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(1)d. Relation between the Atmospheric Pressures and the Min. Potential for Formation ' of Lichtenberg Figures By. '. Bunji ARAI Institute of Tchnology. (Received Ma¥ 29, 1965). Synopsis The authors observed that the Lichtenberg figures appeared when photo. films were used, and even under 1.4 (kV) in reduced atmospheric pressure. Again they experimented in the various reduced atmospheric pressures. They found that the minimum potential for formation of the Lichtenberg figures was 1.1 (kV) for both figures, and these were almost independent of reduced pressures in these studies. But the size of both figures was enlarged by the. reduced pressures. When the atmospheric pressure was reduced, the shape the positive Lichtenberg figures became wider in width, longer in length,. e. l. smaller in branches as well as in numbers of the dendritic streamers. Especially, they discovered the small branches at the tip of each wide streamer under the atmospheric pressure at about 15 (cm Hg). Besides,in thenegative Lichtenberg figures the shape changed from the radial ordered short straight streamer to the uniform diffused circular form. In the lower crest voltage, they observed an circular dark ring around the bar electrode. Also they caught a wave form of a supplied impulse voltage by the PULSCOPE and photographed it at the same time with the Lichtenberg figure. From the analysis of the wave forms of supplied impulse voltage got by the PULSCOPE, they observed that the value of wave front and the wave tail were from O.05 to O.17 (ptS) and from O.10 to O.45 (ptS), and most frequent occurrence value were O.08 (ptS). and O.30 (ptS) respectively. The gradient of the crest voltage (dE/dt) was about 2×107 (kV/S).. 1 Introduction The Lichtenberg figures were marked by the supply of an impulse voltage on an emulsion surface of photo. dry plates or films. But the authors and others discovered that more than some crest values impulse voltage had been needed for formation of Lichtenberg figuresi). The fact was that the figures did not appear untill the supplied impulse voltage had attained some potential..

(2) 24 B. ARAI. .And then, they observed that certain minimum electrical energy was needed to produce the Lichtenberg figures. This phenomenon is physically a very interesting fact. This fact taught us that the crest value of the formation for 'the Lichtenberg figures had the threshold value of the electric potential. During their former studies2), from the enlargement of the Lichtenberg figures taken 'in the reduced atmospheric pressure, they thought that the lower threshold 'value would be given in the reduced pressure.. They thought that knowing the details of wave forms for the impulse. .. 6. voltage supplied when the Lichtenberg figures were marked may be given some important facts about mechanisms for the formations of the figures. So they tried to record the condition of the impulse voltage supplied in reality, that is. the change of the voltage with time (form of the impulse voltage) bY the. direct ways. For this purpose they took up the PULSCOPE. Because the PULSCOPE (a kind of a Synchroscope) could catch the change of the non repeated and very fast electrical transient phenomena.. To investigate the minimum electrical potential and form of impulse voltage which was necessary to make the positive or the negative Lichtenberg figures on the photo. films under the reduced pressure, the experiments were ta.ken as follows.. 2 Apparatus and Experimental Procedure 2.1 Klydonogrmph camera and photo. Mms used A KIydonograPh camera was the special camera which was used in the 'former experiment for the Lichtenberg figures. This was reconstructed from. the MALCAFLEX (Brownie size refiex) camera. This camera was required .not only to keep light tight but also to have enough dielectric strength for .high tension, Refer to Fig. 2 in p. 23 of the former report3) with the detail ･of this construction. For same reasons described in the experiments, they took a Brownie size roll (6.0cmx80cm) for 12 exposure of the FUJI X-ray indirect photographing film (FluorograPhy). They used 24 times impressed voltage or more than that as the figures were small in size, and for as many figures as possible in a series of the same emulsion surface on one roll film.. .. (. 2.2 Equipment for reducing pressures . The KZydonograPh camera loaded with the roll film was put 'in a vacuum desiccator with three holes in it. The two side holes plugged in the rubber spigots respectively, which through the copper leading wires, connected to the terminals of the camera, and the other holes on the upper side connected to 'the vacuum pipe. The atmospheric pressure in this desiccator was extracted through the trap by the GAEDE's rotary air pump.. The desired pressures were -adjusted by the leak cock. The reduced pressure was read by the Bourdon'tube gauge (metallic manometer), and the fine reading of pressure was given by the open tube mercury manometer. Refer to Fig. 1..

(3) Pressures and Min.. r. ct¥gH!CEIm.. Nes. .e. ". ,. N. ,. op ,sf. Potential of Lichtenberg Figures 25. '. i. s3'' i iilliiiil"i [ L ,fsB t. 'P iii;{ii･tsl[ ,.ilillil.tsp,u.p S2. R, D. C3 '. P. '. oo. Fig. 1.High tension impulse circuitand equipment for reducing pressures. Ci, C2, C3: High tension condensers [Tokyo-Shibaura Electric Works, 5 (pt F)]. " respectively. Si, S2, S3: Combined knife switches. M: Handdriven Megger [YEW, type L-5, 1 (kV)]. Vs: Static voltmeter [YEW, type EP-J]. 'R : Discharging resistor [Shimada Rikakogyo K.K., SPC Metalohm RS 2D]. r: Resistance for damper of impulse wave., P: PULSCOPE [Ando Denki K.K., type BP-2305]. [reduction ratjo 10:1, type PB-2]. p: Probe. K: KlydonograPhcamera. D: Vacuum desiccator with three Bourdon-tubemanometer. O: Open tube manometer. L: Leak cock. Tr:Trap.. holes.. -B :. 2.3 High tension impulse circuit Theformer impulse circuit was used in this experiment. That consisted ef three hightension condensers; C,, C,, C,, three kinds of switches; S,, S,, S, a series of discharging resister R, and resistor r'for damper of impulse. These condenserswere charged in parallel connections with the switch Si by the hand driven 1000(V) Megger (YEW, type L-5). Next Si off, S2 on. The three condenserswere connected in series. The high tension source was given by such method. Its potential was read by the static voltmeter V. (made in the YEW). This range was from O to 3.0 (kV). Discharging resistor was the non inductive metal coating resistance (SPC Metalohm RS 2D 10%) which was. made by the Shimada Rikakogyo K.K. The value of one resistor was 1±O.1 (k9). These resistor were used with the series connection of 10. Both termi-. nals of the KlydonograPh camera put in the vacuum desiccator were connected in parallel onthis discharging resistor. The small series resistor r in this. was used not only for damping resistor but also for changing impulsecircuit ' the gradient of crest voltage, by changing the value of resistor. These r's. wereprepared as 9.1 (k9), 4,9 (k9) of carbon coating resistance, 2.2 (k9) of carbon rodresistance and 12 (9) of metal wire resistance respectively..

(4) ￠. B. ARAI. 26. 2.4 Observations of impulse voltage wave forms and photography. They took up the PULSCOPE (type BP-2305, the ANDO Denki K.K.･･･ commercial name of the Synchroscope) for the observations of the impulse voitage wave forms. The terminals of the signal in this instrument were. -. connected to a part 1 (k9) from the earth side of the discharging resistor. In this experiment, the discharge resistance was used as the potential divider or. potentlometer. ･. ' In the PULSCOPE, the forcus and the astigmatism of the electron beam .. g. were adjusted sharply with the dials this instrument. The intensity dial was adjusted to max. brightness of the beam for very fast sweep of O.5 (ptS/cm), for following very fast phenomena. The scale illumination was adjusted for suitable lighting with the method of cut and try. As the input voltage was very hlgh. a probe (type PB-2, reduction ratio; 10:1) was connected to this. instrument. For the photography of the impulse wave form was used the CANON Osilloscope unit (CO-133-IV), with the CANONFLEX RP fixed. This lens was the SUPPER-CANOMATIC R, f=50 (mm), F=1.8. As the motion of the bright spot was very fast, they photographed as follows for getting a clear. wave form of impulse voltage. The F number of lens was set at 1.8 and the shutter at B.. 2.5 Treatment of photograph The FUJI X-ray indirect photographing films were developed by the FUJI RENDOL of the indicated developer in the developing tank at 200C, for 6 minutes, and fixed by the FUJI FIX, 200C, for 15 minutes. After washing it in the running water for 1 hour, and desiccating with natural drying after it. was immersed for 30 seconds in the DRYWELL (a commercial name for a kind of a surface activator).. The FUJI NEOPAN SSS 35 (mm) roll films were used the photography of the impulse wave forms. This film is of max. sensitivity (ASA 2000) in this country now. As higher sensitivity for these films was needed, they were developed by the FUJI PANDOL in the developing tank at 200C, for 18 minutes. The sensitivity of these films was increased as high as ASA 12000 by the extension of developing time interval. And then some of these films were developed by the sPecial develoPer of high sensitivity and high resolving power.. It was made by the favour of the FUJI PHOTO-Film Research Laboratory. The sensitivity of this films was increased as high as ASA 18000, by using this special developer. These treatmentswere done to observe the fine structure at fast variation of the gradient of crest voltage.. 3. Expeimental Result and Discussion. 3.1 The relation between the reduced atmospheric pressure and min･ potential for Lichtenberg figures In this experiment, the atmospheric pressure was tried on the reduction. A.

(5) Pressures and Min. Potential of Lichtenberg Figures 27 only, and not on the compression. The authors investigated the Lichtenberg figures of the polarity which were given in various reduced pressures; -20,. -40, -60 (cm Hg), and the various crest voltages, 1.5, 1.4, 1.3, ･･･ 1.1, 1.0 (kV).. a. When the values of low crest voltages were supplied to the terminals of the･ KlydonograPh camera, and in such case the Lichtenberg figures did not appear. on the emulsion surface. ･ ft. The first stage of this experiment was tried with the ciruuit of r=:O.. They obtained the minimum potentials in various reduced pressures for forma-tion of the Lichtenberg figures in the repeated observations. These results are･. shown on the Table 1 (a) and (b). In this Table are shown the numbers of thefigures formed by the supplied various crest values of impulse voltage, those of figures which were not formed, and the rate of the formations of the figures.. ･ Table1.Relationsbetweensuppliedcrestvoltageandrate of formation of figures in various pressures.. (a) Positive figures. Na/Ns(%) Reduced pressure (cm Hg). v.(kv). Normal pressure. - 20. - 40. - 60. 55. 6. 63. 7. 44. 4. L5 L4. 88. 9 69. 2. 28. 6. 44. 4. 33. 3. 1. 3. 57. 1. 26. 6. 35. 7. 26. 6. 1. 2. 17. 6. 20. 0. 16. 7. 16. 7. 10. 1. 1. 9. 1. 1. 0. (b) Negative figures. Na/Ns(%). '. Reduced pressure (cm Hg). v.(kv). Normal pressure. - 20. - 40. 100. - 60. 1. 5. 100. 88. 9. 1. 4. 100. 75. 0. 85. 7. 70. 0. 90. Q. 1. 3. 60. 0. 70. 0. 63. 6. 38. 5. L2. 27. 3. 8. 3. 27. 3. 15. 4. 1. 1. 9;1. 25. 0. 1. 0. Vs: Supplied crest voltage.. Na: Numbers Ns: Numbers. of figures formed by Vs. of supplied impulse voltage. Na/Ns: Rate of formations of figures. .. 14. 3.

(6) 28 ' B. ARAI. The rate of the formations was calculated by the ratio (shown in percentage) ef the numbers of the formation of figures and those of the supplied impulse VOit engetSie p6siti"e figures, the min. potentiai was i.2 (kv) in normai pressure. and -20 (cm Hg), and 1.1 (kV) in the pressures of -40, -60 (cm Hg). In the negative figures, these values were 1.2 (kV) in -40 (cm Hg), and 1.1 (kV) in the normal pressure, -20, -60 (cm Hg) respectively. They observed that the fall of value of min. potential was not,caused by -the reduced pressures. The results of this investigation compared with the 'former results showed the lower valtie, but the rate of the formation of the. -. .4. figures was very small. But the figure though obtained only once, the potential. must be recognized as the value of the formed figure. Fig. 2 showed these .relations, between the rate of the formation of figures and the supplied crest. voltage.･ The parameter was the pressure. -. IOO. A v 80 i. o----o. :,22(c::,n Hs./). ￠ 60. /. e. . co. ･ac. 40 .e･･oe... )?> 20. L. '. .c(;t. tV"V 6O. tt. tr 2 c'ill`. <'Eli"'. ?. AS. 1. f tfs. ,/J)Y. - -... e. vt. i so. cF----o. o-----o -60 ,,. dw. too. H Norm a( preSS.. lti. ,' l. ,,1 6/. 40. g,t ,,. /t/I /;22; /y'b/. ,cefl-.. o. /. ". o. f.O t.2 L4 LO 1.2 L4 ' v(s-.(kv) ' v{;-----.-(kv)･'. Fig. 2. Relations between V. and Na/Nsboth for Lichtenberg figures.. Vs:Suppliedcrestvoltage.The parameterwasthepressure.. 3.2Changeoffiguresbysuppliedcrest voltageandreducedpressures They observed and measured the Lichtenberg figures which were enlarged 'to 5 times. These figures formedlowbycrest voltage were comparatively small. The relation of the supplied crest voltages and the max. Iength of the. streamerinthevariousreducedpressures were showninFig.3,4,5,6.They Lobserved that the fiuctuations of the lehgth of negative streamers were included clearly inthepositiveone,butthesewere separatedfromthegreupsofthe.

(7) Pressures and Min. Potential of Lichtenberg Figures 29 '. f5 N.!Hli:g-N･-t---?H ' lrs -F-+..P--.-. > ' M C'--"--O At･4 F6IHt!.!ssH--`----+-H ilS)t`4. ". '. e-----. IIfi･3 "kl'Lzs-'d--Hi ' ¥1･3 .-U:b---'i---i. sl311i .O '" ･ {l2I12, .-E'I'--"'--" .J. p. '. t･O 024 1.0 '. '. o246. Max･ Ra4. of Ft's. -(mm) Maxt Radd of Fi3. --.(mm> Fig. 3. Relations between supplied Fig. 4. Relations between supplied crest voltage and the max. radius of crest voltage and the max. radius of both' figures in the normal atmospheric both figures in reduced atmospheric. . pressure[--20(cmHg)].. pressure.. P: Range of fiuctuations in positive figures.. . N:Rangeoffluctuationsinnegativefigures. .. ' '. ･P. '. t･5 Nb-=e=6'}i-+--Hr ･N ' '. A L4. "v>. i sc. I,3 ,. I.Z. T. o----.-oF+----"'-d--l '. NF-F-d-･-H Hdi==.=6. 1'. M t.o. O24 68. Max. Rad. of Fis..(rnm) , i. Fig. 5. Relations between supplied crest voltage and the max. radius of both figures in reduced atmospheric pressure [T40 (cm Hg)].. P: Range of fiuctuations in positive figures. N: Range of fiuctuations in negative figures.. '. ' ' ' streamer respectively with the progress of the reduced pressure. The fluctuations of the positive streamer were wide in range compared with the negative one. In the values of over 1.3 (kV), the .ratio of the max. Iength of positive streamer R" and negative one R- was over or equal 2 (R"/R-l.l2)),but this relation was not obtained under 1.2 (kV). They thought from these facts that the mechanisms of formation of both figures would be different. Photo. 1-4 and 5-8 showed the series of typical positive figures and negative one formed by various crest voltage under various reduced pressures, and the forms of supplied impulse voltages.. '.

(8) 30. B. ARAI. N. t.5. S-v. t,4. O---:------. N. .----2t--.. F-------+-------.. 1. 1.3. }----l---------･-----H. L2. H O-o. t'f. o--o .t. lii. t.o. '. q. ' O,2 468 10 t2 ･ Max.Rad.ofFis,-(mha)' '. Fig. 6. Relations between supplied crest voltage and the max. radius of both figures in reduced atmospheric pressures [-60 (cm Hg)].. In the positive figure, when the crest values were lowered, the dendritic streamers became shorter in length, smaller in branches as wel! as in numbers. As the pressure was reduced, the shape of streamers became wider in width, round on the tip, narrower in the ,distance between the streamer and its neighbour. And they di$covered the small sharp branches on the tip of each wids streamer under the pressure about 50-60 (cm Hg). They observed that for this. phenomenon reduced pressure was most dominant effect than the wave form +of impulse voltage and the electrical charge. The coronet which appeared around the electrode was not formed in the normal pressure, but it was gra･dually enlarged in the reduced pressure. It showed the same tendency just like the negative figure under the reduced pressure. The negative figures were formed in the single circular form in all cases, but when the pressure was reduced it showed the enlarged diffused one. And the concentric dark ring around the electrode appeared. Especially, these rings were observed in the figures formed by lower crest voltage under high reduced pressure. Generally, the figures formed near the threshold potential were not sym-. rnetrical in both figures. ' 3.3 Analysis on wave form of impulse voltage. They caught the form of impulse voltage in the formation of Lichtenberg figures by the PULSCOPE at the same time under various conditions of pres-. sures. They observed how the wave forms of impulse voltage, which might ￡hange according as the Ktydonograph camera was connected in this circuit or not. No change was recognized in this result. Refer to Photo. 9.' As the wave front was very fast, the exact research was very difficult. The values of wave front ranged from O.060 to O.15 (ptS) and those of wave tail ranged from O.10 to O.45 (ptS). And most frequent occurrence values were ･O.Og (ptS) and O.30 (ptS) respectively. Refer to Fig. 7 and 8. In these diagrams. shown the relation between the wave fronts and tails for various supplied. ,.

(9) Pressures and Min. Potential of Lichtenberg Figures. P. L5. N. A>tc 1.4 ,. O･---d---o. t.2 O----------･---･K). t't. '. ww. O-.-D-. v1 t., sl?. 31. o---o. o. n - (Ms). O.1 O,2. Fig.7. Relations between Vs and range of fiuctuations in TF (wave front).. P: N:. Range of fluctuations in positive figures. Range of fluctuations in negative figures.. P. t.5. S) f･4. x 1.3. ¥ S5,. 1.2. o,-･!--o. Ll o. O.1. -. O,2 O.3 O.4 O.5 7+ --- (!AS). Fig.8. Relations between Vs and range of fluctuations in TT (wave tail).. P, N: Same i. notations in Fig. 7.. impulse voltage in the same circuit. The gradients of crest voltage in the whole experiment were about 2×107 (kV/S). In the wave front, they discovered the movement of inverse direction in which the gradient of voltage was very very large. They are investigating this phenomenon.. 3.4 Change of figures and impulse wave forms in circuit with series resistance ' Also they observed the relations between the change of the Lichtenberg figures and the supplied impulse wave forms. In this case the various series resistance r's in circuit were connected in this impulse circuit. This purpose ' the crest voltage. was for changing the wave forms, mainly the gradient of The values of these series resistance in circuit were 2.2, 4.9, 9,1 (k9) respec-. tively. Photo. 10, 11, 12 showed the typical ones. The series of those figures. were shown in various reduced pressures with constant r and the constant.

(10) 32 . B. ARAI. supplied crest voltage. Table 2 showed the change of the wave fronts, the wave tails and the gradients of the crest voltages at various r's respectivly.. Fig. 9 and 10 showed those relations between the impulse wave forms (TF and TT) and the series resistance r in circuit as in the diagrams. In' the diagram. .. the dotted line shows the non-existence of r. ' A '. '. '. Table 2. TF, TT and dE/dt for various series resistance r.. ''i. r (k9). TF (ptS) TF <ptS). 2. 2. 4. 9. 9. 1. O. 14,yO. 23. O.25NO.38. O.35NO.50. O. 30. O. 43. O.60･-O.75. O.79,-1.0. 1.G NI.2. 1.5×107. ･9. 0 × 106. 6.5×106. O. 18. TT (ptS). dEldt (kV/S). to. S. -. 8 6. !4. lt-H-Hel. 2. o. ww. --------'. O O･1 O.2 O.3 O.4 O.5 . 7it-----(MS). Fig. 9. Relation between series resistance r and range of fiuctuations in TF. Dotted line shows non-existence of r. ts. to. ew. 8. S6 tt-'N. ¥4,, H-FHt"HH. L2 HHH-H o. F-----------. o Fig. 10.. a2 o.4,a6 o.g l,o 7+ ----paS) ･ Relations between series resistance r and range of fiuctuations in TT.. 1. 2.

(11) if. Pressures and Min. Potential of Lichtenberg Figures 3$. ,. As･the results, they observed that both figures were contracted in their'' extension, and no change of figures was seen in the change of the impulse･ wave forms at this extent. Refer to Photo 13. But, in some of the negative･figures were observed bending dendritic streamers just like a supperposed. positive figure on the negative one. They are now investigating this cause.. May 27, 1965.. Acknowledgements. F. The writer wishes to expresses his hearty thanks to Dr. T. AsAHiNA and'. Dr. C.'MAGoNo who made suggestions to him throughout this work. The･ writer also thanks Mr. M. TAKANo (The Research Laboratory of FUJI Photo-Film Co. Ltd.) and Mr. M. HATTA for his cooperation in this research.. References 1) B. ARAi: Science Reports of the Yokohama National Univ., Sec. I-11 (1964), 21. U. NAKAyA: Butsurigaku Bunkensho (the corrections of the physical authorities),,n. II(1928),206. ･-. MULLER-HiLLEBRAND: Siemens Zeitschrift, 7 (1927), 547. 2) B. ARAi: Science Reports of the Yokohama National Univ., Sec. I-8 (1961), 31. B. ARAi: Japan. J. Appl. Phys., 30-3 (1961), 201. G. PRAToRius: Arch. Elektrotech., 34 (1940), 83.. F.H. MERRiLL and A. voN HippEL: J. of AppL Phys., 10 (1939), 873. J･ STEKoLNiKoF und K. RiAscHENzEF: Arch. Elektrotech., 26 (1932), 491. 3) B. ARAi: Science Reports of the Yokohama National Univ., Sec. I-11 (1964), 23". ,1. t.

(12) Plate 1. ts (k V) tr. 1.5 '. Z4. 1. 3. 1. 2. '. o. 2. 4. 6. 8 10(mm) o. 1. z. 3 (A S). Photo. 1. Positive figures in various crest voltage in normal pressure. and their oscillograms of supplied impulse waves..

(13) Plate 2. vg (kv) :. 1. 5 '. Z4 ･. Z3. f. 2 ). o. 246. 8 tO(mnt!>. o. I. 2. 3 (MS). Photo. 2. Positive figures in various crest voltage in reduced pressure. [-20 (cm Hg)] and their oscillograms of supplied impulse wave..

(14) Piate 3 Nls (k V>. ti. 1.5 a. 1. 4. 1. 3. 1`2. '. M. O510(mm) O 1 2･ Photo. 3. Positive figures in various crest vo!tage in reduced pressure [-40 (cm Hg)] and their oscillograms of supplied impulse wave..

(15) PIate 4. z4 難懸. L3. f．2. 匹1. 0 10 20（η7〃1） 0 1 2 3∼μS）. Photo 4 Posltlve figures ln varlous crest voltage ln reduced pressure. ［一60（cm Hg）］and thelr osclllograms of supplled lmpulse wave.

(16) Plate 5. 聡（髭V） σ. 1．5. あ4. 1．3. f．z. 置. 74. 0246（卿η） 0 7 2 3（μS） Photo．5． Negative figures in various crest voltage in normal pressure. and their oscillograms of supplied impulse wave．.

(17) Plate 6. V6（をy）. 」. 露5. 踊. z4. 払3. 孟2. ｝. 戸’. 0246（田〃7）. 0 7 2. 3（μs）. Photo．6． Negative五gures in various crest voltage in reduced pressure. ［一20（cm Hg）］and their oscillograms of supplied impulse wave．.

(18) Plate 7. vg (kv) eS. ,. le5 s. L4 ･. lt3. L2 '. o io(mm> o. -. 1. 2. 3 <lpt S). Photo. 7. Negative figures in various crest voltage in reduced pressure [-40 (cm Hg)] and their oscillograms of supplied impulse wave. K.

(19) Plate 8. Nls (kV). '. 1.5 '. L4. f. 3. L2. o. '. 1. f. o-/O(mvn) O t 2.3<],LtS) '. Photo. 8. Negative figures in various crest voltage in reduced pressure. [-60 (cm Hg)] and their oscillograms of supplied impulse wave..

(20) Plate 9. L:. '. '. o. 1. 2. 3 (ptS). Photo. 9. 0sc･illogram3 of impulse voltages, Klydonograph camera e. was connected in this circuit (upper) or not (under). In normal pressure, supplied cregt voltage 1.5(kV) respectively..

(21) Plate 10-1. u. p (cvn He). fs (kv5. u. 75-7. Z8 35 8. 2-8. t5･6. Z5 o. ,. o Photo. 10-1.. to. r. 2. 3 qs). 20 (m rn). Positive figures and their oscillograms of supplied impulse voltage in various reduced atmospheric pressures. Series resistance 2.2 (k9) connected..

(22) Plate 10-2. u. p (cm iilsll). ve (rv>. ag. 7S･7. z9. 3S8. 28. f5. 8. Z5. '. O"Oimm) O,---.-.-""/.- 2 3(>uS) Photo. 10-2. Negative figures and their oscillograms of supplied impulse voltage in various reduced atmospheric pressure. Series resistance 2.2 (k9). connected..

(23) Plat.e 11. p (cmi/st>. E. ts (kV). 75.9. z9 35.7. Z8. 157. Z5 75･7. zg 35'.7. Z8 o. e. t. 2. 3 ()xS). t5.7 >. Z5. o to zo(mm) Photo. 11. Both figuresandtheir oscillograms of supplied impulse voltage in. various reduced atmosphric pressures. Series resistance 4.9 (k9) connected..

(24) Plate 12. p (cm. l-(s>. u. 75.7 ". 35.7. 35t7. O 2 4 6(m,tn>. o. 1. 2. 3 (>"S). o5to(mm) o. 1. 2. 3 byS). J. '. 16.q. -. Photo. 12. Both figures and their oscillograms of supplied impulse voltage in various reduced atmospheric pressures. Series reslstance 9.1 (k9) connected. Supplied crest voltage were 2.8 (kV) respectively..

(25) Plate 13. '. p (cr?r}. Hs). VS (kV). r (k 52). '. 35.8. 15･8. Z･ 8. Z2. 2･5. 2･ 2. O 2 4 6 8 fO(mm). L-.-.--..-.L.--. Photo. 13. Bending streamers just like a supperposed positive figure on negatlve one. '. p: Reduced atmospheric pressure (cm Hg), V.: Supplied crest voltage (kV), r: Series resistance in impulse circuit (k9)..

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