Dear Peter and Dave, Please find attached a drawing with the dimensions that will (hopefully) allow you to create the apropriate drawing for the workshop. Here are some comments with respect to your drawing on the TWiki page: - I did not yet calculate the h_light. It depends on the length of the yet not specified sliding feedthrough. - The d_plexi is 20 mm for the existing feedthrough. However, Ron told me that the mounted PMT is a so called 1.8" and not a 2" one. So we probably need to adapt the thickness a bit. However, since the NW40 connector on the pipe has an inner diameter of 40.8mm there is plenty of space for a slightly thicker plexi tube. - I also drew one of these NW40 connectors which are welded to the vacuum pipe. The counter part should have at least the same edge where the vacuum clamp is mounted. - For the length of the vacuum pipe we have the following options: + A 360mm long one plus a 650 mm (with one NW40 connector at 200 mm from the edge) + 1210 mm + 800 mm (with one NW40 connector at 180mm from the edge) I think we should go for the first version since it is similar to the actual length of the beginning of the 8" pipe to the target position (1020 mm). Some comments to the existing feedthrough as an orientation for the new one: - The existing feedthrough has a metal shielding for the plexi with an outer diameter of 25.2 mm. In this version plexi and aluminum are touching but if you prefer a non touching version with alu wrapping that should be fine. - The outer pipe for the feedthrough with the o-rings has an inner diameter of 25.3 mm. So there is only ~0.1mm of space for the two sliding parts. Since we might have a thicker plexi tube the diameters might change but the relative difference should be the same. - I didn't manage today to look at the details of the o-rings in the feedthrough. But I want to extract one tomorrow and check it's size. - I haven't thought yet of a good end for the feedthrough where the PMT is mounted which could enable us to prevent the PMT from being sucked in. But you (Peter) already had something in mind with the set screws, right. Today I also talked to Mr Bugmann from the workshop east. He immediately told me that they are extremely busy until October. However, if we come with good drawings he can better estimate the time they need. If they only had to cut the plexi tube and the metal shielding it would be a few days only. The outer feedthrough that needs to be milled adds some more days. I already checked with Mr Baumann from the Hallendienst and he agreed that they can do the vacuum tight welding of the two NW40 connectors next week. The milling could be done in the workshop west but I first need to ask for their capacities. So we should estimate 1-2 weeks for that being done at PSI. Well, I hope that these information are sufficient to bring up a first version of a design. I'm sure we need another iteration tomorrow. I'll be still online for about half an hour in case I have forgotten to provide some necessary information. Tomorrow I'll be looking around for the PMTs and other mechanics and with a fresh mind I can review any drawings. Best greetings Peter
Attachment:
HaloCounter.ppt
Description: MS-Powerpoint presentation