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Australian Synchrotron

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File:Australian Synchrotron schema.jpg
Australian Synchrotron schema
1 Electron gun
2 Linear accelerator (linac)
3 Booster ring
4 Storage ring
5 Beamline
6 Endstation (or experimental workstation, i.e., laboratory)

The Australian Synchrotron is a 3 GeV synchrotron radiation facility built in Melbourne, Victoria and opened on 31 July 2007.[1][2] Designed by Architectus in conjunction with Thiess[3], the Synchrotron building is located on the former site of the Clayton drive-in theatre on 800 Blackburn Rd, next to the Telstra research laboratories and across the road from the Monash University Clayton Campus.

The Australian Synchrotron is a Light Source facility (in contrast to a Collider). It uses particle accelerators to produce a beam of high energy electrons which are placed within a storage ring that circulates the electrons to create synchrotron light. The light is directed down separate beamlines at the end of which may be placed a variety of experimental equipment contained within the endstations.

Accelerator systems

The interior of the Australian Synchrotron facility in 2006 before the beamlines were installed. Dominating the image is the storage ring, with an experimental endstation at front right. In the middle of the storage ring is the booster ring and linac

.

Electron Gun:
The electrons used to provide the synchrotron light are first produced at the electron gun, by thermionic emission from a heated metal cathode. The emitted electrons are then accelerated to an energy of 90 keV (kilo-electron volts) by a 90 kilovolt potential applied across the gun and make their way into the Linear Accelerator.

Linear Accelerator:
The linear accelerator (or linac) uses a series of RF cavities, operating at a frequency of 3 GHz, to accelerate the electron beam to an energy of 100 MeV, over a distance of around 15 metres. Due to the nature of this acceleration, the beam must be separated into discrete packets, or 'bunches'. This bunching process is done at the start of the linac, using several 'bunching' cavities. The linac can accelerate a beam once every second. Further along the linac quadrupole magnets are used to help focus the electron beam.

Inside the booster ring shielding, the linac is visible at image right extending from the electron gun at the far wall, and joining into the booster ring seen at the left

Booster Synchrotron:
The booster is an electron synchrotron which takes the 100 MeV beam from the linac and increases its energy to 3 GeV. The booster ring is 130 metres in circumference and contains a single 5-cell RF cavity (operating at 500 MHz) which provides energy to the electron beam. Acceleration of the beam is achieved by a simultaneous ramping up of the magnet strength and cavity fields. Each ramping cycle takes approximately 1 second (for a complete ramp up and down).

Storage Ring:
The storage ring is the final destination for the accelerated electrons. It is 216 metres in circumference and consists of 14 nearly identical sectors. Each sector consists of a straight section and an arc, with the arcs containing 2 dipole 'bending' magnets each. Each dipole magnet is a potential source of synchrotron light and most straight sections can also host an insertion device, giving the possibility of 30+ beamlines at the Australian Synchrotron. Two of the straight sections are used to host the storage ring 500 MHz RF cavities, which are essential for replacing the energy that the beam loses through synchrotron radiation. The storage ring also contains a large number of quadrupole and sextupole magnets used for beam focusing and chromaticity corrections. The ring is designed to hold 200mA of stored current with a beam lifetime of over 20 hours.

Vacuum Systems:
The electron beam is kept within a very high vacuum at all times during the acceleration process and within the storage ring. This vacuum is necessary as any beam collisions with gas molecules will quickly degrade the beam quality and reduce the lifetime of the beam. The vacuum is achieved by enclosing the beam in a stainless steel pipe system, with numerous vacuum pump systems continually working to keep the vacuum quality high. Pressure within the storage ring is typically around 10-10 millibar.

Control System
Each digital and analogue I/O channel is associated with a database entry in a customised distributed open source database system called EPICS (Experimental Physics and Industrial Control System). The condition of the system is monitored and controlled by connecting specialised GUIs to the specified database entries. There are about 45,000 database entries (AKA process variables), most of which relate to the physical I/O. About 35,000 of these are permanently archived at intervals ranging from milliseconds to minutes. Some high level control of the physics-related parameters of the beam is provided through MATLAB which also provides data analysis tools and an interface with a computerised model of the accelerator. Personnel and equipment protection is achieved through the use of Programmable logic controller-based systems, these systems also transfer data to EPICS. The Beamlines also use EPICS as the basis for their control.

2009 Management Crisis

An ongoing management crisis was set in motion following the sudden dismissal of the Australia Synchrotron's director, Professor Robert Lamb in late October 2009[4]. Professor Lamb, acknowledged as one of Australia's leading scientists[5], was seconded to the synchrotron from his position as chair of chemistry at the University of Melbourne when the Clayton complex opened in July 2007. His dismissal without explanation by the Board of management led by the chair Ms. Catherine Walter, has caused the international Science Advisory Committee to the Australian Synchrotron to threaten to resign en mass and has resulted in a work-to-rule by the staff at the facility[6][7].

Chair Catherine Walter has appointed former Australian of the Year Sir Gustav Nossal as head of a new advisory body, the National Science Colloquium[8]. The body is not a replacement for the Scientific Advisory Committee, and Sir Gustav's appointment does not solve the current impasse between the beamline scientists and the Scientific Advisory Committee, and the Board. The Colloquium was formed (but not announced) before the crisis and as it was not ratified by the council of members is not a properly defined committee.

Following a meeting on December 9 with synchrotron staff, in which Ms Walter refused to resign, three members of the Scientific Advisory Committee resigned their positions[9] and a further two members have since resigned, with another indicating his intention[10]. The Scientific Advisory Committee are unhappy about the actions of Ms Walter, who has failed to heed their advice, concentrating too much on promoting a corporate culture, and lowered staff morale to an all-time low. The beamline scientists have also extended their work to rule indefinitely[10]. The CFO has also tendered his resignation, citing personal reasons[11]. The State Government of Victoria, which has the largest stake in the project, so far has declined to intervene. [12]

Beamlines and experimental endstations

Soft x-ray beamline and endstation

Funding contributors

The Australian Synchrotron building

See also

References

  1. ^ Official Opening webcast timetable & archive site, from 0020UTC 31 Jul 07
  2. ^ Scientists to unveil monster synchrotron, ABC News (Australia), 31 July 2007
  3. ^ Architectus and Thiess to Design Australian Synchrotron
  4. ^ Stinkatron: chaos at the top, from 8 Nov 09
  5. ^ Synchrotron Board Mute on Crisis, from 22 Nov 09
  6. ^ Scientists' rebellion to cripple synchrotron beam, from 29 Nov 09
  7. ^ Seven scientists at synchrotron issue ultimatum, from 6 Dec 09
  8. ^ Gus Nossal rides to the rescue of troubled synchrotron, from 0858UTC 1 Dec 09
  9. ^ Scientists walk out on Synchrotron
  10. ^ a b Out of sync
  11. ^ Glyn Davis demands answers from synchrotron
  12. ^ "Research Management: Protests by Staff, Advisers Rattle Australian Synchrotron", Science, 1 Jan 2010
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