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Prof. Matthias Liepe (Cornell U.)10/1/18, 9:30 AM
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Dr Ivan Karpov (CERN)10/1/18, 9:45 AMOral presentationThe beam induced power losses and longitudinal coupled-bunch instabilities due to high order modes (HOM) in superconducting radio frequency (RF) cavities can impose significant limitations for the high-current synchrotrons. They strongly depend on the both cavity geometry and filling schemes used in the operation. For the beam stability, the considered HOMs should be damped below a certain...Go to contribution page
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Dr ADOLFO VELEZ (HZB G-ISRF)10/1/18, 11:00 AMOral presentationHZB is pursuing a superconducting upgrade of the BESSY II synchrotron ring in order to allow the machine to simultaneously store both long (15ps) and short (1.7ps) bunches. To achieve this goal higher harmonic cavities (1.5GHz and 1.75GHz) to the 500MHz normal conducting cavities operated in BESSY must be installed. In standard BESSY VSR operation a 300mA beam will be combined with a 20MV/m....Go to contribution page
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Prof. Georg Hoffstaetter (Cornell University)10/1/18, 11:30 AMOral presentationCBETA, the Cornell-BNL ERL Test Accelerator that is currently being constructed at Cornell University combines several forefront accelerator components to a prototyping facility for the Electron-Ion Collider, the US’ next large particle accelerator project. CBETA uses a high-brightness photo-emitter electron source and a high power SRF linac to inject a CW electron beam into a 4-turn ERL. The...Go to contribution page
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Dr Alex Lumpkin (Fermilab)10/1/18, 1:00 PMOral presentationWe report the direct observations of sub-macropulse beam centroid oscillations correlated with higher order modes (HOMs) which were generated by off-axis electron beam steering in TESLA-type SCRF cavities. The experiments were performed at the Fermilab Accelerator Science and Technology (FAST) facility using its unique configuration of a photocathode rf gun injecting beam into two separated...Go to contribution page
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Dr Adam Bartnik (Cornell University)10/1/18, 1:30 PMOral presentationA search for HOMs in Cornell’s ERL main linac cavity installed in a Horizontal Test Cryomodule (HTC) has been carried out using a bunch charge modulation method, as part of the effort towards building an Energy Recovery Linac (ERL). The beam-based HOM measurements offer the significant advantage of being able to detect trapped modes invisible to both the RF pickup probes and HOM damping loads,...Go to contribution page
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Dr Olivier Napoly (FNAL)10/1/18, 2:00 PMOral presentationSuperconducting RF cavities are high quality symmetric resonators that support many different modes of oscillation, with high precision signals and unsurpassable dynamic range. Owing to their approximate axial symmetry, modes can be identified according to their monopole, dipole and quadrupole nature. Higher Order Modes (HOM) excited by bunched beams in SRF cavities hence coupled respectively...Go to contribution page
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Mr Junhao Wei (DESY)10/1/18, 2:30 PMOral presentationFLASH is a free-electron laser driven by a superconducting linac at DESY in Hamburg. It is able to generate high-brilliance XUV and soft X-ray pulses. Many accelerating cavities are equipped with HOMBPMs (Higher Order Mode based Beam Position Monitors) to align the beam and monitor the transverse beam position. We applied an efficient measurement and signal analysis with various data process...Go to contribution page
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William Lou (Cornell University)10/1/18, 3:30 PMOral presentationThe Cornell Brookhaven Energy-Recovery-Linac (ERL) Test Accelerator (CBETA) is currently under construction at the Cornell University's Wilson Laboratory. The primary structures in CBETA for beam recirculation include the Main Linac Cryomodule (MLC) and the FFAG beamline. As the electron bunches pass through the MLC cavities, Higher Order Modes (HOMs) are excited. The recirculating bunches...Go to contribution page
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Mr Nilanjan Banerjee (Cornell University)10/1/18, 4:00 PMOral presentationThe Cornell-BNL ERL Test Accelerator (CBETA) is a new multi-turn high current energy recovery linac currently under construction at Cornell University with a stated goal of 40 mA CW through the injector and 320 mA through the main linac. Higher Order Modes (HOMs) excited by the high current beam will be damped using beamline absorbers and the resulting energy will be converted to heat. In this...Go to contribution page
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ANDREI Lunin (FNAL)10/1/18, 4:30 PMOral presentationProduction and testing of 1.3 GHz cryomodules for the LCLS-II project is ongoing at Fermilab. Each cryomodule is assembled of eight superconducting TESLA-shape elliptical cavities equipped with two High Order Mode (HOM) coupler ports. Measurement of the HOM spectrum is a part of the cavities incoming quality control inspection and the final cryomodule qualification cold test at the Cryomodule...Go to contribution page
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Liling Xiao (SLAC)10/2/18, 9:30 AMOral presentationAbstract: The 1.3GHz 9-cell TESLA cavity has been adopted for the Linac of European X-ray free electron laser (XFEL) and SLAC Linac Coherent Light Source II (LCLS-II). In contrast to the operating modes of the cavities, the beam induced high-order-modes (HOM) will be harmful to the beam quality if they are trapped inside the cavities if not sufficiently damped. The trapped modes below the...Go to contribution page
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Alexander Sukhanov (Fermilab)10/2/18, 10:00 AMOral presentationProton Improvement Plan II (PIP-II) is currently being implemented at Fermilab. Main part of PIP-II is RF linac composed of 5 types of superconducting RF cavies, optimized for acceleration of H- ions in the velocity range from 0.1 to 0.9 of speed of light. Through study of high order modes in PIP-II linac had been performed for 2 mA continues wave operation mode and presented on previous HOMSC...Go to contribution page
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Dr Wencan Xu (bnl)10/2/18, 11:00 AMOral presentationThe RF system of eRHIC e- storage ring has to satisfy wide range of scenarios of eRHIC operation. This presentation will present the considerations and design of the fundamental and high harmonic SRF cavities for the storage ring. And the HOM damping scheme for these cavities will be discussed as well.Go to contribution page
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Mr James Mitchell (CERN)10/2/18, 11:30 AMOral presentationThe Double Quarter Wave (DQW) crab cavity will be installed as part of the High-Luminosity LHC (HL-LHC) upgrade. Proof-of-principle tests are currently on-going in CERN’s Super Proton Synchrotron (SPS). For the tests, the DQW has three on-cell coaxial HOM couplers per cavity. Currently, due to SPS space constraints, the HOM coupler is not optimal and a re-design is necessary for HL-LHC. ...Go to contribution page
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Dr Andranik Tsakanian (Helmholtz-Zentrum Berlin)10/2/18, 1:00 PMOral presentationThe BESSY Variable pulse length Storage Ring (VSR) project is a future upgrade of the 3rd generation BESSY II light source. The key feature of the project is the simultaneous storage of long (ca. 15 ps) and short (ca. 1.7 ps) electron bunches under “standard” user optics. This challenging goal requires installation of SRF higher harmonic cavities of the fundamental 500 MHz at two different...Go to contribution page
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Jiquan Guo (JLAB)10/2/18, 1:45 PMOral presentationTwo accelerator projects at Helmholtz-Zentrum Berlin (HZB), bERLinPro and BESSY-VSR (Variable pulse length Storage Ring) upgrade, need to design three variants of SRF cavities, 1.3GHz cavities for bERLinPro and 1.5GHz/1.75GHz cavities for BESSY-VSR. These cavities have adopted waveguide HOM dampers in their design, with a few tens of watts HOM power in each load for bERLinPro cavities and a...Go to contribution page
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James Maniscalco10/2/18, 2:15 PMOral presentationRecent research into impurity-doped niobium and Nb3Sn have pushed towards unprecedentedly high quality factors and low cryogenic power consumption for SRF accelerators. These open the way to high frequency cavities (above the 1.3 GHz standard in contemporary SRF projects such as EXFEL and LCLS-II) which could significantly decrease costs for new accelerator facilities. In this talk we provide...Go to contribution page
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Erk Jensen (CERN), Prof. Ursula van Rienen (University of Rostock)10/2/18, 3:15 PM
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Mr Shahnam Gorgi Zadeh (Universität Rostock)10/3/18, 9:30 AMOral presentationAn $e^+e^-$ collider is foreseen in the design of future circular collider (FCC-ee) to make precise measurements of the properties of the Z, W, H bosons and the top quark ($\text{t}\bar{\text{t}}$). The two limiting cases from the SRF point of view are the Z operation which is characterized by low voltage and high beam current (1.39 A) and the $\text{t}\bar{\text{t}}$ operation which requires...Go to contribution page
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Jiquan Guo (JLAB)10/3/18, 10:00 AMOral presentationThe JLab Electron-Ion Collider (JLEIC) proposed by Jefferson Lab is a high luminosity collider consists of a few high current sub-complexes, including a 3-12 GeV electron collider ring with up to 3 A beam current, a 20-100 GeV ion collider ring of up to 1 A, and a 20-55 MeV circulation bunched electron cooler ring with up to 1.5 A. Beam induced HOM problems are prevalent in the RF systems of...Go to contribution page
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Dr Nasrin Nasresfahani (Beams Department, RF Group, Beams and RF Studies Section)10/3/18, 11:00 AMOral presentationExtensive beam dynamic studies conducted in the framework of LIU (LHC Injectors Upgrade) project revealed a serious intensity limitation due to HOMs of the 200 MHz travelling wave cavities (TWCS) of SPS in the frequency range of 629-630 MHz. However, finding appropriate distributed damping scheme in cavities with large number of cells (like TWCs of SPS) usually accompanied with the...Go to contribution page
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Prof. Ursula van Rienen (University of Rostock)10/3/18, 11:30 AMOral presentationThe characterization of higher order modes in chains of superconducting cavities with couplers is a challenging task that is typically accomplished using high-performance computers in combination with dedicated software packages. During the last years, an alternative approach has been developed at the University of Rostock. It is referred to as State-Space Concatenations (SSC) and allows for...Go to contribution page
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Prof. Matthias Liepe (Cornell U.)10/3/18, 12:00 PM
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