| Paper | Title | Page |
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| THPEA012 | Various Observables of TW Accelerator Structures Operating 100MV/m or Higher at X-band Facility, Nextef of KEK | 3699 |
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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 disk-loaded structure successfully tested beyond 100 MV/m, a heavily damped structure to be tested from late 2009 and a structure made in a quadrant configuration. These structures follow the same accelerating-mode RF parameter profile, called CLIC-C**, but show different features at high gradient operation. Various observables, such as dark current, vacuum activities, light emission, breakdown rate, and so on, are measured. We discuss the high gradient phenomena related to these observables and the possible improvement for stable operation at a higher gradient. * T. Higo et al., THP038, LINAC06,2006. |
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| THPEA013 | Advances in X-band TW Accelerator Structures Operating in the 100 MV/m Regime | 3702 |
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A CERN-SLAC-KEK collaboration on high gradient X-band accelerator structure development for CLIC has been ongoing for three years. The major outcome has been the demonstration of stable 100 MV/m gradient operation of a number of CLIC prototype structures. These structures were fabricated basically using the technology developed from 1994 to 2004 for the GLC/NLC linear collider initiative. One goal has been to refine the essential parameters and fabrication procedures needed to realize such high gradient routinely. Another goal has been to develop structures with stronger dipole mode damping than those for GLC/NLC. The latter requires that surface temperature rise during the pulses be higher, which may increase the breakdown rate. Structures with heavy damping will be tested in late 2009/early 2010, and this paper will present these results together with some of the earlier results from non-damped structures and structures built with a quadrant geometry. |
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| THPEA014 | TE11/TM11 Mixed-mode Waveguide Valve at X-band | 3705 |
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A waveguide vacuum valve for WR90 waveguide was designed, fabricated and tested. The valve consists of a modified commercial gate valve sandwitched with smooth tapers. The TE10 traveling wave in WR90 waveguide is "transmoded" into TE11+TM11 mode in the taper, going through the gate valve and is tapered back to the normal mode in WR90. The test has been successfully done. The valve stably trasmitted 40MW peak power with 500ns pulse width and this is limited by available RF power source. |
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| THPEA015 | L-band Accelerator System in Injector Linac for SuperKEKB | 3708 |
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In order to improve the capture efficiency of the positron produced at the target in present KEKB Injector linac, a new project has just started to utilize L-band (1298MHz) RF. The present S-band (2856MHz) capture cavities and successive three RF units are to be replaced by those of L-band. The specifications of the L-Band system should fulfill the demands of a positron damping ring downstream which is also to be under study for super KEKB project. Besides the whole design work of the system, our present ongoing work is rather concentrated on establishing L-Band RF source and accelerating structures. |
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| THPEB046 | RF Source of Compact ERL in KEK | 3981 |
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ERL (Energy Recovery Linac) of 5GeV energy is a future plan in KEK and in order to study the technical feasibility, construction of a compact ERL machine (cERL) is considered. Beam energy and current of cERL are 245MeV and 100mA, respectively. As 1.3 GHz frequency and super conducting cavity are chosen for the RF system, similar technology with KEK STF is employed. From 2008, KEK started the preparation of cERL and one RF unit of injector linac is introduced in this fiscal 2009. A new cw klystron of 300kW out put power, 150kW Y-type circulator and high power water load were developed in FY2009. DC power supply was under manufacturing. Preliminary test of HLRF and the high power couplers are scheduled in the Photon Factory site by making use of the old DC power supply. For main accelerator, we also introduced a 30kW IOT and a 35kW klystron and a DC power supply. At the same time, cERL is determined to be constructed in the East Counter Hall in KEK and the design layout is preceded. In this paper, the recent RF source development of cERL is described. Layout of the east counter hall, where cERL is constructed, is progressed and shown in this report. |
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| THPD007 | The Linac Upgrade Plan for SuperKEKB | 4290 |
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The next generation B-factory 'SuperKEKB' project whose target luminosity is 8 ×1035 cm-2s-1 is under consideration. A 'nano-beam scheme' is introduced to the SuperKEKB. In the scheme, an electron beam (Energy = 7 GeV, Charge = 3-4 nC/bunch, Vertical emittance =2.8 x 10-5 m) and a positron beam (Energy = 4 GeV, Charge = 4 nC/bunch, Vertical emittance = 1.6 x 10-5 m), are required at the end of injector linac. They are quite challenging targets for the present linac. In order to meet the requirements, we will introduce some new components to the linac. They are a photo-cathode RF gun for an electron beam, a positron capture section using new L-band cavities, a newly designed positron-generation target system and a damping ring for a positron beam. This presentation shows a strategy of our injector upgrade. |