Testing and Processing of Pre-production 325 MHz Single Spoke Resonator Power Couplers for PIP-II Project

International audienceFundamental 325 MHz power couplers are designed, built and tested for SSR cavities in PIP-II project [1]. Couplers should work in CW mode at power level 7.5kW w/o beam and ~15 kW with the 2 mA beam. At pre-production stage we built and tested 6 couplers, produced by CPI (FNAL) and PMB (IJCLab) and 4 more couplers will be tested soon. Two of tested cou-plers had TiN coated ceramic window. In warm test stand two couplers were mounted on the coupling chamber and tested in SW regime at full reflection with phase controlled by position of short and reflection insert. Couplers were tested at pulse mode (up to 25kW) and cw mode (12kW) with HV bias or without bias. Test results demonstrated that 3.5 kV DC bias completely suppresses multipactor in coupler. Vacuum activity in coupler was controlled by e-pickups and build-in vacuum gauges, located near the vacuum side of window. Power processing without DC bias was done for several couplers with and without TiN coating on ceramic window. Test results are presented and discussing in paper

Development of a a YAG/OTR Monitor

International audienceTo investigate the mechanisms of beam halo formation and its dynamics, a YAG/OTR monitor has been developed and tested at the KEK-ATF. The monitor has four ceramic Ce:YAG  screens for the visualization of the beam core and beam halo and an OTR target to provide complementary beam core measurements. A high dynamic range (>10$^5$) and a high resolution (< 10µm ) have been demonstrated experimentally. Measurements of beam halo using this monitor are consistent with previous results and theoretical modeling, and have allowed further progress in the characterization of the driving mechanisms

Experimental Study of Halo Formation at ATF2

International audienceFor Accelerator Test Facility 2 (ATF2), as well as other high-intensity accelerators, beam halo has been an important aspect reducing the machine performance and activating the components. It is imperative to clearly understand the mechanisms that lead to halo formation and to test the avail- able theoretical models with an adequate experiment setup. In this paper, the experimental measurement of the beam halo formation from beam gas scattering is presented. The upgrading of an OTR/YAG screen monitor for future halo study is also introduced

Vibration and luminosity frequency analysis of the SuperKEKB collider

International audienceThe SuperKEKB collider has entered the physics production phase with the aim to reach its target luminosity of 6×1035 cm−2s−1. Vibrations of the accelerator elements, especially around the Interaction Point (IP), could limit the performance of the collider. Since 2018, a 24-hour monitoring system of vibrations has been put in place on both sides of the Belle II detector. Measurements and analyses of the spectral components of these vibrations and of the transfer function of the mechanical supports are presented, along with measurements of luminosity spectra from the LumiBelle2 detectors, showing good agreement in spectral peak frequencies for several of the vibration sources

Performance Studies of a Single Vertical Beam Halo Collimation System at ATF2

International audienceIn order to reduce the background that could limit the precision of the diagnostics located in the ATF2 post-IP beamline, a single vertical beam halo collimation system was installed in March 2016. In this paper we present the measurements done in March and May 2016 in order to characterize the collimation system performance. Furthermore, the collimator wakefield impact has also been measured and compared with theoretical calculations and numerical simulations in order to determine the most efficient operation mode of the collimation system in terms of halo cleaning and negligible wakefield impact

ATF2 Beam Halo Collimation System Background and Wakefield Measurements in the 2016 Runs

International audienceA single vertical beam halo collimation system has been installed in ATF2 in March 2016 to reduce the background in the IP and Post-IP region. In this paper, we present the results of an experimental program carried out during 2016 in order to demonstrate the efficiency of the vertical collimation system and measure the wakefields induced by such a system. Furthermore, a comparison of the measurements of the collimation system wakefield impact with CST PS numerical simulations and analytical calculations is also presented

Performance of Nanometre-Level Resolution Cavity Beam Position Monitors at ATF2

International audienceA system of three low-Q cavity beam position monitors (BPMs), installed in the interaction point (IP) region of the Accelerator Test Facility (ATF2) at KEK, has been designed and optimised for nanometre-level beam position resolution. The BPMs are used to provide an input to a low-latency, intra-train beam position feedback system deployed in single-pass, multi-bunch mode with the aim of demonstrating intra-train beam stabilisation on electron bunches of charge ~1 nC separated in time by 280 ns. In 2016 the BPM resolution was demonstrated to be below 50 nm using the raw measured vertical positions at the three BPMs. New results will be presented utilising integrated sampling of the raw waveforms, improved BPM alignment and modified cavities to demonstrate a vertical position resolution on the order of 20 nm

Contribution of IN2P3 to PIP-II Project: Plans and Progress

International audienceIJCLab is one of the labs of IN2P3 (National institute of nuclear and particle physics), one of the ten research institutes composing the French National Center for Scientific Research (CNRS). Since 2018, IJCLab has been involved in the PIP-II project, assisting with the design, development, and qualification of accelerator components for the SSR2 (Single Spoke Resonator type 2) section of the superconducting linac. The first pre-production components (cavity, coupler, and tuner) have been fabricated, and some of the first qualification tests have been performed at IJCLab. This paper will summarize the complete scope of IJCLab¿s contributions to PIP-II and give updates on the performances of the first pre-production components