br General scheme and electrode configuration In the

General scheme and electrode configuration In the new Soffron60 analyzer, axial (parallel to the guiding magnetic field) component of Bisindolylmaleimide V Supplier energy is measured with electric cut-off method characterized by high resolution and reliability and allowing data cross-checking. Electron-optics scheme of the apparatus is presented in Fig. 1. A partial beam is cut at the target of the facility with 1 mm input aperture and directed to the probe (Ref. No. 7 in Fig. 1) inside a system of retarding electrodes. To these electrodes, a pulse of negative potential –Uret(t) is applied. Electrons reach the probe only if their axial energy eU0 (in eV) exceeds absolute value of varied retarding potential. Comparison of retarding potential and a probe current Ipass pulses gives sufficient information for reconstruction of axial energy distribution in the partial beam, if its current at the input is constant during the measurement. Otherwise, the input current Iin and/or current of electrons reflected from the negative potential Irefl are to be determined also. For this purpose, special two additional current probes (Ref. Nos. 2 and 3 in Fig. 1) are introduced in the scheme, protected from electrically induced signals with mesh shields 4 and 6. The assembly comprised of the target and all analyzer electrodes can be displaced in two transverse directions, thus allowing scanning of the input aperture over the beam cross-section. For realization of electric cut-off method, application of a large electric potential is necessary, which makes electric strength the key problem, especially in the presence of the dense high-power beam. Special configuration of electrodes was designed to reduce energy loads at electrode surfaces and to suppress the discharge phenomena. The input aperture 1 mm in diameter not only allows to measure parameters of the beam at a local position, but also serves to reduce current density – due to transverse velocities of electrons, the beam cross-section substantially expands in the analyzer soon after the pin-hole. Mesh electrodes are placed in the areas with weak electric field to avoid problems with expansion of plasma and secondary particle flows as well as mesh sparking in strong pulsed fields. High-voltage gaps are 20–30 mm wide. Near the system axis, where the most part of the studied beam propagates, the electric potential varies with approximately constant rate over ∼12 cm length (Fig. 2), thus peak electric field strength is minimized. To reduce secondary emission effects, all apertures have conical shapes with sharp edges. Besides the axial energy distribution measured during a single facility pulse, the new analyzer may be used to define the transverse component of electron energy, even though it requires a series of shots. The special data-processing techniques are discussed in the next section. To implement this function, the analyzer is equipped with built-in coils for magnetic field distribution control in the analyzer volume (see B(z) plots in Fig. 1). This field does not penetrate upstream from the target, thus disturbance of either the whole facility beam or target conditions is practically excluded.
Data processing: approach and technique Soffron60 measurement data (Fig. 3a) have initial form of 5 oscillograms: 2 voltage pulses (facility gun cathode potential U0 and the voltage applied to the retarding electrode Uret) and 3 analyzer collector currents (Iin, Ipass and Irefl, see Fig. 1). In the absence of discharges and other parasitic phenomena, we can expect these current waveforms to be in agreement: where constants a1 and a2 account for non-equivalent collector properties, such as geometric areas, grid transparencies, etc. Considered jointly with the potentials waveforms, the collector currents may be used to calculate normalized integral energy distribution (also known as “cut-off function”) S(u) defined as relative number of electrons having axial energy W sufficient to get over the retarding electric potential characterized by normalized value