Pictures of the rear hodoscope (DCC)

In a video meeting in March, 1998, Mike Wang reported that his analysis suggested that the rear hodoscope counters were not located in a vertical plane, but rather that the center of the counter was ~1/2" upstream (closer to the LH2 target) than the top and bottom of the counter. I said that I would take a trip out to Lab G & look at the hodoscope (which was leaning up against the shield wall near the downstream end of the enclosure) to see if this was plausible. I did so on Saturday, 3/14, and I conclude that it IS plausible.

I took these pictures on Saturday, March 14, 1998. At that time, Lab G housed a 10 MeV He-III RFQ and was interlocked except nights and weekends.

I took the following notes while looking at the counter:

The center of the hodoscope IS currently bowed towards what was the upbeam direction. It is not possible to sight from the frame on one side of the counter to the frame on the other side. This implies that the center is out of vertical with respect to the top and bottom of the array by more than 1/4" (the thickness of the shims holding the Kevlar tape off the frame). The bottom counters are bowed about a counter thickness (1/8") more than the top counters. SOME OR ALL of the bowing may be due to the fact that a four-wheel cart was stored on top of the carts visible in [1] leaning against the counters. I removed this cart before it occurred to me to take a picture of it. The cart was leaning against the beam right (photo left) counters about 1/2 way between the wire & the Kevlar tape.

[1]

[2]

[1] As mounted on JGG - bottom right is Beam Left Bottom; [2] Center of array

[3]

[4]

[5]

[3] Bottom is further out of plane than top; [4] Looking from beam left ; [5] Kevlar tape held off frame with 1/4" shim

[6]

[7]

[8]

[6] Wire holds counters by the lightguides; [7] Looking from beam left - upbeam side - (wire touches counters on upbeam side only) ; [8] Looking from the back - note that counters don't all touch shims