text:
Separation of U235 and U238 isotopes by converting a mixture of these isotopes to organic compounds or to silicon compounds and then irradiating the isotope compounds selectively to change their chemical (and/or physical) properties, thereby to facilitate separation. In a preferred embodiment of the invention the uranium compounds are selected from the group having a chemical moiety R bonded directly to the U atom, the U-R bond having a fundamental, overtone, or combination virbational absorption frequency between 900 and 1100 cm-1. The selected U mixture is then irradiated with a frequency-selective CO2 laser.
1. Apparatus for separating isotopes of a metallic element to provide an iostopically-enriched product, said apparatus comprising:
reaction chamber means for retaining a chemical composition including a plurality of isotopic species of the metallic element,
valve means for controlling introduction of the chemical composition into said reaction chamber means,
means for controlling atmospheric composition within said reaction chamber means,
temperature control means to regulate the temperature interiorly of said reaction chamber means,
generator menas including power supply means for producing a beam of radiated energy,
means including electrode means to direct said beam to impinge upon said chemical composition contained in said chamber means to interact with and to modify properties of said chemical composition so as to facilitate the separation of isotopic components thereof.
2. The apparatus as set forth in claim 1 and further comprising photo detector means for monitoring interaction of said beam with said composition.
3. The apparatus as set forth in claim 1 and further comprising reservoir means for storage of said chemical composition, and heat exchange means for regulating the temperature of the composition stored in said reservoir means.
4. The apparatus as set forth in claim 1 and further comprising a reservoir for storage of reaction and buffer gas, and valve means for regulating introduction thereof into said reaction chamber.
5. The apparatus as set forth in claim 1 and further comprising vacuum pump means for exhausting gases from said reaction chamber.
6. The apparatus as set forth in claim 1 wherein said generator means includes means for generating a tunable CO2 infra-red laser.
7. The apparatus as set forth in claim 1 wherein said temperature control means comprises an expansion nozzle connected to said valve means and positioned in said reaction chamber means.
8. The apparatus as set forth in claim 1 wherein said generator means includes means for generating tunable infra-red radiation.
9. The apparatus as set forth in claim 1 wherein said generator means includes means for generating tunable infra-red radiation and for generating ultra violet radiation.
10. Apparatus for separating isotopes of a metallic element to provide an isotopically-enriched product, said apparatus comprising:
generator means to produce a beam of radiated energy,
irradiation chamber means disposed to receive a beam of radiated energy from said generator means,
movable substrate means for supporting a composition to be irradiated,
means for supporting and moving said substrate means and a composition including a plurality of isotopic species carried thereon through said irradiation chamber means,
reaction chamber means and means communicating with said irradiation chamber means to permit passage of said substrate means therethrough from said irradiation chamber means to said reaction chamber means,
drive means for propelling said substrate means through said reaction chamber means to facilitate interaction between the substrate-carried composition and a reactant contained in said reaction chamber means.
11. The apparatus as set forth in claim 10 and further comprising temperature control means for regulation of the temperature in said reaction chamber means.
Isotope separation is an area of profound importance not only to chemists and physicists but to the entire populace as well. The use of infra-red lasers to separate isotopic species is suggested in the prior art. Described techniques involve selectively exciting gaseous molecules of a given isotope with intense, highly monochromatic laser radiation. It is required that the frequency of the radiation be coincident with a fundamental, combination, or overtone in the vibrational spectrum of the molecule. The vibrational excitement of the molecules may lead to spontaneous decomposition, or it may be necessary to introduce a second agent, which reacts selectively with the excited species. In some cases, simultaneous laser and ultraviolet or visible radiation have been employed. In all cases, the objective is selectively to transform the molecules of a single isotope into an enriched material which can be separated (on the basis of solubility, volatility, electrical charge, etc.) from the molecules containing the other isotope(s). To prevent energy transfer between isotopically different molecules, it may be desirable to operate at low pressures and/or to add an inert diluent.
The above concepts have been proposed for the photoexcitation separation of the uranium isotopes U235 and U238. Robieux, U.S. Pat. No. 3,443,087, describes the selective ionization of UF6 by a combination of infra-red (IR) and ultra violet (UV) laser irradiation to facilitate electrostatic separation of U235 in the vapor phase, and Belgian Pat. No. 821,823 describes selective dissociation of UF6 by a combination of IR and UV, facilitating chemical separation of U235.
However, the fundamental vibrational resonance frequencies of UF6 are 624 cm-1, and 186 cm-1, values which are not presently available from electrically pumped transitions in gas lasers. Semiconductor lasers are available which can be tuned to this frequency, but their output power is limited to fractions of a watt. This low power results in an intensity that is insufficient for multiphoton absorption to cause dissociation. Any reactions induced would occur at low rates which are impractical for production processes. Other prior art separation processes such as those in UK Pat. No. 1,284,620 describe the method of isotope separation by selectively stimulating chemical reactions effected by irradiating an isotope mixture with a laser frequency corresponding to the vibrational absorption frequency. Specifically, it is there disclosed to use a CO2 laser in combination with the molecules UF6, UFn Cl6-m, UCl6, or U(BH4)4. However, none of these molecules is known to have fundamental vibration frequencies in the CO2 laser output range- Since the most stable and reliable, and the most economical source of infra-red laser radiation is a carbon dioxide gas laser, the most effective range of which 9.2-11.0μ, 1086-909 cm-1, the above molecules would not absorb sufficient radiation for usable excitation. None is reported to have fundamental or overtone metal-ligand vibrations in the appropriate region of the spectrum.
It is an important feature of the present invention that it teaches the use, in laser induced separations of uranium isotopes, of compounds having vibrational sensitivites accessible to a CO2 laser.
In achieving the aims of the present invention, two properties are most desirable as initial criteria for the suitability of uranium compounds. In one embodiment, the compounds must be sufficiently volatile to be irradiated in the gas phase. In the second embodiment the compounds may be condensed from the gas phase in a matrix or applied as a solution. The molecules must have metal-ligand fundamental or overtone (preferably the former) vibrations in the region accessible to a CO2 laser, i.e. 900-1100 cm-1 in the preferred mode of irradiation. These criteria encompass a surprisingly wide range of compounds.
Coordination number and coordinative saturation appear to play a major role in determining the volatility of neutrally charged uranium compounds. In low oxidation states, e.g. +4 a uranium complex with non-bulky ligands will attempt to expand its coordination number beyond 4 by coordinating additional ligands, or, when these are unavailable, by forming ligand briding bonds to neighboring uranium ions. This leads to polymeric structure, high lattice energies, and low volatility. Two approaches can be used to circumvent this problem. In higher oxidation states, the uranium will have a smaller ionic radius, hence a smaller desired coordination number, and generally more ligands per metal ion. This usually leads to higher volatility. Another way to reduce intermolecular interactions is by employing sterically bulky ligands. ##STR1## For example, in the alkoxide series, U(OCH3)4 is essentially non-volatile, insoluble, and is probably extensively associated in the solid state. In contract, U i-OC3 H7 !4 is more soluble and can be sublimed. Further confirmation of these concepts is found in U(OC2 H5)5 which is dimeric and rather volatile (boiling point 123�/0.001 mm pressure) and in U(OC2 H5)6 which is monomeric and even more volatile (boiling point 72�-74�/0.001 mm pressure). Thus, maximizing the oxidation state and the coordinative saturation are feasible approaches to increased volatility. Also important, but apparently less critical, is keeping the molecular weight as low as possible.
The foregoing discussion is believed to be relevant to reaction design for uranium iostope separation. One attractive strategy is to employ those laser-induced reactions which disassociate a ligand (or ligands) from the uranium, or which promote the substitution of a less bulky ligand. Starting with, for example, a U(VI) compound, laser promoted homolytic
UL6 → UL5 +L.sup..
ul5 → ul4 +l.sup..
cleavages would reduce the uranium to the accessible +5 then +4 oxidation states. The UL5 and UL4 species are entities markedly less volatile than UL6 and are separable. Alternatively, reactions such as
produce a U(IV) complex with different properties (e.g. volatility, solubility) than UL4, since the L' is less bulky and may also form intermolecular bridges.
The compounds selected for use in the first embodiment must be stable to the thermal conditions necessary to volatalize them. In the Pearson terminology, uranium is a "hard" acid. It will have the greatest affinity for negatively charged, non-polarizable ligands. Such qualitative rules are relevant in developing syntheses and also in promoting, via laser irradiation, ligand substitution reactions. Fortunately, many of the properties which impart volatility afford, in addition, some resistance to thermal degradation. Studies of the mechanism of thermal decomposition of several classes of uranium organometallics indicate that corrdinative saturation of the uranium ion can greatly retard thermal decomposition. This presumably arises because immobilization of the coordination sphere blocks the lower energy pathways for thermolysis. Thus, the approaches which should foster higher volatility are, in addition, reasonable initial approaches to enhance thermal stability. Such concepts clearly illustrate that decompposition of the desired molecules by energetic photons facilitates separation from undecomposed molecules by the resulting differences in chemical and physical properties.
The following is a partial enumeration of useful classes of compounds, for the purposes of the present invention. The frequency of the metal-ligand stretching (and to a lesser extent, deformation) fundamental is important in the practice of the invention. The magnitude of the frequency difference in ν 238U-X versus ν 235U-X will depend on the particular molecular system. For uranyl complexes (O═U+2 ═O) the difference should be ca. 0.7 cm-1 for the antisymmetric O═U═O stretch. Application of the Teller-Redlich product rule yields a value for the Tlu U-O stretching mode of ca. 1.5 cm-1 in U(OCH3)6, treating the methoxy ligands as point masses (a crude qualitative approximation). The most accurate analysis of metal ligand fundamentals is through high resolution metal isotopic substitution studies, an area which has recently seen rapid development.
A number of known volatile uranium complexes, not suggested for such use in the literature, are, in accordance with the invention, employed for the laser-induced separation of uranium isotopes. These compounds have metal-ligand fundamental or overtone vibrations in the spectral region accessible to a CO2 laser, and, as herein disclosed, are susceptible to isotope-selective excitation and interception. Arranged by class, compounds useful in the practice of the invention include the following:
These complexes of the BH4 - ligand have been found to have a tridentate metal-ligand geometry. Under C3v local symmetry, the A1 and E bridging modes, which are believed to have considerable .sup.ν M-H character, occur in the region ca. 1100-1230 cm-1. All have sufficient volatility to make them ##STR2## attractive. Examples are given below.
Most of these complexes can be prepared by displacing halide with BH4 - or BD4 - in an ethereal solvent. Indeed, we have found borohydride derivatives to be some of the most accessible for a number of organoactinide systems studies. Additional ##STR3## volatile derivatives are prepared by sequences such as,
U(OR)n HCl U(OR)n-1 Cl NaBH.sbsp.4 U)OR0n-1 BH4
in several of the compounds, for example U(BH4)4, the desired normal mode is above the frequency accessible to the CO2 laser for U(BH4)4 ν = 1230 cm-1). Deuteration shifts this absorption to ca. 926 cm-1. Deuterated compounds are accessible via commercially available NaBD4 or LiBD4.
These are complexes which incorporate the O═U═O functionality, usually in a pantagonal (A) or hexagonal (B) bipyramidal arrangement (a few octahedral examples are also known). The antisymmetrically coupled ν O═U═O stretching vibration usually occurs in the region 910-940 cm-1. ##STR4##
Another compound for laser irradiation is uranyl superphthalocyanine, prepared in a template reaction as shown below. ##STR5## This compound has very high chemical and thermal stability and sublimes in vacuo at 400�. Still other organic "monomers" providing macrocyclic uranyl complexes of lower molecular weight, and greater volatility include: ##STR6##
Uranyl alkoxides, UO2 (OR)2, also reported in the literature, are generally of low volatility, and are particularly suited for the second embodiment. Complexes with bulky fluorinated alcohols are also useful in the practice of the invention. While known uranyl β-diketonates are not appreciably volatile, very bulky ligands such as fod, shown below, complexed to uranium are of interest. ##STR7## Also, aluminum alkoxide ligands impart volatility. A possible route to such complexes for U(VI) is, ##STR8##
Complexes with OR- ligands may be prepared for uranium on a large scale and in a variety of oxidation states. Many are quite volatile; some are distillable liquids. The known analogous silicon compounds are also appreciably volatile. Representative species are shown below, and it is apparent that they offer a wide flexibility in terms of possible variation of oxidation state, symmetry, and volatility.
______________________________________U(OR)4 U(OSiR3)4U(OR)5 U(OSiR3)5U(OR)5 U(OSiR3)6R = variety of organic groups______________________________________
A u-o fundamental (except possibly for uranium in the +6 oxidation state) will not absorb in the desired frequency region. For example, the Ti-O stretches in Ti(OCH3)4 have been assigned at 588 and 553 cm-1, those in Ti(OC2 H5)4 at 625 and 500 cm-1, and those in Nb(OEt)5 at 571 cm-1. Though the fundamental U-O stretches in the aforementioned alkoxides may not be in the CO2 laser range, overtones are. The fundamental U-O stretch occurs in the region 460-550 cm-1. Hence, the first overtone is in the region 920-1100 cm-1. By appropriate selection of ligands to "tune" the symmetry and various force constants, it is possible to bring a U-O overtone or combination band into Fermi resonance with another fundamental (e.g. ν C-O ≈ 1000 cm-1), thereby increasing the excitation cross section. In addition, high power lasers operative at the U-O fundamental frequencies are expected to be available in the near future.
The uranium alkoxides also appear to be excellent precursors to other derivatives. Typical reaction schemes to introduce a variety of new ligands are shown below. ##STR9##
Mixed complexes in which one or more of the OR or OSiR3 groups is replaced by a β-diketonate, a borodeuteride, or an alkyl group are within the concept of the present invention.
These compounds include complexes of the formula Ln URn-4 where L═C5 H5, an alkoxide or siloxide, or borodeuteride and R is an alkyl (e.g. methyl, ethyl, isopropyl, t-butyl, benzyl, neopentyl) or aryl (e.g. phenyl) group. The U-C stretching - vibration occurs in the region of 500 cm-1. Thus, the first overtone is in the region of 1000 cm-1. Uranium alkyl compounds are thermally stable only if sufficient coordinative saturation is present to hinder various intramolecular decomposition processes. Thus (C5 H5)3 UR compounds (with π -bonded C5 H5 ligands) possess rather high thermal stability. For R= methyl or vinyl, the complexes are sublimable. ##SPC1##
Systems such as (C5 H5)3 UR offer the attractive feature that products of a homolytic laser-induced cleavage would be (C5 H5)3 U, which is nonvolatile, and R-radicals, which could be scavenged. Other attractive uranium alkyl systems are presented below.
CH2 (C5 H4)2 UCl2 RLi CH2 (C5 H4)2 UR2
uo2 cl2 RLi UO2 R2
(c5 h5)ucl3 �2THF RLi (C5 H5)UR3
thf = tetrahydrofuran
Particularly interesting, in terms of imparting thermal stability, are bulky R groups (e.g. t-butyl), those without β-hydrogen atoms (e.g. tri-methylsilylmethyl) and chelating alkyls (e.g. those derived from 1, 4-dilithiobutane).
The stability of W(CH3)6 suggests the utilization of U)CH3)6, which is expected to be quite volatile.
UCl6 CH.sbsp.3Li U(CH3)6
The diethylamide of uranium U N(C2 H5)2 !4 is volatile enough to be distilled or sublimed. Until recently, it was the only known uranium dialkylamide. Since the U-N stretch falls in the 500 cm-1 region, the first overtone is in the region of 1000 cm-1. The amido complexes of uranium contain the U-NR2 functionality; examples include U(NR2)4, Ln U(NR2)n-4 where L = B diketonate, alkoxide or siloxide, alkyl group, or borodeuteride. Some approaches to a variety of compounds are proposed below. ##STR10## The existence of W N(CH3)2 !6 is impetus to investigate uranium oxidation states higher than +4.
In the above cases, the complexes may be irradiated in the gas phase or in the frozen solid phase at the fundamental, combination, or overtone metal (either U238 or U235) - ligand frequency, with a high power CO2 gas laser. This is carried out both with and without simultaneous ultraviolet or visible irradiation. Reactive agents such as methanol, styrene, thiols, etc. can also be added to trap the excited molecules. In the first embodiment, the reactions are conducted preferably at low pressures, and it is possible to add an inert diluent such as methane, neon, argon, etc. In all cases, the selectively excited molecules react to form an iostopically enriched (in U238 or U235 depending on the irradiation frequency) product which is chemically different from the starting material. The product is then isolated from the starting materials on the basis of volatility, solubility, and/or electrical charge.
It is also possible, in accordance with the second embodiment of the present invention, to effect isotopic substitution by condensing or spraying the proposed compounds in an appropriate matrix at cryogenic temperatures. Selective excitation, as proposed for the gas phase procedures, is preferably carried out with a CO2 laser, but other tunable, stable infra-red lasers may be used. The matrix is designed to react with the selectively excited uranium compounds. Suitable matrix components include alcohols, ketones, thiols, styrene, organic nitroxides, etc. Again, the reaction products differ sufficiently from the starting materials to allow separation when the matrix is warmed to ambient temperature.
The present invention will be more fully described with reference to the drawings depicting suitable apparatus for effectuating the method of the invention and in which
FIG. 1 illustrates one embodiment of the invention in which a pulsed CO2 laser, controlled in frequency and intensity, is used to irradiate a gaseous U-organic isotope mixture;
FIG. 2 illustrates a second embodiment in which the radiation from a CO2 laser is combined with a UV source to irradiate a gaseous U-organic isotope mixture; and
FIG. 3 illustrates a third embodiment in which lasers irradiate a solid-state U-organic isotope mixture frozen in a glassy matrix.
Referring now more particularly to FIG. 1 of the drawing, a gaseous mixture of U235 and U238 incorporated in a U-organic compound, for example, a uranium alkoxide U(OEt)6 is irradiated in a reactor 10 by a laser beam 12 from a pulsed CO2 laser source 16. The reactor includes a one meter long monel reaction tube 18 having an entry window 20 for entry of the laser beam 12 and an exit window 24 for exit of the beam 12. The beam entry and exit windows 20, 24 may be of NaCl or other suitable materials such as ZnSe that transmit the 9-11 micron CO2 laser radiation. The windows 20, 24 are positioned at the Brewster angle to the beam 12 to minimize loss of beam energy. A photo-detector 26 monitors the unabsorbed portion of the beam 12, and a monitor window 28 of quartz, connected by a side tube 32 to the reaction tube 18, may be used to monitor the visible and UV fluorescence from the reaction. The U-organic composition is stored in a reservoir 34, fitted with a heat exchange coil 34a, and a reactive or buffer gas may be stored in a second reservoir 36.
The U-organic composition, (or the U-silicon composition) is introduced into the reaction tube 18 through a metering valve 38 which may incorporate a converging-diverging nozzle 40 for expansion cooling, designed as is well known in the art to provide a velocity of approximately Mach 1 or larger. A reaction or buffer gas in reservoir 36 is introduced (when desired) into the reaction tube 18 through a second metering valve 42. A heating coil 44 adjusts the temperature in the reactor 18 for the desired vapor pressure. A vacuum pump 46 exhausts the gases in the reaction tube 18 through an aperture 48, to a second chamber or zone 54 the temperature of which is controlled by a heat exchanger 56. A third chamber or zone 54a may be used to condense unreacted components as well as volatile by-products. Pump 46 exhausts into a storage tank 58. The tetra alkoxide, U(OEt)4 is a principal reaction product, together with organic fragments. The less volatile tetra alkoxide is then separated from the more volatile constituents of the mixture to achieve the desired isotope enrichment. A focusing lens 60 focuses the laser beam 12 through the entry window 20 to a spot on the optical axis of the reaction tube 18 to position the reaction above nozzle 40 of the valve 38.
The laser source 16 uses a pulsed electrical discharge between a pair of bronze electrodes 62, 64 to attain output power between the limits of 104 and 1010 watts per cm2. The upper value of beam intensity is limited in some cases by breakdown of the gases and formation of a plasma. The electrodes 62, 64, in a preferred embodiment of the invention, are 50 cm long � 2 cm wide and are separated by 1 cm. The lasing gas, which may be a 1,1,8 molar mixture of CO2 N2,He stored in a pressurized tank 68 is introduced through a reducing valve 70 into the circulating and cooling system 72 of laser source 16. The electrodes 62, 64 are symmetrically positioned above and below the axis of an acrylic laser tube 76. The tube ends are sealed by Brewster angle, NaCl end windows 78, 80. An optical resonator is formed between an adjustable grating 84 and a 95% reflecting germanium (Ge) mirrow 88 which are centered about the optical aXIS (which is slightly off-set from the center axis of the electrodes 62, 64 when the beam passes through the end windows 78, 80). Depending on whether a stable or unstable resonator is desired, the Ge mirror 88 may be convex, flat, or concave, as presented to the grating 84. The grating 84 acts as a plane, frequency-selective mirror which is adjusted for the particular U-organic used. The grating 84 and the Ge mirror 88 may be positioned inside the laser tube 76 eliminating the end windows 78, 80. However wide mirror spacing is desired to improve frequency characteristics.
Electrical power to the electrodes 62, 64 is supplied by a power supply 92, 94, through suitable leads 96, 98. The electrical pulse from supply 92, 94 is a fast rise-time pulse of typical magnitude 47 KV per cm of spacing between the electrodes 62, 64 and per atmosphere of lasing gases. The power supplies 92, 94 may be a Blumlein or equivalent design with low-inductance circuit elements. Alternatively a commercial, triggered spark-gap may be used for the power supply 92, in which case the lead 96 is connected directly to ground eliminating supply 94.
To facilitate a uniform glow discharge at high lasing gas pressures in the laser tube 76, a thin (0.007 inch) tungsten wire 102 is positioned at mid-plane but outside the edges of the electrodes 62, 64 and connected through a small capacitor 104 (typically 50 pF or less) to the lead 98. Thus, the rising voltage from the power supply 92, which increases the potential difference between the electrodes 62, 64, also increases the potential difference between the wire 102 and the electrode 62. However, the Townsend breakdown voltage between the wire 102 and the electrode 62 is adjusted to be lower than between the electrodes 62, 64 thereby causing limited breakdown and preionization of the lasing gas prior to breakdown between the electrodes 62, 64. Other pre-ionization circuits may be used such as naked spark-gaps positioned outside the electrodes 62, 64 along the mid-plane to UV-irradiate the gap between the electrodes 62, 64. Also, a low ionization-potential liquid such as tri-butylamine may be applied to the electrodes 62, 64 to reduce sparking.
Hot lasing gases from the gap between the electrodes 62, 64 are recirculated and cooled through a cooling tube 106 of the refrigerator 72 by ducts 110, 112 by means of a pump (not shown). A cooling coil 116 extracts the heat, from the lasing gases, added by power absorbed from the power supply 92 during the electrical discharge. The ducts 110, 112 are ideally located to circulate lasing gases directly through the space between the electrodes and may use a diffuser if turbulence is required to stabilize the discharge.
The most convenient operating pressure of lasing gases in the laser tube 76 is atmospheric. However, the value can be above or below one atmosphere, depending on desired output characteristics. In some cases it may be necessary to raise the pressure to attain tunability above the natural transitions as broadening of the CO2 lines increases 3GHz per atmosphere up to 10 atmospheres where CO2 laser lines overlap.
Thus in operation, the laser source 16 is switched on the aligned with the optical axis of the reaction tube 18 of the reactor 10. To obtain the proper output frequency selection of the laser source 16, the reaction tube 18 is evacuated and backfilled with U-organic compound enriches in U235. Absorption is noted while laser lines are selected with the grating 84. The U-organic feedstock in reservoir 34 is then admitted through the reducing nozzle 40 and irradiated. Non-volatile reaction products are condensed in Chamber 54 and non-volatile products as well as reacted U-organic are condensed in a second cold zone 54a.
Of course, other U-organics may be used with the laser source 16 tuned by the grating 84 to the desired frequency and with the intensity selected to the proper value. In each case the reaction proceeds from the focal spot back up-stream toward the laser source 16 until the intensity falls below the minimum value.
The apparatus of FIG. 2 differs from that of FIG. 1 primarily in the arrangement of the "laser source", two sources being used in the FIG. 2 embodiment. For the most part, the reactor of FIG. 2 is the same as for FIG. 1 and, therefore, the corresponding mechanical components of FIG. 2 are designated by "primes" (').
Referring now to FIG. 2, tunable CO2 infra-red laser source 120 and tunable argon ion laser source 130 direct laser beams 134 and 136 through Brewster angle input windows 140 and 142 to a common focal spot. The second input window 142 is made from a silica or Vycor plate, transparent to UV and visible radiation while the remaining parts, designated with subscripts "a" and "b", of the two laser apparati are similar to those described with reference to FIG. 1. However, since fewer IR photons are required, sufficient intensity may be obtained from the laser source 120 without use of a focusing lens, which is omitted, or by means of a CW CO2 laser with sufficient output intensity (power per unit area).
In operation, on proper frequency tuning, the laser source 120 excites the vibrational states in the U-organic compound and the laser source 130 raises the electronic states sufficiently to dissociate the desired chemical bond attached directly to the U atom or to stimulate a chemical reaction. Laser 130 may be replaced with a filtered Hg lamp or other UV source of sufficient intensity to dissociate the desired bond in the cases that sufficient isotope selectivity is obtained through vibrational excitation by irradiating with laser 120. A frequency doubler (not shown) may be used with the tunable laser 130, depending upon the particular U-organic.
Referring to FIG. 3, laser sources 150 and 160 provide laser beams 164 and 166 to irradiate U-organics in the frozen solid state transported on a ribbon-like substrate 170 through a reaction chamber 172 between two adjacent irradiation sections 174, 176 in which the atmosphere may be controlled. Laser 160 may be replaced with a filtered Hg lamp or other UV source of sufficient intensity to dissociate the desired bond in the cases that sufficient isotope selectivity is obtained through vibrational excitation by irradiating with laser 150. In the irradiation section 174, the substrate 170, which may be thin stainless steel foil, is moved from a take-off spool 180 onto a hollow, rotating first drum 182 which is cooled by liquid N2 injected through a hollow journal 186. A nozzle 188 sprays on U-organic such as Ln UO2 where L is a macrocyclic ligand such as superphthalocyanine mixed with a matrix such as 3 methylpentane in the molar ratio of 1/100. Alternatively, the matrix may be selected from several gases or organic liquids or gases which do not absorb photons at the laser frequencies used and which do not broaden the U-organic vibrational absorption substantially. The frozen U-organic and matrix on the substrate 170 is irradiated by a beam 164, from a CO2 laser source 150 transmitted through a NaCl window 194 (or ZnSe2) and a beam 166 from an argon ion laser source 160 through a silica window 202. An auxiliary lens 204 may be used to focus the beam 164 onto the substrate 170 to increase its intensity. The CO2 laser source 150 is tuned to the vibrational absorption frequency of the U-organic and the argon laser source 160 is tuned to the electronic absorption frequency to effect dissociation of the U-bond or to induce a reaction with a reactant such as Cl2 incorporated in the matrix. Other reactants may be HCl, HI, etc. Alternatively, as in FIG. 1, the CO2 laser source 150 may supply photons of sufficient intensity to cause dissociation of a U-bond. The limits of such intensity are between 104 watts/cm2 and 1010 watts/cm2. In this case the argon laser source is not used. Subsequently, the substrate 170 containing the reaction products from irradiation and unreacted feestock is moved through a slit 208 in a section-separating partition 212 of the chamber 172 over a second hollow drum 214 and onto a takeup spool 216. The temperature of the drum 214 is controlled by introducing a fluid from a heat exhcnager, (not shown) through a hollow journal 220. The temperature of the second drum 214 is adjusted to raise the temperature of reaction products of the U-organic on substrate 170 to cause a reaction with the reactive material to facilitate separation. This temperature may be as low as a few degrees above the temperature of the first drum 182 or may be higher to facilitate separation of reaction products by their resulting volatility differences. The atmosphere in the chamber sections 174, 176 may be controlled by evacuation through pipes 224, 226 and backfilling through tubes 228, 230. Reactive material may be introduced through a tube 234 directly onto the moving substrate 170. The substrate 170 is then removed from the take up spool 216 and modified U235- organic adhered thereto is chemically separated. Other U-organics may be used in all embodiments, provided a fundamental overtone or combination vibrational absorption occurs in the 900-1100 cm-1 CO2 laser output range. Also, tunable laser sources 130 and 160 may be tunable dye lasers with suitable frequency doublers (not shown), depending on the electronic energy levels of the U-L bond.
Patent Citations
Referenced by
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Stephen M. WIENS 1871–1956
Portrait painter and sculptor, a grandson of the German poet Ferdinand Freiligrath. Born 26 February 1871 in London. Educated partly in Germany; studied at the R.A. Schools from 1890. Exhibited at the R.A. from 1893. Changed his name from Siegfried to Stephen in 1920. Died in Worthing 25 June 1956.
Published in:
Mary Chamot, Dennis Farr and Martin Butlin, The Modern British Paintings, Drawings and Sculpture, London 1964, II

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User:Benjamin Y. Ko
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Contact Info
Benjamin Y. Ko
Department of Chemical Engineering
Shriram Center
443 Via Ortega
Stanford University
Stanford, CA 94305-5025
I work in the Swartz Lab at Stanford University.
- 2010--present, PhD candidate, Stanford University
- 2003, MS Chemical Engineering, Stanford University
- 2002, BS Chemical Engineering, Stanford University
Research interests
- Protein engineering
- Cell-free protein synthesis
- Antibody purification
Prostate cancer is an increasingly prevalent disease for which improved methods of tumor detection are needed in order for new treatment options to be truly safe and effective. My project aims to introduce a novel tool for prostate tumor detection by engineering virus-like particles (VLPs) which are loaded with superparamagnetic iron oxide (SPIO) nanoparticles and surface-coated with antibody fragments. The SPIO nanoparticles, as effective MRI contrast agents, lend sensitivity to these VLP constructs, while the antibody fragments, with affinity to prostate cancer cell surface markers such as PSMA, give the VLPs the ability to target prostate cancer cells with high specificity. Such engineered VLPs have the potential to enable clinicians to make earlier and more accurate diagnoses of prostate cancer, thus helping to improve the survival rate for this deadly disease. The goals of my research are to develop SPIO nanoparticles which are suitable for loading into VLPs, develop production and loading methods for the VLPs, and, in collaboration with colleagues in the School of Medicine, demonstrate the efficacy of these constructs in murine studies.
- Surface functionalization of iron oxide nanoparticles for biological encapsidation applications (AIChE National Meeting, 2013)
- Design of a platform parvovirus filtration step to streamline MAb purification process development (ACS National Meeting, Spring 2010)
- Goldbeter A and Koshland DE Jr. . pmid:6947258.
- JACOB F and MONOD J. . pmid:13718526.
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EastPoint Sports 4-Player Table Tennis Set and Organizer
About this item
The Eastpoint Sports 4-Player Table Tennis Set is durable, convenient and stylish. This table tennis racket set and organizer comes complete with four EPS 2.0 pips-out rubber table tennis paddles. Additionally, this Eastpoint 4-Player Table Tennis Set features six one-star 40 mm table tennis balls and a deluxe paddle and ball organizer, allowing for quick and easy organizing of accessories and ensuring they are ready for use when needed.
EastPoint Sports 4-Player Table Tennis Set and Organizer:
- 4 EPS 2.0 pips-out rubber table tennis paddles
- 6 one star 40mm table tennis balls
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Diamond anvil cell
A diamond anvil cell (DAC) is a device used in scientific experiments. It allows compressing a small (sub-millimeter sized) piece of material to extreme pressures, which can exceed 600 gigapascals (6,000,000 bars / 6 million atmospheres)[1]
The device has been used to recreate the pressure existing deep inside planets, creating materials and phases not observed under normal conditions. Notable examples include the non-molecular ice X,[2] polymeric nitrogen[3] and metallic xenon (an inert gas at lower pressures).
A DAC consists of two opposing diamonds with a sample compressed between the culets (tips). Pressure may be monitored using a reference material whose behavior under pressure is known. Common pressure standards include ruby[4] fluorescence, and various structurally simple metals, such as copper or platinum.[5] The uniaxial pressure supplied by the DAC may be transformed into uniform hydrostatic pressure using a pressure transmitting medium, such as argon, xenon, hydrogen, helium, paraffin oil or a mixture of methanol and ethanol.[6] The pressure-transmitting medium is enclosed by a gasket and the two diamond anvils. The sample can be viewed through the diamonds and illuminated by X-rays and visible light. In this way, X-ray diffraction and fluorescence; optical absorption and photoluminescence; Mössbauer, Raman and Brillouin scattering; positron annihilation and other signals can be measured from materials under high pressure. Magnetic and microwave fields can be applied externally to the cell allowing nuclear magnetic resonance, electron paramagnetic resonance and other magnetic measurements.[7] Attaching electrodes to the sample allows electrical and magnetoelectrical measurements as well as heating up the sample to a few thousand degrees. Much higher temperatures (up to 7000 K)[8] can be achieved with laser-induced heating,[9] and cooling down to millikelvins has been demonstrated.[6]
- 1 Principle
- 2 History
- 3 Components
- 4 Measuring Pressure
- 5 Uses
- 6 Innovative uses
- 7 High Temperature Techniques
- 9 See also
- 10 References
- 11 External links
The operation of the diamond anvil cell relies on a simple principle:
where p is the pressure, F the applied force, and A the area.
Therefore high pressure can be achieved by applying a moderate force on a sample with a small area, rather than applying a large force on a large area. In order to minimize deformation and failure of the anvils that apply the force, they must be made from a very hard and virtually incompressible material, such as diamond.
The study of materials at extreme conditions, high pressure and high temperature uses a wide array of techniques to achieve these conditions and probe the behavior of material while in the extreme environment. Percy Williams Bridgman, the great pioneer of high-pressure research during the first half of the 20th century, revolutionized the field of high pressures with his development of an opposed anvil device with small flat areas that were pressed one against the other with a lever-arm. The anvils were made of tungsten carbide (WC). This device could achieve pressure of a few gigapascals, and was used in electrical resistance and compressibility measurements. The principles of the DAC are similar to the Bridgman anvils but in order to achieve the highest possible pressures without breaking the anvils, they were made of the hardest known material: a single crystal diamond. The first prototypes were limited in their pressure range and there was not a reliable way to calibrate the pressure.
Following the Bridgman anvil, the diamond anvil cell became the most versatile pressure generating device that has a single characteristic that to this day sets apart from the other pressure devices. This provided the early high pressure pioneers with the capability to directly observe the properties of a material while under pressure. With just the use of a microscope, phase boundaries, color changes and recrystallization could be seen immediately without the collect of x-ray diffraction or spectroscopic measurements and their subsequent analysis. The potential for the diamond anvil cell was realized by Alvin Van Valkenburg while he was preparing a sample for IR spectroscopy and was checking the alignment of the diamond faces.
The diamond cell was created at the National Bureau of Standards (NBS) by Charles E. Weir, Ellis R. Lippincott, and Elmer N. Bunting. Within the group each member focused on different applications of the diamond cell. Van focused on making visual observations, Charles on XRD, Ellis on IR Spectroscopy. The group was well established in each of their techniques before outside collaboration kicked off with university researchers like William A. Bassett and Taro Takahashi at the University of Rochester.
During the first experiments using diamond anvils, the sample was placed on the flat tip of the diamond, the culet, and pressed between the diamond faces. As the diamond faces were pushed closer together, the sample would be pressed and extrude out from the center. Using a microscope to view the sample, it could be seen that a smooth pressure gradient existed across the sample with the outer most portions of the sample acting as a kind of gasket. The sample was not evenly distributed across the diamond cutlet but localized in the center due to the "cupping" of the diamond at higher pressures. This cupping phenomenon is the elastic stretching of the edges of the diamond culet, commonly referred to as the "shoulder height". Many diamonds were broken during the first stages of producing a new cell or any time an experiment is pushed to higher pressure. The NBS group was in a unique position where almost endless supplies of diamonds were available to them. Custom officials occasionally confiscated diamonds from people attempting to smuggle them into the country. Disposing of such valuable confiscated materials could be problematic given rules and regulations. A solution was simply to make such materials available to people at other government agencies if they could make a convincing case for their use. This became an unrivaled resource as other teams at the University of Chicago, Harvard University and General Electric entered the high pressure field.
During the following decades DACs have been successively refined, the most important innovations being the use of gaskets and the ruby pressure calibration. The DAC evolved to be the most powerful lab device for generating static high pressure.[10] The range of static pressure attainable today extends to the estimated pressures at the Earth's center (~360 GPa).
There are many different DAC designs but all have four main components:
Force-generating device[edit]
Relies on the operation of either a lever arm, tightening screws, or pneumatic or hydraulic pressure applied to a membrane. In all cases the force is uniaxial and is applied to the tables (bases) of the two anvils
Two opposing diamond anvils[edit]
Made of high gem quality, flawless diamonds, usually with 16 facets. They typically weigh 1/8 to 1/3 carat (25 to 70 mg). The culet (tip) is ground and polished to a hexadecagonal surface parallel to the table. The culets of the two diamonds face one another, and must be perfectly parallel in order to produce uniform pressure and to prevent dangerous strains. Specially selected anvils are required for specific measurements—for example, low diamond absorption and luminescence is required in corresponding experiments.
A gasket used in a diamond anvil cell experiment is a thin metal foil, typically 0.3 mm in thickness, which is placed in between the diamonds. Desirable materials for gaskets are strong, stiff metals such as rhenium or tungsten. Steel is frequently used as a cheaper alternative for experiments not going to extreme pressures. The above-mentioned materials cannot be used in radial geometries where the x-ray beam must pass through the gasket. They are not transparent to X-rays, and thus if X-ray illumination through the gasket is required then lighter materials, such as beryllium, boron nitride,[11] boron[12] or diamond[13] are used as a gasket.
Gaskets are preindented using the diamonds and a hole is drilled in the center of the indentation. By creating this confined space the sample can be immersed in the fluid while under pressure. The sample chamber created by the gasket also allows for liquids and gasses to be studied under pressure.
Pressure-transmitting medium[edit]
The pressure transmitting medium is the compressible fluid that fills the sample chamber and transmitting the applied force to the sample. Hydrostatical pressure is preferred for high pressure experiments because variation in strain throughout the sample can lead to distorted observations of different behaviors. In some experiments stress and strain relationships are investigated and the effects of non-hydrostatic forces are desired. A good pressure medium will remain a soft, compressible fluid to high pressure.
- Gasses: He, Ne, Ar,
- Liquids: 4:1 Methanol/Ethanol, Silicone Oil, Fluorinert, Daphne 7474 Cyclohexane
- Solids: NaCl
The full range of techniques that are available has been summarized in a tree diagram by William Bassett. The ability to utilize any and all of these techniques hinges on being able to look through the diamonds which was first demonstrated by visual observations.
Measuring Pressure[edit]
The two main pressure scales used in static high pressure experiments are X-ray diffraction of a material with a known equation of state and measuring the shift in ruby fluorescence lines. The first began with NaCl, for which the compressibility has been determined by first principles in 1968. The major pitfall of this method of measuring pressure is that you need X-rays. Many experiments do not require X-rays and this presents a major inconvenience to conduct both the intended experiment and a diffraction experiment. In 1971, the NBS high pressure group was set in pursuit of a spectroscopic method for determining pressure. It was found that the wavelength of ruby fluorescence emissions change with pressure, this was easily calibrated against the NaCl scale.
Once pressure could be generated and measured it quickly became a competition for which cells can go the highest. The need for a reliable pressure scale became more important during this race. Shock-wave data for the compressibility's of Cu, Mo, Pd and Ag were available at this time and could be used to define equations of states up to Mbar pressure. Using these scales these pressures were reported: 1.2 Mbar in 1976, 1.5 Mbar in 1979, 2.5 Mbar in 1985, and 5.5 Mbar in 1987.
Both methods are continually refined and in use today. However, the ruby method is less reliable high temperature. Well defined equations of state are needed when adjusting temperature and pressure, two parameters that affect the lattice parameters of materials.
Prior to the invention of the diamond anvil cell, static high-pressure apparatus required large hydraulic presses which weighed several tons and required large specialized laboratories. The simplicity and compactness of the DAC meant that it could be accommodated in a wide variety of experiments. Some contemporary DACs can easily fit into a cryostat for low-temperature measurements, and for use with a superconducting electromagnet. In addition to being hard, diamonds have the advantage of being transparent to a wide range of the electromagnetic spectrum from infrared to gamma rays, with the exception of the far ultraviolet and soft X-rays. This makes the DAC a perfect device for spectroscopic experiments and for crystallographic studies using hard X-rays.
A variant of the diamond anvil, the hydrothermal diamond anvil cell (HDAC) is used in experimental petrology/geochemistry for the study of aqueous fluids, silicate melts, immiscible liquids, mineral solubility and aqueous fluid speciation at geologic pressures and temperatures. The HDAC is sometimes used to examine aqueous complexes in solution using the synchrotron light source techniques XANES and EXAFS. The design of HDAC is very similar to that of DAC, but it is optimized for studying liquids.[14]
Innovative uses[edit]
An innovative use of the diamond anvil cell is testing the sustainability and durability of life under high pressures. This innovative use can be used in the search for life on extrasolar planets. One reason the DAC is applicable for testing life on extrasolar planets is panspermia, a form of interstellar travel. When panspermia occurs, there is high pressure upon impact and the DAC can replicate this pressure. Another reason the DAC is applicable for testing life on extrasolar planets is that planetary bodies that hold the potential for life may have incredibly high pressure on their surface.
Anurag Sharma, a geochemist, James Scott, a microbiologist, and others at the Carnegie Institution of Washington performed an experiment with the DAC using this new innovative application. Their goal was to test microbes and discover under what level of pressure they can carry out life processes. The experiment was performed under 1.6 GPa of pressure, which is more than 16,000 times Earth's surface pressure (Earth's surface pressure is 985 hPa). The experiment began by placing a solution of bacteria, specifically Escherichia coli and Shewanella oneidensis, in a film and placing it in the DAC. The pressure was then raised to 1.6 GPa. When raised to this pressure and kept there for 30 hours, only about 1% of the bacteria survived. The experimenters then added a dye to the solution. If the cells survived the squeezing and were capable of carrying out life processes, specifically breaking down formate, the dye would turn clear. 1.6 GPa is such great pressure that during the experiment the DAC turned the solution into ice-IV, a room-temperature ice. When the bacteria broke down the formate in the ice, liquid pockets would form because of the chemical reaction. The bacteria were also able to cling to the surface of the DAC with their tails.[15]
However, there is some skepticism with this experiment. People debate whether carrying out the simple process of breaking down formate is enough to consider the bacteria living. Art Yayanos, an oceanographer at the Scripps Institute of Oceanography in La Jolla, California, believes an organism should only be considered living if it can reproduce. Another issue with the DAC experiment is that when high pressures occur, there are usually high temperatures present as well, but in this experiment there were not. This experiment was performed at room-temperature, which causes some skepticism of the results.[15]
Moving past the 10 years of skepticism, new results from independent research groups [16] have shown the validity of Sharma et al. (2002) [17] work. This is a significant step that reiterates the need for a new approach to the old problem of studying environmental extremes through experiments. There is practically no debate whether microbial life can survive pressures up to 600 MPa, which has been shown over the last decade or so to be valid through a number of scattered publications.[17] What is significant in this approach of Sharma et al. 2002 work is the elegantly straightforward ability to monitor systems at extreme conditions that have since remained technically inaccessible. While the simplicity and the elegance of this experimental approach is mind-boggling; the results are rather expected and consistent with most biophysical models. This novel approach lays a foundation for future work on microbiology at non-ambient conditions by not only providing a scientific premise, but also laying the technical feasibility for future work on non-ambient biology and organic systems.
There is another group of scientists performing similar tests with a low-pressure diamond anvil cell. This low-pressure DAC has better imaging quality and signal collection. It is designed to sense pressures in the 0.1–600 MPa range, much lower than the high pressure DAC. The new low-pressure DAC also has a new asymmetric design, as opposed to a symmetric design the old, high pressure DAC used. In this experiment Saccharomyces cerevisiae is the microbe being observed. Saccharomyces cerevisiae is more commonly known as baker's yeast. These microbes can only grow in pressures ranging from 15–50 MPa, while pressures over 200 MPa are likely to kill the cells. The microbes were also incubated at 30 °C. Their tests showed that the yeast completed its cell cycle in 97±5 minutes.[18]
Single Crystal X-ray Diffraction[edit]
Good single crystal diffraction experiments in diamond anvil cells require sample stage to rotate on the vertical axis, omega. Most diamond anvil cells do not feature a large opening that would allow the cell to be rotated to high angles, a 60 degrees opening is considered sufficient for most crystals but larger angles are possible. The first cell to be used for single crystal experiments was designed by a graduate student at the University of Rochester, Leo Merrill. The cell was triangular with beryllium seats that the diamonds were mounted on; the cell was pressurized with screws and guide pins holding everything in place.
High Temperature Techniques[edit]
Heating in diamond-anvil cells is typically done by two means, external or internal heating. External heating is defined as heating the anvils and would include a number of resistive heaters that are placed around the diamonds or around the cell body. The complementary method does not change the temperature of the anvils and includes fine resistive heaters placed within the sample chamber and laser heating. The main advantage to resistive heating is the precise measurement of temperature with thermocouples, but the temperature range is limited by the properties of the diamond which will oxide in air at 700 °C [19] The use of an inert atmosphere can extend this range above 1000 °C. With laser heating the sample can reach temperature above 5000 °C, but the minimum temperature that can be measured when using a laser-heating system is ~1200 °C and the measurement is much less precise. Advances in resistive heating are closing the gap between the two techniques so that systems can be studied from room temperature to beyond 6000k with the combination of the two.
The development of laser heating began only 8 years after Charles Weir, of the National Bureau of Standards (NBS), made the first diamond anvil cell and Alvin Van Valkenburg, NBS, realized the potential of being able to see the sample while under pressure. William Bassett and his college Taro Takahashi had the idea to focus a laser beam on the sample while under pressure. The first laser heating system used a single 7 joule pulsed ruby laser that heated the sample to 3000 °C while at 260 kilobars. This was sufficient to convert graphite to diamond.[20] The major flaw of in the first system was control and temperature measurement.
Temperature measurement was initially done by Basset using an optical pyrometer to measure the intensity of the incandescent light from the sample. Colleagues at UC Berkeley were better able to utilize the black body radiation and more accurately measure the temperature.[21] The hot spot produced by the laser also created large thermal gradients in between the portions of sample that were hit by the focused laser and those that were not. The solution to this problem is ongoing but advances have been made with the introduction of a double-sided approach.
Double-sided Heating[edit]
The use of two lasers to heat the sample reduces the axial temperature gradient, this which allows for thicker samples to be heated more evenly. In order for a double-sided heating system to be successful it is essential that the two lasers are aligned so that they are both focused on the sample position. For in situ heating in diffraction experiments, the lasers need to be focused to the same point in space where the X-ray beam is focused.
Laser heating systems at Synchrotron Facilities[edit]
The three major synchrotron user facilities in the United States all have beamlines equipped with laser heating systems. The respective beamlines with laser heating systems are at the Advanced Photon Source (APS), 13-ID-D GSECARS and 16-ID-D HP-CAT; at the National Synchrotron Light Source, X17B3; and at the Advanced Light Source, 12.2.2. Laser heating has become a routine technique in high pressure science but the reliability of temperature measurement is still controversial.
Temperature Measurement[edit]
In the first experiments with laser heating, temperature came from a calibration of laser power made with known melting points of various materials. When using the pulsed ruby laser this was unreliable due to the short pulse. The YAG lasers that quickly become the standard heat for relatively long duration and allow for observation of the sample throughout the heating process. It was with the first use of YAG lasers the Bassett used an optical pyrometer to measure temperatures in the range of 1000 °C to 1600 °C.[20] The first temperature measurements had a standard deviation of 30 °C from the brightness temperature, but due to the small sample size was estimated to be 50 °C with the possibility that the true temperature of the sample being was 200 °C higher than that of the brightness measurement. Spectrometry of the incandescent light became the next method of temperature measurement used in Bassett's group. The energy of the emitted radiation could be compared to known black body radiation spectra to derive a temperature. Calibration of these systems is done with published melting points or melting points as measured by resistive heating.
Application of laser heating[edit]
Laser heating is used to heat micrograms of sample in diamond-anvil cells when studying matter under extreme conditions. This typically means one of four things:
- Thermal equation of states
- Measuring the pressure-volume-temperature state of a material. In DAC work, this is done by applying pressure with the diamond anvils, applying temperature with lasers/resistive heaters, and measuring the volume response with X-ray diffraction. The thermal expansion and compressibility can then be defined in an equation of state with the independent variable of volume.
- High pressure/temperature synthesis
- Using a diamond-anvil cell and laser heating to reach high pressures and temperatures achieve novel synthesis routes not accessible at ambient pressure that can produce unique high pressure phases.
- Phase transition studies
- Providing excess kinetic energy to a sample in order to observe a kinetically unfavorable transition. Developing phase diagrams over the high pressure range.
- High pressure melting
- Measuring the dependence of the melting point on pressure. Pressure commonly elevates the melting point of solids.
Current Challenges[edit]
As laser and spectroscopy technology continues to improve there are ever persisting challenges in their application. Temperature plateaus are observed where an increase in power does not respond to an increase in temperature or time.[22] It was suggested in 2012 that large changes in the thermal conductivity could account for some of these plateaus and minor increases in the reflectivity can explain all of the plateaus.
Thermal gradients in the sample are continuously a challenge. After the introduction of the double-sided system the gradient was reduced in the axial direction, but still problematic in the radial direction. Raster scanning can be done to heat larger portions of the sample but does not eliminate the large temperature gradients. For continuous heating the beam spot is typically in the fundamental transfer mode TEM00 or Gaussian profile. The use of a multimode output with a beam profile with a relatively flat top reduces the radial temperature gradient in the center of the laser heated spot.
See also[edit]
- ^ Improved diamond anvil cell allows higher pressures Physics World November 2012
- ^ Goncharov, A. F.; Struzhkin, V. V.; Somayazulu, M. S.; Hemley, R. J.; Mao, H. K. (Jul 1986). "Compression of ice to 210 gigapascals: Infrared evidence for a symmetric hydrogen-bonded phase". Science 273 (5272): 218–230. Bibcode:1996Sci...273..218G. doi:10.1126/science.273.5272.218. PMID 8662500.
- ^ Eremets, MI; Hemley, RJ; Mao, Hk; Gregoryanz, E (May 2001). "Semiconducting non-molecular nitrogen up to 240 GPa and its low-pressure stability". Nature 411 (6834): 170–174. Bibcode:2001Natur.411..170E. doi:10.1038/35075531. PMID 11346788.
- ^ Forman, Richard A.; Piermarini, Gasper J.; Barnett, J. Dean; Block, Stanley (1972). "Pressure Measurement Made by the Utilization of Ruby Sharp-Line Luminescence". Science 176 (4032): 284–5. Bibcode:1972Sci...176..284F. doi:10.1126/science.176.4032.284. PMID 17791916.
- ^ Kinslow, Ray; Cable, A. J. (1970). High-velocity impact phenomena. Boston: Academic Press. ISBN 0-12-408950-X.
- ^ a b Jayaraman, A. (1986). "Ultrahigh pressures". Reviews of Scientific Instruments 57 (6): 1013. Bibcode:1986RScI...57.1013J. doi:10.1063/1.1138654.
- ^ Bromberg, Steven E.; Chan, I. Y. (1992). "Enhanced sensitivity for high-pressure EPR using dielectric resonators". Review of Scientific Instruments 63 (7): 3670. Bibcode:1992RScI...63.3670B. doi:10.1063/1.1143596.
- ^ Chandra Shekar, N. V. et al. (2003). "Laser-heated diamond-anvil cell (LHDAC) in materials science research". J. Mater. Sci. Techn. 19: 518.
- ^ Subramanian, N. et al. (2006). "Development of laser-heated diamond anvil cell facility for synthesis of novel materials". Current Science 91: 175.
- ^ Block, S. and Piermarini, G. (1976). "The Diamond Cell Stimulates High-Pressure Research". Physics Today 29 (9): 44. Bibcode:1976PhT....29i..44B. doi:10.1063/1.3023899.
- ^ Funamori, N; Sato, T (2008). "A cubic boron nitride gasket for diamond-anvil experiments". The Review of scientific instruments 79 (5): 053903. Bibcode:2008RScI...79e3903F. doi:10.1063/1.2917409. PMID 18513075.
- ^ Lin, Jung-Fu; Shu, Jinfu; Mao, Ho-Kwang; Hemley, Russell J.; Shen, Guoyin (2003). "Amorphous boron gasket in diamond anvil cell research". Review of Scientific Instruments 74 (11): 4732. Bibcode:2003RScI...74.4732L. doi:10.1063/1.1621065.
- ^ Zou, Guangtian; Ma, Yanzhang; Mao, Ho-Kwang; Hemley, Russell J.; Gramsch, Stephen A. (2001). "A diamond gasket for the laser-heated diamond anvil cell". Review of Scientific Instruments 72 (2): 1298. Bibcode:2001RScI...72.1298Z. doi:10.1063/1.1343864.
- ^ Bassett, W.A. et al. (1993). "A new diamond anvil cell for hydrothermal studies to 2.5 GPa and from −190 to 1200 °C". Review of Scientific Instruments 64 (8): 2340. Bibcode:1993RScI...64.2340B. doi:10.1063/1.1143931.
- ^ a b Couzin, J. (2002). "Weight of the world on microbes' shoulders". Science 295 (5559): 1444–1445. doi:10.1126/science.295.5559.1444b. PMID 11859165.
- ^ Vanlinit, D. et al. (2011). "Rapid Acquisition of Gigapascal-High-Pressure Resistance by Escherichia coli". mBio 2 (1): e00130–10. doi:10.1128/mBio.00130-10.
- ^ a b Sharma, A. et al. (2002). "Microbial activity at Gigapascal pressures". Science 295 (5559): 1514–1516. Bibcode:2002Sci...295.1514S. doi:10.1126/science.1068018. PMID 11859192.
- ^ Oger, Phil M.; Daniel, Isabelle; Picard, Aude (2006). "Development of a low-pressure diamond anvil cell and analytical tools to monitor microbial activities in situ under controlled p and t". Biochimica et Biophysica Acta (BBA) 1764 (3): 434–442–230. doi:10.1016/j.bbapap.2005.11.009. PMID 16388999.
- ^ Jayaraman, A. (1983). "Diamond Anvil Cell and High-Pressure Physical Investigations.". Reviews of Modern Physics 55 (1): 65–108.
- ^ a b Ming, L. and W. A. Bassett (1974). "Laser-Heating in Diamond Anvil Press Up to 2000 Degrees C Sustained and 3000 Degrees C Pulsed at Pressures up to 260 Kilobars.". Review of Scientific Instruments 45 (9): 1115–1118.
- ^ Bassett, W. A. (2009). "Diamond anvil cell, 50th birthday". High Pressure Research 29 (2): CP5–186.
- ^ Geballe, Z. M. and R. Jeanloz (2012). "Origin of temperature plateaus in laser-heated diamond anvil cell experiments". Journal of Applied Physics 111 (12).
External links[edit]
|Wikimedia Commons has media related to Diamond anvil cell.
- "Putting the Squeeze on Materials". Retrieved 2009-05-05.


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Indeed. But Railey says the fair was never intended as a reaction against other local music festivals. "People thought for years that Corndog was the 'anti-Atlantis,' when it really wasn't. The whole idea that a songwriter or band from Atlanta somehow has to go through [the industry-related music festivals] to have a career in music, is simply not true. In your town, it's up to you to just do something, not with apathy and bitterness, but with good old-fashioned creativity, originality and vision."
This year, Corndogorama spans two days, inside and outside of The Earl in East Atlanta. A slew of hard-rocking bands play Friday night while Saturday features more pop-oriented fare. Saturday afternoon will also feature field-day activities in the parking lot. Beer will flow, literally, as the malt beverage plays an important role in many of the outdoor games, especially the "Beer Factor," which starts at 1 p.m. Saturday.
"It's like TV's 'Fear Factor,'" Railey explains, "except there's beer involved." Plastic kiddie pools will be filled with beer and contestants will then vie to see who can swim the most laps in the foamy froth. "It's all based on what people do on 'Fear Factor' for money, but this is a lot milder."
In addition to overseeing the spectator sports, Railey will perform in bands both nights. His '90s-era band Ancient Chinese Secret plays a rare reunion show Friday, while his current band, American Dream, plays Saturday night. The group has played a different venue every week this month.
"A lot of bands -- and this is probably smarter -- don't play but every three to six months in Atlanta," Railey says. "But until we tour nationally, I just want to play as much as possible." Since the second American Dream album was released last year, the guitarist says he has written enough material for two more full-length albums. Now, with a new band lineup, Railey says he is having fun again and preparing for a September release of a disc full of new material. "Now it's just a matter of finding a label," he says. "If not, then we'll just do it ourselves."
The do-it-yourself mindset is nothing new to Railey. "I come from that early punk Atlanta scene where if you really wanted to do something, you could," he says. "I remember my first show at the White Dot in '88. Deacon Lunchbox gave me a slot at his songwriter night, not because I had a big hype, but because I could name the whole cast of 'The Dukes of Hazzard.'"
Railey won't take credit for the idea of Corndogorama, and insists that the event really belongs to the entire independent scene. "This is everybody's festival. This is what everybody could do, all the time, or at least once a month, if they really gave a shit." The success of the previous eight editions of the enduring free-for-all speaks volumes about its popularity. Says Railey, "There's this underlying apathy in our scene to think it's not gonna be good or enjoyable, but when they show up it's like, 'Wow, man, we had no idea this was actually gonna be fun.'"
And yes, there will be corndogs. Many, many corndogs.
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Lawrence Francis Kroetsch (born 1887)
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Lawrence Francis Kroetsch (born 1887) was born on March 9, 1887. He was born into the Kroetsch family.
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- Regina Kroetsch
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- John Baptist (Battish) Kroetsch
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- Mary Josephine (Josephine) Kroetsch
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- Albert Aloysius Kroetsch
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- Rosabel Orillia Kroetsch
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- Joseph J. Kroetsch
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- Rosabel Orillia (Kroetsch) Connolly
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- Elizabeth Ann (Kroetsch) Minning
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- Mary Josephine (Kroetsch) Melius
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- Angeline (Chartrand) Kroetsch
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