HISPEC: H i-resolution I n-beam SPEC troscopy at FAIR:

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

Exploring the Limits of Nuclear Existence

OverviewOverview

• 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!

Towards a predictive (and unified) description of nuclei

What is Nuclear Physics / Nuclear Structure for?What is Nuclear Physics / Nuclear Structure for?

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Experiment-led....Experiment-led....

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Need access to exotic nuclei – radioactive beams...Need access to exotic nuclei – radioactive beams...

Stable beam + Stable target:

• Fusion-Evaporation • Compound Nucleus near stability

Radioactive beams...two methodsRadioactive beams...two methods

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Radioactive beams...the FRAGMENTATION methodRadioactive beams...the FRAGMENTATION method

Gamma-ray Detector Array around target...

Primary target e.g.9Be or 12C

Secondary target(Reaction of Interest)

Primary (Stable) Beam>109 pps, ~ 10’s GeV

Exotic Fragment ~100 MeV/u

~ 104 pps

Fragment Identification

FRAGMENT SEPARATOR

FIDIPRO-EFES - Bentley 7

112Sn →Au

Relativistic Coulomb excitation / fragmentation

excited nucleus

Coulomb interaction

PrefragmentEquilibrated

nucleus

The secondary reaction...The secondary reaction...

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NSCL Experiment #5117, March 2007 – Bentley et al

0.5 -1.0 × 106 pps (70% 56Ni)

188 mg/cm2 Be

1011 pps 58Ni, 150 MeV/u

600 mg/cm2 Be target

S800 Spectrograph

Fragmentation Example: Proton Rich Fragmentation Example: Proton Rich 5353Ni...Ni...

Few 105 pps 56Ni, 75 MeV/u

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S800 – Fragment ID

Z

A/Z

Drip line

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

Fragmentation Example: Proton Rich Fragmentation Example: Proton Rich 5353Ni...Ni...

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A=53 T=3/2 analogue statesA=53 T=3/2 analogue states

53Mn – 3p removal

53Ni – 3n removal

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

N=ZZ

N

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A=49 T=3/2 analogue statesA=49 T=3/2 analogue states

49V – 5p,2n removal

49Fe – 2p,5n removal

?

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49V 49Fe

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

N=ZZ

N

A=49 T=3/2 analogue statesA=49 T=3/2 analogue states

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Project launched on November 7, 2007

FAIR: A European Fragmentation Facility FAIR: A European Fragmentation Facility

Super FRS – Provider of Exotic Beams...Super FRS – Provider of Exotic Beams...

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to rings

Low-Energy Branch

Super-FRS

Primary target

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AGATAAGATA(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

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

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Doppler shift Doppler broadening

Issues with relativistic beamsIssues with relativistic beams

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

Tracking Arrays based onPosition Sensitive Ge Detectors

Large Gamma Arrays based onCompton Suppressed Spectrometers

40 — 20 % ( M=1 — M=30)

10 — 5 % ( M=1 — M=30)

GAMMASPHEREEUROBALL GRETAAGATA

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

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Pulse Shape Analysisto decompose

recorded waves

Highly segmented

HPGe detectors

· ·

··

Identified interaction

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

Reconstruction of tracks

e.g. by evaluation of permutations

of interaction points

Digital electronicsto record and

process segment signals

1

2 3

4

reconstructed -rays

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

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AGATA

HISPEC

FAIR

Exotic Fragments at FAIRExotic Fragments at FAIR

Target

Fragment detectors

Flight path <4m

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

Lund-York-Cologne CAlorimeter (LYCCA)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.04/22/23 20Surrey Minischool - June 09 - Bentley

Particle ID:Z – from energy loss in DSSSD YES!!A – from total energy NO!!

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

52Fe : σ ~ 30 mb 53Fe : σ ~ 50 mb

47V : σ ~ 19 mb48V : σ ~ 20 mb49V : σ ~ 9 mb

Simulation

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A LYCCA module (LUND)

Si DSSSD (position and E)

CsI Total E

The LYCCA-0 Prototype

CVD diamond (York/Surrey) –

time of flight stop

Fast Plastic (Lund) time-of-flight stop

Target and CVD Diamond (ToF start)

LYCCA – Energy, Position and Time of FlightLYCCA – Energy, Position and Time of Flight

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AA σσ (mb) (mb)42 0.0550

43 0.7896

44 5.3086

45 15.926

46 19.819

47 9.906

48 2.7932

49 0.4612

LYCCA – prototype simulationLYCCA – prototype simulation

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2m

3m

Titanium fragments - simulations

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LYCCA@HISPECLYCCA@HISPECIdentify Fragments through ENERGY, ENERGY LOSS and TIME-OF-FLIGHT

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

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CVD Polycrystalline Diamond Project CVD Polycrystalline Diamond Project ((York, Surrey, GSI, Diamond Detectors LtdYork, 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

DETECTOR of CHOICE = DIAMOND!LYCCA@HISPECLYCCA@HISPEC

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Reaction Target

Time-of-flight “start”

Time-of-flight “stop”

UK will design and construct the “Diamond

Wall”

0.3m

0.4m

LYCCA@HISPECLYCCA@HISPEC

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• 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)

Science with HISPEC – some personal highlightsScience with HISPEC – some personal highlights

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

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Nuclear Shells – cornerstone of understanding?Nuclear Shells – cornerstone of understanding?

The Nuclear Landscape Feature 1: Shell Effects

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Systematics of Ground-state Deformation

Nuclear Shells – cornerstone of understanding?Nuclear Shells – cornerstone of understanding?

Mass model predictions of nuclear masses for the Cs isotopes

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

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No problems where we have known masses (stars) but the various theoretical prescriptions diverge as soon as we move to unknown masses.

Wood-Saxon+ spin-orbit

diffuse surface+ spin-orbitHow does the ordering of quantum states alter?Ho

w d

oes t

he o

rder

ing

of q

uant

um st

ates

alte

r?

‘normal’ ‘neutron rich’

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

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Standard magic numbers: 2, 8, 20

New magic number: 16 20

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

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100100Sn?Sn?

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• 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?

100100Sn?Sn?

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

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The Nuclear Landscape:Neutron-Proton Symmetry

Why Exotic Nuclei?Why Exotic Nuclei?

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8 8 8 8 8 8

1120910

20109

2011 FNeNa

0+

2+

4+

3-

MeV

2+

4+

3+

MeV MeV MeV

2+

4+

3+

2+

4+

3+

Neutron-Proton SymmetryNeutron-Proton Symmetry

JT,JT,JT,JJ c**zzz

Δ2E2E*ETED 011

N=ZZ

N

Mirror Energy Differences (MED)

J/T,J/T,JJ bzz

Δ*E*EMED 2121

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

(differences of excitation energies)

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Coulomb Energy DifferencesCoulomb Energy Differences

N=ZZ

N

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

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Why Exotic Nuclei? – ISOSPIN SymmetryWhy Exotic Nuclei? – ISOSPIN Symmetry

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Why Exotic Nuclei? – ISOSPIN SymmetryWhy Exotic Nuclei? – ISOSPIN SymmetryWhat are the symmetry-breaking effects?

Where in the nuclear landscape does the symmetry break down?

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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

Future research at HISPEC....Future research at HISPEC....

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A=53 T=3/2 analogue statesA=53 T=3/2 analogue states

53Mn – 3p removal

53Ni – 3n removal

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

N=ZZ

N

53Mn

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Charge-Symmetry Breaking?Charge-Symmetry Breaking?

53Ni

= full shell model calculation (with CSB) = shell model calculations without CSB J=2 effect

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

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

28 26 26 28

5454Ni : At the limits of proton binding....Ni : At the limits of proton binding....

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

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PRL 97 (2006) 152501

2%98%5(1)%95(1)%

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The Formalism of Isospin... (yuch)

What is expected? Tz -dependence of transition matrix element (hence decay probabilities) between isobaric analogue states?ASSUME: • Charge-symmetry and charge independence• No isospin mixingWigner-Eckart theorem extracts Tz-dependence (T=0)

Rule 1: E1s identical in mirror nucleiISOSPIN MIXING: • TT+1 and T+1T components can break the rule.....

ifz

zz TiHTfTTT

TiHfTTiHHTTf ;;

112;; 1010

E1

Rule 2: E2s: B(E2) Tz

ISOSPIN MIXING: • TT+1 and T+1T components can break the rule.....

Not tested – at least not systematically and accurately !

D

E’ E”to the ray detector

12C 500 m

93Nb 100 m

”=0.28’=0.342 To particleidentification

114Pd=0.354

E~70 MeV/u E’~60 MeV/u E”~44 MeV/u

• Incoming cocktail beam:

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

Differential Plunger Techniquee.g.114Pd with Coulomb excitation

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Lifetimes at relativistic energies....

target/ degrader diameter: 4 cmtarget/ degrader separation: 0 - 2,5 cm precision : ~ 1 μmtarget/ degrader thickness: ~1μm -1mm

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Differential Plunger....

114Pd:τ =118 (20) ps

110Pd:τ=67 (8) ps

A. Dewald et al. submitted to

PRC/Rapid

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Differential Plunger....

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Isospin Symmetry in T=1 triplets, A~70Isospin Symmetry in T=1 triplets, A~70

Analysis from B S Nara Singh et al, PRC 75 061301(R) 2007

N=ZZ

N

Difference in excitation energy EA* - EB

*

AB

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Neutron-proton pairing effects ?

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

Isospin Symmetry in T=1 triplets, A~70Isospin Symmetry in T=1 triplets, A~70

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Neutron-proton pairing effects ?

Shape-changing effects ?

Isospin Symmetry in T=1 triplets, A~70Isospin Symmetry in T=1 triplets, A~70

R. Sahu et al, JPG 13, 603 (1987)Def Shell model calcs →Stretch in β2 from 0.18 to 0.33CED ~ -75 keV

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

74Sr 74Se 74Kr

476

782

575

769

558

455

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Isospin Symmetry in T=1 triplets, A~70Isospin Symmetry in T=1 triplets, A~70Prediction: if “Shape effect” Prediction: if “Pairing effect”

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

NUclear STructure Astrophysics and ReactionsHISPEC (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 @ FAIRNuSTAR @ FAIR

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Hard work, and interesting times ahead