[en] The SLED method was invented at SLAC in order to produce more electron (and positron) energy from the existing klystrons. The LEP injector LINAC, also now is supposed to operate in the SLED-2 mode. At DESY similar developments have been undertaken too, to improve the linac performances. However in all cases the accelerating sections were not initially optimized for such a mode of operation, and in most cases the designers ended with long accelerating sections making a more efficient use of the klystron power, with rectangular pulses, sometimes at the expense of a longer linac. The present study deals with new approaches for designing linacs, and in particular compact linacs, considering from the beginning a pulse compression scheme, where the main feature consists of having an exponential pulse shape instead of rectangular. Moreover a detailed comparison is made between constant impedance and constant gradient travelling wave (TW) accelerating structures. As a matter of fact the constant impedance structure when optimized looks sligthy better than the second one. In addition short structures appear to be more efficient for a given number of RF sources. Consequently linear accelerators can be made more simple and less expensive, and if one allows for higher tolerable accelerating gradients they can be made even compact

[en] A power supply for the filament of the MEA klystrons is described. The supply is a 1 KW 625 Hz generator. Between the supply and the filament a high-voltage separation-transformator with rectifier is positioned. Since the filament has to be heated up gradually, the filament supply rules up in about 20 minutes. The finishing of the ruling up is signalized. Subsequently another 20 minutes has to be waited before the klystron is allowed to be put on high voltage. The output voltage of the supply is adjustable from about 200 to 400 volts. The supply is protected against short-circuiting and interruption of the output. This results in switching-off of the supply and in signalizing 'too low resistance' respectively too high resistance'. If by an internal disturbance the desired voltage and the output voltage deviate from each other, the supply drops down and indicates the error report over-voltage' or under-voltage'. The supply can be put on 'stand-by' or 'on' externally. Also external protections canb e connected to it, like: cooling, vaccuum etc.. When one of the protections drops down, the supply will drop down and give an error report. (author). 15 figs.; 1 tab

[en] Lead-plating for superconducting RF resonators historically has been directed toward reducing grain size and eliminating spikes on the surface. Investigations were made of degassing lead-plated surfaces under RF resonant electron discharge or multipacting. The mass-spectra of the residual atmosphere showed that decomposition of hydrocarbons on the surface took place. Discolouration of the lead surface, due to the formation of a carbon layer, was easily observed. A method of cleaning surfaces by ion bombardment employing chemically active gases, was proposed and tested. An RF discharge, initiated by multipacting at pressure 10^-2 - 10^-1 torr was used. The first step, discharge treatment in a CO₂ atmosphere, assures oxidation of carbon and hydrocarbons into gaseous compounds which are removed by pumping. During the second step, discharge treatment in a hydrogen atmosphere, lead oxides are reduced to metal

[en] A 3 MeV Van de Graaff accelerator has been in operation at Lucas Heights for 21 years achieving over 77,000 hours operation. With the ageing of the accelerator, there has been a decrease in the amount of fundamental research and an increase in applications work. The present accelerator offers a unique tool to be used in assessing the suitability of components and systems for applications in an environment where electrostatic fields and radiation pose a significant problem. It also lends itself as a suitable injection stage to study post acceleration techniques

[en] Comments on the use of two phase helium in a closed circuit tubular cooling system and some results obtained with the TPC superconducting magnet are given. Theoretical arguments and experimental evidence are given against a previously suggested method to determine helium two phase flow regimes. Two methods to reduce pressure in the magnet cooling tubes during quenches are discussed; (1) lowering the density of helium in the magnet cooling tubes and (2) proper location of pressure relief valves. Some techniques used to protect the refrigerator from too much cold return gas are also mentioned. 10 refs., 1 fig., 5 tabs

[en] The control system for the NPL Linac is based on a Microvax II host computer connected in a star network with 9 satellite computers. These satellites use single board varsions of DEC's PDP 11 processor. The operator's console uses high performance graphics and touch screen technology to display the current linac status and as the means for interactively controlling the operation of the accelerator

[en] Several improvements have been done recently in injector RF system and were described. The frequency automatic tuning system and the amplitude stabilization system of the injector SFC have been improved. The accuracy of the frequency tuning and the stability of the amplitude are within +-1 x 10^-5 and +-1 x 10^-3 respectively after developing the two systems. The low energy buncher B₀ was designed and constructed in order to modulate the continuous beams from ECR ion source and to match the RF accelerating phase of the injector SFC. The buncher B₀ runs well and the extraction beams from SFC are three to seven times bigger than that without using it. The Dee box was redesigned and reconstructed in order to meet the requirement of the SFC centre region for injection condition of the ECR ion source. The multipactoring levels were much reduced after the Dee box was replaced by new one and the cavity is more stable in operation

[en] The CV-28 Cyclotron at IPEN-CNEN/SP is used mainly for radioisotope production to be utilized in nuclear medicine for diagnostic purposes. For this, target facilities were developed which allow irradiations with external and internal beam. In this work the advantages and disadvantages in the utilization of the internal beam target which was modified, installed and tested in production conditions were analysed. Many points are emphasized in both cases such as the available beam current intensity, that is an important factor in the radioisotope production, the stability and sharpe of the beam, the irradiation time, the physical state of the target and the changes of accelerated particles. (author). 10 refs., 4 figs., 1 tab

[en] The two kinds of cavities commonly used, the nose-coned and the bell-shaped cavities, are investigated for the RF cavity optimum design of the SSRF (Shanghai Synchrotron Radiation Facility). The maximum shunt impedance available for the former is about 45% higher than for the latter, and the latter has the stronger HOM (high order modes)

[en] A method of designing a low impedance, lumped parameter, nonuniform capacitance pulse forming network (PFN) to fit in with the needs of a high voltage, large turns ratio, low impedance pulse transformer with large leakage inductance are introduced. Combining with computer optimization design, a 100 kV, 1.4 Ω, 6 stage lumped parameter Blumlein network has been achieved, shortened the rise time and fall time of output pulses, improved pulse waveform and successfully used in 500 kV long pulse accelerator