The POSH intense keV Positron Beam

General Information

Instrument: High intensity positron beam: POSH, 2D-ACAR  and Coincidence Doppler Broadening

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 annihilation (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)

 2D-ACAR: two position sensitive gamma ray detectors, angular resolution (at 23 m detector separation distance) ca. 1.1 x 1.4 mrad2. Coincidence Doppler Broadening :  two high resolution Ge-detectors

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.

Contact details:  POSH beam-line

Dr. Henk Schut

Section NPM2 (Neutron and Positron Methods in Materials)
Department RST (Radiation Science and Technology)
Faculty of Applied Sciences
Mekelweg 15, 2629 JB Delft, The Netherlands
Tel : +31 (0)15 27 81961
E-mail :


Contact details:  2D-ACAR 

Dr Eijt, S.W.H.
Applied Sciences (TNW), Section Fundamental Aspects of Materials and Energy (FAME),

Department RST (Radiation Science and Technology)
Mekelweg 15, 2629 JB Delft
Tel : +31 (0)15 27 89053
E-mail :