Appendix to Table 1

These simulations build upon configuration 8, with the following small adjustments to the geometry.

The upstream face of the wall is now 110cm upstream of the RadPhi target instead of the 150cm which was used for simulation 8.
The hole in the lead wall is now 6.7cm in diameter instead of the 6cm which was used for simulation 8.

These changes have only slight affects on the pairs rate. Moving the lead wall closer to the target has the effect of increasing the rate of soft gammas by about 30%. These gammas have a very soft spectrum and so are not taken as a serious background in this study. Configuration 8 is included again in the table for comparison. The distribution of pairs with distance from beam at the target position is shown in Fig. 1.

Fig. 1

Table 1b.
Test #	Setup E_beam= 4GeV, N_tag=10⁶/s	Charged E_e > 1 MeV 4cm < R < 50cm	Photons E_gamma > 1 MeV 4cm < R < 50cm
8.	Collimation (8mm + 16mm) CLAS target Helium tube (25cm diameter) Shield wall (6cm hole 10cm thick) (with helium tube extended through the wall to 10cm from target) No sweeping magnet after CLAS	32 KHz	320 KHz
8a.	Collimation (8mm + 16mm) CLAS target Helium tube (25cm diameter) Shield wall (6.7cm hole 10cm thick) (with helium tube extended through the wall to 37cm from target) No sweeping magnet after CLAS	51 KHz	440 KHz
8b.	Collimation (8mm + 16mm) CLAS target Helium tube (25cm diameter) Shield wall (6.7cm hole 10cm thick) (with helium tube extended through the wall to 55cm from target) No sweeping magnet after CLAS	59 KHz	450 KHz
8c.	Collimation (8mm + 16mm) CLAS target Helium tube (25cm diameter) Shield wall (6.7cm hole 10cm thick) (with helium tube up to wall 110cm upstream from target) No sweeping magnet after CLAS	104 KHz	470 KHz
8d.	Collimation (8mm + 16mm) CLAS target Helium tube (10cm diameter 50um thick) Shield wall (6.3cm hole 10cm thick) (with helium tube extended through the wall to 37cm from target) No sweeping magnet after CLAS	48 KHz	420 KHz