Paper | Title | Other Keywords | Page | ||||
---|---|---|---|---|---|---|---|
MOYBPA02 | Operation of High-luminosity Meson Factories and the Challenge to go to the Next Generation | luminosity, factory, feedback, electron | 19 | ||||
|
This talk will present an overview of the operational status of B- and Phi-Factories, and address their present luminosity performance and limitations, such as electron cloud effects. It will also discuss upgrade plans, including motivation and beam dynamics challenges, new ideas, R&D and machine experiments in view of the next generation of meson factories with ~100 times more luminosity. In particular, it will address machine tests with strong RF focusing, crab cavity developments and first operational experience at KEKB.
|
|
|
Transparencies
|
|
||
MOPCH121 | Ground Motion Measurement at J-PARC | ground-motion, site, KEK, SLAC | 330 | ||||
|
In the next generation accelerator, construction of the machine on the stable ground is preferable for accelerator beam operation. We have measured ground motion at the J-PARC site under construction, where the ground is very close to the Pacific Ocean. In this paper, some of the observed results are shown, comparing the results of the previous observation at some accelerator facilities and next generation accelerator candidate sites in Japan.
|
|
|
||||
MOPLS030 | Recent Progress of KEKB | luminosity, optics, electron, vacuum | 610 | ||||
|
We summarize the machine operation of KEKB during the past one year, focusing on progress for this period.
|
|
|
||||
MOPLS031 | Beam Orbit Control System for the KEKB Crab Cavities | feedback, target, controls, damping | 613 | ||||
|
KEKB is an electron-positron collider with an 8 GeV electron ring (HER) and a 3.5 GeV positron ring (LER). The two beams currently collide at one interaction point with a finite horizontal crossing angle of 11 mrad. The design luminosity of 10 /nb/sec was first reached in May 2003 and the peak luminosity exceeded 16 /nb/sec in December 2005. Simulations predict a luminosity boost if a crab crossing scheme is introduced. The installation of two superconducting crab cavities, one in each ring, is scheduled in March 2006 in order to implement the crab crossing scheme. For stable operation, the horizontal beam position in the crab cavity must be carefully controlled. This is needed to avoid loss of control of the crabbing mode field due to beam loading. A beam position feedback system at the crab cavity has been prepared and tested. Its performance will be discussed in this report.
|
|
|
||||
MOPLS032 | Beam-beam Limit and the Degree of Freedom | emittance, damping, simulation, luminosity | 616 | ||||
|
Beam-beam limit is caused by chaotic diffusion due to the strong nonlinear force of beam-beam interaction. Degree of freedom in the colliding system is essential for the diffusion. We discuss the diffusion using several models.
|
|
|
||||
MOPLS124 | The KEK Injector Upgrade for the Fast Beam-Mode Switch | linac, positron, electron, injection | 855 | ||||
|
The KEK linac is a 600-m-long linear accelerator with maximum energy 8-GeV electron and 3.5-GeV positron, and it is used as an injector for 4-rings (KEKB e-/ e+, PF, PF-AR). To increase the operation efficiency, we have an injector upgrade plan for the quasi-simultaneous injection. In this paper, we will present the operation scheme and the construction of a new beam transport line in detail.
|
|
|
||||
TUPCH056 | A Simpler Method for SR Interferometer Calibration | extraction, closed-orbit, luminosity, synchrotron | 1136 | ||||
|
Previous methods of performing absolute calibration of the SR interferometer used at KEKB (measuring mirror distortion with a pinhole mask, virtual beam broadening via local bumps, physical beam broadening via dispersion bumps) are very time-consuming, and require dedicated machine time to take the necessary data. We report on a new, simpler method we have developed, wherein we create small local bumps at the SR source point and observe the resulting shifts in the phase of the interference fringes. From these data we can calibrate the total magnification of the system, including the effects of mirror distortion. The calibration data can be taken in a very small amount of time (tens of minutes), and in parallel with physics running, without stopping the beam-size measurement system or interfering with its use for luminosity tuning. By taking the calibration data at different beam currents and correlating the magnification at each current with the appropriate interference pattern fit parameters, we can also obtain the parameters needed for real-time mirror distortion correction.
|
|
|
||||
TUPCH057 | A Diagnostic System for Beam Abort at KEKB | beam-losses, vacuum, KEK, controls | 1139 | ||||
|
A controlled beam abort system has been installed at KEKB for the protection of the hardware components of the accelerator and detector from damage by ampere-class beam currents. In order to identify the reason for each abort and optimize the abort system to handle each type of problem as well as improve machine operation, a diagnostic system has been developed. Fast signals, such as beam currents, accelerating voltages of the RF cavities and beam loss monitor signals from PIN photo-diodes are recorded and analyzed by a data logger system with a high sampling rate at the moment of each abort. Beam oscillations, radiation dose at the detector and vacuum pressure are also examined to classify the reasons for beam loss and aborts. Statistics and typical examples of these aborts will be discussed.
|
|
|
||||
TUPCH127 | Fine Grooving of Conductor Surfaces of RF Input Coupler to Suppress Multipactoring | electromagnetic-fields, simulation, KEK, coupling | 1310 | ||||
|
An RF input coupler to feed high power into an accelerating cavity with heavy beam loading undergoes many multipactoring zones due to the wide range of the input RF power. Furthermore, a regular coaxial line is more subject to multipactoring than a rectangular waveguide because of the uniformity of the electromagnetic field. Grooving the conductor surfaces of the coaxial line is a promising method to suppress multipactoring under any conditions expected in the above cases. This paper reports results of our multipactoring simulation study and the high power test of the input coupler with a grooved coaxial line.
|
|
|
||||
TUPCH179 | R&D on Copper Beam Ducts with Antechambers and Related Vacuum Components | electron, wiggler, vacuum, photon | 1438 | ||||
|
A beam duct with antechambers is able to reduce the effect of photoelectrons and, as a result, to suppress the electron cloud effect of positron or proton beam. It will be adopted for a future high current positron/proton rings and also a damping ring of a linear collider. Copper beam ducts with one or two antechambers were manufactured for test and the feasibility was studied. The test chambers were then installed into the KEK B-factory positron ring and the performance was investigated with a beam current up to 2000 mA. The temperature, the pressure and the electron density in the beam channel were measured during the beam operation. The photoelectron, for example, was found to be well suppressed as expected compared to that of a simple circular beam duct. The related vacuum components, such as a connection flange, a bellows chamber and a gate valve with the same cross section to the beam duct, were also developed and tested together with the beam duct.
|
|
|
||||
TUPLS003 | A Perfect Electrode to Suppress Secondary Electrons inside the Magnets | electron, dipole, positron, quadrupole | 1489 | ||||
|
Electron cloud due to multipacting in the positron ring of B-factories is one of the limitations on the machine performance. Electron cloud in the drift region can be suppressed by solenoid. However, solenoid doesn't work inside a magnet. Numerical studies show that there is strong multipacting in the dipole magnet of the B-factory positron ring. Electrons also can be trapped inside quadrupole and sextupole magnets. The electron cloud from the dipole magnet and wiggler in the positron damping ring of the ILC is a critical limitation on the choice of damping ring circumference, which directly results in a choice of two 6km rings as the baseline for the positron damping ring. Various electrodes have been studied using the program CLOUDLAND. Our studies show that a wire type of electrode with a few hundred voltages works perfectly to kill the secondary electrons inside various magnets.
|
|
|
||||
TUPLS010 | New Beam Transport Line from LINAC to Photon Factory in KEK | linac, injection, emittance, optics | 1505 | ||||
|
The e+/e- injector LINAC in KEK usually injects into four rings which are Low Energy Ring (LER) of KEKB (3.5GeV/e+), High Energy Ring (HER) of KEKB(8.0GeV/e-), Photon Factory (PF)(2.5GeV/e-) and Advanced Ring for pulse x-rays (PF-AR)(3.0GeV/e-). While LINAC continuously injects into LER and HER alternately about every five minutes, both of the KEKB rings usually store almost full operating currents. Time for PF or PF-AR, which includes switching time, took about 20 minutes several times a day. During this, the storage currents in KEKB rings decreased, and the optimum points of luminosity tuning had been lost. It had taken more than two hours to recover the luminosity. It is so useful for KEKB to shorten the time for switch LINAC KEKB to/from PF or PF-AR. In summer of 2005, the transport line from LINAC to PF were renewed, in which a DC bending magnet only for PF line apportions electron beam from the end of LINAC to the new line. We succeeded to reduce the occupancy time for PF injection to about five minutes. In this paper design of the new PF beam transport line and the practical performance achieved according to the design are described.
|
|
|
||||
WEPCH026 | Recent Progress of Optics Measurement and Correction at KEKB | optics, sextupole, betatron, closed-orbit | 1981 | ||||
|
We present the progress of the optics measurement and the correction scheme of the KEKB operation for example off-momentum beta correction.
|
|
|
||||
WEPCH078 | Measurement of Wake Effects by Means of Tune Shift in the KEKB Low-Energy Ring | electron, positron, betatron, single-bunch | 2101 | ||||
|
The electron cloud produced by the positron beam induces single-bunch and coupled-bunch wakes, in addition to a tune shift. Effects of the dipole wake-field including the electron cloud were tried to measure in the KEKB Low Energy Ring. A test bunch was placed behind a bunch-train of the positron beam, even though a test bunch itself might interact with the remaining electron cloud. We measured a current-dependent tune-shift of a test bunch under constant train-current, while changing the bucket position of a test bunch. The tune shift indicated a strong defocusing field, however, tended to a focusing field when a test bunch approached a train with high train-current. The results are discussed, considering variations of the electron cloud density.
|
|
|
||||
WEPLS138 | Operation Status and Statistics of the KEK Electron/Positron Linac | linac, positron, injection, klystron | 2700 | ||||
|
The KEK electron/positron linac has been operated since 1982, surpassing the total operation time of more than 100,000 hours. It delivers four different beams to four different rings quite stably, even frequently switching beam modes. The operation time per year has reached 7,000 hours since 1999 when the KEKB entered a normal operation mode. Operation status and statistics will be reported with the emphasis on continuing efforts in various kinds of machine improvements, which have ensured the stable operation.
|
|
|
||||
THPCH049 | Simulation Study of Transverse Coupled-bunch Instabilities due to Electron Cloud in KEKB LER | electron, simulation, quadrupole, positron | 2895 | ||||
|
In this paper we report simulation results on the transverse coupled-bunch instabilities (TCBI) due to electron cloud at the KEKB Low Energy Ring (LER). The formation of electron cloud and related TCBI is investigated based on realistic solenoid field model. Studies on electron cloud in Quadrupole which could induce TCBI are also presented in this paper.
|
|
|
||||
THPCH050 | Further Studies on Betatron Sidebands due to Electron Clouds | electron, betatron, synchrotron, feedback | 2898 | ||||
|
We have observed vertical betatron sidebands in the transverse beam spectra of positron bunches at the KEKB LER which are associated with the presence of electron clouds in single-beam studies*, and which are also associated with a loss of luminosity when the KEKB beams are in collision**. The sidebands may be signals of a fast head-tail instability due to short-range wakes within the electron cloud, providing a diagnostic for exploring the mechanism for transverse beam blow-up due to electron clouds. We report here on further studies on the behavior of the sidebands under varying beam conditions, including varying initial beam size below the beam blow-up threshold, chromaticity, RF voltage and fill pattern.
|
*J. W. Flanagan et al. PRL 94, 054801 (2005).**J. W. Flanagan et al. Proc. PAC05, p. 680 (2005). |
|
||||
THPCH051 | The Effect of the Solenoid Field in Quadrupole Magnets on the Electron Cloud Instability in the KEKB LER | electron, quadrupole, simulation, dipole | 2901 | ||||
|
The electron cloud instability which causes vertical beam blowup in the KEKB LER is largely suppressed by applying a weak solenoid field to vacuum chambers in the drift region. However the blowup is still observed when the bunch spacing is reduced to 3.27 rf buckets or shorter. A question is where the remaining electron clouds are. To investigate the electron clouds in the quadrupole magnets, solenoids made of flat cables were developed and installed in 88 quadrupole magnets. The field strength of the solenoid is 17 Gauss. The effect of the solenoid field on the blowup is now under beam study. So far no clear effect of the solenoids on the luminosity and the sideband accompanied by the blowup is found. We report on the solenoid system, the results of the experiments and comparison of the experimental results with simulations.
|
|
|
||||
THPCH115 | Timing System Upgrade for Top-up Injection at KEK Linac | injection, linac, KEK, controls | 3071 | ||||
|
KEK Linac provides electrons and positrons to Photon Factory (PF) and B-Factory (KEKB). Because of the nature of those factory machines both quantity and quality of the beams are required. In order to improve the injections, quasi top-up injections of electrons to PF and KEKB rings have been planned and a new beam transport line was built. Fast beam switching mechanisms are being developed and installed. The timing and control system is also reinforced to realize fast (50Hz) switching of rf timing pulses, low-level rf, beam instrumentation parameters, and beam feedback parameters. The present timing system provides precise (jitters down to 5ps) timing pulses to 150 devices. Many of the signals will be upgraded to enable the fast switching scheme with an event system. At the same time a double-fold synchronization between asynchronous Linac and PF rf signals was developed to achieve precise injection timing mainly because both rings have independent circumference correction systems.
|
|
|
||||
THPCH116 | Continuous Circumference Control and Timing System for Simultaneous Electron-positron Injection at the KEKB | linac, injection, controls, positron | 3074 | ||||
|
We have continuously controlled ring circumference with a new method of synthesizer control at the KEKB. The new method stands for continuous controlling of reference frequency of synthesizers. Due to the new circumference control, we stabilized the KEKB circumference within about 6 micrometers. In Fall 2006, KEKB will introduce simultaneous electron-positron injection scheme. We have to change the timing system of KEKB to control the injection phase with pulse-to-pulse injection. We show the plan of the new timing system due to the simultaneous injection scheme.
|
|
|