SRF2013 - List of Keywords (power-supply)

Paper	Title	Other Keywords	Page
TUP094	Influence of Heat Treatments on Field Emitters on Nb Crystals	vacuum, cavity, site, status	690
	S. Lagotzky, G. Müller Bergische Universität Wuppertal, Wuppertal, Germany A. Matheisen, D. Reschke DESY, Hamburg, Germany
	Funding: Funding by HGF Alliance and the BMBF project 05H12PX6 Systematic investigations of the enhanced field emission (EFE) of HPR-cleaned large grain (LG) and single crystal (SC) Nb samples (Ra < 0.5μm) revealed an exponential increase of the emitter number density N with electric surface field Es and strong activation effects of the remaining particulates. Different types of EFE activation were observed: by high E partially combined with a micro-discharge or by heat treatments (HT) [1]. In cavities, EFE activation might also occur due to enhanced rf losses of particulates. Therefore, we have started a test series with two LG and two SC typically prepared Nb samples (40 μm BCP, 140 μm EP and HPR at DESY). At first all emitters (1 nA) up to Es = 160 MV/m were localized by means of correlated field emission microscopy (FESM). Then systematically varied in-situ HT between 122°C (24 h) and 400°C (2 h) were applied to investigate the activation of emitters due to the change of the natural Nb oxide. For all samples a significant increase of N with stronger HT up to 32 emitters/cm² at 400°C were obtained resulting in some activated emitters already at Es = 40 MV/m. Final SEM images of the activated emitters will also be discussed. [1] A. Navitski et. al, subm. to PRSTAB 2013

Paper

Title

Other Keywords

Page

TUP094

Influence of Heat Treatments on Field Emitters on Nb Crystals

vacuum, cavity, site, status

690

S. Lagotzky, G. Müller
Bergische Universität Wuppertal, Wuppertal, Germany
A. Matheisen, D. Reschke
DESY, Hamburg, Germany

Funding: Funding by HGF Alliance and the BMBF project 05H12PX6
Systematic investigations of the enhanced field emission (EFE) of HPR-cleaned large grain (LG) and single crystal (SC) Nb samples (Ra < 0.5μm) revealed an exponential increase of the emitter number density N with electric surface field Es and strong activation effects of the remaining particulates. Different types of EFE activation were observed: by high E partially combined with a micro-discharge or by heat treatments (HT) [1]. In cavities, EFE activation might also occur due to enhanced rf losses of particulates. Therefore, we have started a test series with two LG and two SC typically prepared Nb samples (40 μm BCP, 140 μm EP and HPR at DESY). At first all emitters (1 nA) up to Es = 160 MV/m were localized by means of correlated field emission microscopy (FESM). Then systematically varied in-situ HT between 122°C (24 h) and 400°C (2 h) were applied to investigate the activation of emitters due to the change of the natural Nb oxide. For all samples a significant increase of N with stronger HT up to 32 emitters/cm² at 400°C were obtained resulting in some activated emitters already at Es = 40 MV/m. Final SEM images of the activated emitters will also be discussed.
[1] A. Navitski et. al, subm. to PRSTAB 2013