Main Page/PHYS 4210/Mass Spectrometer - Revision history

Gloria at 15:00, 19 March 2018

2018-03-19T15:00:25Z

Gloria at 14:53, 19 March 2018

2018-03-19T14:53:43Z

Mgeorge at 19:49, 10 April 2015

2015-04-10T19:49:11Z

Mgeorge at 19:51, 5 March 2014

2014-03-05T19:51:01Z

Mgeorge at 17:02, 5 March 2014

2014-03-05T17:02:56Z

Mgeorge at 20:43, 4 March 2014

2014-03-04T20:43:04Z

Mgeorge at 20:42, 4 March 2014

2014-03-04T20:42:18Z

Mgeorge at 20:41, 4 March 2014

2014-03-04T20:41:22Z

Mgeorge at 20:40, 4 March 2014

2014-03-04T20:40:16Z

Mgeorge at 18:31, 4 March 2014

2014-03-04T18:31:51Z

@@ Line 117: / Line 117: @@
 <li>Open B-valve to rough out the vacuum chamber; Close B-valve when TC gauge reaches < 150 mTorr again</li>
 <li>Open A-valve to rough the diffusion pump and vacuum chamber (and to back the diffusion pump later)</li>
 <li>When pressure on TC  < 150 mTorr, turn on DIFFUSION pump (switch on metal box with indicator light) </li>
 <li>Wait for 30 minutes</li>

@@ Line 143: / Line 143: @@
 <li>Turn of filament current and accelerating voltage.</li>
 <li>Close VAVLE C. Now the experiment chamber is isolated from the pumping system.</li>
-<li> To bring the experiment chamber to atmospheric pressure, loosen the screw nut at the base of the glass ion gauge. Gently lift the ion gauge- you should be able to hear air rushing into the experiment chamber. Allow the pressures to equalize. </li>
+<li> To bring the experiment chamber to atmospheric pressure, loosen the cap screw located just below the glass ion gauge. Gently lift the ion gauge- you should be able to hear air rushing into the experiment chamber. Allow the pressures to equalize. </li>
 <li> Remove the flange with the filament (watch out when removing the last screw to hold the flange!), and repair/re-coat as necessary.</li>
 <li> It is a good idea at this point to thoroughly rinse the filament to remove any previous coatings so your mass spectra can be more easily interpreted </li>

@@ Line 117: / Line 117: @@
 <li>Open B-valve to rough out the vacuum chamber; Close B-valve when TC gauge reaches < 150 mTorr again</li>
 <li>Open A-valve to rough the diffusion pump and vacuum chamber (and to back the diffusion pump later)</li>
 <li>When pressure on TC  < 150 mTorr, turn on DIFFUSION pump (switch on metal box with indicator light) </li>
 <li>Wait for 30 minutes</li>

@@ Line 185: / Line 185: @@
 <li>Familiarize yourself with the electric circuit shown in Figs. 4 and 5.</li>
 <li>Turn on the magnet power and the gaussmeter. The appropriate range of magnetic field strengths is from 100 to 350 mT. The solenoid current can be tuned by coarse and fine voltage control knobs. Be careful to change the voltages slowly, to not harm the power supply.</li>
-<li>Turn on the AC switch on the accelerating voltage power supply. After a minute turn on the DC. Turn on the recorder, and the picoammeter. The full-scale reading of the electrometer should be in the range of 10 x 10<sup>-11</sup> amps. Watch that the needle does not exceed the scale!</li>
+<li>On the accelerating voltage power supply, lower the voltage control knob fully CCW, and current control knob fully CW. Turn on the electrometer. The full-scale reading of the electrometer should be in the range of 10 x 10<sup>-11</sup> amps. Watch that the needle does not exceed the scale!</li>
-<li>When the vessel has been evacuated to 5x10<sup>-5</sup> Torr or less (ion gauge) and not before, turn the filament supply on (otherwise the filament would burn). Slowly turn the filament setting up to about 2 Volts (30 scalemarks) and watch that the current does not exceed 3 A. If the ammeter does not give a reading, the filament is broken, and must be replaced.</li>
+<li>When the vessel has been evacuated to 2x10<sup>-5</sup> Torr or less (ion gauge) and not before, turn the filament supply on (otherwise the filament would burn). Slowly turn the filament setting up to about 2 Amps. If the ammeter does not give a reading, the filament is broken, and must be replaced.</li>
 <li><p>Ions striking the detector cause a current to pass through the picoammeter. This is amplified, and input to the data collection computer using an LabJack™ Analog-to-Digital (A/D) converter. The accelerating voltage monitored and recorded using another channel of the A/D converter. The accelerating voltage should range from 0 to 400 volts.</p>
 <p><b>Note on the Keithly 610C Electrometer</b> The electrometer being used to measure the ion currents has the unfortunate feature that when the input becomes too large (off scale) the analog output drops to zero. Be aware of this, and monitor the front panel of the electrometer to ensure that the needle is comfortably in the range when on a peak.</p> </li>
@@ Line 205: / Line 205: @@
        </ul>
 </li>
-<li>If may be necessary optimize the output by using the 'focusing' dials and the 'filament supply' dial while 'sitting' on a peak. Do not exceed a filament current of I<sub>f</sub>  = 3A. Data will be collected using a LabJack A/D converter interfaced to a LabView™ control program. </li>
+<li>If may be necessary optimize the output by using the 'focusing' dials and the 'filament supply' dial while 'sitting' on a peak. Do not exceed a filament current of I<sub>f</sub>  = 2A. Data will be collected using a LabJack A/D converter interfaced to a LabView™ control program. </li>
 <li>Attain a mass spectrum for 6 values of applied magnetic field in the range of 0.1T to 0.3T.</li>

@@ Line 162: / Line 162: @@
 <table width=800 align=center><tr><td>
-<p align=justify>[[File:Mspec-fig4.png|350px|border|center]]
+<p align=justify>[[File:MS_ElectronicsLayout.png|350px|border|center]]
 <b>Figure 4a -</b> Electronic System block diagram.
 </p>

@@ Line 171: / Line 171: @@
 <b>Figure 4b -</b> Voltage Divider Box.
 <br clear=right>
 </td></tr></table>

@@ Line 161: / Line 161: @@
 <h2>Experimental Procedure</h2>
-<table width=500 align=center><td>
+<table width=800 align=center><td>
-<p align=justify>[[File:Mspec-fig4.png|500px|border|center]]
+<p align=justify>[[File:Mspec-fig4.png|350px|border|center]]
 <b>Figure 4a -</b> Electronic System block diagram.
 <br clear=right>
@@ Line 168: / Line 168: @@
 </td>
 <td>
-<p align=justify>[[File:Mspec-fig4.png|500px|border|center]]
+<p align=justify>[[File:MS_VoltageDividerBox.png|350px|border|center]]
 <b>Figure 4b -</b> Voltage Divider Box.
 <br clear=right>

@@ Line 101: / Line 101: @@
 <table width=500 align=center><td>
-<p align=justify>[[File:MS_VacuumSystem.png|500px|border|center]]
+<p align=justify>[[File:MS_VacuumSystem.png|400px|border|center]]
 <b>Figure 3 -</b> The Vacuum Pump System.
 <br clear=right>