126107953
STRAIGHTNESS ALIGNMENT OF LINAC BY DETECTING SLOPE ANGLE
Straightness measurement by detecting slope angle[1] was adopted for evaluating the aligning straightness of the 600-m-long KEK e-/e+ injector linac[2]. Here, the slope angles between the centers of the alignment base plates for the 71-m-long part of the linac could be detected with the standard deviation (σ) of 9 μrad by using Talyvel 4, a precise electronic level system. As a result, the straightness could be evaluated with the standard deviation of 26 μm fairly easily, which is hardly achieved by conventional methods. The estimation based on our error propagation model shows that straightness evaluation with the reproducibility of 0.6 mm (2σ) for the distance of 500 m, sufficient for aligning the KEK linac, and that of better than 1 mm (2σ) for the distance of 10 km, expected for the linacs planed in the ILC project[3], can be achieved with this technique. INTRODUCTION The 600-m-long KEK e-/e+ injector linac is expected to be aligned with an accuracy of sub-mm or better in its mechanical alignment (primary alignment) for the future upgrade. The linac is composed of the 125-m-long straight section and the 483-m-long straight section connected with the 180-degree arc section, forming “J” shape. It follows that the aligning straightness of the 483m-straight-section should be evaluated with an accuracy of sub-mm or better. We adopted a straightness measurement method using a level for evaluating the straightness, considering that it is hardly achieved by any other conventional methods (cf. figure 7). Figure 1 shows its schematics. Here, the tangential angles of the profile corresponding to the differential of the straightness are obtained. The straightness is derived by integrating the angles without affected by error in the scanning straightness e(xi), as the detected angles were not affected by the error. The straightness fm(xn) at position xn is derived as
55977743
Simultaneous Top-up Injection for Three Different Rings in KEK Injector Linac
The KEK injector linac provides the beams of different quality sequentially with four storage rings: Low Energy Ring (LER) of KEKB, High Energy Ring (HER) of KEKB, Photon Factory (PF) and Advanced Ring for Pulse X-rays (PF-AR). For the simultaneous top-up injection to KEKB LER, HER and PF, the linac upgrade has been successfully completed in March of 2009. In this upgrade, a new beam transport line of PF is constructed. A pulsed bend and twelve pulsed steering magnets are installed for fast beam orbit control. A positron generation target with a hole is adopted for the fast switching between the electron and positron beams. Toward the simultaneous top-up operation, an operation strategy based on the multi-energy linac scheme is adopted so that the common DC magnet settings are used to accelerate the beams with different energies. In addition, an event-based fast control system is installed for the fast beam energy switching. We report the details of simultaneous top-up injection for three different rings in KEK.
122318830
Cryomodule tests of four Tesla-like cavities in the Superconducting RF Test Facility at KEK
A 6-m cryomodule including four Tesla-like cavities was developed, and was tested in the Superconducting RF Test Facility phase-I at KEK. The performance as a total superconducting cavity system was checked in the cryomodule tests at 2 K with high rf power. One of the four cavities achieved a stable pulsed operation at $32\text{ }\text{ }\mathrm{MV}/\mathrm{m}$, which is higher than the operating accelerating gradient in the ILC. The maximum accelerating gradient (${E}_{\mathrm{acc},\mathrm{max}﻿}$) obtained in the vertical cw tests was maintained or slightly improved in the cryomodule tests operating in a pulse mode. Compensation of the Lorentz force detuning at $31\text{ }\text{ }\mathrm{MV}/\mathrm{m}$ was successfully demonstrated by a piezo tuner and predetuning.
113679678
PRESENT STATUS OF SUPERCONDUCTING CAVITY SYSTEM FOR CERL INJECTOR LINAC AT KEK
Construction of the compact ERL (cERL) [1] is underway and fabrication of a SC Cavity Injector Cryomodule has been started last year at KEK. Status of R&D and design details are reported.
118396635
Slow-roll Inflation with the Gauss-Bonnet and Chern-Simons Corrections
We study slow-roll inflation with the Gauss-Bonnet and Chern-Simons corrections. We obtain general formulas for the observables: spectral indices, tensor-to-scalar ratio and circular polarization of gravitational waves. The Gauss-Bonnet term violates the consistency relation r = −8nT. Particularly, blue spectrum nT > 0 and scale invariant spectrum |8nT|/r << 1 of tensor modes are possible. These cases require the Gauss-Bonnet coupling function of ξ, ~ 108/MPl. We use examples to show new-inflation-type potential with 10MPl symmetry breaking scale and potential with flat region in 10MPl lead to observationally consistent blue and scale invariant spectra, respectively. Hence, these interesting cases can actually be realized. The Chern-Simons term produce circularly polarized tensor modes. We show an observation of these signals supports existence of the Chern-Simons coupling function of ω, ~ 108/MPl. Thus, with future observations, we can fix or constrain the value of these coupling functions, at the CMB scale.
115079519
CONSTRUCTION OF THE S1-GLOBAL CRYOMODULES FOR ILC
In an attempt to demonstrate an average accelerating gradient of 31.5 MV/m as in the design of the ILC, the S1-Global project [1] is a cryomodule being constructed by an international collaboration hosted by KEK and including INFN, FNAL, DESY and SLAC. The S1Global system joins two half-length cryomodules, each 6 m in length and containing 4 cavities, Module-C contains cavities from FNAL and DESY and was constructed by INFN. Module-A contains four KEK cavities and was constructed by KEK. The assembly of the cryomodules started in January 2010, and was just completed in May. In this paper, construction experience of the S1-Global cryomodule is presented. INTRODUCTION The S1-Global cryomodule was proposed and approved as an international collaborative effort at the SCRF meeting of the ILC Global Design Effort in April 2008. The goals of the S1 Global program are to attempt to achieve an average accelerating gradient of 31.5MV/m across 8 cavities. To accomplish this, eight cavities and couplers are contributed from FNAL, DESY and KEK, and installed in two ‘half cryomodules’ each 6 m long: Module-C, a new cryomodule designed and constructed by INFN; and Module-A, a modified STF cryomodule by KEK. The S1-G cryomodule design work was completed in January 2009, and the assembly started in January 2010. The collaborative framework of S1-G is demonstrated in the contributions of the participating laboratories: INFN: Design and construction Module-C and production of the blade tuners for the FNAL cavities. FNAL: Two TESLA type cavities [2], power couplers and integration of the INFN blade tuners in the cavity packages. DESY: Two TESLA type cavities, including Saclaytype tuners, and power couplers. SLAC: Power distribution for Module-C, and aging of FNAL couplers. KEK: Four TESLA-like cavities, with two types of tuner design, Module-A for KEK cavities [3], power distribution for Module-A, and infrastructure for tests. DESIGN OF S1-GLOBAL CRYOMODULE The S1-Global assembly is shown in Fig. 1. Two cavities from FNAL and two form DESY are installed in the Module-C, and four cavities of two types by KEK are installed in Module-A. The total length of the S1-Global assembly is 14.9 m. The parameters of the two cryomodules are listed in Table 1. The cross section of Module-C has the same design as the TTF-type III cryomodule [4]. The cold mass is supported to the vacuum vessel by two composite cylindrical posts spaced 3200 mm apart. All four input couplers are separated by a distance of 1384.15 mm at room temperature. The designs of FNAL and DESY cavity packages differ because of the tuner types, the Blade tuner and the Saclay-type tuner. The difference in length is made up in the bellows between packages. Fig.1: S1-G cryomodule and cavity package of each laboratory. (a): FNAL cavity with Blade tuner, (b): DESY cavity with Saclay-type tuner, (c): KEK-a cavity with slide jack tuner and (d) KEK-b cavity. WEPE008 Proceedings of IPAC’10, Kyoto, Japan 3356 03 Linear Colliders, Lepton Accelerators and New Acceleration Techniques A03 Linear Colliders Table 1: S1-Global Cryomodule Parameters