Since Feb. 2000, DLATR6 (CFD & pre-amp.) was poor condition, because the discharge broke electric circuit board of DLA. For that reason, the YSTOP signal from amplifier was lower than others. Additionally the other board was discharged. (;o;)
Fig 1. is a 2d-image of poor resolution.
The resolution in the x-direction is poor than y-direction, and we can see some stripes in the x-direction. We found the time-sum was bad, i.e. another peak was found in the time-sum spectra.

So we exchanged the broken circuit boards, then got better resolution than before.(Fig. 2) As you seen, the resolution in the x-direction of 2d-image 2 was better than 2d-image 1. But some stripes in the x-direction remained.

We checked the time-sum was bad yet and exchanged boards(A1/A2 and A3/A4). Fig. 3 is a fixed 2d-spectra. But you can see the some spots. Is it by sputtering?

Fig 1. Fig.2 Fig 3.