Handbook of Particle Detection and Imaging

Book Preface

Sophisticated instrumentations and imaging devices have become powerful tools in themodern world of technology. Advances in electronics, fast data processing, image reconstruction, and pattern recognition, just to name a few, have enabled the development of very elaborate investigation techniques that are now used in many different fields of science and many domains of applications. A large number of technological advances were originally developed in particle physics, but then spread to astrophysics, medicine, biology, materials science, art, archaeology, and many other application domains.

The field of imaging has known incredible advances in the recent decades.With atomic force microscopes or scanning force microscopes, very-high-resolution images can now be obtained. Resolutions on the order of fractions of a nanometer, more than 1000 times better than the optical diffraction limit have been reached.With the scanning tunnelingmicroscope, atoms can even be dragged along and positioned to build atomic-scale artificial structures. Increasingly higher resolutions require more and more storage space. A Triumph calculator from the fifties in the last century using ferrite cores had a storage capacity of 32 bits!The LargeHadronCollider (LHC) at CERN will produce roughly 15 petabytes (15 million gigabytes) of data annually.The discovery of a giant magnetoresistance by the 2007 Nobel laureates Peter Grünberg and Albert Fert enabled a breakthrough in gigabyte hard disk drives, and so this technique allows massive number crunching and can cope with huge data files.

Also the image quality and image reconstruction accuracy have substantially increased. For a decent photo one needs more than 100 million photons in the optical range. In observational astronomy the sensitivity of instruments has improved over a period of 380 years – from Galileo’s telescope to the Hubble Space Telescope – by a factor of 100 millions. For the discovery of an X-ray source in our galaxy, approximately 100 photons are sufficient. Using the imaging atmospheric Cherenkov technique, the discovery of a gamma-ray source can be claimed if more than about 10 photons – with little background – come from the same point in the sky.These advances also come about because high-resolution pixel detectors are available. In the 1960s the best charge-sensitive amplifiers used for the readout of semiconductor counters had a noise level equivalent to that of 1000 electrons. Nowadays one can unambiguously count single electrons, because the noise level has decreased by a factor of 1000.

Imaging also plays a major role in medical diagnosis. The old X-ray technique has been improved and has been made more sensitive by using image intensifiers. Antiparticles, discovered in cosmic rays in the thirties of the last century are nowroutinely used in positron emission tomography (PET) for cancer diagnosis and therapymonitoring. Also γ rays are used in gamma cameras, scintigraphy, single photon emission computed tomography (SPECT), and PET, with all sorts of diagnostic indications, including suspicion of heart or brain disease.The operation of Compton telescopes, known from astroparticle physics experiments, has now found its way into medical diagnosis as Compton cameras, although image reconstruction from Compton cameras remains a major challenge.

Beyond diagnostic imaging, nuclear techniques have also entered the domain of medical therapy.The strong ionization of charged particles at the end of their range (Bragg peak) has initiated new methods in cancer treatment (particle therapy) with substantial advantages over therapy with cobalt-60 γ rays. Apart from γ rays and charged particles, also neutrons have important applications in therapy.

On the detector side, a lot of progress has also been achieved. Early detectors, like the Wilson cloud chamber, provided lots of details about charged particles and their interactions. One drawback was a poor time resolution or repetition time. If you can only record one event per minute, such a detector is not suited for accelerator experiments. In the LHC, protons collide every 25 nanoseconds, resulting in a possible event rate of 40 million per second. Modern detectors cannot only measure the spatial coordinates, the energy and momentum of a particle, but they can also determine the identity of the particle. Particle identification is essential for the unambiguous characterization of interactions or new particle production.These techniques are also important in many other fields measuring electromagnetic radiation as γ rays, X rays, terahertz radiation, ultraviolett (UV), or infrared (IR) photons up to microwave photons.

This handbook centers on detection techniques in the field of particle physics,medical imaging, and related subjects. It is structured into four parts.The first two parts deal with basic ideas about particle detectors, like interactions of radiation and particles with matter and specific types of detectors. In the third part applications of these devices in high energy physics and related fields are presented. Finally, the last part concerns the ever-growing field of medical imaging using similar detection techniques.The different chapters of the book are written by well-known experts in their field. Clear instructions on the detection techniques and principles in terms of relevant operation parameters for scientists and graduate students are given. Detailed tables, diagrams, and figures will make this a very useful handbook for the application of these techniques inmany different fields like physics, medicine, biology, other areas of natural science, and applications inmetrology and technology.Also, it is our hope that such a broad presentation of particle detectors and radiation-based imaging can be a source of cross fertilization between different fields of applications.

Irène Buvat and Claus Grupen
Orsay and Siegen