Peter Kneisel

Performance of a CsBr coated Nb photocathode at room temperature

Experiments performed on Nb substrates coated with thin films of CsBr indicate a substantial enhancement of 150 to 800 times of the photoyield at 257 nm relative to the uncoated substrates. Results are presented for several power density illuminations and sample thickness. Further enhancement of photoyield was observed when the laser illumination was interrupted for a short time in samples with 5–10 nm thick CsBr coatings.

Summary of performance of superconducting radio-frequency cavities built from CBMM niobium ingots

Several Nb ingots have been provided by CBMM to Jefferson Lab since 2004 as part of an R&D collaboration aimed at evaluating the performance of superconducting radio-frequency cavities built from ingots with different purity, as a results of different ingot production processes. Approximately 32 multi- and single-cell cavities with resonant frequency between ∼1.3-2.3u2005GHz were built, treated and tested at 2u2005K at Jefferson Lab between 2004 and 2014. The average peak surface field achieved in cavities made of RRR∼260 and RRR∼100-150 ingots was (119 ± 4) mT and (100 ± 8) mT, respectively. Higher quality factor values at 2.0u2005K have been measured in medium-purity, compared to higher purity material.

RF Performance Results of the 2nd ELBE SRF Gun

An improved SRF gun (ELBE SRF Gun II) has been installed and commissioned at HZDR. This new gun replaced the first SRF gun of the ELBE accelerator which had been in operation since 2007. The new gun has an improved 3.5-cell niobium cavity those SRF performances have been studied first with a copper cathode. After the replacement by our standard Cs2Tecathode we observed a tremendous degradation of the cavity gradient paired with an increase of field emission. In this contribution we will report on our in-situ investigations to find the origin and the reason for the particle contamination that happened during the first cathode transfer.