342 



Additional Heating 



In JET the plasma is created and 

 heated by passing a current of up to 5 

 million amperes through the gas As 

 the temperature increases the heating 

 produced by the plasma current 

 becomes less effective Additional 

 heating methods are therefore needed 

 if the temperatures required for fusion 

 are to be achieved 

 The two additional healing methods 

 being usecfon JET are neutral beam 

 iniection heating and radio frequency 

 heating 



Neutral Beam Injection Heating 



The miection of energetic particles into 

 the plasma is a proven method of 

 raising its temperature 

 A beam of charged particles is 

 produced in a plasma source and then 

 accelerated to increase its energy For 

 charged particles to cross the 

 magnetic field, used to confine the 

 plasma, they have to be neutralized 

 This is achieved by passing them 

 through hydrogen gas 



In the plasma the neutral particles give 

 up their energy by collisions and 

 hence raise its temperature JET will 

 have two injection units producing 10 

 million watts (MW) of heating 



Radio-Frequency Heating 



Ions and electrons in the plasma spiral 

 rapidly along the field lines of the 

 magnetic cage Energy can tie given to 

 the ions if radio waves of a given 

 frequency are beamed into the plasma 

 Oh JET radio-frequency waves in the 

 range 25-55 MHz will be used to 

 increase the energy of the ions in the 

 core of the plasma Ten aerials will be 

 fitted to the interior of the vacuum 

 vessel providing 1 5 million watts of 

 tieating 



Control Room 



JET uses a computerised Control and Data Acquisition 

 System (CODAS) to provide a flexible easy and safe 

 method of operation JET is controlled and monitored from 

 the two control rooms using a network of 32 mini-computers 

 The operation of the machine is controlled from one room, 

 while measurements on the plasma are carried out m the 

 other Each computer controls one of the many sub-systems 

 of the apparatus 



Signals to and from the CODAS system are transmitted 

 around the site as light signals via 19 fibre-optic loops at a 

 rate of 5 million bits per second 

 Acquisition of experimental data from the diagnostics 

 equipment requires in excess of l million items of data to be 

 gathered during each pulse 



