Assessment of Static Heat Loads in the LHC Arc, from the Commissioning of Sector 7-8

This note presents first estimates of the static heat loads in the LHC arc cryostats, evaluated experimentally during the commissioning of sector 7-8 in April 2007. Heat loads to the thermal shielding are estimated from the non-isothermal cooling of the supercritical helium in line E, while heat loads to the 1.9K level of the cold masses are estimated from the internal energy balance during a natural warm-up of the sector in the absence of active cooling. A comparison of the measured heat loads with the budgeted heat loads is then presented and discussed.