Temperature, from a physicist's perspective, is not only a measure of hot or cold.

It is also a measure of the energy carried by atoms and molecules: temperature tells us how rapidly these atoms or molecules move within a solid, a liquid or a gas.

Temperature is different from heat. To feel heat on your fingers, you need density: the higher the density, the more heat is transferred to your skin—this explains why a neon tube containing a very hot (~10,000°C) but very tenuous plasma can be touched without harm.

In temperature, there is a theoretical absolute cold ("absolute zero") but no absolute hot: a particle can always move more rapidly but it cannot be more immobile than ... immobile.

When we talk about a 150- to 300-million-degree plasma in ITER, we're describing an environment where particles (the deuterium and tritium ions and the freed electrons) move around at tremendous speed: so fast and with such a high energy that when they collide head on the miracle of fusion happens. The electromagnetic barrier that stands between nuclei is overcome and the nuclei can fuse.

How will the ITER plasma be brought to such extreme temperatures—ten times higher, or more, than the core of the Sun?

Plasma heating in ITER will begin with an electrical breakdown, quite similar to what happens when we turn on the switch of a neon light. In the very tenuous gas mixture that fills the vacuum vessel (one million times less dense than the air we breathe) the electrical discharge strips the electrons from the atoms and the gas becomes a plasma—a particle soup of electrically charged electrons and ions.

"The electrons from the current collide with and communicate their energy to the ions from which they have been stripped," explains Paul Thomas, ITER Deputy Director-General for CODAC, Heating & Diagnostics. "Current intensity grows steadily and, as plasma resistance increases due to the collisions between electrons and ions, temperature also rises—this is Ohmic heating, like in a bread toaster or an electrical radiator."

However, contrary to what happens in metals, plasmas have an unusual property in terms of resistivity: the hotter they get, the less resistive they become. This means that Ohmic heating can heat a plasma only up to a point.

"For a long time," Paul recalls, "some fusion physicists dreamed they would achieve fusion with Ohmic heating alone by increasing the magnetic field. Even today, the project called Ignitor is based on this assumption. The problem is that the more intense the magnetic field, the stronger the mechanical strain on the machine's structure..."

Ohmic was the only heating source on the Soviet T-3, which achieved plasma temperatures in the range of 10 million degrees in the late 1960s—an achievement that left the nascent world fusion community agog and launched the tokamak race worldwide.

Achieving fusion, however, requires temperatures approximately ten times higher than what Ohmic heating alone can provide. In the 1970s, the fusion community began experimenting with additional heating techniques based on radio frequency (RF) waves, or the injection of energetic atoms into the plasma.

Yes, radio waves can heat. Whether at 40-55 MHz, like shortwave radio (ion cyclotron; a few GHz like microwave ovens (lower hybrid) or many tens to hundreds of GHz like very advanced radar (electron cyclotron), sending electromagnetic into the plasma can deliver enough energy to push it into the fusion regime. ITER will be equipped with an electron cyclotron and an ion cyclotron heating system, both delivering 20 MW of power.

But the workhorse of additional heating in tokamaks has been neutral beam heating—the injection of high-energy neutralized particles deep into the plasma.

Neutral beam heating is a bit like heating the milk in a pot by using a jet of hot steam from the espresso machine, what French garçons de café systematically do when you order cappuccino. As hot molecules from the steam jet collide with those of the cold milk, energy is transferred and hot milk is ready to be poured in the coffee cup.

"Exploitation of the neutral beam technologies we will use was pioneered in Japan," says Paul. We have a very strong collaboration with our friends in Naka. Neutral beam technology is also used on JET (ITER's neutral beam system will deliver seven times the energy of JET's).

The challenging technology of ITER's neutral beam system will be tested in a dedicated installation that was inaugurated a year ago almost to the day: the PRIMA Neutral Beam Test Facility in Padua, Italy. In parallel, IPP Garching is developing ELISE, an ion source half the size of ITER's; success on this test bed will greatly reduce the risk associated with the final development of the full-size ITER ion source at the SPIDER test facility.

ITER's three heating systems—electron cyclotron, ion cyclotron and neutral beam—feature different levels of technical complexity, maintainability and ease or convenience of use. The balance between these features is such that all three should be tested on ITER and developed to the point where a decision can be taken on which should heat a reactor, according to Paul.

"The reason we'll have all three systems in ITER is to have them compete in the nuclear environment — this is precisely what the 'technological viability' demonstration is about."

There are more municipalities in France than in all of Europe combined.

Every village, however sparsely populated, is a municipality in its own right and every municipality follows the same procedure to elect its municipal council every six years: at its first meeting, the new municipal council elects the mayor, or "First Magistrate."

Whatever the size of the constituency, madame or monsieur le maire is a major figure in the administrative organization of French society.

ITER was honoured, on Monday 11 March, to welcome no fewer than 53 mayors from neighbouring municipalities—from the smallest (Valavoire, pop. 32) to the largest (Sisteron, pop. 7,500).

Led by Daniel Spagnou, mayor of Sisteron and president of the Association of Mayors of the Alpes-de-Haute-Provence département, the 53 mayors were given a presentation on ITER by Director-General Osamu Motojima and a quick round-up by Agence Iter France director Jerôme Paméla.

"You are our partners in this scientific venture," DG Motojima told the mayors. "Once ITER has demonstrated the technical and scientific feasibility of fusion energy it will be your responsibility, as representatives of the people, to decide on the next steps that will be taken."

Monday 11 March was the second anniversary of the Great East Japan earthquake, tsunami, and resulting nuclear accident at Fukushima—Director-General Motojima insisted during his talk on the fundamental differences between fusion and fission in terms of safety. "A Fukushima-like accident cannot happen in a fusion installation," he stressed.

In 2003, the Alpes-de-Haute-Provence département (pop. 160,000) pledged EUR 10 million to the ITER project. It turned out to be a sound investment: to date, companies based in the département have benefitted from contracts amounting to EUR 29 million.

The Korean Domestic Agency signed a contract with SFA Engineering Corp. for ITER thermal shields on 28 February. The contract covers the detailed design of manifolds/instrumentation, the manufacturing design and the fabrication of the thermal shield system. "For us, this is a big step forward for the Korean contribution to ITER," said Myeun Kwon, president of the National Fusion Research Institute, after the signing.

SFA is a leading company in industrial automation with much experience in the procurement of advanced equipment related to fusion, accelerator, and space technology. SFA was deeply involved in the manufacturing and assembly of the Korean tokamak KSTAR.

The ITER thermal shield will be installed between the magnets and the vacuum vessel/cryostat in order to shield the magnets from radiation. The thermal shield consists of stainless steel panels with a low emissivity surface (<0.05) that are actively cooled by helium gas, which flows inside the cooling tube welded on the panel surface. The temperature of helium gas is between 80 K and 100 K during plasma operation. The total surface area of the thermal shield is approximately 4000 m2 and its assembled body (25 m tall) weighs about 900 tons.

The key challenges for thermal shield manufacturing are tight tolerances, precision welding, and the silver coating of the large structure. The thermal shield also has many interfaces with other tokamak components. "The Korean Domestic Agency is satisfied with this contract because the thermal shield is one of the most critical procurement items in the ITER project. We will do our best in collaboration with the ITER Organization to successfully procure the ITER thermal shield," said Hyeon Gon Lee, DDG of the Korean Domestic Agency, on the occasion of the contract signature.

Surprisingly, some twenty years of sporadic exposure to a temperature of 60 million degrees have left little trace on the C2 antenna's "mouth" — except for a bit of superficial melting here and some black deposits there, Tore Supra's lower hybrid antenna looks almost as new as the day it was installed.

One of the two original lower hybrid antennas of the CEA-Euratom tokamak, C2 greatly contributed to the progress of current drive analysis. It also played a key part in the success of the machine. "It is the hybrid system that allows for long pulses," explains Roland Magne, head of the Radio Frequency Heating and Current Drive group at CEA's Research Institute on Magnetic Fusion (IRFM).

Tore Supra entered operations in 1988 at CEA-Cadarache and still holds the world record of discharge duration with a 6-and-a-half-minute pulse achieved in 2003.

As science and technology steadily progress, vital components in a research installation like Tore Supra must be replaced or upgraded; C2's twin C1 was replaced in the early 1990s and C2 was permanently removed from the installation in 2008 in order to make room for the Passive Active Multijunction (PAM) antenna which was installed two years later. (The PAM is equipped with an integrated cooling system that allows it to deliver more power density to the plasma over longer periods of time.)

"C2 is still in good condition and can be advantageously re-used for current drive experiments on another machine," adds Magne. Recycling has always been part of fusion history: last week, the C2 was being prepared for a long trip to China. The antenna will soon be fitted onto the Chinese tokamak HL-2M, currently under construction at the Center for Fusion Science of China's Southwestern Institute of Physics (SWIP) in Chengdu.

C2 will not travel alone. Tore Supra is also shipping the 8 3.7 GHz, 500 kW klystrons that used to feed the antenna. Although they also operated for more than 20 years, the C2 klystrons (electron tubes that generate and/or amplify the radio-frequency waves) are still in operating condition.

The antenna and the klystrons will set the stage for a collaborative physics experiment between IRFM and SWIP. As a first step, four of the klystrons will be coupled to an antenna that the Chinese are designing for the existing tokamak HL-2A for experiments due to begin in 2014. (HL-2A is the original ASDEX Tokamak that was transferred from IPP Garching to China in 1995, and entered operations at SWIP in 2002.) When HL-2M is operational in 2015, all eight klystrons will be connected to the C2 antenna.

"This collaboration will provide for some very important ITER-relevant physics program," adds Magne.

On Tuesday, as the C2 antenna was about to be packed in its wooden crate, Chinese staff from CEA and ITER, all originally from SWIP, came to bid farewell. By 2015, both the antenna and the klystrons will start a new life in a brand-new tokamak on the other side of the world.

Search for the Ultimate Energy Source: A History of the U.S. Fusion Energy Program, by Fusion Power Associates' president Stephen O. Dean, explains the fundamentals behind fusion power and traces the development of fusion by decade—covering its history as dictated by US government policies, its major successes, and its prognosis for the future.

The reader will gain an understanding of how the development of fusion has been shaped by changing government priorities as well as other hurdles currently facing the realization of fusion power.