Gridded Window Testing Al Moretti, M. Alsharoa ; IIT and Muonsinc. 1 - PowerPoint PPT Presentation

Gridded Window Testing Al Moretti, M. Alsharoa ; IIT and Muonsinc. 1

Outline  Slides 3 and 4 are from the work of Mohamed Alsharoa formally of IIT and Muonsinc Inc.  Slide 3 shows the possible patterns of the grids or grill.  Slide 4 shows Ansys calculation of the electric field gradient.  Describe a ideal that may suppress breakdow in a magnetic field. 2

I. DESCRIPTION OF THE CLOSED CELL 805 MHZ TEST CAVITY  Design variables: • tube outer diameter, tube wall thickness • number of tubes and grids • grid spacing • type of coolant and coolant flow rate • grid configuration: physically and electrically connected grids or plane grid (waffle grid) Fig. 1a Cross-sectional view of the closed-cell 805 MHz test cavity Fig.1.b waffle grid Fig. 1.b connected grids Fig. 1.c Description of the model  The cavity model contains a Be-window from one side and a gridded-tube structure from the other side that was built in place of the other Be- window at the same location.  To reduce the computation time, quarter of cavity is considered, and the tubes are represented as solid cylinders for the modal analysis for solving for E and H fields. 3

 E max at the tube surface/E max at the center of the cavity (tubes field enhancement) = 1.8 Fig. 12 Contour plot of the magnitude of the electric field Fig. 13 Contour plot of the magnitude of the magnetic field 4

Discussion of Idea the Gridded Window Suppress Breakdown  The grids minimize the surface area subjected to the high gradient.  If the grids are rotated 90 Deg. to each other, the surface area is reduced even more.  The RF electric and magnetic field pattern is also different which could effect the focusing efficiency of the DC magnetic field.  This technique works to prevent multipactor in klystrons. It is called castelating.  The aluminum gridded window have been already made.  So I think it should be test at very end of this run. 5