CN2537986Y - Radon-thorium analyzer - Google Patents

Abstract

A radon and thorium analyzer comprises a scintillation chamber, a probe and a counting and measuring device. The inner wall of the scintillation chamber is painted with zinc sulfide scintillating substance. The probe comprises a photomultiplier and a voltage dividing apparatus. The counting and measuring device is a PC. The probe and the PC are connected through a pulse electric circuit which comprises a pulse amplifier, a single channel pulse discriminator and a pulse shaper. The increasing of pulse electric circuit can make the PC as a counting and measuring device to read the pulse signals collected by the probe, thus the size of the whole analyzer is reduced and the operations such as manual counting, etc. are not needed any more. The measuring and counting can be finished by computer program, the automation degree is obviously enhanced and the reliability has better guarantee. The utility model can be used as an emanation measurement device for measuring the content of the radioactive elements of radium and thorium, also can be used to measure the concentration of micro radon emanation in the water sample and the tunnel and the chamber.

Description

Radon thorium analyser

Technical field

The utility model belongs to a kind of radiation measurement assembly, a kind of specifically radon thorium analyser.

Background technology

In the prior art, Indoor Niton thorium analyser is made up of FD-125 type Indoor Niton thorium analyser and FH408 automatic scaler, wherein FD-125 type Indoor Niton thorium analyser comprises scintillation chamber and probe, the FH408 automatic scaler is the count measurement device, and this cover instrument is nuclear industry factory the mid-1970s product.Its shortcoming is: volume is big, and automaticity is low, need manual counting and calculate, and the time have fault to take place, not only take a lot of work, inefficiency, and poor reliability.

Summary of the invention

The purpose of this utility model is to provide that a kind of volume is little, automaticity is high, radon thorium analyser accurately and reliably.

The purpose of this utility model realizes by following scheme: a kind of radon thorium analyser, comprise the scintillation chamber, probe and count measurement device, wherein the inwall of scintillation chamber scribbles zinc sulfide scintillator, comprise photomultiplier and voltage divider in the probe, described count measurement device is a PC, between probe and PC, be connected with the function module circuit of gathering photoimpact, function module circuit comprises pulse amplifier, single-channel pulse discriminator and pulse-shaping device, probe is connected with pulse amplifier, pulse amplifier is connected with the single-channel pulse discriminator, and the single-channel pulse discriminator is connected with the pulse-shaping device.

Effect of the present utility model is: make PC to read the pulse signal that probe is collected as the count measurement device by increasing function module circuit, thereby the volume of a whole set of instrument is greatly reduced, and no longer need operation such as manual counting, measure and calculate and finish by computer program, automaticity obviously improves, and reliability has also had better assurance.

Description of drawings

The utlity model has two accompanying drawings:

Fig. 1 is the composition synoptic diagram of radon thorium analyser;

Fig. 2 is the circuit diagram of pulsing circuit.

1. scintillation chambers (ZnS) (photomultiplier) the 3. dynamo-electric source of pulsing circuit 4. pulse amplifiers 5. single-channel pulse discriminators 6. pulse-shaping device 7.PC machine 8.PC 9. low-voltage modules, 10. high-pressure modulars of 2. popping one's head among the figure

Specific embodiments

In specific embodiments, probe 2 is sealed constructions, in photomultiplier, voltage divider are housed.They all are fixed on the elastic support with retractility, and after guaranteeing to change photomultiplier, photocathode still joins with organic glass end window reliably.Scintillation chamber 1 is made up of two hollow organic glass of semisphere, in scribble zinc sulfide scintillator, it is to reach sealing by means of external packing.Two crossing crystal dividing plates are arranged in the scintillation chamber 1, when being installed, dividing plate must separate two valves, the flow direction of emanating must be by after the valve air inlet, circle and to flow out from another valve around the scintillation chamber, as loading error, bigger influence is arranged during then to eliminating background and survey thoron.During the external packing of loading and unloading scintillation chamber 1, preferably scintillation chamber 1 is evacuated earlier, uses specific purpose tool that gland (dead ring) is tightened then or unscrew, with the unlikely damage of protection gland.Scintillation chamber's volume is 500ml.

Low-voltage module 9 provides the burning voltage of 12V for pulsing circuit 3.

Photomultiplier when work, high-pressure modular 10 should provide+800～+ the 1200V high pressure, it is to realize by high voltage adjusting on the instrument panel that high pressure is selected.

When this radon thorium analyser was worked, photoimpact was to produce during by the circuit working of scintillation chamber 1, photomultiplier and plate-load combination thereof.Behind the introducing scintillation chamber 1 that emanates, emanate the α particle impacting that in the transformation process, produces to zinc sulfide crystal, alpha-particle energy is transferred to zinc sulfide crystal, cause the zinc sulphide atomic excitation and glisten and emit photon, after this photon is received by the photomultiplier in working, on its photocathode, produce photoelectron, finish opto-electronic conversion.Photoelectron is subjected to effect of electric field and focuses on beating by on the plate of photomultiplier, inspire secondary electron, at last, secondary electron is accelerated and zooms into electron stream, forms a pulsating current and export a negative pulse voltage on the anode load resistor of high frequency cable at photomultiplier.

In scintillation chamber 1, the number of α particle is directly proportional with the concentration of emanating, and promptly the frequency with flash of light is directly proportional.Therefore: the pulsed frequency of record photomultiplier output has also just been known the concentration of emanating (being the content or the activity of radium thorium) in the scintillation chamber 1.

For surveying radon (survey radium) since the half life period that radon is emanated than long many of the daughter element half life period of radon,, and write down the α particle that the daughter element of radon is emitted so in measuring process, not only write down the α particle that radon is emanated and produced.Therefore, after introducing was emanated, the umber of pulse that counter was write down in the identical time was to increase in time.According to experiment, to emanate and introduce after the 1-1.5 of scintillation chamber hour, the increase of intensity is just slower.Measuring accuracy just can satisfy the analysis requirement.Therefore, when adopting scintillation chamber 1 to survey radium, suggestion is preferably introduced the scintillation chamber emanating and is measured after 1.5 hours.

When surveying thorium, because the half life period of thoron is shorter, so when measuring, thoron must flow in scintillation chamber 1 (maintenance dynamic equilibrium state), in order to utilize existing equipment in the laboratory, can adopt voltage drop method.

Because the negative pulse voltage amplitude of photomultiplier output is less, and photomultiplier is high output internal resistance device, can not be used for direct trigger data acquisition card, adopt the cmos amplifier AND circuit to design circuit such as amplifier 4, discriminator 5, former 6 for this reason.Exporting same standard count pulse send PC to gather count measurement.

Amplifier 4 is by F ₁F ₂The two poles of the earth amplifier is formed, and effect is to amplify photoimpact.

Photomultiplier output is through resaistance-capacity coupling circuit R ₁C ₁Deliver to amplifier F ₁, for guaranteeing amplification quantity, again through resaistance-capacity coupling circuit R ₅C ₂Deliver to amplifier F ₂, the photoimpact that output is amplified.

Discriminator 5 is by M ₁M ₂M ₃M ₄M ₅Form W ₁W ₂For discriminator up and down provides adjustable discrimination threshold voltage, R ₁₁WY ₁, R ₁₂WY ₂Be starting voltage source up and down, M ₃M ₆M ₇Y ₁Form coincidence circuit, its effect is that reception amplifier is exported and photoimpact is screened, and screens idler Pulse and noise, exports effective photoimpact.

Former 6 is by Y ₂M ₈C ₇R ₁₅The monostable circuit of forming realizes moulding.Effect is to the photoimpact and the machine-shaping of discriminator output, exports same standard count pulse, send capture card.

Capture card is installed in the PC, and its count measurement starts process of measurement by the counting capture card to be realized.

PC 7 (Personal Computer) is used to gather count measurement.PC realizes gathering counting, reading, calculating, printing and preservation by the execution of VB (Visual Basic is visual Basic) application program.Except that the data access, check, check, the function such as backup, also have the special function program: sample-out count program, blank measure program, sample measurement program, electrode coefficient calibrating procedure.

The foundation of programming is a national standard: in the rock sample ²²⁶The analytical approach emanation method GB/T13073-91 of Ra.

The foundation that the instrument quality check program is write is an industry standard: putting radium measurement mechanism effect method Q/AS.J-06.505-93.

The computing formula of using in the programming has: 1. sample measurement formula:

Q={[(K α (pjz-bd))/(1-e ^-0.1813t)]-the kb}/z1 formula in: pjz mean value (counting/60s)

The average background of bd (counting/60s)

T integration time (d)=Measuring Time-off-period (d)

Blank content/the activity (g)/(Bq) of kb

Z1 quality (g)

K α calibration coefficient (Bq/g/ pulse) is mean value pjz computing formula 2.:

pjz＝(N1+N2+......Nn)/n

In the formula: n.... measures number of times

N1, the standard error S2 computing formula of N2...Nn.......n measured value 3. radioactivity statistic fluctuations:

Represent whether one group of measured value meets the statistic fluctuation rule, the probability that its value drops in pjz ± S2 scope is that 68.27%, one group of measured value reaches this requirement, and that just says that this group measured value meets the statistic fluctuation rule, and this group measured value is accurately.

S2＝(pjz) ^1/2

Service condition: mean value pjz＞100 o'clock can be used.4. the overproof discrimination formula of reading:

When the absolute value of certain value and mean value pjz difference was greater than the square root of two times of mean value pjz in one group of measured value, this value was overproof.

|Ni-pjz|＞2(pjz) ^1/2

Former service condition: when each sample is only got two readings, cast out one and also will measure again once, supply two readings, expanded usefulness now.5. square error S1 computing formula:

The levels of precision of representing one group of measured value.Levels of precision is high more to be that S1 is more little, and the expression measured value is very concentrated, and very approaching between the measured value, dispersion degree is little; Otherwise, when S1 is big more, represent that measured value is very concentrated, very approaching between the measured value, that is exactly that degree of accuracy is bad.Square error $S$ $1={[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(\mathrm{Ii}-I)}^2/(n-1)]}^{1/2}$ 6. stability of instrument discrimination formula

S1/S2＜1.5

Formula is set up, and then stability of instrument reaches measurement requirement.Inspection apparatus stability should adopt stable α mark Huai Yuan.

Dispersion degree when between S1/S2＞one group of measured value of 1 expression is greater than the standard error S2 of statistic fluctuation;

When S1/S2=1 represents that one group of dispersion degree between measured value is consistent with the standard error S2 of statistic fluctuation;

Degree of accuracy height when between S1/S2＜one group of measured value of 1 expression;

To making instrument can not be applied to measure, if at this moment the α of scintillation chamber mark source, Huaihe River is no problem, that is exactly that stability of instrument is out of joint to dispersion degree when between S1/S2＞one group of measured value of 1.5 expressions greatly.The inspection problem is in proper order: the α of scintillation chamber standard source-detector-light leak not-inspection of PC-voltage-each circuit; Or powered-down, starting instrument after a while once more, when inspection apparatus stability is defective once more, should overhaul.7. detection efficiency

Under certain high pressure and threshold voltage condition, measurement standard source (GBW04313, or GBW04314, or GBW04315).Write down once in per 60 seconds, 5～10 readings of continuous recording are asked its arithmetic mean, are calculated as follows the detection efficiency of measurement mechanism: $\mathrm{\ϵ}\%=\frac{\mathrm{pjz}}{A_{\mathrm{Ra}}\left({1-e}^{-\mathrm{\λt}}\right)\×60s}\×100$ In the formula: A _RaBe radium standard activity (Bq) (1-e ^{-λ t}) be the accumulation coefficient of radon

The arithmetic mean of pjz reading

Require ε %＞180% (perhaps do not take advantage of 100, promptly represent, then ε＞1.8) without % when formula.

Claims (4)

1. radon thorium analyser, comprise scintillation chamber, probe and count measurement device, wherein the inwall of scintillation chamber scribbles zinc sulfide scintillator, comprise photomultiplier and voltage divider in the probe, it is characterized in that described count measurement device is a PC, between probe and PC, be connected with pulsing circuit, pulsing circuit comprises pulse amplifier, single-channel pulse discriminator and pulse-shaping device, probe is connected with pulse amplifier, pulse amplifier is connected with the single-channel pulse discriminator, and the single-channel pulse discriminator is connected with the pulse-shaping device.

2. radon thorium analyser as claimed in claim 1 is characterized in that the single-channel pulse discriminator is by M ₁M ₂M ₃M ₄M ₅Form W ₁W ₂For discriminator up and down provides adjustable discrimination threshold voltage, R ₁₁WY ₁, R ₁₂WY ₂Be starting voltage source up and down, M ₃M ₆M ₇Y ₁Form coincidence circuit, its effect is that reception amplifier is exported and photoimpact is screened.

3. radon thorium analyser as claimed in claim 1 or 2 is characterized in that the pulse-shaping device is by Y ₂M ₈C ₇R ₁₅The monostable circuit of forming realizes moulding, and effect is to the photoimpact and the machine-shaping of discriminator output, exports same standard count pulse, send capture card.

4. radon thorium analyser as claimed in claim 3 is characterized in that pulse amplifier is by F ₁F ₂The two poles of the earth amplifier is formed, and effect is to amplify photoimpact, and photomultiplier is exported through resaistance-capacity coupling circuit R ₁C ₁Deliver to amplifier F ₁, again through resaistance-capacity coupling circuit R ₅C ₂Deliver to amplifier F ₂, the photoimpact that output is amplified.

Images