1. Particle Accelerators for Research and for Medicine
Prof. Ted Wilson (CERN and Oxford University)
based on the book:
ISBN
This talk:
More than 90 years ago, the great physicist Ernest Rutherford in his inaugural address as president of the Royal Society in London, urged fellow scientists and electrical engineers to invent a reliable machine to accelerate charged particles to a higher energy than was then available from natural radioactive decay. This talk will describe the particle accelerators that followed this plea — some of them the largest scientific tools known to man. It is an endeavour spanning the whole of the twentieth century. It challenged the dedication, ingenuity, and imagination of both physicists and engineers in very much the same way as had the mammoth projects and the technological triumphs — the railways, bridges, steamships and auto mobiles — of the nineteenth century.
The appetite of particle physicists for particles of higher and higher energy seems never to be satisfied and over the last century, many generations of accelerators have been built to provide particles of ever higher energy, for experiments designed to answer the latest questions concerning the ultimate structure of matter.
But not everyone has followed the road map of Rutherford, and accelerators for applications other than high-energy now outnumber the large atom-smashers by two orders of magnitude. The speaker will concentrate on some of the more practical uses of accelerators that directly benefit mankind, including medical diagnosis and therapy.

2. The race to high energies
Rutherford fired the starting pistol
Rutherford fired the starting pistol
At the Royal Society in 1928 he said
“I have long hoped for a source of positive particles more energetic than those emitted from natural radioactive substances”.
At the Royal Society in 1928 he said
“I have long hoped for a source of positive particles more energetic than those emitted from natural radioactive substances”.
Engines of Discovery

3. The Large Hadron Collider (LHC)
The LHC, at CERN, is the primary tool
to which high-energy physicists
are looking. The hope is to discover the
Higgs particle. The machine is 28 km
in circumference.

4. An “exploded” diagram of the ATLAS detector, for the LHC.

5. Wideroe invented the Linac
Particle gains energy at each gap
Lengths of drift tubes follow increasing velocity
Spacing becomes regular as v approaches c
Someone who was inspired by Rutherford was a Norwegian – Rolf Wideroe. A prolific inventor, he is variously credited with the invention of the betatron, the linac, the synchrotron, and storage rings for colliding beam and certainly he built the first pair of linac drift tubes for his Dr. Ing. thesis at Aachen in 1927.
During the war years he had indeed been working in Berlin on betatrons which he was told would serve as a compact X-ray source in field hospitals. (Actually, The Nazi leadership hoped to use it to blind bomber pilots.) He agreed to do this when promised the release of his brother, Viggo, who had been imprisoned by the Nazis on suspicion of spying in Norway.
Can you imagine why this device had to remain (on the shelf) for 15 years before it could be used.
His many other claims as an innovator, though substantiated by patents were often hidden from the free world of science by the clouds of war and had to be re-invented , either independently or subsequently by others. It does seem clear however that his enthusiasm for storage ring colliders prompted his good friend Touschek, himself imprisoned by the Nazis, to build the first such device after the war.
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6. Cyclotron r + Magnet Vdee~ At all radii particles cross
acceleration gap at same moment !

7. The 60-inch cyclotron. The picture was taken in 1939.
He built many machines for medicine encouraged by his brother John who was a doctor – irradiated his grandmother was a master of fund-raising and publicity. Berkeley University president is reported as complaining that “Instead of a University with a Cyclotron Berkeley has become a cyclotron with a University attached. People told him relativity would limit energies to 30 MeV but he just pushed on and built a 184 inch machine.
The 60-inch cyclotron. The picture was taken in 1939.

8. Spect diagnosis
Early imaging techniques mainly used thallium - 201, gallium-67, iodine-123 and indium-111. These isotopes emit single photons and have half-lives of the order of days so that they may be carried to a hospital. The camera which records the pattern of emitted radiation is rotated about the patient to digitize images from a number of directions to reconstruct the three dimensional shape of the source of the photon emission. The same computational algorithms that allow us to produce a three dimensional picture of an organ from multiple x-ray views (CAT scan) are used. This technique is called Single Photon Emission Computed Tomography (SPECT). Resolution achieved is typically of the order of 1 cm.

9. Linacs – an idea waiting for a technology
Luis Alvarez
Ed Ginzton
Linacs had to wait 15 years for this technology – the S-band Klystron
The high powered klystron was invented, during WWII, by
The Varian Brothers and Ed Ginzton. Using it, Bill Hansen
invented the electron linac. A succession of machines at
Stanford culminated in the two-mile accelerator, SLAC,
led by WKH Panofsky. That machine made many important
high-energy physics discoveries and then became the
injector for PEP and PEP II, and now has become the
LCLS.
In the years before World War II, Alvarez was particularly prolific, having discovered the capture of electrons in beta decay (K-capture), determined the stability of He3, and measured, with Felix Bloch, the magnetic moment of the neutron.
With the start of World War II, Alvarez went to the Radiation Laboratory at MIT, where he worked on ground-based radars. He invented the VIXEN method for detecting enemy submarines and, perhaps most importantly, Ground Controlled Approach radar, which is the basis for all such systems, in use to this day for the safe landing of airplanes throughout the world. Shortly later, Alvarez went to Los Alamos, where he developed the shock wave method of measuring the strength of nuclear explosions.
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10. The Dual Axis Radiological Hydrodynamic Test Facility This device is devoted to examining nuclear weapons from two axes rather than just one. This reveals departures from cylindrical symmetry which is a sign of aging which can seriously affect performance
Induction Linacs
The Dual Axis Radiological Hydrodynamic Test Facility This device is to examine nuclear weapons from two axes to reveal departures from cylindrical symmetry which is a sign of aging.
Next came very successful application of induction accelerators, also associated with weaponry, has been to develop intense pulses of x-rays for studying the implosion process of nuclear weapons. The FXR at Livermore was located at their remote “site 300” and, when completed in 1982, produced 3,000 A of 18 MeV electrons (see Fig XIV.3). This machine, beautifully built and, like ETA and ATA, based upon the ERA induction linac technology, has been very useful for flash radiography. In the early 1990s FXR was followed by the Dual-Axis Radiographic Hydrotest Facility, DARHT: a machine constructed at Los Alamos for the same purpose. Under the seemingly innocent name of the Stockpile Stewardship Program it became important to check if nuclear weapons are no longer cylindrically symmetric. This might be due to rust spot developing on one side of the weapon, or simply because it had been stored on one side for decades. A second axis to DARHT has therefore been constructed to find such asymmetries and this facility was run-in during the first years of this centur
The induction accelerator, FXR, at Lawrence Livermore, to study the behavior of the implosion process in nuclear weapons

11. The Synchrotron

12. First electron synchroton
Very soon afterwards a real electron synchrotron was built – where to look for synchrotron radiation.
This 300 MeV electron synchroton at the General Electric Co. at Schenectady, built in the late 1940s. The photograph shows a beam of synchrotron radiation emerging.
Engines of Discovery