A. The report of cosmic test results of the scintillator prototype has been uploaded to the Qweak document web server under Tracking Working Group.

B. Simulation for downstream collimator and shielding design

Based on VT's "final" primary collimator design (seen Juliette's web page), I did a few simulations for the downstream collimator and shielding (The 50 cm thick concrete shielding wall is located at Z=380 cm, with an opening designed based on the old Boston collimator set-up). Below are the results. 1. Histogram of x projection of elastic electron at Cerenkov bar (18 cm wide, 2 m long, at Z=570 cm), and the Histogram of Q^2. The set-up is the same as that of VT. The obtained event rate = 855.5 MHz, mean Q^2= 0.02573 GeV^2 (Juilette got rate=875 MHz, mean Q^2 = 0.0258)





2. Histogram of x projection of elastic electron at Cerenkov bar and the Histogram of Q^2. The set-up is the same as that of VT, but with a tighter opening at the downstream collimator. The obtained event rate = 855.5 MHz, mean Q^2= 0.02575 GeV^2. It is close to the first case.





3. Histogram of x projection of elastic electron at Cerenkov bar and the Histogram of Q^2. The shielding wall was added in this set-up, as well as a tighter opening at the downstram collimator. The obtained event rate = 829.4 MHz, mean Q^2= 0.0261 GeV^2. It seems some electrons are blocked by the shielding wall.





Now, simulation is running to redesign the window of the shielding wall.