Radiative%20Capture%20Reactions%20with%20Radioactive%20Beams%20for%20Nuclear%20Astrophysics%20Using%20DRAGON%20at%20ISAC%20or%2022Na:%20A%20Tag%20for%20Novae

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Radiative Capture Reactions with Radioactive
Beams for Nuclear Astrophysics Using DRAGON at
ISAC or22Na A Tag for Novae

• John M. DAuria
• Simon Fraser University
• For the DRAGON E824 collaboration

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Outline

• Explosvie Astrophysics An Overview
• 22Na a tag for Novae
• The 21Na(p,g)22Mg reaction
• Radioactive Beams and ISAC
• The DRAGON spectrometer
• Results
• Future program

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We are all nuclear debrisWillie Fowler, Nobel
Laureate, 1983

• We stand on the verge of one of thse
  exciting periods which occur in science from time
  to time. In the past few years, it has become
  abundantly clear that there is an urgent need for
  data on the properities and interactions of
  radioactive nuclei..for use in nuclear
  astrophysicsAt the same time methods for
  producing radioactive and isomeric nuclei, and
  for accelerating them in sufficient quantities
  have been proposed and even brought to the design
  stage with estimates for performance and
  cost..Lets get on with it!
• Willie Fowler, Parksville, 1985

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rp-process

• Series of (p,g) and (b,ne) steps, inhibited by
  (p,a)
• High temperatures and short time scales
• Novae, X-ray bursters
• Binary system compact object (white dwarf or
• neutron star) and main sequence or red
  giant star
• Accretion of hydrogen rich material
• Thermonuclear runaway lots of energy
• Radioactive nuclei play a role (fast process)

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Nuclear Astrophysics at ISAC with DRAGON and TUDA
Explosive Astrophysics Sites

• Novae, X-ray bursters, supernovae type 1a
• Binary system compact object (white
• dwarf or neutron star) and main sequence
• or red giant star
• Accretion of hydrogen rich material
• Thermonuclear runaway lots of energy
• High temperatures and short timescales
• Radioactive nuclei important

DRAGON designed for radiative proton and alpha
reactions with radioactive and stable beams
TUDA designed for particle reactions
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22Na a novae observable

• Novae are stellar fusion reactors transforming
  elements to power spectacular outbursts
• The observation of the decay of certain
  radioactive nuclei (18F, 22Na, 26Al) produced can
  provide detailed information on the conditions
  during a nova outburst (and X-ray bursts ??)
• Gamma-ray observatories, such as INTEGRAL, are
  searching for these signatures to test current
  models
• 22Na was not observed with COMPTEL

The INTEGRAL satellite
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22Na formation NeNaMg cycle
INTEGRAL
22
23
24
Mg
Mg
Mg
11.3s
3.8s
21
22
23
Na
Na
Na
22.5s
2.6yr
20
21
22
Ne
Ne
Ne
1.275 MeV
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Direct Measurement of the 22Na(p,?)22MgReaction
Rate ( 20)
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Basic Experimental Approach 21Na p
22Mg ? Inverse kinematics
?
?
Recoil Detector
H2
21Na
Target
22Mg
Advantage ? lt 1 deg, could accept all
recoils Challenges Beam and recoil have
same momentum. Rate of beam gtgtgt rate of
recoils (1011/1). Beam is radioactive leading
to background. Requires Known level
structure of 22Mg Intense source of radioactive
21Na - ISAC Efficient detection of 22Mg Very
efficient rejection of 21Na
DRAGON Windowless hydrogen gas target
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Direct Measurement of the 22Na(p,?)22MgNuclear
Structure of 22Mg
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21Na(p,?) 22Mg
Levels of 22Mg
Proton capture on 21Na dominated by
isolated narrow resonances at T 0.4 GK (novae
temps)
Knowledge of energy levels at start of study
based on transfer reactions, e.g. (p,t)
isospin mirror nucleus 22Ne elastic scattering
with 21Na
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What determines the reaction rate?
Gamow Peak

• Thermonuclear burning proceeds in region defined
  by Coulomb penetrability and thermalised velocity
  distribution
• Rate can be greatly enhanced when resonances lie
  within this window

Cauldrons in the Cosmos, Rolfs Rodney
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What is ?? and how is it measured?

• Narrow Breit-Wigner resonance
• ½ ?2 ?? ?sBW(E) dE

?? spin factor x Gp G? / Gtot

• yield per incident beam particle, thick target
• Yield ½ ?2 ?? (MbMt)/(Mt e)

? de Broglie wavelength e (lab) energy
loss per atom/cm2 in target G width
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21Na(p,?)22Mg
GOAL Measure astrophysical rate at
explosive stellar temperatures (Nova) WHY
Clarify mechanism of nova explosion HOW
Inverse kinematics using 21Na beam PROBLEMS
- Reaction governed by weak resonances -
Requires intense 21Na radioactive beam -
Requires hydrogen gas target - Requires high
beam suppression - Intense gamma background
around target
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RADIOACTIVE BEAMS AND ISACProduction of 22Na
beam
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SFU

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Production of Radioactive Beams
RIA
ISAC
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The TRIUMF-ISAC Radioactive Beams Facility

• ISAC I Project proposed in 1985 funded in 1995
• RB Production by the ISOL Method (500 MeV p)
• RB Accelerated using LINACS (0.15 1.5 MeV/u)
• Two ISAC 1 Experimental Areas (LEBT and HEBT)
• ISAC II funded in 2000 RB above the Coulomb
  Barrier
• Presently seeking funding for ISAC II 1/2
• Major Milestones
• 1998 First RB beam (38mK) to TRINAT
• 2000 First physics (74Rb lifetime with high
  precision)
• 2001 TUDA and DRAGON perform RB
  experiments21Na
• 2002 - 8? and ?-NMR perform physics
• 2003 - TITAN and TIGRESS Funded ISAC II bldg.
  open

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ISAC Production Target
M. Dombsky/TRIUMF
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TITAN
TITAN
TRINAT
Collection Facility Separator floor
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ISAC LINACS Energy 0.15 1.5 MeV/u Pulse
Iteration 86 ns Masses A lt 30 amu
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Direct Measurement of the 22Na(p,?)22Mg
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Basic Experimental Approach 21Na p
22Mg ? Inverse kinematics
?
?
21Na
Recoil Detector
H2
22Mg
Target
Advantage ? lt 1 deg, could accept all
recoils Challenges Beam and recoil have
same momentum. Rate of beam gtgtgt rate of
recoils (1011/1). Beam is radioactive leading
to background. Requires Intense source of
radioactive 21Na - ISAC Efficient detection of
22Mg Very efficient rejection of 21Na
DRAGON Windowless hydrogen gas target
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DRAGON Detector of Recoils And Gammas of Nuclear
Reactions

• For radiative capture reactions - (p,g), (a,g)
• Recoil mass separator
• Windowless gas target
• Gamma array
• End detectors silicon strip detector or ion
  chamber

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Beta Detectors
DSSD or
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DRAGON Gas Target

• Windowless gas target
• Monitor detectors -
• detect elastically scattered particles for
  normalisation
• Typical pressures 4-8 Torr
• Extensive pumping system
• Seven turbo pumps
• Two roots blowers

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DRAGON Gamma Array

• 30 BGO Gamma detectors surrounding gas target
• Geometrical efficiency of 89-92
• Effective efficiency determined from GEANT
  simulations and point source studies.

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DRAGON Separator

• Two stage separator
• Each stage consists of a magnetic dipole and an
  electric dipole plus focusing elements
• Magnetic dipole separates according to charge
  state
• Electric dipole separates according to mass
• Repetition of separation stages improves
  suppression

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The Dragons Eye Beam in the Gas Target
? Telescope CCD camera look upstream through
alignment port of MD1 magnet, through gas
target. ? Inner dark hole is 6 mm entrance
aperture of gas cell. ? Shows beam presence and
position without interrupting data collection
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DRAGON End Detectors

• Choice of end detectors depending on requirements
  of reaction being studied
• Silicon strip detector (DSSSD)
• - yield, timing, position, energy
• Ion chamber (IC) (PGAC?)
• - particle i.d., energy, timing
• Micro-channel plate (MCP)
• - local timing (with DSSSD)

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DRAGON Quantification

• Beam Normalization ( lt 20 )
• - Measured elastic scattering in gas target.
• - Measured betas from scattered radioactive
  beam.
• - Measured light in CCD camera from beam.
• - Normalized to upstream faraday cup.
• - Measure (if possible) charge state
  distribution of recoil.
• Beam Energy
• - Use calibrated NMR probe on MD1

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Calibration/Commissing Reactions
Reaction E keV wg eV lit.
F mrad wg eV 20Ne(p,g) 1112.6 1.13 /-
0.07 3.8 0.92 /-
0.17 21Ne(p,g) 258.6 0.0825 /- 0.0125
14.9 0.21 /- 0.03 21Ne(p,g) 731.5 3.95 /- 0.79
9.4 3.85 /- 0.49 24Mg(p,g) 214.0
0.0127 /- 0.009 5.2 0.0117 /-
0.016 24Mg(p,g) 420.2 0.0416 /- 0.0026
4.0 0.0574 /- 0.0087 24Mg(p,g) 790.4 0.532 /-
0.41 3.3 0.576 /- 0.040
Suppression results
Comparison Studies
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Measurement of 21Na(p,g)22Mg

• 21Na beam on hydrogen target
• Scanned over each resonance in small energy steps
• Detected recoils in singles or in coincidence
  with prompt gammas

Excitation function For ER 821 keV
22Mg recoils in DSSSD (singles) ER738 keV
22Mg
21Na
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Ebeam 220 keV/u Ec.m. 212 keV ? I(21Na)? 2
x 109 s-1

• BGO-DSSD coincidence
• Prompt ? recoil coin.

BGO Efficiency
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Results for 212 Resonance
Thick target yield -only mid point used
Resonance energy Ecm 205.7.5 keV Not 212
keV
Why?
Mass of 22Mg -403.21.3 keV Not 396.8 keV
Elit 214 keV
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Resonance Strength for 5.714 MeV state
Thick target yield
?? 1.03 0.16stat 0.14sys meV
PRL 90(2003)162501
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Results resonance strengths 21Na(p,?)22Mg

• Received 21Na beam (? 2 x 109600 epA)
• Determined resonance strengths for seven states
  in 22Mg between 200 and 1103 keV
• DRAGON operations
• - used DSSSD as focal plane detector
• - used beta activity,FC and elastics for flux
• - used BGO gamma despite high ? bgd.

Subm. to PRC
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Reaction rate

• The lowest measured state at 5.714 MeV (Ecm 206
  keV) dominates for all novae temperatures and up
  to about 1.1 GK
• Updated nova models showed that 22Na production
  occurs earlier than previously thought while the
  envelope is still hot and dense enough for the
  22Na to be destroyed
• This results in lower final abundance of 22Na
• Reaction not significant for XRB

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The DRAGON E824 Collaboration
Simon Fraser Univeristy Shawn Bishop
(RIKEN) John DAuria Mike Lamey Wenjie Liu
(Compl.) Chris Ruiz Mike Trinczek Chris Wrede
(Yale)
TRIUMF Lothar Buchmann Dave Hutcheon Alison
Laird (York) Art Olin Dave Ottewell Joel Rogers
(ret)
Colorado School of Mines Uwe Greife Cybele
Jewett

McMaster University Alan Chen
Saha Insitute of Nuclear Physics Mohan Chatterjee
Yale University Peter Parker Rachel Lewis
University of Northern B.C. Dario Gigliotti
(Compl.) Ahmed Hussein
Ruhr-Universitat Bochum Sabine Engel
(Compl.) Frank Strieder
University of Tokyo Shigeru Kubono S. Mitimasa
Graduate student, Post-Doctoral Fellow, Faculty
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Z ?
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Upcoming measurements at DRAGON

• Reaction
• 19Ne(p,g)20Na
• 13N(p,g)14O
• 12C(a,g)16O
• 17F(p,g)18Ne
• 25Al(p,g)26Si
• 11C(p,g)12N
• 15O(a,g)19Ne
• 26m,gAl(p,g)27Si

• Motivation
• HCNO breakout
• CNO/HCNO
• He burning/C,O prod
• 18F abundance
• 26Al abundance
• Hot pp-chains
• HCNO breakout
• 26Al abundance

• With CSB for ISAC II
• 34Ar(p,?)35K
• 57Cu(p, ?)58Zn

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TRIUMF EEC Experiment ProposalE989
Astrophysical studies using 26Al ground-state and
isomeric beamsC. RuizandE990 Resonant elastic
scattering of isomeric 26Al on protonsC. Ruiz,
A. S. Murphy
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MgAl cycle
26gAl(p,g)27Si, 26mAl(p,g)27Si E989,E990 (C.
Ruiz) DRAGON and TUDA
25Al(p,g)26Si E922 (A.Chen) DRAGON
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27
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Si
Si
Si
4.16s
2.21s
25
27
26
Al
Al
Al
7.18s
0.717Myr
6.35s
24
25
26
Mg
Mg
Mg
1.809 MeV
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26gAl(p,g)27Si

• 26gAl (5) can only form high J states in 27Si
  via low-energy radiative capture
• Several resonances below Ecm900 keV contribute
  for T90.35 Novae burning
• Most recent work includes 18 resonances
  dominant resonance is ER188 keV ? Ex7652 keV
• Calculations for ONe WD Novae (J. Jose) show
  factor 2 change in final 26Al for 30 variation
  in resonance strength
• Previous adopted value (0.064 meV) based on exp.
  limits from transfer reactions
• Resonance at 226 keV for which no experimental
  info exists

Iliadis et al. Astr. J. Sup. 134 151-171 (2001)
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Objectives

• E989 - DRAGON
• Phase 1 Direct measurement of resonance
  strengths in 26gAl(p,g)27Si
• Phase 2 Direct measurement of resonance
  strengths in 26mAl(p,g)27Si isomeric beam
• E990 - TUDA
• Identification of 26mAlp resonances in energy
  region relevant to SNII temperatures

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26gAl(p,g)27Si resonance properties
Excitation Energy (keV) Resonance Energy (keV) Resonance Strength Total Width Estimated Yield
7652 188 0.064 meV - 0.4 x 10-12
7690 226 - - 0.3 x 10-13

• With 109 26Al ions/sec, estimated count rate 0.23
  cts/hr for 188 keV resonance for coincident g-HI
  events
• Can achieve 15 accuracy in measurement of
  resonance strength with 10 days running
• Aim to achieve upper limit on 226 keV resonance
  strength

reactions per incoming ion, calculated for 4
Torr H2 Target (SRIM 2003 calculated stopping
powers were used)
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ISAC (II)
ISAC II March 7, 2003
ISAC II EXPERIMENTAL HALL From SE Entry Door
Planned Facilities TIGRESS HERACLES BIG
DRAGON TUDA II
123 x 90 x 33 h 11000 ft2
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EMMA
TIGRESS
Preliminary Layout of ISAC II Experiments
TOF
TUDA II
HERACLES
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Concluding remarks

• The DRAGON Facility at ISAC is ideal to measure
  radiative capture reactions directly.
• ISAC is capable of producing intense beams of
  radioactive species.
• Program is in progress to measure rates of
  reactions of importance to understanding
  explosive stellar burning.
• Studies of 21Na(p,?)22Mg rate provide some
  understanding of the lack of observation of 22Na
  with gamma telescopes.

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Planned DRAGON Experiments
Radioactive Beams 19Ne(p,?)20Na hot CNO
breakout rp process 13N(p,?)14O DC hot CNO
breakout ECR source 17F(p,?)18Ne hot CNO
breakout ECR source 11C(p,?)12N hot pp
chain (DC Res.) ECR source 25Al(p,?)26Si
rp process 26Al production laser 26m,g
Al(p,?)27Si rp process 26Al production
laser 15O(?,?)19Ne hot CNO breakout x-ray
burst 30P(p,?)31S nova mechanisms rp
process approved experiments
presenting in Dec. 03 ISAC II
Experiments (using CSB for Agt30) 34Ar(p,?)35K
rp process ECR ion source 56Ni(p,?)57Cu
rp process laser ion source 57Cu(p,?)58Zn rp
process laser ion source Stable Beam Studies
12C(?,?)16O helium burning Very important
rx. 12C(12C,?)24Mg carbon burning very
difficult rx.