1. 197 A u at the End of the Dragon Evan O’Connor University of PEI August 2 nd, 2006

2. Outline Nuclear Astrophysics Dragon GEANT Testing Dragon’s Acceptance Summary 197 Au at the End of the Dragon Evan O’Connor

3. Nuclear Astrophysics… …is the branch of physics that examines the formation of elements through nuclear reactions and the rates at which they occur. 197 Au at the End of the Dragon Evan O’Connor These rates determine the evolution and composition of stars and the makeup of solar systems

4. 197 Au at the End of the Dragon Evan O’Connor Enter the Dragon… Gas target,  array, electromagnetic mass separator Uses inverse kinematics for radioactive beams 15 X 16 Y

5. Selecting Mass 197 Au at the End of the Dragon Evan O’Connor

6. Motivation 197 Au at the End of the Dragon Evan O’Connor Important astrophysical reactions ( 12 C(  ) 16 O, 15 O(  ) 19 Ne) have maximum angles ~16 mrad (cone angle) Dragon’s 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? 16 Y 

7. Geant 197 Au at the End of the Dragon Evan O’Connor 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

8. Acceptance Studies 197 Au at the End of the Dragon Evan O’Connor 148 Gadolinium Alpha source in Dragon’s mouth Double-Sided Silicon Strip Detector (DSSSD) Previous Acceptance studies disagree with GEANT Notched collimator to allow for ‘ray-tracing’ 20 mrad half angle Alpha Source

9. Measurements Taken 197 Au at the End of the Dragon Evan O’Connor Five orientations of collimator at three different locations + 1 measurement with no collimator Detector locations

10. Measurements Taken 197 Au at the End of the Dragon Evan O’Connor Transmission percentages between Detector location 1 and 2 for different orientations This will raise a flag to allow for a more in-depth look at Dragon Detector locations

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

12. At Detector 2 197 Au at the End of the Dragon Evan O’Connor Simulation:Experiment: DSSSD Y Position (mm) Counts

13. Moving first Quad 1 mm U p 197 Au at the End of the Dragon Evan O’Connor Simulation:Experiment: DSSSD Y Position (mm) Counts The same behaviour is seen when source is moved down ~2mm

14. Summary 197 Au at the End of the Dragon Evan O’Connor A critical assumption in Dragon’s 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

15. Thanks 197 Au at the End of the Dragon Evan O’Connor Jonty Pearson, Dave Hutcheon Dragon Collaboration TRIUMF Student Summer Program UPEI Co-op Program