Abstract: Apparatus (10) for use in determining values of properties of n layers (16,17) of a borehole (11) formed in the Earth's crust (12) comprises a plurality of at least (2n-1) sensor members (19,21,22) of mutually differing, known or calculable, geometric factors, as defined with reference to a sample under investigation comprising n layers. The sensor members (19,21,22) are capable of detecting reflected or transmitted electromagnetic energy and the apparatus (10) includes one or more supports (24,26?) for supporting the sensor members (19,21,22) in a said borehole (11) adjacent and/or in contact with one or more said layers (16,17), the apparatus (10) being capable of causing transmission of electromagnetic energy along, and/or reflection of electromagnetic energy at, each sensor member (19,21,22) in a manner permitting the calculation of values of properties of such layers (16,17) based on reflected or transmitted energy values detected at the sensor members (19,21,22).

Abstract: A reflectometer sensor element comprises (i) a recess formed in an electrically conducting material, the electrically conducting material defining a connection portion; the recess including an open end at or adjacent a surface of the electrically conducting material; and a transverse cross-sectional area defined by at least one wall of the recess increasing in at least a first region between the connection portion and the open end; (ii) an electrically conducting electrode that is spaced from the said at least one wall of the recess and extends between the open end and a location proximate the connection portion; and (iii) one or more dielectric materials occupying at least part of the recess between the at least one wall of the recess and the electrically conducting electrode. Such an element allows the detection of signals reflected from deeper within subterranean rock than has previously been possible.

Abstract: Apparatus (57, 58) for determining permittivity in a downhole location comprises a sensor (57) including an elongate conducting line (62) supported on or adjacent a first side of a dielectric substrate (61). The sensor (57) also includes at least one conducting ground element (26, 27) that is spaced from the conducting line (62), the conducting line (62) being capable of juxtaposition to a downhole borehole wall (12). The apparatus further includes connected respectively to spaced locations along the conducting line at least two terminals (31, 32; 63, 64) of a vector network analyser (57b) that is capable of detecting one or more signal reflection characteristics whereby when the sensor (57) is juxtaposed to a borehole wall (12) the vector network analyser (57b) generates one or more signals that are processable to indicate the relative permittivity of rock (39) in which the borehole is formed.

Abstract: Apparatus (10) for use in determining values of properties of n layers (16,17) of a borehole (11) formed in the Earth's crust (12) comprises a plurality of at least (2n-1) sensor members (19,21,22) of mutually differing, known or calculable, geometric factors, as defined with reference to a sample under investigation comprising n layers. The sensor members (19,21,22) are capable of detecting reflected or transmitted electromagnetic energy and the apparatus (10) includes one or more supports (24,26?) for supporting the sensor members (19,21,22) in a said borehole (11) adjacent and/or in contact with one or more said layers (16,17), the apparatus (10) being capable of causing transmission of electromagnetic energy along, and/or reflection of electromagnetic energy at, each sensor member (19,21,22) in a manner permitting the calculation of values of properties of such layers (16,17) based on reflected or transmitted energy values detected at the sensor members (19,21,22).

Abstract: A reflectometer sensor element comprises (i) a recess formed in an electrically conducting material, the electrically conducting material defining a connection portion; the recess including an open end at or adjacent a surface of the electrically conducting material; and a transverse cross-sectional area defined by at least one wall of the recess increasing in at least a first region between the connection portion and the open end; (ii) an electrically conducting electrode that is spaced from the said at least one wall of the recess and extends between the open end and a location proximate the connection portion; and (iii) one or more dielectric materials occupying at least part of the recess between the at least one wall of the recess and the electrically conducting electrode. Such an element allows the detection of signals reflected from deeper within subterranean rock than has previously been possible.

Abstract: A method of optimizing the cross-sectional shape of a logging tool sensor includes the step of, for a given major axis dimension, selecting the minor axis dimension such that for a circular borehole geometry the cross-sectional area of the space between the sensor and a said circular borehole with which the sensor is pressed into contact is minimized. Logging tools optimized according to this technique exhibit beneficial sensor stand-off characteristics.

Abstract: A method of optimising the cross-sectional shape of a logging tool sensor includes the step of, for a given major axis dimension, selecting the minor axis dimension such that for a circular borehole geometry the cross-sectional area of the space between the sensor and a said circular borehole with which the sensor is pressed into contact is minimised. Logging tools optimised according to this technique exhibit beneficial sensor stand-off characteristics.

Abstract: Apparatus (57, 58) for determining permittivity in a downhole location comprises a sensor (57) including an elongate conducting line (62) supported on or adjacent a first side of a dielectric substrate (61). The sensor (57) also includes at least one conducting ground element (26, 27) that is spaced from the conducting line (62), the conducting line (62) being capable of juxtaposition to a downhole borehole wall (12). The apparatus further includes connected respectively to spaced locations along the conducting line at least two terminals (31, 32; 63, 64) of a vector network analyser (57b) that is capable of detecting one or more signal reflection characteristics whereby when the sensor (57) is juxtaposed to a borehole wall (12) the vector network analyser (57b) generates one or more signals that are processable to indicate the relative permittivity of rock (39) in which the borehole is formed.

Abstract: An acousto-optic modulator for a Q-switch (300) for a laser includes a monolithic acousto-optic (a-o) medium (311), a series of at least two acoustic transducers (321, 322), bonded spaced apart on the a-o medium, which emit first and second columnar acoustic beams (331, 332). These interact sequentially with an incident optical beam (Light) passing through the modulator. The transducers are oriented so that an optical ray (342) diffracted from the first acoustic column region enters the second acoustic column region at an angle outside the “acceptance angle” of the second acoustical column, i.e. outside the range of incidence angles for which the diffraction efficiency is significant, whereas the remaining light in the zeroth order will undergo further diffraction at the second acoustic column region. This arrangement significantly reduces the amount of light diffracted by the first beam being diffracted back into the zeroth order by the second acoustic beam.

Abstract: An acousto-optic modulator for a Q-switch (300) for a laser includes a monolithic acousto-optic (a-o) medium (311), a series of at least two acoustic transducers (321, 322), bonded spaced apart on the a-o medium, which emit first and second columnar acoustic beams (331, 332). These interact sequentially with an incident optical beam (Light) passing through the modulator. The transducers are oriented so that an optical ray (342) diffracted from the first acoustic column region enters the second acoustic column region at an angle outside the “acceptance angle” of the second acoustical column, i.e. outside the range of incidence angles for which the diffraction efficiency is significant, whereas the remaining light in the zeroth order will undergo further diffraction at the second acoustic column region. This arrangement significantly reduces the amount of light diffracted by the first beam being diffracted back into the zeroth order by the second acoustic beam.