Fusion Engineering and Design 84 (2009) 1937–1940 Contents lists available at ScienceDirect Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes A TIEMF model and some implications for ITER magnetic diagnostics R. Vila ∗ , E.R. Hodgson Euratom/CIEMAT Fusion Association, Avenida Complutense 22, Madrid 28040, Spain article info Article history: Available online 26 May 2009 PACS: E0100 (electrical properties) R0400 (radiation effects: physical properties) Keywords: RIEMF TIEMF RITES Cables Thermopower Magnetic coils ITER abstract Radiation and temperature induced voltages and associated currents (generally termed RIEMF and TIEMF, respectively) have been found to occur in both MI coaxial cables and ceramic coated single cables. This is an important issue because TIEMF will make extremely difficult, if not impossible, to separate the radiation and temperature effects from the required signal for the ITER magnetic diagnostic coils. For operation in ITER, the problem is expected to be worse, the varying neutron energy spectrum and dose over the whole cable path, will give rise to a non-uniform transmutation and could induce TIEMF effects, even in initially perfect cables. It has been previously reported that TIEMF are generated in well localized regions of the central conductor (inhomogeneities). This paper present a model that explains observed TIEMF features and also some predictions concerning the EMF induced at the integrators input. Of particular importance is that some geometric configurations expected to be problematic, result in almost zero TIEMF despite the above mentioned effects, providing a more optimistic view of this problem. Some solutions are provided to mitigate cabling issues. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Work done in recent years has clearly demonstrated that radiation and temperature induced voltages (RIEMF and TIEMF, respectively) appear in all the cables studied so far (MI coaxial cables, ceramic and enamel coated single cables) [1–8]. TIEMF appears as generation of a voltage along the centre conductor of cables due to temperature gradients, (particularly large for MI Cu cored cables) and cable inhomogeneity. The immediate consequence is that TIEMF will make extremely difficult, if not impossible, to separate the radiation and temperature effects from the required signal for some of the ITER magnetic diagnostic coils (low-signal ones). While considerable progress has been made in the understanding and even general modelling of RIEMF, no detailed TIEMF modelling has been fully developed until now. A crucial aspect recently established is that the TIEMF voltages (even without irradiation) are generated in well localized regions of the central conductor, suggesting that some inhomogeneity is present [4,7]. Optical and SEM examination indicates that mechan- ical damage of the inner wire, and/or ceramic incrustation (for MI cables) may be two causes of these inhomogeneities [6]. Impu- rities are also good candidates because very low levels will vary substantially the thermoelectric response [9]. ∗ Corresponding author. Tel.: +34 913466580. E-mail address: rafael.vila@ciemat.es (R. Vila). As previously mentioned, the problem is expected to be worse during ITER operation. Even starting with initially perfect cables, the varying neutron energy spectrum and dose over the whole cable path, will give rise to a non-uniform transmutation (additional inhomogeneity), and induce TIEMF effects [10]. This is known as RITES (radiation induced thermoelectric sensitivity) [11]. As with RIEMF, TIEMF/RITES are problems with no easy solution. It must be fully understood and assimilated into the magnetic diag- nostics design. With this aim, the paper will first present a model that explain the main features of TIEMF from a multiscale point of view, i.e., from microscale defects up to the whole cable signal. In Section 3, using this model we simulate the expected effects on the EMF induced at the magnetic integrators for some magnetic diagnostics configurations. Important conclusions and design rec- ommendations arise from the presented analysis. It is worth noting that a strong interaction between materials/components choice and geometric design exists. 2. TIEMF model A simple model has been developed to try to understand the TIEMF results. A first assumption is that local impurities or phys- ical changes at very small scales (of the order of few millimetres or below) are the most probable causes of TIEMF. This has been validated by all the experimental results obtained so far [7–8]. The second one is that the underlying physical cause is a local change of the Seebeck coefficient. It is well known that impurities (see [9] 0920-3796/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.fusengdes.2009.01.025