1 Proposal of the mechanical support on the Buffer for the 10“ PMTs by Enrique Calvo Alamillo March-2007 Double-Chooz Collaboration Meeting

2 PMT 10” from Hamamatsu PMT 3D Modelized This is the modeled PMT that will be supplied with the Oil-proof BASE offered from Hamamatsu.

3 We will use one first attachment support on the equator of the PMT. And the second on the BASE of the PMT. Main support pieces are made on acrylic material (sky-blue).

4 Both fixations are supported on one L piece that it is the main support of the PMT support structure.

5 On the L piece it is mounted one U inox piece (black blue). On two positions. This ‘U’ is the interface between the PMT support structure and the support profiles (also inox) installed on the buffer, to support the PMTs. Buffer wall Buffer lids

6 This is the support of the two μ-metal shielding layers. Mounted on the two ring assembled between four columns. Each ring has four holes to permit enter/exit the majority of the oil between both shielding skins. But it is also possible the flux between the μ-metal and the two ring, because these pieces are not sealed.

7 The μ-metal double layers assembly is attached to the L main piece support.

8 The light concentrator it is attached on the top ring of the μ-metal support. And it is attached directly on the four columns. The concentrator support should have four holes to permit the pass of the oil.

9 These figs are showing the preliminary main dimensions of the design. The approximated weighs are: -PMT+BASE, 3kg -Acrylic support, 2.2 kg. -μ-metal, kg Total ~6-6.5 Kg. The approximated volumes are: -PMT+BASE, 6.7 liters -Acrylic support, 1.8 liters. -μ-metal, 0.16 liters. Total ~8.6 liters. This means that the ‘buoyancy force’ in the oil is ~ 6.9 kg. And consequently the structure does not experiment big forces when the detector is working. The main forces are when the detector is empty of oil.

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11 The following figs show the basic distribution of the PMTs on the buffer. (270 PMTs+60 PMTs+60 PMTs=390 PMTs) There are 3 different U holes’ s distribution to permit the 9 different orientations on the buffer cylinder. And 8 different U for the distribution on the top and bottom side of the buffer.

12 The following figs show the distribution of the L support profiles on the cylindrical area of the buffer. There are (30+30)x3=180 L profiles distributes on the cylindrical area. To fix the profiles on the buffer is necessary several screwed M6 holes on the U circumferential profiles of the buffer. It is necessary to study the tooling for this operation.

13 Here it is showed the distribution of the support structure on the top and bottom side of the buffer. There are 2 central rings closed on one point. And 3x6=18 ring sectors. To fix these rings are needed weld 66+66=132 pieces (sky blue) on the inner side of the buffer wall. Also it is necessary to study the tooling to do that.

14 Here is shown the distribution for the 30x9=270 PMTs on the cylindrical side.

15 Here is shown the distribution for the 60+60=120 PMTs on the top and bottom side.

16 Here it is shown the possibility to insert several PMTs (10) between the cylindrical area of the buffer for muon shower monitor. Mounted on the L profiles. Also is possible to attach ‘magnetic sensors’ on the L profiles (8+(2+2)). And LEDs (50?) for the optical calibration system.

17 On the top and bottom area is not easy to implement the additional PMTs. But for the magnetic proves and LEDs there are space. The total weight of the inox support structure of the PMT on the buffer is aprox 800 kg. And kg of the 390 PMTs.

18 Next steps: -Introduce the approved modification proposed during this week to fix the dimensional design of the PMT support. -Study the feasibility of implementing the fixation points together with the buffer construction people, to fix the structural support on the buffer. -Optimize the fabrication process of the different mechanic pieces. -Design of the mechanical devices to permit machine/weld the different fixation points on the buffer with the acceptable tolerance. -Study to optimize the assembly process for each PMT support. And each assembly on the buffer. And design the mechanical devices for this.

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