Minutes of the feedthrough meeting of October 12, 1999. Present RK,MF,PP,TH,RL,PB,GV,AD These minutes are long because a lot of work has come to completion in the last week. I will put next weeks agenda at the top for easy access. Agenda for Oct. 18 1999 1. Milestones 2. Quality Plan (Aaron) 3. Cold tests 4. Storage issues and inventory control. Minutes 1. Milestones - Paul Birney has included dates for each of his milestones. He has emailed this page to Michel. - The detailed draft calender of events that Margret produced has been emailed to Michel. - The cold test of the 6 good pin carriers will start this week. - Next delivery of pin carriers is Oct 15 + shipping time. - Bellows prototypes: I've just received a call from Bill Hunter at American BOA. Their shipping date for our five bellows is October 20th. Apparently they may be ready on the 18th but he feels very confident about the 20th. Our original requested date was October 7th but in all fairness, a combination of us being a few days late, plus a trucking foul-up, caused a two week delay in them receiving our machined rings. - RFQ for HEC pigtails and low voltage cables will be delayed two weeks but is in hand. - Mainz test of welding dye started on Oct 11. Will be complete in one week. - Low inclusion steel is scheduled to arrive at Victoria and Glasseal on Oct 15. It should therefore have been shipped already. Terry will call Sandmeyer and Greg Meyers at Glasseal to see what the actual status is. 2. QA/QC Aaron has almost completed the first draft of the QA/QC document we will take to the LARG week. Aaron, Poff and I will meet this afternoon to go over the latest revisions and Aaron says he expects to finish the draft by Thursday noon. 3. Interface issues Roy has made a list of interface issues. 1. What vacuum fittings are to be installed on the warm flange. 2. What temperature probe is to be installed on the warm flange. 3. What heaters are be installed on the warm flange. 4. What superinsulation is to be applied to the Feedthrough and how is it attached. 5. What O-ring is to be used at the Seal Ring/ Cryostat interface. Poff is concerned about the storage of Pin Carriers and suggested one of the steel cabinets in the lab. could be used to store the entire production of Carriers, although that will probably not be required. He mentioned the Pin Carriers fit nicely into the cardboard boxes in which we receive the Pigtail cables, and proposed we store the Pin Carriers in the boxes in the steel cabinet with the doors kept closed (to prevent fall-out from earthquakes). He also mentioned the need for some bubble foam and a plastic bag sealer - Paul said he would look for these items. 4. Summary of LV feedthrough tests at UVic (Oct.4-7.,1999) ======================================================= Horst Brettel visited Victoria and joined us in some tests to explore the special characteristics of the HEC LV feedthrough lines. The tests were aimed to determine: a) The ohmic heating of the LV lines b) The induced cross talk seen by the signal lines if there is a ripple on the LV lines. a) Ohmic heating ---------------- The feedthrough test set-up was equipped with 2 LV vacuum cables and 27 vacuum signal striplines. One of the LV cables was "looped" such that the same current went through all wires of this vacuum cables. The loops connections were done with custom made connectors in the respective slots on the outside of the warm and cold flanges. All AWG28 wires of this LV vacuum cable were tied into one bundle, and a temperature probe was positioned in the centre of this bundle. The second LV cable was connected to a HEC LV pigtail. This pigtail was "jumpered" such that pairs of wires that would feed a particular HEC preamplifier board were short circuited. One single wire of each wire gauge of the vacuum cable was equipped with a temperature probe. The approximate temperature of the individual wires (second LV cable) as a function of wire gauge and current is given in the table below in Kelvin: AWG \ Current[A] \ 0.36 0.5 0.7 0.8 1.0 1.2 1.5 1.6 2.0 2.2 2.5 3.16 28 295 - - 299 - 304 - 312 - - - - 26 - 297 - - 299 - 304 - 310 - 320 - 24 - - - - - 299 - - - 308 - 321 28 (bundle) 307 318 - - - - - - - - - The increase of temperature with time was relatively slow and we came to the conclusion that a "slow" swicth (milliseconds instead of microseconds) for current limiting would be adequate. The current limits should be set to approximately twice the limit of the nominal current limit, which is: 900mA for AWG24, 550mA for AWG26 and 400mA for AWG28. For the currents that were measured, no appreciable run-away effect due to increased resistance with temperature was observed. A slightly higher temperature was observed for the temperature probe that was mounted in the bundle of AWG28 wires. We suspect there are two reasons for this effect: i) The leads of the temperature probe provide a relatively smaller thermal path away from the bundle than from an individual wire and ii) The radiative losses might be less for a bundle than for an individual wire. b) Cross-talk induced from LV ripple ------------------------------------ In order to measure the effects of a ripple in the LV supply on the signal lines, a pair of wires of the first LV cable were treated as a "transmission line", which is short cicuited by the jumper at the end of the pigtail. A 2V square pulse is injected down this line. A nearby signal line, which is "jumpered" over a pigtail is terminated in 50 Ohm and read out with an oscilloscope. A ripple with an amplitude of 2mV is induced on the signal line from the 2V square pulse on the LV line. This means that the cross talk induced on the signal lines is about 0.1% of the size of the LV noise. Horst said that he can easily limit the LV noise to 500mV, which would lead to a 500microvolt induce cross talk on the signal lines. The already amplified HEC signals will not be adversely affected by this. However, it is important to find out during the Larg week, what the requirements are on the EM signal, and whether it is at all technically feasable to filter the LV lines to better than 500mV.