  The 1.7-GeV 100-mA CW proton linac is now under design for the Accelerator
Production of Tritium (APT) Project. The APT linac comprises both the normal
conducting (below 211 MeV) and superconducting (SC) sections. The high current
leads to stringent restrictions on allowable beam losses (<1 nA/m), that
requires analyzing carefully all possible loss sources. While wake-field
effects are usually considered negligible in proton linacs, we study these
effects for the APT to exclude potential problems at such a high current. Loss
factors and resonance frequency spectra of various discontinuities of the
vacuum chamber are investigated, both analytically and using 2-D and 3-D
simulation codes with a single bunch as well as with many bunches. Our main
conclusion is that the only noticeable effect is the HOM heating of the 5-cell
SC cavities. It, however, has an acceptable level and, in addition, will be
taken care of by HOM couplers.
