D. Peterson, for discussion of LC-TPC LP, interface of Endplate and Field cage, Discussion of the LP endplate and field cage geometry A version of the LP endplate to field cage interface was discussed at Valencia, 06-November This describes the next iteration. Dan Peterson Cornell University 15-November-2006

D. Peterson, for discussion of LC-TPC LP, interface of Endplate and Field cage, Overview File:EndplateFieldCageGeometry5 The endplate (shown in blue) attaches to the field cage flange (a sort-of copper color) that is an integral part of the field cage but is made of a more durable material. Readout panels, or modules, attach to the endplate from the inside (but are inserted through the endplate from the outside). Readout panels include a metal frame (red) that is common to all readout technologies and provides all interface to the endplate. The readout structure is mounted on the panel frame. This includes a pad panel (dark green) and the gas-amplification and gate (light green). The example shown is a 3-GEM plus gate. Martin Killenberg has suggested 26 mm as the maximum module thickness from the endplate surface. This includes: structure 8mm pad plane 2mm 3GEM 6mm GEM gate 10mm sum 26mm. This design maintains the thicknesses of the pad plane, GEM and gate but differs in the thickness allocated to the “structure”, which extents into the endplate.

D. Peterson, for discussion of LC-TPC LP, interface of Endplate and Field cage, Geometry details : end flange Refer to the drawing on page 5. The field cage includes an end flange of more durable material. The end flange now has a flat mating surface. Concerns about the limited amount of material in the endplate outer ring, at the point where the endplate steps into the field cage, have been addressed. The end flange includes a “long section” that extends further into the low-density material to increase the strength of the connection. The long section has an inner radius of 37.8 cm, which provides a clearance of 1.2 cm from the field shaping bands. The end flange is also located at 1.2 cm from the field bands in the longitudinal direction. The end flange includes the threaded holes which will be used to attach the endplate. These are shown as Helicoils. With a flattened flange surface and with an adjustment of the location of the “long section”, there should be enough clearance for this size Helicoil. I suggest that we have 36 bolts, with an arc spacing of ~6.8cm. The end flange includes the o-ring slot. If, after considering the relative geometry of the end flange and field band, it is still preferable to have a fiber end flange, the o-ring slot should be moved to the aluminum end plate.

D. Peterson, for discussion of LC-TPC LP, interface of Endplate and Field cage, Geometry details: longitudinal locations of the field bands, readout modules, and end flange. Refer to the drawing on page 5. The endplate has a step that places the panel-mounting surface at the same longitudinal location as the inner surface of the field cage end flange. This shape also increases the overall thickness and, therefore, the stiffness of the endplate. The face surface of the readout panels is displaced by 2.20 cm from the endplate surface. It is the intent that all readout modules place the face surface at this location as described by Martin Killenberg. The face surface of the readout panels defines the location of the intermediate contact to the field shaping bands necessary to define the end of the drift field. A critical dimension of the design is that the face surface of the readout panels is located 4.30 cm from the surface of the field cage end flange. The field shaping bands extend beyond the face surface by 1.0 cm, the offset of a possible gate. A final contact to the field shaping bands allows field shaping over the offset of the gate. A radial clearance of 2 mm is provided between the step in the endplate and the inner wall of the field cage.

D. Peterson, for discussion of LC-TPC LP, interface of Endplate and Field cage, Geometry details File:EndplateFieldCageGeometry5

D. Peterson, for discussion of LC-TPC LP, interface of Endplate and Field cage, Geometry details: endplate. Refer to the drawings on page 5 and 7. The drawing on page 5 shows the cross section at a location where a panel does not extend to the maximum available radius of the instrumented area. This is the case except for the few instances where a corner of a panel reaches the maximum radius. In this case, there is a biased surface located at the same longitudinal position as the face of the readout panel. With the panel displaced from the maximum radius, there can be more metal in the region of the step in the endplate. This will provide extra stiffness for the entire endplate structure. I have not calculated the details. The geometry in the locations where a corner of a readout panel reaches the maximum radius is shown in on page 7. The section between the thick out ring and the surface on which the panels are mounted is very thin. However, this region is very small an will not affect the strength. The mullions are shown on page 2. Note that the cross section has been modified to include a wing section extending to the outside in the longitudinal direction. This stiffens the mullion. For an example case of a (30cm) 2 panel, with 6millibar overpressure, the sagitta of the local bowing of the of a 30cm long mullion is calculated to be 25 microns. The addition of the wing section increases the stiffness by a factor of ~3. Panels are drawn to the endplate with an additional frame mounted on the outside. Screws will pull the panel into the frame. With this arrangement, panels can still be located with precision surfaces. Alternatively, panels may be located with dowels through the frame, into the panel and the endplate.

D. Peterson, for discussion of LC-TPC LP, interface of Endplate and Field cage, Geometry at a corner of a module that comes to the maximum radius