1. TPC Proposal for the 35 Ton Liquid Argon Test Abstract We propose to equip the 35 ton cryostat with one APA and two CPA’s, and all the necessary equipment such as support structure, field cage, feedthroughs, electronics, and high voltage system. A light detection system can and should also be incorporated. TPC proposal for the 35 ton LAr Cryostat1/10/12

2. Purpose The 35 ton test will be the first membrane style cryostat for ultra high purity liquid Argon containment. Once purity has been achieved, the cryostat presents an ideal test bed for the development of anode panel assemblies (APA’s) and cathode panels (CPA’s), along with High voltage cage and HV system Signal preamps, feedthroughs, and DAQ system Light detection The aim would be to complete the developments for the detector for the next stage, e.g. a 1 kton prototype, or a very large deployed detector TPC proposal for the 35 ton LAr Cryostat1/10/12

3. The 35 ton Cryostat TPC proposal for the 35 ton LAr Cryostat1/10/12 The first membrane-style cryostat filled with Liquid Argon will be installed at PC4 next year. It has an Argon Volume of size 2.7m x 4 m x 2.7m deep. It has an access hatch of size 1 m x 2.7 m (with rounded corners)

4. Requirements TPC proposal for the 35 ton LAr Cryostat1/10/12 List of Devices One APA, with cold electronics Two CPA’s Mechanical support structure Field cage around both drift gaps HV feedthrough (maybe two FT’s) HV system low voltage and bias voltage supplies low voltage and bias voltage feedthroughs Signal feedthrough DAQ Trigger system for cosmic rays Light detection system (Bars and PMT’s or SiPM’s) Light detection feedthroughs and external electronics

5. Desirable Features TPC proposal for the 35 ton LAr Cryostat1/10/12 It is important to design the test TPC system to be as close to the final system as possible. Use electronics items (preamps, cards, feedthroughs) that could, in principle, be used in the final detector Design the wire holding method and the many small parts the same way Design the APA and CPA frames nearly identical to the final ones, by: Designing the APA and CPA’s for full width (2.5 m) Shortening them to fit the cryostat. This has minimal effect of the design and the parts. Make it easy to install / remove the detector to test new designs as the effort advances

6. Challenges TPC proposal for the 35 ton LAr Cryostat1/10/12 The limited space is the main challenge. Solutions must be found for support installation, plane installation, field cage installation, cabling, and access during installation. There will be no penetrations to support the TPC. There is very little space above the cryostat.

7. Proposed Parameters TPC proposal for the 35 ton LAr Cryostat1/10/12 APA and CPA size 2.5 m wide x 2 m high Drift distance 1 m We plan to hang the planes from rails a la lbne design.

8. TPC support structure TPC proposal for the 35 ton LAr Cryostat1/10/12 We plan to hang the planes from rails a la lbne design. There will be three rails, one above the APA, and one above each of the two CPA’s. The rails will hang either from existing ceiling penetrations, Possibly using intermediary trusses, Or from cross trusses, supported by four columns located I the corners of the cryostat (see next picture). Both arrangements can work, but more detail work is needed.

9. TPC support Details TPC proposal for the 35 ton LAr Cryostat1/10/12 The structure consists of a 4” diameter stainless tube in each corner. Four stainless trusses run along the inside edges and are bolted to the corner columns. Two additional trusses span across to support the three rails that hold the APA and CPA’s trolleys. The structure is easy to bring in through the hatch, and easy to assemble inside the cryostat. The elements will be light weight and can be assembled by a few workers using ladders or scaffolding.

10. TPC proposal for the 35 ton LAr Cryostat1/10/12 Here is the Proposal

11. TPC proposal for the 35 ton LAr Cryostat1/10/12 Side View

12. Access for Installation TPC proposal for the 35 ton LAr Cryostat1/10/12 Installation, cable connections, and Electronics installation on the APA are done by technicians working in the drift volumes. This requires to get the field cage panels out of the way, And an easy way to re-position them when installation is done (see next picture). Small ladders are sufficient to reach the top of the APA. The cryostat ceiling is at 3.5 m, just 11.5 ft from the floor.

13. TPC proposal for the 35 ton LAr Cryostat1/10/12 Panel Installation

14. TPC proposal for the 35 ton LAr Cryostat1/10/12 Field Cage flip panels, as shown by Bo Yu: Note: For the small drift length (1 m) the panels can be routed from 1/16” thick Cu clad FR4

15. TPC proposal for the 35 ton LAr Cryostat1/10/12 Top View Showing CPA Panel Installation

16. TPC proposal for the 35 ton LAr Cryostat1/10/12 Top View Showing APA Panel Installation

17. TPC proposal for the 35 ton LAr Cryostat1/10/12 Conclusion It is not too early to start deigning the detector panels and infrastructure for this test. I hope the effort will focus the R&D toward a final design. Once the TPC system works, one can design and build the Lar1 Detector with confidence.