Preliminary Results for M12

Frequency and widths

We have ploted the measured channel center frequency and widths for module 12 using the PHS-386 data. These are preliminary results from a quick calculation. The channel frequencys are compared to the results we obtained from a linear fit of the air gap data from Nov'98. We were not able to obtain a reliable estimate of the widths from the air gap data; our rough estimate was something in the ballpark of 25% narrower than nominal. Plot of M12 measured vs nominal freq and width
We have re-run the fit of the SRF width for the air gap data using our best fit of the SRF from the Bruker "386" data". A plot and some comments on the air gap width fits

Average SRF

Here is a plot of the mean SRF for M12 (skipping channels with questionable data). M12 average SRF
Here are text files of the mean srf for m12, along with text files of the array indices of the "good" channels. M12 average srf
M12 good channels
Here are text files of the mean srf for m11, along with text files of the array indices of the "good" channels. M11 average srf
M11 good channels
Here is a text file with the mean SRF for M12 where all the "good" individual channel SRF's have been width-normalized. The x-axis values are the distance from channel center in FWHM. M12 avg SRF width-normalized

Interferogram Phase Correction

Here is a plot of the phase correction used for each M12 channel. Note the slope and fringes....not sure what it means, but interesting. M12 phase correction

Sample SRF

Here is a plot of a typical M12 SRF. This shows the very good agreement between calculations done by JPL and UMBC. There is, however, a ~0.010 cm-1 difference in the calculated frequencies. The calculations are based on using a 6.32992E-5 cm HeNe fringe spacing. Sample SRF

Simulation of SRF

Here is a plot of a simulation of the SRF for a channel near 650 cm-1. The plot shows both the "true" simulated SRF, and the results of the 2.88 cm FTS max OPD sinc function. The effects of self apodization have not been included (it would somewhat reduce the size of the fringes in the convolved simulated measurement spectra) Sim SRF

Rough Fit of Average M12 SRF

We have averaged the "good" channels of Module 12 and fit for the SRF shape. We have included the effects of self-apodization due to a ~2.9 degree field of view as well as a ~0.5 degree off-axis angle. The fit is only approximate; there are too many variables and uncertainties to fit everything in one go. The asymmetry seen in the average SRF can be reasonably well accounted for by a ~0.5 degree off-axis angle, but that is ~5 times larger than what LM expects as the max angle. The approx fitted values are: g_vs_l fraction=0.96, g_exp=2.9, l_exp=1.9. Fit of average M12 SRF

A More Detailed Look At Fitting the M12 Average SRF

Some comments and plots