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| MOP016 | SRF Linac Solutions for 4GLS at Daresbury | linac, acceleration, electron, superconducting-RF | 64 | ||
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The proposed 4th Generation Light Source (4GLS) facility, anticipated to be located at Daresbury Laboratory in the UK, will extensively utilise Superconducting RF (SRF) Linacs for each stage of its multi-beam acceleration. IR, XUV and VUV FEL devices, and particularly the ability to combine these sources for users, provide a unique capability for this Energy Recovery Linac (ERL) based accelerator. The CW mode of operation for the SRF Linacs necessitates that adequate provision is made for delivering the required RF power and also damping of the beam induced HOMs to manageable levels. This paper outlines the RF requirements and proposed solutions for each of the 4GLS Linacs.
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| MOP066 | Wake Fields and Beam Dynamics Simulations for the 3.9-GHz Cavities of the ILC | emittance, simulation, luminosity, dipole | 196 | ||
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Crab cavities are used for the ILC in order to increase the luminosity of the colliding beams. These cavities operate at the 3rd harmonic of the accelerating frequency (1.3GHz). We study the LOM (Lower Order Modes) and HOM (Higher Order Modes) excited by the beam. The corresponding wake field is calculated and simulations are conducted on the beam dynamics of the interaction of the wake field with the multi-bunch beam train.
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| TUP017 | A Damper System for the Electron Cooling Beam in the Recycler | electron, antiproton, feedback, controls | 283 | ||
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The antiproton stacking rate in the Fermilab Recycler has been dramatically improved with the commissioning of the Electron Cooling system last year. Various disturbance sources such as mechanical vibrations in the Pelletron , power line fluctuations and coupling from beam ramps in the nearby Main Injector have added noise components in the electron beam position in the 0.5 to 200 Hz range. An AC coupled damping feedback loop with corrector coils for horizontal and vertical position correction at two upstream points from the BPMs was added to the existing BPM system . The system provides 10 – 20 dB damping in the frequency range above without interfering with other DC beam positioning control loops.
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| TUP062 | Experimental Optimization of TTF2 RF Photoinjector for Emittance Damping | emittance, booster, gun, laser | 391 | ||
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To get lasing and saturation at FEL facilities, we should generate high quality electron beams with a low emittance, a high peak current, and a low energy spread. Generally, the RF photoinjector is a key component to generate such a high quality beams. During DESY TESLA Test Facility (TTF) phase 2 commissioning, we optimized our L-band RF photoinjector and bunch compressor by comparing measurement results and simulation ones. In this paper, we describe our optimization experiences to get about 1.1 mm.mrad transverse normalized emittance for 1.0 nC single bunch charge and 4.4 ps RMS bunch length from TTF phase 2 RF photoinjector.
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| WE2005 | HOM Damping and Power Extraction from Superconducting Cavities | linac, coupling, impedance, electron | 506 | ||
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Damping of Higher Order Modes plays an important role in achieving and preserving low emittance and low energy modulation of beams in accelerators based on the superconducting technology. In the overview, various damping schemes and damping devices and their advantages and disadvantages will be discussed.
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| THP048 | Band Gap Structures of PBG and Rod-loaded Cavities | dipole, lattice, klystron, quadrupole | 688 | ||
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The band-gap structures for rod loaded (RL) and photonic band gap (PBG) cavities are calculated with 2D and 3D frequency domain codes. It is shown that an RL cavity with a single circle of rods can exhibit similar behavior as a conventional single-defect PBG cavity. A systematic method of computing the unloaded Q factor using SUPERFISH has been implemented. Results are compared with GdfidL and Gd1 calculations.
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| THP059 | Coaxial HOM Coupler Designs Tested on a Single-Cell Niobium Cavity | coupling, pick-up, vacuum, simulation | 716 | ||
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Coaxial higher order mode (HOM) couplers have been developed for HERA cavities and are used in TESLA, SNS and Jlab upgrade cavities. The principle of operation is the rejection of the fundamental mode by the tunable filter of the coupler and the transmission of the HOMs. It has been recognized recently that inappropriate thermal designs of the feed through for the pick-up probe of the HOM coupler will not sufficiently carry away the heat generated in the probe tip by the fundamental mode fields, causing a built-up of the heating of the niobium probe tip and subsequently, a deterioration of the cavity quality factor has been observed in cw operation. An improvement of the situation has been realized by a better thermal design of the feed through incorporating a sapphire rf window [1]. An alternative is a modification of the coupler loop (“F” – part) with an extension towards the pick-up probe. This design has been tested on a single cell niobium cavity in comparison to a “standard TESLA” configuration. by measuring the Eacc behavior at 2 K. The measurements clearly indicate that the modified version of the coupler loop is thermally much more stable than the standard version.
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[1] C. Reece et al; http://accelconf.web.cern.ch/accelconf/, paper TPPT082 |
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