Analytical computation of magnetic field in coil-dominated superconducting quadrupole magnets based on racetrack coils

Currently,three types of superconducting quadrupole magnets are used in particle accelerators:cos 2θ,CCT,and serpentine.However,all three coil configurations have complex spatial geometries,which make magnet manufacturing and strain-sensitive superconductor applications difficult.Compared with the three existing quadrupole coils,the racetrack quadrupole coil has a simple shape and manufacturing process,but there have been few theoretical studies.In this paper,the two-dimensional and three-dimensional analytical expressions for the magnetic field in coil-dominated racetrack superconducting quadrupole magnets are presented.The analytical expressions of the field harmonics and gradient are fully resolved and depend only on the geometric parameters of the coil and current density.Then,a genetic algorithm is applied to obtain a solution for the coil geometry parameters with field harmonics on the order of 10^(-4).Finally,considering the practical engineering needs of the accelerator interaction region,electromagnetic design examples of racetrack quadrupole magnets with high gradients,large apertures,and small apertures are described,and the application prospects of racetrack quadrupole coils are analyzed.

Development of short prototype of dual aperture quadrupole magnet for CEPC ring

Main quadrupole magnets are critical for the Circular Electron and Positron Collider(CEPC)and are specifically designed as dual aperture quadrupole(DAQ)magnets.However,the field crosstalk between the two apertures presents challenges.As the CEPC will work at four beam energies of Z,W,Higgs and ttbar mode,the DAQ magnets will operate at four field gradients spanning from 3.18 to 12.63 T/m.The first short quadrupole magnet prototype with the bore diameter of 76 mm and magnetic length of 1.0 m revealed the problems of large magnetic field harmonics and a magnetic center shift within the beam energy range.Accordingly,a compensation method was proposed in this work to solve the field crosstalk effect.By adjusting the gap height at the middle of the two apertures,the field harmonics and magnetic center shift are significantly reduced.After optimization,the short prototype was modified using a new scheme.The field simulations are validated from the magnetic measurement results.Further,the multipole field meets the requirements of the four beam energies.The detailed magnetic field optimization,field harmonics adjustment,and measurement results are presented herein.

Modal analysis of AC quadrupole magnet system for CSNS/RCS

The quadrupole magnet of the China Spallation Neutron Source （CSNS） Rapid-cycling Synchrotron （RCS） is operated at a 25 Hz sinusoidal alternating current which causes severe vibration. The vibration will influence the long-term safety and reliable operation of the quadrupole magnet. By taking the quadrupole magnet and girder as specific model system, a method for analyzing and studying the dynamic characteristic of the system is put forward by combining theoretical calculation with experimental testing. The theoretical modal analysis results coincide with the experimental testing results. It shows that the dynamic characteristic parameters of the structure can be obtained by modal analysis which will provide a theoretical basis for the further study and the magnet girder optimal design of CSNS/PtCS.

Production of Rubidium Bose-Einstein Condensate in an Optically Plugged Magnetic Quadrupole Trap

We experimentally produce the rubidium Bose-Einstein condensate in an optically plugged magnetic quadrupole trap. A far blue-detuned focused laser beam with a wavelength of 532nm is plugged in the center of the magnetic quadrupole trap to increase the number of trapped atoms and to suppress the heating. An rf evaporative cooling in the magneto-optical hybrid trap is applied to decrease the atom temperature into degeneracy. The atom number of the condensate is 1.2（0.4）× 10^5 and the temperature is below lOOnK. We also study characteristic behaviors of the condensate, such as phase space density, condensate fraction and anisotropic expansion.

Magnetic and quadrupole moments of the Z_(c)(4020)^(+),Z_(c)(4050)^(+),and Z_(c)(4600)^(+)states in the diquark-antidiquark picture

The magnetic and quadrupole moments of the Z_(c)(4020)^(+),Z_(c)(4050)^(+),and Z_(c)(4600)^(+)states are calculated within the QCD light-cone sum rules.The compact diquark-antidiquark interpolating currents and the distribution amplitudes of the on-shell photon are used to extract the magnetic and quadrupole moments of these states.The magnetic moments are acquired asμZ_(c)=0.50+0.22−0.22μN,μZ_(c)^(1)=1.22+0.34−0.32μN,andμZ_(c)^(2)=2.40+0.53−0.48μN for the Z_(c)(4020)^(+),Z_(c)(4050)^(+),and Z_(c)(4600)^(+)states,respectively.The magnetic moments evaluated for the Z_(c)4020)+,Z_(c)(4050)+,and Z_(c)(4600)+states are sufficiently large to be experimentally measurable.The magnetic moment is an excellent platform for studying the internal structure of hadrons governed by the quark-gluon dynamics of QCD because it is the leading-order response of a bound system to a weak external magnetic field.The quadrupole moment results are DZ_(c)=(0.20+0.05−0.04)×10^(−3)fm^(2),DZ_(c)^(1)=(0.57+0.07−0.08)×10^(−3)fm^(2),and DZ_(c)^(2)=(0.30+0.05−0.04)×10^(−3)fm^(2)for the Z_(c)(4020)^(+),Z_(c)(4050)^(+),and Z_(c)(4600)^(+)states,respectively.We obtain a non-zero,but small,value for the quadrupole moments of the Z_(c)states,which indicates a non-spherical charge distribution.The nature and internal structure of these states can be elucidated by comparing future experimental data on the magnetic and quadrupole moments of the Z_(c)(4020)^(+),Z_(c)(4050)^(+),and Z_(c)(4600)^(+)states with the results of the present study.