Absolute X‐Ray Efficiencies of Some Phosphors

Poorter, J. A. de; Bril, A.

doi:10.1149/1.2134400

Cited by 40 publications

(9 citation statements)

References 5 publications

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“…To measure radiant efficiencies with x-ray excitation [ 17 – 19 ] thin phosphor layers are used (≈ 100 μ m). This is necessary to minimize the loss in light output due to scattering and absorption of the emitted luminescence.…”

Section: X-ray Excitationmentioning

confidence: 99%

Some methods of luminescence efficiency measurements

Bril

Jager‐Veenis

1976

J. RES. NATL. BUR. STAN. SECT. A.

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M e th ods of abso lut e a nd re lati ve radi a nl a nd q ua ntum effi c ie ncy m eas ure me nts a re described fo r ultrav iole t , vis ibl e , ca thod e-ray, a nd x·ray exc ita tio ns. Da ta o n so me s ta nd a rd lumin esce nt ma te ri a ls a re gjve n.Key word s: Ca th ode· ray exc itation ; lum inesce/lce; lumin esce nce st a n da rd s; phosp ho rs; qu a ntum e fficie ncies; ra di a nt efficie nc ies; UV exc it a ti on; ,· ray exc it a tio n. . IntroductionMe th ods of absolut e radi a nt a nd qu a ntum e ffi cie ncy meas ure me nts are giv e n togeth e r with meth ods of relati ve e ffi c ie ncy meas ure me nts. Th e me th ods are es pec ia ll y s uit ab le fo r powd e r ma te ri als fo r whi c h th e a ngular di s tributi on of th e e mitted lumin esce nt radi ati on is La mbe rti an.Th e re la ti ve meas ure me nts a re perfo rm ed with th e aid of s ta nd a rd ph os ph ors, whose effi cie ncies have previously bee n de te rmin ed by a bsolute meas ure me nts. Methods are give n fo r excita ti on of th e ph os phors by ultraviole t a nd vis ible radiati on , cathod e rays and x rays.F or samples with non-La mbe rti a n e mi ss io n di stributio ns, a me thod is desc ribed in whi c h a n Ulbri c ht 's s phere or an e lliptical mirror is used. . Ultraviolet ExcitationAll powder phosphors are meas ured us in g a thi c k layer (thi c kn ess ab out 2 mm) at th e irradi ated side. Th e detection tak es place pe rpe ndi c ular to th e plan e of the phos phor, t he excitati on is at a n a ngle of 50° with th at plan e (see fi g. 1). Th e e xcita tio n wa vele ngth ( A exc) or regio ns a re iso la ted from a hi gh pressure merc ury la mp by inte rfe re nce filt ers, the arc being foc used on th e phos phor with a qu artz le ns. In thi s way a hi gh excita ti on de nsity is reached , but generally well below th e excitation region where s aturation e ffects s ta rt. This is es peciall y ad vantageo us wh en a rela ti vely in se ns iti ve th erm oele me nt is used as a d etector.* P aper p re se nt ed at th e W ork s hup Sem in a r 'Slandard izat ion in S pec trophutometry a nd L u m in esce lwe Meas ure rn e nl s' held a t the Nat iona l Burea u uf Standards. Ga ithersbu rg , Md .. Nove mbe r 19

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Section: X-ray Excitationmentioning

confidence: 99%

Some methods of luminescence efficiency measurements

Bril

Jager‐Veenis

1976

J. RES. NATL. BUR. STAN. SECT. A.

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“…In these studies data obtained under cathode ray excitation [31] were initially used. It is accepted that intrinsic conversion efficiencies under X-ray or cathode ray excitation do [4], since they depend on intrinsic phosphor properties and on temperature. The latter was practically constant during experiments; however, it was finally found that X-ray excitation values were higher.…”

Section: Theoretical Calculationsmentioning

confidence: 99%

“…The light emission efficiency [1,2,3,4,5,6,7,8,9,10,16], which was evaluated by determining the number of emitted photons (NEP) of light per incident X-ray 2. The modulation transfer function (MTF), which describes the variation of image contrast with spatial frequency and expresses spatial resolution [5,10,11,12,13,14].…”

mentioning

confidence: 99%

Experimental and theoretical assessment of the performance of Gd2O2S:Tb and La2O2S:Tb phosphors and Gd2O2S:Tb–La2O2S:Tb mixtures for X-ray imaging

Kandarakis

Cavouras

2001

Eur Radiol

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The purpose of this work was to investigate and compare the imaging performance of Gd2O2S:Tb and La2O2S:Tb phosphors as well as of Gd2O2S:Tb and La2O2S:Tb mixtures for use in X-ray imaging detectors (intensifying screens). Phosphors were supplied in powder form and were used to prepare test screens. Three types of screens were prepared: Gd2O2S:Tb; (Gd50La50)O2S:Tb; and La2O2S:Tb. Screens were excited by X-rays with tube voltages from 40 to 120 kV and their efficiency (light intensity or light energy flux over exposure) was measured with a photomultiplier and a dosimeter. The light spectrum was also measured with a monochromator. From these measurements, the number of emitted photons per incident X-ray (NEP) and the zero frequency detective quantum efficiency (DQE(0)) of the screens were determined. Additionally, modulation transfer function (MTF) was measured by the square wave response function (SWRF) method. A theoretical model calculating NEP and DQE was also developed to fit experimental data and predict the performance of Gd2O2S:Tb-La2O2S:Tb mixtures by weight from 10-90% to 90-10%. Gd2O2S:Tb screens exhibited highest NEP, DQE, and MTF at tube voltages higher than 55 kV and lower than 45 kV, whereas La2O2S:Tb screens had better NEP, DQE, and MTF within the 45- to 55-kV range. Maximum NEP values were higher than 700 at 100-120 kV while maximum DQE(0) was 0.314 at 80 kV. Gd2O2S:Tb screens are more efficient for high X-ray tube voltage applications (e.g., abdominal imaging, chest radiography, lumbar spine radiography, CT) and for very low voltage applications (e.g., mammography). La2O2S:Tb screens are useful for medium-range X-ray voltages (e.g., pediatric radiography).

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“…X-ray phosphors, whose materials emit some fluorescence by X-ray radiation, have been investigated for almost 30 years [1][2][3][4][5]. Particularly, in the medical field, some X-ray phosphors have been used with medical films.…”

Section: Introductionmentioning

confidence: 99%