Elliott J. Lawton

Paramagnetic‐Resonance Studies of Irradiated High‐Density Polyethylene. II. Effect of Irradiation Dose on the Radical Species Trapped at Room Temperature

The previous paper presented a study of the radical species in irradiated Marlex‐50 at low dose levels. This paper extends that study to a level of 4000 megaroentgens. The kind and relative number of each radical trapped at room temperature (RT) depends on the degree and tightness of the crystalline and crosslinked fractions during irradiation. At least two of three distinct species, having different hyperfine structures (six‐, five‐, and a single‐line) are present in varying concentrations at all doses. The six‐ and five‐line radicals are trapped in the crystal, whereas the single‐line radical is trapped in the highly crosslinked medium. During irradiation at RT and liquid‐nitrogen (LN) temperature, the crystal is not as effective in trapping the six‐line radical as in the absence of irradiation. At 640 megaroentgens the six‐line radical does not survive during irradiation at RT, leaving the five‐ and single‐line radicals above this level. The single‐line radical appears at 320 megaroentgens and increase...

The Choice of Operating Mode for Standing Wave Type Linear Accelerators for Electrons

Experimental studies of the wave‐length spacing between modes of the spectrum of arrays of 10 and 16 cavities with different cavity‐to‐cavity couplings have been made. The results indicate greatest mode separation near the center, π/2 mode of the mode spectrum making this mode best for operation. Use of the end π‐mode of the spectrum should lead to a limiting length of approximately 3 to 6 ft., while choice of the center π/2 mode would result in a limiting accelerator length of 10 to 20 ft. at 10.7 cm.

Experimental Results on Standing Wave Type Linear Accelerators for Electrons

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...