SU1191979A1 - Sensor tube for measuring high-speed light processes - Google Patents

Description

The invention relates to a sensor tube, which serves for direct measurements of light-optical processes of short duration, in particular, in devices for measuring 5 ultrashort light pulses, for example, ultrashort laser pulses and light pulses of a plasma discharge.

Known cathode-ray sensor tube, designed to measure high-speed light processes (OSH patent number 3761.614, CL. 313-94, 1977).

The photo coming out of the photocathode is 15

• electrons in the immediate vicinity of the cathode are accelerated by an electrode consisting of a metal lattice.

Electrostatic focusing electrode, 20

anode, diaphragm system, deflection system and phosphorescent screen.

In the absence of voltage, the picture of a small 25-height strip on the photocathode is clearly depicted on the photo screen on the deflecting system. When measuring fast light-optical processes, the voltage on the deflecting system is chosen in such a way that from the beginning of the light-optical process, a narrow 30 pattern is depicted at the upper edge of the photo screen. The voltage on the deflecting system changes with time in this way, in a short time interval, for example, 1 ns, the image of the photocathode moves from the upper edge to the lower edge of the phosphorescent screen. The resulting image can be captured by a camera or a vidicon camera. · Amplification of radiation power is, as a rule, depending on the photocathode material or phosphorus, at an anode voltage of 10 kV it is 1 - 40 kV. Amplification of radiation power. is the ratio of the total output radiation power to the incident radiation power at the maximum spectral sensitivity of the photocathode. When you take a picture of a phosphorescent screen 50 on a film or on a Vidicon, there is a loss of light, so that the full increase in radiation power becomes less. A significant improvement in the gain of this cathode-ray tube can be obtained as a result of a microchannel plate placed in front of the phosphorescent screen. The individual channels of the microchannel plate work as a channel multiplier and lead to a large gain. A cathode ray tube with a microchannel plate receives a force of radiation power up to several tens of kilovolts.

The purpose of the invention is to increase the speed of the tube when obtaining high temporal and one-dimensional resolutions in the image, with high sensitivity and the lowest cost than before.

The invention is based on the task of creating a dispersive sensor tube for measuring fast light processes that would allow for the measurement of fast electronic optical processes to directly convert electron energy into electrical signals and eliminate the inefficient conversion of electron energy into phosphorescent light and its recording by a camera or video camera, a · would also allow light to be measured at low intensities.

To measure fast light processes by deploying an image of a luminous slit containing a photocathode, at least one accelerating electrode or anode, deflecting electrodes and a focusing system for an electron beam, the first accelerating electrode is installed directly behind the photocathode, deflecting electrodes that develop an electron beam perpendicular to the slit direction , are parallel to the beam, and a semiconductor detector array is located behind the deflecting electrodes, with the dimensions The detectors in the direction perpendicular to the slit image do not exceed the width of the slit image on the detector array. The detector matrix can be a vidicon-on silicon diode matrix, and the vidicon is additionally embedded in the tube. Photoelectrons emanating from the photocathode at a small height of the slit image are accelerated to high energies, for example, to 10 keV. By means of electric or magnetic focusing optics and electrical deflecting plates, photoelectrons are directed to the reverse side of the detector array, with

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This accelerated and deflected photoelectrons produced by the internal photoelectric effect of a pair of charge carriers, thereby causing a change in charge in the individual. 5 detectors, and these changes in charge on the front or planar side of the semiconductor detector array are read by the electron beam of a vidicon. The first accelerating electrode 10 or anode. It can be located directly after the photocathode and have a gap for the photo passing through it. electrons. The width of the slit of the first accelerating electrode does not exceed the height of the row of the semiconductor detector array reduced to the photocathode. Installation of detectors in a semiconductor detector array is carried out in rows and columns. 20 Deviation occurs perpendicular to the lines, so that the height of the image of the slit, the height of the line, the speed of the deviation, the increase and distortion of the electron-beam system are. 25 determining for the obtained temporary resolution. The height of the image of the slit and the diameter of the focus of the semiconductor detector matrix, read by the electron beam, are of the order of the height of the row of the detector matrix. The resolution inside the row is determined by the slit width of the semiconductor detector array, the magnification and distortion of the image of the electron-beam system. Conventional diode arrays have about 500 rows and columns. During a 1 ns deviation of 500 lines, a temporary resolution can be achieved, up to. several ₄₀ picoseconds. As an electro-optical system, it is possible to use the known electric magnetic systems of lenses.

The deviation of electrons is carried out using ordinary deflecting plates. The system for reading the semiconductor diode array from the front or planar sides corresponds to the Vidicon system. $ 0

The photocathodes used are the usual compounds Na-K-Cz-8b and Ia-K-Zb for the ultraviolet and visible region and Ag-O-Cz for the visible and infrared region. Electrons accelerated by the anode electric field fall on the uncovered reverse side of the semiconductor detector,

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matrix, consisting mainly of silicon, and produce there a pair of charge carriers, about 300 with an energy of 1 keV each. This takes place for energies in the range of 5–10 keV and occurs in the volume of the silicon detector array, which on the reverse side of the surface reaches a depth of about 1000 nm. A significant part of the produced charge carriers recombines on the surface of a semiconductor flake. With the help of the corresponding drift field, resulting from subsidizing foreign atoms of the back surface of the diode matrix, it is possible to reduce the recombination losses on the surface in such a way that approximately 200 out of 300 pairs of charge carriers are recorded as a signal. Radiation damage does not occur when the electron intensities are not too high, leading to thermal heating in the region up to 1 meV. Further, the sensor tube for measuring fast light processes can be arranged in such a way that the deflecting system is installed in front of the integrated semiconductor detector array of diodes or MIP capacitances in the sensor tube and the semiconductor detector matrix is charged either directly electrically periodically or selectively according to charge and read at its charge. dovevoe condition. Accelerated and deflected electrons fall on the unstructured and uncovered reverse side of the semiconductor detector matrix, create a pair of charge carriers in the semiconductor volume and cause a change in charge in the diodes or MIP capacitances.

The invention allows both temporal dispersion and one-dimensional image resolution in a tube with high sensitivity, so that even individual photons can be detected. So far, this resolution required a temporal resolution image converter and a Vidicon. Due to the high energies of the electrons in the deflecting system, it is possible to reduce the dispersion of time, pro-. the run of electrons and the running time inside the deflector plate, so as to achieve the highest

1191979

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which temporal resolution. ti.

The drawing shows a section of the sensor tube. 'five

The image is shown as a strip with a height of several tenths of a millimeter and a width of a few millimeters through the quartz window 15 in the middle of the Na-K-Cz-8b photocathode 10

having a bias voltage of approximately 17 kV. After the photocathode 14, an accelerating electrode 16 is installed in the form of a lattice with a bias voltage of about - 16 kV and a focusing electrode ₁₅ is located 4 with a bias voltage of about - 18 kV. The anode 13 has an offset voltage of V.

The focusing electrode 4 depicts the view of the strip on the photocathode on the reverse side of the matrix of the silicon diode 10. The magnification reaches about 1.

In this case, by controlling the potential on the deflecting plates 12 in the 25 time sequence, the matrix is read from top to bottom. The pairs of charge carriers produced by the accelerated electrons on the diode matrix are discharged by means of charged diode capacitances through a stream of electrons on the front or planar side of the matrix. The corresponding discharge state is proportional to the flux falling on. the reverse side of the electrons and, thus, the accelerating power of the photocathode T4; With the new charge of diode capacitances by the electron flow, the front and planar sides of the matrix will simultaneously occur

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reading the discharge state, which is perceived as a current signal by the electrode 11.

The flow of electrons to charge and read the diode capacitances out. from the cathode 5, passes through the control diaphragm 6, the accelerating electrode 7, the focusing cylinder 8, the field network 9 and falls on the front or planar side of the matrix. The beam formation system produces: a thin stream of electrons. By means of a deflection device consisting of a focusing coil 3,

deflecting coil 2 and the correction coil or magnet '1, the electron flow is focused and directed line by line for reading on the silicon diode matrix 10. For sufficient sharpness setting, the potential of the focusing electrode 8 has several hundred volts,

10 The potential of the field network 9 is higher than the potential of the electrode 8, but does not exceed 350 V.

The noise electrons produced at the photocathode by thermal emission at room temperature of the cathode used and the active surface of 1 mm ² lie in the range below 100 electrons per second. The dark current from the photocathode due to the fast flowing measurement process can be neglected. An electron with an energy of 10 kzV causes a change in the charge of the diode capacitance of about 3-10 ^ ⁶ Ac. This equates to a tenfold change in 25 charge arising from the dark current of the diode at room temperature during a read time of 32 ms. Changes in charge due to individual photoelectrons also have an effect on the change in charge, which lies significantly above the background of the diodes.

The reading time and, thus, the integration time of the diodes cannot be extended at room temperature to more than 0.2 s, since then a significant quenching of the accumulated charge takes place due to the dark current. To reduce the amount of dark current in silicon, the rule is that over 25 ° C of cooling, the dark current decreases by a factor of 10. Thus, when cooling the matrix on silicon diodes, the integration time can already reach several minutes. This gives 4 $ the possibility, when measuring light pulses of very low intensity during the integration time, to produce multiple repetitions of these light pulses and thereby significantly improve the signal-to-noise ratio ..

Recognized as an invention based on the results of the • examination carried out by the Office for the Invention of the German Democratic Republic.

Claims (3)

1. TOUCH PIPE FOR MEASUREMENT. QUICK LIGHTING PROCESSES. using deployment . images of a luminous gap containing a photocathode consistently located in a vacuum flask, at least one accelerating electrode,. focusing system and deflecting electrodes, characterized in that, in order to increase the speed of the tube, the first accelerating · the electrode is located directly behind the photocathode, deflecting electrodes, sweeping electron beam · perpendicular to the slit direction, are parallel to the beam, · and a semiconductor detector array is located behind the deflecting electrodes, with the dimensions of the detectors not exceeding the width of the slit image on the detector matrix . 2. The tube pop. 1, denounced by the fact that the first accelerating electrode has a single slit diaphragm. 3. The tube on the PP. 1 and 2, which is based on the fact that the slit width of the first accelerating electrode does not exceed the row height of the semiconductor detector array, reduced to the photocathode. with . . 5 and ... 1191979 > one 1191979 2