JP2001304709A - Dilution refrigerating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce running costs and enable long time continuous operation by eliminating the use of exhaust pressure reduced liquid helium as in the case of the prior arts as a means for cooling 3 He gas to the proximity of 1 K in an initial cooling in a dilution refrigerating machine. SOLUTION: A small-sized mechanical refrigerating machine such as GM refrigerating machine or the like is used to cool 3 He has fed into a main body to several Kelvin by a vacuum pump in the initial cooling, and 3 He gas is further cooled to the proximity of 1 K through adiabatic expansion. As the structure for this process, parts other than the GM refrigerating machine is constituted as a rod-like unit as a whole, and the unit can be inserted into and removed from an inner tube in a heat insulated container.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid helium (3H
e, 4He) using a dilution refrigerator for continuously obtaining an ultra-low temperature of 1 to 10 ^-3 K.

[0002]

2. Description of the Related Art As is well known, a mixture of a liquid phase of 3He and a liquid phase of 4He is separated into two phases at a temperature of 0.8 K or less, and a dilute phase containing 6.4% of 3He at a low temperature. , 3He is 1
A dense phase containing 00% coexists. And 3He of rich phase
Is dissolved (diluted) in the dilute phase, heat is absorbed from the outside, and as a result, an extremely low temperature of 1 to 10 ^-3 K can be obtained. A refrigerator utilizing such a phenomenon is called a dilution refrigerator, and has recently been put to practical use.

The principle of the dilution refrigerator is described, for example, in Journal of the Physical Society of Japan, Vol. 37, No. 5, No. 409 (1982).
Pages 418 to 418 (Principles and Design Issues of 3He-4He Dilution Refrigerator I), 595-600 (3He-4H) of the Journal of the Physical Society of Japan, Vol. 37, No. 7, (1982).
The principle of the e-dilution refrigerator and problems in design II) are described, and the principle configuration is shown in FIG.

In FIG. 4, a first vacuum pump 1A is
This is for forcibly circulating He gas.
The 3He gas at a temperature of about 300K sent out from the vacuum pump 1A is supplied to the liquid 4H by the second vacuum pump 1B.
e is evacuated and evacuated and liquefied in a condenser (condenser) 3 which is in thermal contact with a 1K pot 2 kept at about 1.3K and further sent to a heat exchanger 6 in a fractionator 5 via an impedance 4. Can be This fractionator 5 has a 3
Utilizing the difference between the saturated vapor pressures of He and 4He, 4He-3
Although it is for selectively discharging 3He from the He mixture, 3He sent from the condenser 3 is heat-exchanged in the heat exchanger 6 in thermal contact with the fractionator 5, It is cooled to about 0.5-0.7K. Further, the 3He is cooled to about 100 mK in the heat exchanger 8 via the impedance 7 and sent to the mixing chamber 9. In the mixing chamber 9, the 100% 3He rich phase as described above and 4He-6.4% 3 in which 3He is dissolved in 4He.
The two layers are separated from the He dilute phase, and the lower layer becomes a dilute phase (4He-6.4% 3He) and the upper layer becomes a dense phase (3He phase) due to the density difference. And 3H sent to the rich phase
When e dissolves in the dilute phase, heat absorption occurs, as described above, and it is cooled to a very low temperature of the order of 10 mK. That is, since the mixing chamber 9 serves as a cold head as a refrigerator, if an object to be cooled (sample) is held in this portion, the sample can be cooled to the order of 10 mK.

[0005] The 3He concentration in the dilute phase of the mixing chamber 9 is maintained at 6.4%, while the 4He-3He in the fractionator 5 is maintained.
Since only 3He is gasified and discharged from the mixed solution due to the difference in saturated vapor pressure between 4He and 3He, the 3He concentration in the fractionator 5 becomes about 1% at 0.5 to 0.7K, Therefore, a concentration difference of 3He occurs between the dilute phase in the mixing chamber 9 and the liquid mixture in the fractionator 5, and 3He is drawn into the fractionator 5 from the dilute phase in the mixing chamber 9 due to a concentration gradient between the two. Rare, 100% in mixing room 9
The dissolution of 3He from the 3He rich phase to the lean phase will occur continuously. While 3He is drawn into the fractionator 5 from the mixing chamber 9, the 3He is transferred to the heat exchanger 8
To cool the above-mentioned 3He on the outward path side.

[0006] In the fractionator 5, as described above, due to the difference in the saturated vapor pressure, the 3H mixture is removed from the 4He-3He mixture.
Only e evaporates and is evacuated by the aforementioned vacuum pump 1A. The 3He sucked by the vacuum pump 1A is sent to the condenser 3 again and repeats the same process.

As described above, in the dilution refrigerator, 10
An ultra-low temperature of the order of mK can be obtained.

A simple dilution refrigerator utilizing such a principle is disclosed in "Cryog" published in the UK.
Enics "1993 Vol33, No9, p92
3 to 925, "One-day dilution r"
efrigator ". This simple dilution refrigerator is described in "Low Temperature Center Newsletter" No. 16 (January 1993)
This is also shown in “Prototype production of simple dilution refrigerator” on p.

FIG. 5 shows a schematic configuration of the simplified refrigerator according to the above proposal.

In FIG. 5, a liquid helium (normal liquid 4He) 14 as a refrigerant is injected into a bottomed cylindrical outer container 12 surrounded by an outer vacuum heat insulating layer 10, and this outer container A liquid helium decompression port 16 is provided in the upper part of the side wall of 12, and this decompression port 16 is led to a second vacuum pump 45. A cylindrical inner container 18 with a bottom is immersed in the liquid helium 14 in the outer container 12. A vacuum heat insulating layer 20 is provided on a lower wall portion (a portion immersed in the liquid helium 14) of the inner container 18, and a 3He outlet 21 is formed near the upper end of the inner container 18. ing.

Further, liquid helium (liquid phases 23 and 25 to be described later) is accommodated in a lower portion of the inner container 18, and a column / evacuation pipe 22 is provided in the liquid helium from above.
The hollow plunger 24 is immersed in a state where the plunger 24 is suspended. In a middle position of the column / evacuation pipe 22 (above the plunger 24 and above the liquid surface 23A), a good heat of copper or the like is used so that the column / evacuation pipe 22 penetrates vertically. A heat conduction block 26 made of a conductive material is fixed, and a 3He passage 27 penetrating the heat conduction block 26 vertically is formed in the heat conduction block 26. Due to the arrangement of the plunger 24 and the heat conduction block 26 as described above, the lower portion of the heat conduction block 26 in the inner container 18 is mixed with the mixing chamber 38 below the plunger 24 and the upper side of the plunger 24 and heat. It is divided into a fractionation chamber 40 below the conduction block 26. A gap 42 exists between the outer peripheral surface of the plunger 24 and the inner peripheral surface of the inner container 18.
Thus, the mixing chamber 38 and the fractionating chamber 40 communicate with each other, and the liquid level 23 </ b> A is located in the fractionating chamber 40. In addition, the heat conduction block 26 is in thermal contact with the inner surface of the inner container 18 via a copper spring member or the like (not shown), but at least a part around the heat conduction block 26 has the heat conduction block. There is an unavoidable gap 41 that connects the upper space of 26 with the lower space (fractionation chamber 40).

A 3He supply pipe 28 is inserted into the inner container 18 from above. The 3He supply pipe 28 is guided downward in the inner vessel 18 and is connected to a condenser (condenser) 30 made of a copper powder sintered porous body or the like that is integrated into the heat conduction block 26 described above. The lower outlet side of the condenser 30 is connected via a pipe 32 to a heat exchanger 34, which is also a coil tubular fractionation chamber.
The fractionation chamber heat exchanger 34 is immersed in the liquid helium (liquid phase 23) in the fractionation chamber 40. The lower exit side of the fractionation chamber heat exchanger 34 is connected to a heat exchanger 36 disposed in a gap 42 between the plunger 24 and the inner wall surface of the inner container 18. Is introduced into the mixing chamber 38, and 3He is introduced into the mixing chamber 38.
Is provided. Note that the above 3
A first vacuum pump 46 is interposed between the He outlet 21 and the 3He supply pipe 28 outside the inner container 18.

In the simple dilution refrigerator described above,
The space 15 between the inner surface of the outer container 12 and the outer surface of the inner container 18 has liquid helium (normal 4He) 1 as described above.
4 is injected, and the space 15 is evacuated and depressurized from the liquid helium depressurization port 16 by the second vacuum pump 45, and is kept at a low temperature near 1K. Therefore, this space 15 corresponds to the 1K pot 2 in FIG. 4 and contributes to cooling the heat conduction block 26 to about 1.3K.
On the other hand, in the fractionation chamber 40 of the inner container 18, 4He-10% 3He is set so that the liquid level 23A is located in the middle of the fractionation chamber 40.
Liquid phase 23 consisting of
It is filled with a liquid phase 25 consisting of a dense phase of 0% 3He and a dilute phase of 4He-6.4% 3He. 3H in such a state
e is led to the condenser 30 through the 3He supply pipe 28 by the vacuum pump 46, and is introduced into the 3He by the heat conduction block 26.
Is cooled to about 1.3K and liquefied. Liquefied 3H
e is further cooled through the fractionation chamber heat exchanger 34 and the heat exchanger 36, and is discharged from the discharge port 44 into the mixing chamber 38. In the mixing chamber 38, as already described for the mixing chamber 9 in FIG. 4, the discharged 3He dissolves in the upper 100% 3He dense phase, and a part of the rich phase 3He is lower 4He-6. Dissolves in a 4% 3He dilute phase. At this time, heat absorption occurs and an ultra-low temperature of the order of 10 mK is obtained.

On the other hand, since the mixing chamber 38 is in communication with the fractionating chamber 40, 3He in the dilute phase in the mixing chamber 38 is
However, since the fractionation chamber 40 has a low temperature of 1 K or less, only 3He is evaporated due to a large difference in saturated vapor pressure between 3He and 4He. The first vacuum pump 4 passes from the space above the inner container 18 through the passage 27 through the 3He outlet 21.
6 is exhausted. Accordingly, the 3He concentration in the liquid helium in the fractionation chamber 40 is reduced to about 1%, so that the 3He concentration in the fractionation chamber 40 (about 1%) and the 3He concentration in the dilute phase in the mixing chamber 38 are reduced. (6.4%), 3He atoms are separated from the dilute phase in the mixing chamber 38 by the separation chamber 40.
Led to. In addition, as the 3He concentration in the dilute phase in the mixing chamber 38 decreases, 3He continuously dissolves into the dilute phase from the 3He 100% rich phase.

In this way, 3He is continuously circulated, and the ultra-low temperature of the order of 10 mK is continuously maintained by the incorporation of 3He into the dilute phase in the mixing chamber 38.

The present inventors have already proposed in Japanese Patent No. 2689230 a dilution refrigerator having an improved part of the simple dilution refrigerator shown in FIG. 5 as described above. Typical functions are the same as those shown in FIG.

[0017]

The conventional dilution refrigerator as shown in FIG. 4 or 5 has the following problems.

That is, in the dilution refrigerator shown in FIG. 4, in order to obtain a low temperature of about 1.3K in the 1K pot 2, the liquid helium in the 1K pot 2 is evacuated and reduced by the second vacuum pump 1B. Therefore 1K pot 2
The liquid helium inside is gradually consumed and its amount is reduced. In the case of the dilution refrigerator shown in FIG.
Liquid helium is held in the space 15 between the inner surface of the container 2 and the inner container 18 and the space 15 is evacuated and decompressed by the second vacuum pump 45 to obtain a low temperature of about 1.3K. And the space portion 15 is the aforementioned 1
This corresponds to a K pot, but also in this case, the liquid helium in the space portion 15 gradually decreases due to the exhaust pressure reduction.

As described above, in the conventional dilution refrigerator, 3H
Since liquid helium is separately used to cool the e-gas to about 1.3K and the liquid helium is evacuated and decompressed, the liquid helium gradually decreases, so that liquid helium must be replenished as needed. In this case, it is generally difficult to operate the dilution refrigerator continuously for a long time because the operation of the dilution refrigerator must be stopped in order to supply liquid helium. There is a risk that it will interfere with the test.

In addition, since liquid helium is extremely expensive, the conventional diluting refrigerator that consumes it has a problem that the running cost must be extremely high.

In addition, various types of dilution refrigerators have been proposed or put into practical use in addition to the dilution refrigerators shown in FIGS. 4 and 5 described above. In many cases, such as when exchanging samples to be cooled to cryogenic temperatures, the vacuum must be broken to insulate the components of the dilution refrigerator. There was also a problem that required. Furthermore, in the conventional dilution refrigerator, the structure for sealing the parts constituting the dilution refrigerator at low temperature, especially the part that becomes extremely low temperature, becomes special and expensive, and work for sealing again at low temperature after exchanging the sample is required. There is also a problem that it is often complicated.

The present invention has been made in view of the above circumstances, and as a means for initially cooling 3He gas fed by a vacuum pump to near 1K, a liquid helium (liquid) which has been evacuated and depressurized as in the prior art is used. 4H
By not using e), continuous operation can be performed for a long time and running costs can be reduced. Further, handling is easy, and evacuation of the vacuum insulation portion after sample replacement does not require a long time. It is an object of the present invention to provide a dilution refrigerator that does not require low-temperature sealing at an ultra-low temperature part.

[0023]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, in the dilution refrigerator of the present invention, basically, 3H pumped into the dilution refrigerator main body by a vacuum pump.
In order to initially cool the e-gas to about several K, a small mechanical refrigerator represented by a GM refrigerator (Gifford-McMahon refrigerator) is used.
Considering that it is difficult to cool the condensing / liquefaction temperature of the 3He gas with the refrigerator, the 3He gas cooled to about several K by the GM refrigerator is further cooled to near 1K by adiabatic expansion.

Specifically, the dilution refrigerator according to the first aspect of the present invention has a vacuum pump for circulating 3He gas, and a dilution refrigerator body for receiving 3He gas sent by the vacuum pump, The dilution refrigerator main body includes a small mechanical refrigerator having a cooling head, a heat transfer block made of a good heat conductive material extended from the cooling head of the small mechanical refrigerator, and a heat transfer block thermally connected to the heat transfer block. And a main heat exchanger for cooling the 3He gas delivered from the vacuum pump and the 3He gas cooled by the main heat exchanger.
A JT expander for cooling the gas to below the condensation temperature of 3He gas by adiabatic expansion, and 3He by holding a 4He-3He mixed liquid and by a difference in vapor pressure between 4He and 3He.
A fractionator in which gas is sucked out toward the vacuum pump by the suction pressure of the vacuum pump, and a liquid 3He guided from the JT expander passes therethrough and passes through 4He-3H in the fractionator.
e, a fractionator heat exchanger for further cooling by the mixed liquid, and a forward path and a return path which are separated from each other so as to be capable of exchanging heat with each other, and which is guided from the fractionator heat exchanger to the forward path. Reciprocating heat exchanger for cooling the liquid 3He in the outward passage to a temperature of 0.8 K or less by the heat of the returning liquid 3He by the cool heat in the inbound passage, and the reciprocating heat exchanger on the bottom side through the reciprocating heat exchanger. A mixing chamber formed so as to communicate with the bottom side of the fractionator and into which the liquid 3He is introduced from the outward passage of the reciprocating heat exchanger and the liquid 4He is stored in advance. When the 3He gas sent from the vacuum pump passes through the main heat exchanger, it is cooled to a predetermined low temperature through the heat transfer block by the cold of the cooling head of the refrigerator, and further passes through the JT expander. Condensed and liquefied It is characterized in that the liquefied liquid 3He is configured to be fed into the mixing chamber through the outward side passage of the reciprocating heat exchanger.

As described above, in the dilution refrigerator according to the first aspect of the present invention, the 3He gas is cooled to about several K using a small mechanical refrigerator such as a GM refrigerator, and further cooled to a condensation temperature or lower by adiabatic expansion. Therefore, there is no need to use decompressed liquid helium for initial cooling, unlike the conventional dilution refrigerator shown in FIGS. 4 and 5. Therefore, long-term continuous operation is possible and running cost is reduced.

A dilution refrigerator according to a second aspect of the present invention structurally defines the dilution refrigerator according to the present invention.

According to a second aspect of the present invention, in the dilution refrigerator of the first aspect, the dilution refrigerator main body is provided inside a vacuum-insulated container from a cooling head chamber and a bottom of the cooling head chamber. A dilution freezing room extending downward is provided, and a hollow bottomed inner tube extending from the upper lid portion to the bottom of the dilution freezing room through the cooling head chamber is provided in the container, A part of the middle position of the inner tube in the vertical direction is made of a heat transfer part for the main heat exchanger by using a good heat transfer material, and the inner space of the inner tube has an inner space of a cooling head room and an inner space of a dilution freezing room. The cooling head of the small mechanical refrigerator is inserted from above into the cooling head chamber, and the heat transfer block extends from the cooling head to the heat transfer portion of the inner pipe. Yes A diluting refrigeration unit having a rod shape as a whole is inserted into the inner tube so as to be insertable and removable from above, and the diluting refrigeration unit discharges the 3He gas by receiving the 3He gas sent from the vacuum pump. A reflux port is formed at the upper end to guide the mixture to the vacuum pump, and the mixing chamber with a sample holder is formed at the lower end, and a forward passage from the receiving port to the mixing chamber. A main heat exchanger, a JT expander, a fractionator, and a return-side flow path from the mixing chamber to the inflow port, and interposed in the forward-side flow path and the return-side flow path.
The heat exchanger of the fractionator and the reciprocating heat exchanger are integrally formed, and between the heat transfer portion of the inner tube and the outward flow path in the dilution refrigeration unit at a position corresponding thereto. Are thermally contacted with each other to form the main heat exchanger at that portion.

In the dilution refrigerator according to the second aspect of the present invention, at the time of exchanging the sample, the dilution / refrigeration unit in the inner tube may be extracted and the sample exchanged, and the dilution / refrigeration unit may be inserted into the inner tube again. Replacement becomes extremely simple. In addition, since the sealing between the inner tube and the dilution refrigeration unit may be performed in the vicinity of the lid of the container, that is, in the vicinity of room temperature, no special and expensive low-temperature sealing is required,
The cost is reduced and the sealing operation is simplified.

According to a third aspect of the present invention, in the dilution refrigerator of the second aspect, the return path from the mixing chamber to the fractionator has a rod-like shape as a whole that can be inserted into and removed from the inner tube. Is formed between the outer surface of the dilution refrigeration unit and the inner peripheral surface of the inner tube.

In the dilution refrigerator according to the third aspect of the present invention, the lower portion of the space inside the inner tube is 4He.
The + 3He mixed liquid will be filled, and the upper part will be filled with 3He gas. Therefore, except for a part of the dilution refrigeration unit (for example, a part of the reciprocating heat exchanger), there is no need to perform vacuum insulation particularly inside the inner tube. Does not take a long time.

According to a fourth aspect of the present invention, in the dilution refrigerator of the first aspect, between the main heat exchanger and the JT expander in the outward flow path, cold heat in the return flow path is received. The heat exchanger for pre-cooling before JT expansion is interposed.

In the dilution refrigerator according to the fourth aspect of the present invention, since the 3He gas cooled by the main heat exchanger is further cooled by the low-temperature 3He gas on the return path side, cold heat is effectively used. Thus, the overall cooling efficiency can be increased.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION

[0034]

FIG. 1 shows the basic structure of a dilution refrigerator according to the present invention.

In FIG. 1, reference numeral 51 denotes a vacuum pump for circulating 3He gas. The 3He gas (usually room temperature) sent out by the vacuum pump 51 is diluted through a liquid nitrogen trap 53 and a supply pipe 55. It is sent to the receiving port 59 of the refrigerator main body 57. Here, the liquid nitrogen trap 53 is supplied with 3He pumped from the vacuum pump 51.
This is for removing oil and the like from the gas. In the dilution refrigerator main body 57, a forward flow path 63 for guiding the 3He gas through the receiving port 59 to a mixing chamber 61, which will be described later, and a 3He gas from the mixing chamber 61 to the reflux port 64 (provided that the 3He gas is introduced). In the lower section, a return path 65 for the liquid 4He is provided). Further, in the forward passage 63 and the backward passage 65, as will be described later, a main heat exchanger 67, a pre-JT expansion pre-cooling heat exchanger 69, a JT expander 71, a fractionator 73, The fractionator heat exchanger 75 and the reciprocating heat exchanger 77 (the forward passage 77A and the backward passage 77B) are interposed.

The dilution refrigerator main body 57 has, for example, 4.2
A small mechanical refrigerator (hereinafter referred to as a GM refrigerator) 79 such as a GM refrigerator that generates a low temperature of about K is provided, and a cooling head 79A of the GM refrigerator 79 is provided. A heat transfer block 81 made of a good heat transfer material such as copper is horizontally extended from a cooling head 79A of the dilution refrigerator main body 57 from above, and a tip end of the heat transfer block 81 is connected to the outward passage 63. It is thermally connected to the heat transfer section 67A of the provided main heat exchanger 67, and cools 3He flowing in the outward passage 63 to about 4.2K. In the illustrated example, the heat transfer portion 67A of the main heat exchanger 67 is configured to be in thermal contact with the return passage 65.

Further, the outlet side of the main heat exchanger 67 in the outward passage 63 is led to a pre-JT expansion pre-cooling heat exchanger 69. The pre-cooling heat exchanger 69 is for pre-cooling the 3He gas to, for example, about 2.6K before the adiabatic expansion of the 3He gas by the JT expander 71, and flows in the return passage 65. In order to receive the cool heat of the returning 3He gas, it is thermally connected to the return path 65.

The outlet side of the main heat exchanger 69 in the outward passage 63 is led to the JT expander 71. The JT expander 71 cools the 3He gas to a temperature lower than its condensing temperature, for example, about 1.5K by Joule-Thomson expansion to condense and liquefy the 3He gas. 3H on the return path flowing through the flow path 65
In order to utilize the cold heat of the e-gas, it is thermally connected to the return path 65.

The JT expander 7 in the outward passage 63
The outlet side of 1 is a fractionator heat exchanger 7 disposed in the fractionator 73.
It is led to 5. The fractionator heat exchanger 75 is for cooling the forward 3He gas to, for example, about 1.1K by the 4He-3He mixed liquid in the fractionator 73 as will be described later. 4He- in the vessel 73
It is provided so as to be in thermal contact with the 3He mixed liquid.

The outlet side of the fractionator heat exchanger 75 in the outward passage 63 is led to the outward passage 77 A of the reciprocating heat exchanger 77. The reciprocating heat exchanger 77 includes a forward path 77A and a return path 77B. Although the forward path 77A and the return path 77B are structurally separated from each other, they are thermally separated. The liquid 3He passing through the outward passage 77A is arranged so as to be capable of exchanging heat with each other, and is cooled to a low temperature of 0.8K or less, for example, about 100 mK by the 4He + 3He mixed liquid in the return passage 77B. It is configured.

Further, the outlet of the forward passage 77A of the reciprocating heat exchanger 77 in the forward passage 63 is led to the upper part of the mixing chamber 61. The mixing chamber 61 has an outlet 6 at its bottom.
1A, in which a liquid 4
He is stored, and the liquid 3He guided from the outward passage 63 is mixed with the liquid 4He. 4 and 5, two phases are separated as a dilute phase (lower layer) 62A containing about 6.4% of 3He and a 100% rich phase (upper layer) 62B containing 3He, and the two-phase separation in the rich phase 62B is performed. When 3He dissolves in the dilute phase 62A, a very low temperature of the order of 10 mK, for example, a very low temperature of about 60 mK is obtained.
Therefore, by providing a sample holder (not shown) in the mixing chamber 61, the sample can be cooled to, for example, about 60 mK.

From the outlet 61 A at the bottom of the mixing chamber 61, the above-mentioned return-side flow path 65 is led upward toward the reflux port 64. A return path 77B of the reciprocating heat exchanger 77 is provided at a position closest to the mixing chamber 61 in the return path 65.
The outlet side of B is guided to the bottom of the fractionator 73, and the upper part of the fractionator 73 is guided to the reflux port 64,
The suction is performed by the vacuum pump 51. Here, the 4He-3He mixed liquid is held in the fractionator 73, but the 3He gas is selectively discharged due to the difference in saturated vapor pressure between 3He and 4He. Then, this 3He gas is again sent to the receiving port 59 of the dilution refrigerator main body 57 by the vacuum pump 51 through the recirculation port 64.

As described above, in the dilution refrigerator according to the embodiment of the present invention shown in FIG. 1, the 3He gas sent into the dilution refrigerator main body 57 by the vacuum pump 51 is GM.
Cooled to about 4.2K by the refrigerator 79, further cooled to about 2.6K in the pre-cooling heat exchanger 69, and subsequently cooled to about 1.5K below the condensing temperature in the JT expander 71 to liquefy, The liquid 3He is cooled to about 1.1K in the fractionator heat exchanger 75, further cooled to about 100mK in the outward passage 77A of the reciprocating heat exchanger 77, and finally in the mixing chamber 61 at a very low temperature of the order of mK. For example, a very low temperature of 60 mK can be obtained.

Next, FIG. 2 shows an embodiment embodying the principle configuration shown in FIG.

In FIG. 2, a container 83 constituting the dilution refrigerator main body 57 has a double wall structure of an outer wall 83A and an inner wall 83B.
The space inside 3B is divided into two chambers, an upper cooling head chamber 87A and a lower dilution freezing chamber 87B. The lower dilution freezing chamber 87B has a smaller diameter than the upper cooling head chamber 87A, and is formed so as to hang downward from a part of the bottom of the cooling head chamber 87A. Here, the outer wall 8
The space 85 between the inner wall 3B and the inner wall 83B and the inner chamber of the container 83 (ie, the cooling head chamber 87A and the dilution freezing chamber 87)
B) are interconnected and are vacuum insulated.

Further, a container 8 is provided in the cooling head chamber 87A.
The second-stage cooling head 79A of the GM refrigerator 79 is vertically inserted from the lid 83C at the upper end of the third GM refrigerator 79. Where G
As the M refrigerator 79, the first which generates a low temperature of about 20K
Stage (first stage) cooling head 79B, 4.2K
A two-stage (two-stage) type having a second-stage (second-stage) cooling head 79A that generates a low temperature is used. The first-stage cooling head 79B is an inner wall 83B of the container 83. , And the second stage cooling head 79A is inserted into the cooling head chamber 87A.
At the lower end of the second stage cooling head 79A, a horizontal thick plate-like heat transfer block 81 made of a good heat transfer material such as copper is fixed.
B extends horizontally to a position above the upper end opening.

In the container 83, an inner tube 89 having a hollow cylindrical shape with a bottom as a whole is vertically inserted from above the lid 83C. The inner pipe 89 penetrates vertically through the cooling head chamber 87A, its lower part is inserted into the dilution freezing chamber 87B, and its lower end is located near the bottom of the dilution freezing chamber 87B. A portion of the inner tube 89 corresponding to the heat transfer block 81 in the cooling head chamber 87A is locally a first heat transfer portion 89A made of a good heat transfer material such as copper.
The portion corresponding to the inner wall 83B of the container 83 is also locally a second heat transfer portion 89B made of a good heat transfer material such as copper. The first heat transfer section 89A and the heat transfer block 81 are mechanically coupled to each other and thermally connected,
The second heat transfer portion 89B and the inner wall 83B are also mechanically connected to each other and are also thermally connected. These heat transfer portions 89A and 89B are configured such that not only are their outer peripheral surfaces connected to the heat transfer block 81 or the inner wall 83B, but also their inner peripheral surfaces are exposed to the inner space 89C of the inner tube 89. . The inner pipe 89 is attached so that its inner space 89C is airtightly isolated from the cooling head chamber 87A and the dilution freezing chamber 87B.

Further, a dilution refrigeration unit 91 is inserted into the inner tube 89 from above so as to be able to be inserted and withdrawn. The dilution refrigeration unit 91 has a vertical rod shape as a whole, and details thereof are shown in FIG.

In FIG. 3, the dilution refrigeration unit 91 comprises:
The lid portion 91A and the upper-stage hollow tube portion 91 are directed downward from above.
B, a configuration in which a second heat transfer block 91C, an intermediate hollow tube portion 91D, a first heat transfer block 91E, a lower hollow tube portion 91F, and a plunger 91G having an empty space 91H formed therein are connected and fixed to each other in this order. In addition, the plunger portion 9 is positioned near the central axis from above the lid portion 91A.
An exhaust pipe 91I penetrating up to 1G is provided. The upper hollow tube portion 91B of the dilution refrigeration unit 91 has an upper portion protruding above the lid portion 83C of the container 83, and a flange portion 93 is formed at that portion. Sealed. This sealing does not need to be a special low-temperature sealing as described later,
Around normal temperature is sufficient.

The above-described receiving port 59 (see FIG. 1) is formed in the lid 91A at the upper end of the dilution refrigeration unit 91. From this receiving port 59, the outward path side corresponding to the outward path channel 63 (see FIG. 1). The flow pipe 95 is inserted into the unit 91. The above-described reflux port 64 is formed on a side surface of the upper hollow tube portion 91B. The receiving port 59 and the recirculation port 64 are connected to a vacuum pump 51 for circulating 3He gas and a liquid nitrogen trap 53 as shown in FIG.

The outgoing-side flow path pipe 95 passes through the inside of the upper hollow tube portion 91B from above and is provided in the second heat transfer block 91C. It reaches the upper end of 101. Second heat transfer block 91C
Is made of a good heat transfer material such as copper, and is made to be in thermal contact with the sub heat exchanger 101;
As will be described later, it is formed so as to vertically penetrate a communication hole 97 corresponding to a part of the return path 65 (see FIG. 1), and the unit 91 is inserted into the inner pipe 89. The outer peripheral surface of the second heat transfer block 91C is configured to be in thermal contact with the inner peripheral surface of the second heat transfer portion 89B on the inner tube 89 side. Specifically, for example, the second heat transfer section 8
A heat transfer spring member 99 made of a good heat transfer elastic material such as, for example, belt-shaped beryllium copper is attached to one of the inner peripheral surface of 9B and the outer peripheral surface of the second heat transfer block 91C. What is necessary is just to comprise so that the heat-transfer spring member 99 may contact the other surface.

Further, the outlet side (lower end) of the sub heat exchanger 101 in the outward passage pipe 95 is provided in the first heat transfer block 91E below the intermediate hollow pipe portion 91D, for example. It reaches the upper end of the main heat exchanger 67 made of a copper powder sintered porous body or the like. The first heat transfer block 91E is made of a good heat transfer material such as copper.
7, and is formed so as to penetrate vertically through a communication hole 103 corresponding to a part of the return path 65 (see FIG. 1), as described later. With the unit 91 inserted into the inner tube 89, the outer peripheral surface of the first heat transfer block 91E is in thermal contact with the inner peripheral surface of the first heat transfer portion 89A on the inner tube 89 side. Have been. Specifically, for example, one of the inner peripheral surface of the first heat transfer portion 89A and the outer peripheral surface of the first heat transfer block 91E has a good heat transfer elastic material such as a belt-like beryllium copper. A heat transfer spring member 105 made of
What is necessary is just to comprise so that the heat transfer spring member 105 may contact the other surface.

Subsequently, the outlet side (lower end side) of the main heat exchanger 67 in the outward flow path pipe 95 is connected to the lower hollow pipe section 91.
F, and a pre-cooling heat exchanger 69 and a JT expander 71 disposed in the space inside the lower hollow tube portion 91F.
(See FIG. 1) in that order.

Further, JT in the lower hollow tube portion 91F
A partition 107 is provided below the expander 71 to divide the partition into upper and lower parts, and an umbrella-shaped or inverted cup-shaped 3He gas collecting member 109 hangs down from the partition 107. The upper end of the inner space of the 3He gas collecting member 109 is communicated with the space above the partition wall 107 in the lower hollow tube portion 91F via the communication tube 111 constituting a part of the return path 65. I have.

The lower end of the lower hollow tube portion 91F is connected to the upper end of the plunger portion 91G. However, a cutout communicating portion 113 for communicating a space on the outer peripheral side of the plunger portion 91G with a lower inner space of the lower hollow tube portion 91F is formed at a lower end portion of the lower hollow tube portion 91F. Here, a portion below the partition wall 107 in the lower hollow tube portion 91F and above the upper end of the plunger portion 91G constitutes the above-described fractionator 73 (see FIG. 1). 7
The liquid level 115 of the 4He + 3He mixed liquid is located in 3;
The 3He gas collecting member 109 described above has a liquid level 11 below.
It is positioned so that it is immersed below 5.
Further, the JT expander 71 in the outward passage channel piping 95 is also provided.
Exit side (lower end side) passes through partition 107 and fractionator 73
And a heat exchanger 75, for example, a coiled tubular fractionator provided at a position below the liquid level 115 of the fractionator 73.
Is led to.

Further, the outlet side (lower end side) of the fractionator heat exchanger 75 in the outward passage pipe 95 is, for example, a reciprocating heat exchanger outward passage 77A wound on a coil around the outer periphery of the plunger portion 91G. (See FIG. 1). The plunger part 91G has a vacuum chamber 91H for vacuum heat insulation formed inside, and a mixing chamber 61 (see FIG. 1) opened to the lower side with a partition wall 119 formed below the hollow chamber 91H. It is. And vacant room 91H of plunger part 91G
Is evacuated by an external vacuum pump 121 via the above-described exhaust pipe 91I connected to the upper end thereof.

Here, the space on the outer peripheral side of the plunger portion 91G (the gap between the inner peripheral surface of the inner pipe 89) and the forward passage 65
The return passage 77B of the reciprocating heat exchanger 77 interposed between the return heat exchanger 77 (see FIG. 1) is formed. Therefore, the outward passage 77A
Is in thermal contact with the return path 77B.

The lower end (outlet side) of the reciprocating heat exchanger outward passage 77A in the outward passage flow pipe 95 is connected to the plunger 9.
It is open to the upper part of the mixing chamber 61 through the 1G partition wall 119. A sample holder 123 for holding a sample to be cooled is provided in the mixing chamber 61.

Here, in the examples of FIGS. 2 and 3, the return path 65 (see FIG. 1) extends from the lower end of the plunger portion 91G (the lower end of the mixing chamber 61) to the outer peripheral surface of the plunger portion 91G and the inner pipe 89. Through the space between the inner peripheral surface (return path 77B of the reciprocating heat exchanger 77) and the notch communicating portion 113, the space below the partition 107 in the lower hollow tube portion 91F (fractionator). 73), further passes through the space above the partition 107 in the lower hollow tube portion 91F (the space where the JT expander 71 and the pre-cooling heat exchanger 69 are located) through the communication tube 111, and the first. Communication hole 10 of heat transfer block 91E
3, the space reaches the inner space of the middle hollow tube portion 91D, and further from the inner space of the upper hollow tube portion 91B to the reflux port 64 through the communication hole 97 of the second heat transfer block 91C.

In the embodiment shown in FIGS. 2 and 3, when the dilution refrigeration unit 91 is inserted into the inner pipe 89, the first heat transfer block 91E and the second heat transfer block 91C are used. Are the first heat transfer sections 8 on the inner pipe 89 side, respectively.
9A, and is thermally connected to the second heat transfer section 89B. Therefore, the 3He gas at room temperature or so introduced from the receiving port 59 is supplied to the first cooling head 79B of the GM refrigerator 79B first.
By the cold heat of about 0K, it is preliminarily cooled to about 20K in the sub heat exchanger 101 via the second heat transfer section 89B and the second heat transfer block 91C.
9, the first heat transfer section 89A and the first heat transfer block 9 are cooled by about 4.2K of the second stage cooling head 79A.
It will be cooled down to about 4.2K by the main heat exchanger 67 via 1E. Thereafter, the 3He gas passes through the pre-cooling heat exchanger 69 and the JT expander 71, is cooled to a temperature of, for example, about 1.5 K or less, which is lower than the condensation temperature, as described above, and passes through the fractionator heat exchanger 75. The reciprocating heat exchanger 7 is cooled to about 1.1K and further provided above the plunger portion 91G.
7 is cooled to about 100 mK in the outward passage 77A, and reaches the mixing chamber 61, where the mixing chamber 61 is already in a rough state.
In 100% 3He rich phase and 4He + 6.4% 3
An ultra-low temperature of the order of 10 mK, for example, an ultra-low temperature of about 60 mK can be obtained by the action with the He dilute phase.

Here, the sample exchange is performed in the dilution refrigeration unit 91.
Can be pulled out from the inner tube 89. Then, after exchanging the sample, the dilution refrigeration unit 91 is inserted into the inner tube 89, and the flange 8 at the upper end of the inner tube 89 is inserted.
It is sufficient to seal the space between 9D and the flange portion 93 of the dilution refrigeration unit 91. However, since this sealed portion is always in an environment near room temperature, there is no need to perform special low-temperature sealing, and room-temperature sealing is not required. Is sufficient.

In a portion inside the inner pipe 89, vacuum insulation is performed by the vacant chamber 9
1H only, the vacuum insulation of this portion does not need to be broken at the time of sample exchange, that is, at the time of insertion / removal of the dilution / refrigeration unit 91. Therefore, a long time is required for evacuation for heat insulation at the time of material exchange. No need.

In the above description, the GM refrigerator is used as the small mechanical refrigerator. However, if a small mechanical refrigerator that does not consume liquid helium, for example, a pulse tube refrigerator or the like may be used. Is possible.

[0064]

As is apparent from the above description, according to the dilution refrigerator of the first aspect, the 3He gas is cooled to about several K using a small mechanical refrigerator such as a GM refrigerator. Since it is cooled to the condensing temperature by adiabatic expansion and liquefied, there is no need to use decompressed liquid helium for initial cooling as in a conventional dilution refrigerator, and therefore, it is much longer continuous than before. Driving becomes possible and running costs are significantly reduced.

According to the dilution refrigerator of the second aspect of the invention, at the time of exchanging the sample, the dilution / refrigeration unit in the inner tube is taken out, the sample is exchanged, and the dilution / refrigeration unit is inserted into the inner tube again. Is extremely simple, and the sealing between the inner tube and the dilution refrigeration unit can be performed in the vicinity of the lid of the container, that is, at a portion near room temperature, so that a special and expensive low-temperature sealing is not required, The cost is reduced and the sealing operation is simplified.

According to the dilution refrigerator of the third aspect of the invention, the lower part of the space inside the inner tube is filled with the mixed liquid of 4He + 3He, and the upper part is filled with the gas of 3He. It is not necessary to perform vacuum insulation, especially inside the inner tube, except for a part of the inside (for example, the part of the reciprocating heat exchanger). Time is not required, so that the efficiency of an ultra-low temperature test or the like using a dilution refrigerator can be improved.

Further, according to the dilution refrigerator of the fourth aspect of the present invention, the forward 3He gas cooled by the main heat exchanger is further cooled by the returning low-temperature 3He gas on the backward path, so Can be used effectively to increase the overall cooling efficiency.

[Brief description of the drawings]

FIG. 1 is a block diagram showing in principle one embodiment of a dilution refrigerator of the present invention.

FIG. 2 is a cutaway front view showing a specific configuration of an embodiment of the dilution refrigerator of the present invention.

FIG. 3 is a longitudinal sectional view of a dilution refrigeration unit used in the dilution refrigerator of FIG. 2;

FIG. 4 is a block diagram showing the principle of a conventional dilution refrigerator.

FIG. 5 is a schematic view showing an example of a conventional simple dilution refrigerator.

[Explanation of symbols]

 51 Vacuum pump 57 Dilution refrigerator main body 59 Receiving port 61 Mixing chamber 63 Outgoing flow path 64 Reflux port 65 Return flow path 67 Main heat exchanger 69 Pre-cooling heat exchanger before JT expansion 71 JT expander 73 Fractionator 75 Fractionator heat exchanger 77 Reciprocating heat exchanger 77A Outbound path 77B Inbound path 79 GM refrigerator 79A Cooling head 81 Heat transfer block 83 Container 89 Inner tube 89A Heat transfer unit 91 Dilution refrigeration unit 91E Heat transfer block 123 Sample holding Department

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[Procedure amendment]

[Submission date] June 30, 2000 (2006.3.3)
0)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction contents]

A 3He supply pipe 28 is inserted into the inner container 18 from above. The 3He supply pipe 28 is guided downward in the inner vessel 18 and is connected to a condenser (condenser) 30 made of a copper powder sintered porous body or the like that is integrated into the heat conduction block 26 described above. Further, the lower outlet side of the condenser 30 is connected to a coil-shaped fractionating-chamber heat exchanger 34 via a pipe 32. The fractionation chamber heat exchanger 34 is immersed in the liquid helium (liquid phase 23) in the fractionation chamber 40. The plunger 24 and the inner container 18
The lower end of the heat exchanger 36 is guided to the mixing chamber 38, and 3He is introduced into the mixing chamber 38. A discharge port 44 for discharging is provided. The inner container 18 is provided between the 3He outlet 21 and the 3He supply pipe 28 described above.
A first vacuum pump 46 is interposed outside the device.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

In the simple dilution refrigerator described above,
The space 15 between the inner surface of the outer container 12 and the outer surface of the inner container 18 has liquid helium (normal 4He) 1 as described above.
4 is injected, and the space 15 is evacuated and depressurized from the liquid helium depressurization port 16 by the second vacuum pump 45, and is kept at a low temperature near 1K. Therefore, this space 15 corresponds to the 1K pot 2 in FIG. 4 and contributes to cooling the heat conduction block 26 to about 1.3K.
On the other hand, in the fractionation chamber 40 of the inner container 18, 4He-10% 3He is set so that the liquid level 23A is located in the middle of the fractionation chamber 40.
Liquid phase 23 consisting of
It is filled with a liquid phase 25 consisting of a dense phase of 0% 3He and a dilute phase of 4He-6.4% 3He. 3H in such a state
e is guided to the condenser 30 through the 3He supply pipe 28 by the first vacuum pump 46, and 3He is cooled to about 1.3K and liquefied by the heat conduction block 26. The liquefied 3He is further cooled through the fractionation chamber heat exchanger 34 and the heat exchanger 36, and is discharged from the discharge port 44 into the mixing chamber 38. In the mixing chamber 38, as already described for the mixing chamber 9 in FIG. 4, the discharged 3He dissolves in the upper 100% 3He rich phase, and
Part of He dissolves in the lower 4He-6.4% 3He dilute phase. At this time, heat absorption occurs and an ultra-low temperature of the order of 10 mK is obtained.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

On the other hand, since the mixing chamber 38 is in communication with the fractionating chamber 40, 3He in the dilute phase in the mixing chamber 38 is
However, since the fractionation chamber 40 has a low temperature of 1 K or less, only 3He is evaporated due to a large difference in saturated vapor pressure between 3He and 4He. The first vacuum pump 4 passes from the space above the inner container 18 through the passage 27 through the 3He outlet 21.
6 is exhausted. Accordingly, the 3He concentration in the liquid helium in the fractionation chamber 40 is reduced to about 1%, so that the 3He concentration in the fractionation chamber 40 (about 1%) and the 3He concentration in the dilute phase in the mixing chamber 38 are reduced. (6.4%), 3He atoms are extracted from the dilute phase in the mixing chamber 38 by the fractionation chamber 40.
Led to. In addition, as the 3He concentration in the dilute phase in the mixing chamber 38 decreases, 3He continuously dissolves into the dilute phase from the 3He 100% rich phase.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0043

[Correction method] Change

[Correction contents]

As described above, in the dilution refrigerator according to the embodiment of the present invention shown in FIG. 1, the 3He gas sent into the dilution refrigerator main body 57 by the vacuum pump 51 is GM.
It is cooled to about 4.2K by the refrigerator 79,
It is cooled to about 2.6K in the pre-T expansion precooling heat exchanger 69, then cooled to about 1.5K below the condensing temperature in the JT expander 71 and liquefied, and the liquid 3He is a fractionator heat exchanger. 75, is cooled to about 1.1K, and further cooled in the forward passage 77A of the reciprocating heat exchanger 77.
It is cooled to about 0 mK, and finally an ultra-low temperature of the order of mK, for example, an ultra-low temperature of 60 mK can be obtained in the mixing chamber 61.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0049

[Correction method] Change

[Correction contents]

In FIG. 3, the dilution refrigeration unit 91 comprises:
The lid portion 91A and the upper-stage hollow tube portion 91 are directed downward from above.
B, a second heat transfer block 91C, an intermediate hollow tube portion 91D, a first heat transfer block 91E, a lower hollow tube portion 91F, and a plunger portion 91G having an empty space 91H formed therein are connected and fixed to each other in this order. Further, an exhaust pipe 91I penetrating from above the lid portion 91A to the plunger portion 91G is provided near the central axis of the whole. The upper portion of the upper hollow tube portion 91B of the dilution refrigeration unit 91 projects upward from the lid portion 83C of the container 83,
A flange portion 93 is formed at that portion, and the inner tube 89 is formed.
Is sealed with respect to the upper end flange portion 89D. Note that this sealing does not need to be a special low-temperature sealing as described later, and is sufficient at around normal temperature.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0056

[Correction method] Change

[Correction contents]

Further, the outlet side (lower end side) of the fractionator heat exchanger 75 in the outward passage pipe 95 is, for example, a reciprocating heat exchanger outward passage 77A wound in a coil shape on the outer periphery of the plunger portion 91G. (See FIG. 1). The plunger part 91G has a vacuum chamber 91H for vacuum heat insulation formed inside, and a mixing chamber 61 (see FIG. 1) opened to the lower side with a partition wall 119 formed below the hollow chamber 91H. It is. And vacant room 91H of plunger part 91G
Is evacuated by an external vacuum pump 121 via the above-described exhaust pipe 91I connected to the upper end thereof.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0057

[Correction method] Change

[Correction contents]

Here, the space on the outer peripheral side of the plunger portion 91G (the gap between the inner peripheral surface of the inner pipe 89) is formed in the return passage 65.
The return passage 77B of the reciprocating heat exchanger 77 interposed between the return heat exchanger 77 (see FIG. 1) is formed. Therefore, the outward passage 77A
Is in thermal contact with the return path 77B.

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0060

[Correction method] Change

[Correction contents]

In the embodiment shown in FIGS. 2 and 3, when the dilution refrigeration unit 91 is inserted into the inner pipe 89, the first heat transfer block 91E and the second heat transfer block 91C are used. Are the first heat transfer sections 8 on the inner pipe 89 side, respectively.
9A, and is thermally connected to the second heat transfer section 89B. Therefore, the 3He gas at room temperature or so introduced from the receiving port 59 is supplied to the first cooling head 79B of the GM refrigerator 79B first.
By the cold heat of about 0K, it is preliminarily cooled to about 20K in the sub heat exchanger 101 via the second heat transfer section 89B and the second heat transfer block 91C.
9, the first heat transfer section 89A and the first heat transfer block 9 are cooled by about 4.2K of the second stage cooling head 79A.
It will be cooled down to about 4.2K by the main heat exchanger 67 via 1E. Thereafter, the 3He gas passes through the pre-cooling heat exchanger 69 and the JT expander 71, is cooled to a temperature of, for example, about 1.5 K or less, which is lower than the condensation temperature, as described above, and passes through the fractionator heat exchanger 75. The reciprocating heat exchanger 7 is cooled to about 1.1K and further provided above the plunger portion 91G.
7 is cooled to about 100 mK in the outward passage 77A, and reaches the mixing chamber 61.
In 100% 3He rich phase and 4He + 6.4% 3
An ultra-low temperature of the order of 10 mK, for example, an ultra-low temperature of about 60 mK can be obtained by the action with the He dilute phase.

[Procedure amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0067

[Correction method] Change

[Correction contents]

According to the dilution refrigerator of the fourth aspect of the present invention, the forward 3He gas cooled by the main heat exchanger is further cooled by the return low-temperature 3He gas on the backward path. The overall cooling efficiency can be increased by effectively utilizing the cold heat.

[Procedure amendment 10]

[Document name to be amended] Statement

[Correction target item name] Explanation of sign

[Correction method] Change

[Correction contents]

[Description of Signs] 51 Vacuum pump 57 Dilution refrigerator main body 59 Reception port 61 Mixing chamber 63 Outgoing side flow path 64 Reflux port 65 Return path side flow path 67 Main heat exchanger 69 JT expansion pre-cooling heat exchanger 71 JT expander 73 fractionator 75 fractionator heat exchanger 77 reciprocating heat exchanger 77A forward path 77B return path 79 GM refrigerator 79A cooling head 81 heat transfer block 83 container 89 inner tube 89A first heat transfer section 91 dilution refrigeration Unit 91E First heat transfer block 123 Sample holder

[Procedure amendment 11]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG.

FIG. 2

FIG. 3

FIG. 4

FIG. 5

Claims (4)

[Claims] 1. A small machine having a vacuum pump for circulating 3He gas and a dilution refrigerator main body for receiving 3He gas sent by the vacuum pump, wherein the dilution refrigerator main body is provided with a cooling head. -Type refrigerator, a heat transfer block made of a good heat conductive material extended from a cooling head of the small mechanical refrigerator, and 3He gas which is in thermal contact with the heat transfer block and is sent from the vacuum pump. A main heat exchanger for cooling, a JT expander for cooling the 3He gas cooled by the main heat exchanger to a temperature lower than the condensation temperature of the 3He gas by adiabatic expansion, and holding a 4He-3He mixed liquid; 4He and 3
A fractionator in which 3He gas is sucked toward the vacuum pump by the suction pressure of the vacuum pump due to a difference in vapor pressure with He, and a liquid 3He guided from the JT expander passes through the fractionator. A fractionator heat exchanger for further cooling with a 4He-3He mixed liquid in the vessel, a forward path and a return path which are isolated from each other so as to be capable of exchanging heat with each other; Liquid 3 led from exchanger
The reciprocating heat exchanger for passing He through the return path to cool the liquid 3He in the outward path to a temperature of 0.8 K or less by the cool heat of the return path, and the bottom part is connected to the reciprocating heat exchanger through the return path. A mixing chamber formed so as to communicate with the bottom side of the fractionator, the liquid 3He being introduced from the outward passage of the reciprocating heat exchanger, and the liquid 4He being previously stored therein; The 3He gas delivered from the chiller is cooled to a predetermined low temperature through the heat transfer block by the cold heat of the cooling head of the refrigerator when passing through the main heat exchanger, and further passes through the JT expander to condense and liquefy. Wherein the liquefied liquid 3He is sent to the mixing chamber through the outward passage of the reciprocating heat exchanger. 2. The dilution refrigerator according to claim 1, wherein the dilution refrigerator main body is provided inside a vacuum-insulated container,
A cooling head chamber and a dilution freezing chamber extending downward from the bottom of the cooling head chamber are provided, and in the container,
A hollow bottomed inner tube extending from the upper lid portion to the bottom of the dilution freezing room through the cooling head chamber is provided, and a portion of the inner tube in the vertical direction is mainly made of a good heat transfer material. The heat transfer section for a heat exchanger, and the inner space of the inner tube is hermetically isolated from the room space of the cooling head room and the room space of the dilution refrigeration room. The cooling head of the type refrigerator is inserted, the heat transfer block extends from the cooling head to the heat transfer portion of the inner tube, and further, in the inner tube, a dilution refrigeration unit having a rod-like shape as a whole is located upward. The dilution refrigeration unit has a receiving port for receiving the 3He gas sent from the vacuum pump and a return port for discharging the 3He gas and guiding it to the vacuum pump. Is formed at the upper end, and the mixing chamber with the sample holding section is formed at the lower end, and further, from the receiving port to the mixing chamber, from the outward flow path and from the mixing chamber to the outlet. A main heat exchanger, a JT expander, a fractionator, a fractionator heat exchanger, and a reciprocating heat exchanger so as to be interposed in the forward flow path and the return flow path. The heat transfer portion of the inner tube and the forward passage in the dilution refrigeration unit at a position corresponding to the heat transfer portion are in thermal contact with each other, and the main heat is applied to that portion. A dilution refrigerator, wherein an exchanger is formed. 3. The dilution refrigerator according to claim 2, wherein the return-side flow path from the mixing chamber to the fractionator is:
A dilution refrigerator, wherein the dilution refrigerator is formed between an outer surface of a rod-shaped dilution refrigeration unit as a whole which can be inserted into and removed from an inner tube and an inner peripheral surface of the inner tube. 4. The pre-cooling JT expansion pre-cooling heat exchanger that receives cold heat in a return flow path between a main heat exchanger and a JT expander in the forward flow path in the dilution refrigerator according to claim 1. A dilution refrigerator having a vessel interposed.