New Mexico Geochronology Research Laboratory
Hardware — UV Laser

Note: The description of hardware below is out of date and will be revised soon.

The UV laser system used by the NMGRL:

• Advantages of a UV laser system
  • capable of very small (> 10 micron) beam spot sizes needed for in situ argon extraction
  • ablates material rather than heating/fusing. This means it will not effect argon sites immediately adjacent to current analysis spot.
• Disadvantages of a UV laser system
  • expensive to purchase and maintain
  • not capable of step-heating

Schematic of NGMRL UV laser system

Components of the NMGRL UV laser system.

1. Rear mirror/intra cavity shutter
2. Q-switch
3. Oscillator pumping chamber
4. Output coupling mirror
5. Steering mirrors
6. Second harmonic generator
7. Third/Fourth harmonic generator
8. HSA2 Dichroic mirror harmonic separator, UV beam exit to sample chamber

Video Clip of UV laser ablation

Explanation

The field of view in the video is approximately 1 mm across. The computer moves the sample chamber/tray (x-y-z position) to the next location to be analyzed and activates the UV laser. The laser begins to ablate the surface of the muscovite grain. The sample stage rises gradually to keep the bottom of the ablating pit at a constant level. After approximately 15 seconds, the laser is deactivated and the argon gas is cleaned and moved to the mass spectrometer to be analyzed.

The muscovite grain at left is approximately 2 mm across (short axis). The ablation pits were used to determine the argon (age) distribution across the grain.