Cryogenic Current Comparators for Larger Beamlines
The new version of a cryogenic current comparator with eXtended dimensions (CCC-XD) for the beam monitoring of charged particles, which is currently in the optimization cycle, is presented herein. The CCC-XD is designed for a nondestructive, highly sensitive monitoring of a few nA beam intensities for 150-mm beamline diameters at the Facility for Antiproton and Ion Research at GSI (Helmholtz Center of Heavy Ion Research). The new CCC comprises a combined superconducting pickup loop, a magnetic shield, and a ferrite core with superconducting quantum interference device based readout. Compared to the previous CCC currently running at CERN, the niobium shield exhibits enlarged geometric dimensions, which results in a more effective suppression of magnetic stray fields from the beamline environment. First results of laboratory measurements as well as simulations of the electrical behavior are presented in this paper. The CCC-XD system—in combination with a newly developed cryostat—will be ready for testing in the beamline of CRYRING at GSI in 2018.
Coreless SQUID-based cryogenic current comparator for non-destructive intensity diagnostics of charged particle beams
We report on a novel concept and prototype development of a coreless SQUID-based charged-particle beam monitor as a non-destructive diagnostic tool for accelerator facilities. Omitting the typically used pickup coil with a high magnetic permeability core leads to a significant improvement in low-frequency noise performance. Moreover, a revised shielding geometry allows for very compact and rather lightweight device designs. Based on highly sensitive SQUIDs featuring sub-micron cross-type Josephson tunnel junctions, our prototype device exhibits a current sensitivity of about 6 pA Hz−1/2 in the white noise region. Together with a measured shielding factor of about 135 dB this opens up the way for its widespread use in modern accelerator facilities.
Copper Phthalocyanine Improving Nonaqueous Catalysis of Pseudomonas cepacia Lipase for Ester Synthesis
The nonaqueous catalysis of lipases is significant for synthesis of high pure esters, but they usually behave low catalytic activity due to denaturation and aggregation of enzyme protein in organic phases. To improve the nonaqueous catalysis, the inexpensive copper phthalocyanine was taken as a new carrier on which Pseudomonas cepacia lipase was immobilized by physical absorption, and used for synthesis of hexyl acetate, an important flavor, via transesterification of hexanol and vinyl acetate. Results showed that the desired loading was 10 mg lipase immobilized on 10 mg copper phthalocyanine powder. When the immobilized lipase was employed in the reaction system consisted of 1.5 mL hexanol and 1.5 mL vinyl acetate at 37℃ and 160 rpm, the conversion was five fold of that catalyzed by native lipase after 1 h, and reached 99.0% after 8 h. Undergoing six times of 8-h reuses, the immobilized lipase had an activity attenuation rate 1.22% h− 1, lower than 1.77% h− 1 of native lipase, which meant that the immobilized lipase was more stable. Even at the room temperature and the static state without shaking or stirring, the immobilized lipase could bring conversion 42.8% after 10 h and the native lipase gave 20.1%. Obviously, the immobilized lipase is an available biocatalyst in organic phase and has great potential in food industry.