Category: News

Research with the HAWC Gamma-Ray Observatory

The High Altitude Water Cherenkov detector, or HAWC detector, is a high-energy gamma-ray observatory. It is currently under construction in Mexico at 4,100 m (13,450 feet) altitude. Gamma rays are part of the electromagnetic spectrum, like radio waves or x-rays. The main difference is that gamma rays are the most energetic photons that we know so far.

The HAWC detector is already measuring the secondary particles produced by the electromagnetic interactions of gamma rays with the particles that make up the atmosphere. The detection of the secondary particles with 300 water Cherenkov detectors, or WCDs, provides information about the direction of the primary gamma-ray photon and its energy.

I am doing my research with Dr. Petra Hüntemeyer. Part of my research is focused on the calibration system of the detector. I maintain the software to control a laser that is used to calibrate the timing and the charge of the WCDs. A view of the HAWC detector is shown in Figure 1.

The second part and main goal of my research is the study of the Galactic Diffuse Emission (GDE) at TeV energies. This emission is formed mostly of photons that were produced by the interaction of cosmic ray particles with gas and radiation fields in the Milky Way Galaxy. Since the gamma-ray photons are a product of the high-energy cosmic rays, studying the GDE will help us understand how cosmic rays propagate and distribute in the galaxy. Currently, I am analyzing data from the Fermi Space Telescope to study GDE in different regions of the sky, like the Cygnus arm of our galaxy. I am also doing simulations to understand how well HAWC will detect the GDE. Figure 2 shows the result of one of these simulations with statistical excesses of gamma rays along regions of the Galactic Plane.

by Hugo Ayala

Bishnu Tiwari is a graduate student in the Engineering Physics program at Michigan Technological University. He has been working with Professor Yoke Khin Yap since the beginning of 2012. Professor Yap’s group is investigating the fundamentals of synthesis, characterization and applications (in electronics and the biological sector) of novel nanomaterials such as carbon nanotubes (CNTs), boron nitride nanotubes (BNNTs), boron nitride nano sheets, graphene, and B-C-N nanostructures, as well as in developing the quantum dot nano devices. The fabrication of the nanomaterials is done by the techniques of pulsed laser vapor deposition (PLD), chemical vapor deposition (CVD), and so on. Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), UV-visible measurement of the sample, and scanning electron microscopy (SEM) are the techniques we utilize for characterization of materials.

Tiwari is also interested in the applications of nanomaterials in biological sectors. The group has recently started a project to test the toxicity of various kinds of nanomaterials in HeLa Cells, in collaboration with Dr. Caryn Heldt’s group in the Department of Chemical Engineering. The purpose of this experiment is to understand the nature of conflicting results regarding the toxicity of nanomaterials which are being considered as prospective materials for drug delivery.

Members of the High Altitute Water Cherenkov (HAWC) Gamma-Ray Observatory met at Michigan Tech on September 23-25, 2013. The meeting was attended by about 60 international members. The meeting was coordinated by Assistant Professor of Physics Petra H. Huentemeyer.

Professors John Jaszczak (Physics) and Paul Bergstrom (ECE), with PhD students Madhusudan Savaikar and Douglas Banyai, published a paper, “Simulation of charge transport in multi-island tunneling devices: Application to disordered one-dimensional systems at low and high biases” in the latest issue of Journal of Applied Physics (vol. 114 issue 11).

Recent work published by Professor Yoke Khin Yap (Physics) on transistors without semiconductors has gained attention at the Center for Nanophase Materials Sciences (CNMS) at Oak Ridge National Laboratory (ORNL). Yap’s work “Room Temperature Tunneling Behaviors of Boron Nitride Nanotubes Functionalized with Gold Quantum Dots,” first appeared in CNMS Research Highlights, and then later in the September issue of the CNMS User Newsletter.

This work is now being highlighted by Dr. Sean Smith, Director of CNMS, during his overview talk in the Triennial Review of CNMS. The triennial review is being held on September 24-26, 2013 at CNMS as attended by the review team of the U.S. Department of Energy, the CNMS Advisory Committee Review Panel, and scientists in CNMS.

On September 25, Professor Yap presented an invited talk entitled “Transistors without semiconductors: tunneling behavior of functional boron nitride nanotubes” during the review. The highlights are related to a Yap article recently published in Volume 25, Issue 33/2013, pages 4544-4548 of Advanced Materials (http://onlinelibrary.wiley.com/doi/10.1002/adma.201301339/abstract).

Yap’s coauthors include Professor John Jaszczak, research scientist Dongyan Zhang, postdoctoral researchers Chee Huei Lee and Jiesheng Wang, and graduate students Madhusudan A. Savaikar, Boyi Hao and Douglas Banyai of Michigan Tech; Shengyong Qin, Kendal W. Clark and An-Ping Li of the Center for Nanophase Materials Sciences at ORNL; and Juan-Carlos Idrobo of the Materials Science and Technology Division of ORNL.