Protovec-1

General Characteristics

• GE180 cell with 5:1 K/Rb alkali ratio and filled to 6.7amg 3He. Protovec-1 fill data & Protected spreadsheet of Protovec-1 fill data.
• Fabricated by Mike Souza mid-July 2011 at Princeton University. Requested Cell and String dimensions for Prototype Convection Cell.
• Filled by Al Tobias Sept 15, 2011 at the University of Virginia. The image below on the left shows the cell attached to the gas system and (sitting on the gas system table) stainless steel tubing that comes down and circles around in a rectangle and back up. This is our LHe Cold Trap for the purposes of purifiying our 3He gas before it goes into the cell. Both the LHe Cold Trap and the cell are immersed in LHe in our box dewar Mollie, as shown in the image on the right. The 3He gas is first sent thru the stainless steel loop then into the cell.

Protovec-1 attached to glass manifold on the UVa gas system.

Protovec-1 immersed in LHe-4 dewar box Mollie during a gas filling procedure.

• Actual Dimensions of Protovec-1. Note about cell dimensions from Al Tobias -- "I regret that we forgot to measure the distance between the transfer tubes right under the pumping chamber. I remember making a rough measurement of the tubes, and found that they are indeed just under 2-inches apart (from central axis to central axis). I'll try to accurately measure this as soon as I have safe access to the cell. Let me know what distance below the pumping chamber your cell holder plate for the oven will attach to the cell's transfer tubes. Also note that I believe I kept the pull-off height less than 1.5" long. This dimension is hard to measure since the pumping chamber is not really spherical. So I measured from the bottom of the pumping chamber to the top of the pull-off."

Buoyancy Measurement

• The sealed glass 3He target cell's internal volume can be determined via the Buoyancy Measurement. To determine the internal volume with this method, one must measure the mass of the cell, mass of cell + block in water and mass of block in water (by itself with cell removed).

Protovec-1 tied up with a block for the Cell + Block mass determination of the buoyancy measurement.

Pumping Chamber view of Protovec-1 tied up for buoyancy measurement.

View of block tied to Protovec-1 target chamber for buoyancy measurement.

The buoyancy "mass of cell + block" measurement for Protovec-1.

Cell Mounting

• At UVa, we mount our cells onto an Alumina Silicate Ceramic plate via Kapton tape. We do not use Silicone RTV (like at JLab) because we like to deliver a clean cell to JLab after our tests at the University. Kapton tape removes cleanly and acetone can help remove any stubborn silicone adhesive that is left behind from the Kapton tape.

Mounting cell with Kapton tape onto an Alumina Silicate Ceramic oven plate.

Spacer used to set proper height of cell so that a 3.5" pumping chamber will be centered on oven windows.

Kapton taping the underside of cell mounting plate.

Closeup of Kapton tape on underside of cell mounting plate.

Cell mounted on plate with Kapton tape on both top and bottom surfaces.

Cell securely mounted on oven cell holder plate.

Protovec-1 prepared to go into UVa SEOP Oven.

Protovec-1 installed in UVa SEOP Oven.

• The UVa Oven "cell mounting plate" is 7.0-inch outer diameter round. The bottom or "base plate" of the actual oven is square but has a 5.5-inch

diameter round hole. That leaves about 0.75-inch overlap. We use a red silicone gasket ring to help make air-tight seal when installing mounting plate w/ cell into the oven.

a) convection cell mounting plate with two transfer tube access
b) oven bottom or "base plate" with the 5.5-inch hole 
c) transversity cell mounting plate with single transfer tube access
d) front and back walls of oven which hold pump laser windows

• If you mean the height adjustment ceramic piece as the "spacer" I do not have a drawing. It is about 3.325" tall for installing 3.5" Pumping Chamber cells.

Pickup Coils

• Initially, Protovec-1 was fitted with three coils at UVa, in addition to the normal pair used just outside the main oven of the UVa spin exchange optical pumping (SEOP) system. The large solenoid fitted around the transfer tube on the left in the image below is the pNMR coil which has 80-turns of 24-gauge insulated copper wire. The two solenoids on the target chamber are the TC coils which have 50-turns of 24-gauge insulated copper wire each.

Wrapping a 50-turn solenoid TC pickup coil on Protovec-1 target chamber.

Wrapping an 80-turn solenoid pNMR coil on Protovec-1 1-inch bulb.

View of three coils, a pNMR and two TC coils on Protovec-1.

View of Protovec-1 installed in oven, pNMR coil on the left and two RTDs used to control and monitor the Convection Drive Oven.

Convection Drive Oven

• Here Protovec-1 was installed in transverse mode into the UVa SEOP oven (Oct/Nov 2011). The Convection Drive Oven system forces filtered compressed air thru a HotWatt PF12 Pure Flow Air Heater and into the Drive oven box that encloses the vertical part of the right transfer tube. The Drive oven was constructed with 1/4" thick Calcium Silicate board wrapped in Kapton tape. It has dimensions 4.5" High x 2.0" Wide x 5.5" Deep looking into the oven along the pumping laser beam path.

Drive oven parts.

Drive oven partially installed.

View of Drive oven with Pure Flow heater and thermocouple in foreground.

Side view of Drive oven with pNMR in front of it.

UVa flow test

Yunxiao did measurements with convection drive oven temperatures between 60C and 120C. The optimum temperature (to obtain highest 3He polarization in "convection flow" mode) was about 80C for Protovec-1

When the convection oven temperature was set at 80C, the main oven that contains pumping chamber was set at 235C, PC temperature after temperature test correction was 246.8C, TC temperature was 27.7C. The temperature of the other transfer tube that was not in the convection oven was 34C. The convection speed was 6.3cm/min. Max pol was about 60%. We were using comet laser, and laser power was about 55W(total power of 3 comet lasers).