This is a collaborative award to support the scientists who will work on the construction, commissioning and initial analysis of data from the High Altitude Water Cherenkov (HAWC) gamma-ray observatory being built at the Sierra Negra in Mexico. The HAWC collaboration consists of 14 US and 11 Mexican institutions. The observations of HAWC will probe the most extreme environments in the Universe, providing a unique view of non-thermal processes in the Galaxy and beyond. The key science goals of HAWC are to: (a) Measure the spectrum of Galactic sources to the highest energies; (b) Map the Galactic diffuse gamma-ray emission from 1 TeV to 100 TeV, measuring the cosmic-ray flux and spectrum across the Galaxy; (c) Study transient emission from active galactic nuclei (AGN); (d) Monitor the sky for 100 GeV emission from gamma-ray bursts; and (e) Search for new TeV physics with HAWC's unbiased sky survey. HAWC measurements have the potential to shed light on the fundamental symmetries of nature, including the search for Lorentz violation at extreme energies, the search for the dark matter in the universe, and the direct detection of massive relic particles. HAWC is a water Cherenkov air-shower detector consisting of 300 large water tanks. The tanks will be densely packed to cover an area of about 20,000 square meters. The goal is to begin taking data while the array is under construction and to have the full detector online within approximately three years.
Broader Impacts: HAWC is an all-sky instrument that will serve as a TeV "finder" telescope for Imaging Atmospheric Cherenkov Telescopes (IACTs) and IceCube and will have the sensitivity to extend the measurement of satellite-discovered sources to TeV. HAWC will build on the strong outreach record of Milagro to bring this exciting field of research to students and the general public. Since HAWC is a joint US-Mexican project, this will be an excellent opportunity to attract talented Hispanic students to the field of Particle Astrophysics and to Physics in general. The project has developed an outreach video about HAWC and web materials about HAWC and Particle Astrophysics in both Spanish and English.
The PI Ignacio Taboada and postdoctoral fellow Andreas Tepe have participated in the construction of the High Altitude Water Cherenkov (HAWC) gamma ray observatory. The objective of HAWC is to map a large fraction of the sky using very high energy gamma rays. HAWC operates by observing at ground level particles produced by gamma rays interacting in the upper atmosphere. These particles are detected in water tanks via bue Cherenkov light with photomultiplier tubes (PMTs). The Georgia Tech group has developed the high voltage system that is used to operate the PMTs. This task required selecting the appropriate hardware and laboratory testing. The high voltage system is scheduled to be installed at site in early 2013. The Georgia Tech group has also developed the scaler system. The main task of the scalers is to monitor the health of the PMTs. This is accomplished by counting noise in the PMTs in fixed time windows. A healthy PMT in HAWC should produced approximately 30,000 (60,000) counts per second for 8" (10") diameter. For this task hardware was selected. The hardware was tested in the laboratory. Data adquisition software was written. The hardware has been installed and operated at the HAWC site for many months. The system has been shown to be very reliable, with an intrinsic uptime of 99.9%. The system has already been useful in identifying and fixing issues with the detector. An example was a water tank that was accidentally opened while the PMTs were powered and thus exposed them to day light. The Georgia Tech group has realized that the scalers have the potential to observed Gamma Ray Bursts (GRBs) with energies exceeding 30 GeV. Detector simulations were conducted at Georgia Tech that lead to a refereed publication in the journal astroparticle physics that predicts the sensitivity of HAWC to GRBs.
