ISSN:
0951-4198
Keywords:
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Physics
Notes:
The exact determination of electrostatic potential is vital in specifying the resolution in ion-beam focusing devices such as quadrupole mass spectrometers (QMS). Current numerical routines are marked by poor convergence on boundaries and become unwieldy when the number of electrodes, 2n, is greater than four, or when the structure is modified. Using a conformal transformation we have succeeded in finding the exact electrostatic potential distribution everywhere within a QMS which contains four cylindrical electrodes. All the coefficients in the multipole expansion of the potential are readily calculated. The boundary value problem is solved by matching coefficients on the electrode surface, which is a circle embedded in the transformed coordinate frame. We have proven that for every allowed position of the electrode centre, R, there exists a corresponding electrode radius, r, for which the dodecapole term in the potential expansion vanishes. Our analytically obtained relationship between the above-mentioned parameters differs slightly from that in current use. As these parameters are based on an exact solution, their practical use in mass determination may be considerable.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/rcm.1290081206
Permalink
