Alexander M. Prokhorov

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.

The New Streak Image Tube PIF-01

A new, small-size image-converter tube type PIF-01 has been developed for recording of various high speed phenomena with subpicosecond time resolution. The designing goal of the new image-converter tube having four electrodes geometry (photocathode, acceleration mesh, focusing electrode, anode diaphragm) and incorporating with a modern deflection system, was to simultaneously improve temporal resolution and dynamic range.Preliminary experimental results confirm the efficiency of the software developed for picofemtosecond streak tube computation and optimization.

Recent research and development in electron image tubes/cameras/systems

Recent results in development of the principal components of picosecond image converter recording systems are reviewed focusing on image tubes, streak and framing cameras, and CCD readout devices. Attention is also given to new laser sources capable of generating very stable femtosecond and picosecond optical pulses for dynamic calibration of image tubes and cameras and application of the designed instruments in laser research.

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.

Multialkali photocathodes grown by molecular beam epitaxy technique

A new technique of bialkali photocathodes growth by molecular beam epitaxy (MI3E) nhas been developed. The photocathode film was deposited onto the substrate from nmolecular beams produced by simultaneously operating molecular sources of Sb, Na and nK. Thus suggested procedure is noticeably differed from the classical one. Growth nrate was about 1 A/sec and complete cycle of photocathode fabrication was 15-20 nminutes. A special ultra high vacuum (UHV) chamber for MBE of multialkali nphotocathodes has been designed. The chamber is a part of UHV system consisting of an nanalysis vessel supplied with Auger and ESCA electron spectrometer and low energy nelectron diffractometer (LEED), the MBE chamber itself and a chamber for cold sealing nof photocathodes with device body through indium ring. The system gives a possibility nto carry out investigations of multialkali photocathode physics and to produce ncommercial devices. Developed technique can be used for fabrication of vacuum devices nincluding streak tubes.

FIELD-ASSISTED SEMICONDUCTOR PHOTOCATHODES FOR STREAK TUBES

Field-assisted semiconductor photocathodes (pCs) based on In0.53Ga0.47As/InP heterostructures with a Schottky barrier for the spectral range of 1.0 to 1.7 µm are investigated. A technique is presented for manufacturing PCs. The method for ultrahigh vacuum transfer of the PC into vacuum devices is discussed. It is shown that the sensitivity of a PC in a sealed-out device at ? = 1.55 µm is two to three orders of magnitude higher compared to traditional Ag-Cs-O PCs, and approaches 400 µA/W at ? = 1.6 µm for PCs with Schottky barriers of Au film. It is shown that PCs with Schottky Au barriers can be activated with Cs only and without O, and the stability is considerably better than with a Ag barrier. A strong decrease of the internal photoeffect is discovered in the case when the PC is illuminated from the metallic film side. The developed PCs can be used for time analyzing tubes to record picosecond pulses with milliwatt peak intensity.

Simplified picosecond streak image tube for designing inexpensive commercial cameras

The current demand for inexpensive streak camera manufacturing leads to the necessity in development of a variety of relatively simple and low cost image-converter tubes. One such tube, known as PIF-C, designed and manufactured in the Photoelectronics Department of the General Physics Institute (GPI), is now commercially available. Its experimentally measured time resolution in streak mode has approached one picosecond, and 3 ps in synchroscan mode at 82 MHz operation frequency. In single frame mode at 100 ns exposure time, the spatial resolution over 6 mm input area is within 15 lp/mm. Electron optical magnification of the tube is 1.5 x. PIF-C tubes may be supplied with one of the S1/S20/S25 photocathodes, fabricated either on borosilicate glass, UV-glass, or MgF2 substrate. Its P11 phosphor screen is deposited onto the fiber optic window. EBI of the PIF-C/S1 tube is in the range of 5 (DOT) 10-10 A/cm2.

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.

Designing and application of solid state lasers for streak cameras calibration

A family of specially developed solid-state lasers intended for dynamic calibration of various type streak cameras is presented. The developed lasers are able to generate either ultrasho,rt single pulses or harmonically modulated signals of nanosecond duration. 5±lps light pulses of 0.5% output energy instability were emitted by YAlO :Nd crystal laser with hybrid mode-locking and passive intracavity negative feedback produced by the action of a GaAs plate. After compression of single pulse inside the fiber optics compressor, the minimum available pulse duration approaches 300fs. 100 percent sinousoidally modulated nanosecond optical radiat ion with modulation period adjustable in the 0 .3ps - 6. 6ns range was generated by electro-optical positive feedback Nd:glass laser. Both ultrashort pulses and harmonically modulated radiation were utilized for streak cameras dynamic parameters evaluation. It is shown that for our streak camera equiped with PVOO1 tube its minimum temporal response function approaches to O.7ps, while its intrinsic triggering jitter does not exceed

Sensitivity and stability of IR photocathodes based on In0.53Ga0.47As/InP heterostructures with Schottky barrier intended for streak tubes

Some technique is presented for IR photocathodes manufacturing on the basis of In0.53Ga0.47As/InP heterostructures with Shottky barrier. Discussed is a method for ultra-high vacuum transfer of the photocathodes into vacuum devices. It is shown that the sensitivity of photocathodes in a sealed out device at (lambda) equals 1.55 micrometers is two orders of magnitude higher comparing to the sensitivity of traditional Ag-Cs-O photocathodes. The developed photocathodes may be used in time analyzing image tubes covering the spectral range from 0.9 to 1.7 micrometers .