| Clue | Source | Date |
|---|---|---|
| Ray of charged particles | Universal | 03 Aug 2019 |
| Emission from a duoplasmatron | The Washington Post Sunday | 07 Jul 2019 |
| Ray of charged particles | ||
| Ray gun ray | New York Times | 27 Mar 2015 |
| Charged ray used in particle therapy | ||
| Ray gun ray | ||
| Radiotherapy deliverer | ||
| Radiotherapy ray |