HV Distribution Box for Stavelet

1. HV Distribution Box for Stavelet P. Kuczewski, D. Lynn (BNL) Stave Meeting, Oxford, UK, Feb 2012

2. AC and DC Referencing Schemes

3. Update on EPC GaN devices • Aug 2011 Irradiation of 200V GaN device, 30-45Mrad, 1 x 1015 protons/cm2 • Just finished re-testing • Showed 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-irradiation

4. 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 us

5. 1700 V SiC Transistor Off-State Leakage

6. 1700 V SiC Transistor Off-State Leakage

7. 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 V

8. 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.

9. 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 cable • Will 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 also

10. Near Term Plan • First will test SiC and GaN transistors biasing the module at BNL • Then will build HV distribution box and ship to RAL • Will 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