Coaxial dual inlet valve for pulse tube cryocoolers

Abstract

A Gifford-McMahon (GM) type dual inlet pulse tube system for providing cooling at low temperatures is provided. The system has a coaxial dual inlet valve comprising: a base having an adjustable port, a fixed needle partially engaged at one end of the adjustable port, an adjustable needle partially engaged at the other end of the adjustable port, and a body for accommodating the base, the fixed needle, and the adjustable needle. The base is configured to be adjustable in an axial direction. The adjustable needle is arranged coaxially with the fixed needle. The adjustable port and the adjustable needle are configured to control alternating current (AC) flow and direct current (DC) flow between a valve stem port and an end port, and to generate DC flow in either direction between the stem port and the end port.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application Serial No. 63 / 071,240, filed on August 27, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to an improved dual inlet valve for a Gifford-McMahon (GM) type pulse tube cryocooler which simplifies adjustment for obtaining good cooling capacity. Background Art

[0004] The Gifford-McMahon (GM) pulse-tube cooler is a cryogenic cooler similar to the GM cooler. It derives cooling from gas compression in a compressor connected to an expander via supply and return hoses. The expander circulates gas through a regenerator via inlet and outlet valves to a cold expansion space. While the GM expander creates the cold expansion space through the reciprocating motion of a solid piston (when the displacement volumes above and below the piston are connected by a regenerator, the piston is often referred to as a displacer) in a cylinder, the pulse-tube expander creates the cold expansion space through the reciprocating motion of a "gas piston." A pulse-tube cooler has no moving parts in its cold head, instead featuring an oscillating gas column within the pulse tube that acts as a compressible piston. The piston contains the gas that resides in the pulse tube during pressurization and decompression. The elimination of moving parts in the cold end of a pulse-tube cooler significantly reduces vibration and improves reliability and service life. Two-stage GM pulse-tube coolers typically use an oil-lubricated compressor to compress helium and consume 5 to 15 kilowatts or more of input power. The main application today is cooling MRI (magnetic resonance imaging) and NMR (nuclear magnetic resonance imaging) magnets, where they cool heat shields at temperatures around 40 K and recondense helium at around 4 K. They are also being used in the early development of quantum computers. These applications require low levels of vibration and low levels of EMI (electromagnetic interference).

[0005] GM pulse tube coolers were developed in parallel with Stirling pulse tube coolers, which provide pressure circulation directly from the piston of a reciprocating compressor to the regenerator and pulse tube. These are widely used to cool infrared detectors in ground and space systems operating at temperatures close to 70K. They are typically much smaller and run at higher speeds, such as 60 Hz, compared to 1 to 2 Hz for GM pulse tubes. Stirling pulse tubes are more efficient than GM pulse tubes because they recover most of the expansion work, but the way the flow between the warm end of the pulse tube and the buffer volume is controlled is different, and they are not as efficient at low temperatures.

[0006] W.E. Gifford, co-inventor of the GM cycle refrigerator, also envisioned an expander that replaced a solid piston with a gas piston, calling it a "pulse tube" refrigerator. This was first described in his U.S. Patent No. 3,237,421 (the "'421 patent"), which showed a pulse tube connected to a valve, much like the earlier GM refrigerator. Early developments of the pulse tube expander showed that gas entered a vertically oriented tube at the bottom and flowed through a flow-smoothing mesh, forming a stratified gas column that heated as it was compressed and pushed toward the top. The tube had a copper cap at the top that absorbed some of the heat, so that as the gas exited the tube and cooled as it expanded, it cooled the flow-smoothing mesh and the adjacent copper at the so-called cold end. As reported in 1984, Mikulin et al. significantly improved the basic GM pulse tube by adding a buffer volume at the warm end and using a throttling valve to control the gas flow in and out. This is now known as the basic orifice-type pulse tube or single-inlet valve pulse tube. Subsequent development work resulted in the design of several different throttling schemes that improved the performance of the pulse tube expander.Most Stirling-type pulse tubes are single-inlet designs.

[0007] For GM-type pulse tubes, it was discovered that adding a second orifice between the warm end of the pulse tube and the inlet to the regenerator improved performance, making it possible to achieve temperatures below 4K with a two-stage pulse tube. This is now known as a dual-inlet pulse tube, and the second throttling device is called a dual-inlet valve. Just as single-inlet valves have taken different forms, dual-inlet valves have also taken different forms. This invention is a new dual-inlet valve that allows for easy fine-tuning of the valve settings to achieve good performance.

[0008] Gifford's U.S. Patent No. 3,205,668 ("the '668 patent") describes a GM expander with a solid piston having a valve stem attached to the warm end. The valve stem drives the displacer up and down by causing the pressure cycle above the actuating valve stem to be out of sync with the pressure cycle in the expansion space. A rotary valve is the most common means of cycling pressure between high (Ph) and low (Pi). It can be argued that flow control at the warm end of the pulse tube is optimized if the cold boundary of the gas piston essentially follows the same pattern as the cold end of the solid piston. The expander cycle described in the '668 patent begins with the displacer depressed and the inlet valve opened, increasing the pressure to Ph. The piston then moves upward. At approximately three-quarters of the way up, the inlet valve closes, causing the pressure to decrease as the piston moves to the top. The outlet valve then opens, causing the pressure to decrease to Pi. The piston then moves downward. At approximately three-quarters of the way down, the outlet valve closes, causing the pressure to increase as the piston moves to the bottom. The area (PV) is a measure of the amount of cooling produced per cycle. The differences between solid pistons and gas pistons are numerous. They include: 1) the length and stroke depend on the pressure ratio and how much gas is allowed to flow into and out of the cold end of the pulse tube; 2) asymmetries in valve timing and flow resistance can cause more gas to flow into or out of one end of the pulse tube per cycle than out or in, known as direct current (DC) flow; and 3) it is difficult to simultaneously balance the flow into and out of the cold and warm ends to establish a cold boundary, known as alternating current (AC) flow, which simulates the motion and PV relationship of the solid piston. A Stirling cycle pulse tube with a single inlet valve avoids the first problem because the compressor piston has a fixed displacement, and it also avoids the second problem because the amount of gas flowing out of the buffer volume is the same as the amount of gas flowing into the buffer volume.

[0009] While this gas piston to solid piston analogy provides a physical description of the process, it is more common to describe the flow pattern in terms of the phase relationship between the pressure cycle and the mass flow cycle. A good description of a phase control device for a Stirling-type single-inlet pulse tube cryocooler is provided in patent application US2011 / 0100022 by Yuan et al. ("the '022 application"). Figure 2 A resistance device is shown and is described as comprising an orifice, a short tube, and closely spaced plates. Figure 2An inertia tube is shown, which is a long, small diameter tube that acts as an inductor in the electrical simulation. Figure 8 of the '022 application shows how these devices can be combined using circuit simulation to optimize the phase relationship between the pressure cycle and the mass flow cycle to provide maximum cooling. Figure 7 of the '022 application is a schematic diagram of a single inlet valve that consists of a resistance device in parallel with the inertia device. It is important to note that the inertia device is practical in the Stirling type pulse tube because it operates at high frequencies. At the low frequencies of the GM type pulse tube, only the resistance device is practical. It is also important to note that all of the devices described in the '022 application have the same flow characteristics for flow in any direction.

[0010] Efforts to increase the cooling capacity of two-stage GM-type coolers at 4K have included the development of a four-valve design. Xu's U.S. Patent No. 10,066,855 (the "'855 patent") describes a four-valve pulse tube. The name comes from a phase-shift mechanism consisting of a pair of inlet and outlet valves connected to the warm end of the regenerator and a second pair of inlet and outlet valves connected to the warm end of the pulse tube. The '855 patent describes flow control mechanisms for balancing gas flow to the second- and third-stage pulse tubes, each requiring an additional pair of valves. Four-valve pulse tubes, which do not utilize a buffer volume, offer slightly better performance than current dual-inlet pulse tube designs. However, they are disadvantaged when the valve motor and rotary valve must be separated from the regenerator. Dual-inlet pulse tubes require only a single hose between the valve assembly and the pulse tube / regenerator assembly (referred to as the cold end), while four-valve pulse tubes require a hose connected to the regenerator and smaller diameter hoses connected to the warm end of each pulse tube in a multi-stage pulse tube. The improved performance of the dual inlet pulse tube of the present invention enables performance as good as a four-valve pulse tube to be obtained in a unit having a remote valve assembly and a single connecting hose. A patent application has recently been filed for the improved connecting hose.

[0011] Ogura's Japanese (JP) patent No. 3917123 describes the use of a needle valve for a dual inlet valve and a replaceable bushing having a short hole for the first inlet valve to pass through. Under the same flow conditions, the short hole through the bushing has the same flow restriction in either direction. It is a symmetrical flow restrictor. On the other hand, as described, the needle valve has a port at the end looking into the needle tip and a port on the side looking into the valve stem, and under the same conditions, the flow restriction in different directions is different. The flow restriction is asymmetric. The degree of asymmetry depends on many factors, such as the slope of the inlet of the port, the length of the hole of the port, etc. By simplifying the adjustment means, the improvement of the phase shift is made possible.

[0012] In addition to optimizing the phase shift mechanism for controlling the PV relationship of a GM-type pulse tube operating near 4K, it was found that controlling the DC flow is also important. Xu's U.S. Patent No. 9,157,668 (the "'668 Patent") describes a dual-inlet pulse tube with an additional drainage line between the buffer volume and the compressor return line. Figure 1 A basic dual inlet pulse tube of the prior art is shown and the flow pattern through the dual inlet valve is described, which creates excessive DC flow from the warm end to the cold end of the pulse tube. A drainage line from the buffer volume back to the compressor return side reduces the DC flow to a rate that optimizes cooling. This has the disadvantage of requiring additional connecting lines when the valve assembly is remote from the cold end. A two-stage dual inlet pulse tube has two parallel pulse tubes extending from room temperature to first and second stage temperatures. The warm end of each pulse tube is connected to its own buffer volume and has its own dual inlet valve. The second stage regenerator is an extension of the first stage regenerator, so the pressure drop through the first stage regenerator to the cold end of the first stage pulse tube is less than the pressure drop to the cold end of the second stage pulse tube. Optimizing DC flow in a two stage pulse tube may require having upward DC flow in the second stage and downward DC flow in the first stage.

[0013] The present invention is a dual inlet valve that simplifies the setting of AC flow and DC flow to optimize the available cooling. It also requires only a single connecting hose between the remote valve assembly and the cold head. Summary of the Invention

[0014] A coaxial dual inlet valve for dual inlet GM type pulse tube cryocoolers comprising a fixed needle and an opposed axially adjustable needle in series with an axially adjustable port. The overall flow resistance can be adjusted and the asymmetry of the flow can be adjusted in either direction. The valve is normally located in the warm flange of the cold head and can be accessed from one end for adjustment. Standard size valves can be used for the first and second stage of a two stage pulse tube or for pulse tubes of different sizes. The valve simplifies the setting of AC flow and DC flow to optimize the cooling that can be obtained. In applications where isolation of the cold head from vibration and electromagnetic interference is important, the dual inlet valve pulse tube requires only a single connecting hose to the remote valve assembly.

[0015] These advantages and other advantages are achieved by providing cooling at low temperatures by the GM type dual inlet pulse tube system. The GM type dual inlet pulse tube system includes a coaxial dual inlet valve, which includes: a base having an adjustable port, a fixed needle partially engaged at one end of the adjustable port, an adjustable needle partially engaged at the other end of the adjustable port, and a body for accommodating the base, the fixed needle and the adjustable needle. The base is configured to be adjustable in an axial direction. The adjustable needle is arranged coaxially with the fixed needle. The base defines a cavity connected to a valve stem port formed on the body, and the body defines a cavity connected to an end port formed on the body, and the adjustable port is located between the cavity of the base and the cavity of the body. The adjustable port and the adjustable needle are configured to control AC flow and DC flow between the valve stem port and the end port, and to generate DC flow in either direction between the valve stem port and the end port. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings depict one or more embodiments of the present invention by way of example only and not by way of limitation. In the drawings, like reference numerals designate like or similar elements.

[0017] Figure 1 A schematic diagram of a single-stage GM type dual-inlet pulse tube system with a coaxial dual-inlet valve of the present invention is shown.

[0018] Figure 2 A schematic diagram of a coaxial dual inlet valve of the present invention is shown.

[0019] Figure 3 A schematic diagram of a two-stage GM type dual-inlet pulse tube system having two coaxial dual-inlet valves of the present invention is shown. DETAILED DESCRIPTION

[0020] In this section, some embodiments of the present invention will be described more fully with reference to the accompanying drawings, in which preferred embodiments of the present invention are shown. However, the present invention can be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided to make this disclosure thorough and complete and to convey the scope of the present invention to those skilled in the art. The same reference numerals refer to the same elements throughout, and apostrophes are used to represent similar elements in alternative embodiments. Identical or similar parts are marked with the same reference numerals in the accompanying drawings and are generally not repeated.

[0021] refer to Figure 1, shows a schematic diagram of a single-stage GM-type dual-inlet pulse tube system 100 with a coaxial dual-inlet valve 1 according to the disclosed invention. The coaxial dual-inlet valve 1 is shown in the context of the overall system. The single-stage GM-type dual-inlet pulse tube system 100 includes a compressor 10, a valve assembly 12 having valves 12a and 12b, and a pulse tube coldhead 101 connected to the valve assembly 12 via connecting line 7a. The compressor 10 is connected to the supply valve 12a, V1, via supply line 11a, and to the return valve 12b, V2, via return line 11b. Lines 11a and 11b are typically flexible metal hoses 5 to 20 meters long, and valves 12a and 12b are typically slots in motor-driven rotary valves that rotate on ports in a fixed seat. Gas—typically helium—circulates between supply and return pressures, typically between 2.2 MPa and 0.6 MPa, as it flows through connecting line 7a to the warm end of the dual-inlet pulse tube 17. Compressor 10 supplies gas at supply pressure via supply line 11a and receives gas at return pressure via return line 11b. Valves 12a and 12b are connected to supply and return lines 11a, respectively, allowing gas to circulate between supply and return pressures via connecting line 7a to pulse tube coldhead 101. If valves 12a and 12b are integral to the coldhead 101, connecting line 7a can be a few millimeters long, or, if the valves are remote, it can be a single flexible hose up to 0.5 meters or more.

[0022] Pulse tube coldhead 101 includes: a regenerator 16 having a warm end 16a and a cold end 16b; a pulse tube 17 having a warm flow smoother 17a at the warm end and a cold flow smoother 17b at the cold end; a line 18 connecting the regenerator cold end 16b of regenerator 16 to the cold flow smoother 17b of pulse tube 17; a line 7b extending from connecting line 7a to the warm end 16a of regenerator 16; a line 9a extending from line 7b to the coaxial dual inlet valve 1; a line 8 extending from the warm flow smoother 17a of pulse tube 17 through the single inlet valve 2 to the buffer volume 15; and a line 9b extending from the coaxial dual inlet valve 1 to line 8 and the warm flow smoother 17a of pulse tube 17. Circulation flow continues through line 7b to the warm end 16a of regenerator 16 and through line 9a to the coaxial dual inlet valve 1, line 9b, and line 8. Line 8 is connected at one end to the warm end of the pulse tube 17, containing the warm flow smoother 17a, and at the other end to the single inlet valve 2, which in turn is connected to the buffer volume 15. The cold end 16b of the regenerator 16 is connected by line 18 to the cold end of the pulse tube 17, containing the cold flow smoother 17b.

[0023] refer to Figure 2, shows a schematic diagram of a coaxial dual-inlet valve 1. The valve body 6 of the coaxial dual-inlet valve 1 is typically the warm flange of the pulse tube cold end 101, but can also be part of an external piping assembly. Needle 5a is integral with needle seat 5, which is fixed in the valve body 6. A valve port base 4, which has a hole for gas flow, is coaxially aligned with needles 3a and 5a and is axially adjustable via a threaded engagement within the valve body 6. Needle 3a is integral with an adjustable needle seat 3, which is axially adjustable via a threaded engagement in port base 4. Port base 4 has an adjustable port 4a into which needles 3a and 5a can be partially inserted. Grooves 3b and 4b allow a tool to be engaged to independently rotate needle seat 3 and port base 4 from the same end of the valve body 6 for adjustment. Seals 3c and 4c ensure a gas-tight seal for the coaxial dual-inlet valve 1.

[0024] refer to Figure 2 The body 6 has a hole 6a inside the body 6, and the fixed needle seat 5 and the valve port base 4 are set in the hole 6a. The valve port base 4 has an adjustable port 4a and a hole (or cavity) 4d inside the valve port base 4, and the adjustable needle seat 3 is set in the hole 4d. The hole 4d is connected to the valve stem port 4e, and the valve stem port 4e is connected to the pipeline 9a, and the pipeline 9a is connected to the pipeline 7b. Figure 1 As shown. The adjustable needle 3a extending from the adjustable needle seat 3 is arranged in the hole 4d and partially arranged in the adjustable port 4a. The fixed needle 5a extending from the fixed needle seat 5 is arranged in the hole 5b and partially arranged in the adjustable port 4a. When the valve port base 4 and / or the adjustable needle seat 3 are adjusted along the axial direction Z, the size of the hole 4d and the length of the portion of the needle 3a arranged in the adjustable port 4a can be adjusted. When the valve port base 4 is adjusted along the axial direction Z, the adjustable port 4a moves along the axial direction Z, and the length of the portion of the needle 5a arranged in the adjustable port 4a can be adjusted.

[0025] A hole (or cavity) 5b may be formed between the valve port base 4 and the fixed needle seat 5 and communicate with the hole 4d through the adjustable port 4a. The fixed needle body 5 is disposed between the hole 5b and the end port 5c and has at least one connection port 5d. The end port 5c is connected to the port 5b through the connection port 5d. The end port 5c is connected to the pipeline 9b, and the pipeline 9b is connected to the pipeline 8, as shown in FIG. Figure 1While the figures illustrate specific shapes (but not dimensions) for needles 3a and 5a and port 4a, other configurations are within the scope of the present invention. If needles 3a and 5a are withdrawn symmetrically from port 4a, AC flow increases symmetrically. If one opens more than the other, the flow becomes asymmetrical, with the needle that engages more to the base creating a greater flow resistance than the needle that engages less. This asymmetry introduces DC flow, which can be set in either direction depending on which of the two needles is more engaged.

[0026] refer to Figure 3 , shows a schematic diagram of a two-stage GM-type dual-inlet pulse tube system 200 having multiple coaxial dual-inlet valves 1a and 1b according to the disclosed invention. The two-stage GM-type dual-inlet pulse tube system 200 comprises a compressor 10, a valve assembly 12 having valves 12a and 12b, and a pulse tube coldhead 201 connected to the valve assembly 12 via connecting line 7a. Compressor 10 is connected to supply valve 12a, V1, via supply line 11a, and to return valve 12b, V2, via return line 11b. Lines 11a and 11b are typically flexible metal hoses 5 to 20 meters long, while valves 12a and 12b are typically slots in motor-driven rotary valves that rotate on ports in a fixed seat. Gas—typically helium—circulates between supply and return pressures, typically between 2.2 MPa and 0.6 MPa, as it flows through connecting line 7a to the warm ends of the dual-inlet pulse tubes 17 and 21. Compressor 10 supplies gas at supply pressure via supply line 11a and receives gas at return pressure via return line 11b. Valves 12a and 12b are connected to supply line 11a and return line 11b, respectively, allowing gas to circulate between supply and return pressures via connecting line 7a to pulse tube coldhead 201. If valves 12a and 12b are integral to coldhead 201, connecting line 7a can be a few millimeters long, or if the valves are remote, it can be a single flexible hose up to 0.5 meters or more.

[0027] refer to Figure 3The pulse tube cold head 201 includes: a first-stage regenerator 16' having a warm end 16a' and a cold end 16b'; a second-stage regenerator 20 attached to the cold end 16b' of the first-stage regenerator 16' and having a cold end 20b; a first-stage pulse tube 17 having a warm flow smoother 17a at the warm end and a cold flow smoother 17b at the cold end; a second-stage pulse tube 21 having a warm flow smoother 21a at the warm end and a cold flow smoother 21b at the cold end; a pipeline 18 connecting the regenerator cold end 16b' to the cold flow smoother 17b of the pulse tube 17; a pipeline 22 connecting the cold end 20b of the second-stage regenerator 20 to the cold flow smoother 21b of the pulse tube 21; and a pipeline 7 b, which extends from the connecting pipeline 7a to the warm end 16a' of the regenerator 16'; pipeline 9a, which extends from the pipeline 7b to the coaxial double inlet valve 1a; pipeline 9a', which extends from the pipeline 7b to the coaxial double inlet valve 1b; pipeline 8, which extends from the warm flow smoother 17a of the pulse tube 17 through the single inlet valve 2 to the buffer volume 15; pipeline 8a, which extends from the warm flow smoother 21a of the pulse tube 21 through the single inlet valve 2a to the buffer volume 15a; pipeline 9b, which extends from the coaxial double inlet valve 1a to the pipeline 8 and the warm flow smoother 17a of the pulse tube 17; and pipeline 9b', which extends from the coaxial double inlet valve 1b to the pipeline 8a and the warm flow smoother 21a of the pulse tube 21.

[0028] The first coaxial dual inlet valve 1a is connected to the first-stage pulse tube 17, and the second coaxial dual inlet valve 1b is connected to the second-stage pulse tube 21. The second coaxial dual inlet valve 1b includes the same components as the first coaxial dual inlet valve 1a. The end port 5c of the second coaxial dual inlet valve 1b can be connected to the pipeline 9b', and the valve stem port 4e of the second coaxial dual inlet valve 1b can be connected to the pipeline 9a'. The second coaxial dual inlet valve 1b is equivalent to the first coaxial dual inlet valve 1a, but the adjustable port 4a, needle 3a and needle 5a can have different sizes. Figure 3 As shown, the second-stage regenerator 20 is an extension of the first-stage regenerator 16'. The second-stage pulse tube 21 is separate from the first-stage pulse tube 17, with its warm end at room temperature. The cold end 20b of the regenerator 20 is connected to the cold end of the pulse tube 21, which has a flow smoother 21b, via line 22. The warm end of the second-stage pulse tube 21 has a flow smoother 21a and is connected to line 8a, which is connected to a coaxial dual-inlet valve 1b and a buffer volume 15a via a single-inlet valve 2a.

[0029] The terms and descriptions used herein are set forth by way of illustration only and are not meant to be limiting. Those skilled in the art will recognize that many variations are possible within the spirit and scope of the invention and the embodiments described herein.

Claims

1. A Gifford-McMahon (GM) type dual inlet pulse tube system for providing cooling at cryogenic temperatures, comprising: A coaxial double-inlet valve, comprising: an adjustable base having a port; a fixed pin partially engaging an end of a port in the adjustable base; an adjustable needle adjustably and partially engaged with the other end of the port in the adjustable base, wherein the adjustable needle is coaxially disposed with the port in the adjustable base and the fixed needle; and A body is provided for accommodating the adjustable base, the fixing needle and the adjustable needle.

2. The Gifford-McMahon (GM) type dual inlet pulse tube system of claim 1, wherein the adjustable base and the adjustable needle are adjustable from the same side of the body.

3. A Gifford-McMahon (GM) type dual inlet pulse tube system according to any one of the preceding claims, wherein the adjustable base defines a cavity connected to a valve stem port formed on the body, the body defines a cavity connected to an end port formed on the body, and the port in the adjustable base is located between the cavity of the adjustable base and the cavity of the body.

4. The Gifford-McMahon (GM) type dual inlet pulse tube system of claim 3, wherein the port in the adjustable base and the adjustable needle are configured to control alternating current (AC) flow and direct current (DC) flow between the stem port and the end port.

5. The Gifford-McMahon (GM) type dual inlet pulse tube system of claim 3, wherein the port in the adjustable base and the adjustable needle are configured to produce DC flow in either direction between the stem port and the end port.

6. The Gifford-McMahon (GM) type dual inlet pulse tube system of claim 3, wherein the coaxial dual inlet valve further comprises an adjustable needle seat located within the cavity of the adjustable base, and the adjustable needle is integral with the adjustable needle seat.

7. A Gifford-McMahon (GM) type dual inlet pulse tube system for providing cooling at cryogenic temperatures, comprising: a compressor that supplies gas at a supply pressure through a supply line and receives gas at a return pressure through a return line; a valve assembly connected to the supply line and the return line; a pulse tube cold head connected to the valve assembly, wherein the valve assembly circulates gas to the pulse tube cold head through a connecting pipeline between the supply pressure and the return pressure, the pulse tube cold head comprising: a regenerator having a warm end and a cold end; a pulse tube having a warm end and a cold end; A coaxial double-inlet valve, comprising: an adjustable base having a port; a fixed pin partially engaging an end of a port in the adjustable base; an adjustable needle adjustably and partially engaged with the other end of the port in the adjustable base, wherein the adjustable needle is coaxially disposed with the port in the adjustable base and the fixed needle; and a body, the body being used to accommodate the adjustable base, the fixing needle and the adjustable needle; a first pipeline extending from the connecting pipeline to the warm end of the regenerator, wherein the coaxial dual inlet valve is connected to the first pipeline; a second line connecting a cold end of the regenerator to a cold end of the pulse tube; a third line extending from the warm end of the pulse tube through a single inlet valve to a buffer volume; and A fourth line extends from the coaxial dual inlet valve to a warm end of the pulse tube.

8. The Gifford-McMahon (GM) type dual inlet pulse tube system of claim 7, wherein the adjustable base and the adjustable needle are adjustable from the same side of the body.

9. A Gifford-McMahon (GM) dual inlet pulse tube system according to any one of claims 7-8, wherein the adjustable base defines a cavity connected to a valve stem port formed on the body, the body defines a cavity connected to an end port formed on the body, and the port in the adjustable base is located between the cavity of the adjustable base and the cavity of the body.

10. The Gifford-McMahon (GM) type dual inlet pulse tube system of claim 9, wherein the valve stem port is connected to the first pipeline and the end port is connected to the fourth pipeline.

11. The Gifford-McMahon (GM) type dual inlet pulse tube system of claim 9, wherein the port in the adjustable base and the adjustable needle are configured to control alternating current (AC) flow and direct current (DC) flow between the stem port and the end port.

12. The Gifford-McMahon (GM) type dual inlet pulse tube system of claim 9, wherein the port in the adjustable base and the adjustable needle are configured to produce DC flow in either direction between the stem port and the end port.

13. The Gifford-McMahon (GM) type dual inlet pulse tube system of claim 9, wherein the coaxial dual inlet valve further comprises an adjustable needle seat located within the cavity of the adjustable base, and the adjustable needle is integral with the adjustable needle seat.

14. The Gifford-McMahon (GM) type dual inlet pulse tube system according to any one of claims 7-8, wherein the connecting line between the valve assembly and the pulse tube cold head is a single flexible hose.

15. The Gifford-McMahon (GM) dual-inlet pulse tube system according to any one of claims 7-8, wherein the connecting pipeline between the valve assembly and the pulse tube cold head is at least 0.5 meters long.

16. The Gifford-McMahon (GM) dual-inlet pulse tube system according to any one of claims 7-8, wherein the pulse tube cold head further comprises: a second-stage regenerator connected to a cold end of the regenerator; a second-stage pulse tube, the second-stage pulse tube having a warm end and a cold end; The second-stage coaxial dual-inlet valve is connected to the first pipeline, and the second-stage coaxial dual-inlet valve includes: an adjustable base having a port; a fixed pin partially engaging an end of a port in the adjustable base; an adjustable needle adjustably and partially engaged with the other end of the port in the adjustable base, wherein the adjustable needle is coaxially disposed with the port in the adjustable base and the fixed needle; and a body, the body being used to accommodate the adjustable base, the fixing needle and the adjustable needle; a fifth pipeline connecting a cold end of the second-stage regenerator and a cold end of the second-stage pulse tube; a sixth line extending from the warm end of the second stage pulse tube through the second stage single inlet valve to the second stage buffer volume; and A seventh line extends from the second stage coaxial dual inlet valve to the warm end of the second stage pulse tube.

17. The Gifford-McMahon (GM) type dual inlet pulse tube system of claim 16, wherein at least one of the adjustable port, fixed needle, and adjustable needle of the second stage coaxial dual inlet valve is a different size than a corresponding one of the adjustable port, fixed needle, and adjustable needle of the coaxial dual inlet valve.

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