Parametric phase locking in an electron rf oscillator.

We propose a way to achieve phase locking of output rf radiation produced by an oscillator driven by a cw electron beam. The locking mechanism is provided by fast periodic modulation of electromagnetic properties of the operating cavity. Ohmic loss and/or the eigenmode frequency are modulated using induced photoconductivity of a semiconductor insert, as affected by a laser with a pulse repetition rate equal to twice the rf frequency.

Long-pulse operation at constant output power and single-frequency mode of a high-power electrostatic free-electron maser with depressed collector.

The Fusion Free-Electron Maser (FFF) is the prototype of a high-power, tunable source of mm-wave radiation, for use on fusion plasma devices. In previous experiments a net output power of 730 kW at 206 GHz was generated in short pulses. The present experiment has been equipped with a system to recover the charge and energy of the spent electron beam. We present experimental results which show output of mm-wave radiation at constant power level during the full pulse length, as well as single-frequency operation; even though the cavity is highly overmoded; the latter is reached by effective suppression of spurious modes by the feedback system.

Free-electron RF-pulse compressor.

A spatially modulated (corrugated) electron beam provides Bragg-type scattering of two waveguide modes. This allows the use of corrugated beams as quick active elements in rf-pulse compressors. In an illustrative example shown with a peak power compression ratio of 20-40, a 10-20 ns output pulse with a peak power of tens of MW is predicted for a millimeter-wavelength compressor.

Cyclotron resonance maser with a tapered magnetic field in the regime of "nonresonant" trapping of the electron beam.

A different version of the regime of electron trapping is proposed for electron microwave amplifiers. The use of this regime in a cyclotron resonance maser with a weakly relativistic electron beam can simultaneously provide efficiency as high as 50%, a very broad (tens of percent) frequency band, and very weak sensitivity to the spread in electron velocity.

High-power electrostatic free-electron maser as a future source for fusion plasma heating: experiments in the short-pulse regime.

A high-power, frequency-tunable electrostatic free-electron maser, being developed at the FOM Institute for Plasma Physics "Rijnhuizen," shows lasing at various frequencies. An output power of 730 kW at 206 GHz is generated by a 7.2-A, 1.77-MeV electron beam, and 380 kW at 165 GHz is generated by a 7.4-A, 1.65-MeV electron beam. In the present experimental setup, without recovery of the spent electron beam power, the pulse length is limited to 12 micros. Nevertheless, the main issues, such as the possibility of high-power, single-mode operation and frequency tuning, have been confirmed. The experimental results and the dynamics of the laser process are well in accordance with simulations.

[On-board equipment-based study of psycho-physiological and biochemical responses dynamics of operators during 135-day isolation in the "Mir" orbital station phantom]. / Issledovanie s pomoshchíu bortovoí apparatury dinamiki psikhofiziologicheskikh i biokhimicheskikh reaktsií obsleduemykh v usloviiakh 135-sutochnoí izoliatsii v makete orbital'noí stantsii "Mir".

There present the investigative findings of the dynamics of psycho-physiological and biomedical responses of the test subjects during simulated emergencies at different stages of adaptation to 135-day isolation in the Mir orbital station mock-up. Ehe main operating factor of an emergency was the 2-day sleep deprivation in combination with the continuous complex and intensive operator work which included the elements of the professional activity of the cosmonauts, among them the simulation of the regular and emergency docking of the spacecraft. By and large the observed physiological responses were characterized by moderate degree of manifestation, they were of functional character and were adequate for the investigated experimental conditions. The impaired quality of performing the applied psychophysiological tests and what is especially important the operations simulating the cosmonauts, professional activity in the extreme emergency conditions is noteworthy. Judging from some indicators the manifestation was dictated by the duration of operator isolation in the Mir orbital station mock-up and by the duration of a contingency simulation. In the degree of manifestation and in the time of development some changes in the state and working capacity of the operators were characterized by the individual differences.

[Human cardiac activity during the 1st hours and days of exposure to antiorthostatic hypokinesia (according to the results of echocardiography)]. / Deiatel'nost' serdtsa cheloveka v pervye chasy i sutki prebyvaniia v usloviiakh antiortostaticheskoi gipokinezii (po dannym ékhokardiografii).

Six healthy volunteers (aged 19-24) were exposed to head-down tilt (at-10 degrees) for 7 days. The study revealed phasic changes of intracardiac circulation and the pump function which were not accompanied by contractility disorders. On the whole, the changes represented a manifestation of cardiovascular adaptation to hemodynamic shifts that are typical of this type of simulated weightlessness. The echocardiographic parameters varied similarly during the head-down tilt test and the joint Soviet-French experiment onboard Salyut-7.

[Effect of a combination of head-down posture and LBNP on human tracking performance and spatial orientation]. / Issledovanie vliianiia kombinatsii antiortostaticheskogo polozheniia i ODNT na kachestvo slezheniia i prostranstvennuiu orientirovku cheloveka.

Test subjects exposed to a head-down tilt at--30 degrees for an hour participated in the experiment. The use of LBNP during tilting improved precision of arrow orientation on the round-shaped screen (during continuous tracking) but did not influence orientation relative to the gravitational axis and the long axis of the body. The selective effect of LBNP on the orientation can be attributed to the increased importance of inner coordinates due to the pressure of interior walls of the LBNP suit on the foot surface, and blood pooling in the dependent part of the body.

[Effect of an increased level of hydration on human tolerance to orthostatism and the action of LBNP]. / Vliianie povyshennogo urovnia gidratsii na ustoichovost' cheloveka k ortostazu i vozdeistviiu ODNT.

Intake of fluid, water-salt solutions, water and sodium chloride resulted in hyperhydration, the level and duration of which varied with respect to the pattern and composition of the ingredients consumed. As applied to real space flights, fractional consumption of water and sodium chloride proved most promising. This regimen yielded a distinct and prolonged hyperhydration and incrased orthostatic and LBNP tolerance of the test subjects.