A quick method for Detector Voltage calibration
Occasionally we need to re-calibrate Detector Voltage. This is required when Tb159 Max Intensity / Pulse Count ratio (called Detector Gain) is <3 or >5.
The current manual instructions are to use the DAC Channel Setup tab in the Instrument Setup window and walk through select values of Detector Voltage.
It occurred to me that we have a ramp-up module that can be used for this purpose. The procedure I use is listed below.
- 1. Start by running tuning solution through the syringe pump (of course).
2. Open the Data Acquisition Settings window. In the Parameter area enter the following settings:
- a. For Parameter choose Detector Voltage.
b. For Start Value type in the low end of the range you want to test (e.g., -2800).
c. For End Value type in the high end of the range you want to test (e.g., -2200).
d. For Step Value type in 5 (or 10 if you want to cover a larger range quicker).
e. For Settling Time type in 2000.
f. Leave Pushes / Reading at 76800.
g. Leave Dual Count Start Point at 0.1.
- a. Set to Pulse Count.
b. Set max Y value to 300,000 (or less according to your instrument's performance).
c. Select Mass: All or Tb.
- a. Select Mass: Tb
b. Set max Y value to 1,000,000.
c. Check the Show History box.
When the read is done, in the ToF Range Per Reading window hover over the peak of choice (say the 3rd curve from the bottom) to get the Tb Max Intensity, then hover over that same step in the Masses Per Reading window to get the Pulse Count. Calculate the ratio.
The image below shows what my screen looks like when preforming Detector Voltage calibration.
Here is another image of this method run after CyTOF cleaning and XY realignment.
Warning: Do not place high values (let alone zero) in the End Value field. You WILL fry your detector!
If you have been around in previous software (and user manual) version you may remember the Ir191 process, that used Detector Voltage ramp up and slope calculations. The initial steps described here are not dissimilar.
I hope you find this method useful, and would be very interested in hearing back from other CyTOFers on how well this works and if any problems come up.