Varian Associates

About: Varian Associates is a based out in . It is known for research contribution in the topics: Beam (structure) & Wafer. The organization has 2160 authors who have published 2591 publications receiving 46002 citations.

Neutron irradiation therapy machine

Abstract: In a neutron irradiation therapy machine for treating patients with a beam of high energy neutrons, a gantry is provided which supports a non-superconducting cyclotron proton accelerator and target for generating a neutron beam and which permits rotation of the accelerator and neutron beam around an axis of revolution coaxial with a patient treatment zone. A counter-weight is carried from the gantry in a diametrically opposed relation to the cyclotron and behind the support bearing for counter-weighting the cyclotron and its associated equipment rotationally and longitudinally. The cyclotron includes an enclosing magnetic return yoke having a re-entrant portion in axial alignment with the magnetic poles of the cyclotron for reducing the weight of the yoke. The enclosing magnetic return yoke, and any additional surrounding material such as boron loaded polyethylene and lead, provide radiation shielding to protect the patient. An alternative patient table is coaxially mounted of the gantry and supported from a rotor portion thereof via a bearing assembly so that the rotor rotates around the stationary patient table. A neutron beam stopper is carried from the rotator of the gantry in axial alignment with the neutron beam and diametrically opposed to the cyclotron for absorbing neutrons passing through the patient treatment zone. Evacuable radio frequency transmission lines are provided for feeding RF power to the cyclotron and which pass through the yoke and are connected in gas communication with a vacuum pump for evacuating the cyclotron via the intermediary of the RF transmission lines. The cyclotron accelerates a beam of charge particles, such as protons, to relatively high energy, as of 30 MeV, to bombard a target formed of first and second materials. The first target material has a relatively high yield for high energy neutrons at proton energies in excess of 15 MeV, whereas a second portion of the target has a low yield for neutrons at proton energies less than 15 MeV, for stopping the protons. Tungsten shielding elements are disposed surrounding the neutron producing target and other regions for attenuation of neutrons falling outside of the desired neutron beam lobe. An adjustable and rotatable neutron beam collimator is arranged for varying the orientation and cross sectional dimensions of the neutron beam as applied to the patient treatment zone.

Charge monitor for high potential pulse current dose measurement apparatus and method

Abstract: A charge measuring system for determining implantation dose in a PI3 system with means to compensate for current in the charge sensor which does not arise from positive ions arriving on the wafer.

Superconducting oxide multilayers and superlattices: Physics, chemistry, and nanoengineering

Abstract: A technique has been developed for synthesis of heterostructures containing various Bi- and Dy-based cuprates and other complex oxides, with a high level of control of deposition of individual atomic monolayers as well as capability for atomic-layer engineering. It produces multilayers and superlattices which display striking long-range crystalline order and atomically abrupt interfaces; this enables deposition of one-unit-cell thick 2212 layers which display HTSC, and of barriers less than 1 nm thick with no pinholes over macroscopic areas. Employing Dy-doped 1278 barriers, trilayer Josephson junctions with I c R n =5−7 mV have been fabricated. Phase locking is seen in stacked junctions. Tunneling transport (but no supercurrent) is observed in junctions with insulating titanate barriers. Modulation doping is attained by omitting or inserting entire monolayers, and artificial metastable high-T c compounds have been synthesized in this way. Finally, long-range proximity effects are seen in 2212-2201-2212 trilayers.

Narrow bore micro-particulate column packing process and product

Abstract: A process for packing narrow bore chromatographic columns and the resulting product are provided. A flexible column, preferably of fused silica, of inner diameter less than 500 μm is selected. A slurry is formed in a reservoir from a mobile solvent and particles of specified diameter. For liquid chromatography the particle size ranges from 3 μm to 10 μm; for gas chromatography the particle size ranges from 3 μm to 100 μm. An end restriction is placed in the end of the column to permit the flow of mobile solvent and to restrict the passage of particles out the end of the column. The reservoir is attached to the column and the slurry is caused to flow under pressure into the column. A two-step pressure sequence is used to first set up the bed of particles and then to compress the bed. First, an initial pressure is maintained for an initial period, preferably less than 10 minutes. Next, the pressure is raised from the initial pressure to a maximum pressure and is maintained at the maximum pressure for a second period. The product in either case is a stable, loose packed column having a high plate number per unit length.