Photon and Electron Background Study (3)

• Recalculated the photon and electron background from elastic, inelastic and Moller scattering for the following three cases, by weighing the background number with the number of photoelectrons it may generated based on the energy of these particles.
  (1) "Standard" VT primary collimator (made of 21.83 cm thick lead), theta_max= 10.53, 50 cm thick Lead shield wall, with 2 cm clearance, WITHOUT lintel.
  
  (2) Moving "Standard" VT primary collimator 25 cm upstream (made of 5.25 cm tungsten), theta_max= 10.25, adding 11.2 cm thick non-defining lead behind the primay collimator, 50 cm thick Lead shield wall, with 2cm clearance, WITHOUT lintle.
  
  (3) All conditions are the same as case (2), except WITH lintel (made of 5.25 cm thick x 16 cm high x 56 cm wide Tungsten, at Z= -80 cm).
  
  In summary, when using the VT "final" primary collimator, the electron and photon background is larger than other two cases. By moving the collimator 25 cm upstream, using a smaller theta_max and a lintle, we can greatly reduce the electron and photon background from moller scattering and the electron background from the inelastic scattering.
  
  Table 1. Background from elastic reaction, inelastic reactions, and Moller scattering for the above three cases.
  
  

  Reaction	Photon Background	Photon Background from collimator region only	Electron Background	Case #
  ep elastic	0.21%	0.038%		1
  ep elastic	0.2%	0.032%		2
  ep elastic	0.16%	0.004%		3
  ep inelastic	0.014%		0.12%	1
  ep inelastic	0.015%		0.037%	2
  ep inelastic	0.013%		0.041%	3
  Moller	0.44%		0.183%	1
  Moller	0.38%		0.18%	2
  Moller	0.11%		0.125%	3

  
  
  
• Comparison of the background for three different shield wall design.
  (a) All conditions are the same as case (3) reported above, except that the shield wall is made of 2 inch Lead + 44.92 cm concrete.
  
  (b) All conditions are the same as case (3) reported above, except that the shield wall is made of 4 inch Lead + 39.84 cm concrete.
  
  (c) All conditions are the same as case (3) reported above, except that the shield wall is made of 2 inch Lead + 44.92 cm concrete, and the 4 inch concrete at the shielding window lips is replaced with 4 inch Lead.
  
  In summary, when changing the 50 cm Lead shield wall to a more realistic shield wall (2 inch Lead plus concrete), the photon background does not change much for the elastic, inelastic, and Moller scattering. Only the inelastic electron background increase from 0.041% to 0.074% (comparison of case (3) with case (c)). Further study is needed to address this background.
  
  Table 2. Background from elastic reaction, inelastic reactions, and Moller scattering for the above three cases.
  
  

  Reaction	Photon Background	Photon Background from collimator region only	Electron Background	Case #
  ep elastic	0.16%	0.0048%		a
  ep elastic	0.15%	0.0025%		b
  ep elastic	0.186%	0.003%		c
  ep inelastic	0.0137%		0.1%	a
  ep inelastic	0.011%		0.092%	b
  ep inelastic	0.0176%		0.074%	c
  Moller	0.1%		0.173%	a
  Moller	0.13%		0.13%	b
  Moller	0.12%		0.12%	c

  
  
  
• Ntuple of ep inelastic scattering for case (c), and the GEANT3 geometry files with the lintel.
  
  

  ep inelastic scattering ntuple

  GEANT3 geometry file for case (3)

  GEANT3 geometry file for case (c)