The work that was done in this laboratory on the development of a resonant cavity type linear accelerator is briefly described. The experimental results demonstrate that electrons entering at low energies will accelerate to a higher energy in passing through a group of cavities of equal β(λ0/2) spacing and along which appears a standing wave field distribution. Starting at 57 kv, an energy of 0.345 Mev was attained with two cavities. An 8-cavity accelerator of cavity length corresponding to β=0.75 had a maximum output of 0.57 Mev. Experimentally determined energies were in fair agreement with theoretical values at equal axial gradients. Excitation power was found to be proportional to [(Mev)2/Length](1/Q)×coupling coefficient. The power required for an axial gradient of 1 Mev/ft., even for the most favorable design, was high and would require the full output of one HK7 type magnetron for each foot of accelerator length. Energy spread in the accelerated beam was large for the two cavity tubes but small for the longer 8-cavity tube. It is believed that the apparent low energy spread observed in the 8-cavity case resulted from a limited range in entering angle brought about by the reduced axial gradient. There was little evidence of radial defocusing. A change in resonance wave-length amounting to +0.000225 cm per degree centigrade was observed. There was indication that the magnetron would follow a resonance change of approximately 5°C.
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