Walter C. Pettus
Experimental Particle Astrophysics

Postdoctoral Researcher

CENPA and Department of Physics

University of Washington

pettus (at) uw.edu

About Me


I am a postdoctoral research associate at the University of Washington's Center for Experimental Nuclear Physics and Astrophysics (CENPA) working with Professors Hamish Robertson and Gray Rybka. My primary research focus is with Project 8, a novel experiment to precisely measure the tritium beta decay spectrum endpoint and thus directly probe the effective electron neutrino mass. Please contact me for more information, as this webpage hasn't been thoroughly updated since moving.


Previously, I was a postdoctoral associate at Yale University's Wright Laboratory working with Professors Karsten Heeger and Reina Maruyama. My primary research focus is with DM-Ice, a direct detection dark matter experiment based on NaI(Tl) scintillating crystals. This experimental program is seeking to measure an annual modulation of the dark matter signal to resolve a long-standing debate in the field regarding the interpretation of the DAMA experimental result. Towards this end, we have been operating several NaI detectors - DM-Ice17, a first-stage detector at the geographic South Pole, and DM-Ice37, an R&D detector setup at the Boulby Underground Lab, UK. The sucessor experiment, COSINE-100, has recently begun taking data with 100 kg of crystal mass in Yangyang Underground Lab, South Korea.


Always passionate about advanced instrumentation, I have been actively involved in preparation and deployment of all DM-Ice detectors. On-site work has taken me to the South Pole, Boulby (UK), Yangyang (Korea), and Fermilab where I have lead various efforts. During my four year tenure operating DM-Ice17, we demonstrated >99% uptime and temperature stability of <0.025°C (daily RMS fluctuation). My analysis emphasis has been on cosmogenic and other time-varying backgrounds in our NaI detectors. Details of DM-Ice17 operations and cosmogenic activation are presented in detail in my Ph.D. thesis work.


My graduate work on DM-Ice was completed in June 2015 at the University of Wisconsin-Madison's Physics Department and Wisconsin IceCube Particle Astrophysics Center under the direction of Karsten Heeger. Four years of my graduate career was supported as a fellow of the NNSA's Stewardship Science Graduate Fellowship.