Download or read book Experimental High Gradient Testing of a 17 1 GHz Photonic Band gap Accelerator Structure written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper, we report the design, fabrication, and high gradient testing of a 17.1 GHz photonic band-gap (PBG) accelerator structure. Photonic band-gap (PBG) structures are promising candidates for electron accelerators capable of high-gradient operation because they have the inherent damping of high order modes required to avoid beam breakup instabilities. The 17.1 GHz PBG structure tested was a single cell structure composed of a triangular array of round copper rods of radius 1.45 mm spaced by 8.05 mm. The test assembly consisted of the test PBG cell located between conventional (pillbox) input and output cells, with input power of up to 4 MW from a klystron supplied via a TM01 mode launcher. Breakdown at high gradient was observed by diagnostics including reflected power, downstream and upstream current monitors and visible light emission. The testing procedure was first benchmarked with a conventional disc-loaded waveguide structure, which reached a gradient of 87 MV=m at a breakdown probability of 1.19 × 10-1 per pulse per meter. The PBG structure was tested with 100 ns pulses at gradient levels of less than 90 MV=m in order to limit the surface temperature rise to 120 K. The PBG structure reached up to 89 MV=m at a breakdown probability of 1.09 × 10-1 per pulse per meter. These test results show that a PBG structure can simultaneously operate at high gradients and low breakdown probability, while also providing wakefield damping.
Download or read book Experimental Studies of Novel Accelerator Structures at 11 GHz and 17 GHz written by Brian James Munroe and published by . This book was released on 2015 with total page 185 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photonic band-gap (PBG) structures are promising candidates for electron accelerators capable of high-gradient operation because they have the inherent damping of high order modes required to avoid beam breakup due to instabilities. A key challenge for PBG structures is high-gradient operation without structure damage due to rf-field-induced breakdowns. This thesis reports theoretical results on the design of PBG structures and the generation of wakefields in such structures. It also reports experimental results on PBG structure breakdown testing at high power at both 11 and 17 GHz. A single-cell photonic band-gap (PBG) structure was designed with an inner row of elliptical rods (PBG-E) to reduce ohmic heating relative to a round-rod structure. The PBG-E structure was built and tested at high power at a 60 Hz repetition rate at X-Band (11.424 GHz) at the SLAC accelerator test stand, achieving a gradient of 128 MV/m at a breakdown probability of 3.6 x 10-3 per pulse per meter at a pulse length of 150 ns. The PBG-E structure showed major improvement in breakdown rate relative to a round-rod PBG structure designed at MIT and previously tested at SLAC. A test stand was designed and built at MIT for testing single-cell structures at 17.1 GHz, a frequency 50% higher than the SLAC frequency. This test stand provides comparable diagnostics to those used at SLAC, adding optical diagnostic access which can be used for open PBG structures. A conventional disc-loaded waveguide structure, MIT-DLWG, was tested at MIT at up to a 2 Hz repetition rate. This structure reached a maximum gradient of 87 MV/m at a breakdown probability of 1.19 x 10-1 per pulse per meter. A round-rod PBG structure, MIT-PBG-2, has also been tested at MIT at up to a 2 Hz repetition rate and 100 ns pulse length, demonstrating operation up to 89 MV/rn at a breakdown probability of 1.09 x 10-1 per pulse per meter. These test results show that a PBG structure can simultaneously operate at high gradients and low breakdown probability, while also providing wakefield damping. This makes PBG structures viable candidates for future collider applications.
Download or read book 17 GHz High Gradient Accelerator Research written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This is a report on the MIT High Gradient Accelerator Research program which has included: Operation of the 17 GHz, 25 MeV MIT/Haimson Research Corp. electron accelerator at MIT, the highest frequency, stand-alone accelerator in the world; collaboration with members of the US High Gradient Collaboration, including the design and test of novel structures at SLAC at 11.4 GHz; the design, construction and testing of photonic bandgap structures, including metallic and dielectric structures; the investigation of the wakefields in novel structures; and the training of the next generation of graduate students and postdoctoral associates in accelerator physics.
Download or read book Experimental Studies of Hybrid Photonic Band Gap Accelerator Structures written by JieXi Zhang and published by . This book was released on 2016 with total page 217 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis reports the first high power tests of a hybrid photonic band gap (PBG) accelerator structure. PBG structures can support a single electromagnetic mode, thus damping higher-order modes (HOMs) generated by wakefields. We have designed, built and successfully tested a 17.14 GHz hybrid PBG (HPBG) structure containing both dielectric and metallic elements. Dielectric elements have low loss and the potential to survive high surface electromagnetic fields. The HPBG structure was constructed as a triangular lattice array with sapphire rods inside and copper rods outside sandwiched between copper plates. The lattice parameter and the rod pattern were adjusted to excite a high-Q TM0 2 mode and to suppress HOMs. This overmoded operation is a unique and novel feature of the hybrid design. The design included the birefringence of sapphire. Simulations showed relatively high surface fields at the triple point where sapphire, copper and vacuum meet as well as in any gaps between components in the clamped assembly. Three structures were tested with later structures designed to sequentially reduce the surface electric field. The third structure used sapphire rods with pin extensions at each end and obtained the highest gradient of 19 MV/m, corresponding to a surface E field of 78 MV/m, with a breakdown probability of 5 x 10 1 /pulse/m in 45-ns pulses. Operation above 20 MV/m gradient led to runaway breakdowns with extensive light emission and eventual damage. For all three structures, multipactor light emission was observed at gradients well below the breakdown threshold. Breakdown damage was found at the triple point where surface fields peaked. The deposition of copper onto sapphire resulting from breakdowns might eventually degrade the cavity quality. This research indicated that multipactor triggered at the triple point limited the operational gradient of the hybrid structure. These experiments represent the first high power tests of a hybrid PBG structure. The gradient achieved of 19 MV/m is the highest achieved with a dielectric structure. The gradient was found to be limited by multipactor and breakdown. The overmoded cavity with relatively large beam apertures might still find applications at high frequency or in high current transmission.
Download or read book X Band Photonic Band Gap Accelerator Structure Breakdown Experiment written by and published by . This book was released on 2012 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: In order to understand the performance of photonic band-gap (PBG) structures under realistic high gradient, high power, high repetition rate operation, a PBG accelerator structure was designed and tested at X band (11.424 GHz). The structure consisted of a single test cell with matching cells before and after the structure. The design followed principles previously established in testing a series of conventional pillbox structures. The PBG structure was tested at an accelerating gradient of 65 MV/m yielding a breakdown rate of two breakdowns per hour at 60 Hz. An accelerating gradient above 110 MV/m was demonstrated at a higher breakdown rate. Significant pulsed heating occurred on the surface of the inner rods of the PBG structure, with a temperature rise of 85 K estimated when operating in 100 ns pulses at a gradient of 100 MV/m and a surface magnetic field of 890 kA/m. A temperature rise of up to 250 K was estimated for some shots. The iris surfaces, the location of peak electric field, surprisingly had no damage, but the inner rods, the location of the peak magnetic fields and a large temperature rise, had significant damage. Breakdown in accelerator structures is generally understood in terms of electric field effects. These PBG structure results highlight the unexpected role of magnetic fields in breakdown. The hypothesis is presented that the moderate level electric field on the inner rods, about 14 MV/m, is enhanced at small tips and projections caused by pulsed heating, leading to breakdown. Future PBG structures should be built to minimize pulsed surface heating and temperature rise.
Download or read book High Gradient Accelerator Research written by and published by . This book was released on 2016 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of the MIT program of research on high gradient acceleration is the development of advanced acceleration concepts that lead to a practical and affordable next generation linear collider at the TeV energy level. Other applications, which are more near-term, include accelerators for materials processing; medicine; defense; mining; security; and inspection. The specific goals of the MIT program are: • Pioneering theoretical research on advanced structures for high gradient acceleration, including photonic structures and metamaterial structures; evaluation of the wakefields in these advanced structures • Experimental research to demonstrate the properties of advanced structures both in low-power microwave cold test and high-power, high-gradient test at megawatt power levels • Experimental research on microwave breakdown at high gradient including studies of breakdown phenomena induced by RF electric fields and RF magnetic fields; development of new diagnostics of the breakdown process • Theoretical research on the physics and engineering features of RF vacuum breakdown • Maintaining and improving the Haimson / MIT 17 GHz accelerator, the highest frequency operational accelerator in the world, a unique facility for accelerator research • Providing the Haimson / MIT 17 GHz accelerator facility as a facility for outside users • Active participation in the US DOE program of High Gradient Collaboration, including joint work with SLAC and with Los Alamos National Laboratory; participation of MIT students in research at the national laboratories • Training the next generation of Ph. D. students in the field of accelerator physics.
Download or read book An Update on the DOE Early Career Project on Photonic Band Gap Accelerator Structures written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We performed fabrication of two SRF PBG resonators at 2.1 GHz and demonstrated their proof-of-principle operation at high gradients. Measured characteristics of the resonators were in good agreement with theoretical predictions. We demonstrated that SRF PBG cavities can be operated at 15 MV/m accelerating gradients. We completed the design and started fabrication of the 16-cell PBG accelerating structure at 11.7 GHz for wakefield testing at AWA.
Download or read book High Energy Density and High Power RF written by David K. Abe and published by Springer Science & Business Media. This book was released on 2006-01-04 with total page 526 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the seventh in a series of international workshops on high-power and high-energy density microwave devices for accelerator, plasma physics, and defense applications. The scope of this workshop included accelerators for high energy physics, plasma heating and current drive in controlled thermonuclear fusion research, radar and directed energy/high power microwave systems, THz sources and technologies, and advanced 2D/3D computational tool development.
Download or read book Observation of Wakefield Suppression in a Photonic Band Gap Accelerator Structure written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We report experimental observation of higher order mode (HOM) wakefield suppression in a room-temperature traveling-wave photonic band gap (PBG) accelerating structure at 11.700 GHz. It has been long recognized that PBG structures have potential for reducing long-range wakefields in accelerators. The first ever demonstration of acceleration in a room-temperature PBG structure was conducted in 2005. Since then, the importance of PBG accelerator research has been recognized by many institutions. However, the full experimental characterization of the wakefield spectrum and demonstration of wakefield suppression when the accelerating structure is excited by an electron beam has not been performed to date. We conducted an experiment at the Argonne Wakefield Accelerator (AWA) test facility and observed wakefields excited by a single high charge electron bunch when it passes through a PBG accelerator structure. Lastly, excellent HOM suppression properties of the PBG accelerator were demonstrated in the beam test.
Download or read book Novel Photonic Band Gap Structures for Accelerator Applications written by Evgenya I. Smirnova and published by . This book was released on 2005 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis I present the design and experimental demonstration of the first photonic band gap (PBG) accelerator at 17.140 GHz. A photonic band gap structure is a one-, two- or three-dimensional periodic metallic and/or dielectric system (for example, of rods), which acts like a filter, reflecting rf fields in some frequency range and allowing rf fields at other frequencies to transmit through. Metal PBG structures are attractive for the Ku-band accelerators, because they can be employed to suppress wakefields. Wakefields are unwanted modes affecting the beam propagation or even destroying the beam. Suppression of wakefields is important. In this thesis, the theory of metallic PBG structures is explained and the Photonic Band Gap Structure Simulator (PBGSS) code is presented. PBGSS code was well benchmarked and the ways to'benchmark the code are described. Next, the concept of a PBG resonator is introduced. PBG resonators were modelled with Ansoft HFSS code, and a single-mode PBG resonator was designed. The HFSS design of a travelling-wave multi- cell PBG structure was performed. The multicell structure was built, cold-tested and tuned. Finally, the hot-test PBG accelerator demonstration was performed at the accelerator laboratory. The PBG accelerating structure was installed inside a vacuum chamber on the Haimson Research Corporation (HRC) accelerator beam line and powered with 2 MW from the HRC klystron. The electron bunches were produced by the HRC accelerator. The electron beam was accelerated by 1.4 MeV inside the PBG structure.
Download or read book Experimental Study of Photonic Band Gap Accelerator Structures written by Roark A. Marsh and published by . This book was released on 2009 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: (cont.) No breakdown damage was observed on the iris surface, the location of peak electric field, but pulsed heating damage was observed on the inner rods, the location of magnetic fields as high as 1 MA/m. Breakdown in accelerator structures is generally understood in terms of electric field effects. PBG structure results highlight the unexpected role of magnetic fields on breakdown. The hypothesis is presented that the low level electric field on the inner rods is enhanced by pulsed heating surface damage, and causes breakdown. A new PBG structure was designed with improved pulsed heating, and will be tested. These results greatly further the understanding of advanced structures with wakefield suppression that are necessary for future colliders.
Download or read book Experimental Work With Photonic Band Gap Fiber written by Robert Siemann and published by . This book was released on 2006 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the laser acceleration project E-163 at the Stanford Linear Accelerator Center, work is being done toward building a traveling wave accelerator that uses as its accelerating structure a length of photonic band gap fiber. The small scale of the optical fiber allows radiation at optical wavelengths to be used to provide the necessary accelerating energy. Optical wavelength driving energy in a small structure yields higher accelerating fields. The existence of a speed-of-light accelerating mode in a photonic band gap fiber has been calculated previously [1]. This paper presents an overview of several of the experimental challenges posed in the development of the proposed photonic band gap fiber accelerator system.
Download or read book Advanced Accelerator Concepts written by Manoel Conde and published by American Institute of Physics. This book was released on 2006-12-13 with total page 954 pages. Available in PDF, EPUB and Kindle. Book excerpt: This workshop covered the general field of advanced particle accelerators, exploring the science and technology of a multitude of novel acceleration schemes. Various schemes under study utilize combinations of plasmas, laser beams, dielectric materials, and RF power. The development of technologies that will enable the design of future high energy physics machines is the underlying goal of this workshop.
Download or read book High gradient Experiment at the Accelerator Test Facility written by H. Matsumoto and published by . This book was released on 1992 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental Studies of Internal Dark Currents in High Gradient Accelerator Structures at 17 GHz written by Haoran Xu (Ph. D.) and published by . This book was released on 2020 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents the measurement of the internal dark current in normal conducting single cell standing wave disk-loaded waveguide (DLWG) accelerator structures that operate at 17 GHz, and its comparison with theory. Dark current is the unwanted current of electrons generated by field emission, multipactor on the accelerator inner surfaces, or both. It is in distinction from the primary beam propagating along the accelerator axis. Dark current that propagates to the ends of the accelerator has been extensively studied, but this is the first detailed study of the internal dark current generated at the structure sidewalls by multipactor. Theoretical calculations indicate that the collision of electrons on the accelerator sidewall will lead to secondary electron emission and subsequent resonant multipactor discharges. Simulations of the multipactor modes were carried out with both our inhouse particle tracking code and with the commercial CST PIC code. Multipactor modes of different orders were predicted to appear at the sidewall with increasing acceleration gradient. The first tested cavities were fabricated from copper and had a sidewall that was either uncoated or coated with diamond-like carbon or titanium nitride. The dark current was measured by a downstream current monitor and by current monitors behind two thin slits opened on the cavity sidewall. With increasing gradient, the downstream dark current increased monotonically, as expected for field emission. The variation of the internal, side dark current was not monotonic but showed the onset of peaks at gradients near 45 and 65 MV/m, in good agreement with simulations using the CST code as well as the in-house code. These were identified as the N = 2 and N = 1 single surface one-point multipactor resonances. The total internal dark current was estimated at ~15 - 30 A. The coated sidewall cavities showed the same multipactor resonances as the uncoated structure. A second set of tests was conducted with a structure with an axisymmetric elliptical central cell sidewall, which was predicted to suppress the internal dark current. After conditioning with 2.2×105 pulses to 93 MV/m, the multipactor modes were completely suppressed and no multipactor resonances were observed. Studies of internal dark current may help to understand the rf conditioning and the ultimate breakdown performance of high gradient rf accelerator structures.
Download or read book Design And Testing of Advanced Photonic Bandgap PBG Accelerator Structures written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Government Reports Announcements Index written by and published by . This book was released on 1994-05 with total page 1232 pages. Available in PDF, EPUB and Kindle. Book excerpt:
