Personal webpage of Jack Hare

Left to right: Deer, Jack Hare.

I study plasmas, the hot matter which make up most of the universe. I am an experiment physicist, so I’m most comfortable in the lab, looking at data and saying “huh, that’s odd.” I mostly study high-energy-plasmas, which is a catch-all name for plasmas which are hot and dense, which distinguishes them from magnetically confined plasmas (which are hot and sparse) and atmospheric discharges used in industry (which are cold and dense).

In particular, I create plasmas using intense electrical currents (around 1 MA), which heat initially solid materials to the plasma state. This processes also generates very large magnetic fields (10s T or more) which accelerate the plasmas to high speeds (100s km/s). These hot, dense, magnetised plasmas are ideal for testing fundamental concepts in plasma physics, and mimicking the extreme conditions found in astrophysical objects.

I’m currently a post doc at the MAGPIE group at Imperial College London. From early 2021, I will join the faculty at the Nuclear Science and Engineering Department at MIT, where I’ll be developing a new pulsed-power generator for producing high-energy-density plasmas.

Unlike most of the universe, the Earth is not a plasma, which allows me to go hiking, canyoning, caving, ski touring etc. when I’m not in the lab.

This website is a mixture of information about my research, and the trips I’ve been on. Posts fall into one of the three broad categories below – the titles link to all the posts in that category.


Laboratory Astrophysics

A long exposure image of a plasma gun inside the MAGPIE vacuum chamber. Read more

I started this blog during my PhD at Imperial College London in the MAGPIE group of Sergey Lebedev. Here I worked on pulsed-power driven magnetic reconnection, creating high energy density plasmas from carbon rods (literally pencil leads!) in which strong magnetic fields were forced together and rapidly annihilated. Magnetic reconnection is a fundamental process in plasma physics, in which magnetic fields lines come together, annihilate each other and create new field lines. This annihilation is accompanied by a conversion of magnetic to thermal and kinetic energy, resulting in hot, fast moving plasma jets.

Most plasmas in the universe are also turbulent, and threaded with magnetic fields. This fields are twisted and tangled up by the turbulent motions, and some of them reconnect. This reconnection can be unstable, generating plasmoids which tear apart the reconnection layers, cascading energy down to ever smaller scales.

Building on my PhD project, I have designed several platforms for generating magnetised turbulence in the laboratory, as well as new diagnostics for measuring turbulence. This projects have shown that there is a need for microsecond or longer pulsers, which can sustain turbulence in a quasi-steady state, and I have been involved in the conceptual design of such devices.

Diagnostics for Fusion

The ITER Bolometry Vacuum test stand at IPP, a vacuum oven used to test bolometer prototypes for ITER.

In 2019, I spent a year at the Max-Planck Institute for Plasma Physics in Garching bei München. Here I worked on diagnostics for ITER, the massive international collaboration to build an experimental thermonuclear fusion reactor. I specifically worked on bolometers (which measure the radiated power from the plasma) and pressure gauges (which measure the pressure of the neutral gas inside the vacuum vessel). Since April 2020 I am again working at Imperial College London.

Adventures

Canyoning in Sardinia. Read more.

Fortunately I’m not always doing physics, and I escape as often as possible to the outdoors, where I enjoy hiking, cross country skiing, canyoning, caving, and cycling, among other things. I’ve found detailed trip reports extremely useful for planning my own trips, and many of these can be found on blogs, rather than tourist info sites or monolithic apps like Strava. I hope by blogging here that I can help others find more information which they can use to plan their adventures, and of course the blog acts as a good resource for me to remember what exactly it was that I did.