About

Cristiano Galbiati is a professor of physics at Princeton University who joined the Physics Department in 1999 after graduating from Università degli Studi di Milano and Accademia Navale in Leghorn. His research interests include solar and supernova neutrinos, dark matter, double beta decay, nucleon decay, low-counting experiments, radioactive background, ultra-high energy cosmic rays, and neutrinos. He has served on several scientific committees, including the Fermilab Long Baseline Neutrino Committee, the Fermilab Physics Advisory Committee, and the Scientific Committee of the Laboratorio Subterráneo de Canfranc. Galbiati is a Fellow of the American Physical Society and has acted as a referee for the U.S. National Science Foundation and the Office of Science of the U.S. Department of Energy. He holds several patents for innovative technologies, such as a cryogenic distillation column for isotopic separation and systems for onboard storage of ammonia and hydrogen production without carbon and NOX emissions. During the COVID-19 emergency, he co-led the development of the Mechanical Ventilator Milano with Prof. Art McDonald of Queen’s University, which is noted as the only ventilator developed by the research community that received full approval in the U.S., Canada, and the EU, and went into production.

Research topics

• Physics
• Nuclear physics
• Computer Science
• Astrophysics
• Particle physics
• Optics

Selected publications

• The Darkside-20k Data Acquisition System

  HAL (Le Centre pour la Communication Scientifique Directe) · 2026-04-03

  preprintOpen access

  DarkSide-20k is a WIMP search experiment using liquid argon as a target, designed to perform a background-free search for dark matter with unprecedented sensitivity, and is currently under construction at INFN Laboratori Nazionali del Gran Sasso, Italy. The detector comprises a dual-phase Time Projection Chamber complemented with external veto systems and is equipped with a total of 2720 SiPM-based readout channels. This work presents the DAQ system designed for DarkSide-20k. The system is capable of continuous, triggerless digitisation of the waveforms with high single-photoelectron detection efficiency and online processing, ensuring data reduction for long-term storage. The DarkSide-20k DAQ system employs commercial CAEN VX2745 digitisers with custom FPGA firmware implementation. Timing and synchronisation across all 48 digitisers are provided by custom Global and Crate Data Manager boards distributing a phase-aligned clock derived from a disciplined rubidium standard. Waveform segments are processed in real time by Front End Processor machines. Data are organised into collections containing whole detector information and distributed across a farm of Time Slice Processors for event reconstruction, classification, and further reduction before storage and offline analysis. A full "Quadrant" of the system, corresponding to one quarter of the final DAQ, has been assembled and validated at TRIUMF laboratory in Canada. The Quadrant has been stress-tested with simultaneous pulses and demonstrated sustained digitizer readout exceeding expected physics rates and stable long-term performance.

  PublisherOA PDFDOI

• Construction and characterisation of the DarkSide-20k veto silicon photo-multiplier tiles

  HAL (Le Centre pour la Communication Scientifique Directe) · 2026-04-02

  otherOpen access

  International audience

  PublisherOA PDF

• The Darkside-20k Data Acquisition System

  ArXiv.org · 2026-04-03

  articleOpen access

  DarkSide-20k is a WIMP search experiment using liquid argon as a target, designed to perform a background-free search for dark matter with unprecedented sensitivity, and is currently under construction at INFN Laboratori Nazionali del Gran Sasso, Italy. The detector comprises a dual-phase Time Projection Chamber complemented with external veto systems and is equipped with a total of 2720 SiPM-based readout channels. This work presents the DAQ system designed for DarkSide-20k. The system is capable of continuous, triggerless digitisation of the waveforms with high single-photoelectron detection efficiency and online processing, ensuring data reduction for long-term storage. The DarkSide-20k DAQ system employs commercial CAEN VX2745 digitisers with custom FPGA firmware implementation. Timing and synchronisation across all 48 digitisers are provided by custom Global and Crate Data Manager boards distributing a phase-aligned clock derived from a disciplined rubidium standard. Waveform segments are processed in real time by Front End Processor machines. Data are organised into collections containing whole detector information and distributed across a farm of Time Slice Processors for event reconstruction, classification, and further reduction before storage and offline analysis. A full "Quadrant" of the system, corresponding to one quarter of the final DAQ, has been assembled and validated at TRIUMF laboratory in Canada. The Quadrant has been stress-tested with simultaneous pulses and demonstrated sustained digitizer readout exceeding expected physics rates and stable long-term performance.

  PublisherOA PDF

• Flow and thermal modelling of the argon volume in the DarkSide-20k TPC

  Journal of Instrumentation · 2025-06-01 · 1 citations

  articleOpen access

  Abstract The DarkSide-20k dark matter experiment, currently under construction at LNGS, features a dual-phase time projection chamber (TPC) with a ∼ 50 t argon target from an underground well. At this scale, it is crucial to optimise the argon flow pattern for efficient target purification and for fast distribution of internal gaseous calibration sources with lifetimes of the order of hours. To this end, we have performed computational fluid dynamics simulations and heat transfer calculations. The residence time distribution shows that the detector is well-mixed on time-scales of the turnover time (∼ 40 d). Notably, simulations show that despite a two-order-of-magnitude difference between the turnover time and the half-life of 83m Kr of 1.83 h, source atoms have the highest probability to reach the centre of the TPC 13 min after their injection, allowing for a homogeneous distribution before undergoing radioactive decay. We further analyse the thermal aspects of dual-phase operation and define the requirements for the formation of a stable gas pocket on top of the liquid. We find a best-estimate value for the heat transfer rate at the liquid-gas interface of 62 W with an upper limit of 144 W and a minimum gas pocket inlet temperature of 89 K to avoid condensation on the acrylic anode. This study also informs the placement of liquid inlets and outlets in the TPC. The presented techniques are widely applicable to other large-scale, noble-liquid detectors.

  PublisherDOI

• Fermionic sub-GeV Dark Matter from evaporating Primordial Black Holes at DarkSide-50

  ArXiv.org · 2025-05-19

  preprintOpen access

  We present a search for boosted dark matter from Primordial Black Holes (PBH) evaporation using the DarkSide-50 ionization-signal-only dataset corresponding to the experiment's ($12202\pm180$) ${\rm kg\: d}$ exposure. We focus on evaporation of PBHs with masses in the range [$10^{14},\,10^{16}$] g producing Dirac fermionic dark matter particles with sub-GeV kinetic energy. These relativistic particles, with energies up to hundreds of MeV, can generate detectable signals for masses below $\mathcal{O}(100)$ MeV. The absence of a signal enables setting complementary limits to those derived from cosmological observations and direct detection searches for cosmic ray-boosted dark matter.

  PublisherOA PDFDOI

• 3D<i>π</i>: three-dimensional positron imaging, a novel total-body PET scanner using xenon-doped liquid argon scintillator

  Physics in Medicine and Biology · 2025-02-26 · 3 citations

  article

  Abstract Objective. This paper introduces a novel PET imaging methodology called 3-dimensional positron imaging (3D π ), which integrates total-body coverage, time-of-flight (TOF) technology, ultra-low dose imaging capabilities, and ultra-fast readout electronics inspired by emerging technology from the DarkSide collaboration. Approach. The study evaluates the performance of 3D π using Monte Carlo simulations based on NEMA NU 2-2018 protocols. The methodology employs a homogenous, monolithic scintillator composed of liquid argon (LAr) doped with xenon (Xe) with silicon photomultipliers (SiPMs) operating at cryogenic temperatures. Main results. Substantial improvements in system performance are observed, with the 3D π system achieving a noise equivalent count rate of 3.2 Mcps at 17.3 kBq ml −1 , continuing to increase up to 4.3 Mcps at 40 kBq ml −1 . Spatial resolution measurements show an average FWHM of 2.7 mm across both axial positions. The system exhibits superior sensitivity, with values reaching 373 kcps MBq −1 with a line source at the center of the field of view. Additionally, 3D π achieves a TOF resolution of 151 ps at 5.3 kBq ml −1 , highlighting its potential to produce high-quality images with reduced noise levels. Significance. The study underscores the potential of 3D π in improving PET imaging performance, offering the potential for shorter scan times and reduced radiation exposure for patients. The Xe-doped LAr offers advantages such as fast scintillation, enhanced light yield, and cost-effectiveness. Future research will focus on optimizing system geometry and further refining reconstruction algorithms to exploit the strengths of 3D π for clinical applications.

  PublisherDOI

• Ultra-low-background physics: lessons from BOREXINO and future steps

  2025-03-20

  articleOpen access

  The Borexino experiment concluded the data acquisition at the end of 2021 and among the solar neutrino experiments it has been the only one capable of reconstructing the position and the energy on an event-by-event base, with an energy threshold of 150 keV, thanks to its ultra-high radio-purity. The experimental techniques and analysis methods that allowed Borexino to reach such unprecedented levels of radio-purity are now a standard and the legacy that Borexino leaves to the next low energy neutrinos and rare event searching experiments. This contribution is aimed to present the methods and the main achievements of the Borexino and to summarize the broad experimental effort presently in progress in the field of ultra-low background physics to further improve the sensitivity with massive underground detectors and new techniques.

  PublisherOA PDFDOI

• Benchmarking the design of the cryogenics system for the underground argon in DarkSide-20k

  Journal of Instrumentation · 2025-02-01 · 3 citations

  articleOpen access

  Abstract DarkSide-20k (DS-20k) is a dark matter detection experiment under construction at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy. It utilises ∼ 100 t of low radioactivity argon from an underground source (UAr) in its inner detector, with half serving as target in a dual-phase time projection chamber (TPC). The UAr cryogenics system must maintain stable thermodynamic conditions throughout the experiment's lifetime of over 10 years. Continuous removal of impurities and radon from the UAr is essential for maximising signal yield and mitigating background. We are developing an efficient and powerful cryogenics system with a gas purification loop with a target circulation rate of 1000 slpm. Central to its design is a condenser operated with liquid nitrogen which is paired with a gas heat exchanger cascade, delivering a combined cooling power of more than 8 kW. Here we present the design choices in view of the DS-20k requirements, in particular the condenser's working principle and the cooling control, and we show test results obtained with a dedicated benchmarking platform at CERN and LNGS. We find that the thermal efficiency of the recirculation loop, defined in terms of nitrogen consumption per argon flow rate, is 95 % and the pressure in the test cryostat can be maintained within ±(0.1–0.2) mbar. We further detail a 5-day cool-down procedure of the test cryostat, maintaining a cooling rate typically within -2 K/h, as required for the DS-20k inner detector. Additionally, we assess the circuit's flow resistance, and the heat transfer capabilities of two heat exchanger geometries for argon phase change, used to provide gas for recirculation. We conclude by discussing how our findings influence the finalisation of the system design, including necessary modifications to meet requirements and ongoing testing activities.

  PublisherDOI

• Sensitivity to low-mass WIMPs with an improved liquid argon ionization response model within the DarkSide programme

  ArXiv.org · 2025-11-17

  preprintOpen access

  Dark matter detection experiments using liquid argon rely on a precise characterization of the ionization response to nuclear recoils, especially in the keV energy range relevant for light dark matter interactions. In this work, we present a comprehensive analysis that combines new measurements from the ReD setup, part of the DarkSide experimental program, with calibration data from DarkSide-50, as well as results from the ARIS and SCENE experiments. These combined datasets enable improved constraints on atomic screening effects in the modeling of the ionization response of liquid argon to nuclear recoils. The analysis is performed within the Thomas-Imel recombination framework adopted in previous DarkSide studies, and is here further constrained by the inclusion of ReD data, which allow the screening function to be determined from calibration measurements. By including the updated ionization model into the DarkSide-50 analysis framework, we obtain stronger exclusion limits on low-mass WIMP interactions, setting new world-leading constraints in the 1-3 GeV/c^2 WIMP mass range. Finally, we recast the sensitivity projections for the upcoming DarkSide-20k detector, demonstrating a significantly enhanced discovery potential for low-mass dark matter candidates.

  PublisherOA PDFDOI

• Production, Quality Assurance and Quality Control of the SiPM Tiles for the DarkSide-20k Time Projection Chamber

  ArXiv.org · 2025-07-09

  preprintOpen access

  The DarkSide-20k dark matter direct detection experiment will employ a 21 m^2 silicon photomultiplier (SiPM) array, instrumenting a dual-phase 50 tonnes liquid argon Time Projection Chamber (TPC). SiPMs are arranged into modular photosensors called Tiles, each integrating 24 SiPMs onto a printed circuit board (PCB) that provides signal amplification, power distribution, and a single-ended output for simplified readout. 16 Tiles are further grouped into Photo-Detector Units (PDUs). This paper details the production of the Tiles and the quality assurance and quality control (QA-QC) protocol established to ensure their performance and uniformity. The production and QA-QC of the Tiles are carried out at Nuova Officina Assergi (NOA), an ISO-6 clean room facility at LNGS. This process includes wafer-level cryogenic characterisation, precision flip-chip bonding, wire bonding, and extensive electrical and optical validation of each Tile. The overall production yield exceeds 83.5%, matching the requirements of the DarkSide-20k production plan. These results validate the robustness of the Tile design and its suitability for operation in a cryogenic environment.

  PublisherOA PDFDOI

Recent grants

• Study of Argon for WIMP Dark Matter Detectors and Earth Sciences

  NSF · $2.0M · 2007–2012

• Collaborative Research: A Depleted Argon Detector for a Dark Matter Search

  NSF · $4.7M · 2010–2015

• Collaborative Research: Direct Search for Dark Matter with Underground Argon at LNGS

  NSF · $3.2M · 2014–2019

• Collaborative Research: R & D Toward DarkSide-G2, a Second-Generation Direct Search for Dark Matter

  NSF · $2.8M · 2012–2016

• MAX - Multi-ton Argon and Xenon TPCs

  NSF · $3.5M · 2009–2013

Frequent coauthors

• D. Franco

  University of Chicago

  1061 shared

• Y. Suvorov

  522 shared

• A. Razeto

  501 shared

• M. Pallavicini

  493 shared

• G. Korga

  489 shared

• F. Ortica

  University of Chinese Academy of Sciences

  467 shared

• A. Sotnikov

  434 shared

• O. Smirnov

  431 shared

Education

• Dottoranto in Fisica (env. Ph.D. in Physics), Physics

  Università degli Studi di Milano

  1999

• Commissioned Officer

  Accademia Navale

  1999

• Laurea in Fisica (eqv. Master in Physics), Physics

  Università degli Studi di Milano

  1995

Awards & honors

• Fellow of the American Physical Society