Rob IJsselsteijn

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The performance of an optically pumped Mx magnetometer with miniaturized Cs cell at earth's magnetic field strength (50 μT) is investigated. Operation using detuned high intensity laser light is shown to be superior to the conventional resonant operation in terms of the projected shot-noise-limited ( 50 fT/√Hz) and the actual noise-limited sensitivity using(More)
We compare the performance of two methods for the synchronization of the atomic spins in optically pumped magnetometers: intensity modulation of the pump light and the classical M(x) method using B(1) field modulation. Both techniques use the same set-up and measure the resulting features of the light after passing a micro-fabricated Cs cell. The(More)
We describe a method for charging atomic vapor cells with cesium and buffer gas. By this, it is possible to adjust the buffer gas pressure in the cells with good accuracy. Furthermore, we present a new design of microfabricated vapor cell arrays, which combine silicon wafer based microfabrication and ultrasonic machining to achieve the arrays of thermally(More)
We show the operation of an optically pumped magnetometer array in a 50 μT magnetic field. The various components for a fully optical and non-magnetic detector unit were constructed and evaluated, from which a prototype unit was assembled with fiber coupled electronics. In this unit the magnetometers were operated using the intensity modulated method and(More)
We have measured the current-phase relationship I(varphi) of symmetric 45 degrees YBa2Cu3O7-x grain boundary Josephson junctions. Substantial deviations of the Josephson current from conventional tunnel-junction behavior have been observed: (i) The critical current exhibits, as a function of temperature T, a local minimum at a temperature T*. (ii) At T(More)
SQUID magnetometers used in Transient Electromagnetics (TEM) surveys have become a valuable tool for exploring difficult targets during the last decade. Over the past 12 years, IPHT has developed SQUID systems for TEM applications, based on "High Temperature" Superconductors (HTS, Yttrium-Barium-Copper-Oxide YBCO), cooled with liquid nitrogen at 77 K. Test(More)
Directly coupled dc SQUID gradiometers on the basis of YBqCu,O, for unshielded NDE measurements are investigated. The influence of different SQUID layout parameters on the field sensitivity is shown. A sensitivity of 500 ffl(crn.JHz) is achieved with a baseline of 3.6 mrn. A slit in an aluminium plate was detected in an demonstration of NDE in 1 cm depth(More)
SQUID systems, using either high temperature or low temperature superconductors, were developed for sensitive measurements in magnetically disturbed environments. They include the SQUIDs and fast SQUID electronics. Magnetometer SQUID systems are used for geophysical sounding, where they show superiority when compared to conventional induction coils for very(More)
Focused ion beam etching has been used to pattern dc SQUIDs into previously characterised template biepitaxial grain boundary junctions. In this way, the screening parameter ~t~ can be optimised for a chosen temperature (in our case 30 K). Electrical characteristics, including noise measurements, are presented. A minimal white noise level of 22 ~tqbo.HZ m(More)