SuperKEKB Interaction Region Research Articles

Prototype HTS Sextupole Magnet for SuperKEKB Interaction Region

A prototype high-temperature superconductor (HTS) sextupole magnet for the SuperKEKB Interaction Region was fabricated and tested in order to gain experience in the fabrication of HTS magnets as well as to understand their characteristics. The designed field strength of the sextupole magnet is 200 T/m2 at 30 K. The coil of the magnet has an inner radius of 75 mm and a length of 200 mm. Furthermore, the magnet consists of six rectangular coils wound with a REBa2Cu3O7-x (REBCO) coated conductor, which is 4 mm wide and was impregnated with epoxy resin. After fabrication, the magnet was tested in LN2 and it was confirmed that the magnet had been fabricated with no degradation of the conductor properties. In this paper, we briefly present the design and fabrication of the magnet, and the test results at 77 K including the properties of the magnetic field.

Design and Construction of the Magnet Cryostats for the SuperKEKB Interaction Region

The beam final focus system in the SuperKEKB interaction region consists of 55 superconducting magnets including eight main quadrupole magnets. Two cryostats for these magnets were required to be operated inside the Belle-II particle detector because of the magnet positions by the SuperKEKB beam optics. The cryostats were designed under constraints of the space and the electromagnetic forces with Belle-II. Construction of the cryostats was completed, and they were installed into the SuperKEKB interaction region. Cold tests of the cryostats were performed, and all magnets were successfully excited at the operation currents. In this paper, the design and the construction of the cryostats are presented.

Remote monitoring system for the cryogenic system of superconducting magnets in the SuperKEKB interaction region

A remote monitoring system was developed based on the software infrastructure of the Experimental Physics and Industrial Control System (EPICS) for the cryogenic system of superconducting magnets in the interaction region of the SuperKEKB accelerator. The SuperKEKB has been constructed to conduct high-energy physics experiments at KEK. These superconducting magnets consist of three apparatuses, the Belle II detector solenoid, and QCSL and QCSR accelerator magnets. They are each contained in three cryostats cooled by dedicated helium cryogenic systems. The monitoring system was developed to read data of the EX-8000, which is an integrated instrumentation system to control all cryogenic components. The monitoring system uses the I/O control tools of EPICS software for TCP/IP, archiving techniques using a relational database, and easy human-computer interface. Using this monitoring system, it is possible to remotely monitor all real-time data of the superconducting magnets and cryogenic systems. It is also convenient to share data among multiple groups.

Experimental study on heat transfer through a few layers of multilayer insulation from 300 K to 4.2 K

The final focusing magnet system at the SuperKEKB interaction region has been designed under stringent space constraints and consists of 8 main Superconducting (SC) quadrupole magnets, 4 compensation SC solenoids, and 43 SC correction coils. SC correction coils are directly wound on the inner containment tubes of liquid helium (LHe) vessels, which serve as support bobbins for SC cables. Beam pipes, which are kept at room temperature (∼300 K), are inserted into the cold bores of the vessel inner tubes. Between them, the minimal radial gaps are only 3.5 mm. Heat transfer from the warm beam pipes causes the raised operation temperatures of SC cables and increases heat leaks into cryostats. Multilayer insulation (MLI) is adopted to reduce heat flux in the narrow gaps. MLI performance as a function of the layer number was studied with a vertical anti-cryostat of dedicated design. The measurements were carried out by a calorimeter of thermal conduction and a modified LHe boil-off method. This paper presents the cryogenic measurement system and discusses the experimental results for the cryostats of the SuperKEKB final focusing SC magnets.

Newly Fabricated Resistive Magnets of SuperKEKB Interaction Region

SuperKEKB is an electron-positron circular collider with a 3-km circumference that aims to achieve a peak luminosity of 8 × 10 35 cm -2 s -1 using the so-called “nanobeam” scheme. The magnets in the entire interaction region and in the straight sections on either side of the interaction point have been replaced to realize collisions of nanosize beams. The magnet design and field measurement results are reported.

Development of HTS Sextupole Magnet for SuperKEKB Interaction Region

The SuperKEKB project underway at KEK will increase the KEKB luminosity by 40 times using nanobeam-interaction-region focusing optics. To achieve this high luminosity, the chromaticity correction of the collision beams is crucial; thus, special sextupole magnets, which can simultaneously produce normal and skew sextupole fields, are required in the straight sections around the interaction point. As a candidate for the sextupole, a cryocooled high-temperature superconducting magnet was proposed; development has begun. Here, the basic magnet design and the results of a small coil test are presented. The test studied the quench characteristics of the REBCO-impregnated coil.

Construction and Testing of the Final Focus Quadrupole R&D Magnet for the Super-KEKB Interaction Region

Super-KEKB is designed to be a next generation particle accelerator with a target luminosity of 4 times 1035 cm-2s-1. For the interaction region, a final focus quadrupole R&D magnet was designed and constructed. The design field gradient and effective magnetic length were 40.12 T/m and 0.299 m, respectively. The magnet consists of 6 layer coils. After construction, the magnet was tested at 4.2 K and a preliminary field measurement was performed. The magnet was energized to a current of 1800 A, which corresponds to 95.8% of the conductor limit, and the quadrupole component error was 0.23 % of the design value.