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WATER COOLED DPSS POWER SUPPLY WITH RF AOM DRIVER USED IN YAG AND DPSS STUDIES
RF AOM DRIVER
The RF AOM driver was designed to power up to 100 watts of 24 Mhz TTL gain modulated output to drive a Shear wave fused silica AOM at 50watts. The AOM is a Control Laser model# QS-109 water cooled. On the driver board 2 - 10 turn trimmer pots set the TTL oscillator to provide the q switch pulse rate and the RF squelched time. Basically the unit was setup at 250 usec on time with 8 usec off time to allow the cavity to generate the laser pulse.
block.gif Block diagram of RF driver. Power Amps from http://www.communication-concepts.com/hf_amplifiers.htm
aom1.gif Oscilloscope view of the RF output. Below is the amp inverted NE555 gating pulse to the MC1350P IF amplifier to turn off the RF. As you can see there is a delay before the MC1350P gain drops.
aom2.gif Expanded view to see that the RF output is totally squelched.
aom3.gif Timing of turn off time is 121.8 usecs for a q switch pulse rep rate of 8,210 pulses per second. This was later adjusted to approx 4000 rep rate with 8 usec off time to maximize peak pulse power for higher efficiency of KTP harmonic conversion.
A Laser head can be cooled by a closed loop water system. Water passes through copper cooling block of laser diode/yag mount and then to the AOM and then back to the power supply case over 3/8 inch lines to a Danner magdrive 250 gph pump, then a heater core radiator and back out again. The radiator, RF driver board, and Current regulator board are mounted inline cooled by a Papst 150x 38mm 2850rpm 211.9 cfm 12vdc 1amp fan. Aluminum Case holds power and cooler with front panel switches, current adjust controls, temp displays etc.
Laser head consumes 100 watts and runs 2.5 degrees C above ambient.
Some articles on water cooling used in the pc market. http://www.overclockers.com/topiclist/index31.asp#WATER%20COOLING
Lab work with YAG Rod