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22 May 2007 Cosener's House 1
Alex MurphyAlex Murphy
Nuclear astrophysics http://www.ph.ed.ac.uk/nuclear/Dark Matter http://hepwww.rl.ac.uk/ukdmc/ukdmc.html/
The Future of Nuclear Astrophysics in the
UK
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Outline
Who we are
What we do
The Future: Three examples
Other projects/programmes
Summary
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Who we are…
In virtually every nuclear physics proposal, at some point there are the words ‘…is of Astrophysical relevance…’
Significant contributions from many nuclear physicists
It is highly multidisciplinary and interdisciplinary
Specialist groups in the UK are: Edinburgh & York~6 Academic Staff, +RA.s, +Students
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What we do…
Aims of Nuclear Astrophysics An understanding of the origin & evolution of the elements An understanding of the mechanisms driving astrophysical
phenomena
Timeliness Remarkable observations from new telescopes. New experimental facilities and techniques
Our role is to provide the key nuclear inputs that are needed
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abun
danc
e
Mass number
Fe
“The 11 Greatest Unanswered Questions of Physics”National Academy of Science Report, Committee for the Physics of the Universe, 2002
“How were the elements from iron to uranium made?”
These are important questions!
Abundance curve of the elements
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Our Science Objectives:
How were the elements from iron to uranium made?
What leads to the abundances observed in novae?
What governs other explosive phenomena?
What is the role of nuclear physics in stellar evolution?
Crab Nebula SN 1054
Artist’sconception
Chandra observation
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World Context:
Europe: FAIR, REX-ISOLDE upgrade, SPIRAL-II, Eurisol US: Facility for Rare Isotope Beams Canada: ISAC-II Japan: BigRIPS China: HIRFL (Lanzhou) …
The desire to understand astrophysical phenomena is a major motivation for significant investment in new facilities around the world.
The UK has a strong track record and is well placed to play a major role in these activities
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The Future: Three examples…
AIDA
TACTIC
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Advanced Implantation Detector Array (AIDA)
Scientific Motivation:
The r-process
Collaboration:
The University of Edinburgh (lead)
The University of Liverpool
CCLRC DL & RAL
Project Manager:
Tom Davinson
Further information: http://www.ph.ed.ac.uk/~td/AIDA Technical Specification:
http://www.ph.ed.ac.uk/~td/AIDA/Design/AIDA_Draft_Technical_Specification_v1.pdf
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AIDA: Science Case
[Fe/H] < -3.0 ‘Unique’ r-process What is its site? How does it operate?
Recent Observations of Metal Poor Stars
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132Cd 48 82
R – abundances Details of nuclear properties
R-process studies
Z
N 211s
211p
231p
231d
251d
212s
211s
211p
231p
231d
251d
212s
neutrons protons
Key sources of uncertainty are the properties of highly neutron rich nuclei
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GSI todayGSI today Future facilityFuture facility
FAIR
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AIDA Concept
R-process nuclei implanted into multi-plane, highly segmented DSSD array Observe subsequent decays: p, 2p, p, n … Measure half lives, branching ratios, decay energies … Tag interesting events for coincident gamma and neutron detector arrays Long half-lives, requiring high segmentation 4096 channels & Application Specific Integrated Circuits
Significant advance on present technology
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Scientific Motivation:
Direct measurements of low energy nuclear astrophysical reactions using radioactive beams
Collaboration:
The University of York (lead)
TRIUMF, Canada
(ACTAR-EURONS)
Project leader:
Alison Laird
Further information: http://tactic.triumf.ca/
TRIUMF Annular Chamber for Tracking and Identification of Charged particles (TACTIC)
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Why TACTIC?
Allows exploration of previously impossible-to-access reactions
Gas targets Low energies Tracking Particle ID Direct measurements Large solid angle / High efficiency Radiation Hard Can be complemented with -ray array Optimised for 8Li(,n) : But much much more too!
Opens up many new scientific possibilities Radical, adventurous project for UK nuclear physics
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Schematic design of TACTIC detector
--
--
----
GEM readout Design: Completed
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Construction:
Almost complete
In-beam testing:
Aug 2007
TACTIC: Status
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Experimental Low Energy Nuclear Astrophysics (ELENA)
Scientific Motivation:
Direct measurements nuclear astrophysical reactions at the Gamow energy
Proposer:
The University of Edinburgh
Marialuisa Aliotta
Technical Specification:
Contact: Marialuisa Aliotta
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ELENA
Motivation Cosmic ray induced backgrounds hamper rare event
searches Key astrophysical important reactions would be much
better studied in a cosmic ray free environment There exists an underground science laboratory in
the UK at Boulby
Proposal An underground low energy accelerator for nuclear
astrophysics
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a working potash and salt mine Cleveland - North East England the deepest mine in Britain (850m to 1.3km deep)
Plymouth
London
Birmingham
Liverpool
Newcastle
Edinburgh
Inverness
Belfast
Dublin
Redcar
Hartlepool
Peterlee
Middlesbrough
Billingham
Newton Aycliffe
Stockton
Darlington
Middlesborough
Whitby
Staithes
York
Sylvanite
courtesy: S. Paling
Boulby Mine
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Map of excavations
Mine Shafts
Dark Matter Research Areas
Underground science established
1km
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Requirements for an underground lab...
Low Backgrounds• Deep (to shield from cosmic rays)• Low background rock/lab (and/or adequate shielding)
Plenty of Laboratory space
Easy access for equipment
Good infrastructure + facilities
2805 mwe attenuates CR by ~106Salt is low in Uranium & Thorium
Virtually unlimited potential for expansion
Via mine shaft (4m lengths)+ Transport underground
JIF laboratory, CPL Support
Why is Boulby Special?
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1400 1600 1800 2000 2200 2400 2600 2800 3000
1E-3
0.01
0.1
1
10
100
1000
coun
ts /h
/keV
E [keV]
Gran Sasso shielded Gran Sasso unshielded Bochum det. shiel. surface Bochum det. unshiel. surface Boulby unshielded
Advantage of salt mine: extremely low background at E < 2-3 MeV
Why is Boulby Special?
Gran Sasso
Boulby
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What will be involved?
3 MV single-ended machine (e.g. NEC, Pelletron) ECR source (e.g. for high intensity (~500 A) 12C beam at high charge states) Beam-lines + detection systems (gamma, neutron, charged particles)
Ion (charge state) Particles per second
H+ 5.0x1014
He+ 5.0x1013
He2+ 1.0x1013
Xe17+ 2.9x1012
Kr15+ 4.1x1011
Ar11+ 5.6x1011
Ne6+ 1.0x1012
Fe11+ 5.7x1011 (estimated)
Ni11+ 5.7x1011 (estimated)
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Is there a role for ELENA?
Only other comparison is LUNA at the Gran Sasso …a 400 kV machine Limited to acceleration of H and He beams Only direct kinematics studies are possible
beam-induced background on target impurities a problem Reactions producing neutrons are not allowed Space limited
Key studies: Carbon burning in advanced stages of stellar evolution Neutron sources for s-process Ne, Na, Mg and Al nucleosynthesis in AGB stars
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ELENA
Statement of Interest has been submitted to STFC
Background level ~ factor 10-30 lower than at GS
No space constraints (no interference with other experiments)
Existing support and safety facilities
Opportunities for involvement at various level
Workshop planned in Edinburgh
July 2007
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Not enough time to mention…
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TIGRESS-SHARC
York contribution to TIGRESS Light ion transfer reactions E.g. 59,60Fe(d,p) to determine supernova (n,) rates New silicon barrel and Bragg detector
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ERAWAST
See next month’s Nuclear Physics News.
Aim is to make use of long lived radionuclides that have built up from irradiation of the PSI beam dumps
E.g. 44Ti (t½ = 60 yr) 44Ti(,p), relevant to 44Ti abundance
in SNe Rate is needed to allow comparison
of -ray observation of 44Ti with core collapse models
Unique diagnostic of the collapse mechanism
Exotic Radionuclides from Accelerator Waste for Science and Technology
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Ongoing programmes of research
Louvain-la-Neuve
Pioneering radioactive nuclear beams. LEDA – Pioneering large segmented Si Measuring nuclear properties relevant to
novae & XRBs
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Ongoing programmes of research
TRIUMF
TUDA
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Other ongoing/planned activities
Plus, unique needs of certain experiments require activity at other locations, e.g.
ANL REX-ISOLDE GANIL Orsay ORNL ANU …
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Summary
ExcitingScience
New Ideas
New Scientific Opportunities
Use of Many Experimental Techniques
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Extra slides
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25,26Al(p,)26,27Si reactions influence predicted flux of the cosmic γ-ray
emitter 26Al
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12C
13N 14N
15O14O
15N
13C
16O 17O 18O
unstable
stable
HCNO
23Mg21Mg 22Mg
25Al24Al
24Mg 25Mg
26Al
26Mg
27Al
27Si 28Si
rp-processonset
17F 18F
18Ne 20Ne19Ne
21Na 22Na20Na
19F
21Ne 22Ne
23Na
HCNO breakout
NeNacycle
(,)(p,)
(+)(p,)
(,p)
some key reactions:
14O(,p)17F
18Ne(,p)21Na
21Na(p,)22Mg
15O(,)19Ne
19Ne(p,)20Na
20Na(p,)21Mg
18F(p,)15O
26Al(p,)27Si
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3 4 5 6 7 8
9 10
11 12 13
14
C (6) N (7)
O (8) F (9)
Ne (10)Na (11)
M g (12)
T1/2=1.7s
3 flow
T~3*108 K
gm.cm-2
Hot CNO Cycle
Key unknown reaction rates are dominated by resonance reactions
17F(p,Ne, 14O(p)17F, 18F(p,
Experiments require intense radioactive beams ~1 MeV/u
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breakout
processing beyond CNO cycle
after breakout via:
T8 ≥ 3 15O(,)19Ne
18Ne(,p)21NaT8 ≥ 6
3 4 5 6 7 8
9 10
11 12 13
14
C (6) N (7)
O (8) F (9)
Ne (10)Na (11)
M g (12)
3 flow
For X-ray bursters a similar scenario prevails although in this case material accretes onto the surface of a neutron star rather than a white dwarf
Consequently higher T and can result in breakout from the hot CNO cycles
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12C+12Cimportance: evolution of massive starsGamow region: 1 – 3 MeV min. measured E: 2.1 MeV (by -ray spectroscopy)
passive lead & concrete shielding
Major improvements expected for measurements underground!
Crab Nebula SN 1054
Aguilera et al. PRC 73 (2006) 64601
Spillane et al PRL 98 (2007) 122501
channel
p channel
12C(12C,)20Ne and 12C(12C,p)23Na channels
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13C(,n)16O
Contributions from sub-threshold states?
Mainly hampered by cosmic background good case for underground investigation
importance: s-process in AGB starsGamow region: 130 - 250 keV min. measured E: 270 keV
M. Heil, PhD Thesis - Karlsruhe, 2002
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Similar considerations apply also to 22Ne(,)25Mg reaction
Jaeger PRL 87 (2001) 202501
22Ne(,n)25Mgimportance: s-process in AGB starsGamow region: 400 - 700 keV min. measured E: ~550 keV
mainly hampered by cosmic background good case for underground investigation
reaction rate still uncertain by orders of magnitude
uncertain nucleosynthesis predictions
Karakas et al ApJ 643 (2006) 471
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Abundances of Ne, Na, Mg, Al, … in AGB stars and nova ejectaaffected by many (p,) and (p,) reactions
Iliadis et al. ApJ S134 (2001) 151; S142 (2002) 105; Izzard et al A&A (2007) submitted
!! new measurements underground are very much needed !!
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M.S. Smith and K.E. Rehm,Ann. Rev. Nucl. Part. Sci, 51 (2001) 91-130
The vast majority of reactions encountered in these processes involve UNSTABLE species
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