Measurements of the Plasma Characteristics of the Trips Source at INFN-LNS

Summary form only given. The TRASCO (TRAsmutazione SCOrie) project is an R&D program whose goal is the design of an accelerator driving system (ADS) for nuclear waste transmutation. The high current CW proton linear accelerator will drive a sub critical system devoted to the transmutation of nuclear wastes. The TRasco intense proton source (TRIPS) is a high intensity 2.45 GHz microwave source whose goal is the injection of a maximum proton current of 35 mA in the following RFQ, with a rms normalized emittance lower than 0.2 mmrad; the operating voltage is 80 kV. Current measurements with the 8 mm hole plasma electrode have given results largely exceeding the TRASCO design current: up to 61 mA were extracted at 80 kV and about 90% of this current was transported to the beam stop. Such result was obtained by means of an accurate RF matching: the microwave coupling with the matching transformer and the automatic tuning unit allows to operate with low values of reflected power (below 5%) and a high electric field on the axis, thus increasing either the proton fraction and the current density, up to 200 mA/cm², close to the Child-Langmuir limit. Today the TRIPS source routinely produces a proton beam of 40 mA with a 6 mm extraction hole at full voltage. In order to verify the possibility of further improvements, a series of measurements of plasma characteristics with a Langmuir probe have been carried out and are described in the paper. An overview of the possible upgrade and of the application of some other diagnostics tools will be presented