ASTRID
Encyclopedia
Subatomic particle
In physics or chemistry, subatomic particles are the smaller particles composing nucleons and atoms. There are two types of subatomic particles: elementary particles, which are not made of other particles, and composite particles...
storage ring
Storage ring
A storage ring is a type of circular particle accelerator in which a continuous or pulsed particle beam may be kept circulating for a long period of time, up to many hours. Storage of a particular particle depends upon the mass, energy and usually charge of the particle being stored...
at Department of Physics and Astronomy Aarhus University, Aarhus
Aarhus
Aarhus or Århus is the second-largest city in Denmark. The principal port of Denmark, Aarhus is on the east side of the peninsula of Jutland in the geographical center of Denmark...
, Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
. ASTRID was designed, constructed and is operated by ISA (Institute for Storage Ring Facilities in Aarhus), a Danish National Facility where research is carried out in Physics, Chemistry, Materials Science, Laboratory Astrophysics and Biology using accelerators and storage rings.
History
Designs for ASTRID started in 1985. The original concept for the ring was to store low-energy heavy ions for laser spectroscopic and laser cooling experiments and for atomic collision studies. It was soon realised during the design phase that it would also be possible to store energetic electron beams in the ring and therefore ASTRID could operate as a synchrotron radiation (SR) source, providing photons in the UV to soft x-ray region. In 1988 the Natural Sciences Faculty at Aarhus University was awarded 16.7 M DKK for establishing an Instrument centre in Synchrotron Radiation Research, thus forming ISA. By late 1989 ASTRID was operating in ion storage mode with the first experiments being carried out on laser cooling a stored beam of Li+ ions to 1 mK .Electrons were first stored in ASTRID in 1991 and by this time two beamlines had been constructed to make use of the synchrotron light, a surface science beamline (SX700) and an x-ray microscope (XM). Ion storage in ASTRID dominated in the early 90s, with many successful experiments storing both positive and negative ions ranging in mass from 1 (hydrogen atom) to 840 (carbon 70 cluster). Meanwhile the synchrotron radiation based research at ISA was expanding, and by 1995 ASTRID was operated 50% of the time in ion storage mode and 50% for synchrotron radiation. With the construction of the Electrostatic Storage Ring for Ions, at Aarhus (ELISA) in 1998, and an increasing demand for synchrotron radiation (by 2000 there were 7 beamlines on ASTRID using the light source), the ion storage runs were gradually reduced, until finally in 2005 ASTRID operated in ion storage mode for the last time. Since then ASTRID has been operating in electron storage mode producing synchrotron radiation throughout the year, with 3 or 4 electron runs, separated by shutdown periods for maintenance and development of the ring.
In December 2008, a contract was awarded to design and build ASTRID2, a 46 meter storage ring which will be built adjacent to ASTRID. Rather than having an electron beam which decays over time, ASTRID2 will be continually "topped up" by a feed from ASTRID, allowing nearly constant current. It is expected to be completed by the end of 2011. It will generate synchrotron radiation
Synchrotron radiation
The electromagnetic radiation emitted when charged particles are accelerated radially is called synchrotron radiation. It is produced in synchrotrons using bending magnets, undulators and/or wigglers...
to provide a tunable beam of light, expected to be of "remarkable" quality, with wavelengths from the ultraviolet through to soft x-rays.
Technical details for electron storage.
The ASTRID storage “ring”, with a circumference of only 40 m, is actually a square, formed by four sets of two 45 degree dipole bending magnets. There are eight pairs of quadrupole magnets used for horizontal and vertical focusing of the electrons and eight pairs of sextupole magnets for chromaticity correction. Electrons are injected via a septum magnet into the ring from a 100 MeV race-track microtron in 4-5 mA pulses, and captured by a 105 MHz RF system which bunches and accelerates the electrons as they pass through the RF cavity. Many of these pulses of electrons are accumulated at 100 MeV to reach more than 180 mA of current in the ring, which then is accelerated to 580 MeV with negligible loss of beam. The lifetime of a stored beam at 160 mA is 100 to 120 hours.Technical parameters
The table below shows the typical operating parameters for ASTRID when running in electron storage mode.| Parameter | Value |
|---|---|
| Maximum Energy | 580 MeV |
| Max. Current (2005) | 286 mA |
| Typical Stored Current | 180–220 mA |
| Lifetime (at 160 mA) | 100–120 hours |
| Horizontal emittance | 0.14 mm mrad |
| RF Frequency | 104.9 MHz |
| No. of bunches | 14 |
| SR critical energy | 0.38 keV |
| Dipole rigidity | 1.9 Tm |
| Quadrupole max gradient | 6.7 T/m |
Beamlines on ASTRID
There are eight operational SR beamlines on ASTRID. The characteristics of these beamlines are summarised in the table below and their location shown in the schematic drawing. Please follow the links in the table for further information and descriptions of the individual beamlines.| Station | Source | Spectral Range Wavelength In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a... (λ)Conversions between eV and nm are italicized. |
Resolving power | Typical flux (1010 photons/sec) |
Applications | ||
|---|---|---|---|---|---|---|---|
| eV Electronvolt In physics, the electron volt is a unit of energy equal to approximately joule . By definition, it is equal to the amount of kinetic energy gained by a single unbound electron when it accelerates through an electric potential difference of one volt... |
nm Nanometre A nanometre is a unit of length in the metric system, equal to one billionth of a metre. The name combines the SI prefix nano- with the parent unit name metre .The nanometre is often used to express dimensions on the atomic scale: the diameter... |
gratings Diffraction grating In optics, a diffraction grating is an optical component with a periodic structure, which splits and diffracts light into several beams travelling in different directions. The directions of these beams depend on the spacing of the grating and the wavelength of the light so that the grating acts as... |
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| SGM 1 | Bending magnet | 30–650 | 1.9–41 | 3 | 5,000–14,000 | 2 | Surface Science |
| SX700 | Bending magnet | 6–700 | 1.8–205 | 2 | 200–2,500 | 1 | Surface Science |
| XRM | Bending magnet | 410–830 | 1.5–3.0 | 0 | 2,000 | 2 | X-Ray Microscopy, Imaging |
| MIYAKE | Undulator | 15–180 | 6.9–83 | 1 | 2,000 | 20 | Atomic and Molecular Physics |
| SGM 2 | Undulator | 12–40 | 31–105 | 1 | 10,000–20,000 | 20 | Atomic and Molecular Physics |
| SGM 3 | Undulator | 8–150 | 8.3–155 | 3 | 15,000 | 20 | Surface Science |
| UV 1 | Bending magnet | 1.5–12 | 105–830 | 2 | 1,000–5,000 | 20 | CD Spectroscopy, Photobiology, UV Spectroscopy |
| CD 1 | Bending magnet | 1.8–9.9 | 125–700 | 1 | <500 | 100 | CD Spectroscopy |