Realisation of Hybrid Trapped Field Magnetic Lens (HTFML) consisting of REBCO bulk lens and REBCO bulk cylinder at 77 K

Abstract: A hybrid trapped field magnet lens (HTFML) can reliably generate a concentrated magnetic field, B c, in the centre of the magnetic lens higher than the trapped field of the trapped field magnet (TFM) and the applied magnetic field, B app, even after the external magnetizing field decreased to zero. In this paper, the performance of HTFMLs consisting of EuBaCuO bulk TFM with various heights and a GdBaCuO bulk magnetic lens was investigated at 77 K using liquid nitrogen. A concentrated magnetic field of B c = 0.80 T was achieved at the centre of the HTFML for the tallest TFM after removing an applied magnetic field of B app = 0.50 T. The influence of the height of the outer TFM cylinder on the final concentrated field was studied experimentally and discussed using numerical simulation

Design Optimization of a Hybrid Trapped Field Magnet Lens (HTFML)

The concept of a hybrid trapped field magnet lens (HTFML) was recently proposed by the authors, which consists of a trapped field magnet (TFM) cylinder exploiting the “vortex pinning effect,” combined with a superconducting bulk magnetic lens exploiting the “diamagnetic shielding effect.” This HTFML can generate, within its bore, a magnetic field higher than the applied magnetic field, even after external field decreases to zero. In this paper, a design optimization of the inner GdBaCuO magnetic lens within the GdBaCuO TFM cylinder was carried out using numerical simulations based on the finite element method, in order to maximize the concentrated magnetic field. The HTFML with an optimized shape and size achieved a concentrated magnetic field of Bc = 5.6 and 12.8 T at the center of the lens for applied magnetic fields of Bapp = 3 and 10 T, respectively. A maximum tensile stress of +135 MPa exists in the outer GdBaCuO TFM cylinder during the magnetizing process for Bapp = 10 T, which exceeds the fracture strength of the bulk. This result suggests that mechanical reinforcement is necessary to avoid mechanical fracture under such high magnetic field conditions

Transport AC Loss Measurements of a Triangular, Epoxy-Impregnated High Temperature Superconducting (HTS) Coil

In this paper, the transport AC losses in a triangular, epoxy-impregnated high temperature superconducting (HTS) coil made from YBCO coated conductor, intended for use in a prototype axial flux HTS electric machine, are measured using two different electrical techniques at 77 K. The first set of AC loss measurements of the coil are carried out at the University of Cambridge using a technique based on a lock-in amplifier. The coil is then measured at the Center for Advanced Power Systems (CAPS), Florida State University, using a technique based on a high accuracy data acquisition (DAQ) measurement system. The two different methods show consistent results, validating the accuracy of these two techniques for transport AC loss measurements of superconducting coils. Multiple voltage taps are utilized within the coil to study the details and distribution of the AC loss in different sections of the coil. Losses are also measured with a flux diverter made of ferromagnetic material to analyze its effect on the AC losses.The work of D. Hu was supported by Churchill College, the China Scholarship Council, and the Cambridge Commonwealth, European and International Trust. The work of M. D. Ainslie was supported by a Royal Academy of Engineering Research Fellowship

Study of the acoustic signature of UHE neutrino interactions in water and ice

The production of acoustic signals from the interactions of ultra-high energy (UHE) cosmic ray neutrinos in water and ice has been studied. A new computationally fast and efficient method of deriving the signal is presented. This method allows the implementation of up to date parameterisations of acoustic attenuation in sea water and ice that now includes the effects of complex attenuation, where appropriate. The methods presented here have been used to compute and study the properties of the acoustic signals which would be expected from such interactions. A matrix method of parameterising the signals, which includes the expected fluctuations, is also presented. These methods are used to generate the expected signals that would be detected in acoustic UHE neutrino telescopes.Comment: 21 pages and 13 figure

Realisation of Hybrid Trapped Field Magnetic Lens (HTFML) consisting of REBCO bulk lens and REBCO bulk cylinder at 77 K

Abstract A hybrid trapped field magnet lens (HTFML) can reliably generate a concentrated magnetic field, B c, in the centre of the magnetic lens higher than the trapped field of the trapped field magnet (TFM) and the applied magnetic field, B app, even after the external magnetizing field decreased to zero. In this paper, the performance of HTFMLs consisting of EuBaCuO bulk TFM with various heights and a GdBaCuO bulk magnetic lens was investigated at 77 K using liquid nitrogen. A concentrated magnetic field of B c = 0.80 T was achieved at the centre of the HTFML for the tallest TFM after removing an applied magnetic field of B app = 0.50 T. The influence of the height of the outer TFM cylinder on the final concentrated field was studied experimentally and discussed using numerical simulation.- Adaptable and Seamless Technology transfer Program through Target-driven R&D (A-STEP) from Japan Science and Technology Agency (JST), Grant No. VP30218088419 - JSPS KAKENHI Grant No. 19K0524

Self-Control in Cyberspace: Applying Dual Systems Theory to a Review of Digital Self-Control Tools

Many people struggle to control their use of digital devices. However, our understanding of the design mechanisms that support user self-control remains limited. In this paper, we make two contributions to HCI research in this space: first, we analyse 367 apps and browser extensions from the Google Play, Chrome Web, and Apple App stores to identify common core design features and intervention strategies afforded by current tools for digital self-control. Second, we adapt and apply an integrative dual systems model of self-regulation as a framework for organising and evaluating the design features found. Our analysis aims to help the design of better tools in two ways: (i) by identifying how, through a well-established model of self-regulation, current tools overlap and differ in how they support self-control; and (ii) by using the model to reveal underexplored cognitive mechanisms that could aid the design of new tools.Comment: 11.5 pages (excl. references), 6 figures, 1 tabl

REACT-1 round 13 interim report: acceleration of SARS-CoV-2 Delta epidemic in the community in England during late June and early July 2021

Background Despite high levels of vaccination in the adult population, cases of COVID-19 have risen exponentially in England since the start of May 2021 driven by the Delta variant. However, with far fewer hospitalisations and deaths per case during the recent growth in cases compared with 2020, it is intended that all remaining social distancing legislation in England will be removed from 19 July 2021. Methods We report interim results from round 13 of the REal-time Assessment of Community Transmission-1 (REACT-1) study in which a cross-sectional sample of the population of England was asked to provide a throat and nose swab for RT-PCR and to answer a questionnaire. Data collection for this report (round 13 interim) was from 24 June to 5 July 2021. Results In round 13 interim, we found 237 positives from 47,729 swabs giving a weighted prevalence of 0.59% (0.51%, 0.68%) which was approximately four-fold higher compared with round 12 at 0.15% (0.12%, 0.18%). This resulted from continued exponential growth in prevalence with an average doubling time of 15 (13, 17) days between round 12 and round 13. However, during the recent period of round 13 interim only, we observed a shorter doubling time of 6.1 (4.0, 12) days with a corresponding R number of 1.87 (1.40, 2.45). There were substantial increases in all age groups under the age of 75 years, and especially at younger ages, with the highest prevalence in 13 to 17 year olds at 1.33% (0.97%, 1.82%) and in 18 to 24 years olds at 1.40% (0.89%, 2.18%). Infections have increased in all regions with the largest increase in London where prevalence increased more than eight-fold from 0.13% (0.08%, 0.20%) in round 12 to 1.08% (0.79%, 1.47%) in round 13 interim. Overall, prevalence was over 3 times higher in the unvaccinated compared with those reporting two doses of vaccine in both round 12 and round 13 interim, although there was a similar proportional increase in prevalence in vaccinated and unvaccinated individuals between the two rounds. Discussion We are entering a critical period with a number of important competing processes: continued vaccination rollout to the whole adult population in England, increased natural immunity through infection, reduced social mixing of children during school holidays, increased proportion of mixing occurring outdoors during summer, the intended full opening of hospitality and entertainment and cessation of mandated social distancing and mask wearing. Surveillance programmes are essential during this next phase of the epidemic to provide clear evidence to the government and the public on the levels and trends in prevalence of infections and their relationship to vaccine coverage, hospitalisations, deaths and Long COVID