Rotating Target Holder Research Articles

A CFD analysis of the rotating target holder of the 14-MeV neutron generator

An accelerator based 14-MeV neutron generator is installed at Institute for Plasma Research, Gandhinagar to generate high energy neutrons by using a water-cooled rotating tritium target. In this device, neutrons would be generated from the nuclear reaction 3H(D, n)4He by bombarding accelerated deuterium ions on a solid tritium target. The rotating target holder mainly consists of a rotating copper disc water-cooled case mounted on the rotating shaft. The high-energy deuterium ion beam impacted on solid TiT target fitted on the copper case imparting its energy to the case. This energy is taken away from the system through the water passing through the annulus cavity of the shaft. This paper presents details of the engineering CFD (computed fluid dynamics) analysis carried out for optimizing two important parameters of the rotating target. Firstly optimization of the location of flow parameters of the water as mass flow rate and Secondly optimization of speed of the rotating target and the design of fins inside the copper case.

Matrix assisted pulsed laser evaporation of cinnamate-pullulan and tosylate-pullulan polysaccharide derivative thin films for pharmaceutical applications

We have demonstrated the successful thin film growth of two pullulan derivatives (cinnamate-pullulan and tosylate-pullulan) using matrix assisted pulsed laser evaporation (MAPLE). Our MAPLE system consisted of a KrF* laser, a vacuum chamber, and a rotating target holder cooled with liquid nitrogen. Fused silica and silicon (1 1 1) wafers were used as substrates. The MAPLE-deposited thin films were characterized by transmission spectrometry, profilometry, atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy. The deposited layers ranged from 250 nm to 16.5 μm in thickness, depending on the laser fluence (0.065–0.5 J cm −2) and number of pulses applied for the deposition of one structure (1500–13,300). Our results confirmed that MAPLE was well-suited for the transfer of cinnamate-pullulan and tosylate-pullulan.

Batch treatment of industrial components using plasma immersion ion implantation and deposition

Surface modifications of industrial components, such as the balls, inner and outer rings of bearings, are very difficult to perform for their sophisticated shapes. Plasma immersion ion implantation and deposition (PIIID) offers an effective way for surface treatment of such components. However, implantation doses of these components are not uniform in a conventional PIIID process. To obtain uniform surface modifications, we designed a rotating target holder. Using the target holder and proper process parameters, the PIIID batch treatment of sophisticated-shape components has become easy work. In the PIIID batch treatments of balls, outer and inner surfaces of cylinder-like components, the dose uniformity can be evidently improved by using sample rotation, short width high frequency implantation pulse, and middle-frequency and -voltage glow discharge, respectively. The practical test results reveal that the life of these components can be improved significantly by this novel PIIID batch treatment.

Preparation of Doped Lanthanum Gallate Electrolyte for SOFC by Pulsed Laser Deposition

AbstractIn this study, doped lanthanum gallate (LSGM with the composition La0.9Sr0.1Ga0.8Mg0.2O3-δ, LSGMC with the composition La0.8Sr0.2Ga0.8Mg0.15Co0.05O3-δ) films for an electrolyte of the solid oxide fuel cell (SOFC) were prepared by pulsed laser deposition (PLD) technique. In the vacuum chamber, LSGM or LSGMC targets were set on the rotating target holder. A KrF excimer laser was introduced into the chamber at an incident angle of about 45 degree. The doped LaGaO3 film was deposited onto NiO substrates without heating in argon ambient gas. The NiO substrate can be used directly as an electrode in the fabrication of the SOFC. The deposited LSGM films were characterized by X-ray diffraction (XRD), secondary ion mass spectroscopy (SIMS) and scanning electron microscopy (SEM). As-deposited films were amorphous. After post annealing at 1273K for 6-10 hours, crystalline LaGaO3 was obtained. Films with thickness greater than several 10 μm showed an uniform and dense morphology. No gas leakage was found using thick films, which is an important characteristic for an electrolyte in fuel cells. The composition of the deposited films was slightly different to that of the target.

A new analysis chamber with a rotating target holder for total-sample PIXE analysis of aerosol deposits collected in Berner impactors

We describe an external PIXE analysis chamber provided with means for determining the total amount of aerosol material sampled in Berner impactors. The deposits are concentrated in equally spaced small spots along a circle with a diameter of 50 mm. To pass the whole distribution of material through the probing proton beam, the thin backing film is mounted on a rotatable target holder. Driven by a motor, the holder is rotating at a speed of typically 1/min. Depending on the total duration of the analysis, the sample is rotated 3–10 times through the beam. For high sample throughput the analysis chamber is coupled to a helium-backfilled transfer box in which six holders can be stored, at the same pressure as in the analysis chamber. Loading of the transfer box, with a minimum loss of helium, is accomplished by activating load locks on either side of the box. The first experience gained with aerosol samples as well as with dedicated reference standards is discussed with particular reference to the uniformity of aerosol deposits.

New rotating target holder for laser ablation and ion beam sputter deposition of multicomponent and multilayered thin films

A versatile ultrahigh vacuum rotating target holder has been designed and constructed for use in ion beam sputter and laser ablation deposition systems for producing multicomponent and/or multilayered thin films. The device features a capability for rotating the targets continuously during exposure to the beams to minimize the development of an undesirable surface topography that otherwise would occur if the targets were still during irradiation. In addition, each individual target holder can be tilted at a predetermined angle. The combined tilting and rotation produces a wobbling movement of the target surface that can be used advantageously to achieve a more uniform distribution of the materials ejected from the targets, which in turn can result in better composition and thickness uniformity of thin films over large area substrates. The device can be baked up to 150 °C depending on the choice of driving motor.

Segregation in Fe substituted YBa2Cu3O7 films

Understanding of the role played by the Cu(2)-O and the Cu(1)-O chains is crucial in the high Tc material YBa2Cu3O7 (YBCO). One approach has been to substitute other atoms such as Co, Fe, Ni and Zn for some of the Cu. A linear decrease in the Tc has been observed for several dopants, in particular for Fe substituted bulk samples, Tc⟶0 at 14-15%. Bulk sample studies show some variation in the amount of Tc suppression with concentration, possibly related to the method of materials preparation. The materials discussed here were prepared using the laser ablation technique. Successive ablations from a series of targets was used in order to achieve in principle a mixing on an atomic scale as the components are deposited about an atomic layer at a time. An XeCl laser deposition system was used, equiped with a computer controlled rotating target holder enclosed in a water-cooled shroud.

Computer-controlled ion beam deposition systems for high T c superconductor and other multi-component oxide thin films and layered structures

A single beam, multiple target (SBMT) deposition system which features a rotating target holder with either elemental or simple compound targets has been developed for the production of layered thin film structures and multicomponent oxide, silicade or other compound thin films. We are employing the SBMT ion beam sputtering system for the deposition of high temperature superconducting, electro-optic and ferroelectric thin films and multilayered structures. The beam-target-substrate geometry and ion beam characteristics are designed to minimize scattering of the ion beam from the target (which results in resputtering of, and inert gas incorporation into the film) while maintaining high deposition rates. The amount of energy which is deposited into the film may be controlled by means of a secondary reactive or inert ion beam impacting on the growing film. This secondary beam may provide enough energy to promote activated processes, such as the in-situ formation of oriented crystal structures of high temperature superconducting materials. All parameters necessary to control the film properties are under computer control. A deposition cycle, defined as a number of sequential steps, may be easily modified or added to previously existing deposition cycles, thereby permitting the creation of complicated deposition procedures suitable for the production of films with highly reproducible properties for research purposes, and the in-situ fabrication of complex devices for technological applications. Examples are given of the capabilities of the technique as they apply to the production of high T c superconducting devices.

Characterization of the inverted tetrahedral twin particles in the heteroepitaxial KNbO3 thin films

Perovskite potassium niobate (KNbO3) possesses good electrooptic properties for modulated channel waveguide applications, Epitaxial KNbO3 thin films were deposited onto (100) MgO substrates using an ion beam sputtering technique equipped with a novel computer-controlled rotating target holder , Conventional transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) were employed to perform defect structure and microstructure analysis. Special TEM sample preparation procedures have been developed, which will be reported elsewhere, Tetrahedral twin particles (TTP's) were observed in the epitaxial KNbO3 thin films. Since, the orientation difference between the TTP's and the matrix may affect the polarization switching properties, it is essential to understand their origin and eliminate them if possible.A selected area diffraction pattern of a KNbO3 thin film taken along the substrate (012) (figure 1) reveals twin and double diffraction spots. The mirror planes are determined to be of the {211} family. Figure 2(a) shows the electron diffraction pattern taken along the substrate (100). Twin spots coincide with some of the matrix spots indicating that the twin also maintains an epitaxial relationship with the MgO substrate. The orientation relationship between the twins and the matrix is [221]twin//[100]matrix.

YBa2Cu3O7−δ films deposited by a novel ion beam sputtering technique

Superconducting films of YBa2Cu3O7−δ have been synthesized in a novel ion beam sputter deposition system which features a rotating target holder with BaO2, CuO, and Y2O3 as the sputtering targets. The dwell time of the ion beam on each oxide target is determined by a computer-controlled feedback loop using the signal from a programmable quartz crystal resonator. The sputtered fluxes of all film components originate from the same spatial location, ensuring homogeneous film composition. The results presented demonstrate for the first time an automated ion beam sputter deposition system with the capability of producing high Tc superconducting films by controlled sputtering of either elemental metallic components or oxide precursors. The concept may be extended to include processes such as patterning, production of layered structures (junctions), and film encapsulation necessary for microcircuit manufacturing based on high Tc superconducting films.

Characterization of KNbO3 Thin Films Deposited by Ion Beam Sputtering using a Computer-Controlled Rotating Target Holder

ABSTRACTKNbO3 is a strong candidate as a material for use as channel waveguides due to a high electrooptic figure of merit. High quality single crystals are difficult to obtain due to incongruent melting of the compound. Control of cation concentration and oxygen incorporation are problems encountered in current thin film processing routes.In order to overcome the problems discussed above, an ion beam deposition system featuring a computer-controlled rotatable target holder and quartz crystal resonator (QCR) feedback loop has been developed. Multicomponent films are produced via sputtering from elemental or compound targets sequentially exposed to an ion beam. Initial results are presented on the use of this new technique for the deposition of KNbO3. Pressed KNbO3, Nb2O5, and KO2 powders were used as sputtering targets. By varying the programmed thickness of deposited film from each target being sputtered, the ratio of K:Nb could be reproducibly controlled. The variation in sticking coefficients due to substrate temperature was also compensated for in this manner.Thin films were analyzed by X-ray diffraction and TEM to determine phases present and film microstructure. Film morphology and composition has been studied as a function of substrate temperature, layer thickness, and ion beam process parameters. The relation between deposition parameters and film characteristics are discussed.

Targets Produced in Mass Separators

Isotopically enriched nuclear targets are prepared directly in electromagnetic mass separators by allowing the resolved ion species to impinge on a suitable substrate. The calutron, a multi-milliampere mass separator, has been successful in producing ion-implanted targets for nuclear research and in the doping of semiconductors. By using flat magnetic shims, a rotating target holder, and a sliding indexing shutter, multiple targets with uniform implantation have been achieved. The typical accelerating energy for this method is 40 keV, although this can be increased by using multiply charged ions. For production of highly enriched targets from materials in which the desired isotope is of low natural abundance, the 180° Oak Ridge Sector Isotope Separator (ORSIS) has proven particularly successful. This machine, which is an exceptionally high-resolution separator, is interfaced with an on-line computer for surveillance and control. Isotopic enhancement factors of 4 × 105 have been achieved for targets prepared in this machine. Targets are prepared by placing the host material (typically carbon, aluminum, or nickel foils) at the receiver, 1 cm above the normal straight-line beam path. The desired ion species is steered onto the target through an electrostatic beam deflection system, thereby minimizing neutral particle contamination. The energy of an ion at impact, and hence the deposition depth, is controlled by applying a suitable potential (-40 to +40 kV) at the collector. Ion deposition energies from a few electron volts to several hundred kiloelectron volts have been achieved.

A rotating target holder for low melting point nuclear targets

Using a ferromagnetic feedthrough a simple rotating target holder has been constructed for an Ortec 600 series scattering chamber. In actual measurements we obtained significant improvement in the maximum beam current, which a selenium target could tolerate.