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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 beam can be accelerated and transported from a RF photocathode electron gun to the cooling section without significantly increasing its emittance. The evolution of longitudinal slices of the beam under a combination of space charge and magnetization is investigated, using paraxial envelope equations and numerical simulations. We find that we must modify the traditional method of compensating for emittance as used for normal non-magnetized beam with space charge to account for magnetization. The results of computer simulations of successful compensation are presented. Alternately, we show an electron bunch density distribution for which all slices propagate uniformly and which does not require emittance compensation. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

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 requirements are different to have best compensation for them. The beam waist is far in front of linac entrance to have best compensation for the RF field and chromatic effect induced emittance. For low field RF gun with high charge electron bunch this compensation is more important. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

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 region proper of the “gun” through a Negative Electron Affinity surface of the diamond. The advantages of the new approach include the following: 1. Reduction of the required number of primary electrons by the large SEY, i.e. we can utilize a very low laser power in a photocathode producing the primaries. 2. Low thermal emittance due to the NEA surface and the rapid thermalization of the electrons.3. Protection of the cathode from possible contamination from the gun, allowing the use of large quantum efficiency but sensitive cathodes. 4. Protection of the gun from possible contamination by the cathode, allowing the use of superconducting gun cavities. 5. Production of high average currents, up to ampere class. 6. Encapsulated design, making the “load-lock” systems unnecessary. This paper presents the criteria that need to be taken into account in designing the amplifier. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]