A beam optics scheme has been designed for the future circular collider-e+e− (FCC-ee). The main characteristics of the design are: beam energy 45 to 175 GeV, 100 km circumference with two interaction ...points (IPs) per ring, horizontal crossing angle of 30 mrad at the IP and the crab-waist scheme P. Raimondi, D. Shatilov, and M. Zobov, arXiv:physics/0702033; P. Raimondi, M. Zobov, and D. Shatilov, in Proceedings of the 22nd Particle Accelerator Conference, PAC-2007, Albuquerque, NM (IEEE, New York, 2007), p. TUPAN037. with local chromaticity correction. The crab-waist scheme is implemented within the local chromaticity correction system without additional sextupoles, by reducing the strength of one of the two sextupoles for vertical chromatic correction at each side of the IP. So-called “tapering” of the magnets is applied, which scales all fields of the magnets according to the local beam energy to compensate for the effect of synchrotron radiation (SR) loss along the ring. An asymmetric layout near the interaction region reduces the critical energy of SR photons on the incoming side of the IP to values below 100 keV, while matching the geometry to the beam line of the FCC proton collider (FCC-hh) A. Chancé et al., Proceedings of IPAC’16, 9–13 May 2016, Busan, Korea, TUPMW020 (2016). as closely as possible. Sufficient transverse/longitudinal dynamic aperture (DA) has been obtained, including major dynamical effects, to assure an adequate beam lifetime in the presence of beamstrahlung and top-up injection. In particular, a momentum acceptance larger than ±2% has been obtained, which is better than the momentum acceptance of typical collider rings by about a factor of 2. The effects of the detector solenoids including their compensation elements are taken into account as well as synchrotron radiation in all magnets. The optics presented in this paper is a step toward a full conceptual design for the collider. A number of issues have been identified for further study.
KEKB, the B-Factory at High Energy Accelerator Research Organization (KEK) recently achieved the luminosity of 1×1034cm-2s-1. This luminosity is two orders higher than the world's level at 1990 when ...the design of KEKB started. This unprecedented result was made possible by KEKB'S innovative design and technology in three aspects-beam focusing optics, high current storage, and beam-beam interaction. Now KEKB is leading the luminosity frontier of the colliders in the world.
Lattice of the KEKB colliding rings Koiso, Haruyo; Morita, Akio; Ohnishi, Yukiyoshi ...
Progress of theoretical and experimental physics,
03/2013, Letnik:
2013, Številka:
3
Journal Article
Recenzirano
Odprti dostop
This paper describes a few outstanding features of the beam-optical lattice of the KEKB colliding rings. A chromaticity correction scheme with non-interleaved sextupole pairs, a new cell structure ...with 2.5π betatron phase advances, etc. have been introduced. The lattice successfully squeezed the vertical beta functions at the interaction point, which greatly contributed to the achievement of the world's highest luminosity.
The KEKB injector linac Akemoto, Mitsuo; Arakawa, Dai; Enomoto, Atsushi ...
Progress of theoretical and experimental physics,
03/2013, Letnik:
2013, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The KEKB injector linac has been continuously improved to enhance the stability of many devices and the efficiency of beam operation. These improvements include the development of the new C-band ...accelerating structure, pulse compressor, klystron, rf window, compact modulator, and the new positron production target using crystalline tungsten. We have also achieved two-bunch beam acceleration, the development of an energy spread monitor, a safety system upgrade, and an event-based timing and control system. These developments and practical applications for advanced linac beam handling result in the success of the simultaneous top-up injection among the three independent storage rings. This result greatly improves the integrated luminosity and the operation stability of the KEKB rings. In this paper, we present the progress of the KEKB injector linac in this decade.
Published in ICFA beam dynamics newsletters 67, August 2015 This article reviews the beam dynamics issues, such as intra-beam scattering,
beam-beam interaction, lattice nonlinearity, and space ...charge, in SuperKEKB
before its commissioning.
Multi-laminated HTS tape conductors wound into double-pancake (DP) coils are planned to be used widely in the production of large superconducting coils. If the HTS tapes are simply laminated to form ...the conductor, the current distribution in the laminated tape conductor of the coil is not homogeneous because of the different inductances of all the tapes. Non-uniform current distribution should be avoided because it causes increased AC loss and decreased critical current in the conductor. Transposition of these tapes at the innermost or outermost layer of the coil so as to arrange the tapes symmetrically is effective for inducing homogeneous current distribution. However, geometrically, this method does not result in perfect symmetry of the conductor for tapes with more than double-lamination and restricts the coil arrangement. In this paper, we analyze the current distribution in the tape conductor using an electrical circuit model, and then discuss how to obtain homogeneous current distribution in multi-laminated HTS tape conductors wound into DP coils for various coil arrangements. We propose a new method to obtain uniform current distribution by adjusting gaps between HTS tapes in the conductor, and apply this method to tapes laminated four times and wound into solenoid coils and a toroidal coil. In this paper, the solenoid coils are composed of two or three DP coils and the toroidal coil is composed of eight unit coils made of a single DP coil. The homogeneous current distribution in the multi-laminated HTS tapes for the arbitrary solenoid coil and toroidal coil composed of multiple DP coils can be obtained by symmetrical transposition at the middle of the unit coil and insertion of appropriate additional thickness between tapes.
LHC is now delivering proton and heavy ion collisions at the highest energy. Upgrading the LHC beyond its design performance is a long term program that started during the LHC construction, with some ...fundamental R&D programs. The upgrade program is based on a vigorous superconductor and magnet R&D, aimed at increasing the field in accelerator magnets from 8 T to 12 T for the luminosity upgrade, with the scope of increasing the collider luminosity by a factor 5 to 10 from 2022. The upgrade program might continue with the LHC energy upgrade, which would require magnets producing field in the range of 16-20 T. The results obtained so far and the future challenges are discussed together with the possible plan to reach the goals.
Cryogenic slush fluids such as slush hydrogen and slush nitrogen are solid-liquid, two-phase fluids containing solid particles in a liquid. As a functional thermal fluid, there are high expectations ...for use of slush fluids in various applications such as fuels for spacecraft engines, clean-energy fuels to improve the efficiency of transportation and storage, and as refrigerants for high-temperature superconducting equipment. Experimental flow tests were performed using slush nitrogen to elucidate pressure-drop characteristics of converging-diverging (C-D) pipes and corrugated pipes. The results of pressure-drop tests for two different types of C-D pipes, long-throated and short-throated, both with an inner diameter of 15 mm, confirmed a pressure-drop reduction for the short-throated pipe at a flow velocity of 1.5 m/s or greater, and a maximum pressure-drop reduction of 40-50% compared to liquid nitrogen. In the case of two different types of corrugated pipes with an inner diameter of either 12 mm or 15 mm, a pressure-drop reduction was confirmed at a flow velocity of 2 m/s or greater, and reached a maximum value of 37% at 30 wt. % compared to liquid nitrogen. The greater the solid fractions, the smaller the pipe friction factor became, and the pipe friction factor at the same solid fraction showed a constant value regardless of the Reynolds number. From the observation of the solid particles' behavior using a high-speed video camera and the PIV method, the pressure-drop reduction mechanisms for both C-D and corrugated pipes were demonstrated.
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