Stavelet P Kuczewski D Lynn BNL Stave Meeting Oxford UK Feb 2012 AC and DC Referencing Schemes Update on EPC GaN devices Aug 2011 Irradiation of 200V GaN device 3045Mrad 1 x 10 ID: 322871
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Slide1
HV Distribution Box for Stavelet
P.
Kuczewski
,
D. Lynn (BNL)
Stave Meeting, Oxford, UK, Feb 2012Slide2
AC and DC Referencing SchemesSlide3
Update on EPC GaN devices
Aug 2011 Irradiation of 200V
GaN
device, 30-45Mrad, 1 x 10
15
protons/cm
2Just finished re-testingShowed negligible change. A very radiation hard 200 V transistor exists!Recent communication with EPC suggests 600 V samples available soon (but who knows)
Pre-irradiation
Post-irradiationSlide4
SemiSouth
1200 V and 1700 V
SiC
devices
Just finished characterization of 1200 V and 1700 V packaged devices
1700 V device preferred due to lower leakage, but both could work for usSlide5
1700 V
SiC
Transistor Off-State LeakageSlide6
1700 V
SiC
Transistor Off-State LeakageSlide7
On-state gate current
Both 1200 V and 1700 V devices require a sharp increase in gate (or more properly base) current above 2.5 V. Fortunately we do not have to operate above 2.5 V
Ned Spencer suggested circuit on right to decrease off-state current. While now this appears perhaps unnecessary, it looks like a good idea to place us further (0.6V) from the high on-state current near 2.5 VSlide8
Status of SiC Transistor investigation
We will in 2-3 months irradiate the packaged 1700 V and 1200 V devices at BNL
We do not wish to irradiate packaged parts at a proton or neutron facility as the package appears to contain a large amount of metal (we were not able to see the die inside with x-rays).
After several months of legal back-and-forth,
SemiSouth
will now sell us bare die that can be used for these
irradiations. We have just ordered them.Depending on time scale, we will irradiate them in the summer at Los Alamos (if their program continues). Or we may irradiate them at a neutron facility in Massachusetts. Else maybe a European facility??? (will need to get permission from
SemiSouth to do so.)
We also characterized some CREE SiC devices and will irradiate them at BNL for completeness. They require too large of a gate voltage to easily work for us, Vgs
> 5V. We also bought a transistor from TransSic. These devices costs $200, so we only bought one. It has taken several months trying to obtain it (I had to agree not to use it in nuclear or biological weapons. Customs has gotten involved).
It has just arrived, but we won’t get to testing it for awhile.Slide9
HV Distribution Box for
Stavelet
Schematic below originally intended to mate with Peter’s HV box via HV
lemos
Lemo
connectors are unavailable, will replace with different connectors and
glenair pigtail cableWill begin soon and have it sent before end of February to RAL.
Note: Only DC-referencing architecture of SP can be tried; AC referencing will have to await next SP stave and cable bus redesign for flexibility
Circuit can be used on DC-DC stavelet alsoSlide10
Near Term Plan
First will test
SiC
and
GaN
transistors biasing the module at BNL
Then will build HV distribution box and ship to RALWill layout and fabricate PCB for SemiSouth die for irradiation
Irradiate with gammas packaged SiC parts and retest
Arrange somewhere irradiation of bare die
Other Would like to consider bus changes for next serially powered stavelet to permit AC referencing as well as DC referencing option