Explaining Instrument Optimisation in a 5600 TripleToF
Understanding this process is a good way to get insight to how your instrument is performing and allow you to optimise your instrument for best resolution and sensitivity
This is an example of instrument optimisation on a 5600 tripleTof. Customers often find me staring at these and wonder how I interoperate these to know what my next step is to solve their issues with their tripleToF.
I have added text in bold that explains each voltage.
The first issue you can the Voltage for the detector was optimised at 2400V, This detector is close to the end of its life and will need changing in the next 3 months.
Optimal Detector voltage: 2400
Setting Detector voltage for both polarities.
Resolution optimization started
Original Values
RO2: 29.29
VS1: 0.31
HST: -0.92
FOR: 6.05
OFS: 10.81
MGV: -974.93
RO2: 29.36
This is the Rod Offset voltage for Q2, it’s the potential difference between the entrance (IQ2) and the exit (IQ3) of the collision cell (Q2), the software splits the channels and you can only see Channel 1 and Channel 4, the RO2 voltage is used to balance the two channels so they are similar in peak height. if channel 1 and 4 are tuned correctly channel 2 and 3 should align.
Adjusting ITC to: 5.0
The system will always use the ITC to choke the signal to less than 1000 counts, it does this so it can get a true reading of resolution and not overload the TDC (For an explanation of this please refer to my other post). Normally when you run the Instrument optimisation on a 5600 the instrument opt should use an ITC of less than 10. If you have this value on your final scans of the Instrument Optimsation you know your sensitivity should be satisfactory
VS1: 0.31
VS1 is Vertical steering 1, this is a voltage on the TOF entrance lens, this voltage should lay in the range of plus or minus 2, if the maximum on the ramp is off scale then you may have contamination of your ToF entrance lens or Q2.
HST: -0.91
HST is horizontal steering, this is a voltage on the TOF entrance lens, this voltage should lay in the range of plus or minus 2, if the maximum on the ramp is off scale then you may have a contamination issue with your ToF entrance lens or Q2. This is usually a little flatter than the VS1 but if you look at the graph you can see the top is very flat and not off scale. Quite often here you can see double peaks, if this is the case if your bigger peak is not off scale it should be OK but could indicate a contamination issue that may cause issues in time.
OFS: 13.35
OFS is offset voltage, this is a voltage used to tune the resolution and is supplied by the pulser HVPS. If this is off scale you could have an issue with your ToF entrance lens or your accelerator.
MGV: -974.91
MGV is your mirror grid voltage, this voltage is used to tune the resolution, it should be around -975V in a 5600.
FOR: 5.99
FOR is the focusing orifice, it is a lens on the TOF entrance lens, this can vary in range from 3V to 12V, sometimes can be completely flat.
MGV: -974.93
Final Values
RO2: 29.36
VS1: 0.31
HST: -0.91
FOR: 5.99
OFS: 13.35
MGV: -974.93
Aligning channels
Final Aligment Values
Chan 0 Alignment Positive-0.029393,-26.651865
Chan 2 Alignment Positive0.007408,3.230766
Chan 3 Alignment Positive-0.007580,-10.005968
Since we have split the channels they need to be aligned once again, this is a correction so each of the 4 channels lie on top of each other to form one peak.
This is a brief explanation of each of the ramps, you can get a lot of information from watching the instrument optimisation and can correct issues before they have an affect on your analysis
