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TPC Design Concept: From MicroBooNE to LAr20

TPC Design Concept: From MicroBooNE to LAr20. Bo Yu Brookhaven National Lab. Outline. TPC Signal Characteristics MicroBooNE TPC Design Scaling Issues LAr20 TPC Concepts. Point Charge Induction on 3 Planes of Wires.

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TPC Design Concept: From MicroBooNE to LAr20

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  1. TPC Design Concept:From MicroBooNE to LAr20 Bo Yu Brookhaven National Lab

  2. Outline • TPC Signal Characteristics • MicroBooNE TPC Design • Scaling Issues • LAr20 TPC Concepts

  3. Point Charge Induction on 3 Planes of Wires Under proper bias condition, the first two planes of wires see bipolar induction signals, but do not collect any net charge. The 3rd wire plane collects 100% of the signal charge, enabling precise measurement of the ionization of a particle track Simulations using “Garfield” have given us a better understanding of the TPC signals

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  5. At large track angles, the induction wire signal amplitude diminishes, making dE/dx measurement difficult. Pulse width is largely determined by the wire plane spacing and the electron drift velocity 5

  6. Major Components in the MicroBooNE TPC Signal feedthrough 9% ullage (Argon Gas) Cold electronics Top ground plane High voltage feedthrough(-128kV) Wire planes Field cage Cathode plane PMT frame Rails for TPC installation CD-1 Readiness Directors Review

  7. Major Parameters of the TPC Gas argon (9% ullage) Wire Arrangment: U,V,Y Nominal Wire Length: Y: 2.5m U, V: 5m Number of Wires: Y: 3840 U, V: 2592 each Total: 9024 2.33m 3mm wire pitch 3mm wire plane spacing 2.56m 11.5m

  8. Wire Termination and Carrier • Stainless steel wire (150µm) with copper and gold plating to increase conductivity • Break strength ~ 4kg at LN2 temperature; CTE compatible with structural material • Printed circuit board based wire carrier modules allow accurate wire placement and integration with front end electronics

  9. A Detailed View of the TPC The TPC with the cold electronics will be completely assembled and then inserted into the cryostat. Preampmotherboard Top ground plane Top field cage support beam and bracket Wire frame Wire carriers Shielding mesh 3 wire planes

  10. Scale to Larger Detectors Key issue is how to make the wire planes: Modular: can be pre-fabricated. (<4m width, ~ 10m length to fit in the mine lift) Self-supporting: preferably not tied into the cryostat structure. Minimize dead space The use of cold electronics gives us great flexibility in designing the TPC. ASIC with multiplexed readout significantly reduces the power dissipation and the amount of cable inside the cryostat. The designs of both the TPC and the cryostat can be optimized

  11. Wire Length Capacitance: ~20pF/m Electronics Noise: ENC ~ 300e + 3e per pF (JFET @ 90K) At 10m, ENC ~ 900e rms; A 3mm MIP track segment gives ~ 6000e (30% recombination loss, drift 1 lifetime); A signal to noise ratio of 7:1. Gravitational Sagging: ~ L2/T (~0.5mm @1kg, 5m) Electrostatic deflection: probably negligible, with large tension. Intermediate wire supports will be considered in case lower wire tension is needed.

  12. Wire Pitch Wire pitch and wire plane spacing should be about the same Determines the minimal signal level: MIP over the wire pitch Determined by the Transverse Diffusion of electrons (DT~ 16cm2/s) At 5m drift, s=3mm (FWHM~7mm) Over 2.5m drift Electron spatial distributions after 2.5m (red) and 5m(blue) of drift

  13. Membrane Cryostat Concept

  14. Modular Cryostat Concept (LANNDD) Backup design if evacuation is necessary to achieve sufficient electron life time (LAPD outcome) Internally supported by a cubic lattice structure, capable of withstanding vacuum evacuation

  15. TPC Concept for the Modular Cryostat Wire chamber 4 Cathode 2 Wire chamber 3 Cathode 1 Wire chamber 2 Wire chamber 1 TPC design closely coupled to the cryostat structure FERMILAB June 18-19, 2009 Franco Sergiampietri

  16. TPC Module Concepts (Membrane Cryostat) Key consideration is to minimize the dead space in the TPC Self supporting frame module 2-3” dead space between frames 6-8” dead space between wire planes Hanging from the ceiling or standing on the floor Light weight open frame module ~8” dead space between frame No dead space through the wire planes Hanging from the ceiling Continuous hanging construction One 6” wide dead zone in mid height of the chamber Hanging from the ceiling Cathode plane will be constructed with one layer of mesh, hanging from a rail and tensioned by weights at the bottom.

  17. Self Supporting Frame Module(Double sided MicroBooNE Style Wire Frame) Wire Length: Y: 4m, U: 8m, V: 8m Number of Wires@3mm pitch Y: 3333, U: 2243, V: 2243Total: 7819 each side At 2.5m drift: -> ~56ch/ton Frame Load @ 1kg wire tension: 500kg/m on long edge, 667kg/m on short edge @5mm pitch Y: 2000, U:1346, V: 1346Total: 4692 each side, 33.5ch/ton Readout electronics on 3 sides

  18. Self Supporting Frame Module Dead space ~ 1” Cross section of an edge of the frame ~ 6” minimum Include PMTs or light guides for light collection?

  19. Light Weight Open Frame Module Temporary support during frame assembly Full depth of the cryostat Full length of the cryostat

  20. Light Weight Open Frame Module Frame cross section: Dead space* ~20cm * It is possible to construct the field shaping electrodes to deflect the electrons away from the frames and onto the wire electrodes, eliminating this dead space.

  21. Joining Wires In MicroBooNE style wire arrangement, the U & V wires are always twice as long as the Y wires. To equalize the capacitive load on the preamps from all three planes, we can join two wires mechanically and read them out from both ends Insulating wire joints can be constrained by SS bars to maintain wire pitch Metal wire terminations can be constrained by insulating bars to maintain wire pitch

  22. Continuous Hanging Construction roof joists rigid beams electronics enclosures wire joint strips Needs a lot of force to keep the wires properly tensioned: Load on the bottom beam: 1ton/m (6 wire planes, 2U, 2V, 2Y, 1kg per wire, 3mm pitch 600kg/m, @ 5mm pitch 1/3 more load on the two vertical beams

  23. Continuous Hanging Construction No dead space along beam direction, no dead space across wire planes, minimal dead space in one horizontal plane at mid depth. All wires are 8m long, U & V planes have insulating joints. Eliminate most of the short corner wires in framed modules Requires additional weights or tensioners to keep the wires stretched. A MicroBooNE style wire arrangement will require 1ton/m load at the bottom of each wire “curtain”. Field cage Cathode plane Cold electronics Sensing wires

  24. Next Steps • Study the impact of the dead space on the detector’s performance (fiducial cut). This may indicate which concept is the most advantageous • Develop a cost and schedule based on the experience on MicroBooNE design. • A dry mockup of the membrane cryostat will be constructed to study the construction issues. A full scale TPC prototype module will be built and installed in this mockup

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