197Au at the End of the Dragon

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197Au at the End of the Dragon
Evan OConnor University of PEI August 2nd, 2006
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Outline

• Nuclear Astrophysics
• Dragon
• GEANT
• Testing Dragons Acceptance
• Summary

197Au at the End of the Dragon

Evan OConnor
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Nuclear Astrophysics

• is the branch of physics that examines the
  formation of elements through nuclear reactions
  and the rates at which they occur.

These rates determine the evolution and
composition of stars and the makeup of solar
systems
197Au at the End of the Dragon

Evan OConnor
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Enter the Dragon

• Gas target, g array, electromagnetic mass
  separator
• Uses inverse kinematics for radioactive beams

197Au at the End of the Dragon

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Selecting Mass
197Au at the End of the Dragon

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Motivation

• Important astrophysical reactions (12C(a,g)16O,
  15O(a,g)19Ne) have maximum angles 16 mrad (cone
  angle)
• Dragons nominal cone angle is 20 mrad
• When cone angles approach 20 mrad are all
  recoil particles transmitted fully through
  Dragon? If not, can we accurately predict the
  losses using computer software?

197Au at the End of the Dragon

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Geant

• Computer simulation package specializing in
  simulating elementary particle trajectories
• Upgrades were made to the simulated Dragon
  which include the addition of beam pipes and
  electrodes in dipoles
• Source energy distribution model was
  re-evaluated to obtain an accurate fit to
  observed spectrum assuming detector efficiencies

197Au at the End of the Dragon

Evan OConnor
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Acceptance Studies

• 148Gadolinium Alpha source in Dragons mouth
• Double-Sided Silicon Strip Detector (DSSSD)
• Previous Acceptance studies disagree with GEANT
• Notched collimator to allow for ray-tracing

20 mrad half angle
197Au at the End of the Dragon

Evan OConnor
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Measurements Taken

• Five orientations of collimator at three
  different locations 1 measurement with no
  collimator

197Au at the End of the Dragon

Evan OConnor
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Measurements Taken

• Transmission percentages between Detector
  location 1 and 2 for different orientations
• This will raise a flagto allow for a more
  in-depthlook at Dragon

Detector locations
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Transmission 1-2
Percent transmission between detector position 1
and position 2 E (Experiment) S (Simulation)
E 93.4 /- 0.5 S 99.0 /- 0.8
E 62.9 /- 0.6 S 80.7 /- 0.7
E 88.7 /- 0.9 S 95.9 /- 0.7
E 96.4 /- 0.4 S 99.7 /- 0.8
E 98.7 /- 1.0 S 99.0 /- 0.8
197Au at the End of the Dragon

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At Detector 2
Simulation
Experiment
Counts
DSSSD Y Position (mm)
197Au at the End of the Dragon

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Moving first Quad 1mm Up
Simulation
Experiment
The same behaviour is seen when source is moved
down 2mm
Counts
DSSSD Y Position (mm)
197Au at the End of the Dragon

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Summary

• A critical assumption in Dragons work is that
  all recoils are transmitted to the end. This is
  an issue with upcoming reactions approved for
  Dragon
• To answer my two questions

Yes particles are lost in Dragon when cone angles
are large
Simulations show agreement with experiment AND
are probing problems observed with experiments
197Au at the End of the Dragon

Evan OConnor
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Thanks

• Jonty Pearson, Dave Hutcheon
• Dragon Collaboration
• TRIUMF Student Summer Program
• UPEI Co-op Program

197Au at the End of the Dragon

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