SRF2011 - List of Authors (Toropov, E.)

Paper

Title

Page

Optical Inspection of SRF Cavities at Fermilab

515

E. Toropov, D.A. Sergatskov
Fermilab, Batavia, USA

The production of an SRF cavity includes a string of multiple treatments at different facilities before the cavity can be RF-tested in a cryogenic system. Many of the processing steps change the cavity surface and affect the RF performance of the cavity. Interjection of optical inspections between these steps provides us with an instant feedback on the processes involved as well as giving us new insight on the mechanisms responsible for forming surface abnormalities. The major drawback of inclusion of frequent optical inspections is the increased amount of time and labor in the cavity production cycle. An optical inspection of equatorial and iris welds of a 1.3GHz TESLA-shape cavity produces about two thousand pictures. We developed an automated procedure where a computer takes over the most of the routine operations including adjusting the camera focus. With that automation, the inspection currently takes about three hours and little operator time. We will describe the developed system including the focusing algorithm and discuss the ways to further optimize the procedure.

Poster TUPO053 [0.736 MB]

TUPO054

SRF Cavity Surface Topography From Optical Inspection

519

E. Toropov, D.A. Sergatskov
Fermilab, Batavia, USA

Characteristics of the cavity surface geometry such as roughness affect cavity performance. The optical cavity inspection system at Fermilab allows us to obtain pictures of cavity surface at different lightning conditions. By analyzing the images of some fixed location inside the cavity taken while the light source moves progressively along the axis we can deduce some topographical information of that surface. In the large-grain cavities after BCP, grains are oriented at distinct angles to the surface and, therefore, reflect light in different directions. We developed a simple algorithm to calculate the angle distribution of the grains and thus to estimate the roughness. We discuss this method and the results of the analysis of the actual cavity surface.

Poster TUPO054 [0.643 MB]

THPO051

Laser Re-Melting Influence on Nb Properties: Geometrical and Chemical Aspects

846

A.V. Dzyuba, L.D. Cooley, E. Toropov
Fermilab, Batavia, USA
A.V. Dzyuba
NSU, Novosibirsk, Russia
G.M. Ge
CLASSE, Ithaca, New York, USA
G. Wu
ANL, Argonne, USA

We present recent results on Laser re-melting system used to smoothen niobium surfaces of superconducting RF cavities in order to overcome quench. In the work we studied both chemical and geometrical aspects of the melting by means of electron backscattered diffraction microscopy and laser confocal microscopy. BCP, EP and HF impacts have been investigated on both single and large grain niobium samples. Appropriate post processing has been suggested.

Paper	Title	Page
TUPO053	Optical Inspection of SRF Cavities at Fermilab	515
	E. Toropov, D.A. Sergatskov Fermilab, Batavia, USA
	The production of an SRF cavity includes a string of multiple treatments at different facilities before the cavity can be RF-tested in a cryogenic system. Many of the processing steps change the cavity surface and affect the RF performance of the cavity. Interjection of optical inspections between these steps provides us with an instant feedback on the processes involved as well as giving us new insight on the mechanisms responsible for forming surface abnormalities. The major drawback of inclusion of frequent optical inspections is the increased amount of time and labor in the cavity production cycle. An optical inspection of equatorial and iris welds of a 1.3GHz TESLA-shape cavity produces about two thousand pictures. We developed an automated procedure where a computer takes over the most of the routine operations including adjusting the camera focus. With that automation, the inspection currently takes about three hours and little operator time. We will describe the developed system including the focusing algorithm and discuss the ways to further optimize the procedure.
	Poster TUPO053 [0.736 MB]

TUPO054	SRF Cavity Surface Topography From Optical Inspection	519
	E. Toropov, D.A. Sergatskov Fermilab, Batavia, USA
	Characteristics of the cavity surface geometry such as roughness affect cavity performance. The optical cavity inspection system at Fermilab allows us to obtain pictures of cavity surface at different lightning conditions. By analyzing the images of some fixed location inside the cavity taken while the light source moves progressively along the axis we can deduce some topographical information of that surface. In the large-grain cavities after BCP, grains are oriented at distinct angles to the surface and, therefore, reflect light in different directions. We developed a simple algorithm to calculate the angle distribution of the grains and thus to estimate the roughness. We discuss this method and the results of the analysis of the actual cavity surface.
	Poster TUPO054 [0.643 MB]

THPO051	Laser Re-Melting Influence on Nb Properties: Geometrical and Chemical Aspects	846
	A.V. Dzyuba, L.D. Cooley, E. Toropov Fermilab, Batavia, USA A.V. Dzyuba NSU, Novosibirsk, Russia G.M. Ge CLASSE, Ithaca, New York, USA G. Wu ANL, Argonne, USA
	We present recent results on Laser re-melting system used to smoothen niobium surfaces of superconducting RF cavities in order to overcome quench. In the work we studied both chemical and geometrical aspects of the melting by means of electron backscattered diffraction microscopy and laser confocal microscopy. BCP, EP and HF impacts have been investigated on both single and large grain niobium samples. Appropriate post processing has been suggested.