Preliminary List of Questions on the Mechanical Assembly for the 8 8 Prototype

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Dylan Russell
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1 Revision History May 24, 2009 Initial Creation HJF Preliminary List of Questions on the Mechanical Assembly for the 8 8 Prototype 1 Window (Top Plate) Window Transmission Spectral Range nm Window Reflection (total both surfaces) Window material? Borosilicate glass Ceramic Window construction? Flat plate Ribbed Plate Window outside dimensions Window thickness Window flatness (under pressure) Window coating (photo-cathode) 2 Sidewalls What material? Borosilicate glass Ceramic? How thick? Optimum thickness for pins??? Optimum thickness for top seal?? Method of seal to top? Ceramic cement?? Laser weld, Indium, Surlyn,..? Method of seal to base? Fuse with Frit? Laser weld, Ceramic cement? Can we laser seal to base?? - Is one piece tray (sides/base) better? - 3 Bottom Plate Bottom plate material? Borosilicate glass Ceramic Bottom plate construction? Flat plate Ribbed Plate Bottom plate outside dimensions Bottom plate thickness Bottom plate flatness (under pressure) 1

2 4 Anode Signal and HV Pins HV Pin material? HV Pin conductor dimensions HV Method of seal to sidewall? Wire/glass bond Signal Pin Impedance (Sig-Gd pair) 50 ohms Signal Pin geometry Strip-line Parallel wire pair Signal Pin conductor dimensions 3 mm S/G conductor separation 1.5 mm S/G Pin channel-to-channel separation 3.2 mm (16/inch) Signal Pin material? Signal Surrounding material Borosilicate glass Signal Method of seal to sidewall Fused prefab insert? Signal Method of connection to ASIC Bump-bond on glass Daughter PC card 5 Internal Electrical Contacts Number of HV pins 6 HV pin functions PC,MCP1 IN,MCP1 OUT, MCP2 IN, MCP2 OUT,HV GD HV pin connections Wire with slip-on connectors HV wire material HV internal pin and finger connectors HV PC and MCP contact method spring-loaded grid HV PC and MCP contact dimensions spring-loaded grid 1 -square (like spacer),with HV tabs HV PC and MCP contact material Kovar Titanium? Anode pin functions Signal and Gd Anode pin connections Plane with springy fingers Anode connector material gold-plated Kovar? HV PC and MCP contact dimensions 6 Spacers Spacer material? Borosilicate glass Moldable ceramic? Spacer outside dimensions Spacer geometry Spacer thickness Spacer flatness (under pressure) Spacer asymptotic cost 2

3 7 Getters What pressure do we need to maintain? What temperature do we bake at? 400C? What gas(es) are the main problem? What is the surface area of the capillaries? What ratio of surface areas (getter/capil.) do we need? How do we activate the getter? Current through pins RF; baking module. Do we need to be able to reactivate the getter? Where is the getter located? What is the geometry of the getter(s)? What are the cost considerations for getters? Are there adequate getters available now? Which? 8 Glossary Here s a short glossary (See Figure 1). Below the anode 1. Window- The clear plate that forms the top of the vacuum volume where light comes in. The photo-cathode (PC) is deposited on the inside of the window. 2. Spacers- air pressure on the top and bottom plates will be countered by open thinwall lattices that transmit these forces through the MCP stack and anode much like load-bearing walls in a house. 3. Side walls- the side walls of the vacuum volume, which may or may not be separate from the bottom plate. The window is sealed to the top of the side walls. 4. MCP Stack (aka Innards)- the 8 -square chevron made of 2 MCP s. The MCP closest to the PC is MCP1. 5. Anode plane- a separate plane, presumably glass or ceramic, with strip-lines and grounds. 6. Transmission lines/strip-lines- the actual anodes, which are 50-ohm strip lines. The associated ground is either on the other side of the plane or possibly coplanar on the top side. 7. Bottom Plate- the bottom plate of the vacuum volume. May be a flat sheet or may be integral with the side walls. 8. Tray- The assembly of side-walls and bottom plate- may be one integral piece (molded or poured.) 9. HV feedthroughs/pins- the 6 pins for HV for the PC, the top and bottom of each of the two MCP s, and HV ground. 10. Signal feedthroughs/pins- each stripline has 2 pins, the signal and ground. Geometry to be determined by RF and vacuum properties. 3

4 9 Sketches Figure 1 shows a preliminary sketch of the overall mechanical assembly. Figure 1: A sketch of the mechanical glass assembly. 4

5 Figure 2 shows a preliminary sketch of the mechanical and electrical details of the glass assembly. The squiggly things are metal spring clips much like the ones used in commercial MCP s to make electrical contact with surfaces. The pins through the glass are purely notational at this point; design work is ongoing on matching the 50Ω of the transmission lines through the connection and wall directly into the front-end sampling ASIC. Figure 2: A sketch of the internals of the glass assembly. The squiggly things are metal spring clips much like the ones used in commercial MCP s to make electrical contact with surfaces. 5

6 Figure 3 shows the dimensions of an internal spacer grid. These grids support the pressure on the top and bottom windows much as load-bearing walls in a house support the forces between the basement and roof. We are exploring inexpensive ways of making these in quantity. Figure 3: A sketch of one of the internal spacer grids that support the pressure on the top and bottom windows much as load-bearing walls in a house support the forces between the basement and roof. We are exploring inexpensive ways of making these in quantity. 6

O.H.W. Siegmund, Experimental Astrophysics Group, Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720

O.H.W. Siegmund, Experimental Astrophysics Group, Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720 O.H.W. Siegmund, a Experimental Astrophysics Group, Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720 Microchannel Plate Development Efforts Microchannel Plates large