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High intensity positron beam: POSH and 2D-ACAR

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Contact details

Eijt, S.W.H. Dr.
Applied Sciences (TNW), Section Fundamental Aspects of Materials and Energy (FAME), Department R3
Mekelweg 15, 2629 JB Delft
Tel : +31 (0)15 27 89053
E-mail : S.W.H.Eijt@tudelft.nl
Website : Not available

General Information

Instrument:

High intensity positron beam: POSH and 2D-ACAR

Location:

Experimental hall, Reactor Institute Delft, Mekelweg 15, Delft (building #50)

Key words:

Positron Annihilation, positronium, positron beam, angular correlation, electron momentum distribution, open volume defects, vacancies, vacancy-dopant complexes, nano-precipitates, surfaces, interfaces, thin films

Measured quantity:

one measures the annihiliation (gamma) radiation of a positron-electron annihilation event (511 keV)

Main application:

determination of the electron momentum distribution in nano-precipitates and nano-crystals, and characterization of open volume defects in sub-surface regions and at interfaces.

Instrument specification

Positron source:
Via pair production near the reactor core of the HOR, magnetostatic positron beam transport to target chamber in Experiment Hall.

Positron beam intensity:
2 x 108 e+ s-1

Positron beam diameter at target:

ca. 3 mm.

Maximum positron energy :
20 keV (corresponding to 2 micron penetration depth in Si)

Detectors:

two position sensitive gamma ray detectors, angular resolution (at 23 m detector separation distance) ca. 1.1 x 1.4 mrad2.

Target chamber:

equipped with a closed loop cryostat (20 – 300 K) and a heater (max. 900 K) for measurements at cryogenic or moderate temperatures.

A separate 22Na source (2 GBq) and target chamber is available for bulk 2D-ACAR studies using the POSH-ACAR position sensitive detectors.

Other contact:
Dr. Henk Schut
Section NPM2 (Neutron and Positron Methods in Materials)
Department R3 (Radiation, Radionuclides and Reactors)
Faculty of Applied Sciences
Mekelweg 15, 2629 JB Delft, The Netherlands
Tel : +31 (0)15 27 81961
E-mail : h.schut@tudelft.nl

Positron facilities and positron research activities at RID and R3
The Positron Centre Delft is a research facility established at the Delft University of Technology. It provides access to the equipment (as part of RID) and scientific expertise concentrated in the sections FAME and NPM2 of the department R3 of the faculty of Applied Science.
The majority of the experimental Positron Annihilation (PA) techniques developed to this aim are based on the analysis of the annihilation radiation. They can be classified into two groups, which are distinguished by the positron’s sensitivity to the local electron density (positron lifetime, PALS) and to the local electron momentum distribution (Dopplerbroadening (PADB) and Angular Correlation (2D-ACAR)).