The 15 UD pelletron is a versatile, heavy ion tandem type of electrostatic accelerator. In this machine, negative ions are produced and preaccelerated to ~300KeV in Ion Source and injected into strong Electrical field inside an accelerator tank filled with SF₆ insulating gas. At the centre of the tank is a terminal shell which is maintained at a high voltage (~15 MV).The negative  ions on traversing through the accelerating tubes  from the column top of the tank to  the positive  terminal gets  accelerated. On  reaching the  terminal  they pass through a stripper which removes some electrons from the negative ions, thus transforming the negative ions into positive ions. These positive ions are then repelled away  from  the positively  charged  terminal  and are  accelerated  to ground  potential  to the  bottom of the tank. In this manner same terminal potential is used twice to accelerate the ions. On exiting from the tank, the ions are bent into  horizontal plane by analyzing magnet, which also select a   particular beam of ion. The switching  magnet  diverts  the high  energy ion beams into various beam lines into the  different  experimental  areas of  the beam hall. The entire machine is computer controlled and is operated from the control room.
 

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