A long, narrow garden bed needs watering, but you can't move the hose: you can only turn the water on and off. If you just open the tap, water flows in a steady stream and floods everything at once. But if you quickly flip the lever, you can send short bursts of water: each landing exactly where it's needed. That's how the new proton irradiation scheme works: the accelerator delivers not a continuous beam but a series of rapid pinches — slices along the particle bunch. Each slice is directed to the right spot in the tumor, and it all happens in the time it takes to blink.
Why the rush? In particle physics, it's long been noted that ultra-fast irradiation, FLASH, spares healthy tissue better than conventional, drawn-out doses. But to achieve the effect, the entire dose must be delivered within tenths of a second. Conventional accelerators can't switch the beam from point to point that quickly. Here, the trick is not to move the beam in space but to slice it in time. A special monitor measures particle density in real time, and an algorithm instantly decides which portion to send to the next point.
When a slice contains too many particles, precision drops, like a too-large burst from the hose splashing the neighboring plants. Calculations show that 20 billion protons is the optimal number. At this beam intensity, the dose error stays within acceptable limits, and the fraction of particles that hit the channel walls is less than one percent. That matters: lost protons can create unwanted radiation background. This is how you build a machine capable of burning through a tumor faster than it can react — all because physicists have learned to slice time into thin pieces.
The FLASH effect was discovered by accident: mice were given a huge dose of radiation in a fraction of a second, expecting severe burns, but instead the tissues were barely damaged, as if the body simply 'didn't notice' the hit.
In the series 'The Expanse', Martian ships use a similar principle of ultra-fast pulses for their drives, to avoid frying the crew with radiation.