AMS Hardware / Upgrades / Development

Transcription

1 AMS Hardware / Upgrades / Development Performance Operational Problems, failures and some general comments AMS Users Meeting Oct. 13, 22 Hardware Upgrades Planned for 21 Adjustable lens system 16 mm Quad system Differentially pumped ionizer/quad region Alcatel hybrid pump Channel apertures Porous conical heater with thermocouple Redesigned electronics boxes/reduced cabling Inlet pressure gauge for sample flow rate.

2 Summary of AMS Systems Chamber Delivery Owner Serial No. Date Comment 1 Caltech 25-1 Sep- Upgraded, June-2 2 ARI - I Jun- 3 UMIST Sep- Upgraded, May-2 4 U. Colorado-Toohey Jun-1 5 SUNY Mar-1 Upgraded, April-2 6 Arizona Mar-1 7 CEH-Scotland Jun-1 8 MPI -Mainz Jun-1 Upgraded, April-2 9 ARI - II Jan-2 1 U. Tokyo Mar-2 First w/v31 on front 11 UMIST Flight Jun-2 12 NOAA May-2 13 Env. Canada May-2 15 DOE Jun-2 First with sm. Ionizer 14 U. Colorado-Jimenez Julich NIES/Sanyu 17 JCAP/Sanyu 18 Utah State No differential Pumping of ionizer 8mm Quad systems New chamber design V31 on inlet. Supports high thru-put lens Performance Upgrades Ionizer Component Status Result/Impact High emission current ionizer Tested Balzers IS42 special Signals increase linearly (~4x) up to 8 ma. (increased V6/V7 Detrimental to tungsten resolution) filament lifetime. Need to evaluate filament coatings to reduce work function. Reduced volume ionizer Closed source ionizer Tested evaluation unit from Balzers Tested ~2x increase in NO 3 IE. Selectively improves particle plume ionization. ~5% increase in IE. Ionizer magnets Tested ~2x increase in IE but also increase single particle pulse width size resolution.

3 Standard Cross Beam Ionizer Modification Standard Ionizer Before modification After modification 1/4 x 1/4 x stainless steel shim stock. Lightly spot weld this piece (~6 W*Sec) to top of ionizer to cover hole. 5% increase in signal. Close-up ionizer more... Effect of Magnets on Single Particle Pulse Width 5 Single Particle Signal (NO 2 + ion) No magnets, std. ionizer Magnets on sm. vol. ionizer 18 IPP 35 nm NO 3 IE ~8x Time (s) x1-6 Approximately doubles pulse width. Long tail affects size resolution measurement.

4 High Emission Current Operation Mass spectra at normal (2.5 ma) medium and high emission current settings MSClosed_R85 6 ma MSClosed_R81 4 ma MSClosed_R ma Mass Double and triple charged W ions dominate 2 High Emission Current Operation Summary x AB_Hz (28) W_Sig (m183) IE (35nm NH4NO3) IPP_3_46 (35nm NH4NO3) 6x1-6 8 IPP (3+46) Tungsten Signal (Hz) Ionization Eff. (Ions/Molec.) Air Beam (Hz) Emission Current (ma) Signals as a function of emission current increase linearly up to 5mA then appear to saturate, except tungsten [log scale] (small contribution of surface ionization?). Ionizer was retuned at each new emission current setting.

5 Tungsten ion signal increases as the 7.6 power of emission current 16 ln(w signal) fit_lnw_sig= W_coef[]+W_coef[1]*x W_coef={.62732,7.6277} a = ±.478 b = ± ln(emission Current, ma) Filament lifetime: If the lifetime of the filament is directly proportional to its vapor pressure (ion signal) and that the average life time of the filament at 2.5 ma is 1.5 years then at 5 ma it may last 1.5 days and at 6 ma only 8 hours! Evaluate filament coatings Want more emission at lower temperature/power Reduce W work function. ln(w sig / N2 Diff Sig) m/z % Thoriated Tungsten Pure Tungsten Ln(mA) This result compares standard tungsten to 2% thoriated tungsten filament. No apparent reduction in tungsten signal for the thoriated filament set (??) Alloy vs surface coating?

6 Summary of Ionizer Enhancements IPP = 4 IPP = 8 IPP = 2 IPP = 8+? Closed ionizer (5% increase in signal) Small Volume Ionizer (2x increase in S/N) IE 2x1-6 IE 4x1-6 IE 8x1-6 IE 3x1-5 Magnets (~2x increase, impact on size res.) High emission current ionizer (~4x increase, dynamic range limited...) Need to evaluate S/N increase Component Status Result/Impact High throughput lens Performance Upgrades other Designed. Needs to be built. 2-3 times more sample flow SIGNAL. Requires V31 on front. Converging inlet Conversion dynode mltiplier Tested qualitatively, find someone who can fabricate it. Tested Balzers SEV218. Mass bias eliminated but ion collection reduced. Increase transmission of micron size particles. (PM1 vs PM2.5 measurement) Eliminate mass bias. Enhance ion collection efficiency. Restek (glass) coating on detection cylinder. Implemented. Not yet quantified. To reduce water and organic adsorption.

7 Conversion Dynode Result ETP AF133 SEM 218 with CD (Balzers) SI, relative to mz usres/jayne/igor/sge_multgain.pxp Ion Mass Not shown, but ion collection efficiency with SEV218 ~ 2x less than SEV217 Summary of Performance Upgrades Combining ionizer improvements + high throughput lens expect mass concentrations detection limits approaching several ng m -3 in several minutes Achieving ionization efficiencies in the 1-5 range. Probably reached the limit?

8 Operational Upgrades/Development Component Result/Impact Status Temperature Get to the bottom of the Tested, being revised. controlled inlet. scaling factor. Inlet temperature, pressure and RH measurement. New rack system. More information on sample conditions. Transport fully assembled, simplifies setup. Needs to be implemented. On the drawing table. Beam width probe. Get to the bottom of the scaling factor Needs to be engineered. Optical Particle Detection. Detection on non volatile particles. Higher size resolution measurement. Prototype being tested. Under development. Monitor key board TPC EC QMG422 PS Computer UPS 24 41

9 Design allows instrument to be mounted left of right handed Top portion of rack can be easily removed to service AMS Moveable Wire Measures Beam Width 1. Transmission µm diameter wire 35 nm NH 4 NO 3 DOP wires.pxp Wire Position (mm) Is scaling factor related to beam width and decreased particle collection?

10 Temperature Regulated Inlet Optional temperature port Sample flow from isokinetic inlet (.1 LPM) Heating/cooling fluid flow Type K thermocouple with exposed junction To AMS Couples to 1/8 Cajon fitting housing critical aperture 1/8 Swagelok Union with Teflon and graphite ferrules. Position TC junction in gas stream without contact to walls New design using Peltier cooler being tested at BC Light Scattering Module sub-assemblies Diode pumped green laser 532 nm 25 mw Main development challenge is reducing scatter light Test version deployed during ITCT

11 Most Important Developments are going to be... Beam width probe (solve the scaling factor) Converging aperture (a true PM2.5 instrument) Hardware Failures Premature bearing failure of turbo pumps on front end Inlet and back pressure too high Alcatel Hybrid bearing problems new release planned for Oct. 22 National Instruments fast board DAC failure. Balzers Components RF QMH 41-5, IS42, recessed pins in ionizer connector

12 Hardware Failures, cont d V31 premature bearing failure infant mortality case. Vacuum Interlock (TP6), shut down of multiplier/heater/heater bias. V7 controller reverts to low speed operation. Pin-Hole assembly - tightening over-tightening, deformation of disc low pressure side O-ring disrupts particle transmission 5V regulator failure on TPC related to Alcatel modification Difficulties... Cabling which cable goes where, some left unconnected. AMS Acquisition Program corrupt AMSmenu.prm Balzers IS42 Loss of V6 and V7. Power glitch that resets SEM to FC and disables V6 and V7. Computer Instabilities Dual vs Single CPU. User Manual...troubleshooting and debugging section

13 Chopper Zero Issue Ion Signal (mz 46) Particle TOF Spectra for 35 nm NH4NO3 DMA particles Chopper freq (Hz) Peak TOF (s) 4.6x TOF (s) x /Chopper Frequency 25x1-3 If not zeroed exactly Particle velocity calibration will only be accurate for the chopper frequency it was calibrated. Maintenance Pin-hole assembly, check O-rings replace with 2-6 After a field mission clean the chamber and filters on all electronic components. Routine check for leaks.

14 We ve come a long way AMS system that demonstrated proof of concept ETP AF133 SEM 218 with CD (Balzers) SI, relative to mz usres/jayne/igor/sge_multgain.pxp Ion Mass FC biased with V7 (11V) FC at GND Signal AMU

15 Is there an advantage of operating at high emission current? 15x1-3 5x1-3 4 Compare S/N for two different emmision currents Ambient sulfate signal 2 sec average time Sig_p48_R86 5. ma Sig_p48_R ma 1 m/z48 at 5 ma m/z 48 at 2.5 ma TOF (s) This result suggests that operating at 5 ma does not have a significant advantage since the S/N is the same as operating at lower current (2.5 ma). (A big disadvantage of high emission current operation is the large tungsten signal and reduced filament lifetime)