research curriculum vitae publications presentations

GRAMS (Gamma-Ray and AntiMatter Survey) is a novel project that is the first to target both astrophysical observations with MeV gamma-rays and an indirect dark matter search with antimatter. The GRAMS instrument is designed with a cost-effective, large-scale LArTPC (Liquid Argon Time Projection Chamber) detector surrounded by plastic scintillators. The astrophysical observations at MeV energies have not yet been well-explorered (the so-called 'MeV-gap') and GRAMS can open a new window in this energy region.

GRAMS can improve sensitivity by more than an order of magnitude compared to previous experiments. The GRAMS detector is also optimized for cosmic-ray antimatter surveys to indirectly search for dark matter. In particular, low-energy antideuterons will provide an essentially background-free dark matter signature. With an exceptional sensitivity, GRAMS would be able to detect antideuterons from dark matter annihilation or decay even with a single balloon flight. GRAMS would also be able to investigate and validate possible dark matter signatures suggested by the Fermi Gamma-ray Space Telescope and the Alpha Magnetic Spectrometer.


The SuperCDMS (Cryogenic Dark Matter Search) SNOLAB experiment, the fourth generation of the CDMS project, is a DOE/NSF funded direct detection dark matter search experiment that exploits the nuclear recoil energy induced by dark matter-nucleus scattering through phonon and ionization signals.

The phonon signal warms up the tungsten TESs (transition-edge sensors) and the current change in the input coil is measured with SQUID (superconducting quantum interference device) arrays while the HEMT (high electron mobility transistor) amplifier is used to measure the ionization signal. There are two types of detectors, iZIP (interleaved Z-dependent Ionization and Phonon) and HV (high-voltage) detectors, where the phonon and ionization signals in the iZIP detector provide an excellent signal-to-noise ratio while the HV detector can have a significantly low energy threshold with the enhanced phonon signal from the Neganov-Luke effect. Detectors are deployed in the underground facility and operated at temperatures about 50 mili-Kelvin to minimize the background and noise.


The General AntiParticle Spectrometer (GAPS) is a novel approach for the indirect dark matter search that exploits cosmic antideuterons. GAPS utilizes a distinctive detection method using atomic X-rays and charged particles from the exotic atom as well as the timing, stopping range and dE/dX energy deposit of the incoming particle, which provides excellent antideuteron identification.

In anticipation of a future balloon experiment, an accelerator test was conducted in 2004 and 2005 at KEK, Japan, in order to prove the concept and to precisely measure the X-ray yields of antiprotonic exotic atoms formed with different target materials.

A simple, but comprehensive cascade model has been developed not only to evaluate the measurement results but also to predict the X-ray yields of the exotic atoms formed with any materials in the GAPS instrument. The cascade model is extendable to any kind of exotic atom (any negatively charged cascading particles with any target materials), and it was compared and validated with other experimental data and cascade models for muonic and antiprotonic exotic atoms. The X-ray yields of the antideuteronic exotic atoms are predicted with a simple cascade model and the sensitivity for the GAPS antideuteron search was estimated for the proposed long duration balloon program, which suggests that GAPS has a strong potential to detect antideuterons as a dark matter signature.

A GAPS prototype flight (pGAPS) was launched successfully from the JAXA/ISAS balloon facility in Hokkaido, Japan in summer 2012 and a proposed GAPS science flight is to fly from Antarctica in the austral summer of 2017-2018.