SQUIDS and their applications in the measurement of weak magnetic fields

Squid biomagnetic measurements

“…The purpose of making a measurement of CP is to deduce from it the number of iron atoms per unit volume in the organ of interest. However, as we will now show, for normal iron concentrations the direct contribution of iron to the flux given by Equation 12 is generally very small. Suppose for the moment that the whole body has a position independent susceptibility x and that & is a uniform field supplied by large coils.…”

“…We will also suppose that the detector coil is large enough to produce a uniform BD over the body. From Equation 12 we then have that the ratio @(organ)/@(torso) is just the associated volume ratio. In the following discussion we focus on the liver which is largest organ of interest but even for the liver the ratio is only aboht 2%.…”

Biomagnetic Methods: Technologies Applied to Pharmaceutical Research

“…Magnetic flux quantization means that the magnetic flux through a superconducting loop is always an integer multiple of the magnetic flux. Josephson junction consists of two superconductors separated by a thin insulating barrier that allows tunneling of a pair of electrons (Cooper pair) through the barrier to maintain phase coherence (86,88). Cooper pair tunneling through the barrier introduces a phase shift in the supercurrent that translates in an intensity given by I=I 0 sinδ, where I 0 is the critical current and δ is the phase difference as the current tunnels the two insulating barriers in the superconductors.…”

A proposed method for measuring the electric dipole moment of the neutron using acceleration in an electric-field gradient and ultracold neutron interferometry

“…Reduction of Effects of Variations. The variation of the magnetic fields can be examined with SQUID gradiometers [17] but the ultimate test will have to be done with UCN. This could be done by measuring P x as a function of frequency (Fig.…”