Download or read book Investigations on rf breakdown phenomenon in high gradient accelerating structures written by Jiahang Shao and published by Springer. This book was released on 2018-01-19 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book mainly focuses on the experimental research of rf breakdown and field emission with novel methods, including triggering rf breakdown with high intensity laser and pin-shaped cathodes as well as locating field emitters with a high resolution in-situ imaging system. With these methods, this book has analyzed the power flow between cells during rf breakdown, observed the evolution of field emission during rf conditioning and the dependence of field emission on stored energy, and studied the field emitter distribution and origination. The research findings greatly expand the understanding of rf breakdown and field emission, which will in turn benefit future study into electron sources, particle accelerators, and high gradient rf devices in general.
Download or read book Rf Breakdown Measurements in Electron Beam Driven 200 GHz Copper and Copper silver Accelerating Structures written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This study explores the physics of vacuum rf breakdowns in subterahertz high-gradient traveling-wave accelerating structures. We present the experimental results of rf tests of 200 GHz metallic accelerating structures, made of copper and copper-silver. These experiments were carried out at the Facility for Advanced Accelerator Experimental Tests (FACET) at the SLAC National Accelerator Laboratory. The rf fields were excited by the FACET ultrarelativistic electron beam. The traveling-wave structure is an open geometry, 10 cm long, composed of two halves separated by a gap. The rf frequency of the fundamental accelerating mode depends on the gap size and can be changed from 160 to 235 GHz. When the beam travels off axis, a deflecting field is induced in addition to the longitudinal field. We measure the deflecting forces by observing the displacement of the electron bunch and use this measurement to verify the expected accelerating gradient. Furthermore, we present the first quantitative measurement of rf breakdown rates in 200 GHz metallic accelerating structures. The breakdown rate of the copper structure is 10-2 per pulse, with a peak surface electric field of 500 MV/m and a rf pulse length of 0.3 ns, which at a relatively large gap of 1.5 mm, or one wavelength, corresponds to an accelerating gradient of 56 MV/m. For the same breakdown rate, the copper-silver structure has a peak electric field of 320 MV/m at a pulse length of 0.5 ns. For a gap of 1.1 mm, or 0.74 wavelengths, this corresponds to an accelerating gradient of 50 MV/m.
Download or read book High Gradient Accelerating Structure Proceedings Of The Symposium On The Occasion Of 70th Birthday Of Junwen Wang written by Wei Gai and published by World Scientific. This book was released on 2014-10-24 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: This proceedings volume, for the symposium in honor of Junwen Wang's 70th anniversary, is dedicated to his many important achievements in the field of accelerator physics.It includes the discussions of recent advances and challenging problems in the field of high gradient accelerating structure development.
Download or read book High Precision X Ray Measurements written by Alessandro Scordo and published by MDPI. This book was released on 2019-08-26 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since their discovery in 1895, the detection of X-rays has had a strong impact on and various applications in several fields of science and human life. Impressive efforts have been made to develop new types of detectors and new techniques, aiming to obtain higher precision both in terms of energy and position. Depending on the applications, solid state detectors, microcalorimeters, and various types of spectrometers currently serve as the best options for spectroscopic and imaging detectors. Recent advancements in micron and meV precision have opened the door for groundbreaking applications in fundamental physics, medical science, astrophysics, cultural heritage, and several other fields. The aim of this Special Issue is to compile an overview, from different communities and research fields, of the most recent developments in X-ray detection and their possible impacts in various sectors, such as in exotic atom measurements, quantum physics studies, XRF, XES, EXAFS, plasma emission spectroscopy, monochromators, synchrotron radiation, telescopes, and space engineering. All the papers included in this Special Issue contribute to emphasizing the importance of X-ray detection in a very broad range of physics topics; most of these topics are covered by the published works, and several others are mentioned in the paper references, providing an interesting and very useful synopsis, from a variety of different communities and research fields, of the most recent developments in X-ray detection and their impact in fundamental research and societal applications.
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 A Dual Moded Cavity for RF Breakdown Studies written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The phenomenon of rf breakdown presents a technological limitation in the application of high-gradient particle acceleration in normal conducting rf structures. Attempts to understand the onset of this phenomenon and to study its limits with different materials, cell shapes, and pulse widths has been driven in recent years by linear collider development. One question of interest is the role magnetic field plays relative to electric field. A design is presented for a single, nonaccelerating, rf cavity resonant in two modes, which, driven independently, allow the rf magnetic field to be increased on the region of highest electric field without affecting the latter. The design allows for the potential reuse of the cavity with different samples in the high-field region. High power data is not yet available.
Download or read book EPAC 90 written by P. Marin and published by Atlantica Séguier Frontières. This book was released on 1990 with total page 1054 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book CERN written by and published by . This book was released on 1996 with total page 522 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ultra High Accelerating Gradients in Radio Frequency Cryogenic Copper Structures written by Alexander Cahill and published by . This book was released on 2017 with total page 221 pages. Available in PDF, EPUB and Kindle. Book excerpt: Normal conducting radio-frequency (rf) particle accelerators have many applications, including colliders for high energy physics, high-intensity synchrotron light sources, non-destructive testing for security, and medical radiation therapy. In these applications, the accelerating gradient is an important parameter. Specifically for high energy physics, increasing the accelerating gradient extends the potential energy reach and is viewed as a way to mitigate their considerable cost. Furthermore, a gradient increase will enable for more compact and thus accessible free electron lasers (FELs). The major factor limiting larger accelerating gradients is vacuum rf breakdown. Basic physics of this phenomenon has been extensively studied over the last few decades. During which, the occurrence of rf breakdowns was shown to be probabilistic, and can be characterized by a breakdown rate. The current consensus is that vacuum rf breakdowns are caused by movements of crystal defects induced by periodic mechanical stress. The stress may be caused by pulsed surface heating and large electric fields. A compelling piece of evidence that supports this hypothesis is that accelerating structures constructed from harder materials exhibit larger accelerating gradients for similar breakdown rates. One possible method to increase sustained electric fields in copper cavities is to cool them to temperatures below 77~K, where the rf surface resistance and coefficient of thermal expansion decrease, while the yield strength (which correlates with hardness) and thermal conductivity increase. These changes in material properties at low temperature increases metal hardness and decreases the mechanical stress from exposure to rf electromagnetic fields. To test the validity of the improvement in breakdown rate, experiments were conducted with cryogenic accelerating cavities in the Accelerator Structure Test Area (ASTA) at SLAC National Accelerator Laboratory. A short 11.4~GHz standing wave accelerating structure was conditioned to an accelerating gradient of 250~MV/m at 45~K with $10^8$ rf pulses. At gradients greater than 150~MV/m I observed a degradation in the intrinsic quality factor of the cavity, $Q_0$. I developed a model for the change in $Q_0$ using measured field emission currents and rf signals. I found that the $Q_0$ degradation is consistent with the rf power being absorbed by strong field emission currents accelerated inside the cavity. I measured rf breakdown rates for 45~K and found $2*10^{-4}/pulse/meter$ when accounting for any change in $Q_0$. These are the largest accelerating gradients for a structure with similar breakdown rates. The final chapter presents the design of an rf photoinjector electron source that uses the cryogenic normal conducting accelerator technology: the TOPGUN. With this cryogenic rf photoinjector, the beam brightness will increase by over an order of a magnitude when compared to the current photoinjector for the Linac Coherent Light Source (LCLS). When using the TOPGUN as the source for an X-ray Free Electron Laser, the higher brightness would allow for a decrease in the required length of the LCLS undulator by more than a factor of two.
Download or read book Proceedings of the XVIII International Linear Accelerator Conference written by C. Hill and published by . This book was released on 1996 with total page 518 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book RF BREAKDOWN STUDIES USING PRESSURIZED CAVITIES written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Part of the problem is that RF breakdown in an evacuated cavity involves a complex mixture of effects, which include the geometry, metallurgy, and surface preparation of the accelerating structures and the make-up and pressure of the residual gas in which plasmas form. Studies showed that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas, as needed for muon cooling channels, without the need for long conditioning times, even in the presence of strong external magnetic fields. This positive result was expected because the dense gas can practically eliminate dark currents and multipacting. In this project we used this high pressure technique to suppress effects of residual vacuum and geometry that are found in evacuated cavities in order to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of magnetic field, frequency, and surface preparation. One of the interesting and useful outcomes of this project was the unanticipated collaborations with LANL and Fermilab that led to new insights as to the operation of evacuated normal-conducting RF cavities in high external magnetic fields. Other accomplishments included: (1) RF breakdown experiments to test the effects of SF6 dopant in H2 and He gases with Sn, Al, and Cu electrodes were carried out in an 805 MHz cavity and compared to calculations and computer simulations. The heavy corrosion caused by the SF6 components led to the suggestion that a small admixture of oxygen, instead of SF6, to the hydrogen would allow the same advantages without the corrosion in a practical muon beam line. (2) A 1.3 GHz RF test cell capable of operating both at high pressure and in vacuum with replaceable electrodes was designed, built, and power tested in preparation for testing the frequency and geometry effects of RF breakdown at Argonne National Lab. At the time of this report this cavity is still waiting for the 1.3 GHz klystron to be available at the Wakefield Test Facility. (3) Under a contract with Los Alamos National Lab, an 805 MHz RF test cavity, known as the All-Seasons Cavity (ASC), was designed and built by Muons, Inc. to operate either at high pressure or under vacuum. The LANL project to use the (ASC) was cancelled and the testing of the cavity has been continued under the grant reported on here using the Fermilab Mucool Test Area (MTA). The ASC is a true pillbox cavity that has performed under vacuum in high external magnetic field better than any other and has demonstrated that the high required accelerating gradients for many muon cooling beam line designs are possible. (4) Under ongoing support from the Muon Acceleration Program, microscopic surface analysis and computer simulations have been used to develop models of RF breakdown that apply to both pressurized and vacuum cavities. The understanding of RF breakdown will lead to better designs of RF cavities for many applications. An increase in the operating accelerating gradient, improved reliability and shorter conditioning times can generate very significant cost savings in many accelerator projects.
Download or read book Experimental Measurements of Rf Breakdowns and Deflecting Gradients in Mm wave Metallic Accelerating Structures written by and published by . This book was released on 2016 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: Here, we present an experimental study of a high gradient metallic accelerating structure at sub-THz frequencies, where we investigated the physics of rf breakdowns. Wakefields in the structure were excited by an ultrarelativistic electron beam. We present the first quantitative measurements of gradients and metal vacuum rf breakdowns in sub-THz accelerating cavities. When the beam travels off axis, a deflecting field is induced in addition to the longitudinal field. We measured the deflecting forces by observing the displacement and changes in the shape of the electron bunch. This behavior can be exploited for subfemtosecond beam diagnostics.
Download or read book Rf Breakdown Tests of Mm wave Metallic Accelerating Structures written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Here, we are exploring the physics and frequency-scaling of vacuum rf breakdowns at sub-THz frequencies. We present the experimental results of rf tests performed in metallic mm-wave accelerating structures. These experiments were carried out at the facility for advanced accelerator experimental tests (FACET) at the SLAC National Accelerator Laboratory. The rf fields were excited by the FACET ultrarelativistic electron beam. We compared the performances of metal structures made with copper and stainless steel. The rf frequency of the fundamental accelerating mode, propagating in the structures at the speed of light, varies from 115 to 140 GHz. The traveling wave structures are 0.1 m long and composed of 125 coupled cavities each. We determined the peak electric field and pulse length where the structures were not damaged by rf breakdowns. We calculated the electric and magnetic field correlated with the rf breakdowns using the FACET bunch parameters. The wakefields were calculated by a frequency domain method using periodic eigensolutions. Such a method takes into account wall losses and is applicable to a large variety of geometries. The maximum achieved accelerating gradient is 0.3 GV/m with a peak surface electric field of 1.5 GV/m and a pulse length of about 2.4 ns.
Download or read book High Gradient RF Breakdown Studies written by Lisa Leanne Laurent and published by . This book was released on 2002 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book RF Properties of Periodic Accelerating Structures for Linear Colliders written by J. W. Wang and published by . This book was released on 1989 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Frontiers Of Accelerator Technology Proceedings Of The Joint Us cern japan International School written by Melvin Month and published by World Scientific. This book was released on 1999-03-23 with total page 875 pages. Available in PDF, EPUB and Kindle. Book excerpt: The motivation to conceive and build accelerators comes from a most fundamental need of man — to understand and control the world around us. With beams and their associated accelerators, scientists and engineers can gain understanding of the nature of matter and modify matter, which is not possible by other means. The areas already influenced by the developments in accelerator technology are high energy and nuclear physics, atomic and molecular physics, condensed matter physics and the biological sciences. There are also a growing number of applications in medicine and industry.This book summarizes all the currently available knowledge on the rf technology driving the development of particle beams for science, medicine and industry. It is a unique collection of information on this technology.
Download or read book RF Breakdown in X Band Waveguides written by and published by . This book was released on 2004 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: Next generation of linear accelerators will have multimegawatt rf systems. The RF system of the Next-Linear Collider (NLC) will have hundreds of waveguide components and high-gradient accelerating structures. Waveguide components should reliably handle up to 600 MW of a 400 ns, 11.424 GHz rf pulse [1]. RF breakdown at such high power could damage these components. For example, breakdown damage is a major issue for long term operation of high-gradient accelerating structures [2]. An extensive experimental and theoretical program to study phenomena of rf breakdown is under way in SLAC. This work is a part of this program. Our experiments with rf breakdowns in a copper low-magnetic field waveguide are described in [3]. Here we discuss study of a copper high-magnetic-field waveguide and a low-magnetic-field waveguide with walls made of copper, gold and stainless steel. All experiments are done at a frequency of 11.424 GHz.
