Beam Dynamic Analysis of RF Modulated Electron Beam Produced by Gridded Thermionic Guns (original) (raw)
Related papers
IEEE Transactions on Electron Devices
In this paper, the design and simulation of an electron injector based on a thermionic RF modulated electron gun for particle accelerator applications is presented. The electron gun is based on a gridded thermionic cathode with the geometry based on a Pierce-type configuration. Both theory and numerical simulation were used to explore the relationship between the bunch length and charge. The reasons for the pulse widening were also analyzed. The beam dynamics simulations showed that a minimum pulse length of 106 ps could be achieved with a bunch charge of 33 pC when the driving RF frequency was 1.5 GHz. The average transverse emittance was about 17 mm⸱mrad from the particle-in-cell simulations. Operating at a higher RF frequency did not significantly reduce the micro-pulse length.
Design and Construction of a Thermionic Cathode RF Electron Gun for Iranian Light Source Facility
2014
We present a program for the design and construction of a thermionic cathode RF gun to produce bright electron beams, consisting in the first step toward the possible development of S band linac based pre-injector at Iranian Light Source Facility (ILSF). The program is aimed at the goal to attain a beam quality as requested by ILSF. As a first step within this mainstream, we are currently developing a thermionic cathode side coupling RF electron gun which is expected to deliver 100 pC bunches with emittances below 2 mm-mrad at 2.5 MeV. We report the performed simulation and design activity, as well as cold test results of first fabricated prototype, which are in good agreement with simulation results.
A New Thermionic RF Electron Gun for Synchrotron Light Sources
2017
A thermionic RF gun is a compact and efficient source of electrons used in many practical applications. RadiaBeam Systems and the Advanced Photon Source of Argonne National Laboratory collaborate in developing of a reliable and robust thermionic RF gun for synchrotron light sources which would offer substantial improvements over existing thermionic RF guns and allow stable operation with up to 1A of beam peak current at a 100 Hz pulse repetition rate and a 1.5 μs RF pulse length. In this paper, we discuss the electromagnetic and engineering design of the cavity, and report the progress towards high power tests of the cathode assembly of the new gun.
Thermionic Cathode-Grid Assembly Simulations for RF Guns
The projected electron RF gun [1] of the BINP Microtron-Recuperator injector employs a commercial thermionic cathode-grid assembly with 0.08 mm gap, that conventionally used in metal-ceramic RF tubes. Three-dimensional (3D) computer simulations have been performed that use the mesh refinement capability of the both Microwave Studio (MWS) and 2D SAM codes to examine the whole region of the real cathode-grid assembly in static fields in order to illustrate the beam quality that can result from such a gridded structure. These simulations have been found to reproduce the beam current dependency on applied potentials that are observed experimentally. Based on it ASTRA RF beam simulations also predict a complicated time-dependent response to the waveform applied to the grid during the current turn-on, calculation of the dissipated power by electrons at the grid, and particle tracking downstream of the grid into RF gun cavity and further on. These simulations may be representative in other...
Multi-Bunch Electron Beam Generation Based on CS-Te Photocathode RF-Gun at Waseda University
2010
At Waseda University, we have been studying a high quality electron beam generation and its application experiments with Cs-Te photocathode RF-Gun. We have already succeeded in generating a stable high-charged singlebunch electron beam. To generate more intense electron beam, we designed a multi-bunch electron linac and developed the multi-pulse UV laser which irradiates to the cathode. The target values of the number of electron bunch and bunch charges are 100bunches/train and 800pC/bunch, respectively. In addition, we adopted the method of the amplitude modulation of the incident RF pulse to the S-band klystron in order to compensate the energy difference in each bunch because of the slow rise time of acceleration voltage in cavity and beam loading effect in the accelerating structure.
Nuclear Instruments and Methods in Physics Research, 2002
Adverse effect of back-streaming electrons onto a thermionic cathode in an S-band 4.5-cell RF gun was studied. A numerical model is presented based on an equivalent circuit of the RF gun, taking beam-loading effect into account through 2-dimensional particle-in-cell simulations. Experimentally observed time evolutions of RF power reflected from the RF gun, and of output beam energy were both well reproduced by the present numerical model which takes a cathode temperature rise during the RF macro-pulse. In conclusion, observed undesirable decrease of beam energy during the macro-pulse is due to an increase of beam loading caused by a considerable increase of the cathode temperature due to back-streaming electrons hitting the cathode.
RF Guns for Generation of Polarized Electron Beams
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.
A Novel RF Excited Plasma Cathode Electron Beam Gun Design
IEEE Transactions on Electron Devices, 2014
This paper presents a new radio frequency (RF) excited plasma-cathode electron beam (EB) gun design and experimental results at a frequency of 84 MHz. The design offers the following benefits over thermionic-cathode triode EB guns: unlimited cathode lifetime and as a result reduced maintenance costs; no requirement for a grid electrode, avoiding beam aberration; and rapid beam pulsing. The construction of the diode gun was completed and the results of this work demonstrate that the electron beam can be switched on in 200 ns and off within 800 ns. Electrons were extracted from a 2-3 mm plasma chamber and then accelerated by an electric field applied in a vacuum chamber at 10-5 to 10-6 mbar producing a collimated electron beam. The ionized gas used was nitrogen at a 0.5 to 1 bar pressure. The EB gun has been operated at-60 kV accelerating potential and has produced beams of up to 3.2 kW power continuous wave (CW). Modulation of the RF signal was used to control the beam power. Details of the design features of the plasma device are given and evidence of the advantages over conventional EB guns is provided through empirical results.
Microwave thermionic electron gun for synchrotron light sources
Journal of Physics: Conference Series, 2019
Thermionic RF guns are the source of electrons used in many practical applications, such as drivers for synchrotron light sources, preferred for their compactness and efficiency. RadiaBeam Systems has developed a new thermionic RF gun for the Advanced Photon Source at Argonne National Laboratory, which would offer substantial improvements in reliable operations with robust interface between the thermionic cathode and the cavity, as well as better RF performance, compared to existing models. This improvement became possible by incorporating new pi-mode electromagnetic design, robust cavity back plate design, and a cooling system that will allow stable operation for up to 1 A of beam current and 100 Hz rep rate at 3.0 μs RF pulse length, and 70 MV/m peak on axis field in the cavity. In this paper we discuss the electromagnetic and engineering design of the cavity and provide the test results of the new gun.
A rationalized approach to thermionic rf gun design
2001
The Advanced Photon Source (APS), in conjunction with Advanced Electronics Technologies Associates (AET), is developing newly designed thermionic-cathode rf guns to replace our aging (circa 1992) guns. Each of the three third-generation injectors will meet or exceed the present high-performance electron beam of its second-generation predecessor. Moreover, the new injector design addresses the historical difficulties of maintenance, reliability, and sparse documentation associated with the previous injectors. Engineering design improvements and required performance of the guns will be presented following a brief examination of the APS second-generation guns for comparison