Patent Application
20140264012
Not applicable.
No listing.
The invention pertains to the low-level, time-series determination of 3He and 4He stable isotopes in the environment. Calculating the ratio of these isotopes can help to characterize the systematics of deep Earth processes such as crust-mantle interactions, seismicity and earthquake activity of the crust and upper mantle, and the movement of magma beneath the Earth's surface.
An instrument design and application method is disclosed that can make precise and sensitive measurements of the isotopic abundance of 3He and 4He stable isotopes remotely and in near real time. The instrument is designed to work in the field in harsh environments. Helium and hydrogen are accumulated into an ultra-high vacuum (UHV) through a heated quartz glass window, and hydrogen isobars that may interfere with helium isotope analysis by mass spectrometry are removed by fast gettering. Exposure to noble diode ion pumps is used to clean the UHV after analysis. The isotope ratio of 3He/4He can be measured in artificial (e.g., process, waste) gases and in natural gases such as those in the atmosphere, in the ground or in seeps, wells and deep boreholes, and in dissolved gases in natural and artificial solutions. The instrument is rugged, portable, low power, and is capable of autonomous operation with internal recording and/or communication of the data remotely in near real time.
Helium Resources
Helium is the second most abundant element in the universe, after hydrogen. There are only two stable isotopes, 3He and 4He. Because of its light mass and noble chemical behavior, the mobility of helium allows its escape from planetary atmospheres like the Earth's, so little original or primordial helium presently exists at the surface. Most helium found near the Earth's surface is produced by the ongoing alpha particle decay of long-lived U and Th with daughter radioisotopes in crustal rocks and sediments, producing 4He. The far less abundant 3He isotope is only stored as residual primordial helium in the Earth's mantle and core, with some minor additions from solar and cosmic ray spallation production in the upper atmosphere and as absorbed helium enriched in 3He in the Moon's regolith and in interplanetary dust particles (IDP) that are constantly drawn down to Earth's surface from interplanetary space.
Most commercial helium today is produced as a by-product of natural gas production from deep wells in the Amarillo, Tex. national helium reserve. By 2015, the Amarillo national facility's helium gas supply is projected to be totally depleted. New supplies from plants coming on line in late 2012 in Wyoming and in foreign natural gas fields (Russia, Australia and Qatar) will not ease the present supply crisis, and the nation could be faced with recycling and other conservation measures such as rationing. With a shortage on, the price of helium may rise considerably, and many present uses could be curtailed. The rare 3He gas is used in neutron detectors by the US military, Dept. of Energy and Dept. of Homeland Security (DHS), in oil and gas exploration, and in advanced medical research. One supplier of 3He we recently contacted, Cambridge Isotope Laboratories, Inc. of Andover, Mass., is quoting it as “currently not available”. Under these developing circumstances, a portable, sensitive sensor capable of detecting both 3He and 4He gas could be useful in process monitoring, exploration, and conservation efforts.
Magma and Earthquake Monitoring
Because of the primordial signature of the helium isotope ratio in the Earth's mantle, it has been useful for earth scientists to compare and monitor the 3He to 4He mass abundance ratio in rocks, sediments and volatiles such as free gases and those dissolved in water. The R/Ra ratio, where Ra=air 3He/4He ratio of 1.4×10−6, varies from 1 in the atmosphere (by definition) to values <1 in continental rocks that are enriched in U and Th (sources of radiogenic 4He), from 0 to 8 in ocean and arc crustal rocks, depending upon age, mixing, and weathering effects, to 8±1 in fresh Mid-Ocean Ridge Basalt (MORB) and volatiles (volcanic gases, hydrothermal fluids) (as described by Poreda, R. J. and Craig, H., 1989, “Helium isotope ratios in cir cum-Pacific volcanic arcs”, Nature 338, 473-478, which is hereby incorporated as reference), to as high as 10-35 in hotspot basalts (gases trapped in glass/vesicles) and in hotspot fumarolic gases and hydrothermal fluids. The higher hotspot values reflect the deep mantle origin of hotspot magma generation (as described by Rison, W. and Craig, H., 1983, “Helium isotopes and mantle volatiles in Loihi Seamount and Hawaiian island basalts and xenoliths”, Earth Planet. Sci. Lett. 66, 407-426, which is hereby incorporated as reference; and by Hilton, D. R., McMurtry, G. M., and Kreulen, R., 1997, “Evidence for extensive degassing of the Hawaiian mantle plume from helium-carbon relationships at Kilauea volcano”, Geophys. Res. Lett. 24, 3065-3068, which is hereby incorporated as reference).
The 3He/4He ratio has been shown to be an effective mantle or magma monitor (as described by Sano, Y. and Wakita, H., 1988, “Helium isotope ratio and heat discharge rate in Hokkaido island, northeastern Japan”, Geochem. J. 22, 293-303, which is hereby incorporated as reference; and by Sano, Y., Nakamura, Y., Wakita, H., Urabe, A., and Tominaga, T., 1984, “Helium-3 emission related to volcanic activity”, Science, 224, 150-151, which is hereby incorporated as reference; and by Sano, Y., Nakamura, Y., Notsu, K. and Wakita, H., 1988, “Influence of volcanic eruptions on helium isotope ratios in hydrothermal systems”, Geochim. Cosmochim. Acta 52, 1305-1308, which is hereby incorporated as reference; and by Sakamoto, M., Sano, Y. and Wakita, H., 1992, “3He/4He ratio distribution in and around the Hakone volcano”, Geochem. J. 26, 189-195, which is hereby incorporated as reference). A very convincing slow rise in the 3He/4He ratio of groundwater following new magmatic activity (earthquakes, seismic tremor) at active Oshima Volcano in Japan was described by Sano, Y., Gamo, T., Notsu, K. and Wakita, H., 1995, “Secular variations of carbon and helium isotopes at Izu-Oshima volcano, Japan”, J. Volcanol. Geotherm. Res. 64, 83-94, which is hereby incorporated as reference. The rise of this ratio in fumarolic gases has also been recorded to follow seismic swarms beneath Mammoth Mountain, Calif. (Long Valley Caldera) associated with underground magma movements there (as described by Sorey, M. L., Kennedy, B. M., Evans, W. C., Farrar, C. D. and Suemnicht, G. A., 1993, “Helium isotope and gas discharge variations associated with crustal unrest in Long Valley Caldera, Calif., 1989-1992”, J. Geophys. Res. 98, 15,871-15,889, which is hereby incorporated as reference). The 3He/4He ratio has been useful in delineating buried active fault segments (as described by Umeda, K. and Ninomiya, A., 2009, “Helium isotopes as a tool for detecting concealed active faults”, Geochemistry, Geophysics, Geosystems, 10, doi: 10.1029/2009GC002501, which is hereby incorporated as reference); time-series variations of the 3He/4He ratio in well waters were shown to correlate with seismic swarms in non-volcanic areas of Japan (as described by Wakita, H., Sano, Y. and Mizoue, M., 1987, “High 3He emanation and seismic swarm activities observed in a non-volcanic, frontal arc region”, J. Geophys. Res. 92, 12539-12546, which is hereby incorporated as reference) and in 1997-98 along active fault zones in Italy (as described by Italiano, F., Martinelli, G., and Nuccio, P. M., 2001, “Anomalies of mantle-derived helium during the 1997-1998 seismic swarm of Umbria Marche, Italy”, Geophys. Res. Lett., 28, 839-842, which is hereby incorporated as reference; and by Italiano, F., Martinelli, G., and Rizzo, A., 2004, “Geochemical evidence of seismogenicinduced anomalies in the dissolved gases of thermal waters: A case study of Umbria (Central Apennines, Italy) both during and after the 1997-1998 seismic swarm”, Geochemistry, Geophysics, Geosystems, 5, doi:10.1029/2004GC000720, which is hereby incorporated as reference). Large earthquakes, such as the Kobe, Japan earthquake in 1995 may be important mechanisms in the release of He from Earth (as described by Sano, Y., N. Takahata, G. Igarishi, N. Koizumi, and N. C. Sturchio, 1998, “Helium degassing related to the Kobe earthquake”, Chem. Geol., 150, 171-179, doi: 10.1016/S0009-2541(98)00055-2, which is hereby incorporated as reference). More recently, the North Anatolian Fault in Turkey was shown to exhibit 3He/4He ratio changes over time thought to be associated with changes in the flow paths of fluids within the fault zone (as described by Dogan, T., Sumino, H. Nagao, K. Notsu, K. Tuncer, M. K. and Celik, C., 2009, “Adjacent releases of mantle helium and soil CO2 from active faults: Observations from the Marmara region of the North Anatolian Fault zone, Turkey”, Geochemistry, Geophysics, Geosystems, 10, doi:10.1029/2009GC002745, which is hereby incorporated as reference).
Barry et al. (2009) describe a method of helium collection in groundwaters and geothermal fluids called SPARTAH (Barry, R H., Hilton, D. R., Tryon, M. D., Brown, K. M., and Kulongoski, J. T., 2009, “A new syringe pump apparatus for the retrieval and temporal analysis of helium in groundwaters and geothermal fluids”, Geochemistry, Geophysics, Geosystems, 10, doi:10.1029/2009GC002422, which is hereby incorporated as reference). It works upon the principle of slow diffusion of dissolved gases collected in narrow copper tubes over time. This slow diffusion allows recovery of water samples collected in coils of copper tubing using an automatic syringe pump, which are then crimped into labeled sections for later analysis in the laboratory using conventional 3He to 4He mass abundance detection. This analysis involves skillful vacuum line extraction and is usually performed with a large noble gas ratio mass spectrometer (MS), such as the Helix SFT made by Thermo Scientific. While such helium collection approaches are useful for advancing knowledge, they do not provide real-time data that could be helpful to hazard mitigation efforts, nor do they provide for changes to the sampling resolution other than that pre-programmed by the water pump speed. The data collection is also limited to dissolved gases. The field instrumentation costs are comparatively modest, but the isotopic data depend upon an established noble gas isotope laboratory for the analyses, which are both costly and labor intensive to produce.
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a. The detector is a cylindrical design of overall length 1 and diameter 4. It consists of two major sub-compartments: 2 a pressure or hermetically-sealed housing 25 containing the detector vacuum components 21-24, 26-and electronic circuit boards 29; and 3 a sampler housing containing the quartz glass membrane assembly 15-17 and heater jacket 19. The heater jacket surrounds the quartz glass membrane assembly upon an inner metal cage support with perforations for flow 20. An outer metal gas-tight case 18 holds the gas or fluid sample as detailed in
1
b. Welded sampler endcap 5 with tubular sample in 8 and out 9 ports and a connector containing the heater and temperature electrical feed-thrus 10.
1
c. Vacuum bulkhead 6 containing the UHV vacuum purge port 11, vacuum port to ion pumps 12, port for the NEG assembly 22, and port for the mass spectrometer 23. The dashed circle 30 denotes the inside diameter of the UHV housing.
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d. Removable endcap 7 with electrical feed-thru connector ports for power 13 and communications 14.
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a. A gas-tight metal housing or case 18 of some overall length 3 and diameter 4 contains the gas sample IN 8 and OUT 9 tubular ports and a connector for the heater and temperature electrical feed-thrus 10 inside a through-hole 38 drilled on a welded endcap 5. It can be constructed by two circular metal welds 39 of a pipe or other cylindrical metal piece to the sample endcap 5 and the sealing rear sample chamber assembly 50. In this preferred embodiment, cold sample gas is confined to a spiral of eight metal coils with a series of small egress holes 36 facing the glass window assembly 15-17, outlined as shown 37. The fit of the outside diameter of the glass port 46 with inside 47 and outside 48 diameters of the diffuser coil are shown.
3
b. The welded endcap 5 contains high-vacuum, temperature-resistant epoxy cement 40 seals to the gas sample IN 8 and OUT 9 tubular ports. This sealing method is preferred over metal welds if the sampler tubing needs to be removed for periodic cleaning, etc. The endcap also contains a pressure-relief valve 41 to prevent over-pressuring of the sampler housing by introduced sample gas.
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c. The sealing rear sample chamber assembly 50 consists of a metal rear chamber mount 42 and a custom high-temperature gasket 43. The entire gas-tight metal housing is mounted to the outer Conflat-type vacuum flange of the UHV 22 with bolts through threaded mount holes in the metal 42 and thru-holes in the gasket 45. It is designed to attach outside of the maximum inside diameter of the sample chamber 49.
5
a. A circular glass disc of diameter d and thickness n (63). Given d=3.0 inch, r=1.5 inch, A=πr2=7.065 in2
5
b. A hollow glass sphere of diameter d and thickness n (64). A=4πr2=28.26 in2
5
c. A hollow cylinder of diameter d (65), length h (66) and thickness n. Given d=3.0 inch, r=1.5 inch, h=6.0 inch, A=2πr2+2πrh=14.13+56.52=70.65 in2
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d. A set of multiple hollow cylinders of diameter m<d 67, length h 66 and thickness n. Given d=1.0 inch, r=0.50 inch, h=6.0 inch×4 tubes in parallel, A=4[2πr2+2πrh]=4[6.28+37.68]=175.84 in2
Hollow glass tubes in 5b-5d indicate passageways to UHV 68. Arrows indicate direction of molecular flow from glass ports 69. Scaling factors relative to the area of the circular disc are:
Disc: 1
Sphere: 4
Cylinder: 10
Multiple cylinders (4): 25
Multiple cylinders (8): 50
Lowered cost.
Sampling in remote locations.
Sampling in environments from near vacuum to full ocean depths.
Sampling in near real time.
Sampling autonomously.
Preprocessing data to lower communication link bandwidth.
Sample sequestration for later lab analysis.
Introducing calibration standards in the field.
In situ field sampling.
Sampling in harsh environments.
High mass resolution sampling.
Sampling from pressurized water.
Sampling from non pressurized water.
A prototype of the instrument has been designed, fabricated and tested. Even the proof-of-concepts, bench-top prototype is relatively low power, compact and rugged. The design can be scaled and optimized for more compact and rugged instrumentation. Sketches of some of the current embodiments of the invention are presented in the figures (
αc/αt=D∇2c,
where C, the concentration of gas within the solid, varies with time and distance through a unit of cross section, and D is the diffusion constant. In the case of permeation of gas through a solid (or slow moving liquid such as glass), the concentration gradient in Fick's Law can be expressed as a pressure gradient, so that Fick's Law becomes:
K∇2ρ=0,
where K is the permeation constant, equal to the product of the solubility S and the diffusion constant D (as described by Altemose, V. O., 1961, “Helium diffusion through glass”, J. Appl. Phys. 32, 1309-1316; doi: 10.1063/1.1736226, which is hereby incorporated as reference). For a plane membrane, with pressure gradient p, cross-sectional area A, and thickness d, the quantity of gas q per unit time t, to pass through it is given by:
q=KAΔpt/d
Spherical samples where d is small compared with the radius of the sphere also reduce to the above equation (Altemose, 1961).
To obtain a high value of q, the principal features of the method and invention include:
1) A quartz glass window comprising the quartz glass membrane. This quartz glass window is composed of either natural or artificial quartz glass composition, that is of high purity for greater diffusion of helium and hydrogen gases. No other gases can permeate the glass window to add to the Ultra High Vacuum (UHV) (Altemose, 1961).
2) A quartz glass window that is thin (small d), within the practical range of 0.5 to 2 mm wall thickness, to allow a greater diffusion of helium and hydrogen gases.
3) A quartz glass window that has high surface area (large A), in either flat sheet, spherical, cylindrical or other tubular forms that allow greatest exposure of the sample gas to the window. Herein, the cylindrical window geometry was chosen over other possible shapes, as it was commercially available and less complex to manufacture than the more optimal designs known to us (
4) A quartz glass window that is sealed to a vacuum chamber so that an ultra high vacuum (UHV) can be attained.
5) A quartz glass window that is heated, from ambient temperatures (0-45° C.) to temperatures of several hundred degrees C., so that diffusion of helium and hydrogen gases is enhanced, with helium diffusion at rates 45 times greater than hydrogen as H2 at 512° C. (as described by Taylor, N. W. and Rast, W., 1938, “The diffusion of helium and of hydrogen through Pyrex chemically resistant glass”, J. Chem. Phys. 6, 612-619; doi: 10.1063/1.1750133, which is herby incorporated as reference; and by Rogers, W. A., Buritz, R. S., and Alpert, D., 1954, “Diffusion coefficient, solubility, and permeability for helium in glass”, J. Appl. Phys. 25, 868-875; doi: 10.1063/1.1721760, which is herby incorporated as reference).
Other important components of the method and invention include:
1) A mass spectrometer, with high enough spectral resolution that the 3He peak can be easily separated from the 4He peak. A peak resolution of 100 M/dM or better is preferred, where M=mass in amu (Daltons).
2) Aa mass spectrometer, with the capability to frequency sweep or to collect electrometer peak spectral response for the 3He peak that can be easily separated from frequency sweep or electrometer collection of the spectral response of the 4He peak.
3) A mass spectrometer, with the ability to switch between analog and digital electrometer peak spectral response, for low-level, single ion counting of the 3He.
4) A mass spectrometer, with high scan speed, that is also compact, low-power and low in cost to purchase and maintain.
Further features include:
1) A non-evaporable getter (NEG) pump, that both maintains the ultra high vacuum and preferentially pumps hydrogen gas and other reactive, polar and non-polar gases but does not pump noble gases such as helium.
2) A non-evaporable getter pump, that can be purchased from a commercial vendor as a heated vacuum-mountable component, or can be made as a coating of titanium or palladium metal inside the UHV that has similar ability to preferentially pump hydrogen gas and other reactive, polar and non-polar gases but does not pump noble gases such as helium.
3) A small diode ion pump, that can be used as a UHV Total Pressure Gauge, while preferentially pumping hydrogen gas and other reactive, polar and non-polar gases but does not pump noble gases such as helium. A commercial HV or UHV gauge that does not pump noble gases can be used in place of, or in addition to, the small diode ion pump as a Total Pressure Gauge.
4) A noble diode ion pump, that is separated from the rest of the UHV by a manual or automated UHV valve (bellows, gate valve or similar) which can pump both noble gases such as helium and hydrogen gas and other reactive, polar and non-polar gases.
5) A purge vacuum port with UHV cutoff valve, to periodically connect the UHV to a portable vacuum station, usually equipped with a turbomolecular-roughing pump and a commercial, full-range atmosphere to HV or UHV pressure gauge for maintenance of the NEG and ion pumps. This port also provides for small sample or standards introduction to the UHV (see
6) An embedded computer and microprocessor with associated circuit boards to record environmental sensors (e.g., ambient temperature, pressure) compute and record mass spectral and total pressure data, run programmed heat ramps and duration, run gas circulation pumps, control automatic opening and closing of UHV valves, and I/O communicate with remote computers via Ethernet and external modem links.
Principles of Operation:
Referring to the flow chart of major operational steps (
At temperatures from ca. −80° C. to up to 800° C., helium will diffuse through the glass at increasing rates (as described by Norton, F. J., 1953, “Helium diffusion through glass”, J. of the American Ceramic Society, 36(3), 90-96, which is hereby incorporated as reference; and by Taylor and Rast (1938); and by Rogers et al., 1954; and by Altemose, 1961). Once the heating ramp is complete and held for a user-specified amount of time, cooling the glass window back to temperatures of 0-45° C. effectively closes the UHV to further helium (and hydrogen) gas diffusion (step d). The sample is now trapped within the UHV and will dominate the vacuum pressure above background gases until they are removed.
Environmental hydrogen gas that diffuses along with helium through the quartz glass window plus any hydrogen that outgases from the materials within the UHV is quickly removed by the NEG pump. Removal of hydrogen gas both lowers the pressure within the UHV, thus concentrating the helium gas analyte, and removes HD, a minor molecular form of hydrogen gas that poses an important isobaric interference with low-abundance 3He measurement by mass spectrometry (as described by Burnard, P., Zimmerman, L. and Sano, Y., 2012, “The noble gases as geochemical tracers: history and background”, in Burnard, P. (ed.) The Noble Gases as Geochemical Tracers, Advances in Isotope Geochemistry, Springer, Berlin, 1-15, which is hereby incorporated as reference). Tritium (3H) poses another potential isobaric interference with 3He measurement by mass spectrometry, but is generally in extremely low environmental abundance and would also be quickly removed by the NEG pump.
Helium isotope analysis (step e) can be accomplished by a small, compact, low-power and low cost mass spectrometer with only modest peak resolution of 100 to 200 M/dM because no HD is present to interfere with the low-abundance 3He measurement. The need for a large and expensive mass spectrometer with peak resolution of greater than 600 M/dM to resolve HD (and 3H) from 3He is obviated by the disclosed design. Absolute partial pressures of 3He and 4He stable isotopes are calculated based upon the relative peak spectral response of the mass spectrometer and the total UHV pressure, as measured by the small diode ion pump or a commercial HV or UHV gauge that does not pump noble gases.
A programmed, embedded PC computes and records the isotopic, total pressure, and the temperature profile data onto flash memory (step f). The same embedded PC and associated circuit boards (CBs) also control the pumped gas circulation cycle, heat ramp and duration, and UHV valve open/close operation (i.e., step g) as well as record the pertinent environmental parameters (e.g., ambient temperature, pressure, seismicity, tilt).
Next, the UHV valve isolating the noble diode ion pump is opened and the helium gas is sequestered (step g). The 4He partial pressure is monitored and recorded (step h). If the helium gas concentration is below a set threshold, the UHV valve is closed (step j) and (if this option is chosen) the data are telemetered to the base PC (step l). If the helium gas concentration is above the set threshold, the sample collection is stopped (step k), the results telemetered to base (step l), and the instrument is shut down (step n). If the sample collection is not stopped, the instrument waits for a user-specified amount of time and repeats the sample collection steps (Step o,
Disclosed is an improved compact, portable 3He/4He stable isotope detector and means for efficiently making precise and sensitive measurements of the isotopic abundance of 3He and 4He stable isotopes from gas or fluid samples at pressures varying from high vacuum to atmospheric to full ocean depth equivalence, of greater than 650 bars hydrostatic. Transmittance is through a heated quartz glass membrane shaped as a disc, hollow sphere, hollow cylinder, or a set of multiple hollow cylinders. This heated quartz glass membrane has pressure backing support consisting of: no pressure backing support, pressure backing support of a sintered metal structure, pressure backing support of a sintered ceramic structure, pressure backing support of a metal structure drilled with holes, or pressure backing support of a metal structure with machined slots. This pressure backing support provides additional pressure support permitting the heated quartz glass membrane to withstand the hydrostatic pressure of the contained sample and provide ease of transmittance of selected gases as molecular flow into the surrounding vacuum chamber. It is comprised of two major sub components consisting of the sampler housing with the heated quartz glass membrane, and a chamber with the mass spectrometer, vacuum components, and electronics. These major subcomponents are separated by a vacuum bulkhead.
This stable isotope detector provides improvements of: lower cost, compact size, lower power requirements, field portability, near real time data output, autonomous operation, telemetry capability, operation from near vacuum to full ocean depths, sample sequestration for later lab analysis, high sensitivity, ruggedized for harsh environments, internal data recording, sampling from pressurized water, sampling from non pressurized water, and in situ operation.
The unit has three basic configurations. A horizontal sampler housing chamber for sampling from gases consisting of: a gas-tight metal housing, a gas sample in port, a gas sample out port, heater and temperature electrical feed-thrus, an endcap, a spiral of a predetermined number of coils of metal tubing with a series of small egress holes facing the glass window port assembly, a quartz glass membrane assembly, a heater jacket, a temperature sensor, a perforated metal support cage, and a metal vacuum bulkhead.
A vertical sampler housing chamber for sampling from gases consisting of: a gas-tight metal housing, a gas sample in port, a gas sample out port, heater and temperature electrical feed-thrus, an endcap, a gas flow damper, a circular diffuser surrounding the quartz glass membrane assembly, a quartz glass membrane assembly, a heater jacket, a temperature sensor, a perforated metal support cage, and a metal vacuum bulkhead. The gas flow damper is used to adjust the exit gas flow rate providing regulation of the glass membrane temperature and regulation of desired gas transmittance through the glass membrane.
A horizontal sampler housing chamber for sampling from fluids consists of a gas and fluid-tight metal housing, a fluid sample in port, a fluid sample out port, fluid and water proof heater and temperature electrical feed-thrus, an endcap, a heater jacket, a temperature sensor, and a metal vacuum bulkhead. It further includes a glass port assembly comprised of a quartz glass tube over a porous sintered pressure support which in high pressure applications has additional pressure support provided by an inner metallic cylinder with drilled holes or machined slots providing the ease of transmittance of selected gases as molecular flow into the surrounded vacuum chamber in which said assemblage provides for samples with relatively high hydrodynamic pressures.
The horizontal sampler housing chamber for sampling from gases provides for selective separation of helium and hydrogen into the vacuum chamber from gaseous samples. The vertical sampler housing chamber for sampling from gases provides for selective separation of helium and hydrogen into the vacuum chamber from gaseous samples. The horizontal sampler housing chamber for sampling from fluids provides for selective separation of helium and hydrogen into the vacuum chamber from fluid and or water samples.
The chamber with the mass spectrometer, vacuum components, and electronics consists of: a sample collection unit, a mass spectrometer, a high vacuum chamber, a non-evaporable getter pump, a diode ion pump, a noble diode ion pump, a purge vacuum port with ultra high vacuum valve, ultra high vacuum total pressure gauge, electronics, wiring, solenoid valves, controls, temperature and pressure sensors, and an embedded computer and microprocessor. The sample collection unit consists of: an ultra high vacuum valve, two solenoid valves, tubing and interconnections, two UltraTorr™ valves, a gas tight tubing clamp, and an end crimped copper tubing. The sample collection unit provides for sequestering of a predetermined sample within a section of copper tubing which can be gas tight crimped and removed for further in lab analysis. The mass spectrometer provides for spectrum analysis of the sample within the high vacuum chamber. The high vacuum chamber consists of the free space of the interconnected vacuum components of this apparatus. The non-evaporable getter pump maintains the ultra high vacuum and preferentially pumps hydrogen gas and preferentially pumps other reactive polar gases and preferentially pumps other reactive non-polar gases but does not pump noble gases such as helium. The diode ion pump preferentially pumps hydrogen gas and preferentially pumps other reactive polar gases and preferentially pumps other reactive non-polar gases but does not pump noble gases such as helium. The noble diode ion pump is selectively separated or connected to the high vacuum chamber by a manual or automated ultra high vacuum valve. The noble diode ion pump can pump both noble gases such as helium and hydrogen gas and other reactive polar gases and other reactive non-polar gases. The purge vacuum port with ultra high vacuum valve provides for periodic connection of the high vacuum chamber to a portable vacuum station, introduction of small sample standards to the high vacuum chamber, and sequestration of small sample standards from the high vacuum chamber. The embedded computer and microprocessor record data from environmental sensors including temperatures and pressures; compute and record mass spectral and total pressure data; control preprogramed operation of heat ramps, gas circulation pumps, opening and closing of valves, execution of input and output, and communicate with remote computers via ethernet and external remote communication links.
The heated quartz glass membrane functions as a quartz window between the sample chamber and the high vacuum chamber providing selective transmittance of hydrogen and helium gases as molecular flow into this vacuum chamber. It is impermeable to all other gases other than hydrogen and helium and provides for exclusive transmittance of hydrogen and helium into the high vacuum chamber. The rate of hydrogen transmittance differs from the rate of helium transmittance. The rate of helium transmittance through the glass window is affected by the purity of the quartz glass, the thickness of the quartz glass wherein helium diffusion increases inversely with thickness, the surface area of the quartz glass window wherein diffusion increases proportionally with surface area, with the pressure differential across the quartz glass window wherein diffusion increases proportionally with increased pressure differential, with temperature wherein diffusion increases proportionally with increases in temperature. The differential diffusion of helium becomes greater than that of hydrogen with increased temperature. The helium diffusion rate is 45 times greater than molecular hydrogen at 512 degrees Celsius.
The mass spectrometer functions to measure the abundance of gas species by mass. Desirable performance characteristics of said mass spectrometer include: High spectral resolution with sufficient spectral resolution to resolve helium 3 verses helium 4. A resolution of 100 M/dM or better where M is mass in Daltons. The ability to produce and analog output representation of abundance. The ability to produce a digital output based on pulse hight. High scan speed, compact size, low power consumption, low cost, and high dynamic range.
The vacuum bulkheads comprises a circular metallic structure capable of withstanding the applied hydrodynamic differential pressure. The vacuum bulkhead provides a mounting location for: the sampler housing, the chamber with the mass spectrometer, vacuum components, and electronics, the ultra high vacuum purge port, the vacuum port to the noble diode ion pump, the port for the non-evaporable getter pump, the port for the diode ion pump, and the port for the mass spectrometer.
This improved compact, portable 3He/4He stable isotope detector functions by the following operations: A sample is introduced into the sample chamber. The quartz glass window is heated to a predetermined temperature and this heated quartz glass window provides for exclusive diffusion of helium and hydrogen. With higher temperatures the heated quartz glass window more preferentially diffuses helium.
The hydrogen gas diffused into the high vacuum chamber is selectively pumped and sequestered by the non-evaporable getter pump. The heating of the quartz glass window is stopped after a predetermined amount of time with cooling the quartz glass window below 45 degrees Celsius effectively closing the quartz glass window to further hydrogen and helium diffusion. The mass spectrometer measures the helium 3 and helium 4 abundance and electronics calculates and records the helium 3 to helium 4 ratio. The ultra high vacuum valve opens and exposes the vacuum chamber to the noble diode ion pump and the noble diode ion pump pumps and sequesters the helium gas level to below a set threshold as measured by the ultra high vacuum total pressure gauge. The apparatus is now prepared to receive another sample and the process is repeated. In the event that the helium is not pumped by the noble diode ion pump to below the set threshold in a predetermined amount of time such an indication is recorded. If telemetry is available this indication of not reaching a predetermined helium threshold level is telemetered the unit is then shut down.
These improved means of making precise and sensitive measurements of the isotopic abundance of 3He and 4He stable isotopes from gas or fluid samples provide: lowered cost, sampling in remote locations, sampling in environments from near vacuum to full ocean depths, sampling in near real time, sampling autonomously, preprocessing data to lower communication link bandwidth, sample sequestration for later lab analysis, introducing calibration standards in the field, in situ field sampling, sampling in harsh environments, high mass resolution sampling, sampling from pressurized water, and sampling from non pressurized water.
This improved compact, portable 3He/4He stable isotope detector and means for efficiently making precise and sensitive measurements of the isotopic abundance of 3He and 4He stable isotopes from gas or fluid samples at pressures varying from high vacuum to atmospheric to full ocean depth equivalence, of greater than 650 bars hydrostatic. It is small, efficient, rugged, autonomous providing a unit for field survey work and monitoring. It has three embodiments. A horizontal sampler housing chamber for sampling from gases provides for selective separation of helium and hydrogen into the vacuum chamber from gaseous samples. A vertical sampler housing chamber for sampling from gases provides for selective separation of helium and hydrogen into the vacuum chamber from gaseous samples. A horizontal sampler housing chamber for sampling from fluids provides for selective separation of helium and hydrogen into the vacuum chamber from fluid and or water samples.
In the descriptions above, we have put forth theories of operation that we believe to be correct, such as the making precise and sensitive measurements of the isotopic abundance of 3He and 4He stable isotopes. While we believe these theories to be correct, we don't wish to be bound by them. While there have been described above the principals of this invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and is not as a limitation to the scope of the invention. Other embodiments of these approaches to efficient dissolved gas and volatile organic compound transmittance from a fluid will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification be considered as exemplary only, with the true scope and spirit of the invention being indicated by the appended claims and their legal equivalents, rather than by the examples given.
“This application claims the benefit of Provisional Patent Application Ser. No. 61/852,113, filed 2013 Mar. 15 by the present inventor.”
| Number | Date | Country | |
|---|---|---|---|
| 61852113 | Mar 2013 | US |
