Thu Apr 06, 2017 11:25 pm by mleipold
Hi Andrew,
I know that Helios instruments definitely run at a higher Current. This happens with out-of-the-box Helios. It *also* happens with v2-to-Helios upgrades (I know of at least two instances); since the cones are not typically changed during the upgrade, this means it has to happening because of something involved in the upgrade itself. From some discussions I've had, most likely it's due to the Helios injector doing a better job of focusing the cell events into the plasma and therefore more on target into the cones. If so, then the skimmer-reducer (which is affected by the Current value) might need more Current to "steer" the ions into the instrument.
I know that some people are putting Helios injectors into their v2 instrument; I would be curious to hear whether they also notice a jump of ~2 units in Current.
For v1 and v2 instruments, I agree, a brand-new shiny skimmer-reducer should start out in the Current = 3-4.5 range. By the time they get to 8-8.5, they're usually in need of a change: ; it was usually physical damage that would make you need to swap them out (non-centrosymmetric orifice, overly widened orifice, physical chipping/pitting, etc), rather than maxing out the Current = 10. So, 4-5 Current units of lifetime, *easy*.
In a year and a half of Helios instruments, we've replaced the cones on each, once. For Helios instruments, you generally have a starting Current value ~7-8 for a shiny new cone right out of the packaging. Which, if you have a max Current lifetime = 10, would mean you only have 2-3 Current units of lifetime.....I don't think that's correct.
After only 2-3 months or so, we had hit Current = 10, and our Tb and Tm Duals continued to decrease. Fluidigm was insisting it was a skimmer-reducer problem, I insisted a remote session to check. When the Fluidigm Markham engineer remoted in, he did a Current Sweep (like you used to be able to do in v1 and v2) and noticed that the Current hadn't peaked during initial Tuning. Looking at the full sweep, the Current optimum was ~11 (ie, one unit above the software upper limit).
So, he increased our upper limit to Current = 15, and we've been fine ever since (after Oct 2015): the Tb and Tm went back to where they had been with the new installation, etc. In my case, the skimmer-reducer needed to be replaced in the 12-13 range, which would be the typical 4-5 Current units of lifetime. We replaced another one this week, which had reached Current = 11.5.
In short: in my experience, Helios skimmer-reducers need higher Current, and therefore the upper limit of your Helios *should* be ~15, not the default 10....they're definitely usable above 10, and at a few thousand dollars apiece, aren't a component you want to replace too often if you can avoid it!
Mike