FS-78 - Fast Beam Shutter

The FS-78 is a high-speed high-power physical beam stop intended to be integrated into the beamline of a particle therapy system or other high-energy particle systems. Pyramid designed the FS-78 to fulfill the need for fast emergency shuttering of the beam in the event of a normal turn-off failing and to ensure no unexpected radiation escapes the beamline.

Our ICQ-3 Quadrant Detector or PX-3 pixelated low-scattering ion chamber can be optionally fitted to the FS-78 in order to provide a convenient mounting location for beam monitoring on the upstream side. This provides a system for particle therapy systems where the beam can be stopped from reaching the treatment room while final beam tuning is performed using ion chamber data.

All necessary electronics are included and packaged in a 6U 19” cabinet containing the motion amplifier unit, cooling fan, power distribution, low voltage power supplies, a MX1 to provide user interface connection, and space for adding additional units such as FX4 or IX256 electrometer for ionization chamber readout. The FS-78 is supplied with an integrated ADK with motion settings optimized for maximum performance. No user tuning is required for normal operation.

Beam power handling allows for up to 10W continuous, up to 100W for 100 seconds with a 200-second cooldown, and up to 1 kW for 10 sec with a 200-second cooldown. Beam stopping material is a Nickel-plated OFHC copper cylinder 114mm long and 68mm in diameter mounted on a high-speed rotary actuator. The beam aperture is 36mm in diameter, with parallel sides. The minimum stopping length is 78mm. Recommended beam size 7mm sigma maximum on both axes.

Movement Demonstration

Visit our youtube for a display of the FS-78 movement.


  • Physical blocking of particle beam
  • Proton energies up to 250 MeV are stopped
  • Opens or closes in < 100 milliseconds
  • Capable of in-air operation
  • Available with integrated PX-3 ionization chamber
  • Redundant position readout switches


  • Particle therapy fast mechanical beam shutter
  • Beam shutter for nozzle systems
  • Beam stop to allow beam tuning

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