The LP-TPC Fieldcage Project

1. The LP-TPC Fieldcage Project Ties Behnke, DESY Goal: design, develop and build a field cage for a “Large Prototype” (LP) to be used for studies and development work towards a TPC at the ILC. Members of the fieldcage group: DESY, University Hamburg as part of EUDET

2. The fieldcage Size and boundary conditions: defined through availablity of magnet (PCMAG) Main parameters: Length: 60 cm drift Radius: 80 cm (to allow external Si detectors, if wanted) Lightweight, stable, flexible support more than one endplate with different readout technologies and ideas.

3. The Prototype

4. Layout Anode: Interface will be defined to allow easily interchangable endplates Studies are needed to verify gas tightness etc Studies are needed to understand the HV distribution Studies are needed to understand the Gas supply at the anode Cathode: At the moment no realistic design is planned. (no lightweight cathode at least in the first iteration) Construction of the field cage will be done in close cooperation with industry

5. Material Studies Field cage wall: composite structure, HV insulation through Kapton layers mechanical strength through GFK – NOMEX – GFK structure Plans: HV studies of the wall material this fall investigate several “new” materials in place of Kapton discussion with industry on ways how to wind the LP field cage are ongoing

6. Optimization of Layout Work by Peter Schade, DESY Configurations of different field strips: Mirror strips Field strips anode Inside chamber cathode Questions: mirror strips, yes or no? Arrangements of mirror strips

7. Layout of Field Strips Divider for field strips, mounted inside the chamber Divider for mirror strips mounted inside the chamber Mirror strips (backside) Field strips (front side) Not to scale

8. 5 4 3 2 1 0 Field Optimzation Anode Cathode No mirror strips Large field distortions, particularly at cathode (>5%) Inhomogeneous field for main drift region of O(1.5%) Relative field strength

9. 5 4 3 2 1 0 With optimised mirror strips Anode Cathode Mirror strips, at intermediate potential Deviations in field volume small (< 0.5%) Some residue deviations at anode of O(<1%) (need optimization of interface endplate - drift volume)

10. Plans: Field cage design has started in earnest, negotiations with industry to build the field cage have started End 2006: freeze the final design, including all interface questions and material questions mid 2007: have the fieldcage available

11. Endplate Plans The “German” groups within LC-TPC have applied for a grant to design, build and operate an endplate for the LP (members of this grant request are Aachen, Hamburg, Rostock, Siegen; external member is Cornell) The idea: design, construct and test an endplate for GEM readout

12. The GEM Endplate Some first ideas: Light composite structure for the endplate Use fairly “large” GEM modules Main point is development of GEM modules, and ways to minimise material and (large) dead areas Provide readout structure optimised for large number of points on track Pad geometries optimised for large field operations Readout electronics etc as defined by the EUDET Readout project

13. Outlook and Schedule Funding situation: expect serious work on the endplate can only start in 2007 This will be “second generation” endplate compared to the Cornell one The German groups are committed to this project, but we are very open to collaboration and sharing of tasks and responsibilities with other groups