Search

We developed a differential current transformer (CT) for electron beam charge measurement in noisy environments, such as near high-power pulse sources. This CT has four pickup wires coiled at equal intervals (90 deg.) on a toroidal core and each coil is wound for two turns. The midpoint of the coil is connected to the body ground so that a balanced differential signal is generated at both ends. A beam pipe with a ceramics insulation gap is inserted into the toroidal core to obtain a signal from a charged-particle beam. The four pairs of signals are transmitted through a CAT6 differential cable and fed into differential amplifiers. The common-mode noise from the noisy ground at the CT is canceled out by the amplifier. The four signals are then summed and digitized by an AD converter. We produced differential CTs and installed them into the new injector linac of NewSUBARU (*). Before the installation, the frequency response was measured in a laboratory and a flat response of up to 100 MHz was obtained as expected. Common-mode noise cancellation was also confirmed at NewSUBARU and the CTs have been utilized for beam charge monitoring stably., Proceedings of the 11th International Beam Instrumentation Conference, IBIC2022, Kraków, Poland

A compact and low-cost 1 GeV injector linac was designed and constructed to provide injection beams to the soft X-ray synchrotron radiation facility NewSUBARU instead of the SPring-8 injector system, which will be shutdown. The total length of the injector linac needs to be less than 70 m to fit into the existing tunnel. To this end, an RF electron gun with a gridded thermionic cathode directly attached to a 238 MHz RF cavity was developed and adopted. The 500 keV, 0.6 ns, 1 nC beam emitted from the cavity is compressed to 3 ps by velocity bunching driven by a 476 MHz RF cavity and a S-band RF structure. The short-pulsed beams are accelerated up to 1 GeV with 16 C-band RF structures. In the C-band accelerator section, the klystron output of 50 MW is multiplied 4 times by a pulse compressor and fed to the 4 RF structures to generate a high accelerating field of 31 MV/m. A low-level RF system consisting of a MTCA.4 based high-speed digitizers and RF frontend boards has been constructed. This injector system is used at the 3 GeV SR facility currently under construction in Sendai. In this paper, we report the design outline and the operational performance of the injector system., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

Photon sources are looking for performance upgrades by pursuing higher photon brilliance and coherence these years. The trend is pushing the lattice design to lower the beam emittance, which naturally results in the narrower dynamic aperture. One bottleneck in the upgrades is a beam injection system capable of accumulating required beam intensity and keeping top-up operations with such narrow apertures. Beam injection with a nonlinear kicker and transverse/longitudinal on-axis injections are now in the limelight. However, these techniques still need time to be put into practical use. We take an alternative approach for the SPring-8 upgrade, SPring-8-II, renovating the off-axis beam injection scheme to address the following requirements for the coming diffraction-limited storage rings (DLSRs): minimizing of both injection beam amplitude and perturbation to stored beam, and topping-up functionality. This presentation will overview the renewed off-axis beam injection scheme and report the development status of the following three key components: 1) permanent magnet based DC septum magnet, 2) in-vacuum pulse septum magnet, and 3) twin kickers driven by a single solid state pulser., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

The magnet lattice design of the SPring-8 upgrade, SPring-8-II, is a five bend achromat composed of one normal and four longitudinal gradient bending magnets. Permanent magnet has been chosen for both types of the dipoles, and the high gradient multipole magnets are all electromagnets. This presentation will overview the magnet developments and precise alignment schemes for SPring-8-II, focusing specifically on the following features. Temperature insensitive magnetic circuits with a function of fine magnetic field tuning have been developed for the permanent magnet dipoles. Narrow bore multipole magnets with compact coil assemblies have been designed. We optimized the shimming for enough good field regions, and minimized ohmic loss at the coils for suppressing thermal deformation. To improve the accuracy of vibrating wire magnet alignment, practical wire sag distributions have been quantitatively evaluated. In 2018, a test half-cell was constructed by which the feasibilities of the magnets and the overall alignment precisions including the effects of the thermal deformation of magnets, a repeatability of magnet reassembly has been confirmed., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

For precise beam position measurement using a beam position monitor (BPM), a recursive correction which is expressed by the higher-order polynomials of beam positions are usually adopted. We recognized that the higher-order polynomials came from the higher-order moments and that beam position measurement is consequently influenced by a transverse beam shape. To investigate what order was required for adequate correction, we performed a successive iteration for the six-electrode BPM holding an inner radius of 16mm (circular cross-section). The successive iteration is a method to obtain a self-consistent solution for the higher-order correction. An amplitude of static electric field due to a beam charge was calculated by two-dimensional mirror charge method. As a result of the successive iteration, the convergence region was large enough for ordinary measurements (from lower than -5mm to higher than 5mm horizontally and vertically). In the convergence region the root mean square of the differences between the set and calculated vertical position were obtained as 0.487mm (without correction), 0.030mm (with third-order correction) and 0.003mm (with fifth-order correction)., Proceedings of the 28th Linear Accelerator Conf., LINAC2016, East Lansing, MI, USA

An SF6 waveguide system for the injector section of SPring-8 linac has been replaced in a vacuum waveguide system including a newly developed vacuum circulator and an isolator. This paper describes developed RF components, a waveguide configuration and an RF conditioning of the system., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

We report the design, performance, and installation of the beam diagnostic system of XFEL/SPring-8. The electron beam bunches of an XFEL accelerator are compressed from 1 ns to 30 fs by bunch compressors without emittance growth and peak-current fluctuation which directly cause SASE fluctuation. To maintain the stable bunch compression process, the accelerator requires rf caivty beam position monitors (BPM) with 100 nm resolution, OTR screen monitors (SCM) with a few micro-meter resolution, fast beam current monitors (CT) and temporal structure measurement systems with resolution under picosecond. The performance of the developed monitor instruments, such as the BPM, the SCM, and the CT, was tested at the SCSS test accelerator and satisfied with the requirements. To measure the temporal structure of the electron bunch, three type measurement systems, which are a streak camera, an EO sampling measurement, and a transverse deflecting cavity with a resolution of few-tens femtosecond, are being prepared. The streak camera and EO sampling shows the resolution of sub-picosecond. The installation of these beam diagnostic systems is going on smoothly., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan