Dr
Ivan Karpov
(CERN)
10/1/18, 9:45 AM
Oral presentation
The 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...
Dr
ADOLFO VELEZ
(HZB G-ISRF)
10/1/18, 11:00 AM
Oral presentation
HZB 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....
Prof.
Georg Hoffstaetter
(Cornell University)
10/1/18, 11:30 AM
Oral presentation
CBETA, 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...
Dr
Alex Lumpkin
(Fermilab)
10/1/18, 1:00 PM
Oral presentation
We 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...
Dr
Adam Bartnik
(Cornell University)
10/1/18, 1:30 PM
Oral presentation
A 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,...
Dr
Olivier Napoly
(FNAL)
10/1/18, 2:00 PM
Oral presentation
Superconducting 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...
Mr
Junhao Wei
(DESY)
10/1/18, 2:30 PM
Oral presentation
FLASH 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...
William Lou
(Cornell University)
10/1/18, 3:30 PM
Oral presentation
The 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...
Mr
Nilanjan Banerjee
(Cornell University)
10/1/18, 4:00 PM
Oral presentation
The 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...
ANDREI Lunin
(FNAL)
10/1/18, 4:30 PM
Oral presentation
Production 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...
Liling Xiao
(SLAC)
10/2/18, 9:30 AM
Oral presentation
Abstract: 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...
Alexander Sukhanov
(Fermilab)
10/2/18, 10:00 AM
Oral presentation
Proton 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...
Dr
Wencan Xu
(bnl)
10/2/18, 11:00 AM
Oral presentation
The 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.
Mr
James Mitchell
(CERN)
10/2/18, 11:30 AM
Oral presentation
The 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. ...
Dr
Andranik Tsakanian
(Helmholtz-Zentrum Berlin)
10/2/18, 1:00 PM
Oral presentation
The 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...
Jiquan Guo
(JLAB)
10/2/18, 1:45 PM
Oral presentation
Two 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...
James Maniscalco
10/2/18, 2:15 PM
Oral presentation
Recent 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...
Erk Jensen
(CERN), Prof.
Ursula van Rienen
(University of Rostock)
10/2/18, 3:15 PM
Mr
Shahnam Gorgi Zadeh
(Universität Rostock)
10/3/18, 9:30 AM
Oral presentation
An $e^+e^-$ 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...
Jiquan Guo
(JLAB)
10/3/18, 10:00 AM
Oral presentation
The 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...
Dr
Nasrin Nasresfahani
(Beams Department, RF Group, Beams and RF Studies Section)
10/3/18, 11:00 AM
Oral presentation
Extensive 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...
Prof.
Ursula van Rienen
(University of Rostock)
10/3/18, 11:30 AM
Oral presentation
The 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...
