EU Cell Calibration Procedure

For the EU cell, I slightly changed the way the calibrations are being done, taking into account what we have learnt from Ryan's team during their first few weeks.

First, I am using a constantan wire kindly provided by Nicolas, it has the same metallic composition as the active ones, it is the same size (0.2mm diam. 1m long), but it is coated with an (unknown yet) oxide layer, insulating and preventing hydrogen uptake. This is very important, Francesco Celani told us, even bare constantan wire absorbs small quantities of hydrogen.

After a few tests, the drop in resistivity in this specific constantan wire was only 2.4% compared to the 18%+ we had with the active wire ran by the US lab. Moreover, this drop occurred at very low temperature, where the active wire dropped at 170°C. To me, it looks pretty convincing that no hydrogen was loaded into the wire. Maybe I am wrong. Let me know your thoughts.

So the cell calibrations will be performed in the same conditions as with the active wire (75%H2 + 25%Ar @3.5, 2 and 1 bar because it will leak through overtime) with a range of power that is close to the operating powers (28W, 38, 43, 47, 52, 58, 63, 69, 73, 78, 83, 88, 92 and 100W, the last one is not necessary...). After one hour of temperature stabilisation we sample one point that will be used to plot the polynomial cuve used as a baseline for calculation of excess energy. The choice of which Tc to use is boggling since T_in is influenced by the gas mixture. We tend to use T_out but it is highly influenced by ambient temperature...
T_well is the last option, but it is broken on Cell#2.

I did another one this afternoon using the same gas mixture at 1 bar pressure for each power step.

This gives a set of 3 curves for a gas mixture. 1 for constant pressure. It is also worthwhile to use 50-50 mixture because the hydrogen is the most inclined to leak through the cell. All this curves will help to interpolate and anticipate experimentally the future behaviour of the cell.

Then we have to consider low pressure case. So I use 0.5b of pure H2, I also do 1b of pure H2 because I might try this way at the end. However the cell will leak...air inside, hence it is also necessary to do a 50-50:Questo indirizzo email è protetto dagli spambots. È necessario abilitare JavaScript per vederlo. ; and acquiring data during that time too to detect endothermic/exothermic reactions.

The question of the leakage is related to the fact that we are doing replication as much close to what Francesco was doing in NI week and ICCF. We also want to run the cell "until it dies".

But that is not sufficient for the calibrations, as we have to do calibrations for third parties with activated wire (as a reminder, we plan on shipping the cell to universities). Calibrations runs with He under 3.5b, 2, 1b and 0.5b will be helpful for future users.
When this will be the necessary, she can uses Francesco's technique of heating the wire under vacuum that can help releasing H for the wire's lattice. It can also be lethal for the wire too if too much power is injected in (especially in vacuum because of the absence of convection). 1.9A is the maximum current that Francesco recommends.
The use of oil-free vacuum pump is mandatory because of possible back-streaming of oil inside the cell reaching the wire.

Finally, we have the loading phase that require to use of 3b of pure H2 then rise temperature of absorption: ~170°C.
Then the gaz mixture is introduced and the power is immediately turned on to reach 48W operating power.

I have already done the first batch of calibrations with the mixture, taking advantage of the programmed calibration script, I did ran the cell 24/7. I will make my best to reach operational run as soon as I am done with all these.