DTIC ADA473328: Remote Measurement of High Temperatures pdf

DTIC ADA473328: Remote Measurement of High Temperatures

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The environment inside a railgun makes conventional temperature sensing techniques ineffective. Large time-varying magnetic fields induce noise into sensors with electrical connections. The high rate of change of temperature requires a fast thermal response and a fast sampling rate. Finally, the intense heat generated requires a sensor that is thermally stable over a large range of temperatures. To overcome such environmental challenges, this project utilized an interferometric technique where the temperature is measured remotely with a low power laser and a thin sapphire sensor. A sapphire sensor with a semi-reflective coating on one side and a near totally reflective coating on the other side was designed, constructed, and evaluated. To design the sensor for maximum sensitivity a computational model was developed to determine optimal coating thicknesses. To construct the sensor, nickel and nickel oxide coatings were deposited onto a sapphire dye with the use of electron-beam metal vapor deposition.

A laser was directed at the sensor at normal incidence, and the reflection from the sensor was collected with a photodiode. As the sensor s temperature was manipulated between 26 C and 355 C its reflectance changed due to variations in the optical properties of the sapphire, nickel oxide, and nickel. The data indicated the sensor responded in a manner similar to the theoretical model. Based on that data, an algorithm was developed to convert the collected optical signal into temperature data, creating a functional temperature sensing system. The system was then taken to the Naval Research Laboratory in Washington D.C. where it was used to monitor the temperature of a hollowed stainless steel cylinder through which high density current pulses were forced. The optical system s performance under such conditions was compared against a type K thermocouple, and the system demonstrated superior time response and relative immunity to electromagnetically induced noise

• Creator/s: Defense Technical Information Center
• Date: 5/7/2007
• Year: 2007
• Book Topics/Themes: DTIC Archive, Lord, Scott F, NAVAL ACADEMY ANNAPOLIS MD, *MAGNETIC FIELDS, *HIGH TEMPERATURE, *REMOTE SYSTEMS, THERMAL PROPERTIES, MATHEMATICAL MODELS, ALGORITHMS, HIGH POWER, LOW POWER, QUICK REACTION, REACTION TIME, COATINGS, VARIATIONS, TIME, SENSITIVITY, LASERS, REFLECTION, VAPOR DEPOSITION, STAINLESS STEEL, INTENSITY, IMMUNITY, HEAT, REFLECTANCE, NOISE, DYES, NAVAL RESEARCH LABORATORIES, THINNESS, SAMPLING, HIGH DENSITY, NICKEL COMPOUNDS, METAL VAPORS, ELECTRIC CONNECTORS, PHOTODIODES, SIGNALS, RESPONSE, CYLINDRICAL BODIES, OXIDES, PULSES, INTERFEROMETRY, ELECTRON BEAMS, SAPPHIRE, ELECTROMAGNETIC GUNS, HIGH RATE, MEASUREMENT, OPTICAL PROPERTIES, OPTICS, TEMPERATURE, THICKNESS

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