Long Term Stability of Fermilab Energy Saver Magnets

The quench and field properties of Energy Saver dipole and quadrupole magnets are measured at the Fermilab Magnet Test Facility shortly after the magnets have been produced. It is important that magnet properties remain unchanged with time. This question has been investigated by remeasuring magnets at a later time and comparing the two sets of measurements. Three sets of unbiased data are available: 1) Fifteen dipole magnets were remeasured after they were removed from the "B12" cryoloop test location. At B12, they were subjected to repeated thermal cycles, quenches at high current, steady state operation at high current, and ramping to high current with an accelerator type ramp cycle. The average time between the original measurement and the remeasurement was 22 months. 2) Five standard length (66 inch) quadrupole magnets were remeasured after an elapsed time averaging 5 months. These magnets were in storage during the period between the two sets of measurements. 3) Six long (99 inch) quadrupole magnets were remeasured after an average time of 12 days. These were also in storage. The remeasurements agree well with the original measurements. The measurement techniques and magnet properties obtained from the full magnet samples are described elsewhere.