Prof. Dr.-Ing. Dr. h. c. Uwe Hampel

Experimental Thermal Fluid Dynamics
Phone: +49 351 260 2772

Gamma densitometry

Gamma densitometry has been used in our department for reference purposes to various two-phase measuring techniques. The advantage of gamma densitometry is to measure the void fraction absolutely and contactless. The absorption of gamma rays within a medium only depends on density and atomic number. We know very well the constituents of flow and their atomic number. Therefore the measured absorption of gamma rays gives to us the averaged density or void fraction along the ray. For this reason gamma densitometry can be used to calibrate and check the measuring probes used and developed in our department.

The gamma densimeter

The gamma densimeter on the MTLoop test facility

The gamma densitometer on the MTLoop test facility uses a Cs-137 gamma-source (480 MBq) and a NaI(Tl)-scintillation detector, both inserted in a shielding container made from tungsten with integrated collimator. The gamma ray restricted by the collimators has a diameter of 5 mm.

data from gamma densimeter

Comparison of data from gamma-densitometer (x-axis) and wire-mesh sensor (y-axis)

Also on the TOPFLOW facility gamma densitometry will be used to calibrate the wire-mesh sensors.


  • H.-M. Prasser, „Messung von Blasengrößenverteilungen mit Gittersensoren” in H.-M. Prasser (ed.), „Workshop Meßtechnik für stationäre und transiente Mehrphasenströmungen”, Rossendorf 24./25.9.1998, Proceedings FZR-241, Nov. 1998, pp. 157-164
  • H.-M. Prasser, „Wire-Mesh Sensors for Two-Phase Flow Investigations” in F.-P. Weiß, U. Rindelhardt (ed.), „Annual Report 1998, Institute of Safety Research”, FZR-268, Juli 1999, pp. 23-28
  • H.-M. Prasser, „High-speed Measurement of the Void Fraction Distribution in Ducts by Wire-mesh Sensors”, International Meeting on Reactor Noise, Oct 11-13 2000, Athens, Greece, Proceedings, pp. 257-270