Cos-$\theta$ design of dipole inserts made of ReBCO-Roebel or BSCCO-Rutherford cables

Next generation of dipole magnets with field higher than 16 T are considered for future particle colliders. To do so, combined-technology magnets - made of Nb-Ti, Nb$_{3}$Sn and HTS materials - have to be developed to reduce the cost of such a magnet. Therefore, in the framework of the EuCARD-2 project, many HTS dipole magnet designs have to be investigated so as to find the most effective design for the HTS insert in a graded magnet. This paper discusses the Cosθ option. A 5 T standalone configuration of the HTS accelerator magnet (the first goal of EuCARD2) appears to be achievable, whereas mechanical stress distribution shows that its use as insert in graded magnet is very challenging. This paves the way for alternative designs as the so-called slot or motor-like design, briefly introduced here.