Title :
High power free electron maser based on a two-dimensional Bragg cavity
Author :
Konoplev, I.V. ; McGrane, P. ; Cross, A.W. ; Phelps, A.D.R. ; He, W. ; Whyte, C.G. ; Ronald, K. ; Ginzburg, N.S. ; Peskov, N.Y. ; Sergeev, A.S. ; Thumm, M.
Author_Institution :
Dept. of Phys., Strathclyde Univ., Glasgow, UK
Abstract :
Summary form only given. The use of two-dimensional (2D) Bragg structures has been suggested for application in microwave electronics and integrated optics to synchronise radiation from different parts of an oversized active medium and to improve mode selection inside the interaction space. Computational modelling and experimental measurements of the field evolution inside co-axial 2D Bragg structures as well as recent progress in the use of these structures to define the cavity of a high power Free Electron Maser (FEM) will be presented. The 2D Bragg cavity has been designed and constructed. Microwave measurements have been performed using a Vector Network Analyser. Good agreement between the measured transmission properties of the 2D Bragg structures and PIC code (MAGIC) simulations was obtained. The high current accelerator to drive the FEM consists of a Marx bank power supply which resonantly charges a transmission line which subsequently discharges through a high pressure (16 Bar) nitrogen-filled spark gap providing a 200 ns duration flat-top high voltage pulse to an explosive emission electron (EEE) gun diode immersed in a 0.6 T guide field provided by a 30 cm diameter 2.25 m long solenoid. The guide magnetic field insulates and confines an annular relativistic electron beam of energy 500 keV. The oversized (7 cm diameter) annular electron beam was passed through an azimuthally symmetric wiggler with the interaction space defined by two-dimensional (2D) Bragg structures. The maximum possible beam current transportable through the diode region and interaction space was calculated using the 2.5 D PIC code KARAT. An electron beam of power 750 MW has been measured in the experiment. An FEM output efficiency of up to 15% has been predicted by the calculations. This paper will present the progress made towards the generation of /spl sim/100 MW of power from the co-axial 2D Bragg FEM operating at a frequency of 37.5 GHz.
Keywords :
diodes; electron guns; explosions; field emission electron microscopy; free electron lasers; high-frequency discharges; integrated optics; masers; microcavity lasers; plasma transport processes; relativistic electron beams; sparks; 100 MW; 2.25 m; 200 ns; 30 cm; 37.5 GHz; 7 cm; Bragg structure; FEM; KARAT code; MAGIC PIC code; Marx bank power supply; annular relativistic electron beam; beam current transport; computational modelling; current accelerator; diode region; discharge; high power free electron maser; interaction space; magnetic field insulate; microwave electronics; microwave measurement; nitrogen filled spark gap; symmetric wiggler; synchronise radiation; transmission line; two-dimensional Bragg cavity; vector network analyser; Computational modeling; Diodes; Electron beams; Integrated optics; Magnetic field measurement; Masers; Microwave measurements; Power measurement; Pulsed power supplies; Transmission line measurements;
Conference_Titel :
Plasma Science, 2004. ICOPS 2004. IEEE Conference Record - Abstracts. The 31st IEEE International Conference on
Conference_Location :
Baltimore, MD, USA
Print_ISBN :
0-7803-8334-6
DOI :
10.1109/PLASMA.2004.1340010