Every time a component of the monochromator (MC) is adjusted (light source, input slit, output position, etc), the feed from the monochromator MC requires calibration anew.
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- Calibrate spectrograph (not necessary if spectrograph is already calibrated)
- Take monochromator MC data on spectrograph
- Use gathered data to calibrate spectrograph
We detail an example below. In this example, we use the StellarNet Inc Black Comet spectrograph, which we calibrate with the Ocean Optics KR-1 calibration light source. Future re-calibrations of the monochromator MC should be able to use the same calibration of the StellarNet spectrograph, which we include in the GitHub repository with the calibration scripts:
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- You need to determine your wavelength solution (reported wavelength vs true wavelength) of your calibrating spectrograph.
- This step does not need to be repeated every time monochromator MC requires new calibration, provided the old spectrograph calibration data is available.
- Pick a very small optical fiber to connect your calibration light and the spectrograph
- Very small as the raw KR-1 source is too bright for the spectrograph if not attenuated
- Take an image of KR1 lamp with spectrograph
STEP 2: Take monochromator data with spectrograph
- Plug optical fiber from monochromator output into Black Comet spectrograph
- MC end of fiber SHOULD NOT BE moved
- Move monochromator to 700 nm, and set spectrograph exposure time to ~10ms
- Place an ND filter in spectrograph input path, selected to make Black Comet peak intensity at this exposure time and wavelength ~10-20k
- The spectograph sensitivity with the ThorLabs halogen light peaks around 700nm. So we make a minimal exposure time give good S/N at that wavelength.
- Take a data series, starting from ~350 nm and ending at ~1050 nm.
- Use Python to step MC forward
- Use Black Comet to save the data.
- This requires manually saving the black comet files, and so cannot be easily automated.
- Here is an example of the run python scripts:
$ cd Documents/PythonScripts/CBP
*** Save the file, such as BC_mono_XXXnm_XXXms.SSM. Then press a button ****
$ python
>>> import monochromator as mono
>>> my_mono = mono.CornerStone260('COM3') #Need to check which COM port mono is read at
>>> waves = list(range(350, 1051, 52))
>>> for wave in waves:
my_mono.GoWave(wave)
input('Monochromator at wavelength ' + str(wave) + ' nm. Press any key to move to next wavelength (SAVE THE FILE FIRST THOUGH!!!!)') - You will need to adjust the exposure time to keep the number of counts in a good range (~5k-40k).
STEP 3: Run the wavelength solution
- Run the XXX script.