Experimental Experience with a Thermionic RF-Gun (original) (raw)
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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
Development of a Thermionic Triode RF Gun
2009
A thermionic triode rf gun is being developed to mitigate the adverse effect of electron back-bombardment onto the cathode inherent in conventional rf guns. An coaxial rf cavity with a thermionic cathode on the inner rod of the coax was designed and fabricated, which is to be installed in an existing conventional rf gun to configure the rf triode structure. The rf coupler geometry between the coaxial cavity and the rf waveguied was designed by use of a 3-D electromagnetic field solver. Numerical comparisons were made between two candidates, namely W and LaB 6 , for the thermionic cathode material. As the result, unlike in the conventional rf gun, W cathode is found to enable a longer macro-pulse duration for the same back-bombardment power. Expected macro-pulse duration by the triode rf gun is twice as long as the conventional gun with ~10 times higher peak current without degradation in emittance.
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.
Photocathode operation of a thermionic RF gun
Nuclear Instruments and Methods in Physics Research Section a Accelerators Spectrometers Detectors and Associated Equipment, 2009
The thermionic RF gun using a BaO cathode at the MAX-lab linac injector has been successfully commissioned for additional operation as a photocathode gun. By retaining the BaO cathode, lowering the temperature below thermal emission and illuminating it with a UV (263 nm) 9 ps laser pulse a reduced emittance and enhanced emission control has been achieved. Measurements show a normalised emittance of 5.5 mm mrad at 200 pC charge and a maximum quantum efficiency of 1:1 Â 10 À4. The gun is now routinely switched between storage ring injections in thermionic mode and providing a beam for the MAX-lab test FEL in photocathode mode.
ADAPTION OF AN RF-GUN FROM THERMIONIC TO PHOTO CATHODE
2004
The thermionic RF-gun operating at the injector at MAX-lab is being adapted to a photo cathode. A 5 ns laser system will produce pulses suitable for the new 100 MHz RF system of the storage rings and allow for a reduced emittance and beam loading.
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.
Thermocathode radio-frequency gun for the Budker Institute of Nuclear Physics free-electron laser
Physics of Particles and Nuclei Letters, 2016
A radio-frequency (RF) gun for a racetrack microtron-recuperator injector driving the free-electron laser (FEL) (Budker Institute of Nuclear Physics) is being tested at a special stand. Electron bunches of the RF gun have an energy of up to 300 keV and a repetition rate of up to 90 MHz. The average electro-beam current can reach 100 mA in the continuous operation regime. The advantages of the new injector are as follows: long lifetime of the cathode for high average beam current; simple scheme of longitudinal beam bunching, which does not require an additional bunching resonator in the injector; absence of dark-current contamination of the injector beam; and comfortable RF gun operation due to the absence of a high potential of 300 kV at the cathode control circuits. In this study we describe the RF gun design, present the main characteristics of the injector with the RF gun, and give the results of testing.
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.
2005
We have investigated the use of triode structure in a thermionic rf gun in order to minimize the inherent backbombardment of electrons onto the cathode. By using an rf powered extractor grid in the triode structure, the electric fields in the vicinity of the cathode surface can be controlled independent from the phase of rf field in the main accelerating cells. Significant reduction of backbombardment power up to 99% is shown with rf input powers of ~40 kW to the extractor grid, using a twodimensional particle simulation code. Also, preliminary refinement of the triode configuration has shown reasonably acceptable emittance degradation at the first cell exit in a 4.5-cell structure and a rather higher peak current than the conventional rf gun.
Beam Dynamic Analysis of RF Modulated Electron Beam Produced by Gridded Thermionic Guns
2021
A thermionic cathode gridded electron gun used in injectors for different types of circular and linear particle accelerators and for energy recovery configurations was studied. Both theory and numerical simulation were used to explore the relationship between the bunch charge and bunch length. The electron gun is based on a Pierce-type geometry. It was initially designed using Vaughan synthesis followed by optimization using a 2D electron trajectory solver TRAK. After optimization, the grid in front of the cathode was inserted and the RF field was introduced through a coaxial waveguide structure. The complete gun was simulated using the PIC code MAGIC. High duty cycle operations at frequencies 1.5 GHz and 3.0 GHz, were investigated using different combinations of both the bias and the RF voltage applied between the cathode and the grid. The beam dynamics results from the PIC showed that a minimum bunch length of 10⁶ ps could be achieved with a bunch charge of 33 pC when the driving ...