7th international summer school on particle accelerators and detectors, bodrum, 21-26 august 2011 1...

7TH INTERNATIONAL SUMMER SCHOOL ON PARTICLE ACCELERATORS AND DETECTORS, BODRUM, 21-26 AUGUST 20111

Nuclear Astrophysics Nuclear Astrophysics Applications of AcceleratorsApplications of Accelerators

Alex Murphy([email protected])

These slides are online athttps://files.me.com/alexsmurphy/3enros

mailto:[email protected]

https://files.me.com/alexsmurphy/3enros


Additional material!Additional material!

✦ I have written 6 questions, based on the material in this talk.

✦ One is to be used in your EXAM!

✦ ...There are also solutions (“Phew!”)

✦ I hope these questions allow you to think about the material further

✦ Questions (and solutions) will be made available by the organisers

These slides are online athttps://files.me.com/alexsmurphy/3enros


Motivation


Stellarium: tonight 10pm.Stellarium: tonight 10pm.


What What areare the stars? the stars?

✦ Hertzsprung Russell diagram

✦ Clearly shows that there are several distinct categories of star

✦ What more can we know of them?

✦ What is the “physics”?✦ Start with their source of

power...


A simple calculation...A simple calculation...

Our Sun.✦We receive ~1.38 kW/m2 at the Earth’s surface✦Distance to the Sun: 1.5x1011 m✦ ➔ total luminosity = 3.9x1026 W✦Mass of Sun = 2x1030 kg✦Coal outputs ~35 kJ/kg+

✦ ➔ If the Sun is chemically burning, then it’s <5.5 years old. ✘

✦p-p chain: 0.7% mass converted to energy✦~1011 years supply* ✔ *but not all the sun burns

+ is this typical?


What is the Universe is made of...?

7

Atomic FractionAtomic Fraction Mass FractionMass FractionAtomic FractionAtomic Fraction Mass FractionMass Fraction

Look at the Sun, the stars, distant Galaxies...

>99% of matter is Hydrogen or Helium


Chemical evolutionChemical evolution

✦ However, variations in A>4 chemical abundances are seen in various types of stellar object

✦ There appears to be a universal ‘primordial’ abundance ✦ Older stars - less O, Fe✦ Novae - enhancements in C, N, O, Ne...✦ Supernovae - ‘scaled’ solar abundance (esp. for high

masses)✦ Meteorites - certain abundance ratios show strong

deviations from solar/terrestrial material✦ Gamma rays indicate recent nucleosynthesis

✦ 26Al (halflife 7.4x105 yrs) seen in interstellar medium✦ 44Ti (halflife 59 yrs) seen in supernova remnant

Stars are the furnaces of chemical elements


A few examples...A few examples...

Scaled solar abundances match r-process; indicates ‘primary process’

1 4N

/1 5N

12C/13CX - SNe origin

Y,Z, Mainstream - AGB starsA+B grains - Source unknown


NovaeNovae


Abundances linked to Nuclear PhysicsAbundances linked to Nuclear Physics

✦ Odd-even stagger✦ Peaks correspond

to magic numbers

✦ Suggests nuclear physics as key to understanding abundances of the elements


Astrophysical processesAstrophysical processes✦ Broad mechanisms now understood✦ Various processes occur in the different

stellar sites depending on the the particular environment (F (T, P, Z, τ, Rot, B...))

✦ BBN ✦ p-p chains ✦ CNO cycles✦ rp-process✦ α-process ✦ r-process✦ s-process✦ p-processes✦ NSE...

Alpher-Bethe-Gamow, Phys. Rev. 73 (1948) 803

All still actively researched!


Stellar energies


Thermonuclear Reaction EnergiesThermonuclear Reaction Energies

✦ Typical environment temperatures:✦ Our Sun: ~15x106 K kT ~ 1 keV✦ Novae: ~4x108 K kT ~ 35 keV✦ BBN, Supernovae: ~1010 K kT ~ 2 MeV

✦ The rate of nuclear reactions is determined by the cross section and the energies of the particles in the reaction

✦ Cross sections increase with energy (penetration through Coulomb barrier)✦ Temperatures described by Maxwell Boltzmann

Energies are relatively LOW

[cm3 mole-1 s-1]


Reaction ratesReaction rates

Gamow peak and window

✦Indicates the energy region where nuclear physics is likely to be important✦Typically ~ a few × kT✦Cross sections for quiescent burning scenarios pb≲✦Cross sections for explosive scenarios ≳ μ

Most nuclear astrophysics (to date) explores explosive scenarios

Shorter timescales, by definition, means radioactive nuclei become important

Low energy radioactive ion beams often desirable

←Difficult!←Very difficult!


Example: BBN


Big bang nucleosynthesisBig bang nucleosynthesis


An example of a BBN experiment...An example of a BBN experiment...

✦ Explore a reaction that might impact results...✦ Production of 6Li (to compare to some recent observations)

✦ Sputter source generates 7Li beam: VdG ~ 20 MeV✦ 8Li beam produced with 9Be(7Li,8Li)8Be: ~10-15 MeV; ~105 pps✦ 2 mg/cm2 CD2 experimental target foil ✦ 4He and 6He ions detected in silicon arrays.


Example: Novae


NovaeNovae

• Classical Novae

• accretion of H on CO or ONe WD

• Temp’ and densityincrease; ‘flash’

• Our understanding to date is based on…

• Light curves

• Spectra

• Meteoritic data

• Problems…

• Limited information in light curves

• Spectra give chemical abundances

• Spectra give ~final abundances

• Meteoritic data also is ‘delayed’ & complex

• A better probe would be gamma-rays

Artist’sconception

Chandra observation


Gamma ray probes of NovaeGamma ray probes of Novae

Overall novae gamma-ray emission is dominated by 511 keV γ-rays from 18F +

decay

Need to know rates of reactions creating and destroying 18F

Large Uncertainties remain, especially in 18F(p,α)15O

Rate is determined by resonant contributions from states in 19Ne

M Hernanz, JINA 2005


ISOL TechniqueISOL Technique

TRIUMF

✦ 500 MeV proton driver✦ SiC, Ta, UCx targets✦ Re-acceleration in RF

cavities, DTL, SC LINAC...✦ ISAC-I: 0.25-1.6 MeV/A

A~<40✦ ISAC-II: 1.5-6.5 MeV/A

Any A✦ TUDA ✦ DRAGON✦ TIGRESS✦ SHARC✦ (EMMA)✦ Others

18F has halflife of 110 minutes : RIB necessary


1818F(p,F(p,α))1515O at TUDAO at TUDA

18F9+ beam 1.6 MeV/A 105 pps 2mm beamspot, ~1ns wide bunches


Typical dataTypical data

Energy

Lin

eari

sed

Tim

e of

Fli

ght

1H(18F,1H)

1H(18F,α)

12C(18F,12C)

12C(18F,12C)

Fusion-Evaporation protons

18F()

α contamination in the chamber


DataData

ASM et al. PRC 79 (2009)

✦ R-matrix analysis

✦ Deduce E,ΓΓαl, (interference)


Recent direct dataRecent direct data

A direct thin target measurement of the 18F(p,α) reaction at 250, 330, 453 & 673 keV

PRC 82 (2011) 042801R


Effect of Coulomb barrierEffect of Coulomb barrierClare Beer, Thesis, 2010

~1 hour at Ecm=673 keV

~3 hours at Ecm=453 keV

~1 day at Ecm=330 keV

~1 week at Ecm=250 keV

Rate at low energies (Gamow window) is very lowBackgrounds become critical!


Context of 1 reaction rate!Context of 1 reaction rate!

Slide: Anuj Parikh


Example (proposed): Supernova


Text


QuickTime™ and aGIF decompressor

are needed to see this picture.


The CCSN Neutrino MechanismThe CCSN Neutrino Mechanism

Massive star (>8–10 M) Stellar evolution onion-skin-like structure At maximum of BE/A, thermal support lost Collapse Huge flux of neutrinos “re-energises” explosion Neutrino driven wind – an excellent candidate site for the r-process

The main source of 44Ti is thought to be from deep

within CC supernova


Astrophysical Gamma Ray EmittersAstrophysical Gamma Ray Emitters

Nucleus lifetime Emission Source13B 862 s 511 keV CO Novae

ONe Novae

18F 158 m 511 keV CO Novae

ONe Novae

7Be 77 d 478 keV CO Novae

22Na 3.75 yr 1275 keV ONe Novae

26Al 1.0 Myr 1809 keV WR, CC SNe?

44Ti 87 yr 1157 keV CC SNe

60Fe 2.2 Myr 1173,1333 keV CC SNe


4444Ti production as a diagnosticTi production as a diagnostic

Amount ejected sensitively depends on location of the ‘mass cut’

Material that ‘falls back’ is not available for detection

44Ti yield a sensitive diagnostic of the explosion mechanism

Thus, very useful for models to make comparisons against

Timmes et al. (1996)

Wilson. (1985)

44Ti(α,p) is the key reaction


The ERAWAST ProjectThe ERAWAST Project

Would like to measure 44Ti(α,p) reaction directly. 44Ti target difficult (half-life ~59 yr) 44Ti RIB difficult What about feeding 44Ti into a ‘stable’ ion source? Obtain 44Ti from activated material, e.g. copper beam dump

Many other uses for this technology


ERAWAST workshopERAWAST workshop


The S and R processesThe S and R processes

✦ Consider isotopes sitting in a neutron ‘bath’.WEAK

The S(low) Process

STRONG

The R(apid) ProcessZ

N

Stable

Long lived

Short lived

Very short lived

(n,γ)

beta decay


Example: The R-process


The r-processThe r-process

✦ Produces the heavy elements✦ Rapid neutron capture

✦ Rapid compared to beta-decay ( τn<<ττn~μs)✦ Requires very high flux of neutrons (Φn~1024-1030/cm3)✦ Candidate sites: Supernovae or Neutron star mergers

Observable Effect

Sn Path

T1/2 Abundance pattern, timescale

Pn Freezeout abundance pattern

‘Cause and Effect’


GSI... and FAIRGSI... and FAIR

The biggest development ever in European Nuclear Physics?

Nuclear astrophysics was a lead driver of the science case!


Predicted SuperFRS yieldsPredicted SuperFRS yields


Major new instrumentation neededMajor new instrumentation needed

✦ Aim to look at beta-delayed decays shortly after implantation

✦ High rate; huge energy mis-match; demanding resolution

8cm x 8cm wafers; 0.5 mm position resolutionNovel spectroscopic ASIC readout


AIDA prototypingAIDA prototyping


Finally... something a bit different...


‘‘Another’ nuclear astrophysicsAnother’ nuclear astrophysics

✦ Which was the first accelerator...?

✦ Which accelerator has the highest energies...?

✦ Which accelerator has the most intense flux...?

✦ Nature!

✦ Access to new physics✦ Access to new, more exotic

astrophysical environments


Some particle astrophysics Some particle astrophysics expts...expts...

Pierre Auger, 3000 km2


SUMMARYSUMMARY

✦ When you next look at the stars... I hope you spend a moment thinking about what they are!

✦ The study of nuclear astrophysics covers a diverse range of phenomena

✦ Nuclear astrophysics experiments use many different accelerator technologies, ranging from the small ‘in-house’ Van de Graaff to the major new facilities such as FAIR

✦ No one technology will provide all the answers✦ Only the tip of the ice berg has been covered here!

Thank you

7th international summer school on particle accelerators and detectors, bodrum, 21-26 august 2011 1...

Documents

particle accelerators

a4 chemical abundances

online athttps

material furtherquestions

bbn pp chains cno cycl

4x105 yrs

source of power

furnaces of chemical