Nagoya Workshop on Technology and Instrumentation in Future Liquid Noble Gas Detectors

ES635 (KMI Science Symposia)


KMI Science Symposia

Masatoshi Kobayashi (KMI, Nagoya University), Shingo Kazama (Nagoya University)

The International research unit for innovative dark matter search at Kobayashi-Maskawa Institute (KMI), Nagoya University will host the international workshop “Technology and Instrumentation in Future Liquid Noble Gas Detectors” from February 14 through 16, 2024. The goals of this workshop is to share, review and discuss about recent progress in technologies and instrumentations of liquid noble gas detectors, particularly in the field of future dark matter search experiments.

Workshop website:

The oral presentations will be by invitation only, but we encourage for poster presentations. Poster presentations are welcome on a wide range of topics, not only on liquid noble gas detectors, but also on any topic related to dark matter and neutrino experiments, or low BG technologies and so on.

You can register for the workshop here.

Deadline for poster abstract submission is Feb. 2, 2024
Deadline for registration only is Feb. 2 2024.

The organizing committee 
Shingo Kazama, Masatoshi Kobayashi, Yoshitaka Itow


  • Hotel: We have arranged the accommodation for invited speakers at Hotel Mielparque located near Chikusa station. 
  • Conference Venue: All the sessions will be held at KMI Symposia (ES635) on the 6th floor of the ES Building at Nagoya University, Higashiyama campus. The access information can be found here
  • Welcome Reception: There will be a welcome reception at 5:30 PM on Feb 13 at the conference venue
  • Poster Session: A poster session is scheduled in the evening on the first day (Feb 14th).
  • Conference Dinner: The conference dinner will be hosted at Kisoji, located near Sakae station on Feb 15 (19:30 - 21:30). The fee for the dinner is 9000 Yen, payable in cash during the registration on the first day. A receipt will be provided. 
  • Zoom connection: connection information will be sent to those who registred
  • Lunch: map






  • Amos Breskin
  • Anh Van Thi Nguyen
  • Caio Takanori Oba Ishikawa
  • Carter Hall
  • Evan Angelico
  • Federico Gabriele
  • Fei Gao
  • Francesco Lombardi
  • Francesco Toschi
  • Giacomo Gallina
  • Giovanni Volta
  • Hiroki Kochi
  • Hiroshi Ogawa
  • Hiroyuki Sekiya
  • Hiu Sze Wu
  • Isaac Arnquist
  • Jianyang Qi
  • Jingke Xu
  • Jose Cuenca Garcia
  • José Matias
  • Julia Müller
  • Kaede Hiraoka
  • Kai Martens
  • Kaixuan Ni
  • Khai Bui
  • Kiseki Nakamura
  • Ko Abe
  • Krishan Mistry
  • Lingyin Luo
  • Lutz Althüser
  • Marc Schumann
  • Masaki Yamashita
  • Masato Kimura
  • Masatoshi Kobayashi
  • Masayuki Wada
  • Paloma Cimental
  • Peter Sorensen
  • Pranati Kharbanda
  • Qing Lin
  • Raymond Bunker
  • Robert James
  • Ryuta Miyata
  • Satoshi Mihara
  • Shingo Kazama
  • Tom Shutt
  • Tomoya Hasegawa
  • Toshiyuki Iwamoto
  • Yanina Biondi
  • Yi Wang
  • Yoshino Kaminaga
  • Yoshitaka Itow
  • Zhou Wang
    • 1
      Seminar: Performance of novel Silicon Photo-Multipliers for the nEXO and Darkside-20k experiments.

      Silicon Photomultipliers (SiPMs) have emerged as a compelling photosensor solution for detecting single photons in applications ranging from particle physics to medical imaging and beyond. SiPMs consist of an array of tightly packaged Single Photon Avalanche Diodes (SPADs) operated above the breakdown voltage so that they generate self sustaining charge avalanches upon absorbing an incident photon. Generally, SiPMs are a compelling photosensor solution in liquid noble gases due to their low-voltage operation, insensitivity to magnetic field, and compact and flat form factor. For these reasons, SiPMs are the adopted solution in the MEG2 and DUNE experiments. In addition, SiPMs have very low residual natural radioactivity, making them especially appealing for low-background experiments such as nEXO and DarkSide-20k. In this talk, we will show results on the characterization of the newest vacuum ultra-violet sensitive SiPMs by Fondazione Bruno Kessler, the VUVHD3 devices specifically designed for nEXO. Moreover we will preset results on the Quality Assurance and Quality Control (QA/QC) of the production wafers made with FBK~NUV-HD-Cryo SiPMs manufactured by LFoundry s.r.l. (Avezzano, AQ, Italy) for the Darkside-20k experiment. Various SiPM parameters, such as dark noise, gain, direct crosstalk, correlated avalanches and photon detection efficiency were measured as a function of the applied over voltage and wavelength at liquid xenon and liquid argon temperature. Finally we will briefly introduced the nEXO and DS-20k SiPM electronic with a special focus on the readout of large area SiPMs used on the just mentioned experiments.

      Speaker: Dr Giacomo Gallina (Princeton)
    • 5:30 PM
      Registration & Welcome Reception
    • 9:00 AM
    • 2
      Welcome Speech
    • 3
      Overview of future LXe-based DM searches
      Speaker: Prof. Marc Schumann (University of Freiburg)
    • 4
      Where We Go with Liquid Ar-based Dark Matter Searches?

      The quest for detecting Weakly Interacting Massive Particles (WIMPs), considered as prominent candidates for dark matter, has been ongoing for several decades. This presentation will provide an overview of the current progress in major searches conducted using experiments aimed at detecting both high-mass and low-mass (<10 GeV) WIMPs. The discussion will also cover existing technological constraints and future possibilities for overcoming these limitations in upcoming dark matter exploration, particularly focusing on next-generation liquid argon detectors.

      Speaker: Prof. Masayuki Wada (AstroCeNT, CAMK PAN)
    • 10:35 AM
      Coffee Break
    • 5
      Development of a crystalline xenon TPC for neutrino-limited dark matter search
      Speaker: Dr Peter Sorensen (LBL)
    • 6
      The development of Hermetic Quartz Detector for the DARWIN experiment
      Speaker: Prof. Masatoshi Kobayashi (KMI, Nagoya University)
    • 7
      The development of Hermetic TPC for the DARWIN experiment
      Speaker: Prof. Marc Schumann (University of Freiburg)
    • 12:35 PM
    • 8
      Charge Amplification in Liquid Xenon with a Needle Electrode and Development of a Spherical Detector
      Speaker: Prof. Hiroyuki Sekiya (ICRR, The University of Tokyo)
    • 9
      On the feasibility of the single phase liquid xenon proportional scintillation counter for low-energy nuclear recoil based physics searches

      Liquid phase xenon electroluminescence allows us to achieve a perfect extraction efficiency by eliminating the liquid-gas interface, at the cost of having a low single-electron gain. For low-energy searches, we are concerned with the discrimination between electronic and nuclear recoils (ER and NR), as well as the single-electron background. In this talk, we shall show evidence that ER/NR discrimination can be maintained even with a low single-electron gain, but that the single-electron background following a large ionization signal is still present and characteristically similar to that of the dual phase xenon TPCs.

      Speakers: Jianyang Qi (UCSD), Prof. Kaixuan Ni (University of California San Diego)
    • 10
      PANCAKE - Freiburgs DARWIN demonstrator and Freiburgs single phase TPC
      Speaker: Julia Müller
    • 11
      Micro-structured multiplier concepts for single-phase detectors
      Speaker: Prof. Amos Breskin
    • 4:05 PM
      Coffee Break
    • 12
      Design and performance of the XENONnT TPC electric field

      Considering the fundamental role of the electric drift field in the formation and collection of the signals produced in the active volume of a dual-phase time projection chamber (TPC), significant effort was dedicated to the design and simulation of the field cage of the XENONnT TPC. The outcome of this work is an innovative double-array structure connected by an easily accessible voltage partitioner. Additionally, the field cage is independently biased, allowing for real-time tuning of the electric field during operation. As XENONnT has been operational since late 2020, the finite element simulations were compared to the calibration data using Kr-83m, indicating the presence of charge accumulation on the panels of the TPC. This was modeled with a linear distribution, returning a good match in the reconstructed spatial distribution and resolving inconsistencies in the electron lifetime measurements from different calibration sources. This presentation explores the electric drift field of the XENONnT TPC, tracing its journey from design and simulations to the validation against calibration data, and including insights from a dedicated test on the impact of tuning the field cage.

      Speaker: Dr Francesco Toschi (Karlsruhe Institut of Technology/University of Heidelberg)
    • 13
      Design and performance of the LZ TPC electric field
      Speaker: Prof. Tom Shutt (SLAC)
    • 14
      The NEXT-100 electroluminescent grid design

      NEXT-100 is a high-pressure gaseous time projection chamber searching for neutrinoless double beta decay with enriched xenon-136. Ionisation electrons are amplified in the detector through the use of electroluminescent (EL) amplification which enables proportional gain with minimal fluctuations enabling sub-percent energy resolution. The experiment is in the final stages of construction (detector commissioning is planned for early 2024) with the EL region and cathode consisting of large-scale (1m diameter) photochemically etched hexagonal grids recently installed. Significant challenges were needed to overcome the exacting requirements in the design of the NEXT-100 EL region including radiopurity, optical transparency, planarity, high-voltage operation, and mechanical and electrical robustness. In this talk, the design considerations for the NEXT-100 EL region will be described along with prospects for the construction of even larger grids for future experiments.

      Speaker: Dr Krishan Mistry (University of Texas at Arlington)
    • 6:05 PM
      Poster Session
    • 15
      LZ search for new physics via low-energy electron recoils

      Present the status of the LZ experiment searches for new physics via low-energy electron recoils using first science run data, focusing on two monoenergetic signals: axion-like particles (ALPs) and hidden photons (HP).

      Speaker: Anh Van Thi Nguyen (University of Edinburgh)
    • 16
      Estimation of 85Kr background in the XENONnT using delayed coincidence count

      The Xe-based dark matter search experiment XENONnT searches for rare events such as dark matter recoil and solar pp neutrino signals. It requires accurate estimates of the background. The radioactive isotope 85Kr in Xe is one of the background sources in these searches. To reduce the uncertainty of its abundance, 85Kr abundance estimation using delayed coincidence counting has been introduced. This poster shows the details of this method and its results and performance.

      Speaker: Yoshino Kaminaga (ICRR, the University of Tokyo)
    • 17
      Development of Hermetic Liquid Xenon Detector for the DARWIN experiment
      Speaker: Ryuta Miyata (Nagoya University)
    • 18
      Development of a hybrid-photodetector for the DARWIN experiment
      Speaker: Tomoya Hasegawa
    • 19
      Field Emission Array (FEA) for electron/hole emission into liquid xenon

      We are investigating the use of field emission arrays (FEAs) made of silicon to purify a liquid xenon detector. It is known that electronegative contaminants can be drifted by attaching electrons to them and using an external field. Our main objective is to see if either electrons or holes can be used to drift Rn in LXe, with the ultimate goal being to use this to remove Rn from LXe. We are currently in the stage to look into properties of the FEAs such as current output, total charge and stability. Two tests resulted in current injection.

      Speaker: Caio Takanori Oba Ishikawa
    • 20
      Development of ultralow radioactive zeolite for the radon removal from gases

      The amount of radioactive impurities contaminated in the detector gases is required to be kept at a very low level for rare event particle physics such as dark matter search experiments. Zeolite is one of the possible candidates for removing radon and impurities from gases. A development of a new ultralow radioactive zeolite as a product of the selection of ultralow radioactive materials is reported. Results on the radon removal from argon gas and air are shown. Also, the results of more efficient radon adsorption tests with silver zeolite will also be reported.

      Speaker: Dr Hiroshi Ogawa
    • 21
      Radon Emanation Measurement and Mitigation

      Radon is a key background consideration in experiments that search for rare events such as dark matter interactions and neutrinoless double-beta decay. For future noble-liquid and -gas detectors, radon emanated into the detection medium will need to be tightly controlled through radon emanation screening of the wetted materials. I will present systems for low-level measurement of radon emanation and for cryogenic emanation that achieve high sensitivity through use of custom high-efficiency ultra-low-background proportional counters. To achieve target sensitivities in future detectors, additional techniques maybe be required to mitigate emanation from large-area surfaces. I will also discuss PNNL’s copper electroforming capability and its potential use to mitigate radon emanation via plating of high-purity copper as a surface treatment.

      Speaker: Dr Raymond Bunker (Pacific Northwest National Laboratory)
    • 22
      Dust and Cables: Addressing Major Background Concerns in Rare-Event Ultralow Background Physics Experiments

      Dust particulate fallout on materials in use for rare-event searches is a concerning source of radioactive backgrounds due to the presence of the naturally occurring radionuclides. Much effort is dedicated to understanding backgrounds from dust and evaluating mitigation procedures. In this work, an ICP-MS based methodology is presented that demonstrates a direct determination of fallout rates of radionuclides and stable isotopes of interest from dust particulate at the SNOLAB facility. This work validates the mitigation procedures in place at SNOLAB and informs dust backgrounds during laboratory activities. Fallout rates of major constituents of the local rock were measured two to three orders of magnitude lower in the clean experimental areas compared to non-clean transition areas from the mine to the laboratory. Increased radiocontaminant fallout rates were measured in clean experimental areas during activities generating particulate. Flexible printed cables and circuitry based on copper-polyimide materials are widely used in experiments looking for rare events due to their unique electrical and mechanical characteristics. However, past studies have found copper-polyimide flexible cables to contain 400-4700 pg 238U/g, 16-3700 pg 232Th/g, and 170-2100 ng natK/g, which can be a significant source of radioactive background for many current and next-generation ultralow background detectors. This work presents a comprehensive investigation into the fabrication process of copper-polyimide flexible cables and the development of custom low radioactivity cables for use in rare-event physics applications. Radiopure material alternatives were identified, and cleaner production processes and treatments were developed to significantly reduce the imparted contamination. Through the newly developed radiopure fabrication process, fully-functioning cables were produced with radiocontaminant concentrations of 20-31 pg 238U/g, 12-13 pg 232Th/g, and 40-550 ng natK/g, which is significantly cleaner than cables from previous work and sufficiently radiopure for current and next-generation detectors. This approach, employing witness samples to investigate each step of the fabrication process, can hopefully serve as a template for investigating radiocontaminants in other material production processes.

      Speaker: Dr Isaac Arnquist (Pacific Northwest National Laboratory)
    • 23
      Measurements of the anisotropic response of ZnWO4 scintillators to neutrons for Developing the Direction-Sensitive Dark Matter Detector

      We are developing a dark matter direction sensitive detector based on ZnWO_4_ crystals which have anisotropic scintillation response . In this poster, we discuss quantitatively the anisotropy of scintillation of oxygen nuclear recoils for a 670 keV neutron beam produced by T(p,n) reaction at AIST.

      Speaker: Hiroki Kochi (ICRR)
    • 24
      FlameNEST: powerful statistical inference for the LZ and XLZD experiments

      FlameNEST is a novel approach to statistical inference for liquid xenon time projection chambers that enables the incorporation of higher-dimensional observable spaces and correlated shape-varying nuisance parameters in a computationally efficient manner. It is currently being used for statistical inference and detector calibration fits enabling dark matter searches with the world-leading LUX-ZEPLIN (LZ) experiment, as well as for sensitivity studies towards a next-generation liquid xenon experiment within the XLZD consortium. Here we present the principles behind the framework, and examples of its use for both LZ and XLZD. We highlight future activities for both projects and the role that FlameNEST will play in each.

      Speaker: Dr Robert James (The University of Melbourne)
    • 25
      The Xenon liquefaction, purification, and storage system XeLiPS

      This is an introduction to the new Liquid Xenon R&D facility currently under construction at the Johannes Gutenberg University Mainz (JGU Mainz) in the new Centre for Fundamental Physics (CFP-II). The Xenon liquefaction facility is designed to store, purify, and distribute up to 500kg of liquid xenon to two neighboring laboratories eventually. The liquid xenon can be recuperated by gravity in a cryogenic storage tank, which also serves as a pressure vessel to safely contain the gas at room temperature. Initially, one laboratory will be equipped with a complete cooling system, while the connection to the second laboratory has only been prepared for a potential future extension. In this presentation I will describe the different parts of the facility and some new solutions for the design of the storage tank cooling system. The maximum flow in the purification system is about 20 l/min of Xenon, corresponding to about 500 kg of purified Xenon per day. The liquefaction of the Xenon is done by a thermoacoustic pulse tube refrigerator (PTR) cryocooler (max power 120-140 W @T=160-180 K), supported by an auxiliary LN2 cryocooler that can provide up to 170 W of additional cooling power, or can be used in place of the PTR in case of power failure. Xenon purification is performed in the gas phase, making use of a custom-built plate heat exchanger, reducing up the 90% the required cooling power of about 600 W in total. The remaining 10% of cooling power (60 W) is provided by the cryocooler. A fast recovery system provides safe operation and can freeze xenon in the central cryostat with a cooling power of 500 W.

      Speaker: Dr Francesco Lombardi (J Gutenberg University Mainz)
    • 26
      Spurious Electron and S2-only backgrounds at Darkside-50

      DarkSide-50 is a direct dark matter search experiment using a dual phase argon time projection chamber filled with low-radioactivity underground argon. Based solely on the ionization spectrum, it has set the most stringent exclusion limits for several low-mass dark matter candidates. Such analyses suffer from so-called spurious electron (SE) events at the lowest detectable energy region and are prevented from exploring the most sensitive part for low-mass dark matter searches. This presentation focuses on the progress toward understanding of the spurious electron background. It is indicated that a significant fraction of the SE events is related to the impurities in the TPC. While a full understanding of the source of the SE events will require dedicated R&D, possible mechanisms and mitigation strategies are discussed, in light of the observations in DarkSide-50. Requirements for future experiments to improve the sensitivity are also discussed, with special attention given to potential background sources.

      Speaker: Dr Masato Kimura (AstroCeNT/NCAC PAS)
    • 27
      S2-only background and Accidental Coincidence backgrounds in XENON1T and XENONnT
      Speaker: Prof. Fei Gao (Tsinghua University)
    • 28
      Low-energy ionization background in LUX and LZ

      Liquid xenon TPCs have observed high rates of pathological electrons in the low-energy region, which impair their sensitivities in dark matter searches. They are a direct background to low-mass dark matter interactions that may only produce sub-keV nuclear recoils, and also contribute accidental coincidence backgrounds in large experiments. I will review the studies of low-energy photon and electron backgrounds in both the LUX and the LZ experiments and discuss their implications for future experiments.

      Speaker: Dr Jingke Xu (Lawrence Livermore National Laboratory)
    • 29
      Accidental pileup and single-electron backgrounds in PandaX-4T

      The PandaX-4T experiment employs a liquid xenon time projection chamber (TPC) to investigate keV-scale nuclear recoils, with the primary objective of directly detecting heavy cold dark matter (10GeV – 10TeV). Additionally, PandaX-4T has expanded its exploration to the sub-keV energy range by reducing the analysis threshold. As a result, it has achieved remarkable sensitivities in searching for solar B8 neutrinos via the coherent elastic neutrino-nucleus scattering (CEvNS) channel and light dark matter through its interaction with shell electrons. However, this reduction in threshold has given rise to significant challenges, including the increased accidental pileups and single electron backgrounds. In this presentation, I will primarily focus on elucidating our model and understanding for these two backgrounds and discussing the corresponding techniques we have developed to mitigate them. Furthermore, I will touch upon a proposal involving a single-phase TPC that shows promise in eliminating such background sources.

      Speaker: Prof. Qing Lin (University of Science and Technology of China)
    • 11:00 AM
      Coffee Break
    • 30
      SiPMs in the liquid xenon gamma-ray detector for MEG II experiment

      The MEG II experiment searches for new physics like SUSY-GUT/SUSY-seesaw through the lepton flavor violating mu+->e+ gamma with ten times better sensitivity than the MEG expriment( B(mu+ -> e+ gamma) < 4.2x10-13 at 90% CL in 2016). Because the sensitivity of the MEG experiment was already limited by accidental background, the MEG detector was upgraded to realize one order of magnitude better sensitivity. Since the MEG and the MEG II experiment uses the 900l liquid xenon to detect 52.8 MeV gamma-rays, the photo sensors must be sensitive to the VUV light (175nm) and be operational at 165K. The MEG experiment utilized 846 2inch PMTs, and the MEG II experiment replaced 216 2inch PMTs on the gamma incident face with 4092 15x15mm2 MPPCs (SiPMs produced by Hamamatsu) to improve the energy, position resolutions. The MEG II experiment has started the physics run in 2021, and the first result was published in October 2023. In this talk, after the MEG II experiment and the initial results are briefly introduced, the SiPM characteristics including the calibration methods and the stabilities will be summarized based on the operation experience during the MEG II physics run for a few years.

      Speaker: Prof. Toshiyuki Iwamoto (ICEPP, the University of Tokyo)
    • 31
      Performance of novel VUV-sensitive Silicon Photo-Multipliers for nEXO

      Liquid xenon time projection chambers are promising detectors to search for neutrinoless double beta decay (0$\nu \beta \beta$), due to their response uniformity, monolithic sensitive volume, scalability to large target masses, and suitability for extremely low background operations. The nEXO collaboration has designed a five-tonne time projection chamber that aims to search for 0$\nu \beta \beta$ of \ce{^{136}Xe} with projected half-life sensitivity of $1.35\times 10^{28}$~yr. To reach this sensitivity, the design goal for nEXO is $\leq$1\% energy resolution at the decay $Q$-value ($2458.07\pm 0.31$~keV). Reaching this resolution requires the efficient collection of both the ionization and scintillation produced in the detector. The nEXO design employs Silicon Photo-Multipliers (SiPMs) to detect the vacuum ultra-violet, 175 nm scintillation light of liquid xenon. In this talk, we will show results on the characterization of the newest vacuum ultra-violet sensitive SiPMs by Fondazione Bruno Kessler, the VUVHD3 devices specifically designed for nEXO. We will also present measurements on new test samples of previously characterised Hamamatsu VUV4 Multi Pixel Photon Counters (MPPCs). Various SiPM and MPPC parameters, such as dark noise, gain, direct crosstalk, correlated avalanches and photon detection efficiency were measured as a function of the applied over voltage and wavelength at liquid xenon temperature (163~K). The results from this study are also used to provide updated estimates of the achievable energy resolution at the decay $Q$-value for the nEXO design.

      Speaker: Dr Giacomo Gallina (Princeton)
    • 12:30 PM
    • 32
      Low dark-count VUV SiPM for the DARWIN experiment
      Speaker: Prof. Shingo Kazama (Nagoya University)
    • 33
      Quality Assurance and Quality Control of the 25 m^2 SiPM production for the Darkside-20k dark matter experiment

      Liquid Argon Time Projection Chambers (TPC) are promising detectors for dark matter search due to their response uniformity, scalability to large target masses, and suitability for extremely low background operations. The DarkSide-20k experiment is a new dark matter detector under construction at Istituto Nazionale di Fisica Nucleare (INFN) Laboratori Nazionali del Gran Sasso (LNGS) that aims to push the sensitivity for Weakly Interacting Massive Particles (WIMP) detection into the neutrino fog. The core of the apparatus is a dual-phase TPC, serving both as WIMP target and detector, filled and surrounded by low-radioactivity Underground Argon (UAr). Fondazione Bruno Kessler (FBK) NUV-HD Cryo Silicon Photomultipliers (SiPM)s have been selected as the photon sensors of choice to instrument the two $25~\text{m}^2$ Optical Planes and the two veto detectors of the experiment. This talk focuses on the Quality Assurance and Quality Control (QA/QC) of the production wafers made with FBK~NUV-HD-Cryo SiPMs manufactured by LFoundry s.r.l. (Avezzano, AQ, Italy). Several SiPMs characteristics such as breakdown voltage, leakage current in the pre-breakdown region, quenching resistor and correlated noise are measured at the wafer level, at 77~K, with a custom design probe station. Overall up to September 2023 we tested 207 of the 1400 production wafers. The wafer yield is measured to be $94.3\pm2.3$~\% being not only in-spec but actually exceeding the 80\% expected by the original DarkSide-20k production plan.

      Speaker: Dr Giacomo Gallina (Princeton)
    • 34
      Current status of Xenoscope, a full-scale vertical demonstrator for the DARWIN observatory
      Speaker: Dr Jose Cuenca Garcia (Cuenca Garcia)
    • 3:30 PM
      Coffee Break
    • 35
      AXEL: High pressure xenon gas TPC

      AXEL group is developing a high pressure xenon gas detector to search for neutrinoless double beta decay. We will report on our dedicated electron readout system ELCC (electroluminescence collection cell).

      Speaker: Prof. Kiseki Nakamura (Tohoku University)
    • 36
      The R&D of the dual phase argon TPC, from DarkSide-50 to DarkSide-20k
      Speaker: Prof. Yi Wang (IHEP, CAS)
    • 37
      High voltage in large structures: challenges and progress
      Speaker: Dr Yanina Biondi (KIT)
    • 7:30 PM
      Workshop Dinner
    • 38
      Purification results from the LZ WIMP search
      Speaker: Prof. Carter Hall (University of Maryland)
    • 39
      XENONnT Purification
      Speaker: Prof. Masaki Yamashita (Kavli IPMU, the University of Tokyo)
    • 40
      PandaX Purification System and Cryogenic Distillation System
      Speaker: Dr Zhou Wang (Shanghai Jiao Tong University)
    • 11:30 AM
    • 41
      Development of low-background photomultiplier tubes for future liquid xenon detectors

      Photomultiplier tube (PMT) is one of the best best candidate device as the photo sensor for rare event search experiments, such as dark matter particle interactions and neutrinoless double beta decay events.
      For future experiments, one of the issue that needs to be addressed is its relatively large RI amount due to large amount of material used for the device.
      R13111 is a very low-background PMT developed during XMASS experiment for such future experiments.
      Low radioactivity was achieved mainly by three components: (1) the low-radioactive-contamination glass; (2) the photocathode with 39K-enriched potassium; and (3) the purest grade of aluminum vacuum seal. Achieved amount of RIs are about 0.4 mBq of 226Ra, less than 2 mBq of 238U, 0.3 mBq of 228Ra, 2 mBq of 40K and 0.2 mBq of 60Co.
      Together with such low level RI, good performance, large angular acceptance with high collection efficiency, good timing resolution, and long-term stable operation were also realized.

      Speaker: Dr Ko Abe (Kamioka Observatory, ICRR, The Univ. of Tokyo)
    • 42
      PMT readout for PandaX liquid xenon detectors
      Speaker: Lingyin LUO (Peking University)
    • 43
      Analog charge readout at nEXO & Cold ASIC electronics submerged in LXe

      The nEXO detector, a 5 ton-scale single-phase liquid xenon time projection chamber enriched to 90% in the isotope 136Xe, plans to observe the groundbreaking phenomenon of neutrinoless double beta decay, producing first data in 2030. Its projected sensitivity is robust against backgrounds and “unknown unknowns” due to the use of multiple observables for signal-to-background discrimination, not limited to but including its design energy resolution of <1% resolution at the 0vbb Q-value. The ionization-charge readout system is at the heart of each of the observables used in nEXO. In this talk, I will discuss the properties of this charge detection plane, which lends itself to the use of liquid-xenon submergible amplifying and digitizing electronics. Submerged electronics allow for amplification and digitization to occur directly at the sensor, resulting in lower analog noise due to reduced capacitance, data serialization that reduces the number of cables, and higher channel-count capabilities. Tests of prototype combined modules of charged detector and electronics readout will be presented.

      Speaker: Dr Evan Angelico (Stanford University)
    • 2:30 PM
      Coffee Break
    • 44
      UAr production for Darkside-20k: Urania, Aria, and DArT Projects.

      The innovative Underground Argon (UAr) Production is part, and a fundamental pillar of the Argon Dark Matter search program, led by the Global Argon Dark Matter Collaboration (GADMC). The aims of the UAr Production is to achieve the procurement of large amounts of low-radioactive UAr, which will be firstly used by the DarkSide-20k experiment. The UAr Production is composed by three projects which are currently in development, and specifically; the Urania project, for the extraction of the argon from underground source, the Aria project for the purification of the detector target mass, and the DArT project for the characterisation of it. In this talk, we will discuss the status of the 3 mentioned projects, and their latest results.

      Speaker: Dr Federico Gabriele (INFN - Cagliari Division)
    • 45
      Radon distillation for future LXe experiments
      Speaker: Dr Lutz Althüser (University of Münster)
    • 46
      Mitigation of radon background by surface coating for the next generation of liquid xenon dark matter detectors

      To satisfy the sensitivity requirements for the next generation of liquid xenon dark matter detectors, the radon-induced background must be reduced at least by one order of magnitude with respect to the level reached by the current detector generation (XENONnT 222-Rn activity ~ 1 muBq/kg). The existing technology might not be sufficient to reach this goal; therefore, other strategies must be studied. In particular, 222-Rn, the daughter of 226-Ra, which is present in every material, enters the active region by emanation from the detector surfaces. Therefore, at the Max-Planck-Institut für Kernphysik (MPIK), different surface coating techniques have been intensely studied as radon barriers. Electrodeposition of pure copper has been demonstrated to be a promising mitigation technique: We have achieved a thousandfold Rn reduction on a 2×2 cm2 stainless steel sample previously irradiated with 226-Ra at the ISOLDE facility at CERN. Following the successful small-scale tests, the setup underwent an upgrade, which allowed the coating of larger vessel-like samples. The state of the coating project will be presented, and upcoming operations will be discussed.

      Speaker: Dr Giovanni Volta (Max-Planck-Institut für Kernphysik)
    • 4:30 PM
      Concluding Remarks