The Bremsstrahlung Cone Profile

Abstract

Situated almost 40m downstream from the bremsstrahlung radiator in Hall B, the RadPhi experiment relies upon good collimation properties of the photon beam to ensure that the beam is essentially contained within the 2.5cm diameter target, and that the tails extending into the acceptance of the calorimeter and charge-particle veto are small. Using a small piece of thin scintillator mounted on the movable target platform at the nominal target position, scans of counting rate versus horizontal position were performed during the May 1997 run. These results are compared with what would be expected, based upon the bremsstrahlung cross section, for an ideal electron beam (zero emittance) to look for sensitivity of the photon beam profile to electron beam tune. Some evidence for electron beam effects are present; however it appears that these are minor and that, under the conditions of the May run, the self-collimation of the bremsstrahlung process is sufficient for the needs of this experiment.