Enable Recite

Subscribe options

Select your newsletters:

Please enter your email address:

@

Your email address will only be used for the purpose of sending you the ITER Organization publication(s) that you have requested. ITER Organization will not transfer your email address or other personal data to any other party or use it for commercial purposes.

If you change your mind, you can easily unsubscribe by clicking the unsubscribe option at the bottom of an email you've received from ITER Organization.

For more information, see our Privacy policy.

News & Media

Latest ITER Newsline

  • Construction | Art around every corner

    Most of us have experienced it. Turning a corner in one of the Tokamak Building galleries and looking up at the graphic pattern of embedded plates in the concre [...]

    Read more

  • Machine | Ensuring port plugs will work as planned

    The stainless steel plugs sealing off each Tokamak port opening are not only massive, they are also complex—carrying and protecting some of the precious payload [...]

    Read more

  • Networks | Ensuring real-time distributed computing at ITER

    Many of the control systems at ITER require quick response and a high degree of determinism. If commands go out late, the state of the machine may have changed [...]

    Read more

  • Fusion codes and standards | Award for ITER Japan's Hideo Nakajima

    Hideo Nakajima, a senior engineer at ITER Japan, has received an award from the Japan Society of Mechanical Engineers (JSME) for his contribution to the develop [...]

    Read more

  • Machine assembly | First magnet in place

    When it travelled the ITER Itinerary last year, or during cold tests in the onsite winding facility, poloidal field coil #6 (PF6) felt rather large and massive. [...]

    Read more

Of Interest

See archived entries

Powerful lasers

A mockup to demonstrate safety

During ITER operation, high-powered lasers will gather important diagnostic information on the properties and behaviour of the plasma, such as density, temperature and internal magnetic field.  An integrated safety system will ensure that the lasers operate safely in all circumstances, including the unexpected.

The safety system for the lasers moving between the Diagnostics Building and the vacuum vessel consists of several layers, including physical barriers and instrumented interruption functions, explains diagnostic physicist Christopher Watts. (Click to view larger version...)
The safety system for the lasers moving between the Diagnostics Building and the vacuum vessel consists of several layers, including physical barriers and instrumented interruption functions, explains diagnostic physicist Christopher Watts.
Lasers are common objects in our daily lives, found in CD/DVD players, office printers, the computer mouse, and laser pointers. But the lasers employed in ITER's diagnostic systems, according to diagnostic physicist Christopher Watts, are "about 100,000 more powerful than a laser pointer."

High-powered laser beams generated in the Diagnostics Building will be relayed by a series of mirrors along beam tubes through the galleries and port cells into the vacuum vessel. There, they will focus on various locations inside the plasma to obtain the needed data and return to the Diagnostics Building with their precious information.

Because unprotected laser beams—many radiating in the invisible spectrum—could be hazardous to the human eye, the beams are enclosed in metal pipes along the entire transmission line. But safety must be ensured even in the case of an accidental or unexpected breach in the laser enclosure.

Watts has been working with occupational safety engineer Roger Victori from the Control System Division to develop a reactive safety system that can respond in all situations (normal or accidental) and during all phases (operation, servicing, alignment). "We have developed a several-layer system that includes physical barriers as well as instrumented interruption functions," Watts explains.

In order to test the safety features of the system, they developed a tabletop mockup that employs a low-powered laser that is safe under all conditions. The mockup mimics the lasers' journey between the Diagnostic Building and the vacuum vessel, simulating the key elements of dormant safety measures that spring into action when a breach in the laser enclosure triggers an alert.

The mockup's controls and sensors are coupled to an automated logic system controlling the safety aspects. These measures include automated laser beam "blocks" at various locations along the transmission path that can engage to keep the laser confined to a certain region. If physical shielding is insufficient to mitigate the safety risk, electrical actuators interrupt the electrical power supply, shutting the laser down.

Already the mockup has proven useful, as it has helped identify key safety and operational interdependencies. Once the logic and specifications of the safety functions are worked out in detail, the mockup safety system will be provided to the laser diagnostic suppliers as an example of a system that meets ITER's safety requirements.

 


return to the latest published articles