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US 5,293,410 AGranted
Neutron generator
AssigneeSchlumberger Technology Corporation
InventorsFelix K. Chen, Arthur D. Liberman
Life of this patent
Estimating the term…
Abstract
A neutron generator, comprising: (i) an ion source comprising an anode and a thermionic cathode disposed in an ionizable gas environment (e.g. hydrogen isotope); (ii) means for heating the cathode so that the latter emits electrons which, when colliding with the gas atoms, generate ions; (iii) a target; (iv) an electrical gap to accelerate ions from the ion source towards the target upon impingement of the ions; and (v) control means for applying voltages to the anode, cathode and electrical gap. The cathode is of the dispenser type or volume type, and preferably comprises one block of material comprised of a substrate impregnated with an electron emitting material.
Claims39
A neutron generator comprising:
- (i) an ion source comprising an anode and a dispenser cathode disposed in an ionizable gas environment;
- (ii) means for heating said cathode so that the latter emits electrons which, when colliding with said gas atoms, generate ions;
- (iii) a target;
- (iv) an electrical gap to accelerate ions from said ion source towards said target upon impingement of said ions;
- and
- (v) control means for applying voltages to said anode, cathode and electrical gap, wherein a voltage applied to said anode by said control means is between 100 and 300 Volts to substantially reduce metal sputtering within the neutron generator.
3 more elements
A neutron generator comprising:
- an ion source comprising an anode and a dispenser or volume type cathode disposed in an ionizable gas environment including at least one hydrogen isotope;
- means for heating said cathode so that the latter emits electrons which, when colliding with said gas atoms, generate ions;
- a target;
- an electrical gap to accelerate ions from said ion source towards said target upon impingement of said ions;
- and
- control means for applying voltages to said anode, cathode and electrical gap, wherein a voltage applied to said anode by said control means is between 100 and 300 Volts to substantially reduce metal sputtering within the neutron generator.
3 more elements
A logging tool for investigating earth formations surrounding a borehole, comprising a sonde incorporating at least one radiation detector and a neutron generator, said neutron generator comprising:
- (i) an ion source comprising an anode and a dispenser cathode disposed in an ionizable gas environment;
- (ii) means for heating said cathode so that the latter emits electrons which, when colliding with said gas atoms, generate ions;
- (iii) a target;
- (iv) an electrical gap to accelerate ions from said ion source towards said target upon impingement of said ions;
- and
- (v) control means for applying voltages to said anode, cathode and electrical gap, wherein a voltage applied to said anode by said control means is between 100 and 300 Volts to substantially reduce metal sputtering within the neutron generator.
3 more elements
A neutron generator for logging applications, comprising:
- a source of ionizable gas;
- an ion source for ionizing said gas and including an anode and a dispenser type cathode designed to emit electrons able to impinge on gas atoms so as to generate ions;
- a target spaced apart from said ion source by an accelerating gap, and being able to emit neutrons upon impingement of ions issued from said ion source;
- control means for applying voltages to said anode, cathode and electrical gap;
- and
- means for operating said control means such that the rise time for the neutron output to reach 90% of the maximum output plateau), measured from the time when the neutron output is 10% of said plateau, is less than 1 microsecond.
3 more elements
A neutron generator for logging applications, comprising:
- a source of ionizable gas;
- an ion source for ionizing said gas and including an anode and a dispenser type cathode designed to emit electrons able to impinge on gas atoms so as to generate ions;
- a target spaced apart from said ion source by an accelerating gap, and being able to emit neutrons upon impingement of ions issued from said ion source;
- control means for applying voltages to said anode, cathode and electrical gap;
- and
- means for operating said control means such that the time lag between the instant when the voltage is applied to said cathode and the instant time when the instantaneous neutron output reaches 10% of the maximum output (plateau), is less than 0.5 microsecond.
3 more elements
A neutron generator for spectral logging applications, comprising:
- a source of ionizable gas;
- an ion source for ionizing said gas and including an anode and a dispenser type cathode designed to emit electrons able to impinge on gas atoms so as to generate ions;
- a target spaced apart from said ion source by an accelerating gap, and being able to emit neutrons upon impingement of ions issued from said ion source;
- control means for applying pulsing voltages to said anode, cathode and electrical gap;
- and
- means for operating said control means such that the neutron output reaches a maximum value (or plateau) which remains constant within a 10% range thereof, over a pulse time width comprised between 18 and 25 microsecond.
3 more elements
A neutron generator for logging applications, comprising:
- a source of ionizable gas;
- an ion source for ionizing said gas and including an anode and a dispenser type cathode designed to emit electrons able to impinge on gas atoms so as to generate ions;
- a target spaced apart from said ion source by an accelerating gap, and being able to emit neutrons upon impingement of ions issued from said ion source;
- control means for applying voltages to said anode, cathode and electrical gap;
- and
- means for operating said control means such that the fall time between the instant when the voltage applied to said cathode is turned off and the instant time when the instantaneous neutron output falls to 10% of the maximum output (plateau), is less than 0.5 microsecond.
3 more elements
A neutron generator for spectral logging applications, comprising:
- a source of ionizable gas;
- an ion source for ionizing said gas and including an anode and a dispenser type cathode designed to emit electrons able to impinge on gas atoms so as to generate ions;
- a target spaced apart from said ion source by an accelerating gap, and being able to emit neutrons upon impingement of ions issued from said ion source;
- control means for applying voltages to said anode, cathode and electrical gap;
- and
- means for operating said control means such that the time required for the instantaneous neutron output to reach its maximum (plateau) value, measured from the instant time when the voltage is applied to said cathode, is less than 1.5 microsecond.
3 more elements
A method for investigating earth formation surrounding a borehole, comprising the steps of:
- irradiating, at a first given location in the borehole, the borehole materials and the earth formation with bursts of neutrons from a neutron generator including an ion source comprising an anode and a dispenser cathode disposed in an ionizable gas environment, by applying voltage pulses to the cathode and heating the dispenser cathode;
- detecting, at a second given location in the borehole, radiation resulting from interaction of the neutrons with the formation;
- generating signals representative of the radiation;
- controlling the neutron output during the start of the neutron burst such that the rise time for the neutron output to reach 90% of its plateau, measured from the time when the neutron output is 10% of the plateau, is less than 1 microsecond;
- and
- determining from the signals a characteristic of the earth formation surrounding the borehole.
3 more elements
A method for investigating earth formation surrounding a borehole, comprising the steps of:
- generating bursts of neutrons from a neutron generator including an ion source comprising an anode and a dispenser cathode disposed in an ionizable gas environment, by applying voltage pulses to the cathode and heating the cathode;
- irradiating, at a first given location in the borehole, the borehole materials and the earth formation with bursts of neutrons;
- detecting, at a second given location in the borehole, radiation resulting from interaction of the neutrons with the formation;
- generating signals representative of the radiation;
- controlling the neutron burst during the start of the neutron burst such that the time lag between the instant when the voltage is applied to the cathode and the instant time when the instantaneous neutron output reaches 10% of its plateau, is less than 0.5 microsecond;
- and
- determining from the signals a characteristic of the earth formation surrounding the borehole.
4 more elements
A method for investigating earth formation surrounding a borehole, comprising the steps of:
- irradiating, at a first given location in the borehole, the borehole materials and the earth formation with bursts of neutrons from a neutron generator including an ion source comprising an anode and a dispenser cathode disposed in an ionizable gas environment, by applying voltage pulses to the cathode and heating the dispenser cathode;
- detecting, at a second given location in the borehole, radiation resulting from interaction of the neutrons with the formation;
- generating signals representative of the radiation;
- controlling the neutron output such that the neutron output reaches a plateau which remains constant within a 10% range thereof, over a burst time width comprised between 18 and 25 microsecond;
- and
- determining from the signals a characteristic of the earth formation surrounding the borehole.
3 more elements
A method for investigating earth formation surrounding a borehole, comprising the steps of:
- generating bursts of neutrons from a neutron generator including an ion source comprising an anode and a dispenser cathode disposed in an ionizable gas environment, by applying voltage pulses to the cathode and heating the cathode;
- irradiating, at a first given location in the borehole, the borehole materials and the earth formation with bursts of neutrons;
- detecting, at a second given location in the borehole, radiation resulting from interaction of the neutrons with the formation;
- generating signals representative of the radiation;
- controlling the neutron output such that the fall time between the instant when the voltage applied to the cathode is turned off and the instant time when the instantaneous neutron output falls to 10% of its plateau, is less than 0.5 microsecond;
- and
- determining from the signals a characteristic of the earth formation surrounding the borehole.
4 more elements
A method for investigating earth formation surrounding a borehole, comprising the steps of:
- generating bursts of neutrons from a neutron generator including an ion source comprising an anode and a dispenser cathode disposed in an ionizable gas environment, by applying voltage pulses to the cathode and heating cathode;
- irradiating, at a first given location in the borehole, the borehole materials and the earth formation with bursts of neutrons;
- detecting, at a second given location in the borehole, radiation resulting from interaction of the neutrons with the formation;
- generating signals representative of the radiation;
- controlling the neutron output during the neutron burst such that the time required for the instantaneous neutron output to reach a plateau, measured from the instant time when the voltage is applied to the cathode, is less than 1.5 microsecond;
- and
- determining from the signals a characteristic of the earth formation surrounding the borehole.
4 more elements
A method for investigating earth formation surrounding a borehole, comprising the steps of:
- generating bursts of neutrons from a neutron generator including an ion source comprising an anode and a dispenser cathode disposed in an ionizable gas environment, by applying voltage pulses to the cathode and heating the cathode;
- irradiating, at a first given location in the borehole, the borehole materials and the earth formation with bursts of neutrons;
- detecting, at a second given location in the borehole, radiation resulting from interaction of the neutrons with the formation;
- generating signals representative of the radiation;
- controlling the neutron output such that:
- (i) the rise time for the neutron output to reach 90% of its plateau, measured from the time when the neutron output is 10% of the plateau, is less than 1 microsecond;
- (ii) the fall time between the instant when the voltage applied to the cathode is turned off and the instant time when the instantaneous neutron output falls to 10% of the plateau, is less than 0.5 microsecond;
- and
- determining from the signals a characteristic of the earth formation surrounding the borehole.
6 more elements
A method for investigating earth formation surrounding a borehole, comprising the steps of:
- generating bursts of neutrons from a neutron generator including an ion source comprising an anode and a dispenser cathode disposed in an ionizable gas environment, by applying voltage pulses to the cathode and heating the cathode;
- irradiating, at a first given location in the borehole, the borehole materials and the earth formation with bursts of neutrons;
- detecting, at a second given location in the borehole, radiation resulting from interaction of the neutrons with the formation;
- generating signals representative of the radiation;
- controlling the neutron output such that:
- (i) the rise time for the neutron output to reach 90% of its plateau, measured from the time when the neutron output is 10% of the plateau, is less than 1 microsecond;
- (ii) the fall time between the instant when the voltage applied to the cathode is turned off and the instant time when the instantaneous neutron output falls to 10% of its plateau, is less than 0.5 microsecond;
- and (iii) the neutron output reaches a plateau which remains constant within a 10% range thereof, over a pulse time width comprised between 18 and 25 microsecond;
- and
- determining from the signals a characteristic of the earth formation surrounding the borehole.
7 more elements
Dependencies are inferred from the claim text.