Year : 2022, Volume : 47, Issue : 1
First page : ( 25) Last page : ( 29)
Print ISSN : 0379-0479. Online ISSN : 2349-2120. Published online : 2022 January 04.
Article DOI : 10.5958/2349-2120.2022.00005.X

Preliminary studies on the development of planar inductor-based sensors for RRR measurement of thin-film Nb-coated samples

Venugopal Namitha, Nazer K H Abdul, Raj Hrithik Krishna, Sagar Pankaj^*

Department of Instrumentation, Cochin University of Science and Technology

^*E-mail ID: pankajs@cusat.ac.in

Online published on 4 December, 2023.

Bulk Niobium (Nb) based superconducting RF (SRF) cavities are the main component of a particle accelerator. The thermal performance of these SRF cavities can be estimated by the Residual Resistivity ratio (RRR) of the Nb used for its fabrication. RRR is the ratio of resistivity at 300K to resistivity at just above the critical temperature. More and more research is happening in thin film (TF) SRF cavities. RRR plays an important role in determining the Q factor of these cavities. The conventional method to measure RRR is by a four-probe resistance measurement technique. This technique is destructive and gives an average value of RRR over the entire length. Hence, a method that is more local and non-destructive is required. This work uses a planar inductor as a sensing element and TF Nb on a Copper (Cu) substrate as the target. The slope of the lift-off line (SLOC) is obtained from the impedance characteristics of a planar inductor by changing the distance between the sensor and the target (lift-off) at various frequencies. SLOC can be used for indirectly evaluating the resistance of the target. When this is cooled to a low temperature, there will be a change in the slope of the LOC, which can be directly correlated to the RRR of TF Nb. The impedance characteristics of the planar inductor are modeled in Ansoft Maxwell, and their results are discussed here.

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Keywords

Superconducting RF cavity, Residual Resistivity ratio, Eddy current, Planar inductor.

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