Transmitting oscillation suppression of low-Tc SQUID TEM system based on RC serial and multi-parallel capacity snubber circuit

Abstract

A low-temperature superconducting quantum interference device (low-Tc SQUID) can improve the depth of exploration. However, a low-Tc SQUID may lose its lock owing to oscillations in the current or the occurrence of spikes when the transmitter is switched off. If a low-Tc SQUID loses its lock, it becomes impossible for the low-Tc SQUID TEM system to function normally and stably for a long period of time. This hinders the practical use of the system. In field experiments, the transmitting current is accurately measured, the voltage overshoot and current spike data are recorded, and the gradient of the primary magnetic field at the center of the transmitting loop is calculated. After analyzing the results of field experiments, it was found that when the gradient of the primary magnetic field far exceeds the slew rate of a low-Tc SQUID, the low-Tc SQUID loses its lock. Based on the mechanisms of the transmitting oscillation, an RC serial and multi-parallel capacity snubber circuit used to suppress such oscillation is proposed. The results of simulation and field experiments show that, when using a 100 m×100 m transmitting loop, the gradient of the primary magnetic field is suppressed from 101.4 to 2.4 mT/s with a transmitting current of 40 A, and from 29.6 to 1.4 mT/s with a transmitting current of 20 A. Therefore, it can be concluded that the gradient of the primary magnetic field is below the slew rate of a low-Tc SQUID after adopting the proposed RC serial and multi-parallel capacity snubber circuit. In conclusion, the technique proposed in this paper solves the problem of a lost lock of a low-Tc SQUID, ensuring that the low-Tc SQUID TEM system functions stably for a long period of time, and providing technical assurance for ground TEM exploration at an additional depth.

Keywords

low-Tc SQUID / transmitter / oscillation / snubber circuit

References

[1] McCumberD E. Effect of AC impedance on DC voltage-current characteristics of superconductor weak-link junctions [J]. Journal of Applied Physics, 1968, 39(7): 3113-3118

[2] JosephsonB D E. Possible new effect in superconductive tunnelling [J]. Physics Letters, 1962, 1(7): 251-253

[3] LeslieK E, BinksR A, LamS K H, SullivanP A, TilbrookD L, ThornR G, FoleyC P. Application of high-temperature superconductor SQUIDS for ground-based TEM [J]. The Leading Edge, 2008, 27(1): 70-74

[4] BickM, PanaitovG, WoltersN Z Y, BousackH, BraginskiA I, KalberkampU, BurkhardtH, MatzanderU. A HTS rf SQUID vector magnetometer for geophysical exploration [J]. IEEE Transaction on Applied Superconductivity, 1999, 9(2): 3780-3785

[5] StolzR. SQUID technology for geophysical exploration [C]. SEG Annual Meeting, 2006894899

[6] PanaitovG, BickM, ZhangY, KrauseH J. Effect of repetitive transmitter signals on SQUID response in geophysical TEM [J]. IEEE Transactions on Applied Superconductivity, 2001, 11(1): 888-891

[7] ZhangY, LiuC, SchmelzM, KrauseH J, BraginskiA I, StolzR, XieX-m, MeyerH G, OffenhausserA, JiangM-heng. Planar SQUID magnetometer integrated with bootstrap circuitry under different bias modes [J]. Superconductor Science and Technology, 2012, 25(12): 4600-4609

[8] ChwalaA, StolzR, SchulzM, BauerF, IjsselsteijnR, KostlinE, MeyerH G. Liquid nitrogen cooled SQUID magnetometer for TEM [C]. AAPG International Conference and Exhibition, 20072629

[9] ChwalaA, SmitJ P, StolzR, ZakosarenkoV, SchmelzM, FritzschL, BauerF, StarkloffM, MeyerH G. Low temperature SQUID magnetometer systems for geophysical exploration with transient electromagnetics [J]. Superconductor Science and Technology, 2011, 24(12): 125006-125009

[10] ChangK, ZhangY, WangY-l, ZengJ, XuX-f, QiuY, KrauseH J, XieX-m, OffenhausserA. A simple SQUID system with one operational amplifier as readout electronics [J]. Superconductor Science and Technology, 2014, 27(11): 115004-115007

[11] NabighianM N. Time-domain electromagnetic methods of exploration: Foreword and introduction [J]. Geophysics, 1984, 49(7): 849-853

[12] OskueeM R J, KarimiM, NaderiN, RavadaneghS N, HosseiniS H. A new multilevel voltage source inverter configuration with minimum number of circuit elements [J]. Journal of Central South University, 2017, 24(4): 912-920

[13] QiLinKey technology and experiment of time-domain airborne electromagnetic transmitter [D], 2012, Changchun, Jilin University

[14] FuZ-h, ZhouL-w, SuX-f, DuXiong. Two novel quasi-resonant steep current impulse rectifying circuits [J]. Proceedings of the CSEE, 2006, 26(5): 70-75

[15] DengY, ZhaoZ-m, YuanL-q, HuS-d, WangX-song. IGBT model for analysis of complicated multi-IGBT circuits [J]. Proceedings of CSEE, 2010, 30(9): 1-7

[16] NingH-y, SunX-x, YangYuan. A high-power IGBT drive protection method based on diC/dt feedback control [J]. Transactions of China Electrotechnical Society, 2015, 30(5): 33-41

[17] ChenZ-j, CaiM, HeX-y, XuKen. 2.7-4GHz PLL with dual-mode auto frequency calibration for navigation system on chip [J]. Journal of Central South University, 2016, 23(9): 2242-2253

[18] JiY-juAll-time secondary electromagnetic field extraction in high resolution transient electromagnetic system for subsurface imaging [D], 2004, Changchun, Jilin University

[19] LiuY, RongL-l, JiangK, ChangK, KongX-y, XieX-ming. Simulation and experimental on shielding effect of radio frequency for superconducting magnetometer [J]. Chinese Journal of Low Temperature Physics, 2014, 36(2): 136-139