Le Naour, S
Wolf, R
Billan, J
Genest, J
Test Station for Magnetization Measurements on Large Quantities of Superconducting Strands
IEEE Trans. Appl. Supercond.
3086-9
11
In the superconducting main magnets of the Large Hadron Collider (LHC), persistent currents in the superconductor determine the field quality at injection field. For this reason it is necessary to check the magnetization of the cable strands during their production. During four years, this requires measurements of the width of the strand magnetization hysteresis loop at 0.5 T, 1.9 K, at a rate of up to eight samples per day. This paper describes the design, construction and the first results of a magnetization test station built for this purpose. The samples are cooled in a cryostat, with a 2-m long elliptic tail. This tail is inserted in a normal conducting dipole magnet with a field between ± 1.5 T. Racetrack pick-up coils, integrated in the cryostat, detect the voltage due to flux change, which is then integrated numerically. The sample holder can contain eight strand samples, each 20 cm long. The test station operates in two modes: either the sample is fixed while the external field is changed, or the sample is moved while the field remains constant. First results of calibration measurements with nickel and niobium are reported.
eng
2001
http://documents.cern.ch/cgi-bin/setlink?base=generic&categ=public&id=cer-002237262;
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-451;
http://cds.cern.ch/record/483489/files/cer-002237262.pdf;
http://cds.cern.ch/record/483489/files/lhc-project-report-451.pdf;
http://cds.cern.ch/record/483489/files/lhc-project-report-451.ps.gz;
Imported from Invenio.
Bottura, L
Pugnat, P
Siemko, A
Vlogaert, J
Wyss, C
Performance of the LHC Final Design, Full-Scale Superconducting Dipole Prototypes
IEEE Trans. Appl. Supercond.
1554-7
11
Within the LHC magnet program, a series of six, final design, full-scale superconducting dipole prototypes are presently being built in industry and tested at CERN. The main features of these magnets are: two-in-one structure, 56 mm aperture, six-block two layer coils wound from 15.1 mm wide graded NbTi cables, and all-polyimide insulation. This paper reviews the main test results of magnets tested to day at 4.2 K and 1.8 K. The results of the quench training, conductor performance, magnet protection, sensitivity to ramp rate and field quality are presented and discussed in terms of the design parameters and the aims of the full scale dipole prototype program.
eng
2001
http://documents.cern.ch/cgi-bin/setlink?base=generic&categ=public&id=cer-002237263;
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-452;
http://cds.cern.ch/record/483490/files/cer-002237263.pdf;
http://cds.cern.ch/record/483490/files/lhc-project-report-452.pdf;
http://cds.cern.ch/record/483490/files/lhc-project-report-452.ps.gz;
Imported from Invenio.
Bottura, L
Breschi, M
Schneider, M
Measurements of Magnetic Field Pattern in a Short LHC Dipole Model
IEEE Trans. Appl. Supercond.
1605-8
11
The magnetic field in superconducting accelerator magnets has a fine structure with longitudinal periodicity. This periodic pattern, with period identical to the cable twist pitch, is originated by uneven current distribution within the cable. Here we present results of measurements of the periodic pattern performed in an LHC dipole model. We report in particular the results obtained powering the magnet with simple current steps and typical operation cycles as will be used during accelerator operation. The main result of the analysis is the time variation of the amplitude of the periodic pattern, from which we infer the evolution of the current distribution in the cable. We discuss the dependence of the pattern amplitude on ramp and pre-cycle parameters.
eng
2001
http://documents.cern.ch/cgi-bin/setlink?base=generic&categ=public&id=cer-002237264;
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-453;
http://cds.cern.ch/record/483491/files/cer-002237264.pdf;
http://cds.cern.ch/record/483491/files/lhc-project-report-453.pdf;
http://cds.cern.ch/record/483491/files/lhc-project-report-453.ps.gz;
Imported from Invenio.
Bottura, L
Haverkamp, M
Kuijper, A
den Ouden, A
ten Haken, B
ten Kate, H H J
Interaction between Current Imbalance and Magnetization in LHC Cables
IEEE Trans. Appl. Supercond.
1609-12
11
The quality of the magnetic field in superconducting accelerator magnets is associated with the properties of the superconducting cable. Current imbalances due to coupling currents DI, as large as 100 A, are induced by spatial variations of the field sweep rate and contact resistances. During injection at a constant field all magnetic field components show a decay behavior. The decay is caused by a diffusion of coupling currents into the whole magnet. This results in a redistribution of the transport current among the strands and causes a demagnetization of the superconducting cable. As soon as the field is ramped up again after the end of injection, the magnetization rapidly recovers from the decay and follows the course of the original hysteresis curve. In order to clarify the interactions between the changes in current and magnetization during injection we performed a number of experiments. A magnetic field with a spatially periodic pattern was applied to a superconducting wire in order to simulate the coupling behavior in a magnet. This model system was placed into a stand for magnetization measurements and the influence of different powering conditions was analyzed.
eng
2001
http://documents.cern.ch/cgi-bin/setlink?base=generic&categ=public&id=cer-002237265;
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-454;
http://cds.cern.ch/record/483492/files/cer-002237265.pdf;
http://cds.cern.ch/record/483492/files/lhc-project-report-454.pdf;
http://cds.cern.ch/record/483492/files/lhc-project-report-454.ps.gz;
Imported from Invenio.
Khomenko, B A
Pugnat, P
Rijllart, A
Sanfilippo, S
Siemko, A
Statistical Diagnosis Method of Conductor Motions in Superconducting Magnets to Predict their Quench Performance
IEEE Trans. Appl. Supercond.
1705-8
11
Premature training quenches are usually caused by the transient energy released within the magnet coil as it is energised. Two distinct varieties of disturbances exist. They are thought to be electrical and mechanical in origin. The first type of disturbance comes from non-uniform current distribution in superconducting cables whereas the second one usually originates from conductor motions or micro-fractures of insulating materials under the action of Lorentz forces. All of these mechanical events produce in general a rapid variation of the voltages in the so-called quench antennas and across the magnet coil, called spikes. A statistical method to treat the spatial localisation and the time occurrence of spikes will be presented. It allows identification of the mechanical weak points in the magnet without need to increase the current to provoke a quench. The prediction of the quench level from detailed analysis of the spike statistics can be expected.
eng
2001
http://documents.cern.ch/cgi-bin/setlink?base=generic&categ=public&id=cer-002237266;
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-455;
http://cds.cern.ch/record/483493/files/cer-002237266.pdf;
http://cds.cern.ch/record/483493/files/lhc-project-report-455.pdf;
http://cds.cern.ch/record/483493/files/lhc-project-report-455.ps.gz;
Imported from Invenio.