For the past 28 years, the Laser Hardened Materials Evaluation Laboratory (LHMEL) at the Wright-Patterson Air Force Base, OH, has worked with CO2 lasers capable of producing continuous energy up to 150 kW. These lasers are used in a number of advanced materials processing applications that require accurate spatial energy measurements of the laser. Conventional non-electronic methods are not satisfactory for determining the spatial energy profile. This paper describes a new method in which a continuous, real-time electronic spatial energy profile can be obtained for very high power, (VHP) CO2 lasers.
Pulsed laser capabilities at the Laser Hardened Material Evaluation Laboratory are described relevant to optical coupling, impulse generation and laser propulsion. Capabilities of the Nd:Glass laser are presented as well as supporting test systems.
The operational characteristics of a 135 kW continuous wave carbon dioxide laser system are described. A brief description of the fast-flowing electrical discharge coaxial laser system is presented followed by a detailed discussion of the operational and output characteristics of the device. Diagnostics systems configured to measure electrical discharge voltage and current, mass flow, laser cavity pressure, laser output power, output spatial intensity distribution and output temporal stability are described. The data collected with these systems are summarized with subsequent analyses presented and compared with theory. The 135 kW carbon dioxide laser is located at the Laser Hardened Materials Evaluation Laboratory (LHMEL) at Wright-Patterson Air Force Base, Ohio, USA. The device was developed and is currently operated for the purpose of characterizing the thermal response of materials.
When developing a high-heat-flux system, it is important to be able to test the system under relevant thermal conditions and environmental surroundings. Thermal characterization testing is best performed in parallel with analysis and design. This permits test results to impact materials selection and systems design decisions. This paper describes the thermal testing and characterization capabilities of the Laser Hardened Materials Evaluation Laboratory located at Wright-Patterson Air Force Base, Ohio. The facility features high-power carbon dioxide (CO2$ and neodymium:glass laser systems that can be teamed with vacuum chambers, wind tunnels, mechanical loading machines and/or ambient test sites to create application-specific thermal and environmental conditions local to the material sample or system. Representative results from recently conducted test series are summarized. The test series described demonstrate the successful use of a high power CO2 laser paired with environment simulation capability to : 1) simulate the expected in-service heat load on a newly developed heat transfer device to ensure its efficient operation prior to design completion, 2) simulate the heat load expected for a laser diode array cooler, 3) produce thermal conditions needed to test a radiator concept designed for space-based operation, and 4) produce thermal conditions experienced by materials use din solid rocket motor nozzles. Test diagnostics systems used to collect thermal and mechanical response data from the test samples are also described.
Researchers from the United States and Russia conducted laser-material interaction tests at the LOK Company, St. Petersburg, Russia. These tests were conducted using a one-of-a-kind, continuous wave, supersonic, e-beam-sustained carbon monoxide (CO) laser. The purpose of these tests were to characterize the laser while performing collaborative research between scientists from Russia and the United States. Additionally, the testing verified previously- reported laser characteristics. All planned laser-material interaction tests were successfully conducted. Several material samples were irradiated by the CO laser to allow calculation of the laser energy and power levels. Statistical errors were reduced by testing materials with different characteristics at varying laser energy and power levels. Laser-material interaction tests were also conducted at varying distances from the laser output window to assess beam quality and divergence.
Supporting laser/materials interactive testing for the past 15 years, the Laser-Hardened Materials Evaluation Laboratory (LHMEL) has efficiently performed low-cost high-volume testing of materials samples placed in various environmental simulation conditions. The capabilities of the upgraded LHMEL facility carbon dioxide laser and related test support systems are described. The LHMEL facility is part of Wright Laboratories Materials Directorate and is located at Wright-Patterson Air Force Base, Ohio. Two lasers producing a 10.6 micron wavelength, continuous wave output and having a flat-top spatial intensity distribution are currently available for testing. The test parameters achievable with the 15 kW LHMEL I and the 100 kW LHMEL II devices are discussed. In addition, various test environmental simulation capabilities are described. Vacuum environments in the 1 X 10-6 torr range are routinely achieved for samples ranging in size from 1 cm to 120 cm. Atmospheric velocities approaching Mach 1 for samples up to 7 cm are provided. Mechanical loads up to 55,000 lbs of force can be incorporated into ambient or high velocity testing schemes. Finally, the capability of the facility data acquisition system is described.
The application of laser systems to the investigation of the properties of materials has become an important part of materials research in recent years. The demand for laser systems capable of supplying high-energy, high-quality output beams on a reliable basis has sparked increased activity in the area of research and prototyping of such devices. Accordingly, the design and construction methods used to produce a 65 kdowatt Carton Dioxide Electric Discharge Coaxial Laser (EDCL) device are discussed. Specific design criteria are identified in accordance to the critical performance requirements for the laser device. Furthermore, the unique construction methods and support system requirements essential to EDCL technology are described along with test results. The 65 kilowatt C02 EDCL laser was constructed for the Laser Hardened Materials Evaluation Laboratory of the Air Force Materials Laboratory located at Wright-Patterson Air Force Base, Ohio under contract F33615-84-C-5086.