Shigekatsu Sugawara

Production and measurement of the MQXA series of LHC low-/spl beta/ insertion quadrupoles

The inner triplet quadrupole magnets (MQXA) for the LHC low-beta insertion have been developed. The quadrupoles provide a field gradient of 215 T/m at 1.9 K in a coil aperture of 70 mm diameter and with an effective magnetic length of 6.37 m. The series of 20 magnets have been produced in industry, and full testing has been done at KEK. We present an overview of the production and the results from mechanical and magnetic measurements.

Construction of Superconducting Magnet System for the J-PARC Neutrino Beam Line

Following success of a prototype R&D, construction of a superconducting magnet system for J-PARC neutrino beam line has been carried out since 2005. A new conceptual beam line with the superconducting combined function magnets demonstrated the successful beam transport to the neutrino production target.

Test Results of Superconducting Combined Function Prototype Magnets for the J-PARC Neutrino Beam Line

Superconducting combined function magnets are adopted for the 50 GeV, 750 kW proton beam line for the J-PARC neutrino experiment, and two full-scale prototype magnets have been developed successfully at KEK. In the cold tests, both prototypes were excited up to 7700 A without spontaneous quenches. The measured field quality of the both prototypes agreed well with the design field, indicating that the fabrication process has no major problem. The heater quench tests of the first prototype, however, showed that the magnet was not self-protected. Consequently, the design was revised and quench protection heaters were adopted. In quench heater tests of the second prototype magnet using small sheet heaters, the fundamental characteristics of the quench protection heaters were studiedSuperconducting combined function magnets for the J-PARC (Japan Proton Accelerator Research Complex) neutrino experiment have been successfully developed at High Energy Accelerator Research Organization, KEK. The first prototype magnet reassembled for the quench protection studies, and the cold test result indicated that the eight quench protection heaters are effective for the safe protection of the magnet. Three production magnets have been fabricated and tested at 4.5 K, 1 atm, in a vertical cryostat, and the excellent excitation and quench performances are observed. In the field measurement during cold tests, all the magnets indicated the field qualities good enough to fulfill the specification. The field measurement at room temperature has been also performed with the three production magnets for checking the dipole field component. The results are consistent with the computation.

Production and performance of the LHC interaction region quadrupoles at KEK

The MQXA superconducting low-beta quadrupole magnets for the LHC interaction regions are required to generate a field gradient of up to 215 T/m at 1.9 K along an effective magnetic length of 6.37 m. After completion of an R&D program on short models and full length prototypes, the series production of magnets has started, with to date five series magnets subsequently tested at KEK. Basic characteristics such as normal training, subsequent full energy dump, thermal cycle, ramp rate dependence and temperature dependence have been studied and results indicate that magnets have satisfactory quench performance. Magnetic field measurements performed at 1.9 K show the field quality to be uniform and to satisfy the stringent beam optics requirements.

Performance Tests of Superconducting Combined Function Magnets in the First Full-Scale Prototype Cryostat for the J-PARC Neutrino Beam Line

The first full-scale prototype magnet system assembled with the cryostat for the J-PARC proton beam line of neutrino experiment was successfully developed and tested. Two superconducting combined function magnets have been installed into the cryostat. The magnets were successfully cooled down to 4.5 K by forced flow supercritical helium and excited up to the current of 7345 A which is the nominal current of 50 GeV proton beam. The spot heater quench test showed that the quench characteristics in the supercritical helium were very similar to that in the liquid helium at 4.2 K, 1 atm. The quench protection scheme with both cold diodes and quench protection heaters was tested, and it has been verified that the magnet can be protected with safe margin.

Test Results of Superconducting Magnets for the J-PARC Neutrino Beam Line

Fabrication and cold tests of 32 superconducting combined function magnets including 4 backup magnets for the J-PARC neutrino have been completed. All the magnets reached 7700 A, 105% of maximum operation current, without any spontaneous quenches. Quench protection performance was also confirmed to be safe. In the field measurement during cold tests, all the magnets showed sufficient field quality to fulfill the specification. Reproducibility of the field quality was evaluated to be about the same order of that observed in ordinary cos-thetas magnets, indicating good manufacturing reproducibility.

Magnetic Field Measurement System in Superconducting Combined Function Magnets for the J-PARC Neutrino Beam Line

Magnetic field measurements have been performed for the first full-scale magnet system assembled with the cryostat for the J-PARC proton beam line of neutrino experiment. In the measurement system, the probe position with respect to magnet central axis is measured by a Helium Neon laser and a position sensitive detector, PSD, in order to obtain an exact dipole field strength. Errors associated with the PSD misalignment and influences on the PSD signals by the magnetic field were evaluated. The measured dipole components approached to the design values by compensating those with the probe position. The latest beam simulation indicated that the measured values of magnetic field were good enough for the primary proton beam transport.

8-kA HTS current leads for 1.9 K test facility at KEK

A pair of 8 kA HTS current leads for an accelerator magnet test facility at KEK has been designed and fabricated. The HTS current lead is composed of a copper section in the high temperature region and a HTS section in the low temperature region. The copper section of the lead consists of copper wires bundled into a stainless steel pipe. The HTS section consists of 12 HTS tape units made by Bi2223/Ag-1 at% An tapes arrayed onto the outer surface of a stainless steel tube with a diameter of 54 mm. The whole length and the maximum diameter of the lead are 1465 mm and 71 mm, respectively. The entire length of the current lead is cooled with helium gas. The design heat load and the helium gas flow rate of the lead in a steady state 8 kA-operation are less than 0.2 W and 0.4 g/sec, respectively and temperatures of the high and low temperature ends of the HTS section under the condition are 50 K and 4.4 K, respectively. The thermal performance test was carried out, and the results agreed well with the calculated values. So, we verified the validity of the thermal analysis and design. The corresponding heat load is estimated to be 0.15 W. These values of 0.4 g/s and 0.15 W are only 89% and 1.5% of the conventional gas cooled current lead, respectively.

Cooling performance of a pressurized HEII Cryogenics system for the superconducting magnet test facility at KEK

Publisher Summary This chapter describes a new cryogenic test facility developed at KEK for research and development on high field superconducting magnets. It was constructed and tested. A magnet was attached to the vertical double bath cryostat and was cooled down by the refrigeration or liquefier with the automatic computer control system. The cryostat has 8 W of refrigeration power at 1.9 K and it took 6 hours to cool down from 4.2 K to 1.9 K with 450 L of liquid helium and 2 tons of the model magnet. The system could be recovered within 2 hours after a quench at 1.9 K. The fast recovery to 1.9 K after a magnet quench permits several quenches per day and a maximum of five have been demonstrated. It consists of a vertical

Status of LHC low-/spl beta/ quadrupole magnets, MQXA, AT KEK

KEK has developed a superconducting quadrupole magnet, MQXA, for the LHC interaction region. This magnet is required to generate an operating field gradient of 215 T/m in the magnet bore of 70 mm and have an effective magnetic length of 6.37 m. For the accelerator operation, sixteen MQXA magnets will be installed in total for four interaction regions, and the cold tests of ten MQXA magnets of them have been completed. These ten magnets had good quench performance and satisfactory field quality for the requirement of beam optics. This paper describes the production quality and the magnet performance of the MQXA magnets.