Flat detector ghost image reduction by UV irradiation

Snoeren, Rudolph M.; Steinhauser, H.; Alving, Lex; Stouten, Hans

doi:10.1117/12.811842

Cited by 4 publications

(4 citation statements)

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“…More recently Nagarkar et al proposed to reduce the hysteresis effect by codoping the crystal with Sm 2+ , 13 while Snoeren et al proposed a method based on traps filling by UV irradiation. 14 The bright burn phenomenon was also observed in Al 2 O 3 :C, that is of particular interest in medical application for optical stimulated luminescence (OSL) dosimetry. 15 Some further interesting results were very recently obtained in Lu 1.8 Y 0.2 SiO 5 :Ce (LYSO:Ce), also codoped with Ca 2+ : emission spectra modifications and light yield increase following prolonged X-ray irradiation were found to occur and were related to the progressive filling of oxygen vacancies located close to Ce 3+ ions and competing with them in free charge carrier capture.…”

Section: Introductionmentioning

confidence: 97%

“…The result is an increase of light yield during irradiation. More recently Nagarkar et al proposed to reduce the hysteresis effect by codoping the crystal with Sm 2+ , while Snoeren et al proposed a method based on traps filling by UV irradiation . The bright burn phenomenon was also observed in Al 2 O 3 :C, that is of particular interest in medical application for optical stimulated luminescence (OSL) dosimetry .…”

Section: Introductionmentioning

confidence: 99%

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Defect-Driven Radioluminescence Sensitization in Scintillators: The Case of Lu₂Si₂O₇:Pr

et al. 2013

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A prompt transport of radiation induced free carriers toward luminescence centers is a key factor for an efficient conversion of high energy radiation into light in scintillator materials. However, the transport stage of the scintillation process can be hampered by the presence of lattice imperfections. In this study, we investigated the increase of radioluminescence (RL) efficiency after prolonged material irradiation. The general character of the phenomenon was revealed by its occurrence in several scintillator crystals like Lu2Si2O7:Pr, Bi3Ge4O12, Lu3Al5O12:Ce, and Lu0.3Y0.7AlO3:Ce. A detailed investigation was carried out for Lu2Si2O7:Pr. We demonstrated that the RL efficiency increase is due to the progressive filling of traps responsible for the thermoluminescence glow peaks at 460 and 515 K, which compete with Pr3+ centers in free carrier trapping during irradiation. Correspondingly, their emptying results in the recovery of the initial lowest RL efficiency. Spatial correlation between traps and Pr3+ ions was evidenced by the detection of an a-thermal tunneling afterglow between trap levels and 4f excited states of Pr3+. Such hysteresis phenomenon represents a memory of previous irradiations that remains stored in the crystal. It is a further effect caused by traps, which deserves attention like other manifestations of defects in scintillators like the reduction of light yield and the occurrence of slow tails in the scintillation time decay.

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Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Defect-Driven Radioluminescence Sensitization in Scintillators: The Case of Lu₂Si₂O₇:Pr

et al. 2013

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“…Apart from radiation damage, increase of scintillation yield following previous irradiation has also been observed. − This effect, also known as “memory effect”, “bright burn”, or “luminescence hysteresis”, is particularly critical in X-ray imaging and dosimetry even at a few percent level, since it leads to the formation of ghost images or to dose misevaluations. The physical processes involved in the bright burn effect are substantially related to competition phenomena among traps and radiative recombination centers in the trapping of free carriers created during irradiation.…”

Section: Introductionmentioning

confidence: 99%

Radioluminescence Sensitization in Scintillators and Phosphors: Trap Engineering and Modeling

et al. 2014

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The role of charge carrier trapping in determining radioluminescence (RL) efficiency increase during prolonged irradiation of scintillators has been studied by using YPO4:Ce,Nd as a model material. The Nd3+ ions act as efficient electron traps minimizing the role of intrinsic defects. Different Nd contents were considered in order to point out the correlation between the trap concentration and the detected RL efficiency dose dependence. RL measurements as a function of temperature clarified the role of the trap thermal stability in determining the shape and the magnitude of such effect. We propose also a model based on trap filling which is able to describe accurately the complex processes which are involved.

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“…Such an effect has been observed in several matrices, [9][10][11][12][13][14] and it is particularly critical in X-ray imaging and dosimetry even at a few percent levels, since it leads to the formation of ghost images or to dose misevaluations. 15,16 Also the scintillator light yield appears to be affected by such a phenomenon. 12,17 Despite its relevant role in many detection or imaging devices and its relatively common presence in various materials, it has been studied in rather little detail, 9 mainly because of its critical dependence on material reproducibility in terms of traps which are related to uncontrolled defects in standard scintillators.…”

Section: Introductionmentioning

confidence: 99%

Deep traps can reduce memory effects of shallower ones in scintillators

Moretti

Patton

Belsky

et al. 2016

Phys. Chem. Chem. Phys.

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X-ray induced luminescence sensitization results have been obtained on three commercially relevant scintillators, namely CsI:Tl, YAG:Ce and LSO:Ce. The obtained curves have been used to validate a model based on the competition among trapping and recombination of free charge carriers. The model was able to accurately describe the complex phenomenology of the detected sensitization curves. We also used the model to predict the role of a high temperature and concentration trap in shaping the sensitization curves. Based on these modelling results we also proposed a novel, and rather counterintuitive, strategy to deal with the sensitization phenomenon based on the deliberate introduction of deep traps which can significantly reduce the bright burn effect.

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Flat detector ghost image reduction by UV irradiation

Cited by 4 publications

References 5 publications

Defect-Driven Radioluminescence Sensitization in Scintillators: The Case of Lu₂Si₂O₇:Pr

Defect-Driven Radioluminescence Sensitization in Scintillators: The Case of Lu₂Si₂O₇:Pr

Radioluminescence Sensitization in Scintillators and Phosphors: Trap Engineering and Modeling

Deep traps can reduce memory effects of shallower ones in scintillators

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Flat detector ghost image reduction by UV irradiation

Cited by 4 publications

References 5 publications

Defect-Driven Radioluminescence Sensitization in Scintillators: The Case of Lu2Si2O7:Pr

Defect-Driven Radioluminescence Sensitization in Scintillators: The Case of Lu2Si2O7:Pr

Radioluminescence Sensitization in Scintillators and Phosphors: Trap Engineering and Modeling

Deep traps can reduce memory effects of shallower ones in scintillators

Contact Info

Product

Resources

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Defect-Driven Radioluminescence Sensitization in Scintillators: The Case of Lu₂Si₂O₇:Pr

Defect-Driven Radioluminescence Sensitization in Scintillators: The Case of Lu₂Si₂O₇:Pr