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A signal input coil made of superconducting thin film for improved signal-to-noise ratio in a high-Tc SQUID-based ultra-low field nuclear magnetic resonance system

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2013 Supercond. Sci. Technol. 26 115008
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Supercond. Sci. Technol. 26 (2013) 115008 (4pp)


A signal input coil made of superconducting thin film for improved signal-to-noise ratio in a high-Tc
SQUID-based ultra-low field nuclear magnetic resonance system
Kuen-Lin Chen1,2 , Chin-Wei Hsu3 , Yue-Bai Ku3 , Hsin-Hsien Chen3 ,
Shu-Hsien Liao3 , Li-Min Wang2 , Herng-Er Horng3 and
Hong-Chang Yang1,2

Department of Electro-Optical Engineering, Kun Shan University, Tainan 710, Taiwan
Graduate Institute of Applied Physics and Department of Physics, National Taiwan University,
Taipei 106, Taiwan
Institute of Electro-Optical Science and Technology, National Taiwan Normal University, Taipei 116,


Received 8 July 2013, in final form 27 August 2013
Published 7 October 2013
Online at
Resonant coupling schemes are commonly used in SQUID-based ultra-low field (ULF) nuclear magnetic resonance (NMR) systems to couple the spin relaxation signals from samples to the SQUID. Generally, in NMR systems, a resonant coupling scheme is composed of two solenoid coils which are made of enamel insulated wires and a capacitor connected in series. In this work, we tried to replace the metal solenoid input coil with a planar high-Tc superconducting spiral coil to improve the signal-to-noise ratio (SNR) of the ULF NMR signal. A measurement of the free induction decay signal of water protons was performed to demonstrate the improved performance of the system. This improvement is due to the fact that the planar superconducting spiral coil possesses a higher mutual inductance with the SQUID.
Therefore, it is a promising way to enhance the SNR of high-Tc SQUID-based ULF
NMR/MRI systems.
(Some figures may appear in colour only in the online journal)

1. Introduction

etc. Furthermore, a multifunctional magnetoencephalography
(MEG) and ULF MRI integrated system has been developed and demonstrated [12–14]. The potential of practicability and commercialization for ULF NMR/MRI systems is gradually maturing. The reader who is interested in the recent development and perspectives of ULF NMR/MRI systems may refer to [15]. From the viewpoint of its applications, the high-Tc SQUID-based ULF NMR system has attracted more and more attention because of its economic cryogenic cooling.

SQUID-based ultra-low field nuclear magnetic resonance
(ULF NMR) systems have been in the spotlight for several years because of their strong application potential, especially in the research field of biomagnetism. Several works have been reported showing that a SQUID-based
ULF NMR system can successfully be applied to chemical
J-coupling measurements [1–5], magnetic resonance imaging
(MRI) [1, 4, 6–9] and immunoassay detection [9–11],


c 2013 IOP Publishing Ltd Printed in the UK & the USA

Supercond. Sci. Technol. 26 (2013) 115008

K-L Chen et al

In the development of ULF NMR/MRI systems, the detection of signals with high quality is always a very important topic. The resonant coupling scheme is an effective method which has been widely used in both high-Tc and low-Tc ULF NMR systems to transfer NMR signals to the
SQUID. It is generally composed of two coils and a capacitor
C in series. One of these…