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Showing papers by "Varian Associates published in 1992"


Journal ArticleDOI
TL;DR: It has been concluded that a dose control monitor unit calculation procedure that has been applied to the use of conventional secondary field-shaping blocks can be applied toThe multileaf collimator dosimetry.
Abstract: In order to initiate the use of a multileaf collimator (MLC) in the clinic, a set of technical procedures needs to be available sufficient to create MLC leaf settings and to deliver an accurate dose of radiation through the MLC-shaped field. Dosimetry data for clinical use of the MLC were measured. Dosimetric characteristics included central axis percent depth dose, output factors, and penumbra. In this paper, it has been concluded that a dose control monitor unit calculation procedure that has been applied to the use of conventional secondary field-shaping blocks can be applied to the multileaf collimator dosimetry. The multileaf collimator penumbra (20% to 80%) is only slightly wider (1-3 mm) than the penumbra of the conventional collimator jaws. Beam's-eye-view comparisons made between the isodose curves in fields shaped by conventional Cerrobend blocks and isodose curves in fields shaped by the multileaf collimator demonstrated that the 50% isodose line at 10-cm depth exhibited the discrete steps of the multileaf collimator leaves, but that the 90% and 10% isodose curves of the multileaf were close to those shaped by Cerrobend blocks.

133 citations


Journal ArticleDOI
TL;DR: Clinical and engineering design tradeoff's for practical devices are discussed and a summary of clinical experiences with a series of 915-MHz microstrip array applicators satisfying these criteria have been developed and clinically tested.
Abstract: The optimal treatment with hyperthermia of superficially located tumors which involve large surface areas requires applicators which can physically conform to body contours, and locally alter their power deposition patterns to adjust for nonuniform temperature caused by tissue inhomogeneities and blood flow variations. A series of 915-MHz microstrip array applicators satisfying these criteria have been developed and clinically tested. Clinical and engineering design tradeoff's for practical devices are discussed. Measurements taken in tissue equivalent phantoms and a summary of clinical experiences with these microstrip arrays are presented. >

89 citations


Journal ArticleDOI
TL;DR: A 3D optimized, refocused HNCA experiment is demonstrated to yield a dramatic increase in sensitivity when applied to [13C,15N]-labeled human carbonic anhydrase II, a 29-kDa protein.
Abstract: A 3D optimized, refocused HNCA experiment is described. It is demonstrated to yield a dramatic increase in sensitivity when applied to [13C, 15N]-labeled human carbonic anhydrase II, a 29-kDa protein. The reasons for the gain in sensitivity are discussed, and 3 distinct areas for further development are indicated.

68 citations


Patent
30 Sep 1992
TL;DR: In this article, a method for improving sample concentration in capillary electrophoresis by extracting the sample buffer from the capillary column using the electro-osmotic flow while the sample components are stacked into the support buffer utilizes a system for this technique.
Abstract: The method for improving sample concentration in capillary electrophoresis by extracting the sample buffer from the capillary column using the electro-osmotic flow while the sample components are stacked into the support buffer utilizes a system for this technique. The system has a separation column (11), sample introduction means (16) for injecting the sample solution, an injection detector means (20) for detecting the volume of injected sample solution, a separation detector means (21) for detecting the sample components, power supply means (17) for applying a high voltage along the separation column (11) for reversing the direction of the electro-osmotic flow thereby causing extraction of the sample buffer from the separation column and afterward providing the separation sample into its components.

50 citations


Patent
29 May 1992
TL;DR: In this paper, a method for isolating an ion in a QIT was proposed, employing values from a mass axis calibration chart to establish the maximum DAC value to scan to in order to scan out m(p)-1 and less during ramp up of RF trapping field while applying a specifically selected fixed supplemental frequency applied during said calibration.
Abstract: A method for isolating an ion in a QIT (1) employing values from a mass axis calibration chart to establish the maximum DAC value to scan to in order to scan out m(p)-1 and less during ramp up of RF trapping field while applying a specifically selected fixed supplemental frequency applied during said calibration; and employing values from the calibration curve to establish the DAC value to scan out m(p)+1 and greater during ramping down of RF trapping field, while applying a previously determined fixed broadband spectrum to the QIT end caps.

40 citations


Journal ArticleDOI
T.A. Treado1, R.A. Bolton1, T.A. Hansen1, Paul D. Brown1, J.D. Barry1 
TL;DR: In this article, a 60MW, 60% efficient, 35 J/pulse secondary-emission magnetron at S-band is described and experimental results from this moderate voltage ( >
Abstract: A 60-MW, 60% efficient, 35 J/pulse secondary-emission magnetron at S-band is described and experimental results from this moderate voltage ( >

39 citations


Patent
Gary Virshup1
02 Mar 1992
TL;DR: In this article, a gallium-arsenide optical power receiver with a pn junction formed over a substrate and buffer layer has a window layer of a first alloy of aluminum gallium arsenide (Al x Ga 1-x As) and a conductive layer of another alloy of aluminium gallium arsenic (Al 1 -x Ga x As).
Abstract: A gallium-arsenide optical power receiver of the type having a pn junction formed over a substrate and buffer layer has a window layer of a first alloy of aluminum gallium arsenide (Al x Ga 1-x As) and a conductive layer of a second alloy of aluminum gallium arsenide (Al 1-x Ga x As). Alternatively, the gallium arsenide optical power receiver has a second window layer of the first alloy of aluminum gallium arsenide disposed on the conductive layer, and a cap layer of gallium arsenide disposed on the second window layer. The sheet resistance of the emitter layer is negated by being in parallel with the low sheet resistance of the conductive layer to minimize the thickness and conductivity of the emitter may therefore be optimized solely for energy conversion efficient.

31 citations


Patent
Arthur Sherman1
09 Nov 1992
TL;DR: In this article, an electrostatic chuck (4) is used for holding a workpiece in a low pressure environment, where the dielectric substrate is fabricated of a material that does not contain polar molecules that are free to move in response to the application of an electric field.
Abstract: An electrostatic chuck (4) for holding a workpiece (2) in a low pressure environment. The chuck (4) comprises a dielectric substrate (8) fabricated of a material that does not contain polar molecules that are free to move in response to the application of an electric field (V). This avoids the problem of the workpiece (2) sticking to the chuck (4) after the energizing voltage (V) has been removed. In an environment in which high temperatures are employed, the dielectric (8) is coupled to a metallic heat conductor (23) via a plurality of metallic pins (22) that couple heat and are free to flex in response to motion caused by differentials in thermal expansion coefficients between the metal (23) and the dielectric (8). The chuck (4) is preferably fabricated from two substantially planar dielectric members (30,33) sandwiched around a brazing compound (11,13) which become electrically conductive electrodes (11,13) after the assembly is heated and then cooled.

30 citations


Patent
13 Aug 1992
TL;DR: In this paper, a monolens optical detection system for on-column optical detection with capillary separation columns is presented. But the method is not suitable for the detection of capillary separations.
Abstract: On-column optical detection apparatus and method for use with capillary separation columns are shown. The apparatus and method minimize the adverse effects of light scattered from the walls of the column, thereby improving detection sensitivity and providing greater dynamic range. Light from a conventional source is focussed onto a column. Spatial filter means are positioned in front of the column to prevent at least some light from striking the column wall. Another spatial filter is positioned in front of a light collecting means which gathers light emanating from the column. In a specific embodiment, a unique monolens design is shown comprising collecting and focussing lens formed as an integral unit with a bore for a capillary column.

23 citations


Patent
29 May 1992
TL;DR: In this article, a method and apparatus for inducing collisional disassociation of isolated ions in a QIT which employs low frequency modulation of the secular frequency of oscillation of the trapped ions so as to permit sufficient frequency coincidence with the fixed frequency tickle generator to induce collisionality was presented.
Abstract: Method and apparatus for inducing collisional disassociation of isolated ions in a QIT which employs low frequency modulation of the secular frequency of oscillation of the trapped ions so as to permit sufficient frequency coincidence with the fixed frequency tickle generator to induce collisional disassociation.

23 citations


Patent
Capetti Emilio1
16 Sep 1992
TL;DR: In this article, an electronic braking device for asynchronous motors with magnetic suspensions was proposed, comprising a circuit for recovering the kinetic energy of the rotor during decelerating phase due to the absence of feeding electric current from the mains, which is adapted to return an electric current that can be used for the emergency feeding the magnetic suspensions.
Abstract: The invention relates to an electronic braking device for asynchronous motors particularly for asynchronous motor equipped with magnetic suspensions such as those employed in turbomolecular pumps, comprising a circuit for recovering the kinetic energy of the rotor during the decelerating phase due to the absence of feeding electric current from the mains, which is adapted to return an electric current that can be used for the emergency feeding the magnetic suspensions (8). Such circuit can further comprise an auxiliary battery (10) for feeding a circuit (9) controlling the magnetic suspensions (8) during the final phase of the stopping cycle of the motor (5) caused by the absence of mains current.

Patent
09 Jan 1992
TL;DR: In this paper, a method employing low pressure plasma having high electron density for rapid oxide etching employing hydrogen and argon and specific electron clyclotron resonance (ECR) operating parameters in an ECR having a non-oxygen contributing environment in the reaction chamber.
Abstract: Method employing low pressure plasma having high electron density for rapid oxide etching employing hydrogen and argon and specific electron clyclotron resonance (ECR) operating parameters in an ECR having a non-oxygen contributing environment in the reaction chamber.

Patent
09 Jul 1992
TL;DR: A mammography X-ray tube providing increased Xray intensity for shortening patient exposure times to eliminate motion artifacts is described in this article, where the cathode design permits superpositioning of electron beam from multiple filaments.
Abstract: A mammography X-ray tube providing increased X-ray intensity for shortening patient exposure times to eliminate motion artifacts. The cathode design permits superpositioning of electron beam from multiple filaments.

Patent
28 Oct 1992
TL;DR: A rotatable vacuum flange as discussed by the authors includes a flange ring (10) having a recess (20), an insert (30) mounted in the recess of the flange, and a wire spring (50) positioned between the wire spring and the insert.
Abstract: A rotatable vacuum flange includes a flange ring (10) having a recess (20), an insert (30) mounted in the recess (20) in the flange ring (10), the insert (30) including a seal portion (34) and being adapted for vacuum-tight attachment to a vacuum conduit (40), and a wire spring (50) positioned between the flange ring (10) and the insert (30). The wire spring (50) retains the insert (30) in the recess (20) in the flange ring (10) and permits rotation of the insert (30) relative to the flange ring (10). The flange ring (10) and the insert (30) include grooves (44) located in opposing alignment to receive the wire spring (50).

Patent
18 Dec 1992
TL;DR: Improved NMR sample tube shapes and inserts for standard tubes to shape the sample for greater homogeneity to provide symmetry of liquid sample and tube to a greater distance from the observe region for the same volume of sample as used in the prior art as discussed by the authors.
Abstract: Improved NMR sample tube shapes and inserts for standard tubes to shape the sample for greater homogeneity to provide symmetry of liquid sample and tube to a greater distance from the observe region for the same volume of sample as used in the prior art.

Patent
31 Jul 1992
TL;DR: In this article, a method for improving the sensivity of a QIT by overcoming deleterious space charge effects on the collection of higher mass ions in the collection by rejecting residual air gas ion during ionization and by rejecting other ions during ionisation employing a 1/m/z weighting of the amplitude of each secular frequency.
Abstract: A method for improving sensivity of a QIT by overcoming deleterious space charge effects on the collection of higher mass ions in a QIT by rejecting residual air gas ions during ionization and by rejecting other ions during ionization employing a 1/m/z weighting of the amplitude of each secular frequency, where m/z is the mass to charge ratio of the ions

Proceedings ArticleDOI
Ayers1, Zambre1
01 Jan 1992
TL;DR: In this article, a numerical model which handles relativistic, electromagnetic, and nonlinear effects in such a way as to achieve a full transient analysis of the coupled cavity traveling wave tube was presented.
Abstract: Computer analysis of Drive Induced Oscillation (DIO) requires a large-signal program which does not restrict itself to treating disturbances which propagate at a single frequency or at a number of related frequencies, known in advance This paper describes a numerical model which handles relativistic, electromagnetic, and nonlinear effects in such a way as to achieve a full transient analysis of the coupled cavity traveling wave tube >

Patent
26 Feb 1992
TL;DR: In this paper, a reagent gas flow control system for use with an ion trap mass spectrometer is presented, where the reagent gases flows from a source to the ion trap through a first gas flow restrictor (70) connected to the inputs of second (80) and third (90) flow restrictors.
Abstract: A reagent gas flow control system for use with an ion trap mass spectrometer is shown. The reagent gas flows from a source (5) through a first gas flow restrictor (70) connected to the inputs of second (80) and third (90) gas flow restrictors. The output of the second restrictor (80) is connected to the ion trap (10) where reagent gas is used, and the output of the third restrictor (90) is connected to a vacuum pump (20), which may be the roughing pump used by the ion trap. At least one of the three restrictors is a variable restrictor. The configuration of the present invention allows the use of simple and inexpensive parts to provide exacting flow control.

Patent
Eiji Tanabe1
25 Feb 1992
TL;DR: In this article, a standing wave type of microwave linear particle accelerator (40) has a sequence of microwave cavities (42), (43), (44), operated in the standing wave mode, with drift tube conduits (31, (32), (33), between them to permit the passage of a beam of charged particles which are accelerated by the electric fields in each cavity.
Abstract: A standing wave type of microwave linear particle accelerator (40) has a sequence of microwave cavities (42), (43), (44), operated in the standing wave mode, with drift tube conduits (31), (32), (33), between them to permit the passage of a beam of charged particles which are accelerated by the electric fields in each cavity. The first cavity (42) into which the particles enter has a conduit (30) comprising a drift region connected to the particle entrance port (2), outlined by a re-entrant nose (3) extending into the first cavity (42). The drift tube conduit (31) between the first and second cavities (42, 43) has a tapered interior, and the diameter at the upstream end is less than the diameter of the conduit (30) in the re-entrant nose (3) of the first cavity (42). This structure significantly reduces the back bombardment of particles moving backward through the port (2), and increases the efficiency of particle focusing and bunching in the first cavity (42 ).

Patent
23 Dec 1992
TL;DR: In this article, an electronic device for amplifying microwave or millimeter wave signals is described, where a gated field emission array produces a density modulated beam of electrons containing about 1 billion to 1,000 billion bunches or pulses per second which in turn illuminates a thin diamond target in a diamond switch connecting a load to a high voltage source.
Abstract: An electronic device for amplifying microwave or millimeter wave signals. A microwave or millimeter wave input signal stimulates a gated field emission array to produce a density modulated beam of electrons containing about 1 billion to 1,000 billion bunches or pulses per second which in turn illuminates a thin diamond target in a diamond switch connecting a load to a high voltage source. Each electron in each pulse creates a large number of electron hole pairs in the diamond. The high voltage bias across the diamond causes most of the very large number of pairs to be swept through the diamond target producing a high current surge in less than one half the period of the designed output frequency. Induced RF currents are set up within the resonant output cavity in response to the current flowing within the diamond. In summary, each surge of current produces an electromagnetic pulse at the load. Thus, an electromagnetic millimeter wave is produced with a frequency equal to the frequency of the signal output.

Journal ArticleDOI
TL;DR: In this paper, a polystyrene-divinylbenzene column was used for the separation of four different classes of flavonoids and flavonoid glycosides using either methanol-water or acetonitrile-water gradients.
Abstract: A polystyrene-divinylbenzene column was investigated for the separation of four different classes of flavonoids and flavonoid glycosides. These analytes were separated using either methanol-water or acetonitrile-water gradients. Acetonitrile-water gradients were judged to be superior for the overall separation of the four classes of flavonoids and flavonoid glycosides. Correlations between chemical structure, and retention and separability are discussed for the various HPLC gradient systems.

Journal ArticleDOI
TL;DR: In this article, the VA-949J klystrons were replaced with VKX-7864A klystron for the X-band planetary radar transmitter on the Goldstone, CA, 70 m antenna.
Abstract: Jet Propulsion Laboratory contracted with Varian Associates to design, build, and deliver replacements for VA-949J klystrons in the X-band planetary radar transmitter on the Goldstone, CA, 70 m antenna. Output power was to be increased from 200 kW to 250 kW CW per klystron, and full DC beam power was to be dissipated in the collector. Replacements were to be made with a minimum of transmitter modifications. Two model VKX-7864A klystrons were subsequently built and delivered. The design of these klystrons and the results of their performance testing are described. The planetary radar transmitter is now operating with these two klystrons. >

Patent
15 Oct 1992
TL;DR: In this paper, an improved metal center (70) rotating anode x-ray tube (400) is shown, which includes means for preventing the build-up of charge on the anode glass portion (480) of the tube envelope where the glass flares (486) by constraining the equipotential lines of the electric field in the vicinity of the flare to parallel the surface.
Abstract: An improved metal center (70) rotating anode x-ray tube (400) is shown. The improved x-ray tube includes means for preventing the build-up of charge on the anode glass portion (480) of the tube envelope where the glass flares (486) by constraining the equipotential lines of the electric field in the vicinity of the flare to parallel the flare surface. Parallelism may be achieved by controlling the angle of flare and sealing the flare directly to the metal section (70), modifying the anode rotor (450) to include a flare conforming to the glass flare (486), and including a ground plane screen in the tube housing.

Proceedings ArticleDOI
01 Jun 1992
TL;DR: In this paper, the authors developed 60 MW, 60% efficient, 35 Joule/pulse secondary emission magnetron at S-band, and reported on experimental results from this moderate-voltage (120 kV), repetitively pulsed (10 Hz), injection-locked (14-15 dB gain) magnetron.
Abstract: The authors have developed 60 MW, 60% efficient, 35 Joule/pulse secondary emission magnetron at S-band. They report on experimental results from this moderate-voltage (120 kV), repetitively pulsed (10 Hz), injection-locked (14-15 dB gain) magnetron. Limits imposed by high-voltage breakdown, RF breakdown, and thermal loading are discussed. By increasing the voltage, the drive power, and the magnetron length and by using a tungsten alloy anode, 120 MW should be achievable for approximately 4- mu s pulses at 130 kV with the pulse length limited by transient heating of the anode. >

Proceedings ArticleDOI
01 Apr 1992
TL;DR: In this paper, the authors developed a 60 MW, 60% efficient, 35 Joule/pulse secondary emission magnetron at S-band, and reported on experimental results from this moderate voltage (120 kV), repetitively pulsed (10 Hz), injection locked (14 - 15 dB gain) magnetron.
Abstract: We have developed a 60 MW, 60% efficient, 35 Joule/pulse secondary emission magnetron at S-band. We report on experimental results from this moderate voltage (120 kV), repetitively pulsed (10 Hz), injection locked (14 - 15 dB gain) magnetron. Results from particle-in-cell code computer simulations are presented which compare very well with the experiment when space-charge-limited emission is achieved. Experimental results from a proof-of-principle, low power (6 MW) two-magnetron array are also described.

Patent
05 Oct 1992
TL;DR: In this paper, a PPM coupled-cavity traveling wave tube has an RF structure comprising several cavities separated by iron pole pieces with penetrating slots to provide RF coupling between the cavities.
Abstract: A PPM coupled-cavity travelling wave tube has an RF structure comprising several cavities separated by iron pole pieces (5), (6), (7), with penetrating slots (10), (11), (19) to provide RF coupling between the cavities. Re-entrant copper bars (8), (16), (17), (18) are attached to both sides of the pole pieces (5), (6) that define the boundaries between adjacent pairs of cavities. These bars (8), (16), (17), (18) extend diametrially across the cavity interior around beam drift tubes (9), (24). The re-entrant bars (8), (16), (17), (18) on adjacent pole pieces are rotated relative to each other by 90 degrees about the beam axis. The bars (8), (16), (17), (18) are hollow along their length, and thereby provide channels for coolant flow around the drift tubes (9), (24). These channels communicates through apertures (20), (21), (22), (23) with coolant distribution channels (12), (13), (14), (15) in the outer cavity walls (1), (2), (3), (4) extending along the length of the traveling-wave tube. In an alternative embodiment, the coolant is distributed through external piping to tubes (25), (26), (27), (28) extending outward from the cavity walls (1), (2), (3), (4), which tubes communicate with the channels in the re-entrant bars (8), (16), (17), (18). The direct cooling structure allows the traveling-wave tube to operate at higher power over a broad range of frequencies.

Patent
17 Sep 1992
TL;DR: In this article, a new method for accurately and sequentially growing monolayers and creating new superlattice structures employing a MBE thermal source control technique employing a quasi-double beam atomic absorption background correction measurements with the beam blocked and with beam unblocked and calculating the concentration based on the: ##EQU1## and applying corrections for nonlinear absorption curves because of comparable spectral bandwidth of the molecular beam.
Abstract: A new method for accurately and sequentially growing monolayers and creating new superlattice structures employing a MBE thermal source control technique employing a quasi-double beam atomic absorption background correction measurements with the beam blocked and with the beam unblocked and by calculating the concentration based on the: ##EQU1## and applying corrections for non-linear absorption curves because of comparable spectral bandwidth of the molecular beam.

Patent
09 Mar 1992
TL;DR: A microwave waveguide window has a pair of window plates (12,14) with means (16) for circulating fluid coolant between them in order to counteract the coolant pressure as discussed by the authors.
Abstract: of EP0505066A microwave waveguide window has a pair of window plates (12,14) with means (16) for circulating fluid coolant (20) between them. In order to counteract the coolant pressure, mechanical means are provided near the centers of the window plates for exerting a compensating force in order to reduce stress in the plates. The plates may have apertures (22) through which a metallic tensile member (18) passes to exert the compensating force.

Proceedings ArticleDOI
DeHope1, Hu1, Mizuhara1, Neilson1, Schumacher1, Chong, Lin, Luhmann, McDermott, Stewart 
01 Jan 1992
TL;DR: In this paper, the design of a high power, 95 GHz gyrotron-TWT amplifier with wide bandwidth is described, and the development of a complete tube is under way, capable of 10% duty operation, with predicted performance of 80 kW peak power at an efficiency of 23% and a bandwidth of 3% about 95 GHz.
Abstract: The design of a high power, 95 GHz gyrotron-TWT amplifier with wide bandwidth is described. The development of a complete tube is under way, capable of 10% duty operation, with predicted performance of 80 kW peak power at an efficiency of 23% and a bandwidth of 3% about 95 GHz. >

Journal ArticleDOI
TL;DR: In this article, the reaction of 1-methyl-3,4-dihydro-β-carboline with methyl glycidate gave the novel tetracyclic conjugated γ-lactam, 2-methylpyrrolo[1′,2′:1,2]pyrido[3, 4]-indol-3-one 5.