119017224
Estimation of synchrotron-radiation background based on a real beam orbit
Some high-energy experiments have suffered from synchrotron-radiation background. As a measure, we have developed a new calculation method of synchrotron radiation based on a real beam orbit, aiming at quantitative estimations and the construction of a possible alarm system for the background. An explanation and a demonstration of our method are given.
54944635
Various Observables of TW Accelerator Structures Operating 100MV/m or Higher at X-band Facility, Nextef of KEK
Under the CERN-SLAC-KEK collaboration, we have been developing the high gradient TW accelerator structures. One of the main focuses is the feasibility study of CLIC accelerator structure at X-band. A high power facility, Nextef, was established at KEK in 2007. A few structures have been tested, including an un-damped diskloaded structure successfully tested beyond 100 MV/m, a heavily damped structure being tested now and a structure made in a quadrant configuration. These structures follow the same accelerating-mode RF parameter profile of the CLIC design, called CLIC-C, but showed very different features at high gradient operation. Various observables, such as dark current, vacuum activity, light emission, breakdown rate, and so on, were measured. We discuss the high gradient phenomena related to these observables. INTRODUCTION The collaboration program of the feasibility study on CLIC [1] accelerator structure was started since 2007 mainly lead by CERN, SLAC and KEK. At test facility Nextef of KEK, we have been testing three prototype structures to date. Last year, we have proved the operation of 100 MV/m [2]. Since then, we have tested two more structures, both equipped with heavy damping feature with magnetically coupled damping waveguides facing the accelerator cell. The surface temperature rise within a pulse has been recognized as a possible cause of breakdown trigger, though the mechanism not understood. The two structures tested last year are classified in this group with high surface pulse temperature rise. In the present paper are described those structure test results in various aspects of the high gradient performance to understand the physics behind. TEST ACCELERATOR STRUCTURES The test structures were electrically designed by CERN [3]. All the structures are equipped with 18 accelerating cells. The information on fabrication is listed in the Table 1. The un-damped structure (T18) and damped structure (TD18) was made each as one of the twins through SLAC –KEK collaboration based on GLC/NLC technology [4]. Another structure, called Quad_#5, was made by KEK with CuZr material [5]. The structures were tested with 60Hz at NLCTA of SLAC and with 50Hz at Nextef of KEK. Each one of the twins (T18_Disk and TD18_Disk) was tested at each laboratory, while the quadrant Quad_#5 described in this paper was tested at KEK. HIGH GRADIENT TEST RESULTS The test results compiling all those from SLAC and KEK are discussed [6].
121413098
Multipactoring suppression by fine grooving of conductor surfaces of coaxial-line input couplers for high beam current storage rings
123321012
Performance and operation results of the RF systems at the KEK B-Factory
KEK B-Factory (KEKB) was terminated in 2010 after achieving the world record luminosity of 2.11 × 1034 cm−2s−1. This paper describes the design features, performance, and operation results of the KEKB RF systems, which include a lot of original RF technologies and methods to store an electron/positron beam over 1 A stably. To cope with beam instabilities caused by large beam currents, two new types of normal and superconducting (SC) cavities with large stored energy were developed and successfully operated. For a new beam colliding scheme called crab crossing, two SC crab cavities were introduced and boosted the peak luminosity. Performance of these cavities is reported, along with the lowlevel and high-power RF systems, and the cryogenic system for the SC cavities. The status of the RF system upgrade towards SuperKEKB, which aims at a luminosity of 8.0 × 1035 cm−2s−1, is briefly described. © The Author(s) 2013. Published by Oxford University Press on behalf of the Physical Society of Japan. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Disclaimer: Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department. Copyright © 2013 The Physical Society of Japan Other Oxford University Press sites: Oxford University Press
199536560
RF ACCELERATING STRUCTURE FOR THE DAMPING RING OF THE SuperKEKB INJECTOR
A positron damping ring (DR) is under consideration to meet the requirement of the low-emittance beam injection to the main rings (MRs) of SuperKEKB based on the nano-beam scheme. We present design of an RF accelerating structure, including its higher-order-mode (HOM) dampers. This structure is based on the normal-conducting accelerating cavity system ARES, where 32 ARES cavities have been successfully operated so far in the KEKB MRs with extremely low trip rates. All the HOM absorbers on the cavity are made of silicon carbide (SiC) ceramics, bullet-shaped, and to be directly water cooled; the structure presented in this paper can be also a prototype for accelerating beams of the order of 10 A stored in the SuperKEKB MR in the high-current scheme.
15081704
DESIGN OF POSITRON DAMPING RING FOR SUPER-KEKB
Super-KEKB, an upgrade plan of the present KEKB collider, has recently changed its baseline-design from “high current” option to “nano-beam” scheme. The current is relatively low(4A/2.3A for LER/HER ring) compared to that of the high-current option(9.4A/4.1A), while the vertical beam size is squeezed to 60 nm at the interaction point to get the high luminosity. Since the Tousheck lifetime of LER is very short(600 sec), the intensity of the positron beam is as high as 8 nC/pulse. The emittance of the injected positron beam should be small enough to be accepted in the aperture of the LER. A damping ring has been proposed for the high-current option[1]. In this paper an updated design optimized to the nano-beam scheme is presented.
126145657
Simple vector WIMP dark matter
119177190
Probing LHC Higgs Signals from Extended Electroweak Gauge Group
We study the effects of the extended electroweak gauge sector on the signal strengths of the Higgs boson at the LHC. Extension of the Higgs sector associate with the extension of the electroweak gauge symmetry. In our setup, there are two neutral Higgs states ($h$, $H$) and three new gauge bosons ($W'^{\pm}$, $Z'$). We assume the lightest scalar, $h$, is what LHC found and its mass is 125 GeV. We find the enhancement of $\mu(gg \to h \to \gamma \gamma)$. On the other hand, other decay processes are same as or smaller than the SM expectation.