2012-Don-CandelaDon Candela has been in the UMass, Amherst Physics Department since 1986.  He carries out research in two main areas, quantum fluids and solids at very low temperatures and soft-matter systems such as flowing granular matter and fluids in porous media.


Nicholas Popowich is a Physics alumnus and current Mechanical Engineering grad student. He has developed probes and equipment for using PFG-NMR/MRI on granular systems, and he is working on simulations of granular systems including granular-memory numerical experiments.

Eamon Dwight is a physics major working on computer simulations of granular systems.

Former Group Members and Collaborators

PhD student Kevin Facto carried out experiments on gravity-driven flows of granular media using both NMR and force-transducer time series (the latter supervised by co-advisor Narayanan Menon).  His measurements of flow fluctuations in a narrow channel demonstrated that an apparent plug-like flow was in fact dominated by random, transient flow stoppages due to intermittent force networks.  Thesis: Measurements of gravity driven granular channel flows.


PhD student Chao Huan made detailed measurements of the granular temperature profiles in a vibrofluidized bed for comparison with Dufty’s theory for granular hydrodynamics.  Separately, he constructed an NMR-compatible gas fluidized bed and used it to study the motions of voids in the bubbling regime.  Thesis: NMR experiments on vibrofluidized and gas fluidized granular systems.  Current position: NHMFL, Gainesville, FL.

PhD student Xiaoyu Yang built a system to vibrofluidize a granular bed inside an NMR magnet, and used this system to test the energy scaling and granular hydrodynamics for a granular gas.  He also carried out experiments using MRI to measure the scaling of a front of oil displacing water in a porous medium.  Thesis: Granular media and two-phase flow in porous media.  Current position: Quality Electrodynamics, Cleveland.

Postdoc Neven Biskup did experiments to test the feasibility of hyperpolarizing dilute 129Xe using the properties of 3He and 4He  at low temperatures to switch the nuclear relaxation on and off.


Postdoc Hikota Akimoto worked with University of Florida collaborator Neil Sullivan to measure spin diffusion and viscosity of  3He-4He  mixtures at the NHMFL High B/T facility in Gainesville.  His experiments demonstrated a thousand-fold increase in in viscosity for the nearly 100% spin polarization achieved at 15 T and millikelvin temperatures.  Current position: RIKEN, Saitama, Japan.


PhD student  Lijuan Wei used a vibrating-wire viscometer to observe the increase in viscosity of a 3He-4He  mixture when it was spin-polarized by the application of an 8 T magnetic field.  In separate experiments on pure 3He using spin echoes she made the first unambiguous observation of spin diffusion anisotropy in a spin-polarized Fermi liquid.  Thesis: Momentum and spin transport properties of spin polarized Fermi systems.  Current position: Monterey Peninsula College, California.

MS student Takato Handa developed NMR methods to measure flows of oil and water in porous media, using chemical shifts and relaxation times to separately image the oil and water phases.  Thesis: Development of NMR methods to study multiphase flow in porous media.


PhD student Aimin Ding used PFG-NMR to measure hydrodynamic (Taylor) dispersion in water flowing through a porous medium over a broad range of Peclet numbers.  He also used this system to make the first systematic measurements of nonlocal (frequency and wavenumber dependent) dispersion. Thesis: PFG NMR study of hydrodynamic dispersion in porous media.  Current position: Cisco Systems, Boston


PhD student Neal Kalechofsky used NMR to study the nuclear magnetism of  3He filling the open space in silica aerogel at temperatures down to 5 mK.  Using pure  3He he found enormous effects due to the solid-like 3He layers localized on the aerogel strands, while these effects were suppressed when 4He was added to displace the localized 3He. Thesis: Nuclear magnetism of pure helium-3 and helium-3-helium-4 mixtures in aerogel.   Current position: Millikelvin Technologies LLC.


PhD student Don McAllaster used a small spherical resonator to observe spin waves in dilute 3He-4He  mixtures at temperatures down to 6 mK.  The spin diffusion and spin rotation that he measured using this technique agreed with new calculations by Mullin and Jeon, unlike earlier experiments. Thesis: Spin transport in dilute, spin-polarized solutions of helium-3 in helium-4.  Current position: Apple, Cambridge MA.