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compactness, the low-voltage power supply and the physical hardness are very useful features for

industrial applications of the fabricated CsI(Tl)/PIN diode sensor.

r radiely inTheseed witsical

(Chavanelle and Parmentier, 2003). The good spectral match

compact nature of the resulting detector has led to the wide-

ing amoveeventof ad SiC

to obtain optical grade. The sizes of the used powders were 1, 0.3,

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Contents lists availabl

else

io

Applied Radiation and Isotopes 67 (2009) 14631465PTFE tape and an optical grease were used for maximizing lightspread application of CsI(Tl)/PIN-type sensors in industrial (Rozsa,1989; Bandyopadhyay and Swapan, 1996; Stebel et al., 2006;Safavi-Naeini et al., 2008).

and 0.05mm.CsI(Tl) has an emission spectrum (around 550nm), which ts

the absorption spectrum of silicon. To match the polished CsI(Tl)with a PIN diode, a optical grease and a PTFE tape was used. A

collection and for optical coupling, respectively. Several layers ofPTFE tapes also contribute to the prevention of CsI(Tl) crystal

Corresponding author. Tel./fax: +82222202354.

E-mail address: ykkim4@hanyang.ac.kr (Y.K. Kim).0969-80

doi:10.1between the emission from CsI(Tl) scintillators and thespectral response of PIN diodes, together with the rugged,

paper to remove scratches. The grinded CsI(Tl) was polishedseveral times on a micro-cloth with various sized Al2O3 powdersavalanche photodiode. Use of PMT requires high-voltage supplyand lead to bulky and sensitive magnetic elds. Use of Avalanchephotodiodes also requires high-voltage supply and temperaturestability in order to insure energy measurement stability

as the active size of a PIN diode (Hamamatsu 3590-08), by usdiamond string saw. Methyl alcohol was used not only to reheat and sludge during cutting process but also to prreaction with moisture due to the hygroscopic propertyCsI(Tl). The cut CsI(Tl) was grinded with various numbereCurrently, compound semiconductor materials are more expen-sive than scintillator crystals. So, scintillator detectors are stillpromising candidates for an NDT and a radiation monitoringsystem.

For indirect detection, scintillator crystal converts gammaphoton energy into light photons. The light output readout can beperformed by photomultiplier tube (PMT) or PIN diode including

2. Material and methods

The density and the Mohs hardness of a CsI(Tl) scintillator are4.51 g/cm3 and 2, respectively (Carini et al., 2007). And hygro-scopic property of a CsI(Tl) makes the processes cautious. A CsI(Tl)ingot was cut into 10 (W)10 (L)20 (H)mm3, which is the same1. Introduction

Room temperature semiconductoCdZnTe, CdTe, and HgI2 are widmeasurements (Carini et al., 2007).very good energy resolution comparbut detection efciency and phy43/$ - see front matter & 2009 Elsevier Ltd. A

016/j.apradiso.2009.02.042& 2009 Elsevier Ltd. All rights reserved.

ation detectors such asvestigated in nuclears semiconductors offerh scintillator detectors,rigidity is very low.

In this work, the fabrication processes were addressed indetail and the responses for various standard gamma sourcesincluding 137Cs and 60Co for NDT system, were measured to verifyfeasibility. The directional dependency for the incident gamma-rays was also measured due to the anisotropic geometry of theprocessed CsI(Tl).Fabrication and performance characterisensor for industrial applications

Han Soo Kim a, Jang Ho Ha a, Se Hwan Park a, Seuna Korea Atomic Energy Research Institute, Daejeon 305-353, Republic of Koreab Department of Environmental Engineering, Yonsei University, Wonju 220-710, Repubc Department of Nuclear Engineering, Hanyang University, Seoul 133-791, Republic of K

a r t i c l e i n f o

Keywords:

CsI(Tl)

PIN diode

Photon counting

Gamma rays

NDT

a b s t r a c t

CsI(Tl)/PIN diode radiation

an environmental radiatio

optical grade from a CsI(Tl

external impact. The pho

amplier. At room tempe

energy resolution of 7.9%

directional dependency w

journal homepage: www.

Applied Radiatll rights reserved.sors were fabricated for application in various elds such as an NDT and

onitoring system. CsI(Tl) crystals of 111121mm3 were processed asot and matched with PIN diodes in consideration of the light loss and the

ode signal is amplied by a low-noise preamplier and a pulse shape

re, the fabricated CsI(Tl)/PIN diode radiation sensors demonstrate an

r 660keV gamma rays and 4.9% for 1330keV. The uctuation of the

elow 14% from 0 to 90 degree for the incident 660keV gamma rays. Theics of a CsI(Tl)/PIN diode radiation

eon Cho b, Yong Kyun Kim c,

Korea

e at ScienceDirect

vier.com/locate/apradiso

n and Isotopes

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anH.S. Kim et al. / Applied Radiation1464cracks from external impact as an absorber and from temperaturedifferences due to different hardness between the CsI(Tl) and themolder. The fabricated CsI(Tl)/PIN diode radiation sensors areshown in Fig. 1.

The fabricated CsI(Tl)/PIN diode sensor and electronicswere installed in a experimental shielding box to preventexternal electro-magnetic waves. A Cremat CR-110 and a CR-200hybrid chips were used as a preamplier and a shapingamplier. A feedback resistor and a feedback capacitance were

Fig. 1. The fabricated CsI(Tl)/PIN diode sensors.

CSI (TI)/PINdiodesensor

Cf

Rf

Preamp. Amp. MCA

f = RfCf

Fig. 2. Pulse amplication and detection circuit. Rf and Cf are 100MO and 1.4pF,respectively.

Fig. 3. 133Ba (276, 302, 356, and 383 keV) energy spectra.d Isotopes 67 (2009) 14631465100MO and 1.4 pF, respectively. A diagram of pulse amplicationand detection circuit is shown in Fig. 2. An Amptek ADMCA wasused as a MCA.

Fig. 4. 137Cs (660 keV) energy spectrum at the various bias voltages.

Fig. 5. 60Co (1173 and 1130keV) energy spectrum at the various bias voltages.

Fig. 6. Directional dependency from 0 to 90 degrees for the incident 660 keVgamma rays.

Energy spectra of 54Mn, 152Eu, and 109Cd were also measuredwith the fabricated CsI(Tl)/PIN diode radiation sensor to verifyfeasibility in an environmental RIs analysis and environmentalradiation monitoring (Fig. 7).

4. Conclusion

A CsI(Tl)/PIN diode-type radiation sensor was fabricated andtested to apply in an NDT and an environmental RIs analysis.Fabrication processes were established. We observed that thefabricated CsI(Tl)/PIN diode have a good performance from thespectrum results for several standard gamma point sourcesincluding standard RIs used in NDT. The fabricated CsI(Tl)/PINdiode-type radiation sensor can be applied with relatively highsensitivity not only in an NDT by the analysis of two attenuatedgamma energies from 60Co (1170 and 1330keV) through a sample

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H.S. Kim et al. / Applied Radiation and Isotopes 67 (2009) 14631465 14653. Results and discussion

The energy spectra for various gamma energies were measuredwith the fabricated CsI(Tl)/PIN diode sensor. The live time andthreshold were all set at 600 s and 30 ch through experiments. Thedistance of standard sources was 15mm from the surface ofthe CsI(Tl)/PIN diode sensor. To evaluate the charge collection ofthe PIN diode due to bias voltages, a 10mCi 133Ba standard pointsource was used. The bias voltages were varied from 5 to 30Vto nd an optimal bias voltage. This is shown in Fig. 3. When thebias voltage was above 30V, two energy peaks (356 and383keV) was observed more clearly than the lower bias voltages.Count numbers were also high.

Figs. 4 and 5 show the energy spectra with the various biasvoltages as for the 137Cs and 60Co standard point sources, whichare usually used in an NDT. The energy resolutions for 660 and1330keV were 7.9% and 4.9%, respectively. Peaks of 1170 and1330keV are clearly observed. These two peaks from 60Co can beused in a level gauge and a component analysis of dense materialsby attenuation difference of these two peaks. The directional

Fig. 7. Energy spectra for 54Mn (835keV), 152Eu (122, 244, 344, 488, 779, 867, 964,1213, and 1408keV) and 109Cd (88 keV).dependency was also measured with 137Cs source. The uctuationof the directional dependency was below 14% from 0 to 90 degreesfor the incident 660keV gamma rays. This is shown in Fig. 6. imaging. J. Microelectron. 37, 15981609.Acknowledgments

This work has been carried out under the nuclear R&D programof the Ministry of Science and Technology (MOST) and under theEco-technopia 21 Project of the Ministry of Environment (ME) ofKorea. We are also supported by the iTRS Science Research Center/Engineering Research Center program of MOST/Korea Science andEngineering Foundation (grant # R11-2000-067-02001-0) andwas partially supported by the BK21 program of the KoreaResearch Foundation (KRF).

References

Bandyopadhyay, D., Swapan, K.B., 1996. Performance of a prototype CsI(Tl)-PINdetector. Nucl. Instrum. Methods A 373, 194197.

Carini, G.A., Bolotnikov, A.E., Camarda, G.S., James, R.B., 2007. High-resolution X-raymapping of CdZnTe detectors. Nucl. Instrum. Methods A 579, 120124.

Chavanelle, J., Parmentier, M., 2003. A CsI(Tl)-PIN photodiode gamma-ray probe.Nucl. Instrum. Methods A 504, 321324.

Rozsa, S., 1989. Nuclear Measurement in Industry. Elsevier, New York, pp. 8990.Safavi-Naeini, M., Lerch, M.L.F., Petasecca, M., Pignatel, G.U., Reinhard, M.,

Rosenfeld, A.B., 2008. Evaluation of pixellated, back-sided planar photodetec-tors for high-resolution imaging instrumentation. Nucl. Instrum. Methods A589, 259267.

Stebel, L., Tommasi, M., Carrato, S., Cautero, G., Petasecca, M., Pignatel, G.,Marzocca, C., Tauro, A., Dragone, A., Corsi, F., Dalla, G.B., Fazzi, A., Zorzi, N.,2006. Development of a prototype detector for use in scintimammographybut also in an environmental RI analysis.

Fabrication and performance characteristics of a CsI(Tl)/PIN diode radiation sensor for industrial applicationsIntroductionMaterial and methodsResults and discussionConclusionAcknowledgmentsReferences