Acoustic detection in superconducting magnets for performance characterization and diagnostics

Quench diagnostics in superconducting accelerator magnets is essential for understanding performance limitations and improving magnet design. Applicability of the conventional quench diagnostics methods such as voltage taps or quench antennas is limited for long magnets or complex winding geometries, and alternative approaches are desirable. Here, we discuss acoustic sensing technique for detecting mechanical vibrations in superconducting magnets. Using LARP high-field Nb3Sn quadrupole HQ01 [1], we show how acoustic data is connected with voltage instabilities measured simultaneously in the magnet windings during provoked extractions and current ramps to quench. Instrumentation and data analysis techniques for acoustic sensing are reviewed.Comment: 5 pages, Contribution to WAMSDO 2013: Workshop on Accelerator Magnet, Superconductor, Design and Optimization; 15 - 16 Jan 2013, CERN, Geneva, Switzerlan

Acoustic thermometry for detecting quenches in superconducting coils and conductor stacks

Quench detection capability is essential for reliable operation and protection of superconducting magnets, coils, cables, and machinery. We propose a quench detection technique based on sensing local temperature variations in the bulk of a superconducting winding by monitoring its transient acoustic response. Our approach is primarily aimed at coils and devices built with high-temperature superconductor materials where quench detection using standard voltage-based techniques may be inefficient due to the slow velocity of quench propagation. The acoustic sensing technique is non-invasive, fast, and capable of detecting temperature variations of less than 1 K in the interior of the superconductor cable stack in a 77 K cryogenic environment. We show results of finite element modeling and experiments conducted on a model superconductor stack demonstrating viability of the technique for practical quench detection, discuss sensitivity limits of the technique, and its various applications

Observation of correlated vortex flow in NbSe2 with magnetic decoration

Article / Letter to editorLeids Instituut Onderzoek Natuurkund

Determinación de arsénico en aguas de consumo humano en la localidad De Lavaisse (San Luis)

La presencia de arsénico en aguas de consumo representa un riesgo para la salud cuando su concentración excede el valor recomendado (0,01 mg/L) por la Organización Mundial de la Salud. Muchas comunidades rurales no tienen acceso a la red de agua potable y sólo disponen de fuentes de aguas subterráneas contaminadas naturalmente con arsénico. Se tomaron muestras de agua de consumo humano en la localidad de Lavaisse y alrededores. Se determinaron las concentraciones de arsénico y flúor, pH, y conductividad. La determinación de arsénico total se realizó mediante el método Vasak-Sedivek, la concentración de fluoruro se hizo por S.M. 4500-D (Método SPADNS). El análisis de los resultados evidencia que las concentraciones de arsénico están entre 0,055 y 0,069 mg/L, entre 5 y 7 veces por encima de los valores recomendados, incrementándose así el riesgo en la salud de los pobladores. Los otros parámetros se encuentran dentro de los valores considerados aptos para consumo humano.The presence of arsenic in drinking water represents a health risk when the concentration exceeds the World Health Organization recommended value (0.01 mg/L). Many rural populations only use As-polluted groundwater sources since they do not have access to potable water distribution systems. Samples of drinking water were collected in Lavaisse and surroundings. Arsenic and fluorine concentrations, pH, and conductivity were determined. The determination of total arsenic was performed by the Vasak-Sedivek method, while the fluoride concentration was determined by S.M. 4500-D (SPADNS Method). The results show that the arsenic concentrations are between 0.055 and 0.069 mg/L, i.e. between 5 and 7 times above the recommended values, increasing the health risk of the inhabitants. The other parameters are within the values considered suitable for human consumption.Fil: Vidal Treber, Juan. Universidad Nacional de San Luis.Fil: Curvale, Daniela. Universidad Nacional de San Luis.Fil: Marchevsky, Natalia J. Universidad Nacional de San Luis.Fil: Barroso Quiroga, María M.. Universidad Nacional de San Luis

Magnetic Quench Antenna for MQXF Quadrupoles

High-field MQXF-series quadrupoles are presently under development by LARP and CERN for the upcoming LHC luminosity upgrade. Quench training and protection studies on MQXF prototypes require a capability to accurately localize quenches and measure their propagation velocity in the magnet coils. The voltage tap technique commonly used for such purposes is not a convenient option for the 4.2-m-long MQXF-A prototype, nor can it be implemented in the production model. We have developed and tested a modular inductive magnetic antenna for quench localization. The base element of our quench antenna is a round-shaped printed circuit board containing two orthogonal pairs of flat coils integrated with low-noise preamplifiers. The elements are aligned axially and spaced equidistantly in 8-element sections using a supporting rod structure. The sections are installed in the warm bore of the magnet, and can be stacked together to adapt for the magnet length. We discuss the design, operational characteristics and preliminary qualification of the antenna. Axial quench localization capability with an accuracy of better than 2 cm has been validated during training test campaign of the MQXF-S1 quadrupole

Policies and reporting guidelines for small biopsy specimens of mediastinal masses

目前，胸腺恶性肿瘤治疗方案大多是根据术\ud 后病理确定，然而，多数临床治疗决策需要在术前\ud 通过活检小标本的病理报告来制定。所以，术前活\ud 检小标本的正确获取和病理解读对治疗决策的制定\ud 显得非常重要[1]。这些标本包括细针活检标本，带\ud 芯穿刺活检标本和手术切取活检标本[2-7]。由于胸\ud 腺肿瘤的病理诊断对组织的获取方法和获取量都有较高\ud 的要求，加之对病理的描述也没有统一的标准，使得小\ud 标本在诊断胸腺瘤方面存在诸多问题。为此，ITMIG在\ud 病理科医生和外科医生回顾相关文献和提出初步建议的\ud 基础上，经集体讨论制定了活检规范操作流程，提出了\ud 对纵隔肿物小活检标本处理和病理报告的建议。旨在为\ud 术前患者的治疗提供一个统一和具有循证医学证据的方\ud 法；同时，将有利于全球数据之间的比较和开展合作研\ud 究，充分利用医疗资源

Performance correlation between YBa2Cu3O7-δ coils and short samples for coil technology development

A robust fabrication technology is critical to achieve the high performance in YBa Cu O (YBCO) coils as the critical current of the brittle YBCO layer is subject to the strain-induced degradation during coil fabrication. The expected current-carrying capability of the magnet and its temperature dependence are two key inputs to the coil technology development. However, the expected magnet performance is not straightforward to determine because the short-sample critical current depends on both the amplitude and orientation of the applied magnetic field with respect to the broad surface of the tape-form conductor. In this paper, we present an approach to calculate the self-field performance limit for YBCO racetrack coils at 77 and 4.2 K. Critical current of short YBCO samples was measured as a function of the applied field perpendicular to the conductor surface from 0 to 15 T. This field direction limited the conductor critical current. Two double-layer racetrack coils, one with three turns and the other with 10 turns, were wound and tested at 77 and 4.2 K. The test coils reached at least 80% of the expected critical current. The ratio between the coil critical currents at 77 and 4.2 K agreed well with the calculation. We conclude that the presented approach can determine the performance limit in YBCO racetrack coils based on the short-sample critical current and provide a useful guideline for assessing the coil performance and fabrication technology. The correlation of the coil critical current between 77 K and 4.2 K was also observed, allowing the 77 K test to be a cost-effective tool for the development of coil technology. 2

V-I characteristics in the vicinity of order-disorder transition in vortex matter

The shape of the V-I characteristics leading to a peak in the differential resistance r_d=dV/dI in the vicinity of the order-disorder transition in NbSe2 is investigated. r_d is large when measured by dc current. However, for a small Iac on a dc bias r_d decreases rapidly with frequency, even at a few Hz, and displays a large out-of-phase signal. In contrast, the ac response increases with frequency in the absence of dc bias. These surprisingly opposite phenomena and the peak in r_d are shown to result from a dynamic coexistence of two vortex matter phases rather than from the commonly assumed plastic depinning.Comment: 12 pages 4 figures. Accepted for publication in PRB rapi