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NSRL User Guide

I. Beamline Hardware


An adjustable tungsten-based heavy metal collimator is available at any location on the beam line. The rectangular aperture can be closed down to millimeter scale sides or retracted fully out of the beam. Digital calipers can be used in both dimensions of the collimator to ensure accurate dimensions of the collimated area.

tungsten collimators

For some applications we make use of heavy metal alloy collimator blocks to shape the radiation field. There are a variety of sizes and thicknesses that can be stacked to produce beam spots and shielded areas which would otherwise be in the path of the beam.

For certain applications, pre-assembled static-shape collimators made from layers of Lucite, aluminum and polyethylene are also available. These collimators have precision holes that allow the beam to pass through in selected regions. The holes are typically 5mm to 1cm in diameter and can be square or round. The make-up of the collimator is optimized to stop the beam without producing many penetrating fragments. The Lucite is the first stage with a thickness of 85 mm. Aluminum is the second stage of 75 mm thickness.  The final stage is polyethylene which is 90 mm thick. See images of the collimators below.

When using the layered collimators, it is best to start with heavy ion beams of relatively lower energy, such as 600 MeV/u iron beams. In this way the leakage dose, or dose in the regions covered by the collimator can be kept below about 3% of the dose in the holes. At higher beam energies, the leakage will be greater.

Contact the liaison physicist for special collimation requirements.

Collimator Collimator Collimator Collimator