tpc design concept: from microboone to lar20
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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TPC Design Concept:From MicroBooNE to LAr20
Bo Yu
Brookhaven National Lab
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Outline
TPC Signal Characteristics MicroBooNE TPC Design Scaling Issues LAr20 TPC Concepts
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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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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
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6CD-1 Readiness Directors Review
Major Components in the MicroBooNE TPC
High voltage feedthrough(-128kV)
Cathode plane
Cold electronicsTop ground plane
PMT frame
Wire planes
Field cage
Rails for TPC installation
Signal feedthrough
9% ullage (Argon Gas)
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Major Parameters of the TPC
2.33m
2.56m
11.5m
Wire Arrangment:U,V,Y
Gas argon (9% ullage)
3mm wire pitch 3mm wire plane spacing
Nominal Wire Length:Y: 2.5mU, V: 5m
Number of Wires:Y: 3840U, V: 2592 each
Total: 9024
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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
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A Detailed View of the TPC
Top ground plane
Preampmotherboard
Top field cage support beam and bracket
Wire frameWire carriers
3 wire planesShielding mesh
The TPC with the cold electronics will be completely assembled and then inserted into the cryostat.
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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
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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.
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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, =3mm (FWHM~7mm)
Over 2.5m drift
Electron spatial distributions after 2.5m (red) and 5m(blue) of drift
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Membrane Cryostat Concept
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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
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15FERMILAB June 18-19, 2009 Franco Sergiampietri
Wire chamber 4
Wire chamber 3
Wire chamber 2Wire chamber 1
Cathode 2
Cathode 1
TPC Concept for the Modular Cryostat
TPC design closely coupled to the cryostat structure
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TPC Module Concepts (Membrane Cryostat)
Key consideration is to minimize the dead space in the TPC
1. Self supporting frame module2-3” dead space between frames6-8” dead space between wire planesHanging from the ceiling or standing on the floor
2. Light weight open frame module~8” dead space between frameNo dead space through the wire planesHanging from the ceiling
3. Continuous hanging constructionOne 6” wide dead zone in mid height of the chamberHanging from the ceiling
Cathode plane will be constructed with one layer of mesh, hanging from a rail and tensioned by weights at the bottom.
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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 pitchY: 2000, U:1346, V: 1346
Total: 4692 each side, 33.5ch/ton
Readout electronics on 3 sides
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Self Supporting Frame Module
Cross section of an edge of the frame
Include PMTs or light guides for light collection?
Dead space ~ 1”
~ 6” minimum
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Light Weight Open Frame Module
Full d
epth
of t
he cr
yosta
t
Full length of the cryostat
Temporary support during frame assembly
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Light Weight Open Frame ModuleFrame 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.
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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
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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
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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”.
Sensing wires
Cathode plane
Cold electronics
Field cage
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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