W. B. Herrmannsfeldt

Results of Simulations of High-Power Klystrons

The MASK code is a 2-1/2 dimensional particle-in-cell code which has been applied to the simulation of a number of microwave devices. We discuss implementation of algorithms for the simulation of high-power klystrons. These algorithms use the cavity properties and the MASK results to find selfconsistent solutions in both the linear (small signal) parts of the klystron as well as for the high-power cavities. The method is used to model the existing 35 MW tube and the 50 MW tube being built for the SLC project. Dependence of magnetic field profile and geometry on tube performance is discussed. Effects of radial beam dynamics on efficiency are described. Simulation results are compared to experimental data.

The Electron Beam for the Fermilab Electron Cooling Experiment

We describe the design and construction of the electron beam for the Fermilab Electron Cooling Experiment. Important parameters are (1) 110 keV kinetic energy; (2) 26 A current; (3) 0.5 eV rest frame temperature; (4) space charge neutralization; (5) beam modulation; (6) efficient energy recovery at the collector. The 5 m overlap region between the electron beam and the storage ring orbit represents 4% of the total ring circumference.

Sensitivity of Perveance to Cathode Placement in a Low Perveance Electron Gun

The SLAC ELECTRON TRAJECTORY PROGRAM1 (EGUN) has been used to simulate a low perveance electron gun which will produce an 800 mA space charge limited beam at 130 kV. The simulations indicate that axial displacements of the cathode by + 0.5 mm from its nominal position can produce a factor of two variation in the perveance of the electron gun. This sensitivity is due to the boundary conditions of the electrostatic potential near the cathode. Movement of the cathode relative to a fixed focus electrode produces an enhanced variation of the electric field near the cathode surface over that which occurs when both cathode and electrode are moved together. The simulations are in agreement with experimental data.

Operating Experience with a High Current Cs+1 Injector for Heavy Ion Fusion

The construction and assembly of a Cs ion injector consisting of a pulsed source and 3 pulsed drift tubes has been complete since April, 1980. The measurement program, underway since then to characterize the beam, has been interspersed with the development of diagnostic equipment. The Cs contact ionization source and each of the 3 drift tubes are driven by 500 kV Marx generators. The injector has been operated reliably at 300 kV/stage at a repetition rate of 1 pulse/4 sec. About 105 pulses have been accumulated. The space charge limited diode and drift tube acceleration system were designed with the aid of the EGUN code of Herrmannsfeldt. Measurements of the beam envelope have been made by means of a movable biased charge collector. Good agreement with the EGUN calculation is found. Measurements of the beam emittance have been made at the exit of the third drift tube. The normalized emittance ¿ ¿N = 2 x 10-6 ¿ m-rad is of better optical quality than that required for further acceleration and transport in a Heavy Ion Fusion (HIF) Induction Linac Driver.

SLC Injector Modeling

The injector for the Stanford Linear Collider is being studied using the fully electromagnetic particle-in-cell program MASK. The program takes account of cylindrically symmetrical RF fields from the external source, as well as fields produced by the beam and DC magnetic fields. It calculates the radial and longitudinal motion of electrons and plots their positions in various planes in phase space. Bunching parameters can be optimized and insights into the bunching process and emittance growth have been gained. The results of the simulations are compared to the experimental results.

Studies of the Electron Beam for the Fermilab Electron Cooling Experiment

We describe the design and construction of the electron beam for the Fermilab Electron Cooling Experiment. Important parameters are (1) 110 keV kinetic energy; (2) 26 A current; (3) 0.5 eV rest frame temperature; (4) space charge neutralization; (5) beam modulation; (6) efficient energy recovery at the collector. The 5 m overlap region between the electron beam and the storage ring orbit represents 4% of the total ring circumference.

Feasibility Study of a Two-Mile Superconducting Linac

Assuming that investigations now underway will result in superconducting accelerator structures capable of withstanding gradients of 33 MeV/m, a feasibility study of a two-mile 100 GeV superconducting electron linac with 6% duty cycle has been made at frequencies of 1428 and 2856 MHz. Tentative machine parameters and the preliminary design of components and systems have been examined. These studies are based upon a traveling-wave accelerator structure with RF feedback in each 20-ft section.

Precision Alignment of a Large Beam Transport System

The beam criteria for the SLAC beam switchyard and the effect of these criteria upon alignment tolerances and placement of components in the switchyard are discussed. The methods developed in the shop and in the field for meeting the stringent alignment tolerances are also covered.

The Magnetic Shielding System for the Stanford Two-Mile Accelerator

The magnetic shielding system for the Stanford two-mile accelerator consists of a 0.006-inch-thick layer of high quality commercial magnetic shielding material wrapped around the accelerator. It is surrounded by a system of degaussing wires, consisting of two orthogonal sets of four wires spaced to provide uniform fields to cancel the vertical and transverse horizontal components of the earths magnetic field.

A 45° Inflection System for the Stanford Two-Mile Accelerator

A 45° inflector for the off-axis injectors is described. The system features second-order isochronous corrections to preserve accelerator bunch length. The correction is made with a combination sextupole-quadrupole, the design for which is also included.