Nowadays there is a great deal of interest in the scientific community in developing nextgeneration accelerator magnets based on high-J sub(c)Nb sub(3)Sn Rutherford cables. Inside a cable the wires ...are subjected to the combined effect of axial and transverse load. Since Nb sub(3)Sn is a strain sensitive material, electromechanical characterization of cables is essential for magnet design. Testing a full-size Rutherford cable is an extremely complex and involved task. For this reason special Walters springs have been developed at the University of Geneva to test single wires under longitudinal and transverse load. In this work we analyze three PIT wires under transverse compressive load. To better understand the experimental results, a finite element model was developed. This model enabled better understanding of the mechanical behavior of the three samples and investigation of the mechanisms that determine wire performance degradation upon loading.
The short model coil (SMC) dipole magnet has been designed and constructed in the framework of the European project EuCARD as a test bed for Nb 3 Sn magnet R&D in terms of coil fabrication technology ...and testing of Rutherford-type cables. Two pairs of racetrack coils were successfully tested in 2012, obtaining 12.5 T in the winding at 1.9 K, thus demonstrating SMC as a valid magnet design for conductor tests. These successful results prompted a new test campaign of SMC using the cable of the 11-T dipole project. The size of this cable is such that only one double pancake can be accommodated in the mechanical structure. During the latest tests using the 11-T cable, a new record field of 13.5 T was achieved, confirming the excellent capability of SMC to qualify a conductor, providing precise information of the stability and general cable performance, and to test insulation techniques, instrumentation systems, and coil fabrication processes. This paper describes the challenges of this new assembly, indicating novelties in the fabrication technology and reports on the measurements and the performance of SMC using CERN's 11-T-dipole-type conductor.
The quadrupole magnets for the LHC High Luminosity (Hi-Lumi) upgrade will be based on Nb 3 Sn Rutherford cables that operate at 1.9 K and experience magnetic fields larger than 12 T. Because of the ...large stored energy, one of the major issues in the design of these magnets is their protection. To study the quench propagation in Nb 3 Sn Rutherford cables for the Hi-Lumi Quadrupole magnets, a campaign of measurements was carried out in the FRESCA test station at CERN. In addition to the critical and stability current measurements at 4.3 K and 1.9 K, we performed a series of tests where the quenches were induced by resistive heaters impregnated in the cable. The longitudinal and transversal speeds of the normal zone propagation were investigated at different magnetic fields and operating currents. In this paper, the numerical and experimental results are reported, compared and discussed.
In the LHC main magnets, using Rutherford type cable, the eddy current loss and dynamic magnetic field error depend largely on the electrical resistance between crossing (Rc) and adjacent (Ra) ...strands. Cables made of strands with pre-selected coatings have been studied at low temperature using a DC electrical method. The significance of the inter-strand contact is explained. The properties of resistive barriers, the DC method used for the resistance measurement on the cable, and sample preparation are described. Finally the resistances are presented under various conditions, and the effect is discussed that the cable treatment has on the contact resistance.
Powder-in-tube (PIT) Nb sub(3)Sn wires are competing with Restacked-Rod-Process (RRP(R)) for the realization of the high luminosity upgrade of the Large Hadron Collider (LHC) at CERN. These two ...conductors have different properties and microstructures that are in both cases averages of an inhomogeneous A15 microstructure. PIT has in general a smaller fraction of A15 in the non-Cu cross-section than RRP(R) and a lower non-Cu J sub(c) (12 T, 4.2 K) (2500-2700 A mm super(-2) versus 2900-3000 A mm super(-2)) but it can be made in smaller filament diameters, which is an important property for LHC magnets. Another characteristic of PIT A15 is that ~25% is made up of ~1-2 mum sized grains (typically ~10 times the small grain (SG) diameter) and their contribution to transport is uncertain. Here we studied a 192 filament Ta-doped, 1 mm diameter PIT wire and combined multiple characterization techniques in order to distinguish the different wire components, to determine their individual properties and to identify which components are current-carriers. We found multiple evidence that the large A15 grains, which are also the highest-T sub(c) grains, do not contribute to transport at high field and that the only current-carrying A15 is the SG with T sub(c) <17.7 K. However, because of the high density of grain boundaries in the SG A15 layer, PIT has an exceptionally high SG-layer J sub(c) and high specific grain boundary pinning force, Q sub(GB). These findings clearly show that it is essential to increase the ratio of small to large and disconnected grains in order to improve PIT performance.
The CERN Large Hadron Collider (LHC) is envisioned to be upgraded in 2020 to increase the luminosity of the machine. The major upgrade will consist in replacing the NbTi quadrupole magnets of the ...interaction regions with larger aperture magnets. The rm Nb 3 rm Sn technology is the preferred option for this upgrade. The critical current density J c of rm Nb 3 rm Sn strands have reached sufficiently high values (in excess of 3000 rm A / mm 2 at 12 T and 4.2 K) allowing larger aperture/stronger field magnets. Nevertheless, such large J c values may cause magneto-thermal instabilities that can drastically reduce the conductor performance by quenching the superconductor prematurely. In rm Nb 3 rm Sn magnets, a relevant parameter for preventing premature quenches induced by magneto-thermal instabilities is the Residual Resistivity Ratio ( RRR ) of the conductor stabilizing copper. An experimental and theoretical study was carried out to investigate how much the value of the RRR affects the magnet stability and to identify the proper conductor specifications. In this paper the main results are presented and discussed.
The production of more than 60% of superconducting cables for the main dipoles of the Large Hadron Collider has been completed. The results of the measurements of cable magnetization and the ...dependence on the manufacturers are presented. The strand magnetization produces field errors that have been measured in a large number of dipoles (approximately 100 to date) tested in cold conditions. We examine here the correlation between the available magnetic measurements and the large database of cable magnetization. The analysis is based on models documented elsewhere in the literature. Finally, a forecast of the persistent current effects to be expected in the LHC main dipoles is presented, and the more critical parameters for beam dynamics are singled out.
The so-called CERN-LHC DS upgrade relies on the use of 11-T dipole magnets. For these magnets, 40 strands Nb 3 Sn type Rutherford cables based on 0.7-mm wires are being developed. Recently, four ...samples of the cables were characterized in the CERN FRESCA cable test station. The critical current and the premature quench current due to magneto-thermal instability were measured at 1.9 and 4.3 K in a background magnetic field between 0 and 9.6 T (the peak magnetic field on the conductor, including the self-field of the cable, ranges from ~ 2 T to ~ 12 T). Two cable samples were based on Powder-In-Tube (PIT) wire and two on Restacked-Rod-Process (RRP) wire. The PIT samples were identical and without a core in the cable while one of the RRP samples features a 25- μm-thick stainless steel core. All cables samples tested have a width and a thickness of about 14.7 and 1.25 mm, respectively. Cables and sample holders were manufactured at CERN. In this paper, we report and discuss the cable test results and compare them to the performance of witness strands, heat treated and measured on ITER-VAMAS type sample holders.
When using superconducting magnets in particle accelerators like the LHC, persistent currents in the superconductor often determine the field quality at injection, where the magnetic field is low. ...This paper describes magnetization measurements made on LHC cable strands at the Technical University of Vienna and the Institute of Physics of the Polish Academy of Sciences in collaboration with CERN. Measurements were performed at T=2 K and T=4.2 K on more than 50 strands of 7 different manufacturers with NbTi filament diameter between 5 and 7 micrometer. Two different measurement set-ups were used: vibrating sample magnetometer, with a sample length of about 8 mm, and an integrating coil magnetometer, with sample length of about 1 m. The two methods were compared by measuring the same sample. Low field evidence of proximity effect is discussed. Statistics like ratio of the width of the magnetization loop at 4.2 K and 2 K, and the initial slope dM/dB after cooldown are presented. Decrease of the magnetization with time, of the order of 2% per hour, was observed in some samples.
Lung cancer belongs to the most common cancers in Switzerland. We examined trends in lung cancer incidence, with focus on sex, histology and laterality, in the Canton of Zurich since 1980.
Registry ...data consisting of 16 798 lung cancer cases from 1980 to 2010 were analysed. Cases were classified into adenocarcinoma (ADC), squamous cell carcinoma (SCC), small-cell carcinoma (SCLC), large cell tumour and carcinoid tumour. Age-standardised (European standard) incidence rates (IR) per 100 000 person-years, male-to-female incidence-rate ratio (M/F-IRR), and left-to-right lung incidence-rate ratio (L/R-IRR) were calculated.
Over the study period, ADC occurred most frequently (31.9%), followed by SCC (29.1%), SCLC (15.4%), large cell carcinoma (6.3%), and carcinoid tumour (1.5%). Other/unspecified subtypes accounted for 15.7%. In men, the IR of SCC decreased from 34.2/100 000 (95% confidence interval CI 32.5-35.9) in 1980 to 12.8/100 000 (12.0-13.6) in 2010, but increased in women from 3.4/100 000 (2.7-4.0) to 4.0/100 000 (3.4-4.5). The IR of ADC increased in women from 5.1/100 000 (4.1-5.8) to 12.6/100 000 (11.8-13.4) and in men from 15.1/100 000 (14.0-16.3) to 19.4/100 000 (18.4-20.4). Overall M/F-IRR was 2.61; the highest ratio (5.8) was seen for SCC and the lowest (0.77) for carcinoid tumour. All histological subtypes showed a higher susceptibility of the right lung.
Our data reflect the global increase of lung cancer in women. ADC increased over time in women and men, whereas SCC decreased markedly among men. These trends may have occurred owing to changes in smoking behaviour and cigarette composition.
PDF
