29th Symposium on Fusion Technology (SOFT 2016)

P3.027 Beam duct for the 1 MW neutral beam heating injector on TCV

Sep 7, 2016, 11:00 AM

1h 20m

Foyer 2A (2nd floor), 3A (3rd floor) (Prague Congress Centre)

Board: 27

Poster B. Plasma Heating and Current Drive P3 Poster session

Speaker

Matthieu Toussaint (Swiss Plasma Center)

Description

The Tokamak à Configuration Variable (TCV) has been recently equipped with a 1 MW neutral beam heating (NBH) injector¹1. Two new stainless steel ports with rectangular aperture of 170x220mm have been manufactured and installed for this purpose. The NBH injector is connected to one of them via a stainless steel port extension. The port and its extension together form the beam duct between the vacuum vessel (VV) and the injector. A preliminary thermal analysis of the beam duct showed no expectation of thermal events such as overheating. Indeed, although the beam power flux near the internal faces of the beam duct reaches a maximum of 2 kW/cm²2, the very grazing incidence angle was expected to reduce the effective wall flux by an order of magnitude. As a result, the design and manufacturing of the beam duct did not include any provision for cooling. However, early in 2016 the commissioning of the NBH injector showed high overheating of the port extension, resulting in local melting and ultimately loss of vacuum insulation. This paper describes the thermal measurements and improvement of the installed uncooled beam duct and the design, analysis, manufacturing and installation of a new beam duct with an integrated cooling system. This work was supported in part by the Swiss National Science Foundation. [1] A. N. Karpushov et al., Neutral beam heating on the TCV tokamak. This conference.