Nav: Home

Clocking electrons racing faster than light in glass

February 06, 2018

Living life in the fast lane can be tremendously exciting, giving us the 'time of our lives' but how long does it really last? Experiments at the Tata Institute of Fundamental Research (TIFR), Mumbai have answered this question for a bunch of electrons traveling faster than light (fasten your seatbelts!) through a piece of glass. This study, done in collaboration with the Rutherford Appleton Laboratory in the UK and Centre for Intense Laser Studies and Applications (CELIA) in France has appeared in the Physical Review Letters on 5 February 2018.

Why is this question important? There are many reasons. Firstly, these electrons drive giant current pulses (millions of ampere) that can generate some of the most exotic states of matter that man has ever produced, mimicking conditions found in stars and planet cores in an earth bound lab. And that is not all. They are at the centre of technologies producing advanced x-ray, electron, and ion sources for applications in industry and medicine for one major reason-they can be generated on a small table top, unlike in conventional methods involving huge accelerators.

These electron pulses are produced by a high power laser irradiating a glass target hosted in a vacuum chamber on a table top. The laser, focused to a micrometre spot creates such a monstrous intensity that it not only ejects the electrons in the glass instantly from their locations but also kicks them, nearly instantaneously, to speed approaching that of light in free space. Since the light pulse that drives these electrons is ultrashort (10's of femtoseconds in our case), these electron pulses are also extremely short. Light however, is slowed down in glass and as a result many of these electrons end up traveling faster than light inside that medium. Under these conditions, the electrons emit a special type of radiation called Cherenkov radiation. This radiation therefore gives a measure of the number of 'faster than light' electrons and their "lifetime" in the medium.

How long does this radiation last? The challenge in measuring this is that the timescale of this emission is below the lowest that can be measured with normal electronic circuits, which is typically a few billionth of second. The team therefore generates a 'light-induced ultrafast shutter' lasting two trillionths of a second, which is activated by the same laser. With this ultrafast shutter, they are able to measure the temporal evoloution of the Cherenkov signal (and therefore the lifetime of these super-luminal electrons) with a 1000 x improved temporal resolution. They discovered the surprising result that the fast electrons live much longer inside a solid - much longer than the time they should theoretically take to traverse the target, lasting over 2000 times longer than the exciting laser pulse. Modelling done by scientists at CELIA sheds light on some of this peculiar behaviour.

How is this finding useful? For one, the knowledge of the lifetime of these fast electrons helps in unravelling their transport process in solids, which is crucial for several areas of high energy density science ranging from laser-driven fusion to developing advanced radiation sources for industrial and medical applications .

Life in the fast lane is not just exciting but can be useful too!
-end-


Tata Institute of Fundamental Research

Related Radiation Articles:

Cloudy with a chance of radiation: NASA studies simulated radiation
NASA's Human Research Program (HRP) is simulating space radiation on Earth following upgrades to the NASA Space Radiation Laboratory (NSRL) at the US Department of Energy's Brookhaven National Laboratory.
Visualizing nuclear radiation
Extraordinary decontamination efforts are underway in areas affected by the 2011 nuclear accidents in Japan.
Measuring radiation damage on the fly
Researchers at MIT and elsewhere have found a new way to measure radiation damage in materials, quickly, cheaply and continuously, using transient grating spectroscopy.
Radiation that knocks electrons out and down, one after another
Researchers at Japan's Tohoku University are investigating novel ways by which electrons are knocked out of matter.
Novel advancements in radiation tolerance of HEMTs
When it comes to putting technology in space, size and mass are prime considerations.
Radiation-guided nanoparticles zero in on metastatic cancer
Zap a tumor with radiation to trigger expression of a molecule, then attack that molecule with a drug-loaded nanoparticle.
Graphene is both transparent and opaque to radiation
A microchip that filters out unwanted radiation with the help of graphene has been developed by scientists from the EPFL and tested by researchers of the University of Geneva (UNIGE).
Radiation causes blindness in wild animals in Chernobyl
This year marks 30 years since the Chernobyl nuclear accident.
No proof that radiation from X rays and CT scans causes cancer
The widespread belief that radiation from X rays, CT scans and other medical imaging can cause cancer is based on an unproven, decades-old theoretical model, according to a study published in the American Journal of Clinical Oncology.
Some radiation okay for expectant mother and fetus
During pregnancy, approximately 5 to 8 percent of women sustain traumatic injuries, including fractures and muscle tears.

Related Radiation Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Don't Fear Math
Why do many of us hate, even fear math? Why are we convinced we're bad at it? This hour, TED speakers explore the myths we tell ourselves and how changing our approach can unlock the beauty of math. Guests include budgeting specialist Phylecia Jones, mathematician and educator Dan Finkel, math teacher Eddie Woo, educator Masha Gershman, and radio personality and eternal math nerd Adam Spencer.
Now Playing: Science for the People

#517 Life in Plastic, Not Fantastic
Our modern lives run on plastic. It's in the computers and phones we use. It's in our clothing, it wraps our food. It surrounds us every day, and when we throw it out, it's devastating for the environment. This week we air a live show we recorded at the 2019 Advancement of Science meeting in Washington, D.C., where Bethany Brookshire sat down with three plastics researchers - Christina Simkanin, Chelsea Rochman, and Jennifer Provencher - and a live audience to discuss plastics in our oceans. Where they are, where they are going, and what they carry with them. Related links:...