A High Power Liquid Hydrogen Target for Parity Violation Experiments

Parity-violating electron scattering measurements on hydrogen and deuterium, such as those underway at the Bates and CEBAF laboratories, require luminosities exceeding 1038cm−2s−1, resulting in large beam power deposition into cryogenic liquid. Such targets must be able to absorb 500 watts or more with minimal change in target density. A 40 cm long liquid hydrogen target, designed to absorb 500 watts of beam power without boiling, has been developed for the SAMPLE experiment at Bates. In recent tests with 40 μA of incident beam, no evidence was seen for density fluctuations in the target, at a sensitivity level of better than 1%. A summary of the target design and operational experience will be presented.