SIO Paleomag Lab blog

Filled BUBBA with about 30 liters of liquid helium yesterday. The fill went smooth and took about 25 minutes. Julie and Yongjae assisted with the fill.

The SI-4 AF Demagnetizer is up and running. The PA04 power amplifiers burnt out (failed) because of insufficient air flow. The air filter was clogged with lint and dust. The air filters are easily removed and need to be cleaned out about every 6 months with water. In case of another power failure, the PA04 power amplifiers can be purchased from Apex utech volume 7 price list.

Having a good vacuum on the helium reservoir is necessary for maximizing liquid helium use. Because FLO is at room temperature and at atmospheric pressure, the system needs to be pumped down. After 4 days of vacuuming the system, an acceptable pressure is achived. (~2x10^-6 torr).

Filled BUBBA with about 30 liters of liquid helium yesterday. The fill went smooth and took about 25 minutes. Roi assisted with the fill.

The SI-4 AF Demagnetizer isn't working. The control unit seems to be fine, though it's unable to be tuned and the coil no longer builds a charge after it's triggered. The coil, control unit, cradle, and power supply are being sent back to M. Stupavsky for servicing.

Filled BUBBA with approximately 30 liters of liquid helium (8/3/05). This was the first smooth fill in a couple of months. Julie helped with fill and it took about 20 minutes to complete. An obvious change in the plume occured this time. BUBBA'a reservoir was then measured with the dip stick, measuring ~28 inches meaning it's 100% full.

To run programs from anywhere within the terminal, three (hidden) files must be placed in the user's directory. The first file should be called .bashrc and looks like the following

if [ -f /sw/bin/init.sh ]; then
  . /sw/bin/init.sh
fi

The second file should be called .bash_profile

if [ -f ~/.bashrc ]; then
  . ~/.bashrc
fi
export BASH_ENV=$HOME/.bashrc

The third hidden file should be called .profile

test -r /sw/bin/init.sh && . /sw/bin/init.sh

Filled BUBBA with about 25 liters of liquid helium today. The fill went smooth and took about 15 minutes. Roi assisted with the fill.

The 2G magnetometer (FLO) is temporarily down. During annual maintenance of the adsorber, the brass hose line began to fail. A loose o-ring in the connector may have been the cause of this failure. Later during this maintenance the system was exposed to atmospheric pressure. The first instant the system reached atmospheric pressure there was a cracking/popping noise that came from the coldhead. The noise may have been ice forming instantly inside the coldhead sleeve. After this, the coldhead motor was kind of running but the piston didn't seem to be moving at all. 12 hrs later, the pressure in the liquid helium reservior had reached about ~8psi (safety valve pops at 10psi) and the vent valve was completely frozen over. The extreme buildup of pressure in the initial 12 hours may have been due to the coldhead was running, trying to pump helium in though unable to recycle any out. After turning the cold head off, defrosting the ice around the vent valve, and depressurrizing back to ~2.5psi the system began to boil off liquid helium at a safer rate. About 65 liters of liquid helium boiled off in 8 days. Best case scenario for the 2G is that only the coldhead will have to be replaced. Then we can make a new vacuum, use the cryocooler to precool the reservoir, and fill her up with liquid helium.

Normal operating pressure for the CTI 8200 Compresor is about 270-290 psig and static pressure should be around 245-255 psig. If the normal operating pressure increases above 295 the pressure needs to be lowered. In order to bleed the pressure down, follow these steps.

1.  Turn off the compressor
    
2.  If the static pressure is higher than 250 psig,  SLOWLY open the
    helium gas fitting and charge valve.  The pressure will begin to 
    slowly decrease.  Bleed the pressure down to 250.  

3.  Turn on the compressor nominal operting pressure should be about
    270-290 psig)