Radial Cataphoresis in Hg-Ar Fluorescent Lamp Discharges at High Power Density

Transcription

1 [NWP.19] Radal Cataphorss n Hg-Ar Fluorscnt Lamp schargs at Hgh Powr nsty Y. Aura, G. A. Bonvallt, J. E. Lawlr Unv. of Wsconsn-Madson, Physcs pt.

2 ABSTRACT Radal cataphorss s a procss n whch th lowr onzaton potntal atoms (Hg) ar prfrntally onzd and xplld from a mult-componnt (Hg-Ar) dscharg. Ths procss s mportant at hgh powr dnsts whch occur n som typs of fluorscnt lamps (.g. th lctrodlss Endura/Ictron lamp dvlopd at Osram Sylvanc Inc.). Rcnt attmpts to rconcl xtnsv absolut masurmnts on Ictron lamp dschargs wth slf-consstnt numrcal modls wr only partally succssful [2]. Radal catphorss as wll as som othr hgh powr dnsty phnomna nd to b r-xamnd. W hav st up an axal absorpton xprmnt at 185 nm on th ground lvl Hg atoms n an opratng Ictron lamp. Th Hgh Snstvty Absorpton Spctroscopy (HSAS) faclty at th Synchrotron Radaton Cntr n Stoughton WI s usd n ths study. Th HSAS faclty provds an ntns synchrotron radaton contnuum, vry hgh spctral rsolvng powrs from a 3 m focal lngth vacuum chll spctromtr, and suprb S/N ratos from a CC dtctor array. Prlmnary rsults wll bprsntd and dscussd. [1] Supportd by th NSF amp; USHIO Inc. Exprmntal lamp provdd by OSRAM-SYLVANIA Inc. [2] J. J. Curry, G. G. Lstr, J. E. Lawlr, J. Phys. : Appl. Phys. 35, 2945 (22)

3 Exprmntal Lamp Exprmntal lamp has two flat HIGH QUALITY Suprasl wndows at th nd of on arm. No phosphor Ar 4Pa(3mTorr) + Lqud Hg Hg prssur s controlld by tp tmpratur cm INLET WINOW OUTLET WINOW SR BEAM To SPECTROMETER TIP

4 Th Hgh Snstvty Absorpton Spctroscopy (HSAS) faclty Th Hgh Snstvty Absorpton Spctroscopy (HSAS) faclty at th Synchrotron Radaton Cntr n Stoughton WI Lght Sourc : Synchrotron radaton (SRC) Spctromtr: Sya-Namoka + vry hgh spctral rsolvng powrs from a 3 m focal lngth vacuum chll spctromtr tctor : suprb S/N ratos from a CC dtctor array. Lght path : Vacuum or N2 flushd (Lamp Box) Sya-Namoka spctromtr Synchrotron SRC@Stoughton,WI 3 m focal lngth vacuum chll spctromtr

5 Poston of masurmnts Lamp s on mchancal translaton stag Masur n two dm., vrtcal and horzontal. Synchrotron Radaton (SR) gvs bam dvrgnc and cross scton (bam ~Ф1mm) UPWOR +.9 [Inchs] SR BEAM -.9 INSIE OUTSIE -.9 OWNWOR OUTLET WINOW

6 Spctrum Analyss (1) Problm : Establshng a rlabl zro absorpton background Whn th lamp s off, thr s stll Hg vapor whch absorbs th SR bam. If th lamp s rmovd from th optcal path, th algnmnt s changd and O2 absorpton bcoms a problm. Soluton Assum ntnsty of th SR s th sam at narly wavlngths. Background spctrum can b masurd wthout turnng off th lamp. Absorpton I Hg Hg [ SR + Lamp] = [ SR + Lamp] S S 1/ 2 6 Spctrum 1 λ λ P sp bg P 1/ 2 [ Lamp] [ Lamp] λ λ sp bg 185nm 194.2nm Hg Hg + on Absorpton spctrum 185nm 194.2nm Background spctrum 186nm 193nm

7 Spctrum Analyss (2) Transmtanc.6.4 A B Ar Transmtanc.6.4 A B Ar Pxl Hg Absorpton spctrum 185nm Pxl Hg + Absorpton spctrum 194.2nm

8 Curv of growth Equv. Wdth [mk] Equv. Wdth [mk] Column nsty [ x 1 15 cm -2 ] Curv of 185nm Column nsty [ x 1 11 cm -2 ] Curv of 194.2nm

9 Hg + Ion dnsty vs. poston cold spot tmpratur = 5C wth varous currnt Horzontal strbuton of Hg + on nsty Cold spot 5C 3A 4.5A 6A 7.7A Vrtcal strbuton of Hg + on nsty Cold spot 5C 3A 4.5A 6A 7.7A Hg + on nsty [1 14 cm -2 ] Hg + on nsty [1 14 cm -2 ] poston [nchs] Insd Outsd poston [nchs] Bottom Top

10 Fttng wth Bssl functon Assum cylndrcal symmtry and lowst ordr ambpolr dffuson mod Hg + on dnsty dstrbuton can b wrttn as a Bssl functon nsty [1 14 cm -2 ] ata Bssl Functon nsty= n J ( x) = k= J ( x) k ( 1) k! Γ( k + 1) x 2 2k stanc [nchs] UP OWN Bottom Top

11 Hg + Ion dnsty n vs. Lamp Currnt cold spot tmpratur = 5C wth varous currnt nsty n [1 14 cm -2 ] Hg + on dnsty s almost lnar to th lamp currnt Lamp Currnt [A]

12 ata for ffuson Equatons N px = k Hg Hg d nhg dn N = a dr N dr a 2.42r ( T, r) = NHg( T) nj R = ρk T P k kt 1/ 2 P 3/ 2 k = Hg + ION dffuson coffcnt Assumpton T=1V=116K n=n Hg Nutral Hg dffuson coffcnt 21 ρk n T k 1/ 2 T R r NHgo Ambpolr Hg dffuson coffcnt a a = cold spot tmpratur [K] T >> Radus =.9 [nchs] Poston of radus [nchs] # n vapor prssur + + kt + + >> T T T

13 Nutral Hg dnsty vs. poston cold spot tmpratur = 5C wth varous currnt Horzontal strbuton of Hg nsty Cold spot 5C Vrtcal strbuton of Hg nsty Cold spot 5C 3A 4.5A 6A 7.7A 3A 4.5A 6A 7.7A Hg nsty [1 16 cm -2 ] Hg nsty [1 16 cm -2 ] poston [nchs] Insd Outsd poston [nchs] Bottom Top

14 Comparson wth Calculaton usng dffuson quatons Horzontal strbuton of Hg nsty Cold spot 5C Vrtcal strbuton of Hg nsty Cold spot 5C A 4.5A 6A 7.7A 3A-smulaton 4.5A-smulaton 6A-smulaton 7.7A-smulaton A 4.5A 6A 7.7A 3A-smulaton 4.5A-smulaton 6A-smulaton 7.7A-smulaton Hg nsty [1 16 cm -2 ] Hg nsty [1 16 cm -2 ] poston [nchs] Insd Outsd poston [nchs] Bottom Top

15 Concluson nsty dstrbuton can b masurd by usng th Hgh Snstvty Absorpton Spctroscopy (HSAS) faclty Hg and Hg + on dnsty dstrbuton shows thr s radal cataphorss n ICETRON lamps. Hg dnsty dstrbuton s consstd wth Hg+ on dstrbuton and dffuson quatons.

16 Futur work ffrnt cold spot tmpratur analyss Corrcton of modl for lamp shap Incluson of ffcts from gas hatng Spcal thanks th NSF; OSRAM-SYLVANIA Inc. ; USHIO Inc. r. P. Moskowtz, OSI r. J. J. Curry, NIST