Scintillation Response Comparison Among Ce-Doped Aluminum Garnets, Perovskites and Orthosilicates

1142 IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 55, NO. 3, JUNE 2008

Scintillation Response Comparison Among Ce-DopedAluminum Garnets, Perovskites and Orthosilicates

Jiri A. Mares, Martin Nikl, Eva Mihokova, Alena Beitlerova, Anna Vedda, and Carmelo D’Ambrosio

Abstract—This paper deals with some aspects of scintillation re-sponse of Ce-doped Y-Lu aluminum garnets or perovskites in com-parison with Ce-doped orthosilicates. An essential difference be-tween the Ce-doped aluminum garnets/perovskites and orthosili-cates consists in larger fluctuations of photoelectron yield of thelatter scintillators where differences can reach up to 50% and mea-sured values critically depend on the recent history of the sample(illumination by day light, thermal annealing, etc.). This behaviorof Ce-doped silicates seems to be due to the vicinity of the 5d1level of Ce3+ from the conduction band, which makes the mate-rial more sensitive to the presence of deep electron traps monitoredby thermo-luminescence above room temperature. The presence ofsuch electron trapping sites thus appears more critical than in alu-minum garnets/perovskites

Index Terms—Ce-doping, hybrid photomultiplier, perovskitesand orthosilicates, scintillation response, Y-Lu aluminum garnets.

I. INTRODUCTION

AT present time some Ce-doped complex oxide scintil-lators reached a high level of efficiency and became

widely used in various applications as PET, well loggingetc. [1], [2]. Recently, new Ce-doped rare earth halides wereproposed, among which e.g., :Ce has a very high lightyield (L.Y.) and excellent energy resolution[3]. However, :Ce or :Ce crystals are highly hy-groscopic and require special atmosphere-tight sealing. OtherCe-doped inorganic complex oxide crystals as Y-Lu aluminumgarnets, perovskites and also orthosilicates are non-hygro-scopic, hard, chemically and mechanically stable [2], [4]–[9].Among them :Ce (LSO:Ce) exhibits the highest L.Y.up to [4], [5], while the other ones showvalues ranging between 1.2–2.5 .

Manuscript received June 29, 2007; revised February 7, 2008. This work wassupported in part by the GA AV under Grant S100100506 and in part by the Insti-tute of Physics AS CR– Institutional Research Plan AVOZ10100521. Some ex-periments were carried out at CERN Institute in Geneve, Switzerland at PH-DT2group and this cooperation is supported by the committee for cooperation ofCzech Republic with CERN.

J. A. Mares, E. Mihokova, and A. Beitlerova are with the Institute ofPhysics AS CR, Prague 16253, Czech Republic (e-mail: [email protected];[email protected]; [email protected]).

M. Nikl is with the Institute of Physics AS CR, Prague 6, 162 53, Czech Re-public, and also with the Dipartimento di Scienza dei Materiali dell’ Universitadi Milano “Bicocca,” Milano 20125, Italy (e-mail: [email protected]).

A. Vedda is with Dipartimento di Scienza dei Materiali dell’ Universita diMilano “Bicocca,” Milano 20125. Italy (e-mail: [email protected]).

C. D’Ambrosio is with the PH-DT2 Group, CERN, Geneva CH 1211,Switzerland (e-mail: Carmelo.D’[email protected]).

Color versions of one or more of the figures in this paper are available onlineat http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TNS.2008.922840

Among the undesirable properties of the Lu-based com-pounds belongs the background activity due to the presenceof 2.6% of radioactive isotope (it is characterized bythe energies of the three gamma rays to be 306, 203 and 89keV in cascade with emission and it has very long half-life

[10]). Furthermore, slow decay compo-nents and afterglow influence negatively scintillation timingproperties as well as L.Y. [11]–[14]. An essential differencebetween perovskite and garnet crystals containing and

ions was observed in their L.Y. time dependence becausethat of scintillators based on ions increases only about20% in the integration time range 0.25 – 5 while that ofcrystals containing ions increases of about 60 – 80% inthe same time span [14]. This points to the existence of slowdecay processes which are mainly caused by charge carrierre-trapping at shallow traps and delayed radiative recombina-tion at centers. [5], [12]–[18].

The main goal of this paper is to present a comparison ofscintillation response and timing behavior among Ce-doped alu-minum garnets, perovskites and orthosilicates, especially. De-tailed studies of scintillation response of Ce-doped garnets andperovskites has been reported and investigated in [2], [6], [8],[19], [20], especially for those containing as lattice ions.Regarding LSO:Ce and LYSO:Ce crystals some problems werestill not well explained, like the origin of L.Y. fluctuations, theinfluence of overlap between emission and the nearest ab-sorption, the role of very slow decay components, the afterglowand the influence of traps and defects [4], [5], [13]).

II. EXPERIMENTAL

A. Hybrid Photomultiplier

Scintillation response was measured using a hybrid photo-multiplier (HPMT) [8], [14], [19]. We used the HPMT PPO475B produced by DEP company, Roden, The Netherlands. Abasic difference between the HPMT and a classical PMT is thatthe HPMT consists of only front photocathode and a Si-PINdiode used as an anode (no dynodes are used in HPMT). TheHPMT can be easily and directly calibrated in photoelectronsand its noise is lower than that of the classical PMT.

Detailed description of the experimental set-up for scintil-lation response measurements (photoelectrons – orlight yield – L.Y.(E), energy resolution, non-proportionality ofthe yields, etc.) was given in [8], [6], [19]. We use different X- or

-ray lines in the energy range 8 keV–2 MeV to measure pulsedheight spectra, especially their photo-peaks [19]. The electronicpart of the set-up consists of a current preamplifier coupledwith the HPMT, an Ortec model 672 amplifier/shaper, multi-channel analyzer and PC. The integration time can be varied in

0018-9499/$25.00 © 2008 IEEE

MARES et al.: SCINTILLATION RESPONSE COMPARISON 1143

TABLE ISCINTILLATION PARAMETERS OF SELECTED LSO:Ce, LYSO:Ce, Ce-DOPED Y-LU ALUMINUM GARNETS AND PEROVSKITESAND CRYSTALS MEASURED ON

DIFFERENT CRYSTAL SAMPLES FROM VARIOUS SOURCES (SOME CRYSTAL SAMPLES WERE OBTAINED FROM THE SAME CRYSTAL BOULE BUT FROM ITS

DIFFERENT PARTS (THEY ARE DESCRIBED AS TABLE ROWS 8,9 IN COLUMN 1.).

the range 0.25 – 5 (6 fixed values), which is exploited formeasurement of the time development of photoelectricyield [15]. A time stability of yield measurement is verygood within (each integration time needs calibration) butan accuracy of measurements (repeating of measurements withthe same sample after time period – it is removed and put again)is [19]. But yield measurements can be influencede.g., by irradiation (UV, X-rays) of crystals, by a presence oftraps, colour centres etc.

B. Samples – Description and Measurements

Cerium doped Y or Lu aluminum garnet and perovskitesamples were provided by Crytur company (Palackeho 175,Turnov, Czech Republic). Ce-doped LSO and LYSO crystalswere from different sources as from St. Gobain, Photonics,Crystal Photonics and CTI companies and Shangai Institute ofCeramics. Mainly plates of 10 mm diameter and 1, 2 or 5 mmthickness were used but for some measurements, bigger sam-ples were employed (see Table I). All measured samples weretaken from crystal boules (grown mainly by the Czochralskimethod) and their density was 7.5 of pure LSO:Ce orlower for LYSO:Ce ones. These crystals and the others con-taining in their lattice belongs to heavy scintillators whilethose containing are the intermediate ones (their density

is between ). Compositions of LYSO:Ce samples isgiven in Table I and Ce concentrations are between 0.1–1 at.%.

Front and back sides of the samples were optically polishedand Tyvec or Teflon tapes were used as reflection layers [19].One of the polished sides was optically coupled with the outersurface of the HPMT photocathode window using silicongrease.

III. EXPERIMENTAL RESULTS

A. LYSO:Ce and LSO:Ce Scintillation Response

Plates of 1, 2 or 5 mm thickness together with thicker sam-ples of up to 20 mm long (almost full absorption of X- and -raylines within all the used energy range) were measured. A largevolume LYSO:Ce sample of 12 mm in diameter and 18 mm long(and similar samples) was wrapped with Teflon tape and was puta few days before measurements into darkness (no day light illu-mination, especially the UV one). and L.Y.(E) weremeasured from energy dependence of different X-and -ray lines in the range . In Figs. 1 and2 pulsed height spectra of X-ray line of ( )or lines (up to three lines can be measured 511, 1275and 1786 keV) are displayed, respectively. Detailed calcula-tions of FWHM were determined from treatment of individualphoto-peaks using Gaussian fit. A summary of obtained scintil-lation parameters of selected crystals is given in Table I. This


Fig. 1. Pulsed height spectra of 17.8 keV energy line of Mo measured withvarious Ce-doped Y-Lu aluminum garnets/perovskites and orthosilicates withan integration time of � 1 �s (all samples were 10 mm thick and either of 10mm in diameter or of area 10� 10 mm (LSO:Ce)). Am energy line (59.6keV) arises in the source used where it is used to excite 17.8 keV Mo line.

Fig. 2. Pulsed height spectra of 511, 1275 and 1786 keV lines fromNa mea-sured with various Ce-doped Y-Lu aluminum garnets/perovskites and orthosil-icates with an integration time of � 0:5 �s (all samples were 10 mm thick andeither of 10 mm in diameter or of area 10� 10 mm (LSO:Ce)).

Table shows the large differences in L.Y. of measured sampleswhich range from up to .

Previous studies of LSO:Ce and LYSO:Ce crystals also re-vealed large differences in their L.Y. values (from 10000 upto 30000 ph/MeV). According to their photoelectron orL.Y. yields we can divide them into two groups as (i) thosehaving high light yield (H) and (ii) those with low light yield (L)as was described earlier by Lempicki and Glodo [11]. Similarbehaviour of LSO:Ce yields were also observed by Dorenbos etal. [5], Kapusta [4] and Rogers and Batty in [13]. In these studiesthe crystals were sometimes placed into darkness and scintil-lation measurements were carried out after a waiting period atleast of 24 hours to recover from room light illumination [13].

photoelectron yield, energy resolutions (FWHM) andnon-proportionality of measured LSO:Ce or LYSO:Ce crystalsexhibit roughly similar properties (see Table I) and also theirnon-proportionality is similar to that observed on other crys-tals [4], [11], [13]. For example, L.Y. of LYSO:Ce large volumecrystal ( 12 18 mm) is and its FWHM at511 keV is 14.9%.

In Fig. 1 pulsed height spectra of weighted mean energyX-ray lines of ( ) are displayed ( hasX-ray and lines and weighted energy is 17.8 keV).These lines are generated by 59.6 keV -ray line ofsealed source (AMC.2084). This sealed source can generateup to 6 various elements X- or -ray lines (from Cu, Rb,Mo, Ag, Ba and Tb) by 59.6 keV -ray line of .pulsed height spectra of 17.8 keV X-ray line consist of eitherphoto-peak of this energy (this is at lower channel number

for YAP:Ce) or also from another broad photo-peak of59.6 keV -ray energy line (this is at higher channel

number for YAP:Ce).Fig. 2 shows pulse height spectra of -ray energy lines

(three lines at 511, 1275 and 1786 keV). All three energylines are clearly observed in LYSO:Ce and LuAG:Ce crystalsbut not in YAP:Ce and YAG:Ce ones. This can be explainedby a much higher -ray absorption in Lu contained compounds(due to higher density and ) compared with that of Y con-taining ones [2]. Another important effect observed in LSO:Ceor LYSO:Ce crystals is that their pulsed height spectra measuredunder various X- or -ray energy lines are stable only after a fewseconds or even one minute after the start of the measurementsat variance with Y-Lu aluminium garnets and perovskites whichdisplay good stability.

Figs. 1 and 2 evidence another important fact concerning thelevel of noise in individual crystals. LSO:Ce pulse height spec-trum of at 17.8 keV energy line (see Fig. 1) does not ex-hibit a photo-peak (no band is resolved) while the photo-peaksare well resolved in the other crystals. Also “noisy background”part of pulse height spectrum of LSO:Ce from the beginning upto the 17.8 keV energy is much higher compared with that ofother Ce-doped crystals. With LSO:Ce only the broad photo-peak of 59.6 keV energy line of is observed in Fig. 1.Detailed pulse height spectra of LSO:Ce under excitation withenergy lines ranging from (Cu X-ray weighted and

lines) through the others of Rb (13.6 keV), Mo (17.8 keV),Ag (22.1 keV) did not show clear photo-peaks and only with32.6 keV energy line of (and with higher energy lines) aclear broad photo-peak was observed.

Pulse height spectra of -ray energy lines (see Fig. 2)of LSO:Ce behave similarly as those measured with low ener-gies in Fig. 1. The comparison of LSO:Ce pulse heightspectra with those of other Ce-doped crystals shows again thatLSO:Ce spectrum is characterized by higher signal (highernoise) than those of the other crystals. Furthermore, Comptonedge and backscattering peak are not observed in pulseheight spectra of LSO:Ce while both values are observed onLuAG:Ce.

B. Time Development of Scintillation Response of Ce-DopedGarnets, Perovskites and Orthosilicates

Time development of scintillation response ( ) ofCe-doped garnets, perovskites and orthosilicates was measuredin the time integration range 0.25 – 5 (or for shaping time0.5 – 10 ) [14]. Again, we measured thick samples andper 1 MeV was derived from dependence in the en-ergy range . The use of various integra-tion times allows us to evaluate the influence of slow decay


Fig. 3. N per 1 MeV photoelectron yield time development of Ce-dopedYAP, YAG and LuAG reference crystals normalized to the shortest integrationtime of 0.25 sec. All measured crystals were cylindrical with dimensions � 10mm and 10 mm length.

components. Fig. 3 shows time development of per 1MeV of Ce-doped LuAG, YAG and YAP selected referencecrystals. A difference between crystals containing latticeions and ions (LuAG crystal) is clearly observed. Thesemeasurements indicate that LuAG:Ce crystals have more slowcomponents compared with YAG:Ce and YAP:Ce. This findingshould be correlated with thermo-luminescence glow curves atlow temperatures, which reflect the presence of shallow traps inthe material [21], [22]. However, calculated de-trapping timesfrom the dominant traps both in perovskite and garnet scintil-lators seem too long [22] to explain observed trends and differ-ences in Fig. 3. Sub-gap tunnelling processes in LuAG:Ce weresuggested in [22], [23] to tunnelling processes in LuAG:Ce weresuggested in [22], [23] to explain slower scintillation compo-nents in the times scale of hundreds of ns – microseconds, butthis problem needs further investigation.

Fig. 4 presents time development of per 1 MeVof LYSO:Ce, which shows a rather strange non-monotoniccourse. Measurements were carried out at different integrationtimes and for each time-gate it was necessary to calibrate theHPMT of the experimental set-up. LYSO:Ce crystal appearedsensitive to even visible light irradiation and in-between thesemeasurements the sample was not put into darkness for atleast a few hours. This result demonstrates the complexity ofenergy storage and release processes in Ce-doped LYSO hostin comparison with the Ce-doped (Y-Lu) aluminium garnetor perovskite scintillators where such effects have never beenobserved.

In Fig. 5 thermo-luminescence glow curves above room tem-perature are given for representative samples from each materialgroup. Curves integrals ratios normalized to YAP are 1:0.45:0.1:0.1 for YAP, LYSO, YAG, and LuAG, respectively. In the caseof YAP:Ce the composite glow curve structure has been inter-preted as due to thermally assisted tunnelling from an oxygenvacancy-based electron trap situated at different distances from

recombination center [16]; a similar mechanism couldoperate in the case of LYSO:Ce too [22], while in the case ofLuAG:Ce a classical thermal de-trapping via conduction bandtakes place [24].

Fig. 4. N per 1 MeV photoelectron yield time development of Ce-dopedLYSO crystal normalized to the shortest integration time 0.25 �s (measuredcrystal was of dimensions � 12� 18 mm from St. Gobain company).

Fig. 5. Thermo-luminescence glow curves of various Ce-doped crystals afterx-ray irradiation at room temperature. Intensity is spectrally corrected andcurves can be compared quantitatively.

In fact, the glow curve patterns and their total intensities givenby the curve integrals do not suggest a clear correlation betweenthe presence and concentration of deep electron traps and L.Y.values and instabilities among these four materials (see also [6],[14]).

IV. DISCUSSION

As mentioned at the beginning of this paper the Ce-dopedinorganic scintillators based on (Y-Lu) aluminum garnets,perovskites and orthosilicates reached high level of efficiencywhich triggered their use in various applications. However,some aspects of their scintillation behavior have not beenexplained satisfactorily, especially regarding orthosilicates.Indeed, our scintillation response measurements of Ce-dopedLYSO show lower stability and very high sensitivity to thesample history with respect to the Ce-doped Y-Lu garnets andperovskites. LSO:Ce crystal is being studied from more than15 years and its anomalous behavior was partly explained byDorenbos et al. [5] as due to the charge trap filling. However,despite of similar TSL intensities above room temperatureand similar TSL mechanism suggested in LYSO:Ce and

:Ce, such effects have never been noted inthe latter material. In YAG:Ce and LuAG:Ce where classicalthermal de-trapping of localized electrons via the conduction


band takes place, TSL total intensity is practically the same, butL.Y. of LuAG:Ce is typically less than 60% of that of YAG:Ce.No L.Y. instabilities have been observed like those in orthosili-cates. Hence, the occurrence and concentration of deep electrontraps in orthosilicates does not seem to be a primary reasonfor the observed instabilities. However, it is worth noting thatin the orthosilicate host the relaxed level of centeris close to the bottom of the conduction band (about 0.45eV, [24]). This has been recognized as a key factor resultingin electron delocalization from centers due to directphoto-ionization, thermal ionization, and tunnelling processes[24]. Despite of the recent progress in the growth technology ofLSO:Ce or LYSO:Ce [25] LSO:Ce crystals exhibit frequentlymuch lower L.Y. values than reported 30000 ph/MeV. In paper[25] it is also shown that ions should not be the primarycause of L.Y. decrease as they have not been detected neither inhigh nor in low L.Y. LSO:Ce. The question remains, however,what is the detection limit of the experimental technique usedto this purpose.

Here, majority of scintillation response measurements werecarried out on different samples and from different sourcesbut not exact sample history was known (e.g., UV or otherillumination) with exception of some of large crystals, espe-cially LYSO:Ce of 12 mm and 18 mm long (see Fig. 4). TSLglow curve spectra clearly show that a lot of traps is present inCe-doped orthosilicate crystals (see Fig. 5). Also irradiation bylow X-ray lines (e.g., see Fig. 1) shows a different mechanismin LSO:Ce or LYSO:Ce compared with other Ce-doped andmeasured crystals (much more “noisy background”). Besidescharge trap filling or large influence of deep electron traps inCe-doped orthosilicates [4], [5], [12], [13] also other mech-anisms can influence yield as (i) the overlap between

emission and the nearest absorption [8], (ii)non-radiative pathways of dissipating heat in centers or(iii) samples taken from different parts of the crystal boules.Now, we selected a few LSO:Ce and LYSO:Ce samples whichhistory is known well (mainly illumination) and these samplesare further investigated to explain their scintillation behaviour( photoelectron yield, their time behaviour, the presenceof traps and various defects).

V. CONCLUSIONS

Our investigation of scintillation properties of Ce-doped(Y-Lu) aluminum garnet, perovskite and orthosilicate singlecrystals has shown that scintillation time response and efficiencyin LSO:Ce or LYSO:Ce is subjected to much larger fluctuationsand instabilities, which depend also on the sample history.The occurrence and concentration of deep traps monitoredby thermo-luminescence above room temperature seems to becomparable in orthosilicates and aluminum perovskites/garnets.However, the close proximity of the level of to theLSO conduction band enables auto-ionization of excitedion and makes the material more sensitive to the presence ofdeep electron traps. Comparatively to aluminum perovskitesand garnets it thus appears more important for orthosilicates tosuppress such deep electron traps related to oxygen vacanciesin order to enhance the overall scintillation figure-of-merit.

ACKNOWLEDGMENT

The authors thank to B. Chai (Crystal Photonics, USA) andG. Ren (Shanghai Institute of Ceramics, China) for providingus with LSO:Ce and LYSO:Ce samples. The authors are alsograteful to I. Fontana for performing TSL measurements.

REFERENCES

[1] C. L. Melcher, “Perspectives on the future development of new scintil-lators,” NIM Phys. Res., vol. A537, pp. 6–14, 2005.

[2] C. W. E. van Eijk, J. Adriessesn, P. Dorenbos, and R. Visser, “Cedoped inorganic scintillators,” NIM Phys. Res., vol. A348, pp. 546–550,1994.

[3] E. V. D. van Loef, P. Dorenbos, C. W. E. van Eijk, K. Kramer, and H. U.Gudel, “High energy resolution scintillator: Ce activated LaBr ,”Appl. Phys. Lett., vol. 79, pp. 1573–1575, 2001.

[4] M. Kapusta, P. Szupryczynski, C. L. Melcher, M. Moszynski, M.Balcerzyk, A. A. Carey, W. Czarnicki, M. A. Spurrier, and A. Synt-feld, “Nonproportionality and thermoluminescence of LSO:Ce,” IEEETrans. Nucl. Sci., vol. 52, no. 4, pp. 1098–1104, Aug. 2005.

[5] P. Dorenbos, C. W. E. van Eijk, A. J. J. Bos, and C. L. Melcher, “Af-terglow and thermoluminescence properties of Lu SiO scintillationcrystals,” J.Phys.: Condens. Matter, vol. 6, pp. 4167–4180, 1994.

[6] J. A. Mares, A. Beitlerova, M. Nikl, N. Solovieva, C. D’Ambrosio, K.Blazek, P. Maly, K. Nejezchleb, and F. de Notaristefani, “Scintillationresponse of Ce-doped or intrinsic scintillation crystals in the energyrange up to 1 MeV,” Rad. Measur., vol. 38, pp. 353–356, 2004.

[7] H. Ishibashi, K. Kurashige, Y. Kurata, K. Susa, M. Kobayashi, M.Tanaka, K. Hara, and M. Ishii, “Scintillation performance of largeCe-doped Gd SiO single crystal,” IEEE Trans. Nucl. Sci., vol. 45,no. 3, pp. 518–521, Jun. 1998.

[8] J. A. Mares, M. Nikl, A. Beitlerova, N. Solovieva, C. D’Ambrosio,K. Blazek, P. Maly, K. Nejezchleb, P. Fabeni, and G. P. Pazzi,“Ce -doped scintillators: Status and properties of (Y,Lu) aluminumperovskites and garnets,” NIM Phys. Res., vol. A537, pp. 271–275,2005.

[9] M. Moszynski, M. Balcerzyk, M. Kapusta, D. Wolski, and C. L.Melcher, “Large size LSO:Ce and YSO:Ce scintillators for 50 MeVrange -ray detector,” IEEE Trans. Nucl. Sci., vol. 47, no. 4, pp.1324–1328, Aug. 2000.

[10] J. R. Arnold, “Energy levels of Lu and Hf ,” Phys. Rev., vol. 93,pp. 743–745, 1954.

[11] A. Lempicki and J. Glodo, “Ce-doped scintillators: LSO and LuAP,”NIM Phys. Res., vol. A416, pp. 333–344, 1998.

[12] R. Visser, C. L. Melcher, J. S. Schweitzer, H. Suzuki, and T. A.Tombrello, “Photostimulated luminescence and thermoluminescenceof LSO scintillators,” IEEE Trans. Nucl. Sci., vol. 41, no. 4, pp.689–693, Aug. 1994.

[13] J. G. Rogers and C. J. Batty, “Afterglow in LSO and its possible ef-fect on energy resolution,” IEEE Trans. Nucl. Sci., vol. 47, no. 2, pp.438–445, Apr. 2000.

[14] J. A. Mares, A. Beitlerova, M. Nikl, A. Vedda, C. D’Ambrosio,K. Blazek, and K. Nejezchleb, “Time development of scintillatingresponse in Ce- or Pr-doped crystals,” Phys. Stat. Sol. (c), vol. 4, pp.996–999, 2007.

[15] M. Nikl, E. Mihokova, J. A. Mares, A. Vedda, M. Martini, K.Nejezchleb, and K. Blazek, “Traps and timing characteristics ofLuAG:Ce scintillator,” Phys. Stat. Sol., vol. 181, pp. R10–R12,2000.

[16] A. Vedda, M. Martini, F. Meinardi, J. Chval, M. Dusek, J. A. Mares, E.Mihokova, and M. Nikl, “Tunneling processes in thermally stimulatedluminescence of mixed Lu Y ALO :Ce crystals,” Phys. Rev., vol.B61, pp. 8081–8086, 2000.

[17] A. Vedda, D. Di Martino, M. Martini, J. Mares, E. Mihokova, M.Nikl, N. Solovieva, K. Blazek, and K. Nejezchleb, “Trap levels inY-aluminum garnet scintillating crystals,” Rad. Measur., vol. 38, pp.673–676, 2004.

[18] M. E. Casey, C. Reynolds, D. M. Binkley, and J. M. Rochelle, “Analysisof timing performance for an ADP-LSO scintillation detector,” NIMPhys. Res., vol. A504, pp. 143–148, 2003.

[19] J. A. Mares and C. D’Ambrosio, “Hybrid photomultipliers – Theirproperties and application in scintillation studies,” Opt. Mat., vol. 30,pp. 22–25, 2007.


[20] J. A. Mares, A. Beitlerova, M. Nikl, N. Solovieva, K. Nitsch, M.Kucera, and M. Kubova, “Scintillation and optical properties ofYAG:Ce films grown by LPE,” Rad. Measur., vol. 42, pp. 533–536,2007.

[21] M. Nikl, V. V. Laguta, and A. Vedda, “Energy transfer and charge car-rier capture processes in wide-band-gap scintillators,” Phys. Stat. Sol.(a), vol. 204, pp. 683–689, 2007.

[22] M. Nikl, E. Mihokova, J. Pejchal, A. Vedda, M. Fasoli, I. Fontana, V.V. Laguta, V. Babin, K. Nejezchleb, A. Yoshikawa, H. Ogino, and G.Ren, “Scintillator materials – Achievements, opportunities and puz-zles,” IEEE Trans. Nucl. Sci., vol. 55, no. 3, Jun. 2008.

[23] A. Vedda, D. Di Martino, M. Martini, V. V. Laguta, M. Nikl, E. Mi-hokova, J. Rosa, K. Nejezchleb, and K. Blazek, “Thermoluminescenceof Zr-codoped Lu Al O :Ce crystals,” Phys. Stat. Sol. (a), vol. 195,pp. R1–R3, 2003.

[24] E. van der Kolk, S. A. Basun, G. F. Imbusch, and W. M. Yen, “Tem-perature dependent spectroscopic studies of the electron delocalizationdynamics of excited Ce ions in the wide band gap insulator Lu SiO ,”Appl. Phys. Lett., vol. 83, pp. 1740–1742, 2003.

[25] C. L. Melcher, S. Friedrich, S. P. Cramer, M. A. Spurrier, P.Szupryczynski, and R. Nutt, “Cerium oxidation state in LSO:Cescintillators,” IEEE Trans. Nucl. Sci., vol. 52, no. 5, pp. 1809–1812,Oct. 2005.

Documents

Scintillation Response Comparison Among Ce-Doped Aluminum Garnets, Perovskites and Orthosilicates