A. Clippingdale

An ultra-low-noise electrical-potential probe for human-body scanning

In this paper we describe a new very-low-noise, high-input-impedance probe developed to make non-contact measurements of electrical potentials generated by currents flowing in the human body. With a noise level of 2 µV Hz-1/2 at 1 Hz, down to 0.1 µV Hz-1/2 at 1 kHz, and an operational bandwidth from 0.01 Hz to 100 KHz, this probe would seem well suited to the detection of a wide range of electrical activity in the body.

Ultrahigh impedance capacitively coupled heart imaging array

We describe a prototype electrocardiographic (ECG) array system comprising 25 ultrahigh impedance sensors, which does not require ohmic electrical contact with the body.

Non-contact VLSI imaging using a scanning electric potential microscope

We describe the design and use of a novel scanning microscope which detects changes in electric potential above a surface. We demonstrate that this can be employed to image integrated circuits of considerable complexity in various modes of operation and at a spatial resolution of m. We discuss the advantages of applying this imaging technique to the non-invasive evaluation of very large scale integrated circuits and consider possible limits to its resolution and sensitivity in this role.

The Response of a Superconducting Weak-Link Ring to External Adiabatic Noise (*).

SummaryWe discuss the response of a superconducting weak-link ring to externally applied adiabatic noise and show that this can be used as a probe of the low-lying energy eigenstates of the ring. We compare the observable consequences of this with new experimental results.

Non-invasive dielectric measurements with the scanning potential microscope

The scanning potential microscope (SPM) is a new form of scanning microscope, which maps distributions of spatial potential by direct measurement. The SPM may be used to study, non-invasively, the electrical properties of samples through the potential distribution created near the sample in response to an applied electric field. Spatial resolution and sample to SPM spacing are both close to 1 mu m at the present stage of development of the instrument. We present an SPM study of a test sample comprising three dielectric layers with differing relative permittivities: a 35 mu m film of cellulose acetate (CA, epsilon r approximately=5); a 25 mu m film of polyvinylidenefluoride (PVDF, epsilon r approximately=8.4); and a 50 mu m film of polytetrafluoroethylene (PTFE, epsilon r approximately=2-2.1). In the experimental set-up a small, audio-frequency electric displacement was applied through the sample. SPM mapping of the resultant potential distribution close to the sample yielded values of relative permittivity that were within 2% of the material specifications.

Probing the non-linear electric susceptibility of ultra-small capacitance weak links

Abstract We describe a noise fluctuation technique to monitor the voltage periodic electric susceptibility of ultra-small capacitance (⋍ 10 −16 F) superconducting weak links operating at liquid helium temperatures. We show that this can yield information on the ground and low lying excited states of these weak links.

Adding dissipation to the Schrdinger equation from the quantum-potential viewpoint

We discuss methods of adding dissipation to the Schrödinger equation in light of the quantum-potential interpretation of quantum mechanics. This favors nonlinear equations in general and Kostins Schrödinger-Langevin equation in particular. We give a simple example, the damping of small coherent oscillations.

Non-linear behaviour in the rf-SQUID magnetometer

Abstract Using a particular example, the radio frequency SQUID magnetometer we introduce a novel type of non-linear system, where a non-linearity arises in a linear classical oscillator due to the presence of a macroscopic quantum object. The non-linear behaviour found in this system is discussed and related to possible experimental investigation of the joint system, and of the quantum object in particular.

Pair charge superpositions in ultra small weak link structures

Abstract We show that it is perfectly practicable to probe quantum superpositions of pair charging states in ultra small capacitance (10 −16 to 10 −17 F) superconducting weak link structures. We demonstrate experimentally that these superpositions can be inferred from the noise fluctuations in a classical resonant circuit coupled to the weak link. These voltage dependent superpositions are also reflected in the dynamical behaviour of the weak link when driven by this external resonant circuit.

SQUID rings as macroscopic quantum objects: The quantum‐classical interface

We consider the interaction of a SQUID ring in the ultra small capacitance quantum limit. We show that the energy level structure of such a SQUID ring, arising from its quantum mechanical behaviour, leads to a novel spectroscopy. We give examples of the way in which this spectroscopy is made manifest through the interation of SQUID ring with a classical circuit apparatus. (AIP)