Thomson scattering diagnostics at the Globus M2 tokamak

The paper is devoted to the Thomson scattering (TS) diagnostics recently developed for the Globus-M2 spherical tokamak and prototyping the ITER divertor TS diagnostics. The distinctive features of the system are the use of spectrometers, acquisition system and lasers that meet the base requirements for ITER TS diagnostics. The paper describes the diagnostic system that allows precise measurements of TS signals, as well as the results of the first measurements of electron temperature and density in both central region of the plasma column and scrape-off layer. The system provides measurements of electron temperature $T_{e}$ in the range of 5 eV to 5 keV and density $n_{e}$ in the range of $5{\cdot}10^{17}{\div}3.25{\cdot}10^{20} m^{-3}$. The use of two ITER-grade probing lasers of different wavelengths (Nd:YAG 1064.5 nm and Nd:YLF 1047.3 nm) allows reliable measurement of $T_{e}$ in multi-colour mode, i.e., assuming that spectral calibration is unknown

Terahertz wakefields and their effect on the superconducting cavities in TESLA

Operation with very short bunches for the TESLA X-ray FEL generates wakefields in a frequency regime above the threshold for Cooper pair break-up (750 GHz) in superconducting Niobium. The impact of these wakefields on the cavity quality factor is investigated and an estimate of the additional heat load at the 2 K level in the TESLA linac during FEL-opration is given

The GaAs electron source: simulations and experiments

In this paper we calculate electron emission from GaAs photocathodes using the Monte Carlo technique. Typical data of energy spread of the electron beam are presented. For photoenergy ranging from 1.6 to 2.1 eV, the calculated longitudinal and transverse energy spreads are 14.4–78 and 4–14.7 meV respectively. Temporal response measurement of GaAsphotocathodes has been performed. The preliminary results show that the temporal response is faster than 200 ps

Device For Electron Bunch Length Measurement In the Picosecond Region

We designed, created, and tested a device for measuring electron bunch length in the picosecond region. The basic idea behind the method is a circular scanning of the electron bunch in the rotating magnetic field of a TM110 rf cavity. As a result, the longitudinal position of the electrons is transformed into an angular position in a plane orthogonal to the axis. The resolution limit of the instrument is 4 ps (rms)

Experimental study of the response time of GaAs as a photoemitter

An experimental investigation was carried out to measure the response time of GaAs in negative electron affinity conditions as a photoemitter. During the experiment, the photocathode was excited by a short-pulse (38 ps rms) frequency-doubled Nd:YLF laser. Results show that the rms response time of GaAs is shorter than 40 ps

Modulator For Klystron 5045

The first modulator for a forinjector klystron of VEPP -- 5 is being tested now in BINP in Novosibirsk. The forinjector of VEPP -- 5 will involve a 510 MeV Linac consisting of four accelerating modules. The Klystron 5045 manufactured at SLAC [1] was chosen to drive the accelerating modules. This paper presents a design and some testing results of this modulator. I. INTRODUCTION The modulator is a conventional line type modulator with some supplementary characteristics. A simplified electrical layout of this modulator is shown in Fig. 3. The voltage value in a filter capacitor CF is determined by a phase-control system with six SCRs. The CF charging current is limited by three 500#H inductors connected to the primary winding of the rectifier transformer. In addition, this system provides "soft-start" capability and fast protection. The PFN is resonantly charged through a charging high-voltage SCR-switch (HV-switch), a charging inductor, and de-spiking circuits. The resonant PFN charge..

Measurements of the Beam-Beam Interaction at PEP-II

The beam-beam interaction is one of the performance limitations at PEP-II. The peak luminosity in PEP-II has reached 3.4x1033/cm2/s with 693 bunches with a positron current of 1.6 A and an electron current of 0.84 A. The beam-beam tune shift limits have exceeded 0.06 horizontally and 0.03 vertically. A model of the luminosity with current using the measured beam sizes has been developed. Studies are underway to increase theluminosity toward 1034/cm2/s and beyond by increasing the number of bunches, raising the beam currents, lowering the betas at the interaction points, and shortening the bunch lengths[1]