Collimation of the neutron beam

The collimation of the neutron beam a aSPECT provides for a neutron beam in the DV with a defined geometry, that does not hit the walls of the DV to prevent background radiation.

In the course of the aSPECT beam times the collimation system close to aSPECT was modified several times to also accomodate

  • UHV compatibility in order not to worsen the vacuum in aSPECT
  • Conductive surfaces in order not to charge up due to the decay products from the beta-decay of neutrons and thus change the potential in the DV in an unknown way.

In order to facilitate this the holding structure of the collimation for the beam time in 2013 was made from commercial electrically conductive Boronnitride (BN) which absorbs the halo of the neutron beam, is UHV compatible and is easily machinable. The inner beam collimation was made from LiF which was coated with Titanium for electrical conductivity. The LiF pieces were glued onto the holding structure using mostly UHV compatible glue.

Pieces of the collimation holding structure from conductive BN:

aSPECT internal collimation 2013

One of the assembled holding structures from conductive BN:

aSPECT internal collimation 2013

Holding structure from conductive BN including the LiF inner collimation with the Ti-coating:

aSPECT internal collimation 2013

The collimation system inserted into aSPECT:

aSPECT internal collimation 2013