The quartz cuvette was held in a metal jacket which has been machined with channels to allow for water to circulate through the metal block in order to control the temperature of the quartz cuvette using a water bath and pump (Figure ). A thermocouple was fitted to the block to allow for accurate temperature control. During the THz-TDS measurement, the assembled crystallisation cell was positioned at the focal position of the measurement chamber and the terahertz beam propagated through the centre of the cuvette with a beam width of about 2 mm.