[en] The experimental program in 1979 was directed toward the preparation of two major detectors: the new multiparticle spectrometer facility for the Fermilab tagged photon beam and the lepton/total energy detector (MAC) for PEP. The two large Cerenkov counters were installed and made operational during a test beam run at Fermilab and substantial progress was made on the track reconstruction programs. The MAC central drift chamber was completed and delivered at SLAC and operational tests were started. Work produced by the theory group included studies of color separation in multi-hadron jet production, diffractive jet production in photo-induced reactions, the relation between the several generations of leptons and quarks, tests of unified gauge theories, gauge hierarchies, and several problems in grand unified theories

[en] The experimental program in 1978 was focused on the construction of parts of two major detectors: the new multiparticle spectrometer facility for the Fermilab tagged photon beam and the lepton/total energy detector (MAC) for PEP. Both experiments are in collaboration with other institutions. The first of two large Cerenkov counters was shipped to Fermilab, while the second was near completion at the end of the year. Fabrication of all parts for the MAC central drift chamber was completed in preparation for the final assembly and wire stringing. Track reconstruction computer programs were developed for both the tagged photon spectrometer and the MAC central detector. The theory group has produced results, among others, strengthening previously conjectured sum rules for the radiative weak decays of baryons, and clarifying the possible heirarchies (generated by the Higgs mechanism) of interaction strengths in unified gauge theories of the weak, em, and strong interactions. New scientific personnel are research associate James Elliott (experimental) and visiting Assistant Professor James Randa (theoretical). A list of publications is incuded

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[en] The phase and amplitude signals of JET heterodyne reflectometers show varying levels of high frequency turbulence superimposed on a slow changing mean. The phase signal also shows multi-radian (>1 fringe) variations with two quite different time scales (2-10ms and sub-ms). In both cases the mean reflected power, together with turbulent phase and amplitude fluctuation levels, are modulated synchronously with the phase fringes. The slow fringes appear to result from radial movement of the cutoff layer with the amplitude modulation possibly due to multiple reflection between plasma and wall. The fast fringes occur in intermittent bursts and appear to be phase runaway resulting from antenna misalignment. Using a 2D physical optics simulation code it is possible to replicate the fast bursts of phase runaway from steady-state turbulence and misaligned antennas. This offers a possible alternative explanation for some of the observations of bursting turbulence seen in reflectometer signals. (author)

[en] Equilibrium analysis is one of the essential tools for determining the plasma shape and profiles, in particular the current density and safety factor, as well as global physical quantities. We report on recent developments of the equilibrium code EFIT, which is used for the routine analysis of JET Tokamak discharges. A new method to treat the iron transformer surrounding the JET device is presented. This is one of the prerequisites for the development of a real-time discharge analysis and feedback of physical quantities. A new type of constraint derived from the shape of the ECE temperature profile has been implemented which allows for an enhanced precision of the position of the magnetic axis and the safety factor. (author)

[en] Different methods of aircrew dose assessment are under discussion and evaluation by several international research groups. The TEPC (tissue-equivalent proportional counter) has been used very successfully to describe the radiation field during in-flight measurements. Cosmic ray transport calculations of effective dose have been compared with TEPC measurements, with good results. Several active conventional photon and neutron detectors, as well as a passive dosemeter, have been prepared and characterised for in-flight radiation measurements. A novel method, combining measurements with a conventional radiation detector and results of cosmic ray transport calculations is at present under evaluation in the European research project ACREM (Air Crew Radiation Monitor). Superimposed on the regular and more-or-less predictable eleven year cosmic ray intensity variation, events on the sun will occasionally result in high energy particle fluxes that will impact on the tellurian atmosphere and result in unforeseen high additional radiation exposures. Appropriate methods to determine the resulting radiation dose rates will be described. (author)

[en] Results are presented from a series of dedicated experiments carried out on the Joint European Torus (JET) in tritium, deuterium-tritium, deuterium and hydrogen plasmas to determine the dependence of the H-mode power threshold on the plasma isotopic mass. The P_THRES ∝ A_eff^-1 scaling is established over the whole isotopic range. This result makes it possible for a fusion reactor with a 50:50 DT mixture to access the H-mode regime with about 20% less power than that needed in DD. Results on the first systematic measurements of the power necessary for the transition of the plasma to the Type I ELM regime, which occurs after the transition to H-mode, are also in agreement with the A_eff^-1 scaling. For a subset of discharges measurements of T_e and T_i at the top of the profile pedestal have been obtained, indicating a weak influence of the isotopic mass on the critical edge temperature thought to be necessary for the H-mode transition. (author)

[en] The scaling of the energy confinement in H-mode plasmas with different hydrogenic isotopes (H, D, D-T and T) is investigated in JET. For ELM-free H-modes the thermal energy confinement time τ_th is found to decrease weakly with the isotope mass (τ_th ∼ M^-0.25±0.22) whilst in ELMy H-modes the energy confinement time shows practically no mass dependence (τ_th ∼ M^0.03±0.1). Detailed local transport analysis of the ELMy H-mode plasmas reveals that the confinement in the edge region increases strongly with the isotope mass whereas the confinement in the core region decreases with mass (τ_thcore ∝ M^-0.16 ) in approximate agreement with theoretical models of the gyro-Bohm type (τ_gB ∼ M^-0.2). (author)