LTCC and Thick-film Ceramic Magnetic Sensors for Tokamak Nuclear Fusion

Maeder, Thomas; Jacq, Caroline; Testa, D.; Toussaint, M.; Stöck, Martin; Corne, Adrien; Güniat, Lucas; Ellenrieder, Benoit R.; Jiang, Xinyue; Windischhofer, Philipp; Schlatter, Christian; Ryser, Peter

doi:10.1016/j.proeng.2016.11.235

Cited by 6 publications

(3 citation statements)

References 9 publications

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“…The LTCC processing and results obtained with these inductive magnetic sensors are presented in refs. [2][3][4][5][6][7][8][9]. Figure 1 shows a 3D design of an LTCC magnetic sensor: multiple planar turns (m) are screen-printed on a ceramic substrate and then multiple layers (n) are electrically connected in series using vertical tracks (the vias).…”

Section: Introductionmentioning

confidence: 99%

“…As can be easily seen in figure 2 (reproduced from [2]), when many turns (all with the same 𝑑𝑑1 = 100 μm = 𝑠𝑠1) are needed to obtain the desired 𝑁 𝐴 EFF , the inner-most turns on the same plane (= 𝑚) contribute significantly less to the effective area 𝑁 𝐴 EFF (𝑚 × 𝑛), while still adding to the self-inductance of the sensor 𝐿 SELF ∼ (𝑚 × 𝑛) 2 . In this example, a sensor was built for each planar design always using 𝑛 = 4 layers, and varying 𝑚 = [1,5,10,20]. The measurements for the effective area and self-inductance of these sensors are presented in table 1.…”

Section: Introductionmentioning

confidence: 99%

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First developments towards producing inductive magnetic sensors using state-of-the-art photolithography techniques

Testa,

Cemes,

Douhane

et al. 2023

J. Inst.

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Inductive magnetic sensors are needed for tokamak operation to provide the low-frequency (LF) measurements leading to the equilibrium reconstruction and to monitor the higher frequency (HF) instabilities; the HF magnetic sensors are often also used as a back-up to the LF ones. For the HF inductive magnetic sensors (fluctuation measurements), we need to minimize the self-inductance (L SELF) provided that the effective area (N A EFF) remains sufficiently large, typically requiring L SELF < 100 μH and N A EFF ∼ 0.01 m2. For the LF inductive magnetic sensors (equilibrium reconstruction), the only physics-based design criteria are that of maximizing N A EFF > 0.10 m2, essentially independently of the resulting L SELF. Due to these rather different measurement specifications, it is quite the common case that different sets of LF and HF inductive magnetic sensors are used, which significantly complicates the R&D activities and the ensuing manufacturing processes. Starting in 2007, our group at the Swiss Plasma Centre at the Ecole Polytechnique Fédérale de Lausanne (EPFL) has originally developed the Low-Temperature Co-fired Ceramic (LTCC) technology for producing inductive magnetic sensors, this technology being exceptionally suitable for operating temperatures up to ∼1'000C in very harsh environmental conditions. The similarly named High-Temperature (HTCC) technology uses the same processes but different materials, and it is then suitable for operating temperatures up to ∼1'600C. ITER will have about ∼250 such LTCC sensors, of EPFL design and prototyped at the EPFL, but manufactured by a commercial entity to technical specifications lower than those achieved at the EPFL in terms of track width, track separation and overall manufacturing yields. While state-of-the-art in 2007, the LTCC and HTCC technologies are now at least 20 years old and new processes have been developed for commercial applications, essentially based on different photolithography (PL) techniques. Recent, and already industrialized, advances in microfabrication using PL techniques offer the possibility to create more compact and optimized designs starting from current industrial standards, therefore extremely facilitating the very costly lab-to-fab step of production, namely all the activities that lead from the ideas in the lab to the actual (industrialized) fabrication. Our goal is to continue to push the frontier of magnetic sensors, bring a commercially viable design that can be used in tomorrow's scientific projects, such as nuclear fusion and astronomy/astrophysics (for instance, in the new generations of miniaturized satellites). The main advantage of the PL techniques is that a much smaller track width (dd1) can be achieved, down from the routine dd1 = 100 μm of the EPFL LTCC sensors (for ITER: dd1 = 400 μm) to dd1 < 10 μm. A smaller dd1 allows to pack more planar winding loops (m) enclosing a larger area over a smaller geometrical surface. Therefore, PL coils can have a lower self-inductance L SELF ∝ m2 while having the same effective area N A EFF ∝ m compared to coils manufactured by other more common technologies. Therefore, with PL techniques a similar design could be used for both HF and LF applications, the difference simply being the number of stacked-up layers (n) used to make-up the entire sensor. In this paper we will present the first developments towards the production of inductive magnetic sensors using PL techniques. Whilst providing the possibility of designing better performing and more compact sensors, the introduction of PL techniques in the manufacturing processes for inductive magnetic sensors has uncovered new limitations and obstacles, such as the required vertical track thickness that is poorly suited for the existing deposition techniques, the need for stacking up multiple wafers and the connection between the sensor and the in-vessel cabling.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

First developments towards producing inductive magnetic sensors using state-of-the-art photolithography techniques

Testa,

Cemes,

Douhane

et al. 2023

J. Inst.

Self Cite

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“…High reliability and temperature stability completed by a wide freedom in design and the possible integration of low resistivity conductor paths made of gold or silver boosts their application as radio frequency (RF) devices [18][19][20][21] and for smart system integration [22][23][24]. The composite character of the fired ceramic allows the variation of functional properties, such as permittivity, thermal expansion, or insulation resistance [25,26].…”

Section: Introductionmentioning

confidence: 99%

Magnetron Sputtered AlN Layers on LTCC Multilayer and Silicon Substrates

et al. 2018

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This work compares the deposition of aluminum nitride by magnetron sputtering on silicon to multilayer ceramic substrates. The variation of sputter parameters in a wide range following a fractional factorial experimental design generates diverse crystallographic properties of the layers. Crystal growth, composition, and stress are distinguished because of substrate morphology and thermal conditions. The best c-axis orientation of aluminum nitride emerges on ceramic substrates at a heater temperature of 150 • C and sputter power of 400 W. Layers deposited on ceramic show stronger c-axis texture than those deposited on silicon due to higher surface temperature. The nucleation differs significantly dependent on the substrate. It is demonstrated that a ceramic substrate material with an adapted coefficient of thermal expansion to aluminum nitride allows reducing the layer stress considerably, independent on process temperature. Layers sputtered on silicon partly peeled off, while they adhere well on ceramic without crack formation. Direct deposition on ceramic enables thus the development of optimized layers, avoiding restrictions by stress compensating needs affecting functional properties.

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Producing high quality LTCC sensors for ITER in-vessel magnetic diagnostics

Adaikkan¹,

Walach

et al. 2022

Fusion Engineering and Design

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LTCC and Thick-film Ceramic Magnetic Sensors for Tokamak Nuclear Fusion

Cited by 6 publications

References 9 publications

First developments towards producing inductive magnetic sensors using state-of-the-art photolithography techniques

First developments towards producing inductive magnetic sensors using state-of-the-art photolithography techniques

Magnetron Sputtered AlN Layers on LTCC Multilayer and Silicon Substrates

Producing high quality LTCC sensors for ITER in-vessel magnetic diagnostics

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