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Overview. HISPEC: H i-resolution I n-beam SPEC troscopy at FAIR: Exploring the Limits of Nuclear Existence . What is HISPEC? Fragmentation Reactions and in-beam spectroscopy? Experimental Method – what do we need? HISPEC at FAIR and the UK

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Hispec h i resolution i n beam spec troscopy at fair

Overview

HISPEC: Hi-resolution In-beam SPECtroscopy at FAIR:

Exploring the Limits of Nuclear Existence

  • What is HISPEC?

  • Fragmentation Reactions and in-beam spectroscopy?

  • Experimental Method – what do we need?

  • HISPEC at FAIR and the UK

  • Some personal scientific highlights!

Surrey Minischool - June 09 - Bentley


Towards a predictive and unified description of nuclei

What is Nuclear Physics / Nuclear Structure for?

Towards a predictive (and unified) description of nuclei

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Experiment-led....

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Need access to exotic nuclei – radioactive beams...

  • Stable beam + Stable target:

  • Fusion-Evaporation

  • Compound Nucleus near stability

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Radioactive beams...two methods

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Radioactive beams...the FRAGMENTATION method

Secondary target

(Reaction of Interest)

Primary target

e.g.9Be or 12C

Exotic Fragment

~100 MeV/u

Primary (Stable) Beam

~ 104 pps

>109pps, ~ 10’s GeV

Gamma-ray Detector Array around target...

FRAGMENT SEPARATOR

Fragment Identification

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

The secondary reaction...

Prefragment

Equilibrated

nucleus

Relativistic Coulomb excitation / fragmentation

112Sn →Au

Coulomb

interaction

excited

nucleus

FIDIPRO-EFES - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Fragmentation Example: Proton Rich 53Ni...

1011 pps 58Ni, 150 MeV/u

600 mg/cm2 Be target

0.5 -1.0 × 106 pps (70% 56Ni)

188 mg/cm2 Be

S800 Spectrograph

Few 105 pps 56Ni,

75 MeV/u

NSCL Experiment #5117,

March 2007 – Bentley et al

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Fragmentation Example: Proton Rich 53Ni...

J.R. Brown et al. (YORK) in prep (2008)

S800 – Fragment ID

Drip line

Z

A/Z

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

A=53 T=3/2 analogue states

Z

N=Z

53Mn – 3p removal

N

53Ni – 3n removal

First gamma-rays from N=Z-3 system above 33Ar.

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

A=49 T=3/2 analogue states

49V – 5p,2n removal

49Fe – 2p,5n removal

?

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

A=49 T=3/2 analogue states

49V

49Fe

Z

N=Z

N

Examine breakdown of isospin (proton-neutron) symmetry – see later

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

FAIR: A European Fragmentation Facility

Project launched on November 7, 2007

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Super FRS – Provider of Exotic Beams...

Low-Energy Branch

Super-FRS

Primary target

to rings

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

AGATA – The world’s best gamma-ray detector...

AGATA(Design and characteristics) 4-array for Nuclear Physics Experiments at European accelerators providing radioactive and high-intensity stable beams

  • 180 large volume 36-fold segmented Ge crystals in 60 triple-clusters

  • Digital electronics and sophisticated Pulse Shape Analysis algorithms allow

  • Operation of Ge detectors in position sensitive mode  -ray tracking

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Issues with relativistic beams

Doppler effects at v/c ~ 50% - TOUGH SPECTROSCOPY

Doppler shift

Doppler broadening

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

AGATA – Tracking of Gamma-rays – a NEW technology...

Large Gamma Arrays based on

Compton Suppressed Spectrometers

Tracking Arrays based on

Position Sensitive Ge Detectors

EUROBALL

GAMMASPHERE

AGATA

GRETA

e~ 10 — 5 %

( Mg=1 —Mg=30)

e~ 40 — 20 %

( Mg=1 —Mg=30)

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

AGATA – Tracking of Gamma-rays – a NEW technology...

4

1

Reconstruction of tracks

e.g. by evaluation ofpermutations

of interaction points

Identified

interaction points

Highly segmented

HPGe detectors

(x,y,z,E,t)i

g

·

·

Pulse Shape Analysisto decomposerecorded waves

·

·

2

3

Digital electronics

to record and process segment signals

reconstructed

g-rays

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Exotic Fragments at FAIR

The Lund-York-Cologne Calorimeter (LYCCA) – Identification of the Exotic Fragments

FAIR

Target

AGATA

Flight path <4m

HISPEC

Fragment detectors

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Lund-York-Cologne CAlorimeter (LYCCA)

1. Target (Be, Au..), position (DSSD) and time start (CVD diamond)

2. Light CP array (position, energy loss, energy) – prompt p, alpha decay

3. Main array (~26 LYCCA modules) – ~3.5-4.0 m downstream from target

4. Possible configuration of LYCCA modules at the focal plane of a spectrometer – add A/Q to measurement of position, ToF, energy loss, E etc.

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Isotope ID from Energy (Loss) – (RISING DATA 2003, GSI)

Particle ID:

Z – from energy loss in DSSSDYES!!

A – from total energy NO!!

Simulation

47V : σ ~ 19 mb48V : σ ~ 20 mb

49V : σ ~ 9 mb

52Fe : σ ~ 30 mb

53Fe : σ ~ 50 mb

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

LYCCA – Energy, Position and Time of Flight

A LYCCA module (LUND)

CsI Total E

Si DSSSD (position and E)

Fast Plastic (Lund) time-of-flight stop

CVD diamond (York/Surrey) – time of flight stop

The LYCCA-0 Prototype

Target and CVD Diamond (ToF start)

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

LYCCA – prototype simulation

2m

3m

Titanium fragments - simulations

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

[email protected]

Identify Fragments through ENERGY, ENERGY LOSS and TIME-OF-FLIGHT

Key UK Role: High timing resolution TIME-OF-FLIGHT array

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

[email protected]

DETECTOR of CHOICE = DIAMOND!

CVD Polycrystalline Diamond Project

(York, Surrey, GSI, Diamond Detectors Ltd)

  • Diamond Pros:

  • Good timing resolution measured with Rel. H.I I. ~ 50-60 ps FWHM

  • Radiation Hard (106 pps easy)

  • Diamond Cons:

  • NO company makes fabricated diamond detectors

  • Such large-areas not been tested

  • VERY expensive

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

[email protected]

0.3m

Time-of-flight “stop”

0.4m

Reaction Target

UK will design and construct the “Diamond Wall”

Time-of-flight “start”

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Science with HISPEC – some personal highlights

How does our understanding of fundamental nuclear properties evolve as we move towards the extremes of nuclear existence?

  • Ordering of quantum levels: shell effects far from stability (spectroscopy of neutron rich nuclear matter)

  • 100Sn: One of the holy grails (spectroscopy at N=Z)

  • Isospin (n-p) symmetry and its breakdown: beyond the Coulomb force (spectroscopy of proton rich nuclear matter)

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Nuclear Shells – cornerstone of understanding?

The Nuclear Landscape Feature 1:

Shell Effects

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Nuclear Shells – cornerstone of understanding?

Systematics of Ground-state Deformation

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

How good are Nuclear Models – how well are we doing?

Mass model predictions of nuclear masses for the Cs isotopes

No problems where we have known masses (stars) but the various

theoretical prescriptions diverge as soon as we move to unknown masses.

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Why Exotic Nuclei – Magic Numbers in Danger....?

‘neutron rich’

‘normal’

Wood-Saxon

+ spin-orbit

diffuse surface

+ spin-orbit

Nuclear potential

How does the ordering of quantum states alter?

How does the ordering of quantum states alter?

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Why Exotic Nuclei – Magic Numbers in Danger....?

Standard magic numbers:

2, 8, 20

New magic number:

16 20

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

100Sn?

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

100Sn?

  • Very close to drip line

  • Heaviest N=Z doubly magic nucleus – n-p degree of freedom?

  • Sn is Longest chain of semi- magic nuclei known

  • Evolution depends on single-particle and collective effects

  • Unique correlations possible between n & p spin-orbit partners

  • Core polarisation effects of neutrons and protons?

HISPEC: B(E2) of 0+→2+100Sn can be done

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Why Exotic Nuclei?

The Nuclear Landscape:

Neutron-Proton Symmetry

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Neutron-Proton Symmetry

MeV

MeV

MeV

4+

8

8

8

8

8

8

3+

2+

3-

4+

MeV

2+

0+

4+

4+

3+

3+

2+

2+

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Coulomb Energy Differences

(differences of excitation energies)

Z

Mirror Energy Differences (MED)

N=Z

N

Tests the charge symmetry of the interaction

Triplet Energy Differences (TED)

Tests the charge independence of the interaction

MED and TED are of the order of 10’s of keV

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Why Exotic Nuclei? – ISOSPIN Symmetry

Z

N=Z

N

Warner, Bentley, Van Isacker, NATURE Phys 2 (2006) 311.

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Why Exotic Nuclei? – ISOSPIN Symmetry

What are the symmetry-breaking effects?

Where in the nuclear landscape does the symmetry break down?

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Future research at HISPEC....

Spectroscopy at or beyond the proton dripline....

  • What effects break the proton-neutron symmetry?

  • Spectroscopy of proton-unbound structures

  • Pairing between protons and neutrons

  • Testing predictions of isospin formalism

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

A=53 T=3/2 analogue states

Z

N=Z

53Mn – 3p removal

N

53Ni – 3n removal

First gamma-rays from Tz= -3/2 system above 33Ar.

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Charge-Symmetry Breaking?

Question: Origin of this effect – where else does it appear?

53Mn

= full shell model calculation (with CSB)

= shell model calculations without CSB J=2 effect

53Ni

J.Brown et al, submitted to PRC (R) 2009

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

54Ni : At the limits of proton binding....

98%

2%

95(1)%

5(1)%

28262628

D.Rudolph et al, Phys. Rev. C78 (Rap. Comm.) 2008 021301

PRL 97 (2006) 152501

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

The Formalism of Isospin... (yuch)

E1

  • What is expected? Tz -dependence of transition matrix element (hence decay probabilities) between isobaric analogue states?

  • ASSUME:

  • Charge-symmetry and charge independence

  • No isospin mixing

  • Wigner-Eckart theorem extracts Tz-dependence (DT=0)

  • Rule 1: E1s identical in mirror nuclei

  • ISOSPIN MIXING:

  • TT+1 and T+1T components can break the rule.....

  • Rule 2: E2s: B(E2)  Tz

  • ISOSPIN MIXING:

  • TT+1 and T+1T components can break the rule.....

Not tested – at least not systematically and accurately !

Surrey Minischool - June 09 - Bentley


Differential plunger technique e g 114 pd with coulomb excitation

Lifetimes at relativistic energies....

E~70 MeV/u

E’~60 MeV/u

E”~44 MeV/u

12C 500 mm

D

114Pd

To particle

identification

b=0.354

b”=0.28

b’=0.342

Eg”

Eg’

93Nb 100 mm

to the g-ray detector

Differential Plunger Techniquee.g.114Pd with Coulomb excitation

  • Incoming cocktail beam:

    …..116Ag , 15% 114Pd ( ~ 1500pps), 112Rh……

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Differential Plunger....

target/ degrader diameter: 4 cm

target/ degrader separation: 0 - 2,5 cm

precision : ~ 1 μm

target/ degrader thickness: ~1μm -1mm

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Differential Plunger....

114Pd:

τ =118 (20) ps

110Pd:

τ=67 (8) ps

  • Dewald et al.

  • submitted to PRC/Rapid

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Isospin Symmetry in T=1 triplets, A~70

Z

N=Z

Difference in excitation energy EA* - EB*

A

B

Analysis from B S Nara Singh et al,

PRC 75 061301(R) 2007

N

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Isospin Symmetry in T=1 triplets, A~70

Neutron-proton pairing effects ?

Odd-odd nucleus dominated by T=1 np-pairs, hence fewer T=1 pp pairs... (see LenziPRC 60 (2001)021303)

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Isospin Symmetry in T=1 triplets, A~70

Neutron-proton pairing effects ?

If β2 changes from -0.3 to 0.35, CED ~ -7keV

Shape-changing effects ?

R. Sahu et al, JPG 13, 603 (1987)

Def Shell model calcs →

Stretch in β2 from 0.18 to 0.33

CED ~ -75 keV

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

Isospin Symmetry in T=1 triplets, A~70

Prediction: if “Pairing effect”

Prediction: if “Shape effect”

782

769

558

575

476

455

Question: what is the effect of shape-driving effects on isospin symmetry – different ground states?

74Sr 74Se 74Kr

Surrey Minischool - June 09 - Bentley


Hispec h i resolution i n beam spec troscopy at fair

HISPEC (but not alone!!) helps address all these questions:

What are the limits for existence of nuclei?

How does the nuclear force depend on varying proton-to-neutron ratios?

How to explain collective phenomena from individual motion?

How are complex nuclei built from their basic constituents?

Which are the nuclei relevant for astrophysical processes

and what are their properties?

NuSTAR @ FAIR

NUclear STructure Astrophysics and Reactions

Hard work, and interesting times ahead

Surrey Minischool - June 09 - Bentley


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