Questions:

1) What is the volume of LN2 that is converted to GN2 for each shoot. Within the first second,minute. Are we still talking about a total LN2 volumn of 100 liters?

2) What are the chemical characteristics of the foam installation.

3) During the MIT testing can we determine whether trapped LO2 is present or not—and how much?

4) Do you have an estimate of the remain volume of LN2 after the purge preceding the shot?
 

Answers:

1) To cool the magnet down from 100 to 69 K, 22 MJ is required. (I don’t have a quick number for 80 K to 110K? but it will be a bit larger) Approximately, this will vaporize 22e6/199000 = 110 kg of liquid. At 66K, and 1 atm, the specific volume of the gas is .937 M^3/kg. 103.6 m^3 of 66K gas would be produced. Using the ideal gas law, this will be 103.6*292/66= 458 cu meter at room temperature. This would fill an 8m cube, or a big percentage of the LDX cell. Most of this is vented in the first 200 seconds or so. The peak gas evolution is a function of how much surface of the magnet is exposed to LN2. At MIT I intend to avoid filling the cryostat, - just filling the lower volume and relying on gas cooling. This will require more than 20 min to cool between shots. – more like an hour.

2) CTD cryofoam sprayed or toweled on is fire retardant, and has good adhesive properties and is used by NASA for Liguid Hydrogen lines. It traps no solid or liquid Oxigen. Because of the good adhesive properties, making it difficult to access flange bolts etc. we may not apply this foam at MIT – we may use fiberglass blankets, and when we are sure we don’t need to take anything apart. I attached whjat I know about cryofoam. I think CTD could supply chemical composition if they knew want the concern was so that they could respond without giving away their recipe.

3) we don’t have a way to estimate the O2 accumulation –except from the traces in commercial LN2. We won’t run enough shots to accumulate much. I have included 900 liters in the cost estimate. I could estimate an upper bound. But I don’t think that is what you want. C-Mod has data in their safety analysis of ozone generation, and decided after many thousands of liters of LN2, that it wasn’t a problem. I can provide their analysis.

4) I think Kirk McDonald did the volume integral of the sloped can remnants. As I remember it was .7 liter.