197Au at the End of the Dragon

Evan O’ConnorUniversity of PEIAugust 2nd, 2006

Outline

Nuclear Astrophysics

Dragon

GEANT

Testing Dragon’s Acceptance

Summary

197Au at the End of the Dragon Evan O’Connor

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

197Au at the End of the Dragon Evan O’Connor

These rates determine the evolution and

composition of stars and the makeup of solar

systems

197Au at the End of the Dragon Evan O’Connor

Enter the Dragon…Gas target, array, electromagnetic mass

separatorUses inverse kinematics for radioactive beams

15X

16Y

Selecting MassErq

pmc

1)(2

crmmvqE

2)(

197Au at the End of the Dragon Evan O’Connor

crvmqE2

Motivation

197Au at the End of the Dragon Evan O’Connor

Important astrophysical reactions (12C()16O, 15O()19Ne) 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?

16Y

Geant

197Au 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

Acceptance Studies

197Au at the End of the Dragon Evan O’Connor

148Gadolinium 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

Measurements Taken

197Au at the End of the Dragon Evan O’Connor

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

Detector locations

Measurements Taken

197Au at the End of the Dragon Evan O’Connor

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

Transmission 1-2

197Au 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)

At Detector 2

197Au at the End of the Dragon Evan O’Connor

Simulation: Experiment:

DSSSD Y Position (mm)

Cou

nts

Moving first Quad 1mm Up

197Au at the End of the Dragon Evan O’Connor

Simulation: Experiment:

DSSSD Y Position (mm)

Cou

nts

The same behaviour is seen when source is moved down ~2mm

Summary

197Au 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

Thanks

197Au at the End of the Dragon Evan O’Connor

Jonty Pearson, Dave Hutcheon

Dragon Collaboration

TRIUMF Student Summer Program

UPEI Co-op Program