International Linear Collider

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The International Linear Collider (ILC) is a proposed linear particle accelerator. It is planned to have a collision energy of 500 GeV initially, and to be completed in the late 2010s.[1] A later upgrade to 1000 GeV is possible. As of March 2008, the host country of the accelerator has not been chosen.

It will collide electrons with positrons. It will be between 30 km and 40 km long, more than 10 times as long as the 50 GeV Stanford Linear Accelerator, the longest existing linear particle accelerator. The proposal was previously known by various names in different regions; see below.

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[edit] Comparison with LHC

There are two basic shapes of accelerators. Linear accelerators ("linacs"), such as the Stanford Linear Accelerator Center (SLAC), accelerate elementary particles along a straight path. Circular accelerators, such as the Tevatron, the LEP, and the under-construction Large Hadron Collider (LHC), use circular paths. While circular geometry, is preferred for hadron colliders (since particles can be accelerated over longer distances as they go around and around and that particles that do not collide on the first pass may go around and collide on a subsequent pass), it is impractical for electron accelerators due to synchrotron radiation losses.

Even if the effective collision energy at the LHC will be higher than the ILC collision energy (14,000 GeV for the LHC[2] vs. ~500 GeV for the ILC), measurements could be made more accurately at the ILC. Collision between electrons and positrons are much simpler to analyze than collisions between many quarks, antiquarks and gluons. As such, one of the roles of the ILC would be making precision measurements of the properties of particles discovered at the LHC.

[edit] ILC physics

It is widely expected that effects of physics beyond that described in the current Standard Model will be detected by experiments at the LHC and ILC. In addition, particles and interactions described by the Standard Model are expected to be discovered and measured. At the ILC physicists hope to be able to:

[edit] Merging of regional proposals into a worldwide project

In August 2004, the International Technology Recommendation Panel (ITRP) recommended a Superconducting RF technology for the accelerator. After this decision the three existing linear collider projects - the Next Linear Collider (NLC), the Global Linear Collider (GLC) and Teraelectronvolt Energy Superconducting Linear Accelerator (TESLA) - joined their efforts into one single project (the ILC). Physicists are now working on the detailed design of the accelerator. Steps ahead include obtaining funding for the accelerator, and choosing a site. On 8 February 2007 the Draft Reference Design Report for the ILC was released.[3]

In March of 2005, the International Committee for Future Accelerators (ICFA) announced the appointment of Dr. Barry Barish as the Director of the Global Design Effort. Barry Barish was previously head of the ITRP.

[edit] Design

The electron source for the ILC will use 2-nanosecond laser light pulses to eject electrons from a photocathode, a technique allowing for up to 80% of the electrons to be polarized; the electrons then will be accelerated to 5 GeV in a 250-meter linac stage. Synchrotron radiation from high energy electrons will produce electron-positron pairs on a titanium-alloy target, with as much as 60% polarization; the positrons from these collisions will be collected and accelerated to 5 GeV in a separate linac.

To compact the 5 GeV electron and positron bunches to a sufficiently small size to be usefully collided, they will circulate for 0.2 seconds in a pair of damping rings, 7 km in circumference, in which they will be reduced in size to a few mm in length and less than 100 μm diameter.

From the damping rings the particle bunches will be sent to the Superconducting RF main linacs, each 12 km long, where they will be accelerated to 250 GeV. At this energy each beam will have an average power of about 10 megawatts. Five bunch trains will be produced and accelerated per second.

After acceleration the bunches will be focused to a few nm in height and a few hundred nm in width. The focused bunches then will be collided inside two large particle detectors.

[edit] Cost and time estimates

The Draft Reference Design Report estimates the cost of building the ILC, excluding R&D, prototyping, land acquisition, underground easement costs, detectors, contingencies, and inflation, at US$6.65 billion.[citation needed] From formal project approval, completion of the accelerator complex and detectors is expected to require seven years. The host country would be required to pay $1.8 billion for site-specific costs like digging tunnels and shafts and supplying water and electricity.

[edit] Notes

  1. ^ ILC Design Summary Document. ILC web site (8 February 2007). Retrieved on 2007-02-09. (PDF)
  2. ^ Since the actual collisions happen between the constituent of protons—quarks, antiquarks and gluons—the effective energy for collisions will be lower than 14,000 GeV but still higher than 500 GeV), a typical collision at the LHC will be of higher energy than a typical ILC collision.
  3. ^ ILC Draft Reference Design Report. ILC web site (8 February 2007). Retrieved on 2007-02-09. (PDF)

[edit] External links