| Paper | Title | Page |
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| WEPE033 | Considerations for a Dielectric-based Two-beam-accelerator Linear Collider | 3428 |
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In this paper, we present a linear collider concept based on drive beam generation from an RF photoinjector, and employing dielectric structures for power extraction and acceleration. The collider is based on a modular design with each module providing 100 GeV net acceleration. A high current drive beam is produced using a low frequency RF gun (~ 1GHz), and subsequently accelerated to ~1 GeV using conventional standing wave cavities. High frequency (20 GHz) RF power, extracted from the drive beam using a low impedance dielectric structure, is used to power the main linacs, which are based on high impedance high gradient dielectric loaded accelerating structures. We envision this scheme will produce high gradients (300 MeV/m), leading to a very compact design. The modularity of the design will allow a staged construction that will enable extension to multi-TeV energies. |
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| THPD016 | Upgrade of the Drive LINAC for the AWA Facility Dielectric Two-Beam Accelerator | 4310 |
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We report on the design of a 7 cell, standing wave, 1.3 GHz LINAC cavity and the associated beam dynamics studies for the upgrade of the drive beamline for the Argonne Wakefield Accelerator (AWA) facility. The LINAC design is a compromise between single bunch operation (100 nC @ 75 MeV) and minimizing the energy droop due to beam loadning along the bunch train during bunch train operation. The 1.3 GHz drive bunch train target parameters are: 75 MeV, 10-20 ns macropulse duration, 16x60nC microbunches; this is equivalent to a macropulse current and beam power of 80 Amps and 6 GW, respectively. Each LINAC structure accelerates approximately 1000 nC in 10 ns by a voltage of 11 MV at an RF power of 10 MW. Due to the short bunch train duration desired (~10 ns) and the existing frequency (1.3 GHz), compensation of the energy droop along the bunch train is difficult to accomplish with the two standard techniques: time-domain or frequency-domain beam loading compensation. Therefore, to minimize the energy droop, our design is based on a large stored energy LINACs. In this paper, we present our LINAC optimization method, detailed LINAC design, and beam dynamics studies of the drive beamline. |
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| THPD062 | Argonne Wakefield Accelerator Facility (AWA) Upgrades | 4425 |
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The AWA Facility is dedicated to the study of advanced accelerator concepts based on electron beam driven wakefields. The facility employs an L-band photocathode RF gun to generate high charge short electron bunches, which are used to drive wakefields in dielectric loaded structures, as well as in metallic structures. Accelerating gradients as high as 100 MV/m have been reached in dielectric structures, and RF pulses of up to 44 MW have been generated at 7.8 GHz. In order to reach higher accelerating gradients and higher RF power levels, several upgrades are underway: (a) a new RF gun with higher QE photocathode will replace the present drive gun; (b) the existing RF gun will generate a witness beam to probe the wakefields; (c) three new 25 MW L-band RF power stations will be added to the facility; (d) five additional linac structures will bring the beam energy up from 15 MeV to 75 MeV. The drive beam will consist of bunch trains of up to 32 bunches, with up to 60 nC per bunch. The goal of future experiments is to reach accelerating gradients of several hundred MV/m and to extract RF pulses with GW power level. |
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| THPD066 | Observation of Wakefields in a Beam-Driven Photonic Band Gap Accelerating Structure | 4431 |
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Wakefield excitation has been experimentally studied in a 3-cell X-band standing wave Photonic Band Gap (PBG) accelerating structure. Major monopole (TM01- and TM02-like) and dipole (TM11- and TM12-like) modes were indentified and characterized by precisely controlling the position of beam injection. The quality factor Q of the dipole modes was measured to be ~10 times smaller than that of the accelerating mode. A charge sweep, up to 80 nC, has been performed, equivalent to ~30 MV/m accelerating field on axis. A variable delay low charge witness bunch following a high charge drive bunch was used to calibrate the gradient in the PBG structure by measuring its maximum energy gain and loss. Experimental results agree well with numerical simulations. |
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| THPD067 | The First Experiment of a 26 GHz Dielectric Based Wakefield Power Extractor | 4434 |
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High frequency, high power rf sources are needed for many applications in particle accelerators, communications, radar, etc. We have developed a 26GHz high power rf source based on the extraction of wakefields from a relativistic electron beam. The extractor is designed to couple out rf power generated from a high charge electron bunch train traversing a dielectric loaded waveguide. The first high beam experiment has been performed at Argonne Wakefield Accelerator facility. The experimental results successfully demonstrate the 15ns 26GHz rf pulse generated from the wakefield extractor with a bunch train of 16 bunches. Meanwhile, ~ 30MW short rf pulse has been achieved with a bunch train of 4 bunches. Beam Breakup has prevented charge transport through the power extractor beyond 10nC. We are doing simulations and developing methods to alleviate the BBU effect. |
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| THPD068 | Experiment on a Tunable Dielectric-Loaded Accelerating Structure | 4437 |
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Dielectric-Loaded Accelerating (DLA) structures are generally lack of approaches to tune frequency after the fabrication. A tunable DLA structure has been developed by using an extra nonlinear ferroelectric layer. Dielectric constant of the applied ferroelectric material is sensitive to temperature and DC voltage. Bench test shows the +14MHz/°C, and 6MHz frequency tuning range for a 25kV/cm of DC bias field. A beam test is planned at Argonne Wakefield Accelerator facility before the IPAC conference. Detailed results will be reported. |