Calculation of the allowed aperture for a gas storage cell in IP8

In the framework of the Physics Beyond Collider studies, a working group was created in order to study some specific proposals to perform fixed-target physics experiments at the Large Hadron Collider. Among these proposals, the possibility has been described of installing an internal gas target, injecting unpolarized or polarized gas inside a storage cell (SC) located around the beam, close to the LHCb detector. In this work, the minimum acceptable radius for such a storage cell has been calculated in order to ensure safe operational conditions. An acceptable value is found to be between 3.0 mm and 3.5 mm depending on the SC longitudinal distance from the interaction point (IP) 8, taking into account various beam and optical configurations.