Kiyosumi Tsuchiya

Study of thermal radiation shields for the ILC cryomodule

The main linacs of the International Linear Collider are composed of 1824 cryomodules. As part of the R&D on the cryomodule, simplifications of the design were considered to reduce the construction and installation costs, including the possibility of removing a portion of the 5 K thermal shield. For this investigation the heat load measurements of a 6 meter cryomodule with and without the 5 K shield were performed, and used to determine emissivity coefficients. A thermal model of a full cryomodule was then created, and the heat loads of the cryomodule with the full set of the 5 K shield and without the lower 5 K shield were calculated with these parameters. By using a modified cooling scheme for the high temperature thermal shielding, we showed that the heat loads at 2 K between two models are substantially equivalent, and indeed, the thermal model without the 5 K lower shield requires 2% less work from the refrigerator.

Compact 8-lead unit for the SC correction coils of the SuperKEKB IR magnet system

In the proposed SuperKEKB interaction region (IR) magnet system 40superconducting (SC) correction coils are designed to perform some specific functions withcurrent of about 50 A. To energize these coils, 80 current leads will be mounted in thecryostats where the stringent spatial constraint and the cryogenic operation require acompact and optimum design. We propose a compact unit to integrate 8 helium vaporcooled leads (4 pairs). The 8 leads are made of brass and consist of two structures for thetransported current and helium vapor, which are designed and simulated by finite elementmodel (FEM). This paper will introduce the material selection and structure details. To equalize the temperature profiles of the individual leads under the different currents and helium flows, some copper blocks are placed between leads. In the cold test, the 8 leadswere operated in the nominal mode and responded safely to some transient situation. This paper will present the thermal and electrical comparison between the experi...

Test results of spare TRISTAN insertion quadrupole magnet with yoke added in superfluid helium

One of the TRISTAN insertion quadrupole magnets, iron-free magnet with an inner aperture of 140 mm and a length of 1.45 m, was tested at 1.8 K with a thick iron yoke assembled around the magnet. Two testing cycles were performed, and during the first test, the magnet current reached 5086 A after six training quenches, which corresponds to 94% of the short sample critical current. After warming up to room temperature, the second test was performed where the magnet current reached 5067 A without a training quench. The current was almost the same as the maximum current during the first test, indicating that the previous training effect was not lost after warmed up to room temperature.

Field quality measurements of spare TRISTAN insertion quadrupole magnet with yoke added

One of the TRISTAN insertion quadrupole magnets was yoked and tested. The original magnet was an iron free magnet. The magnetic field measurements of the original and the yoked magnets were performed at 4.2 K. The transfer functions of the original and yoked magnets were measured and compared. The multipole fields as a function of axial position and magnet current are presented for the both magnets.

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.

Design and Construction of the QC2 Superconducting Magnets in the SuperKEKB IR

The first stage commissioning of SuperKEKB is going on without the final focus system from Feb. 2016. The final focus system, which consists of 55 superconducting magnets, is still in the construction stage. The 8 main superconducting quadrupole magnets are designed to consist of quadrupole doublets as QC1 and QC2 for each beam line. All of the quadrupole magnets were constructed. In this paper, the design and the construction of the quadrupole magnets, QC2, are presented. INTRODUCTION SuperKEKB with a target luminosity of 8×10, which is 40 times higher than KEKB [1], is now being operated without the final focus system from February 2016 as the Phase-1 commissioning [2]. The accelerator design is based on the Nano Beam Scheme [3] with a large horizontal crossing angle of 83 mrad between the electron (e-) and positron (e+) beams and the beam sizes of about 50 nm at the interaction point (IP), where the beam energies of eand e+ are 7 GeV and 4 GeV, respectively. The final focus system [4] was designed with 55 superconducting magnets of 8 main quadrupoles, 4 compensation solenoids and 43 correctors [5]. Final beam focusing is obtained with quadrupole doublets of the main quadrupoles, QC1 and QC2, for each beam. For the e+ beam line, QC2LP and QC2RP were constructed for the left and right hand side to IP, respectively, and for the ebeam line, QC2LE and QC2RE were constructed. These superconducting magnets are assembled into two cryostats, and they are installed inside of the particle detector, Belle II [6]. Therefore, the final focusing system is operated under the magnetic field of 1.5 T by the Belle solenoid. For reducing the influence of this solenoid field on the beam collision, the compensation solenoids, which generate the solenoid fields of the opposite field direction, are installed into the cryostats. QC2LP and QC2RP are assembled inside of the compensation solenoid bores. QC2LE and QC2RE are assembled out of the solenoids. The QC1 magnets were already reported in the reference [7]. In this paper, the design and the construction of the QC2 magnets are reported.