Wyniki wyszukiwania - BazTech

1

Performance of a plastic scintillator and GM pancake tubes as alpha and beta contamination detectors in dosimetric stand

Machaj B., Mirowicz J., Kowalska E.

Nukleonika

|

2011

|

Vol. 56, No. 1

53-56

EN

A model of detection probe with a plastic scintillator (230 × 105 × 1 mm3) with a ZnS(Ag) layer at the top, and a model with six pancake Geiger-Müller (GM) counters were investigated as alpha particles (Am-241) and beta radiation (Sr-90) contamination detection probes at a dosimetric stand. A detection probe, 166 × 104 mm2 of active area, with a proportional counter was also investigated for comparison. The scintillation probe showed a higher alpha detection efficiency and a comparable beta detection efficiency with respect to the probe containing the proportional counter. The GM probe shoved a higher alpha detection efficiency, and a lower beta detection efficiency than the proportional counter probe. Detection efficiency of the scintillation probe strongly depends on the distance from the photomultiplier tube (PMT) photocathode. Active area of the GM probe of all counters constitutes approximately 50% of its measuring area.

2

Large area scintillation detector for dosimetric stand with improved light collection

Machaj B., Mirowicz J., Kowalska E.

Nukleonika

|

2011

|

Vol. 56, No. 4

317-321

EN

In order to improve scintillation light collection from a thin plastic scintillator, the shape of a light reflector, and a new concept of extraction scintillation light trapped inside the scintillator were investigated. The trapped scintillation light is extracted from the scintillator by cutting the scintillator into two pieces with the edges machined at an angle of 45 centi grade and polished. Considerable improvement of detection efficiency can be achieved when the extracted and the escape scintillation light are collected together. Prototype of such a scintillation probe was constructed and investigated.

3

Application of dose reader CD-07 for depth-dose distribution measurements in the process of microbiological radiation decontamination

Gryczka U., Jakowiuk A., Migdał W., Kałuska I., Machaj B.

Nukleonika

|

2009

|

Vol. 54, No. 4

261-265

EN

Dose reader CD-07 has been introduced for measurements of a dose distribution during dose mapping exercises and for calculations of electron beam energy. This instrument consists of an SP-880 spectrophotometer equipped with a driving motor to move a dosimetric foil across light beam in the front of narrow light aperture. To control the movement of the foil and to present and store the measuring results a specialized software has been developed. In this paper the use of dose reader CD-07 in Performance Qualification of irradiated herbs was described.

4

Metrological features of a beta absorption particulate air monitor operating with wireless communication system

Jakowiuk A., Urbański P., Świstowski E., Machaj B., Pieńkos J., Kowalska E.

Nukleonika

|

2008

|

Vol. 53, suppl. 2

37--42

EN

A system for measurements of particulate matter in the ambient air, employing beta absorption instrument AMIZ-2007 with wireless communication facilities based on GPRS technology, is presented. Uncertainty of measurements caused by the counting statistics was analyzed and it was found that at least 3 h of sampling time is needed to achieve coefficient of variation lower than 20% for the average concentration of particulate matter in the ambient air exceeding 10 μg/m3. Application of a C-14 beta ray source instead of Pm-147 improves sensitivity of the measurement ca. two times. Some results of on-line operation of the system with PM10 and PM2.5 samplers are also shown.

5

Measurement of radon (222Rn) and thoron (220Rn) concentration with a single scintillation cell

Machaj B., Urbański P., Bartak J.

Nukleonika

|

2007

|

Vol. 52, nr 4

167-171

EN

. A single scintillation cell (ö 54 × 74 mm) is used for the measurement of radon and thoron. The radon and thoron laden air is filtered and forced to flow at 1 dm3/min through the scintillation cell in the period of 1 10 min. The count number from alpha radiation is registered in the periods of 3 10 min and 20 30 min. Two values of detection and deposition efficiency of alpha radiation are used for radon (at air flow and air at rest in the cell) and for thoron. Measurements of radon laden air and thoron laden air showed good agreement between the reference concentration and the measured concentration, not worse than 1% for radon and not worse than 2% for thoron. Combination of radon + thoron concentration showed also a small interference ("cross talk") not worse than 1%.

6

Influence of aerosol concentration and multivariate processing on the indication of radon progeny concentration in air

Machaj B., Urbański P.

Nukleonika

|

2004

|

Vol. 49, nr 3

123-129

EN

Measurements of radon progeny concentration in air by a radon progeny monitor are sensitive to the concentration of particles suspended in air. Minimum detectable concentration and accuracy of the measurement are determined by random errors of the monitor. Multivariate data processing can be used to decrease these random errors. Influence of aerosol concentration on the measured results of radon progeny concentration in air, by an RGR-30 mining radiometer, operating on the principle of alpha radiation detection from radon progeny deposited on an air filter, were determined in a radon chamber experiment. The air suspended particle concentration and the radon concentration in the radon chamber were controlled and the corresponding radon progeny concentration was measured by the radon progeny monitor. Additionally, count rate from the monitor detector, originating from the alpha activity deposited on the air filter, was measured at intervals of one minute and was then used for the three-interval, and Principal Component Regression (PCR) data processing. It was found that for the aerosol concentration in air from 40 p/cm3 to approximately 9,000 p/cm3 indications of the radon progeny monitor depends considerably on the aerosol concentration. Radon daughter concentration normalized to the radon concentration against aerosol concentration varied from 0.3 to 0.9. In mines, where the aerosol concentration generally is high, this phenomenon has little effect on the indication of the radon progeny monitor. At low aerosols concentration, appropriate correction of radon progeny concentration has to be taken. Comparison of random errors when measured signal of the monitor (count rate against time) was processed employing the three-interval method and PCR data processing shows that PCR ensures a lower random error.

7

Fast measurement of radon concentration in water with Lucas cell

Machaj B., Bartak J.

Nukleonika

|

2004

|

Vol. 49, nr 1

29-31

EN

Abstract Fast method of measurement of radon concentration in water based on flushing (bubbling) water sample with air in closed loop with Lucas cell is presented. The main feature of the method is washing radon from large sample of water to small volume of air including the volume of Lucas cell, thanks to which high radon concentration in the air and considerable sensitivity of measurement is achieved. Estimated measuring sensitivity is S = 8.5 cpm/(Bq/dm3). Random error due to statistical fluctuations of count rate at radon concentration 1, 100, 10 000 Bq/dm3 is: 11, 1.1, 0.1% correspondingly at counting (measuring) time 10 min. Minimum detectable radon concentration in water for such counting time is 0.11 Bq/dm3.

8

Principal component data processing in radon metrology

Machaj B., Urbański P.

Nukleonika

|

2002

|

Vol. 47, nr 1

39-42

EN

A gauge for the measurement of radon and radon daughters concentration was tested in a radon chamber. Count rate distribution in time at the output of radiation detectors was measured and registered. The count rate distribution in time was then processed employing Principal Component Analysis (PCA) and the Root Mean Square Error (RMSE) of the count rate was investigated. It was found that PCA processing removes great part of count rate random fluctuations originating from radiation statistics, which is resulting in a decrease of the count rate random error and in random error of concentration. The RMSE of radon daughters concentration is about 3 times lower when "raw" results are PCA processed. Such decrease of error, without PCA signal processing, would require 9 times higher air flow through the air filter on which the radon daughters are deposited. In case of the measurements of the radon concentration the drop of the error is 2-3 times higher in case of long counting time.

9

A gauge for measuring the dose rate and activity of ophthalmic applicators

Machaj B., Świstowski E., Do H. C., Bilski P., Olko P.

Nukleonika

|

2002

|

Vol. 47, nr 3

107-111

EN

A gauge was developed for determining the dose rate distribution and surface activity of ophthalmic brachytherapy applicators, particularly for 106Ru applicators. A plastic fi 2×2 mm scintillator is used as the radiation detector, featuring a high pulse count rate, which results in a low 0.5% random error, due to good counting statistics. Automatic gain control of the photomultiplier tube (PMT) is achieved using a LED as the reference light source. The PMT operates in pulse mode. Long term gain variation due to fatigue of the PMT or ambient temperature variation is thus compensated for. The count rate error due to inaccurate setting of the high voltage supply of the PMT is 0.4%, and the instability error over 7 hours of continuous operation does not exceed 1-2%, peak-to-peak.

10

Modification of the RGR monitor of radon daughters concentration in air

Machaj B.

Nukleonika

|

1999

|

Vol. 44, nr 3

479-490

EN

It has been shown that determination of the a-activity of the radon daughters nuclides in triple time intervals, which employs air sample deposition on the air filter, are independent on the degree of the radiation disequilibrium. To decrease random errors, some additional simulations and gauge model measurements have been carried out in the radon chamber. The simulations indicate that small random errors are achieved for the counting time intervals of 1-7 min, 8-20 min and 21-30 min, 5 min deposition time, at reasonably long measuring cycle of 30 min. The counting begins parallely with the start of air pump which forces the air flow through the air filter. The radon daughter concentrations measured in such a way correspond well to the real changes of activity against time. The root mean square error of the a potential energy of radon decay products does not exceed 7.5% at about 8 µJ/m3.

PL

Prace wykazały, że wskazania metody pomiaru stężenia produktów rozpadu radonu w powietrzu przez osadzanie próbki powietrza na filtrze powietrza oraz dokonującej pomiaru aktywności promieniowania alfa w trzech interwałach czasu są niezależne od stopnia równowagi promieniotwórczej pomiędzy produktami rozpadu. W celu zmniejszenia błędów statystycznych wykonane zostały dalsze obliczenia symulacyjne i pomiary modelu miernika w komorze radonowej. Obliczenia symulacyjne wskazują, że niskie błędy statystyczne pomiaru uzyskuje się dla zliczania impulsów w interwałach pomiarowych 1-7 min, 8-20 min, 21-30 min, rozpoczynających się wraz ze startem pompowania powietrza wymuszającym przepływ powietrza przez filtr, przy rozsądnej długości cyklu pomiarowego 30 min i 5 min czasu pompowania powietrza. Zmierzone w ten sposób stężenia dobrze odwzorowują rzeczywisty przebieg zmian aktywności w funkcji czasu, średni błąd kwadratowy pomiaru energii potencjalnej alfa produktów rozpadu nie przekracza 7.5% przy stężeniu energii potencjalnej alfa ok. 8 µJ/m3.

11

Continuous measurement of radon concentration in the air with the Lucas cell by periodic sampling

Machaj B., Urbański P.

Nukleonika

|

1999

|

Vol. 44, nr 4

579-594

EN

The Lucas cell was investigated as an α-radiation detector for continuos measurement of radon concentration in the air with air sampling by means of a pump. The investigations indicate that all the short lived radon decay products produced inside the Lucas cell ø 54x74 mm (0.17 l) are attached to the internal walls of the cell and are not removed when the cell is flushed with some fresh air. This effect, and the well known effect of increase of the radon daughters concentration when only radon is introduced into the cell, result in a delay of response of the gauge to variations of the radon concentration. The response of the gauge to step variation of radon concentration is computer simulated and measuring errors of the gauge are estimated. Multivariate processing of the measured signal using Principal Component Analysis technique can improve accuracy of the gauge.

PL

Badano komorę Lucasa jako detektor promieniowania α w ciągłych pomiarach radonu w powietrzu z wymuszonym poborem próbki powietrza za pomocą pompki powietrza. Badania wskazują, że wszystkie krótkożyciowe produkty rozpadu osadzają się na wewnętrznych ściankach komory Lukasa o wymiarach ø 54.74 mm (0,171) i nie są usuwane, gdy komora przepłukiwana jest czystym powietrzem. Efekt ten i znany efekt narastania stężenia produktów rozpadu radonu, gdy do komory wprowadzony jest tylko radon, powoduje opóźnioną odpowiedź miernika na zmiany stężenia radonu. Symulowana jest odpowiedź miernika na skokową zmianę stężenia radonu oraz szacowany jest błąd pomiaru. Wielowymiarowa obróbka wyników pomiaru z wykorzystaniem techniki analizy głównych składowych może poprawić czułość pomiaru miernika.

12

Simulation of the activities of radon daughters on RGR monitor air filter

Machaj B., Bartak J.

Nukleonika

|

1998

|

Vol. 43, nr 2

175-184

EN

To assess errors of a grab sample methods for measurement of radon-222 decay products concentration in air, a computer program simulating deposition of radon daughters on a filter and of variation of their activity against time was developed. Employing this program a measuring procedure of three selected methods of measurement were simulated: measurement of decay product alpha activity in three time intervals, in two time intervals and in one time interval. The count numbers registered in selected time intervals for RaA:RaB:RaC ratio from 200:200:200 ... 200:0:0 dis/min at counting efficiency η = 0.3 were processed according to the equations corresponding to the method under investigations and relative errors resulting from statistics of counting and from deficiency of the method were computed. The results of computations of two interval method were compared with practical measurements from international intercomparison of such gauges. Computations show that the three interval method eliminates errors of the method but large statistic error remains resulting from the uncertainty of measurement of alpha radiation in selected intervals reaching 9.4% relative of alpha potential energy. Two interval method exhibits errors resulting from deficiency of the measuring method 18.3% and from the statistics of pulse counting 7.3%. Measurements at international intercomparison of such gauges showed precision of measurement (statistical error plus method error) 12.6% of alpha potential energy. Computer simulation of one interval method showed 13.5% error related to the deficiency of the method and 3.4% statistic error.

PL

W celu oceny błędów metody pomiaru stężenia produktów rozpadu radonu-222 w powietrzu, opartej na poborze próbki powietrza, opracowany został program komputerowy symulujący osadzanie produktów rozpadu na filtrze oraz zmianę ich aktywności w funkcji czasu. Za pomocą tego programu symulowano trzy wybrane metody pomiaru: pomiar aktywności promieniowania alfa produktów rozpadu w trzech, w dwu i w jednym interwale czsu. Rejestrowana (symulowana)liczba impulsów w wybranych przedziałach czasu dla stosunku RaA : RaB : RaC w granicach 200 : 200 : 200 do 200 :0 :O rozp./min przy sprawności delekcji η=0.3 poddana była obróbce wg. równań dla danej metody, wyliczone zostały również błędy wynikające z metody pomiaru oraz błędy statystyczne. Wyniki obliczeń dla metody dokonującej pomiaru w dwu przedziałach czasu porównane zostały z wynikami międzynarodowych pomiarów porównawczych. Obliczenia symulacyjne wykazują, że metoda trzyinterwałowa eliminuje błędy wynikające z metody pomiaru, pozostaje natomiast duży błąd statystyczny wynikający z niepewności pomiaru promieniowania alfa w wybranych przedzaiłach czasu, dochodzący do 9,4% względnie energii potencjalnej alfa. Metoda dwuinterwałowa wykazuje błędy niedoskonałości metody 18,3% i wynikające ze statystyki liczenia impulsów 7,3%. Międzynarodowe pomiary porównawcze wykazały precyzję pomiaru 12,6% energii potencjalnej alfa (błąd statystyczny plus błąd metody). Symulacja komputerowa metody jednointerwałowej wykazuje błąd metody 13,5% i błąd statystyczny 3,4%.