The Effect of Transducer Response Rate on Thermal Radiation Data

Abstract

Abstract The Thermal Radiation Source (TRS) at ARL is used as a research tool to develop a reliable TRS unit for integration with the 2.44 m probative tube. Part of this study includes measuring the rise and fall times as well as the extent of flux variation of the TRS events. The Garden type gage is the primary transducer used to measure the flux output. This gage consists of a constantan diaphragm welded to a copper wire and body. This creates two thermocouple junctions. The electrical output of the gage is linearly related to the incident thermal radiation on the face of the diaphragm. A concern is about the response rate of these gages. The typical gage used in TRS work has a response rate of one time constant within 50 ms. In the past, the transient output of the TRS was considered slow. A faster acting gage was not necessary. To test this theory, a mathematical correction formula was applied to existing TRS data. The correction formulation was to demonstrate the actual incident radiation on the gage face by assuming a response rate. The data was processed using the correction formula. The results of the correction processing yielded a higher rise and fall time, as expected, but demonstrated a much higher flux variation during a TRS event. The overall fluence remained the same. To verify the correction formula is accurate, a special gage was constructed. It has a response rate of 6 ms to the first time constant. An experiment was conducted by placing the special gage next to a regular gage. The results show the faster acting gage produces a signal that matches the corrected signal of the slower gage, with one exception. The overall fluence increased. The most profound effect of this gage is realized when attempting to improve the performance of a TRS system. By realizing the capabilities of the gages, a more accurate determination of the thermal output of future TRS systems can be assessed. This will have direct impact on future Nuclear Survivability criterion by realizing the true capabilities of TRS systems.