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ADVANCED ACCELERATOR CONCEPTS: Eleventh Advanced Accelerator Concepts Workshop Date: 21-26 June 2004 Location: Stony Brook, New York (USA) ISBN: 0-7354-0220-5 Editor(s): Vitaly Yakimenko

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Review of Beam Driven Plasma Wakefield Accelerators

C. Joshi

AIP Conf. Proc. 737, pp. 3-10; doi:http://dx.doi.org/10.1063/1.1842531 (8 pages)

Online Publication Date: 14 December 2004

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The current status of the beam‐driven plasma wakefield accelerators is reviewed. © 2004 American Institute of Physics
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52.40.Mj Particle beam interactions in plasmas
52.59.-f Intense particle beams and radiation sources
41.75.Fr Electron and positron beams

Advances in Laser Driven Accelerator R&D

Wim Leemans

AIP Conf. Proc. 737, pp. 11-28; doi:http://dx.doi.org/10.1063/1.1842532 (18 pages) | Cited 1 time

Online Publication Date: 14 December 2004

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Current activities (last few years) at different laboratories, towards the development of a laser wakefield accelerator (LWFA) are reviewed, followed by a more in depth discussion of results obtained at the L’OASIS laboratory of LBNL. Recent results on laser guiding of relativistically intense beams in preformed plasma channels are discussed. The observation of mono‐energetic beams in the 100 MeV energy range, produced by a channel guided LWFA at LBNL, is described and compared to results obtained in the unguided case at LOA, RAL and LBNL. Analysis, aided by particle‐in‐cell simulations, as well as experiments with various plasma lengths and densities, indicate that tailoring the length of the accelerator has a very beneficial impact on the electron energy distribution. Progress on laser triggered injection is reviewed. Results are presented on measurements of bunch duration and emittance of the accelerated electron beams, that indicate the possibility of generating femtosecond duration electron bunches. Future challenges and plans towards the development of a 1 GeV LWFA module are discussed. © 2004 American Institute of Physics
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52.38.Kd Laser-plasma acceleration of electrons and ions
41.75.Jv Laser-driven acceleration
41.75.Ht Relativistic electron and positron beams
52.65.Rr Particle-in-cell method

Advanced Accelerator System Requirements for Future Linear Colliders

G. Dugan

AIP Conf. Proc. 737, pp. 29-60; doi:http://dx.doi.org/10.1063/1.1842533 (32 pages) | Cited 2 times

Online Publication Date: 14 December 2004

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This paper will review the requirements on advanced accelerator systems as applied to next‐generation linear colliders. The design issues and requirements for TeV‐scale linear colliders will be discussed, and the challenges involved in developing affordable extensions to higher energies, utilizing advanced accelerator concepts, will be presented. © 2004 American Institute of Physics
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41.75.Lx Other advanced accelerator concepts

EM Structures and Laser Acceleration

Levi Schächter

AIP Conf. Proc. 737, pp. 61-74; doi:http://dx.doi.org/10.1063/1.1842534 (14 pages)

Online Publication Date: 14 December 2004

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Several dielectric optical acceleration structures that have been designed in recent years are being compared. The unique properties of these structures entail challenging design of an overall acceleration module. Four possible configurations are being analyzed. Two important concepts are discussed: train of micro‐bunches and feedback loop. While the former facilitates acceleration of a large number of electrons, the latter enables energy recovery leading to higher efficiency. Their implications are considered and some rough estimates of luminosity are considered. © 2004 American Institute of Physics
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41.75.Jv Laser-driven acceleration
41.75.Lx Other advanced accelerator concepts

Advances in simulation capability: A path towards modeling 10–100 GeV plasma accelerator stages

W. B. Mori

AIP Conf. Proc. 737, pp. 75-85; doi:http://dx.doi.org/10.1063/1.1842535 (11 pages)

Online Publication Date: 14 December 2004

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A path towards modeling 10–100 GeV plasma accelerator stages is described. Modeling such stages including the self‐consistent evolution of the driver, the plasma dynamics, and the beam loading of the trailing particles necessitates the use of particle methods. In a previous proceedings, I reviewed the status of particle based methods and stated that new methods needed to be developed if one hoped to routinely model the full scale in three‐dimensions of 10+ GeV plasma accelerator stages. In this article, I describe the development of a new fully parallelized algorithm that reproduces the results from standard particle‐in‐cell methods with at least a 100 times savings in CPU time. I also describe how standard methods are being used to discover new physics. © 2004 American Institute of Physics
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52.40.Mj Particle beam interactions in plasmas
52.30.-q Plasma dynamics and flow
52.65.Rr Particle-in-cell method

An Afterburner at the ILC: The Collider Viewpoint

Tor O. Raubenheimer

AIP Conf. Proc. 737, pp. 86-94; doi:http://dx.doi.org/10.1063/1.1842536 (9 pages)

Online Publication Date: 14 December 2004

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The concept of a high‐gradient plasma wakefield accelerator is considered as an upgrade path for the International Linear Collider, a future linear collider. Basic parameters are presented based on those developed for the SLC “Afterburner.” Basic layout considerations are described and the primary concerns related to the collider operation are discussed. © 2004 American Institute of Physics
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52.40.Mj Particle beam interactions in plasmas

Longitudinal Phase Space Measurements of Short Electron Bunches Using a 17 GHz Circularly Polarized Beam Deflector

J. Haimson

AIP Conf. Proc. 737, pp. 95-108; doi:http://dx.doi.org/10.1063/1.1842537 (14 pages)

Online Publication Date: 14 December 2004

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Operation of a chopper‐prebuncher high voltage injection system and a high gradient 17 GHz linac having an inherent ability to generate 1 degree (162 fs) electron bunches emphasized the need for a simple means of accurately measuring very short electron bunches while also providing on‐line guidance for optimizing the injector and linac bunch length controls. To meet this need, a fast diagnostic for the direct measurement of short bunch longitudinal phase space, with a time resolution of less than 100 fs, has recently been installed on the 17 GHz linac at the MIT Plasma Science and Fusion Center. The diagnostic system, having a high field (0.2 MA/m) circularly polarized 17 GHz beam deflector, is described; images of 17 GHz electron bunches are shown; and bunch charge distributions mapped with a matrix of 150 micron diameter collimators spaced on 240 micron centers (sampling intervals of 40 fs and 0.4% Δp/p) are presented. The minimum time resolution of this fast diagnostic device is linearly dependent on the emittance limited beam spot size and is, therefore, especially suited for very low beam emittance, ultra short bunch applications. Direct and simple calibration, real time viewing and extreme phase coherence of the RF system are added advantages of this time domain diagnostic. © 2004 American Institute of Physics
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41.75.Fr Electron and positron beams
41.85.Ar Particle beam extraction, beam injection
29.27.Ac Beam injection and extraction
29.27.Hj Polarized beams

Gas Lasers for Strong Field Applications

I. V. Pogorelsky

AIP Conf. Proc. 737, pp. 109-124; doi:http://dx.doi.org/10.1063/1.1842538 (16 pages)

Online Publication Date: 14 December 2004

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Atomic, molecular and excimer gas lasers employ variety of pumping schemes including electric discharge, optical, or chemical reactions and cover a broad spectral range from UV to far‐IR. Several types of gas lasers are capable to produce multi‐kilojoule pulses and kilowatts of average power. Among them, excimer and high‐pressure molecular lasers have sufficient bandwidth for producing pico‐ and femtosecond pulses. Projects are under way and prospects are open to bring ultra‐fast gas laser technology to the front lines of the advanced accelerator applications. © 2004 American Institute of Physics
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
41.75.Jv Laser-driven acceleration
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

A Review of Laser Guiding Experiments

Simon M. Hooker

AIP Conf. Proc. 737, pp. 125-136; doi:http://dx.doi.org/10.1063/1.1842539 (12 pages)

Online Publication Date: 14 December 2004

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In many cases the length over which particles can be accelerated in a laser‐driven plasma accelerator is limited by refraction or diffraction of the driving laser pulse. In order to overcome this limitation the driving pulse must be guided or channeled through the plasma. In this paper we briefly review of the techniques used to guide laser pulses with peak intensities up to 1019 W cm−2, and describe recent experimental results. © 2004 American Institute of Physics
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52.38.-r Laser-plasma interactions
41.75.Jv Laser-driven acceleration

Diagnostics for Laser Accelerators

C. E. Clayton

AIP Conf. Proc. 737, pp. 137-159; doi:http://dx.doi.org/10.1063/1.1842540 (23 pages) | Cited 1 time

Online Publication Date: 14 December 2004

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This tutorial paper discusses, at a basic level, some of the diagnostics used in plasma accelerators laboratories. Covered are measurements of laser beams, using probe laser beams to characterize the plasma itself (as opposed to the plasma wave accelerating structure) in various ways, including density fluctuations in the plasma and also static or near‐static density structures in the plasma. Also covered are laser probe techniques that are especially suitable for studying the properties of the relativistic electron plasma wave that is ultimately the particle accelerator. © 2004 American Institute of Physics
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52.38.Kd Laser-plasma acceleration of electrons and ions
41.75.Jv Laser-driven acceleration
52.27.Ny Relativistic plasmas
52.35.-g Waves, oscillations, and instabilities in plasmas and intense beams
52.70.-m Plasma diagnostic techniques and instrumentation

Very High Energy Gain at the Neptune Inverse Free Electron Laser Experiment

P. Musumeci, S. Ya. Tochitsky, S. Boucher, A. Doyuran, R. J. England, C. Joshi, C. Pellegrini, J. Ralph, J. B. Rosenzweig, C. Sung, S. Tolmachev, G. Travish, A. Varfolomeev, A. Varfolomeev, Jr., T. Yarovoi, et al.

AIP Conf. Proc. 737, pp. 160-170; doi:http://dx.doi.org/10.1063/1.1842541 (11 pages) | Cited 1 time

Online Publication Date: 14 December 2004

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We report the observation of energy gain in excess of 20 MeV at the Inverse Free Electron Laser Accelerator experiment at the Neptune Laboratory at UCLA. A 14.5 MeV electron beam is injected in an undulator strongly tapered in period and field amplitude. The IFEL driver is a CO2 10.6 μm laser with power larger than 400 GW. The Rayleigh range of the laser, ∼ 1.8 cm, is much shorter than the undulator length so that the interaction is diffraction dominated. A few per cent of the injected particles are trapped in a stable accelerating bucket. Electrons with energies up to 35 MeV are measured by a magnetic spectrometer. Three‐dimensional simulations, in good agreement with the measured electron energy spectrum, indicate that most of the acceleration occurs in the first 25 cm of the undulator, corresponding to an energy gradient larger than 70 MeV/m. The measured energy spectrum also indicates that higher harmonic Inverse Free Electron Laser interaction takes place in the second section of the undulator. © 2004 American Institute of Physics
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41.75.Jv Laser-driven acceleration
41.75.Fr Electron and positron beams
41.60.Cr Free-electron lasers

Femtosecond Beam Sources and Applications

Mitsuru Uesaka

AIP Conf. Proc. 737, pp. 171-177; doi:http://dx.doi.org/10.1063/1.1842542 (7 pages)

Online Publication Date: 14 December 2004

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Short particle beam science has been promoted by electron linac and radiation chemistry up to picoseconds. Recently, table‐top TW laser enables several kinds of short particle beams and pump‐and‐probe analyses. 4th generation SR sources aim to generation and application of about 100 fs X‐ray. Thus, femtosecond beam science has become one of the important field in advanced accelerator concepts. By using electron linac with photoinjector, about 200 fs single bunch and 3 fs multi‐bunches are available. Tens femtoseconds monoenergetic electron bunch is expected by laser plasma cathode. Concerning the electron bunch diagnosis, we have seen remarkable progress in streak camera, coherent radiation spectroscopy, fluctuation method and E/O crystal method. Picosecond time‐resolved pump‐and‐probe analysis by synchronizing electron linac and laser is now possible, but the timing jitter and drift due to several fluctuations in electronic devices and environment are still in picoseconds. On the other hand, the synchronization between laser and secondary beam is done passively by an optical beam‐splitter in the system based on one TW laser. Therefore, the timing jitter and drift do not intrinsically exist there. The author believes that the femtosecond time‐resolved pump‐and‐probe analysis must be initiated by the laser plasma beam sources. As to the applications, picosecond time‐resolved system by electron photoinjector/linac and femtosecond laser are operating in more than 5 facilities for radiation chemistry in the world. Ti:Sapphire‐laser‐based repetitive pump‐and‐probe analysis started by time‐resolved X‐ray diffraction to visualize the atomic motion. Nd:Glass‐laser‐based single‐shot analysis was performed to visualize the laser ablation via the single‐shot ion imaging. The author expects that protein dynamics and ultrafast nuclear physics would be the next interesting targets. Monograph titled “Femtosecond Beam Science” is published by Imperial College Press/World Scientific in 2004. © 2004 American Institute of Physics
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52.38.Kd Laser-plasma acceleration of electrons and ions
41.75.Fr Electron and positron beams
41.75.Jv Laser-driven acceleration

Diamond Amplifier For Photocathodes

Triveni Rao, Ilan Ben‐Zvi, Andrew Burrill, Xiangyun Chang, Steven Hulbert, Peter D. Johnson, and Jörg Kewisch

AIP Conf. Proc. 737, pp. 178-190; doi:http://dx.doi.org/10.1063/1.1842543 (13 pages)

Online Publication Date: 14 December 2004

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We report a new approach to the generation of high‐current, high‐brightness electron beams. Primary electrons are produced by a photocathode (or other means) and are accelerated to a few thousand electron‐volts, then strike a specially prepared diamond window. The large Secondary Electron Yield (SEY) provides a multiplication of the number of electrons by about two orders of magnitude. The secondary electrons drift through the diamond under an electric field and emerge into the accelerating region proper of the “gun” through a Negative Electron Affinity surface of the diamond. The advantages of the new approach include the following: 1. Reduction of the required number of primary electrons by the large SEY, i.e. we can utilize a very low laser power in a photocathode producing the primaries. 2. Low thermal emittance due to the NEA surface and the rapid thermalization of the electrons.3. Protection of the cathode from possible contamination from the gun, allowing the use of large quantum efficiency but sensitive cathodes. 4. Protection of the gun from possible contamination by the cathode, allowing the use of superconducting gun cavities. 5. Production of high average currents, up to ampere class. 6. Encapsulated design, making the “load‐lock” systems unnecessary. This paper presents the criteria that need to be taken into account in designing the amplifier. © 2004 American Institute of Physics
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41.75.Fr Electron and positron beams

EM Structure‐Based Accelerators Working Group Summary

W. D. Kimura and S. M. Lidia

AIP Conf. Proc. 737, pp. 193-205; doi:http://dx.doi.org/10.1063/1.1842544 (13 pages)

Online Publication Date: 14 December 2004

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This Working Group (WG) focused on EM Structure‐Based Accelerators, which covers a broad area of mechanisms and experiments. Topics covered included dielectric wakefield accelerators (DWA), photonic bandgap accelerators (PBGA), inverse free electron lasers (IFEL), vacuum laser accelerators (VLA), other novel schemes, and supporting analysis and modeling. In addition, this WG was tasked at the Workshop with developing conceptual (strawman) designs for a 1‐GeV accelerator system based upon any of the experimentally‐proven approaches covered in this WG. Two strawmen designs were developed based upon IFELs and DWAs. The presentations given and strawmen designs indicate great progress has been made in many areas. Proof‐of‐principle experiments will occur shortly in PBGA and VLA. Other well‐proven devices, such as IFELs, are becoming accepted as “workhorse” providers of microbunches. © 2004 American Institute of Physics
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41.75.Jv Laser-driven acceleration

e‐Beam Driven Accelerators: Working Group Summary

P. Muggli, Group Leader and J. S. T. Ng, Co‐group Leader

AIP Conf. Proc. 737, pp. 206-216; doi:http://dx.doi.org/10.1063/1.1842545 (11 pages)

Online Publication Date: 14 December 2004

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The working group has identified the parameters of an afterburner based on the design of a future linear collider. The new design brings the center of mass energy of the collider from 1 to 2 TeV. The afterburner is located in the final focus section of the collider, operates at a gradient of ≈4 GeV/m, and is only about 125 m long. Very important issues remain to be addressed, and include the physics and design of the positron side of the afterburner, as well as of the final focus system. Present plasma wakefield accelerator experiments have reached a level of maturity and of relevance to the afterburner, that make it timely to involve the high energy physics and accelerator community in the afterburner design process. The main result of this working group is the first integration of the designs of a future linear collider and an afterburner. © 2004 American Institute of Physics
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52.40.Mj Particle beam interactions in plasmas
41.75.Fr Electron and positron beams

High Energy Density Physics and Exotic Acceleration Concepts

Tom Katsouleas and Robert Noble

AIP Conf. Proc. 737, pp. 217-222; doi:http://dx.doi.org/10.1063/1.1842546 (6 pages)

Online Publication Date: 14 December 2004

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The reported results and discussions in the Working Group on High Energy Density Physics and Exotic Acceleration Concepts are summarized. The working group focused largely on laser‐generated proton and ion beams from solid targets, but also considered laser vacuum acceleration results, active media accelerator proposals, ferroelectric‐based accelerator technology advances and beam conditioning concepts for free electron lasers. The charge to the working group was to develop a laser‐based proton injector exceeding current capabilities in at least one important parameter. © 2004 American Institute of Physics
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41.75.Jv Laser-driven acceleration
41.75.Lx Other advanced accelerator concepts

Summary Report of Working Group: Laser‐Plasma Acceleration

Eric Esarey, Sergei Tochitsky, Howard M. Milchberg, and Carl B. Schroeder

AIP Conf. Proc. 737, pp. 223-230; doi:http://dx.doi.org/10.1063/1.1842547 (8 pages)

Online Publication Date: 14 December 2004

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A summary is given on the work presented and discussed in the Laser‐Plasma Acceleration Working Group at the 2004 Advanced Accelerator Concepts Workshop, including the Plasma Acceleration Subgroup (Group‐Leader: Eric Esarey; Co‐Group‐Leader: Sergei Tochitsky) and the Plasma Guiding Subgroup (Group‐Leader: Howard Milchberg; Co‐Group‐Leader: Carl Schroeder). © 2004 American Institute of Physics
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52.38.Kd Laser-plasma acceleration of electrons and ions
41.75.Jv Laser-driven acceleration

Computational Accelerator Physics Working Group Summary

John R. Cary and Courtlandt L. Bohn

AIP Conf. Proc. 737, pp. 231-242; doi:http://dx.doi.org/10.1063/1.1842548 (12 pages) | Cited 2 times

Online Publication Date: 14 December 2004

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The working group on computational accelerator physics at the 11th Advanced Accelerator Concepts Workshop held a series of meetings during the Workshop. Verification, i.e., showing that a computational application correctly solves the assumed model, and validation, i.e., showing that the model correctly describes the modeled system, were discussed for a number of systems. In particular, the predictions of the massively parallel codes, OSIRIS and VORPAL, used for modeling advanced accelerator concepts, were compared and shown to agree, thereby establishing some verification of both codes. In addition, a number of talks on the status and frontiers of computational accelerator physics were presented, to include the modeling of ultrahigh‐brightness electron photoinjectors and the physics of beam halo production. Finally, talks discussing computational needs were presented. © 2004 American Institute of Physics
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41.75.Lx Other advanced accelerator concepts
41.75.Fr Electron and positron beams

Advanced Accelerator System Requirements for Synchrotron Radiation Facility Linacs

G. Dugan

AIP Conf. Proc. 737, pp. 245-250; doi:http://dx.doi.org/10.1063/1.1842549 (6 pages)

Online Publication Date: 14 December 2004

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In this paper, the general electron beam requirements of few GeV electron linacs for the production of synchrotron radiation will be reviewed, with an emphasis on the requirements which could be satisfied using advanced accelerator systems. The article will cover the beam requirements needed for the generation of the synchrotron radiation in wigglers and undulators driven by conventional electron storage rings, energy‐recovery linacs, and SASE free‐electron lasers. © 2004 American Institute of Physics
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41.75.Fr Electron and positron beams

Conceptual Design for a 1‐GeV IFEL Accelerator

W. D. Kimura, P. Musumeci, D. C. Quimby, S. C. Gottschalk, and C. Pellegrini

AIP Conf. Proc. 737, pp. 251-257; doi:http://dx.doi.org/10.1063/1.1842550 (7 pages)

Online Publication Date: 14 December 2004

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A conceptual design for a multistaged 1‐GeV IFEL laser‐driven accelerator (laser linac) was developed using the Staged Electron Laser Acceleration (STELLA) inverse free electron laser (IFEL) model created at STI Optronics. A comparison with the UCLA TREDI model yields good agreement with the STELLA model. The 1‐GeV IFEL laser linac consists of an IFEL buncher for forming microbunches and four IFEL acceleration stages. Electrons enter the laser linac from a conventional microwave‐driven linac (51 MeV). The acceleration stages are driven by 10‐TW laser beams at 1.06‐μm. It is found good trapping occurs as the electrons are accelerated; however, refocusing of the e‐beam between acceleration stages is needed to control detrapping effects. The energy spread of the trapped electrons is also small. This design exercise was in support of the task placed upon the EM Structure‐Based Accelerators Working Group at the 2004 Advanced Accelerator Concepts Workshop. It demonstrates that a 1‐GeV IFEL laser linac is feasible with present technology. © 2004 American Institute of Physics
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41.75.Jv Laser-driven acceleration
41.60.Cr Free-electron lasers
41.75.Fr Electron and positron beams

High Power rf Test on X‐band MgxCa1−xTiO3 Based Dielectric‐Loaded Accelerating Structure

C. Jing, R. Konecny, W. Gai, S. H. Gold, J. G. Power, A. K. Kinkead, and W. Liu

AIP Conf. Proc. 737, pp. 258-264; doi:http://dx.doi.org/10.1063/1.1842551 (7 pages)

Online Publication Date: 14 December 2004

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In this paper, we report experimental results on a series of high‐power rf tests for dielectric‐loaded accelerating (DLA) structures using a high power X‐band Magnicon at the Naval Research Laboratory. The dielectric material loaded into this DLA structure is a commonly used high‐Q ceramic, MgxCa1−xTiO3 (MCT), with a dielectric constant of 20. The purpose of these experiments is to study high‐power phenomena in the DLA structure. Two important phenomena have been observed during these experiments. First, multipactor effects are strongly dependent on the dielectric material used in the DLA structure. In this case, the multipactor‐induced power absorption threshold and trend to higher power differ when MCT is used instead of alumina. Second, although we did not observe dielectric breakdown in the bulk dielectric, breakdown occurred at the butt‐joint between adjacent dielectric sections in the MCT structure. This occurs because of manufacturing imperfections of the joint that cause large, local field enhancements. © 2004 American Institute of Physics
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84.40.Az Waveguides, transmission lines, striplines
41.75.Lx Other advanced accelerator concepts

Experimental Study of Multipactor Suppression in a Dielectric‐Loaded Accelerating Structure

J. G. Power, W. Gai, S. H. Gold, A. K. Kinkead, R. Konecny, C. Jing, and W. Liu

AIP Conf. Proc. 737, pp. 265-271; doi:http://dx.doi.org/10.1063/1.1842552 (7 pages)

Online Publication Date: 14 December 2004

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High power tests are currently being conducted on RF‐driven dielectric‐loaded accelerating (DLA) structures to determine their viability as traveling‐wave accelerators. These tests are a collaborative effort between Argonne National Laboratory (ANL) and the Naval Research Laboratory (NRL). In a previous high power test, single‐surface multipactor was reported to be capable of absorbing more than half of the RF power incident on an alumina‐based DLA structure. In this paper, we report on the most recent set of high power tests that are attempting to further understand multipactor and eventually suppress it. Several methods were employed to suppress multipactor including: the use of a magnetic field; a TIN surface coating; and a different dielectric material (Magnesium‐Calcium‐Titanate based). The effectiveness of these three methods are presented and discussed in the paper. © 2004 American Institute of Physics
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84.40.Az Waveguides, transmission lines, striplines
41.75.Lx Other advanced accelerator concepts

Transformer Ratio Enhancement for Structure‐Based Wakefield Acceleration

A. Kanareykin, W. Gai, J. G. Power, and P. Schoessow

AIP Conf. Proc. 737, pp. 272-280; doi:http://dx.doi.org/10.1063/1.1842553 (9 pages)

Online Publication Date: 14 December 2004

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A limiting factor in the efficiency of wakefield accelerators is the fact that the transformer ratio R, the parameter that characterizes the energy transfer efficiency from the accelerating structure to the accelerated electron beam, is less than 2 for most technologically realizable beam‐structure configurations. We are planning an experiment to study transformer ratio enhancement in a 13.625 GHz dielectric wakefield structure driven by a ramped bunch train. In this paper we present an experimental program for the demonstration of this Enhanced Transformer Ratio Dielectric Wakefield Accelerator (ETR‐DWA). © 2004 American Institute of Physics
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41.75.Fr Electron and positron beams

Development of a 20 MeV Dielectric‐Loaded Accelerator Test Facility

Steven H. Gold, Allen K. Kinkead, Wei Gai, John G. Power, Richard Konecny, Chunguang Jing, Sami G. Tantawi, Christopher D. Nantista, Y. Hu, H. Chen, C. Tang, Y. Lin, Ralph W. Bruce, Robert L. Bruce, Arne W. Fliflet, et al.

AIP Conf. Proc. 737, pp. 281-287; doi:http://dx.doi.org/10.1063/1.1842554 (7 pages)

Online Publication Date: 14 December 2004

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This paper describes a joint project by the Naval Research Laboratory (NRL) and Argonne National Laboratory (ANL), in collaboration with the StanFord Linear Accelerator Center (SLAC), to develop a dielectric‐loaded accelerator (DLA) test facility powered by a high‐power 11.424‐GHz magnicon amplifier. The magnicon can presently produce 25 MW of output power in a 250‐ns pulse at 10 Hz, and efforts are in progress to increase this to 50 MW. The facility will include a 5 MeV electron injector being developed by the Accelerator Laboratory of Tsinghua University in Beijing, China. The DLA test structures are being developed by ANL, and some have undergone testing at NRL at gradients up to ∼8 MV/m. SLAC is developing a means to combine the two magnicon output arms, and to drive an injector and accelerator with separate control of the power ratio and relative phase. RWBruce Associates, Inc., working with NRL, is developing a means to join short ceramic sections into a continuous accelerator tube by ceramic brazing using an intense millimeter‐wave beam. The installation and testing of the first dielectric‐loaded test accelerator, including injector, DLA structure, and spectrometer, should take place within the next year. The facility will be used for testing DLA structures using a variety of materials and configurations, and also for testing other X‐band accelerator concepts. The initial goal is to produce a compact 20 MeV dielectric‐loaded test accelerator. © 2004 American Institute of Physics
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84.40.Az Waveguides, transmission lines, striplines
41.75.Lx Other advanced accelerator concepts
84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)

An Optimal Design for a THz Slab‐Symmetric Dielectric‐Loaded Accelerator

R. B. Yoder and J. B. Rosenzweig

AIP Conf. Proc. 737, pp. 288-294; doi:http://dx.doi.org/10.1063/1.1842555 (7 pages)

Online Publication Date: 14 December 2004

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A slab‐symmetric dielectric‐loaded accelerator structure, consisting of a vacuum gap between dielectric‐lined conducting walls, is analyzed theoretically and computationally. The device is to be resonantly excited by an external laser source of wavelength 340 μm. Analytical results for infinite and finite‐width geometries are summarized, and 2D electromagnetic simulation is used to demonstrate the time‐dependent filling of the structure from the external source. The resonant accelerating fields, which are nearly constant along the short transverse direction, are found to have between 10 and 15 times the amplitude of the driving radiation, with only a small (< 10%) admixture of other non‐accelerating modes. Field gradients are near 100 MV/m when the structure is driven with 100 MW of terahertz power. The resonance is highly dependent on the geometry of the slots used to couple radiation into the structure, with effects on the overall Q‐factor, frequency detuning, and field pattern. Possible manufacturing methods are discussed, along with an all‐dielectric version of the design that would allow scaling of the structure to a wavelength of 10 μm. © 2004 American Institute of Physics
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84.40.Az Waveguides, transmission lines, striplines
41.75.Lx Other advanced accelerator concepts
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