improved version Sept. 1985
aluminium sphere
38 cm
moderator20 litres of boiling liquid deuterium (25 K)
flux enhancement

3 Å (4.5 x 1014 /cm2/sec

x1.7 between 3 to 6 Å

The Vertical Cold Source (VCS) is an aluminium sphere of 38 cm diameter filled with boiling liquid deuterium at 25 K. This localy improves the neutron flux at wavelengths above 3 Å (4.5 1014 n/cm2.sec).

Its design features are as follows:

  • a sphere incorporating a re-entrant cavity 10 cm wide and 20 cm high with a penetration depth of 25 cm. The cavity is a magnesium vessel, filled with gaseous deuterium. Its design is optimised with respect to the six horizontal cold guides (3 x 20 cm). These are H14, H15, H16, H17, H18 and H113.
  • a vertical service tube  sufficiently large to incorporate a vertical neutron guide of 7cm diameter constructed of aluminium and lined with a thin (0.15 mm) nickel tube. This is followed by a curved square guide (7 x 7 cm2) with a radius of 13 m and length of 13 m. The guide supplies very cold neutrons (VCN) to the "neutron turbine" and also directly to some instruments. The turbine provides ultra cold neutrons (UCN) to a number of experiments (see description of instrument PF2).