Area Layout

  Figure 2.7 shows the area layout for the Panofsky Ratio measurement. The 116 MeV/c negative pion beam comes from the right of the figure. The CsI and NaI detectors are placed 180 apart. The liquid hydrogen target is positioned in the beam, between the CsI and NaI arrays. The B0 and B1 beam counters are located immediately before the quadrupole and before the target, respectively.

  
Figure 2.7: Beam area () layout for Panofsky Ratio measurement. The 116 MeV/c beam comes from the right of the figure, and stops in the liquid hydrogen target (shown as the small circular object in the figure). The CsI (larger circular object) and NaI arrays are shown to be positioned 180 apart, out of the path of the beam.

With this experimental layout, it is possible to detect the nearly anti-collinear photons from the reaction , as shown in Fig. 2.8.

  
Figure 2.8: Experimental layout for the Panofsky Ratio measurement, showing the detection of the two nearly anti-collinear photons from the reaction

This detection requires a ``two arm trigger'' (See Sec. 2.2.5).