Beam halo and background Bremsstrahlung photon spectrum modeling Update on 9 th Nov. 2007

Flat HALO 50 and 200  50 and 200  in x, y, xp, yp 0.1% Gaussian Energy Spread 100% events in HALO (have more statistics) Hypothesis  0.1 to 1% HALO electrons HALO Shape  Non Gaussian (polynomial).

Losses along the line 50  Halo 200  Halo

Next steps Better estimate the HALO  + theory considerations (Raubenheimer) Halo has the same Energy spread than Beam core ? Better describe the geometry: Default chamber has 24mm inner diameter and 32mm outer diameter. It will be made by a stainless steel. Some special chamber for BEND will have another dimensions.  Nobuhiro Modify BDSIM in order to be able to use flat HALO and renormalize later on with more complicated one

Other background effects Beam dump  backscattered particles KEK) also Neutrons production and transport? Beam pipe gas  small effect ? SR ? What else ?

KEK with Shintake Group As of now, we consider that the detector study for the Shintake-monitor takes top priority during the nest sets of the beam times. So, if the detector study takes time, we may not be able to do the HALO and Background measurements. Our plans are: 1. measure gamma-rays from "e-beam"-"tungsten-wire" collision to understand the detector response for the background-like photos. (will do at the end of November, if no complications.) When the laser-wire is ready, we will start to 2. measure gamma-rays from "e-beam"-"laser-wire" collision to understand that for the signal-like photos, even if the study 1) will not finish. (will do at the beginning of December, if no complications.) After the study 1) and 2) finish or the 1) finish but the laser-wire is not ready, 3. measure HALO distribution and the background radiation around the Beam Dump. I am sorry we can not say the exact schedule for the HALO and Background measurements.  Taikan and Yoshio