The Transmission Line for the SPIDER experiment

Passive protections against breakdowns between accelerating grids in SPIDER experiment

“…This is obtained by the realization of an Outer Screen OS (in blue in Fig. 1), which is formed by the vessel itself and by the external screen of the Transmission Line and is connected to the sheet on the floor of the HV Deck HVD, the insulated platform hosting all the power supplies for the Ion Source [3]; clearly the effectiveness of the screening is improved by reducing the current flowing along the OS; at this purpose, the AGPS is connected to the TL and to the HVD by a 100 kV coaxial cable, screened by a sheet connected to the OS; the HF common mode currents flowing in the OS loop are blocked by a core inductor (in blue in the picture) coaxial to the HV cable. The con- nection between the OS and the Inner Screen IS (in green) is made by the RS resistors.…”

“…These effects are the grid damage, due to energy deposition by arcing, and the generation of strong Electro Magnetic Interference (EMI), due to the fast transient current flowing on the Transmission Line TL. A comprehensive strategy is proposed, including passive elements together with the TL design, reported in [3]. These components are an Output Filter (OF, constituted by a R-L parallel impedance) inserted in series to the Acceleration Grid Power Supply (AGPS), a Damping Resistor (DR, called also Damper) connecting the last accelerating grid to the vessel and a Distributed Core Snubber (DCS) consisting on a series of 10 ferrite magnetic cores wound on the central conductor of the TL, the High Voltage Screen (HVS).…”

The thermal measurement system for the SPIDER beam source

“…On the other hand, the part of the TC cables in the transmission line inner conductor [5] will have the same potential as the electric bushing flange, that is the potential of the plasma grid. This electrical layout introduces voltages between the ion source frame and the connection box for bias plate and plasma grid TCs (see Table 1), and between the electric bushing flange and the connector for ion source TCs; furthermore, very high transient over-voltages can occur during breakdowns.…”

Analysis of breakdown on thermal and electrical measurements for SPIDER accelerating grids

“…In order to calculate all the capacitive and inductive couplings between the 15 conductors a preliminary 2-D finite element analysis was made on a TL section. The design of the TL was taken from [7]. Table 1 reports the description of the 15 TL conductors.…”