Patent ID: 8009000

Claim:
An apparatus for applying a magnetic field to a sample, comprising: at least first and second bodies each configured as a loop and together arranged to define a common passage for the sample, each of the first and second bodies including magnetic material; the first and second bodies being disposed so as to be rotatable relative to one another about a common axis of said common passage; each of the first and second bodies comprising at least two segments, the at least two segments of both of the first and second bodies being connected by coupling devices, the coupling devices and the segments being configured to provide for selective displacement of a first set of segments formed of segments of each of said first and second bodies relative to a second set of segments formed of segments of each of said first and second bodies from a closed loop relative position to an open loop relative position creating an opening between said first set of segments and said second set of segments breaking said loops and permitting introduction of said sample into said common passage through said opening; said second body being disposed within said first body so as to rotate relative said first body about the common axis of the common passage; said at least two segments of said first body each including as the magnetic material permanent magnets arranged circumferentially with varying orientations relative circumferentially adjacent ones of said magnets to form a first circuitous magnetic array; said at least two segments of said second body each including as the magnetic material permanent magnets arranged circumferentially with varying orientations relative circumferentially adjacent ones of said magnets to form a second circuitous magnetic array; and said first magnetic array and said second magnetic array being rotatable relative each other from a first position whereat the first and second magnetic arrays align to constructively combine magnetic fields to provide a maximum magnetic field in said common passage, to a second position whereat the first and second magnetic arrays align to destructively combine magnetic fields to provide a minimum magnetic field in said common passage with said first set of segments aligned and said second set of segments aligned to permit said selective displacement of said first set of segments relative to said second set of segments to said open loop relative position facilitated by the minimum magnetic field minimizing force required for said selective displacement to said open loop position to form said opening and allow introduction of said sample through said opening; wherein the first and second bodies are made of non-ferromagnetic material housing the magnets as the magnetic material; and wherein the permanent magnets have a polygonal cross-section having n/2 corners for an even number n of permanent magnets used.