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Handbook of Optoelectronics Concepts, Devices, and Techniques Volume one John P. Dakin, Robert G. W. Brown

Incandescent, discharge, and arc lamp sources

Publication details https://www.routledgehandbooks.com/doi/10.1201/9781315157009-3 David O. Wharmby Published online on: 11 Oct 2017

How to cite :- David O. Wharmby. 11 Oct 2017, Incandescent, discharge, and arc lamp sources from: Handbook of Optoelectronics, Concepts, Devices, and Techniques Volume one CRC Press Accessed on: 24 Sep 2021 https://www.routledgehandbooks.com/doi/10.1201/9781315157009-3

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The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The publisher shall not be liable for an loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. Downloaded By: 10.3.98.104 At: 19:06 24 Sep 2021; For: 9781315157009, chapter3, 10.1201/9781315157009-3 3.5 3.6 Incandescent, d Incandescent, discharge lamps. The majority of these are sold as soldare these of majority The lamps. discharge and incandescent of range wide is a Therevery 3.1 3.1 DAVID O. WHARMBY a 3.4 3.2 3.3 rc l rc OVERVIEW OF SOURCES 3.4.5 3.5.1 l Discharge 3.4.6 3.4.4 3.5.2 Types of LP d Types LP of 3.6.1 3.4.3 Overview of s of Overview 3.4.2 3.3.6 3.3.5 3.4.1 l Incandescent 3.3.4 3.3.3 3.3.2 3.3.1 p Light Radiation f amp sources amp roduction Lamps with IR r IR with Lamps Stable d Stable s IR Lamps with i with Lamps d Electrode r Electrode Low- d l oft Varieties Tungsten– m fromRadiation a t p Color Emission ofl Use Étendue e and Absorption r Full l amps imits on e on imits emperature ofs emperature ischarges with e ischarges olecules in e olecules ources undamentals amps with e p adiator r

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48 48 50 45 42 42 44 42 49 49 49 49 43 47 47 47 47 51 41 51 3 3.9 d 3.8 3.10 References Appendix 3A 3.7 ers also make lamps for applications other than than other for applications lamps make also ers manufactur lamp specialty numerous and panies, com major The lamp applications. optoelectronic to suited are but many sources, lighting general 3.8.2 3.8.1 3.9.3 3.9.2 3.9.1 d m Other 3.8.3 Electrical c Electrical 3.7.3 3.7.2 3.6.2 3.7.4 c p the from LEDs HP d HP 3.7.1 onventional l ischarges ischarges and , and ischarges Steady s Steady d s and Breakdown m byi Excitation b Dielectric l Pulsed o AC c l d ofHP Applications p Operating m HP d ofLP m Applications h d f General amps haracteristics ethods of e of ethods alide l alide ischarge l ischarges ischarge l icrowaves

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This chapter will concentrate on principles on concentrate principles will chapter This There are a number of useful books about light light about books useful of are a Therenumber Chapter in detail covered in are sources LED As particle densities increase in the source, the the source, the in increase densities particle As radiation synchrotron in exceptions; are There Incandescent, discharge, and arc lamp sources IH PRODUCTION LIGHT and catalogues. A selected list of manu list Aselected catalogues. and transitions col 10. 10. ------Convenient units for spectral radiance are Wm are radiance for spectral Convenient units lamps. discharge and incandescent found in those of 3.1 typical Figure for in temperatures plotted is radiance spectral defined). The also are quantities photometric and (Chapter where radiometric 8, equation by Planck’s given is tor body or black comparatively rare, T rare, comparatively are particles heavy and electrons between lisions col which but for in low-pressure (LP) discharges temperature to the value in efficiency and the radiance of the the source. of radiance the and efficiency energy the distribution, spectral on the limit mental funda a sets This randomized. motion is electron the which in source any from mayobtained be that radiance to the limit afundamental forms therefore equation The Planck temperature. gas the than 3.3.1 3.3 application. for the quality rect cor of the by copious radiation accompanied also is ionization this that to ensure is designer lamp the of task The avolume process. is emission light any gas; of the of ionization result the is duction con lamps, discharge In of ahot material. surface spectra). of selection for a [5]cations Instruments (see Appendix—Oriel appli for optical critical often are of spectra types The continuum. to afull atomic lines narrow from sr T temperature electron an by characterized be usually can that established is function distribution energy electron velocity. An the mean than is field much less electric applied the in theelectrons of velocity drift the interest, cal of practi cases all In randomized. motion is tron elec lamps, discharge and incandescent in Both emission of radiation. of emission subsequent with atoms, the excite that tribution dis of the tail high-energy the in electrons the is It low, conditions. are densities transient or under particle when Maxwellian from far may be tion charge sources the electron temperature T temperature electron the sources charge Chapter 8by 10Chapter −1 In incandescent lamps, the radiation is from the the from is radiation the lamps, incandescent In The spectral radiance L radiance spectral The For incandescent or high-pressure (HP) dis or high-pressure For incandescent nm AITO FUNDAMENTALS RADIATION Full −l l , obtained by multiplying the value of c value the by multiplying , obtained imits r adiator r on e on −9 . mission e may be very much higher much higher very may be adiation and e e . The distribution func distribution . The ( T λ of the solid or vapor, solid of the , T ) of the full radia full ) of the e is close close is 1 in in −2 ------

Downloaded By: 10.3.98.104 At: 19:06 24 Sep 2021; For: 9781315157009, chapter3, 10.1201/9781315157009-3 that states law [6] Kirchhoff’s arguments, thermodynamic general very from Derived emittance. spectral as known also is quantity This angle. and wavelength temperature, same body) at the (black radiator full of a to that surface the from emission thermal the from an absorbing material. absorbing an from acavity by forming made be can approximation agood unity; is radiator of afull emittance spectral ray and the normal to the surface. to the normal the and ray a θbetween angle and temperature wavelength, the depend on they In general, respectively. reflectance, T region of high emittance in the IR. the in emittance of high region have a usually oxides refractory whereas lengths, off at longwave tails emittance the metals in als; of materi most characteristic is emittance Selective 3.2) (Figure [1]. tungsten is material characterized absorber, α For aperfect law showing in the peak shift radiance to wavelengths shorter as the temperature increases. where the fractions α fractions where the on asurface falling For radiation 3.3.2 3.1 Figure , θ All real materials have ε materials real All The spectral emittance ε emittance spectral The ) are known as absorbance, transmittance and and transmittance absorbance, as known ) are Absorption and and Absorption αλ ()

Spectral radiance of a full radiator (Wm radiator afull of radiance Spectral ,, Tt ελ 100,000 θ+

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the sun is about 1.5 is sun the 3.5 about therefore is sun at lens the subtended by the aboutis 1.4the sun of diameter The a surface. onto sun of the image an projecting Imagine issues. but never decreases. (ideal) or increases, same the stays either system optical an through passing rays of étendue The of a bundle system. the through increases étendue or diffraction, ing, scatter by aberrations, caused losses are there if system; optical alossless in conserved étendue is > are ces indi refractive when used is form A more general of radiation. no mention of amounts with metric, geo are units the that Notice radiating. it is which d and consideration, under θd where cos ε étendue called concept general on avery depends behavior This system. optical by the used be can source by generated the radiation much of the how determines geometry systems optical For all 3.3.3 with an area A area an with so that its area area its that so of f length focal 3,000 K , also known as geometric extent [6–8]. extent geometric as known , also −1

A definition étendueis of A definition A simple example demonstrates some of the some of the demonstrates A simple example th (nm) × nm 10 700 Étendue −1 −27 ). The broken line is Wien’s displacement 1 [6]. Energy conservation requires that that requires 1 [6]. conservation Energy

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Downloaded By: 10.3.98.104 At: 19:06 24 Sep 2021; For: 9781315157009, chapter3, 10.1201/9781315157009-3 image area is therefore A therefore is area image the conserved, étendue is that so system optical of about 0.5 diameter image an ing radiance radiance to the related is beam the powerhow in Φ(W) the code. design optical an by using e.g., numerically, done to be has 3.3 Equation in integration the eral, gen étendue.In increase that losses also are tion diffrac and Scattering étendue. increasing above, predicted area outside the to fall light some of the cause then lens anonideal in Aberrations length. focal to have ashorter needs area same ofa lens the 44 be wasted. On the other hand, if the étendue of the étendue of the the if hand, other the On wasted. be gate and light the miss will some light this, than greater is source étendue of the the If lens. jection pro associated its with gate light or film the be will this étendue.Often (limiting) smallest the has that system. optical by an increased never be can radiance that means of of energy étendue and optics). Conservation (and lens of the related transmittance the t is ε Sources 3.2 Figure angle angle f at adistance a focus will confirm:

=

Étendue is also the quantity that determines determines that quantity the Étendue also is spot, onto sun asmaller the to focus we want If In a projector, there is always some component a projector,In always is there A Incandescent, discharge, and arc lamp sources S Ω Ω 0 , Macmillan, London, 1972

≈ L

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0.05 0.15 0.25 0.35 0.45 2 0.1 0.2 0.3 0.4 0.5

= −2 −9 0 8× sr 100 m Φ Φ −1 in a converging beam of solid of solid beam aconverging in 10 2 =ε sr. The image is sr.to brought image The ), as inspection of the units units of the inspection ), as Lt −3 sr. Assuming a perfect aperfect sr. Assuming I

() = W

ε / Ω (3.4) L

≈ .) mm. 7× 10 −7 m 2 , giv Wa - - - - veleng 1,000 greatly exceed ε exceed greatly not £sdoes order In that gate. light of the that be LED headlights for cars are apossibility. are for cars headlights LED why is a reason this fluxes; lowrelatively radiated the use of efficient low étendue allows their that is LEDs of benefits one of For the example, lanterns. street to optics fiber from system illumination any angle is 4 is angle (lm) lumens in Chapter [3, flux The luminous 1] of Use 3.3.4 A of area asource has aprojector lamp that Suppose gate. light the misses that of light amount the mize mini will étendue. This limiting the than greater much usually it is since possible, as far as source étendue of the to reduce the therefore be must aim The illuminated. not fully be gate will the then source of the that than much gate is larger light limiting étendue ε limiting an effective area in the region the0.1of region mm in area effective an 1 as small gap as arc an with arcs HP to use have been projector lamps in Major advances large. so is angle solid source the because small very be must source of the area the S that radiates in all directions so that the solid solid the that so directions all in radiates that th (nm) The étendue concept is very general. to It applies general. étendueis The conceptvery and the source étendue is ε étendue is source the π and Φ= ve L , with consequent wastage of light, of light, consequent wastage , with l ight in s in ight 683 L of the system will be usually usually be will system of the ∫ 380 780 mm (see Section 3.7.4) (seemm Section and Φλ λ ystems V () 10,000 d λ (3.5) S

= 4 2 . π A S The The - Downloaded By: 10.3.98.104 At: 19:06 24 Sep 2021; For: 9781315157009, chapter3, 10.1201/9781315157009-3 tually reaches the eye, every system includes most most includes system every eye, the reaches tually To even system. that generate light complete lighting of a view shows 3.3 aschematic Figure future. the in maintained be will trend this and by electronics confusion. for possibility of this aware be should users circuit; lamp the in losses the it contains because power greater is latter verts verts con lamp The lamp. the from radiation the of aspects various represent arrows broad The lamp. power coming from the electricity supply P electricity the from power coming converted into visible power by weighting with the eye sensitivity curve to give power P power give to curve sensitivity eye the with byweighting power visible into converted encompasses most of the radiation emitted. A fraction of this P this of Afraction emitted. radiation the of most ­encompasses W photopic (Chapter vision 8). (lm 683 factor The as some electrodeless lamps) P some electrodeless as fluorescentlamps),system as a sold (such lamps or (such compact sources as self-contained whereas lamp, the of powertheinto terminals as defined is input power the lamps, commercial For many is source a of efficacy (luminous) The and where P wall the from 3.3 Figure reflects light into the eye. All powers P powers All eye. the into light reflects 683 is flux ofradiation efficiency the luminous to define useful −1 Many lighting systems are driven and controlled controlled and driven are systems lighting Many ) converts power to luminous flux. It is also also is It flux. power to luminous ) converts V( P cir Φ λ P to radiation P ) is the spectral luminous efficiency for efficiency luminous spectral the ) is e wall λ is the spectral radiant flux in W nm in W flux radiant spectral the is × η Schematic diagram of at lighting each Theconversion system. efficiency is shown. Power

vis P vis = ∫Φ η= . That power is transmitted/reflected by an imperfect optical system onto a surface that that surface a onto system optical imperfect an by transmitted/reflected is power . That 380 wall η 780 vv dc is converted to dc power P power dc to converted is eλ =P Φ V K A (λ) pf ~1 dc /l C/D P =Φ rad /P dλ/P in P ; a convenient measurement and integration range is 200–2500 nm, which which nm, 200–2500 is range integration and measurement ; aconvenient wall vi () C s ve mW vi /. Φ s (3.6) in P –1 is taken to be the the to be taken is dc Control . (3.7) La η cir here are in watts and the spectral powers P powers spectral the and watts in are here mp dr = P wall ci iver r Im dc /P . The optics , which is used by the lamp circuit to input P input to circuit lamp bythe used is , which dc pe P −1 rf in - ec

P ci t rc then is efficiency system the and aloss is chromaticity coordinates). The color appearance coordinates).color The appearance chromaticity color appearancecolor [3, Marsden 3]. Chapter and Coaton by given also is lighting of color in discussion Acomprehensive 8. Chapter in given to color are belowmentioned related of quantities Definitions Color 3.3.5 system. lighting ated oper to battery omitted, to is ac sion mains from converthe if and, illuminator afiber-optic lamp, a projector, lamp, to a street a self-ballasted well equally applies 3.8 Equation that Notice improved. be can efficiency how system to discover examined to be needs production of light chain this in stage Each 3.3. inFigure aredefined terms various The P 3.3 Figure in tity quan the efficiencies, calculate we can power that so of order In terms to work shown. in steps the or all An important color property of any source is is source of any color property important An La η VR η= mp η sy t

ef = ∫Φ sd emperature ofs emperature f 200 =P VR 2500 is in the visible region. This is then then is This region. visible the in is η× eλ ef P dλ/P f ef /P cc f p vi or chromaticity or vis s ci η× η roperties c and P rc VR

rad = ir 3.3

= ∫Φ Φ 380 Radiation fundamentals η× 780 v /683. For each stage in there there /683. in stage For each ra eλ dV dλ/P Illuminate η× surface ( λ rad ources P ) are in Wnm in ) are Rv VR (specified by the by (specified vis η×

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Not surprisingly a surface illuminated by these by these illuminated asurface Not surprisingly hav (that is, chromaticity of agiven Sources those for only defined is Color temperature Incandescent, discharge, and arc lamp sources capability of a light source is is source of alight capability rendering color (Equation 3.6) for light from the the 3.6) from (Equation for light (CCT) [10,11],in defined K (bluish white). K (bluish Other ------and R Kand of optimization simultaneous However, case. the usually is this and too, should lamps quality high then spectra, have continuous color rendering “perfect” give that sources the since that think lamp.might the One of efficacy reference illuminants. Planckian and by natural color illuminated when to their pared com as illuminant test by the illuminated when coloredof surfaces series shown by a color shifts daylight sources have R have sources daylight optimization.) of review [4] al. et auseful give (Zukauskas LEDs light white to optimize used now are being niques tech Similar wavelength. critical to the close emit that phosphorsband narrow use lamps The tions. installa new all in now are standard that lamps triphosphor the in exploited been has experiment, by confirmed vision, of human feature 610 and This 540 at nm. 450, bands narrow in ted emit is light the if maximized are quantities both result; asurprising shown has color temperature lamps have R have lamps (CMH) halide metal ceramic HP and cent lamps fluores triphosphor as such for lighting interior 80 be should homes, and restaurants illumination, quality high- requiring premises commercial in ing R (CRI) or Index Color Rendering General CIE the is used colorof rendering The measure sources. light a major for is requirement commercial this nance, lumi high or efficacy high with Along spectra. lighting have R lighting for street used (HPS) lamps sodium pressure High- phosphor coatings. with lamps mercury orescent lamps have R orescent lamps barely noticeable. barely are have, they as color such differences respect; this in are preeminent andCMH fluorescent triphosphor illumination high-quality for lamps the Amongst obvious. very be it will replaced are lamps when otherwise small very be must life during color shift the but also small, very be color spreadin initial the Not should stores. only and offices as such installations large in used are where lamps especially manufacturers, for lamp provedmajorhas be a to challenge This vision. peripheral in colorin differences [13]particularly a (see 8) Chapter [12,23]. R The better the color rendering, thethe lower colorthe rendering, better The The CIE CRI is defined so that tungsten and tungsten that so defined is CRI CIE The Human vision is extremely sensitive to small to small sensitive extremely is vision Human a

≥ or higher. Good quality sources sources quality or Good higher. a

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=

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Suppose, we view a nonuniform extended extended anonuniform we view Suppose, emission emission the isotropic, is emission the Since ) =10 ) is the line shape function having an area area an having function shape line the ) is ) of a surface, which is a dimensionless quantity. adimensionless is which ) of asurface, atom density and is given by the radiation radiation by the given is and atom density NADSET LAMPS INCANDESCENT Emission aito from Radiation is Planck’s constant in Js in constant Planck’s h is ×ε ε m λ ∫ −9 ()

xN ελ olecules in e in olecules 0 ελ D ( = [14] with the spectral emittance ε emittance [14] spectral the with x λ ) from a volume element) from at position () 10 u × 4 xx atoms or molecules in the excited excited the in atoms or molecules hc π − λ hc 9 d( λ . The spectral radiance along a radiance spectral . The P =− −1 () uu Wm λ () . EE xA uI (W −− xtended s 21 l sr ms a toms and (J −− 31 nm A )

rn ul (s − −1 1 is the the cis and ). −1 m)

). The emit − 1 ources .

(3.10) (3.11) (3.9) 1 (J) (J) ( λ - - - - , IEE Proc. T.G.Parham, IEE > wavelengths at is fraction remaining The nm. 2000 750 and between fraction IR the is line full The radiation). UV of fraction small avery with but visible (mostly < at radiated power of fraction the is line dashed The temperature. of afunction as filament tungsten coiled atypical from emitted 3.4 Figure regions. The tungsten halide thus produced is a thus produced halide tungsten The regions. cooler the in tungsten evaporated with gen reacts halo the lamp of the operation During sealed. it is before lamp to the added or bromine—is of iodine [16]. lamp aconventional with compared lamp ahalogen in 100 Khigher operated be can filament the life and wattage of Forsimilar lamps household bulb. standard the in than temperatures higher at be operated to filaments tungsten allows [15] cycle transport chemical Use of ahalogen Tungsten– 3.4.2 temperature. ( tion frac visible the whilst temperature, tungsten the of independent approximately is nm 750–2000 region the in of power radiated fraction the that shows3.4 Figure IR. the in cut-off or silica glass the and nm 750 between is emitted filament sten applications. optical have many that lamps tungsten–halogen perature tem higher the on concentrate will section This life. acceptable an give and evaporation to limit chosen is lowtemperature comparatively The type. on the depending K, of 2800 region the in perature tem at a is operated filament the household bulbs Fraction of radiated power The halogen—usually a fraction of aμ fraction a halogen—usually The atung from of radiation fraction A substantial 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 2,000 < 750 nm) doubles for an increase of 500 K in Kin of 500 750 nm) increase doubles for an

Calculation of fractions of power power of fractions of Calculation 2000 nm. (From Bergman, R.S. and and R.S. Bergman, (From nm. 2000 Tu 2,500 ngsten temp h , 140A, 418–428, 1993.), 140A, 418–428, alogen l alogen 3.4 Incandescent Incandescent lamps erature (K 3,000 amps 750 nm ) mol cm mol 3,500 47 −3 - - - - -

Downloaded By: 10.3.98.104 At: 19:06 24 Sep 2021; For: 9781315157009, chapter3, 10.1201/9781315157009-3 to 1 part in 10 in to 1part controlled current supply with current constant dc a from operated be should lamps stability, For best stability. excellent of having sources other over all information. for consulted be should data manufacturers’ voltage; dependent on operating strongly also is Life of of afew hours. tens have alife temperature K(filament of 3400 ture at acolor tempera operating Filaments lamp. the of life the shorter the and of evaporation rate the K. 3500 of up to about at temperatures operated may be tungsten of Kr, the or Xe, even pressures high ing contain bulbs stronger smaller, With evaporation. suppress weight molecular of high gas of inert pressures High strong. and small very made be can output. light do not affect that lamp of the to regions wall the from tungsten the to therefore transport is cycle the of effect net The lead. filament of the region at a place takes mainly dissociation cleanup. The for further halogen releasing and tungsten iting depos where it dissociates regions, to hotter tion andconvec by diffusion transported is that vapor 48 even greater are available. In some cases, these are are these some cases, In available. are greater even 25–1000 Wor range the powers in versions with color temperature 3.5. High Figure in shown are Examples silica). fused than quality optical better have can glass (hard used of glass type the and wall, bulb of the thickness and quality the to it, normal or axis bulb the with concentric is coil the whether cylindrical, aflat or is coil the whether coil, of the winding of evenness and tightness the filament, the of size the by affected is This beam. atight into light the to focus ability the often is consideration important most the applications For optical duced. intro being of products new thousands in resulted has lamps developmentThe tungsten–halogen of of Varieties 3.4.3 ble lamps (Appendix—Oriel Instruments, Ealing). Instruments, (Appendix—Oriel ble lamps sta particularly equipment select suppliers optical irradiance) of spectral (as standards in for example at premium is stability lamp When not exceeded. is lamp of the rating voltage the that to ensure set be should current The lamps. calibration operating

Tungsten–halogen lamps have the advantage Tungsten–halogen advantage have the lamps greater the temperature filament the higher The bulb the clean, remain walls lamp the Because Incandescent, discharge, and arc lamp sources l amps 4 —this is the technique used for used technique the is —this t ungsten– ≈ h 3330 K) will 3330 will K) alogen alogen ------(a) 900 W and CCT is 3200 K. (Philips photographs.) (Philips K. 3200 is CCT Wand 900 to up ratings in available projectors; overhead in use for lamp voltage (c) amains is Lamp cations. appli video for reflectors in use for suitable ment fila axial an (b) has Lamp projection. for suitable especially filament (a) aflat has Lamp K. 3500 as high as cases some in and more K or 3000 of CCT a at voltage low from (a) (b) operate and ment. replace accurate allow to pre-focused is that base aceramic in mounted are All scale). to (not 3.5 Figure shows examples. shows 3.6 Figure illuminators. and fiber optic microfilm overhead projection, as such applications of optical anumber in used are versions that special make manufacturers major lamp the all addition, sive. In inexpen relatively are they therefore and lighting accent and displays of commercial sorts forbers all K. of about 3000 a color temperature 40° up to afew degrees from divergences beam with to 35 down 50 from vary diameters Reflector lamps. tungsten–halogen silica by fused emitted is that wave UV of short amount small already reduce the that cover glasses with ted be fit also may They cool. comparatively is beam the that means this reflector; of the rear the from to escape radiation some IR allowing ter) coating (interference or have adichroic fil aluminized, be may Thereflectors reflectors. small into built lamps tungsten–halogen of range wide is a There with Lamps 3.4.4 applications. optical for particular designed lamps for “special” websites wave UV.of short manufacturers’ Consult to prevent doped is emission that silica from made These reflector lamps are used in large num large in used are lamps reflector These . Typically wattages vary from 12 to 75 W with 12 to 75 from Wwith vary wattages . Typically Examples of tungsten–halogen lamps ofExamples tungsten–halogen (b ) i ntegral r ntegral mm. Versionsmm. made are (c) eflectors ------Downloaded By: 10.3.98.104 At: 19:06 24 Sep 2021; For: 9781315157009, chapter3, 10.1201/9781315157009-3 are also available from most manufacturers. most from available also are purposes optical specific for Lamps (Philips). tion illumina optic fiber for designed specially been (b)has Assembly (Osram). reflector the in ment reduced to show the positioning of the axial fila axial the of positioning the show to reduced been has coating the of (a) reflectance In the reflectors. prefocused integral in lamps halogen 3.6 Figure There are also low heat capacity carbon ­ carbon capacity lowalso heat are There Instruments). (see data Appendix—Oriel turers’ manufac in given are devices versions of similar More recent IR. the in emittance of selective use makes This spectrophotometers. in illuminator IR an as used K, to 2000 heated electrically emitter oven. conventional a than time response amuch shorter has and precisely controlled be can that source is a heat benefit main (Appendix—Heraeus). processes The heating trial indus in radiation IR of the use make bon emitters or car tungsten either using lamps Incandescent IR 3.4.6 light. of of generation visible ciency effi improvementthe an in is 40% benefit of up to main The coating. by the slightly degraded is ity qual optical although emitted radiation IR less is there cooler since is beam The output. light a given in power for therefore saving isa benefit main The temperature. design at the coil tungsten the tain [16]. CVD LP to main input power needed is Less by deposited filters interference multilayer using by achieved eventually was success Commercial absorbed. be wherecan it filament to the radiation some of this to return made have been attempts Many wasted. is so and region IR the in is lamps tungsten–halogen from radiation of the 90% Over 3.4.5 (a) The Nernst source is an example of a ceramic ceramic of a example an is source The Nernst Lamps with IR with r Lamps Examples of low voltage tungsten– voltage low of Examples s ources (b ) eflectors emitters emitters ------trons from the cathode (Section 3.9.2). (Section cathode the from trons of elec or no emission little with self-limiting and (DBDs) transient are discharges barrier Dielectric or microwave sources. induction using frequency 3.9) (Section at high operated are discharges Other surface. cathode of of ion the bombardment a result cold cathode cold In lamps. fluorescent hot cathode and lamps discharge HP all are thermionically—examples emits cathode the which in discharge a to mean taken often it is arc term The emission. by thermionic plasma the into released are electrons hot; is cathode the which in have electrodes charges power supply. to the ner of coupling Most dis features. unique their describe sections Later 3.5.2. Section in aredescribed regions electrode The types. of both features common the with concerned 3.5.1 is Section discharges. HP and LP in occur processes physical same The equal. approximately are temperatures both that atoms ensure gas and electrons between collisions frequent relatively temperature electron so atoms and gas the with sions second per few colli relatively make electrons the discharges, LP In ­(low-pressure) types. (high-pressure) HP and LP into lamps discharge to group One way is 3.5 (Appendix—Hereaus). at low frequencies modulated be can that (Figure 3.7). Other lamps including HP lamps have lamps HP including 3.7). lamps (Figure Other example an as fluorescentlamps in used type the mercury LP the using charge (Section 3.8.3). on ac operate lamps of commercial majority the although discharges consider dc will we effects To main of the radiation. production demonstrate the to conduct is gas by-product the of causing A gas. conducting the through to anode cathode from passed be must circuit external rent an from (an and electron) cur conducting, gas the to make applied be must voltage ahigh To adischarge, start Stable 3.5.1 Another way to group discharges is by the man by the is discharges way to group Another We will illustrate the main features of dis adc features main the illustrate We will ELECTRODES WITHDISCHARGE LAMPS d ischarges with e with ischarges 3.5 ≫

gas temperature. In HP discharges, discharges, HP In temperature. gas Discharge lamps with electrodes d ischarge o ischarge lamps, the electrodes emit as as emit electrodes the lamps, is not uniquely defined, but defined, not is uniquely -rare-gas discharge of discharge -rare-gas lectrodes peration of peration

49 ------Downloaded By: 10.3.98.104 At: 19:06 24 Sep 2021; For: 9781315157009, chapter3, 10.1201/9781315157009-3 cent lamp case. lamp cent 50 where is approximately density Therefore,current electrons. by the mainly carried is current the ions and of the that than much is greater mobility their because cathode; the towards ions to drift the and anode the towards to drift electrons the causes field electric applied the established, been has discharge the Once of energies. distribution not exist. does PC the that small so are for UV producing used lamps deuterium or neon indicators as such Some discharges ume. vol ions unit per and of electrons number equal are there so (PC)—is aplasma, column positive 3.7—the in Figure discharge of The bulk to see. small too usually are that have dimensions trodes elec the around regions but the features, similar n densities electron Typical current. a stable V which dimensions are dependent on vapor and pressure. The lower diagram shows the voltage drop in regions cathode and anode the with together length, any be may which (PC), column positive the shows picture upper The discharges. other in present also are they but discharge, lamp fluorescent 3.7 Figure LP discharges, most of the recombination occurs occurs recombination of most the discharges, LP In by ionization. caused of rate gain to the equal ions be must with by recombination of electrons of loss rate the that is for operation stable dition signs). display Acon of commercial ply (think sup the from available is voltage open-circuit density. ity, | ity, along the lamp. The cathode fall field adjusts so that sufficient electrons are extracted to maintain maintain to extracted are electrons sufficient that so adjusts field fall cathode The lamp. the τ along

In the PC, electrons form a near Maxwellian Maxwellian anear form electrons PC, the In The PC can be any length as long as sufficient sufficient as as long any length be can PC The Incandescent, discharge, and arc lamp sources e | the electron charge and n and charge electron | the E is the electric field, field, electric the is

Structure of a dc discharge. This schematic diagram shows features visible in a typical atypical in visible features shows diagram schematic This discharge. adc of Structure jn Ca ~10–15 V Ca =µ th Ca tho od ee tho V (volt) de fall eE e T de sheath () 10 µm μ Am e T n the electron mobil electron the Negative glow e e ~9000K ~ 10 –2 F arad 18

e the electron electron the m ay –3 darkspac e (3.12) and electron temperatures and T electron e n Distanc e - - - - - ~ 10 PC PC Hg 6mTo Electrons emitted thermionically (hot cathode cathode (hot thermionically emitted Electrons not self-sustaining. be will discharge the erwise oth cathode, the from one moreat least electron of emission the cause that events initiates cathode leaves the that electron each that so themselves have to adjust surface cathode at the conditions electrons. to attract positively charges it required current the to collect small; too is area anode the Normally current. random the collect only would anode the then no sheath was there If sheath. charge space of a 3.7).is a result (Figure This increases usually voltage the Adjacent anode to the 3.5.2 of 0.5–1.5 region the in energy to a mean accelerated are electrons that dominate. to recombination volume for enough high are densities particle discharges, HP in wall; the to diffused have carriers the after tron temperature of about T temperature tron the voltage. the higher the lamp longer the the gas, agiven in so constant, is thePC in field electric the shows that 3.7 Figure by lost recombination. electrons the replacing atoms, to ionize electrons high-energy enough contains then distribution energy electron 16 T leng m e e ~12,000K The cathode is more complex cathode Chapter The 4].[2, The so itself adjusts column the in field electric The –3 th Electrode Electrode rr Ra re gas ar Ano gon 2torr 0.3 mm de sheath eV corresponding to an elec to an eV corresponding e r are shown for the fluores egions fall ~5 Ano e of 6000–18000 K. The K. of 6000–18000 de V - - - Downloaded By: 10.3.98.104 At: 19:06 24 Sep 2021; For: 9781315157009, chapter3, 10.1201/9781315157009-3 fraction of these ( of these fraction A sheath. cathode the through accelerated are that ions of positive production (NG) the glow causing negative of the edge cathode the penetrates region CF the from of electrons (CF) Abeam region. fall cathode the field of high the in accelerated are case) or by (cold ion case) bombardment cathode UV sources for photochemical and photobiological photobiological and for photochemical sources UV in and fluorescentlamps in used discharge rare-gas mercury LP the is type important most the far By 3.6 [17]. hollow cathodes by reduced using be can lamp of 100–200 region the in typically are voltages CF Cold ion bombardment. as such processes by secondary extracted be must electrons because much is CF larger the lamps, ode 3.7). (see Figure cold species cath In ionized easily most of the potential ionization the than greater PC. the in distribution random the into CF the from coming function distribution electron anisotropic highly the to change serve therefore FDS NG and The PC. of the start the marks this and increases excitation again, field the from energy to gain start electrons the as Finally distribution. Maxwellian anear giving randomized been motion has electron (FDS). point, space At dark this Faraday as known is light little comparatively of region This decrease. of to atomic levels excitation for the energy enough have lost NG they end of the the By NG region. the in direction the in randomized gradually is beam This anode. the toward directed strongly emission. more producing thermionic tures, tempera to higher surface cathode ment the heats ion bombard extra resulting the and increases CF the increases, work function the if regulating; self- is entirely The process cathode. out of the In hot cathode lamps, the CF is usually a little alittle usually is CF the lamps, hot cathode In are theCF leaving electrons of The velocities TYPES OF L TYPES YEO Name Table 3.1 Halophosphate BAM CBT LAP CAT ~ Phosphors commonlyusedinfluorescent lamps 0.1) knocks further electrons electrons 0.1) further knocks P DISCHARGES V. cathode coldin CF The Y Ca BaMg GdMgB LaPO Ce 2 O 5 0.65 (PO 3 :Eu 4 Tb 2 :Ce Al 4 5 3+ ) 0.35 Formula O 3 16 F, ( 3+ O 10 MgAl , Tb Cl):Sb :Eu 27 :Eu 3+ 2+ 11 2+ O 3+ 19 , Mn - - - that optimize color rendering and efficacy. and color rendering optimize that 610 and wavelengths 540 nm 450, to the are peaks Table noted in ones are 3.1; how the notice close wavelengths and then re then and wavelengths at short absorb that activators with doped materials [3,radiation 7]. Chapter phosphors ionic are Lamp 185 and at 254 lines resonance mercury the in of UV emitter efficient ahighly is discharge cent lamp The fluores discharge. of the properties nate the domi atoms they mercury of the density number Pa (0.6about 0.8 m of pressure at the drop liquid the from evaporates mercury the temperatures, wall Atlamp. typical the in place coolest at the collects which ligrams, afew mil weighing of liquid drop asmall as added (a few torr). is pascal of a few hundred Mercury at apressure of these, or neon or mixtures krypton argon, usually gas, arare contain lamps mercury LP 3.6.1 discharges. laser LP of variety wide a also are There analysis. for chemical sources spectral cathode hollow LP and illuminators UV as used lamps efficiency,deuterium luminous high of very ing light for street used sodium, LP here are described not 3.6.1). (Section discharges LP purposes Other rendering index ( index rendering colorand efficacy high combine that wavelengths at the emit phosphors these as based rare-earth ionic the are important Particularly available. are color CCTs and properties other different many of light white giving fluorescentlamps and of phosphors [3, range large 7], avery Chapter is There 50%. conversion typically is the loss lighting in used fluorescentlamps In vibrations. lattice into Stokes this in deficit The energy 2+ Phosphors are used to convert UV to visible to visible UV to convert Phosphors used are nm ( nm Low- Wavelength ofpeakoutput(nm) r > are- 70%). g p a ressure m ressure Broad bands s d R a Torr). low relatively the Despite —Section 3.3.5). The principle —Section 3.6 450 545 544 543 611 ischarges emit Types of LP Types of at longer wavelengths. at longer wavelengths. ercury ercury ’ shift is converted converted is ’ shift discharges

51 - - - - Downloaded By: 10.3.98.104 At: 19:06 24 Sep 2021; For: 9781315157009, chapter3, 10.1201/9781315157009-3 of mercury above the amalgam is less than that that than less is amalgam above the of mercury vapor The pressure indium. and bismuth example, for containing, amalgam a solid as dosed is cury the mer these, In hot fixtures. in for operation aredesigned fluorescentlamps compact multilimb of Some types necessary. may be some cooling ing backlight as such uses, For other fixtures. lighting commercial in to optimum close to run designed are Lamps to optimum. close is pressure mercury the that so to operate lamps the holding or unit fixture for the to arrange important it is cent lamps present at about 42 cury mer of liquid amount asmall by having achieved is pressure optimum This at amaximum. is tion radia UV of of generation efficiency the at which 3.7.1.) Section in described is lamps HP low.in process related (The atoms is mercury to excited lead that of collisions fraction the but then of steps, number a small in escape can energy excitation initial low is the sure pres vapor mercury the When increases. collision a in nonradiatively energy excitation the of losing chance the that walk random the in steps many so are there high, is pressure mercury the When walk. random in a wall the reaches before it finally times many reabsorbed and photon absorbed is atom nearby. state by The aground absorbed to be energy correct the photon at exactly is emitted the center of lamp, the near atom excited is a mercury When iswhich generated. it with efficiency the and emitted of radiation amount the controlling tor in research. ­painstaking of phosphors man-years represent many these of of each existence the so empirical, largely still Table in als themateri of complexity The replaced. largely have they that halophosphates the with compared phosphors of rare-earth cost high the is vantage disad The ment fluorescent oflamps. compact develop the possible made that property this It is power leadings. at high discharges mercury by to degradation resistance ­phosphors their is unity. to close are efficiencies Quantum function. same this has lattice host the some cases, In light. visible emit and UV to absorb centrations con small at relatively ion deliberately added an is activator The of lattice:activator. host position 52

This means there is a mercury vapor pressure vapor pressure thereis a mercury means This fac is a dominant vapor pressure The mercury rare-earth benefit of important One very in com The notation Table chemical the 3.1is Incandescent, discharge, and arc lamp sources 3.1 is such that phosphor research is is 3.1 phosphor research that such is ° C. When using fluores using When C. ------show up fluorescence in materials. in show up fluorescence phosphor sources) that to UVA light” (as “black in a using converted be or it can processes; logical or photobio photochemical in used is discharges rare-gas mercury hot cathode from wave radiation Short ATM as such levels machines. ambient light high in used are that displays to backlight used be can and light produce fluorescentmorelamps ode Hot end product. cath the in incorporated readily are efficient power low supplies and cost, quently; fre switched be can they long; are lives purpose; the efficientfor enough are low they powers needed at the thin; very to be screens allowing diameter in be small can they ofhave benefits: anumber fluorescentlamps cathode Cold of displays. ing backlight the etc.) in and (copiers, machines, fax equipment in office are for tions fluorescentlamps lighting. ment for incandescent replace efficiency cent (CFL) ahigh as designed compact fluoresof variety wide a also are There premises. industrial and commercial all nearly in lighting ceiling in used lamps long thin the are iar formats different [3,Chapter famil 7]. Themost many to itself lends discharge lamp The fluorescent 3.6.2 ­optimum [18]. to close is pressure mercury the over which range ambient temperature the increases substantially also amalgam of an use but mercury, the above free introduce radiating species into the vapor. the into species radiating introduce to halides metal use that those and elements, eous or gas volatile use that those are of lamp classes below.twomain The described are discharges HP of properties Some of the needed. is brightness high and projected be must light which in used are discharges of HP types other Many applications. different suit to end) at each configurations nection (one con at one end) double-ended nections and in exist Lamps premium. are ata life and long colorquality good efficacy, high flux, luminous high which in premises, cial other commer and offices of and stores mination illu interior and lighting for street used are them of Most discharges. HP of variants aremany There 3.7 Other than illumination, important applica important illumination, than Other P DISCHARGES HP d ofLP m Applications ischarges single-ended ercury ercury (both con (both ------Downloaded By: 10.3.98.104 At: 19:06 24 Sep 2021; For: 9781315157009, chapter3, 10.1201/9781315157009-3 local temperature in the plasma. The electron electron The plasma. the in temperature local dependent on the are properties the that means (LTE) [14]. equilibrium thermodynamic This radiance. spectral ing increas thus temperature, axis increases and tion conduc thermal vapor.reduces This of mercury efficient (120 lm/lamp watt) efficientlong-lived ( lm/lamp (120 highly as used are lamps outer These bulb. a glass within contained is tube arc the lamps HP many with As sodium. from to attack resistant mina, alu translucent from made tube arc anarrow into inserted electrodes has lamp HPS An example. an as lamp sodium) (high-pressure HPS the by using discharges of HP operation the illustrate We will General 3.7.1 dering properties ( properties dering CCT with golden light apleasant give that lights street lamps usually also contain about 10 contain also usually lamps Sodium direction. axial the along uniform column apositive is discharge of the length Most of the K. about 1500 is temperature wall the Kand 4000 about is center temperature the which develops in 1.4 about is pressure its until sodium evaporates and heats discharge The resulting down. breaks gas rare the avoltage applying On metal. of sodium afew milligram and gas of rare pressure a small contain They lamps. for lower wattage decreasing dimensions with Wrating, for tips 400 electrode 70 with diameter internal Number densityofsodiumatoms Table 3.2 Fraction ofsodiumatomsthat are Fraction ofsodiumatomsexcitedto Note: and ions

The positive column is approximately in local in local is approximately column positive The The dimensions of the tube are typically 7 typically are tube the of dimensions The × 10 ionized the statesradiatingat589 = 2000 K, albeit with rather poor color poor ren rather with albeit K, 2000 4 d Pa (100 sets themaximum plasmatemperature toabout4000K. CalculatedusingEquations3.13 and3.15. to carrythecurrent andtheplasmatemperature adjuststomakethisso.For steadystatesodiumarcs this lowering ofthevalueathighelectron densities.Thearc operatessothattheelectron densityissufficient characteristic orangesodiumDradiation. Theionizationpotentialis5.14 Electron density is equal to ion density. There are two excited states at about 2.1 ischarge l ischarge Shows howtheplasmatemperature affects thenumberdensity(m Torr). profile temperature Aradial R f eatures ofHP a

= 25). amps mm length between the the between length mm 5 Pa (760 > h) 20,000 4.8 7.3 1.5 Torr) 2000 mm mm × 10 × 10 × 10 - - - - 23 −5 −6 stant. Since the hot gas is a plasma a plasma is hot gas the Since stant. con Boltzmann’s kis and density) electron high for corrections (including potential ionization the

current density is proportional to n proportional is density current the Since temperatures. at vapor various sodium Table pressure. of ne gas in shows 3.2 values the n [19] equation Saha the called action by aversion law given of mass is of the density is given by the gas law n so gas by the given T is region. temperature high the in flowmainly is current the atom, whilst g atom, whilst ber of atoms excited to the upper state depends depends upper state of to the ber atoms excited The respectively. num upper states, and ground ture through the exponential factor, where E exponential the through ture atom.ion S and for the functions partition are Ufactors where the where where density density state, state, LTE u) by formula: another given is (labeled a is the density of atoms (number m density per the is The population n population The Plasma temperature (K) E n n u 3.2 1.9 8.8 n e is the energy (J) of the upper state of the of the upper state of the (J) energy the is 0 and n and 3000 a is the density of atoms in the ground ground the of atoms in density the is in an elementary volume at temperature volume at temperature elementary an in × 10 × 10 × 10 ST n () u 0 −4 23 −3 and g and = i are the electron and ion densities, ion densities, and electron the are ( =× nn T g n g ei 4.83 × ) depends strongly on tempera strongly ) depends u a eV before correction ismadefor n u exp( of an energy level of an atom of level an energy of an u 0 = are the statistical weights of weights statistical the are ex ST 2.4 6.4 3.5 10 –/ () p( 4000 −3 Ek    21 ) ofexcitedstates × 10 × 10 × 10 − i (/ kT (m UU E 3.7 eV giving rise to the T u ia 23 −2 −3 a − )(   

3

= ) HP m) m) P n )

T / e − e − discharges kT it is clear that that clear it is

3 3 = 3/ 2 n is where Pis (3.15) 1.9 2.3 2.2

i . The atom 3 5000 ) and ) × 10 × 10 × 10 i (3.13) (3.14) (J) is is (J) 23 −1 −2

53 - - - Downloaded By: 10.3.98.104 At: 19:06 24 Sep 2021; For: 9781315157009, chapter3, 10.1201/9781315157009-3 54 only travel about 10 about travel only atoms can sodium photons excited from that high so is pressure sodium the lamp, HPS an In sures. at low pres radiates sodium at which wavelength the nm, 589at radiation no significant is there shows 3.8 Figure As discharges. sodium HP in nant domi especially is and lamps discharge HP many 3.15 Table in shown is 3.2. 3.13Equations of and importance The arc. term of the origin upwards—the part bright the bows convection horizontally operates discharge a HP LTE When of an arc. feature acharacteristic is ance appear “corded” resulting the of atoms excited; numbers significant are discharge of the parts test hot the in Only temperatures. highest ateven the small very uis state excited the of atoms in fraction exponential of the Because on temperature. exponentially temperature. maximum the at body ablack for that than lower substantially is radiance peak the 3.1 that Figure shows with Comparison 1500 K. of temperature awall Kand 4000 of ture sures. The calculation has been done for a parabolic radial temperature profile for a center tempera 3.8 Figure and it has a dominating effect on the operation of the operation on effect adominating it has and self-reversal called is 3.8). behavior (Figure This escape can light before the to be, has wavelength center the line the from further the pressure, the higher The levels. energy perturbed strongly having atom an from escape can energy the until energy excitation storing as considered therefore be can The hot center atplasma 589 nm. line the from far at wavelengths radiates that it so atom sufficiently radiating the perturb atoms can sodium other with collisions close very that achance is there atom. However, state by aground absorbed being

Self-absorption dominates the spectrum of spectrum the dominates Self-absorption Incandescent, discharge, and arc lamp sources The formation of self-reversed lines in high-pressure sodium lamps at two sodium pres sodium two at lamps sodium high-pressure in lines self-reversed of formation The in Equation 3.15, Equation in the factor Boltzmann

Spectral radiance 100 200 300 400 500 600 −7 0 550 at the line center before line m at the 560 570 580 25,000 pa Wa - - - - veleng 590 ● ● ● cient white light sources of good color quality for color of good quality sources light cient white chemistry. reactive the least has which the iodide, usually is halide The as follows: are ones The principal lamps. HP in used be to volatile sufficiently are that halides important). most (of the by gases Xefar is which permanent the and sulfur, sodium, mercury, being important most the discharges, HP as operated to be sures and lines spectral have that elements well-placed few are very There HP 3.7.2 pressures. at different Dlines sodium the of self-reversal of color the photographs beautiful [19] Vliet van by Groot and de book of the shows [3, 5.6.3].cover The Section discharges HP many ● ● ● th (nm) Metal halide lamps are extensively used as effi as used extensively are lamps halide Metal at low continuous resolution. appears that trum aspec emit that molecules monohalide stable relatively form that halides similar Sn, Pb, and resolution. at moderate continuous appears spectrum the that together close so lines visible weak relatively have many metals the which in halides earth) (and rare Dy Fe, other Sc, atomic lines. fewhave strong relatively metals the which in halides Ga Tl, In, I, Na, havethat elementsmetal 50 perhapsare There 15,000 pa 600 m etal h etal 610 sufficiently high vapor pres high sufficiently alide l alide 620 amps 630 - - - - - Downloaded By: 10.3.98.104 At: 19:06 24 Sep 2021; For: 9781315157009, chapter3, 10.1201/9781315157009-3 such as psoriasis (Appendix—Osram). psoriasis as such conditions versions for medical special include lamps halide of metal uses Other processes. similar for used also are lamps mercury HP increased. be can productivity sources UV suitable with so the processes, in bottleneck the often is of curing speed The industries. packaging and printing the in processes production of large part as installed (Appendix—Heraeus).are lamps These curing or glue drying ink as such processes, merization for photopoly for of UV production extensively used are lamps halide metal to use, tailored be can spectrum the (Appendix). them Because make ers manufactur major lamp all illumination; general to give a partial pressure of about 10 pressure apartial to give added is mercury enough Usually added. are ing for gas start arare and TlI of solid few milligram a made, is lamp the When discharge. TlI of aHP 3.9 diagram shows aschematic Figure discharges. halide metal produced in is light how the trate to illus asimple case as considered is TlI (TlI). iodide thallium contain lamps halide metal Many Operating 3.7.3 more constrained by requirements of optimization) optimization) of requirements by constrained more is ratio to diameter (for length lamps the HPS which poor.However, rather coloris rendition their efficiency). (luminous efficacy good quite and tures color tempera of different discharges light white provide can of these proportions the Altering lines. spectral self-reversed orange and blue, green emit that iodides sodium and thallium of indium, tures mix used lamp halide of metal types first of the one For example, vapors. and liquids of the istry chem to the due consideration with chosen to be discharges. halide metal all in occurs tion ioniza and excitation dissociation, evaporation, progressive This current. the to carry needed trons elec the producing ionized is Tl the axis the near Finally, illumination. for underwater useful be can that efficiency of high light green intense emits and excited is Tl the still temperatures At higher Iatoms. and Tl into dissociates TlI the regions, temperature higher In to evaporate. them causing TlI Hg and up the heats discharge gas rare the ated, 3.7.1). (Section voltage ing oper is lamp the When operat to adjust and conduction reduce thermal Metal halide arc tubes are generally shorter than than shorter generally are tubes arc halide Metal has of salts ratio the of halides mixtures With h alide l alide amps p rinciples ofm rinciples 6 Pa (10 bar) to etal etal ------melting and then vaporizing the T gas, rare the in starts discharge The gas. rare (T iodide thallium solid example this In discharge. halide 3.9 Figure for containing Na, Dy, Tl, HgI metal halide arcs. arcs. halide metal Dy, HgI Na, Tl, for containing tubes arc ceramic alumina of translucent use the in recent A improvementmajor been offices. has and of stores lighting the as such applications critical in acceptable it is that so tubes arc silica in lamps halide of metal color stability improved the has R&D Detailed life. showduring some color shift lamps halide metal all rates; at different occur walls tube the components and various the between of 10,000 lives through stant efficacy. and properties color initial the on influence have astrong all tions propor relative their and pressures vapor their used, halides The efficacy. and color performance much improved with lamps halide metal mixed 40 opment last over the light. the more using efficient lamps at these using fixtures andmay make étendue on effect an has This shape. in to spherical close may be even and several bars to reduce thermal conduction losses. conduction thermal reduce to bars several at introduced also is vapor mercury lamp, tical a prac In axis. the to wall the from increases ture here, but blend into each other as the tempera schematically shown as sharp not are regions ous vari the between boundaries The nm. 535 at line radiate green strongly with their characteristic T temperature At this K. 5000 above be to needs axis on temperature the happen to this For T byionizing provided is current the state It is important that these properties stay con stay properties these that It important is anddevel research extensive been Therehas T l*, Tl TlI liquid arc tu ceramic Silica or Tl l Tl I) is dosed into the lamp along with a with along lamp the into dosed is I)

+ I The principle of operation of a metal ametal of operation of principle The be years that has produced has that years h or more. Reactions h or more. Reactions 3.7 el Tu el Tu

ec HP ec ngsten l ngsten I. In the steady steady the In I. tr tr discharges od od e e l atoms. atoms l atoms

- 55 - - - - - Downloaded By: 10.3.98.104 At: 19:06 24 Sep 2021; For: 9781315157009, chapter3, 10.1201/9781315157009-3 (see Figure 3.1).(see Figure high very be can axis to the close gas of the ance radi the K, 5500 around usually is halides metal of temperature axis the Because used. universally are tubes arc silica automotivetor lamps, head and forFor projec projection. a major disadvantage is tube arc by the scattering but the issue, not an is tube arc of the transparency where the nation life. through color stability and color uniformity major improvementther initial in afur provided has this and silica with slower than envelope much are the with reactions halide Metal 56 projection and related uses (Appendix). short In uses related and projection for lamps arc xenon short and of metal-halide avariety make manufacturers major lamps the All for illumination. than other of applications electrodes. by the stabilized mainly is arc the which in lamp arc ashort is lamp CMH The wall. tube by the stabilized are that ters centime of several of length columns positive with [3, 1]. Appendix increases ing as power rat increases efficacy Generally type. and application one indicated for the typical afairly is given rating but the one power rating, more than in exist types All expected. to be characteristics best of some idea the with available of types range It to show intended is the illumination. for general used lamps about HP Table information gives 3.3 3.7.4 HPS Lamp type Table 3.3 High CRI HP mercury Metal halide CMH

Most metal halide lamps are used for illumi used are lamps halide Most metal Manufacturers’ websites give many examples examples many give websites Manufacturers’ arcs are table the in are that lamps Most of the vapor Incandescent, discharge, and arc lamp sources l ofHP d Applications amps + phosphor Indicative characteristicsofHPdischarge lampsusedforgeneralighting Road lighting lighting Prestige town Road lighting stores Prestige outdoor, Commercial interiors Application examples ischarge ischarge Power (W) ------400 400 400 400 100 (length lamps arc sure (1.5sure pres high very This GE Lighting). and Osram 3.11 Figure ment in shown is (Appendix—Philips, develop recent A relatively applications. different to suit available are divergences Various beam tors (Appendix—Welch others). Ushio and Allyn, reflec or elliptical parabolic prefocused into grated simulators. solar as such applications more specialized other and applications entertainment and projection of for avariety used are that of lamps examples 3.10 Figure shows luminance. in increase an be there may of efficacy to areduction leads erally gen this Although electrode. adjacentjust to the greatest is volume of arc power unit per the that field means and density current in increase bined com The hot spot. cathode the toward contracts arc the as increases normally density current the moreover conduction; to maintain to increase has theelectrodes to close field the and arc, the cool electrodes the because forms temperature arc high of region This temperature. arc high particularly have that electrodes to the close regions usually video projectors. video or data in used wholeassembly the and reflector a prefocused in operated to be designed are lamps 1.2gap of only arc an With color good rendition. giving tinuum con intense an is there and broadening extreme show lines Spectral amillimeter. more than hardly of length arc an in dissipated 130 Ware that is arctemperature high the for The reason perature. tem arc high of extremely its because luminance Short arc metal-halide lamps can readily be inte be readily can lamps metal-halide arc Short (lm W × 10 Initial 125 100 60 90 90 7 Pa or 150 bar) has extremely high high Pa or 150 bar) extremely has −1 mm the étendue is very small. The small. very étendue is the mm ) < Life (10 few millimeters) there are are there few millimeters) 30 24 24 24 12.5 3 h) CCT (K) 2000 2200 3500 4000 3000 25 60 55 70 85 R a ------Downloaded By: 10.3.98.104 At: 19:06 24 Sep 2021; For: 9781315157009, chapter3, 10.1201/9781315157009-3 (a) quently low étendue. (Philips, Osram, GE Lighting.) GE Osram, (Philips, étendue. low quently 1.2 about of 150 gap than bar. arc more of The pressure amercury Kwith 6200 about of at a and CCT W 130 operates It reflector. the in used tube arc (b) The beam. the in IR of amount the reduce to filter adichroic has and possible as low as unit prefocused the of étendue keep to designed 3.11Figure low afew ohms. as as be can that a resistance conductor agood into with insulator excellent an from converted be must lamp the in The gas and Breakdown 3.8.1 3.8 10 between ratings Kand 6000 around CCT with operating lamp halide (c)(Osram). A10W metal W 12000 and 450 between ratings in available K, 6000 of aCCT with dc from operated lamp xenon pressure ahigh of example (b) An (Philips). W 575 12000 and between ratings in available K, 6000 about of aCCT with applications ment entertain for lamp halide ametal of example (a) An scale. to Not shown. is discharges HP with 3.10Figure W (Welch-Allyn). ELECTRICAL CHARACTERISTICS CHARACTERISTICS ELECTRICAL OF DISCHARGES OF d ischarge l ischarge (a) A prefocused projection unit designed for LCD projectors. The reflector is carefully carefully is reflector The LCD projectors. for designed unit projection (a) Aprefocused The large range of powers possible possible powers of range large The (b ) (a) amps s (c) tarting in tarting - rials such as Kr as such rials mate of radioactive amounts of small addition the by aided is breakdown reliable cases other In lamp. of the materials the in radioactivity or natural rays by cosmic ionization from result they means, not by other provided If necessary. is of electrons diagram. this in voltage lamp highest of the excess able in avoltage to provide be must circuit the lamp, the order In to start equations. circuit the satisfy to needed value the at stabilizes it finally until idly rap increases current the breakdown, After rents. of cur range wide over avery of current function Figure cathode operation, in which the electrons released released electrons the which in operation, cathode of cold region the long too in Staying cleanly. and 3.12 quickly Figure achieved be must in to arc glow abnormal from transition the achieved been has breakdown Once thermionically. emit that odes before breakdown. lag time longer the the and to be, needs voltage starting the higher the electrons initial fewer the the that is rule eral gap. Agen main for the electrons initial provides gap then this assured; is gap, breakdown small this across applied is voltage the When electrode. main the includedadjacent to often is electrode trigger [2]. athird electrons enough provides lamps, HP In emission thermionic field-enhanced the peratures at low applied: tem is voltage before heated the be can theelectrodes fluorescentlamps hot cathode of UV. source In external by asmall caused faces (b ) In order to achieve breakdown some source some source breakdown orderIn to achieve The majority of lamps operate with hot cath hot with operate lamps of majority The 3.8

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There are various schemes for starting fluores schemes forstarting various are There Incandescent, discharge, and arc lamp sources Discharge voltage as a function of current (dashed line) over a wide range of currents. currents. of range awide over line) (dashed current of afunction as voltage Discharge

Voltage (V) 100 150 200 250 300 350 400 450 50 –8.0 0 –6.0 glow Normal glow Abnormal –4.0 Log ------(c urrent sets itself to maintain this current. An additional additional An current. this to maintain itself sets terminals the between voltage the and device; 3.12).(Figure a current-controlled is A discharge cold resistance. the than higher or more times 15 be can hot resistance the which in lamps tungsten in happens what is This increases. resistance the and decreases mobility carrier the increases temperature to voltage—Ohm’s law. the proportional is If current the constant remains temperature the long As as ers. carri the of velocity drift mean the changes simply voltage the changing so of current, independent is of carriers number conductor ohmic the an For Steady 3.8.2 long life. to ensure cleanly and rapidly 3.12 Figure occurs in transition to arc glow the that to ensure work together designers lamp and Ballast available. voltage circuit open the and quality processing fill, lamp design, trode to elec related factors to many sensitive is arc the glowthe to from transition of speed The used. are ignitor of pulse Various immediately. types restart some tens of require kV to will off it on turning atmospheres; many may be pressure the stabilized has lamp HP an After needed. are some kilovolts ofPa region (0.1 the in voltages bar), breakdown 10 around is pressure cold the when from Starting 10 Discharges show strongly nonohmic show strongly Discharges option. not is an preheating For lamps, HP 5 Ω i/A) –2.0 c haracteristics 10 3 s Ω tate e tate 0.0 Ar 10 Ω lectrical lectrical c 2.0 behavior behavior - - - - 4

Downloaded By: 10.3.98.104 At: 19:06 24 Sep 2021; For: 9781315157009, chapter3, 10.1201/9781315157009-3 V voltage increases into a region where d where aregion into increases voltage the resistor voltage V voltage resistor the stable unless there is a ballast in the circuit. the in aballast is there unless stable not is but this characteristic, resistance a positive alowglowhas CF. has region which abnormal The regime, arc to the atransition makes and ionically therm to emit begins cathode the and temperature cathode the increases ion bombardment resulting CF. the The across dropped is voltage lamp of the major part the regions, abnormal and normal the glow the abnormal called is This increases. terminals the across voltage the and to increase has density current the point, At this as well. the leads often and area cathode the all covers finally glow the further, rent increased is cur the As regime. glow the normal called is This constant. is cathode of the surface at the density current the that implying constant, remains age volt the whilst area in increases glow the current, the increasing On cathode. on the visible is glow a which in to aplateau region decreases voltage the of current low from values Increasing nitude. orders over of mag many increased is current the low. comparatively is age 3.12 volt end of lamp Figure hand where the right the arc on region the to corresponds This small. quite usually is current of with voltage decrease rate Theof V–I characteristic. or falling negative, so-called the is This terminals. their across age volt the by respond decreasing discharges cathode hot current to increasing response In current. the aballast called impedance d 3.13Figure stabilizing ballast resistor. The voltage across the circuit is now the sum of the lamp voltage V voltage lamp the of sum the now is circuit the across voltage The resistor. ballast stabilizing a of effect the (b) zero. Shows to decrease or limit without increase to current the cause would tions R n

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) is needed needed Ris resistance aseries For discharge adc Despite what the manufacturers’ data sheets sheets data manufacturers’ the what Despite V otential S 3.8 discharges of characteristics Electrical (V dn ) e /dt >0 dn dn Cu VV e e rr /dt =0 /dt <0 TS en = t i(A) T then –( IR V V V R V) T R + V (3.16) T T and and - 59 ------S

Downloaded By: 10.3.98.104 At: 19:06 24 Sep 2021; For: 9781315157009, chapter3, 10.1201/9781315157009-3 The total circuit voltage V voltage circuit The total resistor. ballast 3.13bseries of a effect shows the Figure extinguishes. discharge the and decreases current the production, exceeds loss the line the below is voltage applied the If to increase. ues circuit voltage moves into a region where moves voltage d aregion into circuit total the then to increase, current the causes tion afluctua If current. supply at voltage acertain of points for which d forof which points the locus is 3.12).end of Figure characteristic This hand right of the (part characteristic arc falling Waymouth [2, 2]. Chapter 3.13a Figure shows the by given argument an by using explained consider. can user the that an option is this applications for specific 60 can also provide programmed start and run-up run-up and start programmed provide also can circuits electronic efficiency; PC in increase an and loss electrode in of reduction because tion UV produc of improvement efficiency an is in therelamps in fluorescent of benefits: number a are there ballasts, magnetic than expensive more Although power supplies. electronic from voltage. mains rms of the about half not should exceed voltage lamp rms the inductance, a series with supplies on mains ac ity For likely. stabil less is extinction so rent reverses, cur the that time at the available is voltage large a that mean circuit inductive an in relationships The phase extinguish. will lamp supply the voltage the exceeds voltage restrike this If cycle. previous the of part latter the during decayed has it after density electron to restore the needed is voltage extra This zero. current after voltage restriking At 50 ballast. a resistive for waveforms on afluorescentlamp current and 17].Chapter 3.14 Figure voltage lamp shows the [3, ballasts as inductances magnetic supply using mains ac the from operate lamps Commercial lossy. but are work satisfactorily, ballasts Resistive AC 3.8.3 the current again. current the age decreases so that d that so decreases age volt circuit total the then decreases, current the < d increases this and increases, current the so loss, the exceeds of ionization rate more the the line this n 0, thus immediately decreasing the current. If If current. the decreasing immediately thus 0,

e The reason for needing a ballast is best best is ballast a for The needing reason Most lamps are now to operate are developed Most lamps Incandescent, discharge, and arc lamp sources /d t , with the result that the current contin current the that result the , with o peration n e n Hz there is an appreciable an is there Hz /d e /d T t

+ = t

IR 0. The further above further The0. > 0, thus increasing increasing thus 0, now intersects the the now intersects n e /d ------t waveforms is caused by oscilloscope digitization. byoscilloscope caused is waveforms 50 of frequencies at operated lamp afluorescent for waveforms 3.14 Figure ceptible 50 or 100 50 ceptible no per is there prolong life; that lamp sequences lamps. of tungsten-halogen stability excellent already to control the used be also can device A similar System). Control Intensity Light Instruments, (Appendix—Oriel lamp power the into the adjust it to using output and light the by measuring achieved be also can improvement stability in [20]. reversal on current A great termination movement reduce the arc of the can waveforms wave supply square modified found that been movement. arc It recently in has resulting tion termina cathode the in changes by small caused is this of two. percentby a Part or fluctuates benefits. important power (andcontrol color) lamp thus are over life to ability the and of flicker lack the discharges, of 90–500 region the in frequency at times transition fast wave with square dc—a acommutated from lamp the to operate then is [19]. arc of the distortions option electronic The movements or gross in result that resonances tic acous cause can frequencies at high operation at 50 forms Figure peak. restrike no is there and frequency; at high circuits electronic 09 09 The optical radiation from discharge sources sources discharge from radiation The optical

V Measured voltage and current i kHz. In the case of HP discharges, discharges, of HP case the In kHz. 0 0 50 and Hz Ph Hz flicker from lamps run from run fromlamps flicker Hz i as e angle(º V 180 180

3.14 shows typical wave 3.14 typical shows kHz. Noise on the the on Noise kHz. ) 50 kHz 50 Hz 270 270 Hz. For HP Hz. 360 360 - - - - Downloaded By: 10.3.98.104 At: 19:06 24 Sep 2021; For: 9781315157009, chapter3, 10.1201/9781315157009-3 and an increase in peak radiance. peak in increase an and radiation wavelength short of the enhancement an due to usually is The result state. steady in than values higher substantially reach can temperature electron that output are or transient pulsed using of effects The accordingly. constructed be must electrodes and of amperes thousands may reach currents Peak lamp. the through a capacitor ing by discharg is Operation of hertz. up to hundreds frequencies repetition with order of microseconds the is of flash the of duration The studies. entific for sci source atransient as and beacons warning for as photography, used pumping, tube laser [21].tion the xenonflash is example The obvious opera for pulsed designed are of lamps A number Pulsed 3.9.1 3.9 range from about 10 from range pressure the DBDs in operated may be processes. for photochemical radiation UV far generating and for for generation ozone purification water as such processes industrial for large-scale used DBDs have been discharge, ofA form transient 3.9.2 uniform luminance of > luminance uniform up to 540 diagonals format with square in made are lamps efficiency. At present, luminous of reasonable area tile-shaped lit formly uni a very provides This developed. been has lamp The discharge therefore comprises a series of series therefore a comprises discharge The pulse. next for the conditions starting the viding pro decays, the ionization period off the During time for a lasts discharge The to cathode. up, anode from charges anode the when then, and anode to cathode from first flows current Electron field. theelectric reversing finally and reducing thus surface, up the charge anode at the arriving gap. the Electrons breaches that avalanche an form and anode the towards accelerated are electrons pulse, voltage ahigh applying On glass. as such strength breakdown of high insulator an with ered cov is one of at which least electrodes, two between (of pulses applied voltage some kilovolts) are High [23]. Osram) Recently a DBD light source, the Osram Planon Planon Osram the source, aDBD light Recently The operating principle of a DBD is as follows. of a as follows. principle DBDis The operating EXCITATION DISCHARGES OF OTHER METHODS OF Dielectric Dielectric l ight s ight 2 to 10 to b arrier d 6000 cd m cd 6000 ources 5 Pa [22]. Pa ischarges −2 mm having a having mm (Appendix— ~ μ s. s. ------with Xe at about 1.4 with filled and sealed is whole structure the and spacers by apart are held two plates The efficacy. for high necessary is that sequence pulse optimized the to produce power supply designed electronic an from is operated lamp The illumination. uniform in very results structure electrode of form This ers. lay barrier to the form glass with coated are trodes elec Both deposited. is structure anode a metal with interlaced cathode lower ametal the plate, On UV production. of efficiency high to leading favored, is molecules atoms and rare-gas of states of resonance excitation the of this Because electrons. energy high many are there which in distributions energy non-Maxwellian extremely on. DBDs have turned is pulse the time every occur Microdischarges spacing. electrode to the equal approximately extent lateral with microdischarges 9600 lm. The Osram Endura or Icetron lamp which which lamp or Endura Icetron Osram The lm. 9600 and 2800 between packages lumen with fixtures high-bay be will these Typically fixtures. cessible of 100,000 a life with QL which, Philips versions are Other compactness. and supply. ofarelife the long Benefits impedance internal the of the result is ballasting The coil. the surrounding in a torus to flow acurrent causes This direction. azimuthal the in avoltage induces about 2.6 of frequency at a driven centeris the in coil The example. compact 3.15Figure shows aparticularly discharge. fluorescentlamp on the variants are [3, 11]. Chapter manufacturers major lamp the All from commercially have available become lamps coupled of inductively anumber decade, last the In by Excitation 3.9.3 excimer excimer function copiers. function multi in used are technology same on the based lamps Cylindrical a requirement. is luminance high and where auniform equipment applications equipment. of office confines the in it does as cold weather outside in well as just works lamp the so temperature lamp of the independent almost theis output that ofuse Xe means The tion. radia to visible UV the converts walls inner the at about 172 Phosphor UV nm. on vacuum the in 3.9 The Planon lamp is formed from two glass plates. plates. glass two from is formed lamp The Planon The main applications are in displays and office and office displays in are applications main The discharges of excitation of methods Other m Xe MHz. The rate of change of magnetic flux flux magnetic of rate change Theof MHz. icrowaves ∗ 2 (excited dimer) that radiates efficiently efficiently (excited radiates dimer) that × 10 h, is designed for use in inac in for use designed is h, 4 (100 i nduction and by and nduction Torr). an Xe forms 61 - - - - - Downloaded By: 10.3.98.104 At: 19:06 24 Sep 2021; For: 9781315157009, chapter3, 10.1201/9781315157009-3 an impedance R is circuit the of primary The coil. excitation the L inductance with atoroid is plasma the that shows left the on diagram schematic The (GE Genura). 3.15Figure 62 lm W lm 100 [24] reaching LED assemblies trichromatic Already distribution. Planck by the not limited therefore is radiance maximum the random; from far is region recombination the into carriers the motion of the LED, an In randomized. motion is theelectron that is The reason temperature. tron elec at the radiance body black by the limited is lamps conventional by light The of generation about LEDs. information 10Chapter detailed gives 3.10 S by emitted is radiation the which in discharge fur pioneered sul a has HP Fusion Lighting charges. of 80,000 life arated and lm of 8000–12,000 packages and cacy effi higher has configuration torus astretched has in many other LED publications, if this is the flux flux the is this if publications, LED other many in power dissipated in the plasma. the in dissipated power the on depends which impedance, plasma the of distribute the light efficiently around buildings. around efficiently light the distribute to used be can means optical that means sources such of radiance high The very buildings. large ing light in used is source the so high very are levels of of generation microwave power. output Light efficiency poor relatively of the because reduced is efficiency The overall source. light white other any up to be 170 than can watt—higher lm/microwave of generation efficiency the Kand of 6000 region induction coil holds Re-entran and Hg wi dose Bul a 2 and resistance R resistance and molecules. The light is white with a CCT in the in CCT a with white is light The molecules. th Kr

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+ jωL 1 - - - - - single LED approaches the level of flux required, required, oflevel flux approaches the LED single No LEDs. from flux low luminous the is issue the however: fromclear far is future The cent lamps. ofday present fluores efficiency the of exceeding possibility Much of made the is premises. mercial other com and offices for lighting lamps rescent of fluo huge replacement numbers of the the be too expensive. not is substitution the long as as by LEDs replaced now probably be can lamps conventional levels, low relatively flux requiring application any In etc. lighting, path stairwell, desk, interiors, car as such inroads, make will where LEDs lighting task ized local highly as such markets niche other also are There light. of using ways new produce interesting to designers stimulating are properties where their lighting artistic and aesthetic decorative, in cations signs. transport air and sea land, in market lamp signal of the a complete takeover see to expect we so can systems, LED of the cost extra pay for the advantages these All improved. is safety so signal, traffic of the complete failure the to cause not have does LED of an failure catastrophic that is advantage further A lights. traffic conventional with compared costs maintenance reduces cally dramati which long life, their is advantage main But the damage. without switched frequently be may they and wind, and traffic of heavy aresult as experience they vibration the to withstand suited well GW [4]. particularly Moreover, are LEDs the by reduced 0.4 be would consumption electricity LEDs, the to USA in were converted lights traffic all if that estimated It been has consumption. at met much be therefore lower power can ues val luminance signal recently. The required until used lamps tungsten filtered the with compared as needed, wavelengths at the only colored light the LEDs generate The signals. traffic is example ous The obvi lamps. to conventional superior far are LEDs where areof applications a Therenumber businesses. manufacturing lamp conventional the needed. it is where to more efficiently directed be can light the that low 3.3.3) means étendue (Section which their is applications for many of LEDs advantage further A 3.3.5. Section mentioned in lamps triphosphor to the similar colorimetrically are lamps these that watt.)plug Note wall per or flux watt lamp per The ultimate target for the LED industry must must industry LED the for target ultimate The appli many now are finding LEDs light White on impact asubstantial made have already LEDs ------Downloaded By: 10.3.98.104 At: 19:06 24 Sep 2021; For: 9781315157009, chapter3, 10.1201/9781315157009-3 the case of fluorescent lamps, most of the material thematerial of most of fluorescentlamps, case the In lamps. the to make used materials of the cost the may to come down scale on aglobal equivalents LED replacement so, ofby fluorescent If lamps els. lev to comparable by competition down driven be will industries both in costs manufacturing that expected is It dependent on flux. weakly very is lamps conventional of making cost the whereas flux, with linearly approximately increases source light LED an of making cost the that is fact hard the But installations. LED for required levels flux may reduce the étendue advantage the although levels, flux required to produce the LEDs many require will installation competitive any so REFERENCES 5. 4. 3. 2. Welch Allyn Ushio Toshiba Lighting Stanley Philips Lighting Oriel Instruments Osram Iwasaki Heraeus Noblelight Harrison Electrical GE Lighting Fusion Lighting Ealing Electro-Optics Cathodeon 1. Arnold). Lighting and Lamps 1983. A.M. Marsden, and M.A. Cayless, York:(New Wiley). Lighting to Solid-State Introduction 2002. R. Caska, and Shur. A., M.S. Zukauskas, (London: Arnold). lamps) of spectra range wider and more includes Marsden and byCayless edited Lamps and Lighting and Lamps 1997. A.M. Marsden, and J.R. Coaton, Lamps J.F.Waymouth, 1971. Electric Discharge Macmillan). W. 1972.Elenbaas, Light Sources (Cambridge: MIT Press). , 3rd ed. (London: (London: ed. , 3rd edition 3rd (the ed. , 4th Lamps forspecialapplications Wide rangelampsforaudio-visual,entertainment, Full rangeoflampsforilluminationandspecialpurposes Cold cathodefluorescent Full rangeoflampsforilluminationandspecialpurposes Lamp units for integration into optical systems, spectra of lamps Full rangeoflampsforilluminationandspecialpurposes Full rangeoflampsforilluminationandspecialpurposes Special lampsmainlyforindustrialandscientificprocesses Cold cathodefluorescent Full rangeoflampsforilluminationandspecialpurposes Microwave discharge lamps Lamp unitsforintegrationintoopticalsystems Lamps forscientificinstruments (London: photographic, scientific/mediaandindustrialprocesses

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