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Nd:YAG lasers
[edit | edit source]We have three Nd:YAG lasers on the ground floor of FELIX - one at the diagnostic station (10 Hz) and two next to the MB arm of FELICE (10 Hz and 20 Hz). They all are the same model INDI, manufactured by Spectra-Physics, now part of MKS Instruments.
| Wavelength fundamental | 1064 nm |
| Wavelength fundamental | 532 nm |
| Pulse length | 5-8 ns |
| Specced power fundamental | XX W (10 Hz) |
| Specced power 2nd harmonic | YY W (10 Hz) |
| Flash lamp lifetime | 36M shots |
| Flash lamp product number | |
| Particle filter product number | |
| De-ionizer filter product number |
Distilled water should be used for the chiller. Water should be circulated in the system every few weeks at minimum, to avoid buildup of contamination.
A copy of the manual can be found here.
Cleaning the flash lamp pump chamber
[edit | edit source]If the power output is low, it may be due to contaminated reflector surfaces. This is apparently made much more likely to appear if the water has not circulated in the system for a long time.
To clean the pump chamber,
- Disconnect the Nd:YAG laser from the power supply and open up the housing.
- Remove the flash lamp and unscrew the three screws holding the chamber to the baseplate.
- Carefully remove the six outer-most screws from both sides of the pump chamber. This will let you pull out the reflectors.
- Carefully remove the two internal screws that hold each of the four side-mirrors inside the cavity. Try not to disturb the plastic rings, and do not lose the screws.
- Unscrew the two elliptical reflectors from their mounting plates.
- Soak all contaminated reflectors in a (roughly) 10% HCl solution. Note that HCl is an unpleasant chemical to say the least, so perform the soaking inside the fume cupboard in the ChemLab and do NOT let any HCl reach your skin, face etc.
- After about an hour, remove the reflector and wash it liberally in distilled water. Most likely you should change your gloves here as well, since your gloves came in contact with HCl.
- The HCl only softens the calcium deposits. Using a lens tissue, rub the softened deposits off the mirrors. If the mirrors are particularly bad, you may also see some algae coming off as well. Wash the mirrors again with distilled water to remove all HCl.
- Repeat this cleaning process for all the reflectors, and carefully reassemble the pump chamber. Clamp the pump chamber back to the baseplate - once the springs under the screws are compressed fully, the pump chamber is aligned.
- Reinsert the flash lamp and check for leaks.
- Using long-pulse mode, slowly increase the power and check the spot profile is round.
- The output power should now be much better (e.g. after the cleaning performed in the picture below, the output power at 520nm went from <0.1W to almost 0.9W)
