detector T1 was 0.7 m.

Mostly, the setup was the same as in our previous work [@sokol00; @sokol08] but a few useful changes have been made:

-   $\Delta E_i$ detectors have been placed after the time-of-flight interval T1-T2. This enabled us to have a better $\pi^\pm/p$ separation and time resolution.

-   A transverse size of the start detector T1 was cut off according to required geometry. This reduced a background load of the C-arm.

-   A thickness of the start detector was also reduced in order to improve time resolution.

-   All unnecessary layers of absorbers used previously to suppress radiative backgrounds have been removed from the time-of-flight interval, with the effect of reducing the $e^+/e^-$ background created by photons from $\pi^0$ decays.

[r]{}[0.4]{} ![image](fig-2dim-bb.eps){width="35.00000%"}

General tests of the setup, including preliminary time calibrations of the arms, have been done in special runs, in which the quasifree reaction $\gamma p\to\pi^+n$ inside carbon nuclei was observed. In such runs the two arms of the setup have been moved to the angles $50^\circ{-}50^\circ$ where the high count rate enabled one to do the calibrations quickly. Lead convertors used in these runs provided reliable ultrarelativistic reference points $\beta=1$ for particle’s velocities $\beta_C$ and 