Detectors

The detector design group, led by Ron Cooper is responsible for supporting the design of the instruments by developing the necessary infrastructure and acquiring detector components that will be used to complete the functionality of the instruments. The group's mission also includes supporting detector R&D for the different types of instruments with their different needs. The support effort for instrument design entails monitoring detector development worldwide. Neutron facilities around the globe are getting upgraded and adopting the newest technologies.

2-D Position Sensitive Detectors Click image for a larger version.

To be able to use and implement these new technologies the SNS detector requirements are presented to the R&D community. Currently, the research focus is changing to spallation sources with SNS being built and ESS and JSNS under development. Those three next generation neutron scattering facilities will set the detector R&D agenda in the future. Therefore, it is important to support the detector selections for the instruments under design, review detector requirements for these instruments, and determine the best available detector option.

As examples, for different detector needs the SNS base line instruments will be discussed. It is important to consider the fact that different neutron scattering instruments have very diverse requirements. For specific instruments out of the future SNS scattering instrument suite, diffractometers, reflectometers, and spectrometers, the types of detectors being closely looked at will be shown.

1. Powder Diffractometer Requirements

Powder Diffractometer Click image for a larger version.

• Instrument Scientist: Jason Hodges
• Detector area: 13m2 +
• Sensitivity to 1 eV neutrons
• Position resolution: 4 x 0.5 cm
• Maximum rate: 106 n/s over entire detector system
• Possible detectors:
  • Scintillator detectors, ISIS-GEM design is mature
  • Scintillator detectors, wavelength shifting fiber design looks practical

A current example for this kind of instrument is GEM at ISIS, RAL, UK. Scintillation Detector with wavelength shifting light fiber optics was chosen.

Backscattering Spectrometer Vacuum Tank Click image for a larger version.

2. Backscattering Spectrometer Requirements

• Instrument Scientist: Jason Hodges
• Detector area: 13m2 +
• Sensitivity to 1 eV neutrons
• Position resolution: 4 x 0.5 cm
• Maximum rate: 106 n/s over entire detector system
• Possible detectors:
  • Scintillator detectors, ISIS-GEM design is mature
  • Scintillator detectors, wavelength shifting fiber design looks practical

A current example for this kind of instrument is GEM at ISIS, RAL, UK. Scintillation Detector with wavelength shifting light fiber optics was chosen.

3. Liquids Reflectometer Requirements

Liquids and Magnetism Reflectometers Click image for a larger version.

• Instrument Scientist: John Ankner
• Detector area: 20 x 20 cm
• Sensitivity to 20 meV neutrons
• Position resolution: 1 x 1 mm
• Maximum rate: 106 n/s for 100 pixels
• Possible detectors:
  • 3He filled 2-D PSND
  • Micro-pin or pixel cell array with parallel read out
  • Cascade
  • Solid state

4. Magnetism Reflectometer Requirements

• Instrument Scientists: Haile Ambaye & Rick Goyette
• Detector area: 20 x 20 cm
• Sensitivity to 30 meV neutrons
• Position resolution: 1 x 1 mm
• Maximum rate: 106 n/s for 100 pixels
• High magnetic fields
• Possible detectors:
  • 3He filled 2-D PSND
  • Pixel cell array with parallel read out
  • Cascade
  • Solid state

5. Extended-Q SANS Instrument Requirements

Extended-Q SANS Click image for a larger version.

• Instrument scientist: J.K. Zhao
• Detector area: 1 x 1 m SANS, 0.8m2 high
  angle bank
• Sensitivity to 80 meV neutrons
• Position resolution: 5 x 5 mm
• Maximum rate: 5 x 107 n/s over entire detector
• Gamma sensitivity is a primary issue
• Possible detectors:
  • 3He filled 2-D PSND for SANS
  • 3He filled tubes for high angle bank

Recent Infrastructure Developments will give the detector team the opportunity to do in-situ testing of detector parts and components. Laboratory space at ANL was acquired for independent detector development and test equipment was obtained. Beta and neutron sources were installed and a SNS detector test station on QUIP at IPNS was established. To ease the transition temporary lab space at ORNL was acquired to set up a scintillator evaluation station, for further development of 3He from DP for use in gas detectors, was obtained.

Wavelength Shifting Fiber Design Click image for a larger version.

Planned Infrastructure Development for the near future are to develop an active detector test station at HFIR that gives useful information for detector performance as well as outfitting two detector laboratories on the SNS site with installed calibration sources. Therefore the R&D is closely focused on instrument needs and will zoom in on glass scintillators by measuring light yield and pulse shape and optimizing yield for an efficient use at future neutron source. This will also include development of manufacturing techniques for thick scintillators and shifting fiber coupled scintillators. On the backend further development is under way for read out electronics. A prototype was evaluated at IPNS in February 2001. The detector will also provide a segmented beam monitor and will fabricate a prototype with 10 pads to study pad geometry and cross talk issues. Further R&D effort will be spent on novel anger camera design that is currently being developed as a joint project with IPNS. We are also monitoring sol gel scintillator development worldwide.