Kipp&Zonen Brewer MkIII - Manual (Page 104)

MKIII OPERATOR’S MANUAL 101
FILTER #1/1 AND FILTER #2/1
GMT DEADTIME
191424 4.48950597E-08
191449 4.58755779E-08
191513 4.49521729E-08
191538 4.67340357E-08
191603 4.49957964E-08
191627 4.81735377E-08
191652 4.55349271E-08
191716 4.51368558E-08
191741 4.53192958E-08
191805 4.58533414E-08
45.747 ± 1
Following each block of measurements the deadtime mean and deadtime standard deviation (in
nanoseconds) are calculated and printed. The high- and low-intensity deadtime means should
agree (within an acceptance tolerance of two standard deviations), and should lie in the range 35 to
50 nanoseconds. Failure to meet this criterion indicates possible difficulties with either the slitmask
motor operation, the high-voltage circuitry, or photon counting circuitry.
This newly determined deadtime constant should not be entered into the instrument Constants File
unless it is significantly different (by more than about 5 ns) from the old value (if you are confident
that the instrument is currently running properly). You should contact the factory before altering the
stored constant since a complete recalibration may be required.
HG: MERCURY-LINE WAVELENGTH CALIBRATION
The HG test precisely locates the mercury line-spectrum, then repositions the micrometer so that
the diffraction grating disperses the five operating wavelengths onto the appropriate exit slits. The
test uses the mercury discharge lamp and the Hg calibration slit (slitmask position 0).
The software establishes the position of the mercury line-spectrum by scanning the micrometer
forwards from step position 50 to step 280 in 10-step increments, then reversing direction and
scanning from step 280 back to step 50 (note: 1 micrometer step 0.007 nm). At each position the
light intensity dispersed through the calibration slit is recorded, building a 24-point profile of the
mercury spectrum. This measured spectrum is compared with an internally-stored reference
spectrum to determine that step position which
maximizes the correlation between the measured
and stored spectra. If this interpolated step number falls within the acceptance limits
[147.00..149.99] the mercury spectrum is deemed to have been located, and the micrometer is
moved to its operational setting (step number 286 ± 3, or 13 ± 3 micrometer steps below the
mercury calibration point; this small displacement is an instrument-dependent constant known as
the 'offset' stored in the instrument Constants File, and is determined by the SC test).
If, however, the mercury calibration point falls outside the acceptance range, the micrometer is
reset to the newly calibrated step number and the test repeated. Iterations continue until the
calibration point converges correctly.