RU856U1 - Device for measuring the power of optical pulses - Google Patents

Abstract

1. A device for measuring the power of optical pulses, containing a vacuum photoelectronic device connected to an integrating capacitor, a discharge key and a voltmeter, characterized in that between the integrating capacitor and the voltmeter the contacts of a normally open electromagnetic relay are introduced, in addition, an electronic control unit connected to electromagnetic relay winding. 2. The device according to claim 1, characterized in that the electronic control unit is also connected to the control inputs of the voltmeter and the discharge key.

Description

The alleged invention relates to the field of radio engineering and experimental physics and can be used in apparatus for recording weak pulsed light fluxes, for example, in apparatus using a scintillation counter or in an intensimeter for measuring scattered light from a pulsed laser.

To measure the power of pulsed optical radiation, devices based on a semiconductor photodetector (FP) connected to an operational amplifier (OA) are widely used, and a resistor is introduced into the feedback circuit, which is (taking into account the gain of the OA) the resistive load of the FP / I /. TB in the FPI circuit, the voltage at the op amp output is proportional to the power of the optical pulse. If an electromagnetic impulse arrives at such a device, then it causes an oscillatory process in the FP circuit, which is detected by the semiconductor phase converter, amplified by the opamp, and the output is recorded as well as a useful signal. If the interference signal comes simultaneously with a light pulse, then at the output it is fundamentally inseparable from the Aesian signal.

A pulse photometer based on a vacuum photocell with a resistive load in the anode circuit connected to a voltage meter with a signal cable is also known. To suppress impulse noise, a compensation cable / 2 / is installed parallel to the signal one. Both of these cables at the input of the voltage meter are connected to an analog circuit in which the interference signal arising on the compensation cable is subtracted from the total interference signal and useful on the signal cable. Due to the impossibility of building and, identical signal and compensation channels of the ego, the device is not sufficiently anti-interference.

Closest to the claimed is a device based on a vacuum photoelectronic device, for example, a photoelectronic multiplier, the anode of which is connected to an integrating cotensor connected to a discharge key and a voltmeter / 3 /. In this device, the oscillatory process that occurs under the influence of electromagnetic interference in the anode-coddenser circuit is not detected, since there are no nonlinear elements in the circuit of the photoelectronic device, and the gap of the anode-photocathode for interference is equivalent to an open circuit. However, the interference passes through a galvanic connection to the input of the voltmeter and is detected inside the voltmeter itself, which also distorts the useful signal, especially in the case of a weak measured optical pulse.

The alleged invention allows to measure the power of light pulses of low intensity in the presence of powerful pulsed noise, acting almost simultaneously with the light source.

This is achieved due to the fact that an electromagnetic relay is introduced into the known device for measuring the power of optical pulses containing a vacuum photoelectronic device connected to an integrating capacitor, an internal key and a voltmeter, an electromagnetic relay between the integrating capacitor and a voltmeter.

In the proposed device, a useful signal proportional to the power of the optical pulse and determining the amount of charge on the integrating co-capacitor is supplied to the voltmeter only after the attenuation of the oscillatory processes induced by electromagnetic interference. For the duration of the interference, the circuit between the integrator and the voltmeter is open, and the electromagnetic relay, unlike semiconductor switches, provides a complete galvanic circuit break and reliably cuts off the interference from the detecting effect of the input circuit of the voltmeter.

Figure 1 presents a structural diagram of the inventive device, figure 2 is a plot of signals explaining the operation of the device.

The device comprises a vacuum photoelectronic device I, for example, a photoelectronic multiplier, the photocathode of which is connected to a high-voltage power source Z. The anode of the photoelectronic device I is connected to an integrating co-capacitor 3 and a discharge switch 4 connected in parallel with the capacitor 3, made, for example, on a field-effect transistor, the gate of which is connected with an electronic control unit 5. In addition, the integrating co-capacitor 3 is connected to the voltmeter 7 through the contacts of the electromagnetic relay b. The voltmeter 7 must be controlled Digital with high input impedance. The relay coil b and the control input of the voltmeter 7 are connected to the electronic control unit 5. The connections of the photoelectronic device I with a power source 2 and a capacitor 3 are made by a shielded cable.

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- - In FIG. 2a shows the control voltage on the key 4, in FIG. 26 - current at the anode of the photoelectronic device I, in FIG. 2c, the voltage across the integrating capacitor 3, in FIG. 2d - control siMa5 d§R§l§ShyyZh111 ° §, 5 N Zhtrls reading at the control input of a digital voltmeter 7 and Fig.2e - reset pulse to discharge; bottom switch 4 and relay coil b.

The device operates as follows.

In the normal state, the key 4 is open, which prevents the capacitor 3 from being charged by the current of the photoelectronic device I. The input of the digital voltmeter 7 is grounded through the contacts of relay b to prevent charge leakage on the stray input capacitance when waiting for an event.

At the beginning of each measurement cycle from the control unit 5, a start pulse (Sphig. 2a) arrives, which locks the bit key 4. The measured optical pulse, converted into an electrical pulse (Fig. 26) by photoelectronic device I, charges the integrating censor 3, the charge on the capacitor 3 proportional to the power of the optical pulse. A powerful electromagnetic interference that occurs simultaneously with the measured optical pulse causes an oscillatory process in the circuit of the integrating capacitor. The oscillatory process is decaying in nature and stops within a few microsecucci. The co-censor 3 remains charged to a voltage caused only by the measured optical pulse. With a delay relative to the start pulse of approximately I ms, sufficient to attenuate the noise, the control unit 5 generates a signal for switching the contacts of the electromagnetic relay b, which enters the relay b coil. After the transient processes associated with switching the contacts of relay b, the digital voltmeter 7 receives a read pulse from the control unit 5 (Fig.), And the voltmeter 7 makes a measurement. The cycle ends with a reset pulse (Fig.2e), opening the key 4 and switching the relay b.

Thus, the introduction of a mechanical circuit breaker with an integrating capacitor and a voltmeter eliminates the detection of the oscillatory process that occurs in the circuit of a photoelectronic coddenser device, and only the useful signal on the integro-capacitor due to the optical signal is measured with a time delay.

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- Comparative tests of the inventive device and prototype were carried out when placing a photomultiplier in the immediate vicinity of a pulse voltage generator with an pulse amplitude of 150-200 kV and a pulse duration of 10 nsec. A precision digital voltmeter V7-E8 was used as a voltmeter. The degree of suppression of interference by the claimed device compared to the prototype was 5 pore, dkov. The inventive device allows you to reliably measure optical pulses with a power of 0.01 microns; j, duration 10 nsec with an accuracy of 1-2%,

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Authors: YA Lobanov OV

- Kozlov B.C.

Nye; A.F.

Literature:

1.S.P. Kalashnikov, A.A. Matsveiko.

Photodiode laser power meter. PTE, 1Zh, No. 2, p. 189.

2. A.P. Fedotov, V.V. Pyankov, A.I. Kvasha, V.M. Rodnyuk, Yu.V. Semenov.

A system for measuring the loss of an ion beam in a linear accelerator METAN. Diagnostics of charged particle beams in accelerators. (Collection). Radio Engineering Institute of the Academy of Sciences of the USSR, sh., 1984, p. 3.

3.O.V. Lobanov, M.V. Stabnikov.

Proton beam monitoring during the operation of a hybrid gas-liquid chamber. Preprint of Leningrad Institute of Nuclear Physics, 1983, No. 857.

 9303 (

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Claims (2)

1. A device for measuring the power of optical pulses, containing a vacuum photoelectronic device connected to an integrating capacitor, a discharge key and a voltmeter, characterized in that between the integrating capacitor and the voltmeter the contacts of a normally open electromagnetic relay are introduced, in addition, an electronic control unit connected to winding electromagnetic relay. 2. The device according to claim 1, characterized in that the electronic control unit is also connected to the control inputs of the voltmeter and the discharge key.