Download or read book Polarized Electrons Using the PWT RF Gun written by and published by . This book was released on 2002 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: Future colliders that require low-emittance highly-polarized electron beams are the main motivation for developing a polarized rf gun. However there are both technical and physics issues in generating highly polarized electron beams using rf guns that remain to be resolved. The PWT design offers promising features that may facilitate solutions to technical problems such as field emission and poor vacuum. Physics issues such as emission time now seem to be satisfactorily resolved. Other issues, such as the effect of magnetic fields at the cathode-both those associated with the rf field and those imposed by schemes to produce flat beams-are still open questions. Potential solution of remaining problems will be discussed in the context of the PWT design.
Download or read book Polarized RF Guns written by and published by . This book was released on 1998 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: RF guns employing photocathodes are now well established as viable electron sources for accelerator applications. For high energy accelerators the desirable properties of such sources include the relative ease of pulse formation (using the source laser system to establish the pulse shape and number) and a low transverse beam emittance, eliminating the need for rf chopping and bunching systems and reducing the demands on emittance-reducing damping rings. However, most high-energy accelerators now require polarized electrons. Polarized electron beam scan in principle be generated by substituting a 3--5 semiconductor, such as GaAs, for the traditional photocathode in a conventional rf gun structure. In the past, the principal criterion for selection of photocathodes for rf guns has been the ability to maintain a reasonable quantum yield from the cathode over a relatively long operating period. It is well known that GaAs is significantly more sensitive to the vacuum environment than any of the cathode types that have been used to date. However, advances in the understanding of how to operate GaAs cathodes in hostile environments combined with similar advances in the ability to prepare gun structures that will significantly reduce dark current and rf breakdown lend credibility to the prospect of successfully operating an rf gun with the activated GaAs cathode. The status of research related to polarized rf guns is reviewed and the outline of a future polarized rf source combining the best of what is known. Today.
Download or read book ILC SLAC R D Program for a Polarized RF Gun written by and published by . This book was released on 2006 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photocathode rf guns produce high-energy low-emittance electron beams. DC guns utilizing GaAs photocathodes have proven successful for generating polarized electron beams for accelerators, but they require rf bunching systems that significantly increase the transverse emittance of the beam. With higher extraction field and beam energy, rf guns can support higher current densities at the cathode. The source laser system can then be used to generate the high peak current, relatively low duty-factor micropulses required by the ILC without the need for post-extraction rf bunching. The net result is that the injection system for a polarized rf gun can be identical to that for an unpolarized rf gun. However, there is some uncertainty as to the survivability of an activated GaAs cathode in the environment of an operating rf gun. Consequently, before attempting to design a polarized rf gun for the ILC, SLAC plans to develop an rf test gun to demonstrate the rf operating conditions suitable for an activated GaAs cathode.
Download or read book Polarized RF Guns for Linear Colliders written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The ICFA Workshop on Polarized RF Guns for Linear Colliders was held at Fermilab during April 18-20, 2001. It was attended by 37 scientists from 14 institutions. A list of participants is appended. An RF photoemission gun that delivers polarized electrons at low emittance would be an attractive electron source for a linear collider. Moreover, recently it has been demonstrated that an RF gun in conjunction with nearby injection system optics can deliver a beam with a high ratio of transverse emittances; a simplification of a linear collider's damping system could result. However, at present RF electron gun technology has not developed sufficiently to assure that such a source is feasible. The purpose of the workshop was to review the status of polarized RF gun development with linear collider application in mind, and outline a possible program for the future. A table lists the requirements for the electron injector for proposed linear colliders. The specifications are given for the beam before and after the electron damping ring.
Download or read book RF Guns for Generation of Polarized Electron Beams written by R. E. Kirby and published by . This book was released on 2005 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Several accelerators, including the SLC, JLAB, Mainz, Bates/MIT, and Bonn have successfully operated for medium and high energy physics experiments using polarized electron beams generated by dc-biased guns employing GaAs photocathodes. Since these guns have all used a bias on the order of 100 kV, the longitudinal emittance of the extracted bunch is rather poor. Downstream rf bunching systems increase the transverse emittance. An rf gun with a GaAs photocathode would eliminate the need for separate rf bunchers, resulting in a simpler injection system. In addition, the thermal emittance of GaAs-type cathodes is significantly lower than for other photocathode materials. The environmental requirements for operating activated GaAs photocathodes cannot be met by rf guns as currently designed and operated. These requirements, including limits on vacuum and electron back bombardment, are discussed in some detail. Modifications to actual and proposed rf gun designs that would allow these requirements to be met are presented.
Download or read book Polarized Sources and Targets written by Tomohiro Uesaka and published by World Scientific. This book was released on 2007-04-26 with total page 269 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polarized beams and targets have been irreplaceable tools in nuclear and particle physics experiments for a long time and have provided us rich information on the role played by spin-degrees of freedom in the sub-nuclear world. In addition, techniques to obtain large nuclear polarization have recently been applied to new fields such as materials and medical sciences. The scope of these proceedings covers recent progress of state-of-the-art techniques in spin polarization, the cryogenic method, the atomic beam method, the optical pumping method and the nuclear reaction method.
Download or read book Polarized Sources Targets and Polarimetry written by Giuseppe Ciullo and published by World Scientific. This book was released on 2011 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book collects the most recent experimental results, new ideas and prototypes in the field of nuclear gaseous and solid polarized targets and polarimetry. It contains the contribution of the biennial meeting on the topics of Polarized Sources, Targets and Polarimetry. Therefore includes the most recent developments and performances in the field and new proposals. The contributing authors are the experts of the field. The topics covered include: Polarized Electron Sources, Polarized Proton and Deuterium Sources, Polarized Internal Targets, Polarized 3He Ion Sources and Targets, Polarimetry (e, p, d) at Low and High Energy, Polarized antiprotons, Polarized Solid Targets.
Download or read book Progress on a Cryogenically Cooled RF Gun Polarized Electron Source written by H. Edwards and published by . This book was released on 2006 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: RF guns have proven useful in multiple accelerator applications. An RF gun capable of producing polarized electrons is an attractive electron source for the ILC or an electron-ion collider. Producing such a gun has proven elusive. The NEA GaAs photocathode needed for polarized electron production is damaged by the vacuum environment in an RF gun. Electron and ion back bombardment can also damage the cathode. These problems must be mitigated before producing an RF gun polarized electron source. In this paper we report continuing efforts to improve the vacuum environment in a normal conducting RF gun by cooling it with liquid nitrogen after a high temperature vacuum bake out. We also report on a design of a cathode preparation chamber to produce bulk GaAs photocathodes for testing in such a gun. Future directions are also discussed.
Download or read book The Polarized SRF Gun Experiment written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: RF electron guns are capable of producing electron bunches with high brightness, which outperform DC electron guns and may even be able to provide electron beams for the ILC without the need for a damping ring. However, all successful existing guns for polarized electrons are DC guns because the environment inside an RF gun is hostile to the GaAs cathode material necessary for polarization. While the typical vacuum pressure in a DC gun is better than 10−11 torr the vacuum in an RF gun is in the order of 10−9 torr. Experiments at BINP Novosibirsk show that this leads to strong ion back-bombardment and generation of dark currents, which destroy the GaAs cathode in a short time. The situation might be much more favorable in a (super-conducting) SRF gun. The cryogenic pumping of the gun cavity walls may make it possible to maintain a vacuum close to 10−12 torr, solving the problem of ion bombardment and dark currents. Of concern would be contamination of the gun cavity by evaporating cathode material. This report describes an experiment that Brookhaven National Laboratory (BNL) in collaboration with Advanced Energy Systems (AES) is conducting to answer these questions.
Download or read book An RF Gun as a Polarized Source for TESLA written by Siegfried Schreiber and published by . This book was released on 1997 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Prospects for Generating Polarized Electron Beams for a Linear Collider Using an RF Gun written by and published by . This book was released on 1993 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: The next generation of linear colliders--represented by the Japanese Linear Collider (JLC) and the Next Linear Collider (NLC)--will probably utilize polarized electrons generated by a photocathode gun. A photocathode gun with high polarization (P{sub e}) photocathodes (up to Pe(approximately)80% achieved to date) is currently providing polarized electrons for the SLC. The SLC source requires subharmonic bunching at low energy to reduce the bunch length prior to S-band bunching and a damping ring at high energy to reduce the transverse emittance. The use of an RF gun can eliminate the former and possibly simplify the latter. However, RF guns as presently developed have serious problems with vacuum contamination, which would quickly lower the quantum efficiency (QE) of a semiconductor photocathode. In addition, the ''charge limit'' previously reported for high peak current pulses puts a limit on the laser power usable for photoexciting a low QE cathode near the bandgap threshold. These problems have so far precluded any serious attempt to design an RF gun for polarized electrons. Several technical advances that now improve the prospects for a practical polarized electron RF gun are described. Finally, new ideas for high polarization photocathodes that permit operation in a relatively poor vacuum and techniques being explored to mitigate the low QE ''charge-limit'' are discussed.
Download or read book Polarized Electrons from High gradient Guns written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: To take advantage of the lower emittance associated with extraction fields” 10 MV/m, a number of technological hurdles must be overcome before photocathodes appropriate for generating polarized electrons can be utilized in high-gradient guns. Both rf guns and very fast ultra-high gradient ([ge] 1 GV/m) diode guns are anticipated. The known problems--some of which may be more than just technical--are delineated, and the present status of relevant research is reviewed.
Download or read book Der kurpf lzische Hofbildhauer Paul Egell 1 1988 written by Klaus Lankheit and published by . This book was released on 1988 with total page 605 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurement and Control of Charged Particle Beams written by Michiko G. Minty and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt: From the reviews: "This book is a very welcome and valuable addition to the accelerator literature. As noted by the authors, there is relatively little material in the book specifically for low-energy machines, but industrial users may still find it useful to read." Cern Courier
Download or read book The Physics and Applications of High Brightness Electron Beams written by Jamie Rosenzweig and published by World Scientific. This book was released on 2003 with total page 563 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains the contributions to the Workshop on the Physics and Applications of High Brightness Electron Beams, held in July 2002 in Sardinia, Italy. This workshop had a broad international representation from the fields of intense electron sources, free-electron lasers, advanced accelerators, and ultra-fast laser-plasma, beam-plasma and laser-beam physics. The interdisciplinary participants were brought together to discuss advances in the creation and understanding of ultra-fast, ultra-high brightness electron beams, and the unique experimental opportunities in frontier high-energy-density and radiation-source physics which are offered by these scientific tools.The proceedings have been selected for coverage in: ? Index to Scientific & Technical Proceedings? (ISTP? / ISI Proceedings)? Index to Scientific & Technical Proceedings (ISTP CDROM version / ISI Proceedings)
Download or read book Progress on Using NEA Cathodes in an RF Gun written by T. Anderson and published by . This book was released on 2005 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: RF guns have proven useful in multiple accelerator applications, and are an attractive electron source for the ILC. Using a NEA GaAs photocathode in such a gun allows for the production of polarized electron beams. However the lifetime of a NEA cathode in this environment is reduced by ion and electron bombardment and residual gas oxidation. We report progress made with studies to produce a RF gun using a NEA GaAs photocathode to produce polarized electron beams. We discuss simulations of ion back bombardment and attempts to reduce the residual gas pressure in the gun are discussed. Future directions are also discussed.
