RadiaBeam, Marina del Rey
Purdue University, West Lafayette, Indiana
UCLA, Los Angeles, California
Funding: This work is supported by the US Defense Threat Reduction Agency SBIR contract HDTRA1-08-P-0035.
Conventional X-ray sources used for medical and industrial imaging suffer from low spectral brightness, a factor which severely limits the image quality that can be obtained. X-ray sources based on Inverse Compton Scattering (ICS) hold promise to greatly improve the brightness of X-ray sources. While ICS sources have previously been demonstrated, and have produced high-peak brightness X-rays, so far experiments have produced low average flux, which limits their use for certain important commercial applications (e.g. medical imaging). RadiaBeam Technologies is currently developing a high peak- and average-brightness ICS source, which implements a number of improvements to increase the interaction repetition rate, as well as the efficiency and stability of the ICS interaction itself. In this paper, we will describe these improvements, as well as plans for future experiments.
RadiaBeam, Marina del Rey
UCLA, Los Angeles, California
The fixed-field alternating-gradient (FFAG) betatron has emerged as a viable alternative to RF linacs as a source of high-energy radiation for industrial and security applications. RadiaBeam Technologies is currently developing an FFAG betatron with a novel induction core made with modern low-loss magnetic materials. The principle challenge in the project has been the design of the magnets. In this paper, we present the current status of the project, including results of the magnet design and testing.
UCLA, Los Angeles, California
Funding: Work supported by DOE.
We report experimental observation of narrow-bandwidth pulses of coherent Cherenkov radiation produced when a sub-picosecond electron bunch travels along the axis of a hollow circular cylindrical dielectric-loaded waveguide. For an appropriate choice of dielectric structure properties and driving electron beam parameters, the device operates in a single-mode regime, producing radiation in the THz range. We present measurements showing the emission of a narrowly-peaked spectrum from a fused silica tube 1 centimeter long with sub-millimeter transverse dimensions. We discuss the agreement of this data with theoretical and computational predictions, as well as possibilities for future study and application.
RadiaBeam, Marina del Rey
UCLA, Los Angeles, California
NCSU, Raleigh, North Carolina
INFN/LNF, Frascati (Roma)
Electron beam based additive fabrication techniques have been successfully applied to produce a variety of complex, fully dense, metal structures. These methods, collectively known as Solid Freeform Fabrication (SFF) are now being explored for use in radio frequency (RF) structures. SFF technology may make it possible to design and produce near-netshape copper structures for the next generation of very high duty factor, high gradient RF photoinjectors. The SFF process discussed here, Arcam Electron Beam Melting (EBM), utilizes an electron beam to melt metal powder in a layer-by-layer fashion. The additive nature of the SFF process and its ability to produce fully dense parts are explored for the fabrication of internal cooling passages in RF photoinjectors. Following an initial feasibility study of the SFF process, we have fabricated a copper photocathode, suitable as a drop-in replacement for the UCLA 1.6 cell photoinjector, with internal cooling channels using SFF. Material analysis of the prototype cathode and new designs for a high duty factor photoinjector utilizing SFF technology will be presented.
SLAC, Menlo Park, California
UCLA, Los Angeles, California
Funding: Work supported by U.S. DoE Grant No. DE-FG03-92ER40693.
The first successful attempt to generate ultrashort (1-10 picosecond) relativistic electron bunches characterized by a ramped current profile that rises linearly from head to tail and then falls sharply to zero was recently reported.* Bunches with this type of longitudinal shape may be applied to plasma-based accelerator schemes as an optimized drive beam, and to free electron lasers as a means of reducing asymmetry in microbunching due to slippage. We will review the technique used to generate these bunches, which utilizes a sextupole-corrected dogleg compressor to manipulate the longitudinal phase space of the beam, and examine its potential application in a realistic plasma wakefield accelerator scenario, the proposed FACET project at SLAC.
* R. J. England, J. B. Rosenzweig, G. Travish, Phys. Rev. Lett. 100, 214802 (2008).
RadiaBeam, Marina del Rey
Spectrum Detector, Lake Oswego, Oregon
UGA, Athens, Georgia
UCLA, Los Angeles, California
Funding: Work supported by U.S. DOE Grant Number DE-FG02-07ER84814.
The generation of high peak current, high brightness beams routinely requires compression methods (e.g. four-bend chicane), which produce coherent radiation as a by-product. The sensing of this radiation, coupled with interferometric methods, yields crucial longitudinal bunch length and bunch profile information. This paper discusses the progress of the development of a real-time terahertz interferometer used for longitudinal beam profile diagnosis.
UCLA, Los Angeles, California
RadiaBeam, Marina del Rey
BNL, Upton, Long Island, New York
Funding: NSF grant # IIP-0724505
We describe our effort in the development of a low cost, wide-band detector/camera for generation of spatially resolved images of radiation beams in a multi-spectral range of wavelengths, from IR (infrared) to THz (terahertz). The detector (T-camera) utilizes a TLC (thermochromic liquid crystal) film as the sensitive element in a temperature controlled chamber and a CCD detector array and can be used as a powerful diagnostic for terahertz sources such as a synchrotron or an FEL
PBPL, Los Angeles
UCLA, Los Angeles, California
Manhattanville College, Purchase, NY
The millimeter-scaleμAccelerator Platform (MAP)–essentially a “particle accelerator on a chip”–will ultimately allow for revolutionary medical and industrial applications due to its manageable size and reproducibility. The MAP consists of an electron source and an all-dielectric, laser powered, particle accelerator. The dielectric structure has two slab-symmetric reflecting mirrors with a vacuum gap between them. A periodic coupling mechanism allows laser power to enter transversely through one mirror. This mechanism is analogous to the slots of an optical diffraction grating, with coupling period and vacuum gap equal to the wavelength of the laser (800nm in this study). Work to date has included designing, fabricating and testing a prototype relativistic structure using a patterned gold layer. To go further, we have studied the fabrication techniques and electromagnetic designs of an all-dielectric (non-metallic) structure. Fabrication of the final structure is modeled after Vertical-Cavity Surface-Emitting Lasers (VCSEL) and Distributed Bragg Reflector (DBR) techniques. Preliminary numerical studies of the sub-relativistic structure are also presented.
UCLA, Los Angeles, California
PBPL, Los Angeles
The Micro-Accelerator Platform, a laser-driven accelerating device measuring less than a millimeter in each dimension, has a variety of applications in industry and medicine. The structure consists of two parallel slabs, with each possessing reflective surfaces and with one having periodic slots which allows transversely incident laser light to enter the gap between the two planes. The resonance of the electric field created in the gap can be measured indirectly through the spectral response of the device. Using a combination of an interferometer and a fiber coupled spectrometer, prototype structures are aligned and measured. With the aid of a nanometer-accuracy positioning device, the bottom slab (a mirror) is aligned with the top slotted-structure. The interferometer and a low power laser are used to position the slabs. A 800nm Titanium-Sapphire oscillator with a bandwidth of greater than 100nm is used for the spectral measurements. The spectra of both transmitted and reflected beams have been measured for a number of structures and are compared to simulation results. Various improvements to the initial measurement system as well as alternative future approaches are discussed.
RadiaBeam, Marina del Rey
UCLA, Los Angeles, California
Manhattanville College, Purchase, NY
Funding: This project is supported by DOE SBIR Grant DE-FG02-08ER85038.
Laser-powered dielectric accelerating structures, which have attracted attention in recent years, trade fabrication challenges and extremely small beam apertures for the promise of high gradients and new bunch formats. The slab-symmetric, periodically-coupledμAccelerator Platform (MAP) is one such dielectric accelerator, and has been under development through a RadiaBeam-UCLA collaboration for several years. Intended applications of the structure include the production of radiation for medical treatments, imaging, and industrial uses. Prototype MAP structures are now being fabricated, and a program has been undertaken to test this device using externally injected electron beams. Plans are underway to install structures in the E163 facility at SLAC. In this paper we describe the testing methods, diagnostics and expectations. Progress and results to date are also presented.