A two-ion balance for high precision mass spectrometry

This thesis describes the demonstration of a new technique that allows masses to be compared with fractional uncertainty at or below 1 x 10-11, an order of magnitude improvement over our previous results. By confining two different ions in a Penning trap we can now simultaneously measure the ratio of their two cyclotron frequencies, making our mass comparisons insensitive to many sources of fluctuations (e.g. of the magnetic field). To minimize the systematic error associated with the Coulomb interaction between the two ions, we keep them about 1 mm apart from each other, on a common magnetron orbit. We have developed novel techniques to measure and control all three normal modes of motion of each ion, including the two strongly coupled magnetron modes. With the help of a new computer control system we have characterized the electric field anharmonicities and magnetic field inhomogeneities to an unprecedented level of precision. This allows us to optimize the trap so that our measurement of the cyclotron frequency ratio is to first order insensitive to the field imperfections. Using the ions 13C2H2+ and 14N2+, we performed many tests of our understanding of the ions dynamics and of the various sources of errors in this technique. From these we conclude that there should be no systematic error in our measurements at the level of 5 x 10-12. Thus we feel confident reporting a value for the mass ratio of these ions with an uncertainty of 10-11.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Physics.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2003

Author dc:creator

• Rainville, Simon, 1974-

Advisor dc:contributor.advisor

• David E. Pritchard.

• Physics.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/16934

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/16934