Vacuum Window Research Articles

실측데이터를 이용한 에너지제로주택의 연간 에너지성능평가

Purpose: In this study, we evaluate the annual energy performance of the detached house which was designed with the aim of zero energy. Method: The experimental house which was constructed in Gonju Chungnam in 2013, is the single family detached house of light weight wood frame with <TEX>$100m^2$</TEX> of heating area. Thermal transmittance of roof (by ISO 10211) and building external walls are designed as <TEX>$0.10W/m^2K$</TEX> and <TEX>$0.14W/m^2$</TEX> respectively and low-e coating vacuum window glazing with PVC frame was installed. Also grid connected PV system and natural-circulation solar water heater was applied and 6kWp capacity of photovoltaic module was installed in pitched roof and <TEX>$5m^2$</TEX> of solar collector in vertical wall facing the south. We analyzed the 2014 annual data of the detached house in which residents were actually living, measured though web-based remote monitoring system. Result: First, as a result, total annual energy consumption and energy production (PV generation and solar hot water) are 7,919kWh and 7,689kWh respectively and the rate of energy independence is 97.1% which is almost close to the zero energy. Second, plug load and hot water of energy consumption by category showed the highest numbers each with 33% and 31%, with following space heating 24%, electric cooker 8%, lighting 3% in order. Hot water supply is relatively higher than space heating because high insulation makes it decreased.

Multi-cell disk-and-ring tapered structure for compact RF linacs

A tubular disk-and-ring, tapered accelerating structure for small electron linacs and MicroLinacs is considered. It consists of metal and dielectric elements inserted into a metallic tube to eliminate multi-cell, multi-step brazing. The structure enables a wide range of phase velocities (including non-relativistic), a wide bandwidth allowing large number of cells (for standing wave mode) or short filling time (for traveling wave mode), combination of compensated and purely π-mode cells, alternative periodic focusing built-in to the RF structure (the disks), and combining of RF and vacuum windows. RF and accelerating performance of such a long structure having up to four dozens cells is analyzed. Some of beam dynamics, thermal, and vacuum aspects of the structure and MicroLinac performance are considered as well.

Waveguide transition with vacuum window for multiband dynamic nuclear polarization systems.

A low loss waveguide transition section and oversized microwave vacuum window covering several frequency bands (94 GHz, 140 GHz, 188 GHz) is presented. The transition is compact and was optimized for multiband Dynamic Nuclear Polarization (DNP) systems in a full-wave simulator. The window is more broadband than commercially available windows, which are usually optimized for single band operation. It is demonstrated that high-density polyethylene with urethane adhesive can be used as a low loss microwave vacuum window in multiband DNP systems. The overall assembly performance and dimensions are found using full-wave simulations. The practical aspects of the window implementation in the waveguide are discussed. To verify the design and simulation results, the window is tested experimentally at the three frequencies of interest.

Design and Characterization of the ALMA Band 5 Vacuum Window

This paper summarizes the electromagnetic design process of the vacuum window for the Atacama Large Millimeter/sub-millimeter Array (ALMA) Band 5 (163-211 GHz). We have carried out investigations by means of numerical simulations as well as reflection and transmission measurements. Simulations were performed using the finite element method, an efficient quasi-analytical technique, and rigorous coupled-wave analysis. We used an injection-molded vacuum window prototype as a starting point of the design process and investigated deterioration in the electromagnetic performance caused by different types of manufacturing artifacts. Following these analyses, an optimization of the window has been performed based on simulations. We measured the reflectivity and transmittance of the newly designed window and this paper demonstrates that the optimized window exhibits a return loss better than -20 dB, as required by the ALMA specifications.

Ion beam evaluation of silicon carbide membrane structures intended for particle detectors

Thin ion transmission detectors can be used as a part of a telescope detector for mass and energy identification but also as a pre-cell detector in a microbeam system for studies of biological effects from single ion hits on individual living cells. We investigated a structure of graphene on silicon carbide (SiC) with the purpose to explore a thin transmission detector with a very low noise level and having mechanical strength to act as a vacuum window. In order to reach very deep cavities in the SiC wafers for the preparation of the membrane in the detector, we have studied the Inductive Coupled Plasma technique to etch deep circular cavities in 325μm prototype samples. By a special high temperature process the outermost layers of the etched SiC wafers were converted into a highly conductive graphitic layer. The produced cavities were characterized by electron microscopy, optical microscopy and proton energy loss measurements. The average membrane thickness was found to be less than 40μm, however, with a slightly curved profile. Small spots representing much thinner membrane were also observed and might have an origin in crystal defects or impurities. Proton energy loss measurement (also called Scanning Transmission Ion Microscopy, STIM) is a well suited technique for this thickness range. This work presents the first steps of fabricating a membrane structure of SiC and graphene which may be an attractive approach as a detector due to the combined properties of SiC and graphene in a monolithic materials structure.

Finite Element Analysis of Glass Vacuum Windows of the “COMPASS” Tokamak in Prague

In this paper is described the mechanical stress analysis of glass vacuum windows of the COMPASS tokamak using Finite Element Method. As a reference test problem the problem of uniformly loaded glass vacuum window with circular shape has been chosen, which problem can be solved also analytically. In the case of Finite Element analysis we used two different mechanical models: 3-dimensional (3D) approach and shell modelling. For 3D approach an optimal finite element type - quadratic tetrahedron element with appropriate size - was chosen, and for shell modelling a thin axisymmetric shell element type - shell 209 - was applied. The analytic and both numerical results have been compared and summarized.

Energy performance and economic viability of advanced window technologies for a new Finnish townhouse concept

Among the elements of a typical building envelope, windows are responsible for the greatest energy loss due to their high U-value. Conventional windows tend to have poor glazing properties, which causes significant heat loss during the winter season and undesirable heat gain during the summer season. Advanced window technologies are therefore required to mitigate the energy consumption of buildings. The key hypothesis in this study is that advanced windows become economically viable for end-users if the difference in life-cycle cost between advanced window types and the state-of-the-art (reference) window is equal to zero. To verify this hypothesis, we calculate the allowable additional investment costs (dIC) for three types of advanced windows over a given life span. Different advanced windows; electrochromic, PV and vacuum windows together with a self-cleaning feature were compared with a state-of-the-art window with excellent properties (reference window) in terms of energy performance and life-cycle cost for a conceptual residential house (i.e. townhouse) in Finland. By performing a whole-building simulation using IDA ICE, the impact of these windows on the total delivered energy needs of the townhouse were estimated. Among the alternatives, the vacuum window (lowest U-value) offers the highest dIC value, due to its maximum energy savings. With a generic efficiency of 6%, the PV window holds the intermediate position between the vacuum and reference window in terms of dIC value. Hypothetically, with a U-value of 0.6W/m2K, the PV window would become the most energy efficient window alternative. The self-cleaning feature proved to be a dominant factor toward the increase of dIC value by avoiding maintenance costs. Electrochromic glazing is not economically feasible due to its negative dIC value as it doesn’t offer life cycle cost savings.

Numerical design of polycapillary X-ray optics as both a focusing X-ray lens and a vacuum window

Polycapillary X-ray optics as a new application is proposed to be used as both a focusing X-ray lens and a vacuum window placed in the middle part which connected X-ray source in a clearly high vacuum with sample or detector in a moderate vacuum. Numerical results showed that such polycapillary X-ray optics had a low vacuum conductance, and it could be accordingly used as both such vacuum window for an X-ray source in a clearly high vacuum and a focusing X-ray lens at the same time.

Design of a single-star optical emulator for a fast telescope

The design of a simple lens system is described capable of projecting a diffraction limited f1/.2 point of light through a variety of plane parallel vacuum windows. The system was built for the purpose of testing prototype CCDs for the Large Synpotic Survey Telescope in which lab testing drove the desire to create a beam that matches the telescope's f-ratio and obstruction, and which would have sufficient back-focal distance to allow imaging onto a sensor at least 50 mm away in various dewars with various window thicknesses. Also used as the final optic in an atmospheric turbulence simulator, the lens can simulate the real-world star PSF as it will appear on the Large Synoptic Survey Telescope (LSST) focal plane.

SU‐E‐T‐47: A Monte Carlo Model of a Spot Scanning Proton Beam Based On a Synchrotron Proton Therapy Accelerator

Purpose:To build the model of a spot scanning proton beam for the dose calculation of a synchrotron proton therapy accelerator, which is capable of accelerating protons from 50 up to 221 MeV.Methods:The spot scanning beam nozzle is modeled using TOPAS code, a simulation tool based on Geant4.9.6. The model contained a beam pipe vacuum window, a beam profile monitor, a drift chamber, two plane‐parallel ionization chambers, and a spot‐position monitor consisted of a multiwire ionization chamber. A water phantom is located with its upstream surface at the isocenter plane. The initial proton beam energy and anglar deflection are modeled using a Gaussian distribution with FWHM (Full Widths at Half Maximum) deponding on its beam energy. The phase space file (PSF) on a virtual surface located at the center between the two magnets is recorded. PSF is used to analyze the pencil beam features and offset the pencil beam position. The source model parameters are verificated by fitting the simulated Result to the measurement.Results:The simulated percentage depth dose (PDD) and lateral profiles of scanning pencil beams of various incident proton energies are verificated to the measurement. Generally the distance to agreement (DTA) of Bragg peaks is less than 0.2cm. The FWHM of Gaussian anglar distribution was adjusted to fit the lateral profile difference between the simulation and the measurement to less than 2∼3cm.Conclusion:A Monte Carlo model of a spot scanning proton beam was bullt based on a synchrotron proton therapy accelerator. This scanning pencil beam model will be as a block to build the broad proton beam as a proton TPS dose verification tool.

SU‐E‐T‐534: Level of Residual Radioactivity of Activated Parts of a Decommissioned Cyclotron

Purpose:CTI cyclotron RDS‐111 was used at the Hong Kong Sanatorium and Hospital (HKSH) to produce radiopharmaceuticals and radioactive tracers for diagnostic scans between 1999 and 2007. During the operation, some machine components became radioactive by activation. For the safety of staff, decommissioning took place in 2009, two years after the cyclotron had stopped operation. This study investigates the residual radioactivity and radionuclides found in different cyclotron components in 2014 in compliance with the local regulations in Hong Kong for transfer of radioactive waste.Methods:A representative sample of each part was counted using a high‐purity germanium detector (manufacturer: ORTECT) for at least four hours. GammaVision, a multichannel analyzer software, was used to identify the radionuclides found in the cyclotron components, as well as the associated activities. A standard library and a Mariscotti peak search algorithm were used to identify the present radionuclides. Only radionuclides with half‐life greater than 180 days were considered.Results:Among the components, the Havar target foil has the highest specific activity ((4.6±0.6)×102 Bq/g), with Co‐60 being the most prominent ((3.8±0.5)×102 Bq/g). The total activity of the target foil, however, is still low due to its small mass of 0.04 g. Radioisotopes Mn‐54 (46±6 Bq/g), Na‐22 (6.8±0.8 Bq/g), Co‐57 (7.3±0.9 Bq/g), and Fe‐59 (6.0±0.9 Bq/g) have also been detected in the target foil. The target window holder and the vacuum window register a specific activity of 88.3±0.6 Bq/g and 48.6±0.1 Bq/g, respectively. Other components, such as the collimator, the target tube, the valve body and the beamline, are also found with trace amounts of radionuclides.Conclusion:Even seven years after the cyclotron had stopped operation, some components still exhibited residual radioactivity from activation exceeding the IAEA clearance levels. Special consideration for radiological protection may need to be taken in the disposal of the cyclotron parts.

Simulations of a vacuum window and in-beam ion detection for use in radiobiological experiments with 50 MeV particle beams

The vacuum window and in-beam ion detection of a radiobiological endstation have been studied using the Monte Carlo particle transport code MCNPX 2.5.0, investigating the effects of different elements on an incident beam of 50 MeV protons. The scattering and energy spread as well as secondary particle generation are analysed. A 200 nm thick silicon nitride vacuum window was found to have the least effect on the incident beam, giving an energy spread of 5.01(8)× 10−4 MeV. Placing a silicon pixel detector before the sample caused scattering of the beam of around 15 μm in radius; too much to be used for experiments targeting individual nuclei.

Design of a Proton-induced Quasimonochromatic Micro-XRF Setup for Wet Biological Samples

Abstract We designed and constructed a proton-induced quasimonochromatic micro-XRF system for wet biological samples. A horizontal beam of MeV protons delivered by a 1.6 MV tandem accelerator was bent downward by 45° using a dipole magnet. A copper (Cu) foil target was placed perpendicular to the incident proton beam. The thickness of the foil was 30 μm, which is slightly larger the proton range. This Cu foil was used also as a vacuum window for the X-rays. The proton-induced quasimonochromatic X-rays (QMXRs) emitted to the atmosphere through the foil were focused by a polycapillary X-ray half lens. The monochromaticity and intensity of the QMXR microbeam as a function of the incident proton energy were investigated. The QMXR microbeam impinged on the horizontal sample surface with an incident angle of 45°, and emitted fluorescent X-rays from the sample were collected by a Si-PIN X-ray detector positioned at 90° with respect to the incident microbeam. The size of the X-ray beam was 250 μm × 350 μm. To demonstrate the capability of the micro-XRF setup for in-vivo measurement of trace elements in biological samples, we measured cobalt (Co) accumulated in leaves of duckweed floating on a Co solution surface. By using standard samples which simulated the duckweed leaf, the Co concentration in the leaf in the order of 100 ppm could be quantitatively determined.

Overview video diagnostics for the W7-X stellarator

Considering the requirements of the newly built Wendelstein 7-X stellarator a ten-channel overview video diagnostic system was developed and is presently under installation. The system covering the whole torus interior can be used not only to observe the plasma but also to detect irregular operational events which are dangerous for the stellarator itself and to send automatic warning for the machine safety. The ten tangential AEQ ports used by the diagnostic remain under atmospheric pressure, the vacuum/air interface is at the front window located at the plasma side of the AEQ port. The optical vacuum window is protected by a cooled pinhole. The Sensor Module (SM) of the intelligent camera (EDICAM) – developed especially for this purpose – is located directly behind the vacuum window. EDICAM is designed to simultaneously record several regions of interest of its CMOS sensor with different frame rate and to detect various predefined events in real time. The air cooled SM is fixed by a docking mechanism which can preserve the pointing of the view. EDICAM can withstand the magnetic field (∼3T), the neutron and gamma fluxes expected in the AEQ port. In order to adopt the new features of the video diagnostics system both control and data acquisition and visualization and data processing softwares are developed.

Design of wide-field Nasmyth optical system for a submillimeter camera

A wide-field Nasmyth optical system that connects a planned 10-m Ritchey-Chrétien telescope to a submillimeter camera is reported. This diffraction-limited system has a 1-deg field of view at 850 GHz, filled with a more than 20,000-pixel camera. The system enables us to carry out large field surveys of distant galaxies within reasonable time scales. The size of the Nasmyth optics is reasonably compact and its cryogenic part including the vacuum window, cryogenic lens, and IR block filters can be built using existing technologies at a reasonable cost. This type of optical system can be applied for the optical design of millimeter, terahertz, and other submillimeter instruments.

Interlock system for machine protection of the KOMAC 100-MeV proton linac

The 100-MeV proton linear accelerator of the Korea Multi-purpose Accelerator Complex (KOMAC) has been developed. The beam service started this year after performing the beam commissioning. If the very sensitive and essential equipment is to be protected during machine operation, a machine interlock system is required, and the interlock system has been implemented. The purpose of the interlock system is to shut off the beam when the radio-frequency (RF) and ion source are unstable or a beam loss occurs. The interlock signal of the KOMAC linac includes a variety of sources, such as the beam loss, RF and high-voltage converter modulator faults, and fast closing valves of the vacuum window at the beam lines and so on. This system consists of a hardware-based interlock system using analog circuits and a software-based interlock system using an industrial programmable logic controller (PLC). The hardware-based interlock system has been fabricated, and the requirement has been satisfied with the results being within 10 µs. The software logic interlock system using the PLC has been connected to the framework of with the experimental physics and industrial control system (EPICS) to integrate a variety of interlock signals and to control the machine components when an interlock occurs. This paper will describe the design and the construction of the machine interlock system for the KOMAC 100-MeV linac.

Transmission X-Ray Imaging Detector Captures the Last Light at NSLS

Biological research constitutes a large and expanding scientific focus at synchrotron facilities. Structural biology researchers using x-ray facilities make up the majority of this community, including use of techniques such as macromolecular x-ray crystallography, small-angle x-ray solution scattering, x-ray microscopy, x-ray absorption spectroscopy, x-ray fluorescence and x-ray footprinting. Many of these technologies, as they are developed to take advantage of next-generation synchrotron sources, are trending toward use of high flux beams and/or beams which require enhanced stability and precise understanding of beam position and intensity from the front end of the beamline all the way to the sample. For high flux beams, major challenges include heat load management in optics (including the vacuum windows) and a mechanism of real-time volumetric measurement of beam properties such as flux, position, and morphology. For beam stability in these environments, feedback from such measurements directly to control systems for optical elements or to sample positioning stages would be invaluable. For x-ray footprinting, a focused “white beam” is used to maximize x-ray flux density over a practical sample size using a toroidal mirror. This intense beam can melt beryllium windows and is very complicated to measure, causing difficulties with properly focusing the mirror and with understanding where the beam is and exactly what is being delivered to the sample. To address these challenges, we are developing diamond-based instrumented vacuum windows with integrated volumetric x-ray intensity, beam profile and beam-position monitoring capabilities. The prototype device will be used as the exit window for the XFP beamline currently being developed at NSLS-II for x-ray footprinting. Current progress is presented, including successful demonstration of a >1kilopixel free-standing transmission imaging detector that was used to capture the last x-ray photons at the National Synchrotron Light Source.

1m红外太阳望远镜折轴光路与封窗偏振建模

1m红外太阳望远镜折轴光路与封窗偏振建模

Research on the development mechanism: from two-sided multipactor to one-sided multipactor

Multipactor discharge always causes disastrous damage to a vacuum window in high power microwave system, which actually becomes a limiting factor for the output power of vacuum device. To explore the multipactor phenomenon of complicated pill-box window, the mulitpactor in normal field between the metal boundary and the window disk is studied. Through Monte Carlo (MC) simulations, the susceptive curve is fitted and analyzed. The secondary electrons' avalanche behavior under the normal RF field is discussed. It is noticed that the one-sided multipactor is excited within a very limited Vrf-fD region when two-sided multipactor is excited initially. The development condition from two-sided multipactor to the one-sided multipactor is proposed. Through analyzing and MC simulation, the condition is achieved. When the normal RF electric field can satisfy the phase focus conditions of one-sided multipactor, the two-sided multipactor will develop into one-sided multpactor and then reach a saturation value. Meanwhile, the initial effect of electrostatic field on one-sided multipactor is also discussed. On condition that two-sided multipactor can be excited, the number of secondary electrons can increase up to a saturation value when Edc0 is lower than the minimal saturate value of Edc. When Edc0 is lager than the minimal saturate value of Edc and in the Edc/Erf threshold of one-sided resonant multipactor, the number of secondary electrons can also increase to a saturate value. However, When Edc0 is lager than the minimal saturate value of Edc but beyond the Edc/Erf threshold of one-sided resonant multipactor, secondary electrons will be suppressed.

A WR4 Amplifier Module Chain With an 87 K Noise Temperature at 228 GHz

In this letter we report an ultra-low-noise amplifier module chain in the WR4 frequency range. The amplifier chips were fabricated in a 35 nm InP HEMT technology and packaged in waveguide housings utilizing quartz E-plane waveguide probes. When cryogenically cooled to 22 K and measured through a mylar vacuum window, the amplifier module chain achieves a receiver noise temperature of 87 K at 228 GHz and less than a 100 K noise temperature from 217 to 236 GHz. The LNA modules have 21–31 dB gain and the power dissipation is 12.4–15.8 mW. To the best of authors' knowledge, these are the lowest LNA noise temperatures at these frequencies reported to date.