--- title: "Cherenkov Light & Detector Rings Interactive Lab | Sandbox Physics" description: "When does a cone of light become a ring? When it hits a surface lined with light sensors." canonical_url: "https://sandboxphysics.com/labs/cherenkov-rings/" language: "en" page_type: "lab" alternate_languages: zh-CN: "https://sandboxphysics.com/zh/labs/cherenkov-rings/" last_modified: "2026-10-27" --- Neutrinos · D09 · Water and geometry # Cherenkov Light & Detector Rings **When does a cone of light become a ring?** When it hits a surface lined with light sensors. The particle's speed sets the opening angle of the cone. Its direction and its distance from that surface then decide where the light lands, and so the shape and size of the ring you record. Set a charged particle’s speed and tilt, then follow its light to a flat square detector. Move the emission point to see which parts of the pattern come from the cone’s geometry and which come from the detector’s finite size. > Interactive simulation: open this page in a web browser to change the parameters and run the model. This model traces geometry only. It sends 1200 equal-weight rays from one small emission region through uniform water whose refractive index is 1.333 at every wavelength. The detector is a flat 14 metre square, not the cylindrical Super-K tank. Scattering, absorption, wavelength dependence, particle showers and sensor efficiency are left out. Brightness shows how densely the sampled rays land, not energy or the absolute number of photons. Recorded data from a teaching simulation ## Inspect the measurement Preparing a reproducible teaching record… Read a sample of the record [Scientific reference ↗](https://www-sk.icrr.u-tokyo.ac.jp/en/sk/about/detector/) [Read the worldwide history →](https://sandboxphysics.com/stories/neutrinos/) [2026 Nobel Prize in Physics →](https://sandboxphysics.com/nobel/2026/physics/) Physics tutorial ## A cone meets a measurement plane **Background** The detector plane faces along positive z; x is horizontal and y is vertical, all in metres. The charged particle moves in the plane spanned by x and z. Its small emission region sits at z equal to zero, shifted sideways by the chosen offset. **Why it matters** What changes the cone of light itself, and what only changes the pattern it leaves on the detector? Start with the essentials - **Focus question**: What changes the cone of light itself, and what only changes the pattern it leaves on the detector? - **One-sentence intuition**: The particle’s speed sets the Cherenkov angle; the track’s tilt and the distance to the detector set the shape you record. ### Core mathematical model #### Cherenkov angle and speed threshold $$ \cos\theta_C=\frac{1}{n\beta},\qquad n\beta>1 $$ The speed ratio here is the particle’s speed divided by the speed of light in vacuum. Below the threshold this model emits no light. The refractive index is taken to be the same at every wavelength. #### Where each ray meets the plane, and the radius at normal incidence $$ \mathbf r_D=\mathbf r_0+\frac{z_D}{k_z}\mathbf k,\qquad R_{\alpha=0}=z_D\tan\theta_C $$ The ray’s unit direction is k. Only rays that travel forward and land inside the square are recorded. The radius for a track perpendicular to the plane stays on screen as a reference even when the track is tilted; it is not fitted to the ring. ### Common difficulties #### A cone meets a measurement plane **Typical misconception** The ring is a picture of the neutrino itself. **Better mental model** The ring is light from a charged particle that the neutrino produced. Working back to the neutrino also takes the kinematics of the interaction and the detector response. ### Run the experiment 1. 01 #### Cross the threshold Choose Below threshold. Raise the speed until light appears. **What to observe:** The cone opens from zero angle. Above threshold the model always samples the same number of rays, so the brightness tells you nothing about how much light a real particle gives off. 2. 02 #### Tilt the cone Choose Tilted cone and compare the apparatus with the recorded plane. **What to observe:** A tilted cone leaves a shifted, stretched pattern, and the edge of the square can cut part of it off. 3. 03 #### Change distance only Return to Centered ring and double the emission-to-plane distance. **What to observe:** The ring’s radius doubles while the cone angle stays the same, until the ring runs past the edge of the square. Physical conclusion The particle’s speed sets the Cherenkov angle; the track’s tilt and the distance to the detector set the shape you record. ## Related experiments and articles Continue exploring ### How detectors see a neutrino A neutrino leaves only light, charge or a pair of signals close in time. How does each detector turn that into a direction, an energy or a source? 1. [Lab **Reactor Antineutrino Coincidence** Select prompt and delayed signals against accidental pairs.](https://sandboxphysics.com/labs/reactor-coincidence/) 2. [You are here **Cherenkov Light & Detector Rings** Turn charged-particle geometry into a recorded light pattern.](https://sandboxphysics.com/labs/cherenkov-rings/) 3. [Lab **Liquid Argon Time Projection Chamber** Turn electron arrival times and wire projections into calibrated slice centroids.](https://sandboxphysics.com/labs/liquid-argon-tpc/) 4. [Lab **IceCube: From Sensor Hits to a Track** Infer a track direction from the recorded sensor times.](https://sandboxphysics.com/labs/icecube-reconstruction/) 5. [Lab **Supernova Neutrino Burst Observatory** Scan a frozen burst record, then inspect one interaction at the optical timescale.](https://sandboxphysics.com/labs/supernova-neutrino-burst/) 6. [Lab **Neutrino Sky Search Observatory** Search frozen neutrino directions and compare a local hotspot with paired finite-grid background trials.](https://sandboxphysics.com/labs/neutrino-sky-search/) Neutrinos · Reading path ### Make a source and test its journey Articles on this path that use this experiment, followed by the other experiments they suggest. 1. [Article **How do you make a beam of particles you cannot steer?**](https://sandboxphysics.com/stories/neutrinos/making-an-accelerator-neutrino-beam/) 2. [Lab **Long-Baseline CP Observatory**](https://sandboxphysics.com/labs/long-baseline-cp/) 3. [Lab **Neutrino Flavor Propagation**](https://sandboxphysics.com/labs/neutrino-flavor-propagation/) 4. [Article **K2K and MINOS: test flavor change with a distance you choose**](https://sandboxphysics.com/stories/neutrinos/k2k-minos-controlled-baselines/) 5. [Article **T2K: why look slightly away from the beam axis?**](https://sandboxphysics.com/stories/neutrinos/t2k-off-axis-beam-and-appearance/) 6. [Article **Hyper-K: a larger target still needs a precise comparison**](https://sandboxphysics.com/stories/neutrinos/hyper-kamiokande-mass-and-systematics/) Neutrinos · Reading path ### Start with the prize Articles on this path that use this experiment, followed by the other experiments they suggest. 1. [Article **2026 Nobel Prize in Physics: why look for neutrinos in Antarctic ice?**](https://sandboxphysics.com/stories/neutrinos/nobel-physics-2026/) 2. [Lab **IceCube: From Sensor Hits to a Track**](https://sandboxphysics.com/labs/icecube-reconstruction/) 3. [Article **Five ways a neutrino headline can lead us astray**](https://sandboxphysics.com/stories/neutrinos/neutrino-nobel-common-misconceptions/) 4. [Article **Why do neutrinos keep appearing in the Nobel Prize?**](https://sandboxphysics.com/stories/neutrinos/neutrinos-and-nobel-prizes/) 5. [Lab **Reactor Antineutrino Coincidence**](https://sandboxphysics.com/labs/reactor-coincidence/) 5 more groups Neutrinos · Reading path ### Build a new way to observe the sky Articles on this path that use this experiment, followed by the other experiments they suggest. 1. [Article **SN 1987A: a supernova seen from underground**](https://sandboxphysics.com/stories/neutrinos/sn1987a-burst/) 2. [Lab **Supernova Neutrino Burst Observatory**](https://sandboxphysics.com/labs/supernova-neutrino-burst/) 3. [Lab **Reactor Antineutrino Coincidence**](https://sandboxphysics.com/labs/reactor-coincidence/) 4. [Article **Before IceCube: learning to build telescopes in water and ice**](https://sandboxphysics.com/stories/neutrinos/before-icecube-underwater-telescopes/) 5. [Lab **IceCube: From Sensor Hits to a Track**](https://sandboxphysics.com/labs/icecube-reconstruction/) 6. [Article **IceCube: how do you turn a cubic kilometre of ice into an instrument?**](https://sandboxphysics.com/stories/neutrinos/icecube-ice-sensors-and-calibration/) Neutrinos · Reading path ### What happened to the Sun’s neutrinos? Articles on this path that use this experiment, followed by the other experiments they suggest. 1. [Article **How do you know those neutrinos came from the Sun?**](https://sandboxphysics.com/stories/neutrinos/kamiokande-real-time-solar-neutrinos/) 2. [Lab **Solar Neutrino Flavor Observatory**](https://sandboxphysics.com/labs/solar-neutrino-flux/) 3. [Article **SNO: where did the Sun’s missing neutrinos go?**](https://sandboxphysics.com/stories/neutrinos/sno-flavor-transformation/) Neutrinos · Reading path ### Understand flavor change and mass Articles on this path that use this experiment, followed by the other experiments they suggest. 1. [Article **How does the atmosphere make neutrinos all around us?**](https://sandboxphysics.com/stories/neutrinos/atmospheric-neutrino-production/) 2. [Lab **Atmospheric Neutrino Zenith Experiment**](https://sandboxphysics.com/labs/atmospheric-neutrino-zenith/) 3. [Article **Super-Kamiokande: the neutrinos that took the long way**](https://sandboxphysics.com/stories/neutrinos/super-k-zenith-angle/) Neutrinos · Reading path ### Follow the measurement chain Articles on this path that use this experiment, followed by the other experiments they suggest. 1. [Article **Water, scintillator and argon: what does each detector see?**](https://sandboxphysics.com/stories/neutrinos/neutrino-detector-measurement-chains/) 2. [Lab **Liquid Argon Time Projection Chamber**](https://sandboxphysics.com/labs/liquid-argon-tpc/) 3. [Lab **Reactor Antineutrino Coincidence**](https://sandboxphysics.com/labs/reactor-coincidence/) Particles and detectors · Reading path ### Detecting a passing particle Articles on this path that use this experiment, followed by the other experiments they suggest. 1. [Article **Cherenkov follows the blue light to a moving charge**](https://sandboxphysics.com/stories/particle-evidence/cherenkov-light-cone/) Fields & matter · Starter path ## From a field to an electron microscope Map an electric field and steer a charged particle. Then find the electron's wavelength and use electron beams to see a crystal and a surface. [Start here → **Make an Electric Field Visible** Move the probe around a dipole and check that the field always points downhill on the potential landscape. Observe · 8 min](https://sandboxphysics.com/labs/electric-field/) 1. [1 Make an Electric Field Visible](https://sandboxphysics.com/labs/electric-field/) 2. [2 A Charge Bending through Fields](https://sandboxphysics.com/labs/charged-particle/) 3. [3 Electron Wavelength & Voltage](https://sandboxphysics.com/labs/electron-wavelength/) 4. [4 Electron Diffraction & Reciprocal Space](https://sandboxphysics.com/labs/electron-diffraction/) 5. [5 TEM Bright Field, Dark Field & SAED](https://sandboxphysics.com/labs/tem-mode-selector/) 6. [6 SEM Secondary-Electron Topography](https://sandboxphysics.com/labs/sem-topography/) [View the full path →](https://sandboxphysics.com/topics/fields-and-matter/#starter-path)