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Emittance Compensation for Magnetized Beams

Description: Emittance compensation is a well established technique for minimizing the emittance of an electron beam from a RF photo-cathode gun. Longitudinal slices of a bunch have a small emittance, but due to the longitudinal charge distribution of the bunch and time dependent RF fields they are not focused in the same way, so that the direction of their phase ellipses diverges in phase space and the projected emittance is much larger. Emittance compensation reverses the divergence. At the location where… more
Date: June 25, 2007
Creator: Kewisch, J. & Chang, X.
Partner: UNT Libraries Government Documents Department
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Low Emittance Electron Beams for the Rhic Electron Cooler

Description: An electron cooler, based on an Energy Recovery Linac (ERL) is under development for the Relativistic Heavy Ion Collider (RMIC) at Brookhaven National Laboratory. This will be the first electron cooler operating at high energy with bunched beams. In order to achieve sufficient cooling of the ion beams the electron have to have a charge of 5 nC and a normalized emittance less than 4 {mu}. This paper presents the progress in optimizing the injector and the emittance improvements from shaping the … more
Date: June 25, 2007
Creator: Kewisch, J. & Chang, X.
Partner: UNT Libraries Government Documents Department
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Geometric optimization of the 56 MHz SRF cavity and its frequency table

Description: It is essential to know the frequency of a Superconducting Radio Frequency (SRF) cavity at its 'just being fabricated' stage because frequency is the key parameter in constructing the cavity. In this paper, we report our work on assessing it. We can estimate the frequency change from stage to stage theoretically and/or by simulation. At the operating stage, the frequency can be calculated accurately, and, from this value, we obtain the frequencies at other stages. They are listed in a table tha… more
Date: October 1, 2008
Creator: Chang, X. & Ben-Zvi, Ilan
Partner: UNT Libraries Government Documents Department
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Effects of liquid helium bubble formation in a superconducting cavity cryogenic system

Description: We constructed a simple prototype model based on the geometry of the 56 MHz superconducting cavity for RHIC. We studied the formation, in this prototype, of bubbles of liquid helium and their thermal effects on the cavity. We found that due to the low viscosity of the liquid helium, and its small surface tension, no large bubbles formed. The tiny bubbles, generated from most of the area, behaved like light gas travelling in a free space and escaped from the trapping region. The bubbles that wer… more
Date: March 1, 2011
Creator: Chang, X.; Wang, E. & Xin, T.
Partner: UNT Libraries Government Documents Department
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Compensation for Bunch Emittance in a Magnetization and Space Charge Dominated Beam.

Description: In order to obtain sufficient cooling rates for the Relativistic Heavy Ion Collider (RHIC) electron cooling, a bunched beam with high bunch charge, high repetition frequency and high energy is required and it is necessary to use a ''magnetized'' beam, i.e., an electron beam with non-negligible angular momentum. Applying a longitudinal solenoid field on the cathode can generate such a beam, which rotates around its longitudinal axis in a field-free region. This paper suggests how a magnetized be… more
Date: June 21, 2004
Creator: Chang, X.; Ben-Zvi, Ilan & Kewisch, J.
Partner: UNT Libraries Government Documents Department
open access

Design Considerations for Low Field Short Photo-Injected Rf Electron Gun With High Charge Electron Bunch.

Description: The RF field and space charge effect in a low field RF gun is given. The cell lengths are modified to have maximum accelerating efficiency. The modification introduces an extra RF field slice emittance. The phase space evolution of the following emittance compensation system is presented taking into account the chromatic effect. The emittance compensation mechanics for RF field and chromatic effect induced emittance is similar to that of compensating the space charge induced emittance. But the … more
Date: June 21, 2004
Creator: Chang, X.; Ben-Zvi, Ilan & Kewisch, J.
Partner: UNT Libraries Government Documents Department
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Measurement of the Secondary Emission Yield of a Thin Diamond Window in Transmission Mode.

Description: The secondary emission enhanced photoinjector (SEEP) is a promising new approach to the generation of high-current, high-brightness electron beams. A low current primary electron beam with energy of a few thousand electron-volts strikes a specially prepared diamond window which emits secondary electrons with a current two orders of magnitude higher. The secondary electrons are created at the back side of the diamond and drift through the window under the influence of a strong electrical field. … more
Date: May 16, 2005
Creator: Chang, X.; Rao, T.; Smedley, J. & AL., ET
Partner: UNT Libraries Government Documents Department
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Simulations for preliminary design of a multi-cathode DC electron gun for eRHIC

Description: The proposed electron ion collider, eRHIC, requires a large average polarized electron current of 50 mA, which is more than 20 times higher than the present experimental output of a single, highly polarized electron source, based on cesiated super-lattice GaAs. To meet eRHIC's requirement for current, we designed a multicathode DC electron gun for injection. The twenty-four GaAs cathodes emit electrons in sequence, then are combined on axis by a rotating field (or 'funnelled'). In addition to i… more
Date: May 23, 2010
Creator: Wu, Q.; Ben-Zvi, Ilan; Chang, X. & Skaritka, J.
Partner: UNT Libraries Government Documents Department
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Photocathodes for the Energy Recovery Linacs.

Description: This paper presents an overview of existing and emerging technologies on electron sources that can service various Energy Recovering Linacs under consideration. Photocathodes that can deliver average currents from 1 mA to 1 A, the pros and cons associated with these cathodes are addressed. Status of emerging technologies such as secondary emitters, cesiated dispenser cathodes, field and photon assisted field emitters and super lattice photocathodes are also reviewed.
Date: March 19, 2005
Creator: Rao, T.; Burrill, A.; Chang, X. Y.; Smedley, J. & Al., Et
Partner: UNT Libraries Government Documents Department
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Electron Cooling Simulations for Low-Energy Rhic Operation.

Description: Recently, a strong interest emerged in running the Relativistic Heavy Ion Collider (RHIC) at low beam total energies of 2.5-25 GeV/nucleon, substantially lower than the nominal beam total energy of 100 GeV/nucleon. Collisions in this low energy range are motivated by one of the key questions of quantum chromodynamics (QCD) about the existence and location of critical point on the QCD phase diagram. Applying electron cooling directly at these low energies in RHIC would result in significant lumi… more
Date: September 10, 2007
Creator: Fedotov, A. V.; Ben-Zvi, Ilan; Chang, X.; Kayran, D. & Satogata, T.
Partner: UNT Libraries Government Documents Department
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Optics for High Brightness and High Current Erl Project at Bnl.

Description: An energy recovery linac (ERL), under development at Brookhaven National Laboratory [1,2], will push ERLs further towards high current and high brightness beams. This R&D ERL will operate in two modes: a high current mode and a high charge mode. In this paper we present a lattice of the machine and PARMELA simulations from the cathode to the beam dump. We discuss the design considerations and present main parameters for various modes of operation.
Date: May 16, 2005
Creator: Kayran, D.; Ben-Zvi, Ilan; Calaga, R.; Chang, X. Y. & Al., Et
Partner: UNT Libraries Government Documents Department
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Feasibility of Electron Cooling for Low-Energy RHIC Operation

Description: A concrete interest in running RHIC at low energies in a range of 2.5-25 GeV/nucleon total energy of a single beam has recently emerged. Providing collisions in this energy range, which in the RHIC case is termed 'low-energy' operation, will help to answer one of the key questions in the field of QCD about existence and location of a critical point on the QCD phase diagram. However, luminosity projections are relatively low for the lowest energy points of interest. Luminosity improvement can be… more
Date: April 1, 2008
Creator: Fedotov, A.; Ben-Zvi, Ilan; Chang, X.; Kayran, D.; Litvinenko, V.; Pozdeyev, E. et al.
Partner: UNT Libraries Government Documents Department
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Thermal Emittance Measurement Design for Diamond Secondary Emission

Description: Thermal emittance is a very important characteristic of cathodes. A carefully designed method of measuring the thermal emittance of secondary emission from diamond is presented. Comparison of possible schemes is carried out by simulation, and the most accessible and accurate method and values are chosen. Systematic errors can be controlled and maintained at small values, and are carefully evaluated. Aberration and limitations of all equipment are taken into account.
Date: June 25, 2007
Creator: Wu, Q.; Ben-Zvi, Ilan; Burrill, A.; Chang, X.; Kayran, D.; Rao, T. et al.
Partner: UNT Libraries Government Documents Department
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Diamond Secondary Emitter

Description: We present the design and experimental progress on the diamond secondary emitter as an electron source for high average power injectors. The design criteria for average currents up to 1 A and charge up to 20 nC are established. Secondary Electron Yield (SEY) exceeding 200 in transmission mode and 50 in emission mode have been measured. Preliminary results on the design and fabrication of the self contained capsule with primary electron source and secondary electron emitter will also be presente… more
Date: October 9, 2005
Creator: Ben-Zvi, Ilan; Rao, T.; Burrill, A.; Chang, X.; Grimes, J.; Rank, J. et al.
Partner: UNT Libraries Government Documents Department
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The Penetrability of a Thin Metallic Film Inside the Rf Field.

Description: Thin metallic film was widely applied in various areas. Especially, recently we are planning to apply it in a ''Secondary emission enhanced photo-injector'', in which a diamond cathode is coated with a metallic film on its back to serve as a current path. The thickness of the film is originally considered to be in the order of 10 nm, which is much less than the skin depth, by a factor of almost 200. One would think intuitively that the RF filed would penetrate such a thin film. However, we foun… more
Date: May 16, 2005
Creator: Zhao, Y.; Ben-Zvi, Ilan; Chang, X.; Rao, T.; Chen, W.; Dinardo, R. et al.
Partner: UNT Libraries Government Documents Department
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Electron cooling for low-energy RHIC program

Description: Electron cooling was proposed to increase luminosity of the RHIC collider for heavy ion beam energies below 10 GeV/nucleon. Providing collisions at such energies, termed RHIC 'low-energy' operation, will help to answer one of the key questions in the field of QCD about existence and location of critical point on the QCD phase diagram. The electron cooling system should deliver electron beam of required good quality over energies of 0.9-5 MeV. Several approaches to provide such cooling were cons… more
Date: August 31, 2009
Creator: Fedotov, A.; Ben-Zvi, Ilan; Chang, X.; Kayran, D.; Litvinenko, V. N.; Pendzick, A. et al.
Partner: UNT Libraries Government Documents Department
open access

DIAMOND AMPLIFIER FOR PHOTOCATHODES.

Description: We report a new approach to the generation of high-current, high-brightness electron beams. Primary electrons are produced by a photocathode (or other means) and are accelerated to a few thousand electron-volts, then strike a specially prepared diamond window. The large Secondary Electron Yield (SEY) provides a multiplication of the number of electrons by about two orders of magnitude. The secondary electrons drift through the diamond under an electric field and emerge into the accelerating pro… more
Date: June 21, 2004
Creator: Rao, T.; Ben-Zvi, Ilan; Burrill, A.; Chang, X.; Hulbert, S.; Johnson, P. D. et al.
Partner: UNT Libraries Government Documents Department
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