 2-10 MeV/u

To high-energyexperimental areas

Chargeselector

SPL

HIE-ISOLDEEURISOL precursor

Production techniques

J. Benlliure

Gamma/neutron converters

low-energy nucleus

e-, d

thick target

diffusion

ion source

post-acceleration

mass separatorhigh-energy nucleus

converter

, n

This is the basis of SPIRAL II - one of the precursors of EURISOL, based on deuteron breakup

The emphasis here is on the production of neutron-rich species in the fission of Uranium induced by photons or neutrons.

The advantage of this technique is that it separates power dissipation and isotope production.

RFQ - 0.75A MeV

ECRIS-HI 1mA

“SILHI-deuteron” 5mA

CIME Cyclotron RNB (fission-fragments)

E < 6-7 MeV/u

SC - LINACE = 14.5 AMeV

HI A/Q=3E = 40 MeV - 2H

Int. = 5mA

Production Cave

C converter+UCx target

Low energy RNB

> 1013 fiss./s

•What is SPIRAL2 ?

Note:- LINAG will be a major new accelerator in its own right because of high intensity. System will also produce intense fluxes of fast neutrons. [Parallel operation]

LINAG

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

Regions of the Chart of Nuclei Accesible with SPIRAL 2 beams

Regions of the Chart of Nuclei Accesible with SPIRAL 2 beams

7. High Intensity Light RIB

6. SHE

8. Deep Inelastic Reactions with RNB

•Available Beams

Originally constructed by several CERN member states ~ 15 MCHF

Utilises now 50% ISOLDE running time

REX has accelerated 43 different RIB

Present RIB yield from ISOLDE allows 10% of all 700 radioisotopes be used

REX post-accelerator

Rex photo

REX-ISOLDE2006

MINIBALL(Coulex,transfer)

Halo studiese.g. 10LiJeppesen et alPL B642(2006)449

Coulomb barrier for RIB

Current REX-ISOLDE

HIE-ISOLDE

Radioactive ISOL beam yields

2020

2016

2012

present

GANIL-ISOLDEJan 07 agreement – Complementarity;Collaboration

Projectile Fragmentation Reactions

hotspot

Excited pre-fragment

Finalfragment

projectile

target

Energy (velocity) of beam > Fermi velocity inside nucleus ~30 MeV/uCan ‘shear off’ different combinations of protons and neutrons.Large variety of exotic nuclear species created, all at forward angleswith ~beam velocity. Some of these final fragments can get trapped in isomeric states.

Problem 1: Isotopic identification. Problem 2: Isomeric identification.

Main difficulty:- beam is a cocktail of many species

S t o p p i n g P o w e r o f R e l a t i v i s t i c H e a v y I o n s

B r e a k - d o w n o f t h e r e l a t i v i s t i c B e t h e t h e o r y ,F R S e x p e r i m e n t a l r e s u l t s w e r e t h e m o t i v a t i o no f t h e n e w t h e o r e t i c a l d e v e l o p m e n t b y J . L i n d h a r da n d A . H . S o e r e n s e n

Production of Exotic Nuclei at relativistic Energies

Production techniques

J. Benlliure

In-flight fragmentation

heavy projectile into a light target nucleus (projectile fragmentation) short separation+identification time (100 ns) limited power deposition Independent of Chemistry

thinner targets (10% of range) and lower beam currents (1012 ions/s) beam is a cocktail of different nuclear species

heavy projectile

thin target spectrometerhigh-energy nucleus

Identified by A and Z

In-flight Fragmentation (and Fission)

Ge

Relativistic energy fragmentation: => heavy ions (GSI unique!)

Fragment Recoil Separator

Such Separators exist at MSU, GANIL, RIKEN and GSI

Answer to our identification difficulty : - FRS

We will look at how it works later.

FAIR - Facility for Antiproton and Ion Research

100 m

UNILAC SIS 18

SIS 100/300

HESR SuperFRS

NESR

CRRESR

GSI todayGSI today FAIRFAIR

ESR

FLAIR

Rare-IsotopeProduction Target

AntiprotonProduction Target

Nustar three branches

“Facility for Antiproton and Ion Research (FAIR)” :

SIS 100/300

100 m

FAIRFAIRGSI todayGSI today

SIS 18UNILAC

ESR HESR SuperFRS

SuperFRS

RESR CR

NESR

Rare Isotope Prod.target

For example:DESPEC will have access to some key N=82 and N=126 r-process nuclei

Production techniques

J. Benlliure

Gamma/neutron converters(A variant of ISOL scheme)

Two-step reaction scheme(ISOL + Fragmentation)

e-, d

thick target

diffusion

ion source

post-acceleration

mass separatorhigh-energy nucleus

converter

, n

light projectile

fission

diffusion

ion source

post-acceleration

mass separator fragmentation spectrometer

Production techniques

J. Benlliure

In-flight fragmentation

heavy projectile into a light target nucleus (projectile fragmentation) short separation+identification time (100 ns) limited power deposition Independent of Chemistry

thinner targets (10% of range) and lower beam currents (1012 ions/s) beam is a cocktail of different nuclear species

low-energy nucleus high-energy nucleus

heavy projectile

thin target gas cell spectrometer

Current Schemes for producingbeams of radioactive nuclei

A)The classic ISOLDE scheme

B)The ISOL plus post-accelerator SPIRAL/REX-ISOLDE/LLN/ ISAC/HRIBF

C)Fragmentation -In Flight (GSI,MSU,GANIL,RIKEN)

D)The Hybrid-An IGISOL to replace the ISOL in B) -The basis of RIA

ISOL and In-Flight facilities-Partners

In-Flight ISOL

• Relativistic beams

• Universal in Z

• Down to very short T1/2

• Easily injected into storage rings

• Leads readily to colliding beam experiments

• High intensity beams with ion optics comparable to stable beams

• Easy to manipulate beam energies from keV to 10s of MeV

• High quality beams ideally suited to produce pencil-like beams and point sources for materials and other applied studies

It is probably true to say that if we worked at it virtually all experimentscould be done with both types of facility but they are complementary.

A.Richter, TH Darmstadt

What is the structure of nucleonic matter?

• Can we find a consistent theoretical framework that spans from few-body to many-body systems of nucleons?

• What are the Limits of nuclear existence?• What happens to the “Shell Structure” in highly dilute, neutron matter.• What new forms of nuclear matter will emerge in very loosely bound systems• Do the symmetries seen in near-stable nuclei

appear far from stability?• …..????

Goal: to determine nuclear properties over a wide range of N,Z,I,T, and find a consistent theoretical framework to describe the phenomena observed.

There are many unanswered questions:

Structure of the nucleon and other hadronsThe femtoscale frontier

Goal:- To understand the structure and properties of protons and neutrons and ultimately nuclei, in terms of the quarks and gluons of QCD

There are many unanswered questions:-

● What is the non-perturbative nature of QCD?

● What is the origin of the mass of the nucleon?

● What is the origin of the spin of the nucleon?

●Why do only two colourless configurations of quarks prevail?

●Do glueballs or quark-gluon hybrids exist?

●…………..?????

The role of nuclei in the Universe

Goal: to combine our knowledge of nuclear structure and theory with astronomical observations to model

astrophysical processes.

•The nuclear astrophysical origins of the chemical elements

• Can we identify the site(s) where the heavy elements are made?

•The manipulation of nuclear decay rates by controlling the nuclear medium

•Can we understand the mechanisms by which supernovae explode?

•Can we understand the dynamics of explosive stellar processes.

•Nuclear processes in the Early Universe

•……????

Many unanswered questions or badly understood processes:

Production techniques

J. Benlliure

In-flight fragmentation

heavy projectile into a light target nucleus (projectile fragmentation) short separation+identification time (100 ns) limited power deposition Independent of Chemistry

thinner targets (10% of range) and lower beam currents (1012 ions/s) beam is a cocktail of different nuclear species

high-energy nucleus

heavy projectile

thin target spectrometer

Ge

Detection setup

First half of spectrometer :-Momentum-to-charge selection plus beam rejectionSecond half we measure B, time-of-flight(T) and E in final detector.

Now we know B = mv/q, T = d/v, E = (q/v)2 -three unknowns (m,v and q)

From these measurements we identify A, Z and q for individual ions

In flight fragmentation (and fission) - Fragment Recoil Separator (GSI)

S. Pietri et al.,RISING data 107Ag beam

Cd

Ga

The Present Rare Isotope Facility at GSI

S IS F R S E S R

ALADIN

LAND

INJECTION FROM UNILAC

PROD UCTION TARG ET

12

3 FRS Branches

Low primary beam intensity (e.g. 108 238U /s) Low transmission for projectile fission fragments (4-10% at the FRS) Low transmission for fragments into the storage ring and to the

experimental areas Limited maximum magnetic rigidity (@ FRS: for U-like fragments, @ ESR:cooler performance and magnets, @ALADIN, to deflect

break-up fragments) Limited space in front of the production target Limited space at the experimental area 1 Limited space at the ESR injection area 2 Beam-line magnets, area 3, are not designed for fragment beams

Limitations

FR S

S uper-FR S D egrader

D egrader 1

D egrader 2

FRS (RISING) to Super-FRS(DESPEC)

H. Geissel et al. NIM B 204 (2003) 71

The Future of this kind of measurement

Note:-Super here means superconducting not------

Synchrotron

Synchrotron

Evacuated ring.

Dipole magnets with magnetic radius of curvature bend the particles round the ring.

Quadrupoles maintain focussing

Particles are accelerated in a number of RF cavities with circular frequency ω

Path = straight sections( in RF cavities, quadrupoles & some other sections) plus circular sections in dipoles. Hence R >

Synchrotron

No RF power -Initial E(i) and p(i)

T = 2R = 2RE(i) v p(i)c2

Corresponding circular frequency

Ω = 2 = p(i)c2 ---------- (A) T RE(i)

In addition magnetic field required is given by B = p(i)c q

RF turned on:- now ω = nΩ, where n is an integer. From (A) we see that the applied RF must increase with increasing energy up to the point where pc = E

Magnetic field must also increase:- ω = nΩ = nc pc nc; B =pc R E R q

SIS 18 at GSI

Synchrotron

Advantages:-

a) possible to accelerate electrons, protons, heavy ions etc b) Highest energies possible.

c) Basis of synchrotron radiation sources using electrons

Disadvantages:- a) Pulsed beam-takes 1 sec to accelerate particles in a large machine b) requires injection at high energy otherwise range of RF is too large In other words we need another accelerator to prepare the beam. At FAIR this will be the UNILAC.

The Super-FRS and its Branches

NuSTAR- [Nuclear Structure Astrophysics and Reactions] Collaboration

R3B

EXLELISE

ILIMA

Beam from SIS100/300