TTF Wavelength Calibration

Example Calibrations:

Long-slit spectra taken with the TTF and a CuAr source through four filters: (top L) R1/710 nm, (top R) I3/760 nm, (bottom L) I5/815 nm, (bottom R) I6/910 nm. The long-slit spectrum is achieved with a focal plane slit, stepping the TTF through 80 frequencies synchronized with moving the charge on the detector (charge shuffling). The seven strips correspond to CS 100 coarse settings of (+6, +5, +4, +3, +2, +1, 0) spanning a physical gap range of 12 to 5 micron (left to right). There are three dominant emission lines in all filters, except the 910 nm filter with two lines. The latter is the easiest for seeing the major effect, that the orders separate out easily at small gap where the wavelength free spectral range increases. But note, in particular, that the intrinsic spectral resolution is falling as well.

From fitting to the lines as a function of wavelength against y (row number), we have established the gap and order of interference, m. The line wavelengths are given at the end. In the figure below, we plot the coarse setting against the gap spacing for all four filters. The non-linear variations along a mean slope are real.


Complete Data:

The complete data from this calibration are summarised below. There are four tables, one for each of the TTF blocking filters. Click here for a textfile version.

CuAr Calibration Lines:

Dick Hunstead has estimated better values for the line blends from Morlen (1973) Physica Scripta, 8, 249 with flux weighting. The first number is the relative flux; zero means very faint line. Click here for a textfile version.