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chip, the team etched a plan of the city centre on a glass slide. Fitting a flat lid over the top turned the streets into hollow, connected tubes. They filled these with helium gas, and inserted electrodes at key tourist hubs. When a voltage is applied between two points, electricity naturally runs through the streets along the shortest route from A to B – and the gas glows like a tiny glowing strip light. The approach itself provides a novel visible
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The use of a glow discharge for solution of certain mapping problems was described in 2002. According to a Nature news article describing the work, researchers at
Imperial College London demonstrated how they built a mini-map that gives tourists luminous route indicators. To make the one-inch London
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E and the concentration of neutral particles N is often used, because the mean energy of electrons (and therefore many other properties of discharge) is a function of E/N. Increasing the electric intensity E by some factor q has the same consequences as lowering gas density N by factor q.
138:. At low voltages, the only current is that due to the generation of charge carriers in the gas by cosmic rays or other sources of ionizing radiation. As the applied voltage is increased, the free electrons carrying the current gain enough energy to cause further ionization, causing an
142:. In this regime, the current increases from femtoamperes to microamperes, i.e. by nine orders of magnitude, for very little further increase in voltage. The voltage-current characteristics begins tapering off near the breakdown voltage and the glow becomes visible.
152:, which occurs once the breakdown voltage is reached. The voltage across the electrodes suddenly drops and the current increases to milliampere range. At lower currents, the voltage across the tube is almost current-independent; this is used in glow discharge
241:. For a certain pressure Ă— distance value, there is a lowest breakdown voltage. The increase of strike voltage for shorter electrode distances is related to too long mean free path of the electrons in comparison with the electrode distance.
34:
of the gas. Depending on several factors, the discharge may radiate visible light. The properties of electric discharges in gases are studied in connection with design of lighting sources and in the design of high voltage electrical equipment.
47:
Avalanche effect between two electrodes. The original ionisation event liberates one electron, and each subsequent collision liberates a further electron, so two electrons emerge from each collision: the ionising electron and the liberated
160:, the voltage across the tube gradually increases, and the glow discharge covers more and more of the surface of the electrodes. Low-power switching (glow-discharge thyratrons), voltage stabilization, and lighting applications (e.g.
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of the electrons has to be reasonably long but shorter than the distance between the electrodes; glow discharges therefore do not readily occur at both too low and too high gas pressures.
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The F-H region is a region of glow discharge; the plasma emits a faint glow that occupies almost all the volume of the tube; most of the light is emitted by excited neutral atoms.
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The A-D region is called a dark discharge; there is some ionization, but the current is below 10 microamperes and there is no significant amount of radiation produced.
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The I-K region is a region of arc discharge; the plasma is concentrated in a narrow channel along the center of the tube; a great amount of radiation is produced.
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156:. At lower currents, the area of the electrodes covered by the glow discharge is proportional to the current. At higher currents the normal glow turns into
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256:), to preionize the gas and increase the reliability of electrical breakdown and glow or arc discharge ignition. A gaseous radioactive isotope, e.g.
182:, which occurs in the ampere range of the current; the voltage across the tube drops with increasing current. High-current switching tubes, e.g.
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approach for solving a wide class of maze searching problems based on the properties of lighting up of a glow discharge in a microfluidic chip.
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Reyes, D. R.; Ghanem, M. M.; Whitesides, G. M.; Manz, A. (2002). "Glow discharge in microfluidic chips for visible analog computing".
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Voltage-current characteristics of electrical discharge in neon at 1 torr, with two planar electrodes separated by 50 cm.
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Glow discharge is facilitated by electrons striking the gas atoms and ionizing them. For formation of glow discharge, the
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voltage for the glow discharge depends nonlinearly on the product of gas pressure and electrode distance according to
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A small amount of a radioactive element may be added into the tube, either as a separate piece of material (e.g.
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Reference Data for
Engineers: Radio, Electronics, Computers and Communications
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tubes, the electric discharge in gas has three regions, with distinct
382:"Glow discharge in microfluidic chips for visible analog computing".
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By Wendy
Middleton, Mac E. Van Valkenburg, p. 16-42, Newnes, 2002
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Transition from glow to arc discharge in argon, by increasing the
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by John Dakin, Robert G. W. Brown, p. 52, CRC Press, 2006
252:) or as addition to the alloy of the electrodes (e.g.
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98:I: unstable region: glow-arc transition
16:Current flowing through an ionized gas
328:Handbook of optoelectronics, Volume 1
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82:D: self-sustained Townsend discharge
214:and high-power light sources, e.g.
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283:Application in analog computation
121:current–voltage characteristics
1:
412:Electrical discharge in gases
20:Electric discharge in gases
428:
263:The E/N ratio between the
96:H: abnormal glow discharge
279:(Td) is frequently used.
172:) operate in this region.
222:, operate in this range.
94:G: normal glow discharge
154:voltage-regulator tubes
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61:
49:
392:10.1038/news020520-12
75:B: saturation current
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55:
46:
84:E: unstable region:
70:A: random pulses by
216:mercury-vapor lamps
184:triggered spark gap
220:metal halide lamps
212:mercury-arc valves
140:electron avalanche
132:Townsend discharge
113:
79:Townsend discharge
62:
50:
275:is V·cm, but the
136:breakdown voltage
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361:10.1039/B200589A
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290:analog computing
86:corona discharge
72:cosmic radiation
26:flows through a
24:electric current
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386:. 27 May 2002.
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105:K: electric arc
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39:Discharge types
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265:electric field
228:mean free path
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210:), high-power
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150:glow discharge
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91:glow discharge
89:F: sub-normal
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30:medium due to
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317:0-7506-7291-9
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355:(2): 113–6.
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134:, below the
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117:cold cathode
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102:electric arc
58:gas pressure
22:occurs when
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200:vacuum tube
162:Nixie tubes
296:References
258:krypton-85
208:vacuum arc
202:derivate,
170:neon lamps
32:ionization
246:nickel-63
235:breakdown
198:(and its
192:thyratron
166:decatrons
48:electron.
406:Category
369:15100843
250:krytrons
206:, using
204:sprytron
188:ignitron
273:SI unit
254:thorium
196:krytron
28:gaseous
384:Nature
367:
334:
315:
365:PMID
332:ISBN
313:ISBN
271:Its
233:The
218:and
194:and
388:doi
357:doi
248:in
176:III
115:In
100:J:
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363:.
351:.
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186:,
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164:,
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146:II
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