As mentioned in the previous sections, the tilted Enge spectrometer combined with the splitter magnet lost its original symmetry of the optics and it is essential to measure the particle incident angle as well as its position at the exit of the spectrometer. In order to achieve momentum resolution of 410 (FWHM), position and angular resolutions of 100m and 2 mr (rms), respectively, are required for trajectories incident angles of which vary more than 50 degrees. Furthermore, the detector should stand for singles rate as high as 10 MHz.
A drift chamber with honeycomb cell structure is to be employed to meet above requirements.
|layer configuration||xx' uu' xx' vv' xx' (u,v tilt)|
|cell size||honeycomb (hexagon) with side 5 mm|
|anode wire||tungsten 20m|
|shield/field wire||aluminum 80m|
The effect of multiple scattering was studied with the GEANT simulation. Angular spreads for various gases are listed in Table 14. Standard Ar + CH(50/50) gas barely satisfies the requirement and possibility to use a He-based gas will be investigated.
|Gas||Angular spread (mrad, rms)|
|Ar + CH (50/50)||1.90|
Figure 35 shows an isochrome drift lines for one honeycomb cell calculated with the Garfield program.