AUSTRON,

A Central European Pulsed Spallation Neutron Source

P.J. Bryant

CERN, Geneva

Soon after the disintegration of the Iron Curtain, Austria declared its intention to build a centre of excellence for scientific research in the Central European Region. The choice of a neutron spallation source became clear in 1991-92 and the addition of a medical facility, now known as the Med-AUSTRON, quickly followed.

EPAC 2000, ViennaP.J. Bryant

EPAC 2000, ViennaP.J. Bryant

The mission of AUSTRON

  • To develop the new geopolitical status of the region.
  • To prevent the ‘brain drain’ of young scientists.
  • To improve the balance of scientific exchanges with other regions.
  • To encourage technology transfer and spin-off.
  • To create a post graduate centre.
  • To equip the region with a tool for world class research.

The choice of a neutron spallation source

  • has the right size and relative uniqueness for an international region,
  • would be within the resources of the region and could conceivably receive EU support.,
  • would have a multi-disciplinary user community.
  • A high intensity proton driver, could also be equipped with muon and neutrino targets for basic physics research.
  • The world demand for neutrons was (and still is) expected to outstrip the supply.

The ‘Neutron Drought’

The world’s scientific community has recognised for some time the inevitability of a ‘neutron drought’ in the early decades of the 21st century.

  • Presently, the main source of neutrons for science is continuous flux reactors.
  • The ongoing campaigns to close reactors, the widespread public reluctance to authorise new ones and the increasing severity of safety regulations that raise costs are forecast to cause this ‘drought’.
  • The demand for neutrons as a diagnostic tool is also foreseen to increase the advantages of neutrons become better known.

Physics World, Volume 10, No. 12

December 1997

1994 Feasibility Study

contains the study of the accelerator complex

EPAC 2000, ViennaP.J. Bryant

AUSTRON site layout

EPAC 2000, ViennaP.J. Bryant

Main parameters (1994)

H minus / proton operation
Injection to RFQ [keV] / 70
Injection to DTL [keV] / 750
Injection to RCS [MeV] / 130
Energy on target [GeV] / 1.6
No. of particles delivered per cycle / 3.21013
Repetition rate [Hz] / 50
No. of targets / 2
Average beam power [kW] / 410
Light-ion operation
No. of C4+ or O6+ ions per second / 2109
Energy of partially stripped ions from DTL [MeV/u] / 28
Options
(1)Medical synchrotron delivering 425MeV/u of fully stripped C6+ or O8+ ions for penetrations 30cm and 24cm respectively.
(2)Transmission muon target intercepting 5% of the beam to target no. 1 (assuming both targets receive 25Hz).
(3)Low-intensity beam line for 1012 particle/pulse for detector R&D. The beam would be uniformly spread over 10m2.

Main ring lattice

Envelopes and aperture

  • Vertical beam is shown at injection

(Ez = 476 total).

  • Horizontal beam is shown 1ms into rf cycle when momentum spread is maximum. (Ez=441, p/p = 0.0088, total).
  • Closed orbit magins of 3mm are added. This defines ‘good’ field region.
  • Collimation margins of 17mm are added in ‘poor’ field region. The secondary collimators are set back by 5mm leaving 12mm for multi-turn capture.
  • 5mm minimum is allowed for rf cage.

Key issues

  1. Maintain ‘hands-on-maintenance’ for as much as possible of the accelerator complex - for efficiency, manpower and regulatory reasons.
  1. Reduce the release of radioactivity to the environment - to make AUSTRON more acceptable to regulatory bodies.
  2. Increase the neutron flux - to make AUSTRON more attractive to the user community.

Proposals

  • A multi-frequency magnet cycle is proposed to deal with the most pressing problem of beam loss during injection and acceleration (Points 1 and 2).
  • A modest increase in the stored beam with accumulation of pulses is proposed (Point 3).

Magnet cycle (1)

A practical limit for the power of a spallation source is given by the RF trapping and acceleration losses.

Simulations of the longitudinal beam dynamics in AUSTRON using the code LONG1D (TRIUMPH) show that:

  • 205 kW at 25Hz0.4% loss
  • 410 kW at 50Hz10% loss
  • 500 kW at 50HzLosses too high !!
  • Use of a dual-frequency cycle

reduces loss to only 0.5%.

Magnet cycle (2)

Magnet cycle (3)

Dual frequency cycle

Particle loss during the rf cycle

total loss is 0.48% and

occurs only during trapping

Accumulator ring (1)

  • Reduce the pulse rate to 10Hz, but maintain the average power, e.g. increase the pulse energy (to 50kJ).
  • Can be realized by the addition of a storage ring.
  • The storage ring can be installed over, or around, the RCS and be of similar size.
  • In storage ring, use 4 buckets, i.e. h=4.
  • Change RCS to a single bucket i.e. h=1.
  • Compress the bucket in the RCS to much less than ¼ and transfer 4 bunches into the storage ring. There must be a gap for rise and fall of the injection kicker.

Accumulator ring (2)


Where do we stand?

  • The building of a spallation source is not a small undertaking.
  • The first proposal, ING (Intense Neutron Generator), was in the 1960s for 65MW!!
  • ‘Proof of principle’ was made at Argonne in 1972 with 100W.
  • Pulsed sources have since reached 160kW.
  • Continuous sources have reached 1MW.



Status of AUSTRON

  • 0.5MW pulsed spallation source,
  • 50Hz mode 10kJ/pulse,
  • 10Hz mode 50kJ/pulse,
  • 2 target stations,
  • 4690MATS ( 337.4MEURO),
  • Original Feasibility Study.needs updating for accumulator ring and new main power converters,
  • Optional medical centre,
  • Austrian Government is looking for international partners with a view to starting an execution design.

EPAC 2000, ViennaP.J. Bryant