Development, Simulation, and Prototype Performance Measurements of - PowerPoint PPT Presentation

Development, Simulation, and Prototype Performance Measurements of the Mu2e Straw Tracker Richie Bonventre Fermilab Users Meeting June 20th, 2018 Lawrence Berkeley National Lab

Outline 1. Brief overview of Mu2e and physics motivation 2. Mu2e straw tracker design 3. Tracker Prototype low level measurements 4. Simulating the tracker 5. Comparing resolution + efficiency from prototype data and simulation See upcoming talk by Tomonari Miyashita for more details on the experiment! 1 / 23

Charged Lepton Flavor Violation • Mu2e will search for neutrinoless conversion of a muon to an electron in a nuclear environment: µ − N → e − N • This would violate charged lepton flavor , something that has never been seen before • Any detection of charged lepton flavor violation would be an unambiguous sign of new physics! (SM contribution is < 10 − 50 ) • Mu2e goal is a 10 4 improvement! 2 / 23

The Mu2e Experiment at Fermilab • Stop 10 18 muons on Aluminum • Conversion produces monoenergetic 105 MeV electrons • Main background is decay-in-orbit electrons • Only distinguishable by momentum, want high precision measurement that can handle high rate 3 / 23

The Straw Tracker Detector • Cylindrical straw tracker operating in uniform field • Tracker is in vacuum • Measurement is multiple scattering dominated • Entire detector much less than one radiation length of material 4 / 23

Tracker Configuration • 18 stations, each containing 12x 120 ◦ panels for stereo measurement • Blind to DIO electron momentum peak and beam flash • Expected resolution better than 200 keV/c 5 / 23

The Straw Tracker Detector • ∼ 21,000 low mass straw tubes in vacuum • 5mm diameter, 0.5-1.2m long • 15 µ m mylar wall, 25 µ m tungsten wire • 1 atm of 80/20 Ar:CO 2 , wire at 1425V 6 / 23

What are we measuring • Individual threshold crossings digitized in time (TDC) • Drift time → radial resolution ∼ 200 µ m • Straws are instrumented on both sides • Time division → longitudinal resolution ∼ 4 cm • Falling edge digitized for Time over threshold • Measure of path length / radius independent of t 0 • ADC measures pulse waveform for background rejection 7 / 23

Tracker Electronics Preamp PCB transmission line TDC Output Control & Buffer Readout Controller Straw TDC DAQ (*) Summing optional ∑ Preamp ADC FPGA FPGA Discrete Co��ercial A�alog ICs 8 / 23

Tracker Electronics 8 / 23

Tracker FPGAs and Firmware • Most of functionality in FPGAs - highly configurable • Have already taken advantage to add new features (Time over threshold) • Originally had Altera FPGAs, now using Microsemi SmartFusion2 for radiation tolerance • 2x Digi FPGAs that digitize 48 channels each • Separate TDCs for each end of straw • Continous readout of summed ADC waveform at 50 MHz • Data buffering, DAQ communication, tracker slow controls in ROC FPGA 9 / 23

Firmware TDC Design • Need ∼ 4cm resolution longitudinally along straw • Near speed of light signal → < 100ps time resolution • Achieve resolution in firmware while minimizing resource usage • Initial design based on wave-union design by Jinyuan Wu • Delay chain for sub-clock tick precision • Average multiple chains to subdivide large delays • Auto calibration of bin widths 1 delay chain 3 delay chains 8 delay chains 10 / 23

Firmware Design FPGA resource usage for 48 channel design • Have managed to implement design that fits all 48 channels in a single chip • Learning process dealing with Microsemi FPGAs • Architecture changes from Altera version • Much smaller community, support resources • Difficulties with timing constraints - manual placement of delay chains and ADC interface • Several hour compilation time for full design • Demonstrated readout chain from digitizing FPGAs through to DAQ computer over SERDES 11 / 23

An 8-straw tracker prototype for testing and performance mea- surements • Portable self-contained setup • Cross talk → proton beam from 88” cyclotron at Berkeley Lab • Radiation sensitivity → UC Berkeley High Flux Neutron Source • Straw and electronics parameters → radioactive sources • Efficiency/resolution → cosmic rays • Read out over USB serial using custom DAQ 12 / 23

Sources used to measure gain, energy resolution, time division, simulation tuned to results Mu2e Straw Longitudinal Resolution 55 4 0.06 Fe source at 1.33 ⋅ 10 gain v = 203.0 ± 0.5 mm/ns eff z = -175.0 mm, σ = 29.9 ± 0.7 mm z 8-Straw Prototype z = -87.5 mm, = 30.3 0.6 mm 0.05 σ ± z 0.25 z = 0.0 mm, σ = 26.3 ± 0.5 mm G4 + Straw Simulation z z = 87.5 mm, σ = 34.7 ± 0.9 mm z 0.04 z = 175.0 mm, σ = 35.0 ± 0.9 mm z 55 5.9 keV Fe Peak 0.2 0.03 0.02 0.15 0.01 0.1 0 0 50 100 150 200 250 300 350 400 450 500 ADC peak value (counts) 0.05 4 25 10 × Gain 55 Prototype ( Fe Data) 0 20 − 400 − 300 − 200 − 100 0 100 200 300 400 (v /2) T + z (mm) ⋅ ∆ eff 0 Prototype (Fit) ax + b Fit = e 15 (Tom-Erik Haugen) 10 • Gas gain by measuring current with 55 Fe 5 0 • Energy resolution using 5.9 keV 1200 1250 1300 1350 1400 1450 1500 1550 1600 High Voltage [V] x-ray peak (Andrew Edmonds) 13 / 23

Simulation of the straw tracker response • Detailed Geant4 simulation of full detector • Custom code takes energy deposition in each straw and models physics and electronics response 14 / 23

Simulation of the straw tracker response Simulation of waveform threshold crossing at each end of straw Waveform (mVolts) Waveform (mVolts) 20 20 15 15 10 10 5 5 0 0 − 5 − 5 1000 1050 1100 1150 1200 1000 1050 1100 1150 1200 time (nSec) time (nSec) • Each ion cluster modelled individually, including drift, wire propagation, and electronics response 15 / 23

Simulation of the electronics response Input pulse shape → Apply electronics response Signal (mV) 50 55 Fe waveform, 0 cm 55 40 Fe waveform, 120 cm Fit 30 20 10 0 0 10 20 30 40 50 60 70 80 90 Time (ns) (Data from Manolis Kargiantoulakis) (SPICE sim from Vadim Rusu) • Use unshaped waveforms from source at different distances to model attenuation, dispersion • Fit for transfer function describing preamp and integrator response • Model includes saturation effects, pulse shape distortion • Important for accurately determining proton discrimination, modelling pileup 16 / 23

Reconstructing track position for performance measurements • Use PMT trigger and ATLAS FEI4 pixel detectors to allow precise reconstruction of cosmic ray tracks • MIPs similar to conversion electron signal • Allow resolution and efficiency measurements 17 / 23

Reconstructing track position for performance measurements PIXEL MEASUREMENT Track position (mm) 16 Straw 2 Straw 3 14 Straw 4 12 Straw 5 Straw 6 10 8 6 4 2 0 0 10 20 30 40 50 60 70 80 STRAW MEASUREMENT Drift time (ns) • ATLAS FEI4 detectors measure track position • 2.0x1.9cm chips, 250x50 µ m pixels • PMT trigger gives t 0 for drift time measurement • ∼ 600ps time resolution • Reconstruct relative position and timing of pixels, PMTs, straws, wires with maximum likelihood fit 18 / 23

Transverse resolution 0.0 < DOCA < 0.5 0.5 < DOCA < 1.0 Arbitrary Units Arbitrary Units 0.035 0.05 8-Straw Prototype 0.03 G4 + Straw Simulation 0.04 0.025 0.03 0.02 0.015 0.02 0.01 0.01 0.005 0 0 − 0.5 0 0.5 1 1.5 − 0.5 0 0.5 1 1.5 Drift Radius Residual (mm) Drift Radius Residual (mm) 1.0 < DOCA < 1.5 1.5 < DOCA < 2.0 Arbitrary Units Arbitrary Units 0.05 0.06 0.04 0.05 0.04 0.03 0.03 0.02 0.02 0.01 0.01 0 0 − 0.5 0 0.5 1 1.5 − 0.5 0 0.5 1 1.5 Drift Radius Residual (mm) Drift Radius Residual (mm) • Agrees with simulation tuned to low level 2.0 < DOCA < 2.5 Arbitrary Units 0.07 parameters 0.06 0.05 • Model and simulation include full DOCA 0.04 dependence of resolution 0.03 0.02 • gaussian smearing × exponential with constant τ 0.01 0 • τ encodes effect of cluster statistics − 0.5 0 0.5 1 1.5 Drift Radius Residual (mm) 19 / 23

Transverse resolution 0.0 < DOCA < 0.5 0.5 < DOCA < 1.0 Arbitrary Units Arbitrary Units 0.035 8-Straw Prototype 0.05 8-Straw Prototype Fit 0.03 G4 + Straw Simulation 0.04 G4 + Straw Simulation Fit 0.025 0.03 0.02 0.015 0.02 0.01 0.01 0.005 0 0 − 0.5 0 0.5 1 1.5 − 0.5 0 0.5 1 1.5 Drift Radius Residual (mm) Drift Radius Residual (mm) 1.0 < DOCA < 1.5 1.5 < DOCA < 2.0 Arbitrary Units Arbitrary Units 0.05 0.06 0.04 0.05 0.04 0.03 0.03 0.02 0.02 0.01 0.01 0 0 − 0.5 0 0.5 1 1.5 − 0.5 0 0.5 1 1.5 Drift Radius Residual (mm) Drift Radius Residual (mm) • Agrees with simulation tuned to low level 2.0 < DOCA < 2.5 Arbitrary Units 0.07 parameters 0.06 0.05 • Model and simulation include full DOCA 0.04 dependence of resolution 0.03 0.02 • gaussian smearing × exponential with constant τ 0.01 0 • τ encodes effect of cluster statistics − 0.5 0 0.5 1 1.5 Drift Radius Residual (mm) 19 / 23