Daniel E. Pooley

Materials analysis opportunities on the new neutron imaging facility IMAT@ISIS

A new neutron imaging and diffraction facility, called IMAT, is currently being commissioned at the ISIS pulsed neutron spallation source. IMAT will take advantage of neutron time-of-flight measurement techniques for flexible neutron energy selection and effective energy discrimination. The instrument will be completed and commissioned within the next few months, after neutrons have been recently delivered to the sample area. From 2016 IMAT will enable white-beam neutron radiography and tomography as well as energy-dependent neutron imaging. The facility will offer a spatial resolution down to 50 microns for a field of view of up to 400 cm2. IMAT will be operated as a user facility for material science applications and will be open for developments of time-of-flight imaging methods.

‘GP2’ — An energy resolved neutron imaging detector using a Gd coated CMOS sensor

This paper documents the R&D undertaken jointly by the ISIS Neutron Detector Group and the Oxford University PImMS collaboration. The aim of this project was to develop a high resolution, energy resolved, neutron imaging detector named GP2. This conference record introduces the GP2 detector and lists its key physical properties; however the emphasis here will be on the earlier proof-of-principle work performed with both gadolinium thin films and thick rolled sheets with the prototype PImMS1 sensor and the larger PImMS2 sensor.

Time-of-Flight Neutron Imaging on IMAT@ISIS: A New User Facility for Materials Science

The cold neutron imaging and diffraction instrument IMAT at the second target station of the pulsed neutron source ISIS is currently being commissioned and prepared for user operation. IMAT will enable white-beam neutron radiography and tomography. One of the benefits of operating on a pulsed source is to determine the neutron energy via a time of flight measurement, thus enabling energy-selective and energy-dispersive neutron imaging, for maximizing image contrasts between given materials and for mapping structure and microstructure properties. We survey the hardware and software components for data collection and image analysis on IMAT, and provide a step-by-step procedure for operating the instrument for energy-dispersive imaging using a two-phase metal test object as an example.

Dead-time investigation of SiPMs for application at pulsed muon sources

Until recently a photomultiplier tube (PMT) was the only viable option for photon detection on μSR instruments [1]. A PMT is well suited to this application, as it offers fast rise time, small dead-time (∼15ns) and an excellent spectral match to the scintillator emission. They are also low-noise devices and are relatively inexpensive. However, the PMT has certain limitations, such as a strong sensitivity to magnetic fields, prompting this search for new technologies. Specific requirements depend on the measurement technique, the SiSR instrument, and the type of muon source being used. For example, the PSI high field instrument has successfully implemented siliconphotomultiplier technology (SiPM) to construct compact, field-insensitive, fast timing detectors [2]. At PSI the beam timing structure is ‘continuous’ meaning that there is effectively only one muon being measured at a time, negating the need for high count rate capability. While SiPM technology has been used very successfully at the PSI continuous muon source, benefits at a pulsed muon source have yet to be realized.