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Credit: HEGRA

Astronomers are assessing the damage caused by a fire that raged last week through the site of the High-Energy Gamma Ray Array (HEGRA) at La Palma in the Canary Islands (pictured right), only months before it was due to start operating at full capacity.

The array, a collaborative project run by laboratories in Germany, Spain and Armenia, detects and analyses cosmic rays and gamma rays hitting the Earth, and searches for galactic and extragalactic gamma-ray sources.

The fire appears to have been connected with the burning of scrub during landscaping activities in the national park in which HEGRA is situated. National park regulations stipulate that the site may not be cleared of scrub, and the tinder-dry gorse bushes burning between the detectors caused most of the damage.

HEGRA comprises a 200-square-metre chequerboard system of gamma-ray detectors, known as Cherenkov counters. These are punctuated by six imaging Cherenkov telescopes which are the most sensitive ground-based gamma-ray detectors in the world.

One-third of the array detectors and one of the telescopes were destroyed by the fire, at a cost estimated at between DM1.3 million and DM1.6 million (US$730,000-$900,000). Further damage to the instruments’ sensitive electronics by hydrochloride vapours released from burning plastic may be revealed later, according to Heinrich Völk, a director at the Max Planck Institute for Nuclear Research in Heidelberg, and a spokesman for the project.

Völk says the observatory was saved from complete destruction by scientists based at the site, who tried to bring the fire under control with extinguishers before the fire brigade arrived, as well as by a fortuitous change in wind direction.

In its various stages of completion, HEGRA had been operating for about six years. Four telescopes had been operating since the end of last year. Completion of the entire stereoscopic system of six telescopes was expected this winter.

HEGRA scientists are still able to work with the undamaged detectors and telescopes, but at greatly reduced sensitivity and efficiency. They are discussing possible compensation with insurance agencies. But because of laws restricting insurance cover of equipment bought with public money, the instruments’ total value is not covered.

Also, as Völk points out, money is not the only problem when replacing damaged instruments. “They are not off the shelf,” he points out. Laboratory staff who built them are not necessarily available to rebuild them.

The HEGRA teams will be asking for help from the agencies that have paid most of the costs of the multimillion dollar project — the German federal research ministry and the Max Planck Society.