| New fourth-generation synchrotrons are anticipated to increase the light source brightness by multiple orders of magnitude providing highly coherent x-ray sources. Common to the design of fourth generation ring synchrotrons is the use of swap-out injection of electron bunches. This injection technique and associated issues are examined. Having a lower beam emittance than ALS results in more electron losses and hence lower beam lifetime, requiring more frequent injection of electrons into the system to maintain current. During operation of the upgraded ALS, the storage ring will contain 11 bunch trains, and the accumulator ring will contain one bunch train. A storage-ring bunch train, approximately once a minute, will trade places with the accumulator-ring train. Each injection of electrons from the booster ring, and each swap of the electron trains has an efficiency and loss which lowers beam lifetime. The anticipated dose and dose rates associated with different beam loss scenarios of the Booster-to-Accumulator, Accumulator-to-Storage, and Storage-to-Accumulator transfer lines have been estimated. The loss rates associated with their respective efficiencies were derived. The decrease of electron beam lifetimes displays an inverse-linear relationship with dose. Gas bremsstrahlung (GB) will exist throughout the accumulator ring system as electrons collide with molecules of air within the vacuum chamber. MCNP6 BBREM was used to generate more high-energy photons by biasing each sampling of a bremsstrahlung photon toward a larger fraction of the available electron energy. A BBREM:1/k source spectra comparison of energy, flux, and error indicated the Monte-Carlo simulation approached the analytical expression’s but only to 79.9% of the magnitude of the average bin value. The 1/k spectrum included both higher flux and the decreased angular distribution of GB in contrast to the direct generation method of MCNP6. The temperature inside the storage-ring tunnel will be carefully controlled and the temporal variation limited if the ALS-U is to meet its designed beam emittance. This necessitates several new HVAC penetrations being made inside the inner storage-ring wall. Based upon these analyses, additional shielding will be necessary near all new HVAC penetrations to reduce the photon and neutron dose rates upon upgrade from the current ALS. |