Download or read book Polarization and Charge Limit Studies of Strained GaAs Photocathodes written by Pablo J. Saez and published by . This book was released on 1997 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Polarization and Charge Limit Studies of Strained GaAs Photocathodes written by and published by . This book was released on 1997 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents studies on the polarization and charge limit behavior of electron beams produced by strained GaAs photocathodes. These photocathodes are the source of high-intensity, high-polarization electron beams used for a variety of high-energy physics experiments at the Stanford Linear Accelerator Center. Recent developments on P-type, biaxially-strained GaAs photocathodes have produced longitudinal polarization in excess of 80% while yielding beam intensities of (approximately) 2.5 A/cm2 at an operating voltage of 120 kV. The SLAC Gun Test Laboratory, which has a replica of the SLAC injector, was upgraded with a Mott polarimeter to study the polarization properties of photocathodes operating in a high-voltage DC gun. Both the maximum beam polarization and the maximum charge obtainable from these photocathodes have shown a strong dependence on the wavelength of illumination, on the doping concentration, and on the negative electron affinity levels. The experiments performed for this thesis included studying the effects of temperature, cesiation, quantum efficiency, and laser intensity on the polarization of high-intensity beams. It was found that, although low temperatures have been shown to reduce the spin relaxation rate in bulk semiconductors, they don't have a large impact on the polarization of thin photocathodes. It seems that the short active region in thin photocathodes does not allow spin relaxation mechanisms enough time to cause depolarization. Previous observations that lower QE areas on the photocathode yield higher polarization beams were confirmed. In addition, high-intensity, small-area laser pulses were shown to produce lower polarization beams. Based on these results, together with some findings in the existing literature, a new proposal for a high-intensity, high-polarization photocathode is given. It is hoped that the results of this thesis will promote further investigation on the properties of GaAs photocathodes.
Download or read book Measurement of Charge Limit in a Strained Lattice GaAs Photocathode written by and published by . This book was released on 1993 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: The SLAC Linear Collider (SLC) Polarized Electron Source (PES) photocathodes have shown a charge saturation when illuminated with a high intensity laser pulse. This charge limit in the cesium-activated GaAs crystal seems to be strongly dependent on its surface condition and on the incident light wavelength. Charge limit studies with highly polarized strained lattice GaAs materials are presented.
Download or read book Experimental Studies of the Charge Limit Phenomenon in GaAs Photocathodes written by and published by . This book was released on 1993 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: GaAs photocathodes have been in use for generating high intensity polarized electron beams (up to a peak current of 6 A in 2 ns pulses) for the SLC high energy physics program. If the quantum efficiency (measured at low light intensities) of a GaAs photocathode is below a certain level, the maximum photoemitted charge is found to be limited by the intrinsic properties of the cathode instead of by the space charge limit. We have studied this charge limit phenomenon in a variety of GaAs photocathodes. The effects of the quantum efficiency, excitation laser wavelength, and extraction electric field on the charge limit have been examined. The temporal behavior of the charge limit as manifested in both intrapulse and interpulse effects has also been studied. These results will be discussed in light of possible mechanisms.
Download or read book A Polarization Study of Strained GaAs Photocathode Structures written by and published by . This book was released on 1996 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: The polarized electron source at SLAC has performed extremely well during recent years supplying electrons having a spin polarization of 78% (85%) for high (low) current operation with beam current limited primarily by experimental requirements. However, there is room for improvement in the electron polarization. The less-than-ideal polarizations are a result of both imperfections and depolarizing mechanisms within the photocathode. The structure of the photocathode used at SLAC in the polarized electron source is a single-strained emitting layer structure grown atop a GaAs substrate. Here, the properties of several types of strained GaAs and GaAsP photocathodes have been studied using x-ray diffraction and photoemission.
Download or read book Photodetectors and Power Meters written by and published by . This book was released on 1993 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book European Particle Accelerator Conference Epac 94 In 3 Volumes written by Christine Petit-jean-genaz and published by World Scientific. This book was released on 1994-11-26 with total page 2968 pages. Available in PDF, EPUB and Kindle. Book excerpt: These proceedings aim to provide a comprehensive overview of research, technology and applications in the field of accelerators. Contributions from the entire field of accelerators are presented, including low and high energy machines, and medical and industrial accelerators.
Download or read book Experimental Studies of the Charge Limit Phenomenon in NEA GaAs Photocathodes written by and published by . This book was released on 1994 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: Negative electron affinity GaAs photocathodes have been in continuous use at SLAC for generating polarized electron beams since early 1992. If the quantum efficiency of a GaAs cathode is below a critical value, the maximum photoemitted charge with photons of energies close to the band gap in a 2-ns pulse is found to be limited by the intrinsic properties of the cathode instead of by the space charge limit. We have studied this novel charge limit phenomenon in a variety of GaAs photocathodes of different structures and doping densities. We find that the charge limit is strongly dependent on the cathode's quantum efficiency and the extraction electric field, and to a lesser degree on the excitation laser wavelength. In addition, we show that the temporal behavior of the charge limit depends critically on the doping density.
Download or read book Polarized Beams And Polarized Gas Targets Proceedings Of The International Workshop written by Hans Paetz Gen Schieck and published by World Scientific. This book was released on 1996-03-21 with total page 478 pages. Available in PDF, EPUB and Kindle. Book excerpt: The International Workshop on Polarized Beams and Polarized Gas Targets was held in Cologne, Germany from June 6 to 9, 1995 as the last in a series held at 2-3 years intervals. It was attended by about 110 scientists; there were 47 invited and contributed talks, 5 round-table discussions and 17 poster contributions, all of which will appear as a written contribution in the Proceedings. The main subjects were Optically-Pumped Polarized Targets, Polarized Electron Sources, Atomic-Beam Polarized-Ion Sources, Optically-Pumped Polarized Ion Sources, Targets and Storage Rings. Significant progress and latest developments in this field were covered as well as future developments both from the technical, but also from the physics aspects.
Download or read book Spin Physics written by Donald G. Crabb and published by American Inst. of Physics. This book was released on 2009-08-25 with total page 1236 pages. Available in PDF, EPUB and Kindle. Book excerpt: The topics covered in the conference ranged from the physics that can be done with polarized beams of particles (protons, electrons, gamma-rays, etc.) to the techniques and instrumentation necessary to achieve this. Topics included: nucleon structure measurements (from where does the spin of the proton and neutron come), the acceleration, storage and polarization of particle beams and the polarized targets and sources necessary for mounting the experiments.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1995 with total page 782 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Chemical Abstracts written by and published by . This book was released on 2002 with total page 2002 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2003 with total page 580 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proceedings of the Ninth International Workshop Polarized Sources and Targets written by Vladimir P. Derenchuk and published by World Scientific. This book was released on 2002 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is an up-to-date survey of the science and technology of creating polarized beams and polarized targets. The papers in this collection describe state-of-the-art sources of polarized electrons, ions, atoms, neutrons, and radioactive isotopes, discuss new polarized solid and gas target techniques, present recent advances in polarimetry, and review the use of polarized gas in medical imaging.
Download or read book High Energy Accelerators Heacc 92 Proceedings Of The Xv International Conference In 2 Volumes written by J Rossbach and published by World Scientific. This book was released on 1993-02-10 with total page 1288 pages. Available in PDF, EPUB and Kindle. Book excerpt: The High Energy Accelerator Conference has always been the monitor of the state of the art and the new trends in planning, construction and operation of large particle accelerators. It is held every three years. The 1992 conference is devoted to High Energy Hadron Accelerators and Colliders, Linear Colliders, e⁺e⁻ Storage Rings and related Technologies for these machines. In addition to status reports and contributed papers, the program features twelve survey talks which include summaries of individual poster papers.
Download or read book Polarized Sources And Targets Proceedings Of The Ninth International Workshop written by Vladimir (Laddie) Derenchuk and published by World Scientific. This book was released on 2002-05-16 with total page 397 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is an up-to-date survey of the science and technology of creating polarized beams and polarized targets. The papers in this collection describe state-of-the-art sources of polarized electrons, ions, atoms, neutrons, and radioactive isotopes, discuss new polarized solid and gas target techniques, present recent advances in polarimetry, and review the use of polarized gas in medical imaging.
