User Tools

Site Tools


instruments

Instruments

Different technical solutions for purifying CO2

GC capillary / packed gel column; helium flow / passive flow…

Automated reaction and purification of carbonate samples

Short overview of current designs?

Measurement and correction of baseline shifts

Detection of baseline shifts, i.e. baseline not at 0 for all cups
 Slow hV scan: see both shift in baseline before and after a given peak.
 Peak jump:  that is, switch gas definitions to one with same tune conditions but offset hV.
 Jump position: determine from slow hV scan, pick stable baseline region
 Other signs:  drift in d47 vs D47 slopes for heated/equilibrated gases

Causes of baseline shifts

 Secondary electrons.  Ion beam can kick off electrons when it hits the cups (or walls, other detector components, etc.)  
   This shows up as a negative baseline, especially in the very sensitive cups and wider cups.  
   Scales with main ion beam intensity.
 Peak tailing.  The main ion beam does scatter slightly in flight, and some of those ions can be picked up in other cups.
   This shows up as a positive baseline. 
   Scales with main ion beam intensity.
''to be continued''
instruments.txt · Last modified: 2012/12/17 18:23 by golack