Interaction of an electron beam with a cooled ion beam makes it possible to reduce its phase volume, perform accumulation of particles, and suppress various “heating” effects. The electron beam can also be used as a target for an electron-ion recombination reaction, which offers a chance to carry out atomic physics experiments and ensure slow uniform extraction of the ion beam from the storage ring. A high-perveance electron beam with a variable profile is required for effective cooling, while a high current density and a low energy of transverse motion of electrons in the beam is needed for extraction by means of recombination. It is shown that a convex cathode placed in a magnetic field can be used to form such a beam. A high current density can be attained with this shape of the cathode, but additional efforts must be focused on optimizing the gun’s optics in order to obtain a low energy of transverse motion of particles. Since ions repeatedly pass through the cooling section during their lifetime at different values of the betatron oscillation phase, the rates of recombination and cooling are dependent on the rms electron velocity averaged over the volume in which the beam interaction occurs. The proposed design of the gun with a convex cathode 10.2 mm in diameter ensures formation of a variable-profile electron beam with a nominal current of 1 A and a current density of 1.2 A/cm2. The rms energy of Larmor gyration of electrons at the exit from the gun, averaged over the beam cross section (the “transverse” temperature) is 1 eV. A focusing electrode that forms the Pierce optics near the edge of the cathode, an electrode controlling the beam profile, and an anode are included in the optics of the electron gun.

The e. m. dispersive corrections to the pi N scattering lengths are derived using minimal e. m. coupling in PCAC for the nucleon and Delta pole terms in the heavy baryon limit. Form factors and masses are assumed to have their empirical values, with no free parameter. This approach gives a large correction to the elastic charged-pion isoscalar scattering length. The result is compared to that of chiral effective field theory (EFF) and applied to the 1S energy shift of the pi(-)p atom.

The diagnostic Neutral Beam Injector (DNBI) for the TCV tokamak, Plasma Physics Institute, Lausanne, was developed and commissioned by the BINP team in 1999. The DNBI is capable of providing a beam of hydrogen atoms of 50 kV maximal energy, with an equivalent beam current of up to 1 A. The injector is equipped with all the power supply units needed for operation and for control, including a 50 kV, 2.5 A modulator and 10 kW, 4.6 MHz RF amplifier. The output beam can be extracted continuously over a 2 second period or as an ON/OFF modulated sequence with arbitrary pulse repetition frequency and minimal pulse/pause duration of 2 ms. An increased noise level looks like a normal condition for all subsystem operation. The control system of the DNBI is developed under the pressure of these specific conditions with increased noise. The system includes 8 DAC, up to 64 ADC channels and 64 channels of In/Out digital status control. It operates as a selfsufficient system with minimal data exchange with the global control system of the tokamak, so it becomes flexible to adopt arbitrary external control system.