A new gas system for FEBIAD operation was installed in ITE to enable us to use a calibrated leak which is attached to the target heat shield. This will allow us to control the quantity and purity of the gas going into the system, and to switch quickly between gasese and pressures.

The schematic of the system is attached. The use of the ballast container is likely not needed - it was originally included in case we want to run the system at pressures greater than 1 ATM. The roughing pump inlet limit is 1ATM, so it was envisaged to used the ballast container to reduce the pressure to that level or below before opening the system to the pump. But since it has been difficult to commission the system over 1ATM and this opens the door to several concerns about gas leakage, it was deemed better to keep operation below 1 ATM. This tank will likely be removed.

The storage tank was implemented because we are not sure if irradiated gases will be pulled out of the target lines when we pump on them, and so this was devised as a way to test that. The alternative is to have the exhaust of this pump go directly into nuclear ventilation by way of a plastic tube leaving the faraday cage, however this solution is also quite some work to implement. So the consensus was to start with the storage tank and sample it several times to understand what sorts of radioactivity we are dealing with, then make a decision about future operations.

This system has been tested offline using the development target UCx#44 and appears to work well. Unfortunately there were no protons available for this beam time so the gas sampling part of the system was not tested.

The operation of the rest of the system worked reasonably well. Beam disappeared when pumping out the lines and reappeared when re-opening the gas bottle. It seems that the storage container can be used to pump out the lines about 7 times before it gets up to around atmosphere, as was estimated based on volume. The pump can get the lines down to about 250mTorr as read by the pressure gauge DG2 on the module top, given about 30mins of pumping.

We did have some issue with the gauges, HV sparks destroyed both controllers and so we were unable to monitor pressures as we would have liked. It is possible one gauge itself is broken as well, to be investigated.

It may be that the gas leak we used was too small, but the idea of changing the pressure on the module by changing the needle valve didn't seem to work. This is not sure since we didn't have a reading on the pressure, but watching the ion beam as you turn the gas back on seemed quite binary. You would see no change until you had the needle valve fully open. This may be different with a larger leak, since this leak required about 1ATM in the lines to see anything. It is still not clear why this behaviour was different than the tests at the test stand, in which 0.5ATM of upstream pressure produced about 2nA of beam.

This system is considered a prototype and is not turned over to ops for operation. Further commissioning is required.