Bourdon Gauge

30 04 2009

I ordered a Bourdon Gauge so I can see what’s going on in the chamber before the ion gauge is in range. Stuart tapped a conflat for me in preparation:



30 04 2009

It appears the chamber is not holding a vacuum. The pump and gauge check out (see previous post). But with the chamber attached, I can’t even get down to 5e-2 torr (the top of the gauge’s range) after running for over an hour. So Houston, we have a problem with the chamber.

F*ck me.

Also f*ck WordPress for blocking posts with the word f*ck. What are you? my f*cking nanny?

Sanity Check

30 04 2009

Before I proceed I want to check that the pump is pulling a hard vacuum and the gauge is working. I connected the gauge to the pump directly (no chamber):


Here is a time-lapse of the run:

You can see we get down to ~ 6e-7 torr in about 45 minutes. So suffice to say the pump and the gauge are working just fine. Which brings us to our next post…

Rough Pump Cutout

29 04 2009

So the rough pump is cutting out after about 30 minutes. I spoke with the manufacturer, and two likely causes.

  1. The rough pump is set to 240V (it will run, but will eventually cutoff from overheating)
  2. The diaphram in the rough pump is worn out, causing overheating.

My guess is #2. Investigating.

Here are the rough pumps identifiers:


Mod: MVP-035 2001/01

Mod. – Nr. PKT01200

Lab note: The chamber holds ~150  Liters (0.15 Cubic Meters or 5.2 Cubic Feet). The pumps works at 40 l/s, so it would take 3 secs to rough the chamber? Does that sound right?

Grounding the Chamber

29 04 2009

Proper grounding is really important for any electrical work, esp high voltage work. Even the ion gauge is high voltage. For now I’m just grounding to an outlet. Before we get into the really high voltage domain, I want to ground to a water pipe.

First check the outlet:


Now we fabricate a grounding strap:


Make sure we don’t have any shorts to the hot leads:


Wire it up:


First Descent

28 04 2009

I _think_ (hope) I have all the parts necessary to operate the vacuum chamber for the first time. Tonight I try. I’ll timelapse the progress.

I spoke with MDC about how tight to go on the conflats. He said that for the 2.75″ conflats you want to keep the gasket very parallel. finger tightening in a kris kross pattern. He said not much beyond finger tight. The larger flanges require more torque.

So I was able to get the chamber all buttoned up. I tried running the pump for a while. After about 45 minutes, the rough pump cutout and the turbopump remained on.  Not sure it this is supposed to happen. I’m asking the manufacture if this is normal behaviour.

Here is a timelapse of the setup:

Next up is testing out the Hornet. I have to start by ensuring the chamber itself is properly grounded. Ion gauges use high voltage which could shock you if the chamber is not well grounded.

Loss of Electrical Resistance

22 04 2009

These photos show the drop in electrical resistance when you pour liquid nitrogen on the YBCO. Here is the before at 1.3 ohm:


After liquid nitrogen:

ohmsAs a point of reference, the lowest the meter goes when the clips are connected together is 0.5 Ohm.

Frost forms from the extreme cold:



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