# Appendix Troubleshooting

## Vacuum leaks

If the pressure in the system (pressure is indicated on the pump display) cannot be pumped to lower than 1.0E-4 mbar (at T=290K), there is a problem with vacuum. A leak can lead to condensation on the vacuum shield. Inspect the o-rings connecting the system with the pumping system for possible damage and dirt and clean them with alcohol and try again to pump the system.

## Cold-head or compressor problem

Compressor and cryostat failures are characterized either by an inability to operate or by an increase in the minimum achievable temperature. For checking the operation of the compressor please refer to the manual.