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Beam Based HOM Analysis of Accelerating Structures at the TESLA Test Facility Linac

Description: The beam emittance in future linear accelerators for high energy physics and SASE-FEL applications depends highly on the field performance in the accelerating structures, i.e. the damping of higher order modes (HOM). Besides theoretical and laboratory analysis, a beam based analysis technique was established [1] at the TESLA Test Facility (TTF) linac. It uses a charge modulated beam of variable modulation frequency to excite dipole modes. This causes a modulation of the transverse beam displacement, which is observed at a downstream BPM and associated with a direct analysis of the modes at the HOM-couplers. A brief introduction of eigenmodes of a resonator and the concept of the wake potential is given. Emphasis is put on beam instrumentation and signal analysis aspects, required for this beam based HOM measurement technique.
Date: August 9, 2005
Creator: Wendt, M.; Schreiber, S.; Castro, P.; Gossel, A.; /DESY; Huning, M. et al.
Partner: UNT Libraries Government Documents Department

The 2mrad horizontal crossing angle IR layout for a TeV ILC

Description: The current status of the 2mrad crossing angle layout for the ILC is reviewed. The scheme developed in the UK and France is described and the performance discussed for a TeV machine. Secondly, the scheme developed at SLAC and BNL is then studied and modified for a TeV machine. We find that both schemes can handle the higher energy beam with modifications, and share many common features.
Date: July 27, 2005
Creator: Appleby, R.; Angal-Kalinin, D.; /Daresbury; Bambade, P.; Mouton, B.; /Orsay, LAL et al.
Partner: UNT Libraries Government Documents Department

Monitoring the FLASH Cryomodule Transportation from DESY Hamburg to CEA Saclay: Coupler Contact, Vacuum, Acceleration and Vibration Analysis

Description: With a view to the series production of one hundred, 12 m long XFEL 1.3 GHz cryomodules and their transportation from the assembly site at CEA Saclay (F) to the installation site at DESY Hamburg (D) a test transportation of a FLASH cryomodule has been performed, in the condition foreseen for the mass transportation. The present study examines the stresses induced on the module and verifies the damping capabilities of the transport frame in order to minimize risk of damage to the most critical components. During the transportation, acceleration and vibration have been monitored as well as coupler antenna contacts and vacuum performances. This paper describes the analysis performed and compares those results to the data of a similar transportation study at Fermilab for the CM1 cryomodule.
Date: May 1, 2009
Creator: Barbanotti, S.; Bosotti, A.; Fusetti, M.; Michelato, P.; Bertolini, A.; Berry, S. et al.
Partner: UNT Libraries Government Documents Department

Optimization of Beam Injection Into the First Accelerating Module at TTF With Cavity Dipole Mode Signals

Description: The TESLA Test Facility (TTF) is a user facility for intense VUV-FEL light. The facility is densely equipped with diagnostics, essential in obtaining the necessary beam parameters, in particular the low emittance. However there is no dedicated component for alignment of the beam in the accelerating modules, each containing eight superconducting cavities. Large beam offsets can lead to an increase of the beam emittance. The centering of the beam in these modules is therefore important, mostly at the low energy end. A misalignment of the first TTF module with respect to the gun axis has already been observed using cavity dipole modes. This paper presents the experimental results of the optimization of the beam injection into the first module, based on the monitoring of dipole modes through the couplers installed for wakefield damping. For this we use a spectrum analyzer together with a multiplexer. By scanning the beam position and tilt with two pairs of steerers, we can find the trajectory which minimizes the dipole modes amplitude. The impact of the beam steering in the module on the beam is discussed. A time domain setup is also being presented.
Date: April 10, 2006
Creator: Baboi, N.; Kreps, G.; Schlarb, H.; Wendt, M.; Frisch, J.; McCormick, D. et al.
Partner: UNT Libraries Government Documents Department

Using higher order modes in superconducting accelerating cavities for beam monitoring

Description: Dipole modes have been shown to be successful diagnostics for the beam position in superconducting accelerating cavities at the Free Electron Laser in Hamburg (FLASH) facility at DESY. By help of downmixing electronics the signals from the two higher order mode (HOM) couplers mounted on each cavity are monitored. The calibration, based on sigular value decomposition, is more complicated than in standard position monitors. Position like signals based on this calibration are currently being in the process of being included in the control system. A second setup based on digitizing the spectrum from the HOM couplers has been used for monitoring monopole modes. The beam phase with respect to the RF has been thus monitored. The position calibration measurements and phase monitoring made at the FLASH are presented.
Date: January 1, 2006
Creator: Molloy, S.; Baboi, N.; Eddy, N.; Frisch, J.; Hendrickson, L.; Hensler, O. et al.
Partner: UNT Libraries Government Documents Department

Cavity Alighment Using Beam Induced Higher Order Modes Signals in the TTF Linac

Description: Each nine cell superconducting (SC) accelerator cavity in the TESLA Test Facility (TTF) at DESY [1] has two higher order mode (HOM) couplers that efficiently remove the HOM power [2]. They can also provide useful diagnostic signals. The most interesting modes are in the first 2 cavity dipole passbands. They are easy to identify and their amplitude depends linearly on the beam offset from the cavity axis making them excellent beam position monitors (BPM). By steering the beam through an eight-cavity cryomodule, we can use the HOM signals to estimate internal residual alignment errors and minimize wakefield related beam emittance growth. We built and tested a time-domain based waveform recorder system that captures information from each mode in these two bands on each beam pulse. In this paper we present a preliminary experimental study of the single-bunch generated HOM signals at the TTF linac including estimates of cavity alignment precision and HOM BPM resolution.
Date: July 6, 2005
Creator: Ross, M.; Frisch, J.; Hacker, K.E.; Jones, R.M.; McCormick, D.; O'Connell, C. et al.
Partner: UNT Libraries Government Documents Department

High Precision Superconducting Cavity Diagnostics With Higher Order Mode Measurements

Description: Experiments at the FLASH facility at DESY have demonstrated that the higher order modes induced in superconducting cavities can be used to provide a variety of beam and cavity diagnostics. The axes of the modes can be determined from the beam orbit that produces minimum power in the dipole HOM modes. The phase and amplitude of the dipole modes can be used to obtain high resolution beam position information, and the phase of the monopole modes to measure the beam phase relative to the accelerator rf. For most superconducting accelerators, the existing higher order mode couplers provide the necessary signals, and the downmix and digitizing electronics are straightforward, similar to those for a conventional beam position monitor.
Date: February 12, 2007
Creator: Molloy, S.; Frisch, J.; McCormick, D.; May, J.; Ross, M.; Smith, T. et al.
Partner: UNT Libraries Government Documents Department

Using Higher Order Modes in Superconducting Accelerating Cavities for Beam Monitoring

Description: Dipole modes have been shown to be successful diagnostics for the beam position in superconducting accelerating cavities at the Free Electron Laser in Hamburg (FLASH) facility at DESY. By help of downmixing electronics the signals from the two higher order mode (HOM) couplers mounted on each cavity are monitored. The calibration, based on singular value decomposition, is more complicated than in standard position monitors. Position like signals based on this calibration are currently being in the process of being included in the control system. A second setup based on digitizing the spectrum from the HOM couplers has been used for monitoring monopole modes. The beam phase with respect to the RF has been thus monitored. The position calibration measurements and phase monitoring made at the FLASH are presented.
Date: March 7, 2008
Creator: Molloy, S.; Baboi, N.; Eddy, N.; Frisch, J.; Hendrickson, L.; Hensler, O. et al.
Partner: UNT Libraries Government Documents Department

The 2mrad Crossing Angle Interaction Region and Extraction Line

Description: A complete optics design for the 2mrad crossing angle interaction region and extraction line was presented at Snowmass 2005. Since this time, the design task force has been working on developing and improving the performance of the extraction line. The work has focused on optimizing the final doublet parameters and on reducing the power losses resulting from the disrupted beam transport. In this paper, the most recent status of the 2mrad layout and the corresponding performance are presented.
Date: July 12, 2006
Creator: Appleby, R.; U., Manchester; Angal-Kalinin, D.; Tech, /Cockcroft Inst. Accel. Sci.; Dadoun, O.; Bambade, P. et al.
Partner: UNT Libraries Government Documents Department

Beam Position Monitoring with Cavity Higher Order Modes in the Superconducting Linac FLASH

Description: FLASH (Free Electron Laser in Hamburg) is a user facility for a high intensity VUV-light source [1]. The radiation wavelength is tunable in the range from about 40 to 13 nm by changing the electron beam energy from 450 to 700 MeV. The accelerator is also a test facility for the European XFEL (X-ray Free Electron Laser) to be built in Hamburg [2] and the project study ILC (International Linear Collider) [3]. The superconducting TESLA technology is tested at this facility, together with other accelerator components.
Date: March 20, 2007
Creator: Baboi, N.; Molloy, S.; Eddy, N.; Frisch, J.; Hendrickson, L.; Hensler, O. et al.
Partner: UNT Libraries Government Documents Department

Design of an Interaction Region with Head-On Collisions for the ILC

Description: An interaction region (IR) with head-on collisions is considered as an alternative to the baseline configuration of the International Linear Collider (ILC) which includes two IRs with finite crossing-angles (2 and 20 mrad). Although more challenging for the beam extraction, the head-on scheme is favored by the experiments because it allows a more convenient detector configuration, particularly in the forward region. The optics of the head-on extraction is revisited by separating the e+ and e- beams horizontally, first by electrostatic separators operated at their LEP nominal field and then using a defocusing quadrupole of the final focus beam line. In this way the septum magnet is protected from the beamstrahlung power. Newly optimized final focus and extraction optics are presented, including a first look at post-collision diagnostics. The influence of parasitic collisions is shown to lead to a region of stable collision parameters. Disrupted beam and beamstrahlung photon losses are calculated along the extraction elements.
Date: July 12, 2006
Creator: Appleby, R.; U., /Cockcroft Inst. Accel. Sci. Tech. /Manchester; Angal-Kalinin, D.; Jackson, F.; /Daresbury; Alabau-Pons, M . et al.
Partner: UNT Libraries Government Documents Department

Technical Challenges for the Head-on Collisions and Extraction at the ILC

Description: An interaction region with head-on collisions is considered as an alternative to the baseline ILC configuration. Progress in the final focus optics design includes engineered large bore superconducting final doublet magnets and their 3D magnetic integration in the detector solenoids. Progress on the beam separation optics is based on technical designs of electrostatic separator and special extraction quadrupoles. The spent beam extraction is realized by a staged collimation scheme relying on realistic collimators.
Date: August 14, 2007
Creator: Napoly, O.; Delferriere, O.; Durante, M.; Payet, J.; Rippon, C.; Uriot, D. et al.
Partner: UNT Libraries Government Documents Department

ATF2 Proposal Volume 2

Description: For achieving the high luminosity required at the International Linear Collider (ILC), it is critical to focus the beams to nanometer size with the ILC Beam Delivery System (BDS), and to maintain the beam collision with a nanometer-scale stability. To establish the technologies associated with this ultra-high precision beam handling, it has been proposed to implement an ILC-like final focus optics in an extension of the existing extraction beamline of ATF at KEK. The ATF is considered to be the best platform for this exercise, since it provides an adequate ultra-low emittance electron beam in a manner dedicated to the development of ILC. The two major goals for this facility, called ATF2, are: (A) Achievement of a 37 nm beam size, and (B) control of beam position down to 2 nm level. The scientific justification for the ATF2 project and its technical design have been described in Volume 1 of the ATF2 Proposal [1]. We present here Volume 2 of the ATF2 Proposal, in which we present specifics of the construction plans and the group organization to execute the research programs at ATF2. The sections in this report have been authored by relevant ATF2 subgroups within the International ATF Collaboration. The time line of the project is described in Section 2. Section 3 discuss the structure of the international collaboration. Sections 4 and 5 discuss budget considerations, which are presented as well as the design and construction tasks to be shared by the international collaboration at ATF2. Concluding remarks have been contributed by Dr. Ewan Paterson, Chair of the International Collaboration Board of the ATF collaboration.
Date: February 27, 2006
Creator: Grishanov, B.I.; Logachev, P.; Podgorny, F.; Telnov, V.; /Novosibirsk, IYF; Angal-Kalinin, D. et al.
Partner: UNT Libraries Government Documents Department