Liquid-krypton calorimeter

Liquid-krypton calorimeter
Name	Liquid-krypton calorimeter
Type	Electromagnetic calorimeter
Material	Krypton (liquid)

Liquid-krypton calorimeter. A liquid-krypton calorimeter is an electromagnetic detector using liquid krypton as the active medium to measure energy of ionizing particles. It combines cryogenic technology, high-voltage ionization readout, precision electronics, and calorimetry techniques to provide accurate measurements for experiments at colliders, fixed-target facilities, and neutrino observatories. Its development intersects work by national laboratories, university groups, and international collaborations.

Introduction

Liquid-krypton calorimeters operate in contexts such as the CERN Large Hadron Collider, the SLAC National Accelerator Laboratory, the Brookhaven National Laboratory, and experiments tied to the European Organization for Nuclear Research and the Fermi National Accelerator Laboratory. They are compared with calorimeters using liquid argon, scintillator, lead tungstate, bismuth germanate, and cesium iodide in studies by groups at Imperial College London, the University of Oxford, Massachusetts Institute of Technology, and the Max Planck Society. Design choices reflect influence from projects supported by agencies such as the National Science Foundation, the European Research Council, and the Deutsche Forschungsgemeinschaft.

Principles of operation

Ionization in liquid krypton produces free electrons and ions when traversed by charged particles from decays or collisions studied by collaborations like ATLAS, CMS, ALICE, and LHCb. Under an applied electric field established via feedthroughs designed with guidance from CERN engineering groups and standards from the Institute of Electrical and Electronics Engineers, electrons drift to segmented electrodes associated with readout electronics developed by teams at INFN, CEA Saclay, and Brookhaven National Laboratory. Signal shaping, digitization, and zero-suppression are implemented in ASICs and FPGAs sourced from vendors contracted by collaborations including Belle II, BaBar, and DUNE. Cryogenics to maintain krypton near its boiling point involve cryostats using technology from firms and laboratories that have worked with ITER cryogenic systems and Fermilab refrigeration groups.

Design and construction

Mechanical design borrows methods from cryogenic programs at CERN and fabrication techniques used in detectors such as ATLAS Tile Calorimeter and CMS Electromagnetic Calorimeter. Electrode geometries, spacer systems, and absorber materials are optimized by simulation toolkits like GEANT4 and analysis frameworks developed at institutions including CERN, SLAC, KEK, and DESY. Readout segmentation schemes follow precedents set by projects at DESY and Paul Scherrer Institute, with front-end electronics produced in collaboration with industrial partners in Germany and Italy. Quality assurance procedures reference standards applied by European Organization for Nuclear Research workshops and metrology centers at the National Institute of Standards and Technology.

Performance and calibration

Energy resolution, linearity, and uniformity are characterized in beam tests at facilities such as the CERN SPS, the Fermilab Test Beam Facility, and the DESY II Test Beam Facility. Calibration uses radioactive sources, laser systems, and in-situ techniques exploiting physics channels like Z boson decays, pi0 meson reconstruction, and J/psi resonances recorded by detectors from collaborations such as ATLAS and CMS. Stability monitoring references environmental control systems modeled after ITER standards and relies on data acquisition systems developed by teams at RAL, SLAC, and Brookhaven National Laboratory. Performance metrics are benchmarked against historical calorimeters like those in UA1, UA2, and ALEPH.

Applications in particle physics

Liquid-krypton calorimeters serve precision measurements in searches for phenomena predicted by theories from groups working on Supersymmetry, Dark matter, and Electroweak symmetry breaking. They contribute to precision electroweak measurements exemplified by measurements at the LEP experiments and to flavor physics efforts analogous to those at BaBar and Belle. Experiments studying rare decays, neutrino interactions in projects akin to DUNE and T2K, and fixed-target programs at facilities like CERN SPS have employed liquid noble detectors inspired by liquid-krypton designs. Collaborations with accelerator teams at CERN, Fermilab, and KEK ensure integration with trigger and data acquisition systems.

Historical development and major experiments

The evolution of liquid-krypton calorimetry traces through developments at national laboratories such as CERN, Brookhaven National Laboratory, and SLAC National Accelerator Laboratory, and through university groups at Oxford University, Cambridge University, MIT, and Caltech. Beam-test campaigns at the CERN SPS and contributions from instrumentation programs at DESY and KEK shaped prototype performance. Major experiments that explored liquid-krypton concepts include testbeds associated with collaborations linked to the LHC program and research and development efforts funded by agencies like the European Commission and the U.S. Department of Energy. The technology influenced later calorimeter designs and informed detector choices for precision electromagnetic measurements in successor experiments and upgrade programs managed by institutions such as CERN and the European Laboratory for Particle Physics.

Category:Calorimeters