A submillimeter gyrotron with a pulsed magnetic field

Pulse solenoids seem promising for sumbillimeter wave generation in gyrotrons. In this paper a single-pulse submillimeter gyrotron with a pulsed magnetic field is described. At the wavelength 0.8 mm the output power 120 KW with the efficiency 15% has been obtained.     

A terahertz gyrotron with pulsed magnetic field

We present the results of first experiments with a small-size gyrotron on the basis of a pulsed solenoid with a magnetic field of about 40 T. The generation of microwave radiation in the frequency range from 0.9 to 1.02 THz is obtained. The pulse duration is about 40 µs for a kilowatt power level. The microwave pulse repetition rate is limited by the solenoid cooling capability and is about 1 pulse per minute, which is an order of magnitude higher than that in known foreign analogs.     

Circular polarized coherent thermal radiation from semiconductor layers in an external magnetic field

We investigated, both theoretically and experimentally, the polarization properties of coherent thermal radiation from thin semiconductor planar layers in a weak external magnetic field. For the Faraday configuration, it is shown that the spectrum of thermal radiation is a superposition of two oscillating spectra which correspond to radiation of electromagnetic waves with right- and left-hand circular polarization.     

165 GHz, 1.5 MW-coaxial cavity gyrotron with depressed collector

A further step in the development of a coaxial-cavity gyrotron operated in the transverse electric TE_-31,17 mode at 165 GHz is presented. The gyrotron has been equipped with a quasi-optical output system consisting of a Vlasov launcher with a single cut and two mirrors, one with a quasi-elliptic and the other with a nonquadratic phase correcting surface. The radio frequency (RF) power is transmitted through a single output window. A maximum output power of 1.7 MW has been achieved. At the nominal operational parameters an RF power of 1.3 MW with an efficiency of 27.3% has been measured. The efficiency increases to 41% in operation with a single-stage depressed collector     

Generation of a coherent state of the micromaser field

It is found that a coherent state of the cavity field can be generated in a micromaser with injected atoms in a coherent superposition of the upper and lower states. The dependence of the density matrix elements of the field on the number of injected atoms indicates that due to the same initial atomic coherence the emission of separately injected single atoms in the cavity is a cooperative process.Dedicated to Prof. Asim Barut on the occasion of his 65th birthday. Physicist, philosopher, friend of man, here indeed is a role model for us all.     

Generation of coherent radiation at 61.6 nm by fifth harmonic conversion of radiation from a XeCl laser

Fifth harmonic conversion of radiation from a XeCl laser in Ar and Kr, generating radiation at 61.6 nm, is reported. Fifth power law variation of the generated energy with the pump energy is observed. The effects of continuum absorption are observed in the width of the phase matching peak in Ar.     

Generation of superpositions of coherent states of a cavity field with a driven atom

We propose a cavity QED technique to generate superpositions of a series of coherent states on a circle through the interaction of the cavity field with only one atom driven by a classical field.     

A germanium oscillator in a pulsed magnetic field

Experimental data which confirms the presence of hysteresis of the magnetic threshold field of the helical instability of the plasma in a germanium oscillator are presented. It is shown that hysteresis of the threshold magnetic field is due to the inertia of the change in the effective lifetime of the charge carriers in the specimen when the magnetic field is increased and reduced. The dependence of the hysteresis of the threshold magnetic field on the electric field strength, the magnetic field, and the temperature is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 38–41, July, 1982.The authors thank R. I. Bashirov, and K. M. Aliev for making it possible to carry out the measurements in pulsed magnetic fields, and G. P. Il'yukevich for his technical help.     

The radiation from a charge moving in a plane wave field and a magnetic field

The methods of classical electrodynamics are used to consider the problem of the radiation from an electron moving in the field of a monochromatic circularly polarized wave and a uniform magnetic field directed parallel to the direction of propagation of the wave. Expressions for the total radiation intensity and for the angular spectral distribution of the radiation are derived. Certain particular cases are studied.     

1-THz low-noise SIS mixer with a double-dipole antenna

A quasi-optical mixer containing two Nb/Al/AlO_x/Nb superconducting tunnel junctions integrated into a NbTiN/SiO₂/Al microstrip line is studied experimentally in the 800–1000 GHz frequency range. The mixer is developed as an optional front end of the heterodyne receiver operating in frequency band 3 or 4 and incorporated into the HIFI module of the Herschel space-borne telescope. The double-dipole antenna of the mixer is made of NbTiN and Al films; the quarter-wavelength reflector, of a Nb film. The mixer is optimized for the IF band of 4–8 GHz. The double-sideband noise temperature T _RX measured at 935 GHz is 250 K at a mixer temperature of 2 K and an IF of 1.5 GHz. Within 850–1000 GHz, T _RX remains below 350 K. The antenna pattern is symmetrical with a sidelobe level below −16 dB.     

Dynamic triggering of a spin-transition by a pulsed magnetic field

We report the first study of the effect of a high pulsed magnetic field on a spin transition complex in the solid state. The high spin fraction was determined by optical reflectivity. Sizeable effects are observed for the well-known spin transition solid Fe(Phen)₂(NCS)₂. In the hysteresis loop temperature range, an increase in the HS fraction is obtained, with an irreversible (reversible) character in the ascending (descending) branch of the loop. The time dependence of the HS fraction provides information on the kinetics of the spin-crossover process at the spin transition. Received 23 February 1999 and Received in final form 8 June 1999     

Activation of a semiconductor surface by a pulsed magnetic field

The possibility of semiconductor surface activation, which shows up as a long-term increase in the adsorption capacity in response to a short exposure to a pulsed magnetic field, is demonstrated for the first time. Magnetic-field-induced surface activation is studied on silicon, germanium, and gallium arsenide crystals. The effect revealed extends the capabilities of thin-film growth on the semiconductor surface.     

Creation and manipulation of coherences in molecules with a pulsed magnetic field

We demonstrate the application of a pulsed magnetic field for the creation and manipulation of coherences in molecular systems, using quantum beat spectroscopy for the detection of the dynamics of the molecular superposition states. In all cases, the experiments are performed on energy levels in electronically excited states of the (jet-cooled) CS₂ molecule populated by a short laser pulse. In the basic experiment, following excitation of initially degenerate Zeeman sublevels under zero field conditions with suitable laser polarization, quantum beats are generated at the moment the magnetic field is switched on, even when the field is delayed by several excited state lifetimes. By quenching of the field, it is shown that the molecule may be “frozen” in any superposition state of the participating sublevels. Using a combination of static and pulsed fields with different orientations, the molecule can be prepared in a more general state, described by coherences among all Zeeman substrates. This is achieved by choosing an appropriate time delay for the switched field, without any change to the geometrical parameters of the experiment such as laser polarization or detection direction. Numerical simulations of these dynamical coherence phenomena have been performed to support assignment and interpretation of the experimental results. Received: 8 April 1998 / Accepted: 3 June 1998     

Boson radiation in a periodic magnetic field

The first correction to the boson radiation intensity is obtained in an arbitrary two-component periodic magnetic field. In the ultrarelativistic case, the quantum correction for a specific kind of potential in which spiral motion is realized will agree with the corresponding expression in the theory of synchrotron radiation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 27–32, September, 1989.The authors are grateful to Prof. V. G. Bagrov for attention to the research.