These case studies are taken from work on Continuous modelling of heat radiation and underwater acoustics.

Heat radiation

A calorimeter has been designed and constructed to measure absorbed dose directly in a radiotherapy clinic. The quantity of interest in the clinic is absorbed dose to water (i.e. soft tissue) and the calorimeter is constructed from graphite because the radiation properties of graphite are very similar to those of water. The calorimeter consists of a front end (the calorimeter itself), means for thermal isolation and temperature control, and a measurement system. The temperature control system must be sensitive enough to allow measurements of temperature rises of the order of 1 mK and control of the temperature of the calorimeter to within ± 0.2mK over several hours has been achieved. The system is portable, opening up the possibility of making routine measurements in user radiation facilities.

Near-field to far-field prediction for underwater acoustics

Manufacturers of underwater acoustic transducers want to know the performance characteristics of their devices in the acoustic far-field. However, for some transducers, direct measurement in the far-field requires a large volume of water such as a lake or reservoir, which means making test measurements is an expensive and time-consuming task. As a solution to this problem, NPL has been investigating methods for predicting the far-field response of a transducer from measurements made in the near-field in a laboratory tank. NPL operates a large open tank equipped with a high-resolution positioning system, which is used for the near-field measurement scans.