A photomultiplier dynode film layer preparation system and method

Abstract

This invention discloses a photomultiplier tube (PMT) dynode film preparation system and method belonging to the field of PMT technology. The system includes a PMT, a vacuum system, and an alkali source assembly. The alkali source assembly includes an external glass tube and internal K, Na, and Cs sources. One end of the glass tube is closed, and the other end is connected to the vacuum system via a tail tube. One end of the PMT is also closed, and the other end is connected to the vacuum system via a tail tube. The K, Na, and Cs sources are connected to pin electrodes via nickel wires to form a circuit. Eleven pin electrodes are led out from the inside of the PMT. This invention can accurately and effectively monitor the secondary electron emission capability of the dynode film, solving the problem of lack of quality control in the dynode preparation process. Furthermore, it improves the secondary electron emission coefficient of the dynode film, resulting in a significant increase in overall PMT gain and achieving good consistency.

Description

Technical Field

[0001] This invention relates to the field of photomultiplier tube technology, and in particular to a photomultiplier tube dynode film preparation system and preparation method. Background Technology

[0002] A photomultiplier tube (PMT) is a high-sensitivity vacuum photodetector that converts weak light signals into electrical signals and amplifies them with high gain. Multi-alkali cathode side-window PMTs are mainly used as detector components in scientific instruments such as atomic absorption spectrometers, ultraviolet-visible spectrophotometers, and high-performance liquid chromatographs. The quality of the PMT's dynode film is one of the key factors affecting the product's gain performance.

[0003] In the manufacturing process of multi-alkali cathode side-window photomultiplier tubes, the preparation of the dynode film is carried out simultaneously with the preparation of the photocathode. This process involves the stepwise introduction of various trace amounts of alkali metal (K, Na, Cs) vapors under high temperature and high vacuum conditions to react with the Sb substrate layer, forming a functional film with precise stoichiometry and specific phase structure and morphology. Poor quality dynode film results in a low secondary electron emission coefficient, which in turn affects the anode sensitivity and gain performance of the multi-alkali cathode side-window photomultiplier tube.

[0004] Current technology applies an electric field only between the cathode and the first dynode, monitoring the photocathode film quality by observing the change in photocurrent before and after illumination. However, it does not monitor the film quality of the dynode system. While this method ensures optimal cathode activation and thus achieves high cathode integral sensitivity, it cannot guarantee optimal dynode film quality to achieve overall high sensitivity and high gain performance.

[0005] Therefore, there is a need for a photomultiplier tube dynode film preparation system and method. By improving the equipment monitoring methods in the existing dynode film preparation process, better dynode film preparation quality can be achieved. Furthermore, by increasing the secondary electron emission coefficient of the dynode film, high sensitivity and high gain of the entire tube can be obtained. Summary of the Invention

[0006] The purpose of this invention is to provide a photomultiplier tube dynode film preparation system and preparation method.

[0007] A photomultiplier tube dynode film preparation system includes a photomultiplier tube, a vacuum system, and an alkaline source assembly;

[0008] The alkali source assembly includes an external glass tube and internal K, Na, and Cs sources; one end of the glass tube is closed, and the other end is connected to the vacuum system through a tail tube; one end of the photomultiplier tube is closed, and the other end is connected to the vacuum system through a tail tube; among them, the K, Na, and Cs sources are connected to the pin electrodes through nickel wires to form a circuit, and 11 pin electrodes are led out from the inside of the photomultiplier tube.

[0009] Furthermore, the 11 pin electrodes are the first dynode, second dynode, third dynode, fourth dynode, fifth dynode, sixth dynode, seventh dynode, eighth dynode, ninth dynode, anode, and cathode, which are evenly distributed along the circumference.

[0010] Furthermore, the alkali source component and the photomultiplier tube are symmetrically arranged at the top of the vacuum system.

[0011] A method for preparing a dynode film layer in a photomultiplier tube includes:

[0012] Step 1: Connect the photomultiplier tube and alkali source assembly to the vacuum system station of the exhaust station for leak detection;

[0013] Step 2: Evacuate the vacuum system to 1×10⁻⁶ -4 After heating at Pa, the photomultiplier tube and alkali source assembly are simultaneously evacuated to a vacuum level of 1×10⁻⁶. -5 Pa or above;

[0014] Step 3: Connect the 11 pin electrodes and the alkaline source assembly to the power supply respectively; apply a voltage of 80~120V between any two adjacent pin electrodes inside the photomultiplier tube, and monitor the changes in the output current of the cathode-first dynode and the cathode-anode before and after the photocathode is irradiated by light.

[0015] Step 4: At a temperature of 150~300℃ and a vacuum degree better than 2.0×10 -4 Under the condition of Pa, starting from 1.0 A, the evaporation current of the K source is increased by 0.1~0.3 A / min until photocurrent is generated. The evaporation current of the K source is increased by 0.01~0.1 A / min to 5.0~7.0 A. K vapor diffuses into the interior of the photomultiplier tube and reacts with the Sb film on each electrode until the photocurrent between the cathode and the first dynode and between the cathode and the anode reaches its maximum value. The current of the K source is cut off, and the tube is kept at a temperature of 10~60 min to remove the residual K vapor in the tube and stabilize the film layer.

[0016] Step 5: At a temperature of 150~300℃ and a vacuum degree better than 2.0×10 -4Under Pa conditions, the Na source current is increased from 1.0 A to 3.5 A to degas the Na source. The Na source current is then increased to 5.0-7.0 A at a rate of 0.01-0.1 A / min. Na vapor diffuses into the interior of the photomultiplier tube and reacts with the Sb film on each electrode until the photocurrent between the cathode and the first dynode and between the cathode and the anode reaches its maximum value. The Na source current is then turned off and maintained for 10-60 min to remove residual Na vapor.

[0017] Step 6: At a temperature of 150~250℃ and a vacuum degree better than 2.0×10 -4 Under Pa conditions, the Cs source current is increased from 1.0 A to 3.5 A to degas the Cs source. The Cs source current is then increased to 4.5 to 7.0 A at a rate of 0.01 to 0.1 A / min. The Cs vapor diffuses into the interior of the photomultiplier tube and reacts with the Sb film on each electrode until the photocurrent between the cathode and the first dynode and between the cathode and the anode reaches its maximum value. The Cs source current is then turned off, and residual alkali is extracted for another 10 to 60 min to obtain a stable Na2KSb(Cs) film.

[0018] The beneficial effects of this invention are as follows:

[0019] This invention employs a method of simultaneously monitoring the photocurrent between the cathode and the first dynode, and between the cathode and the anode, during dynode fabrication. This allows for precise and effective monitoring of the secondary electron emission capability of the dynode film, solving the problem of insufficient quality control during dynode fabrication. Furthermore, it improves the secondary electron emission coefficient of the dynode film, resulting in a significant increase in overall transistor gain and achieving good consistency. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the photomultiplier tube dynode film preparation system of the present invention;

[0021] Figure 2 This is a schematic diagram of the structure of 11 pin electrodes. Detailed Implementation

[0022] This invention proposes a system and method for preparing a photomultiplier tube dynode film layer. The invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0023] Figure 1This is a schematic diagram of the photomultiplier tube dynode film preparation system of the present invention, including a photomultiplier tube 4, a vacuum system 5, and an alkali source assembly. The alkali source assembly includes an external glass tube 6 and internal K source 1, Na source 2, and Cs source 3. One end of the glass tube 6 is closed, and the other end is connected to the vacuum system 5 through a tail tube. One end of the photomultiplier tube 4 is closed, and the other end is connected to the vacuum system 5 through a tail tube. K source 1, Na source 2, and Cs source 3 are connected to the pin electrodes via nickel wires to form a circuit. Eleven pin electrodes are led out from the inside of the photomultiplier tube 4. The alkali source assembly and the photomultiplier tube 4 are symmetrically arranged on top of the vacuum system 5. During the preparation of the dynode film, a certain current is applied to K source 1, Na source 2, and Cs source 3 through the pin electrodes, causing them to heat up and release alkali metal vapor, which diffuses into the photomultiplier tube 4 and reacts with the Sb film on each pin electrode inside the tube. Figure 2 This is a schematic diagram of the 11-pin electrode structure, namely the first dynode 401, second dynode 402, third dynode 403, fourth dynode 404, fifth dynode 405, sixth dynode 406, seventh dynode 407, eighth dynode 408, ninth dynode 409, anode 410, and cathode 411, evenly distributed circumferentially. Each electrode is connected to the power supply via a voltage divider base. A voltage of 80~120V is applied between two adjacent electrodes, while simultaneously monitoring the changes in the output current between the cathode and the first dynode, and between the cathode and the anode, before and after the photocathode is irradiated. The real-time data guides the fabrication of the cathode and dynode films.

[0024] A method for preparing the dynode film layer of a photomultiplier tube includes:

[0025] Step 1: Connect the photomultiplier tube 4 and the alkali source assembly to the vacuum system 5 of the exhaust station for leak detection;

[0026] Step 2: Evacuate the vacuum system 5 to 1×10⁻⁶. -4 After heating, the photomultiplier tube 4 and the alkali source assembly are simultaneously evacuated to a vacuum level of 1×10⁻⁶. -5 Pa or above;

[0027] Step 3: Connect the 11 pin electrodes and the alkaline source assembly to the power supply respectively; apply a voltage of 80~120V between any two adjacent pin electrodes inside the photomultiplier tube 4, and monitor the changes in the output current of cathode 411-first dynode 401 and cathode 411-anode 410 before and after the photocathode is irradiated by light.

[0028] Step 4: At a temperature of 150~300℃ and a vacuum degree better than 2.0×10 -4Under the condition of Pa, starting from 1.0 A, the evaporation current of K source 1 is increased by 0.1~0.3 A / min until photocurrent is generated. Then, the evaporation current of K source 1 is increased by 0.01~0.1 A / min to 5.0~7.0 A. K vapor diffuses into the interior of photomultiplier tube 4 and reacts with the Sb film on each electrode until the photocurrent between cathode 411 and the first dynode 401 and between cathode 411 and anode 410 reaches its maximum value. Then, the current of K source 1 is cut off, and the temperature is maintained for 10~60 min to remove the residual K vapor in the tube and stabilize the film layer.

[0029] Step 5: At a temperature of 150~300℃ and a vacuum degree better than 2.0×10 -4 Under Pa conditions, the current of Na source 2 is increased from 1.0 A to 3.5 A to degas Na source 2. The current of Na source 2 is increased to 5.0~7.0 A at a rate of 0.01~0.1 A / min. Na vapor diffuses into the interior of photomultiplier tube 4 and reacts with the Sb film on each electrode until the photocurrent between cathode 411-first dynode 401 and cathode 411-anode 410 increases to its maximum value. Then the current of Na source 2 is turned off and maintained for 10~60 min to remove residual Na vapor.

[0030] Step 6: At a temperature of 150~250℃ and a vacuum degree better than 2.0×10 -4 Under the condition of Pa, the current of Cs source 3 is increased from 1.0 A to 3.5 A to degas Cs source 3. The current of Cs source 3 is increased to 4.5~7.0 A at a rate of 0.01~0.1 A / min. Cs vapor diffuses into the interior of photomultiplier tube 4 and reacts with the Sb film on each electrode until the photocurrent between cathode 411-first dynode 401 and cathode 411-anode 410 increases to the maximum value. The current of Cs source 3 is then turned off, and residual alkali is continued to be removed for 10~60 min to obtain a stable Na2KSb(Cs) film layer.

[0031] Example 1

[0032] Step 1: Connect the photomultiplier tube 4 and the alkali source assembly to the vacuum system 5 of the exhaust station for leak detection;

[0033] Step 2: Evacuate the vacuum system 5 to 1×10⁻⁶. -4 After heating, the photomultiplier tube 4 and the alkali source assembly are simultaneously evacuated to a vacuum level of 1×10⁻⁶. -5 Pa or above;

[0034] Step 3: Connect the 11 pin electrodes and the alkaline source assembly to the power supply respectively; apply a voltage of 80~120V between any two adjacent pin electrodes inside the photomultiplier tube 4, and monitor the changes in the output current of cathode 411-first dynode 401 and cathode 411-anode 410 before and after the photocathode is irradiated by light.

[0035] Step 4: At a temperature of 180℃ and a vacuum degree better than 2.0×10 -4 Under the condition of Pa, starting from 1.0 A, the evaporation current of K source 1 is increased by 0.1~0.3 A / min until photocurrent is generated. Then, the evaporation current of K source 1 is increased to 6 A by 0.01~0.1 A / min. K vapor diffuses into the interior of photomultiplier tube 4 and reacts with the Sb film on each electrode until the photocurrent between cathode 411 and the first dynode 401 and between cathode 411 and anode 410 both reach their maximum values. Then, the current of K source 1 is cut off, and the tube is kept warm for 10 min to remove the residual K vapor in the tube and stabilize the film layer.

[0036] Step 5: At a temperature of 200℃ and a vacuum degree better than 2.0×10 -4 Under Pa conditions, the current of Na source 2 is increased from 1.0 A to 3.5 A to degas Na source 2. The current of Na source 2 is increased to 6 A at a rate of 0.1 A / min. Na vapor diffuses into the interior of photomultiplier tube 4 and reacts with the Sb film on each electrode until the photocurrent between cathode 411 and the first dynode 401 and between cathode 411 and anode 410 increases to the maximum value. Then the current of Na source 2 is turned off and kept for 10 min to remove residual Na vapor.

[0037] Step 6: At a temperature of 170℃ and a vacuum degree better than 2.0×10 -4 Under the condition of Pa, the current of Cs source 3 is increased from 1.0 A to 3.5 A to degas Cs source 3. The current of Cs source 3 is increased to 5 A at a rate of 0.1 A / min. Cs vapor diffuses into the interior of photomultiplier tube 4 and reacts with the Sb film on each electrode until the photocurrent between cathode 411 and the first dynode 401 and between cathode 411 and anode 410 increases to the maximum value. The current of Cs source 3 is then turned off, and residual alkali is extracted for another 10 min to obtain a stable Na2KSb(Cs) film layer.

[0038] Example 2

[0039] Step 1: Connect the photomultiplier tube 4 and the alkali source assembly to the vacuum system 5 of the exhaust station for leak detection;

[0040] Step 2: Evacuate the vacuum system 5 to 1×10⁻⁶. -4 After heating, the photomultiplier tube 4 and the alkali source assembly are simultaneously evacuated to a vacuum level of 1×10⁻⁶. -5Pa or above;

[0041] Step 3: Connect the 11 pin electrodes and the alkaline source assembly to the power supply respectively; apply a voltage of 80~120V between any two adjacent pin electrodes inside the photomultiplier tube 4, and monitor the changes in the output current of cathode 411-first dynode 401 and cathode 411-anode 410 before and after the photocathode is irradiated by light.

[0042] Step 4: At a temperature of 220℃ and a vacuum degree better than 2.0×10 -4 Under the condition of Pa, starting from 1.0 A, the evaporation current of K source 1 is increased by 0.1~0.3 A / min until photocurrent is generated. Then, the evaporation current of K source 1 is increased to 6.5 A by 0.01~0.1 A / min. K vapor diffuses into the interior of photomultiplier tube 4 and reacts with the Sb film on each electrode until the photocurrent between cathode 411 and the first dynode 401 and between cathode 411 and anode 410 reaches its maximum value. Then, the current of K source 1 is cut off and the tube is kept warm for 30 min to remove the residual K vapor in the tube and stabilize the film layer.

[0043] Step 5: At a temperature of 240℃ and a vacuum degree better than 2.0×10 -4 Under Pa conditions, the current of Na source 2 is increased from 1.0 A to 3.5 A to degas Na source 2. The current of Na source 2 is increased to 6.5 A at a rate of 0.1 A / min. Na vapor diffuses into the interior of photomultiplier tube 4 and reacts with the Sb film on each electrode until the photocurrent between cathode 411 and the first dynode 401 and between cathode 411 and anode 410 increases to the maximum value. Then the current of Na source 2 is turned off and maintained for 30 min to remove residual Na vapor.

[0044] Step 6: At a temperature of 200℃ and a vacuum degree better than 2.0×10 -4 Under the condition of Pa, the current of Cs source 3 is increased from 1.0 A to 3.5 A to degas Cs source 3. The current of Cs source 3 is increased to 5.3 A at a rate of 0.1 A / min. Cs vapor diffuses into the interior of photomultiplier tube 4 and reacts with the Sb film on each electrode until the photocurrent between cathode 411 and the first dynode 401 and between cathode 411 and anode 410 increases to the maximum value. The current of Cs source 3 is then turned off, and residual alkali is pumped out for another 30 min to obtain a stable Na2KSb(Cs) film layer.

[0045] Example 3

[0046] Step 1: Connect the photomultiplier tube 4 and the alkali source assembly to the vacuum system 5 of the exhaust station for leak detection;

[0047] Step 2: Evacuate the vacuum system 5 to 1×10⁻⁶. -4After heating, the photomultiplier tube 4 and the alkali source assembly are simultaneously evacuated to a vacuum level of 1×10⁻⁶. -5 Pa or above;

[0048] Step 3: Connect the 11 pin electrodes and the alkaline source assembly to the power supply respectively; apply a voltage of 80~120V between any two adjacent pin electrodes inside the photomultiplier tube 4, and monitor the changes in the output current of cathode 411-first dynode 401 and cathode 411-anode 410 before and after the photocathode is irradiated by light.

[0049] Step 4: At a temperature of 260℃ and a vacuum degree better than 2.0×10 -4 Under the condition of Pa, starting from 1.0 A, the evaporation current of K source 1 is increased by 0.1~0.3 A / min until photocurrent is generated. Then, the evaporation current of K source 1 is increased to 7 A by 0.01~0.1 A / min. K vapor diffuses into the interior of photomultiplier tube 4 and reacts with the Sb film on each electrode until the photocurrent between cathode 411 and the first dynode 401 and between cathode 411 and anode 410 reaches its maximum value. Then, the current of K source 1 is cut off and the tube is kept warm for 50 min to remove the residual K vapor in the tube and stabilize the film layer.

[0050] Step 5: At a temperature of 280℃ and a vacuum degree better than 2.0×10 -4 Under Pa conditions, the current of Na source 2 is increased from 1.0 A to 3.5 A to degas Na source 2. The current of Na source 2 is increased to 7 A at a rate of 0.1 A / min. Na vapor diffuses into the interior of photomultiplier tube 4 and reacts with the Sb film on each electrode until the photocurrent between cathode 411 and the first dynode 401 and between cathode 411 and anode 410 increases to the maximum value. Then the current of Na source 2 is turned off and maintained for 50 min to remove residual Na vapor.

[0051] Step 6: At a temperature of 230℃ and a vacuum degree better than 2.0×10 -4 Under the condition of Pa, the current of Cs source 3 is increased from 1.0 A to 3.5 A to degas Cs source 3. The current of Cs source 3 is increased to 5.5 A at a rate of 0.1 A / min. Cs vapor diffuses into the interior of photomultiplier tube 4 and reacts with the Sb film on each electrode until the photocurrent between cathode 411 and the first dynode 401 and between cathode 411 and anode 410 increases to the maximum value. The current of Cs source 3 is then turned off, and residual alkali is pumped out for another 50 min to obtain a stable Na2KSb(Cs) film layer.

[0052] The multi-alkali cathode side-window photomultiplier tube fabricated using the method of this invention exhibits a significantly improved secondary electron emission coefficient, with the gain increasing from 2 × 10⁻⁶. 6 Increase to 1×10 7 The above is shown in Table 1.

[0053] Table 1. Comparison of gains between new and old multialkali cathode side-window photomultiplier tubes

[0054]

[0055] As can be seen from Table 1, the multi-alkali cathode side-window photomultiplier tube prepared according to the present invention has a gain index that is more than 5 times higher than that of the past at -1000V high voltage, and the secondary electron multiplication capability of the whole tube is significantly increased.

[0056] This invention employs a method that simultaneously monitors the photocurrent between the cathode and the first dynode and between the cathode and the anode during dynode fabrication. This method can accurately and effectively monitor the secondary electron emission capability of the dynode film, solving the problem of lack of quality monitoring in the dynode fabrication process. It improves the secondary electron emission coefficient of the dynode film, resulting in a significant increase in overall tube gain and good consistency.

Claims

1. A system for preparing a dynode film layer for a photomultiplier tube, characterized in that, Includes a photomultiplier tube (4), a vacuum system (5), and an alkali source assembly; The alkali source assembly includes an external glass tube (6) and internal K source (1), Na source (2), and Cs source (3); one end of the glass tube (6) is closed, and the other end is connected to the vacuum system (5) through a tail tube; one end of the photomultiplier tube (4) is closed, and the other end is connected to the vacuum system (5) through a tail tube; wherein, the K source (1), Na source (2), and Cs source (3) are connected to the pin electrodes through nickel wires to form a circuit, and 11 pin electrodes are led out from the inside of the photomultiplier tube (4).

2. The photomultiplier tube dynode film preparation system as described in claim 1, characterized in that, The 11 pin electrodes are the first dynode (401), the second dynode (402), the third dynode (403), the fourth dynode (404), the fifth dynode (405), the sixth dynode (406), the seventh dynode (407), the eighth dynode (408), the ninth dynode (409), the anode (410), and the cathode (411), which are evenly distributed along the circumference.

3. The photomultiplier tube dynode film preparation system as described in claim 2, characterized in that, The alkali source component and the photomultiplier tube (4) are symmetrically arranged on the top of the vacuum system (5).

4. A method for preparing a dynode film layer of a photomultiplier tube, applied to the photomultiplier tube dynode film layer preparation system as described in any one of claims 1 to 3, characterized in that, include: Step 1: Connect the photomultiplier tube (4) and the alkali source assembly to the vacuum system (5) of the exhaust station for leak detection; Step 2: Evacuate the vacuum system (5) to 1×10⁻⁶. -4 After heating at Pa, the photomultiplier tube (4) and the alkali source assembly are simultaneously evacuated until the vacuum reaches 1×10⁻⁶. -5 Pa or above; Step 3: Connect the 11 pin electrodes and the alkaline source assembly to the power supply respectively; apply a voltage of 80~120V between any two adjacent pin electrodes inside the photomultiplier tube (4) and monitor the changes in the output current of the cathode (411)-first dynode (401) and the cathode (411)-anode (410) before and after the photocathode is irradiated by light. Step 4: At a temperature of 150~300℃ and a vacuum degree better than 2.0×10 -4 Under the condition of Pa, starting from 1.0 A, the evaporation current of K source (1) is increased by 0.1~0.3A / min until photocurrent is generated. The evaporation current of K source (1) is increased by 0.01~0.1A / min to 5.0~7.0A. K vapor diffuses into the interior of photomultiplier tube (4) and reacts with the Sb film on each electrode until the photocurrent between cathode (411)-first dynode (401) and cathode (411)-anode (410) both reach their maximum values. The current of K source (1) is cut off and the temperature is maintained for 10~60 min to remove the residual K vapor in the tube and stabilize the film layer. Step 5: At a temperature of 150~300℃ and a vacuum degree better than 2.0×10 -4 Under Pa conditions, the current of the Na source (2) is increased from 1.0 A to 3.5 A to degas the Na source (2). The current of the Na source (2) is increased to 5.0 to 7.0 A at a rate of 0.01 to 0.1 A / min. The Na vapor diffuses into the interior of the photomultiplier tube (4) and reacts with the Sb film on each electrode until the photocurrent between the cathode (411) and the first dynode (401) and between the cathode (411) and the anode (410) reaches its maximum value. Then the current of the Na source (2) is turned off and kept for 10 to 60 min to remove the residual Na vapor. Step 6: At a temperature of 150~250℃ and a vacuum degree better than 2.0×10 -4 Under Pa conditions, the current of the Cs source (3) is increased from 1.0 A to 3.5 A to degas the Cs source (3). The current of the Cs source (3) is increased to 4.5 to 7.0 A at a rate of 0.01 to 0.1 A / min. The Cs vapor diffuses into the interior of the photomultiplier tube (4) and reacts with the Sb film on each electrode until the photocurrent between the cathode (411) and the first dynode (401) and between the cathode (411) and the anode (410) reaches its maximum value. Then the current of the Cs source (3) is turned off, and the residual alkali is extracted for 10 to 60 min to obtain a stable Na2KSb(Cs) film layer.

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