Method and apparatus for imaging microscopic spatial variations in small currents and magnetic fields
AssigneeUniversity of Maryland
InventorsFrederick C. Wellstood, Anna Mathai, Dian Song, Randall C. Black
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Abstract
A magnetic flux microscope that measures the magnetic field about a sample surface. The apparatus uses a thin-film superconducting quantum interference device (SQUID) as the scanning device. Magnetic shielding is provided about the SQUID and is held stationary relative to the SQUID. The apparatus and method provides a very high magnetic image of the sample with a very high spatial and field resolution.
Claims24
An apparatus for obtaining microscopic images of magnetic fields emanating from a sample, said sample being an object or specimen which is to be examined by said apparatus, said magnetic fields emanating from said sample, originating from said sample or being induced in said sample by means of an applied magnetic field, said images having a spatial resolution finer than 1 mm and said apparatus comprising:
- a dewar;
- at least one SQUID contained within said dewar, said SQUID having a loop or body being smaller than 1 mm and disposed within 1 mm of said sample;
- a magnetic shield about said dewar;
- a positioning assembly at least partially within said dewar and attached to said sample and said at least one SQUID, said sample being disposed in said dewar, and said positioning assembly for moving said sample and said at least one SQUID relative to each other while maintaining said SQUID within at least 1 mm of said sample, and for eliminating vibration which may affect said microscopic images having a spatial resolution finer than 1 mm;
- means for controlling the movement of said positioning assembly;
- and means for monitoring voltage across at least one of said SQUIDs within said dewar to obtain microscopic images of magnetic fields emanating from said sample, said voltage being an output from at least one of said SQUIDs and being generated by at least one of said SOUIDs responding to said magnetic fields emanating from said sample.
A method of obtaining images of magnetic fields from a sample, said sample being an object or specimen which is to be examined, said magnetic fields emanating from said sample originating from said sample or being induced in said sample by means of an applied magnetic field, said method comprising the steps of:
- placing a sample inside of a dewar;
- providing a magnetic shield about said dewar;
- moving a positioning assembly, disposed at least partially within said dewar, to position said sample and a SQUID relative to each other within said dewar, said positioning assembly also for maintaining said SQUID within at least 1 mm of said sample and for eliminating vibration which may affect microscopic images having a spatial resolution finer than 1 mm, wherein said SQUID has a loop or body smaller that 1 mm and is disposed within 1 mm of said sample;
- controlling the movement of said positioning assembly to vary the relative position between the SQUID and the sample while maintaining said SQUID within at least 1 mm of said sample;
- and monitoring a voltage across at least one of said SQUIDs within said dewar to obtain microscopic images of magnetic fields emanating from said sample, said voltage being an output from at least one of said SQUIDs and being generated by at least on of said SOUIDs responding to said magnetic fields emanating from said sample;
- and
- generating a microscopic image of magnetic fields emanating from said sample, said microscopic image having a spatial resolution finer than 1 mm, by plotting said output from said SQUID as a function of a position of said positioning assembly so as to represent microscopic spacial dependence of any magnetic fields emanating from said sample.
Dependencies are inferred from the claim text.