Ho-163 source

The production of a sufficient amount of ¹⁶³Ho atoms in a radiochemically pure form is of paramount importance for the success of the ECHo experiment. The production methods for ¹⁶³Ho can mainly be divided into two branches:

• charged particle activation of suitable targets in reactions that lead to ¹⁶³Ho or its precursor ¹⁶³Er which decays to ¹⁶³Ho (EC and β + decay) with a half-life T_1/2 = 75 min;

• thermal neutron activation of enriched 162Er targets.

The reaction that is typically used for the direct activation with proton beams is ^natDy(p;xn)¹⁶³Ho. Another possible direct reaction uses deuteron projectiles, ¹⁶³Dy(d;2n)¹⁶³Ho. Examples for indirect ¹⁶³Ho production are ^natDy(α;xn)¹⁶³Er(EC,β +)¹⁶³Ho and ¹⁵⁹Tb(⁷Li;3n)¹⁶³Er(EC, β +)¹⁶³Ho.

In the ECHo experiment all the described methods for production of ¹⁶³Ho through charged particle activation
processes as well as with neutron irradiation of a ¹⁶²Er target are being considered, as well as possible new methods.

Typically, in the production of ¹⁶³Ho, contaminants nuclides with decay properties that interfere with the desired clean ¹⁶³Ho EC spectrum are produced. These include long-lived β −decaying nuclides like ^166mHo. Thus, a careful separation of ¹⁶³Ho is of paramount importance and will be performed by a combination of chemical and potentially physical separations before as well as after the irradiation of the sample.