SIDON: A simulator of radio-frequency networks. Application to WEST ICRF launchers

Abstract

Abstract. SIDON (SImulator of raDiO-frequency Networks) is an in-house developed Radio-Frequency (RF) network solver that has been implemented to cross-validate the design of WEST ICRF launchers and simulate their impedance matching algorithm while considering all mutual couplings and asymmetries. In this paper, the authors illustrate the theory of SIDON as well as results of its calculations. The authors have built time-varying plasma scenarios (a sequence of launchers front-faces L-mode and H-mode Z-matrices), where at each time step (1 millisecond here), SIDON solves the RF network. At the same time, when activated, the impedance matching algorithm controls the matching elements (vacuum capacitors) and thus their corresponding S-matrices. Typically a 1-second pulse requires around 10 seconds of computational time on a desktop computer. These tasks can be hardly handled by commercial RF software. This innovative work allows identifying strategies for the launchers future operation while insuring the limitations on the currents, voltages and electric fields, matching and Load-Resilience, as well as the required straps voltage amplitude/phase balance. In this paper, a particular attention is paid to the simulation of the launchers behavior when arcs appear at several locations of their circuits using SIDON calculator. This latter work shall confirm or identify strategies for the arc detection using various RF electrical signals. One shall note that the use of such solvers in not limited to ICRF launchers simulations but can be employed, in principle, to any linear or linearized RF problem.

Validation of the ICRF antenna coupling code RAPLICASOL against TOPICA and experiments

“…Instead of comparing the strap impedances when a current vector is non-self-consistently imposed at the strap inputs (as performed in section 5.2), we perform in this section a benchmark between RAPLICASOL and TOPICA through advanced and realistic RF network calculations. The latter are similar to the calculations that are performed for the WEST ICRF launchers [30] and for the JET's ILA [31] to simulate their operation on plasma and to simulate the real-time control of their impedance matching systems. Here the array of straps of figure 18 is excited by the same feeding circuit as the one the WEST ICRF launchers (see figure 23) (for the details about the WEST ICRF launchers and their load-resilient feeding circuit, see [29,30,32]).…”

“…The latter are similar to the calculations that are performed for the WEST ICRF launchers [30] and for the JET's ILA [31] to simulate their operation on plasma and to simulate the real-time control of their impedance matching systems. Here the array of straps of figure 18 is excited by the same feeding circuit as the one the WEST ICRF launchers (see figure 23) (for the details about the WEST ICRF launchers and their load-resilient feeding circuit, see [29,30,32]). Every component of figure 23 is characterized by: an S-matrix derived from HFSS [33] for the feeding circuit (the variable capacitors, the bridges, the impedance transformers, the RF windows and the service stubs) and by a Z -matrix derived from RAPLICASOL or TOPICA for the array of straps.…”

“…For each D vac case, and using a RAPLICASOL or a TOPICA Z -matrix, we assess in this section: (a) the settings of the variable capacitors that impedance-match the launcher (the settings of the variable capacitors is found iteratively using an algorithm similar to the one of [30,31]), and, (b) the maximum power that can be coupled by the launcher at matching ( P inc,1 = P inc,2 is increased until reaching V max or I max at a strap input with V max and I max taken respectively as 35 kV and 1 kA).…”

“…The circuit of figure 23 involves multiport components described by S or Z -matrices and cannot be solved using Kirchhoff's laws. SIDON [30] is instead used here to solve the RF circuit: knowing the S or Z matrices for every component, the connections between them, and the excitations at the launcher's inputs (i.e. the values of P inc,1 , P inc,2 and ∆ϕ), SIDON finds the voltages and currents at all the components ports, in particular at the strap inputs.…”

WEST actively cooled load resilient ion cyclotron resonance heating system results

“…The WEST ICRH RF modelling, described in more details in [22,23], is summarized in this section. The antenna RF model uses a combination of full-wave models of the antenna's elements and equivalent lumped elements circuit of the tuning capacitors deduced from full-wave simulations (Figure 2).…”