Vacuum System Optimization for EAST Neutral Beam Injector

The neutral beam injector (NBI) generates a high-energy ion beam and neutralizes it, and then relies on drift transmission to inject the formed neutral beam into the fusion plasma to increase the plasma temperature and drive the plasma current. In order to better cooperate with the Experimental Advanced Superconductive Tokamak (EAST), part of the Chinese major national scientific and technological infrastructure, in carrying out long-pulse high-parameter physics experiments of 400 s and above, this paper considers the optimization of the current design and operation of the NBI beam line with a pulse width of 100 s. Based on an upgraded and optimized NBI vacuum chamber and the structure of the beam-line components, the gas-source characteristics under the layout design of the NBI system are analyzed and an NBI vacuum system that meets relevant needs is designed. Using Molflow software to simulate the transport process of gas molecules in the vacuum chamber, the pressure gradient in the vacuum chamber and the heat-load distribution of the low-temperature condensation surface are obtained. The results show that when the NBI system is dynamically balanced, the pressure of each vacuum chamber section is lower than the set value, thus meeting the performance requirements for the NBI vacuum system and providing a basis for subsequent implementation of the NBI vacuum system upgrade using engineering.

VACUUM SYSTEM OF KLYSTRON REPAIR FACILITY FOR ELECTRON ACCELERATORS

KIU-12AM “AVRORA” klystron has been the main source of rf power for the accelerators for decades. Large accumulations of malfunctioning klystrons made it possible to recycle them using the donor parts, which are well preserved and still functional. Klystron repair process comprises of few stages and part of these stages requires maintaining the high vacuum inside the klystron and adjacent systems.

Search for sub-eV axion-like resonance states via stimulated quasi-parallel laser collisions with the parameterization including fully asymmetric collisional geometry

We have searched for axion-like resonance states by colliding optical photons in a focused laser field (creation beam) by adding another laser field (inducing beam) for stimulation of the resonance decays, where frequency-converted signal photons can be created as a result of stimulated photon-photon scattering via exchanges of axion-like resonances. A quasi-parallel collision system (QPS) in such a focused field allows access to the sub-eV mass range of resonance particles. In past searches in QPS, for simplicity, we interpreted the scattering rate based on an analytically calculable symmetric collision geometry in both incident angles and incident energies by partially implementing the asymmetric nature to meet the actual experimental conditions. In this paper, we present new search results based on a complete parameterization including fully asymmetric collisional geometries. In particular, we combined a linearly polarized creation laser and a circularly polarized inducing laser to match the new parameterization. A 0.10 mJ/31 fs Ti:sapphire laser pulse and a 0.20 mJ/9 ns Nd:YAG laser pulse were spatiotemporally synchronized by sharing a common optical axis and focused into the vacuum system. Under a condition in which atomic background processes were completely negligible, no significant scattering signal was observed at the vacuum pressure of 2.6 × 10−5 Pa, thereby providing upper bounds on the coupling-mass relation by assuming exchanges of scalar and pseudoscalar fields at a 95% confidence level in the sub-eV mass range.

Occurrence of microdebris in commercial cephalopod

Modern Fish Market of Muara Baru is one of the largest fish markets in Jakarta, which sells various seafood, including fish, shellfish, crustaceans, and others. Previous studies have revealed microdebris contamination of mollusks, particularly in filter-feeders. However, it has not been widely studied at the predator level in cephalopods. We aim to investigate contamination of microdebris in two commercial species of cephalopod, i.e. Loliolus sumatrensis and Sepia recurvirostra, from the market. The digestive tract of the cephalopod was taken and dissolved by adding H2O2 50% then filtered under a vacuum system. The particles of microdebris were observed with a stereo microscope then several particles were analyzed using an FTIR microscope. The abundance of microdebris in L. sumatrensis was higher (3.8 particles/individual) than the abundance that of microdebris in S. recurvirostra (2.8 particles/individual). The size of microdebris was dominated by three of five size classes such as 0.1 − 0.5 mm, 0.5 − 1 mm, and 1 − 5 mm. Microdebris in L. sumatrensis was confirmed as polypropylene (PP), a synthetic polymer (microplastic), while in S. recurvirostra was confirmed as rayon (semi-synthetic). This research shows that microdebris contamination has reached the level of a predator in Mollusca.

Modernization of NASA Johnson Space Center’s Chamber A to support Cryogenic Vacuum Optical Testing of the James Webb Space Telescope (JWST)

NASA is the mission lead for the James Webb Space Telescope (JWST), the next of the “Great Observatories,” scheduled for launch in 2021. NASA is directly responsible for the integration and test (I&T) program that culminated in an end-to-end cryo vacuum optical test of the flight telescope and instrument module in Chamber A at NASA Johnson Space Center. Historic Chamber A is the largest thermal vacuum chamber at Johnson Space Center and one of the largest space simulation chambers in the world. Chamber A has undergone a major modernization effort to support the deep cryogenic, vacuum and cleanliness requirements for testing the JWST. This paper describes the upgrades to the Chamber A facility: Thermal Shrouds, Helium Refrigeration, Liquid Nitrogen System, High Vacuum System, Clean Airflow System, and Utilities.

Study on the Calculation Method for Pumping Process in as Vacuum System

The calculation methods for vacuum system pumping were usually based on some simple theoretical models, the corresponding results had significant deviations from actual situations. In this study, medium and low vacuum systems (including vacuum chambers, pipes and pumps) were taken as research objects. With a measured vacuum system, and relationship between pump’s suction flowrate and inlet pressure, a new calculation method for vacuum pumping time was proposed, in which laminar or turbulent model was selected according to the pipeline’s flow state. New and traditional laminar method were used to calculate the pumping process of the measured system, which found that in the middle and high pressure stage, the pipeline flow was in turbulent state and the resistance was non-negligible. If the influence of turbulence was ignored, the calculated pressure drop would be faster than actual situation. The calculation result was verified by actual measurement result, indicating that new method is practical for vacuum pumping time calculation.

Development and Approbation of Methodology Aimed to Define the Reasons for Turbine Unit Capacity Limitation Based on the Specified Mathematical Model of its Condenser

The purpose of this work is to develop and test the methodology of elucidation of the reasons for turbine unit capacity limitations based on a mathematical model of its condenser. This pur-pose is achieved by using a mathematical model of the condenser as part of the developed methodology, taking into account the separate effects of contamination of the heat exchange surfaces, air suction into the vacuum system and the operating mode of the main ejector. Based on operational data sampling, the value of the limiting pressure in the condenser, excess of which leads to limitation of turbine unit capacity, was determined. It was established that the cause of power limitation is the abnormal operation of the main ejector due to inadmissible high temperature in the intermediate cooler of its first stage. For regimes that were not pressure-limited, using a mathematical model, the degree of tubes contamination, its influence on the condenser pressure and the power generated by the turbine unit, and the influence of actual air suctions on the condenser pressure were determined. The most important result of the study is to determine the possibility and feasibility of using the developed and tested methodology for solv-ing similar problems for any type of turbine unit equipped with a condenser. The significance of the work lies in the fact that the proposed approach expands the possibilities of using mathemat-ical models of this class in terms of solving such problems.

Transportation of Sulfuric Acid with Vacuum Unit

In the chemical industry, for example, in the production of sulfuric acid and the movement of sulfur recovered in refineries, the temperature of liquid substances can vary widely. The study of the effect of aggressive liquid temperature and concentration on the productivity and energy efficiency of vacuum systems for transporting liquids has been carried out. The performance (dry air pumping rate) and the consumed power of the vacuum pump ZhVN-12N depending on the pressure in the working chamber are considered. The correction coefficients of productivity for pumping out humid air have been determined for different temperatures. The performance indicators of a vacuum system for transporting liquids based on ZhVN-12N have been investigated. It was found that an increase in the temperature of the pumped humid air increases the average productivity of the vacuum system for transporting liquids, reducing its energy consumption. It is shown that an increase in the sulfuric acid solution concentration results in a decrease in productivity and an increase in the energy consumption of the vacuum system, while the efficiency decreases slightly.