Gennadii I. Bryukhnevich

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.

Computer modeling of a subfemtosecond photoelectron gun with time-dependent electric field for TRED experiments

In the paper, theoretical and numerical studies on temporal focusing of photoelectron bunch in time-dependent fields are continued. Presented are the results of computer modeling on electron-optical system with combined time-dependent electric and static magnetic fields to ensure both spatial focusing and temporal compressing of photoelectron bunch down to sub-femtosecond level. The peculiarity of space charge effect contribution to the bunch broadening in the case of time-dependent electric field is discussed.

Femtosecond streak tubes designing, manufacturing, and testing

New generation of streak tubes intended for single-shot and synchroscan operations with femtosecond time resolution was computer modelled, designed, manufactured, tested and adopted for further application in laser research. The developed PV-FS type tubes provide close to 100 fs-time resolution in single-shot streak mode. It is important to note that the PV-FS tubes may be equipped with Peltier cooled S1-photocathodes and their spectral sensitivity may cover the range of 115 - 1550 nm. The developed photocathodes have very low surface resistance (tens of Ohm per square unit). New tubes offer a high (more than 50 line pairs/mm) spatial resolution when recording ultrafast optical images with femtosecond time resolution. Due to keeping the PV-FS external geometry similar to the well-known PV-type tubes it becomes possible to install new devices into available streak cameras (AGAT, Imacon 500, etc.).

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.

Femtosecond streak image converter camera

An experimental prototype of a femtosecond streak image converter camera was built around a specially designed femtosecond streak image tube having a cylindrical type electron focusing lens. Experimentally measured temporal resolution of the camera is better than 500 fs while its spatial resolution is not worse than 40 lp/mm across the slit direction.

PV001 streak image tube with an oxide photocathode for application in electron diffraction experiments

A PV001 streak image tube supplied with an atmosphere resistant (AlMgCu)Ox photocathode is reported. Quantum efficiency of such a photocathode being irradiated by 5 ps light pulses at 354 nm wavelength is up to 10-3. It is shown that this photocathode may be exposed for many cycles (> 20) of air admittance without losses in its quantum efficiency. It is believed that the PV001/oxide tube may be used in electron diffraction experiments.

Small-Size Meshless 50 ps Streak Tube

In contrast to the conventional image intensifier with large work area, a streak image tube should possess additional important feature - the comparatively small temporal distortion at the entire work area of the photocathode. With this additional engineering restriction taken into account, a novel small-size meshless streak image tube has been developed by means of numerical optimization. The tube with 25-mm wide work area contains a pair of deflection plates to sweep the electron image along the 25 mm output phosphor screen that is separated by 100 mm from the photocathode. The electron image can be shuttered with a 300 V blanking electric pulse. Electron-optical magnification of the tube is unit; spatial resolution reaches 30 lp/mm over the entire photocathode work area; temporal resolution lies in the 20 - 50 ps range, depending on the accelerating voltage (6 - 15 kV).

Research and development on femtosecond cameras and diffractometers

Current GPI status on femtosecond cameras and diffractometers research and development is overviewed. Discussed are the key components of the femtosecond diffractometer which is now under design. The first experimental prototype of 20 - 40 kV, femtosecond photoelectron diffractometer is computer designed, manufactured and tested.

Fully automated streak camera with EB CCD image tube

An experimental prototype of a fully automated streak camera was designed on the basis of an image tube equipped with a back-side electron bombarded (EB) charge-coupled device (CCD). The developed camera temporal resolution is not worse than 5 ps at a recording dynamic range on the order of 100, and the overall system spatial resolution is 40 lp/mm at 10% MTF. The camera operation mode, its streak speed, and processing of the temporally dispersed image are controlled by a computer.

Picosecond image converter tubes incorporated with EB CCDs readout

A number of time analyzing image converter tubes integrated with thinned, backside- illuminated, electron-bombarded (EB) CCDs were developed. Among them are PV001, PV003, and PIF01 streak tubes, differing from each other by their internal electron optics and external (metal-glass or metal-glass-ceramic) geometry. All tested EB CCD/streak tubes reveal relatively good behavior due to the long-term stability of their input S1 photocathode and reproducibility of the matrix parameters. These tubes differ advantageously from their regular type phosphor screen analogs by their rather high spatial resolution (40 lp/mm at 10 MTF for PV type tubes and 25 lp/mm at 10 MTF for PIF type tubes), reasonably good threshold sensitivity of 10-10 J/cm2 in standard, 10 MHz CCD scanning mode at 850 nm input radiation, and picosecond temporal resolution (better than 5 ps) at a relatively acceptable value of the light transfer function (approximately 102).