Laser

 

(57) Abstract:

The invention relates to the field of quantum electronics, and more specifically to the creation of a frequency-periodic gas lasers with electric pump and x-ray pre-ionization, and can be used in various sectors of the economy. In the laser containing a sealed chamber with the vacuum inlets and active environment with Windows to output radiation blocks the triggering of the discharge cathode and main discharge with shaped anode and common to both blocks electrode, vacuum system, gas exchange and cooling, power generation and output of coherent radiation; the unit initiating discharge is executed from Autonomous systems vacuum and gas exchange and placed coaxially with the camera and executed in the form of a vacuum cavity with glass of dielectric material and a lid in the form of a common electrode, perforated with rows of equally spaced holes and a profile similar to the profile of the anode, and the cathode is made of a plate shape similar to the cross section of the vacuum cavity with a dielectric layer and a metal square grid placed on the surface of the dielectric block the initiating discharge entered braking system ele is Oh, and cooling system made in the form of a set of fans and two heat exchangers containing a number of parallel metal plates, arranged vertically and installed symmetrically with respect to the blocks of the primary and initiating discharge, the system of gas exchange in the form of containers with different gaseous active media, and the shaping unit and output coherent radiation introduced the interchangeable optical elements and two metal translucent screen in a grid, set on a course of radiation symmetrically from the axis of the block main discharge. Achievable technical result is the expansion of the spectrum of the radiation source as in the pulse and frequency-periodic regimes with a simultaneous increase in the output power of the source of coherent radiation. 1 Il.

The invention relates to the field of quantum electronics, and more specifically to the field of creation-frequency periodic gas lasers with electric pump and x-ray pre-ionization, and can be used in various sectors of the economy.

News of the device [1] to obtain coherent radiation with a wavelength of 10.6 microns, containing bit Kama is izala short diffuse discharge, created "runaway electrons". The device also contains the trigger, the main cathode and the common shaped anode electrodes. As the initiator of the cathode uses a series of thin wires stretched parallel to the axis of the discharge chamber.

The application of this device is limited due to the following disadvantages:

1 - the inability to work in the frequency-periodic mode due to the lack of cooling and mixing of the active medium in the working volume;

2 - the absence of a system for damping acoustic waves that affect the dynamics of the device;

3 is an inefficient use of the active mixture, outside the volume of the discharge gap;

4 - no special equipment needed to obtain lasing at wavelengths other than the wavelengths generated by CO2-laser;

5 - high voltage (~ 200 kV), providing the discharge in the main volume of the active medium, which requires a time limit.

Known pulse CO2laser [2] volume self-sustained discharge and pre-ionization soft x-ray radiation. The device comprises a sealed chamber with a vacuum device, the anode remnants of this pulsed laser are: the inability to work on different active media; high voltage on the electrodes of the gun (70 - 80 kV); the inability to work in the frequency-periodic mode due to the lack of efficient cooling system and gas exchange active medium.

Known electric discharge laser of a large volume [3] was chosen for the prototype, containing a discharge chamber with an active environment, blocks initiating the discharge cathodes in the form of a series of delays. The camera has a system of pumping and inlet of the active medium, and the cooling is due to the convective exchange. Coaxially with the block main discharge has an optical resonator. The main parameters of the laser: the voltage across the main discharge electrodes ~ 500 kV, the pre-ionizer ~ 400 kV. The concentration of electrons in the main period of ~ 1012cm-3the deposition of energy in the active volume of 0.35 to 2.0 j/L. the Device can be used as an excimer laser.

The application of this device is limited due to the following disadvantages:

1 - the inability to work in the frequency-periodic mode;

2 - the inability to work on different active media;

3 is an inefficient use of the active environment outside the interelectrode gap;

4 - the use of high voltage is imago of the invention is achieved technical result consisting in the extension of the spectrum of the radiation source as in the pulse and frequency-periodic regimes with a simultaneous increase in the output power of the source of coherent radiation. In accordance with the invention, the technical result is achieved in that the laser containing a sealed chamber with the vacuum inlets and active environment with Windows to output radiation, the unit initiating the discharge cathode and main discharge with shaped anode and common to both blocks electrode, vacuum system, gas exchange and cooling, power generation and output of coherent radiation; the unit initiating discharge is executed from Autonomous systems vacuum and gas exchange and placed coaxially with the camera and executed in the form of a vacuum cavity with walls of dielectric material and a lid in the form of a common electrode, perforated with rows of equally spaced holes and a profile similar to the profile of the anode and the cathode is made of a plate of thickness h1< h shape similar to the cross section of the vacuum cavity with a dielectric layer thickness , and metal square mesh with a side of the square l0> htg(/2) placed on the surface of the dielectric block iniziare D>t/P, and fixed on the surface of a metal foil, and the cooling system is made in the form of a set of fans and two heat exchangers containing a number of parallel metal plates, arranged vertically and placed at a distance of d2< R between them, and installed symmetrically with respect to the blocks of the primary and initiating discharge, the system of gas exchange in the form of containers with different gaseous active media, and the shaping unit and output coherent radiation introduced the interchangeable optical element with a reflection coefficient and two metal translucent screen in a grid with a step of l1< 2vPLtpset on a course of radiation symmetrically from the axis of the block main discharge at a distance of I2> vPLtand+ Ie/2, where

h - the height of the vacuum cavity;

- permittivity dielectric;

d is the distance between the main discharge electrodes;

C0- capacity interelectrode gap:

S, Iethe area and length of the main discharge electrodes;

- the opening angle of the electron beam with a grid element, placed on the surface of the dielectric:

- toasty foil material;

R is the radius of the cross section of the sealed chamber;

L0- the length of the area occupied by the active medium in the interelectrode gap;

k0the gain of the active Medium;

1- the ratio of harmful losses in the resonator;

vPLthe rate of plasma expansion;

tp- the duration of the leading edge of the pulse laser beams are:

tandthe pulse duration of the laser radiation.

The drawing shows a device that implements the present invention, where

1 - vacuum cavity;

2 perforated electrode with holes;

3 - shaped anode;

4 - cathode:

5 - layer dielectric;

6 - metal mesh:

7 - frame with holes;

8 - foil;

9 - fan:

10 - plate heat exchanger;

11 - capacity gas active environments:

12 - set of optical elements;

13 - deaf mirror resonator;

14 - translucent screen (mesh);

15 - sealed Luggage;

16 is a vacuum input:

17 - open for output radiation;

18 - control units.

The device comprises a sealed chamber 15 made of insulating material, with vacuum input 16 is diversified Environment box 17 to output radiation, the unit initiating discharge, made in the form of a vacuum cavity 1 with the walls of dielectric material with a separate vacuum input, and placed inside the cathode node and the cathode 4, the dielectric layer 5 and a metal grid 6, located on a dielectric surface, and the anode of the node that contains the frame with holes 7 and mounted on its surface on the side opposite to cathode foil 8. On the surface of the vacuum cavity posted by General perforated electrode 2 with holes that serves as her cover, and electrically connected with the frame and located on the foil, the block main discharge with shaped anode 3 and opposite him a General shaped and perforated electrode. Coaxially with the Windows 17 and the main discharge electrodes is set interchangeable optical elements 12, deaf mirror resonator 13 and translucent screens (mesh) 14. Symmetrically relative to the center of symmetry of the main discharge electrodes are fans 9, behind which is placed a series of plates of the heat exchanger 10 having a common base and cold running water. On the electrode system device filed specially generated voltage with two rattelser) with pulse duration of the radiation in the range from 100 NS to 1 μs.

After aligning the optical resonator consisting of a semitransparent mirror, the supplied interchangeable optical elements 12, and the rear mirror 13, is consistently pumping through separate vacuum inlets 16, a sealed chamber 15 and the vacuum cavity 1 and run through a special entrance aperture in a sealed chamber of the active medium (a mixture of CO2N2, He) contained in one of the tanks system of gas supply 11.

Next delivery of the pulse of high voltage to the cathode 4, the total perforated electrode with holes 2 unit initiating discharge. In the result, under the action of the electric field near the cathode is formed continuously growing ionized cloud consisting of ions, neutrals and slow electrons. For the case of weak fields, considering that the bulk of the electrons has a Maxwell distribution, and given the fast decay of the Coulomb cross section with increasing speed of the colliding particles, it is possible to show that in these fields the distribution function of electrons in the interelectrode gap is strongly distorted. Thus the equation of motion of the electrons can be written in the form

meeiv of the electron, respectively;

vt- thermal velocity;

< / BR>
the collision frequency of electron concentration n ions [4];

In - Coulomb logarithm.

In experimental studies of nanosecond gas discharge, in heavily congested periods were registered bremsstrahlung x-ray range [5] . Estimate the energy of the electrons is made on the basis of data about energy x-ray radiation, lead to the conclusion about the existence in the discharge of electrons with energy eU0(U0- applied voltage). As a consequence, the total kinetic energy for some Uthenwill be fully defined directional speed determined by the applied voltage. Therefore, the left member of the equation (1) together with equation (2) determine the friction force from the side of the ion cloud, which is inversely proportional to the square of the speed, thus the electron to the free path length is unlimited to accelerate, and this results in dispersion of the primary electron cloud near the cathode, high-energy electrons will ionize the environment at significant distances from their primary localization, so the electric rasra the AE Maxwell distribution near the cathode to the concentration of the runaway electrons is true ratio

< / BR>
where is a constant;

E - the intensity of the applied field.

This is only a very small fraction of all electrons, and creating an effective preionization mode needs to make significant voltage to the electrodes. In [6] as a criterion of the transition from streamer mechanism of the gas discharge to the continuous acceleration of electrons selected the following condition overvoltage:

< / BR>
where is the change of the electron energy on the free path length;

E0- the electric field in the electrode gap.

To ensure the effectiveness of the x-ray preionization mode interelectrode gap main discharge it is necessary to increase the discharge current in the pre-ionizer by increasing the concentration of runaway electrons and their mobility with the purpose of fulfilling the criterion (4). Therefore, in the vacuum cavity near the cathode 4 a metal grid 6, which allows for a given voltage between the electrodes of the system of preionization mode to redistribute the electric field near the cathode in accordance with equation [7]:

E(r)=E0(1+R2/r2) (6)

where r is the distance from the mesh;

R is the radius of the wire is ü in the field of ions and neutrals form a dipole radiation. The electrons, accelerated in the field specified by the formula (6), bombard foil 8, mounted on the frame with the holes 7. To obtain a more uniform flow of the electron beam, and hence to ensure uniform preionization mode metal mesh is made with square cells.

Get the number of groups of electrons based on the geometry of the electrodes. Let S, Ie, L are the area, length and width of the electrode (cathode), h is the distance between the cathode and the profiled electrode 2 (the height of the vacuum cavity). From the experimental data [8] it is known that the divergence of the electron beam in a wide range of applied stress is constant and amounts to ~ 20o. For evaluation, we assume that the optimal condition for overlapping of the electron beam on the anode of the pre-ionizer is their touch, hence we get a grid step:

l0> h tg ( /2), (7)

where h is the height of the vacuum cavity;

~ 20o- the angle of the beams.

If the area of the electrodes S, the number of groups of electrons n is equal to the number of elements of a square grid:

< / BR>
The support grid is a dielectric layer 5 located at periphery the m decreases the heterogeneity of the discharge current, defined by the presence of edge effects at the edges of the electrodes. As is known [9] , the main parameters dependent discharge sustained by the electron beam, the discharge current i, the field strength E and the energy W, is introduced into the discharge depend on resindential capacity, discharge in the gas gap. Therefore, the introduction of additional capacity, which is determined by the dielectric layer, should not change the values of the main parameters i, E, W.

Let0- interelectrode capacitance of the area, which has a dielectric layer with a cross section of S1< S; with the introduction of dielectric drawn to capacity with1defined by the dielectric layer, and C2- capacity air gap. The compensation can be written in the form:

< / BR>
where

where is the dielectric constant of the dielectric;

0- electric constant;

d1the thickness of the dielectric.

From (9) and (10) have

< / BR>
Simplifying (11), we get

< / BR>
The thickness of the cathode is limited by the height of the top of the vacuum cavity, and the lower limit can be determined from the following considerations, which determine the functionality of the cathode.

Under the action of the current pulse through the COI is found in high-current electron accelerators is not associated with the pure autoelectronic emission, and based on the phenomenon of explosive emission of electrons from metal needles. Consider the cathode with a cross section equal to the area of the main discharge electrodes and with a height of h1then reducing the height of the cathode due to ablation of parts of a substance from its surface under the action frequency of the periodic current pulses may be determined by the formula

< / BR>
where m is the initial mass of the cathode;

m0- weight of the cathode, carry out in a single pulse;

f - frequency pulses;

S - area of the cathode;

the density of the cathode material.

For evaluation, we assume that during the passage frequency of the periodic signal explodes only a single emission centre (the tip) and these centers are distributed uniformly over the surface of the cathode and the opening angle of the mass of matter coincides with the angle of scattering of electrons from the tip, the formula (7). The heat balance equation, we write in the form

< / BR>
where c,,'0respectively the specific heat, coefficient of thermal conductivity, the electrical resistivity of the cathode material;

j(t) is the current density in the cross section of the tip;

Q - the cost of radiation from the flame upon the edge of the explosion.

As demonstrated by assessment [10], the cost of heat and islet to be represented in a spherical coordinate system as follows:

< / BR>
where is the opening angle of the edge of the material;

b is the radius of the surface of the ball sector centered in the tip.

The mass of material contained in a spherical sector, will be

m0= Vc= 2/3 b2, (16)

where Vc- volume of a spherical sector,

nc= 2 b sin2(/4) - the height of the ball sector.

Therefore, carry out the mass will be equal to

m0= 4/3b3sin2(/4) (17)

From (15) it follows that

< / BR>
< / BR>
Substituting the value of b in equation (17), we obtain

< / BR>
Thus, after n series the height of the cathode will be reduced by the amount

< / BR>
It follows that, if you want to work with n-series, the thickness of the cathode must be selected larger than the h2.

Once formed, the gas discharge in the vacuum cavity 1 and the mechanism of scattering of electrons, the electron beam is decelerated in the foil 8 is placed on the carrier frame with the holes 7. The diameters of the holes and their number are chosen to provide the maximum area for the bombardment of the electron beam. Restrictions on the size of the holes are determined by the yield strength of the material foilt.

Consider a spherical shell with sacree 15 and the vacuum cavity are different. The equilibrium condition for the shell will write in the form:

F1= F2(22)

where F1= PS - power is determined by the pressure differential on both sides of the shell;

S = R2- the cross-sectional area (R is the radius of the hole),

F2= 2 - power, balanced internal stresses;

- internal voltage;

the thickness of the foil.

Substituting (23) and (24) in (22), we obtain

< / BR>
Therefore, the necessary condition for determining R is >tor

< / BR>
wheret- the tensile strength of the foil material.

The gas path of a laser is a one-dimensional acoustic resonator with closed ends, which is a periodic external effects, and contains a number of parallel metal plates, arranged vertically. Such acoustic resonator has a range of natural frequencies

n= nc/2LAK, (27)

where C is the speed of sound;

LAK- the length of the acoustic resonator: (length sealed chamber);

n = 1, 2, 3...

Since the electrode system of the main discharge is located in the middle of the acoustic resonator, we can assume that oscillations corresponding to n is even, will not affect processes occur is Albania1[11], because the efficiency of excitation of oscillations of higher order is much less [12]. The reflection coefficient of acoustic waves for modes of high order, is expressed by the formula

< / BR>
where n is the number of fashion;

d2- the distance between the plates.

Therefore, the pulse frequency is selected on the basis of conditions

f0<-1)w/po]1/, (31)

where b0- the size of the tube directly after the pulse:

p0initial pressure:

= Cp/Cv;

w is the specific energy input in the discharge.

During the propagation of a sound wave in a gaseous environment, the initial intensity with increasing distance varies according to the law [14]:

J = J0e-2x, (32)

< / BR>
is the absorption coefficient, a is the frequency of the sound wave;

- density environment;

- the viscosity coefficients of the environment;

K - coefficient of thermal conductivity;

cCp- specific heat at constant volume and constant pressure.

When passing through the limiting barrier most of the absorption is due to the effect defined by the presence of the bounding surface, then the absorption coefficient is determined by what Ascoli gas;

l is the free path length;

c is the speed of sound;

= k/cpis the coefficient of thermal diffusivity;

the density of the material bounding surface;

withpc- specific heat.

Factor 1proportional to the energy absorbed per unit time and unit length. So the acoustic wave is reflected from the edge of the resonator, in our case

1~ LAK/R (35)

Due to the fact that the reduced characteristic dimensions of the bounding surface, thanks to the introduction of metal plates of the heat exchanger 10, there will be an increase of the absorption coefficient, defined by the formula (35). In addition, some of the energy of the sound wave when reflected will be absorbed on a common ground, which is fixed to plate heat exchanger.

The absorption coefficient for this case will be determined by the formula [14]:

< / BR>
where < /2 is the angle of incidence.

As the radiation source (gas discharge) has a size of Ie< R, the propagating sound waves have a shape close to spherical, and the condition (37) can be considered as completed. Thus, thanks to the introduction in a sealed chamber, which represents the acoustic RNI, generated acoustic waves in an active environment in the main discharge by pumping the active medium frequency periodic electron bunches.

Sharing fans 9 and two heat exchangers with plates 10 having a common base and cold running water, allows not only the process of suppression of acoustic waves, but also to effectively carry out the cooling process and change the active medium in the interelectrode gap of the main discharge by increasing the surface contact of the active medium with the surface of the heat exchanger.

As is known [15], the threshold is determined by the equation:

k0=1+2, (38)

where k0- the initial gain;

1,2linear attenuation coefficient of the light beam that meets the harmful and helpful losses.

Therefore, to ensure generation to

ko>1+2(39)

Useful loss due care of the energy from the active medium in the form of laser radiation are determined by the formula

< / BR>
where l0- the length of the area occupied by the active medium in the interelectrode gap;

R2~ 1 (polished copper mirror). Then from (40) it should

< / BR>
Harmful losses are determined by a number of factors: the absorption of radiation by particles that are not active centers, scattering through the side surface of the active medium, diffraction, etc., In the General case the expression for the density emerging from the resonator of the light flux has the form [15]

< / BR>
where v is the speed of light in the active medium;

the nonlinearity parameter active transport.

The maximum of the expression (42) is achieved at

< / BR>
Therefore, from (41) it follows for ROpt< / BR>
< / BR>
Thus, for optimum reflection coefficient for a particular wavelength (for the selected example 10.6 μm), you need a set of interchangeable optical elements to provide optics that have beforehand set reflectivities.

As you know, the laws of distribution produced in the laser coherent light beams can be described using a scalar diffraction theory [16], and the condition of the reproduction patterns of the beam after a full crawl of the resonator with an active environment can be represented as [17]

< / BR>
where u(x, y) is the field distribution at the output mirror of the resonator;/SUB> = L' + L0(n-1) is the total optical length of the resonator with the environment;

L' is the distance between the resonator mirrors;

L0- the length of the active medium;

n0the refractive index of the medium:

TO0- gain Environment;

- integral conversion operator bunch of empty resonator with its own functions Umand eigenvalues

< / BR>
where is the phase correction, ensuring the reproduction beam phase length of the resonator:

- coefficient of the diffraction losses m fashion amplitude.

From (45) with (46) for major fashion get

< / BR>
In order for the complex amplitude distribution was reproduced not only in form, but had previous phase, the value must be a valid, therefore, the phase shift should be equal to 2q, where q is an integer. Thus, the change in intensity of the beam after the crawl is

J =2= J0Roptexp(-2)exp(20L0), (48)

where is a coefficient that defines the diffraction loss.

When taking into account the additional losses due to the scattering processes on the active centers and other effects with the passage of the radiation introduced a General factor "bad" loss -1

Let at some initial time t0from the output mirror of the resonator, the supplied interchangeable optical elements 12, the reflected wave intensity J0Roptafter a full pass (double gain), then the total intensity near the grid will have the value

< / BR>
At the same time near the grid, in front of "deaf" mirror of the resonator 13, the total intensity will be determined by the formula:

J2= 2J0Roptexp(-1/2)exp(0L0) (51)

The value of J2determined by amplification in a single pass of the active medium interelectrode gap main discharge is the sum of the intensities of the incident wave coming from the interelectrode gap, and the intensity of the wave reflected from the "deaf" mirrors of the resonator (RRef=1). Since the purpose of our review in this case is the appearance of the plasma formations near the surface of the grids 14, exhibited different sides of their surface and having characterness in the resonator of coherent radiation, calling these plasma formations, consequently, implies the correctness of the operation of summing the intensities of threads radiation, exposing these elements.

Let 20L0-1= 0, then

0L0-1/2 = 0 (52)

the threshold condition generation.

Therefore, near the threshold are:

J1= J2= J0Ropt[1+exp(0)]=2J0Ropt(53)

From (52) we find the loss factor 1:

1= 20L0, (54)

when K0= 0,510-2cm-1, L0= 10 cm get1= 10-1.

For evaluation, we assume that the loss rate constant in the event of generation in the active medium interelectrode gap. Then at maximum gain (saturation), have from (50), (51) and k0= 510-2cm-1find [18]:

J1=J0Ropt[1 + exp(2L05 10-2- 10-1)] 3,5 J0Ropt< / BR>
J2= 2J0Roptexp[L05 10-2- 0,5 10-1] 3,2 J0Ropt(55)

From the analysis of (55) it follows that both grid 14 are under the influence of the same energy density (up to ~ 10%).

With the implementation of the holes 7, and as a result of interaction occurs bremsstrahlung radiation with a continuous spectrum and boundary wavelength [19]:

g~ eUeff/h (56)

where e is the electron charge:

h is the Planck constant;

Ueff= d E, where E is determined from equation (6), and d is the distance between the electrodes of the system of preionization mode.

As emerging bremsstrahlung x-ray radiation is spherically symmetric at low accelerating voltages (up to 50 kV) [19], due to the action of x-ray radiation can cause ionization of the particles of the active medium not only in the volume of the interelectrode gap of the main discharge, but at a considerable distance from these electrodes. For a typical laser mixture of CO2laser (P=1 ATM), the average concentrations of electron preionization mode is ~ 109cm-3at a distance of 40 cm from the foil [20].

When implementing effective preionization mode (n0~ 1016cm-1n0the initial concentration of electrons in the main category) and a certain level of tab energy in the main discharge, provided that the gain is far from saturation, there is a generation of J0in the volume of the active medium between the main discharge electrodes of plecta 12, and the other part of J0Roptback. The result is a translucent screens are the intensity of the J1and J2defined by the formulas (50) and (51).

When a certain threshold of J1I , J2~ 106- 107W/cm2stream of laser radiation with a pulse of microsecond duration with a view of leading picka followed the gentle part, near screens arise plasma formations with maximum radiation in the ultraviolet region of the spectrum. Typical electron concentration n ~ 1018cm-3[21] were found for the moments from 30 NS after the beginning of the occurrence of breakdown and existed up to 100 NSEC after the start of the breakdown.

Since the main contribution to the formation of plasma makes the leading peak of the laser pulse, then the rest of the flat part of the pulse will pass through areas with significant electron concentrations exceeding the threshold and defined by the joint action of the brake x-ray and ultraviolet spectrum of radiation from the plasma formed near the surface of the translucent screens (mesh).

The pumping efficiency of the vibrations of molecules of CO2and NRonov. With this purpose, the calculated energy of the electrons in the volume located coaxially with the active medium of the main discharge in the vicinity of the installation of translucent screens of wire mesh.

Due to the inhomogeneity of the electric field between the main discharge electrodes near the edges of the electrodes interelectrode capacitance is increased by the amount [7]

< / BR>
where C is the capacitance in farads;

L - the width of the electrodes;

d is the distance between the electrodes:

S - the area of the electrodes.

Because the design of the main discharge electrodes is asymmetric form (L < lewhere lethe length of the electrodes) and is limited by the profiled surfaces facing each other and providing uniformity of the electric field inside the discharge gap, and the outer surfaces have radii fillet r < R, where R is the characteristic radius of the fillet surfaces facing to each other, near the part of the external surface of the electrodes will be localized overcharging on the length of the segments with a length of ~ L and a radius r. For evaluation, you can take that overcharging, which determines the capacity associated with edge effects, will be any charge, located on the edges of each electrode may be determined by the formula [7]

< / BR>
where0the potential difference between the two profiled electrodes:

= 1/2, the factor taking into account the presence of two edges of the electrode;

is the coefficient of proportionality dependent on the choice of the system of units.

Thus, the electric field generated by a dipole at a distance r1from the electrodes along the axis of the resonator may be determined by the formula

< / BR>
Substituting the values of (57) and (58) into the formula (59), we get:

< / BR>
when L = 3 10-2m,

le= 1,3 10-1m,

d = 3 10-2m,

S = 4 10-3m2< / BR>
have

< / BR>
The energy provided by the electron on the free path length , the electric field Eis calculated by the formula

W~eE< / BR>
where

(62)

- the average speed of thermal motion;

k - Boltzmann constant;

m is the electron mass,

ei- frequency of electron-ion collisions and is a function of the temperature T0and T1:

ei|To~104K105-106s-1< / BR>
ei|T1~300K 109s-1< / BR>
where T0- temperature in the region of the E. intermediate value forei~107s-1. Thus, we have:

< / BR>
and

< / BR>
As can be seen from (63), the electron energy is sufficient to excite the vibrational levels of the molecules CO2N2[22], so the active medium located in coaxial volumes placed on both sides of the main discharge electrodes with lengths l ~ 10 cm can be reinforcing for the flat part of the pulse CO2-laser. To the flat part of the pulse CO2laser passed through the plasma formation that occurs due to the action of the leader pulse, the plasma frequency must be less than the frequency of CO2laser f=3 1013s-1. Plasma frequency fpmay be determined by the formula

fp~ 9103ne1/2(64)

where nethe concentration of electrons in the plasma.

When low-threshold breakdown near grid ne~ 1014cm-3and

fp= 91031071011s-1(65)

Thus, the transparency is.

It is known that when a minor threshold is exceeded, elasmobranchii plasma breakdown of the environment by the emission of CO2laser at Rp< 1 mm (Rpis the radius of the spot of radiation) is of order of the diameter of the spot on both sides of the main discharge electrodes, is under the action of colliding beams of nearly equal intensity J1and J2(formula (55)), the elements near each of the grids are formed luminous area with characteristic sizes S of the order of vPLwhere vPLthe rate of plasma expansion, the lifetime of the plasma formation.

Therefore, to cover the maximum area is filled with plasma, and, as a consequence, the creation of the necessary concentration of electrons involved in the excitation of the particles of the active environment outside the interelectrode gap, it is necessary to ensure overlap, provided transparency plasma, plasma formations from the neighboring mesh elements, that is, to fulfill the condition

l1< 2 vPLtp(66)

where tp- the duration of the leading edge of the pulse of laser radiation. Additional volume anelectrode active medium can be found by the formula

VSS= kdL l1< / BR>
where k is a factor taking into account the two grids;

d is the interelectrode distance;

L - the width of the electrodes;

l1the grid step.

Thus, the presence of nets leads to additional power output power coherent radiation. When selected by the geometry of unity the influence of the electron clouds of plasma formation, formed near the nets, on the kinetics of the processes in the main discharge to prevent the mesh tape drives need to be installed on the distances l2providing attenuation of the plasma due to relaxation processes, where

l2>vPLp+le/2, (69)

where l2- the distance from the axis of the main discharge electrodes to the place of installation of the grid;

p- the duration of the pulse laser;

le- the length of the main discharge electrodes.

Equation (69) implies that the processes occurring in the plasma, does not affect the bit currents in the circuit of the main discharge.

Due to the formation of blocks 18 two high-voltage pulses with the required frequency and temporal, and amplitude characteristics for the system of the cathode - common perforated electrode and a common perforated electrode is perforated anode serves with a time delay between a pulse of high voltage. After the implementation of the process of x-ray preionization mode, achieve a certain threshold concentration of electrons in the interelectrode gap of the main discharge and feed him high-voltage impulse with one of the blocks 18 Ossetia.

After the passage of one of the pulses of coherent radiation from the series and as a result of processes that determine the characteristics of the laser pulse, occur as the heating of the active medium and the generation of acoustic waves, which degrades the environment settings. Fan 9 with the confuser in the area of the main discharge and plate heat exchangers 10 allows you to simultaneously carry out the process as changing the volume of the active medium, and cooling all sealed chamber 15.

Since the electrodes 2, 3 are smooth shaped surface, this form helps to eliminate turbulence in the flows through the main discharge gap, and laminarinase flow can reduce the gradients of the local electron concentration in it. The choice of pulse repetition frequency on the basis of the conditions (29) allows us to "prepare" active environment for the arrival of the next pulse in the series and to restore the power output of laser energy close to the power output of the previous pulse.

In the above consideration as an example the selected active environment CO2-laser. The described device can be used to generate coherent radiation and Druya 11 contains a number of containers, which are a mixture of SF6:H2, XeCl, ArXe, etc. To obtain generation, such as XeCl 305 nm, it is necessary to carry out the pumping sealed chamber 15, replacing the pre-translucent mirror set 12, to start a new mix.

Thus, the proposed device thanks to the versatility of the design allows you to extend its spectral range and to improve energy performance when working in the frequency-periodicheskom mode.

Currently designed and manufactured to install using the above principles, and conducted preliminary tests in the monopulse mode on mixtures of SF6:H2:C2H6, ArHe, N2at atmospheric pressure, and a mixture of CO2:N2:He generated in pulse-frequency mode.

Sources of information

1. C. F. Basmanov, C. S. Josamycin in. A. Gorokhov and others, ZH, 1982, T. 52, No. 1, S. 128.

2. A., Gordeychik, A., Maslennikov, A. A. Kuchinsky, and others, "Quantum electronics", 1991, T. 18, N 10 , S. 1173.

3. S. N. Baranov, V. C. Gorokhov, V. I. Karelin, A. I. Pavlovsky, P. B. Repin "Quantum electronics", 1991, T. 18, No. 7, S. 891 prototype.

4. L. D. Landau, E. M. Lifshitz. "Physical kinetics". - M.: the HIV. 1972, ZH, T. XIII, 68, S. 1669.

7. L. D. Landau, E. M. Lifshitz. "Electrodynamics of continuous media". - M.: Nauka, 1982, S. 31, 36.

8. The book "Development and application of sources of intense electron beams", Novosibirsk: Nauka, 1976, S. 89.

9. Y. I. Bychkov, Y. D. Korolev, G. A. Month and other "gas Injection electronics", Novosibirsk: Nauka, 1982, S. 78.

10. A collection of Powerful nanosecond pulsed sources of accelerated electrons", Novosibirsk: Nauka, 1974, S. 34.

11. C. Y. Baranov, B. Y. Lyubimov and other "Quantum electronics", 1979, T. 6, No. 1, S. 184.

12. L. A. Weinstein. "Theory of diffraction and the factorization method". - M.: Soviet radio, 1966, S. 253.

13. C. Y. Baranov, Centuries On, D. D. Malyuta, Century, Niziev. "Quantum electronics", 1977, T. 4, No. 9, S. 1861.

14. L. D. Landau, E. M. Lifshitz. "Hydrodynamics". - M.: Nauka, 1986, S. 424.

15. L. C. Tarasov. Physics processes in the generation of coherent optical radiation". - M.: Radio and communication, 1981, S. 90-98.

16. M. Born, E. Wolf. "Principles of optics". - M.: Nauka, 1970.

17. Y. A. Anan'ev. "Optical resonators and the problem of divergence of laser radiation". -M.: Nauka, 1979, S. 63.

18. "Gas lasers". The compilation. - M.: Mir, 1986, S. 296.

19. F. N. Harada. "Oh is the Tronic", 1984, T. 11, S. 524.

21. G. C. Ostrovskaya, A. N. Seidel, Phys, 1973, I. 111, vol. 4, S. 594-595.

22. E. P. Velikhov, V. Y. Baranov, V. S. Letokhov and other "Impulse CO2lasers and their use for the separation of isotopes". - M.: Nauka, 1983, S. 22.

Laser containing a sealed chamber with the vacuum inlets and active environment with Windows to output radiation blocks the triggering of the discharge cathode and main discharge with shaped anode and common to both blocks electrode, vacuum system, gas exchange and cooling, power generation and output of coherent radiation, characterized in that the cooling system is made in the form of a set of fans and two heat exchangers containing a number of parallel metal plates, arranged vertically and placed at a distance of d2< R between them, and installed symmetrically with respect to the blocks of the primary and initiating discharge, the system of gas exchange in the form of containers with different gaseous active media, and the shaping unit and output coherent radiation introduced the interchangeable optical element with a reflection coefficient and two metal translucent screen in a grid with a step of l1<2PLtMENA and made in the form of a vacuum cavity with walls of dielectric material and a lid in the form of a common electrode, perforated with rows of equally spaced holes and a profile similar to the profile of the anode and the cathode is made of a plate of thickness h1< h shape similar to the cross section of the vacuum cavity with a dielectric layer thickness and metal square mesh with a side of the square lo>dtg(/2), placed on a dielectric surface, and the unit initiating discharge entered the braking system of the electron beam, made in the form of a frame with a hole diameter of D>2t/P, and fixed on the surface of the metal foil, where h is the height of the vacuum cavity; - permittivity dielectric; d is the distance between the main discharge electrodes; S, lethe area and length of the main discharge electrodes; - the opening angle of the electron beam from the element mesh, is placed on a dielectric surface; the thickness of the foil; P is the differential pressure in a sealed chamber and the vacuum cavity;t- the tensile strength of the foil material; R is the radius of the cross section of the sealed chamber; L0- the length of the area occupied by the active medium in the interelectrode gap; K0the gain of the active medium;l- the ratio of harmful losses in the resonator;PL- skoroy pulse of laser radiation.

 

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