SRF2011 - List of Authors (Dhakal, P.)

Paper

Title

Page

Summary of the Symposium on Ingot Nb and New Results on Fundamental Studies of Large Grain Nb

319

G. Ciovati, P. Dhakal, R. Myneni
JLAB, Newport News, Virginia, USA

Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
The First International Symposium on the Superconducting Science and Technology of Ingot Niobium was held at Jefferson Lab in September 2010. Significant activities are taking place at laboratories and universities throughout the world to address several aspects related to the science and technology of Ingot Nb: from ingot production to mechanical, thermal and superconducting properties. A summary of the results presented at the Symposium is given in this contribution. New results on the superconducting properties and interstitial impurities content measured in large-grain Nb samples and cavities are briefly highlighted.

TUPO051

High-Temperature Heat Treatment Study on a Large-Grain Nb Cavity

508

G. Ciovati, P. Dhakal, R. Myneni
JLAB, Newport News, Virginia, USA
P. Maheshwari, F.A. Stevie
NCSU AIF, Raleigh, North Carolina, USA

Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
Improvement of the cavity performance by a high-temperature heat-treatment without subsequent chemical etching have been reported for large-grain Nb cavities treated by buffered chemical polishing, as well as for a fine-grain cavity treated by vertical electropolishing [1]. Changes in the quality factor, Q0, and maximum peak surface magnetic field achieved in a large-grain Nb single-cell cavity have been determined as a function of the heat treatment temperature, between 600 °C and 1200 °C. The highest Q0 improvement of about 30% was obtained after heat-treatment at 800 °C-1000 °C. Measurements by secondary ion mass spectrometry on large-grain samples heat-treated with the cavity showed large reduction of hydrogen concentration after heat treatment.
[1] G. Ciovati, G. Myneni, F. Stevie, P. Maheshwari, and D. Griffis, Phys. Rev. ST Accel. Beams 13, 022002 (2010)

THPO057

Superconducting DC and RF Properties of Ingot Niobium

856

P. Dhakal, G. Ciovati, P. Kneisel, R. Myneni
JLAB, Newport News, Virginia, USA

Recently [1, 2], the DC and low frequency magnetic and thermal properties of large-grain niobium samples subjected to different chemical and heat treatment were measured. Here, we extend the similar study to the cylindrical hollow rods of larger diameter, fabricated from new niobium ingots, manufactured by CBMM. The results confirm the influence of chemical and heat-treatment processes on the superconducting properties, with no significant dependence on the impurity concentrations in the original ingots. Furthermore, RF properties such as the surface resistance and quench field of the niobium rods were measured using a TE011 cavity. The hollow niobium rod is the center conductor of this cavity, converting it to a coaxial cavity. The quench field is limited by the critical heat flux through the rods’ cooling channel.
[1] Mondal et al., SRF 2009, Berlin, 2009.
[2] Dhavale et al.,Proc. of the First Int. Symp. on the Superconducting Sci. and Tech. of Ingot Niobium, AIP Conference Proceedings 1352, p. 119 (2011).

Poster THPO057 [1.238 MB]

Paper	Title	Page
TUIOB02	Summary of the Symposium on Ingot Nb and New Results on Fundamental Studies of Large Grain Nb	319
	G. Ciovati, P. Dhakal, R. Myneni JLAB, Newport News, Virginia, USA
	Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 The First International Symposium on the Superconducting Science and Technology of Ingot Niobium was held at Jefferson Lab in September 2010. Significant activities are taking place at laboratories and universities throughout the world to address several aspects related to the science and technology of Ingot Nb: from ingot production to mechanical, thermal and superconducting properties. A summary of the results presented at the Symposium is given in this contribution. New results on the superconducting properties and interstitial impurities content measured in large-grain Nb samples and cavities are briefly highlighted.

TUPO051	High-Temperature Heat Treatment Study on a Large-Grain Nb Cavity	508
	G. Ciovati, P. Dhakal, R. Myneni JLAB, Newport News, Virginia, USA P. Maheshwari, F.A. Stevie NCSU AIF, Raleigh, North Carolina, USA
	Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 Improvement of the cavity performance by a high-temperature heat-treatment without subsequent chemical etching have been reported for large-grain Nb cavities treated by buffered chemical polishing, as well as for a fine-grain cavity treated by vertical electropolishing [1]. Changes in the quality factor, Q0, and maximum peak surface magnetic field achieved in a large-grain Nb single-cell cavity have been determined as a function of the heat treatment temperature, between 600 °C and 1200 °C. The highest Q0 improvement of about 30% was obtained after heat-treatment at 800 °C-1000 °C. Measurements by secondary ion mass spectrometry on large-grain samples heat-treated with the cavity showed large reduction of hydrogen concentration after heat treatment. [1] G. Ciovati, G. Myneni, F. Stevie, P. Maheshwari, and D. Griffis, Phys. Rev. ST Accel. Beams 13, 022002 (2010)

THPO057	Superconducting DC and RF Properties of Ingot Niobium	856
	P. Dhakal, G. Ciovati, P. Kneisel, R. Myneni JLAB, Newport News, Virginia, USA
	Recently [1, 2], the DC and low frequency magnetic and thermal properties of large-grain niobium samples subjected to different chemical and heat treatment were measured. Here, we extend the similar study to the cylindrical hollow rods of larger diameter, fabricated from new niobium ingots, manufactured by CBMM. The results confirm the influence of chemical and heat-treatment processes on the superconducting properties, with no significant dependence on the impurity concentrations in the original ingots. Furthermore, RF properties such as the surface resistance and quench field of the niobium rods were measured using a TE011 cavity. The hollow niobium rod is the center conductor of this cavity, converting it to a coaxial cavity. The quench field is limited by the critical heat flux through the rods’ cooling channel. [1] Mondal et al., SRF 2009, Berlin, 2009. [2] Dhavale et al.,Proc. of the First Int. Symp. on the Superconducting Sci. and Tech. of Ingot Niobium, AIP Conference Proceedings 1352, p. 119 (2011).
	Poster THPO057 [1.238 MB]