Structure Design of SciBar Tracker

Transcription

1 Structure Design of SciBar Tracker H. Maesaka Kyoto University July 26, 2002 Abstract A SciBar tracker will be constracted as a new near detector for the KEK-to-Kamioka long-baseline neutrino oscillation experiment (K2K). Section 1 is an introduction to the tracker. Section 2 and section 3 explains about the steel structure for supporting the detector and a scintillator layer module, which is a scintillator array board, respectively. 1 SciBar Tracker This detector is a scintillator tracker with wave-length shifting (WLS) finber readout. Figure 1 is a shematic view of the detector. The size of each scintillator is 1.3cm-thick, 2.5cm-wide, and 3m length. The scintillator is made in the industrial extrudion process and made of polystylene. In addition, a 0.18cm-diameter hole at the center and 0.25cm-thick reflective coating are also co-extruded. A WLS fiber goes through the hole. Figure 2 shows a CAD drawing of the strip. Scintillators are arranged horizontal and vertical one after another. The whole size of the detector is 3m 3m 1.7m. The net weight of the detector is about 20 tons. When a charged particle penetrate the scintillator, scintillation lights are absorbed by a WLS fiber, and the fiber emitts longer wave-length lights. Some of them go to a photo-detector (64-pixel multi-anode PMT) at the end of the fiber. 2 Steel Structure Figure 3 shows a steel structure for a SciBar tracker. Blue ones are existing beams and pillars which supported old detector (lead glass caloriemeter). 1

2 Photodetector (MAPMT) Wavelength Shifting Fiber Extruded Scintillator ν beam 3m 3m 1.7m Figure 1: A schematic view of SciBar tracker. 2

3 Figure 2: A CAD drawing of the scintillator strip. 3

4 Red ones will be newly added. Figure 4 6 are CAD drawings of the structure. In this case, beams B sag down about 0.2mm at the center. Beams C sag down about 0.3 mm. Without pillars A, beams B sags down about 2mm. 3 Layer Module It is difficult that the detector is constructed at the actual spot, because the space is too small and so on. But though the whole size of the detector is made at a larger place, it cannot install because a crane can only pull up 500 kg. So, layer modules, which are the board that scintillator strips are stacked and glued, will be made at the larger place. Then the modules will be installed in the detector place. Figure 7 is a schematic view of the module, and Figure 8 shows a CAD drawing of it. A layer module consists of one X layer and one Y layer. The two layers are glued. The module also has a aluminum frame and some gamma-ray converters made of lead. Parts of the frame are shown by figure M8 15 socket head cap screws bolt up them. The weight of the module is about 300 kg. The module is too weak to be hung by a crane, it needs a support structure. Figure 15 is a schematic view of the support. The module will be made on it, and after the installation it will be removed. The weight of the support is about 150 kg. Though the crane can pull up only 500 kg, it s OK because the sum of a module and a support weight is about 450 kg. Figure 16 shows a layer module fixed to the support. The module is fixed at 4 points. It is fixed with bolts at the top and with knobs at the bottom. Figure 17 shows how to make the module. After the support is set on the table, horizontal scintillator strips are arranged. Then epoxy glue are spread and vertical strips are stacked. The module is installed as shown in figure 18. At the place whare the module is made, a crane can pull up only 3m. But the module must go over a handrail. So, using a temporary chain block, it is moved above the actual spot and put up. Then it is set on the steel structure, aligned and fixed. Finally, the support is removed. The module is fixed to the structure with 4 bolts as shown in figure 19. 4

5 H 294x200x8x12 H 294x200x8x12 H 194x150x6x9 Detector H 194x150x6x8 H 294x200x8x12 H 194x150x6x9 H 100x100x6x8 Beam C C 150x75x6.5t H 194x150x6x9 H 194x150x6x8 H 194x150x6x9 B H 300x150x6.5x9 C 125x65x6t C 150x75x6.5t C 150x75x6.5t A C 125x65x6t 1.9m existing 3.6m new Figure 3: A schematic view of the steel structure. 5

6 Figure 4: A front view of the upstream steel structure. 6

7 Figure 5: A front view of the downstream steel structure. 7

8 Figure 6: A side view of the steel structure. 8

9 plastic scintillator strip Al frame 3m gamma ray converter (Pb) 3m Figure 7: A schematic view of the layer module. 9

10 Figure 8: A CAD drawing of the layer module. 10

11 Figure 9: part 1 11

12 Figure 10: part 2 12

13 Figure 11: part 3 13

14 Figure 12: part 4 14

15 Figure 13: part 5 15

16 Figure 14: part 6 16

17 100x50 100x50 100x50 L 50x50 L 50x50 3.2m L 50x50 L 50x50 L 50x50 L 50x50 100x50 100x50x4t 100x50 100x50x4t 100x50x4t 100x50x4t 100x50 100x50x4t 3.2m 100x50 Figure 15: A schematic view of the support structure of the layer module. 17

18 screw support structure screw band 3m 3m Figure 16: The layer module with the support structure. 18

19 3m 3m 3m glue (epoxy) 3m Figure 17: How to19make the module.

20 ~3m the actual spot Align and fix Remove the support structure Figure 18: How to install the module. 20

21 Figure 19: How to fix the module to the steel structure. 21