Floating intermediate electrode configuration for downhole nuclear radiation generator.

(54) Title: INTERMEDIATE CONFIGURATION OF FREE ELECTRODE FOR A NUCLEAR RADIATION GENERATOR IN A WELL POINT.

(54) Title: FLOATING INTERMEDIATE ELECTRODE CONFIGURATION FOR DOWNHOLE NUCLEAR RADIATION GENERATOR.

(57) Summary

Improved configuration systems, methods, and devices are provided for downhole nuclear radiation generators. For example, one embodiment of a nuclear radiation generator capable of downhole operations can include a charged particle source, a target material, and an acceleration column between the charged particle source and the target electrode. The acceleration column may include an intermediate electrode that is free at a variable potential and electrically isolated from the rest of the acceleration column.

(57) Abstract

Systems, methods, and devices with improved electrode configuration for downhole nuclear radiation generators are provided. For example, one embodiment of a nuclear radiation generator capable of downhole operation may inelude a charged particle source, a target material, and an acceleration column between the charged particle source and the target material. The acceleration column may inelude an intermedíate electrode that remains floating at a variable potential, being electrically isolated from the rest of the acceleration column.

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Mexican Institute of Industrial Property

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PATENT TITLE NO. 340652

Owner (s): SCHLUMBERGER TECHNOLOGY BV

Address: Parkstraat 83-89m, NL-2514, JG The Hague, NETHERLANDS

Name: INTERMEDIATE CONFIGURATION OF FREE ELECTRODE FOR A NUCLEAR RADIATION GENERATOR IN A WELL POINT

Classification: lnt.CI.8: G01V5 / 10; H05H3 / 06

Inventor (s): JANI REIJONEN; JOEL L. GROVES

Number:

MX / a / 2014/003006

REQUEST

International filing date: September 11, 2012

PRIORITY

Country: Date: Number:

US September 14, 2011 13 / 232,166

Validity: Twenty years

Expiration Date: September 11, 2032, the reference patent is granted based on articles 1, 2 fraction V, 6 fraction III, and 59 of the Industrial Property Law.

In accordance with * Article 23 of the Industrial Property Law, this patent has a non-renewable term of validity of years, counted from the date of filing of the international application and will be subject to the payment of the fee to keep it in force. rights

Whoever subscribes to this title does so based on the provisions of Articles 6 * sections III and 7a bis 2 of the Industrial Property Law (Official Mario de la Federación (DOFJ 06/27/1991, / 10/1996, 12/26/1987, 05/17/1999, 01/26/2004, 06/16/2005, 01/25/2096, 05/06/2009, 06/01/2010, 06/18/2010 / 2010. 06/28/2010, 01/27/2012 and 04/09/2012); Articles f, 3rd fraction V subsection a), 4th and 12th fractions I and lll of the Regulation of the Mewcano Institute of Industrial Property (DOF 12/14/1999, amended on 07/01/2002, 07/15/2004 , 07/28/2004 and 09/07/2007); articles 1, 3, 4, 5^and fraction V subsection a), 16 fractions I and lll and 30 of the E®Jatuto Orgánico of the Mexican Institute of Industrial Property (DOF 12/27/1999, amended on 10/10/2002, 07/29/2004, 08/04/2004 and 09/13/2007); 1, 3 and 5 subsection a) of the Agreement that delegates powers to the Deputy Directors General, Coordinator, Divisional Directors, Holders of the Regional Offices, Divisional Deputy Directors, Departmental Coordinators and other subordinates of the Mexican Institute of Industrial Property. (DOF 12/15/1999, amended on 02/04/2000, 07/29/2004, 08/04/2004 and 09/13/2007).

Issue Date: July 20, 2016

THE DIVISIONAL DIRECTOR OF PATENTS

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INS'I

INTERMEDIATE CONFIGURATION OF FREE ELECTRODE FOR GENERATOR

NUCLEAR RADIATION IN A WELL FUND

BACKGROUND

The present disclosure relates generally to the generation of downhole radiation for nuclear recording in wells and, more particularly, to electrode configurations for downhole nuclear radiation generating tubes.

A downhole generator tube can include three main components: an ionic source, an acceleration column, and a target (target). An ion beam from the ion source can advance through the acceleration column toward the target guided by a potential difference between an electrode close to the ion source and an electrode close to the target. Neutrons and / or gamma rays are generated when the accelerated ions come into contact with the target. However, as the ion beam progresses through the acceleration column, some of the ions may contact an electrode instead of the target. In part, this may occur because the acceleration column of a downhole neutron generator tube may contain a pressurized gas instead of a vacuum, and ions from the ion beam may contact the pressurized gas particles in the acceleration column and change direction.

When an ion in the ion beam strikes an electrode in the acceleration column, it can result in ion-induced spray. Spraying causes the emission and transport of material from the electrodes, which can be generally isotropic and i

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it can generally travel in a straight line from the point of emission. As a result, the electrically conductive electrode material can condense into ceramic high-voltage insulators surrounding the acceleration column. If the high voltage insulators were covered by sprayed electrode material over a large part of the extension of the acceleration column, the short-circuit of the voltage potential between the electrode near the ion source and the electrode near the leaking target with negative consequences. Even if there is no short circuit in the acceleration column, the electrode material sprayed on the high voltage insulator can form a conductive deposited film that takes an intermediate voltage between the potential of the ionic source and the potential of the target. The conductive film can increase the voltage of the electric field on the nearby electrodes and the acceleration column. Increased electric field voltages can result in an increase in high-voltage leakage current, as well as the probability of leakage cases occurring with negative consequences due to current leakage in the insulator or the field emission of one of the electrodes.

Irregular wear to the target surface can also be problematic for the downhole neutron generator. Because the ion beam from the ion source to the target can be weighted average, the ion beam can be unevenly distributed across the light beam upon contact with the target. This Irregular distribution can generate Irregular wear at the target end, which can cause the neutron performance of the neutron generator to decrease as part of the target wears prematurely.

Similarly, a downhole X-ray generator tube may also include

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Three main components: an electron emitter (cathode), an acceleration column, and a target (anode). An ion beam of the cathode can advance through the acceleration column toward the anode guided by a potential difference between an electrode near the electron gun (cathode) and an anode or a nearby electrode. X-rays are generated through Bremsstrahlung or characteristic X-ray emission, followed by ionization of the inner shell when the electrons contact the anode and the material slows down and scatters. However, as the electron beam progresses through the acceleration column, some of the electrons can find an electrode instead of the anode. For this reason, among others, many of the aforementioned problems can affect downhole neutron generating tubes, as well as X-ray generating tubes.

COMPENDIUM

Certain aspects that share the scope of the originally claimed modalities are set forth herein. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms that the described modalities can take and these aspects are not intended to limit the scope of the subject matter disclosed. In fact, the modalities of the subject matter described may encompass a variety of aspects that may not be stated below.

The embodiments described herein refer to devices and methods associated with an improved electrode configuration and method of operation for downhole nuclear radiation generators. An embodiment of a neutron generating tube capable of downhole operation may include a

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OE LA! '!. &lt;H-ι; '' i ion source, a target electrode and an acceleration column located^Nferrite^Lthe ionic filler and the target electrode. The acceleration column may include a variety of electrodes and, more preferably, an extractor electrode closer to the ion source than the target electrode, a suppressor electrode closer to the target electrode than the ion source, and an intermediate electrode located between the extractor electrode and the suppressor electrode. In a preferred method of operation, instead of coupling the intermediate electrode to an external source of energy, the intermediate electrode remains electrically free, such that its potential is defined by the phenomenon that occurs inside the generator tube, such as field emission and secondary electronic emission to and from the intermediate electrode.

BRIEF DESCRIPTION OF THE FIGURES

The advantages of the invention may become apparent upon reading the following detailed description and with reference to the figures, in which:

Figure 1 is a schematic block diagram of a neutron generator, according to one embodiment.

Figure 2 is a schematic cross-sectional view of a neutron generating tube with an electrode configuration that includes an intermediate electrode, in accordance with one embodiment.

Figure 3 is a schematic cross-sectional view of the electrical potential distribution in the upper half of the axial neutron generator tube of Figure 2, of

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according to a modality.

Figure 4 is a schematic cross-sectional view of the electrical potential distribution in the upper half of a neutron generating tube with an electrode configuration with multiple intermediate electrodes, in accordance with one embodiment.

Figure 5 is a graph describing the electric field stresses on the electrode surfaces in the upper half of the neutron generating tube of Figure 4, according to one embodiment.

Figure 6 is a schematic cross-sectional view of the electrical potential distribution in the upper half of another neutron generating tube with an electrode configuration with multiple intermediate electrodes, according to one embodiment.

Figure 7 is a graph depicting the electric field stresses on the electrode surfaces in the upper half of the neutron generating tube of Figure 6 at a first voltage potential, according to one embodiment.

Figure 8 is a graph depicting the electric field stresses on the electrode surfaces in the upper half of the neutron generating tube of Figure 6 at a second voltage potential, according to one embodiment.

Figure 9 is a schematic cross-sectional view of a neutron generating tube with eight intermediate electrodes located in an effective pattern, according to one embodiment.

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Figure 10 is a schematic cross-sectional view of the electrical potential distribution in the upper half of the neutron generating tube with an electrode configuration with multiple intermediate electrodes, according to one embodiment of the

Figure 9.

Figure 11 is a block diagram of a high potential neutron generator employing a high voltage power supply, in accordance with one embodiment.

Figure 12 is a block diagram of a high potential neutron generator employing two high voltage power supplies, in accordance with one embodiment.

Figure 13 is a schematic diagram of the neutron generator illustrated in Figure 12 showing the mechanical support of a grounded Intermediate electrode.

DETAILED DESCRIPTION OF SPECIFIC MODALITIES

The present description generally describes various electrode configurations for an acceleration column of a downhole nuclear radiation generator, such as a neutron generating tube or an X-ray generating tube. While the present description primarily describes such configurations in the context of a neutron generating tube, the electrode techniques and configurations with respect to

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Its disclosed use can equally be applied to an X-ray generator tube. Specifically, the ion source and target electrode of a neutron generator tube can be respectively analogous to the cathode and anode of a background X-ray generator tube. water well. In this way, the acceleration column of a downhole X-ray generator tube can employ the electrode techniques and configurations described with reference to the neutron generator tube. When such electrode techniques and configurations are employed in a downhole X-ray generator tube, an electron beam from the cathode is less likely to collide with any of the intermediate electrodes when targeting the anode, resulting in secondary electron emission and / or parasitic X-rays. A general description of such an X-ray tube can be found in US Patent No. 5 680 431, "X-RAY GENERATOR," to Schlumberger Technology Corporation, which is incorporated herein in its entirety by this reference.

Accordingly, the electrode configurations and associated operating techniques described herein can be applied to any downhole nuclear radiation generator that can generate nuclear radiation by accelerating charged particles through an acceleration column toward a target material. Such a downhole nuclear radiation generator may include a source of charged particles (eg, an ion source and / or a cathode) to emit charged particles (eg, Ions and / or electrons) to a target material (eg. , an electrode and / or a target anode) that can produce nuclear radiation (for example, neutrons and / or X-rays) when charged particles reach it.

IF the above is taken into account, Figure 1 represents a schematic view of

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cross section of a neutron generator 10 suitable for use in a downhole tool. The neutron generator 10 may include a pressure cover 12 with a pressurized insulating gas 3 and various components of the device. For example, the neutron generator 10 may Include an externally controlled high voltage supply 4 via direct external power and / or control supplies 5. This high voltage supply 4 can deliver high voltages in the Range of 50 kV to 150 kV or more via a high voltage negative line 6 to a target electrode 18 in an evacuated neutron generator tube 11. The neutron generator tube 11 also they may include an Ionic source 16 in a vacuum envelope controlled by external direct power and / or control supplies 7. The vacuum envelope may include a high voltage insulator 28 that separates the various electrodes (shown in Figure 3 and described below) that are located between the ion source 16 and the target electrode 18. It is possible to accelerate the Ions generated in the Ionic source 16 to target electrode 18 and a nuclear reaction between the arriving ions and the nuclei located at target electrode 18 can generate neutrons. The neutrons can be generated by the deuteron reaction with tritium (that is, the dT reaction) that generates 14.1 MeV neutrons from d + T -&gt; n + alpha + 17.6 MeV; where d is the nucleus of an atom²H, T is an atom ³H and alpha is the nucleus of the atom ⁴I have.

Target electrode 18 of a neutron generating tube may be a titanium disk saturated with ³H. Ionic source 16 can ionize deuterium gas ²H₂ and the resulting bare nuclei or molecular ions can be accelerated towards target electrode 18 by an electric field between ion source 16 and target electrode 18. The ion beam can be pulsed to obtain neutron discharges. It may also work continuously.

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The neutron generating tube 11 and the high voltage source 4 can be enclosed in a pressure cover 12 containing the insulating gas 3, as well as the sealing sleeves (not shown) that allow the generation and application of the high voltage required in the limited space available. Insulating gas 3 may include SF₆ at pressures ranging from a few psig to over 100 psig. Direct feeds 5 and 7 to pressure cover 12 can supply power to the high voltage sections of neutron generator 11 and monitor the outputs as external controls. Similarly, power can be provided to Ionic source 16, which can include control currents and voltages to regulate and / or pulse the current of the ion beam.

FIG. 2 is a more detailed schematic cross-sectional view of the neutron generator 10 of FIG. 1, particularly illustrating an improved electrode configuration of the neutron generator tube 11. An acceleration column 14, located within the pressure cover 12, can provide a pathway for an ion beam to travel from ion source 16 to target electrode 18. Generally, the acceleration column 14 can remain at a low gas pressure, as is usually required for proper operation of the ion source 16, rather than under vacuum, because the neutron generating tube 10 is a tool for use downhole and neutron generator tube 11 may be sealed. In this way, the differential pressure between the different sections of the neutron generating tube 11 may not be maintained, as is the case in a differentially pumped ion source that is used in many laboratory applications. The ion source 16 can generally produce a pulsed ion beam that can be quickly switched on and off. Such an ion source 16 and other components of the neutron generating tube may generally be described in US Patent ^? 5,293,410, "NEUTRON GENERATOR TUBE," from Schlumberger Technology Corporation, which is incorporated herein in its entirety by this reference.

The ion beam may be guided from the ion source 16 through the acceleration column 14 by various electrons, and preferably an extractor electrode 20, an intermediate electrode 22, and a suppressor electrode 24, before contacting the coating. titanium 26 at target 18. Although the titanium coating 26 covers the entire end of target 18 in the schematic illustration, the titanium coating 26 can cover only a part of the end where the ion beam is expected to contact the Target 18. When the ion beam from ion source 16 collides with titanium coating 26, target electrode 18 can generate neutrons in the manner discussed above. The extractor electrode 20, the intermediate electrode 22 and the suppressor electrode 24 can be electrically separated from each other by an insulator 28 that can be made of aluminum (aluminum oxide ceramic).

One or more high voltage power sources, such as the high voltage power source 4 illustrated in Figure 1, can supply power to electrodes 20, 22, and 24 at various potentials. In particular, the extractor electrode 20 may have a potential approximately 100 kV greater than the potential of a suppressor electrode 24 (ie, the suppressor electrode 24 may have a negative potential relative to the extractor electrode 20). Target electrode 18 may have a nominally higher voltage than suppressor electrode 24 of about 200 V to 1000 V or more to suppress the reverse secondary electron beam generating impact of the ion beam on the target. The io

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intermediate electrode 22 may have voltage potential corresponding to approximately the median voltage potentials of the extractor electrode 20 and the suppressor electrode 24. For example, if the extractor electrode 20 has a potential of 100 kV and the suppressor electrode 24 has a potential At 0 V, intermediate electrode 22 may have a potential of approximately 50 kV. In alternative embodiments, Intermediate electrode 22 may have any suitable intermediate potential. By distributing the potentials between the electrodes 20, 22 and 24 in this way, the electric fields produced by the potentials applied to the electrodes can be relatively evenly distributed in the acceleration column 14, as described in more detail below referring to Figure 3. When the electrode configuration illustrated herein is employed in the acceleration column of an X-ray generator tube, the applied voltage potentials can be substantially the same.

In a particular preferred embodiment in the present application, intermediate electrode 22 is left electrically free (i.e. electrically isolated from contact with acceleration column 14) and not directly coupled to high-voltage power source 4. In such an embodiment, the potential at Intermediate electrode 22 is defined by phenomena occurring in acceleration column 14, such as field emission and secondary electron emission to and from Intermediate electrode 22. Therefore, in such an embodiment , the potential of intermediate electrode 22 is variable.

Extractor electrode 20, Intermediate electrode 22, and suppressor electrode 24 can be shaped to reduce the spray events that can occur when the neutron generator tube 10 is in operation. For example, the extra "extractor electrode 20 may have a rounded shape extending toward the interior of the acceleration column 14 which can guide the ion beam from target to target 18 without contacting the intermediate electrode 22 or the electrode suppressor 24 during normal operation. As mentioned above, interception of the ion beam from ion source 16 with intermediate electrode 22 or suppressor electrode 24 can cause the electrode material to wear out and spray on the acceleration column 14. Therefore, the shape of the extractor electrode 20 can reduce the probability of harmful spraying of the electrode material.

The configuration of the intermediate electrode 22 can further reduce the probability that the insulator 28 will be covered by electrode material due to spray events. The mere presence of intermediate electrode 22 in acceleration column 14 can serve to cover or protect ceramic insulator 28 from conductive material that can be sprayed from suppressor electrode 24. Any material sprayed from the suppressor electrode 24 can be deposited on the intermediate electrode 22 instead of on the ceramic insulator 28. The same considerations apply to any other electrode that protects the ceramic insulator 28 against coating with spray deposits.

It is also possible to shape the intermediate electrode 22 to increase the probability that the pulverized electrode material from the suppressor electrode 24 will deposit on the intermediate electrode 22, instead of being deposited on the ceramic insulator 28. For example, the intermediate electrode 22 it can be inserted between the ceramic insulators 28, approximately halfway between the extractor electrode 20 and the suppressor electrode 24, at a distance approximately from both of them. The end of the electrode

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INC.-iíET, ·.;. C .'.- v ..? · Intermediate 22, which extends from the insulator 28 and into the acceleration column 14, can reach approximately halfway between the ends of the extractor electrode 20 and the suppressor electrode 24, a an approximate distance L₂ from both.

In addition to covering the ceramic insulator 28 from spray events, molding of the intermediate electrode 22 can also reduce electronic leakage and / or leakage cases with negative consequences on the acceleration column 14. Due to the shape of the intermediate electrode 22, the electric field between the extractor electrode 20 and the suppressor electrode 24 can be controlled by the acceleration column 14 so that it can reduce the electric field stresses on the extractor electrode 20, the intermediate electrode 22 and / or the suppressor electrode 24, as well as on the insulators 28 that separate the electrodes. The reduced and / or more predictable electric field voltages on the electrodes 20, 22 and / or 24 can reduce, respectively, the probability of spontaneous electronic emission and / or leakage cases with secondary consequences.

Also, suppressor electrode 24 can be shaped to reduce the probability of spray events. Specifically, the end of the suppressor electrode 24 can extend within the acceleration column 14 and beyond the location of the ice of the Intermediate electrode 22. This arrangement can reduce the likelihood that any electrode material will spray from the surface of the suppressor electrode 24 reaches insulator 28. Because the end of the suppressor electrode 24 extends beyond the start of intermediate electrode 22, any electrode material sprayed from the surface of suppressor electrode 24 is more likely to be shielded by intermediate electrode 22, rather than deposited on the ceramic insulator 28.

It should be noted that, regardless of the shape of the Intermediate 22 electrode,

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Imposing a defined potential at an intermediate position between the suppressor electrode 24 and the extractor electrode 20 can improve the stability and / or longevity of the neutron generating tube 11, even in the presence of some spray materials deposited on the ceramic insulator 28. Alternatively, allowing the intermediate electrode 22 to remain electrically free provides a high degree of operating stability by facilitating the removal of field emissions from the suppressor electrode which could otherwise lead to instability in the acceleration column.

Figure 3 illustrates a schematic cross-sectional view of the electric field distribution in the upper half of the neutron generator tube 11. Due to the axial symmetry of the generator tube 11, only half of the tube is outlined. As illustrated in Figure 3, an electric field 34 distributed approximately uniformly along the end of the extractor electrode 20 and the end of the suppressor electrode 24 can guide an ion beam (not illustrated) from the Ionic source 16 Since the intermediate electrode

22 it can have a voltage potential corresponding to approximately the median of the voltage potentials of the extractor electrode 20 and of the suppressor electrode 24, and the intermediate electrode 22 can be located at a distance corresponding to approximately the median between the extractor electrode 20 and the suppressor electrode 24, and the electric field 34 can be generally evenly distributed between the three electrodes 20, 22 and 24.

Although two main points of electric field voltage 36 and 38 may appear at intermediate electrode 22 and suppressor electrode 24, respectively, the electric field voltages at points 36 and 38 may be substantially lower than those found on single column electrodes. of acceleration having only the extractor electrode 20 and the suppressor electrode 24 (that is, it lacks intermediate electrodes 22). For example, the voltage potential of extractor electrode 20 may be approximately 50 kV higher than that of intermediate electrode 22 and may be approximately 100 kV higher than that of suppressor electrode 24. Point 36 may have an electric field voltage of approximately 192 kV / cm and point 38 can have an electric field voltage of approximately 221 kV / cm. In contrast, in an acceleration column without an intermediate electrode, the electric field voltage on a suppressor electrode can reach 449 kV / cm when a layer of sprayed electrode material is deposited on a nearby ceramic insulator. Because the electric field voltages are reduced at points 36 and 38, the probability of spontaneous electron emission from the electrodes and / or leakage with negative consequences can also be reduced. Furthermore, adjusting the shape of the electrodes 22 and 24 through modeling and experimentation can further reduce the electric field voltages at points 36 and 38.

As described above with respect to Figures 2 and 3, the inclusion of the intermediate electrode 22 in the acceleration column 14 of the downhole neutron generator tube 11 may result in a more uniform distribution 34 of the electric field. Similarly, because multiple intermediate electrodes 22 may distribute the electric field more evenly, Figure 4 illustrates another electrode configuration for neutron generator tube 11 with multiple intermediate electrodes 40-54 instead of one. single intermediate electrode 22. Figure 4 illustrates a simulated electrode configuration with eight intermediate electrodes 22 between extractor electrode 20 and suppressor electrode 24. The eight electrodes 40-54 represent the intermediate electrodes 22 between the extractor electrode 20 and the electrode

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suppressor 24. In the simulation of Figure 4, the extraptQr gO electrode simulates having a voltage potential approximately 100 kV higher than the suppressor electrode 24. Intermediate electrodes 22 may have voltage potentials that can vary between 100 kV and 0 V higher than suppressor electrode 24. For example, electrodes

40-54 can have voltage potentials of approximately 100 kV, 85.7 kV, 71.4 kV,

57.1 kV, 42.9 kV, 28.6 kV, 14.3 kV, and 0 V, respectively, higher than suppressor electrode 24. Target electrode 18 may have a voltage potential approximately 200 V higher than that of the suppressor electrode 24. When the electrode configuration illustrated herein is employed in the acceleration column of an X-ray generating tube, the applied voltage potentials may be substantially the same.

As a result of the relatively small potential differences between the intermediate electrodes 22, the electric field voltages may be relatively less. Similarly, spontaneous electron emission and / or leakage with negative consequences may be particularly unlikely at electrodes 40-54. Furthermore, an electric field distribution 56 can be approximately uniform near the location of the ion beam 32. Uniformity of electric field distribution 56 can decrease the probability of ion beam 32 intercepting suppressor electrode 24, which can also reduce spray events.

Furthermore, the uniformity of the distribution of the electric field 56 can reduce the probability of spontaneous electron emission and / or the cases of leakage with negative consequences due to the electric field stresses on the suppressor electrode 24. This improved convergence effect can produce an ion beam 32 that is substantially parallel to the axis of the neutron generating tube 11 and does not cut it. Such a converging ion beam 32 can further reduce the probability of

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that the neutral ions or atoms caused when the ions that intercept the pressurized gas 3 can contact any electrode other than the target electrode 18.

Figure 5 is a graph 58 describing the relationship between the electric field stresses on the surfaces of the electrodes 20, 40-54 and 24 simulated in Figure 4 and the potential distribution throughout the electrode configuration of the Figure 4. In graph 58, a first ordinate 60 represents the electric field voltage in units of kV / cm and a second ordinate 62 represents the electric potential in units of kV. An abscissa 64 represents the relative axial position of the surfaces of the electrode configuration of Figure 4 extending from behind the extractor electrode 20, to the left, beyond target 18, to the right.

In graph 58 of Figure 5, a dotted line represents the electric field potential 66 as a function of the electrode configuration of Figure 4. As illustrated in Figure 58, instead of decreasing dramatically between any two electrodes, the electrical potential 66 slowly decreases from 100 kV at a point representing the first electrode 40 of the intermediate electrodes 22, to 0 V at a point representing the last electrode 54 of the intermediate electrodes 22. A curve 68 represents the electric field voltages at various points along the electrode configuration of Figure 4. A peak 70 represents a point of maximum electric field voltage at extractor electrode 20, peaks 72-86 represent a point of maximum electric field voltage 40-54, respectively, and a peak 88 represents a point of maximum field voltage electric at the suppressor electrode 24. As shown in graph 58, the maximum electric field voltage for! &gt;&gt; zr ί 1V1

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Simulated electrode configuration in Figure 4 is kept below 140 kV / cm, which may be 300 kV / cm less than the maximum electric field voltage for electrode configurations without Intermediate electrodes.

Figure 6 depicts another electrode configuration for neutron generator tube 11 including multiple electrodes 90-108 instead of a single intermediate electrode 22. In particular, Figure 5 illustrates a simulated electrode configuration with ten intermediate electrodes 22 between the extractor electrode 20 and the suppressor electrode 24. The ten electrodes 90-108 represent the intermediate electrodes 22 between the electrode extractor 20 and the electrode suppressor 24. In the simulation of Figure 5, the electrode extractor 20 is simulated as having a 100 kV higher potential voltage than the electrode suppressor 24 and as having an extrusion shape to uniformly guide the electric field and to reduce voltages of the electric field. The ten intermediate electrodes 90-108 may have voltage potentials that vary between

100 kV and 0 V higher than suppressor electrode 24. For example, electrodes 90108 may have voltage potentials of approximately 100 kV, 88.9 kV, 77.8 kV, 66.7 kV, 55.6 kV, 44, 4 kV, 33.3 kV, 22.2 kV, 11.1 kV, and 0 V, respectively, higher than the suppressor electrode 24. The target electrode 18 may have a voltage potential approximately 200 V higher than that of the electrode suppressor 24. The suppressor electrode 24 can also be shaped to guide the electric field uniformly and to reduce the electric field voltages. When the electrode configuration currently illustrated in the acceleration column of an X-ray generator tube is used, the applied voltage potentials can be substantially the same.

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As a result of the relatively paguañas potential differences between one of the intermediate electrodes 22, the electric field voltages may be relatively lower. Consequently, spontaneous electron emission and / or leakage with negative consequences can be particularly unlikely at the electrodes

90-108. Furthermore, an electric field distribution 110 can be approximately uniform near the location of ion beam 32. Uniformity of electric field distribution 110 can decrease the probability that ion beam 32 affects suppressor electrode 24, which It can also reduce spray events. The uniformity of the distribution of the electric field 110, as well as the shape of the suppressor electrode 24, can also reduce the probability of spontaneous electron emission and / or cases of leakage with negative consequences due to the stresses of the electric field at the suppressor electrode. 24. This improved converging effect can produce an ion beam 32 that is substantially parallel to the axis of the neutron generating tube 11 and does not cut it. Such a converging ion beam 32 can further reduce the probability that the neutral ions or atoms caused when the ions intercept the pressurized gas 3 can contact any electrode other than the target electrode 18.

Figure 7 is a graph 112 depicting a relationship between the electric field voltages 20 at the surfaces of the electrodes 20, 90-108, and 24 simulated in Figure 6, and the electrical potential distribution along the length of the Figure 6 electrode configuration. In graph 112, a first ordinate 114 represents the electric field voltage in units of kV / cm and a second ordinate 116 represents the electric potential in units of kV. An abscissa 118 represents the relative length of the surfaces of the electrode pattern of Figure 6 extending from behind the extractor electrode 20, to the left, beyond target 18, to the right.

In graph 112 of Figure 7 a dotted line represents the electrical potential 120 as a function of the length of the electrode configuration of Figure 6. Like the simulation described in graph 58 in Figure 4, in graph 112 in Figure 7, instead of decreasing dramatically between any two electrodes, the electrical potential 120 slowly decreases from 100 kV, at a point that represents the first electrode 90 of intermediate electrodes 22, at 0 V, at a point representing the last electrode 108 of intermediate electrodes 22. A curve 122 represents the electric field voltages at various points as a function of the electrode configuration of Figure 6. A peak 124 represents a point of maximum electric field voltage at the extractor electrode 20, peaks 126-144 represent a point maximum electric field voltage at electrodes 90-108, respectively, and a peak 146 represents a maximum electric field voltage point at suppressor electrode 24. As shown in Figure 112, the maximum electric field voltage for the simulated electrode configuration in Figure 5 remains less than 80 kV / cm.

Because the configuration of Figure 6 can also reduce the electric field voltages, the electrode configuration of Figure 6 can be adapted for higher voltage potentials potentials. For example, Figure 8 is a graph 148 describing a relationship between the electric field stresses at the surfaces of the electrodes 20, 90-108, and 24 simulated in Figure 6, and the electrical potential distribution along the length of the electrode configuration of Figure 6, when the voltage potentials of the extractor electrode 20 and the intermediate electrodes 22 are

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double. Thus, the extractor electrode 20 can have a voltage potential approximately 200 kV greater than that of the suppressor electrode 24, and the ten intermediate electrodes 90-108 can have voltage potentials ranging from about 200 kV to 0 V higher than suppressor electrode 24. For example, the 90-108 electrodes can have voltage potentials of approximately 200 kV, 177.8 kV, 155.6 kV, 133.3 kV, 111.1 kV, 88.9 kV, 66.7 kV, 44.4 kV, 22.2 kV and 0 V, respectively, higher than the suppressor electrode 24. Target electrode 18 may still have a voltage potential approximately 200 V higher than that of suppressor electrode 24. When the electrode configuration illustrated herein is employed in the acceleration column of an X-ray generator tube, the applied voltage potentials can be substantially the same.

In graph 148 of Figure 8, a first ordinate 150 represents the electric field voltage in units kV / cm, and a second ordinate 152 represents the electric potential in units of kV. An abscissa 154 represents the relative length of the surfaces of the electrode pattern of Figure 6 extending from behind the extractor electrode 20, to the left, beyond target 18, to the right. In graph 148 of Figure 8 a dotted line represents the potential distribution of electric 156 as a function of the length of the electrode configuration of Figure 6.

Like the simulation described in graph 112 in Figure 7, in graph 148 in Figure 8, instead of dramatically decreasing between any two electrodes, the electrical potential 156 slowly decreases from 200 kV, at a point that represents the first electrode 90 of intermediate electrodes 22, at 0 V, at a point representing the last electrode 108 of intermediate electrodes 22. A curve 158 represents the electric field voltages at various points in the electrode configuration of Figure 6. A

<img file="MX340652B_D0018.tif" />

peak 160 at curve 158 represents a maximum point of electric field voltage at extractor electrode 20, peaks 162-182 represent a maximum point of electric field voltage at electrodes 90-108, respectively, and a peak 184 represents a maximum point of electric field voltage at the suppressor electrode 24. As shown in Figure 148, the maximum electric field voltage for the simulated electrode configuration in Figure 6 remains below 140 KV / cm although the voltage potential from extractor electrode 20 to suppressor electrode 24 is approximately 200 kV .

FIG. 9 is a cross-sectional view of a portion of a neutron generator tube 184 containing eight intermediate electrodes 22 arranged in an efficient pattern to guide the electric field along the acceleration column 14. Like the generator tube of neutrons 11, the neutron generator tube 184 can be located within a generator housing 12 and an ion source 16 can provide ions for acceleration through the acceleration column 14 to target 18. In the neutron generator tube 184, the extractor electrode 20 is molded to further reduce the probability that the ions from the ionic source 16 will come into contact with either of the intermediate electrodes 22 or the suppressor electrode 24. The electrodes 186-198 represent Intermediate electrodes 22, of which electrode 192 forms two intermediate electrodes of the same voltage potential. A ceramic insulator 28 separates the outer Intermediate electrodes from electrodes 186-192 and 192-198. The ceramic insulator 28 is not necessarily located between the two electrodes 192, since both electrodes 192 share the same voltage potential.

<img file="MX340652B_D0019.tif" />

To the

Each of the intermediate electrodes 22 can be bent inward in the acceleration column 14. The curvature of the intermediate electrodes 22 can be calculated to guide the electric field through the acceleration column 14 to evenly distribute the electric field. Due to the number and shapes of the intermediate electrodes 22 in the neutron generator tube 184, the acceleration column 14 can extend a greater length than that of the neutron generator tube 10 or similar neutron generator tubes with fewer electrodes. This extended acceleration column 14 can allow ions from ion source 16 to reach the highest energy levels before reaching target 18. At higher energy levels, target 18 can generate a greater number of neutrons.

Electrodes 20, 22, and 24 can be molded to reduce electric field stresses. In particular, the intermediate electrodes 22 can be molded to maintain an approximately equal distance between adjacent electrodes including the extractor electrode 20 and the suppressor electrode 24. Furthermore, the tips 200 of all the electrodes of the neutron generator tube 184 can be molded to minimize a number of electric field stresses that can occur outside of the acceleration column 14, but within the cover of the generator 12. Additionally, the Intermediate electrodes 22 can generally bend to the radial center of the acceleration column 14. The suppressor electrode 24 can also be molded to guide the ions from the ionic source 16 towards the target 18 without excessive spraying events. To the extent that any ion from ion source 16 affects suppressor electrode 24, the variety of intermediate electrodes 22 aligned along acceleration column 14 can prevent any sprayed electrode material from being deposited on insulator 28.

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Graph 202 in Figure 10 illustrates a switched electrical power distribution-204 obtained for the electrode configuration of neutron generator tube 184 in Figure 9. The eight intermediate electrodes 186-198 represent the intermediate electrodes

22 between extractor electrode 20 and suppressor electrode 24. In the simulation of Figure

10, the electrode extractor 20 is simulated as having a potential voltage of 100 kV higher than the electrode suppressor 24 and as having an extrusion shape to uniformly guide the electric field and to reduce the electric field voltages. The eight Intermediate electrodes 186-198 can have voltage potentials that can vary between 100 kV and 0 V higher than the suppressor electrode 24. For example, electrodes 186-198 may have approximately voltage potentials

87.5 kV, 75 kV, 62.5 kV, 50 kV, 37.5 kV, 25 kV and 12.5 kV, respectively, higher than that of suppressor electrode 24. Target electrode 18 may have a potential voltage of approximately 200 V higher than that of the suppressor electrode 24. The suppressor electrode 24 can also be shaped to guide the electric field uniformly and to reduce the electric field voltages. When the electrode configuration illustrated herein is employed in the acceleration column of an X-ray generator tube, the applied voltage potentials can be substantially the same.

Similar to the simulations described above, the relatively small potential differences between each of the Intermediate electrodes 22 can cause the electric field voltages to be relatively lower. Similarly, spontaneous electron emission and / or leakage with negative consequences may be particularly unlikely at electrodes 186-198. Furthermore, an electrical potential distribution 204 can be approximately uniform near the

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center of the acceleration column 14 towards which the ion beam 32 generally travels. Uniformity of electric field distribution 204 can decrease the probability of ion beam 32 contacting suppressor electrode 24 or intermediate electrodes 186-198, which can proportionally reduce spray events. The uniformity of the distribution of the electric field 204, as well as the shape of the suppressor electrode 24, can also reduce the probability of spontaneous electron emission and / or cases of leakage with negative consequences due to the stresses of the electric field at the suppressor electrode. 24. This improved converging effect can produce an ion beam 32 that is substantially parallel to the axis of neutron generator tube 184 and does not shorten it. Such a converging ion beam 32 can further reduce the probability that the neutral ions or atoms caused when the Ions Intercept the pressurized gas 3 can contact any electrode other than the target electrode 18.

Figure 11 illustrates a further study for a neutron generator employing a neutron generator tube 214, which may generally represent the above neutron generator tubes 11 and 184 having one or more intermediate electrodes 22. To assure the potentials of suitable voltage at the different electrodes 20, 22 and 24, the electrodes can be connected to the correct distributed voltages by the high voltage generator 4. This can be accomplished through the use of multiple high-voltage generators 4 and / or by deriving different voltages from a single high-voltage generator 4. However, such an approach may require driving additional high voltages to the electrodes 20 , 22 and 24 and may pose problems due to limited space available.

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Adequate voltage potentials at electrodes 20, 22, and 24 can also be provided by a voltage divider that makes suitable high voltages appear on each of the electrodes. Said voltage divider may include various resistive elements 214, as shown in Figure 11, which may be discrete resistors and / or a resistant coating on the outside of the edge of the insulator 28. The extractor electrode 20 can be connected to ground and the suppressor electrode 24 can be connected to the negative high-voltage potential through the high-voltage negative line 6. The resistant divider provided by various resistive elements 214 can ensure adequate voltage distribution to intermediate electrodes 22. It should be noted that the resistances provided by resistive elements 214 may vary depending on design considerations and the voltage potentials to be applied to the various Intermediate electrodes 22.

Using the improved electrode configurations described above, a downhole neutron generator or X-ray generator can employ a higher voltage potential across the acceleration column 14 from the extractor electrode 20 to the suppressor electrode 24. Accordingly, Figure 12 illustrates one embodiment of a neutron generator configured to supply approximately twice the voltage potential of existing downhole neutron generators. As shown in Figure 12, a high potential neutron generator tube 216 can receive high voltage feedback from two high voltage power supplies 4 electrically connected to the extractor electrode 20 and suppressor electrode 24 respectively. Specifically, a positive output from the high voltage power supply 4 can be coupled to the extractor electrode 20, while a negative output can be coupled to ground to effectively supply a nominal voltage potential of

V 'approximately +100 kV to the extractor electrode 20. Meanwhile, a negative output - ^' of the second high voltage power supply 4 can be coupled to the electrode © supcesQ £ __ ^ _ „_ 24, while a negative output It can be grounded to effectively supply a nominal voltage potential of approximately -100 kV to the suppressor electrode 24. In this way, the total acceleration voltage of 200 kV can be supplied, while the high voltage with respect to ground, and therefore pressure cover 12, cannot exceed 100 kV. In some embodiments, the two high voltages may not be symmetrical. For example, one high voltage generator 4 can supply approximately -120 kV and the other high voltage generator 4 can supply approximately +80 kV, and thus provide a total voltage of approximately 200 kV.

The extractor electrode 20 can be electrically separated from one or more intermediate electrodes 22 by means of one or more resistive elements 214. The resistive elements 214 can include, for example, discrete resistors or a resistant coating on the outside of the column. Acceleration 14, which can be connected to the outer tips of the electrodes and can divide the voltage between the extractor electrode 20 and the suppressor electrode 24. One or more of the intermediate electrodes 22 may or may not be grounded. Similarly, the suppressor electrode 24 can be electrically separated from one or more intermediate electrodes 22 by means of one or more resistive elements 214.

If the neutron generating tube 212 included only a single intermediate electrode 22 that can be grounded, the single intermediate electrode 22 can be maintained at a predetermined potential relative to the other electrodes. Under these conditions,

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a resistive voltage divider could not be employed, but a grounded electrode could facilitate the task of mechanically securing the TOUfrdriés'2T2 ~ generator tube to pressure cover 12 which, as illustrated above with reference to FIG. 1 may surround a neutron generator tube such as neutron generator tube 212. This alternative arrangement can more easily survive the usual rough handling of downhole tools and may also aid in the evacuation of heat from the neutron generating tube 11. If said single intermediate electrode 22 did not bind to a predetermined potential provided by a High voltage power supply 4, one or more resistive voltage dividers 214 can be employed to ensure adequate electrical potentials for electrode 22.

Figure 13 depicts a configuration of neutron generating tube 212 having a grounded mechanical support 216 coupled to one of intermediate electrodes 22. As illustrated, extractor electrode 20 may be separated from suppressor electrode.

24 by the various intermediate electrodes 22. The neutron generating tube 212 may be contained within the pressure cover 12 which includes an insulating sleeve 218. An insulating gas 220 may fill the spaces surrounding the neutron generating tube 212 and may be the same as the insulating gas 3 described above with reference to Figure 1.

A grounded bracket 216 on one of the intermediate electrodes 22 can improve the mechanical strength of the neutron generating tube 212 and can also improve heat evacuation. In the embodiment of Figure 13, the center intermediate electrode 22 is coupled to the ground bracket 216. Additionally or alternatively, the ground bracket

216 can be coupled to any of the intermediate electrodes 22. The configuration

DELA IKOHEDaD MEXICAN INSTITUTE

INDUSTRIAL

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illustrated in Figure 13, it can be particularly advantageous if the positive and negative voltages of the high voltage supply 4 are not symmetrically grounded. Under these conditions, the present configuration can ensure that the intermediate support electrode 22 always remains grounded regardless of the potentials supplied by the high voltage electrical supplies 4.

Although only certain features have been described herein , those skilled in the art will think of many modifications and changes. It should be understood, therefore, that the appended claims are intended to cover all such modifications and changes, which are within the true spirit of the present disclosure.