This paper reports the measurements of beam breakup (BBU) instability performed on the Advanced Test Accelerator (ATA) up to the end of February, 1984. The main objective was to produce a high current usable electron beam at the ATA output. A well-known instability is BBU which arises from the accelerator cavity modes interacting with the electron beam. The dominant mode is TM/sub 130/ at a frequency of approximately 785 MHz. It couples most strongly to the beam motion and has been observed to grow in the Experimental Test Accelerator (ETA) which has only eight accelerator cavities. ATA has one hundred and seventy cavities and, therefore, the growth of BBU is expected to be more severe. In this paper, BBU measurements are reported for ATA with beam currents of 4 to 7 kA. Analysis showed that the growth of the instability with propagation distance was as expected for the lower currents. However, the high-current data showed an apparent higher growth rate than expected. An explanation for this anomaly is given in terms of a ''corkscrew'' excitation. The injector BBU noise level for a field emission brush cathode was found to be an order of magnitude lower than for a cold plasma …

This paper reviews the data on multiplicities in high energy interactions. Results from e/sup +/e/sup -/ annihilation, from neutrino interactions, and from hadronic collisions, both diffractive and nondiffractive, are compared and contrasted. The energy dependence of the mean charged multiplicity, <n/sub ch/>, as well as the rapidity density at Y = 0 are presented. For hadronic collisions, the data on neutral pion production shows a strong correlation with <n/sub ch/>. The heavy particle fractions increase with ..sqrt..s up to the highest energies. The charged particle multiplicity distributions for each type of reaction show a scaling behavior when expressed in terms of the mean. Attempts to understand this behavior, which was first predicted by Koba, Nielsen, and Olesen, are discussed. The multiplicity correlations and the energy variation of the shape of the KNO scaling distribution provide important constraints on models. Some extrapolations to the energies of the Superconducting Super Collider are made. 51 refs., 27 figs.

A recent concept for collective acceleration and focusing of a high energy electron bunch is discussed, in the context of its possible applicability to large linear colliders in the TeV range. The scheme can be considered to be a member of the general class of two-beam accelerators, where a high current, low voltage beam produces the acceleration fields for a trailing high energy bunch.

As a long range goal for the production of high intensity neutrons, Argonne National Laboratory has proposed the construction of a 1.5 GeV FFAG Spiral Sector Accelerator called ASPUN. The 500-MeV injector for this proposed accelerator is a smaller FFAG Spiral Sector Accelerator named Mini-ASPUN. Until such a time as the larger machine could be built, it was planned that Mini-ASPUN would replace the present RCS now being used for the IPNS program at Argonne. In order to obtain an accurate estimation of the orbits and betatron oscillations in such a machine, it is necessary that realistic field values be used in the equations of motion. Obtaining these fields from 3-dimensional relaxation calculations is both time consuming and costly. However, because of the required scaling of the machine, the field-generating potential of three variables can be separated into a known function of the radius and a function of two variables. The second order differential equation satisfied by this function can be solved by ordinary relaxation methods. The fields generated from a mesh of values for this function will be accurate except for the extreme inside and outside orbits, which will be affected by the necessary termination of the inside and …

Attempts to further improve the beam brightness from field emission cathodes are currently centered on the issue of how beam optics and phase mixing within the injector transport tend to ''average down'' the beam brightness. Particle simulation work indicates that beam brightness can be significantly improved by simply reducing the injector transport magnetic field and losing peak transport current, i.e., only transporting that high brightness portion of the total current. The simulation results shown in Figure 8 suggest that beam brightness can be increased perhaps a factor of 5 or more simply by ''tuning for brightness'' rather than tuning for peak transported current. If this can indeed be experimentally realized and the resulting beam matched onto accelerator transport (magnetic and/or laser guided) without emittance degradation then simple field emission cathodes would, at least in the immediately near term, saisfy the needs for 10 micron FEL experiments. 8 refs., 8 figs.

We have written a computer program to calculate the spatial distribution of the radiation from insertion devices operating in nominal wiggler mode (K = 15.6), for which the incoherent emission dominates, and our assumption of negligible coherent emission is valid. This program has been applied to the 15-period wiggler now being designed by the Lawrence Berkeley Laboratory for Beam Line VIII-W on the Stanford Positron-Electron Accumulation Ring (SPEAR). An approximate spreading function has been applied at each photon energy to account for the intrinsic photon divergence. The effects of the finite wiggler length and the spatial and angular spread of the electron beam have been included. Graphical plots are provided for three different electron energies, 1.8 GeV, 3.0 GeV, and 3.4 GeV, and for a range of photon energies. Separate plots are provided for total radiation, parallel polarization component, and perpendicular polarization component. 3 refs., 71 figs., 63 tabs.