Ion Source - Revision history

RichardLefferts at 11:13, 5 October 2010

2010-10-05T11:13:52Z

RichardLefferts at 10:54, 5 October 2010

2010-10-05T10:54:55Z

RichardLefferts at 12:38, 6 September 2010

2010-09-06T12:38:32Z

TaposhiBiswas at 14:40, 27 August 2010

2010-08-27T14:40:11Z

TaposhiBiswas at 14:37, 27 August 2010

2010-08-27T14:37:23Z

TaposhiBiswas at 12:35, 27 August 2010

2010-08-27T12:35:52Z

TaposhiBiswas at 12:35, 27 August 2010

2010-08-27T12:35:16Z

RichardLefferts at 09:15, 27 August 2010

2010-08-27T09:15:25Z

TaposhiBiswas: Reverted edits by TaposhiBiswas (Talk) to last version by RichardLefferts

2010-08-25T12:15:43Z

Reverted edits by TaposhiBiswas (Talk) to last version by RichardLefferts

TaposhiBiswas at 12:14, 25 August 2010

2010-08-25T12:14:40Z

← Older revision		Revision as of 11:13, 5 October 2010
Line 14:		Line 14:
	The sputtered negative ions are ''pulled'' out by the extraction power supply, typically at 15kV.		The sputtered negative ions are ''pulled'' out by the extraction power supply, typically at 15kV.

		+	More information on the inverted sputter source can be found from manufacturers such as [http://www.pelletron.com/negion.htm NEC]

		+	[[Image:IonSource-1.jpg\|500px\|thumb\|left\| Schematic of the 860A]]
		+	[[Image:IonSource-2.jpg\|thumb\|500px\|right\| Photo of the 860A, from HVEE]]
		+
		+	<br>
	==Operation==		==Operation==

@@ Line 1: / Line 1: @@
 ==Background==
-<!-- Herein should be a general intro to ion sources, negative ion sources and our source. A set of links should include one to National Electrostatic Corporations page on their [http://www.pelletron.com/negion.htm SNICS]. -->
+The ion source we will be using is a General Ionex 860A Inverted Sputter negative ion source.  We use negative ions so that we can benefit from (ie. accelerate with) the voltage of the [[Tandem]] Van de Graaff twice. Sources of this type have been commercially available for about 25 years and are still sold by National Electrostatics Corporation (the [http://www.pelletron.com/negion.htm SNICS]), High Voltage Engineering Europa (the [http://www.highvolteng.com/ionsources.html 860A and C] and Peabody Scientific (the [http://www.peabody-scientific.com/page3.html PS-120].
-The ion source we will be using is a General Ionex 860A Inverted Sputter negative ion source.  We use negative ions so that we can benefit from (ie. accelerate with) the voltage of the [[Tandem]] Van de Graaff twice. Sources of this type have been commercially available for about 25 years and are still sold by National Electrostatics Corporation (the [http://www.pelletron.com/negion.htm SNICS]), High Voltage Engineering Europa (the [http://www.highvolteng.com/ionsources.html 860A and C] and Peabody Scientific (the [http://www.peabody-scientific.com/page3.html PS-120].  You should be familiar with all of the components of the ion source, understand what they can do and how you can use them to help you. In addition, all of these components are controlled with [[http://www.ni.com/labview/ LabVIEW]], so you should develop a basic understanding of how LabVIEW works and how to use it.
+==Theory of Operation==
-===The Cesium Boiler===
+An inverted sputter source works by creating a beam of positive ions which hit a sample of the material of interest. The positive ions deposit several atomic layers deep and stimulate the sample to sputter out material. Any negative ions which are released are extracted by a large negative potential.
-<b>Warning:</b> Cesium is a metal in group 1 of the periodic table. This means that like the rest of the group 1 metals (Li, Na, K), it reacts violently with water. So the cesium metal is stored in an airtight glass vial to protect it from oxidizing with water vapor in the air. To load the cesium boiler, the vial must be broken in a dry box, and care must be taken in washing unreacted cesium out of the boiler's storage boat.
+The positive beam in an 860A source consists of cesium plus one (Cs<sup>+</sup>) ions. The source of Cs is called the boiler; it is a small vacuum which holds about 1 gram of Cs with a 40 Watt heater. The Cs boiler temperature is controlled through the current on the boiler power supply.
-The cesium boiler is simply an oven that stores and vaporizes cesium metal. Its temperature is controlled through the current on the boiler power supply.
+Cs vapor enters the source head through a feed tube. The neutral Cs vapor finds the ionizer, a coil of tantalum co-axial wire which is heated to 1200<sup>o</sup>C. Cesium vapor pressure is very high at 1200<sup>o</sup>C so the Cs immediately evaporates. However, Ta has [http://environmentalchemistry.com/yogi/periodic/Ta.html work function] of 4.25 eV while Cs has an [http://environmentalchemistry.com/yogi/periodic/Cs.html ionization potential] of 3.89 eV. Therefore, it is energetically favorable for the Cs to evaporate as Cs<sup>+</sup>.
-===The Ionizer===
+These Cs<sup>+</sup> ions experience an acceleration toward the sample holder of 3-5kV created by the cathode power supply.
+The sputtered negative ions are ''pulled'' out by the extraction power supply, typically at 15kV.
-After the cesium has been evaporated, it condenses in a thin film on the ionizer. This component's function is twofold; it is heated to give Cs atoms enough energy to throw off an electron and ionize to Cs<sup>+</sup>, and it is held at a potential to ensure that these positive particles are focused onto the cathode and sample cone.
-−
-===The Cathode===
-−
-The cathode is held at about -15 kV, attracting the Cs<sup>+</sup> ions and impacting them into the sample cone (which contains titanium infused with hydrogen). Negative H<sup>-</sup>ions "splash" out of the sample cone; due to the shapes of the potential surfaces defined by the cathode and ionizer potentials, these ions are focused into a beam, while other extraneous ions (including the Cs<sup>+</sup> ions) are scattered.
-−
-===The Extraction Electrode===
-−
-The extraction electrode is held at about 15 kV and takes the beam of H<sup>-</sup> ions and accelerates them through a series of [[Ion Optics | optical components]] (Y-Steerer, einzel lens, GS Triplet, LE Steerer). The effectiveness of these beam optics can be judged by measuring the beam current at the [[Faraday Cups | LE Faraday cup]].
@@ Line 57: / Line 48: @@
 ===Tuning===
-* Observe the LE Faraday Cup current on the electrometer. Note that it should be negative. Recently we have found that one must wait 15 minutes for current to appear: Don't Panic. Once current appears you can tune all of the above mentioned parameters (not the ionizer, however!).
+* Observe the LE Faraday Cup [[Faraday Cups | LE Faraday cup]] current on the electrometer. Note that it should be negative. Recently we have found that one must wait 15 minutes for current to appear: Don't Panic. Once current appears you can tune all of the above mentioned parameters (not the ionizer, however!).
 ** If there is no current, note your starting value and scan the Inflection magnet. Hint: mass 16 will be present for any sample unless there is something wrong with the set-up.
@@ Line 63: / Line 54: @@
 If the beam cannot be found or has a low beam current:
-*The cesium boiler can be "pushed"; more current means a higher temperature, which means more vaporized Cs, which means more ionized Cs<sup>+</sup>, which means more of a "splash" from the target.
+*The cesium boiler can be "pushed"; a higher Cs boiler temperature results in higher Cs vapor pressure and higher Cs current.
-*The ionizer may not be working as expected; if Cs is not ionized it will not be focused effectively, and the sample will be relatively untouched.
-−
 Return to [[Lab Manuals]]

@@ Line 1: / Line 1: @@
 ==Background==
-Herein should be a general intro to ion sources, negative ion sources and our source. A set of links should include one to National Electrostatic Corporations page on their [http://www.pelletron.com/negion.htm SNICS].
+<!-- Herein should be a general intro to ion sources, negative ion sources and our source. A set of links should include one to National Electrostatic Corporations page on their [http://www.pelletron.com/negion.htm SNICS]. -->
-The ion source we will be using will be producing negative ions, which is essential because of the way that the tandem accelerator works (see [[Tandem]]). You should be familiar with all of the components of the ion source, understand what they can do and how you can use them to help you. In addition, all of these components are controlled with [[http://www.ni.com/labview/ LabVIEW]], so you should develop a basic understanding of how LabVIEW works and how to use it.
+The ion source we will be using is a General Ionex 860A Inverted Sputter negative ion source.  We use negative ions so that we can benefit from (ie. accelerate with) the voltage of the [[Tandem]] Van de Graaff twice. Sources of this type have been commercially available for about 25 years and are still sold by National Electrostatics Corporation (the [http://www.pelletron.com/negion.htm SNICS]), High Voltage Engineering Europa (the [http://www.highvolteng.com/ionsources.html 860A and C] and Peabody Scientific (the [http://www.peabody-scientific.com/page3.html PS-120].  You should be familiar with all of the components of the ion source, understand what they can do and how you can use them to help you. In addition, all of these components are controlled with [[http://www.ni.com/labview/ LabVIEW]], so you should develop a basic understanding of how LabVIEW works and how to use it.
 ===The Cesium Boiler===
@@ Line 27: / Line 27: @@
 ===Preparation===
 * Checks: DI water, Vacuum, Gates
@@ Line 35: / Line 39: @@
 * Closing the Cage
 * Opening LE Tube Valve
-* Turning on Cathode (-15 kV), Extraction (15 kV) and Glassman (table/injection/pre-accel power supply) (170 kV)
+* Turning on AC power for the Cathode, Extraction and Glassman (table/injection/pre-accel) power supplies
-−
 ===Start-up===
 * Ensure that the ion source drive shaft is on, vacuum is good, power supplies are on, gate is closed, LE Tube valve is open

← Older revision		Revision as of 14:40, 27 August 2010
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	===The Extraction Electrode===		===The Extraction Electrode===

−	The extraction electrode is held at about 15 kV and takes the beam of H<sup>-</sup> ions and accelerates them through a series of [[Ion Optics \| optical components]].	+	The extraction electrode is held at about 15 kV and takes the beam of H<sup>-</sup> ions and accelerates them through a series of [[Ion Optics \| optical components]] (Y-Steerer, einzel lens, GS Triplet, LE Steerer). The effectiveness of these beam optics can be judged by measuring the beam current at the [[Faraday Cups \| LE Faraday cup]].

@@ Line 3: / Line 3: @@
 Herein should be a general intro to ion sources, negative ion sources and our source. A set of links should include one to National Electrostatic Corporations page on their [http://www.pelletron.com/negion.htm SNICS].
-The ion source we will be using will be producing negative ions, which is essential because of the way that the tandem accelerator works (see [[Tandem]]). You should be familiar with all of the components of the ion source, understand what they can do and how you can use them to help you.
+The ion source we will be using will be producing negative ions, which is essential because of the way that the tandem accelerator works (see [[Tandem]]). You should be familiar with all of the components of the ion source, understand what they can do and how you can use them to help you. In addition, all of these components are controlled with [[http://www.ni.com/labview/ LabVIEW]], so you should develop a basic understanding of how LabVIEW works and how to use it.
 ===The Cesium Boiler===
@@ Line 19: / Line 35: @@
 * Closing the Cage
 * Opening LE Tube Valve
-* Turning on Cathode, Extraction and Glassman (table/injection/pre-accel power supply)
+* Turning on Cathode (-15 kV), Extraction (15 kV) and Glassman (table/injection/pre-accel power supply) (170 kV)
@@ Line 42: / Line 58: @@
 * Observe the LE Faraday Cup current on the electrometer. Note that it should be negative. Recently we have found that one must wait 15 minutes for current to appear: Don't Panic. Once current appears you can tune all of the above mentioned parameters (not the ionizer, however!).
 ** If there is no current, note your starting value and scan the Inflection magnet. Hint: mass 16 will be present for any sample unless there is something wrong with the set-up.
 Return to [[Lab Manuals]]

@@ Line 10: / Line 10: @@
 ==Operation==
-====Preparation====
+===Preparation===
 * Checks: DI water, Vacuum, Gates
@@ Line 22: / Line 22: @@
-====Start-up====
+===Start-up===
 This section has been written. We'll find it ....
 Or slap out a quick and dirty version:
@@ Line 38: / Line 38: @@
 * Once the ionizer has 8V (~175 Watts) raise the Cathode Voltage slowly. If you see rapid changes to the Extraction Voltage/current or cathode current or a decrease in the ionizer current there may be sparking. In this case, lower the cathode voltage below the sparking point and wait.  Increase slowly. A good first value will be 2 kV.
-====Tuning====
+===Tuning===
 * Observe the LE Faraday Cup current on the electrometer. Note that it should be negative. Recently we have found that one must wait 15 minutes for current to appear: Don't Panic. Once current appears you can tune all of the above mentioned parameters (not the ionizer, however!).

← Older revision		Revision as of 12:35, 27 August 2010
Line 2:		Line 2:

	Herein should be a general intro to ion sources, negative ion sources and our source. A set of links should include one to National Electrostatic Corporations page on their [http://www.pelletron.com/negion.htm SNICS].		Herein should be a general intro to ion sources, negative ion sources and our source. A set of links should include one to National Electrostatic Corporations page on their [http://www.pelletron.com/negion.htm SNICS].
		+
		+	The ion source we will be using will be producing negative ions, which is essential because of the way that the tandem accelerator works (see [[Tandem]]). You should be familiar with all of the components of the ion source, understand what they can do and how you can use them to help you.
		+
		+	===The Cesium Boiler===
		+

	==Operation==		==Operation==

@@ Line 10: / Line 10: @@
 * Isolating vacuum and preparing Turbo to be off
 * Switching AC Power source
 * Turning on power supplies at Table, Magnet and Source stations
 * Closing the Cage
@@ Line 20: / Line 21: @@
 Or slap out a quick and dirty version:
-* Ensure that the ion source drive shaft is on, power supplies are on, gate is closed, LE Tube valve is open
+* Ensure that the ion source drive shaft is on, vacuum is good, power supplies are on, gate is closed, LE Tube valve is open
 * Ensure that the control system is running. On MasterRT.vi front panel do the rest.
 * Ensure that the LE Faraday Cup is in (Green, as of 8/21/2010) and that the selector switch sends that current to the electrometer