CN101718966B - Active atomic clock of sapphire resonant cavity and method for fabricating resonant cavity - Google Patents

Abstract

The invention discloses an active atomic clock of a sapphire resonant cavity and a method for fabricating the resonant cavity. The active atomic clock of the sapphire resonant cavity comprises the sapphire resonant cavity, the ratio of the radius b of the outer wall of a sapphire cylinder of the sapphire resonant cavity to the radius a of the wall of an outer metal cavity cylinder is that rho 1 is not less than 0.5 and not more than 0.56; the radius a of the wall of the outer metal cavity cylinder is that a is not less than 85mm and not more than 87.5mm; the radius b of the outer wall of the sapphire cylinder is that b is not less than 42.5mm and not more than 47.6mm; and the radius c of the inner wall of the sapphire cylinder is that c is not less than 36.68mm and not more than 40.6mm, and the height of the cylinder is equal to 162.9mm. SrTiO3 circular rings with the thickness of 2mm are respectively formed on the upper end surface and the lower end surface of the sapphire cavity cylinder of the sapphire resonant cavity. The size of the sapphire resonant cavity is calculated through sapphire resonant cavity and finite software simulation analysis, thereby realizing the maser self-excited oscillations of the sapphire resonant cavity and effectively reducing the volume and the quality of the active hydrogen atomic clock. Furthermore, the temperature drift coefficient of the sapphire resonant cavity can be also reduced.

Description

The manufacture method of sapphire resonator cavity active atomic clock and resonator cavity thereof

Technical field

The present invention relates to a kind of hydrogen atomic clock, the active hydrogen atomic clock of sapphire resonator cavity that particularly a kind of temporal frequency technology is relevant.

Background technology

Along with the development of Chinese Space orbit determination technology, high-accuracy time-frequency equipment more and more is that military project and R﹠D institution are required.Hydrogen atomic clock becomes the high-accuracy time-frequency equipment of main flow that land station uses with its outstanding medium-term and long-term stability.Hydrogen atomic clock is divided into active and passive-type according to whether realizing the maser vibration.Traditional active atomic clock (being commonly called as the up-to-date model that " great bell " SOHM-4 is exactly this clock) and sapphire filled media active atomic clock all are to realize the self-oscillatory active atomic clock of maser.

Yet traditional active atomic clock is a kind of volume and all bigger atomic clock of weight, and its performance and reliability also are more outstanding, and begins existing commercial product the seventies at twentieth century.Active hydrogen atomic clock comprises physical piece and electronic section substantially on the concrete structure, physical piece comprises: resonator cavity, radiation shield, vacuum (-tight) housing, C field, heating furnace, magnetic shielding, state selection magnet, ionization bubble, vacuum pump etc.Electronic section comprises receiver, power supply, frequency synthesizer, isolated amplifier, digital display module, chamber hands-off tuning module etc.

The weight and volume of hydrogen atomic clock mainly is by the decision of the volume in most crucial internal resonance chamber.Resonator cavity is in the penetralia of physical piece, and its coated outside radiation shield, vacuum (-tight) housing, and the C field, heating furnace and four layers of magnetic shielding, the size of the physics auxiliary accessories of its outside is by the size decision in internal resonance chamber.Therefore we can say that the volume of hydrogen atomic clock depends primarily on the volume in its internal resonance chamber.Present stage, the active hydrogen atomic clock volume mainly used of ground was big, and weight big (greater than 200kg) is unfavorable for transportation and vehicle-mounted.Also be unfavorable for the foundation of movement station.

Therefore, need to seek the medium of a kind of big specific inductive capacity (9.3) low-loss (the tangent loss is in E-5 magnitude or lower) as the local filling material of resonator cavity, can be with the microwave cavity miniaturization, approaching traditional hydrogen atomic clock on the performance thereby the volume of active hydrogen atomic clock and weight will greatly reduce.Sapphire is to satisfy low tangent loss, the selection of the best of big specific inductive capacity.The sapphire filled media is because its low tangent loss is present unique filled media of using, and it can guarantee the high Q value of resonator cavity, and its specific inductive capacity greatly then can make the volume of resonator cavity reduce a lot.Therefore adopt the active hydrogen atomic clock of sapphire resonator cavity little with its volume, index is good and receive our concern.

But the weak point of sapphire resonator cavity is the dielectric constant with temperature of sapphire crystal and changes, makes the temperature coefficient in sapphire chamber very high.And the drift of sapphire dielectric constant with temperature is bigger, and therefore, the temperature of resonator cavity is floated coefficient ratio big (50kHz-70KHz).These can influence the long-time stability of sapphire resonator cavity.

Summary of the invention

The object of the present invention is to provide the manufacture method of a kind of sapphire resonator cavity active atomic clock and sapphire resonator cavity thereof, by Theoretical Calculation and finite element software simulation analysis, calculate the sapphire resonant cavity size, realize the self-sustained oscillation of sapphire cavity maser, can effectively reduce the volume and the quality of active hydrogen atomic clock.

The present invention also aims to provide a kind of sapphire resonator cavity active atomic clock, can reduce the temperature of sapphire resonator cavity and float coefficient.

A kind of sapphire resonator cavity active atomic clock comprises the sapphire resonator cavity, and this sapphire resonator cavity is made up of outer wire chamber tube and sapphire tube, ratio 0.5≤ρ of described sapphire drum outer wall radius b and the barrel radius a of outer wire chamber tube ₁≤ 0.56; The barrel radius 85mm≤a≤87.5mm of outer wire chamber tube; Sapphire drum outer wall radius 43.75mm≤b≤47.6mm; Sapphire tube inwall radius 36.68mm≤c≤40.6mm, tube high 160mm≤h≤175m.

Preferably, the ratio ρ of the exterior radius b of described sapphire tube and the barrel radius a of outer wire chamber tube ₁=0.5, the chamber wall radius a=87.5mm of outer wire chamber tube; Sapphire drum outer wall radius b=43.75mm; Sapphire tube inwall radius c=36.68mm, the high h=162.9mm of tube.

The upper and lower end face of the sapphire tube of described sapphire resonator cavity respectively has a SrTiO that 2mm is thick ₃Annulus.The ratio ρ of preferred this sapphire drum outer wall radius b and the barrel radius a of outer wire chamber tube ₁=0.56, the barrel radius a=85mm of outer wire chamber tube; Sapphire drum outer wall radius b=47.6mm; Sapphire tube inwall radius c=40.6mm, the high h=162.9mm of tube.

A kind of manufacture method of sapphire resonator cavity of sapphire resonator cavity active atomic clock is characterized in that, comprises the steps:

(1) Theoretical Calculation can satisfy the size of the self-oscillatory sapphire resonator cavity of maser in theory;

(2) with the ansoft HFSS of high frequency simulation software the cavity that Theoretical Calculation obtains is carried out simulation calculation;

(3) the needed sapphire resonator cavity of processing;

(4) on traditional active hydrogen atomic clock frame, it is done the maser oscillation experiment, realize maser self-sustained oscillation.

In the step (1), step (1) comprising: set the barrel radius 85mm≤a≤87.5mm of the outer wire chamber tube of sapphire resonator cavity, tube high 160mm≤h≤175m separates the Maxwell equation of sapphire resonator cavity under the TE011 pattern.

Further being included in sapphire tube inwall in the step (3) carries out silver-plated.

Sapphire resonator cavity active atomic clock of the present invention makes the resonator cavity of original diameter and Gao Yue 292mm narrow down to diameter and height is about 175mm.Volume is reduced to original about 1/4.The volume and the quality of active hydrogen atomic clock have been realized effectively reducing.And by adopting and the opposite SrTiO of sapphire resonator cavity temperature drift coefficient ₃Sapphire resonator cavity to specific dimensions carries out temperature compensation, effectively reduces the temperature coefficient of sapphire resonator cavity.

Description of drawings

For ease of understanding these and other feature and advantage of the present invention, describe the present invention below in conjunction with specific embodiments and the drawings, wherein:

Fig. 1 is the synoptic diagram of the sapphire resonator cavity of sapphire resonator cavity active atomic clock of the present invention;

Fig. 2 is the synoptic diagram of temperature compensating type sapphire resonator cavity of the present invention;

Fill factor, curve factor was with ρ when Fig. 3 was a=87.5mm ₁The curve map that changes;

Fig. 4 is the ansoft HFSS of high frequency simulation software carries out simulation calculation to the sapphire cavity a synoptic diagram;

Fig. 5 is the TE011 field pattern in the sapphire resonator cavity;

Fig. 6 is the maser oscillator signal figure of sapphire resonator cavity;

Fig. 7 has filled the thick SrTiO of 2mm ₃The Q value of the sapphire resonator cavity of annulus is with ρ ₁Change curve.

Embodiment

With reference to the accompanying drawings 1, sapphire resonator cavity active atomic clock of the present invention comprises the sapphire resonator cavity, and this sapphire resonator cavity is made up of outer wire chamber tube 1 and sapphire tube 2.Described outer wire chamber tube 1 is aluminum barrel normally, and the principal ingredient of described sapphire tube is AL ₂O ₃Ratio 0.5≤ρ between the sapphire tube 2 exterior radius b of described sapphire resonator cavity and the barrel radius a of outer wire chamber tube 1 ₁≤ 0.56; The barrel radius 85mm≤a≤87.5mm of outer wire chamber tube 1; Sapphire tube 2 exterior radius 43.75mm≤b≤47.6mm; Sapphire tube 2 inwall radius 36.68mm≤c≤40.6mm, the high h=162.9mm of tube.Preferably, the ratio ρ between the barrel radius a of the sapphire tube 2 exterior radius b of described sapphire resonator cavity and outer wire chamber tube 1 ₁=0.5, the barrel radius a=87.5mm of outer wire chamber tube 1; The exterior radius b=43.75mm of sapphire tube 2; The inwall radius c=36.68mm of sapphire tube 2, h=162.9mm.

The design process of described sapphire resonator cavity is as follows:

At first, the volume of definite resonator cavity that needs is reduced to any degree, and our target is to be reduced to below the 5L, then, separates the Maxwell equation of sapphire resonator cavity under the TE011 pattern: as follows

$\frac{{\mathrm{\γ}}_2[A_2{J}_0\left({\mathrm{\γ}}_{2}b\right)+B_2{N}_0\left({\mathrm{\γ}}_{2}b\right)]}{[A_2{J}_1\left({\mathrm{\γ}}_{2}b\right)+B_2{N}_1\left({\mathrm{\γ}}_{2}b\right)]}=\frac{{\mathrm{\γ}}_0[A_3{J}_0\left({\mathrm{\γ}}_{0}b\right)+B_3{N}_0\left({\mathrm{\γ}}_{0}b\right)]}{[A_3{J}_1\left({\mathrm{\γ}}_{0}b\right)+B_3{N}_1\left({\mathrm{\γ}}_{0}b\right)]}---\left(1\right)$

Wherein $\left\{\begin{array}{c}{\mathrm{<figure-callout\; id="2"\; label="A"\; filenames="H2009101979282E00031.png"\; state="\{\{state\}\}">A</figure-callout>}}_2=({\mathrm{\&gamma;}}_2/{\mathrm{\&gamma;}}_0)J_1\left({\mathrm{\&gamma;}}_{0}c\right)N_0\left({\mathrm{\&gamma;}}_{2}c\right)-J_0\left({\mathrm{\&gamma;}}_{0}c\right)N_1\left({\mathrm{\&gamma;}}_{2}c\right)\\ {\mathrm{<figure-callout\; id="2"\; label="B"\; filenames="H2009101979282E00031.png"\; state="\{\{state\}\}">B</figure-callout>}}_2=J_2\left({\mathrm{\&gamma;}}_{0}c\right)J_1\left({\mathrm{\&gamma;}}_{2}c\right)-({\mathrm{\&gamma;}}_2/{\mathrm{\&gamma;}}_0)J_0\left({\mathrm{\&gamma;}}_{2}c\right)J_1\left({\mathrm{\&gamma;}}_{0}c\right)\end{array}\right.---\left(2\right)$

$\left\{\begin{array}{c}{A}_3=-\frac{\mathrm{\&pi;}}{2}{\mathrm{\&gamma;}}_{0}a{N}_1\left({\mathrm{\&gamma;}}_{0}a\right)\\ {\mathrm{<figure-callout\; id="3"\; label="B"\; filenames="H2009101979282E00031.png"\; state="\{\{state\}\}">B</figure-callout>}}_3=\frac{\mathrm{\&pi;}}{2}{\mathrm{\&gamma;}}_{0}a{J}_1\left({\mathrm{\&gamma;}}_{0}a\right)\end{array}\right.---\left(3\right)$

${\mathrm{\&gamma;}}_i^2={\mathrm{\&omega;}}^2{\mathrm{\&mu;}}_0{\mathrm{\&epsiv;}}_0{\mathrm{\&epsiv;}}_i-{\mathrm{\&pi;}}^2/{\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="H2009101979282E00031.png"\; state="\{\{state\}\}">h</figure-callout>}}^2$

γ ₁＝γ ₃＝γ ₀

${\mathrm{\&gamma;}}_2^2={\mathrm{\&gamma;}}_1^2={\mathrm{\&gamma;}}_3^2={\mathrm{\&gamma;}}_0^2={\mathrm{\&omega;}}^2{\mathrm{\&mu;}}_0{\mathrm{\&epsiv;}}_0-{\mathrm{\&pi;}}^2{/\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="H2009101979282E00031.png"\; state="\{\{state\}\}">h</figure-callout>}}^2$

Each ρ during table 1a=87.5mm ₁Sapphire size under the value

	a(mm)	b(mm)	c(mm)	h(mm)
					ρ 1＝0.4	87.5	35	26	162.9
ρ 1＝0.5	87.5	43.75	36.68	162.9
					ρ 1＝0.6	87.5	52.5	45.97	162.9
ρ 1＝0.7	87.5	61.25	54.383	162.9

As the high h of tube of sapphire tube 2, the barrel radius a of outer wire chamber tube 1, after (they can characterize the volume of whole sapphire resonator cavity) decision, different ρ ₁(ratio between the tube radius a of sapphire drum outer wall radius b and outer wire chamber tube) just representing the different TE011 pattern that can realize resonance frequencies is the sapphire size of 1.42405GHz.Last table is at a=87.5mm., (must set two initial values, just can separate transcendental equation) under the prerequisite of h=162.9mm, and volume is 3.92 liters, satisfies＜5 liters requirement.It is the resonator cavity of 1.420405GHz that different sapphire packing sizes can satisfy TE011 mode oscillation frequency.In these four sizes, we also need consider fill factor, curve factor and Q value, because the Q value is with ρ ₁Increase and reduce, and fill factor, curve factor is at ρ ₁Change gently between=0.5～0.6, and 0.5 maximum.As shown in Figure 3, for ρ ₁＜=0.4 situation, fill factor, curve factor is too little and do not adopt.Preferred sapphire chamber is of a size of: ρ ₁=0.5; A=87.5mm; B=43.75mm; C=36.68mm; H=162.9mm.

With the ansoft HFSS of high frequency simulation software the cavity that designs is carried out simulation calculation, as shown in Figure 4: the oscillation frequency that obtains it is 1.4358GHz; The Q value is about 54727.

Below for this reason sapphire resonator cavity frequency with physical dimension and variation of temperature

	Theoretical Calculation result	Experimental result
			df/da	-7.1MHz/mm	N/A
df/db	-55.2MHz/mm	N/A
			df/dc	59.1MHz/mm	N/A
df/dh	-1.2MHz/mm	-1.24MHz/mm
			df/dT	-55KHz/K	-47KHz/K

Adopt the sapphire resonator cavity of above-mentioned size design, its volume is 1/4 of the wire chamber of traditional great bell or quartzy chamber.

Next, on traditional active hydrogen atomic clock frame, this sapphire resonator cavity is done the maser oscillation experiment.The sapphire resonator cavity is fixed on great bell inside, regulates ionization and steep shinny rose-red (hydrogen gas ionizes becomes hydrogen atom), as shown in Figure 5, strengthen hydrogen flowing quantity and heighten the field intensity of home court, C field, regulate secondary the relation with the home court.And the monitoring chamber changes frequently, regulate every day temperature with frequently drift of compensated cavity (this drift be put into great bell by the sapphire resonator cavity after, unbalanced stress causes, if just can not occur for it designs supporting physical piece specially).Through adjusting after a while, be under the condition of 1～1.1mA (ion pump current) at flow, obtained as shown in Figure 6 the maser oscillator signal of-102dbm.

By another embodiment of the present invention, float coefficient for the temperature that reduces the sapphire resonator cavity, adopt and the opposite SrTiO of sapphire resonator cavity temperature drift coefficient ₃Sapphire resonator cavity to specific dimensions carries out temperature compensation, as shown in Figure 2, the sapphire resonator cavity active atomic clock of temperature compensating type, the upper and lower end face of the sapphire tube 2 of described sapphire resonator cavity respectively has a SrTiO that 2mm is thick ₃Annulus 3.This annulus 3 can bond or otherwise be incorporated into the outside of the upper and lower end face of sapphire tube 2.Preferably, the ratio ρ between the barrel radius a of the sapphire tube 2 exterior radius b of described sapphire resonator cavity and outer wire chamber tube 1 ₁=0.56, the barrel radius a=85mm of outer wire chamber tube 1; Sapphire tube 2 exterior radius b=47.6mm; Sapphire tube 2 inwall radius c=40.6mm, the high h=162.9mm of tube.SrTiO ₃The variation of dielectric constant with temperature opposite with sapphire, therefore change when causing that the chamber drifts about frequently SrTiO when sapphire specific inductive capacity ₃Can cause that the chamber is mobile in the opposite direction frequently, the chamber that produces with compensates drifts about frequently.

The crystal compensation effect depends on the size in sapphire chamber itself, and the thickness of compensated crystal.Sapphire material is AL ₂O ₃Monocrystal, it is a specific inductive capacity opposite sex crystal, vertical with optical axis and parallelly is respectively 9.3 and 11.6.Because we require optical axis parallel with Z axle (promptly parallel with height h Z axle), the specific inductive capacity that influences frequency so under the TE011 pattern is 9.3.9.3 be used for the calculating of following formula sapphire cavity size.We adopt the metal exocoel is metallic aluminium, and in order to promote the Q value of sapphire resonator cavity, we have carried out silver-plated operation to sapphire resonator cavity inwall.

As shown in Figure 7, sapphire tube compensation SrTiO ₃After the crystal, the quality factor q value that characterizes the loss of resonator can descend, when the quality factor of resonator cavity are lower than 40,000, even rule of thumb the self-sustained oscillation of cavity maser signal also can be unstable.So the crystal of compensation must be lower than 3mm.And when just not good with the 1mm compensation effect, chamber temperature drift frequently is still very big.Therefore be preferably 2mm.Compensate the SrTiO of 2mm as seen from the above table ₃Resulting nonloaded Q satisfies the Q value greater than 40000 these basic demands after the ring.

The compensation of 2mmSrTiO3 crystal rings is each ρ of sapphire resonator cavity down ₁Nonloaded Q under the value

Not all sapphire resonant cavity all can obtain more satisfactory compensation effect, compensation effect is decided by the size of sapphire resonant cavity, yet sapphire resonant cavity change in size can cause the variation of Q value and fill factor, curve factor, and these two factors can realize the self-oscillatory ability of hydrogen maer to determining the sapphire resonator cavity.Also we can say the quality that is determining the sapphire resonator cavity.Therefore our the sapphire resonator cavity of designing specific dimensions drifts about with satisfied temperature, Q value, and fill factor, curve factor three parts noodles spare reaches best compensation effect.

As seen from Figure 8, be set at after the 87.5mm at ρ as the barrel radius a of outer wire chamber tube 1 ₁Can obtain zero temperature coefficient point between=0.54 to 0.56.Zero temperature coefficient point can drift about to the right when a=85mm.By the table of top Q value and change in size as can be seen, ρ ₁Big more Q value is more little, so for the satisfied temperature compensation effect, we need not continue to reduce exocoel on the basis of 85mm.

Next the variation of fill factor, curve factor and the relation of size are discussed.Fill factor, curve factor can see that fill factor, curve factor is all more smooth between 0.52 to 0.56 when a=87.5mm with the variation relation of sapphire resonant cavity size as shown in Figure 3.In order to pursue effect temperature compensation, can select in this zone.We are last has obtained a=87.5mm, ρ ₁=0.56 temperature is floated coefficient 8.23kHz/ ℃ and a=85mm, ρ ₁=0.56 temperature coefficient is-4.44kHz/ ℃ two kinds of schemes.The fill factor, curve factor of these two kinds of schemes and Q value are respectively 46445 and 0.5136 and 45860 and 0.5117.Weighing the self-oscillatory parameter of maser is that S parameter maser self-sustained oscillation condition is S＞5900.

With the S parameter-definition of these two kinds of sizes is S ≡ Q _Lη ', Q ₀=(1+ β) Q _LThe Q that calculates is nonloaded Q Q0.By last two formulas, the S parameter that we can calculate top two kinds of schemes is respectively 19878.46 and 19555.47, and they all can realize maser self-sustained oscillation greater than 5900, and differ very little.And temperature coefficient 85mm little a times than 87.5mm.And volume is little, saves cost, and is therefore preferred, ρ ₁=0.56, a=85mm, b=47.6mm, c=40.6mm, h=162.9mm sapphire tube upper and lower end face compensates the SrTiO of 2mm respectively ₃Crystal rings is as our sapphire resonant cavity size that is suitable for temperature compensation most.

Obvious, can do various improvement and conversion to the present invention according to above description.Therefore, be appreciated that within the scope of the appended claims that remove above-mentioned particular implementation exception, the present invention can adopt other modes to implement, and is not limited to described in the above-mentioned instructions.

Claims (9)

1. sapphire resonator cavity active atomic clock, comprise the sapphire resonator cavity, this sapphire resonator cavity is made up of outer wire chamber tube and sapphire tube and is it is characterized in that, the sapphire drum outer wall radius b of described sapphire resonator cavity is ρ with the ratio of the barrel radius a of outer wire chamber tube ₁, 0.5≤ρ wherein ₁≤ 0.56; The barrel radius 85mm≤a≤87.5mm of outer wire chamber tube; Sapphire drum outer wall radius 43.75mm≤b≤47.6mm; Sapphire tube inwall radius 36.68mm≤c≤40.6mm, tube high 160mm≤h≤175m.

2. sapphire resonator cavity active atomic clock according to claim 1 is characterized in that, the sapphire drum outer wall radius b of described sapphire resonator cavity and the ratio ρ of the barrel radius a of outer wire chamber tube ₁=0.5, the barrel radius a=87.5mm of outer wire chamber tube; Sapphire drum outer wall radius b=43.75mm; Sapphire tube inwall radius c=36.68mm, the high h=162.9mm of tube.

3. sapphire resonator cavity active atomic clock according to claim 1 is characterized in that the upper and lower end face of the sapphire tube of described sapphire resonator cavity respectively has a SrTiO that 2mm is thick ₃Annulus.

4. sapphire resonator cavity active atomic clock according to claim 3 is characterized in that, the sapphire drum outer wall radius b of described sapphire resonator cavity and the ratio ρ of the barrel radius a of outer wire chamber tube ₁=0.56, the barrel radius a=85mm of outer wire chamber tube; Sapphire drum outer wall radius b=47.6mm; Sapphire tube inwall radius c=40.6mm, the high h=162.9mm of tube.

5. a manufacture method that is used for the sapphire resonator cavity of hydrogen atomic clock is characterized in that, comprises the steps:

(1) Theoretical Calculation can satisfy the size of the self-oscillatory sapphire resonator cavity of maser in theory, wherein set the barrel radius 85mm≤a≤87.5mm of the outer wire chamber tube of sapphire resonator cavity, tube high 160mm≤h≤175m separates the Maxwell equation of sapphire resonator cavity under the TE011 pattern;

(2) with the ansoft HFSS of high frequency simulation software the cavity of Theoretical Calculation is carried out simulation calculation;

(3) the needed sapphire resonator cavity of processing;

(4) on traditional active hydrogen atomic clock frame, it is done the maser oscillation experiment, realize maser self-sustained oscillation.

6. the manufacture method of sapphire resonator cavity according to claim 5 is characterized in that, the barrel radius a=87.5mm of the outer wire chamber tube of described sapphire resonator cavity; The high h=162.9mm of tube.

7. the manufacture method of sapphire resonator cavity according to claim 5 is characterized in that, the barrel radius a=85mm of the outer wire chamber tube of described sapphire resonator cavity; The high h=162.9mm of tube.

8. the manufacture method of sapphire resonator cavity according to claim 7 is characterized in that, the described upper and lower end face that also is included in described sapphire tube is respectively filled a SrTiO that 2mm is thick ₃Annulus.

9. according to the manufacture method of each described sapphire resonator cavity of claim 5-8, it is characterized in that the inwall that further is included in the sapphire tube in the step (3) carries out silver-plated.

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