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Development of measuring techniques using a silicon diode pin detector for continuous radon monitoring
N,~/. ~
P.nd~. Mau., VoL 22, No* I.-4, PP. 3(~)-Y/2, 1993 Pda~ ia Omatlldmin. 116.00+.00
DEVELOPMI NT OF MEASURING TECHNIQUES USING A SILICON DIODE PIN DETECTOR FOR CONTINUOUS RADON MONITORING D. K/2~,* C. DEVlLLARD,t A. CIIAM]~UI~Ttand R. BARILLONt *Laboratowede M(~tmiog,edes InterfacesTer3tmques, IUT de Belfort-Montb~Jumt,Umvmsm~de Franc,he Com~ BP 427, 25211 Montb~.imrdCedex, Franc.e; tLaboratotre de Mi~oanalyses Nucg,mes, UFR Sctences et Techmques, Uruvemt6 de Franc.he Corot6, La Boulose, 16 mute de Gray, F 25030 Besan~on Cedex, France
ABSTRACT In order to increase the diffe~.nt kinds of alpha-ionizing rsdlmlon measurements, silicon PIN diodes were developed for the continuous ~ m o n t of the concentration in the fields of Em'th Sciences and ]~intlon Protection. The l~qtress made now in microelectronic detection enables the use of silicon PIN detectors in addition to nuclear track polymcdc detectms. For this,a prototype device was built. Diffemm testsand measurement were COmlmne~l with techniques in the laburau3~yand in fieldwork using a standard radon murce. The lust resulm show that t i ~ new technique can be used instead of nuclear uack polymerk detectors with a higher sensitivity. Homewere, the measurements me not yet accurate enough in gases. KEYWORDS silicon diode, radon monitoring, electronic detection, alpha spectrum INTRODUCTION Over the last ten years, we have developed techniques m measure radon 222 c o n c e n ~ . At f'~t, a special electronic device was developed using a proponiomti counm (Klein, 1990 and Chamhaudm et a/.,1991) m measure in continuous radon levels. This potable self-contained nppmams is Im~-nfly ~ e detector with the highest sensitivity and which gives results in the shoru=t anmum of time (30 minuws). It also monitors radon in very severe environmental conditions. This device is recommended for the oomimmus monito~g of radon level fl~_~ons to study the correlation between the radon concenmuion and geophysical or geochemical modifl=tims. However, the high cest and large ~ze of the device make wi6e~sp~aduse hnpmm~ie. A new approach has been token to optimize radon fieldwork, CBaralon eta/, 1991). In addition to the continuous measurement with a proportional counter, nuclear uack detectors were used in passive dosimeters. They were developed especially at the Universit6 de Franche-Comt6 (France) as part of an international ¢ollabutlion (Chambaudet et al, 1992). After one month of expesure and many days of Ireatemem and counting tracks, the radon level was measured. The process was very time-mnsuming but less costly. The progress now being made in m i c r o - e l ~ i c silicon and the reduction in cost make it possible to use silicon technology to replace the usual plastictrack detectors. With this god in mind, tinee silifon diodes were tested to detect alpha pmdcle in envimommml conditions and without bias voltage. This pilot study (Devillard, 1992) helped to design an alpha parfide detector from a commercial silicon phetndiode. The device defining, the response for detecting the radon level in environmemal conditions has been made in a test chamber. SILICON DIODE FOR ALPHA PARTICLE DETECTION Gene~ ~ : Silicon is a very good semi-on~l~tor suited to the manufacture of high-quality radiation debtors. Silicon phowdiode rareused to detectlightbut also they are used to detect_r~i~tion.Fig. I shows the principallayoutof a PJJ~. junction d~_~.or.
369
370
D. KLEIN et al.
"~i02pamvmmlayer .- del,edkyer h~er (n-Si) z+dol~ layer
Fig.1
:
P.I.N. junction detector
Alpha nerticle ~ s ~ Three P.I.N. silicon diodes were tested: two are marketed by Cmbena Industry and one is marketed by Hamamatsu. The Canberra diode has a detection area of 450 mm2 and 25 mm2 covered with a~ aluminium layer. These diodes are sold for alpha particle detection in vacuum conditions and with a bias polarization voltage of 35 and 40 V, respectively. The Hamamatsu photodiode has a detection area of about 100 mm2 (without covered layer) and the polarization voltage recommended for hght detection ts 100V. This last photodiode is the least expensive of the three. The silicon diode responses for alpha particle detection are studicd in the irradiation chamber presented in Fig.2. This chamber enables the detectors to be irradiated with an alpha particle fluenee of 1000 alpha, cm-2.s"1, the alpha energy ranging from 0 to 5.48 MeV (reference energy from americimn source used) depending on the helium gas pressure put into the device. A measurement system made up a Tennelec preamplifier and a Tita card (I-LV. supplied and the multichannel analyzer) connected to a microcomputer was used to evaluate the ~ of the detectors.
II~OV
Ftg.2 : Diagram of the alpha particle-irradiation chamber I- Silicon dtode; 2- Preamphfier; 3- H.V. Voltage; 4- Alpha ~ t o n m t ~ , 5- Rotable detect stand; 6- turn table Results and discussion Figure~ 3, 4, and 5 present the experimental results obtained with the diode ~ as a function of pressure in the chamber (i.e., alpha parucle energy) and as a function of the polarization voltage applied.
Fig.3: Canberra (450mm 2)
Ftg.4: Canberra (25mm2)
Fig.5: Hamamatsu (100ram 2)
These studies show that the Hamamatsu photothode can detect alpha particles with no polarization voltage and the most effectively for high pressmes. Only this diode was used in the following experiment.
RADON MONITORING WITH SILICON DIODE PIN RADON
371
DETECTION
~ t enafigunttion idupes were tested besed on the resea~h cmducted by Remi Badlim (Badllm, 1992). A new special cell with an auneiated electronic was designed (Fig. 6), which has the capacity to measure the following: - alpha particles are taken and measurement in severe induslrial various environmental sip_L~IOnS; an air stream is pumped from the ground, degassing water, buildings or nuclear industry envko~mmts into the d~__~lion chamber, the alpha l~rticles emi~_,~_by the radon and the decay products am then analyzed (l~mifivity: 0,011 pulse.h'l.Bq'l.m'3). A polyethylene membrane can be used to eliminate thonm and its danghters in the detection volume (sensitivity: 0,0085 puise.h'l.Bq'l.m'3). These measurements in association with the l~pordonui counter enable the particles to be counted and the alpha emiuen to be characterized by alpha spectrum analysis under air ~ - radon and thomn exhalation rates from the ground, building materials or nuclear plants ; these measurement are taken and spectrum analysis is conducted in the laboratory or in fieldwork in an atmmphe~lne pressure. In addition, the measurement, in association with the ln~xxtional counter, enable the alpha l~micles to be counted and the alpha emitte~ to be characterized by spectrum analysis if a high level of radon is measured. - radon, as a passive integral dosimeter for environmental conditions in the ground or in water as done the barasol technology (C.E.A., 1989) or in the radon monitoring technology (in Hungary )0-Iunyadi, 1992).
- l I p e e t n H n m u d y o o r in mlero.eomputer 2 - Epmm otorage S - Elootroetlo deteotJon 4 - Pltoto411o41o S - Detection elmmber (i - F l o w i n g o r d e g a z i n o o h a m b e r 7 - Power supply e . Pump I
Fig. 6 : Description of photodiode detection cell. ~esults and discussion The new photodiode detection cell was exposed to radon and its _~__~_yproduce at the L.M.N. radon environmental chamber (fig. 7). The test was conducted with a natural uranium source at the L.M.N.. A dry air current (0.5 L rain -1) swept the source and the detectors were exposed to the flow of radon and decay products in a 125-liter chamber. Radon activity was measured continuously by a ~ counter.
Fig. 7 : Diagram of radon environmental chamber system at rite L.M.N. 1- Gas flow inlet, 2- Nattnl uranium soorce, 3- Inlet filter, 4- Pump, 5- Dessicant trap, 6- Experimental clmmbet, 7- Sample stand, 8- PZOlxrdmui counter, 9- Associated Electronic, 10- Atimenmtion,11 Multichannel Analyaer, 12- PmlX~onal counter and 13- Pump
372 The firg ~
D. ~ t
eta/.
obtainnd using the photediode detection cell are pmsemed in Fig. 8 and 9 Alpha spectnnn e.alysis (acquisition time = I hour):
lO,eO B, O0
!15,00 IO.O0 S,O0 0,0~
. . . . . . . r 0 ,be . ~bO s~e 4~ Leo e0o roe eeo ~.oo ':n,tqW
v,
Fig. 8 : Spucm~ of radon and decay products in the environmental chamber Change in radon measurements
i
,
|
/,/,
--T - - - - ~ - - - - - , 0
--t
0
-
10
20
30
~
40 50 eO Ume tn t~es
- ~ = - - - ~
70
80
90
100
Measure of radon alpha particle count as function of time to fill the analysis chamber CONCLUSION In mmmmizing the results, the silicon photodiode has shown to be capable of measuring radm coucmUatims in eavimmnental conditions. The device is more sensitive than plastic nuclear det_~__to~_but not quite as smsifive as a countes. A joint project to develop a new silicon diode detector has been planned with a french manufuctm~ as a pan of a doctoral dissertation in Physics at the Univemt6 of ~ t ~ . REFERENCES Barillon R., D. Klein, A. Chambaudet, F. Membrey and M. Fromm.(1991). Additional uses of l~lymeric nuclear track detectors (CR 39 and LR 115) for measuring radon emanation Nuct. Tracks Radla:. Meas., Vol. 19, N°I-4.
pp. 291-295. Chambaudet A., M. Cieur, M. H m and D. Klein (1991). A portale system for the continuous measurement of radon 222 in hostilegeophysical environments.Nucl. Inst.and metAod B61, pp. 244-250. Cham~ A., V. Pautov., D. Klein and G. BarenboYm (in preu). Features of a new russian track ~ for radon ~ t , Nucl. Tracks Rnd'mt Meas.. C.E.A. (1989). La balise Barasol, Doc. Techn. C.E.A.C.R.P.M. Devillmd C. (1992), Caracthisatm"n de photodinde silicium pour la mesure du radon. M6mo/re de Dipl0me d'EO_v~. "Physk-Chimics", University of Fraucbe-Comt6. Klein D. (1990). Realisafion et application d'un compteur proportional pour des mesures de tcrrain en continu du radon 222. Plt.D. Chemical-Phy~ca, Unive~ty of l~nmc2~,-Comt~, Hunyndi I. (1992), Real time Monitoring by silicon photndiodes, Second workshop on radon monitoring in
n,~k~mceon
P.nd~. Mau., VoL 22, No* I.-4, PP. 3(~)-Y/2, 1993 Pda~ ia Omatlldmin. 116.00+.00
DEVELOPMI NT OF MEASURING TECHNIQUES USING A SILICON DIODE PIN DETECTOR FOR CONTINUOUS RADON MONITORING D. K/2~,* C. DEVlLLARD,t A. CIIAM]~UI~Ttand R. BARILLONt *Laboratowede M(~tmiog,edes InterfacesTer3tmques, IUT de Belfort-Montb~Jumt,Umvmsm~de Franc,he Com~ BP 427, 25211 Montb~.imrdCedex, Franc.e; tLaboratotre de Mi~oanalyses Nucg,mes, UFR Sctences et Techmques, Uruvemt6 de Franc.he Corot6, La Boulose, 16 mute de Gray, F 25030 Besan~on Cedex, France
ABSTRACT In order to increase the diffe~.nt kinds of alpha-ionizing rsdlmlon measurements, silicon PIN diodes were developed for the continuous ~ m o n t of the concentration in the fields of Em'th Sciences and ]~intlon Protection. The l~qtress made now in microelectronic detection enables the use of silicon PIN detectors in addition to nuclear track polymcdc detectms. For this,a prototype device was built. Diffemm testsand measurement were COmlmne~l with techniques in the laburau3~yand in fieldwork using a standard radon murce. The lust resulm show that t i ~ new technique can be used instead of nuclear uack polymerk detectors with a higher sensitivity. Homewere, the measurements me not yet accurate enough in gases. KEYWORDS silicon diode, radon monitoring, electronic detection, alpha spectrum INTRODUCTION Over the last ten years, we have developed techniques m measure radon 222 c o n c e n ~ . At f'~t, a special electronic device was developed using a proponiomti counm (Klein, 1990 and Chamhaudm et a/.,1991) m measure in continuous radon levels. This potable self-contained nppmams is Im~-nfly ~ e detector with the highest sensitivity and which gives results in the shoru=t anmum of time (30 minuws). It also monitors radon in very severe environmental conditions. This device is recommended for the oomimmus monito~g of radon level fl~_~ons to study the correlation between the radon concenmuion and geophysical or geochemical modifl=tims. However, the high cest and large ~ze of the device make wi6e~sp~aduse hnpmm~ie. A new approach has been token to optimize radon fieldwork, CBaralon eta/, 1991). In addition to the continuous measurement with a proportional counter, nuclear uack detectors were used in passive dosimeters. They were developed especially at the Universit6 de Franche-Comt6 (France) as part of an international ¢ollabutlion (Chambaudet et al, 1992). After one month of expesure and many days of Ireatemem and counting tracks, the radon level was measured. The process was very time-mnsuming but less costly. The progress now being made in m i c r o - e l ~ i c silicon and the reduction in cost make it possible to use silicon technology to replace the usual plastictrack detectors. With this god in mind, tinee silifon diodes were tested to detect alpha pmdcle in envimommml conditions and without bias voltage. This pilot study (Devillard, 1992) helped to design an alpha parfide detector from a commercial silicon phetndiode. The device defining, the response for detecting the radon level in environmemal conditions has been made in a test chamber. SILICON DIODE FOR ALPHA PARTICLE DETECTION Gene~ ~ : Silicon is a very good semi-on~l~tor suited to the manufacture of high-quality radiation debtors. Silicon phowdiode rareused to detectlightbut also they are used to detect_r~i~tion.Fig. I shows the principallayoutof a PJJ~. junction d~_~.or.
369
370
D. KLEIN et al.
"~i02pamvmmlayer .- del,edkyer h~er (n-Si) z+dol~ layer
Fig.1
:
P.I.N. junction detector
Alpha nerticle ~ s ~ Three P.I.N. silicon diodes were tested: two are marketed by Cmbena Industry and one is marketed by Hamamatsu. The Canberra diode has a detection area of 450 mm2 and 25 mm2 covered with a~ aluminium layer. These diodes are sold for alpha particle detection in vacuum conditions and with a bias polarization voltage of 35 and 40 V, respectively. The Hamamatsu photodiode has a detection area of about 100 mm2 (without covered layer) and the polarization voltage recommended for hght detection ts 100V. This last photodiode is the least expensive of the three. The silicon diode responses for alpha particle detection are studicd in the irradiation chamber presented in Fig.2. This chamber enables the detectors to be irradiated with an alpha particle fluenee of 1000 alpha, cm-2.s"1, the alpha energy ranging from 0 to 5.48 MeV (reference energy from americimn source used) depending on the helium gas pressure put into the device. A measurement system made up a Tennelec preamplifier and a Tita card (I-LV. supplied and the multichannel analyzer) connected to a microcomputer was used to evaluate the ~ of the detectors.
II~OV
Ftg.2 : Diagram of the alpha particle-irradiation chamber I- Silicon dtode; 2- Preamphfier; 3- H.V. Voltage; 4- Alpha ~ t o n m t ~ , 5- Rotable detect stand; 6- turn table Results and discussion Figure~ 3, 4, and 5 present the experimental results obtained with the diode ~ as a function of pressure in the chamber (i.e., alpha parucle energy) and as a function of the polarization voltage applied.
Fig.3: Canberra (450mm 2)
Ftg.4: Canberra (25mm2)
Fig.5: Hamamatsu (100ram 2)
These studies show that the Hamamatsu photothode can detect alpha particles with no polarization voltage and the most effectively for high pressmes. Only this diode was used in the following experiment.
RADON MONITORING WITH SILICON DIODE PIN RADON
371
DETECTION
~ t enafigunttion idupes were tested besed on the resea~h cmducted by Remi Badlim (Badllm, 1992). A new special cell with an auneiated electronic was designed (Fig. 6), which has the capacity to measure the following: - alpha particles are taken and measurement in severe induslrial various environmental sip_L~IOnS; an air stream is pumped from the ground, degassing water, buildings or nuclear industry envko~mmts into the d~__~lion chamber, the alpha l~rticles emi~_,~_by the radon and the decay products am then analyzed (l~mifivity: 0,011 pulse.h'l.Bq'l.m'3). A polyethylene membrane can be used to eliminate thonm and its danghters in the detection volume (sensitivity: 0,0085 puise.h'l.Bq'l.m'3). These measurements in association with the l~pordonui counter enable the particles to be counted and the alpha emiuen to be characterized by alpha spectrum analysis under air ~ - radon and thomn exhalation rates from the ground, building materials or nuclear plants ; these measurement are taken and spectrum analysis is conducted in the laboratory or in fieldwork in an atmmphe~lne pressure. In addition, the measurement, in association with the ln~xxtional counter, enable the alpha l~micles to be counted and the alpha emitte~ to be characterized by spectrum analysis if a high level of radon is measured. - radon, as a passive integral dosimeter for environmental conditions in the ground or in water as done the barasol technology (C.E.A., 1989) or in the radon monitoring technology (in Hungary )0-Iunyadi, 1992).
- l I p e e t n H n m u d y o o r in mlero.eomputer 2 - Epmm otorage S - Elootroetlo deteotJon 4 - Pltoto411o41o S - Detection elmmber (i - F l o w i n g o r d e g a z i n o o h a m b e r 7 - Power supply e . Pump I
Fig. 6 : Description of photodiode detection cell. ~esults and discussion The new photodiode detection cell was exposed to radon and its _~__~_yproduce at the L.M.N. radon environmental chamber (fig. 7). The test was conducted with a natural uranium source at the L.M.N.. A dry air current (0.5 L rain -1) swept the source and the detectors were exposed to the flow of radon and decay products in a 125-liter chamber. Radon activity was measured continuously by a ~ counter.
Fig. 7 : Diagram of radon environmental chamber system at rite L.M.N. 1- Gas flow inlet, 2- Nattnl uranium soorce, 3- Inlet filter, 4- Pump, 5- Dessicant trap, 6- Experimental clmmbet, 7- Sample stand, 8- PZOlxrdmui counter, 9- Associated Electronic, 10- Atimenmtion,11 Multichannel Analyaer, 12- PmlX~onal counter and 13- Pump
372 The firg ~
D. ~ t
eta/.
obtainnd using the photediode detection cell are pmsemed in Fig. 8 and 9 Alpha spectnnn e.alysis (acquisition time = I hour):
lO,eO B, O0
!15,00 IO.O0 S,O0 0,0~
. . . . . . . r 0 ,be . ~bO s~e 4~ Leo e0o roe eeo ~.oo ':n,tqW
v,
Fig. 8 : Spucm~ of radon and decay products in the environmental chamber Change in radon measurements
i
,
|
/,/,
--T - - - - ~ - - - - - , 0
--t
0
-
10
20
30
~
40 50 eO Ume tn t~es
- ~ = - - - ~
70
80
90
100
Measure of radon alpha particle count as function of time to fill the analysis chamber CONCLUSION In mmmmizing the results, the silicon photodiode has shown to be capable of measuring radm coucmUatims in eavimmnental conditions. The device is more sensitive than plastic nuclear det_~__to~_but not quite as smsifive as a countes. A joint project to develop a new silicon diode detector has been planned with a french manufuctm~ as a pan of a doctoral dissertation in Physics at the Univemt6 of ~ t ~ . REFERENCES Barillon R., D. Klein, A. Chambaudet, F. Membrey and M. Fromm.(1991). Additional uses of l~lymeric nuclear track detectors (CR 39 and LR 115) for measuring radon emanation Nuct. Tracks Radla:. Meas., Vol. 19, N°I-4.
pp. 291-295. Chambaudet A., M. Cieur, M. H m and D. Klein (1991). A portale system for the continuous measurement of radon 222 in hostilegeophysical environments.Nucl. Inst.and metAod B61, pp. 244-250. Cham~ A., V. Pautov., D. Klein and G. BarenboYm (in preu). Features of a new russian track ~ for radon ~ t , Nucl. Tracks Rnd'mt Meas.. C.E.A. (1989). La balise Barasol, Doc. Techn. C.E.A.C.R.P.M. Devillmd C. (1992), Caracthisatm"n de photodinde silicium pour la mesure du radon. M6mo/re de Dipl0me d'EO_v~. "Physk-Chimics", University of Fraucbe-Comt6. Klein D. (1990). Realisafion et application d'un compteur proportional pour des mesures de tcrrain en continu du radon 222. Plt.D. Chemical-Phy~ca, Unive~ty of l~nmc2~,-Comt~, Hunyndi I. (1992), Real time Monitoring by silicon photndiodes, Second workshop on radon monitoring in
n,~k~mceon