SU851549A1 - Two-channel electron multiplier - Google Patents

Description

The invention relates to a technique for recording charged particles (electrons) and can be used to study the reflection and quantum yield spectra, as well as the energy ⁵ spectra of photoemission and secondary electron emission.

Known electron multiplier containing two consecutive amplification stages made in the form of ^υ microchannel plates (MCP) [1].

Known two-channel electron multiplier for measuring electron emission by comparison, containing common for both channels two cas-15 gain cascade, made in the form of MCP and two electron collectors located behind the last amplification cascade [2].

However, this device does not make it possible to produce 20 wish to set up registratsiyu- signals with large differences in intensity due to the dependence of the gain on the signal level _of saturation of ea MCP channels. *5

The purpose of the invention is the expansion of the measurement range, and automatic continuous registration of the ratio of the quantum outputs of the test sample and the standard. thirty

This goal is achieved by the fact that in a two-channel electron multiplier for measuring electron emission by a comparison method containing two amplification stages common to both channels, made in the form of MCPs, and two electron collectors located behind the last amplification stage, a common control grid is installed between the amplification stages, connected to the reference collector by a negative feedback circuit (OOS) which includes an integrating comparator and a reference signal setter.

The drawing shows a diagram of the proposed device.

The device contains reference 1 and studied 2 targets (photocathodes or secondary emitters), the first 3 and second 4 MCPs (common for both targets), control grid 5 (common for both targets), collectors 6 and 7 of the reference and sample channels, respectively, pulse preamplifiers 8 and 9, pulse counting rate meters (SIS) 10 and 11 with a fixed threshold, a voltage comparator 12 with an integrating output, a fixed potential adjuster 13 (PP-6 3) and a recorder 14 PDS-021 M (EPP-09).

The device operates as follows.

The electrons knocked out from targets 1 and 2 are accelerated by the input field of the MKP-3, multiplied inside the MKP-3 and form electronic showers from each electron at its output. Grid 5 in the absence of a modulating voltage across it passes streams to the MCC 4 and after amplification on it, collectors 6 and 7 receive series of single-electron pulses. The collector 6 from the reference channel through ISS 10 feeds the input of the integrating comparator 12 with a voltage proportional to the number of electrons in 1 s from the reference 1. When this voltage deviates 15 one way or another from the level set by potentiometer 13, the comparator-integrator generates At its output and at grid 5, an increasing or decreasing potential regulating the electron flux (electron gain) in the standard channel (1-3-4-6-8) to such a value that the number of pulses with an amplitude exceeding the ISS threshold 10 supported at the-level specified by potentiometer 13. i.e. in the standard channel. for any intensity of target irradiation, the output counting rate is kept constant, and the recorder in the measurement channel registers the ratio 30

Y _o / y _? . Indeed, suppose that, from the total flow of primary particles N, the fraction σί falls on the standard, and the rest on the sample. For the corresponding quantum outputs Υ _e and γ _{ο, the} output counting rates of the pulses are expressed by N ,, and N (i-oC) Y ₀ . When the spectrum of exciting particles is scanned, N changes in time, however, the receiver feedback system supports the signal N ^ Y ^ - Const. This is tantamount to; that changes the number of effective exciting particles x Const / oi Y _e · In this case, the signal of the second channel, i.e. channel ob- 'raez, expressed N (1 - <Λ) · Y _o = Cons t (1 -с <) Y ₀ / o (Y _g = Const i.e.

the signal will be proportional to the ratio of the quantum outputs of the sample and the standard.

Thus, the proposed two-channel electron multiplier for measuring electron emission by the comparison method allows you to automatically register the ratio of the quantum yields of the sample and the standard, avoiding overloading the MKP-4 and the electronic amplification path and, thus, leaving it from the linear recording mode with large differences in signal intensity at inlet of the MCP 3.

Claims (2)

This invention relates to a technique for detecting charged particles (electrons and can be used to study the reflection spectra and quantum yield, as well as energy spectra of photoemission and secondary electron emission. An electronic multiplier is known that contains two successive amplification stages made in the form of microchannel plates (MKIIlfl. A two-channel electron multiplier is known for measuring the electron emission by the comparison method, containing two amplifiers common to both channels, made in The IDT MCP and two electron collectors located behind the last cascade of amplification R. However, this device does not allow recording of signals with large differences in intensity due to the dependence of the gain on the signal level due to saturation of the MCP channels. and automatic continuous recording of the ratio of the quantum yields of the sample and the sample under study. The goal is achieved by the fact that in a two-channel electron multiplier for measuring the emission the electron method of comparison, containing two amplification stages common for both channels, made in the form of an MCP, and two electron collectors located behind the last amplification stage, a common control grid connected to the reference collector of the feedback standard (OOCj in which includes an integrated comparator and reference signal adjuster. The drawing shows a diagram of the proposed device. The device contains reference 1 and test 2 targets (photocathodes or secondary emitters), the first 3 and the second 4 MCPs (common for breakdown targets), control of a grid 5 (common for both targets), collectors 6 and 7 of the standard and sample channels, respectively pulse preamplifiers 8 and 9, pulse rate meters 10 and 11 with a fixed response threshold, a voltage comparator with an integrating output, a fixed potential setting unit 13 (ПП-бЗ) and a recorder 14 ПДС-021 М (.EPP-09 ). The device works as follows. The electrons knocked out of targets 1 and 2 are accelerated by the MCP-3 input field, multiplied inside MCP-3, and at its output form electron showers from each electron. Grid 5, when there is no modulating voltage across it, passes hyutok to MCC 4, and after amplifying it, collectors 6 and 7 receive a series of one-electron pulses. The collector 6 from the reference channel through the YASS 10 feeds the input of the integrating comparator 12 with a voltage proportional to the number of electrons in 1 s from the standard 1. When this voltage deviates to one side or the other from the level set by potentiometer 13 to the integrator, the integrator produces its output and on grid 5, a growing or decreasing potential regulating the electron flow (electron amplification) in the reference channel (1-3-4-6-8) to such a value that the number of pulses with amplitude exceeding the threshold of the ISS 10 is maintained at given by potential eter 13 Those. in the reference channel, at any intensity of irradiation of the target, the output to the counting rate is kept constant, and the recorder records the ratio YO / Y in the measurement channel. Indeed, from the total flow of primary particles N dol oi. gets on the e-ticket, and the rest on the sample. With the corresponding quantum outputs e and YO, the output pulse count rates are expressed as “2 Yq It N (i-oi-) Yo. When the spectrum of the excitation particles is scanned, N varies in time, however, the receiver's feedback system supports the signal N V -Const. It is equally strong; that the number of Effective excitation particles And Constjd UE changes. In this case, the signal of the second channel, i.e. channel image .ts, expressed N (1 oi). o Const () V / b (3 Const N; 3 / Y9, Te signal will be proportional to the ratio of the quantum outputs of the sample and the reference. Thus, the proposed two-channel electron multiplier for measuring electron emission by the comparison method allows you to automatically record the ratio of the quantum outputs of the sample and the reference , not allowing the overload of the MCP-4 and the electronic amplifying tract and, thus, its exit from the linear-registration mode for large signal intensity at the input of the MCP 3. Invention formula Two-channel electronic a comparison tool for measuring electron emission, containing two amplification stages common for both channels, made in the form of microchannel plates and two electron collectors located behind the last amplification stage, characterized in that in order to expand the measurement range and automatically continuously register the ratio of quantum outputs the test sample and the reference, between the amplification stages, a common control grid, connected to the reference collector by a negative feedback circuit, is installed, in The integrated comparator and reference signal adjuster are included. Sources of information taken into account in the examination 1. Kellog E. High resolution imaging x-ray detector. - Instruments for scientific research, 1976, No. 3, p. 27-30. 2. Instruments for scientific research, 1977, .9, p. 25-30 (prototype).