NEXO@BNL Collaboration News April 8, 2019

1. NEXO@BNLCollaboration NewsApril 8, 2019 Mickey Chiu

2. Practice Talks for APS April Meeting Apr 9-11 • Tues 8:00 - Erin Hansen • Tues 8:20 - Eric Raguzin • Tues 8:40 - Mike Jewell • Wed 9:00 - JohnyEchevers • Wed 9:20 - Ako Jamil • Wed 9:40 - Arun Kumar Soma • Wed 2:00 - Lisa Kaufman • Wed 2:20 - Ty Stiegler • Wed 2:40 - Omar Nusair Topic: John OrrellnEXO meeting - April 8-11 2019Time: This is a recurring meeting Meet anytimeJoin from PC, Mac, Linux, iOS or Android: https://stanford.zoom.us/j/958137914Or iPhone one-tap (US Toll): +18333021536,,958137914# or +16507249799,,958137914#Or Telephone:    Dial: +1 650 724 9799 (US, Canada, Caribbean Toll) or +1 833 302 1536 (US, Canada, Caribbean Toll Free)    Meeting ID: 958 137 914    International numbers available: https://zoom.us/u/acBxwyqs8    Meeting ID: 958 137 914    SIP: 958137914@zoomcrc.com

3. 0𝜈𝛽𝛽 in President’s Budget Request https://www.energy.gov/sites/prod/files/2019/04/f61/doe-fy2020-budget-volume-4.pdf • The Ton-Scale Neutrino-less Double Beta Decay (NLDBD) Experiment MIE, implemented by instrumenting a large volume of a specially selected isotope to detect neutrino-less nuclear beta decays (within a single nucleus, two neutrons decay into two protons and two electrons with no neutrinos emitted) directly supports DOE NP’s mission to explore all forms of nuclear matter. Neutrino-less double beta decay can only occur if neutrinos are their own anti-particles and the observation of “lepton number violation” in such neutrino-less beta decay events would have profound, game changing consequences for present understanding of the physical universe. For example, one exciting prospect is that the observation of neutrino-less double beta decay would elucidate the mechanism, completely unknown at present, by which the mass of the neutrino is generated. The observation of lepton number violation would also have major implication for the present day matter/antimatter asymmetry which has perplexed modern physics for decades. In the current experimental outlook, through FY 2018 a number of demonstrator efforts using smaller volumes of isotopes and various technologies (bolometry in TeO2 crystals, light collection in LXe, charge collection in enriched Ge-76) have been in progress for several years, and all are in the process of delivering new state-of-the-art lifetime limits for 0��� which are of order a few times 1025 years. The goal of a next generation ton-scale experiment is to reach a lifetime limit of 1027 to 1028 years. For reference, the “lifetime limit” discussed is the time one might have to wait to observe neutrino-less double beta decay if observing a single nucleus only. Fortunately, in the ton of isotope planned for the ton-scale neutrino-less double beta decay experiment there are many trillions of nuclei. Thus, such decays, if they exist, should be observable on a much more reasonable timescale (5-10 years) similar to other large modern physics experiments. The FY 2020 Request for a Ton Scale Neutrino-less Double Beta Decay Experiment is $1,440,000 in the first year of TEC funding. CD-0 was approved November 2018 with a TPC range of $215,000,000 - $250,000,000. Three candidates for the down-select: NEXO (136Xe), LEGEND-200 (76Ge), and CUORE (130Te).

4. 0𝜈𝛽𝛽 in President’s Budget Request In addition, there are NEXO R&D (OPC) funds from DOE of about $7-9M (for the whole collaboration) over the next 3 years. BNL may possibly receive $470K for SiPM ASIC development, and 0.5FTE for a ME for interconnects R&D, from this for the coming year (starting in Summer or possibly FY20).

5. NEXO Light Readout System DAQ (hopefully FELIX but could be ATCA/RCE) Regular Optical Fibers + Power Transition Card (LVDS to Fiber) Radiopure High Speed Kapton Cables Stave/SiPM Tiles SiPM ASIC

6. Missing Ingredients Here’s an (incomplete) list of some things that I think still need elucidation or development • Complete list of features for the SoC SiPM ASIC • Where ASIC features are specified, whether we have a reasonable schedule for the development • Daisy-chain readout (token passing), bandwidth (100 Mbps?), Serializer, etc. • Layout of SiPMs and the relationship to ASIC • eg 96 SiPMs/tile, 16ch ASIC or 100 SiPMs/tile, 20 ch ASIC? Parallel ganging? 2 layer board, or 3? • HV distribution (see discussion by Ralph)? LV distribution? Clock? What capacitors and other external components are needed? • What is the minimum testing needed for SiPMs (we’ll need 40,000!), Tiles, and Staves? • How do we mechanically put the tiles and staves together into the TPC that maximizes radiopurity and allows for robust installation?

7. SiPM SoC ASIC Signal Slow Controls (daisy-chained) Bias HV,LV CLK? Bias GND • Extremely challenging design! • Components all designed into ASIC to reduce radioactive materials on board • 100W power budget • All operating at cryogenic temps (160K), where new models are required • Needs to be ready (ie fully tested) before we start assembly of tiles LDO Regulators SiPM Bias (0-5 OV) A.LV Front End AGND ch0 ASIC D.LV DGND ch1 Nx10-12 bit, 2 MSPS ADC Slow Controls CLK Trigger In Controls 2 2-4 ... ... ~10 tiles Buffers 100 Mbps LVDS DATA (IN/OUT) chN-1 Serializer 6-8 chN Coincidence/Local Trigger?

8. Light Readout for NEXO • SiPMs covering the barrel (40,000 cm2SiPMs, in tiles of ~100 SiPMs each) • Cryogenic SoC ASIC sending daisy-chained data tile to tile and finally via cable to warm section, where it will be received by DAQ • We’ll use FELIX for backend readout (but still TBD by NEXO)

9. Further Possible Contributions • Electron Lifetime Calibration Using Laser on Au Photocathode (L3) • Measure electron drift in controlled situation • Ba Tagging Using STEM (upgrade project “L2”) • Single Ba ID robustly achieved, working on single ion extraction F Ba with Ba-Tagging EELS EDXS

10. Further Possible Contributions • Nano-textures to Reduce SiPM Reflectivity (“Black Silicon”) • Possibility to improve QE by 25-50% • R&D has wide applicability, and good synergy with Darkside. • WbLS in Outer Detector (M. Yeh + McGill U.) (L3) • OD (veto for cosmics and external radiaton) will have only 500 PMTs • Hard to compete with Super-K, JUNO, etc, but might have a niche with geoneutrinos if we use WbLS and coat with reflective material • Working with student from McGill on developing scientific case