1. A nuclear magnetic resonance apparatus comprising:
a sample chamber; and
a magnet assembly disposed about the sample chamber and constructed and arranged to provide a substantially non-uniform magnetic field having a known magnetic field gradient inside an approximate center of the sample chamber such that the substantially non-uniform magnetic field is controlled through one of a placement of at least one magnet or by one or more component;
a radio frequency (RF) coil positioned so as to substantially surround the sample chamber;
a controller coupled to the RF coil and constructed and arranged to control the RF coil to produce a RF pulse sequence; and
an RF power supply constructed an arranged to provide RF power to the RF coil to produce the RF pulse sequence.
2. The nuclear magnetic resonance apparatus as claimed in claim 1, wherein the magnet assembly comprises:
a first permanent magnet disposed on a first side of the sample chamber;
a second permanent magnet disposed on a second side of the sample chamber directly opposite the first permanent magnet;
a first pole piece coupled to the first permanent magnet such that the first pole piece is positioned between the first permanent magnet and the sample chamber; and
a second pole piece coupled to the second permanent magnet such that the second pole piece is positioned between the sample chamber and the second permanent magnet.
3. The nuclear magnetic resonance apparatus as claimed in claim 2, wherein the magnet assembly further comprises a magnetic shield disposed so as to substantially surround the first and second permanent magnets, the first and second pole pieces and the sample chamber.
4. The nuclear magnetic resonance apparatus as claimed in claim 2, further comprising a pulsed field gradient module; and wherein the controller is further coupled to the pulsed field gradient module.
5. The nuclear magnetic resonance apparatus as claimed in claim 2, wherein a location and field producing capacity of the first and second permanent magnets are selected so as to produce inside the sample chamber the non-uniform magnetic field with the known magnetic field gradient in at least one direction.
6. The nuclear magnetic resonance apparatus as claimed in claim 2, further comprising a pre-amplifier and a Q-switch;
wherein the Q-switch is coupled between the pre-amplifier and the RF power supply and is constructed and arranged to reduce leakage from the RF power supply to the pre-amplifier during transmission of the RF pulse sequence.
7. A nuclear magnetic resonance apparatus comprising:
an outer magnetic shield;
a first permanent magnet disposed within the outer magnetic shield and proximate a first location on an inner surface of the outer magnetic shield;
a first pole piece coupled to the first permanent magnet such that the first permanent magnet is located between the outer magnetic shield and the first pole piece;
a second pole piece disposed within the outer magnetic shield and proximate a second location on the inner surface of the outer magnetic shield, the second location being directly opposite the first location;
a sample chamber disposed within the outer magnetic shield and located centrally between the first and second pole pieces;
a radio frequency coil disposed about the sample chamber; and
control circuitry coupled to the radio frequency coil and constructed and arranged to control the radio frequency coil to generate a radio frequency pulse sequence,
wherein the first permanent magnet is magnetized in a first direction transverse to a longitudinal axis of the sample chamber, such that a magnetic field gradient exists in along an axis perpendicular to the longitudinal axis of the sample chamber.
8. The nuclear magnetic resonance apparatus as claimed in claim 7, wherein the first and second pole pieces each comprise a flat face, the flat faces being oriented toward one another.
9. The nuclear magnetic resonance apparatus as claimed in claim 8, wherein the second pole piece is constructed and arranged to be rotatable such that the flat face of the second pole piece forms an angle with respect to the flat face of the first pole piece so as to create a magnetic field gradient along a second direction, the second direction being perpendicular to both the first direction and the longitudinal axis of the sample chamber.
10. The nuclear magnetic resonance apparatus as claimed in claim 7, wherein the outer magnetic shield comprises iron.
11. The nuclear magnetic resonance apparatus as claimed in claim 7, further comprising a pulsed field gradient module coupled to the control circuitry.
12. The nuclear magnetic resonance apparatus as claimed in claim 7, further comprising a radio frequency power supply coupled to the radio frequency coil to produce the radio frequency pulse sequence.
13. The nuclear magnetic resonance apparatus as claimed in claim 12, wherein the control circuitry comprises a Q-switch constructed and arranged to reduce leakage from the radio frequency power supply during transmission of the radio frequency pulse sequence.
14. The nuclear magnetic resonance apparatus as claimed in claim 7, wherein the apparatus is integrated with a side-wall coring tool, and wherein the sample chamber is constructed and arranged to receive a core extracted from a formation by the side-wall coring tool.
15. The nuclear magnetic resonance apparatus as claimed in claim 7, wherein the sample chamber comprises a non-conductive and non-magnetic material.
16. The nuclear magnetic resonance apparatus as claimed in claim 15, wherein the sample chamber comprises a plastic material.
17. A method of monitoring a process, the method comprising:
providing a nuclear magnetic resonance apparatus having a sample chamber and a magnet assembly disposed about the sample chamber and constructed and arranged to provide a substantially non-uniform magnetic field having a known magnetic field gradient inside an approximate center of the sample chamber such that the substantially non-uniform magnetic field is controlled through one of a placement of at least one magnet or by one or more component;
directing a series of samples undergoing the process in a continuous stream through the sample chamber without halting the process; and
performing a nuclear magnetic resonance measurement on the series of samples to determine at least one property of the series of samples.
18. The method as claimed in claim 17, wherein performing the nuclear magnetic resonance measurement includes performing a measurement to detect a presence of water molecules in the series of samples.
19. The method as claimed in claim 18, wherein directing the series of samples including directing a series of wood samples through the sample chamber.
20. The method as claimed in claim 17, wherein performing the nuclear magnetic resonance measurement includes determining a ratio of solid to liquid components in each sample of the series of samples.
21. A down-hole method of analyzing a fluid in an earth formation, the method comprising
providing down-hole a nuclear magnetic resonance apparatus having a sample chamber and a magnet assembly disposed about the sample chamber and constructed and arranged to provide a substantially non-uniform magnetic field having a known magnetic field gradient inside an approximate center of the sample chamber such that the substantially non-uniform magnetic field is controlled through one of a placement of at least one magnet or by one or more component;
providing a core from the earth formation, the core containing a sample of the fluid;
placing the core inside the sample chamber; and
performing down-hole a nuclear magnetic resonance measurement on the core to determine at least one property of the fluid.
22. The nuclear magnetic resonance apparatus as claimed in claim 1, wherein the one or more component is from the group consisting of at least one shield, a geometry of at least one shield, at least one material of at least one shield, at least one pole, a geometry of at least one pole, at least one material of at least one pole, a geometry of at least one magnet, at least one material of at least one magnet or any combination thereof.
23. The method as claimed in claim 17, wherein the one or more component is from the group consisting of at least one shield, a geometry of at least one shield, at least one material of at least one shield, at least one pole, a geometry of at least one pole, at least one material of at least one pole, a geometry of at least one magnet, at least one material of at least one magnet or any combination thereof.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. An optical information storage medium having a plurality of grooves and a plurality of lands alternately formed, each of said grooves and each of said lands functioning as recording tracks to form an information storage region, said optical information storage medium comprising:
a first header region having a plurality of first phase pits respectively formed on extensions of said plurality of lands; and
a second header region having a plurality of second phase pits respectively formed on extensions of said plurality of grooves;
wherein each of said grooves has an optical depth of about 38 where is the wavelength of a light beam to be used;
each of said first phase pits has an optical depth smaller than that of each of said grooves;
each of said second phase pits has an optical depth substantially equal to that of each of said grooves; and
said first header region and said second header region are shifted from each other along the extension of each of said grooves.
2. An optical information storage medium according to claim 1, wherein the optical depth of each of said first phase pits is set so that the polarities of push-pull signals obtained by the light beam directed on said first and second phase pits and diffracted in a direction perpendicular to a direction of movement of said first and second phase pits are opposite to each other between said first and second phase pits, and that the polarity of a push-pull signal in said first header region is the same as the polarity of a push-pull signal generated by each land.
3. An optical information storage medium according to claim 2, wherein each of said first phase pits has an effective optical depth of 8.
4. An optical information storage medium having a plurality of grooves and a plurality of lands alternately formed, each of said grooves and each of said lands functioning as recording tracks to form an information storage region, said optical information storage medium comprising:
a first header region having a plurality of first phase pits respectively formed on extensions of said plurality of lands; and
a second header region having a plurality of second phase pits respectively formed on extensions of said plurality of grooves;
wherein said first header region and said second header region are shifted from each other along an extension of each of said grooves;
each of said grooves has an optical depth of (2n1) 8 where A is the wavelength of a light beam to be used and n is a positive integer;
each of said first phase pits has an optical depth of (2n14m) 8 where m is an integer not less than 0;
each of said second phase pits has an optical depth of (2n14s)8 where s is an integer not less than 0; and
said n, m; and s are related so as to satisfy conditions of 2n14m>0 and 2n14s>0.
5. An optical information storage medium according to claim 4, wherein the optical depth of each of said second phase pits is smaller than that of each of said grooves.
6. An optical information storage medium having a plurality of first grooves and a plurality of lands alternately formed, each of said first grooves and each of said lands functioning as recording tracks to form an information storage region, said optical information storage medium comprising:
a plurality of second grooves respectively formed on extensions of said first grooves so as to continue to said first grooves, each of said second grooves having a width smaller than that of each of said first grooves;
a groove header region having a plurality of first phase pits respectively formed so as to overlap said plurality of second grooves; and
a land header region having a plurality of second phase pits respectively formed on extensions of said plurality of lands so that each of said second phase pits is interposed between any adjacent ones of said second grooves;
wherein said groove header region and said land header region are shifted from each other along the extension of each first groove;
all of said first grooves, said second grooves, and said first phase pits have the same optical depth of about (2n1)8 where is the wavelength of a light beam to be used and n is a positive integer;
each of said second phase pits has an effective optical depth of about (2m1)4 where m is a positive integer; and
said n and m are related so as to satisfy a condition of (2m1)4<(2n1)8.
7. An optical information storage medium according to claim 6, wherein:
the optical depths of all of said first grooves, said second grooves, and said first phase pits are set to about 38; and
the optical depth of each of said second phase pits is set to about 4.
8. An optical information storage medium according to claim 6, further comprising a common sector mark region having a plurality of sector marks as third phase pits respectively corresponding to said plurality of first grooves, each of said third phase pits having an optical depth equal to that of each of said first grooves and a width substantially equal to that of each of said first grooves.
9. An optical information storage medium according to claim 8, wherein said sector marks have front edges and rear edges both aligned in a direction perpendicular to an extension of each of said first grooves.