MSc Defense: Final Oral Examination for the Degree Master of Science of David Thomson

Event Details

  • Date:
  • Time: 10:30 AM
  • Location: Science Complex Room 1511

Thesis Title:

"A Monte Carlo Approach to the Simulation of Characteristic X-Ray Yields for the APXS Instrument"


In this thesis a new Monte Carlo simulation (MCYAC) is created and employed, which simulates measurements taken by the Alpha Particle X-ray Spectrometer (APXS) on the Mars Science Laboratory rover. Several consistency checks are conducted to test the validity of MCYAC. The checks verify that the simulation gives consistently reasonable results.

Using the Monte Carlo simulation, a study is conducted to ascertain the impact of alpha particle energy variation due to path angles of alpha particles traversing the titanium foil curium source cover on the characteristic X-ray yield of light elements. Though computational constraints prevent the individual treatment of each Monte Carlo event location, the trend that emerges from the study indicates that the alpha particle energy variation has a very small impact on the characteristic X-ray yield of light elements.

A new approach is taken to determine a pair of geometry-dependent angles that can be used to optimize the X-ray yields found for the X-ray yield equation. These angles, named average angles, more closely match the criterion used to define this angle pair than the effective angles that have been used for APXS data analysis thus far.

Finally, the results of the Monte Carlo simulation are compared to those found experimentally, with experimental X-ray yields per second calculated using the GUAPX least squares fitting program. A systematic discrepancy between the results of the Monte Carlo simulation and GUAPX is observed. The largest source of discrepancy between these programs is thought to come from the geometry values of the APXS instrument used in the Monte Carlo simulation, some of which are unknown.

Examination Committee:

Dr. Paul Garrett, Chair

Dr. Iain Campbell, Advisor

Dr. Joanne O'Meara

Dr. Ralf Gellert


Dr. Iain Campbell