Batygin, Y.K.

Paper	Title	Page
MOP37	Optimization of Positron Capture in NLC	120
	Y.K. Batygin SLAC, Stanford
	In the Next Linear Collider design, the positron capture system includes a positron production target, a flux concentrator, and a linac to accelerate positrons up to 1.9 GeV, the injection energy of the positron pre-damping ring. Two schemes for positron production have been studied: a conventional approach with a 6.2 GeV electron beam interacting with a high-Z target and polarized positron production using polarized photons generated in a helical undulator by a 150 GeV electron beam which then interact with a positron production target. The capture system has been optimized to insure high positron yield into the 6-dimensional acceptance of the pre-damping ring. Various parameters affecting the positron capture have been analyzed, including: positron deceleration after the flux concentrator, transverse and longitudinal electron beam sizes for positron generation, energy compression after acceleration, etc. As a result of these optimization studies, the positron yield in the conventional scheme has been increased from 1.0 to at least 1.5 and for the polarized positron scheme from 0.25 to 0.30 while maintaining 60% positron polarization.
	Transparencies
MOP38	Background from Undulator in the Proposed Experiment with Polarized Positrons	123
	Y.K. Batygin SLAC, Stanford
	E-166 is a proposed experiment for verification of polarized positron production for linear collider. According to polarized positron source design, high energy electrons pass through helical undulator and produce circularly polarized photons, which interact with tungsten target and produce longitudinally polarized positrons. In the proposed E-166 experiment, 50 GeV beam propagates inside 1m long undulator followed by a drift space of 35 m before interaction with target. Polarized positrons are analyzed by Si-W calorimeter, which is placed along the axis. Polarized positrons are analyzed by CsI calorimeter after reconversion of positrons to photons at the second target. Background is an issue for a considered experiment. GEANT3 simulations were performed to model production of secondary particles from primary electrons hitting undulator. Energy density distribution of background particles at the target and effect of background collimation are discussed.
MOP39	Positron Transmission and Polarization in E-166 Experiment	126
	Y.K. Batygin SLAC, Stanford
	The proposed experiment E-166 at SLAC is designed to demonstrate the possibility of producing longitudinally polarized positrons from circularly polarized photons. Experimental set-up utilizes a low emittance 50 GeV electron beam passing through a helical undulator in the Final Focus Test Beam line of SLAC accelerator. Circularly polarized photons generated by the electron beam in undulator hit a target and produce electron-positron pairs. The purpose of post-target optics is to select the positron beam and to deliver it to a polarimeter keeping positron beam polarization as high as possible. Paper analyzes the positron transmission and polarization both numerically and analytically. The value of positron transmission has a maximum of 3% for positron energy of 7 MeV while positron polarization is around 80%.