Tag Archives: detector

testing detectors…

The ISIS detector group has visited our facility to perform some tests with us on their new scintillator detectors. Scintillator detectors are usually more gamma sensitive and less neutron sensitive than the standard 3-He detectors. But since the enormous increase in the price of 3-He, more efforts have been put into the development of scintillator based detectors. The ISIS team came to the RID for tests and demonstration of clear-fibre and wavelength-shifting fibre detectors and a whole set of electronics to evaluate the output of these detectors.

During a three-day test on our reflectometer, we have compared these detectors with the standard 3-He detector of the reflectometer. The preliminary results of these tests show that the neutron detection efficiency is some 70-80% of this 3-He detector and the gamma sensitivity (without optimization of the pulse analysis of the scintillator electronics) is between 20 and 50% higher than the 3-He tube. More involved tests and optimizations need to be done for the gamma-sensitivity. A more severe testing would be counting neutrons in a strong(er) gamma background.

 

detector tests setup

The photo above shows the installation of one of the detectors (the aluminium box) inside the sample-chamber of our neutron-reflectometer at RID. The neutron beam impinges from the left on the scintillators inside the box (not visible) and the light generated by these scintillator crystals is amplified by the photon-multiplier-tubes (PMTs) which are read out by the electronics (not visible). The pulse-shape- and coincidence analysis of these electronics determine whether a neutron or a gamma is detected. The detectors were tested on the reflectometer, so that we could use the time-of-flight option and diafragms of this instrument. 

Institute wide co-operation for the development project

The director of the institute prof. Bert Wolterbeek has formally initiated the ‘task force Diffractometer’ on Monday. Now that the main specs of the instrument are known (those that define the performance of the instrument), we foresee that we could for instance trade off some neutron beam intensity for a lower radiation background. Or the monochromator take-off angle could be reduced for easier accessibility:

Time for team work!

We need to iterate over several designs of the instrument as well as radiation shielding and technical solutions to choose the –over-all– best layout. This means the design engineers need to be involved in detail, together with shielding and radio-protection experts. The management board of the institute keeps an eye on progress.The first meeting of the task force will be coming Monday. A first rough Gantt chart of the planning is done and people need to have their say about it.