Temperature control device and reaction vessel

Reaction vessels are known for use in polymerase chain reaction (PCR). However, temperature cycling of such vessels has been both expensive and complicated to implement. Described herein is processing apparatus which overcomes the problems mentioned above. The apparatus features a temperature control device which comprises two surfaces (46) to contact a reaction vessel (10) sandwiched between them. A heater element (54) is disposed on one side of one of the surfaces (46). The heater element (54) is cooled by means of a gas flow through a cavity (58) which is formed above the surface of the heater element (54). The cavity (58) includes an inlet aperture (60) for delivering cooling gas to the cavity (58) and heater element, and an exhaust aperture (62) for venting the air to atmosphere after it has cooled the heater element (54). Most preferably, there is further included means (76, 78) for providing relative movement between the temperature control device and a reaction vessel (10).