First RF operations of the gyrotron for the DTT ECRH System

The Divertor Tokamak Test (DTT) facility will be equipped with one of the largest ECRH systems envisaged for fusion research. The system is organized in 4 clusters, each one composed of 8 gyrotrons fed in pairs by four main high voltage power supplies (MHVPS), with gyrotrons and MHVPS arranged on two separate floors of a new dedicated building. Since gyrotron specifications are similar to those of ITER, a joint procurement procedure was made between Fusion for Energy and DTT. The first DTT pre-series gyrotron was manufactured by THALES and is now under test at the FALCON facility. Based on successful results of the first tests, the contract for the following 15 units is started, to have the first two clusters available in 2031 for DTT phase 1. This work presents the results of the pre-series gyrotron and the design and manufacturing of an evacuated Quasi-Optical Connection Line (CL) conceived to connect the gyrotron with the RF load in free space propagation. The CL is composed by a shaped mirror to deflect the beam from the exit of gyrotron to the input of RF load. The mirror is additively manufactured in CuCrZr alloy, water cooled, assembled on a support and adjustable in two tilt angles. The mirror mount is placed inside a vacuum chamber that is cooled with an external jacket and equipped with two arms to maintain a vacuum region around the beam path transmitted from the gyrotron to the RF load. The chamber support allows the fine adjustment in x-y-z directions. The CL is designed to enable the tests of the gyrotron output beam and of different mirror technologies for R&D activities. Its optical and mechanical design was conceived to be compatible with the FALCON facility and with DTT ECRH building where will be used also for commissioning the gyrotrons.