06/23/22 Surrey Minischool - June 09 - Bentley 1 HISPEC: H i-resolution I n-beam SPEC troscopy at FAIR: Exploring the Limits of Nuclear Existence Overview Overview • What is HISPEC? • Fragmentation Reactions and in- beam spectroscopy? • Experimental Method – what do we need? • HISPEC at FAIR and the UK • Some personal scientific
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04/21/23 Surrey Minischool - June 09 - Bentley 1
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?
04/21/23 2Surrey Minischool - June 09 - Bentley
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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
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...
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.
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.04/21/23 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
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?H
ow d
oes
the
orde
ring
of q
uant
um s
tate
s al
ter?
‘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+
MeVMeV 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.
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
= 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 !
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