Field ToF-AMS Operation

The purpose of this page is to serve as a repository of best practices on how to calibrate, operate, and document the calibrations/operation of a ToF-AMS during a field study. Much of it will also be relevant for lab studies.

Once the data have been acquired, please refer to the ToF-AMS Field Data Analysis Guide to guide the (very complex) data analysis phase.

This page was created by the Jimenez Group at CU-Boulder

Standard Field Campaign procedures

Make sure you are doing data acquisition with the latest version of Acquisition software whether a ToF or a Quad. GIVE Website (upgrade before field campaign, and check for any problems) ToF-AMS Software: http://cires.colorado.edu/jimenez-group/ToFAMSResources/ToFSoftware/index.html Quad-AMS Software: http://cires.colorado.edu/jimenez-group/QAMSResources/Software/index.html#Acq

Saving Frequency: at least 5 min data on fixed time grid (on the hour).

Mass Range: at least up to 0-300 amu (Q). One should go higher with the ToF instruments around 10-500 is encouraged.

For Q-AMS Particle TOF data the following masses should be used at a minimum: 16, 28, 30, 35, 43, 44, 46, 48, 55, 57, 60, 64

For Q-AMS Jump mass spec mode can be used, but it is not necessary for ground based monitoring unless mass concentrations are very low (remote clean sites).

Oven temperature: 600C is standard.

If you have the ability to dry the aerosol inlet, do that. At the very least a measure of the RH at the AMS inlet is needed if the inlet line is not dried.

Calibration	Frequency	Description
Inline HEPA Filter	At least every 3 days, best to do every day at the site. Also do this every time the instrument has been vented/pumped down.	30 minute (if every 3 days) or 10 min (every day) HEPA filtered, particle free air from inlet. Do not filter at the same time every day. See suggested schedule below. HEPA should be put on inlet outside (if possible) and this will allow a check for leaks in the inlet system, use a CPC. Note that there is an Inlet delay, so one should reinitialize (F5) AMS acquisition after the inlet residence time has elapsed so that the data files are not mixed filter/ambient data
IE calibration	Every Week (minimum) 2x a week better, and anytime the instrument has been pumped down, or there has been a problem. Specifically for a filament and/or MCP/electron multiplier change	Standard Ammonium Nitrate IE calibration.
Baseline / SI calibration	Before every IE calibration	See Instructions for Bitwise below
Size Calibration	Do at beginning and end of Campaign, and if there is a large instrument problem (e.g. loss of a pump etc.)	Standard AMS size calibration Note that size calibration changes if lens pressure changes. So if you change the orifice and the lens P changes more than 3%, you should do another size cal. (changes in P are amplified into larger changes in size)
Clock Synchonization		Computer clocks can drift by up to 1 min per day (occasionally worse). Either set up automatically or keep track of instrument clock in relation to other clocks.

Suggested Filter Times (perform the filter blank during the time interval indicated):

Day of week	Week 1	Week 2	Week 3	Week 4	Week 5
Monday	800-900	1000-1100	1200-1300	1400-1500	1600-1700
Tuesday	1100-1200	1300-1400	1500-1600	1700-1800	900-1000
Wednesday	1200-1300	1400-1500	1600-1700	800-900	1000-1100
Thursday	1500-1600	1700-1800	900-1000	1100-1200	1300-1400
Friday	1600-1700	800-900	1000-1100	1200-1300	1400-1500
Saturday	900-1000	1100-1200	1300-1400	1500-1600	1700-1800
Sunday	1200-1300	1400-1500	1600-1700	800-900	1000-1100

Calibrations

• BitWise

Instructions for use of BitWise

• Lens Alignment
• IE Calibration
• Size Calibration