Power Distribution for Cryogenic Instruments at 6-40K The James Webb Space Telescope Case

The Integrated Science Instrument Module (ISIM) of the James Webb Space Telescope (JWST) operates its instruments passively cooled at around 40 Kelvin (K), with a warm Instrument Electronic Compartment (IEC) at 300K attached to it. From the warm electronics all secondary signal and power harnesses have to bridge this 300-40K temperature difference and minimize the power dissipation and parasitic heat leak into the cold region. After an introduction of the ISIM with its instruments, the IEC with the electronics, and the harness architecture with a special radiator, this paper elaborates on the cryogenic wire selection and tests performed to establish current de-rating rules for different wire types. Finally failure modes are analyzed for critical instrument interfaces that could inject excessive currents and heat into the harness and cold side, and several solutions for the removal of such failures are presented

Study of the Qualitative Characteristics of Rapeseed Oil Obtained by Cold Pressing

Oil from spring rape seeds obtained by cold pressing was selected as the object of this study. Oil samples were obtained under the following technological conditions: the annular gap was 0.7 mm in a grain chamber and the screw rotation speed was 160 rpm at a pressing temperature of 315 K. The oil composition was studied by gas-liquid chromatography on the Chromotech 5000 apparatus. Rapeseed oil characteristics were obtained with chromatograms. An increased content of linoleic acid 20% (ω6) and linolenic acid 12% (ω3) was revealed in the fatty acid composition of the sample. Fatty acids contribute to lipid metabolism regulation. They are of primary importance in the diet. The presence of 58.6% oleic acid (ω9) was identified. The resulting rapeseed oil had healing properties due to the presence of ω3, ω6 and ω9. Vitamin B, vitamin K, traces of vitamin A, and α, β + γ, δ-tocopherols were found. α, β + γ-tocopherols contribute to the oxidation process. According to these results, rapeseed oil can be confidently recommended for introduction into various food recipes. Keywords: rapeseed oil, vitamins, fatty acid compositio

Focusing resonance cones

The potential for an oscillating ring source immersed in cold, magnetized, collisionless plasma in the resonance cone regime (K/K<0) is evaluated exactly and asymptotically, giving insight into the gross spatial behavior of the focusing resonance cones. The nature of the singularity in potential is clarified by the introduction of a noninfinitesimal collision frequency. Thermal effects are considered numerically, revealing an interesting interference structure in potential as well as a density depression near the focus of the cone due to the ponderomotive force

Measurement and Analysis of Axial End Forces in a Full-Length Prototype of LHC Main Dipole Magnets

A full-length, twin aperture prototype (MBP2N1) dipole magnet for the LHC project was assembled at CERN with collared coils delivered by industry. The design of this prototype is close to that foreseen for the dipole series manufacture as far the coil geometry and that of the yoke components are concerned. The bolts that transfer the axial magnetic forces from the coil ends to the cold mass end plates were instrumented to verify the axial coil support. These axial forces were initially measured after partial assembly, during a standard and an accelerated cool down Introduction to 1.9 K, and during magnet excitation up to 9.2 T. High force levels were observed, triggering a comparison with analytical models and measurements routinely made on 1-m single aperture dipole models. The prototype magnet was re-assembled with lower initial axial force settings and with additional instrumentation, to monitor these forces during the entire assembly process, and re-tested, to possibly correlate axial forces with training behaviour. This paper reports about the experimental observations and provides models towards their understandin

Reactive Oxygen Species and the Redox-Regulatory Network in Cold Stress Acclimation

Dreyer A, Dietz K-J. Reactive Oxygen Species and the Redox-Regulatory Network in Cold Stress Acclimation. Antioxidants. 2018;7(11): 169.Cold temperatures restrict plant growth, geographical extension of plant species, and agricultural practices. This review deals with cold stress above freezing temperatures often defined as chilling stress. It focuses on the redox regulatory network of the cell under cold temperature conditions. Reactive oxygen species (ROS) function as the final electron sink in this network which consists of redox input elements, transmitters, targets, and sensors. Following an introduction to the critical network components which include nicotinamide adenine dinucleotide phosphate (NADPH)-dependent thioredoxin reductases, thioredoxins, and peroxiredoxins, typical laboratory experiments for cold stress investigations will be described. Short term transcriptome and metabolome analyses allow for dissecting the early responses of network components and complement the vast data sets dealing with changes in the antioxidant system and ROS. This review gives examples of how such information may be integrated to advance our knowledge on the response and function of the redox regulatory network in cold stress acclimation. It will be exemplarily shown that targeting the redox network might be beneficial and supportive to improve cold stress acclimation and plant yield in cold climate. View Full-Tex

Development of a cold stage for a 80 K vibration-free cooler

Nowadays, many satellites are observing the earth for many purposes (climatology, agriculture, defence and security, etc.) using infrared sensors. One of the key element of these sensors is their high resolution obtained due to their quite low operating temperature provided by mechanical cryocoolers. However, the introduction of vibrations by the most of the cryocoolers is a recurring problem for space applications, and because of that the development of a system that eliminates these vibrations is very important. So, in the framework of a European Space agency project, a 40-80 K vibration-free cooler is being developed that combines two cryocoolers (one that uses Nitrogen that precool another cryocooler that uses Neon), functioning without introducing vibrations in the system. This thesis is focused on the nitrogen cryocooler more specifically on the dimensioning and development of its cold part’s components as the Joule-Thomson valve, the counterflow heat exchanger, and its test systems. The majority of the work on this thesis was focused on the design of the Joule-Thomson (JT) valve. Since Its dimensions and properties are empirically obtained, an extended experimental study of the performance of two different JT valves under several temperatures, pressures and mass flow conditions was made. The data obtained allowed us to dimension a JT valve for the required conditions and also confirm the operating principles of the cryocooler cold part. The counterflow heat exchanger was dimensioned, built and integrated in a Gifford- Mac Mahon cryocooler and is ready to be tested as soon as the Joule Thomson valve is determined

On classification of modular tensor categories

We classify all unitary modular tensor categories (UMTCs) of rank $\leq 4$. There are a total of 70 UMTCs of rank $\leq 4$ (Note that some authors would have counted as 35 MTCs.) In our convention there are two trivial unitary MTCs distinguished by the modular $S$ matrix $S=(\pm1)$. Each such UMTC can be obtained from 10 non-trivial prime UMTCs by direct product, and some symmetry operations. UMTCs encode topological properties of anyonic quantum systems and can be used to build fault-tolerant quantum computers. We conjecture that there are only finitely many equivalence classes of MTCs for any given rank, and a UMTC is universal for anyonic quantum computation if and only if its global quantum dimension $D^2$ is \emph{not} an integer. Discovery of non-abelain anyons in Nature will be a landmark in condensed matter physics. The non-abelian anyons in UMTCs of rank $\leq 4$ are the simplest, and, therefore, are most likely to be found. G. Moore and N. Read proposed that non-abelian statistics could occur in fractional quantum Hall (FQH) liquids. The Read-Rezayi conjecture predicts the existence of anyons related to $SU(2)_k$ in FQH liquids at filling fractions $\nu=2+\frac{k}{k+2}$ for $k=1,2,3$. For $\nu={5/2}$ and $SU(2)_2$, there is a numerical proof and experimental evidence for this conjecture. The Ising anyons might exist in chiral superconductors (strontium ruthenate). There are theoretical designs for the toric code MTC using Josephson junction array, for the $Fib\times Fib$ MTC using optical lattice, and for the $SU(2)_k$ using cold trapped bosonic atoms.Comment: Several references added. Minor revisions of the abstract, introduction and Section 2. Error in one R-matrix eigenvalue for (A_1,2) in the published version correcte

Enhancement of Natural Convection Heat Transfer within Closed Enclosure Using Parallel Fins

yesA numerical study of natural convection heat transfer in water filled cavity has been examined in 3-D for single phase liquid cooling system by using an array of parallel plate fins mounted to one wall of a cavity. The heat generated by a heat source represents a computer CPU with dimensions of 37.5∗37.5mm mounted on substrate. A cold plate is used as a heat sink installed on the opposite vertical end of the enclosure. The air flow inside the computer case is created by an exhaust fan. A turbulent air flow is assumed and k-ε model is applied. The fins are installed on the substrate to enhance the heat transfer. The applied power energy range used is between 15 - 40W. In order to determine the thermal behaviour of the cooling system, the effect of the heat input and the number of the parallel plate fins are investigated. The results illustrate that as the fin number increases the maximum heat source temperature decreases. However, when the fin number increases to critical value the temperature start to increase due to the fins are too closely spaced and that cause the obstruction of water flow. The introduction of parallel plate fins reduces the maximum heat source temperature by 10% compared to the case without fins. The cooling system maintains the maximum chip temperature at 64.68°C when the heat input was at 40W that is much lower than the recommended computer chips limit temperature of no more than 85°C and hence the performance of the CPU is enhanced

The search for the Dark Vector Boson via the Higgs Portal

Abstract: The Standard Model (SM) is known to be incomplete. The introduction of a Dark Sector via an additional U(1)D gauge symmetry added to the SM Lagrangian provides a mechanism to introduce much needed new physics without perturbing the already excellent agreement between the SM theoretical description and the Electroweak Precision Observables (EWPO) experimental constraints. The model has a dark vector boson Zd which can mix with the hypercharge gauge boson with the coupling . This opens the Hypercharge Portal which can mediate the fluctuation of a Z to a Zd, or the decay of the Zd to SM leptons. If a dark Higgs singlet s also exists, this then breaks the U(1)D, opening the Higgs portal and also allowing for Higgs mass mixing between the SM and dark sectors, described by the Higgs mass mixing parameter, k. Including dark fermionic fields in the Lagrangian allows for long-lived cold Dark Matter candidates. The various connections between the Dark and SM sectors allow descriptions of many key astro-physical phenomena. The Model is therefore a fascinating candidate for new physics beyond the SM. It becomes crucial to search for experimental signatures of this model. This contribution discusses a search for the dark force boson Zd using its production via the Higgs Portal and its decay back to SM leptons: H hd ZdZd 4l. The results from ATLAS Run 1 and the further development of the search for Run 2 are presented

On diagnostics of an annular-shape radio-frequency plasma jet operating in argon at atmospheric conditions

One of the driving forces behind the development of cold plasma sources at atmospheric pressure is their application in the biomedical field. In this respect, radio-frequency (RF) plasma jets are of particular importance due to their possible safe operation on humans and the generation of the high amount of reactive species. For this reason, we designed an RF plasma jet in co-axial geometry with the possibility of aerosol introduction, where its characteristics were evaluated by electrical diagnostics, optical emission and laser scattering spectroscopy. The RF plasma jet operation and stability of diffuse mode were analysed based on energy balance. It was observed that alpha-mode diffuse discharge characterised by an effluent length up to 5 mm was sustained at a power density below 30 W cm(-3). The gas and rotational temperature were determined by means of spectroscopy methods and compared with the results of direct laser scattering. It was established that the gas temperature obtained from N-2 emission of transition C(3)n(u) -> B(3)n(g) (0, 2) is highly overestimated whereas the gas temperature estimated from OH transition A(2)sigma+ -> X(2)n(i) (0, 0) gave a reasonable agreement with both Rayleigh and Raman spectroscopy. Based on the Rayleigh scattering method, uniform gas temperature distribution in the discharge effluent was found at a power below 15 W with the average temperature below 340 15 K. The low gas temperature of argon plasma jets would allow use of this source in temperature-sensitive material applications including skin treatments