For an effective Doppler Global Velocimeter (DGV), there is a requirement to
accurately record and tune the frequency content of the laser used. The laser used for
this experiment was an ND:YAG. Adjusting the mean frequency of the ND:YAG is
accomplished by controlling the seed laser diode output, which also narrows the
bandwidth of the laser to below 20 MHz. The exact frequency of operation is critical for
the operation of the system. Standard interferometry techniques that measure laser
frequency content, such as Fabre-Perot and grating based systems, are not able to
provide an adequate spectrum resolution for the 9 ns pulse duration of the ND:YAG
laser. A method was developed that employs a CCD line camera and a laser reference
cell to effectively and cost efficiently solve this problem. The hardware and software for
this real time monitoring system were developed and used with a real time feedback loop
to stabilize the laser operating frequency at a specified value. The receiving optics of
this DGV system were upgraded with 12 bit CCD cameras and a temperature controlled
laser reference cell to decrease the uncertainty to the velocity measurement from over 4 m/s to less than 1 m/s. Recommendations to the effectiveness of the system and future
improvements are provided.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2008-12-181 |
| Date | 15 January 2010 |
| Creators | Nelson, Brent |
| Contributors | Morrison, Gerald L. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis |
| Format | application/pdf |
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