DOM Hub Power
System Description:
The collection of DOM Hubs, located in the counting house (IceCube
Lab) at the south pole, deliver power to, and collect data from
Digital Optical Modules (DOMs) deployed into the ice as part of the
IceCube particle astrophysics detector.
The first generation DOM Hub is housed in an "Industrial PC" chassis
box fitted with a "passive backplane" with 8 PCI slots, and two
slots for a particular family of full-length single board PC. (Only
one of the computer slots are used)
The DOM Hub chassis has fans which interconnect to pin-headers on
the SBC. That feature provides a means of monitoring fan function.
The DOM Hub has a parallel ATA IDE disk, and possibly a CD drive.
The DOM Hub chassis also hosts a pair of 48V AC-DC converters
(switching power supplies) which are shared by all the DOMs on a
string.
The DOM Main Board consumes approximately 3 Watts when acquiring
data in the normal mode. The high voltage mezzanine card which
powers the photomultiplier consumes about 0.5Watts.
As of December 18, 2010, the last of the 86 IceCube and IceCube deep
core strings were deployed.
The IceCube array has a sister array called IceTop consisting of 80
pairs of water tanks with two DOMs embedded in each.
The grand total of DOMs is therefore 5480.
Each in-ice string is hosted by its own DOM Hub. Each IceTop DOM Hub
hosts approximately 30 DOMs for a total of 11.
The cables that deliver power and provide communications with DOMs
are sized to dissipate approximately 7% of the power delivered to
the DOMs, on average. The details were captured in a spreadsheet; they're complicated.
The Acopian power supplies are approximately 80% efficient.
The computer power supplies are approximately 67% efficient.
The uninterruptable power supplies serving the DOM Hubs are
approximately 90% efficient.
Gross power delivers to the DOM Hubs:
Factoring in cable losses, and power conversion losses in the
Acopian power supplies
(5480 DOMs) x (3.5W/DOM) * (1.07 cable loss) / (0.80 power supply
conversion efficiency) = 25.7KW
(97 Hubs) * (8 x 8W/DOR card) + (38W CPU&Fans&Disk) / (0.67
power supply conversion efficiency) = 14.6KW
(14.5KW + 25.7KW) / (0.9 UPS conversion efficiency) = 44.6KW
That's pretty close to the recognized power consumption of 45KW for
the DOMs and DOM Hubs as of the spring collaboration meeting in 2012
Upgrades:
In the past year the notion has been brought forth that the DOM Hubs
could be modernized. The modernization might consist merely of
upgrading the single board computer to one that is both lower power
and more computationally powerful, like a modern dual core mobile
processor based model. More extensive modernizations focused on
complete replacement of DOR cards with something that is smaller,
and uses less power.
It was noted that the computer 67% efficient power supplies in the
DOM Hubs could be replaced by 90+ % efficient power supplies.
Likewise, the +/-48V DOM power supplies could be replaced with 90+ %
efficient power supplies.
A 10% saving of DOM power plus a 20% saving of DOM Hub power might
be worthwhile.
(2.5KW + 2.9KW) / 0.9 = 5.9KW after accounting for the UPS
efficiency
These back-of-the-envelope estimates should, of course, be confirmed
by measurement rather than relying on manufacturer's specifications.
gtp 3/25/2012