[Sbs_gems] [EXTERNAL] Wiener HV modules not recommended for parallel-use.

[John Boyd]

I spoke with the engineers at Wiener today and discussed with them our
ideas for running a higher current (greater than 1 mA) configuration by
running channels/modules in parallel. Both engineers, Bryce and Andreas,
are familiar with our application -- using these for GEMs -- and how
everything is meant to supply and work together (they've worked pretty
extensively with me/us for a few years).

The final conclusion of my conversation with them was that it is not
recommended to run these supplies in parallel to try and get the two 1 mA
supplies to feed more than 1 mA. They even sent this question back to the
main facility in Germany with the same recommendation.

The concern they had was that there would probably be inconsistencies or
problematic issues with the regulation of the voltage or current. If the
supply experienced any oscillation in trying to maintain voltage/current
that was not properly regulated then this oscillation could cause serious
problems to either our devices (GEMs) or the HV modules themselves.

Another issue would be the modules' ability to ensure that the balancing
between the two parallel "legs" is consistent. Without proper redundant
feedback loops and reverse polarity diodes feeding back into the main
control module (so additional modifications would be needed to get this
interfacing at inside the module) it would be difficult to make sure that
both "legs" were trying to occupy an equal portion of the potential (if one
side tried to supply more than it may oscillate into a much higher range
and then reach a current limit thereby tripping and leaving only the other
leg still energized and feeding the single leg).

I hope this all makes sense. I gathered this all through conversation so
hopefully I interpreted and relayed this information correctly.

They did offer to provide us with loaner (old version) HV power supplies
that we could use to test our idea.

The lead time for any of their modules is 12+ weeks.

They do have a HV module that would work (4kV at 2mA) but it has the lead
time stated above.

Thank you and please offer any comments/concerns.

Best,

John
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