[ RadSafe ] Article: Diamonds are a radiation physicist's best friend

[John Jacobus]

>From PhysicWEB at
http://physicsweb.org/articles/news/11/5/6

Diamond maker focuses on particle detectors
3 May 2007

Coveted for their beauty and hardness, diamonds are
also becoming the particle physicist's best friend.
That's because diamond can outperform silicon and
other semiconductors that are normally used as
radiation detectors in high energy physics
experiments. Now, a new company called Diamond
Detectors has been spun out of the UK diamond supplier
Element Six to focus exclusively on building detectors
based on synthetic diamonds.

The diamonds used in detectors must be very pure but
such stones are rare in nature and are difficult to
grow in the lab. Having honed the technique of
chemical vapour deposition, however, Diamond Detectors
says it can produce high-quality synthesized diamonds,
and its detectors have already been installed in
CERN's Large Hadron Collider, which is scheduled to
start up later this year. 

Silicon detectors are often used in high energy
physics to detect incoming charged particles or
radiation. When a charged particle enters a silicon
detector, its energy ionizes nearby atoms, creating
electron-hole pairs. Because silicon is a
semiconductor, these pairs are then free to move, and
so they can be attracted towards electrodes
surrounding the silicon to produce a measurable
signal. Pure diamond, however, can also behave as a
semiconductor, and if it is used in a detector it can
detect particles and radiation from UV to X-rays with
much less noise. In addition, unlike silicon, which
must be cooled using liquid nitrogen, diamond can
operate stably at temperatures well over 100 °C,
making it ideal for monitoring alpha, beta or neutron
radiation from hot nuclear reactors. 

Since the 1980s Element Six (E6), which is named after
carbon's atomic number, has been developing chemical
vapour deposition (CVD) in order to produce synthetic
diamonds. To make diamond via CVD, gases that contain
carbon, such as methane, are passed at low pressure
over a substrate, which is heated so that the gases
break down and form diamond. E6 has recently refined
this technique by altering growth parameters so that
the diamond doesn't grow too quickly, enabling large
crystals with very few imperfections to be
consistently produced. Now Diamond Detectors will take
over the development role and package the diamond into
detectors. 

"We have been selling to quite a few companies, which
is why it seemed like a good time to get the business
started and make it stand on its own two feet," Chris
Wart, the technical manager of Diamond Detectors, told
Physics Web. The firm’s customers include CERN, which
has worked with E6 since 2002 and is now using the
diamond detectors in the large ATLAS detector in its
forthcoming Large Hadron Collider. Its detectors are
also used at the Diamond Light Source synchrotron
facility, which opened recently in the UK. 

Diamond Detectors are also planning to create "body
compatible" detectors for use in radiotherapy. These
instruments will try to take advantage of the fact
that the density of carbon in diamond is similar to
that in soft tissue. "The applications of diamond are
so diverse," Wart added. "We are getting the diamond
synthesis right, and then we're investing in other
'portfolio' companies who can get on with the market
channels and expertise."

About the author
Jon Cartwright is a reporter for Physics Web


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What are the facts? Again and again and again – what are the facts? Shun wishful thinking,. . . avoid opinion, [and] care not what the neighbors think, . . .what are the facts, and to how many decimal places? You pilot always into an unknown future; facts are your single clue. Get the facts!” 
 "Time Enough for Love," Robert Heinlein, 1973

-- John
John Jacobus, MS
Certified Health Physicist
e-mail:  crispy_bird at yahoo.com

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