Argon gas discharge lamp - Revision history

Kunhee: /* Sources */

2022-04-30T16:15:28Z

Sources

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 plt.tight_layout()
 plt.savefig('Argon-lamp-paschen-translated.png')
 </pre>
 ==References==

Kunhee: /* Measurements */

2022-04-30T16:13:46Z

Measurements

← Older revision		Revision as of 16:13, 30 April 2022
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	The figure is from [https://en.wikipedia.org/wiki/Glow_discharge glow discharge].A-D region, F-H region and I-K region separately represent the dark discharge, glow discharge and arc discharge region.		The figure is from [https://en.wikipedia.org/wiki/Glow_discharge glow discharge].A-D region, F-H region and I-K region separately represent the dark discharge, glow discharge and arc discharge region.

	[[File:Current-voltage curve.png\|640px\|thumb\|I-V curve of electrical discharge in neon at 1torr, with two planar electrodes separated by 50cm]]		[[File:Current-voltage curve.png\|640px\|thumb\|500px\|I-V curve of electrical discharge in neon at 1torr, with two planar electrodes separated by 50cm]]

	*In a dark discharge, the carriers are generated during the inonization process by a radiation sorce. The voltage is applied across the anode and cathode.At higher voltage, the freed carriers could obtain enough energy so that additional carriers are freed during collisions.		*In a dark discharge, the carriers are generated during the inonization process by a radiation sorce. The voltage is applied across the anode and cathode.At higher voltage, the freed carriers could obtain enough energy so that additional carriers are freed during collisions.
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	*In an [https://en.wikipedia.org/wiki/Electric_arc arc discharge], electrons leave the cathode by [https://en.wikipedia.org/wiki/Thermionic_emission thermionic emission] and [https://en.wikipedia.org/wiki/Thermionic_emission field emission], and the gas is ionized by thermal means.		*In an [https://en.wikipedia.org/wiki/Electric_arc arc discharge], electrons leave the cathode by [https://en.wikipedia.org/wiki/Thermionic_emission thermionic emission] and [https://en.wikipedia.org/wiki/Thermionic_emission field emission], and the gas is ionized by thermal means.

	[[File:Glow structure.png\|540px\|thumb\|Glow discharge structure.png]]		[[File:Glow structure.png\|540px\|thumb\|500px\|Glow discharge structure.png]]

	We also attach a diagram here to illustrate the distributions of some physics quantities regarding the plasma. <ref>Fuad T.I.(2013) Design and Construction of low-Pressure D.C.-Sputtering plasma system for preparing Gas Sensors. University of Baghdad.</ref>)In our project, we mainly studied the property and characteristics within the glow discharge region, given the limitation of the supplies and pump we had. The figure shows the names of different glowing regions in the Argon as well as the graphs showing the variation of the potential(<math>V</math>), electric field(<math>E</math>), current density(<math>n</math>) along the tube. In our case, the distance between the cathode and anode (<math>d</math>) is 3.164cm.		We also attach a diagram here to illustrate the distributions of some physics quantities regarding the plasma. <ref>Fuad T.I.(2013) Design and Construction of low-Pressure D.C.-Sputtering plasma system for preparing Gas Sensors. University of Baghdad.</ref>)In our project, we mainly studied the property and characteristics within the glow discharge region, given the limitation of the supplies and pump we had. The figure shows the names of different glowing regions in the Argon as well as the graphs showing the variation of the potential(<math>V</math>), electric field(<math>E</math>), current density(<math>n</math>) along the tube. In our case, the distance between the cathode and anode (<math>d</math>) is 3.164cm.

Kunhee: /* Glow Discharge */

2022-04-30T16:09:33Z

Glow Discharge

← Older revision		Revision as of 16:09, 30 April 2022
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	The figure is from [https://en.wikipedia.org/wiki/Glow_discharge glow discharge].A-D region, F-H region and I-K region separately represent the dark discharge, glow discharge and arc discharge region.		The figure is from [https://en.wikipedia.org/wiki/Glow_discharge glow discharge].A-D region, F-H region and I-K region separately represent the dark discharge, glow discharge and arc discharge region.

	[[File:Current-voltage curve.png\|640px\|~~center~~\|I-V curve of electrical discharge in neon at 1torr, with two planar electrodes separated by 50cm]]		[[File:Current-voltage curve.png\|640px\|thumb\|I-V curve of electrical discharge in neon at 1torr, with two planar electrodes separated by 50cm]]

	*In a dark discharge, the carriers are generated during the inonization process by a radiation sorce. The voltage is applied across the anode and cathode.At higher voltage, the freed carriers could obtain enough energy so that additional carriers are freed during collisions.		*In a dark discharge, the carriers are generated during the inonization process by a radiation sorce. The voltage is applied across the anode and cathode.At higher voltage, the freed carriers could obtain enough energy so that additional carriers are freed during collisions.
Line 50:		Line 50:
	*In an [https://en.wikipedia.org/wiki/Electric_arc arc discharge], electrons leave the cathode by [https://en.wikipedia.org/wiki/Thermionic_emission thermionic emission] and [https://en.wikipedia.org/wiki/Thermionic_emission field emission], and the gas is ionized by thermal means.		*In an [https://en.wikipedia.org/wiki/Electric_arc arc discharge], electrons leave the cathode by [https://en.wikipedia.org/wiki/Thermionic_emission thermionic emission] and [https://en.wikipedia.org/wiki/Thermionic_emission field emission], and the gas is ionized by thermal means.

	[[File:Glow structure.png\|540px\|~~center~~\|Glow discharge structure.png]]		[[File:Glow structure.png\|540px\|thumb\|Glow discharge structure.png]]

	We also attach a diagram here to illustrate the distributions of some physics quantities regarding the plasma. <ref>Fuad T.I.(2013) Design and Construction of low-Pressure D.C.-Sputtering plasma system for preparing Gas Sensors. University of Baghdad.</ref>)In our project, we mainly studied the property and characteristics within the glow discharge region, given the limitation of the supplies and pump we had. The figure shows the names of different glowing regions in the Argon as well as the graphs showing the variation of the potential(<math>V</math>), electric field(<math>E</math>), current density(<math>n</math>) along the tube. In our case, the distance between the cathode and anode (<math>d</math>) is 3.164cm.		We also attach a diagram here to illustrate the distributions of some physics quantities regarding the plasma. <ref>Fuad T.I.(2013) Design and Construction of low-Pressure D.C.-Sputtering plasma system for preparing Gas Sensors. University of Baghdad.</ref>)In our project, we mainly studied the property and characteristics within the glow discharge region, given the limitation of the supplies and pump we had. The figure shows the names of different glowing regions in the Argon as well as the graphs showing the variation of the potential(<math>V</math>), electric field(<math>E</math>), current density(<math>n</math>) along the tube. In our case, the distance between the cathode and anode (<math>d</math>) is 3.164cm.
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	[[File:I-V_curve.png\|540px\|~~center~~\|I-V curve of Argon under various pressures]]		[[File:I-V_curve.png\|540px\|360px\|I-V curve of Argon under various pressures]]

	Here the voltage is all larger than the breakdown voltage in the backward direction. Because of the existance of the hysteresis effect, the breakdown voltage which igniting the plasma is different from the value by which the glow plasma extincts. This is discussed below in the hysteresis part. We obtain this curve by first igniting the plasma with the application of the laser high-voltage supply and set the voltage supply to its upper limit. Then we change the voltage at the supply and measure the I-V data points of between the anode and cathode till the plasma extincts. And we repeat the measurement under different pressures.		Here the voltage is all larger than the breakdown voltage in the backward direction. Because of the existance of the hysteresis effect, the breakdown voltage which igniting the plasma is different from the value by which the glow plasma extincts. This is discussed below in the hysteresis part. We obtain this curve by first igniting the plasma with the application of the laser high-voltage supply and set the voltage supply to its upper limit. Then we change the voltage at the supply and measure the I-V data points of between the anode and cathode till the plasma extincts. And we repeat the measurement under different pressures.
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	<br>[https://en.wikipedia.org/wiki/Langmuir_probe Langmuir probe] is a devices used to determine the electron temperature, electron density and electric potential of a plasma. It works by inserting one or more electrodes into a plasma. We get the I-V characteristic curve by measuring the current through it and voltage between it and the anode.		<br>[https://en.wikipedia.org/wiki/Langmuir_probe Langmuir probe] is a devices used to determine the electron temperature, electron density and electric potential of a plasma. It works by inserting one or more electrodes into a plasma. We get the I-V characteristic curve by measuring the current through it and voltage between it and the anode.

	[[File:Probe.png\|360px\|~~center~~\|Typical Langmuir I-V curve]]		[[File:Probe.png\|360px\|thumb\|Typical Langmuir I-V curve]]
	For the region 3 of the I-V curve, since the electrons are subjected to a decelerating potential <math>(V_{p}-V_{f})</math>, only the electrons with higher energy than <math>e(V_{p}-V_{f})</math> can reach the probe. If we assume that the velocities of electrons in plasma obey [https://en.wikipedia.org/wiki/Maxwell%E2%80%93Boltzmann_distribution Maxwell-Boltzmann distribution], then the electron density <math>n_{e}</math>near the probe could be described as,		For the region 3 of the I-V curve, since the electrons are subjected to a decelerating potential <math>(V_{p}-V_{f})</math>, only the electrons with higher energy than <math>e(V_{p}-V_{f})</math> can reach the probe. If we assume that the velocities of electrons in plasma obey [https://en.wikipedia.org/wiki/Maxwell%E2%80%93Boltzmann_distribution Maxwell-Boltzmann distribution], then the electron density <math>n_{e}</math>near the probe could be described as,
	<math display="block">n_{e}=n_{0}exp[\frac{e(U_{p}-U_{s})}{kT_{e}}]</math>		<math display="block">n_{e}=n_{0}exp[\frac{e(U_{p}-U_{s})}{kT_{e}}]</math>

Kunhee: /* Hysteresis */

2022-04-30T16:07:16Z

Hysteresis

← Older revision		Revision as of 16:07, 30 April 2022
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	It is notable that, the measured extinction voltage, if we take it at its face value, poses a challenge to the earlier proposed modification to Paschen's law that provides us with a better fit for the data.		It is notable that, the measured extinction voltage, if we take it at its face value, poses a challenge to the earlier proposed modification to Paschen's law that provides us with a better fit for the data.

	[[File:Argon-lamp-hysteresis.png\|360px\|Hysteresis adjusted]]		[[File:Argon-lamp-hysteresis-added.png\|360px\|Hysteresis adjusted]]

	From the plot above, we find that the adjusted breakdown voltages is in fact lower than the extinction voltage, which contradicts the expected effects of the hysteresis.		From the plot above, we find that the adjusted breakdown voltages is in fact lower than the extinction voltage, which contradicts the expected effects of the hysteresis.

Kunhee: /* Measurements */

2022-04-30T16:06:19Z

Measurements

← Older revision		Revision as of 16:06, 30 April 2022
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	==Measurements==		==Measurements==
	The chief advantage of our setup is the capability to adjust the pressure of the Argon gas.		The chief advantage of our setup is the capability to adjust the pressure of the Argon gas.
			As such, our measurements focus on breakdown voltages, extinction voltages, and I-V characterestics of the glow discharge, at various pressures.

	===Important parameters about plasma===		===Important parameters about plasma===

Kunhee: /* Hysteresis */

2022-04-30T16:00:30Z

Hysteresis

← Older revision		Revision as of 16:00, 30 April 2022
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	===Hysteresis===		===Hysteresis===
	The breakdown voltage which ignites the plasma is different from the value by which the plasma glow goes off due to hysteresis.		The breakdown voltage which ignites the plasma is different from the value by which the plasma glow goes off due to hysteresis.
	[[File:I-V_characteristics.png\|~~400px~~]]
			[[File:I-V_characteristics.png\|thumb\|Hysteresis I-V curve]]

	When increasing the voltage, a special phenomena will occur which is indicated by process A to B in the above figure. [https://en.wikipedia.org/wiki/Corona_discharge Corona discharges] occur in Townsend regime at high electric field near sharp edges, which is prior to electrical breakdown. Corona discharge is caused by the ionization of Argon at the high electric field region. If the coronal currents are high enough, corona discharges can be technically seen as “glow discharges”,which is also visible to human eyes.		When increasing the voltage, a special phenomena will occur which is indicated by process A to B in the above figure. [https://en.wikipedia.org/wiki/Corona_discharge Corona discharges] occur in Townsend regime at high electric field near sharp edges, which is prior to electrical breakdown. Corona discharge is caused by the ionization of Argon at the high electric field region. If the coronal currents are high enough, corona discharges can be technically seen as “glow discharges”,which is also visible to human eyes.
	Nevertheless, when decreasing the voltage, the voltage maintains unchanged at significantly lower currents than at point C and only then makes the transition back to Townsend regime.		Nevertheless, when decreasing the voltage, the voltage maintains unchanged at significantly lower currents than at point C and only then makes the transition back to Townsend regime.

			In our experiment, we observed that the breakdown voltage (voltage at ignition) is higher across all measured pressures than the extinction voltage.

			[[File:Argon-lamp-hysteresis.png\|360px\|Hysteresis original]]

	The occurrences of this hysteresis as well as sudden jumps of the discharge current, when changing the discharge parameters for instance: applied voltage, neutral gas pressure and electrode configuration, are both related to the circuit-related instability due to the onset of a negative differential resistance in the I-V curve of plasma discharge.		The occurrences of this hysteresis as well as sudden jumps of the discharge current, when changing the discharge parameters for instance: applied voltage, neutral gas pressure and electrode configuration, are both related to the circuit-related instability due to the onset of a negative differential resistance in the I-V curve of plasma discharge.
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	The hysteresis loop is related to the load resistance and gas pressure. The area of the hysteresis loop formed by the I-V curves is larger for the small resistor and smaller for the larger resistor. Besides, the area of the hysteresis loop decreases as the pressure declines. In addition, electrode separation distance does not influence the area of the hysteresis loop.		The hysteresis loop is related to the load resistance and gas pressure. The area of the hysteresis loop formed by the I-V curves is larger for the small resistor and smaller for the larger resistor. Besides, the area of the hysteresis loop decreases as the pressure declines. In addition, electrode separation distance does not influence the area of the hysteresis loop.

			It is notable that, the measured extinction voltage, if we take it at its face value, poses a challenge to the earlier proposed modification to Paschen's law that provides us with a better fit for the data.

			[[File:Argon-lamp-hysteresis.png\|360px\|Hysteresis adjusted]]

			From the plot above, we find that the adjusted breakdown voltages is in fact lower than the extinction voltage, which contradicts the expected effects of the hysteresis.
			At the present time, we are unable to arrive at a resolution, and further measurements will be helpful.

	==Summary==		==Summary==

Jingwen: /* Hysteresis */

2022-04-30T15:43:24Z

Hysteresis

← Older revision		Revision as of 15:43, 30 April 2022
Line 165:		Line 165:

	The occurrences of this hysteresis as well as sudden jumps of the discharge current, when changing the discharge parameters for instance: applied voltage, neutral gas pressure and electrode configuration, are both related to the circuit-related instability due to the onset of a negative differential resistance in the I-V curve of plasma discharge.		The occurrences of this hysteresis as well as sudden jumps of the discharge current, when changing the discharge parameters for instance: applied voltage, neutral gas pressure and electrode configuration, are both related to the circuit-related instability due to the onset of a negative differential resistance in the I-V curve of plasma discharge.

			The hysteresis is mainly connected with the power loss. As the applied voltage increases, more ionization occurs, and the charge density also increases. As a result, the current increases. However, the electron-ion recombination also occurs, which cause the loss of charge density. Thus, when the applied voltage decreases (the reverse), the discharge current is less than increasing the applied voltage.

			The hysteresis loop is related to the load resistance and gas pressure. The area of the hysteresis loop formed by the I-V curves is larger for the small resistor and smaller for the larger resistor. Besides, the area of the hysteresis loop decreases as the pressure declines. In addition, electrode separation distance does not influence the area of the hysteresis loop.

	==Summary==		==Summary==

Jingwen: /* Hysteresis */

2022-04-30T14:05:29Z

Hysteresis

← Older revision		Revision as of 14:05, 30 April 2022
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	Nevertheless, when decreasing the voltage, the voltage maintains unchanged at significantly lower currents than at point C and only then makes the transition back to Townsend regime.		Nevertheless, when decreasing the voltage, the voltage maintains unchanged at significantly lower currents than at point C and only then makes the transition back to Townsend regime.

	The occurrences of this hysteresis as well as sudden jumps of the discharge current when changing the applied voltage are both related to the circuit-related instability due to the onset of a negative differential resistance in the I-V curve of plasma ~~diacharge~~.		The occurrences of this hysteresis as well as sudden jumps of the discharge current, when changing the discharge parameters for instance: applied voltage, neutral gas pressure and electrode configuration, are both related to the circuit-related instability due to the onset of a negative differential resistance in the I-V curve of plasma discharge.

	==Summary==		==Summary==

Jingwen: /* Hysteresis */

2022-04-30T13:48:59Z

Hysteresis

← Older revision		Revision as of 13:48, 30 April 2022
Line 159:		Line 159:
	===Hysteresis===		===Hysteresis===
	The breakdown voltage which ignites the plasma is different from the value by which the plasma glow goes off due to hysteresis.		The breakdown voltage which ignites the plasma is different from the value by which the plasma glow goes off due to hysteresis.
	[[File:I-V_characteristics.png\|~~360px~~]]		[[File:I-V_characteristics.png\|400px]]

	When increasing the voltage, a special phenomena will occur which is indicated by process A to B in the above figure. [https://en.wikipedia.org/wiki/Corona_discharge Corona discharges] occur in Townsend regime at high electric field near sharp edges, which is prior to electrical breakdown. Corona discharge is caused by the ionization of Argon at the high electric field region. If the coronal currents are high enough, corona discharges can be technically seen as “glow discharges”,which is also visible to human eyes.		When increasing the voltage, a special phenomena will occur which is indicated by process A to B in the above figure. [https://en.wikipedia.org/wiki/Corona_discharge Corona discharges] occur in Townsend regime at high electric field near sharp edges, which is prior to electrical breakdown. Corona discharge is caused by the ionization of Argon at the high electric field region. If the coronal currents are high enough, corona discharges can be technically seen as “glow discharges”,which is also visible to human eyes.

Jingwen: /* Hysteresis */

2022-04-30T13:48:25Z

Hysteresis

← Older revision		Revision as of 13:48, 30 April 2022
Line 159:		Line 159:
	===Hysteresis===		===Hysteresis===
	The breakdown voltage which ignites the plasma is different from the value by which the plasma glow goes off due to hysteresis.		The breakdown voltage which ignites the plasma is different from the value by which the plasma glow goes off due to hysteresis.
	[[File:I-V_characteristics.png\|~~300px\|thumb\|left~~]]		[[File:I-V_characteristics.png\|360px]]

	When increasing the voltage, a special phenomena will occur which is indicated by process A to B in the above figure. [https://en.wikipedia.org/wiki/Corona_discharge Corona discharges] occur in Townsend regime at high electric field near sharp edges, which is prior to electrical breakdown. Corona discharge is caused by the ionization of Argon at the high electric field region. If the coronal currents are high enough, corona discharges can be technically seen as “glow discharges”,which is also visible to human eyes.		When increasing the voltage, a special phenomena will occur which is indicated by process A to B in the above figure. [https://en.wikipedia.org/wiki/Corona_discharge Corona discharges] occur in Townsend regime at high electric field near sharp edges, which is prior to electrical breakdown. Corona discharge is caused by the ionization of Argon at the high electric field region. If the coronal currents are high enough, corona discharges can be technically seen as “glow discharges”,which is also visible to human eyes.