From SURF: “How do accelerators work?”

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Sanford Underground Research facility

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See bottom of the story for the numbered descriptions. Credit: Matt Kapust

Researchers working on the Compact Accelerator System for Performing Astrophysical Research (CASPAR) will begin studying the processes in stars that create the heavier elements in the universe,. Using a low-energy accelerator on the 4850 Level, they’ll fire a beam of particles at various targets, including a particular type of neon gas (22Ne) as a way to better understand how all of that works.

Sounds simple, but how do particle accelerators really work? Well, that depends on the type of accelerator. CASPAR’s accelerator is modeled on the Van de Graaff accelerator, which is based on concepts developed in the early 1930s. It uses a motorized insulated rotating belt to transport a positive charge from ground to a high-voltage terminal to help accelerate charged particles up to 1 million Volts (for comparison, the LHC can accelerate particles up to almost 7 trillion Volts).

Accelerators rely on an ion or plasma source to produce charged particles. CASPAR uses radio-frequency energy to produce a beam of protons or alpha particles from hydrogen or helium gas.

Once produced, ions enter the accelerating tube, which is kept at high vacuum. The tube, made up of insulating sections separated by metallic electrodes, must hold the entire high voltage between the terminal and ground. Connected to a resistor chain, the electrodes produce a nearly uniform voltage drop and ion acceleration, providing some focusing properties.

The ion beam at the exit of the accelerator has a diameter of less than a few millimeters. Metallic circular rings enclose the belt and tubes, improving stability and keeping the electrical field as uniform as possible.

The entire accelerator structure is placed in a high-pressure tank filled with electrically insulating gas (CO2/N2 mixture at 200 psi). To ensure that only particles with the right energy are directed to the target, a 25-degree bending magnet in CASPAR’s beam line is utilized as an energy filter.

Check out this article in Symmetry http://www.symmetrymagazine.org/article/april-2014/ten-things-you-might-not-know-about-particle-accelerators

1.Turbo molecular pumping system: Used to evacuate the beamlines of air. Transporting particles within a vacuum tube reduces energy loss and scattering that can happen through collisions.
2. Beam profile monitors: These intercept the beam periodically providing information on beam shape, size and position.
3. Quadrupole magnet doublet: Electromagnetic focusing elements used to confine the beam and deliver a focused beam to the target.
4. Faraday cup system: This can be inserted when required and used to intercept the beam and measure the amount of particles per second you are working with.
5. jaw slits: Slit systems are used to define a region you wish to tune the beam of particles through. This can help define the beam shape and size.
6. .Accelerator tank: The accelerator is confined within a steel pressure vessel at ~ 200 psi of insulating gas. This helps maintain the voltage of the accelerator, independent of room conditions.
7. Dipole analyzing magnet: This is an electromagnetic dipole magnet used to deflect ions (25 degrees). This is used to select an ion of interest based on its fundamental properties of mass, velocity and charge state.

See the full article here .

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The Sanford Underground Research Facility in Lead, South Dakota, advances our understanding of the universe by providing laboratory space deep underground, where sensitive physics experiments can be shielded from cosmic radiation. Researchers at the Sanford Lab explore some of the most challenging questions facing 21st century physics, such as the origin of matter, the nature of dark matter and the properties of neutrinos. The facility also hosts experiments in other disciplines—including geology, biology and engineering.

The Sanford Lab is located at the former Homestake gold mine, which was a physics landmark long before being converted into a dedicated science facility. Nuclear chemist Ray Davis earned a share of the Nobel Prize for Physics in 2002 for a solar neutrino experiment he installed 4,850 feet underground in the mine.

Homestake closed in 2003, but the company donated the property to South Dakota in 2006 for use as an underground laboratory. That same year, philanthropist T. Denny Sanford donated $70 million to the project. The South Dakota Legislature also created the South Dakota Science and Technology Authority to operate the lab. The state Legislature has committed more than $40 million in state funds to the project, and South Dakota also obtained a $10 million Community Development Block Grant to help rehabilitate the facility.

In 2007, after the National Science Foundation named Homestake as the preferred site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL), the South Dakota Science and Technology Authority (SDSTA) began reopening the former gold mine.

In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through the Lawrence Berkeley National Laboratory, agreed to support ongoing science operations at Sanford Lab, while investigating how to use the underground research facility for other longer-term experiments. The SDSTA, which owns Sanford Lab, continues to operate the facility under that agreement with Berkeley Lab.

The first two major physics experiments at the Sanford Lab are 4,850 feet underground in an area called the Davis Campus, named for the late Ray Davis. The Large Underground Xenon (LUX) experiment is housed in the same cavern excavated for Ray Davis’s experiment in the 1960s.
LUX/Dark matter experiment at SURFLUX/Dark matter experiment at SURF

In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive detector yet to search for dark matter—a mysterious, yet-to-be-detected substance thought to be the most prevalent matter in the universe. The Majorana Demonstrator experiment, also on the 4850 Level, is searching for a rare phenomenon called “neutrinoless double-beta decay” that could reveal whether subatomic particles called neutrinos can be their own antiparticle. Detection of neutrinoless double-beta decay could help determine why matter prevailed over antimatter. The Majorana Demonstrator experiment is adjacent to the original Davis cavern.

Another major experiment, the Long Baseline Neutrino Experiment (LBNE)—a collaboration with Fermi National Accelerator Laboratory (Fermilab) and Sanford Lab, is in the preliminary design stages. The project got a major boost last year when Congress approved and the president signed an Omnibus Appropriations bill that will fund LBNE operations through FY 2014. Called the “next frontier of particle physics,” LBNE will follow neutrinos as they travel 800 miles through the earth, from FermiLab in Batavia, Ill., to Sanford Lab.

Fermilab LBNE
LBNE