JANUARY 1998 REPORT FOR

W. CHARLES SYMONS, III

As usual, the first priority for the month of December was to submit the final abstract for the Pittsburgh Conference (Pittcon). This year's submission entitled NEAR-FIELD SCANNING OPTICAL MICROSCOPIC IMAGING FROM X-BAND TO NEAR-IR will be presented in New Orleans on March 2, 1998. Additionally, I also modified this Pittcon abstract and retitled it SIMULATING THE NEAR-FIELD ELECTROMAGNETIC SCATTERING PHENOMENA OF A NEAR-FIELD SCANNING OPTICAL MICROSCOPE for presentation at the Computational Science Brown Bag Seminar on March 10, 1998. Once these abstracts were completed, the dermatome code was refined to include a menu such that each motor could be driven step-by-step in either direction. Upon testing this code, it was determined that heat sinks were required to dissipate excess heat from the dermatome motor voltage regulators. Once the heat sinks were installed, a square cutting pattern was added to the menu. At this point, further code development is futile until after the first initial test of the instrument. Once this initial test is complete, a more thorough coding direction can be determined.

In addition to the submitted abstracts and the dermatome project, the Near-Field Scanning Optical Microscope (NSOM) Moment Method code was further tested. These simulations revealed that the convergence rate along the wire sample is determined by both the basis function density in addition to the excitation vector. In order to alleviate this problem, the excitation vector must converge before the current will converge. To this end, a convergence study of the excitation vector was performed as seen in the Figures 1 and 2 below. From these plots, it is evident that the excitation vector varies as the excitation density is increased as 50, 100, 200, 300, 400, and 500 excitation points. Due to this convergence study, the excitation vector routine is currently undergoing revision such that the excitation vector is no longer dependent on basis function density.

Figure 1: Convergence Study of Real Part of Excitation Vector.

Figure 2: Convergence Study of Real Part of Excitation Vector (Zoomed).