The paper presents results of time-resolved measurements of fast deuterons emitted from high-current discharges of the Plasma-Focus (PF) type. The measurements were performed in a modified PF-1000U facility which is operated at the IFPiLM in Warsaw, Poland. The device was equipped with a fast-acting gas valve placed inside the inner electrode and oriented along the z-axis. The valve could inject a small volume of a chosen gas in front of this electrode. The PF discharges were initiated at the initial deuterium pressure equal to 1.6 or 2 hPa, with or without the use of the gas-puffing. Such discharges emitted intense beams of accelerated primary ions and X-ray pulses as well as products of nuclear fusion reactions. <p> </p>The reported measurements of the fast ion beams were performed by means of a Thomson-type spectrometer located at a chosen distance at the z-axis and equipped with miniature scintillation detectors. These detectors were placed in different points upon the deuteron parabola which corresponded to determined energy values. The detectors configuration allowed us to determine instants of the ion emission (using a TOF technique) and to compare them with instants of the X-ray emission. The collected data provided important information about emission characteristics of the modified PF-1000U facility.
The paper presents feasibility and design studies of Cherenkov-type probes, a development of the measuring head construction designed for different tokamak devices, and in particular the acquisition of optical signals to a data storage system. In order to lower the energy threshold of the electron detection the authors applied radiators with the highest values of the refractive index. Different radiator materials, such as aluminium nitride and CVD diamond were applied. Several versions of measuring heads and different manipulators, e.g., a movable vacuum-tight shaft or a fast-moving reciprocating probe, were manufactured and used. The practical application of the Cherenkov probes required also a consideration of spectral characteristics of optical fibres and photomultipliers. The Cherenkov radiation, as generated inside the radiators, is lead out through separate fibres (optical cables) to the atmospheric pressure side. The emitted radiation in the blue (near ultraviolet) spectrum range should be collected and delivered through appropriate optical cables to a control room, amplified within photomultipliers and recorded in a digital form. In order to investigate an electron energy distribution the multi-channel probes have also been designed and applied.
The properties of niobium films obtained by cathodic arc deposition in ultra high vacuum (UHVCA) using constant
and pulsed bias are discussed and compared. UHVCA-produced Nb films are found to have structural and transport
properties closer to Nb bulk ones, providing a promising alternative for niobium coated, high voltage, high Q, copper
RF cavities with respect to the standard magnetron sputtering technique.
A series of sapphire substrate coatings with niobium has been performed at pulsed bias and compared with the films
deposited at cd bias. Using pulsed bias resulted in increasing an average deposition ratio by a factor of 2-3 up to a value
of 0.9 μm/min. The layers coated with pulsed bias reached higher RRR values. Their microstructure is characterized by
much larger, randomly oriented grains, compared to the layers obtained with constant bias, with no evidence of
epitaxial growth and a lattice parameter identical to that of bulk niobium.
The apparatus for coating of a cavity using planar UHVCA sources is presented and discussed. First results on
plasma transport into a cavity cell are presented showing that it is possible to guide the plasma generated by a planar arc
source inside it. Several magnetic configurations have been analyzed and different voltage bias used.
This invited talk describes spectroscopic studies of high-current plasma discharges within PF- and RPI-type facilities, used for basic and application-oriented research. Particular attention is paid to measurements of temporal changes of spectral lines from working gases and impurities. Time-resolved spectral measurements were carried out by means of a Mechelle(R)900 spectrometer, operating in the wavelength range from about 200 nm to 1100 nm, with exposition times varied from 100 ns up to 50 ms. That spectrometer was equipped with a cooled CCD camera coupled with a PC and GRAMS-32(R) software. Spectroscopic studies of the deuterium Balmer-lines and some impurity lines, as observed within the PF-360 experiment, are presented and discussed. Estimates of temporal changes in the electron concentration and temperature are given. Measurements of temporal changes in the emission of the deuterium- and impurity-lines emitted from a mega-joule PF-1000 facility are also described. Capabilities of optical techniques to study the interaction of PF discharges with different targets are discussed. Time-resolved spectroscopic studies of plasma discharges within the RPI-IBIS facility, used for material engineering, are also presented. Optical spectra, as recorded for different operational modes, are compared. The use of spectroscopic techniques to study the interaction of pulsed plasma-ion streams with different materials is considered. The presented results of research on dynamics of pulsed plasma streams (produced in different experimental facilities) as well as the described optical diagnostic techniques are important not only for basic physical studies but also for application-oriented research.
The paper describes efforts of four institutions which are engaged in the realization of the Work Package 4 (Thin Film Cavity Production) of the Joint Research Activity (JRA-1) within a frame of the Coordinated Accelerator Research in Europe (CARE) program. JRA-1 is aimed at developing superconducting RF technology, mainly methods for producing superconducting Nb coated copper cavities which might ensure higher accelerating fields, lower RF losses and considerable reduction of costs, as compared with the present state of art. WP4 is thus focused on the development of a new method to produce thin Nb-coatings by means of arc discharges performed under ultra-high vacuum (UHV) conditions.