V. I. Lozovoi

New Computer Modeling and Experimental Results on Photoelectron Gun with Time-Dependent Electric Field

Presented are the recent, numerically-supported experimental results on temporal compressing of electron bunch in timedependent electric field, derived with the use of a unique photoelectron gun that has been simulated, designed, manufactured, and tested at the Photoelectronics Department of A.M. Prokhorov General Physics Institute, RAS. An original photoelectron bunch generated from the photocathode by a 7 ps laser pulse was compressed down to ~fs. The future prospects of temporal compressing of electron bunch in time-dependent fields are discussed.

Errors of measuring picosecond light pulses by picosecond streak cameras

Errors of measuring time dependences of the light intensities of picosecond laser pulses by two electron-optical systems are studied. The first system is the picosecond streak camera made in Russia, and the second system, designed in Germany, consists of a picosecond streak camera coupled with a double spec-trograph. The manufacturers test similar systems by using femtosecond pulses, however, this does not allow one to predict errors of measuring picosecond pulses. Parameters that characterize just these errors are proposed and measured. Their behavior is determined, when the amplitude (energy) of the measured pulses increases, and the influence of the cross-section shape of the light beam on the measurement accuracy is studied.

Dynamic parameters evaluation for femtosecond streak tubes

Presented are the experimental results on femtosecond streak tubes measurements in dynamic mode. Several streak tube prototypes have been manufactured, with either distributed coaxial-strip line or capacitor-type photocathode-accelerating mesh assembly. Electrical field transition time in the photocathode-accelerating mesh gap was investigated. Tubes have been tested in a variety of regimes, in order to define the most efficient ones. Dynamic parameters of the developed femtosecond streak tubes were measured inside the streak camera prototype. The following dynamic parameters were evaluated: ultimate time resolution, dynamic range, and signal/noise ratio, spectral range, input sensitivity, streak speed and its nonlinearities, etc. The developed and optimized femtosecond streak tubes represent a reliable basis for design of streak cameras being required for photographic recording of ultrafast events in laser and plasma physics, time-resolved spectroscopy, laser interaction with matter, laser fusion, etc.

New computer modeling and experimental results on a photoelectron gun with time-dependent electric field

The paper elucidates some new computer modeling and experimental results on the design of a photoelectron gun with time-dependent electric field. The main essence of the new approach is based on the fact that the properly chosen electric field ramp ensures first-order temporal focusing of photoelectron bunch, which is principally impossible in static field previously used. This new technology allows a real breakthrough in time resolution of photoelectron guns and diffractometers intended for time-resolved electron diffraction experiments (TRED).

Modular streak camera for laser ranging

The perspecitves of the use of a streak camera as a laser ranging system detector is discussed. The development and construction of an modular design streak camera dedicated for laser ranging is described. Both linear and circular sweep modifications have been tested. The first experimental results of a ground target laser ranging are presented.

A PS-1/S1 Picosecond Streak Camera in Experimental Physics

The application of a PS-1/S1 picosecond streak camera (SC), which was developed at the General Physics Institute (Russian Academy of Sciences) for investigating fast processes in semiconductor physics, laser physics, and accelerator engineering, is described. It is shown that using the PS-1/S1 SC it is possible to record one-dimensional images (restricted by a narrow slit) of fast processes with a time resolution of no worse than 1 ps in a wide spectral range: from UV (115 nm) to near-IR (1.5 μm) radiation with a dynamic recording range of ≥10. The presented experimental results show the wide potential capabilities of applying the developed SC in various fields of experimental physics.

Set of versatile streak cameras

A set of versatile streak camera was developed in GPI Photoelectronics Department to meet various experimental requirements in laser and plasma physics, laser ranging, fiber optics communication and ecology. Among these camera there are milli-micro-nanosecond camera intended for explosion studies, nano-picosecond streak camera--for application in communication field and nano-subpicosecond streak camera--for laser and laser plasma research.

Picosecond streak-cameras for bunch diagnostics in accelerators

Temporal parameters of synchrotron pulse radiation at damping ring (DP) installation of VEPP-5 type were measured with the help of PS-1/S1 picosecond streak camera having 1.5 ps time resolution. These measurements were proceeded within 400-900 nm spectral range. It has been shown that our streak camera may record either a train of electron bunches with ns-duration or internal structure inside a single bunch. We were able to record the distance ~ 1.5 ns between separate bunches as well as their amplitude, which depends on particle numbers inside a bunch. Depending on linear accelerator mode of operation it was possible to define a single bunch duration, which was deviated within the range of 20-100 ps. The temporal structure of a single bunch was measured with 1.5 ps time accuracy. As a result, the VEPP-5 damping ring parameters were optimized, and particles injection conditions were improved. In addition, we have measured the temporal parameters of Vavilov-Cherenkov radiation (VCR) emitted by electron beam of linear accelerator. Our results provided important information on electron bunches formation and their quality inside linear accelerator before electrons injection inside a damping ring. Another series of experiments were done at VEPP-4M electron-positron collider. The dependence of beam length of the beam current measured with streak-camera allowed us to compute the wide-band impedance of the accelerator. The same data were obtained at Siberia-2 synchrotron radiation source (NRC “Kurchatov Institute”, Moscow).

10 ps X-ray streak camera

10ps, X-ray streak camera developed at GPI, Photoelectronics Department is intended for photographic recording of high-speed events in visible and soft X-ray spectral regions. The camera contains a picosecond streak tube of PV-003-X type with a photocathode being simultaneously sensitive in visible (250-700 nm) and soft X-ray regions (1-10KeV). Due to this unique feature the camera may be adjusted in the visible light range and afterward, without any further readjustment, be used for high-speed recording in X-ray spectral range. Both single-streak and single-frame modes are available. The streak duration range over the output phosphor screen of 25mm length is 2.5-250ns. Single frame exposure time is between 100 and 500 ns. Dynamic spatial resolution in X-ray spectral range is 7 line pairs/mm. Maximum dynamic recording range is close to 100. The camera triggering delay at maximum streak-speed is less than 50ns with the triggering jitter within ±50ps.

The granulated gold-film-based semitransparent photocathodes in the visible spectrum range for femtosecond time-resolution experiments

Developed is the granulated, Au film-based, semitransparent photocathode consisting of spherical Au nanoparticles. The granulated Au films are activated by a thin layer of cesium and oxygen of about two monolayer thicknesses to decrease the work function down to about 1 eV and gain the photoemission effect in the visible spectrum range. The sensitivity maximum equal to about one mA/W is located in the green spectrum range. The nanoparticles formation and photocathode surface structure are studied with the use of the X-ray photoelectron spectroscopy technique. Those studies have shown that the photoemission effect in the wavelength range &lgr;> 450 nm is conditioned by excitation of the surface plasmons in quasi-spherical Au nanoparticles. This has allowed manufacturing of a streak tube with the introducible, Au nanoparticles-based photocathode, stability of which has been remaining invariant.