Engineering design of the double neutral beam injection system for MAST Upgrade

The objectives of the upcoming upgrade to the Mega-Ampere Spherical Tokamak (MAST) require the construction of a new neutral beam injection system. Although the principle of operation is similar to other beamlines including those on JET, the design process is complicated by strict requirements such as the need for intensive ion source commissioning. A double neutral beamline has been designed which satisfies the requirements. This paper reports the engineering design of the MAST Upgrade double beamline, describing the key challenges and unusual solutions adopted.