Abstract
A thermal radiation detector having a high frequency time constant of 5 μsec (which can easily be improved to better than 1 μsec) is described. The instrument has been used to measure the radiation from a high temperature gas discharge. In the detector a pyroelectric output is obtained when radiation is absorbed on to a piece of ferroelectric material (barium titanate) whose thickness is greater than the thermal diffusion depth for the length in time of the radiation pulse being measured. The electrical signal is examined theoretically and experimentally and is shown to be directly related to either the incident energy or flux, and it is also shown that the upper frequency response is limited by mechanical resonances of the ferroelectric (engendered by thermal expansion) rather than by a thermal time constant.
This device is very convenient since it is simple to construct and requires no auxiliary current supply.