REC beam pipe temperature control

In CESR the clearance between the beam pipe and the REC (Rare Earth Cobalt) magnet is only 1 mm. The 160 cm beam pipe in this section is sloped and has steps to mask the detector from radiation. During high energy operation the beam pipe temperature increases due to synchrotron radiation, higher order modes power loss and image current, and effects the temperature of the REC magnet via convective and radiative heat transfer. The temperature change is proportional to the beam current. This causes a current dependent change in the REC magnetic field strength, resulting in a betatron tune shift of about ΔQ=0.011/°C for each quadrupole. To prevent the temperature changes of the beam pipe in this section, a sensitive temperature control cooling system was developed. The temperature of the beam pipe is stabilized within ±0.1°C. The loss parameter of the sloped pipe and power dissipated by synchrotron radiation was calculated from temperature measurements and used to estimate performance at higher current