A V Smirnov

500-fs photoelectron gun for time-resolved electron diffraction experiments

A photoelectron gun as a source of a photoinduced, monoen- ergetic (energy spread ,0.5 eV), well-collimated (divergence ,0.5 deg), sharp (diameter ,0.7 mm at the 1/e level), and ultrashort (<500 fs) bunch of electrons to be used for time-resolved electron diffraction (TRED) experiments is computer designed, assembled, and tested. In single-shot mode, it generates up to 10 3 of 30 keV electrons, and the electron pulse can be either measured in streak mode or focused onto a solid state target chosen from a set of interchangeable targets. High temporal resolution enables measurement with femtosecond precision of the diffraction pattern perturbation after the exiting laser radiation drops onto a target. Demonstration experiments with a 300-A A1 target in transmission-type mode result in diffraction images of reasonable quality under accumulation of up to 4310 4 500-fs photoelectron pulses.

Calibration of an image-tube picosecond dissector

This paper describes a new image-tube dissector based on a PIF-01 chronographic image-tube device developed and manufactured at the Prokhorov General Physics Institute of the Russian Academy of Sciences (PGPI RAS). The results of the static measurements of the instrumental function of the dissector showing that its temporal resolution can be higher than 4 ps are given. These data are confirmed by direct measurements on the bench of the PGPI RAS with the use of a femtosecond titanium-sapphire laser.

Direct temporal-resolution calibration of new-generation dissector

Recently a new generation of picosecond dissectors were created on the basis of the PIF-01/S1 picosecond streak-image tube designed and manufactured at the GPI Photoelectronics Department. The results of the measurements of instrument characteristics of the new dissector, which were carried out in the static mode, showed that temporal resolution of the dissector can be better than 3-4 ps (FWHM). The results of temporal resolution calibration of the new-generation picosecond dissector carried out at the specialized set-up based on a femtosecond Ti:sapphire laser are given in this work.

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.

On the decay time of luminescent screens of picosecond image tubes when measuring repeated signals in the accumulation mode

When replacing the conventional “slow” luminescent screens (P20, P43) in picosecond image tubes by the “fast” ones (P46, P47), we found an increase in the decay time of “fast” cathodoluminophors (by a factor of 2–5) with increasing the number (from one to a hundred) of measured pulses. The consideration of the detected effect makes it possible to correct the problem statement in developing picosecond dissectors for recording repeated signals in the accumulation mode (e.g., synchrotron radiation).

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).

Development, calibration and application of new generation dissector with picosecond temporal resolution

A dissector is an electron-optical device designed for measurement of periodic light pulses of subnanosecond and picosecond duration. LI-602 dissector developed at Budker Institute of Nuclear Physics (BINP SB RAS) is widely used for routine measurements of a longitudinal profile of electron and positron beams at BINP electron-positron colliders and other similar installations(1,2). LI-602 dissector is a part of many optical diagnostic systems and provides temporal resolution of about 20 ps. Recently a new generation of picosecond dissectors were created on the basis of the PIF- 01/S1 picosecond streak-image tube designed and manufactured at the A.M.Prokhorov General Physics Institute (GPI) Photoelectronics Department(3,4). The results of the measurements of instrument function of the new dissector based on PIF-01/S1, which were carried out in the static mode(5) showed that temporal resolution of the dissector can be better than 3-4 ps (FWHM). The results of temporal resolution calibration of the new-generation picosecond dissector carried out at the specialized set-up based on a femtosecond Ti:sapphire laser and recent results of longitudinal beam profile measurements at BINP damping ring are given in this work.

On the use of a chirped Bragg grating as a cavity mirror of a picosecond Nd : YAG laser

The first experimental evidence is presented that the use of a chirped volume Bragg grating (CVBG) as a cavity mirror of a Q-switched picosecond Nd : YAG laser with self-mode-locking leads to significant changes in the temporal parameters of the laser output. Measurements have been performed at two positions of the CVBG: with the grating placed so that shorter wavelengths reflected from its front part lead longer wavelengths or with the grating rotated through 180°, so that longer wavelengths are reflected first. In the former case, the duration of individual pulses in a train increased from ~35 to ~300 ps, whereas the pulse train shape and duration remained the same as in the case of a conventional laser with a mirror cavity. In the latter case, the full width at half maximum of pulse trains increased from ~70 ns (Nd : YAG laser with a mirror cavity) to ~1 ms, and the duration of individual pulses increased from 35 ps to ~1.2 ns, respectively, which is more typical of free-running laser operation.