- 标题
- 摘要
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- 实验方案
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Characterization of a double Time-Of-Flight detector system for accurate velocity measurement in a storage ring using laser beams
摘要： The Isochronous Mass Spectrometry (IMS) is a powerful tool for mass measurements of exotic nuclei with half-lives as short as several tens of micro-seconds in storage rings. In order to improve the mass resolving power while preserving the acceptance of the storage ring, the IMS with two Time-Of-Flight (TOF) detectors has been implemented at the storage ring CSRe in Lanzhou, China. Additional velocity information beside the revolution time in the ring can be obtained for each of the stored ions by using the double TOF detector system. In this paper, we introduced a new method of using a 658 nm laser range finder and a short-pulsed ultra-violet laser to directly measure the distance and time delay difference between the two TOF detectors which were installed inside the 10?11 mbar vacuum chambers. The results showed that the distance between the two ultra-thin carbon foils of the two TOF detectors was ranging from 18032.5 mm to 18035.0 mm over a measurable area of 20×20 mm2. Given the measured distance, the time delay difference which comes with signal cable length difference between the two TOF detectors was measured to be ??????????????1?2 = 99(26) ps. The new method has enabled us to use the speed of light in vacuum to calibrate the velocity of stored ions in the ring. The velocity resolution of the current double TOF detector system at CSRe was deduced to be ??(??)∕?? = 4.4 × 10?4 for laser light, mainly limited by the time resolution of the TOF detectors.
关键词： Ultra-high vacuum,Ultra-thin carbon foil,TOF detectors,Velocity measurement,Laser range-finder,ps-pulsed UV laser
更新于2025-11-25 10:30:42
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On the Effect of Thin Film Growth Mechanisms on the Specular Reflectance of Aluminium Thin Films Deposited via Filtered Cathodic Vacuum Arc
摘要： The optimisation of the specular reflectance of solar collectors is a key parameter to increase the global yield of concentrated solar power (CSP) plants. In this work, the influence of filtered cathodic vacuum arc deposition parameters, particularly working pressure and deposition time, on the specular and diffuse reflectance of aluminium thin films, was studied. Changes in specular reflectance, measured by ultraviolet–visible and near-infrared spectroscopy (UV-vis-NIR) spectrophotometry, were directly correlated with thin film elemental concentration depth profiles, obtained by Rutherford backscattering spectrometry (RBS), and surface and cross-sectional morphologies as measured by scanning electron microscopy (SEM) and profilometry. Finally, atomic force microscopy (AFM) provided information on the roughness and growth mechanism of the films. The two contributions to the total reflectance of the films, namely diffuse and specular reflectance, were found to be deeply influenced by deposition conditions. It was proven that working pressure and deposition time directly determine the predominant factor. Specular reflectance varied from 12 to 99.8% of the total reflectance for films grown at the same working pressure of 0.1 Pa and with different deposition times. This transformation could not be attributed to an oxidation of the films as stated by RBS, but was correlated with a progressive modification of the roughness, surface, and bulk morphology of the samples over the deposition time. Hence, the evolution in the final optical properties of the films is driven by different growth mechanisms and the resulting microstructures. In addition to the originally addressed CSP applications the potential of the developed aluminium films for other application rather than CSP, such as, for example, reference material for spectroscopic diffuse reflectance measurements, is also discussed.
关键词： structural characterisation,total and specular reflectance,filtered cathodic vacuum arc,thin film deposition conditions
更新于2025-10-22 19:40:53
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[IEEE 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - Greifswald (2018.9.23-2018.9.28)] 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - A Novel Vacuum Interruption Contact Design for High Current DC Vacuum Circuit Breaker
摘要： The vacuum interruption contact structure affect the insulation and breaking performance of DC vacuum circuit breaker directly. A novel vacuum interruption contact system with axial magnetic field (AMF)-double transversal magnetic field (TMF) is investigated for high current interruption in DC vacuum circuit breaker in this paper. It consists of one AMF cup-shaped contact and two concentric TMF contacts, which the internal contact is a disk-shaped structure and the external contact is a cup-shaped structure. The so-called novel TMF-TMF-AMF contact structure has the merits of having a very high axial magnetic flux density at large current condition, and producing rotation Lorentz force for metal vapor arc caused during interruption process. Its performance is compared with that of traditional TMF contact, traditional AMF contact and TMF-AMF contacts using three-dimensional finite-element method and the comparison results verify the validity of this proposed interruption contact structure design.
关键词： Lorentz force,vacuum interruption,finite element method,Axial magnetic flux density,metal vapor arc
更新于2025-09-23 15:23:52
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Definition of design guidelines, construction, and performance of an ultra-stable scanning tunneling microscope for spectroscopic imaging
摘要： Spectroscopic-imaging scanning tunneling microscopy is a powerful technique to study quantum materials, with the ability to provide information about the local electronic structure with subatomic resolution. However, as most spectroscopic measurements are conducted without feedback to the tip, it is extremely sensitive to vibrations coming from the environment. This requires the use of laboratories with low-vibration facilities combined with a very rigid microscope construction. In this article, we report on the design and fabrication of an ultra-stable scanning tunneling microscope (STM) for spectroscopic-imaging measurements that operates in ultra-high vacuum and at low temperatures (4 K). We start from existing designs with sapphire as the main material and improve the stiffness further by performing finite element analysis calculations for the main components of the microscope to guide design choices on the geometry of the parts. With this strategy, we construct a STM head with measured lowest resonant frequencies above f0 = 13 kHz for the coarse approach mechanism, a value three times higher than what has been previously reported and in good agreement with the calculations. This allows us to achieve an average vibration level of ～6 fm/√Hz, without a dedicated low-vibration lab. We demonstrate the microscope’s performance with topographic and spectroscopic measurements on the correlated metal Sr2RhO4, showing the quasiparticle interference pattern in real and reciprocal space with high signal-to-noise ratio.
关键词： ultra-high vacuum,low temperature,spectroscopic imaging,finite element analysis,ultra-stable,scanning tunneling microscopy
更新于2025-09-23 15:23:52
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Screen printing for support-pillar placement for vacuum glazing and the effects of pillar spacing on strength properties
摘要： Maintaining a vacuum between the two glasses to maximize the heat insulating performance, it is indispensable to array the pillar for the vacuum glazing to maintain the vacuum gap. In this paper, to investigate the effect of the spacing of the pillars arranged using the screen printing method on the strength of the glass, a bending strength test was carried out by design and fabricating a ROR bending strength test jig based on the Euro standard. In the strength test results, the experimental results were analyzed using the Weibull distribution, which is a statistical analysis method mainly used for evaluating the breaking strength of brittle material. Based on the analysis results, the placement spacing of the pillars proved validity for maintaining the vacuum glass gaps.
关键词： Weibull analysis,Vacuum glazing,Screen printing,Supporting pillar,Bending strength
更新于2025-09-23 15:23:52
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Ion beam measurements for the investigation of TiN thin films deposited on different substrates by vacuum arc discharge
摘要： Titanium nitride thin films were deposited on different substrates using vacuum arc discharge system. Simultaneous ion beam analysis measurements including elastic backscattering (EBS) and nuclear reaction analysis (NRA); were applied for both composition analysis and thickness measurements of the prepared TiN films. Experimental conditions have been optimized to avoid overlapping of peaks of different nuclear reactions products, especially those related to interaction between ion beam and light elements present in totally different substrates. Independent compliment measurements utilizing time-of-flight elastic recoil detection analysis (TOF-ERDA), scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD) measurements were also applied to verify the experimental findings obtained by EBS and NRA measurements. The results have shown that all prepared TiN films have N/Ti ratio of around 1, with low levels of contamination elements.
关键词： IBA,TiN film,XRD,Substrates,SEM/EDX,Vacuum arc discharge
更新于2025-09-23 15:23:52
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Squeezing-induced giant Goos-H?nchen shift and hypersensitized displacement sensor in a two-level atomic system
摘要： We analyze an efficient scheme to enhance the Goos-H?nchen (GH) shifts of the reflected and transmitted beams in a cavity containing two-level atomic medium. A broadband squeezed vacuum field is injected into the cavity to interact with the atomic medium. In the bad cavity limit, the Bloch equations for the atomic operators are identical to those in the free space, but with the modification of the system parameters. Using experimentally achievable parameters, we identify the conditions under which the squeezed vacuum allows us to enhance the GH shifts of the reflected and transmitted beams beyond what is achievable in the absence of the squeezed vacuum. The enhanced GH shifts originate from the coherent population oscillations controlled by the squeezed vacuum field. Furthermore, we also find that the GH shifts of the reflected and transmitted beams depend sensitively on the relative phase between the control field and the squeezed vacuum field. Subsequently, we propose a scheme for such a configuration of the GH shift as a family of hypersensitized displacement sensors. Based on the numerical analysis, the detection sensitivity and minimum detectable value for the tiny displacement can reach approximately 2340 μm/nm and 14.4 pm, respectively.
关键词： coherent population oscillations,Goos-H?nchen shift,two-level atomic system,displacement sensor,squeezed vacuum
更新于2025-09-23 15:23:52
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[IEEE 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - Greifswald (2018.9.23-2018.9.28)] 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - A Novel Method to Generate Multicomponent Metal Ions by Anodic and Cathodic Vacuum Arc Plasmas with Pure Electrodes
摘要： Usually multicomponent ions are generated from cathodic vacuum arc plasma with compound cathodes. In this paper, a novel method to produce multicomponent ions by simultaneous anodic and cathodic vacuum arc plasmas with pure electrodes has been studied. The vacuum arc discharge has been operated with Al anode and W cathode. To characterize the plasma plume generation, a combination of high-speed camera and time-of-flight mass spectrometer has been used to measure the spot phenomenon and multicomponent ions, respectively. Luminous spots have been simultaneously found on the anode and cathode to produce multicomponent ions, which has been verified by the examination of electrode erosion using SEM. The ion charge state distribution and multicomponent ions have also been measured. For comparison, the characteristic of vacuum arc discharge operated with the exchange of electrodes has been studied, which exhibits obvious discrepancies. This behavior of vacuum arc is considered to be controlled by the difference of cohesive energy, because the heat flow to the electrodes is sufficient to evaporate the electrode, and the ionization process by the plasma occurs in the nonequilibrium layers near the evaporated surface in cathode and anode regions. This interesting result is proposed to use for the synthesis of compound films.
关键词： cohesive energy,vacuum arc,multicomponent ions
更新于2025-09-23 15:23:52
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Vacuum-enhanced optical nonlinearities with disordered molecular photoswitches
摘要： It is well known that nonlinear optical signals such as cross-phase modulation can be coherently enhanced in multilevel atomic gases under conditions of electromagnetically induced transparency, but analogous results in solids are challenging to obtain due to natural energetic disorder. We propose a solid-state cavity QED scheme to enable cross-phase modulation between two arbitrarily weak classical fields in the optical domain, using a highly disordered intracavity medium composed of organic molecular photoswitches. Even in the presence of strong energetic and orientational disorder, the unique spectral properties of organic photoswitches can be used to enhance the desired nonlinearity under conditions of vacuum-induced transparency, enabling cross-phase modulation signals that surpass the detection limit imposed by absorption losses. Possible applications of the scheme include integrated all-optical switching with low photon numbers.
关键词： organic photoswitches,cavity QED,vacuum-induced transparency,cross-phase modulation,disorder
更新于2025-09-23 15:23:52
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[IEEE 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - Greifswald (2018.9.23-2018.9.28)] 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) - Simulation of the Interaction between High Current Vacuum Arc and Macroparticles in Small-Size Trigatron
摘要： This work investigates the interaction between high current vacuum arc (HCVA) and the macroparticle (MP) generated from the cathode spots (CS) in the small-size vacuum trigatron. Magnetohydrodynamic (MHD) model is used to describe the arc column. MPs are added into MHD model, which are described by discrete phase model (DPM). The control equations of MPs include charging equation, motion equation and heat transfer equation, in which the evaporation of MPs is also considered. Based on the above model, the effects of MP diameter and arc current on the characteristics of MPs are studied. Simulation results show that MPs leave the interelectrode gap with a deflection angle larger than the initial angle under the influence of plasma. The motion of MPs is similar to that of projectiles. MPs with smaller diameter are influenced by the arc plasma more significantly. MPs can act as a source of the plasma, but these influences are not obvious in HCVA. What may be more harmful to the trigatron is the charging process of MPs during post-arc process.
关键词： magnetohydrodynamic model,macroparticle,discrete phase model,vacuum arc
更新于2025-09-23 15:23:52