Creep tests on salt samples performed at very small stresses

International audienc

Early Phase 2 Results of LumiBelle2 for the SuperKEKB Electron Ring

International audienceWe report on the early SuperKEKB Phase 2 operations of the fast luminosity monitor (LumiBelle2 project). Fast luminosity monitoring is required by the dithering feedback system, which is used to stabilize the beam in the presence of horizontal vibrations. In this report, we focus on the operations related to the electron side of LumiBelle2. Diamond sensors are located 30 meters downstream of the IP, just above, beside, and below the electron beam pipe. During early Phase 2, the sensors are used to measure the background, arising from beam-gas scattering. We present the hardware design, the detection algorithm, and the analysis of the background measurements taken up-to-date. The results are then compared with a detailed simulation of the background, in order to well understand the physical processes involved. The simulation is performed using SAD for generation and tracking purposes, while Geant4 is used to calculate the energy deposition in the diamond sensors

Creep tests on salt samples performed at very small stresses

International audienc

Preparation of CVD Diamond Detector for fast Luminosity Monitoring of SuperKEKB

International audienceThe SuperKEKB e⁺-e⁻ collider aims to reach a very high luminosity of 8×10 ³⁵ cm'2s'1, using highly focused ultra-low emittance bunches colliding every 4ns. To meet the requirement of the dithering feedback system used to stabilize the horizontal orbit at the IP (interaction point), a relative precision of 10 '3 in 1ms is specified for the fast luminosity monitoring, which can be in principle achieved thanks to the large cross section of the radiative Bhabha process. This paper firstly presents the fraction of detected Bhabha scattering positrons with a new beam pipe arrangement coupled with a Tungsten radiator to be installed in the Low Energy Ring; Then the characteristics of signals from a sCVD diamond detector with thickness of 140'm coupled with a broadband current amplifier were studied based on tests with a Sr-90 source; Finally, simulated results for the reconstructed luminosity and the relative precision with different assumed luminosities are also reported

Fast Luminosity Monitoring for the SuperKEKB Collider (LumiBelle2 Project)

International audienceLumiBelle2 is a fast luminosity monitoring system prepared for SuperKEKB*. It uses sCVD diamond detectors placed in both the electron and positron rings to measure the Bhabha scattering process at vanishing scattering angle. Two types of online luminosity signals are provided, a Train-Integrated-Luminosity at 1 kHz as input to the dithering feedback system used to maintain optimum overlap between the colliding beams in horizontal plane, and Bunch-Integrated-Luminosities at about 1 Hz to check for variations along the bunch trains. Individual beam sizes and offsets can also be determined from collision scanning. The design of LumiBelle2 will be described and its performance during the Phase-2 commissioning of SuperKEKB will be reported

First Tests of Superkekb Fast Luminosity Monitors During 2018 Phase-2 Commissioning

International audienceThe SuperKEKB e⁺e⁻ collider aims to reach a very high luminosity of 8× 10³⁵ cm⁻²s⁻¹, by using highly focused ultra-low emittance bunches colliding every 4 ns, it is essential to have an orbit feedback system at the Interaction Point (IP) to maintain the optimum overlap between two colliding beams. Luminosity monitoring systems including LumiBelle2 and ZDLM as input to dithering feedback system used to stabilize the horizontal orbit at the IP were developed and will be described, including the detectors, mechanical set-up, DAQ. Preliminary measurements and analysis of background and first stage luminosity monitoring data collected will be reported and compared with simulation

First Tests of SuperKEKB Luminosity Monitors during 2016 Single Beam Commissioning

International audienceThe SuperKEKB e⁺e⁻ collider aims to reach a very high luminosity of 8 10³⁵ cm⁻²s^{−1}, using highly focused ultra-low emittance bunches colliding every 4ns. Fast luminosity monitoring is required for luminosity feedback and optimisation in presence of dynamic imperfections. The aimed relative precision is about 10⁻³ in 1ms, which can be in principle achieved thanks to the very large cross-section of the radiative Bhabha process at zero degree scattering angle. Diamond, Cherenkov and scintillator sensors are to be placed just outside the beam pipe, downstream of the interaction point in both rings, at locations with event rates consistent with the aimed precision and small enough backgrounds from single-beam particle losses. The initial configuration installed for the 2016 "phase 1" single beam commissioning will be described, including the sensors, mechanical setup, readout electronics and first stage DAQ. Preliminary measurements and analysis of beam gas Bremsstrahlung loss data collected with the luminosity monitors will be reported and compared with a detailed simulation, for several experimental conditions during the SuperKEKB commissioning

Recent Progress of Dithering System at SuperKEKB

International audienceRecent progress of the dithering system at SuperKEKB is described. Some details of the system layout are shown. Beam orbit and optics related issues are discussed. Preliminary tests of the some components in the Phase 1 beam commissioning or in the bench are described