IN a recent communication1, the performance of a travelling-wave linear accelerator has been given. It was shown that, due to the importance of higher terms in the expansion representing the power flow in the accelerator guide, the series impedance is lower than had been previously assumed. This, of course, leads to a reduction in the energy of the accelerator. The series impedance for the guide
... [Show full abstract] in question (2 cm. pitch, a/λ = 0.168 and phase velocity approximately equal to light velocity) has been determined both theoretically and experimentally, and a value of 3.5 megohms/cm.2 obtained. From this value and experimentally determined data on the position of electron bunching, the energy expected from the accelerator may be calculated for various loading conditions. Such values are shown compared with the measured performance of the accelerator in Fig. 1, and it will be noted that, although agreement at light loading is good, serious discrepancy occurs at higher loading. The discrepancy is attributed to an anomalous attenuation which has been found to occur in the accelerator over a certain range of power flux.
