Precision measurements of neutron beta decay provide important information about the Standard Model of particle physics and permit sensitive searches for new physics. Presently, experiments are limited to an accuracy level of 10-3. The new instrument PERC is designed to improve the sensitivity of neutron decay studies by one order of magnitude.

PERC is being built in collaboration with the Universities of Heidelberg and Mainz, the Technical Universities of Munich and Vienna and the Institut Laue-Langevin, Grenoble. It will be set up at the beam site MEPHISTO of the Forschungs-Neutronenquelle Heinz Maier-Leibniz (FRM II), Munich.

PERC's main component is a 12m long superconducting magnet system. It contains an 8m long active volume in a homogeneous magnetic field and a 6T magnetic filter to improve systematics of the decay measurements.