---
title: Yemi Underground Laboratory (Yemilab)
url: https://www.emergentmind.com/topics/yemi-underground-laboratory-yemilab
type: topic
---

# Yemi Underground Laboratory (Yemilab)

The Yemi Underground Laboratory (Yemilab) is Korea's premier deep underground science facility, designed to enable rare-event searches in neutrino physics, dark matter, double beta decay, and beyond-Standard-Model (BSM) physics. Located beneath Mount Yemi in Jeongseon, Gangwon Province, Yemilab provides up to 2,700 meters water-equivalent (m.w.e.) overburden, housing a large multi-room laboratory complex including a dedicated 6,300 m³ cylindrical cavern for kiloton-scale detectors. The laboratory serves as the principal site for experiments such as AMoRE-II (0νββ decay), COSINE (dark matter), the IsoDAR accelerator-driven neutrino source, and the LSC liquid scintillator detector. Since its completion in 2022, Yemilab has enabled best-in-class backgrounds for cutting-edge rare-event experiments and is positioned to serve as a major international center for underground physics.

## 1. Site Location, Geological Setting, and Infrastructure

Yemilab is situated on the southern flank of Mount Yemi (989 m peak) in Jeongseon-gun, Gangwon Province, Korea. The main experimental caverns are accessed via a 600 m vertical shaft and a 782 m, 5 × 5 m cross-section sloped tunnel (12% grade), leading to an experimental floor up to 1,029 m below surface (≃2,500–2,700 m.w.e.) [2402.13708][2110.10635]. The host rock is predominantly Makdong limestone, with RMR grades 2–3, and was selected for its low uranium/thorium content (∼0.8 ppm U, 3.3 ppm Th [2110.10635]) and minimal radon out-gassing relative to typical hard-rock sites. 

The laboratory consists of 17 modular experimental rooms plus a 20 m diameter × 20 m deep cylindrical pit for large neutrino detectors. The exclusive scientific footprint is ~3,000 m², with overall excavation volume ~65,000 m³ [2402.13708]. Depth and rock composition are optimized to minimize cosmogenic backgrounds and rock-induced radiogenic neutrons and gamma rays. The ambient muon flux at depth (2,500 m.w.e.) is measured at 8.2 × 10⁻⁸ μ/cm²/s, a ×4 reduction relative to the Yangyang Underground Laboratory (Y2L) [2402.13708][2309.13435].

Utilities include 1,600 kW (2,000 kVA) electrical capacity (with UPS and backup generators), forced ventilation (Q=39,000 m³/h main duct), Class 1,000 cleanroom facilities, comprehensive dust and water control, and 1 Gbps fiber-optic communications [2402.13708][2110.10635].

## 2. Background Environment: Neutron and Radon Mitigation

### Neutron Backgrounds

Neutron measurements conducted at three locations in the main tunnel and halls show total neutron fluence rates in the (3.24 ± 0.11)–(4.01 ± 0.10) × 10⁻⁵ cm⁻²s⁻¹ range, with thermal components (E < 0.5 eV) between (1.32 ± 0.05)–(1.51 ± 0.05) × 10⁻⁵ cm⁻²s⁻¹ and fast neutrons (E = 1–10 MeV) at (0.27 ± 0.03)–(0.34 ± 0.10) × 10⁻⁵ cm⁻²s⁻¹ [2601.16928]. The neutron spectrum reveals a substantial contribution from (α, n) processes in both host rock and shotcrete linings, with spatial variation linked to shotcrete U/Th concentration and seasonal humidity. These levels are comparable to Canfranc and CJPL but higher than LNGS/Modane, directly informing detector shielding strategies using polyethylene, borated plastic, and multi-layer passive and active vetoes [2601.16928][2309.13435].

### Radon Backgrounds and Control

Ambient radon levels in the AMoRE hall average 17.6 ± 0.3 Bq/m³, with seasonal excursions up to ~2,000 Bq/m³ [2403.07405][2402.13708]. A dedicated Radon Reduction System (RRS) delivers 50 m³/h radon-suppressed air using a multi-stage (compressor-dryer-charcoal) system, reliably achieving ≥300× reduction (down to 0.058 ± 0.004 Bq/m³ in the cleanroom) and meeting the <0.29 Bq/m³ specification required for AMoRE crystal assembly [2403.07405]. Verification is performed using a bespoke 70 L PIN photodiode radon detector with intrinsic background 23.8 ± 2.1 mBq/m³ and 72 keV FWHM alpha energy resolution at 6.0 MeV [2403.07405]. The approach supports scaling to other experimental halls and is a core part of Yemilab’s low-background infrastructure.

## 3. Laboratory Architecture and Safety Systems

Yemilab employs the New Austrian Tunneling Method (NATM) with staged blasting, rock-bolt/shotcrete reinforcement, and deformation monitoring. All critical rooms use RMR-3 grade reinforcement, dual egress (for rooms >20 m), a 40-person mine refuge, and comprehensive fire and evacuation modeling [2402.13708]. The LSC pit (20 m × 20 m cylinder, V ≈ 6,300 m³) is engineered to support multi-kiloton detectors. Support infrastructure includes:

- Forced ventilation with negative pressure zones, dedicated exhaust, and HEPA/activated-carbon filtration.
- Automated groundwater drainage (yield ≈ 4 t/d).
- Access control, integrated personnel/equipment shafts, and staged heavy-equipment lanes.
- Distributed power (dynamic load sharing) and environmental monitoring throughout.
  
Shotcrete and structural supports are selected based on in situ stress and monitored for convergence and safety margins [2402.13708]. Regulatory compliance covers KGS, ASME BP&V, and ICRP 103 standards [2110.10635].

## 4. Experimental Program and Detector Platforms

### Core Experiments

| Experiment    | Target/Detector       | Science Focus                      | Start (planned/actual)    |
|:--------------|:---------------------|:-----------------------------------|:--------------------------|
| AMoRE-II      | 160 kg Li₂MoO₄ (cryogenic bolometer, T ≈ 10 mK) | 0νββ of ¹⁰⁰Mo                  | Q2 2024 [2402.13708]      |
| COSINE-100U/-200 | NaI(Tl) crystals + LS, cooled shield | Dark matter (annual mod.), low-mass DM | 2024–2025 (relocated from Y2L) |
| LSC (Liquid Scintillator Counter) | 2.26 kt LS / WbLS cylinder (D=15 m, H=15 m) | Solar geo-, reactor-, supernova-ν, BSM | 2024–onward [2309.13435] |
| IsoDAR@Yemilab | 60 MeV/amu cyclotron, Be+⁷Li target, 17 m to LSC | High-statistics ν̄ₑ, sterile neutrinos, NSI, new physics | 2024–2026 [2111.09480][2110.10635] |

The LSC is planned as a three-layer system: an inner acrylic vessel of 2.26 kt LS or WbLS (linear alkylbenzene + PPO + bis-MSB, or ~1% organic scintillator in H₂O), a 1 kt mineral oil buffer (D=17 m, H=17 m) with 3,000–4,000 20” PMTs (49–65% optical coverage), and a 2.4 kt outer water veto with ~200 PMTs [2309.13435]. Purity goals match or exceed Borexino (U/Th < 10⁻¹⁷ g/g). Fiducial mass and optical coverage are optimized for ultra-low backgrounds in solar, reactor, geoneutrino, and supernova neutrino detection, and for coincident BSM physics searches with accelerator and radioactive source deployments [2309.13435][1903.05368].

### Technology and R&D Focus

- WbLS technology (1–10% LS in water) provides simultaneous sensitivity for Cherenkov and scintillation light; decisive for directional and low-threshold physics [1903.05368].
- Advanced PMTs (Hamamatsu H11780, TTS ≃ 1.2 ns, QE ≃ 34%) and LAPPDs (TTS ≈ 60 ps, <1 cm granularity) for timing, vertexing, and signal-background separation.
- Gas stripping, multi-stage distillation, water extraction, and adsorber columns used in LS/WbLS purification; staged calibration with radioactive, beam, and optical sources [2309.13435].

## 5. Physics Reach and BSM Capabilities

### Neutrino Measurements

- Solar neutrinos: <0.5% uncertainty on pp flux, 1% on ⁷Be, 5% on ⁸B after 5 years; energy threshold ≈ 200 keV (LS) enables pp, Be7, pep, and CNO measurements [2309.13435]. Directional and delayed-coincidence cuts for background suppression.
- Reactor ν̄̄: 1,950 IBD events/year, mainly from the Hanul complex (65 km). L/E oscillation spectral analysis enables precision Δm²₂₁, θ₁₂ extraction [2309.13435][2111.09480].
- Geoneutrinos: ∼60 IBD/year and ∼820 ν-e ES events/year constrain Earth's U/Th content [2309.13435].
- Supernova and DSNB: 430–820 events for 10 kpc core-collapse, sensitivity to supernova relic ν's in 12–30 MeV [2309.13435].

### BSM Sensitivities (with LSC + IsoDAR/linac/source)

- Sterile neutrino searches: oscillation-wave mapping in L/E over 9–27 m/MeV, >5σ coverage of 3+1/3+2/decay models [2111.09480][2309.13435].
- Nonstandard interactions (NSI): ν̄ₑ–e scattering, 1.9% measurement of sin²θ_W, εee^L,R reach >5× improvement over existing bounds.
- Dark photon searches (e-linac+LSC): ε² exclusion down to ~10⁻¹⁶ (visible A′ decays) and ~10⁻¹³ (oscillation, m_{A′} < 2mₑ) [2009.11155][2309.13435].
- ALPs and new bosons: Primakoff/Compton processes in linac+LSC, g_{aγ}~10⁻⁷–10⁻⁹ GeV⁻¹ reach over MeV masses [2309.13435].
- Light dark matter: sensitivity parameter Y=ε²α_D(m_χ/m_A′)^4 down to 10⁻¹⁶–10⁻¹⁰ [2309.13435].

A summary of performance metrics and backgrounds for key detector units is tabulated below:

| Detector         | LS/WbLS Mass | Target Physics             | Muon Flux (cm⁻²s⁻¹) | Ambient Radon (Bq/m³) | Neutron Flux (cm⁻²s⁻¹)    |
|:-----------------|:-------------|:--------------------------|:--------------------|:----------------------|:-------------------------|
| LSC (Yemilab)    | 2.26 kt      | Solar/geo/reactor/SN/BSM  | 8.2×10⁻⁸           | <0.06 (RRS+cleanroom) | (3.2–4.0)×10⁻⁵ (total)   |
| AMoRE-II         | —            | 0νββ, rare decay          | 8.2×10⁻⁸           | <0.06 (RRS)           | (appropriate for search) |
| WbLS prototype   | ~1–5 kt      | R&D, directional ν, BSM   | 8.2×10⁻⁸           | <0.06 (targeted)      | (comparable)             |

## 6. Construction Timeline and Outlook

- Construction of the primary access tunnel and shaft was completed by August 2020; LSC pit excavation finalized by August 2022 [2402.13708].
- Scientific fit-outs (crane rails, cleanroom, services) proceeded through 2023, with the staged relocation of facilities from Y2L to Yemilab by end of 2024.
- IsoDAR cyclotron, target caverns, and shielding are fully excavated, with system installation and integration aligned for commissioning and physics data starting in 2024–2026 [2110.10635][2201.10040][2111.09480].
- Yemilab is designed for staged upgrades and programmatic expansion: modular halls and the central pit permit new detectors, expanded cryogenics, and next-generation platforms.

Yemilab combines multi-kiloton detector capacity, deep radiopurity, advanced environmental control, and accelerator access in a single facility. Its scientific output is positioned to inform neutrino and rare-event research at the international level, with infrastructure and operational data serving as a model for future global underground laboratories [2402.13708][2309.13435][2203.08804].

Source: https://www.emergentmind.com/topics/yemi-underground-laboratory-yemilab