  There are strong theoretical arguments in favour of the existence of very
light scalar or pseudoscalar particles beyond the Standard Model which have, so
far, remained undetected, due to their very weak coupling to ordinary matter.
We point out that after HERA has been decommissioned, there arises a unique
opportunity for searches for such particles: a number of HERA's four hundred
superconducting dipole magnets might be recycled and used for laboratory
experiments to produce and detect light neutral bosons that couple to two
photons, such as the axion. We show that, in this way, laser experiments
searching for photon regeneration or polarization effects in strong magnetic
fields can reach a sensitivity which is unprecedented in pure laboratory
experiments and exceeds astrophysical limits from stellar evolution
considerations.
