Status of Nb-Pb superconducting RF-GUN cavities

Abstract

We report on the progress and status of an electron RFgun * made of two superconductors: niobium and lead [1]. The presented design combines the advantages of the RF performance of bulk niobium superconducting cavities and the reasonably high quantum efficiency of lead. The design of RF-gun and performance of 3 test cavities without and with the emitting lead spot are reported in this contribution. Measured quantum efficiency for lead at 2K is presented briefly. More details are reported in [9].

Low temperature laser scanning microscopy of a superconducting radio-frequency cavity

“…This cavity geometry had been used to fabricate prototype cavities for the development of SRF photoinjectors. 11 The resonant frequency of the accelerating mode TM 010 is 1.3 GHz, however a different resonant mode was used for this setup. The TE 011 mode at 3.3 GHz has the advantages of having, ideally, zero surface electric field, thereby avoiding field emission to limit the cavity performance, while having high surface magnetic field in a region of the surface which can be accessed by the laser beam.…”

Photoemission tests of a Pb/Nb superconducting photoinjector

“…The cleaning, preparation and RF performance of this cavity are the subject of a related paper [6]. In brief, the Q 0 of the cavity with a solid niobium plug was 3x10 9 at 2 K, and the peak field was over 40 MV/m.…”

“…This ½ cell, 1.3 GHz cavity had a 4 mm diameter lead spot plated on the center of the back wall via arc deposition. The details of the RF measurements on both of these cavities are reported elsewhere [6].…”

“…The effect of the laser on the RF performance of the cavity was characterized. Further measurements of the cavity RF performance are reported in these proceedings [6]. …”

Superconducting Rf Photoinjectors: An Overview

“…Both cavities reached peak field of ~40 MV/m. The DESY cavity is more difficult to clean and hence demonstrated heavy radiation at the highest gradient [12]. For the preliminary experiment on the relaxation time of broken by irradiation Cooper pairs, the superconducting wall of the TJNAF cavity was exposed to 0.75 W of the excimer laser light at 248 nm.…”