  Semi-insulating, undoped, Liquid Encapsulated Czochralski (SI-U LEC) GaAs
detectors have been irradiated with 1MeV neutrons, 24GeV/c protons, and
300MeV/c pions. The maximum fluences used were 6, 3, and 1.8~10$^{14}$
particles/cm$^{2}$ respectively. For all three types of irradiation the charge
collection efficiencies (cce) of the detector are reduced due to the reduction
in the electron and hole mean free paths. Pion and proton irradiations produce
a greater reduction in cce than neutron irradiation with the pions having the
greatest effect. The effect of annealing the detectors at room temperature, at
200$^{o}$C and at 450$^{o}$C with a flash lamp have been shown to reduce the
leakage current and increase the cce of the irradiated detectors. The
flash-lamp anneal produced the greatest increase in the cce from 26% to 70% by
increasing the mean free path of the electrons. Two indium-doped samples were
irradiated with 24GeV/c protons and demonstrated no improvement over SI U GaAs
with respect to post-irradiation cce.
