CN1020165C - Low-radiation high-stability conveyer-belt nucleon weigher - Google Patents
Low-radiation high-stability conveyer-belt nucleon weigher Download PDFInfo
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- CN1020165C CN1020165C CN 91102590 CN91102590A CN1020165C CN 1020165 C CN1020165 C CN 1020165C CN 91102590 CN91102590 CN 91102590 CN 91102590 A CN91102590 A CN 91102590A CN 1020165 C CN1020165 C CN 1020165C
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Abstract
The present invention relates to a nuclear scale which is used for the on-line measurement of the weight (quality) of materials, such as batching control or transportation measurement in a production process. The belt nuclear scale adopts a long direct proportion counter pipe as a detector. Because the output pulse measurement of the direct proportion counter pipe is more sensitive than the output current measurement of an ionization chamber, the activity of a radiation source used by the nuclear scale is one magnitude lower than that of the ionization chamber. A monoenergetic alpha source used for generating a standard pulse is arranged in the direct proportion counter pipe, a peak stabilizing technology is used for a secondary instrument, and the nuclear scale can stably operate under the condition that a detector and a preamplifier have no constant temperature.
Description
The invention belongs to the nuclear physics field, relate to a kind of nuclear radiation measurement equipment that is used for weight or mass measurement.
The present invention utilizes the transmission of radiation feed belt and during the material that is transmitted, ray is measured the load of belt with belt load (being transmitted the weight of material on the unit strap length) rule that weakens.Measure the running length of belt with the sensor of surveying length (for example measuring running roller revolution), or tachogenerator measures the speed of belt, calculate the unit interval mass flow and be transmitted the general assembly (TW) of material through analog or digital with the belt friction.This scale is used for the weight of material or the Charge Mixture Control of mass metrology and production run.
This method also is applicable to the metering of convey materials in the pipeline.
General uclear scale comprises: 1. radioactive source; 2.A shape frame or C shape frame; 3. nuclear radiation detector; 4. velocity measurement mechanisms; 5. secondary instrument.
Radioactive source can be that point source also can be a line source.If the use point source, the effective length of detector sensitive volume must be greater than belt width.Ray can penetrate the whole materials that are transmitted like this, obtains charge number accurately.If use point probe just must use the uniform line source of length, guarantee that ray penetrates the whole materials that are transmitted greater than belt width.Line source and long detector can certainly be used, the combination of a plurality of point sources and point probe can also be used.
Because ionization chamber is done length easily than other detectors, its life-span is long, self stability good, so use the uclear scale of this detector maximum.But its poor sensitivity, output current is little.The uclear scale of United States Patent (USP) 3.541.332 Patented Nov.17.1970. invention just uses long ion chamber.In order to improve output current, U.S. Kay-Ray company, nuclear energy institute of Tsing-Hua University, company of Huahai have manufactured multi-electrode and have filled anticyclonic ionization chamber.However also to use 3.7 * 10
9The caesium 137 γ sources that Becquerel is above, its output current just can reach 10
-10～10
-9Order of amps will be measured the variation of material and will measure 10
-12The electric current of ampere changes.
The electrometer of measuring so little electric current will use 10
9The resistance that ohm is above, its temperature coefficient is 0.1%/℃ to 0.2%/℃.The every variation ten of environment temperature is spent in other words, and the output voltage of electrometer will change 1%～2%, and this is unallowed to uclear scale.Must be to detector and electrometer constant temperature.
United States Patent (USP) 3.610.925 Patented Oct.5.1971, nuclear energy institute of Tsing-Hua University, company of Huahai, U.S. Kay-Ray company all adopt temperature controller, with detector and electrometer or only to electrometer constant temperature.General constant temperature is about 140 °F.
Adopt the shortcoming of multi-electrode high-pressure ionization chamber: 1. the radioactive source of Shi Yonging is too strong, has limited the popularization of uclear scale.2. only be lower than constant temperature point in environment temperature and could use thermostat, environment temperature is higher than the constant temperature point and can not uses.3. environment temperature is low excessively, and when just heating power can not be offset heat radiation power, thermostat also lost thermostatic effect, and uclear scale will have very mistake.
United States Patent (USP) 3.541.332 Patented Nov.17.1970 has also used a plurality of scintillation counters and a plurality of radioactive source to place the method for arranging of travelling belt above and below respectively.Because the gap between point source and the point probe, some material is not passed by ray and causes error, and the fatigue phenomenon of photomultiplier itself and temperature instability also can cause the uclear scale instability.Use a plurality of point sources to use a point source also to make troubles to protection.
The uclear scale that Shijiazhuang 404 factories radiation development centres uses line source and naI-scintillation counter to do adopts the stability that the way at the steady peak of photopeak of cesium137 is improved uclear scale.This method still has weak point: the first, and use line caesium 137 sources to be difficult to make evenly also bad protection.The secondth, the shape that sees through the gamma-ray photopeak behind the material changes with the composition that is transmitted material and what, and the low energy edge of (the light more small angle scattering of material is many more) photopeak slows down when gamma-rays generation small angle scattering, causes peak position to move.If place the source (for example cobalt source) that energy is higher near detector, though this photopeak shape invariance, but peak counting changes when geometric condition changes, and the Compton effect in this source counting and the caesium source counting that sees through material mix, and has reduced the precision of data processing.
The objective of the invention is to reduce the radioactivity that uclear scale uses, and the method for a kind of better elimination ambient temperature effect and raising uclear scale long-time stability is provided.
Main points of the present invention are a kind of twin long γ of design and alpha ray proportional counter tube.Proportional counter one end is placed the α source of a collimation, produces the monoenergetic α particle pulse of Gaussian distribution, as the reference signal that improves uclear scale stability.Increase α proportional counter anodic wire diameter, the range of limit alpha particle makes the α pulse greater than gamma-ray pulse height, and is more approaching again.The gas of two proportional counters communicates, and anodic wire links to each other, and uses same high voltage supply, puts and leads before shared and put.Secondary instrument is established two wide single tracks, places two edges of α differential spectrum.The counting rate by two single tracks relatively, the power supply high voltage of control proportional counter obtains stable differential spectrum and distributes, thereby guarantees that the influence that γ pulsimeter digit rate is not floated with component ageing by temperature only changes with belt load.
Description of drawings:
Fig. 1: controlled nucleon operated belt conveyor scale synoptic diagram
[1] radioactive source [2] A shape frame or C type frame
[3] detector [4] velocity measurement mechanisms
[5] secondary instrument or microprocessor
Fig. 2: controlled nucleon operated belt conveyor scale block scheme
[6] proportional counter tube [7] velocity measurement mechanisms
[8] prime amplifier [9] main amplifier
[10] single-channel analyzer allows to pass through H
αTo H
α+ △ H
αThe pulse of amplitude.
[11] counter or counting rate meter, record is by the pulse of single track [10].
[12] single-channel amplitude analyzer allows to pass through H
α-△ H
αTo H
αThe pulse of amplitude.
[13] counter or counting rate meter, record is by the pulse of single track [12].
[14] comparer can be that digital comparator also can be analog voltage comparator (analog voltage comparator is a differential amplifier).The counting rate that compares counter [11] and [13].
[15] low-tension supply
[16] high-voltage power supply
[17] single-channel analyzer allows by amplitude H
γ 1To H
γ 2The γ pulse.
[18] processor receives the counting of single track [17] and the output signal of velocity measurement mechanisms, calculates load, belt speed, unit interval flow and general assembly (TW).
Fig. 3: proportional counter tube structural drawing
[19] γ proportional counter tube negative electrode (tube wall)
[20] α proportional counter tube negative electrode
[21], [22], [23] insulator
[24] anodic wire [25] anodic wire
[26] α source
Fig. 4: the differential spectrum of main amplifier output pulse
The transverse axis of Fig. 4 is a pulse height, and the longitudinal axis is step-by-step counting or the counting/road in the unit pulse amplitude.
The I district is the noise range of proportional counter tube
The II district is the gamma ray counting district of proportional counter tube
The III district is the alpha ray counter district of proportional counter tube
For the ease of protection, the present invention adopts point source. Detector adopts the long direct ratio counting tube greater than the feed belt width. The direct ratio counting tube is operated in the direct ratio amplification region of gas discharge curve. Gamma-rays produces secondary electron in direct ratio counting tube tube wall and the gas that fills, secondary electron loses power generation ionization in the gas in pipe. The electronic charge that the anode silk of direct ratio counting tube is collected just Than the energy that in pipe, loses in the gas in secondary electron. If use the Ce 137 source, gamma-ray secondary electron energy is in hundreds of Kev magnitude. Under the atmospheric pressure, the range in the air is a rice magnitude, and secondary electron only loses part energy in diameter is several centimetres direct ratio counting tube. Because the position that secondary electron produces is different with direction, the range of secondary electron in counting tube is just different, the quantity difference that the negative ions of generation is right, and the electron charge that the anode silk is collected is just different. The impulse amplitude that preamplifier [8] and main amplifier [9] obtain after amplifying is different. Therefore among Fig. 4 the II district (γ district) of pulse differential spectrum be one to the gamma-ray pulse differential distribution curve of declivity. Any variation of power supply high voltage [16], preamplifier [8], main amplifier [9] and the single track [17] of this explanation direct ratio counting tube can cause that all the gamma-ray meter digit rate by single track [17] changes, and the load amount that treated device [18] obtains after processing just has very big error.
If the direct ratio counting tube is divided into two parts, but gas communicates part measurement gamma-rays, and the α source of a collimation of another part placement. Its way is to make a call to an aperture at negative electrode, the α source is fixed on the outer surface of negative electrode, and the aperture of negative electrode plays the collimation effect to the α source. Because the energy of α particle is certain, be several Mev, range is several centimetres in an atmospheric gas. The energy of α particle can total loss in the gas of direct ratio counting tube. But in order to reduce the gap of α impulse amplitude and gamma-ray burst amplitude, can with the diameter that reduces direct ratio counting tube α part or dull and stereotyped shape direct ratio counting tube cathode spacing from the way of the range of method limit alpha particle in gas reduce the amplitude of α pulse. Because α particle monoenergetic, range equate that α differential spectrum is remaining Gaussian Profile.
When high pressure, prime amplifier, the drift of main amplifier occurrence temperature or component ageing, α particle pulse amplitude and gamma-ray pulse height change simultaneously, and it is the stretching or the compression of transverse axis along the pulse towards amplitude axis that the differential spectrum takes place.The gamma-ray burst number of the single track [17] by the record gamma-ray burst just changes.Thereby the belt load that processor [18] calculates just has error.
Automatically adjust for the drift of γ counting rate that various factors is caused, being provided with discrimination threshold is H
α, the road is wide to be △ H
αSingle-channel analyzer [10] and discrimination threshold be H
α-△ H
α, the road is wide to be △ H
αSingle-channel analyzer [12].H
αThe peak value of corresponding α pulse differential spectrum.△ H
αBe similar to 1/2nd half widths at α pulse differential spectrum monoenergetic peak.
When drift takes place when, for example upwards drift.The counting rate of the counter [11] of single track [10] back increases, and the counting rate of the counter [13] of single track [12] back reduces.The size that compares counter [12] and [13] counting rate through comparer [14], the output voltage of control low-tension supply [15] reduces, the output high pressure of high-voltage power supply [16] also just reduces, thereby has reduced the output pulse amplitude of proportional counter tube, and the differential spectrum of floating is pulled back.Conversely, the pulsing amplitude reduces, the differential spectrum is the situation of drift downwards, the counting rate of counter [11] reduces, the counting rate of counter [13] increases, and through [14] relatively, improves the output voltage of low-tension supply [15] and high-voltage power supply [16], also just increased the supply voltage of proportional counter tube [6], the output amplitude of proportional counter tube [6] is increased.Like this spectrum of compression is distributed and stretched again.By above spectrum stabilization measure, guarantee that whole differential spectral shape is constant, also just guaranteed by the γ counting rate of single track [17] constant.This has just eliminated the instability that factors such as the temperature of uclear scale and component ageing cause, and obtains stable load capacity.
Because the energy of α particle is about several Mev, gamma-ray electronic secondary only loses portion of energy in the gas of counter tube, be approximately tens kev to 100kev.Must increase the anodic wire diameter of α proportional counter tube, improve the operating voltage of alpha counter tube, reduce the diameter of proportional counter tube negative electrode simultaneously, plate shaped proportional counter tube is reduced between the minus plate distance to reduce the range of α particle in gas.Thereby reduce the pulse height of α particle, when two parts counter tube was powered with same high-voltage power supply, the pulse height of α particle is greater than gamma-ray pulse height, and was still more approaching.Steady preferably peak effect is so just arranged.
The gas of two parts proportional counter tube communicates among the present invention, guarantees that the gaseous state of two parts is identical.The anodic wire of two parts counter tube links to each other, and guarantees to use same high voltage supply, and output signal is imported same prime amplifier.
The radioactive source activity that the radioactive source activity that the controlled nucleon operated belt conveyor scale of manufacturing by the present invention uses is done the uclear scale use of detector than ionization chamber reduces a magnitude, and the radioactive source activity that uses with the uclear scale of naI-scintillation counter more above-mentioned reduces by three times.And detector and prime amplifier there be not very high temperature stability and long-time stability under the situation of constant temperature.
Embodiment: by the BNW type controlled nucleon operated belt conveyor scale of nuclear energy technology design and research institute of Tsing-Hua University and Beijing Nuclear Instrument Factory's development, adopting diameter is 50 millimeters, length is 650 millimeters proportional counter tube, α particle proportional counter tube adopts plate, cathode distance is that 20 millimeters, length are 100 millimeters, americium 241 α sources are adopted in the α source, and activity is 3.7 * 10
4Becquerel.Select 3.7 * 10 for use
8The caesium 137 γ sources of Becquerel obtained for 12000 counting/seconds when belt is unloaded.The steady peak height voltage source that adopts the Beijing Nuclear Instrument Factory to make, prime amplifier and main amplifier are made processor of single chip computer with 8031.This uclear scale detector is worked in-10 ℃ to+50 ℃ environment, does not use thermostat to reach and is better than 1% resultnat accuracy.
Claims (3)
1, a kind of conveyer-belt nucleon weigher is made of radioactive source [1], A shape frame [2], nuclear radiation detector [3], velocity measurement mechanisms [4] and secondary instrument [5], it is characterized in that:
(1) said nuclear radiation detector [3] adopts long proportional counter tube, and this proportional counter tube is divided into two parts; A part is used for measuring the gamma-rays that passes travelling belt and transported material, placed the α source of collimation in another part pipe, the α particle pulse that the generation amplitude is certain, the gas that two parts proportional counter tube fills communicates, the anodic wire of α proportional counter tube [25] is thick than the anodic wire [24] of V counter tube, reduce the diameter of α proportional counter tube simultaneously or reduce distance between dull and stereotyped proportional counter negative electrode, the limit alpha particle range, guarantee that α particle pulse amplitude is greater than gamma-ray pulse height, but amplitude is more approaching, two anodic wires are connected, and with same high-voltage power supply [16] power supply, the pulse signal of generation is imported same prime amplifier [8] and main amplifier [9];
(2) said secondary instrument has adopted the steady peak method at the monoenergetic peak in the α source of installing in the stable proportional counter tube, improve the instability of the uclear scale that temperature and other various factorss cause, two wide single tracks [10] and [12] place two edges at the α monoenergetic peak of differential spectrum respectively, the pulse on high energy limit is by single track [10], count by counter [11], the pulse on low energy limit is by single track [11], count by counter [13], the counting rate that compares [11] and [13] by comparer [14], its result is used for adjusting the output voltage of low-tension supply [15], control is to the output high pressure of the high-voltage power supply [16] of proportional counter tube power supply, and the peak position at the monoenergetic α peak that any reason is caused moves and is withdrawn into the H that differential is composed transverse axis
αOn the point, eliminate proportional counter tube [6], pass through the variation of all output pulse amplitudes after main amplifier [9] amplifies again, guarantee to pass through the amplitude of single track [17] from H through prime amplifier [8]
γ 1To H
γ 2The counting rate of γ pulse be not subjected to the influence of temperature and component variation, only with the load change of travelling belt.
2, conveyer-belt nucleon weigher according to claim 1 is characterized in that said A shape frame also can be C shape frame.
3, conveyer-belt nucleon weigher according to claim 1 is characterized in that counter [11], [13] in the said secondary instrument also can be counting rate meter.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 91102590 CN1020165C (en) | 1991-04-25 | 1991-04-25 | Low-radiation high-stability conveyer-belt nucleon weigher |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 91102590 CN1020165C (en) | 1991-04-25 | 1991-04-25 | Low-radiation high-stability conveyer-belt nucleon weigher |
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| Publication Number | Publication Date |
|---|---|
| CN1055994A CN1055994A (en) | 1991-11-06 |
| CN1020165C true CN1020165C (en) | 1993-03-24 |
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| CN 91102590 Expired - Fee Related CN1020165C (en) | 1991-04-25 | 1991-04-25 | Low-radiation high-stability conveyer-belt nucleon weigher |
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| CN108051069B (en) * | 2018-01-09 | 2023-11-21 | 北京工业职业技术学院 | Calibration method of X-ray nucleon balance and X-ray nucleon balance |
| CN110673191B (en) * | 2019-09-23 | 2021-04-23 | 北京永新医疗设备有限公司 | Channel type radioactive source positioning system and method |
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