The 55 SuperKEKB final focusing superconducting magnets are assembled into two cryostats, located at the left side and the right side of the accelerator interaction point, respectively. The two cryostats are cooled by sub-cooled liquid helium at 0.16 MPa with two independent refrigerators of about 250 W cooling capacity. From August 2016, the two cryostats were installed into the accelerator beam line and were connected with their own sub-coolers and refrigerators. As cryogenic systems, commissioning was carried out to cool down the cryostats, to excite superconducting magnets, and to test system interlock protections against some emergencies. This paper introduces the cryostats and cryogenic systems, and the commissioning processes. The cryostat heat loads were measured and the results are presented in this paper.

Along the beam lines of the SuperKEKB main rings, 218 conventional sextupole magnets are installed, and they are used for tuning the chromaticity of the accelerator rings. Especially, 16 sextupole magnets in the beam straight lines in the Tsukuba area are quite essential for the Crab Waist beam colliding. To make the beam tuning process finer, we are studying the superconducting sextupole magnet system with three types of the corrector magnets. From the operation temperature of the system, A15 compound superconductor is chosen as the cable material, and the development of the react and wind coil production has been tried with the Nb 3 Al cable. The Nb 3 Al super fine strand superconducting cable for the corrector magnets was manufactured, and its superconducting characteristics are being studied. In this paper, as the first test result of the development, the critical current characteristics of the straight cable as variables of temperature and magnetic field are reported. As the results, the critical current of the Nb 3 Al cable was higher than the design values for the corrector magnets, and this level of cable performance also indicates the potential for the cable being used for the main sextupole magnet.

A superconducting rf (SRF) cryomodule for International Linear Collider(ILC) main linac equips superconducting quadrupole magnet combined with dipole correctors. The magnets are superferric magnets with four superconducting (SC) race track coils conductively cooled from a two phase helium pipe of the cryomodule. The quadrupole field gradient and dipole field are 40 T/m and 0.1 T, respectively. The magnet length and iron-pole radius are 1 m and 0.045 m, respectively. It is known that dark current is generated at SRF cavities and accelerated through the following linac string. An orbit of the dark current of electrons is bent by the quadrupole field and the electrons hit the SC coils. An estimated power deposition on the coils may reach more than a few watts and the SC coil temperature may locally reach to critical temperature within a few second, in case of NbTi superconductor. We aim to realize the SC magnet which can be stably operated without quench under a such thermal condition. We plan to develop test coils made of three types of SC materials, NbTi, Nb 3 Sn, and MgB 2 which have different critical temperature. We will develop a short model magnet, based on the test coil results. Here, we will present the magnet design study and the R&D plan.

KEKB was the leading electron-positron collider in the world. Operation ceased in June 2010 in preparation for beginning the upgrade to SuperKEKB, the aim of which was to obtain a luminosity 40 times higher. For the SuperKEKB, over 2,000 magnet power supplies were recycled and approximately 300 power supplies were newly fabricated. The newly fabricated power supplies include high-performance power supplies: main bending/wiggler magnet power supplies and power supplies for final-focus superconducting magnets installed around the interaction point. High-power tests were performed and the results are reported.

The SuperKEKB B-Factory at KEK (Japan), after few years of shutdown for the construction and renovation, has finally come to the Phase-1 commissioning of the LER and HER rings, without the final focus system and the Belle II detector. Vacuum scrubbing, optics tuning and beam related background measurements were performed in this phase. Low emittance tuning techniques have also been applied in order to set up the rings for Phase-2 with colliding beams next year. An update of the final focus system construction, as well as the status of the injection system with the new positron damping ring and high current/low emittance electron gun is also presented.

A full-scale prototype power supply for the Super-KEKB final focus superconducting magnets was developed. The aiming specifications of the power supply are a dc rated output of 2 kA-10 V, a current setting resolution of < 0.1 ppm, current stability of < 2 ppm/8 h, a temperature coefficient of < 0.01 ppm/degree, and a current ripple of < 1 ppm, where the assumed magnet inductance and cable resistance are 0.88-13.28 mH and 5 m Omega, respectively. High-power tests were performed, and expected results were obtained.

In order to maintain an optimum beam collision condition in a double ring collider such as SuperKEKB it is essential to have an orbit feedback system at the interaction point (IP). We have designed such a system based on experiences at KEKB and PEP-II. For the vertical offset and crossing angle, we will rely on the system based on the beam orbit measurement similar to that used at KEKB. For the horizontal offset, however, we will utilize the dithering system which was successfully used at PEP-II. Some hardware devices have been already fabricated and others are in preparation. The present status of the development is reported.

The machine commissioning of KEKB started in December 1998 and its operation was terminated at the end of June 2010 to upgrade KEKB to SuperKEKB. In this paper, we summarize the history of KEKB and show the achievements made there.

Tetsuo Abe1, Kazunori Akai1, Norimasa Akasaka1, Mitsuo Akemoto1, Atsuyoshi Akiyama1, Mitsuhiro Arinaga1, Yunhai Cai2, Kiyokazu Ebihara1, Kazumi Egawa1, Atsushi Enomoto1, Eiji Ezura1, John Flanagan1, Shigeki Fukuda1, Hitoshi Fukuma1, Yoshihiro Funakoshi1,∗, Kazuro Furukawa1, Takaaki Furuya1, Junji Haba1, Kazufumi Hara1, Toshiyasu Higo1, Shigenori Hiramatsu1, Hiromi Hisamatsu1, Hiroyuki Honma1, Teruya Honma1, Kenji Hosoyama1, Takao Ieiri1, Naoko Iida1, Hitomi Ikeda1, Mitsuo Ikeda1, Shigemi Inagaki1, Shigeru Isagawa1, Hitoshi Ishii1, Atsushi Kabe1, Eiichi Kadokura1, Tatsuya Kageyama1, Kazuhisa Kakihara1, Eiji Kako1, Susumu Kamada1, Takuya Kamitani1, Ken-ichi Kanazawa1, Hiroaki Katagiri1, Shigeki Kato1, Takashi Kawamoto1,

The SuperKEKB project requires a positron and electron collider with a peak luminosity of 8 x 10(35) cm(-2) s(-1). This luminosity is 40 times that of the KEKB B-factory, which operated for 11 years up to 2010. SuperKEKB is an asymmetry-energy and double-ring collider; the beam energy of the positron (LER) is 4 GeV and that of the electron (HER) is 7 GeV. An extremely small beta function at the interaction point (IP) and a low emittance are necessary. In addition, in order to achieve the target luminosity, a large horizontal crossing angle between two colliding beams is adopted, as is a bunch length much longer than the beta function at the IP. This method is called the "nano-beam scheme". The beam-beam parameter is assumed to be similar to KEKB, the beta function at the IP is 1/20, and the beam currents are twice those of KEKB in the nano-beam scheme. Consequently, the luminosity gain of 40 with respect to KEKB can be obtained.

We have developed the superconducting final-focus quadrupoles for SuperKEKB, the next generation B-factory experiment in Japan. The system consists of four quadrupole doublets for incoming and outgoing electron and positron beams, respectively. A R&D superconducting quadrupole magnet was fabricated. In this paper, we describe the results on the excitation test and the magnetic field measurements of this R&D magnet.

First beam test with the low output-impedance second harmonic cavity (LOI), was performed in April, 2011 using the ISIS synchrotron at 2.1×10 protons per pulse, which corresponds to the circulating beam current of 2.3~5.2A. The LOI was proven to be stable under such a high intensity beam. The output impedance of LOI was derived from the beam induced voltage across the cavity gap, resulting in 35ohm at 3.4MHz, which agrees well with the measurement by the network analyzer. Issues on the present LOI system and a plan for further beam experiments are also described.

We present the current status and research programs of a multinuclide accelerator mass spectrometry (AMS) system on the 12UD Pelletron tandem accelerator at the University of Tsukuba (Tsukuba AMS system), Japan. A maximum terminal voltage of 12MV is available for the AMS system. The Tsukuba AMS system can measure environmental levels of long-lived radioisotopes of 14C, 26Al, 36Cl and 129I by employing a molecular pilot beam. Recently, enhancements in AMS techniques and equipment, including sample preparation, the ion source and the data acquisition system, have improved the performance of 36Cl-AMS. The standard deviation of fluctuations is typically ±2%, and the machine background level for the 36Cl/Cl ratio is lower than 1×10−15 with a halite sample. We have measured over 500 samples in 1year, including samples for earth and environmental sciences and nuclear safety research.

This study proposes a novel fast magnetic kicker system: the bridged-T network lumped kicker. The rise time is comparable with that of a transmission line kicker, while the input impedance can be matched with the characteristic impedance of the pulse power supply. A lumped magnet core and matching elements form the bridged-T network, so that the complex structure associated with a transmission line magnet is no longer required. A demonstration of the proposed scheme is also performed and the results are as anticipated. INTRODUCTION In order to make a synchrotron compact, a high-field bending magnet that reduces the synchrotron’s ring radius and a high-field gradient accelerating cavity with a wideband RF amplifier are required. These components have been studied with successful results. However, a limited straight-section length and rapid cycling mean that the injection/extraction of beams into/from the synchrotron ring are important issues that need to be addressed in order to make a ring compact. A fast kicker is a high-power pulse magnet system for injection/extraction. It should be compact so that it can be easily installed in a straight section having a limited length, and it should be operated with extremely short rise/fall times. It is difficult to apply a conventional kicker magnet, such as a transmission line magnet [1, 2], to a compact ring. As an alternative to conventional kickers, this study proposes a novel fast magnetic kicker system: the bridged-T network lumped kicker. The bridged-T network is sometimes called an all-pass filter, a constant resistance network or a Zobel network [3]. With this type of network, the input impedance can be purely resistive, while the load impedance depends on the frequency. The bridged-T network transforms a lumped inductive magnet into a complete impedance matched kicker without the need for a complex structure, and the rise time is comparable with that of a transmission line kicker. PROPOSED REFLECTION-FREE KICKER SYSTEM Bridged-T network lumped kicker The proposed kicker system shown in Fig. 1 is a bridged-T network composed of a lumped kicker and elements that follow a matching condition. Thus, the input impedance, z in = v in/i in, is exactly equal to R. This network behaves as a low-pass filter. The current transfer function (G im | i m/(v in/R)|) gives the cut-off (–3 dB) angular frequency ( ) as a solution of G im 2 = 1/2, which is expressed by BTN c BTN c 2 5 1 2.54 . R R L L The step response of this system gives the rise time as BTN rise 2 1.21 . 3 3 L L t R R zin = vin/iin R vin iin im Lumped kicker magnet L

An experiment is proposed to study a novel technique of union phase rotation for storage rings using pulsed alpha-particle injection from a standard radioactive (241)Am source into an ultra-high field gradient RF cavity of a storage ring. The 6-sector PRISM-FFAG ring is specifically considered. The specifications of the pulser, inflector and electrodes for guiding the (241)Am-source to a sector are described based on simulation studies. The method of RF-particle TOF measurement demonstrates the validity of the proposed method.

This study proposes a novel fast magnetic kicker system: the bridged-T network lumped kicker. The rise time is comparable with that of a transmission line kicker, while the input impedance can be matched with the characteristic impedance of the pulse power supply. A lumped magnet core and matching elements form the bridged-T network, so that the complex structure associated with a transmission line magnet is no longer required. The proposed scheme is compared with several conventional schemes. A demonstration of the proposed scheme is also performed and the results are as anticipated.

The evaluation of radioactivity induced in the concrete shield is important for the decommissioning of accelerator facilities. Specific activities of gamma-ray emitters of nuclear spallation products and thermal neutron capture products and beta-ray emitters such as tritium and (14)C, and (36)Cl in the concrete shield along the 12-GeV proton beam line (EP1 beam line, High Energy Accelerator Research Organization) were determined. The depth profiles of the radioactivity of each nuclide in the 6-m-thick concrete shield of the beam lines were compared, and the secondary particles and induced nuclear reactions were discussed.

The magnetic field of three scaled-radial-sector fixed field alternating gradient (FFAG)-magnets has been measured. The magnets have very large horizontal (1 m) and vertical (0.3 m) apertures to store muons and achieve phase rotation in an FFAG ring. The measurements results are compared to a three-dimensional field analysis using the TOSCA code; the generated magnetic field agrees satisfactorily with the TOSCA calculation in a range of 0.5\% for a large transversal (x-y-z) area. The three magnets show satisfactory performance for use in a ten-sector ring for a high-brightness muon source.