Autoresonant Ion Trap Mass Spectrometer The RGA Alternative

Transcription

1 Autoresonant Ion Trap Mass Spectrometer The GA Alternative 1

2 What is a Mass Spectrometer? Ionizer Mass Spectrometer Mass Separator Magnetic Sector, Quadrupole or Ion Trap Detector Partial Pressure Measurement Gas molecules are ionized (+ ions), and the resulting ions are separated, detected and measured according to their mass-to-charge ratios (m/z). 2 Ionizer Field eplaceable Filament Assembly Ion Trap Mass Separator Electron Multiplier Detector 2

3 Mass Separator Modern Trends Magnetic Sector and Quadrupoles are prevalent technologies The Electrostatic Ion Trap is the next generation of low mass separation technology Quadrupole MS Ion Trap MS Ion Source Stable Trajectory To Detector Ion Source Ion Beam Trapped Ions To Detector Entry Plate Unstable Trajectory Exit Plate Ionization is outside the mass separator Mass filter - one m/z at a time Poles get dirty Slow scanning Ionization is inside the trap Trap - all ions stored together Clean Fast spectral output 3

4 Autoresonant Ion Trap Mass Separator Ionizer e Vdc -685Vdc 50 mv P-P 2MHz to 200KHz in 80msec 125 Vdc Electrostatic Ion Trap: Ions confined by purely electrostatic fields oscillate at a resonant frequency inversely proportional to m / z Where, m is mass, z is the total charge of the ion Autoresonance: F scan pushes ions when scan frequency matches ion s resonant frequency Electrostatic confinement = Ultra-low power requirements 4

5 AT MS vs. Quadrupole GA Quad GA = 1.5 sec, Ion Trap MS= 70 msec amu scan How much information you get in a 70 msec scan Quadrupole N (14) H 2 O (18) O 2 (32) N 2 /CO (28) Ar (40) CO 2 (44) Ion Trap MS How much resolution and gas detection you get in 1.5 seconds Quadrupole missed Freon (fluorocarbon) CF 3 C 2 F 3 H 2 Quadrupole missed Water Mass (amu) Ion Trap MS 5

6 Low Mass Comparison 6

7 VQM esolution Typical esolving power 150X 7

8 VQM Sensitivity / Dynamic ange Min detectable partial pressure is 2-3 decades below the max peak partial pressure 3 decades requires averaging Over 3 at UHV

9 VQM Advantages at UHV Capable of running at extreme vacuum levels Experiments run as low as 3E-13 Torr Can fill the trap at any pressure so performance does not degrade Does not over represent H 2 Low CO and CO 2 outgassing No O 2 outgassing Can get up to 4 decades dynamic range Catches fast transients

10 Waveform Comparison GA overestimating H 2 H amu 17 amu 18 amu CO from GA filament much larger than VQM VQM resolution is much better VQM GA Waveforms are normalized to water peak

11 VQM Sees Fast Transients Fast Transient between 3E-11 and 1.5E-10 Torr 253 msec response time Transient generated by turning Extractor Gauge filament on

12 GA Misses Fast Transients H 2 peak Transient is below noise level. GA not fast enough to see transient SS GA: SS=7 4 second scan (135 amu range) EM on; Gain:1000X This is not the transient it s a dropout in the water waveform

13 Mass Spec Comparison 830 GA Feature Comments Speed Scan speed 85 ms vs. 1-3 seconds (for amu) Power 15W vs W Max Calibration Single gas very simple calibration Zero Blast GAs have don t filter accurately below 4 amu Match Controller to Gauge Any controller can drive any gauge UHV Performance VQM has better dynamic range and low outgassing Cleanliness GAs filter ions to poles; 830 clean after a year of use Higher Pressures GAs with Faraday Cup detectors go up to 10-4 Torr Dynamic ange Can get 4-8 decades?

14 Introducing the 830 Vacuum Quality Monitoring System 830 VQM Viewer 830 VQM Controller 830 VQM Gauge Total Pressure Kit 14

15 830 VQM Features Summary Highly Differentiated! Fast (Scan time 85ms) Full amu measurement range Large Pressure ange UHV to 10-5 Torr Unprecedented low power requirements (8W) Single point mass axis calibration Comprehensive, easy to use viewer Small size Electronics remote from sensor Electronics not paired to the sensor 15