Poletip Hadronic Calorimeter (HP)

The poletip hadronic calorimeters are of slightly different design to HB and HE. They lie behind the endcap electromagnetic calorimeters and give coverage of the polar region $0.91 < \vert\cos\theta\vert < 0.99$. They are made of ten layers of detector separated by nine layers of 80 mm thick iron. The gaps between the iron are just 10 mm. Unlike the other parts of HCAL, the detectors in HP are multi-wire chambers operating in high gain mode. They contain 55% CO$_{2}$ and 45% $n$-pentane.