Strategy of Diagnose the Issues Related to REBCO Films Deposited by a Reel-to-Reel PLD Process

In order to further understand the multiplume and multiturn PLD process, we propose a strategy to diagnose the issues of REBa2Cu3O7 films deposited in a reel-to-reel manner. Especially, the test tapes after passing through each turn were deposited. Optical microscopy observation on the test tapes reveals that the void defects on the REBCO films are probably related to grain boundaries of the CeO2 cap layer, and such defects become dense and randomly distributed after more turns deposition. XRD analysis indicates that the test tapes deposited at all the turns exhibit strong c-axis orientation. With increasing the number of turns (i.e., increase the film thickness) by passing more times of deposition zone, enhancement of the crystallinity in the REBCO films is found. However, for the tape deposited at the last turn, both the structure characterization and I-c value suggest that the deposition conditions are out of the temperature window margin for growth of the high-performance REBCO film. The advantage of this method is to obtain superconducting film deposited at each turn without changing the deposition conditions, and the issues of superconducting films deposited at each turn can be easily diagnosed.