The detection and cross-section measurement of Coherent Elastic Neutrino–Nucleus Scattering (CEvNS) are vital for particle physics, astrophysics, and nuclear physics. Therefore, a new CEvNS detection experiment is proposed in China. Undoped CsI crystals, each coupled with two Photon Multiplier Tubes (PMTs), will be cooled down to 77 K and placed at the China Spallation Neutron Source (CSNS) to detect the CEvNS signals produced by neutrinos from stopped pion decays occurring within the Tungsten target of CSNS. Owing to the extremely high light yield of pure CsI at 77 K, even though it only has a neutrino flux 60% weaker than the COHERENT experiment, the detectable signal event rate is still expected to be 0.074/day/kg (0.053/day/kg for COHERENT). Low-radioactivity materials and devices will be used to construct the detector, and strong shielding will be applied to reduce the radioactive and neutron background. Dual-PMT readout should be able to reject PMT dark count background. Using all the strategies mentioned above, we hope to reach a 5.1$\sigma$ signal detection significance within six months of data collection with four 3 kg CsI. This paper will discuss the experiment’s design, as well as the estimation of the signal, various kinds of background, and expected signal sensitivity.

The detection and cross-section measurement of Coherent Elastic Neutrino-Nucleus Scattering (CEνNS) are vital for particle physics, astrophysics, and nuclear physics. Therefore, a new CEνNS detection experiment is proposed in China. Undoped CsI crystals, each coupled with two Photon Multiplier Tubes (PMTs), will be cooled down to 77K and placed at the China Spallation Neutron Source (CSNS) to detect the CEνNS signals produced by neutrinos from stopped pion decays happening within the Tungsten target of CSNS. Owing to the extremely high light yield of pure CsI at 77K, even though it only has a neutrino flux 60\% weaker than the COHERENT experiment, the detectable signal event rate is still expected to be 0.074/day/kg (0.053/day/kg for COHERENT). Low radioactivity materials and devices will be used to construct the detector, and strong shielding will be applied to reduce the radioactive and neutron background. Dual-PMT readout should be able to reject PMT-related background, such as Cherenkov light and PMT dark noise. With all the strategies mentioned above, we hope to reach a 5.1σ signal detection significance within six months of data taking with a 12kg CsI. This presentation will discuss the experiment's design, as well as the estimation of the signal, various kinds of background, and expected signal sensitivity.

A cryogenic detector system based on two 3.3 kg high-purity CsI crystals was developed and characterized at approximately 95 K. Each wedge-shaped crystal was coupled to dual-ended 3-inch photomultiplier tubes (PMTs) for scintillation readout. The measured light yields were $28.7 \pm 0.9$ and $29.3 \pm 1.0$ photoelectrons per keV electron-equivalent (PE/keV$_{ee}$) for the two crystals, with corresponding energy resolutions of 7.2 \% and 7.7 \% (FWHM) at 59.6 keV. The detector demonstrated excellent spatial uniformity, low intrinsic radioactivity, and stable operation over a continuous one-month period. Optical photon simulations using Geant4 reproduced the observed light collection trends, providing guidance for detector optimization. These results establish cryogenic pure CsI as a scalable technology for low-threshold rare-event searches.