In 2018, Professor Gérard Mourou (École Polytechnique) and Professor Donna Strickland (University of Waterloo) jointly won half of the Nobel Prize in Physics for ground breaking inventions in laser physics. “For their method of generating high-intensity, ultra-short optical pulses.”
Chirped Pulses
Professor Mourou and Strickland’s technique uses Chirped Pulse Amplification (CPA), which they initially imagined in 1983 when Stickland was a PhD student. Mourou describes their technique as a karate chop, “you deliver a very important power in a very, very short time”. Therefore, generating ultrashort high-intensity pulses in the lasers in the femtoseconds (10-15s or fs) without damaging the amplified material.
The video below is Professor Donna Strickland’s Nobel lecture explaining CPA.
Video timestamps:-
02:49-Intro
03:14-Is light a particle or wave?
05:24-Photoelectric effect (Albert Einstein)
08:25-Multiphoton Ionisation (Maria Goeppert Mayer)
09:56-Nonlinear interaction (Peter Franklin)
11:12-Birth of maser followed by laser (Theodore Maiman)
13:26-Linear optics
14:44-Laser made nonlinear optics possible (Nicolaas Bloembergen)
15:49-High Order Harmonic Generation (Stephen Harris)
16:49-How do we get an intense laser beam?
22:00-Chirped Pulse Amplification (CPA)
24:08-Pulse stretching
25:44-Reason CPA is called chirped
26:12-Laser Amplification
28:26-Pulse Compression
Applications of CPA
CPA lasers have various applications in astronomy, electronics and medicine. Examples include clearing space debris in earth’s orbit, laser micro-machining, laser eye surgery and proton therapy for treating cancers and tumours.
Below is Professor Gerard Mourou’s Nobel lecture on “Passion for Extreme Light”.
Video timestamps:-
03:00-Intro
04:40-Background of Quantum Optics and Relativistic Optics
08:02-Chirped Pulse Amplification (CPA), How does it work?
09:39-Peak power of the light in petawatt (PW) range for femtosecond (fs)
11:40-15 Evolution of intensity as a function of years
17:30-High precision micro-machining
19:49-CPA femtosecond lasers revolutionised ophthalmology
24:48-Giant Wakefield acceleration in gas and solid – (Tajima et Dawson 1979)
27:04-CERN accelerator vs Wakefield vs High energy X-ray Wakefield
32:00-Changing the Future with CPA – ELI facilities in the Czech Republic, Hungary and Romania
33:05-CPA in Nuclear Medicine
35:14-CPA lasers transmutation of Nuclear Waste
Nuclear Power
31 nations worldwide generated electricity via 455 nuclear reactors. 12% of the world’s electricity stems from nuclear power. In Europe, France relies on nuclear for 71% of its energy. Furthermore, Ukraine, Slovakia, Belgium, Bulgaria, Hungary, Sweden, Slovenia and the Czech Republic have between 56% to 35% of their energy derived from nuclear power.
Before considering installing a nuclear power plant all the positive and negative aspects should be investigated.
Pros and Cons of Nuclear Power
Nuclear powers benefits include: –
1. Cleaner fuel than coal, oil or gas regarding low greenhouse gas emissions
2. No combustion by-products, since no materials are burnt
3. Uranium is the most abundant metal in the world
4. High power output, not reliant on time of day or season like renewable energy
5. The cost of electricity is inexpensive compared to fossil fuels
6. Low operating costs and long plant lifetime, (however must take into consideration the high start-up and decommission costs)
7. Positive economic impact providing 400 to 700 local jobs, which boost the local economy
8. Technology and research related to nuclear power benefits other industries (including medicine, mining, engineering and construction)
The problems with nuclear power: –
1. Nuclear waste takes thousands of years to decompose to safe levels
2. Public perception (1) accidents (Chernobyl 1986 and Fukushima 2011). Although the casualty rates were not high, there are long-lasting environmental damages
3. Public perception (2) the Homer Simpson effect. The public is so used to this character they expect most power stations to be filled with incompetent personnel. The opposite is true. The qualifications, training and continuous professional development required to work in a power station would mean it is highly unlikely Homer Simpson would ever be in the control room or getaway with numerous accidents, incidents and near misses without re-training or disciplinary measures.
4. High upfront costs to build the facility. It takes 5-10 years to build a nuclear power station. Furthermore, the high decommissioning cost to dismantle an end-of-life plant. (Must take into consideration the low operating cost and low cost of electricity)
5. The plant is a security threat
6. Slow to adapt to changes in electricity demand
7. Not a renewable fuel source
Resting Place for Spent Fuel
In 2018, The International Atomic Energy Agency (IAEA) estimated the following inventory for solid waste in storage:-
•2,356,000m³ very low-level waste (VLLW)
•3,479,000m³ low-level waste (LLW)
• 460,000m³ intermediate-level waste (ILW)
• 22,000m³ high-level radioactive waste (HLW)
Treatment and disposal routes?
In the United Kingdom, we recommend you seek a Radiation Protection Adviser (RPA) or a Radioactive Waste Adviser (RWA) to assist with disposal options. Exempt and VLLW are not considered harmful to people or the surrounding environment. Therefore, small quantities of VLLW waste can be disposed of via local refuse or household dustbins. LLW and short-lived ILW are sent to specialist disposal facilities for treatment, conditioning and cementation. However, long-lived ILW and HLW usually require cooling and shielding in storage ponds, followed by dry cask storage and/or deep geological waste repository.
In Finland, they are building Onkalo, the first permanent nuclear waste storage site 458m below ground. Several tunnels at this site will be filled with casks of nuclear waste. Once at capacity, the site will be backfilled with clay. They designed this facility to a near-zero risk of nuclear material leaching into groundwater. Additionally, no security nor oversight is required at this site.
Lasers Transmutation of Nuclear Waste
Professor Mourou estimates that speeding the pulse rate by 10,000 times, CPA lasers have the potential to treat nuclear waste. One major problem with nuclear power is the long half-life of the waste produced. Uranium-235 has a half-life of 703 million years, plutonium-239 has a half-life of 24,110 years and Caesium-137 has a half-life of 30 years.
Professor Mourou explains the potential for lasers to transmute nuclear waste with the CPA technique. He gave the example of an atomic nucleus made up of protons and neutrons. By adding or removing neutrons from this atom, this completely alters everything, changing the atom and its properties. Mourou explained the potential of chopping the life span of nuclear waste from a million years to 30 minutes.
With a high-flux laser, one treatment irradiates a lot of material. Theoretically, this technique is applicable on an industrial scale. Mourou and Professor Toshiki Tajima (University of California Irvine) hope to improve this method over the next 10 to 15 years.
Presently CERN Hadron Collider is 27km long and between 50 to 175m underground. Using Tajima’s Wakefield principle, it would soon be possible to fit a new CERN on a football pitch, approximately 100m long. In the future, with a laser-induced x-ray Wakefield, it would be possible to fit an accelerator on a fingertip.
Professor Mourou is working with all three Extreme Light Infrastructure (ELI) facilities in the Czech Republic, Hungary and Romania towards a 10 petawatt (1015W or PW) objective. Each facility is using different methods. The goal is to work with the laser Wakefield in high energy x-ray region.
The Future of STEM Clean up
Professor Toshiki Tajima says, “It’s time for us to do toilet science, time to clean up what we have produced.” We agree it is time for Science and Technology to clean up its mess and contribution to solving environmental issues.
At Viable AlternativEnergy we look forward to seeing the potential of CPA incorporated in the treatment of hazardous and radioactive wastes. This technique is promising especially for the end of life radioactive wastes that are difficult to treat, recycle or recover. This includes sealed sources, gauges and HLW.
