Medium-temperature baking of 1.3 GHz superconducting radio frequency single-cell cavity

Surface resistance effects of medium temperature baking of buffered chemical polished 1.3 GHz nine-cell large-grain cavities

“…(c) Compared with MTslowImproved450C3h, MTslow Improved450C3h-2 only introduced a small increase in the temperature of high-temperature baking (from 830 • C to 880 • C), resulting in a small increase in the quench field from 17-18 MV m −1 to 21-22 MV m −1 while retaining the level of Q 0 . (d) In all the 2 K vertical test results for our med-T baked cavities there was no 'anti-Q-slope' observed in previous reports [12][13][14][15], which implied some additional mechanism behind the improved superconducting performances. (e) Unlike the typical 'Q-slope' curves and 'anti-Q-slope' curves, quite flat curves of both med-T baked cavities and baseline cavities were obtained when the radiation dose was low and stable, while in some cases the curves had some mild and gradual slopes with certain radiation increases at medium and high fields due to contamination during preparation.…”

“…However, these signals can provide the relative concentrations of the corresponding impurities of different niobium samples under almost the same set of measurement parameters as listed in section 3 of the supplementary data. Since Nb-C compounds did not present promising superconducting properties according to previous reports [40,41], we inferred that higher concentrations of carbon-related impurities in our med-T baking experiments were the reason for the Q 0 not being as high as in previous works [12][13][14][15]. However, one should not ignore the benefit of the increase in interstitial carbon [42], which was reported to have similar effect to interstitial oxygen and nitrogen.…”

“…According to previous reports [12][13][14][15], the main baking parameters, including temperature and duration, are of vital importance for the superconducting performance of the cavities. For further research, we adopted several med-T baking recipes, taking into consideration not only the baking duration but also the temperature ramp time, for use with three largegrain cavities, as listed in tables 1-3.…”

“…To reduce the construction and operating costs of large superconducting radio frequency (SRF) accelerating facilities [1][2][3], several surface treatments including standard surface treatment methods [4][5][6], nitrogen doping [7][8][9] and nitrogen infusion [10,11] have been investigated with 1.3 GHz superconducting cavities to obtain a high accelerating gradient of High Energy Physics [14,15] and the Thomas Jefferson National Accelerator Facility [16]. These baking recipes were first tested on 1.3 GHz single-cell cavities, and then successfully repeated on 1.3 GHz nine-cell cavities.…”

Influence of Furnace Baking on Q-E Behavior of Superconducting Accelerating Cavities

“…The cavities were baked in a temperature range of 200 to 800 • C for 3 h in this vacuum furnace. This baking process is referred to as "furnace baking", which is different from the "mediumtemperature bake" (mid-T bake) that is performed at FNAL and Institute of High Energy Physics (IHEP) 21,22 . The mid-T bake process requires special heat treatment equipment to perform the RF measurement without exposing the inner surface of the cavity to the air after heat treatment at 250 to 400 • C, whereas the furnace baking process is a simple method that can be performed with existing cavity treatment systems because the heat treatment is performed in a vacuum furnace.…”