This paper covers the main eddy current effects in accelerator magnets - field modification (time... more This paper covers the main eddy current effects in accelerator magnets - field modification (time delay and field quality) and resistive power losses. In the first part, starting from the Maxwell equations, a basic understanding of the processes is given and explained with examples of simple geometry and time behaviour. Useful formulas are derived for an analytic estimate of the size of the effects. In the second part the effects in real magnets are analysed and described in comparison with numerical and measured results. Finally, based on the previous parts, design recommendations are given regarding how to minimize eddy current effects.
Proceedings of the 2005 Particle Accelerator Conference
For the FAIR-project at GSI a model dipole was built at BNL with the nominal field of 4 T and a n... more For the FAIR-project at GSI a model dipole was built at BNL with the nominal field of 4 T and a nominal ramp rate of 1 T/s. The magnet design was similar to the RHIC dipole, with some changes for loss reduction and better cooling. The magnet was already successfully tested in a vertical cryostat, with good training behaviour. Cryogenic losses were measured and first results of field harmonics were published. However, for a better understanding of the cooling process, quench currents at several ramp rates were investigated. Detailed measurements of the field harmonics at 2 T/s between 0 and 4 T were performed.
FAIR schematic topology D. Kraemer, 'Current Status of the FAIR-project', THXAB02 P. Spiller, 'St... more FAIR schematic topology D. Kraemer, 'Current Status of the FAIR-project', THXAB02 P. Spiller, 'Status of the FAIR SIS 100/300 Synchrotrons Design', TUPAN014 Main sc magnets of the synchrotrons Number of Magnets Usable Aperture (mm) Eff. Magnet Length (m) Max. Field / Max.Gradient
Superconducting magnets for future accelerators such as the SIS-100 ring of the International Acc... more Superconducting magnets for future accelerators such as the SIS-100 ring of the International Accelerator Facility at GSI-Darmstadt, or a superconducting injector at the LHC, require that the magnetic field is pulsed with high repetition rate and high reliability over periods of several years. As an example the SIS-100 at the IAF is planned to be operated up to 2 T at 4 T/s for more than 100 millions cycles. Achieving these objectives requires that the superconductor has an excellent mechanical stability as well as a sufficient energy margin to tolerate foreseen and unforeseen energy inputs. In addition the cryogenic loss must be controlled at low levels, while the field errors due to coupling currents must be compatible with the beam dynamics requirements. In this paper we describe a cable-in-conduit design that is suitable for the challenging operating conditions described above, we give the expected performances and report on the on-going manufacturing demonstration and planned s...
Up to now, only one synchrotron (Nuclotron at JINR, Dubna) is equipped with fast-pulsed supercond... more Up to now, only one synchrotron (Nuclotron at JINR, Dubna) is equipped with fast-pulsed superconducting magnets. The demand for high beam intensities leads to the requirement of fast-pulsed magnets for synchrotrons. An example is the proposed international 'Facility for Antiproton and Ion Research' (FAIR) at GSI, which will consist of two synchrotrons in one tunnel, and several storage rings. The high field ramp rate and repetition fre- quency introduce many magnet design problems and con- straints on the operation of the accelerator. Persistent cur- rents in the superconductor and eddy currents in wire, cable, iron and vacuum chamber reduce the field quality and generate cryogenic losses. Due to the large number of magnet cycles during the lifetime of such a magnet, spe- cial attention has to be paid to magnet material fatigue problems. The large charging voltages put some con- straints on the use of cold diodes for quench protection. R&D has started at GSI, in collaborat...
1. Status of Operation In 2002 seven different ion species – C, Mg, Ni, Zn, Sn, Xe, and U – were ... more 1. Status of Operation In 2002 seven different ion species – C, Mg, Ni, Zn, Sn, Xe, and U – were accelerated in the SIS. Altogether 5715 h of beam time were provided for experiments. Another 239 h were used for accelerator tune-up and development. The total downtime of 239 h (4.5 % of the total operation time) was to a large extent caused by technical failures in power supplies (73 h) and vacuum valves (78 h). The total user time of 5715 h was distributed among radiotherapy with carbon ions (1382 h or 24 %), production runs for target experiments (2622 h or 46 %), and the ESR (1711 h or 30 %). In September 2002 the electrostatic wire septum for slow extraction had to be replaced since almost all of its wires had broken after a high intensity run with U ions at beam intensities of 2* 10 ions per machine cycle. The installation of a spare septum required 20 days, due to leaks in two quadrupole vacuum chambers, which occurred during the bake-out procedures. The repair time for the electrostatic septum is not counted in the total downtime since the scheduled shutdown could be rearranged, to provide time for the repair. It has been decided to restrict the beam intensities for heavy ion beams to 1·10 ions per machine cycle until June 2003, to enable the repair of the damaged septum wires and to prepare for the installation of the beam collimator in front of the extraction septum, which had been demounted for repair, several years ago.
IEEE Transactions on Applied Superconductivity, 2006
Fast cycling superferric magnets are planned for use in the new International Accelerator Facilit... more Fast cycling superferric magnets are planned for use in the new International Accelerator Facility for Antiprotons and Ion Research (FAIR) at GSI, Darmstadt. The efficiency of this magnet is basically defined by the AC loss at liquid helium temperatures in the construction elements of the dipoles and quadrupoles (iron yoke, coil, beam pipe restraints and suspension). A detailed knowledge of the 3D magnetic field, the eddy current distributions and their transient behavior is necessary to minimize the hysteresis and the eddy current losses through the use of an appropriate design. Methodical problems are considered for finite element calculations (ANSYS) of eddy currents in a laminated iron yoke. The results for window-frame dipoles and quadrupoles of the Nuclotron type are given. We present the influence of nonlinear and anisotropic magnetic and electrical properties of laminated steel and of bulk restraint elements.
IEEE Transactions on Applied Superconductivity, 2006
FAIR, a new international accelerator complex is now being developed by GSI (Darmstadt, Germany).... more FAIR, a new international accelerator complex is now being developed by GSI (Darmstadt, Germany). The synchrotron SIS100 is a part of this complex and will be equipped exclusively with fast-cycling superferric magnets. The magnet system of this accelerator includes 168 identical quadrupoles with a maximum gradient of 33.4 T/m in an elliptical useable aperture of 120 mm 65 mm. An important requirement of the quadrupole design is a field gradient uniformity better than 0.06% for field gradient variation range of 3 T/m-3.3 T/m. This goal is achieved by introducing slots in the central part of the magnet poles, creating the effect of artificial saturation. Simultaneously, these slots reduce the eddy currents in the yoke, induced by the current ramp in the magnet coil. This is important because the whole magnet will be operated near 4.2 K, so the power loss in the yoke should be minimized. Additionally, the shape of the quadrupole pole ends was optimized to provide the necessary integral field quality.
IEEE Transactions on Applied Superconductivity, 2006
New results from the investigation of 2 T superferric model dipoles operating at 4 T/s, 1 Hz are ... more New results from the investigation of 2 T superferric model dipoles operating at 4 T/s, 1 Hz are presented. The works are performed within the R&D program on the design of the SIS100 synchrotron at GSI in Darmstadt. One of the main research goals is minimization of overall AC power losses in the magnet at 4 K level. Different modifications
IEEE Transactions on Applied Superconductivity, 2006
Abstract The eddy-current losses in the yoke of a superconductive dipole magnet are simulated usi... more Abstract The eddy-current losses in the yoke of a superconductive dipole magnet are simulated using a transient, magnetoquasistatic formulation discretized in 3D by the finite integration technique. The laminated yoke material is modeled by an anisotropic, ...
IEEE Transactions on Appiled Superconductivity, 2005
AbstractThe data from the investigation of hollow supercon-ducting cable based on keystoned NbTi... more AbstractThe data from the investigation of hollow supercon-ducting cable based on keystoned NbTi wires are presented. The cable sample, consisting of 15 wires wound around a cooper-nickel tube 5 mm in diameter and cooled with two-phase helium flow has ...
IEEE Transactions on Appiled Superconductivity, 2004
New experimental results from the investigation of a model superferric Nuclotron-type dipole and ... more New experimental results from the investigation of a model superferric Nuclotron-type dipole and quadrupole magnets are presented. The magnets operate at pulse repetition rate f = 1 Hz, providing the peak magnetic field B = 2 T and the field gradient G = 34 T/m in the dipoles and quadrupoles respectively. The superconducting coil is made from a hollow multi-filamentary NbTi cable cooled with two phase helium flow. Different possibilities were investigated to reduce AC power losses in the case of a cold iron yoke (T = 4.5 K). The achieved results are discussed. The value of 9 W/m has been obtained for dipole magnet with the yoke at T = 50 K. The first 50 K yoke quadrupole was designed and tested.
IEEE Transactions on Applied Superconductivity, 2012
The Super-FRS (FRagment Separator) is part of the planned International Facility of Anti-proton a... more The Super-FRS (FRagment Separator) is part of the planned International Facility of Anti-proton and Ion Research—FAIR, at GSI, Darmstadt, Germany. It is intended to produce short-lived radioactive nuclei to be investigated in its different branches. Due to the high radiation level in the vicinity of the target the use of radiation resistant magnets is mandatory. In addition appliances for remote
IEEE Transactions on Applied Superconductivity, 2008
The field quality of the GSI SIS-100 magnet is influenced by the eddy currents generated in the c... more The field quality of the GSI SIS-100 magnet is influenced by the eddy currents generated in the conductive beam tube during ramping. The eddy-current losses are computed on the basis of a transient 2D finite-element model. A sufficient accuracy is guaranteed by adaptively refining the mesh and by the use of error-controlled adaptive time integrators. The 2D model is accomplished by an analytical model dealing with the closing of the currents at the end parts of the beam tube and thus incorporating the most significant 3D effect. The time dependence of the field quality reveals significant differences at low aperture fields, especially for the sextupole component at the beginning of the ramping. Also without conductive beam tube and for low field values, the relative sextupole and decapole components depend on the magnitude of the field, which indicates the presence of a nonlinear effect. When the magnet operates at an injection field, the magnetic flux density in the bridge of the iron yoke is already saturated. Hence, the saturation pattern in and around this bridge changes immediately at the start of the ramping, resulting in a changing field quality.
IEEE Transactions on Applied Superconductivity, 2008
During the design and optimization phase of the superconductive dipole magnets for the new SIS100... more During the design and optimization phase of the superconductive dipole magnets for the new SIS100 synchrotron at GSI Darmstadt, numerical simulations are carried out to predict the losses due to eddy currents in the laminated yoke. In order to represent the ferromagnetic iron in the numerical model, homogenized material models accounting for the anisotropy induced by the lamination are applied. For a simplified geometry of the SIS100 dipole magnet, the eddy-current losses obtained using different anisotropic nonlinear material models are compared.
IEEE Transactions on Applied Superconductivity, 2010
We present the concept design of the cryogenic feedbox for the superconducting dipole and quadrup... more We present the concept design of the cryogenic feedbox for the superconducting dipole and quadrupole/multi-pole magnets of the Super-FRS (FRagment Separator) project. It also includes the warm gas control and management, the instrumentation and the control logic related with different operation modes of the magnet cooling. As one of the most important trip scenarios for cryogenic facilities, the over pressure
This paper covers the main eddy current effects in accelerator magnets - field modification (time... more This paper covers the main eddy current effects in accelerator magnets - field modification (time delay and field quality) and resistive power losses. In the first part, starting from the Maxwell equations, a basic understanding of the processes is given and explained with examples of simple geometry and time behaviour. Useful formulas are derived for an analytic estimate of the size of the effects. In the second part the effects in real magnets are analysed and described in comparison with numerical and measured results. Finally, based on the previous parts, design recommendations are given regarding how to minimize eddy current effects.
Proceedings of the 2005 Particle Accelerator Conference
For the FAIR-project at GSI a model dipole was built at BNL with the nominal field of 4 T and a n... more For the FAIR-project at GSI a model dipole was built at BNL with the nominal field of 4 T and a nominal ramp rate of 1 T/s. The magnet design was similar to the RHIC dipole, with some changes for loss reduction and better cooling. The magnet was already successfully tested in a vertical cryostat, with good training behaviour. Cryogenic losses were measured and first results of field harmonics were published. However, for a better understanding of the cooling process, quench currents at several ramp rates were investigated. Detailed measurements of the field harmonics at 2 T/s between 0 and 4 T were performed.
FAIR schematic topology D. Kraemer, 'Current Status of the FAIR-project', THXAB02 P. Spiller, 'St... more FAIR schematic topology D. Kraemer, 'Current Status of the FAIR-project', THXAB02 P. Spiller, 'Status of the FAIR SIS 100/300 Synchrotrons Design', TUPAN014 Main sc magnets of the synchrotrons Number of Magnets Usable Aperture (mm) Eff. Magnet Length (m) Max. Field / Max.Gradient
Superconducting magnets for future accelerators such as the SIS-100 ring of the International Acc... more Superconducting magnets for future accelerators such as the SIS-100 ring of the International Accelerator Facility at GSI-Darmstadt, or a superconducting injector at the LHC, require that the magnetic field is pulsed with high repetition rate and high reliability over periods of several years. As an example the SIS-100 at the IAF is planned to be operated up to 2 T at 4 T/s for more than 100 millions cycles. Achieving these objectives requires that the superconductor has an excellent mechanical stability as well as a sufficient energy margin to tolerate foreseen and unforeseen energy inputs. In addition the cryogenic loss must be controlled at low levels, while the field errors due to coupling currents must be compatible with the beam dynamics requirements. In this paper we describe a cable-in-conduit design that is suitable for the challenging operating conditions described above, we give the expected performances and report on the on-going manufacturing demonstration and planned s...
Up to now, only one synchrotron (Nuclotron at JINR, Dubna) is equipped with fast-pulsed supercond... more Up to now, only one synchrotron (Nuclotron at JINR, Dubna) is equipped with fast-pulsed superconducting magnets. The demand for high beam intensities leads to the requirement of fast-pulsed magnets for synchrotrons. An example is the proposed international 'Facility for Antiproton and Ion Research' (FAIR) at GSI, which will consist of two synchrotrons in one tunnel, and several storage rings. The high field ramp rate and repetition fre- quency introduce many magnet design problems and con- straints on the operation of the accelerator. Persistent cur- rents in the superconductor and eddy currents in wire, cable, iron and vacuum chamber reduce the field quality and generate cryogenic losses. Due to the large number of magnet cycles during the lifetime of such a magnet, spe- cial attention has to be paid to magnet material fatigue problems. The large charging voltages put some con- straints on the use of cold diodes for quench protection. R&D has started at GSI, in collaborat...
1. Status of Operation In 2002 seven different ion species – C, Mg, Ni, Zn, Sn, Xe, and U – were ... more 1. Status of Operation In 2002 seven different ion species – C, Mg, Ni, Zn, Sn, Xe, and U – were accelerated in the SIS. Altogether 5715 h of beam time were provided for experiments. Another 239 h were used for accelerator tune-up and development. The total downtime of 239 h (4.5 % of the total operation time) was to a large extent caused by technical failures in power supplies (73 h) and vacuum valves (78 h). The total user time of 5715 h was distributed among radiotherapy with carbon ions (1382 h or 24 %), production runs for target experiments (2622 h or 46 %), and the ESR (1711 h or 30 %). In September 2002 the electrostatic wire septum for slow extraction had to be replaced since almost all of its wires had broken after a high intensity run with U ions at beam intensities of 2* 10 ions per machine cycle. The installation of a spare septum required 20 days, due to leaks in two quadrupole vacuum chambers, which occurred during the bake-out procedures. The repair time for the electrostatic septum is not counted in the total downtime since the scheduled shutdown could be rearranged, to provide time for the repair. It has been decided to restrict the beam intensities for heavy ion beams to 1·10 ions per machine cycle until June 2003, to enable the repair of the damaged septum wires and to prepare for the installation of the beam collimator in front of the extraction septum, which had been demounted for repair, several years ago.
IEEE Transactions on Applied Superconductivity, 2006
Fast cycling superferric magnets are planned for use in the new International Accelerator Facilit... more Fast cycling superferric magnets are planned for use in the new International Accelerator Facility for Antiprotons and Ion Research (FAIR) at GSI, Darmstadt. The efficiency of this magnet is basically defined by the AC loss at liquid helium temperatures in the construction elements of the dipoles and quadrupoles (iron yoke, coil, beam pipe restraints and suspension). A detailed knowledge of the 3D magnetic field, the eddy current distributions and their transient behavior is necessary to minimize the hysteresis and the eddy current losses through the use of an appropriate design. Methodical problems are considered for finite element calculations (ANSYS) of eddy currents in a laminated iron yoke. The results for window-frame dipoles and quadrupoles of the Nuclotron type are given. We present the influence of nonlinear and anisotropic magnetic and electrical properties of laminated steel and of bulk restraint elements.
IEEE Transactions on Applied Superconductivity, 2006
FAIR, a new international accelerator complex is now being developed by GSI (Darmstadt, Germany).... more FAIR, a new international accelerator complex is now being developed by GSI (Darmstadt, Germany). The synchrotron SIS100 is a part of this complex and will be equipped exclusively with fast-cycling superferric magnets. The magnet system of this accelerator includes 168 identical quadrupoles with a maximum gradient of 33.4 T/m in an elliptical useable aperture of 120 mm 65 mm. An important requirement of the quadrupole design is a field gradient uniformity better than 0.06% for field gradient variation range of 3 T/m-3.3 T/m. This goal is achieved by introducing slots in the central part of the magnet poles, creating the effect of artificial saturation. Simultaneously, these slots reduce the eddy currents in the yoke, induced by the current ramp in the magnet coil. This is important because the whole magnet will be operated near 4.2 K, so the power loss in the yoke should be minimized. Additionally, the shape of the quadrupole pole ends was optimized to provide the necessary integral field quality.
IEEE Transactions on Applied Superconductivity, 2006
New results from the investigation of 2 T superferric model dipoles operating at 4 T/s, 1 Hz are ... more New results from the investigation of 2 T superferric model dipoles operating at 4 T/s, 1 Hz are presented. The works are performed within the R&D program on the design of the SIS100 synchrotron at GSI in Darmstadt. One of the main research goals is minimization of overall AC power losses in the magnet at 4 K level. Different modifications
IEEE Transactions on Applied Superconductivity, 2006
Abstract The eddy-current losses in the yoke of a superconductive dipole magnet are simulated usi... more Abstract The eddy-current losses in the yoke of a superconductive dipole magnet are simulated using a transient, magnetoquasistatic formulation discretized in 3D by the finite integration technique. The laminated yoke material is modeled by an anisotropic, ...
IEEE Transactions on Appiled Superconductivity, 2005
AbstractThe data from the investigation of hollow supercon-ducting cable based on keystoned NbTi... more AbstractThe data from the investigation of hollow supercon-ducting cable based on keystoned NbTi wires are presented. The cable sample, consisting of 15 wires wound around a cooper-nickel tube 5 mm in diameter and cooled with two-phase helium flow has ...
IEEE Transactions on Appiled Superconductivity, 2004
New experimental results from the investigation of a model superferric Nuclotron-type dipole and ... more New experimental results from the investigation of a model superferric Nuclotron-type dipole and quadrupole magnets are presented. The magnets operate at pulse repetition rate f = 1 Hz, providing the peak magnetic field B = 2 T and the field gradient G = 34 T/m in the dipoles and quadrupoles respectively. The superconducting coil is made from a hollow multi-filamentary NbTi cable cooled with two phase helium flow. Different possibilities were investigated to reduce AC power losses in the case of a cold iron yoke (T = 4.5 K). The achieved results are discussed. The value of 9 W/m has been obtained for dipole magnet with the yoke at T = 50 K. The first 50 K yoke quadrupole was designed and tested.
IEEE Transactions on Applied Superconductivity, 2012
The Super-FRS (FRagment Separator) is part of the planned International Facility of Anti-proton a... more The Super-FRS (FRagment Separator) is part of the planned International Facility of Anti-proton and Ion Research—FAIR, at GSI, Darmstadt, Germany. It is intended to produce short-lived radioactive nuclei to be investigated in its different branches. Due to the high radiation level in the vicinity of the target the use of radiation resistant magnets is mandatory. In addition appliances for remote
IEEE Transactions on Applied Superconductivity, 2008
The field quality of the GSI SIS-100 magnet is influenced by the eddy currents generated in the c... more The field quality of the GSI SIS-100 magnet is influenced by the eddy currents generated in the conductive beam tube during ramping. The eddy-current losses are computed on the basis of a transient 2D finite-element model. A sufficient accuracy is guaranteed by adaptively refining the mesh and by the use of error-controlled adaptive time integrators. The 2D model is accomplished by an analytical model dealing with the closing of the currents at the end parts of the beam tube and thus incorporating the most significant 3D effect. The time dependence of the field quality reveals significant differences at low aperture fields, especially for the sextupole component at the beginning of the ramping. Also without conductive beam tube and for low field values, the relative sextupole and decapole components depend on the magnitude of the field, which indicates the presence of a nonlinear effect. When the magnet operates at an injection field, the magnetic flux density in the bridge of the iron yoke is already saturated. Hence, the saturation pattern in and around this bridge changes immediately at the start of the ramping, resulting in a changing field quality.
IEEE Transactions on Applied Superconductivity, 2008
During the design and optimization phase of the superconductive dipole magnets for the new SIS100... more During the design and optimization phase of the superconductive dipole magnets for the new SIS100 synchrotron at GSI Darmstadt, numerical simulations are carried out to predict the losses due to eddy currents in the laminated yoke. In order to represent the ferromagnetic iron in the numerical model, homogenized material models accounting for the anisotropy induced by the lamination are applied. For a simplified geometry of the SIS100 dipole magnet, the eddy-current losses obtained using different anisotropic nonlinear material models are compared.
IEEE Transactions on Applied Superconductivity, 2010
We present the concept design of the cryogenic feedbox for the superconducting dipole and quadrup... more We present the concept design of the cryogenic feedbox for the superconducting dipole and quadrupole/multi-pole magnets of the Super-FRS (FRagment Separator) project. It also includes the warm gas control and management, the instrumentation and the control logic related with different operation modes of the magnet cooling. As one of the most important trip scenarios for cryogenic facilities, the over pressure
Uploads
Papers by gebhard moritz