As promising magnet types, discrete-cosine-theta and canted-cosine-theta (DCT&CCT) superconducting magnets are designed for the High Energy Fragment Separator (HFRS), a fragment separator of the High Intensity Heavy Ion Accelerator Facility (HIAF). Quench protection is one of the key issues for DCT&CCT superconducting magnets due to low thermal conductivity between each turns and slow transverse quench propagation. Thermal quench-back induced by the center cooper wire as a heater automatically is a feasible quench protection option for the magnet wound with 6+1 type superconducting cables (six superconducting wires and one center cooper wire). In the present paper, an electro-thermal coupling model is developed and validated to deal with the dynamic coupling behaviors of electrical and temperature fields inside the superconducting magnets during quench protection process. The transient evolutions of current and voltage-to-ground are numerically obtained by finite element method, which shows obvious quench-back behaviors and agree well with the experimental measurements of the prototype magnet L800 in first round test. The hot-spot temperature can be reduced significantly considering quench-back effect. Furthermore, the quench protection baselines of temperature and quench integral are analyzed and predicted for L800, indicating that the magnet can be protected properly by the protection method with a quench-back at ultimate current 466A.

Electro-Thermal Coupling Model of Quench Protection With a Quench-Back for DCT&CCT Superconducting Magnets

The High Intensity Heavy-ion Accelerator Facility (HIAF) is a new project under construction in China, which will provide beams of stable and unstable heavy ions with high energies, high intensities, and high quality. This paper discusses the superconducting magnet system for this accelerator complex. It will consist of a Nb3Sn magnet with the peak field of 12 Tesla for the ECR ion source operated at 45 GHz, 52 solenoids typically 676 mm long with an operating field of 7.5 Tesla for the superconducting Linac called iLinac, 11 superferric dipoles with 320 mm wide good field region, 13 coil-dominated multiplets with an aperture of 320 mm, gradient 13 T/m for the fragment separator HFRS. This paper reports the design and prototype development status of the main components.

Superconducting Magnet Development for the HIAF Accelerator Complex

The dynamic quench behavior is investigated for a superconducting dipole magnet wound with the six-round-one superconducting cables (six NbTi/Cu wires and one center copper wire), which is protected by a recently developed protection scheme based on the quench-back effect triggered by the center copper wire automatically. The quench transients were measured based on the real-time data acquisition system and also calculated by our previously developed quench model. During the energy discharge of the magnet, the featuring points can be observed on the evolution curves of coil current, induced current, and voltage, which indicates the occurrence of a quench-back. By comparing the results for the cases with and without quench-back effect, the role of the quench-back on the quench protection is analyzed further. Meanwhile, the adjustable resistor can be utilized to control the quench-back effect to satisfy the quench protection requirements.

Quench Behavior of a Superconducting Dipole Magnet Protected by a Scheme With the Adjustable Quench-Back

The dynamic quench behavior is investigated for a superconducting dipole magnet wound with the six-round-one superconducting cables (six NbTi/Cu wires and one center copper wire), which is protected by a recently developed protection scheme based on the quench-back effect triggered by the center copper wire automatically. The quench transients were measured based on the real-time data acquisition system and also calculated by our previously developed quench model. During the energy discharge of the magnet, the featuring points can be observed on the evolution curves of coil current, induced current, and voltage, which indicates the occurrence of a quench-back. By comparing the results for the cases with and without quench-back effect, the role of the quench-back on the quench protection is analyzed further. Meanwhile, the adjustable resistor can be utilized to control the quench-back effect to satisfy the quench protection requirements. 

Characterization of a Raman-based distributed fiber optical temperature sensor in liquid nitrogen

HIAF (High Intensity heavy ion Accelerator Facility) is the new generation heavy ion accelerator under construction in China. The HFRS (FRagment Separator of HIAF) is a fragment separator and also a transfer-line between the Booster Ring and the Spectrometer ring, which has magnetic rigidity up to 25 Tm. HFRS magnet system is composed of 11 superconducting dipoles and 13 sets of triplets. Several multipole magnets (an octupole coil, a quadrupole coil, and a sextupole coil) are nested together to compact the length of the HFRS-line. All of them feature high field gradients (13 T/m, 25 T/m2, 105 T/m3) and large bores (320 mm). To reduce the cold mass and ensure the field quality, the whole multipole magnets are all designed with coil-dominated magnets of CCT (Canted Cosine Theta) and DCT (Discrete Cosine Theta). This paper will introduce the general design process of an HFRS multipole module. The development process and test results of the prototype will be presented.

DCT&CCT Superconducting Multiplets for HIAF-HFRS

High-precision calibration for strain and temperature sensitivities of Rayleigh-scattering-based DOFS at cryogenic temperatures

A fast ramp superconducting dipole magnet based on the Canted-Cosine-Theta (CCT) type coil with a magnetic field of 2 T, ramping rate of 3 T/s and a bore diameter of 60 mm has been designed for the compact synchrotron. The fast ramp magnet is comprised of four-layers of CCT coils embedded in the formers with high efficiency cooling channel and layer by layer pre-tightening structure to ensure structural reliability and thermal stability. This paper presented the main mechanical structure de-sign, analyze and measurements of the fast ramp CCT magnet. Based on the finite element method (FEM) model with ANSYS, a detailed analysis of the CCT magnet mechanical behavior during cool-down and excitation has been studied. Finally, the magnetic field and strain measurements are measured from a cryogenic test bath cooled with liquid helium, during which the magnet reached the expected goal. Comparisons of the strain measurements with 3D finite element model results are also reported in this paper.

Taolue Yang

Papers

DCT&CCT Superconducting Multiplets for HIAF-HFRS

High-precision calibration for strain and temperature sensitivities of Rayleigh-scattering-based DOFS at cryogenic temperatures

Structure Design and Test of a Fast Ramp Multilayer Canted Cosine Theta (CCT) Magnet