Isotope screening method and device
By ablation of metal compound targets, the particle beam is excited, and combined with cooling and multi-stage ionization technology, the problem of high-quality isotope screening of active metal ions in ion trap quantum computing is solved, and efficient and pure isotope screening is achieved, which improves the efficiency and purity of ion trap quantum computing.
Patent Information
- Application Number
- CN202510330408.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-19
- Publication Date
- 2025-06-06
AI Technical Summary
In ion trap quantum computing, active metal ions (such as barium or calcium) are difficult to make pure single-plasma particles in normal environments, heating furnaces, and the particle beam speed is too fast during laser ablation and dissociation, resulting in Doppler frequency shift, making it difficult to achieve high-quality isotope screening.
The particle beam of neutral atoms is excited by ablating the metal compound target material of the target metal element and is subjected to cooling and deceleration treatment. Then, the atoms are ionized to the high-excited state using a screen pump laser of more than one level, and finally the atoms in the high-excited state are ionized by the direct ionization laser at the last stage, so that they carry a positive charge and obtain a positive charge of the target mass number. The line width of the screening pump laser is smaller than the minimum frequency difference of the isotope frequency shift of the element to be screened to achieve efficient isotope screening.
It reduces the difficulty of obtaining pure target isotope crystals, improves the efficiency of large-scale screening of target isotopes, solves the problem of impurity isotope pollution caused by Doppler shifts, and enhances the purity of ion crystals in ion trap quantum computing.
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Figure CN120102677A_ABST
Abstract
Description
Technical Field
[0001] This article relates to ion quantum computing technology, and in particular to a method and device for isotope screening. Background Art
[0002] Ion trap quantum computing requires the use of electric potential fields in a vacuum to achieve stable trapping of specific types of ions. The purity screening of trapped ions is usually implemented by photoionization. Since different types of elements have different energy level structures, the wavelengths of their ionization lasers vary greatly, which can be used for element screening. In actual operation, by adjusting the frequency of the laser to excite the outermost electrons of a specific type of element, the outermost electrons of the atom can be controllably excited, so that it is ionized into ions and thus trapped. Generally speaking, when inactive metal elements (such as ytterbium) are used for quantum computing in the field of ion trap quantum computing, ytterbium metal can be directly used for thermal evaporation to obtain neutral ytterbium atoms in an ultra-high vacuum. However, for the preparation of ion quantum bits using active metal ions (such as barium or calcium), it is difficult to make a particle heating furnace of active metal elements in a normal environment because active metal ions are easily oxidized at room temperature and pressure. The usual method is to make a target material with an active metal compound, and then use a pulsed laser to ablate the target material to instantly excite and dissociate the metal compound into high-speed atoms and ion vapors. By irradiating the atoms in these high-speed particle beams with an ionizing laser of a specific frequency, the target elements can be ionized into ions, which are then cooled and trapped. However, since the ablation and dissociation of metal salt compounds requires the destruction of chemical bonds, the pulsed laser energy required for ablation and release of atomic vapor is much higher than that for pure metal targets. Therefore, the initial flight velocity of the particles in the ablated high-speed particle beam is extremely fast and the temperature is extremely high. Due to the relativistic effect, a huge Doppler frequency shift will occur, making it difficult to achieve high-quality isotope screening.
[0003] In addition, since the ionization frequencies of different isotopes of the same element often differ very little and very widely, usually in the range of tens to several gigahertz, Doppler shift and Doppler broadening often cover these tiny frequency differences, resulting in the mixing of other isotope ions in actual implementation, contaminating the ion crystal.
[0004] The related technology implements isotope screening by adjusting the frequency of the first-stage ionization light; at the same time, the second-stage ionization light is used to achieve complete ionization, wherein the second-stage ionization light does not have a screening function. Although certain effects can usually be achieved for elements with large differences in the first-stage ionization transition frequencies between different isotopes, such as the 399nm transition frequency shift of ytterbium, which is usually several hundred megahertz, much larger than the transition line width (about 30 megahertz), the effect is not good for elements with smaller frequency differences, such as barium, whose 554nm transition isotope frequency shift is usually in tens of megahertz, which is equivalent to the line width (about 19 megahertz); especially for elements with extremely low natural abundance, such as the natural abundance of calcium-43 isotope is only 0.135%, the purification of isotopes is extremely complex and expensive. In addition, the atoms to be screened emitted by the particle beam usually have a very high speed. Due to the relativistic effect, the external laser felt by these atoms will produce a Doppler frequency shift, and this frequency shift is fatal to isotope screening - the impurity isotopes will be ionized due to the frequency shift caused by the speed; on the other hand, since the ion trap that binds the ionized ions has a certain capacity upper limit, the energy depth of the ion trap is usually less than 0.1eV. Therefore, for particles with kinetic energy greater than 0.1eV at the time of initial emission, even if they have been ionized, they will rush out of the binding area and cannot be retained.
[0005] In summary, when using active metal ions (such as barium or calcium) to prepare ion qubits, the particle beam speed obtained by laser ablation of the target material is too fast, which will cause a huge Doppler frequency shift; it is extremely difficult to achieve isotope screening by simply using frequency modulation of the primary ionization light, especially when obtaining pure target isotope crystals at a scale of more than 10 ions; the isotope screening technology based on photoionization in related technologies cannot achieve efficient isotope screening well, which limits the efficiency of obtaining large-scale ion crystals; in order to realize large-scale ion trap quantum computing, tens of thousands or even millions of pure ion qubits are often required. How to improve the large-scale screening of target isotopes has become a problem that must be solved for large-scale ion trap quantum computing. Summary of the invention
[0006] The present application embodiment provides a method for isotope screening, comprising: ablating a metal compound target of a target metal element and exciting a particle beam containing neutral atoms of a preset mass number; Cooling and decelerating the excited particle beam; Ionize atoms with a preset mass number to a highly excited state by more than one level of screening pump laser; The highly excited atoms are ionized by the final direct ionization laser to carry positive charge, so as to obtain positively charged ions with target mass number; The screening pump laser includes a laser having the following characteristics: it can drive the atoms to undergo transitions, and its line width is smaller than the minimum frequency difference of the isotope frequency shift of the transition spectrum line of the element to be screened, and the minimum frequency difference is the minimum value of all differences obtained by taking the difference between the transition frequencies of all isotopes to be screened.
[0007] In another aspect, the embodiment of the present application further provides an isotope screening device, comprising: a particle beam generating unit, an atom cooling unit, a successive ionization unit and a final ionization unit; wherein, Particle beam generating unit, atomic cooling unit, successive ionization unit and final ionization unit; wherein, The particle beam generating unit is configured to: ablate a metal compound target of a target metal element and excite a particle beam containing neutral atoms of a preset mass number; The atomic cooling unit is configured to: cool and decelerate the excited particle beam; The successive ionization unit is configured to: ionize atoms with a preset mass number to a highly excited state by more than one level of screening pump laser; The final ionization unit is configured to: ionize highly excited atoms through a final direct ionization laser to make them carry positive charges, so as to obtain positively charged ions with a target mass number; The screening pump laser includes a laser having the following characteristics: it can drive the atoms to undergo transitions, and its line width is smaller than the minimum frequency difference of the isotope frequency shift of the transition spectrum line of the element to be screened, and the minimum frequency difference is the minimum value of all differences obtained by taking the difference between the transition frequencies of all isotopes to be screened.
[0008] The disclosed embodiment cools and decelerates a particle beam containing neutral atoms of a preset mass number, ionizes the atoms with the preset mass number to a highly excited state through one or more screening pump lasers, and ionizes the highly excited atoms through a final direct ionization laser, thereby reducing the difficulty of obtaining pure target isotope crystals and providing technical support for improving large-scale screening of target isotopes.
[0009] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or be understood by implementing the present application. Other advantages of the present application can be realized and obtained by the schemes described in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The accompanying drawings are used to provide an understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.
[0011] Figure 1A flow chart of the method for isotope screening according to an embodiment of the present disclosure; Figure 2 A structural block diagram of an apparatus for isotope screening according to an embodiment of the present disclosure; Figure 3 A schematic diagram of isotope screening according to an embodiment of the present disclosure; Figure 4 A schematic diagram of another isotope screening according to an embodiment of the present disclosure; Figure 5 A schematic diagram of another isotope screening according to an embodiment of the present disclosure; Figure 6 It is a partial energy level diagram of barium element; Figure 7 This is a schematic diagram of the isotope transition intensity of an embodiment of the present disclosure; Figure 8 This is a schematic diagram of the incident atomic cooling laser of an embodiment of the present disclosure; Fig. 9 It is a comparison chart of the cooling effect of the embodiment of the present disclosure. DETAILED DESCRIPTION
[0012] The present application describes multiple embodiments, but the description is exemplary rather than restrictive, and it is obvious to those skilled in the art that there may be more embodiments and implementations within the scope of the embodiments described in the present application. Although many possible feature combinations are shown in the drawings and discussed in the specific embodiments, many other combinations of the disclosed features are also possible. Unless specifically limited, any feature or element of any embodiment may be used in combination with any other feature or element in any other embodiment, or may replace any other feature or element in any other embodiment.
[0013] The present application includes and contemplates combinations of features and elements known to those of ordinary skill in the art. The embodiments, features and elements disclosed in the present application may also be combined with any conventional features or elements to form a unique invention scheme. Any features or elements of any embodiment may also be combined with features or elements from other invention schemes to form another unique invention scheme. Therefore, it should be understood that any feature shown and / or discussed in the present application may be implemented individually or in any appropriate combination. Therefore, except for the limitations made according to the attached claims and their equivalents, the embodiments are not subject to other restrictions. In addition, various modifications and changes may be made within the scope of protection of the attached claims.
[0014] In addition, when describing representative embodiments, the specification may have presented the method and / or process as a specific sequence of steps. However, to the extent that the method or process does not rely on the specific order of the steps described herein, the method or process should not be limited to the steps of the specific order described. As will be understood by those of ordinary skill in the art, other sequences of steps are also possible. Therefore, the specific sequence of the steps set forth in the specification should not be interpreted as a limitation to the claims. In addition, the claims for the method and / or process should not be limited to the steps of performing them in the order written, and those skilled in the art can easily understand that these sequences can be changed and still remain within the spirit and scope of the embodiments of the present application.
[0015] Figure 1 Flow chart of the method for isotope screening according to an embodiment of the present disclosure, as shown in Figure 1 As shown, including: Step 101, ablating a metal compound target of a target metal element and exciting a particle beam containing neutral atoms of a preset mass number; In one exemplary embodiment, the disclosed embodiments may utilize a pulsed laser to perform an ablation operation.
[0016] Step 102, cooling and decelerating the excited particle beam; Step 103: Ionize atoms with a preset mass number to a highly excited state by using a screening pump laser of one or more levels. Step 104, ionizing the atoms in the highly excited state by the final stage direct ionization laser to make them carry positive charge, so as to obtain atoms carrying positive charge; Among them, the screening pump laser includes a laser with the following characteristics: it can drive atoms to transition, and the line width is smaller than the minimum frequency difference of the isotope frequency shift of the transition spectrum line of the element to be screened, and the minimum frequency difference is the minimum value of all differences obtained by subtracting the transition frequencies of all isotopes to be screened.
[0017] The disclosed embodiment cools and decelerates a particle beam containing neutral atoms of a preset mass number, ionizes the atoms with the preset mass number to a highly excited state through one or more screening pump lasers, and ionizes the highly excited atoms through a final direct ionization laser, thereby reducing the difficulty of obtaining pure target isotope crystals and providing technical support for improving large-scale screening of target isotopes.
[0018] In an exemplary embodiment, the present disclosure embodiment refers to the related art that a particle beam generator can eject ionized neutral particles with different isotope abundances (the atoms with preset mass numbers mentioned above); an electric potential field is generated by an ion trapping device to confine positively charged atoms.
[0019] In an exemplary embodiment, the target metal element in the embodiment of the present disclosure includes calcium or barium; the preset elements in the embodiment of the present disclosure may also include cesium, rubidium, potassium, sodium, lithium, barium, strontium, etc.
[0020] In an exemplary embodiment, the metal compound target of the embodiment of the present disclosure includes: It is made of a compound containing the target metal element, which is in a solid form with stable physical and chemical properties at room temperature and pressure.
[0021] In an exemplary embodiment, the metal compound target of the embodiment of the present disclosure includes one or any combination of the following metal compounds: Oxides, chlorides, fluorides, sulfate compounds, carbonate compounds and titanate compounds.
[0022] In an exemplary embodiment, the embodiment of the present disclosure performs cooling and deceleration processing on the excited particle beam, including: The particle beam is cooled and decelerated by a predetermined atom cooling laser; Among them, there is an overlapping area between the atomic cooling laser and the particle beam; there is a preset angle between the advancing direction of the atomic cooling laser and the advancing direction of the particle beam, and the preset angle ranges from 90 to 180 degrees.
[0023] In an exemplary embodiment, the screening pump laser in the embodiment of the present disclosure may include a narrow line width laser. The narrow line width laser in the embodiment of the present disclosure can drive the energy level transition of the isotope screened atoms, and its laser frequency varies according to the atomic isotope mass number, thereby playing a screening role.
[0024] In an exemplary embodiment, the embodiment of the present disclosure ionizes atoms with a preset mass number to a highly excited state by screening a pump laser at one level or more, including: Through the first stage screening pump laser of more than two stages of screening pump laser, the energy level of the atom is pumped from the ground state (G) to the first excited state energy level E (1) energy level, realizing the first isotope screening.
[0025] The first ionization in the disclosed embodiment not only performs isotope selection based on frequency, but also produces a velocity screening effect, thereby eliminating particles with excessively high velocities for subsequent ionizations, thereby reducing the impact of Doppler frequency shift.
[0026] In an exemplary embodiment, the disclosed embodiment ionizes atoms with a preset mass number to a highly excited state by using more than one level of screening pump laser, including: The i+1th level screening pump laser of the two or more levels screening pump laser excites the atom from the i-th excited state energy level E(i) energy level to the i+1th excited state energy level E(i+1) energy level (higher excited state energy level); and / or, The atom spontaneously radiates from the i-th excited state energy level E(i) to the i-th auxiliary energy level R(i) energy level, and the i+1-th screening pump laser excites the auxiliary energy level R(i) to the i+1-th excited state energy level E(i+1) energy level (higher excited state energy level).
[0027] In an exemplary embodiment, the final stage direct ionization laser of the embodiment of the present disclosure includes: a laser having a frequency greater than or equal to a preset frequency threshold, wherein the frequency threshold is the frequency of the laser corresponding to the energy level difference between the nth excited state energy level with the highest energy and the continuous energy level reached by the screening pump laser excitation. The final stage direct ionization laser of the embodiment of the present disclosure may be a narrow line width laser, a wide spectrum laser, or a screening pump laser that meets the above energy requirements.
[0028] In an exemplary embodiment, the laser line width of the narrow line width laser in the embodiment of the present disclosure is less than or equal to 10 MHz; the laser line width of the narrow line width laser in the embodiment of the present disclosure may be less than or equal to 1 MHz.
[0029] In an exemplary embodiment, the atom cooling laser in the embodiment of the present disclosure includes: the first-stage screening pump laser of the first-stage screening pump laser that has been modulated and has a longer wavelength, and the laser frequency offset is in the range of 0.1 GHz to 10 GHz. It should be noted that the frequencies of the two beams of light are not completely consistent, and the upper limit of the frequency difference is within 10 GHz, but they can be the light output by the same laser. For example, for the Ba element, both are output by a 553nm laser. Assuming that the wavelength of the first-stage screening pump laser used for the same bit screening is 553.701650nm, the atom cooling laser should be a laser with a longer wavelength, and the wavelength can be 553.702000nm. According to the specific element and particle beam energy, there should be a better wavelength, but it must be a longer wavelength, and the frequency difference is within the range of several hundred megahertz to 10 GHz; this frequency difference can be obtained by using frequency shifting devices such as acousto-optic modulators.
[0030] Figure 2 The structural block diagram of the device for isotope screening of the embodiment of the present disclosure is as follows: Figure 2 As shown, it includes: a particle beam generating unit, an atom cooling unit, a successive ionization unit and a final ionization unit; wherein, Particle beam generating unit, atomic cooling unit, successive ionization unit and final ionization unit; wherein, The particle beam generating unit is configured to: ablate a metal compound target of a target metal element and excite a particle beam containing neutral atoms of a preset mass number; The atomic cooling unit is configured to: cool and decelerate the excited particle beam; The successive ionization unit is configured to: ionize atoms with a preset mass number to a highly excited state by more than one level of screening pump laser; The final ionization unit is configured to: ionize highly excited atoms through a final direct ionization laser to make them carry positive charges, so as to obtain positively charged ions with a target mass number; Among them, the screening pump laser includes a laser with the following characteristics: it can drive atoms to transition, and the line width is smaller than the minimum frequency difference of the isotope frequency shift of the transition spectrum line of the element to be screened, and the minimum frequency difference is the minimum value of all differences obtained by subtracting the transition frequencies of all isotopes to be screened.
[0031] The disclosed embodiment cools and decelerates a particle beam containing neutral atoms of a preset mass number, ionizes the atoms with the preset mass number to a highly excited state through one or more screening pump lasers, and ionizes the highly excited atoms through a final direct ionization laser, thereby reducing the difficulty of obtaining pure target isotope crystals and providing technical support for improving large-scale screening of target isotopes.
[0032] In an exemplary embodiment, the target metal element in the embodiments of the present disclosure includes calcium or barium.
[0033] In an exemplary embodiment, the metal compound target in the embodiment of the present disclosure includes: The invention is made of a compound containing the target metal element, and the compound is in a solid form with stable physical and chemical properties at normal temperature and pressure.
[0034] In an exemplary embodiment, the atomic cooling unit of the present disclosure is configured as follows: The particle beam is cooled and decelerated by a predetermined atom cooling laser; Among them, there is an overlapping area between the atomic cooling laser and the particle beam; there is a preset angle between the advancing direction of the atomic cooling laser and the advancing direction of the particle beam, and the preset angle ranges from 90 to 180 degrees.
[0035] In one illustrative example, the screening pump laser in the disclosed embodiments comprises a narrow linewidth laser.
[0036] In an exemplary embodiment, the successive ionization unit of the present disclosure is configured as follows: The energy level of the atom is pumped from the ground state to the first excited state energy level by the first level screening pump laser of more than two levels of screening pump laser, thereby realizing the first isotope screening.
[0037] In an exemplary embodiment, the successive ionization unit of the present disclosure is configured as follows: The i+1th level screening pump laser of the two or more levels of screening pump laser excites the atom from the i-th excited state energy level to the i+1th excited state energy level; and / or, The atom spontaneously radiates from the i-th excited state energy level to the i-th auxiliary energy level, and the i+1-th screening pump laser excites the auxiliary energy level to the i+1-th excited state energy level.
[0038] In an illustrative example, the final stage direct ionization laser in the embodiment of the present disclosure includes: a laser having a frequency greater than or equal to a preset frequency threshold; The frequency threshold is the frequency of the laser corresponding to the energy level difference between the highest energy n-th excited state energy level reached by the screened pump laser excitation and the continuous energy level.
[0039] In an exemplary embodiment, the laser line width of the narrow line width laser in the embodiment of the present disclosure is less than or equal to 10 MHz.
[0040] In an exemplary embodiment, the atomic cooling laser of the embodiment of the present disclosure includes: the first-stage screening pump laser of the above-stage screening pump lasers is modulated, and the laser frequency offset is in the range of 0.1 GHz to 10 GHz.
[0041] The following briefly describes the embodiments of the present disclosure through application examples. The application examples are only used to illustrate the embodiments of the present disclosure and are not used to limit the protection scope of the embodiments of the present disclosure.
[0042] Application Examples The disclosed embodiment makes full use of the atomic energy level, and sequentially pumps the atomic energy level to the first excited state E(1) energy level, the second excited state E(2) energy level, and the nth excited state E(n) energy level through n (n≥2) level screening pump lasers, and finally uses the final stage direct ionization laser to excite it to the continuous energy level of the atom, thereby achieving a specific type of high-purity ion quantum bit crystal in ion trap quantum computing.
[0043] Figure 3 Schematic diagram of isotope screening in an embodiment of the present disclosure, such as Figure 3As shown, the atom is excited from the ground state energy level G to the first excited state energy level E(1) by the first stage screening pump laser L(1), and then excited from the first excited state energy level E(1) to the second excited state energy level E(2) by the second stage screening pump laser L(2), and so on, until the last stage screening pump laser L(n) excites it to the nth excited state energy level E(n); then the final stage direct ionization laser excites it from the nth excited state energy level E(n) to the ionized state; wherein, the energy level difference between the highest nth excited state energy level E(n) and the continuous energy level corresponds to the laser threshold frequency f, and the final stage direct ionization laser only needs to contain a laser component with a laser frequency greater than f.
[0044] Figure 4 A schematic diagram of another isotope screening of an embodiment of the present disclosure is shown in FIG. Figure 4 As shown, the atom is excited from the ground state energy level G by the first screening pump laser L (1) to the short-lived first excited state energy level E (1) and rapidly spontaneously radiates to the first auxiliary energy level R (1); the second screening pump laser L (2) excites it from the first auxiliary energy level R (1) to the second excited state energy level E (2), and so on, until the last screening pump laser L (n) excites it to the nth excited state energy level E (n); and then the final direct ionization laser excites it from the nth excited state energy level E (n) to the ionized state.
[0045] Figure 5 FIG. 1 is another schematic diagram of isotope screening according to an embodiment of the present disclosure, as shown in FIG. Figure 5 As shown, the atom is excited from the ground state energy level G by the first screening pump laser L (1) to the first excited state energy level E (1) and spontaneously radiates to the first auxiliary energy level R (1). The second screening pump laser L (2) excites it from the first auxiliary energy level R (1) to the second excited state energy level E (2). The third screening pump laser L3 directly excites it to the third excited state energy level E (3), and so on, until it is finally excited to the nth excited state energy level E (n). Then, the final direct ionization laser excites it from the nth excited state energy level E (n) to the ionized state.
[0046] In each stage of the optical pumping process of the disclosed embodiment, an isotope screening process can be realized by utilizing the isotope frequency shift, so the probability of the impurity ions being finally ionized is , the purity of the final ionic crystal is ( .
[0047] Figure 6This is a schematic diagram of some energy levels of the barium (Ba) element. In the figure, the energy level with a small circle in the upper right corner represents the odd parity of the energy level, and the energy level without a small circle represents the even parity of the energy level. Taking barium (Ba) and its isotopes as an example, the stable isotopes of barium in nature are mainly Ba-138, Ba-137, Ba-135, Ba-136, Ba-134 and Ba-132, and their natural abundances are 71.7%, 11.2%, 6.59%, 7.85%, 2.42% and 0.1% respectively. The ground state of barium atoms is usually used. Energy levels and excited states The transition wavelength is The first stage ionization is carried out by transitions such as Figure 6 As indicated by the bold arrows, the transition intensities of these isotopes are Figure 7 As shown; by adjusting The frequency of the laser can achieve isotope selection within a certain limit; for example, in order to obtain the relatively low abundance Ba-137 isotope, the laser frequency should be placed at a relative low frequency relative to the Ba-138 resonance peak. Megahertz, that is Figure 7 At the middle vertical line mark; at this time, according to the relative intensity of the resonance peak, it can be calculated that there is about a 70.62% probability of exciting the transition corresponding to the Ba-137 isotope, and there are also probabilities of 11.06%, 11.96%, 4.5% and 1.75% of non-resonant excitation of Ba-138, Ba-135, Ba-136 and Ba-134 isotopes. If the final direct ionization light is directly used on this basis (the frequency threshold f is about 718.742 terahertz, that is, the wavelength of the final direct ionization light is required to be ), these isotopes will be ionized into ions, making the trapped ion crystal impure; Figure 6 As indicated, in the related art, 405nm broadband laser is usually used to implement the final stage direct ionization. However, if the solution proposed by the present invention is adopted on this basis, at least two screenings are performed. Figure 6 As shown by the dotted line, using narrow line width The laser excites the energy level and excited state energy level The transition line width of this transition is about The theoretical impurity probability is also one percent. Therefore, this transition is used for secondary screening. In the first screening, 29.38% of the impurity ions will only have a probability of further ionization of about 0.3%, so the total impurity rate will be less than 0.9 ten thousandths. The final direct ionization light only needs a wavelength less than Therefore, the first and second screening pump lasers can both serve as the final stage direct ionization without additional introduction.
[0048] Another embodiment is Figure 6 As shown on the right, the first screening pump laser pumps the atomic energy level to an excited state energy level Afterwards, through spontaneous radiation, a large number of layouts spontaneously radiate back to the ground state , and some of the atomic energy levels fall into the auxiliary energy level ; At this time, through the second screening pump laser Pump it to an excited state This process also has only one percent of the transition line width, and the final ionization light requires a wavelength less than , and no additional introduction is required.
[0049] In order to better improve the screening effect and particle utilization, the embodiment of the present disclosure additionally introduces a beam of atomic cooling laser, such as Figure 8 As shown, there is an angle between the atomic cooling laser and the particle beam, and the angle should be greater than 90 degrees, and the closer it is to 180 degrees, the better the effect. There is an overlapping area between the atomic cooling laser and the particle beam, and this overlapping area is the effective area where the cooling laser has a cooling effect on the particle beam. In order to estimate the cooling effect brought by this effect, refer to the relevant technology: for a mass of And the speed is Particles, using the wave vector The driving laser excites it to have a natural line width The average force felt by the energy level transition is:
[0050] Among them, the probability of the upper energy level excited state is: , is the saturation parameter of the laser intensity, is the detuning of the laser frequency, is the reduced Planck constant; Under the low-speed approximation, the average force can be expanded as:
[0051] in, ; Combining the two equations, we can get the initial velocity The entry length is The particles in the overlapping area eventually move at a speed of Leaving this region, the process approximately satisfies:
[0052] To estimate , integrate both sides and solve the equation.
[0053] According to the above two estimates of the embodiment of the present disclosure, for Ba, whose melting point is 900K, when it is ejected at a corresponding speed, after passing through a 10mm long overlap zone, its corresponding particle temperature can be reduced to about 130K (@ ); When laser ablation is used, the average temperature of the particle beam will reach 37413K. As long as the overlap area is extended to 100mm, 37.13K (@ )'s final temperature, thereby greatly reducing the temperature of the particle beam; Fig. 9 As shown in the figure, the velocity of a particle beam with a certain temperature satisfies the Boltzmann distribution. For particle beams at temperatures of 900K and 37413K, it can be seen that the 375m / s velocity line corresponding to the 0.1eV well depth of the ion trap can only cover a small part of the particles, and the utilization rate is low. After deceleration, when the temperature of the particle beam is reduced to 130K and below, almost all the main particles meet the energy requirements for being trapped.
[0054] It will be appreciated by those skilled in the art that all or some of the steps, systems, and functional modules / units in the methods disclosed above may be implemented as software, firmware, hardware, and appropriate combinations thereof. In hardware implementations, the division between the functional modules / units mentioned in the above description does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed by several physical components in cooperation. Some or all components may be implemented as software executed by a processor, such as a digital signal processor or a microprocessor, or implemented as hardware, or implemented as an integrated circuit, such as an application-specific integrated circuit. Such software may be distributed on a computer-readable medium, which may include a computer storage medium (or non-transitory medium) and a communication medium (or transient medium). As is known to those skilled in the art, the term "computer storage medium" includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and can be accessed by a computer. In addition, it is well known to those skilled in the art that communication media typically contain computer-readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media.
Claims
1. A method for isotope screening, characterized in that: include: ablating a metal compound target of a target metal element and exciting a particle beam containing neutral atoms of a preset mass number; Cooling and decelerating the excited particle beam; Ionize atoms with a preset mass number to a highly excited state by more than one level of screening pump laser; The highly excited atoms are ionized by the final direct ionization laser to carry positive charge, so as to obtain positively charged ions with target mass number; The screening pump laser includes a laser having the following characteristics: it can drive the atoms to undergo transitions, and its line width is smaller than the minimum frequency difference of the isotope frequency shift of the transition spectrum line of the element to be screened, and the minimum frequency difference is the minimum value of all differences obtained by taking the difference between the transition frequencies of all isotopes to be screened.
2. The method according to claim 1, characterized in that The target metal element includes calcium or barium.
3. The method according to claim 1, characterized in that The metal compound target comprises: The method is made of a compound containing the target metal element, which is in a solid form with stable physical and chemical properties at normal temperature and pressure.
4. The method according to claim 1, characterized in that The step of cooling and decelerating the excited particle beam comprises: Cooling and decelerating the particle beam by using a predetermined atomic cooling laser; There is an overlapping area between the atom cooling laser and the particle beam; there is a preset angle between the advancing direction of the atom cooling laser and the advancing direction of the particle beam, and the preset angle ranges from 90 to 180 degrees.
5. The method according to claim 1, characterized in that The screened pump laser includes a narrow linewidth laser.
6. The method according to claim 1, characterized in that The step of ionizing atoms with a preset mass number to a highly excited state by screening the pump laser at one level or more comprises: The energy level of the atom is pumped from the ground state to the first excited state energy level by the first level screening pump laser of more than two levels of screening pump laser, thereby realizing the first isotope screening.
7. The method according to claim 6, characterized in that The step of ionizing atoms with a preset mass number to a highly excited state by using more than one level of screening pump laser comprises: The i+1th level screening pump laser of the two or more levels of screening pump laser excites the atom from the i-th excited state energy level to the i+1th excited state energy level; and / or, The atom spontaneously radiates from the i-th excited state energy level to the i-th auxiliary energy level, and the i+1-th screening pump laser excites the auxiliary energy level to the i+1-th excited state energy level.
8. The method according to any one of claims 1 to 6, characterized in that: The final-stage direct ionization laser includes: a laser having a frequency greater than or equal to a preset frequency threshold; The frequency threshold is the frequency of the laser corresponding to the energy level difference between the highest energy n-th excited state energy level and the continuous energy level reached after the screening pump laser excitation.
9. The method according to claim 5, characterized in that The laser line width of the narrow line width laser is less than or equal to 10 MHz.
10. The method according to claim 1 or 5, characterized in that: The atom cooling laser comprises: the first-order screening pump laser of the above-order screening pump lasers which has been modulated, and the laser frequency deviation is in the range of 0.1 GHz to 10 GHz.
11. An isotope screening device, comprising: Particle beam generating unit, atomic cooling unit, successive ionization unit and final ionization unit; wherein, The particle beam generating unit is configured to: ablate a metal compound target of a target metal element and excite a particle beam containing neutral atoms of a preset mass number; The atomic cooling unit is configured to: cool and decelerate the excited particle beam; The successive ionization unit is configured to: ionize atoms with a preset mass number to a highly excited state by more than one level of screening pump laser; The final ionization unit is configured to: ionize highly excited atoms through a final direct ionization laser to make them carry positive charges, so as to obtain positively charged ions with a target mass number; The screening pump laser includes a laser having the following characteristics: it can drive the atoms to undergo transitions, and its line width is smaller than the minimum frequency difference of the isotope frequency shift of the transition spectrum line of the element to be screened, and the minimum frequency difference is the minimum value of all differences obtained by taking the difference between the transition frequencies of all isotopes to be screened.