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: Hodoscope : Description of the Enge : Enge detector package

Honeycomb drift chamber

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 4$\times$10$^{-4}$ (FWHM), position and angular resolutions of 100$\mu $m 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.

表 13: Honeycomb drift chamber parameters
layer configuration xx' uu' xx' vv' xx' (u,v $\pm 30^\circ$ tilt)
effective volume $12^H \times 100^W \times 30^T cm$
cell size honeycomb (hexagon) with side 5 mm
anode wire tungsten $\phi $ 20$\mu $m
shield/field wire aluminum $\phi $ 80$\mu $m

The effect of multiple scattering was studied with the GEANT simulation. Angular spreads for various gases are listed in Table 14. Standard Ar + C$_2$H$_6$(50/50) gas barely satisfies the requirement and possibility to use a He-based gas will be investigated.

表 14: Multiple scattering effects for the scattered electrons
Gas Angular spread (mrad, rms)
He 0.84
Ar 1.90
Ar + C$_2$H$_6$ (50/50) 1.90

Figure 35 shows an isochrome drift lines for one honeycomb cell calculated with the Garfield program.

next up previous
: Hodoscope : Description of the Enge : Enge detector package
Satoshi N. Nakamura 平成16年12月2日