Update on the HPgTPC System Alan Bross Near Detector General Meeting September 5, 2018
High-Pressure gas TPC (HPgTPC) System • 4 Components – HPgTPC itself – ECAL • Also neutron detector – Magnet system (coils + steel) – µ tag (using steel above) 2 Sept. 5, 2018 Near Detector MTG
HPgTPC: Review • The HPgTPC provides two functions – Aids in event containment for ArgonCube – Very-high resolution stand-alone experiment (1t fiducial target mass) • ~ 4 - 5 M n µ CC events in 3 yrs n running • Build copy of ALICE TPC – Re-purpose ALICE readout chambers – Represents significant savings in both hardware and engineering • Tremendous synergy with ArgonCube – Target nucleus • 100% Ar in LAr and 97% Ar in gas. – Raw 3-D data – Similar FE electronics architecture • Front-end chip design (LArPix � GArPix) – Same DAQ – Common data structure 3 Sept. 5, 2018 Near Detector MTG
HPgTPC: Review II • Build copy of ALICE TPC re-purposing their readout chambers (available in 2019) – But run at 10 Atm as opposed to 1 • Active volume ~ 97 m 3 – Central hole instrumented • ~550,000 pads in ~5.3m 1 Atm Ne-CO 2 existing chambers ~5.2m 4 Sept. 5, 2018 Near Detector MTG
High Pessure TPC test stand: GOAT Guillermo Fernandez-Moroni, Jen Raaf, Tanaz Moyahai &AB Now Complete • Reproduce ALICE operation at 1 Atm with Ar-CO 2 – Measure gain, wire stability, noise, etc. • Operate at 10 Atm and study various gas mixtures • Electronics test stand – GArPix GOAT: GAr Operation of the ALICE TPC 5 Sept. 5, 2018 Near Detector MTG
GOAT: ALICE TPC part • Test vehicle is an ALICE inner readout chamber (IROC) – ~5500 pads • Field cage with 8 cm drift 6 Sept. 5, 2018 Near Detector MTG
GOAT: Cosmic Data • Looking for signal coincidence between two sets of pads that have been ganged together. • The distribution should go to zero for time diference larger than the drift length (5 µ s). 7 Sept. 5, 2018 Near Detector MTG
GOAT: Gain Calibration • Is performed using an 55 Fe radiation source which has a X- ray peak at 5.9keV • The active volume illuminated by the source is recorded using high-bandwidth electronics. • An off-line pass band digital filtering scheme is used to extract the X-ray signal. Test pads Reference pads 8 Sept. 5, 2018 Near Detector MTG
Raw signal from the DAQ (anode 1375 V) Each negative jump corresponds to an event in the IROC Raw signal (0.48 mV) X-rays events Time (125ns) 9 Sept. 5, 2018 Near Detector MTG
Signal pulse height vs. Anode voltage (after Digital Filter) Noise peak 5.9 keV peak double event peak 10 Sept. 5, 2018 Near Detector MTG
Gas Gain for Ar-CO2 (90-10), 16 psi abs. press. Preliminary ALICE BIT LOW? 11 Sept. 5, 2018 Near Detector MTG
Gas studies: Fluorescence tag AB • The TPC is an inherently slow device – Drift over 2.5m ~ 50 µ s (for v drift = 5cm/ µ s) • 10 µ s spill – Yields ~ 50 cm uncertainty w/r to where the vertex is. • Not an issue for any event with a charge track leaving the TPC and entering the ECAL. – Having a time stamp would help with the rest • Matching to ECAL hits then becomes straightforward • This is a bit tricky, since many of the conventional gas mixtures (P10) quench all fluorescence. • Promising ternary systems: – Ar + Xe + CH 4 , Ar + Xe + CF 4, Ar + N 2 + CF 4 – Fluorescence light in the visible? 12 Sept. 5, 2018 Near Detector MTG
Another approach • There has been recent work in LAr to measure and use NIR fluorescence for light detection in order to vastly reduce Rayleigh scattering. – http://iopscience.iop.org/article/10.1209/0295-5075/106/32001 – Carlo Escobar’s work at PAB • From IOP article Neumeier et al. 10 ppm XE 13 Sept. 5, 2018 Near Detector MTG
Very strong emission in IR: ~ 127nm for pure LAr 14 Sept. 5, 2018 Near Detector MTG
What about in Gas? • Those data were in LAr. Are there data for gas? • Well some, Neumeier, EPL, 106 (2014) 32001 • Ar-Xe mixtures • ~1.5 Atm @ 100K 1000ppm Xe • Electron beam excitation • Setting up to do spectroscopic measurments at 10 Atm Ar-Xe mixtures @ 300K 15 Sept. 5, 2018 Near Detector MTG
Why is this so interesting? • The ~900nm emission is matched well to a new type of SiPM • Hamamatsu & FBK SiPMs for LIDAR applications – TOF imager for automobiles: self-driving cars • Potentially big market • Good match to the fluorescence in Lindbloom paper – FBK even higher PDE Hamamatsu • Fast • Low noise: 1.5 kHz dark count rate – This is VERY low for SiPM! • Cheap? • Fluorescence timing/tagging within the HPgTPC active volume, while allowing for stable MWPC operation at the gains we need 2-5k, looks possible. • The NIR approach has many details to work out, but would be a game changer, if workable. 16 Sept. 5, 2018 Near Detector MTG
HPgTPC electronics R&D Dan Dwyer, Guillermo Fernandez-Moroni, Jen Raaf, Tanaz Moyahai • Produce a modified design of LArPix (LBNL) • Modifications: – Polarity: induced signal in HPgTPC vs. charge in ArgonCube – Higher clock rate to accommodate larger v drift • Promising in the following sense – LArPix exhibits similar noise for room temperature operation. – HPgTPC chamber pad capacitance similar to LAr pads capacitance. – Noise requirement < 1000ENC less stringent than in LAr – Much larger (easily X10) can be tolerated for the HPgTPC 17 Sept. 5, 2018 Near Detector MTG
LArPix ➛ GArPix All plots from Dan Dwyer 18 Sept. 5, 2018 Near Detector MTG
Software Choices: GArSoft Tom Junk • ALICE software is very thorough and battle-tested. • But it depends on ALICE geometry and is tuned to their physics requirements (heavy ions at the LHC) • The sector geometry of the pads is baked in the lowest levels of simulation, hit finding, and reconstruction. • Tracking efficiency for tracks within 45 degrees of the E field is poor. • We need our own software to work with the DUNE ND complex, and the rest of the experiment. • So – use GArSoft, which was stared by Brian Rebel about a year and a half ago. • GArSoft is based on the art framework and NuTools, like LArSoft 19 Sept. 5, 2018 Near Detector MTG
Simplified Geometry to Get Started • Just to get started, I made a cylinder of 10 bars of 90% argon and 10% methane with the dimensions of the ALICE TPC • No inner field cage since there's no beam pipe. • Added a 30-cm thick ECAL made out of 10 g/cm 3 Pb-C-H mixture • ECAL stops particles (otherwise they loop) • Very little dependence on features of this geometry, so upgrading to new GDML should be easy 20 Sept. 5, 2018 Near Detector MTG
A Better Geometry • From Mike Kordosky. Eldwan Brianne has been working on ECAL simulation in GArSoft using this GDML: • GArSoft now can handle non-(0,0,0) locations of the center of the gas TPC 21 Sept. 5, 2018 Near Detector MTG
The Channel Grid (ALICE chamber approximation) 292140 x 2 = 584280 channels (c.f. 557568 in ALICE, or about 4.6 extra per pad row) 18 sectors 63 pad rows on the inner chambers, 64 pad rows in the inner outer chambers 32 pad rows in the outer outer chambers 22 Sept. 5, 2018 Near Detector MTG
Filling the Hole (new chambers) Rectangular array of pixels • in a disk Pixel size: 6mm x 6mm • c.f. 4 mm x 7.5mm for inner pad rows. Central disk has 62060 pads • per detector side. Total channels per side is • now 354200. About 18% of channels are in the disk. 23 Sept. 5, 2018 Near Detector MTG
Software Status • Simulation is with GEANT4. • GENIE and single-particle interface • Data products produced: - MC Particles (and MC Truth for the neutrino interaction) - Simulated energy deposits (just newly introduced into LArSoft, in GArSoft from the beginning) - Raw Digits (waveforms on each pad) – zero suppressed by default (as ALICE does) - Hits (in LArSoft terminology) – reconstructed pulses - Tracks - Vertices - Other data products, like flux and trigger simulations have initial placeholders but no work yet on them. • 3D Event display shows: MC Particle trajectories, raw digits (thresholded), hits, hits grouped on tracks. 24 Sept. 5, 2018 Near Detector MTG
Raw Digits in Green on the 3D event display Uses the channel geomety, raw::RawDigit simulation, and a drift model. I had to cheat the event time however. A 10 ! s beam spill window width causes visible displacements in raw digits (not shown here). Visible when overlaying MC Truth, but also visible for cathode-crossing tracks 25 Sept. 5, 2018 Near Detector MTG
Hit Finder • Simple initial hit finder -- Just use the Zero-Suppressed blocks of Raw Digits to make hits. • Threshold applied when making zero-suppressed blocks. 5 ADC counts in simulation. No noise, so no fake hits. • 5 extra ticks before and 5 after the above-threshold region to get sub-threshold tails. • Nearby hits are now clustered as ALICE does to improve resolution and simplify pattern recognition and fitting. • Clustering resolution needs to be tested. 26 Sept. 5, 2018 Near Detector MTG
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