The circuit of the 4-junction SQUID is analyzed, which has two series of Josephson junctions in each side of the SQUID coil. The 4-junction SQUID is considered to have the advantage of a larger voltage modulation depth than that of normal dc SQUID. We have tried to make its behavior clear by computer simulations. It has been found that the 4-junction SQUID has a different mode from that of normal dc SQUID in its dynamic behavior, which causes hysteresis in the I-V characteristics. It has also been found that a large voltage modulation depth can be realized in spite of large SQUID coil inductance, so the area of the primary coil can be more than 10 times larger. The noise performance of the 4-junction SQUID is also analyzed, and it is possible that the 4-junction SQUID has higher sensitivity by optimizing the circuit parameters.
Iddingsite in Martian nakhlites contains various secondary minerals that reflect water–rock interaction on Mars. However, the formation processes of secondary Fe minerals in iddingsite are unclear because they include carbonates precipitated under reductive and alkaline conditions and sulfates that are generally precipitated under oxidative and acidic conditions. Mineral types cannot coexist under equilibrium. Herein, we characterize the carbonate phase of meteorite Yamato 000593 as siderite and Mn-bearing siderite via field-emission electron probe microanalyzer (FE-EPMA). Then, we examined the distribution and speciation of trace Cr and S within the carbonates through synchrotron micro-focused X-ray fluorescence-X-ray absorption fine structure and scanning transmission X-ray microscopy (μ-XRF-XAFS/STXM) analysis to estimate the transition history of Eh-pH conditions during siderite formation to explain the coexistence of carbonate and sulfate phases in the nakhlite vein. Specifically, the distribution and speciation of S in the mesostasis and carbonate phases and the heterogeneous distribution of Mn-FeCO3 incorporating Cr(III) in the carbonate constrain the Eh-pH condition. The conditions and transition of the fluid chemistry determined herein based on speciation of various elements provide a new constraint on the physicochemical condition of the water that altered the nakhlite body during the Amazonian epoch.
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