RU180089U1 - Electrostatic energy analyzer of charged particles - Google Patents

Abstract

The utility model relates to the field of energy analysis of charged particles formed as a result of exposure to x-ray radiation, an ion or electron beam on the surface of a solid-state object under study, and is intended for recording these energy spectra in order to determine the composition and properties of substances for studying objects of micro- and nanoelectronics by electronic methods, ion and photoelectron spectroscopy. The technical result is an improvement in the functional characteristics of the analyzer, namely an increase in dispersion of at least 2.6 times and specific dispersion from 486% to 688%. The electrostatic energy analyzer of charged particles contains two electrodes made in the form of cylindrical surfaces, which in each of the planes perpendicular to their rectilinear generators have a shape described by a two-dimensional curve, where the constants are related to the lower and upper electrodes, respectively, and also has additional shielding electrodes , the contours of the boundaries of which are described by a function located at the ends of the electrodes of the energy analyzer, made in the form of cylindrical surfaces. Oh, the lower electrode containing the inlet and outlet openings can be made with an insert of dielectric material, for example fluoroplastic, located between the inlet and outlet openings, and equal in width to the width of these openings. And also the electrostatic energy analyzer additionally has a diaphragm connected to the lower electrode and made of the same material, which is located opposite the outlet of the energy analyzer on the bottom side of the lower electrode parallel to it.

Description

The utility model relates to the field of energy analysis of charged particles formed as a result of exposure to x-ray radiation, an ion or electron beam on the surface of a solid-state object under study, and is intended for recording these energy spectra in order to determine the composition and properties of substances for studying objects of micro- and nanoelectronics by electronic methods, ion and photoelectron spectroscopy.

. У энергоанализатора существует режим работы с более острой фокусировкой второго порядка, но величина энергетической дисперсии при этом снижается до значения

.An analogue of the claimed utility model is an energy analyzer formed by two flat parallel electrodes with inlet and outlet holes in the lower electrode, called in the literature an analyzer with a uniform electrostatic field [Afanasyev VP, Yavor S.Ya. Electrostatic analyzers for charged particle beams. M .: Nauka, 1978. 224 s]. A potential difference, which slows down for the analyzed particles, is applied between the flat electrodes. Entering the energy analyzer through the inlet, particles move along arcuate paths and leave the device through the outlet. The analyzer is simple in design, but its disadvantage is the low value of dispersion and specific dispersion (the ratio of dispersion to the value of the main aberration term, which depends on the angle of the beam in the dispersion plane). The dispersion value, expressed in fractions of the base of the device (the distance between the inlet and outlet), is

. The energy analyzer has a mode of operation with sharper focusing of the second order, but the magnitude of the energy dispersion in this case decreases to a value

.

и высотой

этого прямоугольника, а также при подходящем расстоянии между источником и нижним электродом

удается добиться стигматической фокусировки второго порядка. Так, например, в частном случае при

и

фокусировка второго порядка обеспечивается при угле влета частиц

. Недостаток: невысокая энергетическая дисперсия, составляющая в этом режиме

.An analogue of the claimed utility model is also the box-type electrostatic energy analyzer [Afanasyev VP, Yavor S.Ya. A high-speed energy analyzer with double focusing // Letters to the Journal. those. physics. 1975.V. 1. No. 9. S. 779-783]. It consists of a flat grounded electrode with inlet and outlet openings and a “P” -shaped one, to which a braking potential is applied, that is, the device is a mirror-type analyzer. Particle trajectories in the analyzer field have an arc shape. In cross section, the analyzer is a rectangle. With appropriate ratios between the length

and tall

of this rectangle, as well as at a suitable distance between the source and the lower electrode

it is possible to achieve a second-order stigmatic focus. So, for example, in the particular case when

and

second-order focusing is ensured at the angle of entry of particles

. Disadvantage: low energy dispersion, component in this mode

.

, что даже при малых входной и выходной апертурах существенно ограничивает величину удельной дисперсии.An analogue of the claimed utility model is also an energy analyzer, consisting of two hyperbolic cylindrical electrodes, between which a braking potential difference is applied, which ensures the return of particles to the internal electrode [MM Bredov Multistage electrostatic energy analyzer with combined spatial focusing in two planes // Journal. those. physics. 1959. T. 29. No. 8. S. 1032-1037]. A pair of holes cut in the inner electrode play the role of the inlet and outlet, respectively. Particle motion occurs along curved curves. The disadvantage of this device is the low energy dispersion

, which even with small input and output apertures significantly limits the specific dispersion.

. Таким образом, недостаток известной конструкции: невозможность одновременно обеспечить высокую дисперсию и удельную дисперсию.An analogue of the claimed utility model is also an energy analyzer with a cylindrical shape of the electrodes, which is a cylinder cut into generators into two parts, so that in the plane perpendicular to the cuts, each of the electrodes has an arc shape [Ovsyannikova L.P., Fishkova T.Ya. Energy analyzer with a cylindrical shape of the electrodes // Letters in Journal. those. physics. 2004.V. 30. No. 7. S. 36–41]. In various versions, the ratio of the angular sizes of the electrodes may be different, but in any case, a braking potential difference is applied between the electrodes, which ensures the movement of particles along arcuate paths. The device belongs to mirror-type energy analyzers. The input and output of particles is carried out through holes cut into one of the electrodes. In the device, the energy dispersion can reach significant values, but at the same time, aberration broadenings are large, which leads to a decrease in the specific dispersion. Using modes with a lower level of aberration blur leads to a strong decrease in the energy dispersion to values

. Thus, the disadvantage of the known design: the inability to simultaneously provide high dispersion and specific dispersion.

An analogue of the claimed utility model is also an electrostatic energy analyzer, the falling electrodes of which are made in the form of cylindrical surfaces. The inner electrode is made in the form of two adjacent to each other and electrically connected half-cylinders, and the outer electrode is made in the form of two cylindrical surfaces that are closed at the edges with the inner electrode and quasi-parallel when removed from it [Golikov Yu.K., Utkin K.G., Grigoryev D.V. Inverse problems of the theory of electrostatic energy analyzers. I // Zh. those. physics. 1999.V. 69. No. 9. S. 128–131, A.S. 544307 USSR. Electrostatic energy analyzer / L.N. Gall, R.N. Gall, Yu.K. Golikov, K.G. Utkin: No. 2091369/25; declared 01/03/75.]. Sections perpendicular to the surfaces of the electrodes are described by the equation

,

,

– координаты;

и

– константы, причем

относится к внутреннему электроду, а

к внешнему электроду. Внутренний электрод также содержит входное и выходное отверстия, через которые проходит поток анализируемых частиц. К электродам прикладывается разный по значению потенциал. Таким образом, в объеме анализатора создается тормозящее поле, заставляющее двигаться частицы по дугообразным траекториям. Прибор обладает хорошими фокусирующими свойствами и может обеспечить высокий уровень энергетической дисперсии и удельной дисперсии. Недостатком конструкции являются неучтенные при расчетах паразитные краевые поля, а также весьма сложная форма электрода, через который осуществляется ввод и вывод анализируемых частиц.Where

,

- coordinates;

and

Are constants, moreover

refers to the internal electrode, and

to the external electrode. The inner electrode also contains an inlet and an outlet through which a stream of analyte particles passes. Different potentials are applied to the electrodes. Thus, a braking field is created in the analyzer volume, which forces the particles to move along arcuate paths. The device has good focusing properties and can provide a high level of energy dispersion and specific dispersion. A design flaw is the parasitic edge fields unaccounted for in the calculations, as well as the very complicated shape of the electrode through which the input and output of the analyzed particles is carried out.

An analogue of the claimed utility model is also an electrostatic energy analyzer, which is a component of an electrostatic spectrometer of angular and energy distributions of charged particles according to copyright certificate No. 1150680 [A.S. 1150680 USSR. Electrostatic spectrometer of angular and energy distributions of charged particles / M.A. Berezhkovsky, Yu.K. Golikov, V.Yu. Kolomenkov, A.A. Mayorov, S.I. Slepyshkov, V.A. Fedotov, N.A. Kholin, V.A. Pavlenko: No. 3649172 / 24-21; declared 10/03/83; publ. 04/15/85, Bull. No. 14]. The energy analyzer contains electrodes made in the form of cylindrical surfaces with sections in each of the planes perpendicular to their rectilinear generators, which are Bernoulli lemniscates, that is, algebraic curves given by the equation

,

,

– координаты;

и

– константы, причем

относится к внутреннему электроду, а

к внешнему электроду. Во внутреннем электроде прорезаны входное и выходное отверстия. Лемнискаты имеют разные фокусы и общую узловую точку, при этом узловая точка и фокусы обеих кривых лежат на одной прямой. Между электродами прикладывается тормозящее поле, то есть анализатор является анализатором зеркального типа, который по форме может быть назван лемнискатическим зеркалом. Движение частиц в поле прибора происходит по дуге. При вводе потока заряженных частиц под углом

к оси анализатора величина энергетической дисперсии составляет

. Недостатком указанного спектрометра является невысокое качество фокусировки и как следствие невысокая удельная дисперсия, а также необходимость вводить и выводить пучок через узкие щели, что ограничивает светосилу прибора.Where

,

- coordinates;

and

Are constants, moreover

refers to the internal electrode, and

to the external electrode. The inlet and outlet openings are cut in the inner electrode. The lemniscates have different foci and a common nodal point, while the nodal point and the foci of both curves lie on one straight line. A braking field is applied between the electrodes, that is, the analyzer is a mirror-type analyzer, which in shape can be called a lemniscatic mirror. The movement of particles in the field of the device occurs along an arc. When entering the flow of charged particles at an angle

the magnitude of the energy dispersion to the analyzer axis is

. The disadvantage of this spectrometer is the low quality of focusing and, as a consequence, the low specific dispersion, as well as the need to enter and output the beam through narrow slits, which limits the luminosity of the device.

, а другой содержит входное и выходное отверстия и расположен внутри первого симметрично относительно плоскости, проходящей через ребро двугранного угла и делящей его пополам. Между электродами прикладывается тормозящее поле, под действием которого частицы движутся по дугообразным траекториям. Прибор относится к анализаторам зеркального типа. Устройство способно обеспечивать работу с уровнем энергетической дисперсии

. Недостатком является то, что в расчетах не учтены эффекты краевых полей, чье влияние в условиях больших входной и выходной апертур приведет к сильному аберрационному размытию сфокусированного пучка, следствием которого будет существенное снижение удельной дисперсии.The closest analogue of the claimed utility model (prototype) is an analyzer of the type "dihedral angle" according to copyright certificate No. 1150680 [A.S. 865049 USSR. Electrostatic energy analyzer of charged particles / T.Ya. Fishkova: No. 2921173 / 18-25; declared 05/05.80; publ. 04/15/82, Bull. No. 14]. The device consists of two electrodes, one of which is made in the form of a dihedral angle of magnitude

and the other contains the inlet and outlet openings and is located inside the first symmetrically relative to the plane passing through the edge of the dihedral angle and dividing it in half. A braking field is applied between the electrodes, under the influence of which the particles move along arched paths. The device belongs to mirror-type analyzers. The device is able to provide work with the level of energy dispersion

. The disadvantage is that the calculations do not take into account the effects of edge fields, whose influence under conditions of large input and output apertures will lead to strong aberration blurring of the focused beam, which will result in a significant decrease in specific dispersion.

The technical problem to which the proposed utility model is directed is the creation of a device with high dispersion and specific dispersion.

The technical result of the implementation of the proposed utility model is to improve the functional characteristics of the analyzer, namely an increase in dispersion of at least 2.6 times and specific dispersion from 486% to 688%.

The solution to this technical problem is achieved by the fact that the electrostatic energy analyzer of charged particles contains two electrodes made in the form of cylindrical surfaces, which in each of the planes perpendicular to their rectilinear generators have a shape described by a two-dimensional curve

,

и

константы, относящиеся к нижнему и верхнему электроду соответственно, причем

, а также имеет дополнительные экранирующие электроды, контура границ которых описываются функциейWhere

and

constants related to the lower and upper electrode, respectively, and

, and also has additional shielding electrodes, the contours of the boundaries of which are described by the function

,

located at the ends of the electrodes of the energy analyzer, made in the form of cylindrical surfaces.

In addition, the lower electrode containing the inlet and outlet openings can be made with an insert of dielectric material, for example fluoroplastic, located between the inlet and outlet openings, and with a width equal to the width of these openings.

And also the electrostatic energy analyzer additionally has a diaphragm connected to the lower electrode and made of the same material, which is located opposite the outlet of the energy analyzer on the bottom side of the lower electrode parallel to it.

The authors found that the proposed electrostatic energy analyzer provides a new distribution of electric fields in the region of passage of the studied beams of charged particles, leading to the achievement of a technical result - an increase in dispersion and specific dispersion.

The essence of the utility model is illustrated in the drawing (Fig. 1), which shows a diagram of the proposed device. The device contains electrodes of the electrostatic energy analyzer 1 and 2, additional shielding electrodes 5-14, as well as a diaphragm 3 connected to the electrode 1 and made of the same material, and located opposite the outlet of the energy analyzer from the bottom of the electrode 1 parallel to it. The part of the electrode 1 located between the inlet and outlet openings, and equal in width to the width of these holes, can be made of a dielectric material, such as fluoroplastic, and is indicated in the drawing by the number 4.

The electrodes 1 and 2 are made in the form of two cylindrical surfaces with sections described by the equation

,

,

– координаты;

и

– константы, причем индекс «1» относится к нижнему электроду 1, а индекс «2» к верхнему электроду 2. Значения констант

и

задают форму нижнего и верхнего электрода соответственно. Минимальные геометрические размеры энергоанализатора ограничены областью применимости законов электронной оптики. Нижний электрод 1 заземляется, а на верхний подается тормозящий для анализируемых частиц потенциал

, тем самым между электродами 1 и 2 создается тормозящая для анализируемых частиц разность потенциалов

.Where

,

- coordinates;

and

- constants, and the index "1" refers to the lower electrode 1, and the index "2" to the upper electrode 2. Values of the constants

and

set the shape of the lower and upper electrode, respectively. The minimum geometric dimensions of the energy analyzer are limited by the field of applicability of the laws of electronic optics. The lower electrode 1 is grounded, and the braking potential for the analyzed particles is supplied to the upper one

Thus, between the electrodes 1 and 2, a potential difference is created that inhibits the particles being analyzed.

.

An important component of the energy analyzer is additional shielding electrodes 5 to 14. Each of the electrodes 5 to 14 is an arcuate section, the curvilinear boundary of which is described by the equation

,

,

– координаты;

и

– константы, причем индекс «н» относится к нижней границе секции, а индекс «в» к верхней границе секции. Каждая секция удовлетворяет условию

. На каждую секцию подается потенциал для компенсации краевых полей электростатического анализатора. На значения потенциалов накладываются условия

,

,

,

,

. Конкретная величина потенциалов подбирается в условиях эксперимента.Where

,

- coordinates;

and

- constants, and the index "n" refers to the lower boundary of the section, and the index "b" to the upper boundary of the section. Each section satisfies the condition

. A potential is applied to each section to compensate for the marginal fields of the electrostatic analyzer. Potential values impose conditions

,

,

,

,

. The specific value of the potentials is selected in the experimental conditions.

In addition to the lower electrode 1, a diaphragm 3 can be attached at a fixed distance from its lower boundary. The diaphragm 3 is a plate with a hole through which the analyzed particle flow passes.

. Траектории частиц в тормозящем поле представляют собой дугообразные кривые, сконцентрированные вблизи продольной плоскости симметрии 15. Электростатический энергоанализатор ввиду своих сильных диспергирующих свойств разделяет поток на моноэнергетические составляющие и фокусирует одну из них на выходное отверстие нижнего электрода 1. Покидая объем анализатора через выходное отверстие, частицы проходят через диафрагму 3. Развертка энергетического спектра осуществляется путем изменения значения потенциала

, обеспечивая последовательное прохождение каждой моноэнергетической компоненты через выходное отверстие энергоанализатора. Дополнительные экранирующие электроды 5 – 14 компенсируют паразитное влияние краевых полей электростатического энергоанализатора, что позволяет добиться высоких фокусирующих свойств и, следовательно, высокой удельной дисперсии. Для сохранения оптимальных условий фокусировки при осуществлении развертки спектра путем изменения потенциала

напряжения, поданные на электроды 5 – 14, также должны согласованно изменяться, сохраняя отношения потенциалов

,

,

,

,

и потенциала

неизменными. Наличие диафрагмы 3 позволяет осуществлять дополнительную сепарацию частиц по энергии. Кроме того, входное и выходное отверстия прорезаются в нижнем электроде в области, где форма электрода близка к плоской поверхности и где поле наиболее слабо, что вносит наименьшие паразитные искажения в распределение электростатического потенциала и позволяет анализировать пучки как конической, так и ленточной формы. Компьютерное моделирование в существующих на данный момент программных продуктах для траекторного анализа движения заряженных частиц в электрических полях показывает, что замена части нижнего электрода, расположенной между входным и выходным отверстиями, и по ширине равной ширине этих отверстий, диэлектрическим материалом, например, фторопластом, приводит к повышению удельной дисперсии заявленного в полезной модели анализатора.Energy analyzer works as follows. A beam of analyzed particles is introduced through the inlet of the energy analyzer. Between electrodes 1 and 2 of the electrostatic energy analyzer, a potential difference is created that inhibits the particles being analyzed.

. Particle trajectories in the braking field are arched curves concentrated near the longitudinal plane of symmetry 15. The electrostatic energy analyzer, due to its strong dispersing properties, divides the flow into monoenergetic components and focuses one of them on the outlet of the lower electrode 1. When leaving the analyzer, the particles pass through the outlet through the diaphragm 3. The development of the energy spectrum is carried out by changing the value of the potential

, ensuring the consistent passage of each monoenergetic component through the outlet of the energy analyzer. Additional shielding electrodes 5 - 14 compensate for the parasitic effect of the edge fields of the electrostatic energy analyzer, which allows to achieve high focusing properties and, therefore, high specific dispersion. To maintain optimal focusing conditions when performing a spectrum sweep by changing the potential

the voltages applied to the electrodes 5 - 14 must also be consistent to change, while maintaining the potential relationship

,

,

,

,

and capacity

unchanged. The presence of the diaphragm 3 allows for additional separation of particles by energy. In addition, the inlet and outlet openings are cut in the lower electrode in the region where the shape of the electrode is close to a flat surface and where the field is weakest, which introduces the least spurious distortions in the distribution of the electrostatic potential and makes it possible to analyze beams of both conical and ribbon shapes. Computer simulation in the currently existing software products for trajectory analysis of the movement of charged particles in electric fields shows that replacing the part of the lower electrode located between the inlet and outlet holes and with a width equal to the width of these holes with a dielectric material, for example, fluoroplastic, leads to increase the specific dispersion declared in the utility model of the analyzer.

There are various options for choosing the form and electrical control of the proposed energy analyzer, and the optimality of this choice depends on the specific conditions of the experiment.

Example 1

, полная апертура пучка в плоскости симметрии равна

. При таких входных параметрах пучка целесообразно подчинить форму энергоанализатора следующим условиям. Нижний электрод выбирается таким образом, чтобы его форма вблизи плоскости симметрии 15 была близка к плоской поверхности. Такой форме отвечает выражение Consider the case when the flow of negatively charged particles is investigated. Let the average angle of particle entry into the analyzer in the plane of symmetry with respect to the lower electrode be

, the full aperture of the beam in the plane of symmetry is

. With such input parameters of the beam, it is advisable to subordinate the shape of the energy analyzer to the following conditions. The lower electrode is selected so that its shape near the plane of symmetry 15 is close to a flat surface. This form corresponds to the expression

,

– расстояние между центрами входного и выходного отверстий, а единицы измерения величин

и

совпадают с единицами измерения

. Форма верхнего электрода определяется максимальной высотой подъема потока частиц с заданными средним углом ввода и апертурой, и с энергией настройки, отвечающей заданному значению потенциала

. С учетом запаса по высоте в 10% форма верхнего электрода задается выражениемWhere

- the distance between the centers of the inlet and outlet, and units of measurement

and

coincide with units

. The shape of the upper electrode is determined by the maximum height of the particle flow with a given average input angle and aperture, and with a tuning energy corresponding to a given potential value

. Taking into account a margin of 10% in height, the shape of the upper electrode is given by

.

. При таких параметрах энергоанализатор будет пропускать и фокусировать моноэнергетическую компоненту потока отрицательных частиц, отвечающую энергии 75 эВ.The lower electrode 1 is grounded, and a voltage is applied to the upper electrode 2

. With these parameters, the energy analyzer will transmit and focus the monoenergetic component of the flow of negative particles corresponding to an energy of 75 eV.

As a result of computer simulation, it was found that the best focusing quality will be ensured by a set of shielding electrodes, consisting of 5 pairs of sections, the boundaries of which are described by the following curves.

Sections 13 and 14: Lower Boundary

,

upper bound

.

Sections 11 and 12: lower bound

,

upper bound

.

Sections 9 and 10: lower bound

,

upper bound

.

Sections 7 and 8: Lower Boundary

,

upper bound

.

Sections 5 and 6: lower bound

,

upper bound

.

,

,

,

;

. При таких условиях эксперимента энергетическая дисперсия прибора, выраженная в единицах

, составляет

, а удельная дисперсия

. По сравнению с прототипом энергетическая дисперсия

увеличилась более чем в 2.5 раза, а удельная дисперсия

более чем в 4 раза.Computer simulation found that, to ensure the best quality of beam focusing, the potentials on additional shielding electrodes should be distributed as follows:

,

,

,

;

. Under such experimental conditions, the energy dispersion of the device, expressed in units

is

, and specific dispersion

. Compared to the prototype, energy dispersion

increased by more than 2.5 times, and the specific dispersion

more than 4 times.

Example 2

ниже границы электрода 1. Энергетическая дисперсия составляет

, удельная дисперсия

. The same conditions as in example 1, but opposite the outlet of the energy analyzer an additional diaphragm 3 is installed at a distance

below the boundary of electrode 1. The energy dispersion is

specific dispersion

.

Example 3

, удельная дисперсия

.The same conditions as in example 1 with the difference that the part of the lower electrode 1 located between the inlet and outlet openings and equal in width to the width of these openings is replaced by a dielectric material. The energy dispersion is

specific dispersion

.

Example 4

ниже границы электрода 1. Энергетическая дисперсия составляет

, удельная дисперсия

.The same conditions as in example 3, but opposite the outlet of the energy analyzer an additional diaphragm 3 is installed at a distance

below the boundary of electrode 1. The energy dispersion is

specific dispersion

.

A comparison of the parameters of the proposed device and the prototype are shown in table 1.

Table 1 - Comparison of the parameters of the proposed device and prototype Energy analyzer

Dispersion

Specific dispersion

Type "dihedral angle" (prototype) 7.2 452.21 Proposed device 18.7 2196.69 The proposed device with an additional aperture 18.7 2369.27 The proposed device with a part of the electrode replaced by a dielectric material 19.4 2935.86 The proposed device with a part of the electrode replaced by a dielectric material, with an additional diaphragm 19.4 3110.82

Thus, the proposed electrostatic energy analyzer due to the new distribution of electric fields in the region of passage of the studied beams of charged particles allows to obtain an increase in specific dispersion by more than 4 times compared with the prototype simultaneously with a dispersion increase of 2.6 times. Using a diaphragm for the purpose of additional separation of particles provides an increase in specific dispersion of 524% relative to the prototype. In this case, the dispersion increases by 2.6 times. A variant of the energy analyzer is possible when the part of the electrode containing the inlet and outlet openings located between the inlet and outlet openings and equal in width to the width of these openings is made of dielectric material. The growth of dispersion and specific dispersion compared with the prototype is 269% and 649%, respectively. Adding a diaphragm connected to the electrode containing the inlet and outlet, and located on the lower side of the electrode opposite the outlet of the energy analyzer, provides an increase in specific dispersion of 688% relative to the prototype while maintaining a gain in the level of dispersion.

Claims (7)

1. An electrostatic energy analyzer of charged particles, containing two electrodes made in the form of cylindrical surfaces, which in each of the planes perpendicular to their rectilinear generators have a shape described by a two-dimensional curve

, Where

and

constants related to the lower and upper electrodes, respectively, and

, with additional shielding electrodes, the contours of the boundaries of which are described by the function

, located at the ends of the electrodes of the energy analyzer, made in the form of cylindrical surfaces. 2. The device according to claim 1, characterized in that the lower electrode containing the inlet and outlet openings is made with an insert of a dielectric material, for example fluoroplastic, located between the inlet and outlet openings and equal in width to the width of these openings. 3. The device according to claim 1, characterized in that the electrostatic energy analyzer additionally has a diaphragm connected to the lower electrode and made of the same material, which is located opposite the outlet of the energy analyzer on the lower side of the lower electrode parallel to it.

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